John Hawley

The effects of exercise mode, swimming vs. running, upon bone growth in the rapidly growing female rat

Publisher: Elsevier BV

Date: 10-1992

DOI: 10.1016/0047-6374(92)90073-M

Abstract: The purpose of this study was to compare the effects of two programs of endurance training, of equal duration and intensity, on bone development in female rats. Thirty-eight female Wistar rats were randomly assigned to one of three groups: run-trained (RUN), swim-trained (SWIM) or control (CON). The RUN group ran at a speed of 27 m/min up an 8 degrees incline. Swim trained animals swam with 2% of body weight attached to their tails. Training sessions were 2 h/day, 5 days/week and were conducted over a 10-week period. Hindlimb and forelimb muscles were removed upon sacrifice and analyzed for citrate synthase (CS) activity, liver (LG) and muscle (MG) glycogen. The parametrial fat pads were removed, digested with collagenase, and 2-deoxy-D-[3H]glucose uptake measured in isolated cells. Bone weight, length, diameter, ponderal index and bone mineral content (BMC) were measured in the femur and humerus of each animal. The LG, MG, fat cell volume, glucose uptake of the adipocyte and adrenal weight data indicate that the training response was identical. The CS activity of the muscles indicated that mechanical and recruitment patterns of the upper and lower body differ and could be responsible for bone development patterns found in this study. Exercise had a minimal effect on bone growth in the run-trained animals but did stimulate development in the swim-trained animals. The humerus of the SWIM was significantly (P < 0.05) heavier, wider and had a greater BMC when compared with those of the RUN and CON rats. The results of this study indicate that the muscular forces applied by the swim training protocol produced greater bone adaptations than the forces applied by a running protocol of equal duration and intensity.

The bioenergetics of world class cycling

Publisher: Elsevier BV

Date: 12-2000

DOI: 10.1016/S1440-2440(00)80008-0

Abstract: Professional cycle racing is one of the most demanding of all sports combining extremes of exercise duration, intensity and frequency. Riders are required to perform on a variety of surfaces (track, road, cross-country, mountain), terrains (level, uphill and downhill) and race situations (criterions, sprints, time trials, mass-start road races) in events ranging in duration from 10 s to 3 wk stage races covering 200 m to 4,000 km. Furthermore, professional road cyclists typically have approximately 100 race d/yr. Because of the ersity of cycle races, there are vastly different physiological demands associated with the various events. Until recently there was little information on the demands of professional cycling during training or competition. However, with the advent of reliable, valid bicycle crank dynanometers, it is now possible to quantify real-time power output, cadence and speed during a variety of track and road cycling races. This article provides novel data on the physiological demands of professional and world-class amateur cyclists and characterises some of the physiological attributes necessary for success in cycling at the élite level.

Between-meal sucrose-sweetened beverage consumption impairs glycaemia and lipid metabolism during prolonged sitting: A randomized controlled trial

Publisher: Elsevier BV

Date: 08-2019

DOI: 10.1016/J.CLNU.2018.08.021

Abstract: Chronic overconsumption of sugar-sweetened beverages (SSBs) is associated with unfavourable health effects, including promotion of obesity. However, the acute effects of consuming SSBs on glucose and lipid metabolism remain to be characterized in a real-world, post-prandial context of prolonged sitting. We quantified the acute effects of between-meal SSB consumption compared with water, on glucose and lipid metabolism in habitual soft drink consumers during prolonged sitting. Twenty-eight overweight or obese young adults [15 males 23 ± 3 (mean ± SD) years, body mass index (BMI) 31.0 ± 3.6 kg/m Compared to water, SSB consumption significantly increased the peak responses for blood glucose (20 ± 4% (mean ± SEM)), insulin (43 ± 15%) and C-peptide (21 ± 6%) concentrations. The tAUC for all these parameters was also increased by SSB consumption. The tAUC for triglycerides was 15 ± 5% lower after SSBs and this was driven by males (P < 0.05), as females showed no difference between conditions. The tAUC for NEFAs was 13 ± 5% lower after the SSB condition (P < 0.05). Between-meal SSB consumption significantly elevated plasma glucose responses, associated with a sustained elevation in plasma insulin throughout a day of prolonged sitting. The SSB-induced reduction in circulating triglycerides and NEFAs indicates significant modulation of lipid metabolism, particularly in males. These metabolic effects may contribute to the development of metabolic disease when SSB consumption is habitual and co-occurring with prolonged sitting. Clinical Trial Registry number: ACTRN12616000840482, anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12616000840482.

Carbohydrate availability and training adaptation: Effects on cell metabolism

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 10-2010

DOI: 10.1097/JES.0B013E3181F44DD9

Design and analysis of research on sport performance enhancement

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 03-1999

DOI: 10.1097/00005768-199903000-00018

Abstract: The purpose of this study was to assess research aimed at measuring performance enhancements that affect success of in idual elite athletes in competitive events. Simulations show that the smallest worthwhile enhancement of performance for an athlete in an international event is 0.7-0.4 of the typical within-athlete random variation in performance between events. Using change in performance in events as the outcome measure in a crossover study, researchers could delimit such enhancements with a s le of 16-65 athletes, or with 65-260 in a fully controlled study. S le size for a study using a valid laboratory or field test is proportional to the square of the within-athlete variation in performance in the test relative to the event estimates of these variations are therefore crucial and should be determined by repeated-measures analysis of data from reliability studies for the test and event. Enhancements in test and event may differ when factors that affect performance differ between test and event overall effects of these factors can be determined with a validity study that combines reliability data for test and event. A test should be used only if it is valid, more reliable than the event, allows estimation of performance enhancement in the event, and if the subjects replicate their usual training and dietary practices for the study otherwise the event itself provides the only dependable estimate of performance enhancement. Publication of enhancement as a percent change with confidence limits along with an analysis for in idual differences will make the study more applicable to athletes. Outcomes can be generalized only to athletes with abilities and practices represented in the study. estimates of enhancement of performance in laboratory or field tests in most previous studies may not apply to elite athletes in competitive events.

Nutritional strategies to modulate the adaptive response to endurance training

Publisher: S. Karger AG

Date: 2013

DOI: 10.1159/000345813

Abstract: In recent years, advances in molecular biology have allowed scientists to elucidate how endurance exercise training stimulates skeletal muscle remodeling (i.e. promotes mitochondrial biogenesis). A growing field of interest directly arising from our understanding of the molecular bases of training adaptation is how nutrient availability can alter the regulation of many contraction-induced events in muscle in response to endurance exercise. Acutely manipulating substrate availability can exert profound effects on muscle energy stores and patterns of fuel metabolism during exercise, as well as many processes activating gene expression and cell signaling. Accordingly, such interventions when repeated over weeks and months have the potential to modulate numerous adaptive processes in skeletal muscle that ultimately drive the phenotype-specific characteristics observed in highly trained athletes. In this review, the molecular and cellular events that occur in skeletal muscle during and after endurance exercise are discussed and evidence provided to demonstrate that nutrient availability plays an important role in modulating many of the adaptive responses to training. Emphasis is on human studies that have determined the regulatory role of muscle glycogen availability on cell metabolism, endurance training capacity and performance.

Fatigue revisited

Publisher: Informa UK Limited

Date: 1997

DOI: 10.1080/026404197367245

Abstract: [This corrects the article DOI: 10.1016/j.dib.2022.107828.].

Interrelated but Not Time-Aligned Response in Myogenic Regulatory Factors Demethylation and mRNA Expression after Divergent Exercise Bouts

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 22-09-2023

DOI: 10.1249/MSS.0000000000003049

Abstract: DNA methylation regulates exercise-induced changes in the skeletal muscle transcriptome. However, the specificity and the time course responses in the myogenic regulatory factors DNA methylation and mRNA expression after ergent exercise modes are unknown. This study aimed to compare the time course changes in DNA methylation and mRNA expression for selected myogenic regulatory factors ( MYOD1 , MYF5 , and MYF6 ) immediately after, 4 h after, and 8 h after a single bout of resistance exercise (RE), high-intensity interval exercise (HIIE), and concurrent exercise (CE). Nine healthy but untrained males (age, 23.9 ± 2.8 yr body mass, 70.1 ± 14.9 kg peak oxygen uptake [V̇O 2peak ], 41.4 ± 5.2 mL·kg −1 ·min −1 mean ± SD) performed a counterbalanced, randomized order of RE (4 × 8–12 repetition maximum), HIIE (12 × 1 min sprints at V̇O 2peak running velocity), and CE (RE followed by HIIE). Skeletal muscle biopsies (vastus lateralis) were taken before (REST) immediately (0 h), 4 h, and 8 h after each exercise bout. Compared with REST, MYOD1 , MYF5 , and MYF6 , mean methylation across all CpGs analyzed was reduced after 4 and 8 h in response to all exercise protocols ( P 0.05). Reduced levels of MYOD1 methylation were observed after HIIE and CE compared with RE ( P 0.05). Compared with REST, all exercise bouts increased mRNA expression over time ( MYOD1 at 4 and 8 h, and MYF6 at 4 h P 0.05). MYF5 mRNA expression was lower after 4 h compared with 0 h and higher at 8 h compared with 4 h ( P 0.05). We observed an interrelated but not time-aligned response between the exercise-induced changes in myogenic regulatory factors demethylation and mRNA expression after ergent exercise modes. Despite ergent contractile stimuli, changes in DNA methylation and mRNA expression in skeletal muscle were largely confined to the late (4–8 h) recovery period and similar between the different exercise challenges.

Short-Term High-Fat Diet Alters Substrate Utilization during Exercise but Not Glucose Tolerance in Highly Trained Athletes

Publisher: Human Kinetics

Date: 09-2001

DOI: 10.1123/IJSNEM.11.3.273

Abstract: We determined the effect of a high-fat diet and carbohydrate (CHO) restoration on substrate oxidation and glucose tolerance in 7 competitive ultra-endurance athletes (peak oxygen uptake [V̇O 2peak ] 68 ± 1 ml · kg −1 · min −1 mean± SEM ). For 6 days, subjects consumed a random order of a high-fat (69% fat FAT-adapt) or a high-CHO (70% CHO HCHO) diet, each followed by 1 day of a high-CHO diet. Treatments were separated by an 18-day wash out. Substrate oxidation was determined during submaximal cycling (20 min at 65% V̇O 2peak ) prior to and following the 6 day dietary interventions. Fat oxidation at baseline was not different between treatments (17.4 ± 2.1 vs. 16.1 ± 1.3 g · 20 min −1 for FAT-adapt and HCHO, respectively) but increased 34% after 6 days of FAT-adapt (to 23.3 ± 0.9 g · 20 min −1 , p .05) and decreased 30% after HCHO (to 11.3±1.4 g · 20 min −1 , p .05). Glucose tolerance, determined by the area under the plasma [glucose] versus time curve during an oral glucose tolerance (OGTT) test, was similar at baseline (545±21 vs. 520±28 mmol · L −1 · 90 min −1 ), after 5-d of dietary intervention (563 ± 26 vs. 520 ± 18 mmol · L −1 · 90 min −1 ) and after 1 d of high-CHO (491 ± 28 vs. 489 ± 22 mmol · L −1 · 90min −1 for FAT- adapt and HCHO, respectively). An index of whole-body insulin sensitivity (S I 10000/÷fasting [glucose] × fasting [insulin] × mean [glucose] during OGTT × mean [insulin] during OGTT) was similar at baseline (15 ± 2 vs. 17 ± 5 arbitrary units), after 5-d of dietary intervention (15 ± 2 vs. 15 ± 2) and after 24 h of CHO loading (17 ± 3 vs. 18 ± 2 for FAT- adapt and HCHO, respectively). We conclude that despite marked changes in the pattern of substrate oxidation during submaximal exercise, short-term adaptation to a high-fat diet does not alter whole-body glucose tolerance or an index of insulin sensitivity in highly-trained in iduals.

Symposium: Limits to fat oxidation by skeletal muscle during exercise - Introduction

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 09-2002

DOI: 10.1097/00005768-200209000-00012

Abstract: Lipids, in the form of adipose tissue triacylglycerol (TG), intramuscular triglyceride (IMTG), and dietary-derived fatty acids (FA) from plasma TG (chylomicrons), and very low-density lipoproteins (VLDL), represent the largest store of nutrient energy in humans. Yet despite the abundance of endogenous TG, there is limited capacity for FA oxidation during exercise: there are no mechanisms that match the availability and metabolism of FA to the rate of energy expenditure. Because of the body's limited carbohydrate (CHO) stores, and because depletion of muscle and liver glycogen reserves often coincide with exhaustion, there is interest in several nutritional interventions that increase FA availability and rates of fat oxidation during exercise: such strategies have the potential to slow the rate of glycogen utilization and delay the onset of fatigue. The five papers comprising this symposium provide a synopsis of 1) the regulation of fat oxidation in human skeletal muscle during aerobic exercise 2) selected nutritional techniques that increase fat oxidation, spare endogenous CHO stores, and modify exercise capacity and 3) dietary manipulations that alter macronutrient availability and muscle gene expression.

Dietary regulation of fat oxidative gene expression in different skeletal muscle fiber types

Publisher: Wiley

Date: 12-2003

DOI: 10.1038/OBY.2003.197

Abstract: To determine the effect of a high-fat diet on the expression of genes important for fat oxidation, the protein abundance of the transcription factors peroxisome proliferator-activated receptor (PPAR) isoforms alpha and gamma, and selected enzyme activities in type I and II skeletal muscle. Sprague-Dawley rats consumed either a high-fat (HF: 78% energy, n = 8) or high-carbohydrate (64% energy, n = 8) diet for 8 weeks while remaining sedentary. The expression of genes important for fat oxidation tended to increase in both type I (soleus) and type II (extensor digitorum longus) fiber types after an HF dietary intervention. However, the expression of muscle type carnitine palmitoyltransferase I was not increased in extensor digitorum longus. Analysis of the gene expression of both peroxisome proliferator-activated receptor-gamma coactivator and fork-head transcription factor O1 demonstrated no alteration in response to the HF diet. Similarly, PPARalpha and PPARgamma protein levels were also not altered by the HF diet. An HF diet increased the expression of an array of genes involved in lipid metabolism, with only subtle differences evident in the response within differing skeletal muscle fiber types. Despite changes in gene expression, there were no effects of diet on peroxisome proliferator-activated receptor-gamma coactivator and fork-head transcription factor O1 mRNA and the protein abundance of PPARalpha and PPARgamma.

Omega-3 Polyunsaturated Fatty Acids Mitigate Palmitate-Induced Impairments in Skeletal Muscle Cell Viability and Differentiation

Publisher: Frontiers Media SA

Date: 03-06-2020

DOI: 10.3389/FPHYS.2020.00563

Arctic closure as a trigger for Atlantic overturning at the Eocene-Oligocene Transition

Publisher: Springer Science and Business Media LLC

Date: 22-08-2019

DOI: 10.1038/S41467-019-11828-Z

Abstract: The Eocene-Oligocene Transition (EOT), approximately 34 Ma ago, marks a period of major global cooling and inception of the Antarctic ice sheet. Proxies of deep circulation suggest a contemporaneous onset or strengthening of the Atlantic meridional overturning circulation (AMOC). Proxy evidence of gradual salinification of the North Atlantic and tectonically driven isolation of the Arctic suggest that closing the Arctic-Atlantic gateway could have triggered the AMOC at the EOT. We demonstrate this trigger of the AMOC using a new paleoclimate model with late Eocene boundary conditions. The control simulation reproduces Eocene observations of low Arctic salinities. Subsequent closure of the Arctic-Atlantic gateway triggers the AMOC by blocking freshwater inflow from the Arctic. Salt advection feedbacks then lead to cessation of overturning in the North Pacific. These circulation changes imply major warming of the North Atlantic Ocean, and simultaneous cooling of the North Pacific, but no interhemispheric change in temperatures.

Prediction of maximal oxygen uptake from a 20-m shuttle run as measured directly in runners and squash players

Publisher: Informa UK Limited

Date: 1998

DOI: 10.1080/02640419808559361

Abstract: The aim of this study was to assess the validity of the multistage shuttle run test in predicting maximal oxygen uptake (VO2 max) in athletes trained in sports with different physical demands. Over a 14-day period, 10 male long-distance runners (continuous high-intensity exercise) and 10 male squash players (intermittent high-intensity exercise) performed, in random order, the multistage shuttle run test and a maximal treadmill protocol of increasing elevation which elicited VO2 max. Compared with direct measurement of VO2 max, the shuttle run test significantly underpredicted the VO2 max of the group of runners (n = 10 P < 0.01) and of the athletes as a whole (n = 20 P < 0.01). The correlation (r) between VO2 max determined by the shuttle run test and by the treadmill protocol was 0.61 (P < 0.05) for the squash players, 0.71 (P < 0.05) for the runners and 0.67 (P < 0.01) for the athletes as a whole. As the subjects represented athletes trained specifically in sports with different physical demands, this may explain why the correlations between the shuttle run test and direct measurement of VO2 max are less robust than those reported in previous studies. Furthermore, our results indicate that there are sport-specific differences when predicting VO2 max from the multistage shuttle run test.

Effect of increased fat availability on metabolism and exercise capacity

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 09-2002

DOI: 10.1097/00005768-200209000-00014

Abstract: Several procedures have been utilized to elevate plasma free fatty acid (FFA) concentration and increase fatty acid (FA) delivery to skeletal muscle during exercise. These include fasting, caffeine ingestion, L-carnitine supplementation, ingestion of medium-chain and long-chain triglyceride (LCT) solutions, and intravenous infusion of intralipid emulsions. Studies in which both untrained and well-trained subjects have ingested LCT solutions or received an infusion of intralipid (in combination with an injection of heparin) before exercise have reported significant reductions in whole-body carbohydrate oxidation and decreased muscle glycogen utilization during both moderate and intense dynamic exercise lasting 15-60 min. The effects of increased FA provision on rates of muscle glucose uptake during exercise are, however, equivocal. Despite substantial muscle glycogen sparing (15-48% compared with control), exercise capacity is not systematically improved in the face of increased FA availability.

Genetic loss of AMPK-glycogen binding destabilises AMPK and disrupts metabolism

Publisher: Elsevier BV

Date: 11-2020

DOI: 10.1016/J.MOLMET.2020.101048

Alcohol Ingestion Impairs Maximal Post-Exercise Rates of Myofibrillar Protein Synthesis following a Single Bout of Concurrent Training

Publisher: Public Library of Science (PLoS)

Date: 12-02-2014

DOI: 10.1371/JOURNAL.PONE.0088384

Pre-exercise carbohydrate and fat ingestion: effects on metabolism and performance

Publisher: Routledge

Date: 02-08-2004

DOI: 10.4324/9780203448618-3

Effects of short-term fat adaptation on metabolism and performance of prolonged exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 09-2002

DOI: 10.1097/00005768-200209000-00015

Abstract: The concept of manipulating an in iduals habitual diet before an exercise bout in an attempt to modify patterns of fuel substrate utilization and enhance subsequent exercise capacity is not new. Modern studies have focused on nutritional and training strategies aimed to optimize endogenous carbohydrate (CHO) stores while simultaneously maximizing the capacity for fat oxidation during continuous, submaximal (60-70% of maximal O(2) uptake [(.)VO(2max)] exercise. Such "nutritional periodization" typically encompasses 5-6 d of a high-fat diet (60-70% E) followed by 1-2 d of high-CHO intake (70-80% E CHO restoration). Despite the brevity of the adaptation period, ingestion of a high-fat diet by endurance-trained athletes results in substantially higher rates of fat oxidation and concomitant muscle glycogen sparing during submaximal exercise compared with an isoenergetic high-CHO diet. Higher rates of fat oxidation during exercise persist even under conditions in which CHO availability is increased, either by having athletes consume a high-CHO meal before exercise and/or ingest glucose solutions during exercise. Yet, despite marked changes in the patterns of fuel utilization that favor fat oxidation, fat-adaptation/CHO restoration strategies do not provide clear benefits to the performance of prolonged endurance exercise.

Exercise alters the profile of phospholipid molecular species in rat skeletal muscle

Publisher: American Physiological Society

Date: 11-2004

DOI: 10.1152/JAPPLPHYSIOL.00344.2004

Abstract: We have determined the effect of two exercise-training intensities on the phospholipid profile of both glycolytic and oxidative muscle fibers of female Sprague-Dawley rats using electrospray-ionization mass spectrometry. Animals were randomly ided into three training groups: control, which performed no exercise training low-intensity (8 m/min) treadmill running or high-intensity (28 m/min) treadmill running. All exercise-trained rats ran 1,000 m/session for 4 days/wk for 4 wk and were killed 48 h after the last training bout. Exercise training was found to produce no novel phospholipid species but was associated with significant alterations in the relative abundance of a number of phospholipid molecular species. These changes were more prominent in glycolytic (white vastus lateralis) than in oxidative (red vastus lateralis) muscle fibers. The largest observed change was a decrease of ∼20% in the abundance of 1-stearoyl-2-docosahexaenoyl-phosphatidylethanolamine [PE(18:0/22:6) P 0.001] ions in both the low- and high-intensity training regimes in glycolytic fibers. Increases in the abundance of 1-oleoyl-2-linoleoyl phopshatidic acid [PA(18:1/18:2) P 0.001] and 1-alkenylpalmitoyl-2-linoleoyl phosphatidylethanolamine [plasmenyl PE (16:0/18:2) P 0.005] ions were also observed for both training regimes in glycolytic fibers. We conclude that exercise training results in a remodeling of phospholipids in rat skeletal muscle. Even though little is known about the physiological or pathophysiological role of specific phospholipid molecular species in skeletal muscle, it is likely that this remodeling will have an impact on a range of cellular functions.

Time-Restricted Eating as a Nutrition Strategy for Individuals with Type 2 Diabetes: A Feasibility Study

Publisher: MDPI AG

Date: 22-10-2020

DOI: 10.3390/NU12113228

Abstract: In iduals with type 2 diabetes (T2D) require a long-term dietary strategy for blood glucose management and may benefit from time-restricted eating (TRE, where the duration between the first and last energy intake is restricted to 8–10 h/day). We aimed to determine the feasibility of TRE for in iduals with T2D. Participants with T2D (HbA1c .5 to %, eating window h/day) were recruited to a pre-post, non-randomised intervention consisting of a 2-week Habitual period to establish baseline dietary intake, followed by a 4-weeks TRE intervention during which they were instructed to limit all eating occasions to between 10:00 and 19:00 h on as many days of each week as possible. Recruitment, retention, acceptability, and safety were recorded throughout the study as indicators of feasibility. Dietary intake, glycaemic control, psychological well-being, acceptability, cognitive outcomes, and physiological measures were explored as secondary outcomes. From 594 interested persons, and 27 eligible in iduals, 24 participants enrolled and 19 participants (mean ± SD age: 50 ± 9 years, BMI: 34 ± 5 kg/m2, HbA1c: 7.6 ± 1.1%) completed the 6-week study. Overall daily dietary intake did not change between Habitual (~8400 kJ/d 35% carbohydrate, 20% protein, 41% fat, 1% alcohol) and TRE periods (~8500 kJ/d 35% carbohydrate, 19% protein, 42% fat, 1% alcohol). Compliance to the 9 h TRE period was 72 ± 24% of 28 days (i.e., ~5 days/week), with varied adherence (range: 4–100%). Comparisons of adherent vs. non-adherent TRE days showed that adherence to the 9-h TRE window reduced daily energy intake through lower absolute carbohydrate and alcohol intakes. Overall, TRE did not significantly improve measures of glycaemic control (HbA1c −0.2 ± 0.4% p = 0.053) or reduce body mass. TRE did not impair or improve psychological well-being, with variable effects on cognitive function. Participants described hunger, daily stressors, and emotions as the main barriers to adherence. We demonstrate that 4-weeks of TRE is feasible and achievable for these in iduals with T2D to adhere to for at least 5 days/week. The degree of adherence to TRE strongly influenced daily energy intake. Future trials may benefit from supporting participants to incorporate TRE in regular daily life and to overcome barriers to adherence.

Use of Online Food Delivery Services to Order Food Prepared Away-From-Home and Associated Sociodemographic Characteristics: A Cross-Sectional, Multi-Country Analysis

Publisher: MDPI AG

Date: 17-07-2020

DOI: 10.3390/IJERPH17145190

Abstract: Online food delivery services like Just Eat and Grubhub facilitate online ordering and home delivery of food prepared away-from-home. It is poorly understood how these services are used and by whom. This study investigated the prevalence of online food delivery service use and sociodemographic characteristics of customers, in and across Australia, Canada, Mexico, the UK, and the USA. We analyzed online survey data (n = 19,378) from the International Food Policy Study, conducted in 2018. We identified respondents who reported any online food delivery service use in the past 7 days and calculated the frequency of use and number of meals ordered. We investigated whether odds of any online food delivery service use in the past 7 days differed by sociodemographic characteristics using adjusted logistic regression. Overall, 15% of respondents (n = 2929) reported online food delivery service use, with the greatest prevalence amongst respondents in Mexico (n = 839 (26%)). Online food delivery services had most frequently been used once and the median number of meals purchased through this mode of order was two. Odds of any online food delivery service use were lower per additional year of age (OR: 0.95 95% CI: 0.94, 0.95) and greater for respondents who were male (OR: 1.50 95% CI: 1.35, 1.66), that identified with an ethnic minority (OR: 1.57 95% CI: 1.38, 1.78), were highly educated (OR: 1.66 95% CI: 1.46, 1.90), or living with children (OR: 2.71 95% CI: 2.44, 3.01). Further research is required to explore how online food delivery services may influence diet and health.

Improved running economy in elite runners after 20 days of simulated moderate-altitude exposure

Publisher: American Physiological Society

Date: 03-2004

DOI: 10.1152/JAPPLPHYSIOL.00725.2003

Abstract: To investigate the effect of altitude exposure on running economy (RE), 22 elite distance runners [maximal O 2 consumption (V̇o 2 ) 72.8 ± 4.4 ml·kg -1 ·min -1 training volume 128 ± 27 km/wk], who were homogenous for maximal V̇o 2 and training, were assigned to one of three groups: live high (simulated altitude of 2,000–3,100 m)-train low (LHTL natural altitude of 600 m), live moderate-train moderate (LMTM natural altitude of 1,500–2,000 m), or live low-train low (LLTL natural altitude of 600 m) for a period of 20 days. RE was assessed during three submaximal treadmill runs at 14, 16, and 18 km/h before and at the completion of each intervention. V̇o 2 , minute ventilation (V̇e), respiratory exchange ratio, heart rate, and blood lactate concentration were determined during the final 60 s of each run, whereas hemoglobin mass (Hb mass ) was measured on a separate occasion. All testing was performed under normoxic conditions at ∼600 m. V̇o 2 (l/min) averaged across the three submaximal running speeds was 3.3% lower ( P = 0.005) after LHTL compared with either LMTM or LLTL. V̇e, respiratory exchange ratio, heart rate, and Hb mass were not significantly different after the three interventions. There was no evidence of an increase in lactate concentration after the LHTL intervention, suggesting that the lower aerobic cost of running was not attributable to an increased anaerobic energy contribution. Furthermore, the improved RE could not be explained by a decrease in V̇e or by preferential use of carbohydrate as a metabolic substrate, nor was it related to any change in Hb mass . We conclude that 20 days of LHTL at simulated altitude improved the RE of elite distance runners.

Enhancement of 2000-m rowing performance after caffeine ingestion

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 11-2000

DOI: 10.1097/00005768-200011000-00021

Abstract: To investigate the effect of caffeine ingestion on short-term endurance performance in competitive rowers. In this randomized double-blind crossover study, eight competitive oarsmen (peak oxygen uptake [VO2peak] 4.7+/-0.4 L x min(-1), mean +/- SD) performed three familiarization trials of a 2000-m rowing test on an air-braked ergometer, followed by three experimental trials at 3- to 7-d intervals, each 1 h after ingesting caffeine (6 or 9 mg x kg(-1) body mass) or placebo. Trials were preceded by a standardized warm-up (6 min at 225+/-39 W 75+/-7.7% VO2peak). Urinary caffeine concentration was similar before ingestion (approximately 1 mg x L(-1)) but rose to 6.2+/-3.6 and 14.5+/-7.0 mg x L(-1) for the low and high caffeine doses, respectively. Plasma free fatty acid concentration before exercise was higher after caffeine ingestion (0.29+/-0.17 and 0.39+/-0.20 mM for 6 and 9 mg x kg(-1), respectively) than after placebo (0.13+/-0.05 mM). Respiratory exchange ratio during the warm-up was also substantially lower with caffeine (0.94+/-0.09 and 0.93+/-0.06 for the low and high dose) than with placebo (0.98+/-0.12). Subjects could not distinguish between treatments before or after the exercise test. Both doses of caffeine had a similar ergogenic effect relative to placebo: performance time decreased by a mean of 1.2% (95% likely range 0.4-1.9%) the corresponding increase in mean power was 2.7% (0.4-5.0%). Performance time showed some evidence of in idual differences in the effect of caffeine (SD 0.9% 95% likely range 1.5 to -0.9%). Ingestion of 6 or 9 mg x kg(-1) of caffeine produces a worthwhile enhancement of short-term endurance performance in a controlled laboratory setting.

Interaction of Diet and Training on Endurance Performance in Rats

Publisher: Wiley

Date: 07-2001

DOI: 10.1113/EPH8602158

Abstract: We determined the interaction of diet and training on metabolic adaptations in skeletal muscle and liver, and the consequences of these adaptations for endurance. Eighty rats performed a baseline treadmill run to exhaustion at 16 m min(-1) (RUN1) and were then ided into two groups and given one of two diets: high carbohydrate (CHO) or high fat (FAT). Each dietary group was then ided into one of four subgroups: sedentary control that performed no training (NT) low-intensity running (8 m min(-1) LOW) and two groups who trained at their maximal voluntary running speed without electrical stimulation (28 m min(-1) VMAX). Training volume was identical for LOW and VMAX (1000 m session(-1)) and animals ran 4 days week(-1) for 8 weeks. To assess the interaction of the higher intensity exercise with diet, a second endurance test (RUN2) was undertaken after 6 weeks at either 16 m min(-1) or 28 m min(-1). The NT group ran for a longer duration (increase of 77 %) after FAT than CHO (239 +/- 28 vs. 135 +/- 30 min, P < 0.05) at 16 m min(-1). There were no differences in RUN2 for the LOW group when rats ran at 16 m min(-1) (454 +/- 86 vs. 427 +/- 75 min for CHO and FAT groups, respectively), but rats in the VMAX group fed FAT ran longer than rats fed CHO at 28 m min(-1) (100 +/- 28 vs. 58 +/- 11 min, respectively, P < 0.05). FAT increased the activities of the enzymes citrate synthase, beta-hydroxyacyl-CoA dehydrogenase and carnitine palmitoyl-transferase compared to CHO (P < 0.01), but there was no systematic effect of training. We conclude: (1) there was no additive effect of a high-fat diet on endurance performance when rats performed low-intensity training (2) running performance at 28 m min(-1) was only enhanced by a high-fat diet after more intense training (3) diet-induced and training-induced adaptations that increase exercise capacity may be under independent control. Experimental Physiology (2001) 86.4, 499-508.

Increasing leucine concentration stimulates mechanistic target of rapamycin signaling and cell growth in C2C12 skeletal muscle cells

Publisher: Elsevier BV

Date: 11-2014

DOI: 10.1016/J.NUTRES.2014.09.011

Abstract: Leucine is a key amino acid for initiating translation in muscle cells, but the dose-dependent effects of leucine on intracellular signaling are poorly characterized. This study examined the effect that increasing doses of leucine would have on changes in mechanistic target of rapamycin (mTOR)-mediated signaling, rates of protein synthesis, and cell size in C2C12 cells. We hypothesized that a leucine "threshold" exists, which represents the minimum stimulus required to initiate mTOR signaling in muscle cells. Acute exposure to 1.5, 3.2, 5.0, and 16.1 mM leucine increased phosphorylation of mTOR(Ser2448) (~1.4-fold P < .04), 4E-BP1 (Thr37/46) (~1.9-fold P < .001), and rpS6(Ser235/6) (~2.3-fold P < .001). However, only p70S6k(Thr389) exhibited a dose-dependent response to leucine with all treatments higher than control (~4-fold P < .001) and at least 5 mM higher than the 1.5-mM concentration (1.2-fold P < .02). Rates of protein synthesis were not altered by any treatment. Seven days of exposure to 0.5, 1.5, 5.0, and 16.5 mM leucine resulted in an increase in cell size in at least 5 mM treatments (~1.6-fold, P < .001 vs control). Our findings indicate that even at low leucine concentrations, phosphorylation of proteins regulating translation initiation signaling is enhanced. The phosphorylation of p70S6k(Thr389) follows a leucine dose-response relationship, although this was not reflected by the acute protein synthetic response. Nevertheless, under the conditions of the present study, it appears that leucine concentrations of at least 5 mM are necessary to enhance cell growth.

Acute endurance exercise induces nuclear p53 abundance in human skeletal muscle

Publisher: Frontiers Media SA

Date: 26-04-2016

DOI: 10.3389/FPHYS.2016.00144

Cytokine responses to carbohydrate ingestion during recovery from exercise-induced muscle injury

Publisher: Mary Ann Liebert Inc

Date: 05-2010

DOI: 10.1089/JIR.2009.0079

Abstract: We investigated the effect of carbohydrate ingestion after maximal lengthening contractions of the knee extensors on circulating concentrations of myocellular proteins and cytokines, and cytokine mRNA expression in muscle. Using a cross-over design, 10 healthy males completed 5 sets of 10 lengthening (eccentric) contractions (unilateral leg press) at 120% 1 repetition-maximum. Subjects were randomized to consume a carbohydrate drink (15% weight per volume 3 g/kg BM) for 3 h after exercise using one leg, or a placebo drink after exercise using the contralateral leg on another day. Blood s les (10 mL) were collected before exercise and after 0, 30, 60, 90, 120, 150, and 180 min of recovery. Muscle biopsies (vastus lateralis) were collected before exercise and after 3 h of recovery. Following carbohydrate ingestion, serum concentrations of glucose (30-90 min and at 150 min) and insulin (30-180 min) increased (P < 0.05) above pre-exercise values. Serum myoglobin concentration increased ( approximately 250% P < 0.05) after both trials. In contrast, serum cytokine concentrations were unchanged throughout recovery in both trials. Muscle mRNA expression for IL-8 (6.4-fold), MCP-1 (4.7-fold), and IL-6 (7.3-fold) increased substantially after carbohydrate ingestion. TNF-alpha mRNA expression did not change after either trial. Carbohydrate ingestion during early recovery from exercise-induced muscle injury may promote proinflammatory reactions within skeletal muscle.

Protein coingestion with alcohol following strenuous exercise attenuates alcohol-induced intramyocellular apoptosis and inhibition of autophagy

Publisher: American Physiological Society

Date: 11-2016

DOI: 10.1152/AJPENDO.00303.2016

Abstract: Alcohol ingestion decreases postexercise rates of muscle protein synthesis, but the mechanism(s) (e.g., increased protein breakdown) underlying this observation is unknown. Autophagy is an intracellular “recycling” system required for homeostatic substrate and organelle turnover its dysregulation may provoke apoptosis and lead to muscle atrophy. We investigated the acute effects of alcohol ingestion on autophagic cell signaling responses to a bout of concurrent (combined resistance- and endurance-based) exercise. In a randomized crossover design, eight physically active males completed three experimental trials of concurrent exercise with either postexercise ingestion of alcohol and carbohydrate (12 ± 2 standard drinks ALC-CHO), energy-matched alcohol and protein (ALC-PRO), or protein (PRO) only. Muscle biopsies were taken at rest and 2 and 8 h postexercise. Select autophagy-related gene (Atg) proteins decreased compared with rest with ALC-CHO ( P 0.05) but not ALC-PRO. There were parallel increases ( P 0.05) in p62 and PINK1 commensurate with a reduction in BNIP3 content, indicating a diminished capacity for mitochondria-specific autophagy (mitophagy) when alcohol and carbohydrate were coingested. DNA fragmentation increased in both alcohol conditions ( P 0.05) however, nuclear AIF accumulation preceded this apoptotic response with ALC-CHO only ( P 0.05). In contrast, increases in the nuclear content of p53, TFEB, and PGC-1α in ALC-PRO were accompanied by markers of mitochondrial biogenesis at the transcriptional ( Tfam, SCO2, and NRF-1) and translational (COX-IV, ATPAF1, and VDAC1) level ( P 0.05). We conclude that alcohol ingestion following exercise triggers apoptosis, whereas the anabolic properties of protein coingestion may stimulate mitochondrial biogenesis to protect cellular homeostasis.

Chrono-nutrition for the prevention and treatment of obesity and type 2 diabetes: from mice to men

Publisher: Springer Science and Business Media LLC

Date: 06-08-2020

DOI: 10.1007/S00125-020-05238-W

Novel high-fidelity tyre model for motorcycles to be characterised by quasi-static manoeuvres – rationale and numerical validation

Publisher: Informa UK Limited

Date: 17-12-2022

DOI: 10.1080/00423114.2021.2013506

Skeletal muscle: increasing the size of the locomotor cell

Publisher: Elsevier BV

Date: 09-2010

DOI: 10.1016/J.BIOCEL.2010.05.013

Abstract: Skeletal muscle is the most abundant tissue in the body comprising 40-50% of body mass in humans and playing a central role in maintaining metabolic health. Skeletal muscle protein undergoes rapid turnover, a process that is intricately regulated by the balance between the rates of protein synthesis and degradation. The process of skeletal muscle hypertrophy and regeneration is an important adaptive response to both contractile activity (i.e., exercise) and nutrient availability (i.e., protein ingestion). Ageing and physical inactivity are two conditions associated with a loss of skeletal muscle protein (sarcopenia). Sarcopenia is characterised by a deterioration of muscle quantity and quality, although the precise mechanism(s) underlying this condition remain to be elucidated. This review will (1) summarise our current understanding of the origin and plasticity of skeletal muscle, (2) discuss the major effectors of muscle growth, and (3) highlight the importance of skeletal muscle health in the prevention of several common pathologies.

Ketone Diester Ingestion Impairs Time-Trial Performance in Professional Cyclists

Publisher: Frontiers Media SA

Date: 23-10-2017

DOI: 10.3389/FPHYS.2017.00806

Fat burning during exercise: Can ergogenics change the balance?

Publisher: Informa UK Limited

Date: 09-1998

DOI: 10.3810/PSM.1998.09.1143

Abstract: Endurance athletes and dieters are eager to burn more fat during exercise athletes hope to conserve carbohydrate stores, while dieters wish to decrease fat stores. This article briefly reviews the role of fat as an energy source for physical activity, discusses how exercise intensity and duration affect fat and carbohydrate metabolism, and assesses the nutrition strategies athletes are most likely to use in attempts to promote fat burning during exercise: caffeine ingestion, L-carnitine supplements, medium-chain triglyceride supplements, and high-fat diets. Of this group, caffeine ingestion is the only strategy scientifically proven to enhance athletic performance.

Prevalence and profile of “seasonal frequent flyers” with chronic heart disease: Analysis of 1598 patients and 4588 patient-years follow-up

Publisher: Elsevier BV

Date: 03-2019

DOI: 10.1016/J.IJCARD.2018.12.060

Abstract: Peaks and troughs in cardiovascular events correlated with seasonal change is well established from an epidemiological perspective but not a clinical one. Retrospective analysis of the recruitment, baseline characteristics and outcomes during minimum 12-month exposure to all four seasons in 1598 disease-management trial patients hospitalised with chronic heart disease. Seasonality was prospectively defined as ≥4 hospitalisations (all-cause) AND >45% of related bed-days occurring in any one season during median 988 (IQR 653, 1394) days follow-up. Patients (39% female) were aged 70 ± 12 years and had a combination of coronary artery disease (58%), heart failure (54%), atrial fibrillation (50%) and multimorbidity. Overall, 29.9% of patients displayed a pattern of seasonality. Independent correlates of seasonality were female gender (adjusted OR 1.27, 95% CI 1.01-1.61 p = 0.042), mild cognitive impairment (adjusted OR 1.51, 95% CI 1.16-1.97 p = 0.002), greater multimorbidity (OR 1.20, 95% CI 1.15-1.26 per Charlson Comorbidity Index Score p < 0.001), higher systolic (OR 1.01, 95%CI 1.00-1.01 per 1 mmHg p = 0.002) and lower diastolic (OR 0.99, 95% CI 0.98-1.00 per 1 mmHg p = 0.002) blood pressure. These patients were more than two-fold more likely to die (adjusted HR 2.16, 95% CI 1.60-2.90 p < 0.001) with the highest and lowest number of deaths occurring during spring (31.7%) and summer (19.9%), respectively. Despite high quality care and regardless of their diagnosis, we identified a significant proportion of "seasonal frequent flyers" with concurrent poor survival in this real-world cohort of patients with chronic heart disease.

Nutrition and Football

Publisher: Routledge

Date: 02-11-2006

DOI: 10.4324/9780203967430

Sprinting Toward Fitness

Publisher: Elsevier BV

Date: 05-2017

DOI: 10.1016/J.CMET.2017.04.030

Abstract: Intense intermittent exercise, or interval training, is a powerful stimulus to induce many of the physiological adaptations typically associated with traditional, moderate-intensity continuous training. While coaches and athletes have recognized the value of interval training to enhance performance for over a century, recent scientific interest has focused on the application of this training method for health promotion. Despite renewed attention, the mechanistic basis for the physiological remodeling that occurs after interval training and the role that the stochastic nature of this type of exercise plays in mediating adaptive responses remains to be elucidated.

One-Step Procedure for Peptide Extraction from In-Gel Digestion Sample for Mass Spectrometric Analysis

Publisher: American Chemical Society (ACS)

Date: 06-11-2008

DOI: 10.1021/AC801344Z

Contraction-induced changes in TNFα and Akt-mediated signalling are associated with increased myofibrillar protein in rat skeletal muscle

Publisher: Springer Science and Business Media LLC

Date: 13-03-2010

DOI: 10.1007/S00421-010-1427-5

Abstract: Resistance training results in skeletal muscle hypertrophy, but the molecular signalling mechanisms responsible for this altered phenotype are incompletely understood. We used a resistance training (RT) protocol consisting of three sessions [day 1 (d1), day 3 (d3), day 5 (d5)] separated by 48 h recovery (squat exercise, 4 sets x 10 repetitions, 3 min recovery) to determine early signalling responses to RT in rodent skeletal muscle. Six animals per group were killed 3 h after each resistance training session and 24 and 48 h after the last training session (d5). There was a robust increase in TNFalpha protein expression, and IKK(Ser180/181) and p38MAPK(Thr180/Tyr182) phosphorylation on d1 (P < 0.05), which abated with subsequent RT, returning to control levels by d5 for TNFalpha and IKK(Ser180/181). There was a trend for a decrease in MuRF-1 protein expression, 48 h following d5 of training (P = 0.08). Notably, muscle myofibrillar protein concentration was elevated compared to control 24 and 48 h following RT (P < 0.05). Akt(Ser473) and mTOR(Ser2448) phosphorylation were unchanged throughout RT. Phosphorylation of p70S6k(Thr389) increased 3 h post-exercise on d1, d3 and d5 (P < 0.05), whilst phosphorylation of S6(Ser235/236) increased on d1 and d3 (P < 0.05). Our results show a rapid attenuation of inflammatory signalling with repeated bouts of resistance exercise, concomitant with summation in translation initiation signalling in skeletal muscle. Indeed, the cumulative effect of these signalling events was associated with myofibrillar protein accretion, which likely contributes to the early adaptations in response to resistance training overload in the skeletal muscle.

Acute signalling responses to intense endurance training commenced with low or normal muscle glycogen: Experimental Physiology-Research Paper

Publisher: Wiley

Date: 14-01-2010

DOI: 10.1113/EXPPHYSIOL.2009.049353

Abstract: We have previously demonstrated that well-trained subjects who completed a 3 week training programme in which selected high-intensity interval training (HIT) sessions were commenced with low muscle glycogen content increased the maximal activities of several oxidative enzymes that promote endurance adaptations to a greater extent than subjects who began all training sessions with normal glycogen levels. The aim of the present study was to investigate acute skeletal muscle signalling responses to a single bout of HIT commenced with low or normal muscle glycogen stores in an attempt to elucidate potential mechanism(s) that might underlie our previous observations. Six endurance-trained cyclists/triathletes performed a 100 min ride at approximately 70% peak O(2) uptake (AT) on day 1 and HIT (8 x 5 min work bouts at maximal self-selected effort with 1 min rest) 24 h later (HIGH). Another six subjects, matched for fitness and training history, performed AT on day 1 then 1-2 h later, HIT (LOW). Muscle biopsies were taken before and after HIT. Muscle glycogen concentration was higher in HIGH versus LOW before the HIT (390 +/- 28 versus 256 +/- 67 micromol (g dry wt)(1)). After HIT, glycogen levels were reduced in both groups (P < 0.05) but HIGH was elevated compared with LOW (229 +/- 29 versus 124 +/- 41 micromol (g dry wt)(1) P < 0.05). Phosphorylation of 5 AMP-activated protein kinase (AMPK) increased after HIT, but the magnitude of increase was greater in LOW (P < 0.05). Despite the augmented AMPK response in LOW after HIT, selected downstream AMPK substrates were similar between groups. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was unchanged for both groups before and after the HIT training sessions. We conclude that despite a greater activation AMPK phosphorylation when HIT was commenced with low compared with normal muscle glycogen availability, the localization and phosphorylation state of selected downstream targets of AMPK were similar in response to the two interventions.

Intensified exercise training does not alter AMPK signaling in human skeletal muscle

Publisher: American Physiological Society

Date: 05-2004

DOI: 10.1152/AJPENDO.00462.2003

Abstract: The AMP-activated protein kinase (AMPK) cascade has been linked to many of the acute effects of exercise on skeletal muscle substrate metabolism, as well as to some of the chronic training-induced adaptations. We determined the effect of 3 wk of intensified training (HIT 7 sessions of 8 × 5 min at 85% V̇o 2 peak ) in skeletal muscle from well-trained athletes on AMPK responsiveness to exercise. Rates of whole body substrate oxidation were determined during a 90-min steady-state ride (SS) pre- and post-HIT. Muscle metabolites and AMPK signaling were determined from biopsies taken at rest and immediately after exercise during the first and seventh HIT sessions, performed at the same (absolute) pre-HIT work rate. HIT decreased rates of whole body carbohydrate oxidation ( P 0.05) and increased rates of fat oxidation ( P 0.05) during SS. Resting muscle glycogen and its utilization during intense exercise were unaffected by HIT. However, HIT induced a twofold decrease in muscle [lactate] ( P 0.05) and resulted in tighter metabolic regulation, i.e., attenuation of the decrease in the PCr/(PCr + Cr) ratio and of the increase in [AMP free ]/ATP. Resting activities of AMPKα1 and -α2 were similar post-HIT, with the magnitude of the rise in response to exercise similar pre- and post-HIT. AMPK phosphorylation at Thr 172 on both the α1 and α2 subunits increased in response to exercise, with the magnitude of this rise being similar post-HIT. Acetyl-coenzyme A carboxylase-β phosphorylation was similar at rest and, despite HIT-induced increases in whole body rates of fat oxidation, did not increase post-HIT. Our results indicate that, in well-trained in iduals, short-term HIT improves metabolic control but does not blunt AMPK signaling in response to intense exercise.

Daily Myofibrillar Protein Synthesis Rates in Response to Low- and High-Frequency Resistance Exercise Training in Healthy, Young Men

Publisher: Human Kinetics

Date: 05-2021

DOI: 10.1123/IJSNEM.2020-0274

Abstract: The impact of resistance exercise frequency on muscle protein synthesis rates remains unknown. The aim of this study was to compare daily myofibrillar protein synthesis rates over a 7-day period of low-frequency (LF) versus high-frequency (HF) resistance exercise training. Nine young men (21 ± 2 years) completed a 7-day period of habitual physical activity (BASAL). This was followed by a 7-day exercise period of volume-matched, LF (10 × 10 repetitions at 70% one-repetition maximum, once per week) or HF (2 × 10 repetitions at ∼70% one-repetition maximum, five times per week) resistance exercise training. The participants had one leg randomly allocated to LF and the other to HF. Skeletal muscle biopsies and daily saliva s les were collected to determine myofibrillar protein synthesis rates using 2 H 2 O, with intracellular signaling determined using Western blotting. The myofibrillar protein synthesis rates did not differ between the LF (1.46 ± 0.26%/day) and HF (1.48 ± 0.33%/day) conditions over the 7-day exercise training period ( p .05). There were no significant differences between the LF and HF conditions over the first 2 days (1.45 ± 0.41%/day vs. 1.25 ± 0.46%/day) or last 5 days (1.47 ± 0.30%/day vs. 1.50 ± 0.41%/day) of the exercise training period ( p .05). Daily myofibrillar protein synthesis rates were not different from BASAL at any time point during LF or HF ( p .05). The phosphorylation status and total protein content of selected proteins implicated in skeletal muscle ribosomal biogenesis were not different between conditions ( p .05). Under the conditions of the present study, resistance exercise training frequency did not modulate daily myofibrillar protein synthesis rates in young men.

Effects of live high, train low hypoxic exposure on lactate metabolism in trained humans

Publisher: American Physiological Society

Date: 02-2004

DOI: 10.1152/JAPPLPHYSIOL.00799.2003

Abstract: We determined the effect of 20 nights of live high, train low (LHTL) hypoxic exposure on lactate kinetics, monocarboxylate lactate transporter proteins (MCT1 and MCT4), and muscle in vitro buffering capacity (βm) in 29 well-trained cyclists and triathletes. Subjects were ided into one of three groups: 20 consecutive nights of hypoxic exposure (LHTLc), 20 nights of intermittent hypoxic exposure [four 5-night blocks of hypoxia, each interspersed with 2 nights of normoxia (LHTLi)], or control (Con). Rates of lactate appearance (R a ), disappearance (R d ), and oxidation (R ox ) were determined from a primed, continuous infusion of l-[U- 14 C]lactic acid tracer during 90 min of steady-state exercise [60 min at 65% peak O 2 uptake (V̇o 2 peak ) followed by 30 min at 85% V̇o 2 peak ]. A resting muscle biopsy was taken before and after 20 nights of LHTL for the determination of βm and MCT1 and MCT4 protein abundance. R a during the first 60 min of exercise was not different between groups. During the last 25 min of exercise at 85% V̇o 2 peak , R a was higher compared with exercise at 65% of V̇o 2 peak and was decreased in LHTLc ( P 0.05) compared with the other groups. R d followed a similar pattern to R a . Although R ox was significantly increased during exercise at 85% compared with 65% of V̇o 2 peak , there were no differences between the three groups or across trials. There was no effect of hypoxic exposure on βm or MCT1 and MCT4 protein abundance. We conclude that 20 consecutive nights of hypoxia exposure decreased whole body R a during intense exercise in well-trained athletes. However, muscle markers of lactate metabolism and pH regulation were unchanged by the LHTL intervention.

Fluid Balance in Team Sports

Publisher: Springer Science and Business Media LLC

Date: 07-1997

DOI: 10.2165/00007256-199724010-00004

Abstract: Team sports require players to perform multiple work bouts at near maximal effort, punctuated with intervals of low intensity exercise or rest for the duration of a game. Such activity patterns are associated with a significant loss of body water which has a negative impact on physical and mental performance, as well as temperature regulation. There are a number of ways in which sweat losses incurred during team sports differ from those measured during prolonged, continuous exercise. Firstly, the work rate in team sports is intermittent, largely unpredictable and random in nature. Second, analyses of various team sports reveal that such games are characterised by a high degree of inter and intra-in idual variability in work rates between players from the same sport. Finally, team players are less able to anticipate sweat losses than athletes competing in events which involve prolonged, continuous, moderate intensity exercise. Yet, compared with most endurance events, many team sports offer frequent opportunities to ingest adequate volumes of fluid and thus prevent exercise-induced hypohydration. The present review details the findings of modern studies which have determined body water losses and fluid intake practices of athletes from a variety of team sports. Special considerations which influence sweat loss and fluid intake that are unique to team sports are discussed, and guidelines for sound hydration strategies during training and competition are provided.

Sport performance enhancement: Design and analysis of research (multiple letters)

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 05-1999

DOI: 10.1097/00005768-199905000-00021

Effects of endurance training status and sex differences on Na⁺,K⁺‐pump mRNA expression, content and maximal activity in human skeletal muscle

Publisher: Wiley

Date: 19-01-2007

DOI: 10.1111/J.1748-1716.2006.01635.X

Abstract: This study investigated the effects of endurance training status and sex differences on skeletal muscle Na+,K+-pump mRNA expression, content and activity. Forty-five endurance-trained males (ETM), 11 recreationally active males (RAM), and nine recreationally active females (RAF) underwent a vastus lateralis muscle biopsy. Muscle was analysed for Na+,K+-pump alpha1, alpha2, alpha3, beta1, beta2 and beta3 isoform mRNA expression (real-time reverse transcription-polymerase chain reaction), content ([3H]-ouabain-binding site) and maximal activity (3-O-methylfluorescein phosphatase, 3-O-MFPase). ETM demonstrated lower alpha1, alpha3, beta2 and beta3 mRNA expression by 74%, 62%, 70% and 82%, respectively, than RAM (P<0.04). In contrast, [3H]-ouabain binding and 3-O-MFPase activity were each higher in ETM than in RAM, by 16% (P<0.03). RAM demonstrated a 230% and 364% higher alpha3 and beta3 mRNA expression than RAF, respectively (P<0.05), but no significant sex differences were found for alpha1, alpha2, beta1 or beta2 mRNA, [3H]-ouabain binding or 3-O-MFPase activity. No significant correlation was found between years of endurance training and either [3H]-ouabain binding or 3-O-MFPase activity. Significant but weak correlations were found between the number of training hours per week and 3-O-MFPase activity (r=0.31, P<0.02) and between incremental exercise VO2(peak)) and both [3H]-ouabain binding (r=0.33, P<0.01) and 3-O-MFPase activity (r=0.28, P<0.03). Isoform-specific differences in Na+,K+-pump mRNA expression were found with both training status and sex differences, but only training status influenced Na+,K+-pump content and maximal activity in human skeletal muscle.

Low intrinsic running capacity is associated with reduced skeletal muscle substrate oxidation and lower mitochondrial content in white skeletal muscle

Publisher: American Physiological Society

Date: 04-2011

DOI: 10.1152/AJPREGU.00659.2010

Abstract: Chronic metabolic diseases develop from the complex interaction of environmental and genetic factors, although the extent to which each contributes to these disorders is unknown. Here, we test the hypothesis that artificial selection for low intrinsic aerobic running capacity is associated with reduced skeletal muscle metabolism and impaired metabolic health. Rat models for low- (LCR) and high- (HCR) intrinsic running capacity were derived from genetically heterogeneous N:NIH stock for 20 generations. Artificial selection produced a 530% difference in running capacity between LCR/HCR, which was associated with significant functional differences in glucose and lipid handling by skeletal muscle, as assessed by hindlimb perfusion. LCR had reduced rates of skeletal muscle glucose uptake (∼30% P = 0.04), glucose oxidation (∼50% P = 0.04), and lipid oxidation (∼40% P = 0.02). Artificial selection for low aerobic capacity was also linked with reduced molecular signaling, decreased muscle glycogen, and triglyceride storage, and a lower mitochondrial content in skeletal muscle, with the most profound changes to these parameters evident in white rather than red muscle. We show that a low intrinsic aerobic running capacity confers reduced insulin sensitivity in skeletal muscle and is associated with impaired markers of metabolic health compared with high intrinsic running capacity. Furthermore, selection for high running capacity, in the absence of exercise training, endows increased skeletal muscle insulin sensitivity and oxidative capacity in specifically white muscle rather than red muscle. These data provide evidence that differences in white muscle may have a role in the ergent aerobic capacity observed in this generation of LCR/HCR.

Interaction of contractile activity and training history on mRNA abundance in skeletal muscle from trained athletes

Publisher: American Physiological Society

Date: 05-2006

DOI: 10.1152/AJPENDO.00299.2005

Abstract: Skeletal muscle displays enormous plasticity to respond to contractile activity with muscle from strength- (ST) and endurance-trained (ET) athletes representing erse states of the adaptation continuum. Training adaptation can be viewed as the accumulation of specific proteins. Hence, the altered gene expression that allows for changes in protein concentration is of major importance for any training adaptation. Accordingly, the aim of the present study was to quantify acute subcellular responses in muscle to habitual and unfamiliar exercise. After 24-h diet/exercise control, 13 male subjects (7 ST and 6 ET) performed a random order of either resistance (8 × 5 maximal leg extensions) or endurance exercise (1 h of cycling at 70% peak O 2 uptake). Muscle biopsies were taken from vastus lateralis at rest and 3 h after exercise. Gene expression was analyzed using real-time PCR with changes normalized relative to preexercise values. After cycling exercise, peroxisome proliferator-activated receptor-γ coactivator-1α (ET ∼8.5-fold, ST ∼10-fold, P 0.001), pyruvate dehydrogenase kinase-4 (PDK-4 ET ∼26-fold, ST ∼39-fold), vascular endothelial growth factor (VEGF ET ∼4.5-fold, ST ∼4-fold), and muscle atrophy F-box protein (MAFbx) (ET ∼2-fold, ST ∼0.4-fold) mRNA increased in both groups, whereas MyoD (∼3-fold), myogenin (∼0.9-fold), and myostatin (∼2-fold) mRNA increased in ET but not in ST ( P 0.05). After resistance exercise PDK-4 (∼7-fold, P 0.01) and MyoD (∼0.7-fold) increased, whereas MAFbx (∼0.7-fold) and myostatin (∼0.6-fold) decreased in ET but not in ST. We conclude that prior training history can modify the acute gene responses in skeletal muscle to subsequent exercise.

Thiol-based antioxidant supplementation alters human skeletal muscle signaling and attenuates its inflammatory response and recovery after intense eccentric exercise

Publisher: Elsevier BV

Date: 07-2013

DOI: 10.3945/AJCN.112.049163

Abstract: The major thiol-disulfide couple of reduced glutathione (GSH) and oxidized glutathione is a key regulator of major transcriptional pathways regulating aseptic inflammation and recovery of skeletal muscle after aseptic injury. Antioxidant supplementation may h er exercise-induced cellular adaptations. The objective was to examine how thiol-based antioxidant supplementation affects skeletal muscle's performance and redox-sensitive signaling during the inflammatory and repair phases associated with exercise-induced microtrauma. In a double-blind, crossover design, 10 men received placebo or N-acetylcysteine (NAC 20 mg · kg(-1) · d(-1)) after muscle-damaging exercise (300 eccentric contractions). In each trial, muscle performance was measured at baseline, after exercise, 2 h after exercise, and daily for 8 consecutive days. Muscle biopsy s les from vastus lateralis and blood s les were collected before exercise and 2 h, 2 d, and 8 d after exercise. NAC attenuated the elevation of inflammatory markers of muscle damage (creatine kinase activity, C-reactive protein, proinflammatory cytokines), nuclear factor κB phosphorylation, and the decrease in strength during the first 2 d of recovery. NAC also blunted the increase in phosphorylation of protein kinase B, mammalian target of rapamycin, p70 ribosomal S6 kinase, ribosomal protein S6, and mitogen activated protein kinase p38 at 2 and 8 d after exercise. NAC also abolished the increase in myogenic determination factor and reduced tumor necrosis factor-α 8 d after exercise. Performance was completely recovered only in the placebo group. Although thiol-based antioxidant supplementation enhances GSH availability in skeletal muscle, it disrupts the skeletal muscle inflammatory response and repair capability, potentially because of a blunted activation of redox-sensitive signaling pathways. This trial was registered at clinicaltrials.gov as NCT01778309.

Mimicking exercise: what matters most and where to next?

Publisher: Wiley

Date: 14-01-2021

DOI: 10.1113/JP278761

Abstract: The past decade has witnessed growing scientific and commercial interest in the identification of bioactive oral compounds that mimic or potentiate the effects of exercise, so‐called ‘exercise pills’ or ‘exercise mimetics.’ These compounds have, to date, typically targeted skeletal muscle in an attempt to stimulate some of the adaptations to exercise induced by endurance training. Accordingly, they fail to impart many of the broad health protecting effects of exercise that are seen in tissues and organs other than skeletal muscle. In the context that multiple integrative regulatory and often redundant pathways have evolved to detect and respond to human movement, here we consider the complex challenges of designing a pill that might mimic the extensive range of exercise benefits. In particular, we consider the limits of the current ‘myocentric’ paradigm given the wide‐ranging array of impacts that exercise exerts on atherosclerosis and the cardiovascular system. We discuss the validity and limitations of the concept that low dose cardiovascular polypills, already in large scale trials, may represent one form of cardiovascular exercise mimetic. Finally, given that some calls for an exercise pill stem from a response to the perceived failure of expert advice, evidence‐based guidelines and current public health approaches, we explore possible strategies that might address the global rise in inactivity. In the event that a broad spectrum exercise mimetic might ever be developed, we discuss some generic issues related to adoption and adherence of therapeutic interventions. image

Effects of different interval-training programs on cycling time-trial performance

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 05-1999

DOI: 10.1097/00005768-199905000-00018

Abstract: We have investigated the effect of varying the intensity of interval training on 40-km time-trial performance in 20 male endurance cyclists (peak oxygen uptake 4.8+/-0.6 L x min(-1), mean +/- SD). Cyclists performed a 25-kJ sprint test, an incremental test to determine peak aerobic power (PP) and a simulated 40-km time-trial on a Kingcycle ergometer. They were then randomly assigned to one of five types of interval-training session: 12x30 s at 175% PP, 12x60 s at 100% PP, 12x2 min at 90% PP, 8x4 min at 85% PP, or 4x8 min at 80% PP. Cyclists completed 6 sessions over 3 wk, in addition to their usual aerobic base training. All laboratory tests were then repeated. Performances in the time trial were highly reliable when controlled for training effects (coefficient of variation = 1.1%). The percent improvement in the time trial was modeled as a polynomial function of the rank order of the intensity of the training intervals, a procedure validated by simulation. The cubic trend was strong and statistically significant (overall correlation = 0.70, P = 0.005) and predicted greatest enhancement for the intervals performed at 85% PP (2.8%, 95% CI = 4.3-1.3%) and at 175% PP (2.4%, 95% CI = 4.0-0.7%). Intervals performed at 100% PP and 80% PP did not produce statistically significant enhancements of performance. Quadratic and linear trends were weak or insubstantial. Interval training with work bouts close to race-pace enhance 1-h endurance performance work bouts at much higher intensity also appear to improve performance, possibly by a different mechanism.

High-Intensity Interval Training in Polycystic Ovary Syndrome: A Two-Center, Three-Armed Randomized Controlled Trial

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 12-01-2022

DOI: 10.1249/MSS.0000000000002849

Abstract: Exercise training is recommended to improve cardiometabolic health and fertility in women with polycystic ovary syndrome (PCOS), yet there are few randomized controlled trials on the effects of different exercise protocols on clinical reproductive outcomes. Our aim was to determine the effect of high-intensity interval training (HIT) on menstrual frequency, as a proxy of reproductive function, in women with PCOS. The IMPROV-IT study was a two-center randomized controlled trial undertaken in Norway and Australia. Women with PCOS were eligible for inclusion. After stratification for body mass index or ≥27 kg·m −2 and study center, participants were randomly allocated (1:1:1) to high-volume HIT (HV-HIT), low-volume HIT (LV-HIT), or a control group. Measurements were assessed at baseline, after the 16-wk exercise intervention, and at 12-month follow-up. The primary outcome was menstrual frequency after 12 months. Secondary outcomes included markers of cardiometabolic and reproductive health, quality of life, and adherence to and enjoyment of HIT. We randomly allocated 64 participants to the HV-HIT ( n = 20), LV-HIT ( n = 21), or control group ( n = 23). There were no differences in menstrual frequency at 12 months between the LV-HIT and control groups (frequency ratio, 1.02 95% confidence interval [CI], 0.73–1.42), the HV-HIT and control groups (frequency ratio, 0.93 95% CI, 0.67–1.29), or the LV-HIT and HV-HIT groups (frequency ratio, 1.09 95% CI, 0.77–1.56). Menstrual frequency increased in all groups from baseline to 12 months. More participants became pregnant in the LV-HIT group ( n = 5) than in the control group ( n = 0, P = 0.02). A semisupervised HIT intervention did not increase menstrual frequency in women with PCOS. Clinical Trial Registration Number: ClinicalTrials.gov (NCT02419482).

Transcriptomic and epigenetic responses to short-term nutrient-exercise stress in humans

Publisher: Springer Science and Business Media LLC

Date: 09-11-2017

DOI: 10.1038/S41598-017-15420-7

Abstract: High fat feeding impairs skeletal muscle metabolic flexibility and induces insulin resistance, whereas exercise training exerts positive effects on substrate handling and improves insulin sensitivity. To identify the genomic mechanisms by which exercise ameliorates some of the deleterious effects of high fat feeding, we investigated the transcriptional and epigenetic response of human skeletal muscle to 9 days of a high-fat diet (HFD) alone (Sed-HFD) or in combination with resistance exercise (Ex-HFD), using genome-wide profiling of gene expression and DNA methylation. HFD markedly induced expression of immune and inflammatory genes, which was not attenuated by Ex. Conversely, Ex markedly remodelled expression of genes associated with muscle growth and structure. We detected marked DNA methylation changes following HFD alone and in combination with Ex. Among the genes that showed a significant association between DNA methylation and gene expression changes were PYGM, which was epigenetically regulated in both groups, and ANGPTL4, which was regulated only following Ex. In conclusion, while short-term Ex did not prevent a HFD-induced inflammatory response, it provoked a genomic response that may protect skeletal muscle from atrophy. These epigenetic adaptations provide mechanistic insight into the gene-specific regulation of inflammatory and metabolic processes in human skeletal muscle.

Glucose kinetics during prolonged exercise in euglycaemic and hyperglycaemic subjects

Publisher: Springer Science and Business Media LLC

Date: 03-1994

DOI: 10.1007/BF00388300

Abstract: Gram-positive bacteria ubiquitously produce membrane vesicles (MVs), and although they contribute to biological functions, our knowledge regarding their composition and immunogenicity remains limited. Here we examine the morphology, contents and immunostimulatory functions of MVs produced by three

Reliability and variability of running economy in elite distance runners

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 11-2004

DOI: 10.1249/01.MSS.0000145468.17329.9F

Abstract: To establish the typical error (TE) associated with equipment, testing, and biological variation of a running economy (RE) test in 11 elite male distance runners (VO2max 70.3 +/- 7.3 mL x min(-1) x kg(-1)), and measure the between-athlete variation of 70 highly trained runners (VO2max 69.7 +/- 6.0 mL x min(-1) x kg(-1)) to determine the magnitude of the smallest worthwhile change (SWC) required for RE. Runners performed three 4-min bouts of submaximal treadmill running at speeds of 14, 16, and 18 km x h(-1) (0% grade), on two separate occasions within a 7-d period to determine reliability and once over a 3-yr period to measure the SWC. During all RE tests O2 consumption (VO2), ventilation (VE), respiratory exchange ratio (RER), heart rate (HR), stride rate (SR), and concentration of blood lactate (Lac) were determined. The TE for the pooled data of three running speeds (14, 16, and 18 km x h(-1)) was 2.4% for VO2, 7.3% for VE, 27% for Lac, and ranged between 1 and 4% for RER, HR, and SR. The results demonstrate that although the magnitude of the TE for a submaximal treadmill running protocol of three 4-min work efforts is small (2.4-7.3%) for measures associated with cardiorespiratory parameters, it is three- to fourfold higher for Lac. Given the small TE associated with RE, and a SWC of similar magnitude for this cohort of distance runners, the RE test is useful in detecting changes attributable to training interventions. Changes in RE greater than approximately 2.4% in this cohort of elite distance runners are likely to be "real" and "worthwhile," and not simply related to testing error and typical variation.

Spectroscopic correlation analysis of NMR-based metabonomics in exercise science

Publisher: Elsevier BV

Date: 10-2009

DOI: 10.1016/J.ACA.2009.07.011

Abstract: Spectroscopic studies of complex clinical fluids have led to the application of a more holistic approach to their chemical analysis becoming more popular and widely employed. The efficient and effective interpretation of multidimensional spectroscopic data relies on many chemometric techniques and one such group of tools is represented by so-called correlation analysis methods. Typical of these techniques are two-dimensional correlation analysis and statistical total correlation spectroscopy (STOCSY). Whilst the former has largely been applied to optical spectroscopic analysis, STOCSY was developed and has been applied almost exclusively to NMR metabonomic studies. Using a (1)H NMR study of human blood plasma, from subjects recovering from exhaustive exercise trials, the basic concepts and applications of these techniques are examined. Typical information from their application to NMR-based metabonomics is presented and their value in aiding interpretation of NMR data obtained from biological systems is illustrated. Major energy metabolites are identified in the NMR spectra and the dynamics of their appearance and removal from plasma during exercise recovery are illustrated and discussed. The complementary nature of two-dimensional correlation analysis and statistical total correlation spectroscopy are highlighted.

Impaired skeletal muscle β-adrenergic activation and lipolysis are associated with whole-body insulin resistance in rats bred for low intrinsic exercise capacity

Publisher: The Endocrine Society

Date: 09-10-2009

DOI: 10.1210/EN.2009-0158

Abstract: Rats selectively bred for high endurance running capacity (HCR) have higher insulin sensitivity and improved metabolic health compared with those bred for low endurance capacity (LCR). We investigated several skeletal muscle characteristics, in vitro and in vivo, that could contribute to the metabolic phenotypes observed in sedentary LCR and HCR rats. After 16 generations of selective breeding, HCR had approximately 400% higher running capacity (P & 0.001), improved insulin sensitivity (P & 0.001), and lower fasting plasma glucose and triglycerides (P & 0.05) compared with LCR. Skeletal muscle ceramide and diacylglycerol content, basal AMP-activated protein kinase (AMPK) activity, and basal lipolysis were similar between LCR and HCR. However, the stimulation of lipolysis in response to 10 μm isoproterenol was 70% higher in HCR (P = 0.004). Impaired isoproterenol sensitivity in LCR was associated with lower basal triacylglycerol lipase activity, Ser660 phosphorylation of HSL, and β2-adrenergic receptor protein content in skeletal muscle. Expression of the orphan nuclear receptor Nur77, which is induced by β-adrenergic signaling and is associated with insulin sensitivity, was lower in LCR (P & 0.05). Muscle protein content of Nur77 target genes, including uncoupling protein 3, fatty acid translocase/CD36, and the AMPK γ3 subunit were also lower in LCR (P & 0.05). Our investigation associates whole-body insulin resistance with impaired β-adrenergic response and reduced expression of genes that are critical regulators of glucose and lipid metabolism in skeletal muscle. We identify impaired β-adrenergic signal transduction as a potential mechanism for impaired metabolic health after artificial selection for low intrinsic exercise capacity.

Commentary on Viewpoint: Exercise and cardiovascular risk reduction: Time to update the rationale for exercise?

Publisher: American Physiological Society

Date: 08-2008

DOI: 10.1152/JAPPLPHYSIOL.90362.2008

Self-study in physical education: bridging personal and public understandings in professional practice

Publisher: Informa UK Limited

Date: 02-09-2015

DOI: 10.1080/18377122.2015.1092721

Molecular clocks, satellite cells, and skeletal muscle regeneration

Publisher: American Physiological Society

Date: 06-2023

DOI: 10.1152/AJPCELL.00073.2023

Abstract: Skeletal muscle comprises approximately 50% of in idual body mass and plays vital roles in locomotion, heat production, and whole body metabolic homeostasis. This tissue exhibits a robust diurnal rhythm that is under control of the suprachiasmatic nucleus (SCN) region of the hypothalamus. The SCN acts as a “central” coordinator of circadian rhythms, while cell-autonomous “peripheral” clocks are located within almost all other tissues/organs in the body. Synchronization of the peripheral clocks in muscles (and other tissues) together with the central clock is crucial to ensure temporally coordinated physiology across all organ systems. By virtue of its mass, human skeletal muscle contains the largest collection of peripheral clocks, but within muscle resides a local stem cell population, satellite cells (SCs), which have their own functional molecular clock, independent of the numerous muscle clocks. Skeletal muscle has a daily turnover rate of 1%–2%, so the regenerative capacity of this tissue is important for whole body homeostasis/repair and depends on successful SC myogenic progression (i.e., proliferation, differentiation, and fusion). Emerging evidence suggests that SC-mediated muscle regeneration may, in part, be regulated by molecular clocks involved in SC-specific diurnal transcription. Here we provide insights on molecular clock regulation of muscle regeneration/repair and provide a novel perspective on the interplay between SC-specific molecular clocks, myogenic programs, and cell cycle kinetics that underpin myogenic progression.

Carbohydrate intake during prolonged cycling minimizes effect of glycemic index of preexercise meal

Publisher: American Physiological Society

Date: 12-1998

DOI: 10.1152/JAPPL.1998.85.6.2220

Abstract: We studied the effects of the glycemic index (GI) of preexercise meals on metabolism and performance when carbohydrate (CHO) was ingested throughout exercise. Six well-trained cyclists performed three counterbalanced trials of 2-h cycling at ∼70% of maximal oxygen uptake, followed by a performance ride of 300 kJ. Meals consumed 2 h before exercise consisted of 2 g CHO/kg body mass of either high-GI potato (HGI trial) or low-GI pasta (LGI trial), or of a low-energy jelly (Con trial). Immediately before and throughout exercise, subjects ingested a 10 g/100 ml [U- 14 C]glucose solution for a total of 24 ml/kg body mass. Despite differences in preexercise glucose, insulin, and free fatty acids concentrations among trials, both total CHO oxidation for HGI, LGI, and Con trials, respectively, during steady-state exercise [403 ± 16, 376 ± 29, and 373 ± 24 (SE) g/2 h] and oxidation of the ingested CHO (65 ± 6, 57 ± 6, and 63 ± 5 g/2 h) were similar. There was no difference in time to complete the subsequent performance ride (946 ± 23, 954 ± 35, and 970 ± 26 s for HGI, LGI, and Con trials, respectively). When CHO is ingested during exercise in amounts presently recommended by sports nutrition guidelines, preexercise CHO intake has little effect on metabolism or on subsequent performance during prolonged cycling (∼2.5 h).

A Comparative Study of Electrostatic Repulsion-Hydrophilic Interaction Chromatography (ERLIC) versus SCX-IMAC-Based Methods for Phosphopeptide Isolation/Enrichment

Publisher: American Chemical Society (ACS)

Date: 02-10-2008

DOI: 10.1021/PR800473J

Effects of fat adaptation and carbohydrate restoration on prolonged endurance exercise

Publisher: American Physiological Society

Date: 07-2001

DOI: 10.1152/JAPPL.2001.91.1.115

Abstract: We determined the effect of fat adaptation on metabolism and performance during 5 h of cycling in seven competitive athletes who consumed a standard carbohydrate (CHO) diet for 1 day and then either a high-CHO diet (11 g · kg −1 · day −1 CHO, 1 g · kg −1 · day −1 fat HCHO) or an isoenergetic high-fat diet (2.6 g · kg −1 · day −1 CHO, 4.6 g · kg −1 · day −1 fat fat-adapt) for 6 days. On day 8, subjects consumed a high-CHO diet and rested. On day 9, subjects consumed a preexercise meal and then cycled for 4 h at 65% peak O 2 uptake, followed by a 1-h time trial (TT). Compared with baseline, 6 days of fat-adapt reduced respiratory exchange ratio (RER) with cycling at 65% peak O 2 uptake [0.78 ± 0.01 (SE) vs. 0.85 ± 0.02 P 0.05]. However, RER was restored by 1 day of high-CHO diet, preexercise meal, and CHO ingestion (0.88 ± 0.01 P 0.05). RER was higher after HCHO than fat-adapt (0.85 ± 0.01, 0.89 ± 0.01, and 0.93 ± 0.01 for days 2, 8, and 9, respectively P 0.05). Fat oxidation during the 4-h ride was greater (171 ± 32 vs. 119 ± 38 g P 0.05) and CHO oxidation lower (597 ± 41 vs. 719 ± 46 g P 0.05) after fat-adapt. Power output was 11% higher during the TT after fat-adapt than after HCHO (312 ± 15 vs. 279 ± 20 W P = 0.11). In conclusion, compared with a high-CHO diet, fat oxidation during exercise increased after fat-adapt and remained elevated above baseline even after 1 day of a high-CHO diet and increased CHO availability. However, this study failed to detect a significant benefit of fat adaptation to performance of a 1-h TT undertaken after 4 h of cycling.

Exercise intensity and insulin sensitivity: how low can you go?

Publisher: Springer Science and Business Media LLC

Date: 26-06-2009

DOI: 10.1007/S00125-009-1425-5

Rosiglitazone Enhances Glucose Tolerance by Mechanisms Other than Reduction of Fatty Acid Accumulation within Skeletal Muscle

Publisher: The Endocrine Society

Date: 12-2004

DOI: 10.1210/EN.2004-0659

Abstract: We hypothesized that improved glucose tolerance with rosiglitazone treatment would coincide with decreased levels of im triacylglycerol (IMTG), diacylglycerol, and ceramide. Obese Zucker rats were randomly ided into two experimental groups: control (n = 9) and rosiglitazone (n = 9), with lean Zucker rats (n = 9) acting as a control group for obese controls. Rats received either vehicle or 3 mg/kg rosiglitazone for 6 wk. Glucose tolerance was impaired (P & 0.01) in obese compared with lean rats, but was normalized after rosiglitazone treatment. IMTG content was higher in obese compared with lean rats (70.5 ± 5.1 vs. 27.5 ± 2.0 μmol/g dry mass P & 0.05) and increased an additional 30% (P & 0.05) with rosiglitazone treatment. Intramuscular fatty acid composition shifted toward a higher proportion of monounsaturates (P & 0.05) in obese rosiglitazone-treated rats due to an increase in palmitoleate (16:1 P & 0.05). Rosiglitazone treatment increased (P & 0.05) skeletal muscle diacylglycerol and ceramide levels by 65% and 100%, respectively, compared with obese rats, but elevated muscle diacylglycerol was not associated with changes in the total or membrane contents of the diacylglycerol-sensitive protein kinase C isoforms θ, δ, α, and β. In summary, we observed a disassociation among skeletal muscle IMTG, diacylglycerol and ceramide content, and glucose tolerance with rosiglitazone treatment in obese Zucker rats. Our data suggest, therefore, that rosiglitazone enhances glucose tolerance by mechanisms other than reduction of fatty acid accumulation within skeletal muscle.

Metabolic adaptations to marathon training and racing

Publisher: Springer Science and Business Media LLC

Date: 2007

DOI: 10.2165/00007256-200737040-00014

Abstract: During the past 30 years, considerable progress has been made in our understanding of the cellular and molecular factors regulating fuel metabolism during exercise. In particular, advancements in the fields of exercise biochemistry and cell signalling have helped elucidate the mechanism(s) by which perturbations in energy status are monitored inside contracting muscle cells, and have helped identify target molecules that increase fuel supply to maintain adenosine triphosphate concentration. In this brief commentary, we summarise some of the major cellular and molecular adaptations in human skeletal muscle resulting from the intense endurance training required to run a marathon.

‘Exercise snacks’ before meals: a novel strategy to improve glycaemic control in individuals with insulin resistance

Publisher: Springer Science and Business Media LLC

Date: 10-05-2014

DOI: 10.1007/S00125-014-3244-6

Abstract: The aim of this study was to investigate whether small doses of intense exercise before each main meal ('exercise snacks') would result in better blood glucose control than a single bout of prolonged, continuous, moderate-intensity exercise in in iduals with insulin resistance. Nine in iduals completed three exercise interventions in randomised order. Measures were recorded across 3 days with exercise performed on the middle day, as either: (1) traditional continuous exercise (CONT), comprising 30 min moderate-intensity (60% of maximal heart rate [HRmax]) incline walking before dinner (2) exercise snacking (ES), consisting of 6 × 1 min intense (90% HRmax) incline walking intervals 30 min before each meal or (3) composite exercise snacking (CES), encompassing 6 × 1 min intervals alternating between walking and resistance-based exercise, 30 min before meals. Meal timing and composition were controlled within participants for exercise interventions. ES attenuated mean 3 h postprandial glucose concentration following breakfast (by 1.4 ± 1.5 mmol/l, p = 0.02) but not lunch (0.4 ± 1.0 mmol/l, p = 0.22), and was more effective than CONT following dinner (0.7 ± 1.5 mmol/l below CONT p = 0.04). ES also reduced 24 h mean glucose concentration by 0.7 ± 0.6 mmol/l (p = 0.01) and this reduction persisted for the subsequent 24 h (lower by 0.6 ± 0.4 mmol/l vs CONT, relative to their baselines p = 0.01). CES was just as effective as ES (p > 0.05 for all glycaemic variables) at improving glycaemic control. Dosing exercise as brief, intense 'exercise snacks' before main meals is a time-efficient and effective approach to improve glycaemic control in in iduals with insulin resistance.

'Sarcobesity': a metabolic conundrum

Publisher: Elsevier BV

Date: 02-2013

DOI: 10.1016/J.MATURITAS.2012.10.014

Abstract: Two independent but inter-related conditions that have a growing impact on healthy life expectancy and health care costs in developed nations are an age-related loss of muscle mass (i.e., sarcopenia) and obesity. Sarcopenia is commonly exacerbated in overweight and obese in iduals. Progression towards obesity promotes an increase in fat mass and a concomitant decrease in muscle mass, producing an unfavourable ratio of fat to muscle. The coexistence of diminished muscle mass and increased fat mass (so-called 'sarcobesity') is ultimately manifested by impaired mobility and/or development of life-style-related diseases. Accordingly, the critical health issue for a large proportion of adults in developed nations is how to lose fat mass while preserving muscle mass. Lifestyle interventions to prevent or treat sarcobesity include energy-restricted diets and exercise. The optimal energy deficit to reduce body mass is controversial. While energy restriction in isolation is an effective short-term strategy for rapid and substantial weight loss, it results in a reduction of both fat and muscle mass and therefore ultimately predisposes one to an unfavourable body composition. Aerobic exercise promotes beneficial changes in whole-body metabolism and reduces fat mass, while resistance exercise preserves lean (muscle) mass. Current evidence strongly supports the inclusion of resistance and aerobic exercise to complement mild energy-restricted high-protein diets for healthy weight loss as a primary intervention for sarcobesity.

Carbohydrate availability and exercise training adaptation: too much of a good thing?

Publisher: Informa UK Limited

Date: 19-06-2015

DOI: 10.1080/17461391.2014.920926

Abstract: Traditional nutritional approaches to endurance training have typically promoted high carbohydrate (CHO) availability before, during and after training sessions to ensure adequate muscle substrate to meet the demands of high daily training intensities and volumes. However, during the past decade, data from our laboratories and others have demonstrated that deliberately training in conditions of reduced CHO availability can promote training-induced adaptations of human skeletal muscle (i.e. increased maximal mitochondrial enzyme activities and/or mitochondrial content, increased rates of lipid oxidation and, in some instances, improved exercise capacity). Such data have led to the concept of 'training low, but competing high' whereby selected training sessions are completed in conditions of reduced CHO availability (so as to promote training adaptation), but CHO reserves are restored immediately prior to an important competition. The augmented training response observed with training-low strategies is likely regulated by enhanced activation of key cell signalling kinases (e.g. AMPK, p38MAPK), transcription factors (e.g. p53, PPARδ) and transcriptional co-activators (e.g. PGC-1α), such that a co-ordinated up-regulation of both the nuclear and mitochondrial genomes occurs. Although the optimal practical strategies to train low are not currently known, consuming additional caffeine, protein, and practising CHO mouth-rinsing before and/or during training may help to rescue the reduced training intensities that typically occur when 'training low', in addition to preventing protein breakdown and maintaining optimal immune function. Finally, athletes should practise 'train-low' workouts in conjunction with sessions undertaken with normal or high CHO availability so that their capacity to oxidise CHO is not blunted on race day.

Altering fatty acid availability does not impair prolonged, continuous running to fatigue: evidence for carbohydrate dependence

Publisher: American Physiological Society

Date: 15-01-2016

DOI: 10.1152/JAPPLPHYSIOL.00855.2015

Abstract: We determined the effect of suppressing lipolysis via administration of nicotinic acid (NA) on fuel substrate selection and half-marathon running capacity. In a single-blinded, Latin square design, 12 competitive runners completed four trials involving treadmill running until volitional fatigue at a pace based on 95% of personal best half-marathon time. Trials were completed in a fed or overnight fasted state: 1) carbohydrate (CHO) ingestion before (2 g CHO·kg −1 ·body mass −1 ) and during (44 g/h) [CFED] 2) CFED plus NA ingestion [CFED-NA] 3) fasted with placebo ingestion during [FAST] and 4) FAST plus NA ingestion [FAST-NA]. There was no difference in running distance (CFED, 21.53 ± 1.07 CFED-NA, 21.29 ± 1.69 FAST, 20.60 ± 2.09 FAST-NA, 20.11 ± 1.71 km) or time to fatigue between the four trials. Concentrations of plasma free fatty acids (FFA) and glycerol were suppressed following NA ingestion irrespective of preexercise nutritional intake but were higher throughout exercise in FAST compared with all other trials ( P 0.05). Rates of whole-body CHO oxidation were unaffected by NA ingestion in the CFED and FAST trials, but were lower in the FAST trial compared with the CFED-NA trial ( P 0.05). CHO was the primary substrate for exercise in all conditions, contributing 83-91% to total energy expenditure with only a small contribution from fat-based fuels. Blunting the exercise-induced increase in FFA via NA ingestion did not impair intense running capacity lasting ∼85 min, nor did it alter patterns of substrate oxidation in competitive athletes. Although there was a small but obligatory use of fat-based fuels, the oxidation of CHO-based fuels predominates during half-marathon running.

Discordant skeletal muscle gene and protein responses to exercise

Publisher: Elsevier BV

Date: 11-2202

DOI: 10.1016/J.TIBS.2023.08.005

Effects of steady-state versus stochastic exercise on subsequent cycling performance

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 05-1997

DOI: 10.1097/00005768-199705000-00015

Abstract: The aims of this investigation were to evaluate the physiological responses to laboratory based stochastic exercise and to assess the effects of stochastic versus steady-state exercise on subsequent cycling time trial (TT) performance. Six competitive cyclists (peak power output (PPO) 432 +/- 39 W (values are mean +/- SD) undertook in a random order two 150-min paced rides that were either constant load (58% of PPO) or stochastic in nature (58 +/- 12.2% of PPO). These rides were immediately followed by a 20-km TT performance on an air-braked ergometer. Mean heart rate (HR) responses throughout the 150-min paced rides and during the subsequent TT were not significantly different between trials. Yet, despite the similarities in HR, the mean time for the TT was significantly faster (26:32 +/- 1:30 vs 28:08 +/- 1:47 min, P < 0.05) and the mean power output was significantly greater (340.3 +/- 44.2 vs 302.5 +/- 42.3 W 77.8 +/- 10.2 vs 70.0 +/- 9.8% of PPO, P < 0.05) following the steady-state ride. These results demonstrate that following 150 min of steady-state riding, subsequent 20 km TT performance was significantly improved when compared with 150 min of stochastic exercise.

Daytime pattern of post-exercise protein intake affects whole-body protein turnover in resistance-trained males

Publisher: Springer Science and Business Media LLC

Date: 2012

DOI: 10.1186/1743-7075-9-91

Carbohydrate Dependence During Prolonged, Intense Endurance Exercise

Publisher: Springer Science and Business Media LLC

Date: 11-2015

DOI: 10.1007/S40279-015-0400-1

Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens

Publisher: American Physiological Society

Date: 11-2008

DOI: 10.1152/JAPPLPHYSIOL.90882.2008

Abstract: We determined the effects of a cycle training program in which selected sessions were performed with low muscle glycogen content on training capacity and subsequent endurance performance, whole body substrate oxidation during submaximal exercise, and several mitochondrial enzymes and signaling proteins with putative roles in promoting training adaptation. Seven endurance-trained cyclists/triathletes trained daily (High) alternating between 100-min steady-state aerobic rides (AT) one day, followed by a high-intensity interval training session (HIT 8 × 5 min at maximum self-selected effort) the next day. Another seven subjects trained twice every second day (Low), first undertaking AT, then 1–2 h later, the HIT. These training schedules were maintained for 3 wk. Forty-eight hours before and after the first and last training sessions, all subjects completed a 60-min steady-state ride (60SS) followed by a 60-min performance trial. Muscle biopsies were taken before and after 60SS, and rates of substrate oxidation were determined throughout this ride. Resting muscle glycogen concentration (412 ± 51 vs. 577 ± 34 μmol/g dry wt), rates of whole body fat oxidation during 60SS (1,261 ± 247 vs. 1,698 ± 174 μmol·kg −1 ·60 min −1 ), the maximal activities of citrate synthase (45 ± 2 vs. 54 ± 1 mmol·kg dry wt −1 ·min −1 ), and β-hydroxyacyl-CoA-dehydrogenase (18 ± 2 vs. 23 ± 2 mmol·kg dry wt −1 ·min −1 ) along with the total protein content of cytochrome c oxidase subunit IV were increased only in Low (all P 0.05). Mitochondrial DNA content and peroxisome proliferator-activated receptor-γ coactivator-1α protein levels were unchanged in both groups after training. Cycling performance improved by ∼10% in both Low and High. We conclude that compared with training daily, training twice every second day compromised high-intensity training capacity. While selected markers of training adaptation were enhanced with twice a day training, the performance of a 1-h time trial undertaken after a 60-min steady-state ride was similar after once daily or twice every second day training programs.

Effect of resistance training and protein intake pattern on myofibrillar protein synthesis and proteome kinetics in older men in energy restriction

Publisher: Wiley

Date: 17-04-2018

DOI: 10.1113/JP275246

Resistance exercise with low glycogen increases p53 phosphorylation and PGC-1alpha mRNA in skeletal muscle

Publisher: Springer Science and Business Media LLC

Date: 04-02-2015

DOI: 10.1007/S00421-015-3116-X

Abstract: We determined the effect of reduced muscle glycogen availability on cellular pathways regulating mitochondrial biogenesis and substrate utilization after a bout of resistance exercise. Eight young, recreationally trained men undertook a glycogen depletion protocol of one-leg cycling to fatigue (LOW), while the contralateral (control) leg rested (CONT). Following an overnight fast, subjects completed 8 sets of 5 unilateral leg press repetitions (REX) at 80 % 1 Repetition Maximum (1RM) on each leg. Subjects consumed 500 mL protein/CHO beverage (20 g whey + 40 g maltodextrin) upon completion of REX and 2 h later. Muscle biopsies were obtained at rest and 1 and 4 h after REX in both legs. Resting muscle glycogen was higher in the CONT than LOW leg (~384 ± 114 vs 184 ± 36 mmol kg(-1) dry wt P < 0.05), and 1 h and 4 h post-exercise (P < 0.05). Phosphorylation of p53(Ser15) increased 1 h post-exercise in LOW (~115 %, P < 0.05) and was higher than CONT at this time point (~87 %, P < 0.05). p38MAPK(Thr180/Tyr182) phosphorylation increased 1 h post-exercise in both CONT and LOW (~800-900 % P < 0.05) but remained above rest at 4 h only in CONT (~585 %, P < 0.05 different between legs P < 0.05). Peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) mRNA was elevated 4 h post-exercise in LOW (~200 %, P < 0.05 different between legs P < 0.05). There were no changes in Fibronectin type III domain-containing protein 5 (FNDC5) mRNA for CONT or LOW legs post-exercise. Undertaking resistance exercise with low glycogen availability may enhance mitochondrial-related adaptations through p53 and PGC-1α-mediated signalling.

Time-restricted feeding alters lipid and amino acid metabolite rhythmicity without perturbing clock gene expression

Publisher: Springer Science and Business Media LLC

Date: 16-09-2020

DOI: 10.1038/S41467-020-18412-W

Abstract: Time-restricted feeding (TRF) improves metabolism independent of dietary macronutrient composition or energy restriction. To elucidate mechanisms underpinning the effects of short-term TRF, we investigated skeletal muscle and serum metabolic and transcriptomic profiles from 11 men with overweight/obesity after TRF (8 h day −1 ) and extended feeding (EXF, 15 h day −1 ) in a randomised cross-over design (trial registration: ACTRN12617000165381). Here we show that muscle core clock gene expression was similar after both interventions. TRF increases the litude of oscillating muscle transcripts, but not muscle or serum metabolites. In muscle, TRF induces rhythmicity of several amino acid transporter genes and metabolites. In serum, lipids are the largest class of periodic metabolites, while the majority of phase-shifted metabolites are amino acid related. In conclusion, short-term TRF in overweight men affects the rhythmicity of serum and muscle metabolites and regulates the rhythmicity of genes controlling amino acid transport, without perturbing core clock gene expression.

Fuel utilisation during prolonged low-to-moderate intensity exercise when ingesting water or carbohydrate

Publisher: Springer Science and Business Media LLC

Date: 10-1995

DOI: 10.1007/BF01837411

Disassociation of muscle triglyceride content and insulin sensitivity after exercise training in patients with Type 2 diabetes

Publisher: Springer Science and Business Media LLC

Date: 2004

DOI: 10.1007/S00125-003-1265-7

Abstract: We determined the effect of exercise training on insulin sensitivity and muscle lipids (triglyceride [TG(m)] and long-chain fatty acyl CoA [LCACoA] concentration) in patients with Type 2 diabetes. Seven patients with Type 2 diabetes and six healthy control subjects who were matched for age, BMI, % body fat and VO(2)peak participated in a 3 days per week training program for 8 weeks. Insulin sensitivity was determined pre- and post-training during a 120 min euglycaemic-hyperinsulinaemic cl and muscle biopsies were obtained before and after each cl . Oxidative enzyme activities [citrate synthase (CS), beta-hydroxy-acyl-CoA (beta-HAD)] and TG(m) were determined from basal muscle s les pre- and post training, while total LCACoA content was measured in s les obtained before and after insulin-stimulation, pre- and post training. The training-induced increase in VO(2)peak (approximately 20%, p<0.01) was similar in both groups. Compared with control subjects, insulin sensitivity was lower in the diabetic patients before and after training (approximately 60% p<0.05), but was increased to the same extent in both groups with training (approximately 30% p<0.01). TG(m) was increased in patients with Type 2 diabetes (170% p<0.05) before, but was normalized to levels observed in control subjects after training. Basal LCACoA content was similar between groups and was unaltered by training. Insulin-stimulation had no detectable effect on LCACoA content. CS and beta-HAD activity were increased to the same extent in both groups in response to training ( p<0.001). We conclude that the enhanced insulin sensitivity observed after short-term exercise training was associated with a marked decrease in TG(m) content in patients with Type 2 diabetes. However, despite the normalization of TG(m )to levels observed in healthy in iduals, insulin resistance was not completely reversed in the diabetic patients.

One step forward for exercise

Publisher: Springer Science and Business Media LLC

Date: 27-11-2015

DOI: 10.1038/NRENDO.2015.201

Early signaling responses to divergent exercise stimuli in skeletal muscle from well‐trained humans

Publisher: Wiley

Date: 02-11-2005

DOI: 10.1096/FJ.05-4809FJE

Abstract: Skeletal muscle from strength- and endurance-trained in iduals represents erse adaptive states. In this regard, AMPK-PGC-1alpha signaling mediates several adaptations to endurance training, while up-regulation of the Akt-TSC2-mTOR pathway may underlie increased protein synthesis after resistance exercise. We determined the effect of prior training history on signaling responses in seven strength-trained and six endurance-trained males who undertook 1 h cycling at 70% VO2peak or eight sets of five maximal repetitions of isokinetic leg extensions. Muscle biopsies were taken at rest, immediately and 3 h postexercise. AMPK phosphorylation increased after cycling in strength-trained (54% P<0.05) but not endurance-trained subjects. Conversely, AMPK was elevated after resistance exercise in endurance- (114% P<0.05), but not strength-trained subjects. Akt phosphorylation increased in endurance- (50% P<0.05), but not strength-trained subjects after cycling but was unchanged in either group after resistance exercise. TSC2 phosphorylation was decreased (47% P<0.05) in endurance-trained subjects following resistance exercise, but cycling had little effect on the phosphorylation state of this protein in either group. p70S6K phosphorylation increased in endurance- (118% P<0.05), but not strength-trained subjects after resistance exercise, but was similar to rest in both groups after cycling. Similarly, phosphorylation of S6 protein, a substrate for p70 S6K, was increased immediately following resistance exercise in endurance- (129% P<0.05), but not strength-trained subjects. In conclusion, a degree of "response plasticity" is conserved at opposite ends of the endurance-hypertrophic adaptation continuum. Moreover, prior training attenuates the exercise specific signaling responses involved in single mode adaptations to training.

Metabolic demands of intense aerobic interval training in competitive cyclists

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 02-2001

DOI: 10.1097/00005768-200102000-00021

Abstract: To investigate the metabolic demands of a single session of intense aerobic interval training in highly trained competitive endurance cyclists. Seven cyclists (peak O2 uptake [VO2 peak] 5.14 +/- 0.23 L x min(-1), mean +/-SD) performed 8 x 5 min work bouts at 86 +/- 2% of VO2 peak with 60-s recovery. Muscle biopsies were taken from the vastus lateralis immediately before and after the training session, whereas pulmonary gas exchange and venous blood were s led at regular intervals throughout exercise. Muscle glycogen concentration decreased from 501 +/- 91 to 243 +/- 51 mmol x kg (-1) dry mass (P < 0.01). High rates of total carbohydrate oxidation were maintained throughout exercise (340 micromol.kg(-1).min(-1)), whereas fat oxidation increased from 16 +/- 8 during the first to 25 +/- 13 micromol x kg(-1) x min(-1) during the seventh work bout (P < 0.05). Blood lactate concentration remained between 5 and 6 mM throughout exercise, whereas muscle lactate increased from 6 +/- 1 at rest to 32 +/- 12 mmol x kg(-1) d.m. immediately after the training session (P < 0.01). Although muscle pH decreased from 7.09 +/- 0.06 at rest to 7.01 +/- 0.03 at the end of the session (P < 0.01), blood pH was similar after the first and seventh work bouts (7.34). Arterial oxygen saturation (% S(P)O2) fell to 95.6 +/- 1% during the first work bout and remained at 94% throughout exercise: the 60-s rest intervals were adequate to restore % S(P)O2) to 97%. Highly trained cyclists are able to sustain high steady state aerobic power outputs that are associated with high rates of glycogenolysis and total energy expenditure similar to those experienced during a 60-min competitive ride.

The erosion of physical activity in Western societies: an economic death march

Publisher: Springer Science and Business Media LLC

Date: 08-05-2015

DOI: 10.1007/S00125-015-3617-5

Abstract: By 2030 type 2 diabetes and associated complications will be the seventh leading cause of death globally. In this context, obesity and physical inactivity have emerged as major risk factors for several chronic metabolic disorders. While exercise training exerts numerous health-related benefits in terms of the prevention and treatment of many disease states, including type 2 diabetes, it is currently under-prescribed and under-valued. We contend that unless urgent action is taken to curb the tidal wave of inactivity-related metabolic diseases, the worldwide economic burden associated with the rise in the number of diagnosed cases of type 2 diabetes will trigger the start of an economic death march for both industrial and developing nations alike. In this commentary we look ahead to 2065 and consider the impact that lifestyle interventions and associated strategies are likely to have in curbing the epidemic tide of type 2 diabetes. This is one of a series of commentaries under the banner '50 years forward', giving personal opinions on future perspectives in diabetes, to celebrate the 50th anniversary of Diabetologia (1965-2015).

Sleep, circadian biology and skeletal muscle interactions: Implications for metabolic health

Publisher: Elsevier BV

Date: 12-2022

DOI: 10.1016/J.SMRV.2022.101700

Abstract: There currently exists a modern epidemic of sleep loss, triggered by the changing demands of our 21st century lifestyle that embrace 'round-the-clock' remote working hours, access to energy-dense food, prolonged periods of inactivity, and on-line social activities. Disturbances to sleep patterns impart widespread and adverse effects on numerous cells, tissues, and organs. Insufficient sleep causes circadian misalignment in humans, including perturbed peripheral clocks, leading to disrupted skeletal muscle and liver metabolism, and whole-body energy homeostasis. Fragmented or insufficient sleep also perturbs the hormonal milieu, shifting it towards a catabolic state, resulting in reduced rates of skeletal muscle protein synthesis. The interaction between disrupted sleep and skeletal muscle metabolic health is complex, with the mechanisms underpinning sleep-related disturbances on this tissue often multifaceted. Strategies to promote sufficient sleep duration combined with the appropriate timing of meals and physical activity to maintain circadian rhythmicity are important to mitigate the adverse effects of inadequate sleep on whole-body and skeletal muscle metabolic health. This review summarises the complex relationship between sleep, circadian biology, and skeletal muscle, and discusses the effectiveness of several strategies to mitigate the negative effects of disturbed sleep or circadian rhythms on skeletal muscle health.

Ramping up the signal: promoting endurance training adaptation in skeletal muscle by nutritional manipulation

Publisher: Wiley

Date: 08-2014

DOI: 10.1111/1440-1681.12246

Abstract: Mitochondrial biogenesis in skeletal muscle results from the cumulative effect of transient increases in mRNA transcripts encoding mitochondrial proteins in response to repeated exercise sessions. This process requires the coordinated expression of both nuclear and mitochondrial (mt) DNA genomes and is regulated, for the most part, by the peroxisome proliferator-activated receptor γ coactivator 1α. Several other exercise-inducible proteins also play important roles in promoting an endurance phenotype, including AMP-activated protein kinase, p38 mitogen-activated protein kinase and tumour suppressor protein p53. Commencing endurance-based exercise with low muscle glycogen availability results in greater activation of many of these signalling proteins compared with when the same exercise is undertaken with normal glycogen concentration, suggesting that nutrient availability is a potent signal that can modulate the acute cellular responses to a single bout of exercise. When exercise sessions are repeated in the face of low glycogen availability (i.e. chronic training), the phenotypic adaptations resulting from such interventions are also augmented.

Heart rate responses during a 4-d cycle stage race

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 10-1994

DOI: 10.1249/00005768-199410000-00016

Carbohydrate dependence during prolonged simulated cycling time trials

Publisher: Springer Science and Business Media LLC

Date: 05-02-2016

DOI: 10.1007/S00421-016-3333-Y

Abstract: We determined the effect of suppressing lipolysis via administration of Nicotinic acid (NA) and pre-exercise feeding on rates of whole-body substrate utilisation and cycling time trial (TT) performance. In a randomised, single-blind, crossover design, eight trained male cyclists/triathletes completed two series of TTs in which they performed a predetermined amount of work calculated to last ~60, 90 and 120 min. TTs were undertaken after a standardised breakfast (2 g kg(-1) BM of carbohydrate (CHO)) and ingestion of capsules containing either NA or placebo (PL). Plasma [free fatty acids] were suppressed with NA, but increased in the later stages of TT90 and TT120 with PL (p < 0.05). There was no treatment effect on time to complete TT60 (60.4 ± 4.1 vs. 59.3 ± 3.4 min) or TT90 (90.4 ± 9.1 vs. 89.5 ± 6.6 min) for NA and PL, respectively. However, TT120 was slower with NA (123.1 ± 5.7 vs. 120.1 ± 8.7 min, p < 0.001), which coincided with a decline in plasma [glucose] during the later stages of this ride (p < 0.05). For TTs of the same duration, the rates of whole-body CHO oxidation were unaffected by NA, but decreased with increasing TT time (p < 0.05). CHO was the predominant substrate for all TTs contributing between 83 and 94 % to total energy expenditure, although there was a small use of lipid-based fuels for all rides. (1) NA impaired cycling TT performance lasting 120 min, (2) cycling TTs lasting from 60 to 120 min are CHO dependent, and (3) there is an obligatory use of lipid-based fuels in TTs lasting 1-2 h.

High-intensity exercise training — too much of a good thing?

Publisher: Springer Science and Business Media LLC

Date: 04-05-2021

DOI: 10.1038/S41574-021-00500-6

The Challenge of Maintaining Metabolic Health During a Global Pandemic

Publisher: Springer Science and Business Media LLC

Date: 24-05-2020

DOI: 10.1007/S40279-020-01295-8

Abstract: The ongoing global pandemic brought on by the spread of the novel coronavirus SARS-CoV-2 is having profound effects on human health and well-being. With no viable vaccine presently available and the virus being rapidly transmitted, governments and national health authorities have acted swiftly, recommending ‘lockdown’ policies and/or various levels of social restriction/isolation to attenuate the rate of infection. An immediate consequence of these strategies is reduced exposure to daylight, which can result in marked changes in patterns of daily living such as the timing of meals, and sleep. These disruptions to circadian biology have severe cardiometabolic health consequences for susceptible in iduals. We discuss the consequences of reductions in patterns of daily physical activity and the resulting energy imbalance induced by periods of isolation, along with several home-based strategies to maintain cardiometabolic health in the forthcoming months.

Exercise training enhances white adipose tissue metabolism in rats selectively bred for low- or high-endurance running capacity

Publisher: American Physiological Society

Date: 08-2013

DOI: 10.1152/AJPENDO.00544.2012

Abstract: Impaired visceral white adipose tissue (WAT) metabolism has been implicated in the pathogenesis of several lifestyle-related disease states, with diminished expression of several WAT mitochondrial genes reported in both insulin-resistant humans and rodents. We have used rat models selectively bred for low- (LCR) or high-intrinsic running capacity (HCR) that present simultaneously with ergent metabolic phenotypes to test the hypothesis that oxidative enzyme expression is reduced in epididymal WAT from LCR animals. Based on this assumption, we further hypothesized that short-term exercise training (6 wk of treadmill running) would ameliorate this deficit. Approximately 22-wk-old rats (generation 22) were studied. In untrained rats, the abundance of mitochondrial respiratory complexes I–V, citrate synthase (CS), and PGC-1 was similar for both phenotypes, although CS activity was greater than 50% in HCR ( P = 0.09). Exercise training increased CS activity in both phenotypes but did not alter mitochondrial protein content. Training increased the expression and phosphorylation of proteins with roles in β-adrenergic signaling, including β 3 -adrenergic receptor (16% increase in LCR P 0.05), NOR1 (24% decrease in LCR, 21% decrease in HCR P 0.05), phospho-ATGL (25% increase in HCR P 0.05), perilipin (25% increase in HCR P 0.05), CGI-58 (15% increase in LCR P 0.05), and GLUT4 (16% increase in HCR P 0.0001). A training effect was also observed for phospho-p38 MAPK (12% decrease in LCR, 20% decrease in HCR P 0.05) and phospho-JNK (29% increase in LCR, 20% increase in HCR P 0.05). We conclude that in the LCR-HCR model system, mitochondrial protein expression in WAT is not affected by intrinsic running capacity or exercise training. However, training does induce alterations in the activity and expression of several proteins that are essential to the intracellular regulation of WAT metabolism.

Moderate levels of hypohydration impairs bowling accuracy but not bowling velocity in skilled cricket players

Publisher: Elsevier BV

Date: 06-2001

DOI: 10.1016/S1440-2440(01)80028-1

Abstract: The effects of exercise-induced hypohydration on the motor skill performance of cricket bowling was examined in seven medium-fast bowlers who performed a random order of two experimental trials. Trials consisted of a bowling test (36 deliveries PREBOWL) in a thermoneutral (16+/-2 degrees C) environment followed by approximately 1 hr of intermittent exercise in a heated environment (28+/-2 degrees C) and a further thermoneutral bowling test (36 deliveries POSTBOWL). During one trial fluid intake was restricted (HYPO) whereas in the other, subjects were forced to drink in an effort to maintain euhydration (EUH). During all bowling tests subjects were provided with a fixed target on a cricket pitch and the line, length, and velocity of each delivery was determined. Pre-trial hydration status was confirmed by similar body mass (BM 89.5+/-13.7 vs. 88.9+/-13.4 kg) and haemoglobin concentration (15.0+/-0.8 vs. 14.8+/-0.8 g.100 ml(-1) for EUH and HYPO, respectively). BM loss was greater in HYPO than EUH (2.48+/-0.58 vs. 0.46+/-0.45 kg). Accordingly, the resultant hypohydration was higher after HYPO than EUH (2.78+/-0.49 vs. 0.47+/-0.41% of BM). Whereas HYPO had no effect on bowling velocity (102+/-4 vs. 105+/-8 km x h(-1)), univariate analyses revealed independent differences for both bowling line (2.9+/-0.5 vs 3.4+/-0.6, P<0.01) and length (2.9+/-0.5 vs 3.4+/-0.6, P<0.01) of delivery after HYPO. We conclude that moderate (-2.8% of BM) exercise-induced hypohydration has minimal effect on maximal bowling velocity, but there is a detrimental effect on skilled motor performance in well-trained subjects.

Energy Sensing and Signal Transduction in Skeletal Muscle

Publisher: Springer Berlin Heidelberg

Date: 2009

DOI: 10.1007/978-3-540-29678-2_3021

Global Gene Expression in Skeletal Muscle from Well-Trained Strength and Endurance Athletes

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 03-2009

DOI: 10.1249/MSS.0B013E31818C6BE9

Time-restricted eating and exercise training improve HbA1c and body composition in women with overweight/obesity: A randomized controlled trial

Publisher: Elsevier BV

Date: 10-2022

DOI: 10.1016/J.CMET.2022.09.003

Abstract: Diet modification and exercise training are primary lifestyle strategies for obesity management, but poor adherence rates limit their effectiveness. Time-restricted eating (TRE) and high-intensity interval training (HIIT) improve cardiometabolic health in at-risk in iduals, but whether these two interventions combined induce superior improvements in glycemic control than each in idual intervention is not known. In this four-armed randomized controlled trial (ClinicalTrials.gov NCT04019860), we determined the isolated and combined effects of 7 weeks of TRE (≤10-h daily eating window, with ad libitum energy intake) and HIIT (three exercise sessions per week), compared with a non-intervention control group, on glycemic control and secondary cardiometabolic outcomes in 131 women (36.2 ± 6.2 years) with overweight/obesity. There were no statistically significant effects after isolated TRE, HIIT, or a combination (TREHIIT) on glucose area under the curve during an oral glucose tolerance test (the primary outcome) compared with the control group (TRE, -26.3 mmol/L 95% confidence interval [CI], -82.3 to 29.7, p = 0.36 HIIT, -53.8 mmol/L 95% CI, -109.2 to 1.6, p = 0.057 TREHIIT, -41.3 mmol/L 95% CI, -96.4 to 13.8, p = 0.14). However, TREHIIT improved HbA1c and induced superior reductions in total and visceral fat mass compared with TRE and HIIT alone. High participant adherence rates suggest that TRE, HIIT, and a combination thereof may be realistic diet-exercise strategies for improving markers of metabolic health in women at risk of cardiometabolic disease.

Exercise reverses high-fat diet-induced impairments on compartmentalization and activation of components of the insulin-signaling cascade in skeletal muscle

Publisher: American Physiological Society

Date: 10-2007

DOI: 10.1152/AJPENDO.00230.2007

Abstract: The aims of this investigation were 1) to determine whether endurance exercise training could reverse impairments in insulin-stimulated compartmentalization and/or activation of aPKCζ/λ and Akt2 in skeletal muscle from high-fat-fed rodents and 2) to assess whether the PPARγ agonist rosiglitazone could reverse impairments in skeletal muscle insulin signaling typically observed after high-fat feeding. Sprague-Dawley rats were placed on chow (NORCON, n = 16) or high-fat ( n = 64) diets for 4 wk. During a subsequent 4-wk experimental period, high-fat-fed rats were allocated ( n = 16/group) to either sedentary control (HFC), exercise training (HFX), rosiglitazone treatment (HFRSG), or a combination of both exercise training and rosiglitazone (HFRX). Following the 4-wk experimental period, animals underwent hindlimb perfusions. Insulin-stimulated plasma membrane-associated aPKCζ and -λ protein concentration, aPKCζ/λ activity, GLUT4 protein concentration, cytosolic Akt2, and aPKCζ/λ activities were reduced ( P 0.05) in HFC compared with NORCON. Cytosolic Akt2, aPKCζ, and aPKCλ protein concentrations were not affected in HFC compared with NORCON. Exercise training reversed the deleterious effects of the high-fat diet such that insulin-stimulated compartmentalization and activation of components of the insulin-signaling cascade in HFX were normalized to NORCON. High-fat diet-induced impairments to skeletal muscle glucose metabolism were not reversed by rosiglitazone administration, nor did rosiglitazone augment the effect of exercise. Our findings indicate that chronic exercise training, but not rosiglitazone, reverses high-fat diet induced impairments in compartmentalization and activation of components of the insulin-signaling cascade in skeletal muscle.

Toward a Common Understanding of Diet–Exercise Strategies to Manipulate Fuel Availability for Training and Competition Preparation in Endurance Sport

Publisher: Human Kinetics

Date: 09-2018

DOI: 10.1123/IJSNEM.2018-0289

Abstract: From the breakthrough studies of dietary carbohydrate and exercise capacity in the 1960s through to the more recent studies of cellular signaling and the adaptive response to exercise in muscle, it has become apparent that manipulations of dietary fat and carbohydrate within training phases, or in the immediate preparation for competition, can profoundly alter the availability and utilization of these major fuels and, subsequently, the performance of endurance sport (events min up to ∼24 hr). A variety of terms have emerged to describe new or nuanced versions of such exercise–diet strategies (e.g., train low, train high, low-carbohydrate high-fat diet, periodized carbohydrate diet). However, the nonuniform meanings of these terms have caused confusion and miscommunication, both in the popular press and among the scientific community. Sports scientists will continue to hold different views on optimal protocols of fuel support for training and competition in different endurance events. However, to promote collaboration and shared discussions, a commonly accepted and consistent terminology will help to strengthen hypotheses and experimental/experiential data around various strategies. We propose a series of definitions and explanations as a starting point for a more unified dialogue around acute and chronic manipulations of fat and carbohydrate in the athlete’s diet, noting philosophies of approaches rather than a single/definitive macronutrient prescription. We also summarize some of the key questions that need to be tackled to help produce greater insight into this exciting area of sports nutrition research and practice.

Acute changes to biomarkers as a consequence of prolonged strenuous running

Publisher: SAGE Publications

Date: 02-09-2014

DOI: 10.1177/0004563213492147

Abstract: A single bout of strenuous running exercise results in perturbations to numerous biomarkers. An understanding of these is important when analysing s les from in iduals who have recently performed such exercise. A literature search was undertaken using the search terms, exercise, marathon and delayed onset of muscle soreness. The search was then refined using the terms for key biomarkers known to be altered by exercise. The magnitude of changes to biomarkers is proportional to the severity of the running bout. Familiar, moderate intensity running exercise produces brief transient changes in common biomarkers such as lactate, whereas more severe bouts of running exercise, such as marathons and ultra-marathon events can produce changes to biomarkers that are normally associated with pathology of the muscles, liver and heart. Ex les being changes to concentrations and/or activity of myoglobin, leucocytes, creatine kinase, bilirubin, cardiac troponins, lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase. While persisting for longer, these changes are also transient and full recovery occurs within days, without any apparent long-term adverse consequences. Additionally, unfamiliar exercise involving forceful eccentric muscle contractions, such as running downhill, can cause increases in creatine kinase and delayed onset of muscle soreness that peaks 36–72 h after the exercise bout. Strenuous running exercise can produce changes to biomarkers that are normally associated with disease and injury, but these do not necessarily reflect chronic pathology.

High-Fat Diet versus Habitual Diet Prior to Carbohydrate Loading: Effects on Exercise Metabolism and Cycling Performance

Publisher: Human Kinetics

Date: 06-2001

DOI: 10.1123/IJSNEM.11.2.209

Abstract: We examined the effects of a high-fat diet (HFD-CHO) versus a habitual diet, prior to carbohydrate (CHO)-loading on fuel metabolism and cycling time-trial (TT) performance. Five endurance-trained cyclists participated in two 14-day randomized cross-over trials during which subjects consumed either a HFD ( % MJ from fat) or their habitual diet (CTL) (30 ± 5% MJ from fat) for 10 day, before ingesting a high-CHO diet (CHO-loading, CHO 70% MJ) for 3 days. Trials consisted of a 150-min cycle at 70% of peak oxygen uptake (V̇O 2peak ), followed immediately by a 20-km TT. One hour before each trial, cyclists ingested 400 ml of a 3.44% medium-chain triacylglycerol (MCT) solution, and during the trial, ingested 600 ml/hour of a 10% 14C-glucose + 3.44% MCT solution. The dietary treatments did not alter the subjects’ weight, body fat, or lipid profile. There were also no changes in circulating glucose, lactate, free fatty acid (FFA), and β-hydroxybutyrate concentrations during exercise. However, mean serum glycerol concentrations were significantly higher ( p .01) in the HFD-CHO trial. The HFD-CHO diet increased total fat oxidation and reduced total CHO oxidation but did not alter plasma glucose oxidation during exercise. By contrast, the estimated rates of muscle glycogen and lactate oxidation were lower after the HFD-CHO diet. The HFD-CHO treatment was also associated with improved TT times (29.5 ± 2.9 min vs. 30.9 ± 3.4 min for HFD-CHO and CTL-CHO, p .05). High-fat feeding for 10 days prior to CHO-loading was associated with an increased reliance on fat, a decreased reliance on muscle glycogen, and improved time trial performance after prolonged exercise.

Dynamic proteome profiling of individual proteins in human skeletal muscle after a high-fat diet and resistance exercise

Publisher: Wiley

Date: 30-08-2017

DOI: 10.1096/FJ.201700531R

Postexercise muscle glycogen resynthesis in obese insulin-resistant Zucker rats

Publisher: American Physiological Society

Date: 10-2001

DOI: 10.1152/JAPPL.2001.91.4.1512

Abstract: We determined the effect of an acute bout of swimming (8 × 30 min) followed by either carbohydrate administration (0.5 mg/g glucose ip and ad libitum access to chow CHO) or fasting (Fast) on postexercise glycogen resynthesis in soleus muscle and liver from female lean (ZL) and obese insulin-resistant (ZO) Zucker rats. Resting soleus muscle glycogen concentration ([glycogen]) was similar between genotypes and was reduced by 73 (ZL) and 63% (ZO) after exercise ( P 0.05). Liver [glycogen] at rest was greater in ZO than ZL (334 ± 31 vs. 247 ± 16 μmol/g wet wt P 0.01) and fell by 44 and 94% after exercise ( P 0.05). The fractional activity of glycogen synthase (active/total) increased immediately after exercise (from 0.22 ± 0.05 and 0.32 ± 0.04 to 0.63 ± 0.08 vs. 0.57 ± 0.05 P 0.01 for ZL and ZO rats, respectively) and remained elevated above resting values after 30 min of recovery. During this time, muscle [glycogen] in ZO increased 68% with CHO ( P 0.05) but did not change in Fast. Muscle [glycogen] was unchanged in ZL from postexercise values after both treatments. After 6 h recovery, GLUT-4 protein concentration was increased above resting levels by a similar extent for both genotypes in both fasted (∼45%) and CHO-supplemented (∼115%) rats. Accordingly, during this time CHO refeeding resulted in supercompensation in both genotypes (68% vs. 44% for ZL and ZO). With CHO, liver [glycogen] was restored to resting levels in ZL but remained at postexercise values for ZO after both treatments. We conclude that the increased glucose availability with carbohydrate refeeding after glycogen-depleting exercise resulted in glycogen supercompensation, even in the face of muscle insulin-resistance.

Adaptations of skeletal muscle to prolonged, intense endurance training

Publisher: Wiley

Date: 03-2002

DOI: 10.1046/J.1440-1681.2002.03623.X

Abstract: 1. Endurance exercise induces a variety of metabolic and morphological responses/adaptations in skeletal muscle that function to minimize cellular disturbances during subsequent training sessions. 2. Chronic adaptations in skeletal muscle are likely to be the result of the cumulative effect of repeated bouts of exercise, with the initial signalling responses leading to such adaptations occurring after each training session. 3. Recently, activation of the mitogen-activated protein kinase signalling cascade has been proposed as a possible mechanism involved in the regulation of many of the exercise-induced adaptations in skeletal muscle. 4. The protein targets of AMP-activated protein kinase also appear to be involved in both the regulation of acute metabolic responses and chronic adaptations to exercise. 5. Endurance training is associated with an increase in the activities of key enzymes of the mitochondrial electron transport chain and a concomitant increase in mitochondrial protein concentration. These morphological changes, along with increased capillary supply, result in a shift in trained muscle to a greater reliance on fat as a fuel with a concomitant reduction in glycolytic flux and tighter control of acid-base status. Taken collectively, these adaptations result in an enhanced performance capacity.

Failure to repeatedly supercompensate muscle glycogen stores in highly trained men

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 03-2005

DOI: 10.1249/01.MSS.0000155699.51360.2F

Abstract: It is not known whether it is possible to repeatedly supercompensate muscle glycogen stores after exhaustive exercise bouts undertaken within several days. We evaluated the effect of repeated exercise-diet manipulation on muscle glycogen and triacylglycerol (IMTG) metabolism and exercise capacity in six well-trained subjects who completed an intermittent, exhaustive cycling protocol (EX) on three occasions separated by 48 h (i.e., days 1, 3, and 5) in a 5-d period. Twenty-four hours before day 1, subjects consumed a moderate (6 g.kg)-carbohydrate (CHO) diet, followed by 5 d of a high (12 g.kg.d)-CHO diet. Muscle biopsies were taken at rest, immediately post-EX on days 1, 3, and 5, and after 3 h of recovery on days 1 and 3. Compared with day 1, resting muscle [glycogen] was elevated on day 3 but not day 5 (435+/-57 vs 713+/-60 vs 409+/-40 mmol.kg, P<0.001). [IMTG] was reduced by 28% (P<0.05) after EX on day 1, but post-EX levels on days 3 and 5 were similar to rest. EX was enhanced on days 3 and 5 compared with day 1 (31.9+/-2.5 and 35.4+/-3.8 vs 24.1+/-1.4 kJ.kg, P<0.05). Glycogen synthase activity at rest and immediately post-EX was similar between trials. Additionally, the rates of muscle glycogen accumulation were similar during the 3-h recovery period on days 1 and 3. We show that well-trained men cannot repeatedly supercompensate muscle [glycogen] after glycogen-depleting exercise and 2 d of a high-CHO diet, suggesting that the mechanisms responsible for glycogen accumulation are attenuated as a consequence of successive days of glycogen-depleting exercise.

Hypoxic ventilatory response is correlated with increased submaximal exercise ventilation after live high, train low

Publisher: Springer Science and Business Media LLC

Date: 18-12-2005

DOI: 10.1007/S00421-004-1252-9

Abstract: This study tested the hypothesis that live high, train low (LHTL) would increase submaximal exercise ventilation (V(E)) in normoxia, and the increase would be related to enhanced hypoxic ventilatory response (HVR). Thirty-three cyclists/triathletes were ided into three groups: 20 consecutive nights of hypoxia (LHTLc, n = 12), 20 nights of intermittent hypoxia (4x5-night 'blocks' of hypoxia interspersed by two nights of normoxia, LHTLi, n = 10), or control (CON, n = 11). LHTLc and LHTLi slept 8-10 h per night in normobaric hypoxia (2,650 m), and CON slept under ambient conditions (600 m). Resting, isocapnic HVR (DeltaV(E)/Deltablood oxygen saturation) was measured in normoxia before (PRE) and after 15 nights (N15) hypoxia. Submaximal cycle ergometry was conducted PRE and after 4, 10, and 19 nights of hypoxia (N4, N10, and N19 respectively). Mean submaximal exercise V(E) was increased (P < 0.05) from PRE to N4 in LHTLc [74.4 (5.1) vs 80.0 (8.4) l min(-1) mean (SD)] and in LHTLi [69.0 (7.5) vs 76.9 (7.3) l min(-1)] and remained elevated in both groups thereafter, with no changes observed in CON at any time. Prior to LHTL, submaximal V(E) was not correlated with HVR, but this relationship was significant at N4 (r = 0.49, P = 0.03) and N19 (r = 0.77, P < 0.0001). Additionally, the increases in submaximal V(E) and HVR from PRE to N15-N19 were correlated (r = 0.51, P = 0.02) for the pooled data of LHTLc and LHTLi. These results suggest that enhanced hypoxic chemosensitivity contributes to increased exercise V(E) in normoxia following LHTL.

Impact of First Meal Size during Prolonged Sitting on Postprandial Glycaemia in Individuals with Prediabetes: A Randomised, Crossover Study

Publisher: MDPI AG

Date: 06-06-2018

DOI: 10.3390/NU10060733

Pacing strategy in simulated cycle time-trials is based on perceived rather than actual distance

Publisher: Elsevier BV

Date: 06-2001

DOI: 10.1016/S1440-2440(01)80031-1

Abstract: This study determined the pacing strategies and performance responses of six well-trained cyclists/triathletes (peak O2 uptake 66.4+/-3.7 ml x kg(-1) x min(-1), mean+/-SD) during seven simulated time-trials (TT) conducted on a wind-braked cycle ergometer. All subjects first performed a 40 km familiarisation ride (TT1). They were then informed they would be riding a further four 40 km TT for the purpose of a reliability study. Instead, the actual distances ridden for the next three TT were a random order of 34 (TT2), 40 (TT3) and 46 km (TT4). The only feedback given to subjects during TT1-4 was the percentage distance of that ride remaining. During a further 40 km TT (TT5) subjects were allowed to view their heart rate (HR) responses throughout the ride. Despite the significantly different performance times across the three distances (47:23+/-4:23 vs 55:57+/-3:24 vs 65:41+/-3:56 min for the 34, 40 and 46 km respectively, P<0.001), average power output (296+/-48 vs 294+/-48 vs 286+/-40 W) and HR (173+/-11 vs 174+/-12 vs 173+/-12 beats x min(-1)) were similar. The true nature of the first part of the study was then revealed to subjects who subsequently completed an additional 34 km and 46 km TT TT6-7) in which the actual and perceived distance ridden was the same. Power output and HR responses were similar for both unknown (TT2 and TT6) and known (TT4 and TT7) rides for both distances: 296+/-48 vs 300+/-55 W and 173+/-11 vs 177+/-11 beats x min(-1) (34 km) and 286+/-40 vs 273+/-42 W and 173+/-12 vs 174+/-12 beats x min(-1) (46 km). In conclusion, well-trained cyclists rode at similar power outputs and HR during time trials they perceived to be the same distance, but which varied in actual distance from 34 to 46 km.

Preface

Publisher: Wiley

Date: 2008

DOI: 10.1002/9780470757116

Relationship between upper body anaerobic power and freestyle swimming performance

Publisher: Georg Thieme Verlag KG

Date: 02-1991

DOI: 10.1055/S-2007-1024645

Abstract: The purpose of this study was to examine the role of upper body anaerobic power, as measured by the Wingate Anaerobic Arm Test (WAAT), in 50-m sprint swim performance. Thirty competitive age-group swimmers (14 males and 16 females) participated in this investigation. Subjects had been training daily for 5 months prior to the study, swimming an average of 6,000 m.d-1, 6 d.wk-1. Swimmers performed a WAAT and a 50-m time-trial. Peak power (PP), mean power (MP) and fatigue index (FI) were determined for the WAAT. Subjects also reported their current competition performances for all distances up to 400 m. Significant relationships were obtained between swim speed over 50 m (S50) and PP (r = 0.82, p less than 0.001), S50 and MP (r = 0.83, p less than 0.001), and S50 and FI (r = 0.41, p less than 0.05). PP and MP showed significant but generally decreasing correlations with swim speed as distance increased. Substantial relationships (r = 0.74-0.96, p less than 0.001) were found between S50 and swim speeds over distances up to and including 400 m. This study shows a strong relationship exists between upper body anaerobic power, as measured by the WAAT, and performance in both sprint and longer distance (400 m) swim events. The WAAT may serve as a useful tool for coaches to objectively evaluate and monitor the upper body anaerobic power of competitive swimmers.

Carbohydrate and exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 11-1999

DOI: 10.1097/00075197-199911000-00015

Abstract: Total body carbohydrate stores are limited, and are often less than the carbohydrate requirements of athletic training and competition. However, the availability of carbohydrate as a substrate for muscle metabolism is a critical factor in the performance of both high-intensity intermittent work and prolonged aerobic exercise. The rate of carbohydrate oxidation during exercise is tightly regulated, with glucose availability closely matching the needs of the working muscles. Both the absolute and relative work rate play important roles in the regulation of substrate metabolism: carbohydrate-based fuels predominate at moderate to high power outputs, with muscle glycogen and glucose utilization scaling exponentially to the relative work rate. As such, strategies to maintain or enhance carbohydrate availability, such as the ingestion of carbohydrate before, during and after exercise, are critical to the performance of a variety of sports events, and are a key recommendation in current sports nutrition guidelines.

Metabolic Adaptations to a High-Fat Diet

Publisher: Wiley

Date: 11-10-2013

DOI: 10.1002/9781118692318.CH13

Exercise-Induced Phosphorylation of the Novel Akt Substrates AS160 and Filamin A in Human Skeletal Muscle

Publisher: American Diabetes Association

Date: 06-2006

DOI: 10.2337/DB05-1419

Abstract: Skeletal muscle contraction stimulates multiple signaling cascades that govern a variety of metabolic and transcriptional events. Akt rotein kinase B regulates metabolism and growth/muscle hypertrophy, but contraction effects on this target and its substrates are varied and may depend on the mode of the contractile stimulus. Accordingly, we determined the effects of endurance or resistance exercise on phosphorylation of Akt and downstream substrates in six trained cyclists who performed a single bout of endurance or resistance exercise separated by ∼7 days. Muscle biopsies were taken from the vastus lateralis at rest and immediately after exercise. Akt Ser473 phosphorylation was increased (1.8-fold P = 0.011) after endurance but was unchanged after resistance exercise. Conversely, Akt Thr308 phosphorylation was unaltered after either bout of exercise. Several exercise-responsive phosphoproteins were detected by immunoblot analysis with a phospho-Akt substrate antibody. pp160 and pp300 were identified as AS160 and filamin A, respectively, with increased phosphorylation (2.0- and 4.9-fold, respectively P & 0.05) after endurance but not resistance exercise. In conclusion, AS160 and filamin A may provide an important link to mediate endurance exercise–induced bioeffects in skeletal muscle.

Preexercise Aminoacidemia and Muscle Protein Synthesis after Resistance Exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 10-2012

DOI: 10.1249/MSS.0B013E31825D28FA

Author Correction: Transcriptomic and epigenetic responses to short-term nutrient-exercise stress in humans

Publisher: Springer Science and Business Media LLC

Date: 19-03-2018

DOI: 10.1038/S41598-018-23227-3

Abstract: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Hybridization of Pulsed-Q Dissociation and Collision-Activated Dissociation in Linear Ion Trap Mass Spectrometer for iTRAQ Quantitation

Publisher: American Chemical Society (ACS)

Date: 07-10-2008

DOI: 10.1021/PR800403Z

Skeletal muscle buffering capacity and endurance performance after high-intensity interval training by well-trained cyclists

Publisher: Springer Science and Business Media LLC

Date: 12-1996

DOI: 10.1007/S004210050119

Abstract: Skeletal muscle buffering capacity (beta m), enzyme activities and exercise performance were measured before and after 4 weeks of high-intensity, submaximal interval training (HIT) undertaken by six well-trained competitive cyclists [mean maximal oxygen consumption (VO2max) = 66.2 ml.kg-1.min-1]. HIT replaced a portion of habitual endurance training and consisted of six sessions, each of six to eight repetitions of 5 min duration at 80% of peak sustained power output (PPO) separated by 1 min of recovery. beta m increased from 206.6 (17.9) to 240.4 (34.1) mumol H+.g muscle dw-1.pH-1 after HIT (P = 0.05). PPO, time to fatigue at 150% PPO (TF150) and 40-km cycle time trial performance (TT40) all significantly improved after HIT (P < 0.05). In contrast, there was no change in the activity of either phosphofructokinase or citrate synthase. In addition, beta m correlated significantly with TT40 performance before HIT (r = -0.82, P < 0.05) and the relationship between change in beta m and change in TT40 was close to significance (r = -0.74). beta m did not correlate with TF150. These results indicate that beta m may be an important determinant of relatively short-duration (< 60 min) endurance cycling activity and responds positively to just six sessions of high-intensity, submaximal interval training.

Placebo effect of carbohydrate feedings during a 40-km cycling time trial

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 09-2000

DOI: 10.1097/00005768-200009000-00019

Abstract: The placebo effect, a favorable outcome from belief that one has received a beneficial treatment, may be an important phenomenon in athletic performance. We have therefore investigated the placebo effect of a carbohydrate supplement on endurance performance. Forty-three competitive endurance cyclists (2 female, 41 male) performed two simulated 40-km time trials on an air-braked ergometer. In the first trial they ingested water to establish baseline performance (mean power 265 +/- 46 W for 58 +/- 4 min, mean +/- SD). For the second trial 6-8 d later they were randomized to two groups: one group ingested 16 mL x kg(-1) of a drink containing 7.6 g x 100 mL(-1) carbohydrate the other ingested an indistinguishable noncaloric placebo drink. Cyclists in each group were further randomized to three subgroups according to whether they were told the drink contained carbohydrate, placebo, or either (not told). Changes in mean power in the second trial were: told carbohydrate, 4.3 +/- 4.8% told placebo, 0.5 +/- 5.8% and not told, -1.1 +/- 8.5%. The difference between the told-carbohydrate and told-placebo groups was 3.8% (95% likely range 7.9 to -0.2%). The change in performance in the not-told group was more variable than that of the told groups by a factor of 1.6 (2.6 to 1.0). The real effect of carbohydrate was a slight reduction in power of 0.3% (4.4 to -3.8%). (a) The placebo effect of a potentially ergogenic treatment during unblinded laboratory time trials lasting approximately 1 h is probably a small but worthwhile increase in endurance power. (b) Blinding subjects to the treatment increases in idual differences in endurance effort, which may reduce precision of performance outcomes in controlled trials.

Effects of Ingesting a Sports Bar Versus Glucose Polymer on Substrate Utilisation and Ultra-Endurance Performance

Publisher: Georg Thieme Verlag KG

Date: 05-1999

DOI: 10.1055/S-2007-971126

Abstract: The purpose of this study was to determine whether the ingestion of a sports bar (BAR) containing a mixture of fat (7 g), protein (14 ) and carbohydrate (CHO 19 ) improved ulta-endurance cycling performance compared to when an equicaloric amount of CHO was consumed. On two occasions separated by a minimum of 7 days, six highly trained (peak power output [PPO] 414 +/- 8 W) endurance cyclists rode for 330 min at approximately 50% of PPO (203 +/- 8 W) while ingesting either the BAR or just CHO, before performing a 400 k] time trial as fast as possible. Rates of fat oxidation were significantly greater at the end of the submaximal ride when subjects ingested the BAR compared to CHO (1.09 +/- 0.08 vs 0.73 +/- 0.08g x min(-1) P<0.05), and accordingly total fat oxidation was significantly higher (280 +/- 24 vs 203 +/- 25 g, P < 0.05). However, two subjects failed to complete the time trial after they consumed the BAR during the prolonged, submaximal ride, whereas all subjects managed to finish the time trial when ingesting CHO. In conclusion, ingestion of the sports bar enhanced fat metabolism during prolonged, submaximal exercise, but impaired subsequent high-intensity time-trial performance.

Genetic and Molecular Aspects of Sport Performance

Publisher: Wiley

Date: 25-11-2010

DOI: 10.1002/9781444327335

Carbohydrate loading failed to improve 100-km cycling performance in a placebo-controlled trial

Publisher: American Physiological Society

Date: 04-2000

DOI: 10.1152/JAPPL.2000.88.4.1284

Abstract: We evaluated the effect of carbohydrate (CHO) loading on cycling performance that was designed to be similar to the demands of competitive road racing. Seven well-trained cyclists performed two 100-km time trials (TTs) on separate occasions, 3 days after either a CHO-loading (9 g CHO ⋅ kg body mass − 1 ⋅ day − 1 ) or placebo-controlled moderate-CHO diet (6 g CHO ⋅ kg body mass − 1 ⋅ day − 1 ). A CHO breakfast (2 g CHO/kg body mass) was consumed 2 h before each TT, and a CHO drink (1 g CHO ⋅ kg . body mass − 1 ⋅ h − 1 ) was consumed during the TTs to optimize CHO availability. The 100-km TT was interspersed with four 4-km and five 1-km sprints. CHO loading significantly increased muscle glycogen concentrations (572 ± 107 vs. 485 ± 128 mmol/kg dry wt for CHO loading and placebo, respectively P 0.05). Total muscle glycogen utilization did not differ between trials, nor did time to complete the TTs (147.5 ± 10.0 and 149.1 ± 11.0 min P = 0.4) or the mean power output during the TTs (259 ± 40 and 253 ± 40 W, P = 0.4). This placebo-controlled study shows that CHO loading did not improve performance of a 100-km cycling TT during which CHO was consumed. By preventing any fall in blood glucose concentration, CHO ingestion during exercise may offset any detrimental effects on performance of lower preexercise muscle and liver glycogen concentrations. Alternatively, part of the reported benefit of CHO loading on subsequent athletic performance could have resulted from a placebo effect.

A multi-institution evaluation of deformable image registration algorithms for automatic organ delineation in adaptive head and neck radiotherapy

Publisher: Springer Science and Business Media LLC

Date: 15-06-2012

DOI: 10.1186/1748-717X-7-90

Metabolic and mitogenic signal transduction in human skeletal muscle after intense cycling exercise

Publisher: Wiley

Date: 2003

DOI: 10.1113/JPHYSIOL.2002.034223

Abstract: We determined whether mitogen-activated protein kinase (MAPK) and 5'-AMP-activated protein kinase (AMPK) signalling cascades are activated in response to intense exercise in skeletal muscle from six highly trained cyclists (peak O(2) uptake (.V(O2,peak)) 5.14 +/- 0.1 l min(-1)) and four control subjects (Vdot (O(2))(,peak) 3.8 +/- 0.1 l min(-1)) matched for age and body mass. Trained subjects completed eight 5 min bouts of cycling at approximately 85% of .V(O2,peak) with 60 s recovery between work bouts. Control subjects performed four 5 min work bouts commencing at the same relative, but a lower absolute intensity, with a comparable rest interval. Vastus lateralis muscle biopsies were taken at rest and immediately after exercise. Extracellular regulated kinase (ERK1/2), p38 MAPK, histone H3, AMPK and acetyl CoA-carboxylase (ACC) phosphorylation was determined by immunoblot analysis using phosphospecific antibodies. Activity of mitogen and stress-activated kinase 1 (MSK1 a substrate of ERK1/2 and p38 MAPK) and alpha(1) and alpha(2) subunits of AMPK were determined by immune complex assay. ERK1/2 and p38 MAPK phosphorylation and MSK1 activity increased (P < 0.05) after exercise 2.6-, 2.1- and 2.0-fold, respectively, in control subjects and 1.5-, 1.6- and 1.4-fold, respectively, in trained subjects. Phosphorylation of histone H3, a substrate of MSK1, increased (P < 0.05) approximately 1.8-fold in both control and trained subject. AMPKalpha(2) activity increased (P < 0.05) after exercise 4.2- and 2.3-fold in control and trained subjects, respectively, whereas AMPKalpha(1) activity was not altered. Exercise increased ACC phosphorylation (P < 0.05) 1.9- and 2.8-fold in control and trained subjects. In conclusion, intense cycling exercise in subjects with a prolonged history of endurance training increases MAPK signalling to the downstream targets MSK1 and histone H3 and isoform-specific AMPK signalling to ACC. Importantly, exercise-induced signalling responses were greater in untrained men, even at the same relative exercise intensity, suggesting muscle from previously well-trained in iduals requires a greater stimulus to activate signal transduction via these pathways.

Promoting training adaptations through nutritional interventions

Publisher: Informa UK Limited

Date: 07-2006

DOI: 10.1080/02640410500482727

Abstract: Training and nutrition are highly interrelated in that optimal adaptation to the demands of repeated training sessions typically requires a diet that can sustain muscle energy reserves. As nutrient stores (i.e. muscle and liver glycogen) play a predominant role in the performance of prolonged, intense, intermittent exercise typical of the patterns of soccer match-play, and in the replenishment of energy reserves for subsequent training sessions, the extent to which acutely altering substrate availability might modify the training impulse has been a key research area among exercise physiologists and sport nutritionists for several decades. Although the major perturbations to cellular homeostasis and muscle substrate stores occur during exercise, the activation of several major signalling pathways important for chronic training adaptations take place during the first few hours of recovery, returning to baseline values within 24 h after exercise. This has led to the paradigm that many chronic training adaptations are generated by the cumulative effects of the transient events that occur during recovery from each (acute) exercise bout. Evidence is accumulating that nutrient supplementation can serve as a potent modulator of many of the acute responses to both endurance and resistance training. In this article, we review the molecular and cellular events that occur in skeletal muscle during exercise and subsequent recovery, and the potential for nutrient supplementation (e.g. carbohydrate, fat, protein) to affect many of the adaptive responses to training.

Reassessing the relationship between mRNA levels and protein abundance in exercised skeletal muscles

Publisher: Springer Science and Business Media LLC

Date: 07-09-2022

DOI: 10.1038/S41580-022-00541-3

Reliability of power in physical performance tests

Publisher: Springer Science and Business Media LLC

Date: 2001

DOI: 10.2165/00007256-200131030-00005

Abstract: The reliability of power in tests of physical performance affects the precision of assessment of athletes, patients, clients and study participants. In this meta-analytic review we identify the most reliable measures of power and the factors affecting reliability. Our measures of reliability were the typical (standard) error of measurement expressed as a coefficient of variation (CV) and the percent change in the mean between trials. We meta-analysed these measures for power or work from 101 studies of healthy adults. Measures and tests with the smallest CV in exercise of a given duration include field tests of sprint running (approximately 0.9%), peak power in an incremental test on a treadmill or cycle ergometer (approximately 0.9%), equivalent mean power in a constant-power test lasting 1 minute to 3 hours on a treadmill or cycle ergometer (0.9 to 2.0%), lactate-threshold power (approximately 1.5%), and jump height or distance (approximately 2.0%). The CV for mean power on isokinetic ergometers was relatively large (> 4%). CV were larger for nonathletes versus athletes (1.3 x), female versus male nonathletes (1.4 x), shorter (approximately 1-second) and longer (approximately 1-hour) versus 1-minute tests ( 2 trials: the CV between the first 2 trials was 1.3 times the CV between subsequent trials performance also improved by 1.2% between the first 2 trials but by only 0.2% between subsequent trials. These findings should help exercise practitioners and researchers select or design good measures and protocols for tests of physical performance.

Carbohyrate Ingestion Immediately Before Exercise Does Not Improve 20 km Time Trial Performance in Well Trained Cyclists

Publisher: Georg Thieme Verlag KG

Date: 08-1998

DOI: 10.1055/S-2007-971938

Abstract: This study examined the effects of carbohydrate ingestion on 20 km cycle time-trial (TT) performance in 14 well-trained cyclists (11 males, 3 females peak oxygen uptake [VO2peak] 4.52 +/- 0.60 l/min values are mean +/- SD). All subjects performed two experimental trials on their own bicycles mounted on an air-braked ergometry system (Kingcycle). Subjects were instructed to maintain the same training and dietary regimens before trials, which were conducted in a random order, 3-7 days apart, and at the same time of day for each subject. On the day of a trial, subjects reported to the laboratory and ingested an 8 ml/kg body mass bolus of either a 6.8 g/100 ml commercial carbohydrate-electrolyte (CHO) beverage (39 +/- 4 g of CHO), or a coloured, flavoured placebo. Ten min after finishing the drink, subjects commenced a 5 min warm-up at 150 W, before commencing the 20 km TT. The average power output (312 +/- 40 vs 311 +/- 38 W) and heart-rate (171 +/- 6 vs 171 +/- 5 beats/min for CHO and placebo, respectively) during the two rides did not differ between treatments. Accordingly, the performance times for the two TT's were the same (27:41 +/- 1:39 min:sec, for both CHO and placebo). We conclude that the ingestion of approximately 40 g of carbohydrate does not improve maximal cycling performance lasting approximately 30 min, and that carbohydrate availability, in the form of circulating blood glucose, does not limit high-intensity exercise of this duration.

Sleep in athletes undertaking protocols of exposure to nocturnal simulated altitude at 2650 m

Publisher: Elsevier BV

Date: 06-2005

DOI: 10.1016/S1440-2440(05)80013-1

Abstract: A popular method to attempt to enhance performance is for athletes to sleep at natural or simulated moderate altitude (SMA) when training daily near sea level. Based on our previous observation of periodic breathing in athletes sleeping at SMA, we hypothesised that athletes' sleep quality would also suffer with hypoxia. Using two typical protocols of nocturnal SMA (2650 m), we examined the effect on the sleep physiology of 14 male endurance-trained athletes. The selected protocols were Consecutive (15 successive exposure nights) and Intermittent (3x 5 successive exposure nights, interspersed with 2 normoxic nights) and athletes were randomly assigned to follow either one. We monitored sleep for two successive nights under baseline conditions (B normoxia, 600 m) and then at weekly intervals (nights 1, 8 and 15 (N1, N8 and N15, respectively)) of the protocols. Since there was no significant difference in response between the protocols being followed (based on n=7, for each group) we are unable to support a preference for either one, although the likelihood of a Type II error must be acknowledged. For all athletes (n=14), respiratory disturbance and arousal responses between B and N1, although large in magnitude, were highly in idual and not statistically significant. However, SpO2 decreased at N1 versus B (p<0.001) and remained lower on N8 (p<0.001) and N15 (p<0.001), not returning to baseline level. Compared to B, arousals were more frequent on N8 (p=0.02) and N15 (p=0.01). The percent of rapid eye movement sleep (REM) increased from N1 to N8 (p=0.03) and N15 (p=0.01). Overall, sleeping at 2650 m causes sleep disturbance in susceptible athletes, yet there was some improvement in REM sleep over the study duration.

Metabolomics reveals mouse plasma metabolite responses to acute exercise and effects of disrupting AMPK-glycogen interactions

Publisher: Frontiers Media SA

Date: 24-08-2022

DOI: 10.3389/FMOLB.2022.957549

Abstract: Introduction: The AMP-activated protein kinase (AMPK) is a master regulator of energy homeostasis that becomes activated by exercise and binds glycogen, an important energy store required to meet exercise-induced energy demands. Disruption of AMPK-glycogen interactions in mice reduces exercise capacity and impairs whole-body metabolism. However, the mechanisms underlying these phenotypic effects at rest and following exercise are unknown. Furthermore, the plasma metabolite responses to an acute exercise challenge in mice remain largely uncharacterized. Methods: Plasma s les were collected from wild type (WT) and AMPK double knock-in (DKI) mice with disrupted AMPK-glycogen binding at rest and following 30-min submaximal treadmill running. An untargeted metabolomics approach was utilized to determine the breadth of plasma metabolite changes occurring in response to acute exercise and the effects of disrupting AMPK-glycogen binding. Results: Relative to WT mice, DKI mice had reduced maximal running speed ( p & 0.0001) concomitant with increased body mass ( p & 0.01) and adiposity ( p & 0.001). A total of 83 plasma metabolites were identified/annotated, with 17 metabolites significantly different ( p & 0.05 FDR& .1) in exercised (↑6 ↓11) versus rested mice, including amino acids, acylcarnitines and steroid hormones. Pantothenic acid was reduced in DKI mice versus WT. Distinct plasma metabolite profiles were observed between the rest and exercise conditions and between WT and DKI mice at rest, while metabolite profiles of both genotypes converged following exercise. These differences in metabolite profiles were primarily explained by exercise-associated increases in acylcarnitines and steroid hormones as well as decreases in amino acids and derivatives following exercise. DKI plasma showed greater decreases in amino acids following exercise versus WT. Conclusion: This is the first study to map mouse plasma metabolomic changes following a bout of acute exercise in WT mice and the effects of disrupting AMPK-glycogen interactions in DKI mice. Untargeted metabolomics revealed alterations in metabolite profiles between rested and exercised mice in both genotypes, and between genotypes at rest. This study has uncovered known and previously unreported plasma metabolite responses to acute exercise in WT mice, as well as greater decreases in amino acids following exercise in DKI plasma. Reduced pantothenic acid levels may contribute to differences in fuel utilization in DKI mice.

Integrative Biology of Exercise

Publisher: Elsevier BV

Date: 11-2014

DOI: 10.1016/J.CELL.2014.10.029

Abstract: Exercise represents a major challenge to whole-body homeostasis provoking widespread perturbations in numerous cells, tissues, and organs that are caused by or are a response to the increased metabolic activity of contracting skeletal muscles. To meet this challenge, multiple integrated and often redundant responses operate to blunt the homeostatic threats generated by exercise-induced increases in muscle energy and oxygen demand. The application of molecular techniques to exercise biology has provided greater understanding of the multiplicity and complexity of cellular networks involved in exercise responses, and recent discoveries offer perspectives on the mechanisms by which muscle "communicates" with other organs and mediates the beneficial effects of exercise on health and performance.

Activation of atypical protein kinase Czeta toward TC10 is regulated by high-fat diet and aerobic exercise in skeletal muscle

Publisher: Elsevier BV

Date: 09-2008

DOI: 10.1016/J.METABOL.2008.03.023

Early time course of akt phosphorylation after endurance and resistance exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 10-2010

DOI: 10.1249/MSS.0B013E3181D964E4

Signalling mechanisms in skeletal muscle: Role in substrate selection and muscle adaptation

Publisher: Portland Press Ltd.

Date: 27-11-2006

DOI: 10.1042/BSE0420001

Abstract: Exercise produces a multitude of time- and intensity-dependent physiological, biochemical and molecular changes within skeletal muscle. With the onset of contractile activity, cytosolic and mitochondrial [Ca2+] levels are rapidly increased and, depending on the relative intensity of the exercise, metabolite concentrations change (i.e. increases in [ADP] and [AMP], decreases in muscle creatine phosphate and glycogen). These contraction-induced metabolic disturbances activate several key kinases and phosphatases involved in signal transduction. Important among these are the calcium dependent signalling pathways that respond to elevated Ca2+ concentrations (including Ca2+/calmodulin-dependent kinase, Ca2+-dependent protein kinase C and the Ca2+/calmodulin-dependent phosphatase calcineurin), the 5′-adenosine monophosphate-activated protein kinase, several of the mitogen-activated protein kinases and protein kinase B/Akt. The role of these signal transducers in the regulation of carbohydrate and fat metabolism in response to increased contractile activity has been the focus of intense research efforts during the past decade.

Exercise-induced phospho-proteins in skeletal muscle

Publisher: Springer Science and Business Media LLC

Date: 21-08-2008

DOI: 10.1038/IJO.2008.118

Abstract: Efforts to identify exercise-induced signaling events in skeletal muscle have been influenced by ground-breaking discoveries in the insulin action field. Initial discoveries demonstrating that exercise enhances insulin sensitivity raised the possibility that contraction directly modulates insulin receptor signaling events. Although the acute effects of exercise on glucose metabolism are clearly insulin-independent, the canonical insulin signaling cascade has been used as a framework by investigators in an attempt to resolve the mechanisms by which muscle contraction governs glucose metabolism. This review focuses on recent advances in our understanding of exercise-induced signaling pathways governing glucose metabolism in skeletal muscle. Particular emphasis will be placed on the characterization of AS160, a novel Akt substrate that plays a role in the regulation of glucose transport.

Two weeks of reduced-volume sprint interval or traditional exercise training does not improve metabolic functioning in sedentary obese men

Publisher: Wiley

Date: 16-07-2013

DOI: 10.1111/DOM.12150

Abstract: To investigate the effects of short-term, reduced-volume sprint interval training (SIT) compared to traditional exercise recommendations (TER) in sedentary obese men. Sixteen subjects [37.8 ± 5.8 years body mass index (BMI) 32.8 ± 4.7 kg/m(2)] were randomly allocated to 2 weeks of either SIT (6 sessions of 8-12 × 10 s sprints) or TER [10 sessions of 30 min at 65% peak oxygen consumption (VO(2peak))] cycle exercise. Fasting plasma glucose, insulin, non-esterified fatty acids (NEFA), homeostasis model assessment of insulin sensitivity (HOMA-IR), body composition and VO(2peak) were assessed at baseline and approximately 72 h after the final training bout. Skeletal muscle biopsy s les were also obtained before and 72 h after training and analysed for AS160 phosphorylation and COX II, COX IV, GLUT-4, Nur77 and SIRT1 protein expression. No changes in BMI, body composition, VO(2peak), glucose, insulin, NEFA and HOMA-IR were observed after training, either within or between groups. Skeletal muscle markers of glucose metabolism and mitochondrial function also remained unaltered after 2 weeks of exercise training. Our findings show that 2 weeks of reduced-volume SIT or TER did not elicit any measurable metabolic adaptations in sedentary obese men. Further work is needed to determine the minimal amount of exercise required for short-term adaptations in this population.

Exercise Metabolism: Historical Perspective

Publisher: Elsevier BV

Date: 07-2015

DOI: 10.1016/J.CMET.2015.06.016

Abstract: The past 25 years have witnessed major advances in our knowledge of how exercise activates cellular, molecular, and biochemical pathways with regulatory roles in training response adaptation, and how muscle "cross-talk" with other organs is a mechanism by which physical activity exerts its beneficial effects on "whole-body" health. However, during the late 19(th) and early 20(th) centuries, scientific debate in the field of exercise metabolism centered on questions related to the sources of energy for muscular activity, diet-exercise manipulations to alter patterns of fuel utilization, as well as the factors limiting physical work capacity. Posing novel scientific questions and utilizing cutting-edge techniques, the contributions made by the great pioneers of the 19(th) and early 20(th) centuries laid the foundation on which much of our present knowledge of exercise metabolism is based and paved the way for future discoveries in the field.

PGC-1α gene expression is down-regulated by Akt-mediated phosphorylation and nuclear exclusion of FoxO1 in insulin-stimulated skeletal muscle

Publisher: Wiley

Date: 03-10-2005

DOI: 10.1096/FJ.05-3993FJE

Abstract: There are multiple binding domains on the promoter region of the peroxisome proliferator activator receptor gamma coactivator-1 alpha (PGC-1alpha) gene, including a trio of insulin responsive elements that are activated by the forkhead box class-O (FoxO1) winged helix transcription factor, which is known to be regulated by acute transforming retrovirus thymoma (Akt). Here we show that in skeletal muscle biopsy specimens from healthy humans and cultured human skeletal myotubes, insulin phosphorylates Akt (Ser473) and FoxO1 (Thr24, Ser256), leading to reduced nuclear abundance of FoxO1 total protein. This is associated with an insulin-mediated repression of the mRNA expression PGC-1alpha and downstream genes associated with oxidative phosphorylation. In contrast, in muscle taken from insulin resistant humans or in palmitate-treated insulin resistant myotubes, neither Akt nor FoxO1 was phosphorylated by insulin, resulting in a failure for nuclear exclusion of FoxO1 total protein, and an inability for insulin to repress the mRNA expression of PGC-1alpha and down-stream genes. To determine whether the regulation of FoxO1 was Akt dependent, we next treated Akt2 -/- and wild-type mice with or without insulin. Insulin phosphorylated Akt and FoxO1 (Thr24, Ser256) resulting in a reduced nuclear expression of FoxO1 total protein in wild-type but not Akt2 -/- skeletal muscle. We conclude that insulin decreases the expression of genes involved in oxidative metabolism in healthy but not insulin resistant muscle, due to a decrease in FoxO1 phosphorylation and nuclear exclusion secondary to reduced Akt activity.

Commentary on viewpoint: Perspective on the future use of genomics in exercise prescription

Publisher: American Physiological Society

Date: 04-2008

DOI: 10.1152/JAPPLPHYSIOL.00047.2008

Effects of sleeping with reduced carbohydrate availability on acute training responses

Publisher: American Physiological Society

Date: 15-09-2015

DOI: 10.1152/JAPPLPHYSIOL.00857.2014

Abstract: We determined the effects of “periodized nutrition” on skeletal muscle and whole body responses to a bout of prolonged exercise the following morning. Seven cyclists completed two trials receiving isoenergetic diets differing in the timing of ingestion: they consumed either 8 g/kg body mass (BM) of carbohydrate (CHO) before undertaking an evening session of high-intensity training (HIT) and slept without eating (FASTED), or consumed 4 g/kg BM of CHO before HIT, then 4 g/kg BM of CHO before sleeping (FED). The next morning subjects completed 2 h of cycling (120SS) while overnight fasted. Muscle biopsies were taken on day 1 (D1) before and 2 h after HIT and on day 2 (D2) pre-, post-, and 4 h after 120SS. Muscle [glycogen] was higher in FED at all times post-HIT ( P 0.001). The cycling bouts increased PGC1α mRNA and PDK4 mRNA ( P 0.01) in both trials, with PDK4 mRNA being elevated to a greater extent in FASTED ( P 0.05). Resting phosphorylation of AMPK Thr172 , p38MAPK Thr180/Tyr182 , and p-ACC Ser79 (D2) was greater in FASTED ( P 0.05). Fat oxidation during 120SS was higher in FASTED ( P = 0.01), coinciding with increases in ACC Ser79 and CPT1 as well as mRNA expression of CD36 and FABP3 ( P 0.05). Methylation on the gene promoter for COX4I1 and FABP3 increased 4 h after 120SS in both trials, whereas methylation of the PPARδ promoter increased only in FASTED. We provide evidence for shifts in DNA methylation that correspond with inverse changes in transcription for metabolically adaptive genes, although delaying postexercise feeding failed to augment markers of mitochondrial biogenesis.

Periodization of Carbohydrate Intake: Short-Term Effect on Performance

Publisher: MDPI AG

Date: 25-11-2016

DOI: 10.3390/NU8120755

Fenugreek increases insulin-stimulated creatine content in L6C11 muscle myotubes

Publisher: Springer Science and Business Media LLC

Date: 05-01-2016

DOI: 10.1007/S00394-015-1145-1

Abstract: Creatine uptake by muscle cells is increased in the presence of insulin. Accordingly, compounds with insulin-like actions may also augment creatine uptake. The aim of this study was to investigate whether Trigonella foenum-graecum (fenugreek), an insulin mimetic, increases total intracellular creatine levels in vitro. Total cellular creatine content was measured fluorometrically in L6C11 muscle myotubes treated for 1, 4, and 24 h with 0.5 mM creatine (CR), CR and 20 μg/mL fenugreek seed extract (CR + FEN), CR and 100 nM insulin (CR + INS), and CR + INS + FEN (n = 6 per treatment group). Alterations in the expression of the sodium- and chloride-dependent creatine transporter, SLC6A8, and key signaling proteins in the PI3-K/Akt pathway were determined. Compared to control (CON), CR + INS + FEN increased total creatine content after 4 h (P < 0.05), whereas all conditions increased SLC6A8 protein expression above CON at this time (P < 0.05). Changes in insulin signaling were demonstrated via increases in Akt Fenugreek, when combined with insulin, modulates creatine content via a mechanism which is independent of the activity of SLC6A8, suggesting that an alternative mechanism is responsible for the regulation and facilitation of insulin-mediated creatine uptake in skeletal muscle cells.

Eight-hour time-restricted eating does not lower daily myofibrillar protein synthesis rates: A randomized control trial

Publisher: Wiley

Date: 22-12-2023

DOI: 10.1002/OBY.23637

Abstract: This study aimed to assess the impact of time‐restricted eating (TRE) on integrated skeletal muscle myofibrillar protein synthesis (MyoPS) rates in males with overweight/obesity. A total of 18 healthy males (age 46 ± 5 years BMI: 30 ± 2 kg/m 2 ) completed this exploratory, parallel, randomized dietary intervention after a 3‐day lead‐in diet. Participants then consumed an isoenergetic diet (protein: ~1.0 g/kg body mass per day) following either TRE (10:00 a.m. to 6:00 p.m.) or an extended eating control (CON 8:00 a.m. to 8:00 p.m.) protocol for 10 days. Integrated MyoPS rates were measured using deuterated water administration with repeated saliva, blood, and muscle s ling. Secondary measures included continuous glucose monitoring and body composition (dual‐energy x‐ray absorptiometry). There were no differences in daily integrated MyoPS rates (TRE: 1.28% ± 0.18% per day, CON: 1.26% ± 0.22% per day p = 0.82) between groups. From continuous glucose monitoring, 24‐hour total area under the curve was reduced following TRE (−578 ± 271 vs. CON: 12 ± 272 mmol/L × 24 hours p = 0.001). Total body mass declined (TRE: −1.6 ± 0.9 and CON: −1.1 ± 0.7 kg p 0.001) with no differences between groups ( p = 0.22). Lean mass loss was greater following TRE compared with CON (−1.0 ± 0.7 vs. −0.2 ± 0.5 kg, respectively p = 0.01). Consuming food within an 8‐hour time‐restricted period does not lower daily MyoPS rates when compared with an isoenergetic diet consumed over 12 hours. Future research should investigate whether these results translate to free‐living TRE.

High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans

Publisher: Wiley

Date: 17-01-2018

DOI: 10.1096/FJ.201700993R

A single bout of strenuous exercise overcomes lipid‐induced anabolic resistance to protein ingestion in overweight, middle‐aged men

Publisher: Wiley

Date: 06-03-2019

DOI: 10.1096/FJ.201801917R

The battle against obesity-attacking physical inactivity as a primary means of defense

Publisher: Springer Science and Business Media LLC

Date: 29-07-2008

DOI: 10.1038/NCPENDMET0918

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Publisher: Oxford University Press (OUP)

Date: 2019

DOI: 10.1002/BJS.11051

Abstract: The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89·6 per cent) compared with that in countries with a middle (753 of 1242, 60·6 per cent odds ratio (OR) 0·17, 95 per cent c.i. 0·14 to 0·21, P & 0·001) or low (363 of 860, 42·2 per cent OR 0·08, 0·07 to 0·10, P & 0·001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference −9·4 (95 per cent c.i. −11·9 to −6·9) per cent P & 0·001), but the relationship was reversed in low-HDI countries (+12·1 (+7·0 to +17·3) per cent P & 0·001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0·60, 0·50 to 0·73 P & 0·001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.

Structural analysis and magnetic-microwave absorption properties of natural mineral-derived silica-coated magnetite nanocomposites

Publisher: Elsevier BV

Date: 08-2022

DOI: 10.1016/J.JMMM.2022.169458

Strategies to identify changes in SEMG due to muscle fatigue during cycling

Publisher: IEEE

Date: 2005

DOI: 10.1109/IEMBS.2005.1616036

Isolated and combined effects of high-intensity interval training and time-restricted eating on glycaemic control in reproductive-aged women with overweight or obesity: Study protocol for a four-armed randomised controlled trial

Publisher: BMJ

Date: 02-2021

DOI: 10.1136/BMJOPEN-2020-040020

Abstract: Overweight and obesity in reproductive-aged women is a global problem due to the increased risk of subfertility, pregnancy complications and cardiometabolic diseases. High-intensity interval training and time-restricted eating are two primary lifestyle interventions that, independently, have positive effects on a range of health outcomes. Whether these two strategies have synergistic effects is currently unknown. Our primary aim is to determine the isolated and combined effect of high-intensity interval training and time-restricted eating on glycaemic control in reproductive-aged women with overweight/obesity. The study is a randomised controlled trial with four parallel groups. Women (N=120) aged 18–45 years with body mass index ≥27 kg/m 2 will be randomly allocated (1:1:1:1) to either: (1) high-intensity interval training, (2) time-restricted eating, (3) a combination of high-intensity interval training and of time-restricted eating, or (4) a control group. The duration of each intervention will be 7 weeks. The primary outcome measure will be glycaemic control, determined by the total area under the plasma glucose curve over 2 hours after a 75-gram oral glucose tolerance test. Secondary outcome measurements will include markers of cardiovascular and metabolic health (peak oxygen uptake, blood pressure, blood lipids, body composition, insulin sensitivity), sleep quality, physical activity, diet and adherence rates to the intervention. The Regional Committee Medical Research Ethics, Norway has approved the trial protocol. This study will provide important new knowledge to both the scientific community and the general population about the isolated and combined effects of two novel diet–exercise strategies on cardiovascular and metabolic health among women with overweight/obesity. NCT04019860 .

Effect of meal frequency and timing on physical performance

Publisher: Cambridge University Press (CUP)

Date: 04-1997

DOI: 10.1079/BJN19970107

Abstract: Two areas of sports nutrition in which the periodicity of eating has been studied relate to: (1) the habitually high energy intakes of many athletes, and (2) the optimization of carbohydrate(CHO) availability to enhance performance. The present paper examines how the timing and frequency of food and fluid intake can assist the athlete and physically-active person to improve their exercise performance in these areas. Frequent eating occasions provide a practical strategy allowing athletes to increase energy intake while concomitantly reducing the gastric discomfort of infrequent large meals. The optimization of CHO stores is a special challenge for athletes undertaking prolonged training or competition sessions. This is a cyclical process with post-exercise CHO ingestion promoting muscle and liver glycogen re-synthesis pre-exercise feedings being practised to optimize substrate availability and feedings during exercise providing a readily-available source of exogenous fuel as endogenous stores become depleted. The timing and frequency of CHO intake at these various stages are crucial determinants for optimizing fuel availability to enhance exercise capacity.

Beyond muscle hypertrophy: why dietary protein is important for endurance athletes

Publisher: Canadian Science Publishing

Date: 09-2014

DOI: 10.1139/APNM-2013-0591

Abstract: Recovery from the demands of daily training is an essential element of a scientifically based periodized program whose twin goals are to maximize training adaptation and enhance performance. Prolonged endurance training sessions induce substantial metabolic perturbations in skeletal muscle, including the depletion of endogenous fuels and damage/disruption to muscle and body proteins. Therefore, increasing nutrient availability (i.e., carbohydrate and protein) in the post-training recovery period is important to replenish substrate stores and facilitate repair and remodelling of skeletal muscle. It is well accepted that protein ingestion following resistance-based exercise increases rates of skeletal muscle protein synthesis and potentiates gains in muscle mass and strength. To date, however, little attention has focused on the ability of dietary protein to enhance skeletal muscle remodelling and stimulate adaptations that promote an endurance phenotype. The purpose of this review is to critically discuss the results of recent studies that have examined the role of dietary protein for the endurance athlete. Our primary aim is to consider the results from contemporary investigations that have advanced our knowledge of how the manipulation of dietary protein (i.e., amount, type, and timing of ingestion) can facilitate muscle remodelling by promoting muscle protein synthesis. We focus on the role of protein in facilitating optimal recovery from, and promoting adaptations to strenuous endurance-based training.

Caffeine Ingestion and Cycling Power Output in a Low or Normal Muscle Glycogen State

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 08-2013

DOI: 10.1249/MSS.0B013E31828AF183

Effect of carbohydrate ingestion on metabolism during running and cycling

Publisher: American Physiological Society

Date: 11-2001

DOI: 10.1152/JAPPL.2001.91.5.2125

Abstract: The effects of carbohydrate or water ingestion on metabolism were investigated in seven male subjects during two running and two cycling trials lasting 60 min at in idual lactate threshold using indirect calorimetry, U- 14 C-labeled tracer-derived measures of the rates of oxidation of plasma glucose, and direct determination of mixed muscle glycogen content from the vastus lateralis before and after exercise. Subjects ingested 8 ml/kg body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or water 10 min before exercise and an additional 2 ml/kg body mass of the same fluid after 20 and 40 min of exercise. Plasma glucose oxidation was greater with CHO than with water during both running (65 ± 20 vs. 42 ± 16 g/h P 0.01) and cycling (57 ± 16 vs. 35 ± 12 g/h P 0.01). Accordingly, the contribution from plasma glucose oxidation to total carbohydrate oxidation was greater during both running (33 ± 4 vs. 23 ± 3% P 0.01) and cycling (36 ± 5 vs. 22 ± 3% P 0.01) with CHO ingestion. However, muscle glycogen utilization was not reduced by the ingestion of CHO compared with water during either running (112 ± 32 vs. 141 ± 34 mmol/kg dry mass) or cycling (227 ± 36 vs. 216 ± 39 mmol/kg dry mass). We conclude that, compared with water, 1) the ingestion of carbohydrate during running and cycling enhanced the contribution of plasma glucose oxidation to total carbohydrate oxidation but 2) did not attenuate mixed muscle glycogen utilization during 1 h of continuous submaximal exercise at in idual lactate threshold.

Erosion of organic carbon in the Arctic as a geological carbon dioxide sink

Publisher: Springer Science and Business Media LLC

Date: 05-08-2015

DOI: 10.1038/NATURE14653

A randomized trial of high‐dairy‐protein, variable‐carbohydrate diets and exercise on body composition in adults with obesity

Publisher: Wiley

Date: 02-03-2016

DOI: 10.1002/OBY.21451

Abstract: This study determined the effects of 16-week high-dairy-protein, variable-carbohydrate (CHO) diets and exercise training (EXT) on body composition in men and women with overweight/obesity. One hundred and eleven participants (age 47 ± 6 years, body mass 90.9 ± 11.7 kg, BMI 33 ± 4 kg/m(2) , values mean ± SD) were randomly stratified to diets with either: high dairy protein, moderate CHO (40% CHO: 30% protein: 30% fat ∼4 dairy servings) high dairy protein, high CHO (55%: 30%: 15% ∼4 dairy servings) or control (55%: 15%: 30% ∼1 dairy serving). Energy restriction (500 kcal/day) was achieved through diet (∼250 kcal/day) and EXT (∼250 kcal/day). Body composition was measured using dual-energy X-ray absorptiometry before, midway, and upon completion of the intervention. Eighty-nine (25 M/64 F) of 115 participants completed the 16-week intervention, losing 7.7 ± 3.2 kg fat mass (P < 0.001) and gaining 0.50 ± 1.75 kg lean mass (P < 0.01). There was no difference in the changes in body composition (fat mass or lean mass) between groups. Compared to a healthy control diet, energy-restricted high-protein diets containing different proportions of fat and CHO confer no advantage to weight loss or change in body composition in the presence of an appropriate exercise stimulus.

Revisiting the three component synthesis of isoxazolo[5,4-b]pyridines, 4-aryl-3,7,7-trimethyl-isoxazolo[5,4-b]quinolin-5(6H)-ones and related heterocycles

Publisher: Elsevier BV

Date: 12-2016

DOI: 10.1016/J.POLY.2016.09.011

A Delayed Morning and Earlier Evening Time-Restricted Feeding Protocol for Improving Glycemic Control and Dietary Adherence in Men with Overweight/Obesity: A Randomized Controlled Trial

Publisher: MDPI AG

Date: 17-02-2020

DOI: 10.3390/NU12020505

Abstract: We determined the effects of time-restricted feeding (TRF 8 h/d) versus extended feeding (EXF 15 h/d) on 24-h and postprandial metabolism and subjective opinions of TRF in men with overweight/obesity. In a randomized crossover design, 11 sedentary males (age 38 ± 5 y BMI: 32.2 ± 2.0 kg/m2) completed two isoenergetic diet protocols for 5 days, consuming meals at 1000, 1300 and 1700 h (TRF) or 0700, 1400 and 2100 h (EXF). On Day 5, participants remained in the laboratory for 24 h, and blood s les were collected at hourly (0700–2300 h) then 2-hourly (2300–0700 h) intervals for concentrations of glucose, insulin and appetite/incretin hormones. Structured qualitative interviews were conducted following completion of both dietary conditions and investigated thematically. Total 24-h area under the curve (AUCtotal) [glucose] tended to be lower for TRF versus EXF (−5.5 ± 9.0 mmol/L/h, p = 0.09). Nocturnal glucose AUC was lower in TRF (−4.2 ± 5.8 mmol/L/h, p = 0.04), with no difference in waking glucose AUC or AUCtotal for [insulin]. Attitudes towards TRF were positive with improved feelings of well-being. Barriers to TRF were work schedules, family commitments and social events. Compared to extended feeding, short-term TRF improved nocturnal glycemic control and was positively perceived in men with overweight/obesity.

Fat adaptation followed by carbohydrate restoration increases AMPK activity in skeletal muscle from trained humans

Publisher: American Physiological Society

Date: 11-2008

DOI: 10.1152/JAPPLPHYSIOL.90540.2008

Abstract: We have previously reported that 5 days of a high-fat diet followed by 1 day of high-carbohydrate intake (Fat-adapt) increased rates of fat oxidation and decreased rates of muscle glycogenolysis during submaximal cycling compared with consumption of an isoenergetic high-carbohydrate diet (HCHO) for 6 days (Burke et al. J Appl Physiol 89: 2413–2421, 2000 Stellingwerff et al. Am J Physiol Endocrinol Metab 290: E380–E388, 2006). To determine potential mechanisms underlying shifts in substrate selection, eight trained subjects performed Fat-adapt and HCHO. On day 7, subjects performed 1-h cycling at 70% peak O 2 uptake. Muscle biopsies were taken immediately before and after exercise. Resting muscle glycogen content was similar between treatments, but muscle triglyceride levels were higher after Fat-adapt ( P 0.05). Resting AMPK-α 1 and -α 2 activity was higher after Fat-adapt ( P = 0.02 and P = 0.05, respectively), while the phosphorylation of AMPK's downstream target, acetyl-CoA carboxylase (pACC at Ser 221 ), tended to be elevated after Fat-adapt ( P = 0.09). Both the respiratory exchange ratio ( P 0.01) and muscle glycogen utilization ( P 0.05) were lower during exercise after Fat-adapt. Exercise increased AMPK-α 1 activity after HCHO ( P = 0.03) but not Fat-adapt. Exercise was associated with an increase in pACC at Ser 221 for both dietary treatments ( P 0.05), with postexercise pACC Ser 221 higher after Fat-adapt ( P = 0.02). In conclusion, compared with HCHO, Fat-adapt increased resting muscle triglyceride stores and resting AMPK-α 1 and -α 2 activity. Fat-adapt also resulted in higher rates of whole body fat oxidation, reduced muscle glycogenolysis, and attenuated the exercise-induced rise in AMPK-α 1 and AMPK-α 2 activity compared with HCHO. Our results demonstrate that AMPK-α 1 and AMPK-α 2 activity and fuel selection in skeletal muscle in response to exercise can be manipulated by diet and/or the interactive effects of diet and exercise training.

Postexercise muscle glycogen resynthesis in humans

Publisher: American Physiological Society

Date: 05-2017

DOI: 10.1152/JAPPLPHYSIOL.00860.2016

Abstract: Since the pioneering studies conducted in the 1960s in which glycogen status was investigated using the muscle biopsy technique, sports scientists have developed a sophisticated appreciation of the role of glycogen in cellular adaptation and exercise performance, as well as sites of storage of this important metabolic fuel. While sports nutrition guidelines have evolved during the past decade to incorporate sport-specific and periodized manipulation of carbohydrate (CHO) availability, athletes attempt to maximize muscle glycogen synthesis between important workouts or competitive events so that fuel stores closely match the demands of the prescribed exercise. Therefore, it is important to understand the factors that enhance or impair this biphasic process. In the early postexercise period (0–4 h), glycogen depletion provides a strong drive for its own resynthesis, with the provision of CHO (~1 g/kg body mass) optimizing this process. During the later phase of recovery (4–24 h), CHO intake should meet the anticipated fuel needs of the training/competition, with the type, form, and pattern of intake being less important than total intake. Dietary strategies that can enhance glycogen synthesis from suboptimal amounts of CHO or energy intake are of practical interest to many athletes in this scenario, the coingestion of protein with CHO can assist glycogen storage. Future research should identify other factors that enhance the rate of synthesis of glycogen storage in a limited time frame, improve glycogen storage from a limited CHO intake, or increase muscle glycogen supercompensation.

Effect of different protocols of caffeine intake on metabolism and endurance performance

Publisher: American Physiological Society

Date: 09-2002

DOI: 10.1152/JAPPLPHYSIOL.00249.2002

Abstract: Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O 2 uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 × 1 mg/kg caffeine every 20 min throughout SS (Durcaf), 2 × 5 ml/kg Coca-Cola between 100 and 120 min SS and during TT (Coke), or placebo. Improvements in TT were as follows: Precaf, 3.4% (0.2–6.5%, 95% confidence interval) Durcaf, 3.1% (−0.1–6.5%) and Coke, 3.1% (−0.2–6.2%). In Study B, eight subjects received 3 × 5 ml/kg of different cola drinks during the last 40 min of SS and TT: decaffeinated, 6% CHO (control) caffeinated, 6% CHO decaffeinated, 11% CHO and caffeinated, 11% CHO (Coke). Coke enhanced TT by 3.3% (0.8–5.9%), with all trials showing 2.2% TT enhancement (0.5–3.8% P 0.05) due to caffeine. Overall, 1) 6 mg/kg caffeine enhanced TT performance independent of timing of intake and 2) replacing sports drink with Coca-Cola during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to low intake of caffeine (∼1.5 mg/kg).

Short-term plyometric training improves running economy in highly trained middle and long distance runners

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 2006

DOI: 10.1519/R-18235.1

Chronic rosiglitazone treatment restores AMPKα2 activity in insulin-resistant rat skeletal muscle

Publisher: American Physiological Society

Date: 02-2006

DOI: 10.1152/AJPENDO.00096.2005

Abstract: Rosiglitazone (RSG) is an insulin-sensitizing thiazolidinedione (TZD) that exerts peroxisome proliferator-activated receptor-γ (PPARγ)-dependent and -independent effects. We tested the hypothesis that part of the insulin-sensitizing effect of RSG is mediated through the action of AMP-activated protein kinase (AMPK). First, we determined the effect of acute (30–60 min) incubation of L6 myotubes with RSG on AMPK regulation and palmitate oxidation. Compared with control (DMSO), 200 μM RSG increased ( P 0.05) AMPKα1 activity and phosphorylation of AMPK (Thr 172 ). In addition, acetyl-CoA carboxylase (Ser 218 ) phosphorylation and palmitate oxidation were increased ( P 0.05) in these cells. To investigate the effects of chronic RSG treatment on AMPK regulation in skeletal muscle in vivo, obese Zucker rats were randomly allocated into two experimental groups: control and RSG. Lean Zucker rats were treated with vehicle and acted as a control group for obese Zucker rats. Rats were dosed daily for 6 wk with either vehicle (0.5% carboxymethylcellulose, 100 μl/100 g body mass), or 3 mg/kg RSG. AMPKα1 activity was similar in muscle from lean and obese animals and was unaffected by RSG treatment. AMPKα2 activity was ∼25% lower in obese vs. lean animals ( P 0.05) but was normalized to control values after RSG treatment. ACC phosphorylation was decreased with obesity ( P 0.05) but restored to the level of lean controls with RSG treatment. Our data demonstrate that RSG restores AMPK signaling in skeletal muscle of insulin-resistant obese Zucker rats.

Mitochondrial function: Use it or lose it

Publisher: Springer Science and Business Media LLC

Date: 06-02-2007

DOI: 10.1007/S00125-007-0595-2

Approaches to addressing the rise in obesity levels

Publisher: Springer Science and Business Media LLC

Date: 30-11-2023

DOI: 10.1038/S41574-022-00777-1

Abstract: Levels of obesity and overweight are increasing globally, with affected in iduals often experiencing health issues and reduced quality of life. The pathogenesis of obesity is complex and multifactorial, and effective solutions have been elusive. In this Viewpoint, experts in the fields of medical therapy, adipocyte biology, exercise and muscle, bariatric surgery, genetics, and public health give their perspectives on current and future progress in addressing the rising prevalence of obesity.

Motorcycle steering torque estimation using a simplified front assembly model: experimental validation and manoeuvrability implications

Publisher: Informa UK Limited

Date: 26-03-2023

DOI: 10.1080/00423114.2023.2194542

The effect of morning vs evening exercise training on glycaemic control and serum metabolites in overweight/obese men: a randomised trial

Publisher: Springer Science and Business Media LLC

Date: 19-05-2021

DOI: 10.1007/S00125-021-05477-5

Abstract: We determined whether the time of day of exercise training (morning vs evening) would modulate the effects of consumption of a high-fat diet (HFD) on glycaemic control, whole-body health markers and serum metabolomics. In this three-armed parallel-group randomised trial undertaken at a university in Melbourne, Australia, overweight/obese men consumed an HFD (65% of energy from fat) for 11 consecutive days. Participants were recruited via social media and community advertisements. Eligibility criteria for participation were male sex, age 30–45 years, BMI 27.0–35.0 kg/m 2 and sedentary lifestyle. The main exclusion criteria were known CVD or type 2 diabetes, taking prescription medications, and shift-work. After 5 days, participants were allocated using a computer random generator to either exercise in the morning (06:30 hours), exercise in the evening (18:30 hours) or no exercise for the subsequent 5 days. Participants and researchers were not blinded to group assignment. Changes in serum metabolites, circulating lipids, cardiorespiratory fitness, BP, and glycaemic control (from continuous glucose monitoring) were compared between groups. Twenty-five participants were randomised (morning exercise n = 9 evening exercise n = 8 no exercise n = 8) and 24 participants completed the study and were included in analyses ( n = 8 per group). Five days of HFD induced marked perturbations in serum metabolites related to lipid and amino acid metabolism. Exercise training had a smaller impact than the HFD on changes in circulating metabolites, and only exercise undertaken in the evening was able to partly reverse some of the HFD-induced changes in metabolomic profiles. Twenty-four-hour glucose concentrations were lower after 5 days of HFD compared with the participants’ habitual diet (5.3 ± 0.4 vs 5.6 ± 0.4 mmol/l, p = 0.001). There were no significant changes in 24 h glucose concentrations for either exercise group but lower nocturnal glucose levels were observed in participants who trained in the evening, compared with when they consumed the HFD alone (4.9 ± 0.4 vs 5.3 ± 0.3 mmol/l, p = 0.04). Compared with the no-exercise group, peak oxygen uptake improved after both morning (estimated effect 1.3 ml min −1 kg −1 [95% CI 0.5, 2.0], p = 0.003) and evening exercise (estimated effect 1.4 ml min −1 kg −1 [95% CI 0.6, 2.2], p = 0.001). Fasting blood glucose, insulin, cholesterol, triacylglycerol and LDL-cholesterol concentrations decreased only in participants allocated to evening exercise training. There were no unintended or adverse effects. A short-term HFD in overweight/obese men induced substantial alterations in lipid- and amino acid-related serum metabolites. Improvements in cardiorespiratory fitness were similar regardless of the time of day of exercise training. However, improvements in glycaemic control and partial reversal of HFD-induced changes in metabolic profiles were only observed when participants exercise trained in the evening. anzctr.org.au registration no. ACTRN12617000304336. This study was funded by the Novo Nordisk Foundation (NNF14OC0011493).

Interaction of exercise and diet on GLUT-4 protein and gene expression in type I and type II rat skeletal muscle

Publisher: Wiley

Date: 30-04-2002

DOI: 10.1046/J.1365-201X.2002.00963.X

Improving Reproductive Function in Women with Polycystic Ovary Syndrome with High-Intensity Interval Training (IMPROV-IT): A Two-Centre, Three-Armed Randomized Controlled Trial

Publisher: Elsevier BV

Date: 2021

DOI: 10.2139/SSRN.3750673

Exogenous carbohydrate oxidation from maltose and glucose ingested during prolonged exercise

Publisher: Springer Science and Business Media LLC

Date: 1992

DOI: 10.1007/BF00843762

Attenuated PGC-1α Isoforms following Endurance Exercise with Blood Flow Restriction

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 09-2016

DOI: 10.1249/MSS.0000000000000970

Three weeks of interrupting sitting lowers fasting glucose and glycemic variability, but not glucose tolerance, in free-living women and men with obesity

Publisher: American Physiological Society

Date: 08-2021

DOI: 10.1152/AJPENDO.00599.2020

Abstract: Under free-living conditions, breaking sitting modestly increased activity behavior. Breaking sitting was insufficient to modulate glucose tolerance or the skeletal muscle lipidome. Activity breaks reduced fasting blood glucose levels and daily glucose variation compared with baseline, with a tendency to also decrease fasting LDLc. This intervention may represent the minimal dose for breaking sedentary behavior, with larger volumes of activity possibly required to promote greater health benefits.

Effect of altering substrate availability on metabolism and performance during intense exercise

Publisher: Cambridge University Press (CUP)

Date: 12-2000

DOI: 10.1017/S0007114500002440

Abstract: The purpose of this study was to determine the effect of altering substrate availability on metabolism and performance during intense cycling. Seven highly trained men ingested a random order of three isoenergetic meals 90 min before cycling at 80 % maximal oxygen uptake (VO 2max ) for 20 min (about 310 W), followed by a 600 kJ time trial lasting about 30 min. Meals consisted of either 1·2 g saturated fat/kg body mass (BM) with 3500 U heparin intravenously (HIFAT) to elevate circulating plasma free fatty acid (FA) concentration, 2·5 g carbohydrate/kg BM (CHO) to elevate plasma glucose and insulin concentrations or 2·5 g carbohydrate+20 mg nicotinic acid/kg BM (NA) to suppress lipolysis and reduce free FA concentration. HIFAT elevated free FA concentration (HIFAT 1·3 (SEM 0·2), CHO 0·2 (sem 0·1), NA 0·1 (sem 0·1) mm P ·001), lowered the RER (HIFAT 0·94 (sem 0·01), CHO 0·97 (sem 0·01), NA 0·98 (sem 0·01) P ·01) and increased the rate of fat oxidation (HIFAT 24 (sem 3), CHO 12 (sem 2), NA 8 (sem 3) μmol/kg per min P ·01) during the 20 min ride. Marked differences in fat availability and fuel utilisation, however, had little effect on performance in the subsequent time trial (HIFAT 320 (sem 16), CHO 324 (sem 15), NA 315 (sem 13) W). We conclude: (1) increased fat availability during intense cycling increases the rate of fat oxidation but (2) the reduction in the rate of carbohydrate oxidation in the presence of high circulating plasma free FA is unlikely to enhance intense exercise performance lasting about 1 h (3) substrate selection during intense (about 80 % VO 2max ) exercise is dominated by carbohydrate oxidation.

Effect of short-term fat adaptation on high-intensity training

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 03-2002

DOI: 10.1097/00005768-200203000-00011

Abstract: To determine the effect of short-term (3-d) fat adaptation on high-intensity exercise training in seven competitive endurance athletes (maximal O2 uptake 5.0 +/- 0.5 L x min(-1), mean +/-SD). Subjects consumed a standardized diet on d-0 then, in a randomized cross-over design, either 3-d of high-CHO (11 g x kg(-1)d(-1) CHO, 1 g x kg(-1) x d(-1) fat HICHO) or an isoenergetic high-fat (2.6 g CHO x kg(-1) x d(-1), 4.6 g FAT x kg(-1) x d(-1) HIFAT) diet separated by an 18-d wash out. On the 1st (d-1) and 4th (d-4) day of each treatment, subjects completed a standardized laboratory training session consisting of a 20-min warm-up at 65% of VO2peak (232 +/- 23W) immediately followed by 8 x 5 min work bouts at 86 +/- 2% of VO2peak (323 +/- 32 W) with 60-s recovery. Respiratory exchange ratio (mean for bouts 1, 4, and 8) was similar on d-1 for HIFAT and HICHO (0.91 +/- 0.04 vs 0.92 +/- 0.03) and on d-4 after HICHO (0.92 +/- 0.03) but fell to 0.85 +/- 0.03 (P < 0.05) on d-4 after HIFAT. Accordingly, the rate of fat oxidation increased from 31 +/- 13 on d-1 to 61 +/- 25 micromol x kg(-1) x min(-1) on d-4 after HIFAT (P < 0.05). Blood lactate concentration was similar on d-1 and d-4 of HICHO and on d-1 of HIFAT (3.5 +/- 0.9 and 3.2 +/- 1.0 vs 3.7 +/- 1.2 mM) but declined to 2.4 +/- 0.5 mM on d-4 after HIFAT (P < 0.05). Ratings of perception of effort (legs) were similar on d-1 for HIFAT and HICHO (14.8 +/- 1.5 vs 14.1 +/- 1.4) and on d-4 after HICHO (13.8 +/- 1.8) but increased to 16.0 +/- 1.3 on d-4 after HIFAT (P < 0.05). 1) competitive endurance athletes can perform intense interval training during 3-d exposure to a high-fat diet, 2) such exercise elicited high rates of fat oxidation, but 3) compared with a high-carbohydrate diet, training sessions were associated with increased ratings of perceived exertion.

Reply from M. J. Gibala, J. P. Little, M. J. MadDonald and J. A. Hawley

Publisher: Wiley

Date: 07-2012

DOI: 10.1113/JPHYSIOL.2012.235127

Tissue-specific effects of rosiglitazone and exercise in the treatment of lipid-induced insulin resistance

Publisher: American Diabetes Association

Date: 07-2007

DOI: 10.2337/DB06-1065

Abstract: Both pharmacological intervention (i.e., thiazolidinediones [TZDs]) and lifestyle modification (i.e., exercise training) are clinically effective treatments for improving whole-body insulin sensitivity. However, the mechanism(s) by which these therapies reverse lipid-induced insulin resistance in skeletal muscle is unclear. We determined the effects of 4 weeks of rosiglitazone treatment and exercise training and their combined actions (rosiglitazone treatment and exercise training) on lipid and glucose metabolism in high-fat–fed rats. High-fat feeding resulted in decreased muscle insulin sensitivity, which was associated with increased rates of palmitate uptake and the accumulation of the fatty acid metabolites ceramide and diacylglycerol. Impairments in lipid metabolism were accompanied by defects in the Akt/AS160 signaling pathway. Exercise training, but not rosiglitazone treatment, reversed these impairments, resulting in improved insulin-stimulated glucose transport and increased rates of fatty acid oxidation in skeletal muscle. The improvements to glucose and lipid metabolism observed with exercise training were associated with increased AMP-activated protein kinase α1 activity increased expression of Akt1, peroxisome proliferator–activated receptor γ coactivator 1, and GLUT4 and a decrease in AS160 expression. In contrast, rosiglitazone treatment exacerbated lipid accumulation and decreased insulin-stimulated glucose transport in skeletal muscle. However, rosiglitazone, but not exercise training, increased adipose tissue GLUT4 and acetyl CoA carboxylase expression. Both exercise training and rosiglitazone decreased liver triacylglycerol content. Although both interventions can improve whole-body insulin sensitivity, our results show that they produce ergent effects on protein expression and triglyceride storage in different tissues. Accordingly, exercise training and rosiglitazone may act as complementary therapies for the treatment of insulin resistance.

Disrupting AMPK-Glycogen Binding in Mice Increases Carbohydrate Utilization and Reduces Exercise Capacity

Publisher: Frontiers Media SA

Date: 22-03-2022

DOI: 10.3389/FPHYS.2022.859246

Abstract: The AMP-activated protein kinase (AMPK) is a central regulator of cellular energy balance and metabolism and binds glycogen, the primary storage form of glucose in liver and skeletal muscle. The effects of disrupting whole-body AMPK-glycogen interactions on exercise capacity and substrate utilization during exercise in vivo remain unknown. We used male whole-body AMPK double knock-in (DKI) mice with chronic disruption of AMPK-glycogen binding to determine the effects of DKI mutation on exercise capacity, patterns of whole-body substrate utilization, and tissue metabolism during exercise. Maximal treadmill running speed and whole-body energy utilization during submaximal running were determined in wild type (WT) and DKI mice. Liver and skeletal muscle glycogen and skeletal muscle AMPK α and β2 subunit content and signaling were assessed in rested and maximally exercised WT and DKI mice. Despite a reduced maximal running speed and exercise time, DKI mice utilized similar absolute amounts of liver and skeletal muscle glycogen compared to WT. DKI skeletal muscle displayed reduced AMPK α and β2 content versus WT, but intact relative AMPK phosphorylation and downstream signaling at rest and following exercise. During submaximal running, DKI mice displayed an increased respiratory exchange ratio, indicative of greater reliance on carbohydrate-based fuels. In summary, whole-body disruption of AMPK-glycogen interactions reduces maximal running capacity and skeletal muscle AMPK α and β2 content and is associated with increased skeletal muscle glycogen utilization. These findings highlight potential unappreciated roles for AMPK in regulating tissue glycogen dynamics and expand AMPK’s known roles in exercise and metabolism.

Peak power output predicts maximal oxygen uptake and performance time in trained cyclists

Publisher: Springer Science and Business Media LLC

Date: 1992

DOI: 10.1007/BF01466278

Modulation of autophagy signaling with resistance exercise and protein ingestion following short-term energy deficit

Publisher: American Physiological Society

Date: 09-2015

DOI: 10.1152/AJPREGU.00413.2014

Abstract: Autophagy contributes to remodeling of skeletal muscle and is sensitive to contractile activity and prevailing energy availability. We investigated changes in targeted genes and proteins with roles in autophagy following 5 days of energy balance (EB), energy deficit (ED), and resistance exercise (REX) after ED. Muscle biopsies from 15 subjects (8 males, 7 females) were taken at rest following 5 days of EB [45 kcal·kg fat free mass (FFM) −1 ·day −1 ] and 5 days of ED (30 kcal·kg FFM −1 ·day −1 ). After ED, subjects completed a bout of REX and consumed either placebo (PLA) or 30 g whey protein (PRO) immediately postexercise. Muscle biopsies were obtained at 1 and 4 h into recovery in each trial. Resting protein levels of autophagy-related gene protein 5 (Atg5) decreased after ED compared with EB (∼23%, P 0.001) and remained below EB from 1 to 4 h postexercise in PLA (∼17%) and at 1 h in PRO (∼18%, P 0.05). In addition, conjugated Atg5 (cAtg12) decreased below EB in PLA at 4 h (∼20, P 0.05) however, its values were increased above this time point in PRO at 4 h alongside increases in FOXO1 above EB (∼22–26%, P 0.05). Notably, these changes were subsequent to increases in unc-51-like kinase 1 Ser757 phosphorylation (∼60%) 1 h postexercise in PRO. No significant changes in gene expression of selected autophagy markers were found, but EGR-1 increased above ED and EB in PLA (∼417–864%) and PRO (∼1,417–2,731%) trials 1 h postexercise ( P 0.001). Postexercise protein availability, compared with placebo, can selectively promote autophagic responses to REX in ED.

Fat Adaptation Science: Low-Carbohydrate, High- Fat Diets to Alter Fuel Utilization and Promote Training Adaptation

Publisher: S. Karger AG

Date: 2011

DOI: 10.1159/000329283

Abstract: The effect of manipulating an in idual's habitual diet on skeletal muscle fuel utilization has been of longstanding interest to scientists, and it is now well established that changes in dietary intake that alter the concentration of blood-borne substrates and hormones cause substantial perturbations in the macronutrient storage profile of muscle and exert profound effects on rates of substrate oxidation during exercise. Only recently, however, has it become appreciated that nutrient-exercise interventions can modulate many contraction- induced responses in muscle, and that fuel availability per se provides a 'trigger' for adaptation. Consumption of low-carbohydrate, high- fat diets in the face of endurance training alters patterns of fuel utilization and subsequent exercise responses. Human studies show how low-carbohydrate, fat-rich diets interact with specific contractile stimulus to modulate many of the acute responses to exercise, thereby promoting or inhibiting subsequent training adaptation.

Introduction???Preventing Insulin Resistance through Exercise: A Cellular Approach

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 07-2004

DOI: 10.1249/01.MSS.0000132382.95142.71

Abstract: Insulin resistance is a progressive metabolic disorder associated with inactivity, ageing, genetic predisposition and environmental factors, and is a hallmark feature of a variety of disease states including obesity, dyslipidemia, hypertension, polycystic ovarian syndrome, arteriosclerosis and noninsulin dependent (Type 2) diabetes mellitus. The primary defect in the development of whole body insulin resistance remains unclear. However, during the past decade major advances have been made in our understanding of the molecular and cellular mechanisms regulating the entry of glucose into insulin-sensitive tissues. Such an understanding is critical in the identification of specific glucoregulatory biochemical/molecular sites that can be targeted by treatment strategies (i.e. exercise training) in the prevention and treatment of insulin resistance. The five papers comprising this symposium provide a state-of-the-art synopsis of the metabolic, cellular, and molecular mechanisms positively affected by exercise training in in iduals who are insulin resistant.

Carbohydrate, Fluids and Electrolyte Requirements of the Soccer Player: A Stewiew

Publisher: Human Kinetics

Date: 09-1994

DOI: 10.1123/IJSN.4.3.221

Abstract: Soccer requires field players to exercise repetitively at high intensities for the duration of a game, which can result in marked muscle glycogen depletion and hypoglycemia. A soccer match places heavy demands on endogenous muscle and liver glycogen stores and fluid reserves, which must be rapidly replenished when players complete several matches within a brief period of time. Low concentrations of muscle glycogen have been reported in soccer players before a game, and daily carbohydrate (CHO) intakes are often insufficient to replenish muscle glycogen stores, CHO supplementation during soccer matches has been found to result in muscle glycogen sparing (39%), greater second-half running distances, and more goals being scored with less conceded, when compared to consumption of water. Thus, CHO supplementation has been recommended prior to, during, and after matches. In contrast, there is currently insufficient evidence to recommend without reservation the addition of electrolytes to a beverage for ingestion by players during a game resulting in sweat losses of 4% of body weight.

Metabolic and performance adaptations to interval training in endurance-trained cyclists

Publisher: Springer Science and Business Media LLC

Date: 04-1997

DOI: 10.1007/S004210050164

Abstract: This study examined the effects of sustained high-intensity interval training (HIT) on the athletic performances and fuel utilisation of eight male endurance-trained cyclists. Before HIT, each subject undertook three baseline peak power output Wpeak tests and two simulated 40-km time-trial cycling performance (TT40) tests, of which the variabilities were 1.5 (1.3)% and 1.0 (0.5)%, respectively [mean (SD)]. Over 6 weeks, the cyclists then replaced 15 (2)% of their 300 (66) km.week-1 endurance training with 12 HIT sessions, each consisting of six to nine 5-min rides at 80% of Wpeak, separated by a l-min recovery. HIT increased Wpeak from 404 (40) to 424 (53) W (P < 0.01) and improved TT40 speeds from 42.0 (3.6) to 43.0 (4.2) km.h-1 (P < 0.05). Faster TT40 performances were due to increases in both the absolute work rates from 291 (43) to 327 (51) W (P < 0.05) and the relative work rates from 72.6 (5.3)% of pre-HIT Wpeak to 78.1 (2.8)% of post-HIT Wpeak (P < 0.05). HIT decreased carbohydrate (CHO) oxidation, plasma lactate concentration and ventilation when the cyclists rode at the same absolute work rates of 60, 70 and 80% of pre-HIT Wpeak (P < 0.05), but not when they exercised at the same relative (% post-HIT Wpeak) work rates. Thus, the ability of the cyclists to sustain higher percentages of Wpeak in TT40 performances after HIT was not due to lower rates of CHO oxidation. Higher relative work rates in the TT40 rides following HIT increased the estimated rates of CHO oxidation from approximately 4.3 to approximately 5.1 g.min-1.

Commentaries on Viewpoint: What is the relationship between acute measure of muscle protein synthesis and changes in muscle mass?

Publisher: American Physiological Society

Date: 15-02-2015

DOI: 10.1152/JAPPLPHYSIOL.01069.2014

Divergent skeletal muscle respiratory capacities in rats artificially selected for high and low running ability: a role for Nor1?

Publisher: American Physiological Society

Date: 11-2012

DOI: 10.1152/JAPPLPHYSIOL.00788.2012

Abstract: Inactivity-related diseases are becoming a huge burden on Western society. While there is a major environmental contribution to metabolic health, the intrinsic properties that predispose or protect against particular health traits are harder to define. We used rat models of inborn high running capacity (HCR) and low running capacity (LCR) to determine inherent differences in mitochondrial volume and function, hypothesizing that HCR rats would have greater skeletal muscle respiratory capacity due to an increase in mitochondrial number. Additionally, we sought to determine if there was a link between the expression of the orphan nuclear receptor neuron-derived orphan receptor (Nor)1, a regulator of oxidative metabolism, and inherent skeletal muscle respiratory capacity. LCR rats were 28% heavier ( P 0.0001), and fasting serum insulin concentrations were 62% greater than in HCR rats ( P = 0.02). In contrast, HCR rats had better glucose tolerance and reduced adiposity. In the primarily oxidative soleus muscle, maximal respiratory capacity was 21% greater in HCR rats ( P = 0.001), for which the relative contribution of fat oxidation was 20% higher than in LCR rats ( P = 0.02). This was associated with increased citrate synthase (CS 33%, P = 0.009) and β-hydroxyacyl-CoA (β-HAD 33%, P = 0.0003) activities. In the primarily glycolytic extensor digitum longus muscle, CS activity was 29% greater ( P = 0.01) and β-HAD activity was 41% ( P = 0.0004) greater in HCR rats compared with LCR rats. Mitochondrial DNA copy numbers were also elevated in the extensor digitum longus muscles of HCR rats (35%, P = 0.049) and in soleus muscles (44%, P = 0.16). Additionally, HCR rats had increased protein expression of in idual mitochondrial respiratory complexes, CS, and uncoupling protein 3 in both muscle types (all P 0.05). In both muscles, Nor1 protein was greater in HCR rats compared with LCR rats ( P 0.05). We propose that the differential expression of Nor1 may contribute to the differences in metabolic regulation between LCR and HCR phenotypes.

Molecular responses to strength and endurance training: are they incompatible?

Publisher: Canadian Science Publishing

Date: 06-2009

DOI: 10.1139/H09-023

Abstract: Simultaneously training for both strength and endurance results in a compromised adaptation, compared with training for either exercise mode alone. This has been variously described as the concurrent training effect or the interference effect. It now appears that the genetic and molecular mechanisms of adaptation induced by resistance- and endurance-based training are distinct, with each mode of exercise activating and (or) repressing specific subsets of genes and cellular signalling pathways. This brief review will summarize our current understanding of the molecular responses to strength and endurance training, and will examine the molecular evidence for an interference effect when concurrent training is undertaken. A better understanding of the activation and interaction of the molecular pathways in response to these different modes of exercise will permit sport scientists to develop improved training programs capable of maximizing both strength and endurance.

Protein Availability and Satellite Cell Dynamics in Skeletal Muscle

Publisher: Springer Science and Business Media LLC

Date: 20-03-2018

DOI: 10.1007/S40279-018-0883-7

Abstract: Human skeletal muscle satellite cells are activated in response to both resistance and endurance exercise. It was initially proposed that satellite cell proliferation and differentiation were only required to support resistance exercise-induced hypertrophy. However, satellite cells may also play a role in muscle fibre remodelling after endurance-based exercise and extracellular matrix regulation. Given the importance of dietary protein, particularly branched chain amino acids, in supporting myofibrillar and mitochondrial adaptations to both resistance and endurance-based training, a greater understanding of how protein intake impacts satellite cell activity would provide further insight into the mechanisms governing skeletal muscle remodelling with exercise. While many studies have investigated the capacity for protein ingestion to increase post-exercise rates of muscle protein synthesis, few investigations have examined the role for protein ingestion to modulate satellite cell activity. Here we review the molecular mechanisms controlling the activation of satellite cells in response to mechanical stress and protein intake in both in vitro and in vivo models. We provide a mechanistic framework that describes how protein ingestion may enhance satellite activity and promote exercise adaptations in human skeletal muscle.

Integration of Metabolic and Mitogenic Signal Transduction in Skeletal Muscle

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 2004

DOI: 10.1097/00003677-200401000-00002

Abstract: Exercise has erse effects on metabolic and mitogenic signaling pathways in human skeletal muscle, implying specificity of intracellular signaling cascades. The role of several parallel signaling cascades are discussed in an effort to assign a physiological role for these targets in the regulation of exercise-mediated responses on metabolism and gene expression.

Résultats préliminaires sur la sédimentation pélagique de l'Atlantique tropical au Crétacé et au Tertiaire (plateau de Demerara, Leg ODP 207)

Publisher: Elsevier BV

Date: 04-2005

DOI: 10.1016/J.CRTE.2005.01.011

Postexercise high-fat feeding suppresses p70S6K1 activity in human skeletal muscle

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 11-2016

DOI: 10.1249/MSS.0000000000001009

Concurrent exercise training: do opposites distract?

Publisher: Wiley

Date: 09-10-2017

DOI: 10.1113/JP272270

High reliability of performance of well-trained rowers on a rowing ergometer

Publisher: Informa UK Limited

Date: 1999

DOI: 10.1080/026404199365650

Abstract: High retest reliability is desirable in tests used to monitor athletic performance, but the reliability of many popular tests has not been established. The aim of this study was to determine the reliability of performance of a 2000-m time-trial lasting approximately 7 min performed on a Concept II rowing ergometer. Eight well-trained rowers (peak oxygen uptake 61+/-5 ml x kg(-1) x min(-1) mean +/- standard deviation) performed the time-trials on three occasions at 3-day intervals. Mean power (313+/-38 W in trial 1) improved by 2.3% (95% confidence interval 0.1 to 4.5%) in trial 2 and by a further 0.9% (-1.4 to 3.3%) in trial 3. The variability of performance for in idual rowers expressed as a coefficient of variation for mean power was 2.0% (1.3 to 3.1%), and the retest correlation was 0.96 (0.87 to 0.99). Variability and changes in performance expressed as time to complete the test were approximately one-third those of mean power, apparently because simulated velocity is proportional to the cube root of power on this ergometer. Such high reliability makes this combination of ergometer, athlete and test protocol very suitable for monitoring rowing performance and for investigating factors that affect performance in short, high-intensity endurance events.

The 5′ adenosine monophosphate-activated protein kinase: Regulating the ebb and flow of cellular energetics

Publisher: Elsevier BV

Date: 12-2009

DOI: 10.1016/J.BIOCEL.2009.07.004

Abstract: The 5' adenosine monophosphate-activated protein kinase (AMPK) is a heterotrimeric, evolutionary conserved enzyme which has emerged as a critical regulator of skeletal muscle cellular bioenergetics. AMPK is activated by both chemical (adipokines) and mechanical (stretch, contraction) stimuli leading to metabolic changes within muscle cells that include increased fatty acid oxidation, glucose uptake and glycolysis, as well as the stimulation and regulation of mitochondrial biogenesis. Collectively these acute responses and chronic adaptations act to reduce cellular disturbances, resulting in tighter metabolic control and maintenance of energy homeostasis. This brief review will describe the structure, function and activation of AMPK in skeletal muscle and how this ubiquitous molecule may be a plausible target for the treatment of several lifestyle-related metabolic disorders.

Meteorin-like Is a Hormone that Regulates Immune-Adipose Interactions to Increase Beige Fat Thermogenesis

Publisher: Elsevier BV

Date: 06-2014

DOI: 10.1016/J.CELL.2014.03.065

Divergent regulation of myotube formation and gene expression by E2 and EPA during in-vitro differentiation of C2C12 myoblasts

Publisher: MDPI AG

Date: 23-01-2020

DOI: 10.3390/IJMS21030745

Abstract: Estrogen (E2) and polyunsaturated fatty acids (n-3PUFA) supplements independently support general wellbeing and enhance muscle regeneration in-vivo and myotube formation in-vitro. However, the combined effect of E2 and n-3PUFA on myoblast differentiation is not known. The purpose of the study was to identify whether E2 and n-3PUFA possess a synergistic effect on in-vitro myogenesis. Mouse C2C12 myoblasts, a reliable model to reiterate myogenic events in-vitro, were treated with 10nM E2 and 50μM eicosapentaenoic acid (EPA) independently or combined, for 0–24 h or 0–120 h during differentiation. Immunofluorescence, targeted qPCR and next generation sequencing (NGS) were used to characterize morphological changes and differential expression of key genes involved in the regulation of myogenesis and muscle function pathways. E2 increased estrogen receptor α (Erα) and the expression of the mitogen-activated protein kinase 11 (Mapk11) within 1 h of treatment and improved myoblast differentiation and myotube formation. A significant reduction (p 0.001) in myotube formation and in the expression of myogenic regulatory factors Mrfs (MyoD, Myog and Myh1) and the myoblast fusion related gene, Tmem8c, was observed in the presence of EPA and the combined E2/EPA treatment. Additionally, EPA treatment at 48 h of differentiation inhibited the majority of genes associated with the myogenic and striated muscle contraction pathways. In conclusion, EPA and E2 had no synergistic effect on myotube formation in-vitro. Independently, EPA inhibited myoblast differentiation and overrides the stimulatory effect of E2 when used in combination with E2.

Dietary intakes of age-group swimmers

Publisher: BMJ

Date: 09-1991

DOI: 10.1136/BJSM.25.3.154

Abstract: The purposes of this study were to collect information regarding the dietary habits of male and female age-group swimmers and report the energy consumptions of these athletes in relation to their daily training demands. Twenty competitive swimmers, who were training 6000 m per day 6 days a week, recorded all fluid and food consumed during a 4-day period. Dietary analysis revealed that 11 swimmers (55%) had calcium intakes below recommended dietary allowances (RDA), while 13 (65%) had iron intakes lower than RDA. Despite identical training loads and body mass, male swimmers had significantly greater (P = 0.004) daily mean (s.d.) energy consumption (3072(732) kcal, 12.9(3.1) MJ) than females (2130(544) kcal, 8.9(2.3) MJ) and were maintaining energy balance. Although the contribution of carbohydrate to total daily energy intake was the same for male (55%) and female swimmers (56%), the females ingested significantly less (P = 0.011) carbohydrate (292(87) g) than the males (404(88) g) and could be considered deficient in dietary carbohydrate with respect to their daily training demands.

The effect of exercise and training status on platelet activation: Do cocoa polyphenols play a role?

Publisher: Informa UK Limited

Date: 2006

DOI: 10.1080/09537100600746953

Abstract: Sedentary and trained men respond differently to the same intensity of exercise, this is probably related to their platelet reactivity and antioxidant capacity. There is growing interest in the utilization of antioxidant-rich plant extracts as dietary food supplements. The aim of this study was to investigate the effect of an acute bout of sub maximal exercise on platelet count and differential response of platelet activation in trained and sedentary subjects and to observe if cocoa polyphenols reverse the effect of exercise on platelet function. The practical significance of this study was that many sedentary people engage in occasional strenuous exercise that may predispose them to risk of heart disease. Fasting blood s les were collected from 16 male subjects, pre and post 1-h cycling exercise at 70% of maximal aerobic power (VO2max) before and after consumption of cocoa or placebo. Agonist stimulated citrated whole blood was utilized for measuring platelet aggregation, adenosine triphosphate (ATP) release and platelet activation. Baseline platelet count (221 +/- 33 x 10(9)/L) and ATP release (1.4 +/- 0.6 nmol) increased significantly (P < 0.05) after exercise in all subjects. Baseline platelet numbers in the trained were higher (P < 0.05) than in the sedentary (235 +/- 37 vs. 208 +/- 34 x 10(9)/L), where as platelet activation in trained was lower (P < 0.05) than sedentary (51 +/- 6 vs. 59 +/- 5%). Seven days of cocoa polyphenol supplementation had little effect on any of the parameters measured. We conclude that trained subjects show decreased activation of stimulated platelets when compared to the sedentary subjects and short-term cocoa polyphenol supplementation did not decrease platelet activity in response to exercise independent of prior training status.

Exercise training reverses impaired skeletal muscle metabolism induced by artificial selection for low aerobic capacity

Publisher: American Physiological Society

Date: 2011

DOI: 10.1152/AJPREGU.00338.2010

Abstract: We have used a novel model of genetically imparted endurance exercise capacity and metabolic health to study the genetic and environmental contributions to skeletal muscle glucose and lipid metabolism. We hypothesized that metabolic abnormalities associated with low intrinsic running capacity would be ameliorated by exercise training. Selective breeding for 22 generations resulted in rat models with a fivefold difference in intrinsic aerobic capacity. Low (LCR)- and high (HCR)-capacity runners remained sedentary (SED) or underwent 6 wk of exercise training (EXT). Insulin-stimulated glucose transport, insulin signal transduction, and rates of palmitate oxidation were lower in LCR SED vs. HCR SED ( P 0.05). Decreases in glucose and lipid metabolism were associated with decreased β 2 -adrenergic receptor (β 2 -AR), and reduced expression of Nur77 target proteins that are critical regulators of muscle glucose and lipid metabolism [uncoupling protein-3 (UCP3), fatty acid transporter (FAT)/CD36 P 0.01 and P 0.05, respectively]. EXT reversed the impairments to glucose and lipid metabolism observed in the skeletal muscle of LCR, while increasing the expression of β 2 -AR, Nur77, GLUT4, UCP3, and FAT/CD36 ( P 0.05) in this tissue. However, no metabolic improvements were observed following exercise training in HCR. Our results demonstrate that metabolic impairments resulting from genetic factors (low intrinsic aerobic capacity) can be overcome by an environmental intervention (exercise training). Furthermore, we identify Nur77 as a potential mechanism for improved skeletal muscle metabolism in response to EXT.

Commentaries on Viewpoint: The rigorous study of exercise adaptations: Why mRNA might not be enough

Publisher: American Physiological Society

Date: 08-2016

DOI: 10.1152/JAPPLPHYSIOL.00509.2016

Dysregulation of muscle lipid metabolism in rats selectively bred for low aerobic running capacity

Publisher: American Physiological Society

Date: 06-2007

DOI: 10.1152/AJPENDO.00702.2006

Abstract: As substrate for evaluation of metabolic diseases, we developed novel rat models that contrast for endurance exercise capacity. Through two-way artificial selection, we created rodent phenotypes of intrinsically low-capacity runners (LCR) and high-capacity runners (HCR) that also differed markedly for cardiovascular and metabolic disease risk factors. Here, we determined skeletal muscle proteins with putative roles in lipid and carbohydrate metabolism to better understand the mechanisms underlying differences in whole body substrate handling between phenotypes. Animals ( generation 16) differed for endurance running capacity by 295%. LCR animals had higher resting plasma glucose (6.58 ± 0.45 vs. 6.09 ± 0.45 mmol/l), insulin (0.48 ± 0.03 vs. 0.32 ± 0.02 ng/ml), nonesterified fatty acid (0.57 ± 0.14 v 0.35 ± 0.05 mM), and triglyceride (TG 0.47 ± 0.11 vs. 0.25 ± 0.08 mmol/l) concentrations (all P 0.05). Muscle TG (72.3 ± 14.7 vs. 38.9 ± 6.2 mmol/kg dry muscle wt P 0.05) and diacylglycerol (96 ± 28 vs. 42 ± 8 pmol/mg dry muscle wt P 0.05) contents were elevated in LCR vs. HCR rats. Accompanying the greater lipid accretion in LCR was increased fatty acid translocase/CD36 content (1,014 ± 80 vs. 781 ± 70 arbitrary units P 0.05) and reduced TG lipase activity (0.158 ± 0.0125 vs. 0.274 ± 0.018 mmol·min −1 ·kg dry muscle wt −1 P 0.05). Muscle glycogen, GLUT4 protein, and basal phosphorylation states of AMP-activated protein kinase-α 1 , AMP-activated protein kinase-α 2 , and acetyl-CoA carboxylase were similar in LCR and HCR. In conclusion, rats with low intrinsic aerobic capacity demonstrate abnormalities in lipid-handling capacity. These disruptions may, in part, be responsible for the increased risk of metabolic disorders observed in this phenotype.

Single and Combined Effects of Beetroot Crystals and Sodium Bicarbonate on 4-km Cycling Time Trial Performance

Publisher: Human Kinetics

Date: 06-2017

DOI: 10.1123/IJSNEM.2016-0228

Abstract: When ingested alone, beetroot juice and sodium bicarbonate are ergogenic for high-intensity exercise performance. This study sought to determine the independent and combined effects of these supplements. Eight endurance trained (VO 2 max 65 mL·kg·min -1 ) male cyclists completed four × 4-km time trials (TT) in a doubleblind Latin square design supplementing with beetroot crystals (BC) for 3 days (15 g·day -1 + 15 g 1 h before TT, containing 300 mg nitrate per 15 g), bicarbonate (Bi 0.3 g·kg -1 body mass [BM] in 5 doses every 15 min from 2.5 h before TT) BC+Bi or placebo (PLA). Subjects completed TTs on a Velotron cycle ergometer under standardized laboratory conditions. Plasma nitrite concentrations were significantly elevated only in the BC+Bi trial before the TT (1520 ± 786 nmol·L -1 ) compared with baseline (665 ± 535 nmol·L -1 , p = .02) and the Bi and PLA conditions (Bi: 593 ± 203 nmol·L -1 , p .01 PLA: 543 ± 369 nmol·L -1 , p .01). Plasma nitrite concentrations were not elevated in the BC trial before the TT (1102 ± 218 nmol·L -1 ) compared with baseline (975 ± 607 nmol·L -1 , p .05). Blood bicarbonate concentrations were increased in the BC+Bi and Bi trials before the TT (BC+Bi: 30.9 ± 2.8 mmol·L -1 Bi: 31.7 ± 1.1 mmol·L -1 ). There were no differences in mean power output (386–394 W) or the time taken to complete the TT (335.8–338.1 s) between any conditions. Under the conditions of this study, supplementation was not ergogenic for 4-km TT performance.

Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise

Publisher: Elsevier BV

Date: 09-2011

DOI: 10.3945/AJCN.111.013722

Abstract: Ingestion of whey or casein yields ergent patterns of aminoacidemia that influence whole-body and skeletal muscle myofibrillar protein synthesis (MPS) after exercise. Direct comparisons of the effects of contrasting absorption rates exhibited by these proteins are confounded by their differing amino acid contents. Our objective was to determine the effect of ergent aminoacidemia by manipulating ingestion patterns of whey protein alone on MPS and anabolic signaling after resistance exercise. In separate trials, 8 healthy men consumed whey protein either as a single bolus (BOLUS 25-g dose) or as repeated, small, "pulsed" drinks (PULSE ten 2.5-g drinks every 20 min) to mimic a more slowly digested protein. MPS and phosphorylation of signaling proteins involved in protein synthesis were measured at rest and after resistance exercise. BOLUS increased blood essential amino acid (EAA) concentrations above those of PULSE (162% compared with 53%, P < 0.001) 60 min after exercise, whereas PULSE resulted in a smaller but sustained increase in aminoacidemia that remained elevated above BOLUS amounts later (180-220 min after exercise, P < 0.05). Despite an identical net area under the EAA curve, MPS was elevated to a greater extent after BOLUS than after PULSE early (1-3 h: 95% compared with 42%) and later (3-5 h: 193% compared with 121%) (both P < 0.05). There were greater changes in the phosphorylation of the Akt-mammalian target of rapamycin pathway after BOLUS than after PULSE. Rapid aminoacidemia in the postexercise period enhances MPS and anabolic signaling to a greater extent than an identical amount of protein fed in small pulses that mimic a more slowly digested protein. A pronounced peak aminoacidemia after exercise enhances protein synthesis. This trial was registered at clinicaltrials.gov as NCT01319513.

Factors affecting running economy in trained distance runners

Publisher: Springer Science and Business Media LLC

Date: 2004

DOI: 10.2165/00007256-200434070-00005

Abstract: Running economy (RE) is typically defined as the energy demand for a given velocity of submaximal running, and is determined by measuring the steady-state consumption of oxygen (VO2) and the respiratory exchange ratio. Taking body mass (BM) into consideration, runners with good RE use less energy and therefore less oxygen than runners with poor RE at the same velocity. There is a strong association between RE and distance running performance, with RE being a better predictor of performance than maximal oxygen uptake (VO2max) in elite runners who have a similar VO2max). RE is traditionally measured by running on a treadmill in standard laboratory conditions, and, although this is not the same as overground running, it gives a good indication of how economical a runner is and how RE changes over time. In order to determine whether changes in RE are real or not, careful standardisation of footwear, time of test and nutritional status are required to limit typical error of measurement. Under controlled conditions, RE is a stable test capable of detecting relatively small changes elicited by training or other interventions. When tracking RE between or within groups it is important to account for BM. As VO2 during submaximal exercise does not, in general, increase linearly with BM, reporting RE with respect to the 0.75 power of BM has been recommended. A number of physiological and biomechanical factors appear to influence RE in highly trained or elite runners. These include metabolic adaptations within the muscle such as increased mitochondria and oxidative enzymes, the ability of the muscles to store and release elastic energy by increasing the stiffness of the muscles, and more efficient mechanics leading to less energy wasted on braking forces and excessive vertical oscillation. Interventions to improve RE are constantly sought after by athletes, coaches and sport scientists. Two interventions that have received recent widespread attention are strength training and altitude training. Strength training allows the muscles to utilise more elastic energy and reduce the amount of energy wasted in braking forces. Altitude exposure enhances discrete metabolic aspects of skeletal muscle, which facilitate more efficient use of oxygen. The importance of RE to successful distance running is well established, and future research should focus on identifying methods to improve RE. Interventions that are easily incorporated into an athlete's training are desirable.

Mice with whole-body disruption of ampk-glycogen binding have increased adiposity, reduced fat oxidation and altered tissue glycogen dynamics

Publisher: MDPI AG

Date: 05-09-2021

DOI: 10.3390/IJMS22179616

Abstract: The AMP-activated protein kinase (AMPK), a central regulator of cellular energy balance and metabolism, binds glycogen via its β subunit. However, the physiological effects of disrupting AMPK-glycogen interactions remain incompletely understood. To chronically disrupt AMPK-glycogen binding, AMPK β double knock-in (DKI) mice were generated with mutations in residues critical for glycogen binding in both the β1 (W100A) and β2 (W98A) subunit isoforms. We examined the effects of this DKI mutation on whole-body substrate utilization, glucose homeostasis, and tissue glycogen dynamics. Body composition, metabolic caging, glucose and insulin tolerance, serum hormone and lipid profiles, and tissue glycogen and protein content were analyzed in chow-fed male DKI and age-matched wild-type (WT) mice. DKI mice displayed increased whole-body fat mass and glucose intolerance associated with reduced fat oxidation relative to WT. DKI mice had reduced liver glycogen content in the fed state concomitant with increased utilization and no repletion of skeletal muscle glycogen in response to fasting and refeeding, respectively, despite similar glycogen-associated protein content relative to WT. DKI liver and skeletal muscle displayed reductions in AMPK protein content versus WT. These findings identify phenotypic effects of the AMPK DKI mutation on whole-body metabolism and tissue AMPK content and glycogen dynamics.

Single and combined effects of beetroot juice and caffeine supplementation on cycling time trial performance

Publisher: Canadian Science Publishing

Date: 09-2014

DOI: 10.1139/APNM-2013-0336

Abstract: Both caffeine and beetroot juice have ergogenic effects on endurance cycling performance. We investigated whether there is an additive effect of these supplements on the performance of a cycling time trial (TT) simulating the 2012 London Olympic Games course. Twelve male and 12 female competitive cyclists each completed 4 experimental trials in a double-blind Latin square design. Trials were undertaken with a caffeinated gum (CAFF) (3 mg·kg −1 body mass (BM), 40 min prior to the TT), concentrated beetroot juice supplementation (BJ) (8.4 mmol of nitrate (NO 3 – ), 2 h prior to the TT), caffeine plus beetroot juice (CAFF+BJ), or a control (CONT). Subjects completed the TT (females: 29.35 km males: 43.83 km) on a laboratory cycle ergometer under conditions of best practice nutrition: following a carbohydrate-rich pre-event meal, with the ingestion of a carbohydrate–electrolyte drink and regular oral carbohydrate contact during the TT. Compared with CONT, power output was significantly enhanced after CAFF+BJ and CAFF (3.0% and 3.9%, respectively, p 0.01). There was no effect of BJ supplementation when used alone (–0.4%, p = 0.6 compared with CONT) or when combined with caffeine (–0.9%, p = 0.4 compared with CAFF). We conclude that caffeine (3 mg·kg −1 BM) administered in the form of a caffeinated gum increased cycling TT performance lasting ∼50–60 min by ∼3%–4% in both males and females. Beetroot juice supplementation was not ergogenic under the conditions of this study.

Adaptations to Concurrent Training in Combination with High Protein Availability: A Comparative Trial in Healthy, Recreationally Active Men

Publisher: Springer Science and Business Media LLC

Date: 19-10-2018

DOI: 10.1007/S40279-018-0999-9

Abstract: We implemented a high-protein diet (2 g·kg −1 ·d −1 ) throughout 12 weeks of concurrent exercise training to determine whether interferences to adaptation in muscle hypertrophy, strength and power could be attenuated compared to resistance training alone. Thirty-two recreationally active males (age: 25 ± 5 years, body mass index: 24 ± 3 kg·m −2 mean ± SD) performed 12 weeks of either isolated resistance (RES n = 10) or endurance (END n = 10) training (three sessions·w −1 ), or concurrent resistance and endurance (CET n = 12) training (six sessions·w −1 ). Maximal strength (1RM), body composition and power were assessed pre- and post-intervention. Leg press 1RM increased ~ 24 ± 13% and ~ 33 ± 16% in CET and RES from PRE-to-POST ( P 0.001), with no difference between groups. Total lean mass increased ~ 4% in both CET and RES from PRE-to-POST ( P 0.001). Ultrasound estimated vastus lateralis volume increased ~ 15% in CET and ~ 11% in RES from PRE-to-POST ( P 0.001), with no difference between groups. Wingate peak power relative to body mass displayed a trend ( P = 0.053) to be greater in RES (12.5 ± 1.6 W·kg BM −1 ) than both CET (10.8 ± 1.7 W·kg BM −1 ) and END (10.9 ± 1.8 W·kg BM −1 ) at POST. Absolute VO 2peak increased 6.9% in CET and 12% in END from PRE-to-POST ( P 0.05), with no difference between groups. Despite high protein availability, select measures of anaerobic power-based adaptations, but not muscle strength or hypertrophy, appear susceptible to ‘interference effects’ with CET and should be closely monitored throughout training macro-cycles. T rials Registry : This trial was registered with the Australian-New Zealand Clinical Trials Registry (ACTRN12617001229369).

The Effect of Carbohydrate Ingestion on the Motor Skill Proficiency of Soccer Players

Publisher: Human Kinetics

Date: 12-1996

DOI: 10.1123/IJSN.6.4.348

Abstract: This study examined the effects of ingesting a glucose-polymer (GP) solution on the motor skill proficiencies of association football (soccer) players from two teams playing during two matches in a cool environment. Fifteen minutes before each match and at halftime, players from both teams ingested 5 ml/kg of either placebo or a 6.9% GP solution. GP ingestion did not improve tackling, heading, dribbling, or shooting ability. On the contrary, the mean of successful tackles was lower with GP ingestion than with placebo. The success rate for heading, dribbling, and shooting also tended to be lower in the GP than in the placebo condition. In contrast, success in passing and ball control was similar in the two conditions. Improvements in passing and ball control may have been related to a decrease in the intensity of play in the second half of the game. These data indicate that there are no measurable benefits of GP ingestion for the motor skill proficiencies of soccer players during games played in a cool environment.

A short-term, high-fat diet up-regulates lipid metabolism and gene expression in human skeletal muscle

Publisher: Elsevier BV

Date: 02-2003

DOI: 10.1093/AJCN/77.2.313

Abstract: Dietary fatty acids may be important in regulating gene expression. However, little is known about the effect of changes in dietary fatty acids on gene regulation in human skeletal muscle. The objective was to determine the effect of altered dietary fat intake on the expression of genes encoding proteins necessary for fatty acid transport and beta-oxidation in skeletal muscle. Fourteen well-trained male cyclists and triathletes with a mean (+/- SE) age of 26.9 +/- 1.7 y, weight of 73.7 +/- 1.7 kg, and peak oxygen uptake of 67.0 +/- 1.3 mL x kg(-1) x min(-1) consumed either a high-fat diet (HFat: > 65% of energy as lipids) or an isoenergetic high-carbohydrate diet (HCho: 70-75% of energy as carbohydrate) for 5 d in a crossover design. On day 1 (baseline) and again after 5 d of dietary intervention, resting muscle and blood s les were taken. Muscle s les were analyzed for gene expression [fatty acid translocase (FAT/CD36), plasma membrane fatty acid binding protein (FABPpm), carnitine palmitoyltransferase I (CPT I), beta-hydroxyacyl-CoA dehydrogenase (beta-HAD), and uncoupling protein 3 (UCP3)] and concentrations of the proteins FAT/CD36 and FABPpm. The gene expression of FAT/CD36 and beta -HAD and the gene abundance of FAT/CD36 were greater after the HFat than after the HCho diet (P < 0.05). Messenger RNA expression of FABPpm, CPT I, and UCP-3 did not change significantly with either diet. A rapid and marked capacity for changes in dietary fatty acid availability to modulate the expression of mRNA-encoding proteins is necessary for fatty acid transport and oxidative metabolism. This finding is evidence of nutrient-gene interactions in human skeletal muscle.

Pre-exercise carbohydrate and fat ingestion: Effects on metabolism and performance

Publisher: Informa UK Limited

Date: 2004

DOI: 10.1080/0264041031000140536

Abstract: A key goal of pre-exercise nutritional strategies is to maximize carbohydrate stores, thereby minimizing the ergolytic effects of carbohydrate depletion. Increased dietary carbohydrate intake in the days before competition increases muscle glycogen levels and enhances exercise performance in endurance events lasting 90 min or more. Ingestion of carbohydrate 3-4 h before exercise increases liver and muscle glycogen and enhances subsequent endurance exercise performance. The effects of carbohydrate ingestion on blood glucose and free fatty acid concentrations and carbohydrate oxidation during exercise persist for at least 6 h. Although an increase in plasma insulin following carbohydrate ingestion in the hour before exercise inhibits lipolysis and liver glucose output, and can lead to transient hypoglycaemia during subsequent exercise in susceptible in iduals, there is no convincing evidence that this is always associated with impaired exercise performance. However, in idual experience should inform in idual practice. Interventions to increase fat availability before exercise have been shown to reduce carbohydrate utilization during exercise, but do not appear to have ergogenic benefits.

Carbohydrate-Loading and Exercise Performance

Publisher: Springer Science and Business Media LLC

Date: 08-1997

DOI: 10.2165/00007256-199724020-00001

Abstract: This review suggests that there is little or no effect of elevating pre-exercise muscle glycogen contents above normal resting values on a single exhaustive bout of high-intensity exercise lasting less than 5 minutes. Nor is there any benefit of increasing starting muscle glycogen content on moderate-intensity running or cycling lasting 60 to 90 minutes. In such exercise substantial quantities of glycogen remain in the working muscles at the end of exercise. However, elevated starting muscle glycogen content will postpone fatigue by approximately equal to 20% in endurance events lasting more than 90 minutes. During this type of exercise, exhaustion usually coincides with critically low (25 mmol/kg wet weight) muscle glycogen contents, suggesting the supply of energy from glycogen utilisation cannot be replaced by an increased oxidation of blood glucose. Glycogen supercompensation may also improve endurance performance in which a set distance is covered as quickly as possible. In such exercise, high carbohydrate diets have been reported to improve performance by 2 to 3%.

Strategies to enhance fat utilisation during exercise

Publisher: Springer Science and Business Media LLC

Date: 1998

DOI: 10.2165/00007256-199825040-00003

Abstract: Compared with the limited capacity of the human body to store carbohydrate (CHO), endogenous fat depots are large and represent a vast source of fuel for exercise. However, fatty acid (FA) oxidation is limited, especially during intense exercise, and CHO remains the major fuel for oxidative metabolism. In the search for strategies to improve athletic performance, recent interest has focused on several nutritional procedures which may theoretically promote FA oxidation, attenuate the rate of muscle glycogen depletion and improve exercise capacity. In some in iduals the ingestion of caffeine improves endurance capacity, but L-carnitine supplementation has no effect on either rates of FA oxidation, muscle glycogen utilisation or performance. Likewise, the ingestion of small amounts of medium-chain triglyceride (MCT) has no major effect on either fat metabolism or exercise performance. On the other hand, in endurance-trained in iduals, substrate utilisation during submaximal [60% of peak oxygen uptake (VO2peak)] exercise can be altered substantially by the ingestion of a high fat (60 to 70% of energy intake), low CHO (15 to 20% of energy intake) diet for 7 to 10 days. Adaptation to such a diet, however, does not appear to alter the rate of working muscle glycogen utilisation during prolonged, moderate intensity exercise, nor consistently improve performance. At present, there is insufficient scientific evidence to recommend that athletes either ingest fat, in the form of MCTs, during exercise, or "fat-adapt" in the weeks prior to a major endurance event to improve athletic performance.

Interspersed normoxia during live high, train low interventions reverses an early reduction in muscle Na+, K(+)ATPase acitivity in well-trained athletes

Publisher: Springer Science and Business Media LLC

Date: 25-08-2006

DOI: 10.1007/S00421-006-0280-Z

Abstract: Hypoxia and exercise each modulate muscle Na(+), K(+)ATPase activity. We investigated the effects on muscle Na(+), K(+)ATPase activity of only 5 nights of live high, train low hypoxia (LHTL), 20 nights consecutive (LHTLc) versus intermittent LHTL (LHTLi), and acute sprint exercise. Thirty-three athletes were assigned to control (CON, n = 11), 20-nights LHTLc (n = 12) or 20-nights LHTLi (4 x 5-nights LHTL interspersed with 2-nights CON, n = 10) groups. LHTLc and LHTLi slept at a simulated altitude of 2,650 m (F(I)O(2) 0.1627) and lived and trained by day under normoxic conditions CON lived, trained, and slept in normoxia. A quadriceps muscle biopsy was taken at rest and immediately after standardised sprint exercise, before (Pre) and after 5-nights (d5) and 20-nights (Post) LHTL interventions and analysed for Na(+), K(+)ATPase maximal activity (3-O-MFPase) and content ([(3)H]-ouabain binding). After only 5-nights LHTLc, muscle 3-O-MFPase activity declined by 2% (P < 0.05). In LHTLc, 3-O-MFPase activity remained below Pre after 20 nights. In contrast, in LHTLi, this small initial decrease was reversed after 20 nights, with restoration of 3-O-MFPase activity to Pre-intervention levels. Plasma [K(+)] was unaltered by any LHTL. After acute sprint exercise 3-O-MFPase activity was reduced (12.9 +/- 4.0%, P < 0.05), but [(3)H]-ouabain binding was unchanged. In conclusion, maximal Na(+), K(+)ATPase activity declined after only 5-nights LHTL, but the inclusion of additional interspersed normoxic nights reversed this effect, despite athletes receiving the same amount of hypoxic exposure. There were no effects of consecutive or intermittent nightly LHTL on the acute decrease in Na(+), K(+)ATPase activity with sprint exercise effects or on plasma [K(+)] during exercise.

Influence of preexercise muscle glycogen content on transcriptional activity of metabolic and myogenic genes in well-trained humans

Publisher: American Physiological Society

Date: 04-2007

DOI: 10.1152/JAPPLPHYSIOL.01260.2006

Abstract: To determine whether preexercise muscle glycogen content influences the transcription of several early-response genes involved in the regulation of muscle growth, seven male strength-trained subjects performed one-legged cycling exercise to exhaustion to lower muscle glycogen levels (Low) in one leg compared with the leg with normal muscle glycogen (Norm) and then the following day completed a unilateral bout of resistance training (RT). Muscle biopsies from both legs were taken at rest, immediately after RT, and after 3 h of recovery. Resting glycogen content was higher in the control leg (Norm leg) than in the Low leg (435 ± 87 vs. 193 ± 29 mmol/kg dry wt P 0.01). RT decreased glycogen content in both legs ( P 0.05), but postexercise values remained significantly higher in the Norm than the Low leg (312 ± 129 vs. 102 ± 34 mmol/kg dry wt P 0.01). GLUT4 (3-fold P 0.01) and glycogenin mRNA abundance (2.5-fold not significant) were elevated at rest in the Norm leg, but such differences were abolished after exercise. Preexercise mRNA abundance of atrogenes was also higher in the Norm compared with the Low leg [atrogin: ∼14-fold, P 0.01 RING (really interesting novel gene) finger: ∼3-fold, P 0.05] but decreased for atrogin in Norm following RT ( P 0.05). There were no differences in the mRNA abundance of myogenic regulatory factors and IGF-I in the Norm compared with the Low leg. Our results demonstrate that 1) low muscle glycogen content has variable effects on the basal transcription of select metabolic and myogenic genes at rest, and 2) any differences in basal transcription are completely abolished after a single bout of heavy resistance training. We conclude that commencing resistance exercise with low muscle glycogen does not enhance the activity of genes implicated in promoting hypertrophy.

Low muscle glycogen concentration does not suppress the anabolic response to resistance exercise

Publisher: American Physiological Society

Date: 15-07-2012

DOI: 10.1152/JAPPLPHYSIOL.00395.2012

Abstract: We determined the effect of muscle glycogen concentration and postexercise nutrition on anabolic signaling and rates of myofibrillar protein synthesis after resistance exercise (REX). Sixteen young, healthy men matched for age, body mass, peak oxygen uptake (V̇o 2peak ) and strength (one repetition maximum 1RM) were randomly assigned to either a nutrient or placebo group. After 48 h diet and exercise control, subjects undertook a glycogen-depletion protocol consisting of one-leg cycling to fatigue (LOW), whereas the other leg rested (NORM). The next morning following an overnight fast, a primed, constant infusion of l-[ ring- 13 C 6 ] phenylalanine was commenced and subjects completed 8 sets of 5 unilateral leg press repetitions at 80% 1RM. Immediately after REX and 2 h later, subjects consumed a 500 ml bolus of a protein/CHO (20 g whey + 40 g maltodextrin) or placebo beverage. Muscle biopsies from the vastus lateralis of both legs were taken at rest and 1 and 4 h after REX. Muscle glycogen concentration was higher in the NORM than LOW at all time points in both nutrient and placebo groups ( P 0.05). Postexercise Akt-p70S6K-rpS6 phosphorylation increased in both groups with no differences between legs ( P 0.05). mTOR Ser2448 phosphorylation in placebo increased 1 h after exercise in NORM ( P 0.05), whereas mTOR increased ∼4-fold in LOW ( P 0.01) and ∼11 fold in NORM with nutrient ( P 0.01 different between legs P 0.05). Post-exercise rates of MPS were not different between NORM and LOW in nutrient (0.070 ± 0.022 vs. 0.068 ± 0.018 %/h) or placebo (0.045 ± 0.021 vs. 0.049 ± 0.017 %/h). We conclude that commencing high-intensity REX with low muscle glycogen availability does not compromise the anabolic signal and subsequent rates of MPS, at least during the early (4 h) postexercise recovery period.

The Effect of Exercise on the Skeletal Muscle Phospholipidome of Rats Fed a High-Fat Diet

Publisher: MDPI AG

Date: 15-10-2010

DOI: 10.3390/IJMS11103954

Protein ingestion increases myofibrillar protein synthesis after concurrent exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 2015

DOI: 10.1249/MSS.0000000000000390

Effect Of Training On Activation Of Extracellular Signal‐Regulated Kinase 1/2 And P38 Mitogen‐Activated Protein Kinase Pathways In Rat Soleus Muscle

Publisher: Wiley

Date: 03-07-2002

DOI: 10.1046/J.1440-1681.2002.03713.X

Abstract: 1. The effect of a chronic programme of either low- or moderate-to-high-intensity treadmill running on the activation of the extracellular-signal regulated protein kinase (ERK1/2) and the p38 mitogen-activated protein kinase (MAPK) pathways was determined in rat muscle. 2. Sprague-Dawley rats were assigned to one of three groups: (i) sedentary (NT n = 8) (ii) low-intensity training (8 m/min LIT n = 16) and (iii) moderate-to-high-intensity training (28 m/min HIT n = 16). The training regimens were planned so that animals covered the same distance and had similar glycogen utilization for both LIT and HIT exercise sessions. 3. A single bout of LIT or HIT following 8 weeks of training led to a twofold increase in the phosphorylation of ERK1/2 (P = 0.048) and a two- to threefold increase in p38 MAPK (P = 0.005). Extracellular signal-regulated kinase 1/2 phosphorylation in muscle s led 48 h after the last exercise bout was similar to sedentary values, while p38 MAPK phosphorylation was 70-80% lower than sedentary. One bout of LIT or HIT increased total ERK1/2 and p38 MAPK expression, with the magnitude of this increase being independent of prior exercise intensity or duration. Extracellular signal- regulated kinase 1/2 expression was increased three- to fourfold in muscle s led 48 h after the last exercise bout irrespective of the prior training programme (P = 0.027), but p38 MAPK expression was approximately 90% lower than sedentary values. 4. In conclusion, exercise-training of different intensities/ durations results in selective postexercise activation of intracellular signalling pathways, which may be one mechanism regulating specific adaptations induced by erse training programmes.

Discordant gene expression in skeletal muscle and adipose tissue of patients with type 2 diabetes: effect of interleukin-6 infusion

Publisher: Springer Science and Business Media LLC

Date: 15-03-2006

DOI: 10.1007/S00125-006-0178-7

Abstract: We compared metabolic gene expression in adipose tissue and skeletal muscle from patients with type 2 diabetes and from well-matched healthy control subjects. We hypothesised that gene expression would be discordantly regulated when comparing the two groups. Our secondary aim was to determine the effect of Interleukin-6 (IL6) infusion on circulating adipokines and on gene expression in human adipose tissue. To do this we used real-time RT-PCR. Both diabetic and control subjects underwent basal skeletal muscle and subcutaneous adipose tissue biopsies. A subset of these in iduals underwent a 3-h infusion of recombinant human IL6 and had adipose tissue s les taken before and after infusion. The mRNA gene expression of suppressor of cytokine signalling (SOCS) 3, peroxisome proliferative activated receptor (PPAR) alpha/delta, PPAR gamma, coactivator 1, alpha (PPARGC1A), carnitine palmitoyltransferase 1B and solute carrier family 2 (facilitated glucose transporter), member 4 (formerly known as glucose transporter 4/GLUT4), was higher in adipose tissue, but lower in skeletal muscle of diabetic patients than in that of control subjects. In addition, uncoupling protein 1 (UCP1) gene was detected in the adipose tissue of some of the diabetic patients, but not in the control subjects. The following genes were increased by infusion of recombinant human IL6 in both groups: SOCS1/3, resistin, adiponectin, AMP-activated protein kinase-alpha-1 and PPARA. Plasma tumour necrosis factor alpha, adiponectin and resistin were all unaffected by IL6 infusion, but plasma resistin was lower in the diabetic subjects than in control subjects. The observation that PPARGC1A and the PPARs were upregulated in the adipose tissue of type 2 diabetic patients, along with the finding that adipose tissue from some patients with type 2 diabetes can express UCP1 mRNA, suggests that in these patients white adipose tissue may move towards a brown adipose tissue phenotype.

What's new since Hippocrates? Preventing type 2 diabetes by physical exercise and diet

Publisher: Springer Science and Business Media LLC

Date: 21-01-2012

DOI: 10.1007/S00125-012-2460-1

Abstract: Since the work of Eriksson and Lindgärde, published over two decades ago (Diabetologia 1991 :891-898), we have known that type 2 diabetes can be prevented or delayed by supervised lifestyle interventions (physical exercise and diet modification) in persons at risk of the disease. Here we discuss a novel, time-efficient approach to physical exercise prescription, low-volume, high-intensity interval training (LVHIT), and its efficacy for inducing a range of health benefits in a variety of populations at risk of inactivity-related diseases. We look to the future and suggest that current guidelines for exercise may need to be revised to include different training techniques to deliver the optimum exercise prescription. Indeed, we predict that subsequent exercise guidelines will include LVHIT as part of a comprehensive 'fitness menu' that allows in iduals to select the exercise regimen that best fulfils their medical needs, is suited to their lifestyle and daily time restraints, and meets their personal goals.

Maternal Lifestyle Interventions: Targeting Preconception Health

Publisher: Elsevier BV

Date: 08-2020

DOI: 10.1016/J.TEM.2020.03.002

Training Techniques for Successful Running Performance

Publisher: Wiley

Date: 2008

DOI: 10.1002/9780470757116.CH4

Postexercise muscle triacylglycerol and glycogen metabolism in obese insulin-resistant zucker rats

Publisher: Wiley

Date: 07-2004

DOI: 10.1038/OBY.2004.145

Abstract: To determine the impact of insulin resistance and obesity on muscle triacylglycerol (IMTG) and glycogen metabolism during and after prolonged exercise. Female lean (fa/? N = 40, ZL) and obese insulin-resistant (fa/fa N = 40, ZO) Zucker rats performed an acute bout of swimming exercise (8 times for 30 minutes) followed by 6 hours of carbohydrate supplementation (CHO) or fasting (FAST). IMTG and glycogen were measured in the extensor digitorum longus (EDL) and red vastus lateralis (RVL) muscles. Despite resting IMTG content being 4-fold higher in ZO compared with ZL rats, IMTG levels were unchanged in either EDL or RVL muscles immediately after exercise. Resting glycogen concentration in EDL and RVL muscles was similar between genotypes, with exercise resulting in glycogen use in both muscles from ZL rats (approximately 85%, p < 0.05). However, in ZO rats, there was a much smaller decrease in postexercise glycogen content in both EDL and RVL muscles (approximately 30%). During postexercise recovery, there was a decrease in EDL muscle levels of IMTG in ZL rats supplemented with CHO after 30 and 360 minutes (p < 0.05). In contrast, IMTG content was increased above resting levels in RVL muscles of ZO rats fasted for 360 minutes. Six hours of CHO refeeding restored glycogen content to resting levels in both muscles in ZL rats. However, after 6 hours of FAST in ZO animals, RVL muscle glycogen content was still lower than resting levels (p < 0.05). At this time, IMTG levels were elevated above basal (p < 0.05). In both healthy and insulin-resistant skeletal muscle, there was negligible net IMTG degradation after a single bout of prolonged exercise. However, during postexercise recovery, there was differential metabolism of IMTG between phenotypes.

Exogenous starch oxidation using 14C labeling

Publisher: American Physiological Society

Date: 12-1992

DOI: 10.1152/JAPPL.1992.73.6.2719

Exercise training-induced improvements in insulin action

Publisher: Wiley

Date: 29-10-2008

DOI: 10.1111/J.1748-1716.2007.01783.X

Abstract: In iduals with insulin resistance are characterized by impaired insulin action on whole-body glucose uptake, in part due to impaired insulin-stimulated glucose uptake into skeletal muscle. A single bout of exercise increases skeletal muscle glucose uptake via an insulin-independent mechanism that bypasses the typical insulin signalling defects associated with these conditions. However, this 'insulin sensitizing' effect is short-lived and disappears after approximately 48 h. In contrast, repeated physical activity (i.e. exercise training) results in a persistent increase in insulin action in skeletal muscle from obese and insulin-resistant in iduals. The molecular mechanism(s) for the enhanced glucose uptake with exercise training have been attributed to the increased expression and/or activity of key signalling proteins involved in the regulation of glucose uptake and metabolism in skeletal muscle. Evidence now suggests that the improvements in insulin sensitivity associated with exercise training are also related to changes in the expression and/or activity of proteins involved in insulin signal transduction in skeletal muscle such as the AMP-activated protein kinase (AMPK) and the protein kinase B (Akt) substrate AS160. In addition, increased lipid oxidation and/or turnover is likely to be another mechanism by which exercise improves insulin sensitivity: exercise training results in an increase in the oxidative capacity of skeletal muscle by up-regulating lipid oxidation and the expression of proteins involved in mitochondrial biogenesis. Determination of the underlying biological mechanisms that result from exercise training is essential in order to define the precise variations in physical activity that result in the most desired effects on targeted risk factors, and to aid in the development of such interventions.

Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers

Publisher: Wiley

Date: 14-02-2017

DOI: 10.1113/JP273230

Enhanced Endurance Performance by Periodization of Carbohydrate Intake

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 04-2016

DOI: 10.1249/MSS.0000000000000823

Exercise: it's the real thing!

Publisher: Oxford University Press (OUP)

Date: 03-2009

DOI: 10.1111/J.1753-4887.2009.00185.X

Abstract: The epidemic emergence of modern chronic diseases largely stems from the adoption of a sedentary lifestyle and excess energy intake. However, it has long been known that regular physical activity induces multiple adaptations within skeletal muscle and other organs and these adaptations have positive outcomes for the prevention and treatment of many metabolic disorders. In recognition of such benefits, a recent goal of industry-funded research is to discover orally active compounds that mimic the effects of exercise training, so-called "exercise pills". This article provides an overview of the role of skeletal muscle in health and disease and discusses whether "exercise mimetics" have any potential to combat metabolic diseases.

Nutrient provision increases signalling and protein synthesis in human skeletal muscle after repeated sprints

Publisher: Springer Science and Business Media LLC

Date: 17-12-2010

DOI: 10.1007/S00421-010-1768-0

Abstract: The effect of nutrient availability on the acute molecular responses following repeated sprint exercise is unknown. The aim of this study was to determine skeletal muscle cellular and protein synthetic responses following repeated sprint exercise with nutrient provision. Eight healthy young male subjects undertook two sprint cycling sessions (10 × 6 s, 0.75 N m torque kg(-1), 54 s recovery) with either pre-exercise nutrient (24 g whey, 4.8 g leucine, 50 g maltodextrin) or non-caloric placebo ingestion. Muscle biopsies were taken from vastus lateralis at rest, and after 15 and 240 min post-exercise recovery to determine muscle cell signalling responses and protein synthesis by primed constant infusion of L: -[ring-(13)C(6)] phenylalanine. Peak and mean power outputs were similar between nutrient and placebo trials. Post-exercise myofibrillar protein synthetic rate was greater with nutrient ingestion compared with placebo (~48%, P < 0.05) but the rate of mitochondrial protein synthesis was similar between treatments. The increased myofibrillar protein synthesis following sprints with nutrient ingestion was associated with coordinated increases in Akt-mTOR-S6K-rpS6 phosphorylation 15 min post-exercise (~200-600%, P < 0.05), while there was no effect on these signalling molecules when exercise was undertaken in the fasted state. For the first time we report a beneficial effect of nutrient provision on anabolic signalling and muscle myofibrillar protein synthesis following repeated sprint exercise. Ingestion of protein/carbohydrate in close proximity to high-intensity sprint exercise provides an environment that increases cell signalling and protein synthesis.

High rates of exogenous carbohydrate oxidation from starch ingested during prolonged exercise

Publisher: American Physiological Society

Date: 11-1991

DOI: 10.1152/JAPPL.1991.71.5.1801

Abstract: This study compared the gastric emptying and oxidation of two 15% carbohydrate (CHO) solutions: a 22-chain-length glucose polymer (GP) and soluble starch (SS). Six endurance-trained subjects ingested 1,200 ml of either GP or SS while cycling for 90 min at 70% of maximal oxygen consumption (VO2max). Whereas the calculated total CHO oxidation (GP 266.8 +/- 41.9 g SS 263.6 +/- 28.9 g) and the volume emptied from the stomach (GP 813 +/- 130 ml SS 919 +/- 116 ml) were similar, the appearance of the 14C label in plasma occurred more rapidly from ingested SS than from GP (P less than 0.001). This resulted in a significantly greater rate of SS oxidation than that from GP (SS 105.9 +/- 21.9 g, GP 49.6 +/- 10.2 g P less than 0.001). Exogenous CHO oxidation from GP accounted for 19% of total CHO oxidation, whereas the corresponding value for SS was 40%. This study suggests that the oxidation of SS and GP solutions ingested during exercise at 70% VO2max is not limited by gastric emptying. Rather, it appears to be either the rate of digestion or absorption of these solutions that determines their utilization.

High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine

Publisher: American Physiological Society

Date: 07-2008

DOI: 10.1152/JAPPLPHYSIOL.01121.2007

Abstract: We determined the effect of coingestion of caffeine (Caff) with carbohydrate (CHO) on rates of muscle glycogen resynthesis during recovery from exhaustive exercise in seven trained subjects who completed two experimental trials in a randomized, double-blind crossover design. The evening before an experiment subjects performed intermittent exhaustive cycling and then consumed a low-CHO meal. The next morning subjects rode until volitional fatigue. On completion of this ride subjects consumed either CHO [4 g/kg body mass (BM)] or the same amount of CHO + Caff (8 mg/kg BM) during 4 h of passive recovery. Muscle biopsies and blood s les were taken at regular intervals throughout recovery. Muscle glycogen levels were similar at exhaustion [∼75 mmol/kg dry wt (dw)] and increased by a similar amount (∼80%) after 1 h of recovery (133 ± 37.8 vs. 149 ± 48 mmol/kg dw for CHO and Caff, respectively). After 4 h of recovery Caff resulted in higher glycogen accumulation (313 ± 69 vs. 234 ± 50 mmol/kg dw, P 0.001). Accordingly, the overall rate of resynthesis for the 4-h recovery period was 66% higher in Caff compared with CHO (57.7 ± 18.5 vs. 38.0 ± 7.7 mmol·kg dw −1 ·h −1 , P 0.05). After 1 h of recovery plasma Caff levels had increased to 31 ± 11 μM ( P 0.001) and at the end of the recovery reached 77 ± 11 μM ( P 0.001) with Caff. Phosphorylation of CaMK Thr286 was similar after exercise and after 1 h of recovery, but after 4 h CaMK Thr286 phosphorylation was higher in Caff than CHO ( P 0.05). Phosphorylation of AMP-activated protein kinase (AMPK) Thr172 and Akt Ser473 was similar for both treatments at all time points. We provide the first evidence that in trained subjects coingestion of large amounts of Caff (8 mg/kg BM) with CHO has an additive effect on rates of postexercise muscle glycogen accumulation compared with consumption of CHO alone.

Molecular basis of exercise-induced skeletal muscle mitochondrial biogenesis: Historical advances, current knowledge, and future challenges

Publisher: Cold Spring Harbor Laboratory

Date: 15-05-2018

DOI: 10.1101/CSHPERSPECT.A029686

Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling

Publisher: American Physiological Society

Date: 07-2010

DOI: 10.1152/JAPPLPHYSIOL.00950.2009

Abstract: We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group n = 8) or an energy-matched low-carbohydrate group (Low group n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 μmol·g −1 ·min −1 , P 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g ( P 0.01) in the High group with no change in the Low group. Cycling performance improved by ∼6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance.

Expression of microRNAs and target proteins in skeletal muscle of rats selectively bred for high and low running capacity

Publisher: American Physiological Society

Date: 09-2017

DOI: 10.1152/AJPENDO.00043.2017

Abstract: Impairments in mitochondrial function and substrate metabolism are implicated in the etiology of obesity and Type 2 diabetes. MicroRNAs (miRNAs) can degrade mRNA or repress protein translation and have been implicated in the development of such disorders. We used a contrasting rat model system of selectively bred high- (HCR) or low- (LCR) intrinsic running capacity with established differences in metabolic health to investigate the molecular mechanisms through which miRNAs regulate target proteins mediating mitochondrial function and substrate oxidation processes. Quantification of select miRNAs using the rat miFinder miRNA PCR array revealed differential expression of 15 skeletal muscles (musculus tibialis anterior) miRNAs between HCR and LCR rats (14 with higher expression in LCR P 0.05). Ingenuity Pathway Analysis predicted these altered miRNAs to collectively target multiple proteins implicated in mitochondrial dysfunction and energy substrate metabolism. Total protein abundance of citrate synthase (CS miR-19 target) and voltage-dependent anion channel 1 (miR-7a target) were higher in HCR compared with LCR cohorts (~57 and ~26%, respectively P 0.05). A negative correlation was observed for miR-19a-3p and CS ( r = 0.32, P = 0.015) protein expression. To determine whether miR-19a-3p can regulate CS in vitro, we performed luciferase reporter and transfection assays in C2C12 myotubes. MiR-19a-3p binding to the CS untranslated region did not change luciferase reporter activity however, miR-19a-3p transfection decreased CS protein expression (∼70% P 0.05). The differential miRNA expression targeting proteins implicated in mitochondrial dysfunction and energy substrate metabolism may contribute to the molecular basis, mediating the ergent metabolic health profiles of LCR and HCR rats.

Skeletal Muscle Adaptive Responses to Different Types of Short-Term Exercise Training and Detraining in Middle-Age Men

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 16-04-2021

DOI: 10.1249/MSS.0000000000002684

Abstract: Whether short-term, single-mode exercise training can improve physical fitness before a period of reduced physical activity (e.g., postsurgery recovery) is not well characterized in clinical populations or middle-age adults. We investigated skeletal muscle adaptive responses after endurance exercise training (ENT), high-intensity interval training (HIIT), or resistance exercise training (RET), and a subsequent period of detraining, in sedentary, middle-age men. Thirty-five sedentary men (39 ± 3 yr) were randomized to parallel groups and undertook 6 wk of either ENT ( n = 12), HIIT ( n = 12), or RET ( n = 11) followed by 2.5 wk of detraining. Skeletal muscle fiber characteristics, body composition, muscle thickness, muscle strength, aerobic capacity, resting energy expenditure, and glucose homeostasis were assessed at baseline, and after exercise training and detraining. Lean mass increased after RET and HIIT (+3.2% ± 1.6% and +1.6% ± 2.1%, P 0.05). Muscle strength (sum of leg press, leg extension, and bench press one-repetition maximums) increased after all training interventions (RET, +25% ± 5% HIIT, +10% ± 5% ENT, +7% ± 7% P 0.05). Aerobic capacity increased only after HIIT and ENT (+14% ± 7% and +11% ± 11%, P 0.05). Type I and II muscle fiber size increased for all groups after training (main effect of time, P 0.05). After a period of detraining, the gains in lean mass and maximal muscle strength were maintained in the RET and HIIT groups, but maximal aerobic capacity declined below posttraining levels in HIIT and ENT ( P 0.05). Six weeks of HIIT induced widespread adaptations before detraining in middle-age men. Exercise training–induced increases in aerobic capacity declined during 2.5 wk of detraining, but gains in lean mass and muscle strength were maintained.

Effect of fat adaptation and carbohydrate restoration on metabolism and performance during prolonged cycling

Publisher: American Physiological Society

Date: 12-2000

DOI: 10.1152/JAPPL.2000.89.6.2413

Abstract: For 5 days, eight well-trained cyclists consumed a random order of a high-carbohydrate (CHO) diet (9.6 g · kg −1 · day −1 CHO, 0.7 g · kg −1 · day −1 fat HCHO) or an isoenergetic high-fat diet (2.4 g · kg −1 · day −1 CHO, 4 g · kg −1 · day −1 fat Fat-adapt) while undertaking supervised training. On day 6,subjects ingested high CHO and rested before performance testing on day 7 [2 h cycling at 70% maximal O 2 consumption (SS) + 7 kJ/kg time trial (TT)]. With Fat-adapt, 5 days of high-fat diet reduced respiratory exchange ratio (RER) during cycling at 70% maximal O 2 consumption this was partially restored by 1 day of high CHO [0.90 ± 0.01 vs. 0.82 ± 0.01 ( P 0.05) vs. 0.87 ± 0.01 ( P 0.05), for day 1, day 6, and day 7, respectively]. Corresponding RER values on HCHO trial were [0.91 ± 0.01 vs. 0.88 ± 0.01 ( P 0.05) vs. 0.93 ± 0.01 ( P 0.05)]. During SS, estimated fat oxidation increased [94 ± 6 vs. 61 ± 5 g ( P 0.05)], whereas CHO oxidation decreased [271 ± 16 vs. 342 ± 14 g ( P 0.05)] for Fat-adapt compared with HCHO. Tracer-derived estimates of plasma glucose uptake revealed no differences between treatments, suggesting muscle glycogen sparing accounted for reduced CHO oxidation. Direct assessment of muscle glycogen utilization showed a similar order of sparing (260 ± 26 vs. 360 ± 43 mmol/kg dry wt P = 0.06). TT performance was 30.73 ± 1.12 vs. 34.17 ± 2.48 min for Fat-adapt and HCHO ( P = 0.21). These data show significant metabolic adaptations with a brief period of high-fat intake, which persist even after restoration of CHO availability. However, there was no evidence of a clear benefit of fat adaptation to cycling performance.

Effects of a task-specific warm-up on anaerobic power

Publisher: BMJ

Date: 12-1989

DOI: 10.1136/BJSM.23.4.233

Abstract: Twenty-four untrained (UT) males (age 21 +/- 2.5 yr, height 1.77 +/- 0.05 m, weight 75.3 +/- 10.1 kg, values mean +/- SD) performed the Wingate Anaerobic Test (WT) under two conditions, cold (C) and following a warm-up (WU). Trials were separated by a minimum of 48 h. A modified Monark 818 cycle ergometer was interfaced with an Apple IIE microcomputer and peak power (PEAK), mean power (MEAN) and fatigue index (FI) determined. The WU trial consisted of an 8 min incremental continuous cycling bout (cadence 90 rev.min-1) with 5 min rest before the WT. During the C trial subjects completed only the WT. A repeated measures design was employed with order of trials counterbalanced. ANOVA revealed no significant differences for PEAK or MEAN between WU or C conditions. However FI was significantly greater (p less than 0.05) following the WU. A significant correlation (r = 0.45, p = 0.03) was obtained between WU intensity and FI. These findings suggest that our UT subjects were fatiguing themselves during the WU. Future studies are needed to assess whether a task-specific WU in which FI is not impaired would lead to improvements in PEAK and MEAN. Investigators should be aware that a self-spaced WU may increase FI in the WT in UT subjects.

Improved athletic performance in highly trained cyclists after interval training

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 11-1996

DOI: 10.1097/00005768-199611000-00013

Abstract: This study determined whether a 4-wk high-intensity interval training program (HIT) would improve the 40-km time trial performances (TT40) of 8 competitive cyclists (peak O2 uptake 5.2 +/- 0.4 I.min-1) with a background of moderate-intensity endurance training (BASE). Before intervention, all cyclists were tested on at least three separate occasions to ensure that their baseline performances were stable. In these tests, peak sustained power output (PPO) was measured during a progressive exercise test, muscular resistance to fatigue was determined during a timed ride to exhaustion at 150% of PPO (TF150), and a TT40 was performed on a cycle-simulator. The coefficient of variation for all baseline tests was < 1.7 +/- 1.3% (mean +/- SD). Cyclists then replaced 15 +/- 2% of their approximately 300 km.wk-1 BASE training with HIT, which took place on 6 d and consisted of six to eight 5-min repetitions at 80% of PPO, with 60-s recovery between work bouts. HIT significantly improved TT40 (56.4 +/- 3.6 vs 54.4 +/- 3.2 min P < 0.0001), PPO (416 +/- 32 vs 434 +/- 34 W P < 0.01) and TF150 (60.5 +/- 9.3 vs 72.5 +/- 7.6 s P < 0.01). The faster TT40 was due to a significant increase in both the cyclists' absolute (301 +/- 42 vs 326 +/- 43 W P < 0.0001) and relative (72.1 +/- 5.6 vs 75.0 +/- 6.8% of PPO P < 0.05) power output after HIT. These results indicate that a 4-wk program of HIT increased the PPO and fatigue resistance of competitive cyclists and improved their 40-km time trial performances.

Motorcycle emergency steering assistance: A systematic approach from system definition to benefit estimation and exploratory field testing

Publisher: Elsevier BV

Date: 08-2023

DOI: 10.1016/J.AAP.2023.107116

Circulating MicroRNA Responses between ‘High’ and ‘Low’ Responders to a 16-Wk Diet and Exercise Weight Loss Intervention

Publisher: Public Library of Science (PLoS)

Date: 21-04-2016

DOI: 10.1371/JOURNAL.PONE.0152545

Acute low-intensity cycling with blood-flow restriction has no effect on metabolic signaling in human skeletal muscle compared to traditional exercise

Publisher: Springer Science and Business Media LLC

Date: 25-01-2017

DOI: 10.1007/S00421-016-3530-8

Abstract: Autophagy is an intracellular degradative system sensitive to hypoxia and exercise-induced perturbations to cellular bioenergetics. We determined the effects of low-intensity endurance-based exercise performed with blood-flow restriction (BFR) on cell signaling adaptive responses regulating autophagy and substrate metabolism in human skeletal muscle. In a randomized cross-over design, nine young, healthy but physically inactive males completed three experimental trials separated by 1 week of recovery consisting of either a resistance exercise bout (REX: 4 × 10 leg press repetitions, 70% 1-RM), endurance exercise (END: 30 min cycling, 70% VO END increased ULK1 A single bout of low-intensity cycling with BFR is insufficient to induce intracellular "stress" responses (e.g., high rates of substrate turnover and local hypoxia) necessary to activate skeletal muscle autophagy signaling.

SnapShot: Exercise Metabolism

Publisher: Elsevier BV

Date: 08-2016

DOI: 10.1016/J.CMET.2016.07.013

Abstract: Exercise represents a major challenge to whole-body homeostasis. To meet this challenge, myriad acute and adaptive responses take place at multiple cellular and systemic levels. The molecular bases of skeletal muscle adaptations to exercise are mediated by an array of signaling events, pre- and post-transcriptional processes, regulation of translation, and ultimately the increased abundance and/or maximal activity of key proteins with roles in energy provision.

Effects of medium-chain triglyceride ingestion on fuel metabolism and cycling performance

Publisher: American Physiological Society

Date: 06-1996

DOI: 10.1152/JAPPL.1996.80.6.2217

Abstract: On three occasions separated by 10 days, six endurance-trained cyclists rode for 2 h at 60% of peak O2 uptake and then performed a simulated 40-km time trial (T-trial). During the rides, the subjects ingested a total of 2 liters of a [U-14C]glucose-labeled beverage containing a random order of either 10% glucose [carbohydrate (CHO)], 4.3% medium-chain triglycerides (MCTs) or 10% glucose + 4.3% MCTs (CHO+MCT). Although replacing CHO with MCTs slowed the T-trials from 66.8 +/- 0.4 (SE) to 72.1 +/- 0.6 min (P 0.001), adding MCTs to CHO improved the T-trials from 66.8 +/- 0.4 to 65.1 +/- 0.5 min (P 0.05). Faster T-trials in the CHO+MCT trial than in the CHO trial were associated with increased final circulating concentrations of free fatty acids (0.58 +/- 0.09 vs. 0.36 +/- 0.06 mmol/l P 0.05) and ketones (1.51 +/- 0.25 vs. 0.51 +/- 0.07 mmol/l P 0.01) and decreased final circulating concentrations of glucose (5.2 +/- 0.2 vs. 6.3 +/- 0.3 mmol/l P 0.01) and lactate (1.9 +/- 0.4 vs. 3.7 +/- 0.5 mmol/l P 0.05). Adding MCTs to ingested CHO reduced total CHO oxidation rates from 14 +/- 1 to 10 +/- 1 mmol/min at 2 h and from 17 +/- 1 to 14 +/- 1 mmol/min in the T-trial (P 0.01), without affecting the corresponding approximately 5 and approximately 7 mmol/min rates of [14C]glucose oxidation. These data suggest that MCT oxidation decreased the direct and/or indirect (via lactate) oxidation of muscle glycogen. A reduced reliance on CHO oxidation at a given O2 uptake is similar to an endurance-training effect, and that may explain the improved T-trial performances.

Overweight and obesity in Australia

Publisher: AMPCo

Date: 06-2008

DOI: 10.5694/J.1326-5377.2008.TB01835.X

Skeletal Muscle Fiber Type: Influence on Contractile and Metabolic Properties

Publisher: Public Library of Science (PLoS)

Date: 12-10-2004

DOI: 10.1371/JOURNAL.PBIO.0020348

The Effects of Carbohydrate Loading on Muscle Glycogen Content and Cycling Performance

Publisher: Human Kinetics

Date: 03-1995

DOI: 10.1123/IJSN.5.1.25

Abstract: This study compared the effects of supplementing the normal diets of 8 endurance-trained cyclists with additional carbohydrate (CHO), in the form of potato starch, for 3 days on muscle glycogen utilization and performance during a 3-hr cycle ride. On two occasions prior to the trial, the subjects ingested in random order either their normal CHO intake of 6.15 ± 0.23 g/kg body mass/day or a high-CHO diet of 10.52 ± 0.57 g/kg body mass/day. The trial consisted of 2 hr of cycling at ~75% of with five 60-s sprints at 100% at 20-min intervals, followed by a 60-min performance ride. Increasing CHO intake by 72 ± 9% for 3 days prior to the trial elevated preexercise muscle glycogen contents, improved power output, and extended the distance covered in 1 hr. Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.

Editorial: Cross Adaptation and Cross Tolerance in Human Health and Disease

Publisher: Frontiers Media SA

Date: 08-01-2019

DOI: 10.3389/FPHYS.2018.01827

Selective Modulation of MicroRNA Expression with Protein Ingestion Following Concurrent Resistance and Endurance Exercise in Human Skeletal Muscle

Publisher: Frontiers Media SA

Date: 07-03-2016

DOI: 10.3389/FPHYS.2016.00087

Genes, Exercise, and Glucose and Insulin Metabolism

Publisher: Wiley

Date: 25-11-2010

DOI: 10.1002/9781444327335.CH21

It's all in the genes, so pick your parents wisely

Publisher: American Physiological Society

Date: 06-2006

DOI: 10.1152/JAPPLPHYSIOL.00150.2006

Innovations in athletic preparation: role of substrate availability to modify training adaptation and performance

Publisher: Informa UK Limited

Date: 12-2007

DOI: 10.1080/02640410701607411

Abstract: World records for athletic events continue to improve and in the search for superior methods to gain a competitive edge, coaches and athletes are constantly searching for the latest "magic bullet". Although it is assumed that optimal adaptation to the demands of repeated training sessions requires a diet that can sustain muscle energy reserves, this premise does not consider the unsolved longstanding question of whether it is a lack or a surplus of a substrate that triggers the training adaptation. As such, recent scientific enquiry has re-focused attention on the role of substrate availability before, during, and after training to lify the training adaptation. There has also been a resurgence of interest in the potential for protein ingestion to improve performance and/or promote training-induced adaptations in skeletal muscle. Altitude training (real or simulated) is now an accepted part of competition preparation for many athletic events, and such interventions attract their own nutritional issues. These and other diet-training interactions with the potential to alter training adaptation and performance are discussed.

Specificity of training adaptation: time for a rethink?

Publisher: Wiley

Date: 2008

DOI: 10.1113/JPHYSIOL.2007.147397

Oxidative stress-induced insulin resistance in skeletal muscle cells is ameliorated by gamma-tocopherol treatment

Publisher: Springer Science and Business Media LLC

Date: 18-09-2008

DOI: 10.1007/S00394-008-0739-2

Abstract: Oxidative stress-induced reactive oxygen species are associated with the clinical manifestation of insulin resistance. Evidence suggests that antioxidant treatment may reduce this incidence. This study determined whether glucose oxidase (GO)-induced insulin resistance in cultured skeletal muscle cells could be ameliorated by pre-treatment with gamma-tocopherol (GT). Insulin sensitivity in L6 myotubes was assessed by 2-deoxy-D: -[(3)H]-glucose uptake. The phosphorylation of distal insulin signaling proteins Akt and the Akt substrate AS160 were determined by western blot. One hour treatment with 100 mU/ml GO decreased insulin-stimulated glucose uptake (P < 0.001). Pre-treatment with GT either partially (100 microM) or completely (200 microM) restored insulin-stimulated glucose uptake in cells after GO-induced insulin resistance. GO-induced oxidative stress did not impair insulin stimulated phosphorylation of Akt or AS160, but 200 microM GT increased insulin-stimulated phosphorylation of these key signaling proteins (P < 0.05). High-dose (200 microM) GT treatment ameliorated oxidative stress-induced insulin resistance in cultured rat L6 skeletal muscle cells.

Fat Metabolism

Publisher: Wiley

Date: 14-09-2011

DOI: 10.1002/9781444344905.CH6

Body mass index and complications following major gastrointestinal surgery: a prospective, international cohort study and meta‐analysis

Publisher: Wiley

Date: 09-07-2018

DOI: 10.1111/CODI.14292

Abstract: Previous studies reported conflicting evidence on the effects of obesity on outcomes after gastrointestinal surgery. The aims of this study were to explore the relationship of obesity with major postoperative complications in an international cohort and to present a meta-analysis of all available prospective data. This prospective, multicentre study included adults undergoing both elective and emergency gastrointestinal resection, reversal of stoma or formation of stoma. The primary end-point was 30-day major complications (Clavien-Dindo Grades III-V). A systematic search was undertaken for studies assessing the relationship between obesity and major complications after gastrointestinal surgery. In idual patient meta-analysis was used to analyse pooled results. This study included 2519 patients across 127 centres, of whom 560 (22.2%) were obese. Unadjusted major complication rates were lower in obese vs normal weight patients (13.0% vs 16.2%, respectively), but this did not reach statistical significance (P = 0.863) on multivariate analysis for patients having surgery for either malignant or benign conditions. In idual patient meta-analysis demonstrated that obese patients undergoing surgery for malignancy were at increased risk of major complications (OR 2.10, 95% CI 1.49-2.96, P < 0.001), whereas obese patients undergoing surgery for benign indications were at decreased risk (OR 0.59, 95% CI 0.46-0.75, P < 0.001) compared to normal weight patients. In our international data, obesity was not found to be associated with major complications following gastrointestinal surgery. Meta-analysis of available prospective data made a novel finding of obesity being associated with different outcomes depending on whether patients were undergoing surgery for benign or malignant disease.

The molecular athlete: exercise physiology from mechanisms to medals

Publisher: American Physiological Society

Date: 07-2023

DOI: 10.1152/PHYSREV.00017.2022

Abstract: Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive in iduals with low levels of endurance and strength to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation, and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a “trial-and-error” approach, with the experience and practices of successful coaches and athletes often providing the bases for “post hoc” scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and interin idual differences in exercise capacity and performance, with special consideration given to aging athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise and how such adaptations translate from “molecules to medals.”

Physiological adaptations to low‐volume, high‐intensity interval training in health and disease

Publisher: Wiley

Date: 03-2012

DOI: 10.1113/JPHYSIOL.2011.224725

Hypoenergetic diet-induced reductions in myofibrillar protein synthesis are restored with resistance training and balanced daily protein ingestion in older men

Publisher: American Physiological Society

Date: 05-2015

DOI: 10.1152/AJPENDO.00550.2014

Abstract: Strategies to enhance weight loss with a high fat-to-lean ratio in overweight/obese older adults are important since lean loss could exacerbate sarcopenia. We examined how dietary protein distribution affected muscle protein synthesis during energy balance (EB), energy restriction (ER), and energy restriction plus resistance training (ER + RT). A 4-wk ER diet was provided to overweight/obese older men (66 ± 4 yr, 31 ± 5 kg/m 2 ) who were randomized to either a balanced (BAL: 25% daily protein/meal × 4) or skewed (SKEW: 7:17:72:4% daily protein/meal n = 10/group) pattern. Myofibrillar and sarcoplasmic protein fractional synthetic rates (FSR) were measured during a 13-h primed continuous infusion of l-[ ring- 13 C 6 ]phenylalanine with BAL and SKEW pattern of protein intake in EB, after 2 wk ER, and after 2 wk ER + RT. Fed-state myofibrillar FSR was lower in ER than EB in both groups ( P 0.001), but was greater in BAL than SKEW ( P = 0.014). In ER + RT, fed-state myofibrillar FSR increased above ER in both groups and in BAL was not different from EB ( P = 0.903). In SKEW myofibrillar FSR remained lower than EB ( P = 0.002) and lower than BAL ( P = 0.006). Fed-state sarcoplasmic protein FSR was reduced similarly in ER and ER + RT compared with EB ( P 0.01) in both groups. During ER in overweight/obese older men a BAL consumption of protein stimulated the synthesis of muscle contractile proteins more effectively than traditional, SKEW distribution. Combining RT with a BAL protein distribution “rescued” the lower rates of myofibrillar protein synthesis during moderate ER.

Regulation of fuel metabolism by preexercise muscle glycogen content and exercise intensity

Publisher: American Physiological Society

Date: 12-2004

DOI: 10.1152/JAPPLPHYSIOL.00421.2004

Abstract: To date, the results of studies that have examined the effects of altering preexercise muscle glycogen content and exercise intensity on endogenous carbohydrate oxidation are equivocal. Differences in the training status of subjects between investigations may, in part, explain these inconsistent findings. Accordingly, we determined the relative effects of exercise intensity and carbohydrate availability on patterns of fuel utilization in the same subjects who performed a random order of four 60-min rides, two at 45% and two at 70% of peak O 2 uptake (V̇o 2 peak ), after exercise-diet intervention to manipulate muscle glycogen content. Preexercise muscle glycogen content was 596 ± 43 and 202 ± 21 mmol/kg dry mass ( P 0.001) for high-glycogen (HG) and low-glycogen (LG) conditions, respectively. Respiratory exchange ratio was higher for HG than LG during exercise at both 45% (0.85 ± 0.01 vs. 0.74 ± 0.01 P 0.001) and 70% (0.90 ± 0.01 vs. 0.79 ± 0.01 P 0.001) of V̇o 2 peak . The contribution of whole body muscle glycogen oxidation to energy expenditure differed between LG and HG for exercise at both 45% (5 ± 2 vs. 45 ± 5% P 0.001) and 70% (25 ± 3 vs. 60 ± 3% P 0.001) of V̇o 2 peak . Yet, despite marked differences in preexercise muscle glycogen content and its subsequent utilization, rates of plasma glucose disappearance were similar under all conditions. We conclude that, in moderately trained in iduals, muscle glycogen availability (low vs. high) does not influence rates of plasma glucose disposal during either low- or moderate-intensity exercise.

A Time to Eat and a Time to Exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 11-2020

DOI: 10.1249/JES.0000000000000207

Abstract: This Perspective for Progress provides a synopsis for the potential of time-restricted eating (TRE) to rescue some of the deleterious effects on circadian biology induced by our modern-day lifestyle. We provide novel insights into the comparative and potential complementary effects of TRE and exercise training on metabolic health.

Fat adaptation and prolonged exercise performance

Publisher: American Physiological Society

Date: 03-2004

DOI: 10.1152/JAPPLPHYSIOL.01232.2003

Reproducibility of self-paced treadmill performance of trained endurance runners

Publisher: Georg Thieme Verlag KG

Date: 1998

DOI: 10.1055/S-2007-971879

Abstract: The reproducibility of performance in a laboratory test impacts on the statistical power of that test to detect changes of performance in experiments. The purpose of this study was to determine the reproducibility of performance of distance runners completing a 60 min time trial (TT) on a motor-driven treadmill. Eight trained distance runners (age 27 +/- 7yrs, peak oxygen consumption [VO2peak] 66 +/- 5 ml x min(-1) x kg(-1), mean +/- SD) performed the TT on three occasions separated by 7-10 days. Throughout each TT the runners controlled the speed of the treadmill and could view current speed and elapsed time, but they did not know the elapsed or final distance. On the basis of heart-rate, it is estimated that the subjects ran at an average intensity equivalent to 80-83% of VO2peak. The distance run in 1 h did not vary substantially between trials (16.2 +/- 1.4 km, 15.9 +/- 1.4 km, and 16.1 +/- 1.2 km for TTs 1-3 respectively, p = 0.5). The coefficient of variation (CV) for in idual runners was 2.7% (95% Cl = 1.8-4.0%) and the test-retest reliability expressed as an intraclass correlation coefficient was 0.90 (95% Cl = 0.72-0.98). Reproducibility of performance in this test was therefore acceptable. However, higher reproducibility is required for experimental studies aimed at detecting the smallest worthwhile changes in performance with realistic s le sizes.

Fat adaptation in well-trained athletes: effects on cell metabolism

Publisher: Canadian Science Publishing

Date: 2011

DOI: 10.1139/H10-089

Abstract: The performance of prolonged ( min), continuous, endurance exercise is limited by endogenous carbohydrate (CHO) stores. Accordingly, for many decades, sports nutritionists and exercise physiologists have proposed a number of diet-training strategies that have the potential to increase fatty acid availability and rates of lipid oxidation and thereby attenuate the rate of glycogen utilization during exercise. Because the acute ingestion of exogenous substrates (primarily CHO) during exercise has little effect on the rates of muscle glycogenolysis, recent studies have focused on short-term ( –2 weeks) diet-training interventions that increase endogenous substrate stores (i.e., muscle glycogen and lipids) and alter patterns of substrate utilization during exercise. One such strategy is “fat adaptation”, an intervention in which well-trained endurance athletes consume a high-fat, low-CHO diet for up to 2 weeks while undertaking their normal training and then immediately follow this by CHO restoration (consuming a high-CHO diet and tapering for 1–3 days before a major endurance event). Compared with an isoenergetic CHO diet for the same intervention period, this “dietary periodization” protocol increases the rate of whole-body and muscle fat oxidation while attenuating the rate of muscle glycogenolysis during submaximal exercise. Of note is that these metabolic perturbations favouring the oxidation of fat persist even in the face of restored endogenous CHO stores and increased exogenous CHO availability. Here we review the current knowledge of some of the potential mechanisms by which skeletal muscle sustains high rates of fat oxidation in the face of high exogenous and endogenous CHO availability.

Assessment of the Reproducibility of Performance Testing on an Air-Braked Cycle Ergometer

Publisher: Georg Thieme Verlag KG

Date: 05-1996

DOI: 10.1055/S-2007-972849

Abstract: The purposes of this study were (I) to assess the reproducibility of endurance performance testing on an air-braked cycle ergometer, and (II) to compare laboratory performances to performances in road races. Ten well-trained, competitive cyclists (peak power output [PPO] 443 +/- 37 W, [values are mean +/- SD]) undertook either: (I) three 20 km and three 40 km time trials (TT) on an air braked ergometry system (Kingcycle) (n = 6), and/or (II) three 40 km laboratory TT and two 40 km road TT competitions (n = 8). The time taken for the laboratory simulated 20 km and 40 km TT rides were highly reproducible (coefficient of variation 1.1 +/- 0.9% and 1.0 +/- 0.5%, respectively). However, the mean power output and heart rate were significantly different (p < 0.0001) between the 20 km and 40 km TT (327.5 +/- 16.9 vs 303.9 +/- 14.9 W and 171.4 +/- 5.1 vs 168.3 +/- 4.4 beats/min, respectively). A strong relationship (r = 0.99, p < 0.001) was observed between the mean cycling time and the average sustained power output. A significant correlation (r = 0.98, p < 0.001) was also observed between laboratory and road race times, although road race times were, on average, some 8% slower. These findings indicate that the Kingcycle ergometry system can be used as a reliable method of assessing short term endurance cycling performance.

Swifter, higher, stronger: What’s on the menu?

Publisher: American Association for the Advancement of Science (AAAS)

Date: 16-11-2018

DOI: 10.1126/SCIENCE.AAU2093

Abstract: The exploits of elite athletes delight, frustrate, and confound us as they strive to reach their physiological, psychological, and biomechanical limits. We dissect nutritional approaches to optimal performance, showcasing the contribution of modern sports science to gold medals and world titles. Despite an enduring belief in a single, superior “athletic diet,” ersity in sports nutrition practices among successful athletes arises from the specificity of the metabolic demands of different sports and the periodization of training and competition goals. Pragmatic implementation of nutrition strategies in real-world scenarios and the prioritization of important strategies when nutrition themes are in conflict add to this variation. Lastly, differences in athlete practices both promote and reflect areas of controversy and disagreement among sports nutrition experts.

Nutritional strategies for promoting fat utilization and delaying the onset of fatigue during prolonged exercise

Publisher: Informa UK Limited

Date: 1997

DOI: 10.1080/026404197367326

Abstract: Carbohydrate ingestion before and during endurance exercise delays the onset of fatigue (reduced power output). Therefore, endurance athletes are recommended to ingest diets high in carbohydrate (70% of total energy) during competition and training. However, increasing the availability of plasma free fatty acids has been shown to slow the rate of muscle and liver glycogen depletion by promoting the utilization of fat. Ingested fat, in the form of long-chain (C16-22) triacylglycerols, is largely unavailable during acute exercise, but medium-chain (C8-10) triacylglycerols are rapidly absorbed and oxidized. We have shown that the ingestion of medium-chain triacylglycerols in combination with carbohydrate spares muscle carbohydrate stores during 2 h of submaximal ( 70% by energy). Dietary fat adaptation for a period of at least 2-4 weeks has resulted in a nearly two-fold increase in resistance to fatigue during prolonged, low- to moderate-intensity cycling (< 70% VO2 peak). Moreover, preliminary studies suggest that mean cycling 20 km time-trial performance following prolonged submaximal exercise is enhanced by 80 s after dietary fat adaptation and 3 days of carbohydrate loading. Thus the relative contribution of fuel substrate to prolonged endurance activity may be modified by training, pre-exercise feeding, habitual diet, or by artificially altering the hormonal milieu or the availability of circulating fuels. The time course and dose-response of these effects on maximizing the oxidative contribution of fat for exercise metabolism and in exercise performance have not been systematically studied during moderate- to high-intensity exercise in humans.

Mitochondrial function in metabolic health: A genetic and environmental tug of war

Publisher: Elsevier BV

Date: 04-2014

DOI: 10.1016/J.BBAGEN.2013.12.004

Abstract: The increased prevalence of obesity and its co-morbidities and their strong association with inactivity have produced an 'exercise-deficient phenotype' in which in iduals with a particular combination of disease-susceptible genes collide with environmental influences to cross a biological 'threshold' that ultimately manifests as overt clinical conditions (i.e., risk-factors for disease states). These risk-factors have been linked to impairments in skeletal muscle mitochondrial function. The question of whether 'inborn' mitochondrial deficiencies and/or defective mitochondrial metabolism contribute to metabolic disease, or if environmental factors are the major determinant, will be examined. We contend that impaired whole-body insulin resistance along with impaired skeletal muscle handling of carbohydrate and lipid fuels (i.e., metabolic inflexibility) is associated with a reduced skeletal muscle mitochondrial content which, in large part, is a maladaptive response to an 'inactivity cycle' which predisposes to a reduced level of habitual physical activity. While genetic components play a role in the pathogenesis of metabolic disease, exercise is a powerful environmental stimulus capable of restoring the metabolic flexibility of fuel selection and reduces risk-factors for metabolic disease in genetically-susceptible in iduals. Given the apathy towards voluntary physical activity in most Western societies, it is clear that there is an urgent need for innovative, clinically-effective exercise strategies, coupled with changes in current attitudes and methods of delivering exercise prescription and dietary advice, in order to improve metabolic health and reduce metabolic disease risk at the population level. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.

Nutritional practices of athletes: Are they sub‐optimal?

Publisher: Informa UK Limited

Date: 06-1995

DOI: 10.1080/02640419508732280

Abstract: Athletes' nutritional needs are principally determined by their training load (the intensity x frequency x duration of daily workouts) and body mass. Analyses of the diets of track and field competitors and marathon runners reveal a macronutrient composition similar to that of weight-matched, inactive in iduals. Male athletes generally ingest adequate dietary energy to meet their daily energy expenditure and all vitamin and mineral needs. However, the energy intake of most female athletes is less than might be anticipated based on their training load. As a result, intakes of iron, calcium, vitamin B12 and zinc are often below the recommended daily allowances. Compared with the recommendations of sports nutritionists and exercise physiologists, the majority of athletes consume a diet which might be considered significantly deficient in carbohydrate (CHO). Although there is currently little scientific support for increasing the proportion of daily energy intake from CHO above the 45-55% (approximately 5 g kg BM-1 day-1) chronically consumed by most athletes, such a regimen would probably improve an athlete's training capacity, especially when rapid recovery from intense activity is required.

Arctic closure as a trigger for Atlantic overturning at the Eocene-Oligocene Transition

Publisher: Copernicus GmbH

Date: 23-03-2020

DOI: 10.5194/EGUSPHERE-EGU2020-7493

Abstract: & & & strong& The Eocene-Oligocene Transition (EOT), approximately 34 Ma ago, marks a period of major global cooling and inception of the Antarctic ice sheet. Proxies of deep circulation suggest a contemporaneous onset or strengthening of the Atlantic meridional overturning circulation (AMOC). Proxy evidence of gradual salinification of the North Atlantic and tectonically driven isolation of the Arctic suggest that closing the Arctic-Atlantic gateway could have triggered the AMOC at the EOT. We demonstrate this trigger of the AMOC using a new paleoclimate model with late Eocene boundary conditions. The control simulation reproduces Eocene observations of low Arctic salinities. Subsequent closure of the Arctic-Atlantic gateway triggers the AMOC by blocking freshwater inflow from the Arctic. Salt advection feedbacks then lead to cessation of overturning in the North Pacific. These circulation changes imply major warming of the North Atlantic Ocean, and simultaneous cooling of the North Pacific, but no interhemispheric change in temperatures.& /strong& & &

Exercise-induced skeletal muscle signaling pathways and human athletic performance

Publisher: Elsevier BV

Date: 09-2016

DOI: 10.1016/J.FREERADBIOMED.2016.02.007

Abstract: Skeletal muscle is a highly malleable tissue capable of altering its phenotype in response to external stimuli including exercise. This response is determined by the mode, (endurance- versus resistance-based), volume, intensity and frequency of exercise performed with the magnitude of this response-adaptation the basis for enhanced physical work capacity. However, training-induced adaptations in skeletal muscle are variable and unpredictable between in iduals. With the recent application of molecular techniques to exercise biology, there has been a greater understanding of the multiplicity and complexity of cellular networks involved in exercise responses. This review summarizes the molecular and cellular events mediating adaptation processes in skeletal muscle in response to exercise. We discuss established and novel cell signaling proteins mediating key physiological responses associated with enhanced exercise performance and the capacity for reactive oxygen and nitrogen species to modulate training adaptation responses. We also examine the molecular bases underpinning heterogeneous responses to resistance and endurance exercise and the dissociation between molecular 'markers' of training adaptation and subsequent exercise performance.

Regulation of metabolic genes in human skeletal muscle by short-term exercise and diet manipulation

Publisher: American Physiological Society

Date: 07-2004

DOI: 10.1152/AJPENDO.00557.2003

Abstract: Changes in dietary macronutrient intake alter muscle and blood substrate availability and are important for regulating gene expression. However, few studies have examined the effects of diet manipulation on gene expression in human skeletal muscle. The aim of this study was to quantify the extent to which altering substrate availability impacts on subsequent mRNA abundance of a subset of carbohydrate (CHO)- and fat-related genes. Seven subjects consumed either a low- (LOW 0.7 g/kg body mass CHO) or high- (HIGH 10 g/kg body mass CHO) CHO diet for 48 h after performing an exhaustive exercise bout to deplete muscle glycogen stores. After intervention, resting muscle and blood s les were taken. Muscle was analyzed for the gene abundances of GLUT4, glycogenin, pyruvate dehydrogenase kinase-4 (PDK-4), fatty acid translocase (FAT/CD36), carnitine palmitoyltransferase I (CPT I), hormone-sensitive lipase (HSL), β-hydroxyacyl-CoA dehydrogenase (β-HAD), and uncoupling binding protein-3 (UCP3), and blood s les for glucose, insulin, and free fatty acid (FFA) concentrations. Glycogen-depleting exercise and HIGH-CHO resulted in a 300% increase in muscle glycogen content ( P 0.001) relative to the LOW-CHO condition. FFA concentrations were twofold higher after LOW- vs. HIGH-CHO ( P 0.05). The exercise-diet manipulation exerted a significant effect on transcription of all carbohydrate-related genes, with an increase in GLUT4 and glycogenin mRNA abundance and a reduction in PDK-4 transcription after HIGH-CHO (all P 0.05). FAT/CD36 ( P 0.05) and UCP3 ( P 0.01) gene transcriptions were increased following LOW-CHO. We conclude that 1) there was a rapid capacity for a short-term exercise and diet intervention to exert coordinated changes in the mRNA transcription of metabolic related genes, and 2) genes involved in glucose regulation are increased following a high-carbohydrate diet.

Oxidation of exogenous carbohydrate during prolonged exercise: the effects of the carbohydrate type and its concentration

Publisher: Springer Science and Business Media LLC

Date: 1992

DOI: 10.1007/BF00636220

Can High-Intensity Interval Training Promote Skeletal Muscle Anabolism?

Publisher: Springer Science and Business Media LLC

Date: 29-01-2021

DOI: 10.1007/S40279-020-01397-3

Skeletal muscle respiratory capacity is enhanced in rats consuming an obesogenic Western diet

Publisher: American Physiological Society

Date: 15-06-2012

DOI: 10.1152/AJPENDO.00590.2011

Abstract: Obesity-induced lipid oversupply promotes skeletal muscle mitochondrial biogenesis. Previous investigations have utilized extreme high-fat diets (HFD) to induce such mitochondrial perturbations despite their disparity from human obesogenic diets. Here, we evaluate the effects of Western diet (WD)-induced obesity on skeletal muscle mitochondrial function. Long-Evans rats were given ad libitum access to either a WD [40% energy (E) from fat, 17% protein, and 43% carbohydrate (30% sucrose) n = 12] or a control diet (CON 16% of E from fat, 21% protein, and 63% carbohydrate n = 12) for 12 wk. Rats fed the WD consumed 23% more E than CON ( P = 0.0001), which was associated with greater increases in body mass (23%, P = 0.0002) and adiposity (17%, P = 0.03). There were no differences in fasting blood glucose concentration or glucose tolerance between diets, although fasting insulin was increased by 40% ( P = 0.007). Fasting serum triglycerides were also elevated in WD (86%, P = 0.001). The maximal capacity of the electron transfer system was greater following WD (37%, P = 0.02), as were the maximal activities of several mitochondrial enzymes (citrate synthase, β-hydroxyacyl-CoA dehydrogenase, carnitine palmitoyltransferase). Protein expression of citrate synthase, UCP3, and in idual respiratory complexes was greater after WD ( P 0.05) despite no differences in the expression of peroxisome proliferator-activated receptor (PPAR)α, PPARδ, or PPARγ coactivator-1 mRNA or protein abundance. We conclude that the respiratory capacity of skeletal muscle is enhanced in response to the excess energy supplied by a WD. This is likely due to an increase in mitochondrial density, which at least in the short term, and in the absence of increased energy demand, may protect the tissue from lipid-induced impairments in glycemic control.

Gigahertz Single-Electron Pumping Mediated by Parasitic States

Publisher: American Chemical Society (ACS)

Date: 19-06-2202

DOI: 10.1021/ACS.NANOLETT.8B00874

Abstract: In quantum metrology, semiconductor single-electron pumps are used to generate accurate electric currents with the ultimate goal of implementing the emerging quantum standard of the ere. Pumps based on electrostatically defined tunable quantum dots (QDs) have thus far shown the most promising performance in combining fast and accurate charge transfer. However, at frequencies exceeding approximately 1 GHz the accuracy typically decreases. Recently, hybrid pumps based on QDs coupled to trap states have led to increased transfer rates due to tighter electrostatic confinement. Here, we operate a hybrid electron pump in silicon obtained by coupling a QD to multiple parasitic states and achieve robust current quantization up to a few gigahertz. We show that the fidelity of the electron capture depends on the sequence in which the parasitic states become available for loading, resulting in distinctive frequency-dependent features in the pumped current.

Reduced resting skeletal muscle protein synthesis is rescued by resistance exercise and protein ingestion following short-term energy deficit

Publisher: American Physiological Society

Date: 15-04-2014

DOI: 10.1152/AJPENDO.00590.2013

Abstract: The myofibrillar protein synthesis (MPS) response to resistance exercise (REX) and protein ingestion during energy deficit (ED) is unknown. In young men ( n = 8) and women ( n = 7), we determined protein signaling and resting postabsorptive MPS during energy balance [EB 45 kcal·kg fat-free mass (FFM) −1 ·day −1 ] and after 5 days of ED (30 kcal·kg FFM −1 ·day −1 ) as well as MPS while in ED after acute REX in the fasted state and with the ingestion of whey protein (15 and 30 g). Postabsorptive rates of MPS were 27% lower in ED than EB ( P 0.001), but REX stimulated MPS to rates equal to EB. Ingestion of 15 and 30 g of protein after REX in ED increased MPS ∼16 and ∼34% above resting EB ( P 0.02). p70 S6K Thr 389 phosphorylation increased above EB only with combined exercise and protein intake (∼2–7 fold, P 0.05). In conclusion, short-term ED reduces postabsorptive MPS however, a bout of REX in ED restores MPS to values observed at rest in EB. The ingestion of protein after REX further increases MPS above resting EB in a dose-dependent manner. We conclude that combining REX with increased protein availability after exercise enhances rates of skeletal muscle protein synthesis during short-term ED and could in the long term preserve muscle mass.

Author Correction: Time-restricted feeding alters lipid and amino acid metabolite rhythmicity without perturbing clock gene expression

Publisher: Springer Science and Business Media LLC

Date: 08-10-2020

DOI: 10.1038/S41467-020-19100-5

Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Sex-based comparisons of myofibrillar protein synthesis after resistance exercise in the fed state

Publisher: American Physiological Society

Date: 06-2012

DOI: 10.1152/JAPPLPHYSIOL.00170.2012

Abstract: We made sex-based comparisons of rates of myofibrillar protein synthesis (MPS) and anabolic signaling after a single bout of high-intensity resistance exercise. Eight men (20 ± 10 yr, BMI = 24.3 ± 2.4) and eight women (22 ± 1.8 yr, BMI = 23.0 ± 1.9) underwent primed constant infusions of l-[ ring- 13 C 6 ]phenylalanine on consecutive days with serial muscle biopsies. Biopsies were taken from the vastus lateralis at rest and 1, 3, 5, 24, 26, and 28 h after exercise. Twenty-five grams of whey protein was ingested immediately and 26 h after exercise. We also measured exercise-induced serum testosterone because it is purported to contribute to increases in myofibrillar protein synthesis (MPS) postexercise and its absence has been hypothesized to attenuate adaptative responses to resistance exercise in women. The exercise-induced area under the testosterone curve was 45-fold greater in men than women in the early (1 h) recovery period following exercise ( P 0.001). MPS was elevated similarly in men and women (2.3- and 2.7-fold, respectively) 1–5 h postexercise and after protein ingestion following 24 h recovery. Phosphorylation of mTOR Ser2448 was elevated to a greater extent in men than women acutely after exercise ( P = 0.003), whereas increased phosphorylation of p70S6K1 Thr389 was not different between sexes. Androgen receptor content was greater in men (main effect for sex, P = 0.049). Atrogin-1 mRNA abundance was decreased after 5 h recovery in both men and women ( P 0.001), and MuRF-1 expression was elevated in men after protein ingestion following 24 h recovery ( P = 0.003). These results demonstrate minor sex-based differences in signaling responses and no difference in the MPS response to resistance exercise in the fed state. Interestingly, our data demonstrate that exercise-induced increases in MPS are dissociated from postexercise testosteronemia and that stimulation of MPS occurs effectively with low systemic testosterone concentrations in women.

Nutritional modulation of training-induced skeletal muscle adaptations

Publisher: American Physiological Society

Date: 03-2011

DOI: 10.1152/JAPPLPHYSIOL.00949.2010

Abstract: Skeletal muscle displays remarkable plasticity, enabling substantial adaptive modifications in its metabolic potential and functional characteristics in response to external stimuli such as mechanical loading and nutrient availability. Contraction-induced adaptations are determined largely by the mode of exercise and the volume, intensity, and frequency of the training stimulus. However, evidence is accumulating that nutrient availability serves as a potent modulator of many acute responses and chronic adaptations to both endurance and resistance exercise. Changes in macronutrient intake rapidly alter the concentration of blood-borne substrates and hormones, causing marked perturbations in the storage profile of skeletal muscle and other insulin-sensitive tissues. In turn, muscle energy status exerts profound effects on resting fuel metabolism and patterns of fuel utilization during exercise as well as acute regulatory processes underlying gene expression and cell signaling. As such, these nutrient-exercise interactions have the potential to activate or inhibit many biochemical pathways with putative roles in training adaptation. This review provides a contemporary perspective of our understanding of the molecular and cellular events that take place in skeletal muscle in response to both endurance and resistance exercise commenced after acute and/or chronic alterations in nutrient availability (carbohydrate, fat, protein, and several antioxidants). Emphasis is on the results of human studies and how nutrient provision (or lack thereof) interacts with specific contractile stimulus to modulate many of the acute responses to exercise, thereby potentially promoting or inhibiting subsequent training adaptation.

Fuel metabolism during ultra-endurance exercise

Publisher: Springer Science and Business Media LLC

Date: 25-05-0011

DOI: 10.1007/S004240050624

Abstract: Cyclists either ingested 300 ml 100 g/l U-[14C] glucose solution every 30 min during 6 h rides at 55% of VO2max (n=6) or they consumed unlabelled glucose and were infused with U-[14C] lactate (n=5). Maintenance of euglycaemia limited rises in circulating free fatty acids, noradrenaline and adrenaline concentrations to 0.9+/-0. 1 mM, 27+/-4 nM and 2.0+/-0.5 nM, respectively, and sustained the oxidation of glucose and lactate. As muscle glycogen oxidation declined from 100+/-13 to 71+/-9 micromol/min/kg in the last 3 h of exercise, glucose and lactate oxidation and interconversion rates remained at approximately 60 and 50 and at about 4 and 5 micromol/min/kg, respectively. Continued high rates of carbohydrate oxidation led to a total oxidation of around 270 g glucose, 130 g plasma lactate and 530 g muscle glycogen. Oxidation of some 530 g of muscle glycogen far exceeded the predicted (about 250 g) initial glycogen content of the active muscles and suggested that there must have been a considerable diffusion of unlabelled lactate from glycogen breakdown in inactive muscle fibres to adjacent active muscle fibres via the interstitial fluid that did not equilibrate with 14C lactate in the circulation.

Muscle Na⁺-K⁺-ATPase activity and isoform adaptations to intense interval exercise and training in well-trained athletes

Publisher: American Physiological Society

Date: 07-2007

DOI: 10.1152/JAPPLPHYSIOL.00236.2006

Abstract: The Na + -K + -ATPase enzyme is vital in skeletal muscle function. We investigated the effects of acute high-intensity interval exercise, before and following high-intensity training (HIT), on muscle Na + -K + -ATPase maximal activity, content, and isoform mRNA expression and protein abundance. Twelve endurance-trained athletes were tested at baseline, pretrain, and after 3 wk of HIT (posttrain), which comprised seven sessions of 8 × 5-min interval cycling at 80% peak power output. Vastus lateralis muscle was biopsied at rest (baseline) and both at rest and immediately postexercise during the first (pretrain) and seventh (posttrain) training sessions. Muscle was analyzed for Na + -K + -ATPase maximal activity (3- O-MFPase), content ([ 3 H]ouabain binding), isoform mRNA expression (RT-PCR), and protein abundance (Western blotting). All baseline-to-pretrain measures were stable. Pretrain, acute exercise decreased 3- O-MFPase activity [12.7% (SD 5.1), P 0.05], increased α 1 , α 2 , and α 3 mRNA expression (1.4-, 2.8-, and 3.4-fold, respectively, P 0.05) with unchanged β-isoform mRNA or protein abundance of any isoform. In resting muscle, HIT increased ( P 0.05) 3- O-MFPase activity by 5.5% (SD 2.9), and α 3 and β 3 mRNA expression by 3.0- and 0.5-fold, respectively, with unchanged Na + -K + -ATPase content or isoform protein abundance. Posttrain, the acute exercise induced decline in 3- O-MFPase activity and increase in α 1 and α 3 mRNA each persisted ( P 0.05) the postexercise 3- O-MFPase activity was also higher after HIT ( P 0.05). Thus HIT augmented Na + -K + -ATPase maximal activity despite unchanged total content and isoform protein abundance. Elevated Na + -K + -ATPase activity postexercise may contribute to reduced fatigue after training. The Na + -K + -ATPase mRNA response to interval exercise of increased α- but not β-mRNA was largely preserved posttrain, suggesting a functional role of α mRNA upregulation.

Metabolic and performance responses to constant-load vs. variable- intensity exercise in trained cyclists

Publisher: American Physiological Society

Date: 09-1999

DOI: 10.1152/JAPPL.1999.87.3.1186

Abstract: We studied glucose oxidation (Glu ox ) and glycogen degradation during 140 min of constant-load [steady-state (SS)] and variable-intensity (VI) cycling of the same average power output, immediately followed by a 20-km performance ride [time trial (TT)]. Six trained cyclists each performed four trials: two experimental bouts (SS and VI) in which muscle biopsies were taken before and after 140 min of exercise for determination of glycogen and periodic acid-Schiff’s staining and two similar trials without biopsies but incorporating the TT. During two of the experimental rides, subjects ingested a 5 g/100 ml [U- 14 C]glucose solution to determine rates of Glu ox . Values were similar between SS and VI trials: O 2 consumption (3.08 ± 0.02 vs. 3.15 ± 0.03 l/min), energy expenditure (901 ± 40 vs. 904 ± 58 J ⋅ kg −1 ⋅ min −1 ), heart rate (156 ± 1 vs. 160 ± 1 beats/min), and rating of perceived exertion (12.6 ± 0.6 vs. 12.7 ± 0.7). However, the area under the curve for plasma lactate concentration vs. time was significantly greater during VI than SS (29.1 ± 3.9 vs. 24.6 ± 3.7 mM/140 min P = 0.03). VI resulted in a 49% reduction in total muscle glycogen utilization vs. 65% for SS, while total Glu ox was higher (99.2 ± 5.3 vs. 83.9 ± 5.2 g/140 min P 0.05). The number of glycogen-depleted type I muscle fibers at the end of 140 min was 98% after SS but only 59% after VI. Conversely, the number of type II fibers that showed reduced periodic acid-Schiff’s staining was 1% after SS vs. 10% after VI. Despite these metabolic differences, subsequent TT performance was similar (29.14 ± 0.9 vs. 30.5 ± 0.9 min for SS vs. VI). These results indicate that whole body metabolic and cardiovascular responses to 140 min of either SS or VI exercise at the same average intensity are similar, despite differences in skeletal muscle carbohydrate metabolism and recruitment.

A comparison of the effects of two sitting postures on back and referred pain

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 10-1991

DOI: 10.1097/00007632-199110000-00010

Abstract: This study compared the effects of sitting with portable supports in either a kyphotic or lordotic posture on low-back and referred pain. Two hundred ten patients with low-back and/or referred pain were randomly assigned to either a kyphotic posture or lordotic posture group. The kyphotic and lordotic postures were facilitated by the use of a flat foam cushion or lumbar roll, respectively. Pain location, back pain, and leg pain intensity were assessed over a 24-48-hour period under both standardized clinical settings and general sitting environments. When sitting with a lordotic posture, back and leg pain were significantly reduced and referred pain shifted towards the low back. This study demonstrates that in general sitting environments a lumbar roll results in: 1) reductions in back and leg pain and 2) centralization of pain. These findings do not apply to patients with stenosis or spondylolisthesis, whose symptoms may be aggravated by use of a lumbar roll.

Living high-training low increases hypoxic ventilatory response of well-trained endurance athletes

Publisher: American Physiological Society

Date: 10-2002

DOI: 10.1152/JAPPLPHYSIOL.00381.2002

Abstract: This study determined whether “living high-training low” (LHTL)-simulated altitude exposure increased the hypoxic ventilatory response (HVR) in well-trained endurance athletes. Thirty-three cyclists/triathletes were ided into three groups: 20 consecutive nights of hypoxic exposure (LHTLc, n = 12), 20 nights of intermittent hypoxic exposure (four 5-night blocks of hypoxia, each interspersed with 2 nights of normoxia, LHTLi, n = 10), or control (Con, n = 11). LHTLc and LHTLi slept 8–10 h/day overnight in normobaric hypoxia (∼2,650 m) Con slept under ambient conditions (600 m). Resting, isocapnic HVR (ΔV˙e/ΔSp O 2 , whereV˙e is minute ventilation and Sp O 2 is blood O 2 saturation) was measured in normoxia before hypoxia (Pre), after 1, 3, 10, and 15 nights of exposure (N1, N3, N10, and N15, respectively), and 2 nights after the exposure night 20 (Post). Before each HVR test, end-tidal Pco 2 (Pet CO 2 ) and V˙e were measured during room air breathing at rest. HVR (l · min −1 · % −1 ) was higher ( P 0.05) in LHTLc than in Con at N1 (0.56 ± 0.32 vs. 0.28 ± 0.16), N3 (0.69 ± 0.30 vs. 0.36 ± 0.24), N10 (0.79 ± 0.36 vs. 0.34 ± 0.14), N15 (1.00 ± 0.38 vs. 0.36 ± 0.23), and Post (0.79 ± 0.37 vs. 0.36 ± 0.26). HVR at N15 was higher ( P 0.05) in LHTLi (0.67 ± 0.33) than in Con and in LHTLc than in LHTLi. Pet CO 2 was depressed in LHTLc and LHTLi compared with Con at all points after hypoxia ( P 0.05). No significant differences were observed for V˙e at any point. We conclude that LHTL increases HVR in endurance athletes in a time-dependent manner and decreases Pet CO 2 in normoxia, without change inV˙e. Thus endurance athletes sleeping in mild hypoxia may experience changes to the respiratory control system.

Effects of skeletal muscle energy availability on protein turnover responses to exercise

Publisher: The Company of Biologists

Date: 2016

DOI: 10.1242/JEB.125104

Abstract: Skeletal muscle adaptation to exercise training is a consequence of repeated contraction-induced increases in gene expression that lead to the accumulation of functional proteins whose role is to blunt the homeostatic perturbations generated by escalations in energetic demand and substrate turnover. The development of a specific ‘exercise phenotype’ is the result of new, augmented steady-state mRNA and protein levels that stem from the training stimulus (i.e. endurance or resistance based). Maintaining appropriate skeletal muscle integrity to meet the demands of training (i.e. increases in myofibrillar and/or mitochondrial protein) is regulated by cyclic phases of synthesis and breakdown, the rate and turnover largely determined by the protein's half-life. Cross-talk among several intracellular systems regulating protein synthesis, breakdown and folding is required to ensure protein equilibrium is maintained. These pathways include both proteasomal and lysosomal degradation systems (ubiquitin-mediated and autophagy, respectively) and the protein translational and folding machinery. The activities of these cellular pathways are bioenergetically expensive and are modified by intracellular energy availability (i.e. macronutrient intake) and the ‘training impulse’ (i.e. summation of the volume, intensity and frequency). As such, exercise–nutrient interactions can modulate signal transduction cascades that converge on these protein regulatory systems, especially in the early post-exercise recovery period. This review focuses on the regulation of muscle protein synthetic response-adaptation processes to ergent exercise stimuli and how intracellular energy availability interacts with contractile activity to impact on muscle remodelling.

Greater effect of diet than exercise training on the fatty acid profile of rat skeletal muscle

Publisher: American Physiological Society

Date: 03-2004

DOI: 10.1152/JAPPLPHYSIOL.01003.2003

Abstract: We determined the interaction of diet and exercise-training intensity on membrane phospholipid fatty acid (FA) composition in skeletal muscle from 36 female Sprague-Dawley rats. Animals were randomly ided into one of two dietary conditions: high-carbohydrate (64.0% carbohydrate by energy, n = 18) or high fat (78.1% fat by energy, n = 18). Rats in each diet condition were then allocated to one of three subgroups: control, which performed no exercise training low-intensity (8 m/min) treadmill run training or high-intensity (28 m/min) run training. All exercise-trained rats ran 1,000 m/session, 4 days/wk for 8 wk and were killed 48 h after the last training bout. Membrane phospholipids were extracted, and FA composition was determined in the red and white vastus lateralis muscles. Diet exerted a major influence on phospholipid FA composition, with the high-fat diet being associated with a significantly ( P 0.01) elevated ratio of n-6/n-3 FA for both red (2.7–3.2 vs. 1.0–1.1) and white vastus lateralis muscle (2.5–2.9 vs. 1.2). In contrast, alterations in FA composition as a result of either exercise-training protocol were only minor in comparison. We conclude that, under the present experimental conditions, a change in the macronutrient content of the diet was a more potent modulator of skeletal muscle membrane phospholipid FA composition compared with either low- or high-intensity treadmill exercise training.

Global variation in anastomosis and end colostomy formation following left‐sided colorectal resection

Publisher: Oxford University Press (OUP)

Date: 28-02-2019

DOI: 10.1002/BJS5.50138

Does High Cardiorespiratory Fitness Confer Some Protection Against Proinflammatory Responses After Infection by SARS‐CoV‐2?

Publisher: Wiley

Date: 09-07-2020

DOI: 10.1002/OBY.22849

Circulating and Adipose Tissue miRNAs in Women With Polycystic Ovary Syndrome and Responses to High-Intensity Interval Training

Publisher: Frontiers Media SA

Date: 30-07-2020

DOI: 10.3389/FPHYS.2020.00904

Lipid-induced mTOR activation in rat skeletal muscle reversed by exercise and 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside

Publisher: Bioscientifica

Date: 02-07-2009

DOI: 10.1677/JOE-09-0202

Abstract: The serine/threonine protein kinase, mammalian target of rapamycin (mTOR) is regulated by insulin and nutrient availability and has been proposed to play a central role as a nutrient sensor in skeletal muscle. mTOR associates with its binding partners, raptor and rictor, to form two structurally and functionally distinct complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) respectively. We have investigated the assembly of mTORC1/2 and the activation of their downstream substrates (i.e. Akt, S6K1) in response to known effectors of mTOR, excess lipid availability and AMP-activated protein kinase (AMPK) activation/exercise training in rat skeletal muscle. The in vivo formation of mTORC1 and 2 and the activation of their respective downstream substrates were increased in response to chronic (8 weeks) consumption of a high-fat diet. Diet-induced mTORC activation and skeletal muscle insulin resistance were reversed by 4 weeks of exercise training, which was associated with enhanced muscle AMPK activation. In order to determine whether AMPK activation reverses lipid-induced mTOR activation, L6 myotubes were exposed to 0.4 mM palmitate to activate mTORC1/2 in the absence or presence of 5′-aminoimidazole-4-carboxamide-1-β- d -ribofuranoside (AICAR). Palmitate exposure (4 h) increased insulin-stimulated S6K1 Thr389 phosphorylation by 60%, indicating activation of mTORC1. AMPK activation with 1 mM AICAR abolished lipid-induced mTOR activation in vitro . Our data implicates reductions in mTOR complex activation with the reversal of lipid-induced skeletal muscle insulin resistance in response to exercise training or AICAR and identifies mTOR as a potential target for the treatment of insulin resistance.

Intramuscular Heat Shock Protein 72 and Heme Oxygenase-1 mRNA Are Reduced in Patients With Type 2 Diabetes

Publisher: American Diabetes Association

Date: 09-2003

DOI: 10.2337/DIABETES.52.9.2338

Abstract: To examine whether genes associated with cellular defense against oxidative stress are associated with insulin sensitivity, patients with type 2 diabetes (n = 7) and age-matched (n = 5) and young (n = 9) control subjects underwent a euglycemic-hyperinsulinemic cl for 120 min. Muscle s les were obtained before and after the cl and analyzed for heat shock protein (HSP)72 and heme oxygenase (HO)-1 mRNA, intramuscular triglyceride content, and the maximal activities of β-hyroxyacyl-CoA dehydrogenase (β-HAD) and citrate synthase (CS). Basal expression of both HSP72 and HO-1 mRNA were lower (P & 0.05) by 33 and 55%, respectively, when comparing diabetic patients with age-matched and young control subjects, with no differences between the latter groups. Both basal HSP72 (r = 0.75, P & 0.001) and HO-1 (r = 0.50, P & 0.05) mRNA expression correlated with the glucose infusion rate during the cl . Significant correlations were also observed between HSP72 mRNA and both β-HAD (r = 0.61, P & 0.01) and CS (r = 0.65, P & 0.01). HSP72 mRNA was induced (P & 0.05) by the cl in all groups. Although HO-1 mRNA was unaffected by the cl in both the young and age-matched control subjects, it was increased (P & 0.05) ∼70-fold in the diabetic patients after the cl . These data demonstrate that genes involved in providing cellular protection against oxidative stress are defective in patients with type 2 diabetes and correlate with insulin-stimulated glucose disposal and markers of muscle oxidative capacity. The data provide new evidence that the pathogenesis of type 2 diabetes involves perturbations to the antioxidant defense mechanism within skeletal muscle.

Effects of glucose ingestion or glucose infusion on fuel substrate kinetics during prolonged exercise

Publisher: Springer Science and Business Media LLC

Date: 1994

DOI: 10.1007/BF00843733

Effect of consecutive repeated sprint and resistance exercise bouts on acute adaptive responses in human skeletal muscle

Publisher: American Physiological Society

Date: 11-2009

DOI: 10.1152/AJPREGU.00351.2009

Abstract: We examined acute molecular responses in skeletal muscle to repeated sprint and resistance exercise bouts. Six men [age, 24.7 ± 6.3 yr body mass, 81.6 ± 7.3 kg peak oxygen uptake, 47 ± 9.9 ml·kg −1 ·min −1 one repetition maximum (1-RM) leg extension 92.2 ± 12.5 kg means ± SD] were randomly assigned to trials consisting of either resistance exercise (8 × 5 leg extension, 80% 1-RM) followed by repeated sprints (10 × 6 s, 0.75 N·m torque·kg −1 ) or vice-versa. Muscle biopsies from vastus lateralis were obtained at rest, 15 min after each exercise bout, and following 3-h recovery to determine early signaling and mRNA responses. There was ergent exercise order-dependent phosphorylation of p70 S6K (S6K). Specifically, initial resistance exercise increased S6K phosphorylation (∼75% P 0.05), but there was no effect when resistance exercise was undertaken after sprints. Exercise decreased IGF-I mRNA following 3-h recovery (∼50%, P = 0.06) independent of order, while muscle RING finger mRNA was elevated with a moderate exercise order effect ( P 0.01). When resistance exercise was followed by repeated sprints PGC-1α mRNA was increased (REX1-SPR2 P = 0.02) with a modest distinction between exercise orders. Repeated sprints may promote acute interference on resistance exercise responses by attenuating translation initiation signaling and exacerbating ubiquitin ligase expression. Indeed, repeated sprints appear to generate the overriding acute exercise-induced response when undertaking concurrent repeated sprint and resistance exercise. Accordingly, we suggest that sprint-activities are isolated from resistance training and that adequate recovery time is considered within periodized training plans that incorporate these ergent exercise modes.

Effect of caffeine co-ingested with carbohydrate or fat on metabolism and performance in endurance-trained men

Publisher: Wiley

Date: 2001

DOI: 10.1113/EPH8602072

Abstract: We examined the effect of caffeine co-ingested with either carbohydrate or fat on metabolism and performance in eight endurance-trained subjects who performed a random order of four experimental trials consisting of 120 min of steady-state ergometer cycling at 70 % of maximal O(2) uptake (SS) followed by a time trial in which subjects completed a set amount of work (7 kJ kg-1) as quickly as possible. One hour before SS subjects ingested either 2.6 g kg-1 carbohydrate (CHO) 2.6 g kg-1 CHO + 6 mg kg-1 caffeine (CHO + CAF) 1.2 g kg-1 fat with 2000 U I.V. heparin (FAT) or 1.2 g kg-1 fat with 2000 U I.V. heparin + 6 mg kg-1 caffeine (FAT + CAF). The rate of carbohydrate oxidation was higher (micromol kg-1 min-1: CHO, 243 +/- 39 and CHO + CAF, 239 +/- 30 vs. FAT, 196 +/- 48 and FAT + CAF, 191 +/- 55 P < 0.05, values are means +/- S.D.) and the rate of fat oxidation lower (micromol kg-1 min-1: CHO, 19 +/- 8 and CHO + CAF, 22 +/- 7 vs. FAT, 35 +/- 19 and FAT + CAF, 37 +/- 17 P < 0.05) with carbohydrate than fat ingestion. Yet despite lower carbohydrate use with fat feeding, the time taken to complete the time trial was less after carbohydrate than after fat ingestion (min: CHO, 30.37 +/- 7.42 and CHO + CAF, 29.12 +/- 5.62 vs. FAT, 33.02 +/- 8.50 and FAT + CAF, 32.78 +/- 7.70 P < 0.05). We conclude that (1) caffeine co-ingested with either carbohydrate or fat meals has no additive effect on substrate utilization or exercise performance and (2) carbohydrate ingestion before exercise improves subsequent time trial performance compared with fat ingestion. Experimental Physiology (2001) 86.1, 137-144.

The effects of polyphenols in olive leaves on platelet function

Publisher: Elsevier BV

Date: 02-2008

DOI: 10.1016/J.NUMECD.2006.09.001

Abstract: The phenolic compounds of olive leaves and olive oils in the Mediterranean diet have been associated with a reduced incidence of heart disease. Accordingly, antioxidant-rich diets may prevent the deleterious effects of oxidative metabolism by scavenging free radicals, thus inhibiting oxidation and delaying atherosclerosis. The process involves phospholipase C activation and arachidonic acid metabolism, and is thought to reduce hydrogen peroxide (H(2)O(2)). In our study, an extract of Olea europaea L. leaves was used. The active phenolic compounds in this extract are part of the secoiridoid family, known for their capacity to scavenge H(2)O(2). The results from this study will help to improve our understanding of effects of polyphenol antioxidants in olive leaf extract on platelet function. Full blood examination (FBE), platelet aggregation, and ATP release were performed on s les from fasting, normal, healthy male subjects. Platelet function at increasing concentrations of oleuropein was investigated through measures of platelet aggregation and ATP release from activated platelets. Blood analysis (n=11) revealed a significant dose-dependant reduction in platelet activity with olive extract concentrations of 1.0% v/v (P<0.001). ATP Release showed a similar pattern (P=0.02). Olive leaf polyphenols derived from O. europaea L. leaves inhibited in vitro platelet activation in healthy, non-smoking males. Further bioavailability studies need to be undertaken to determine the in vivo effect of extract on platelet function and to validate the present results.

Carbohydrates for training and competition

Publisher: Informa UK Limited

Date: 2011

DOI: 10.1080/02640414.2011.585473

Abstract: An athlete's carbohydrate intake can be judged by whether total daily intake and the timing of consumption in relation to exercise maintain adequate carbohydrate substrate for the muscle and central nervous system ("high carbohydrate availability") or whether carbohydrate fuel sources are limiting for the daily exercise programme ("low carbohydrate availability"). Carbohydrate availability is increased by consuming carbohydrate in the hours or days prior to the session, intake during exercise, and refuelling during recovery between sessions. This is important for the competition setting or for high-intensity training where optimal performance is desired. Carbohydrate intake during exercise should be scaled according to the characteristics of the event. During sustained high-intensity sports lasting ~1 h, small amounts of carbohydrate, including even mouth-rinsing, enhance performance via central nervous system effects. While 30-60 g · h(-1) is an appropriate target for sports of longer duration, events >2.5 h may benefit from higher intakes of up to 90 g · h(-1). Products containing special blends of different carbohydrates may maximize absorption of carbohydrate at such high rates. In real life, athletes undertake training sessions with varying carbohydrate availability. Whether implementing additional "train-low" strategies to increase the training adaptation leads to enhanced performance in well-trained in iduals is unclear.

Update on the effects of physical activity on insulin sensitivity in humans

Publisher: BMJ

Date: 03-2016

DOI: 10.1136/BMJSEM-2016-000143

Fat and carbohydrate for exercise

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 07-2006

DOI: 10.1097/01.MCO.0000232911.69236.3B

Training techniques to improve fatigue resistance and enhance endurance performance

Publisher: Informa UK Limited

Date: 1997

DOI: 10.1080/026404197367335

Abstract: Despite their best efforts, sports scientists have found it difficult to persuade elite athletes to experiment with their training regimens. Thus, until recently, exercise physiologists have had limited impact on the training practices of successful athletes, with most of the innovations in the training patterns of the best athletes coming from the empirical observations of top-level coaches. One form of training recognized by sports scientists and used by athletes for several decades in interval/transition training. Such training consists of a number of exercise bouts alternated with short rest intervals of more slowly paced activity and is thought to improve the fatigue resistance of the active muscles by exposing them to sustained, high-intensity exercise at the athlete's maximal steady-state pace. Few scientific studies, however, have examined the effects of transition training on the performances of competitive athletes. This paper identifies the physiological factors associated with successful endurance performance, and summarizes the results of investigations on competitive endurance cyclists which examined the time-course of changes in performance in response to a sustained, high-intensity interval training programme.

Prediction of triathlon race time from laboratory testing in national triathletes

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 04-2000

DOI: 10.1097/00005768-200004000-00018

Abstract: Four days after competing in an Olympic-distance National Triathlon Ch ionship (1500-m swim, 40-km cycle, 10-km run), five male and five female triathletes underwent comprehensive physiological testing in an attempt to determine which physiological variables accurately predict triathlon race time. All triathletes underwent maximal swimming tests over 25 and 400 m, the determination of peak sustained power output (PPO) and peak oxygen uptake (VO2peak) during an incremental cycle test to exhaustion, and a maximal treadmill running test to assess peak running velocity and VO2peak. In addition, submaximal steady-state measures of oxygen uptake (VO2), blood [lactate], and heart rate (HR) were determined during the cycling and running tests. The five most significant (P < 0.01) predictors of triathlon performance were blood lactate measured during steady-state cycling at a workload of 4 W x kg(-1) body mass (BM) (r = 0.92), blood lactate while running at 15 km x h(-1) (r = 0.89), PPO (r = 0.86), peak treadmill running velocity (r = 0.85), and VO2peak during cycling (r = 0.85). Stepwise multiple regression analysis revealed a highly significant (r = 0.90, P < 0.001) relationship between predicted race time (from laboratory measures) and actual race time, from the following calculation: race time (s) = - 129 (peak treadmill velocity [km x h(-1)]) + 122 ([lactate] at 4 W x kg(-1) BM) + 9456. The results of this study show that race time for top triathletes competing over the Olympic distance can be accurately predicted from the results of maximal and submaximal laboratory measures.

Big Data in operations and supply chain management: a systematic literature review and future research agenda

Publisher: Informa UK Limited

Date: 23-02-2021

DOI: 10.1080/00207543.2020.1868599

Aerobic Glycolytic and Aerobic Lipolytic Power Systems: A New Paradigm with Implications for Endurance and Ultraendurance Events

Publisher: Springer Science and Business Media LLC

Date: 04-1995

DOI: 10.2165/00007256-199519040-00002

Reduced Neuromuscular Activity with Carbohydrate Ingestion during Constant Load Cycling

Publisher: Human Kinetics

Date: 04-2004

DOI: 10.1123/IJSNEM.14.2.161

Abstract: The purpose of this study was to determine the effect of carbohydrate ingestion before and during intense constant load cycling to volitional fatigue on surface electromyographic (sEMG) activity from the vastus lateralis (VL) and vastus medialis (VM) muscles. After 24-h diet and training control, 8 well-trained subjects [maximal O 2 uptake (VO 2max ) 66 ± 2 ml · kg –1 · min –1 mean ± SD ] ingested 8 ml · kg –1 of either a 6.4% carbohydrate-electrolyte (CHO) or a placebo (PLA) solution immediately before, followed by 2 ml · kg –1 of the same solution every 15 min while cycling to exhaustion at 84 ± 1% of VO 2max . Exercise time to fatigue was 13% longer with CHO ingestion compared to PLA (58:54 ± 8:48 vs. 51:18 ± 5:54 min:s, NS). VO 2 (4.22 ± 0.11 vs. 4.20 ± 0.14 L · min –1 ), heart rate (172 ± 4 vs. 176 ± 4 beats · min –1 ), ratings of perceived effort (18 ± 0.1 vs. 19 ± 0.1), and rates of carbohydrate oxidation (314 ± 28 vs. 324 ± 26 μmol · kg –1 · min –1 ) were similar for both PLA and CHO at exhaustion. There was no main treatment effect of CHO ingestion on blood glucose or lactate concentrations, nor plasma prolactin levels either during exercise or at fatigue. However, CHO ingestion attenuated the rise in EMG root mean square (RMS) activity during the latter stages ( min) of exercise and at the point of exhaustion for both VM (0.325 ± 0.010 vs. 0.403 ± 0.020 mV p = .006) and VL (0.298 ± 0.011 vs. 0.370 ± 0.007 mV p = .0004). We conclude that in well-trained subjects, the ingestion of carbohydrate attenuated the increase in surface electromyographic activity during intense, constant load cycling leading to exhaustion in ~1 h. The precise mechanism(s) underlying this effect cannot be attributed to alterations in CHO availability but, instead, may be linked to changes in afferent sensory input.

Data-Driven Methodology for the Investigation of Riding Dynamics: A Motorcycle Case Study

Publisher: Institute of Electrical and Electronics Engineers (IEEE)

Date: 09-2023

DOI: 10.1109/TITS.2023.3271790

The Relationship between Exercise, Nutrition and Type 2 Diabetes

Publisher: S. Karger AG

Date: 2014

DOI: 10.1159/000357331

Abstract: Type 2 diabetes mellitus and its precursor, insulin resistance, are metabolic disease states characterized by impaired regulation in the delivery, transport, and/or storage of energy substrates (primarily carbohydrate- and fat-based fuels). A hallmark feature of patients with type 2 diabetes is prolonged periods of hyperglycemia due to a decreased responsiveness of metabolically active peripheral tissues to the actions of insulin (i.e., metabolic inflexibility). Accordingly, efforts to modify skeletal muscle substrate handling in type 2 diabetes patients so that the capacity for fat oxidation and metabolic flexibility is improved should be a primary goal for the treatment of these disorders. Two potent interventions for improving whole-body glucose homeostasis are exercise and diet. A single bout of either resistance or endurance exercise reduces the prevalence and duration of hyperglycemic excursions in patients with type 2 diabetes, an effect lasting well into the next day. With regard to diet, the carbohydrate content of a meal and the glycemic index (GI) of the carbohydrate consumed are both major determinants of the postprandial glycemic response. Diets containing high-GI carbohydrates have been shown to be independent risk factors for type 2 diabetes onset, while in obese insulin-resistant in iduals, low-GI diets are effective for inducing both weight loss and improving insulin action and glucose tolerance. The implementation of physical activity and dietary modifications are effective low-cost treatment options for controlling hyperglycemic episodes in patients with type 2 diabetes.

Single-leg cycle training is superior to double-leg cycling in improving the oxidative potential and metabolic profile of trained skeletal muscle

Publisher: American Physiological Society

Date: 05-2011

DOI: 10.1152/JAPPLPHYSIOL.01247.2010

Abstract: Single-leg cycling may enhance the peripheral adaptations of skeletal muscle to a greater extent than double-leg cycling. The purpose of the current study was to determine the influence of 3 wk of high-intensity single- and double-leg cycle training on markers of oxidative potential and muscle metabolism and exercise performance. In a crossover design, nine trained cyclists (78 ± 7 kg body wt, 59 ± 5 ml·kg −1 ·min −1 maximal O 2 consumption) performed an incremental cycling test and a 16-km cycling time trial before and after 3 wk of double-leg and counterweighted single-leg cycle training (2 training sessions per week). Training involved three (double) or six (single) maximal 4-min intervals with 6 min of recovery. Mean power output during the single-leg intervals was more than half that during the double-leg intervals (198 ± 29 vs. 344 ± 38 W, P 0.05). Skeletal muscle biopsy s les from the vastus lateralis revealed a training-induced increase in Thr 172 -phosphorylated 5′-AMP-activated protein kinase α-subunit for both groups ( P 0.05). However, the increase in cytochrome c oxidase subunits II and IV and GLUT-4 protein concentration was greater following single- than double-leg cycling ( P 0.05). Training-induced improvements in maximal O 2 consumption (3.9 ± 6.2% vs. 0.6 ± 3.6%) and time-trial performance (1.3 ± 0.5% vs. 2.3 ± 4.2%) were similar following both interventions. We conclude that short-term high-intensity single-leg cycle training can elicit greater enhancement in the metabolic and oxidative potential of skeletal muscle than traditional double-leg cycling. Single-leg cycling may therefore provide a valuable training stimulus for trained and clinical populations.

Microbiota and muscle highway - two way traffic

Publisher: Springer Science and Business Media LLC

Date: 14-11-2020

DOI: 10.1038/S41574-019-0291-6

Human metabolomics reveal daily variations under nutritional challenges specific to serum and skeletal muscle

Publisher: Elsevier BV

Date: 10-2018

DOI: 10.1016/J.MOLMET.2018.06.008

Maximizing Cellular Adaptation to Endurance Exercise in Skeletal Muscle

Publisher: Elsevier BV

Date: 05-2018

DOI: 10.1016/J.CMET.2018.04.014

Abstract: The application of molecular techniques to exercise biology has provided novel insight into the complexity and breadth of intracellular signaling networks involved in response to endurance-based exercise. Here we discuss several strategies that have high uptake by athletes and, on mechanistic grounds, have the potential to promote cellular adaptation to endurance training in skeletal muscle. Such approaches are based on the underlying premise that imposing a greater metabolic load and provoking extreme perturbations in cellular homeostasis will augment acute exercise responses that, when repeated over months and years, will lify training adaptation.

Water ingestion does not improve 1-h cycling performance in moderate ambient temperatures

Publisher: Springer Science and Business Media LLC

Date: 1995

DOI: 10.1007/BF00854973

Endurance Training

Publisher: SAGE Publications, Inc.

Date: 2012

DOI: 10.4135/9781412994149.N124

Sending the Signal: Muscle Glycogen Availability as a Regulator of Training Adaptation

Publisher: Springer International Publishing

Date: 2017

DOI: 10.1007/978-3-319-72790-5_4

Oxidation of Carbohydrate Ingested During Prolonged Endurance Exercise

Publisher: Springer Science and Business Media LLC

Date: 07-1992

DOI: 10.2165/00007256-199214010-00003

Abstract: Classic studies conducted in the 1920s and 1930s established that the consumption of a high carbohydrate (CHO) diet before exercise and the ingestion of glucose during exercise delayed the onset of fatigue, in part by preventing the development of hypoglycaemia. For the next 30 to 40 years, however, interest in CHO ingestion during exercise waned. Indeed, it was not until the reintroduction of the muscle biopsy technique into exercise physiology in the 1960s that a series of studies on CHO utilisation during exercise appeared. Investigations by Scandinavian physiologists showed that muscle glycogen depletion during prolonged exercise coincided with the development of fatigue. Despite this finding, attempts to delay fatigue during prolonged exercise focused principally on techniques that would increase muscle glycogen storage before exercise. The possibility that CHO ingestion during exercise might also delay the development of muscle glycogen depletion and hence, at least potentially, fatigue, was not extensively investigated. This, in part, can be explained by the popular belief that water replacement to prevent dehydration and hyperthermia was of greater importance than CHO replacement during prolonged exercise. This position was strengthened by studies in the early 1970s which showed that the ingestion of CHO solutions delayed gastric emptying compared with water, and might therefore exacerbate dehydration. As a result, athletes were actively discouraged from ingesting even mildly concentrated (greater than 5 g/100ml) CHO solutions during exercise. Only in the early 1980s, when commercial interest in the sale of CHO products to athletes was aroused, did exercise physiologists again begin to study the effects of CHO ingestion during exercise. These studies soon established that CHO ingestion during prolonged exercise could delay fatigue this finding added urgency to the search for the optimum CHO type for ingestion during exercise. Whereas in the earlier studies, estimates of CHO oxidation were made using respiratory gas exchange measurements, investigations since the early 1970s have employed stable 13C and radioactive 14C isotope techniques to determine the amount of ingested CHO that is oxidised during exercise. Most of the early interest was in glucose ingestion during exercise. These studies showed that significant quantities of ingested glucose can be oxidised during exercise. Peak rates of glucose oxidation occur approximately 75 to 90 minutes after ingestion and are unaffected by the time of glucose ingestion during exercise. Rates of oxidation also appear not to be influenced to a major extent by the use of different feeding schedules.(ABSTRACT TRUNCATED AT 400 WORDS)

Advances in Exercise, Physical Activity, and Diabetes Mellitus

Publisher: Mary Ann Liebert Inc

Date: 02-2016

DOI: 10.1089/DIA.2016.2508

Muscle power predicts freestyle swimming performance

Publisher: BMJ

Date: 09-1992

DOI: 10.1136/BJSM.26.3.151

Abstract: The purpose of this study was to determine the relationship between non-invasive laboratory measures of 'muscle power' and swim performance over sprint (50 m) and middle-distance (400 m) events. Twenty-two swimmers performed an upper and lower body Wingate Anaerobic Test (WAT) and a maximal sustained power output test (MPO) for the upper body. Peak power (PP) and mean power (MP) were determined for the WAT, while peak sustained workload (WLpeak) was determined for the MPO. Timed swims over 50 m and 400 m were undertaken by all swimmers during which the number of arm strokes per length was recorded. Highly significant relationships were found between sprint-swim speed (S50) and mean power of the arms (MP(arms)) (r = 0.63, P less than 0.01), between S50 and mean power of the legs (MP(legs)) (r = 0.76, P less than 0.001) and between S50 and the distance covered with each arm stroke (DS) (r = 0.91, P less than 0.001). Multiple regression analyses revealed that WAT power indices for the legs did not significantly increase explained variance in S50 above that of the arms. The relationship between WL(peak) and S400 was highly significant (r = 0.70, P less than 0.001) and indicates the importance of arm power in the longer distance swim events.

PGC-1α gene expression is down-regulated by Akt-mediated phosphorylation and nuclear exclusion of FoxO1 in insulin-stimulated skeletal muscle (FASEB Journal (2005) DOI: 10.1096/fj.05-3993fje)

Publisher: Wiley

Date: 08-2009

DOI: 10.1096/FJ.05-3993FJERET

Consecutive bouts of diverse contractile activity alter acute responses in human skeletal muscle

Publisher: American Physiological Society

Date: 04-2009

DOI: 10.1152/JAPPLPHYSIOL.91221.2008

Abstract: We examined acute molecular responses in skeletal muscle to ergent exercise stimuli by combining consecutive bouts of resistance and endurance exercise. Eight men [22.9 ± 6.3 yr, body mass of 73.2 ± 4.5 kg, peak O 2 uptake (V̇o 2peak ) of 54.0 ± 5.7 ml·kg −1 ·min −1 ] were randomly assigned to complete trials consisting of either resistance exercise (8 × 5 leg extension, 80% 1 repetition maximum) followed by a bout of endurance exercise (30 min cycling, 70% V̇o 2peak ) or vice versa. Muscle biopsies were obtained from the vastus lateralis at rest, 15 min after each exercise bout, and after 3 h of passive recovery to determine early signaling and mRNA responses. Phosphorylation of Akt and Akt1 Ser473 were elevated 15 min after resistance exercise compared with cycling, with the greatest increase observed when resistance exercise followed cycling (∼55% P 0.01). TSC2-mTOR-S6 kinase phosphorylation 15 min after each bout of exercise was similar regardless of the exercise mode. The cumulative effect of combined exercise resulted in disparate mRNA responses. IGF-I mRNA content was reduced when cycling preceded resistance exercise (−42%), whereas muscle ring finger mRNA was elevated when cycling was undertaken after resistance exercise (∼52% P 0.05). The hexokinase II mRNA level was higher after resistance cycling (∼45% P 0.05) than after cycling-resistance exercise, whereas modest increases in peroxisome proliferator-activated receptor gamma coactivator-1α mRNA did not reveal an order effect. We conclude that acute responses to erse bouts of contractile activity are modified by the exercise order. Moreover, undertaking ergent exercise in close proximity influences the acute molecular profile and likely exacerbates acute “interference.”

Exercise and type 2 diabetes: new prescription for an old problem

Publisher: Elsevier BV

Date: 08-2012

DOI: 10.1016/J.MATURITAS.2012.05.015

Abstract: During the past 50 years, the prevalence of a cluster of chronic, inactivity-related diseases including obesity, insulin resistance and type 2 diabetes mellitus (T2DM), collectively referred to as 'metabolic syndrome' (MetS) has reached global epidemic proportions. Appropriate exercise training is a clinically proven, cost-effective, primary intervention that delays and in many cases prevents the health burdens associated with MetS. Indeed, there is no single intervention with greater efficacy than physical exercise to reduce the risk of virtually all chronic diseases simultaneously. However compliance to National guidelines for physical activity remains low, with "a lack of time" the most frequently cited barrier to exercise participation by adults, irrespective of age, sex and ethnic background. Part of the growing apathy to modify lifestyle habits is that current public health recommendations may be unrealistic and unattainable for the majority of the populace. Hence, there is an urgent need for innovations in exercise prescription that can be incorporated into daily living and induce clinically beneficial health outcomes. Here we focus attention on a novel form of exercise prescription, high-intensity interval training (HIT), and provide evidence that HIT is a time-efficient and well-tolerated therapeutic intervention to improve cardio-metabolic health in a number of pre-clinical and clinical populations.

Carbohydrate ingestion attenuates the increase in plasma interleukin-6, but not skeletal muscle interleukin-6 mRNA, during exercise in humans

Publisher: Wiley

Date: 06-2001

DOI: 10.1111/J.1469-7793.2001.0585A.X

Abstract: 1. The present study was undertaken to examine the effects of exercise and carbohydrate (CHO) ingestion on interleukin-6 (IL-6) gene expression in skeletal muscle and plasma IL-6 concentration. 2. Seven moderately trained men completed 60 min of exercise at a workload corresponding to each in idual's lactate threshold on four randomised occasions. Two trials were conducted on a bicycle ergometer (Cyc) and two on a running treadmill (Run) either with (CHO) or without (Con) the ingestion of a CHO beverage throughout the exercise. Muscle biopsies were obtained from the vastus lateralis before and immediately after exercise and IL-6 gene expression in these s les was determined using real-time PCR. In addition, venous blood s les were collected at rest, and after 30 min during and at the cessation of exercise. These s les were analysed for plasma IL-6. 3. Irrespective of exercise mode or CHO ingestion, exercise resulted in a 21 +/- 4-fold increase (P < 0.01 main exercise effect) in IL-6 mRNA expression. In contrast, while the mode of exercise did not affect the exercise-induced increase in plasma IL-6, CHO ingestion blunted (P < 0.01) this response. 4. These data demonstrate that CHO ingestion attenuates the plasma IL-6 concentration during both cycling and running exercise. However, because IL-6 mRNA expression was unaffected by CHO ingestion, it is likely that the ingestion of CHO during exercise attenuates IL-6 production by tissues other than skeletal muscle.

Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 2002

DOI: 10.1097/00005768-200201000-00014

Abstract: Five days of a high-fat diet produce metabolic adaptations that increase the rate of fat oxidation during prolonged exercise. We investigated whether enhanced rates of fat oxidation during submaximal exercise after 5 d of a high-fat diet would persist in the face of increased carbohydrate (CHO) availability before and during exercise. Eight well-trained subjects consumed either a high-CHO (9.3 g x kg(-1) x d(-1) CHO, 1.1 g x kg(-1) x d(-1) fat HCHO) or an isoenergetic high-fat diet (2.5 g x kg(-1) x d(-1) CHO, 4.3 g x kg(-1) x d(-1) fat FAT-adapt) for 5 d followed by a high-CHO diet and rest on day 6. On day 7, performance testing (2 h steady-state (SS) cycling at 70% peak O(2) uptake [VO(2peak)] + time trial [TT]) of 7 kJ x kg(-1)) was undertaken after a CHO breakfast (CHO 2 g x kg(-1)) and intake of CHO during cycling (0.8 g x kg(-1) x h(-1)). FAT-adapt reduced respiratory exchange ratio (RER) values before and during cycling at 70% VO(2peak) RER was restored by 1 d CHO and CHO intake during cycling (0.90 +/- 0.01, 0.80 +/- 0.01, 0.91 +/- 0.01, for days 1, 6, and 7, respectively). RER values were higher with HCHO (0.90 +/- 0.01, 0.88 +/- 0.01 (HCHO > FAT-adapt, P FAT-adapt, P < 0.05)). On day 7, fat oxidation remained elevated (73 +/- 4 g vs 45 +/- 3 g, P < 0.05), whereas CHO oxidation was reduced (354 +/- 11 g vs 419 +/- 13 g, P < 0.05) throughout SS in FAT-adapt versus HCHO. TT performance was similar for both trials (25.53 +/- 0.67 min vs 25.45 +/- 0.96 min, NS). Adaptations to a short-term high-fat diet persisted in the face of high CHO availability before and during exercise, but failed to confer a performance advantage during a TT lasting approximately 25 min undertaken after 2 h of submaximal cycling.

Topical and systemic antifungal therapy for the symptomatic treatment of chronic rhinosinusitis

Publisher: Wiley

Date: 05-09-2018

DOI: 10.1002/14651858.CD008263.PUB3

The molecular bases of training adaptation

Publisher: Springer Science and Business Media LLC

Date: 2007

DOI: 10.2165/00007256-200737090-00001

Abstract: Skeletal muscle is a malleable tissue capable of altering the type and amount of protein in response to disruptions to cellular homeostasis. The process of exercise-induced adaptation in skeletal muscle involves a multitude of signalling mechanisms initiating replication of specific DNA genetic sequences, enabling subsequent translation of the genetic message and ultimately generating a series of amino acids that form new proteins. The functional consequences of these adaptations are determined by training volume, intensity and frequency, and the half-life of the protein. Moreover, many features of the training adaptation are specific to the type of stimulus, such as the mode of exercise. Prolonged endurance training elicits a variety of metabolic and morphological changes, including mitochondrial biogenesis, fast-to-slow fibre-type transformation and substrate metabolism. In contrast, heavy resistance exercise stimulates synthesis of contractile proteins responsible for muscle hypertrophy and increases in maximal contractile force output. Concomitant with the vastly different functional outcomes induced by these erse exercise modes, the genetic and molecular mechanisms of adaptation are distinct. With recent advances in technology, it is now possible to study the effects of various training interventions on a variety of signalling proteins and early-response genes in skeletal muscle. Although it cannot presently be claimed that such scientific endeavours have influenced the training practices of elite athletes, these new and exciting technologies have provided insight into how current training techniques result in specific muscular adaptations, and may ultimately provide clues for future and novel training methodologies. Greater knowledge of the mechanisms and interaction of exercise-induced adaptive pathways in skeletal muscle is important for our understanding of the aetiology of disease, maintenance of metabolic and functional capacity with aging, and training for athletic performance. This article highlights the effects of exercise on molecular and genetic mechanisms of training adaptation in skeletal muscle.

Sleep disturbance at simulated altitude indicated by stratified respiratory disturbance index but not hypoxic ventilatory response

Publisher: Springer Science and Business Media LLC

Date: 07-06-2005

DOI: 10.1007/S00421-005-1368-6

Abstract: At high altitudes, the clinically defined respiratory disturbance index (RDI) and high hypoxic ventilatory response (HVR) have been associated with diminished sleep quality. Increased RDI has also been observed in some athletes sleeping at simulated moderate altitude. In this study, we investigated relationships between the HVR of 14 trained male endurance cyclists with variable RDI and sleep quality responses to simulated moderate altitude. Blood oxygen saturation (SpO2%), heart rate, RDI, arousal rate, awakenings, sleep efficiency, rapid eye movement (REM) sleep, non-REM sleep stages 1, 2 and slow wave sleep as percentages of total sleep time (%TST) were measured for two nights at normoxia of 600 m and one night at a simulated altitude of 2,650 m. HVR and RDI were not significantly correlated with sleep stage, arousal rate or awakening response to nocturnal simulated altitude. SpO2 was inversely correlated with total RDI (r = -0.69, P = 0.004) at simulated altitude and with the change in arousal rate from normoxia (r = -0.65, P = 0.02). REM sleep response to simulated altitude correlated with the change, relative to normoxia, in arousal (r = -0.63, P = 0.04) and heart rate (r = -0.61, P = 0.04). When stratified, those athletes at altitude with RDI >20 h(-1) (n = 4) and those with <10 h(-1) (n = 10) exhibited no difference in HVR but the former had larger falls in SpO2 (P = 0.05) and more arousals (P = 0.03). Neither RDI (without stratification) nor HVR were sufficiently sensitive to explain any deterioration in REM sleep or arousal increase. However, the stratified RDI provides a basis for determining potential sleep disturbance in athletes at simulated moderate altitude.

The effect of insulin and exercise on c-Cbl protein abundance and phosphorylation in insulin-resistant skeletal muscle in lean and obese Zucker rats

Publisher: Springer Science and Business Media LLC

Date: 03-2004

DOI: 10.1007/S00125-003-1322-2

Abstract: Recruitment of the protein c-Cbl to the insulin receptor (IR) and its tyrosine phosphorylation via a pathway that is independent from phosphatidylinositol 3'-kinase is necessary for insulin-stimulated GLUT4 translocation in 3T3-L1 adipocytes. The activation of this pathway by insulin or exercise has yet to be reported in skeletal muscle. Lean and obese Zucker rats were randomly assigned to one of three treatment groups: (i). control, (ii). insulin-stimulated or (iii). acute, exhaustive exercise. Hind limb skeletal muscle was removed and the phosphorylation state of IR, Akt and c-Cbl measured. Insulin receptor phosphorylation was increased 12-fold after insulin stimulation ( p<0.0001) in lean rats and threefold in obese rats. Acute exercise had no effect on IR tyrosine phosphorylation. Similar results were found for serine phosphorylation of Akt. Exercise did not alter c-Cbl tyrosine phosphorylation in skeletal muscle of lean or obese rats. However, in contrast to previous studies in adipocytes, c-Cbl tyrosine phosphorylation was reduced after insulin treatment ( p<0.001). We also found that c-Cbl associating protein expression is relatively low in skeletal muscle of Zucker rats compared to 3T3-L1 adipocytes and this could account for the reduced c-Cbl tyrosine phosphorylation after insulin treatment. Interestingly, basal levels of c-Cbl tyrosine phosphorylation were higher in skeletal muscle from insulin-resistant Zucker rats ( p<0.05), but the physiological relevance is not clear. We conclude that the regulation of c-Cbl phosphorylation in skeletal muscle differs from that previously reported in adipocytes.

Measurement of maximal oxygen uptake from two different laboratory protocols in runners and squash players

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 08-1999

DOI: 10.1097/00005768-199908000-00022

Abstract: The aims of the study were to assess whether different test protocols used to elicit maximal oxygen uptake values (VO2max) attain similar results, whether different VO2max protocols were preferable for different athletic groups, and to assess whether the noninvasive criteria used to indicate the attainment of VO2max are achieved similarly in different VO2max testing protocols. This study evaluated the attainment of either VO2max or peak VO2 (VO2peak) during two treadmill VO2max protocols: a progressive speed protocol (PSP) and a progressive incline protocol (PIP). Ten runners and 10 squash players were studied to assess whether achievement of VO2max criteria was either sport-specific or protocol-specific, or both. There were no significant differences in the VO2peak values reached in either PSP or PIP protocol (64.4 +/- 5.9 vs 66.5 +/- 6.0 mLO2 x kg(-1) x min(-1)). But HRmax (196 +/- 5 vs 189 +/- 5 beats x min(-1) PSP vs PIP P < 0.01) and RER (1.14 +/- 0.05 vs 1.07 +/- 0.04 PSP vs PIP P < 0.01) were significantly higher during the PSP test. Fifty percent of the subjects reached a plateau in either test, and of these subjects, 90% satisfied the three noninvasive criteria for VO2max in the PSP group, compared with 10% in the PIP group. The indirect criteria used to assess the attainment of VO2max may be limited, as the VO2peak values were higher in the PIP protocol compared with the PSP protocol, although not significantly different, whereas the HR and RER values were significantly lower in the PIP than PSP protocol. Furthermore, only 50% of subjects demonstrated the plateau phenomenon in oxygen uptake with either protocol. It may be concluded that the measured physiological variables coinciding with VO2peak may differ when different protocols are used to elicit VO2max.

Influence of selected carbohydrate drinks on cycling performance and glycogen use

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 02-1987

DOI: 10.1249/00005768-198702000-00008

Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance

Publisher: American Physiological Society

Date: 12-2000

DOI: 10.1152/JAPPL.2000.89.6.2220

Abstract: We investigated the effect of carbohydrate (CHO) ingestion before and during exercise and in combination on glucose kinetics, metabolism and performance in seven trained men, who cycled for 120 min (SS) at ∼63% of peak power output, followed by a 7 kJ/kg body wt time trial (TT). On four separate occasions, subjects received either a placebo beverage before and during SS (PP) placebo 30 min before and 2 g/kg body wt of CHO in a 6.4% CHO solution throughout SS (PC) 2 g/kg body wt of CHO in a 25.7% CHO beverage 30 min before and placebo throughout SS (CP) or 2 g/kg body wt of CHO in a 25.7% CHO beverage 30 min before and 2 g/kg of CHO in a 6.4% CHO solution throughout SS (CC). Ingestion of CC and CP markedly ( mM) increased plasma glucose concentration ([glucose]) compared with PP and PC (5 mM). However, plasma [glucose] fell rapidly at the onset of SS so that after 80 min it was similar (6 mM) between all treatments. After this time, plasma [glucose] declined in both PP and CP ( P 0.05) but was well maintained in both CC and PC. Ingestion of CC and CP increased rates of glucose appearance (R a ) and disappearance (R d ) compared with PP and PC at the onset of, and early during, SS ( P 0.05). However, late in SS, both glucose R a and R d were higher in CC and PC compared with other trials ( P 0.05). Although calculated rates of glucose oxidation were different when comparing the four trials ( P 0.05), total CHO oxidation and total fat oxidation were similar. Despite this, TT was improved in CC and PC compared with PP ( P 0.05). We conclude that 1) preexercise ingestion of CHO improves performance only when CHO ingestion is maintained throughout exercise, and 2) ingestion of CHO during 120 min of cycling improves subsequent TT performance.

Adaptations to Training in Endurance Cyclists

Publisher: Springer Science and Business Media LLC

Date: 2001

DOI: 10.2165/00007256-200131070-00006

Abstract: Our present scientific knowledge of the effects of specific training interventions undertaken by professional cyclists on selected adaptive responses in skeletal muscle and their consequences for improving endurance performance is limited: sport scientists have found it difficult to persuade elite cyclists to experiment with their training regimens and access to muscle and blood s les from these athletes is sparse. Owing to the lack of scientific study we present a theoretical model of some of the major training-induced adaptations in skeletal muscle that are likely to determine performance capacity in elite cyclists. The model includes, but is not limited to, skeletal muscle morphology, acid-base status and fuel supply. A working premise is that the training-induced changes in skeletal muscle resulting from the high-volume, high-intensity training undertaken by elite cyclists is at least partially responsible for the observed improvements in performance. Using experimental data we provide evidence to support the model.

Commentaries on Viewpoint: A time for exercise: the exercise window

Publisher: American Physiological Society

Date: 2017

DOI: 10.1152/JAPPLPHYSIOL.00938.2016

Exercise as a therapeutic intervention for the prevention and treatment of insulin resistance

Publisher: Wiley

Date: 27-08-2004

DOI: 10.1002/DMRR.505

Abstract: During the past half-century, there has been a dramatic increase in the incidence of obesity, insulin resistance and type 2 diabetes. A hallmark feature of these conditions is impaired glucose tolerance (IGT). Cross-sectional and retrospective epidemiological studies have provided direct evidence that a lack of physical activity is strongly associated with IGT. Indeed, physical inactivity is an independent risk factor for insulin resistance and type 2 diabetes. The primary defect(s) in the development of whole-body insulin resistance remain unclear. However, during the past decade significant progress has been made towards an understanding of the molecular basis underlying the beneficial effects of exercise training in stimulating the entry of glucose into insulin-sensitive tissues. Accordingly, it is now well accepted that regular physical exercise offers an effective therapeutic intervention to improve insulin action in skeletal muscle in insulin-resistant in iduals. This review provides evidence that physical inactivity is significantly associated with IGT and directly contributes to the cascade of events that lead to the expression of the 'exercise-deficient phenotype' associated with insulin resistance and type 2 diabetes. In contrast, exercise training will be shown to significantly reduce the risk of developing insulin resistance by improving glucose tolerance and insulin action in in iduals predisposed to develop type 2 diabetes. Several putative mechanisms for enhanced glucose uptake after exercise training will be discussed. A determination of the underlying biological mechanisms that result from exercise training is essential in order to define the precise variations in physical activity that result in the most desired effects on targeted risk factors, and to aid in the development of such interventions.

Effect of high-fat diet and morning or evening exercise on lipoprotein subfraction profiles: secondary analysis of a randomised trial

Publisher: Springer Science and Business Media LLC

Date: 10-03-2023

DOI: 10.1038/S41598-023-31082-0

Abstract: We investigated the effect of a high-fat diet (HFD) on serum lipid subfractions in men with overweight/obesity and determined whether morning or evening exercise affected these lipid profiles. In a three-armed randomised trial, 24 men consumed an HFD for 11 days. One group of participants did not exercise ( n = 8, CONTROL), one group trained at 06:30 h ( n = 8, EXam), and one group at 18:30 h ( n = 8, EXpm) on days 6–10. We assessed the effects of HFD and exercise training on circulating lipoprotein subclass profiles using NMR spectroscopy. Five days of HFD induced substantial perturbations in fasting lipid subfraction profiles, with changes in 31/100 subfraction variables (adjusted p values [ q ] 0.05). Exercise training induced a systematic change in lipid subfraction profiles, with little overall difference between EXam and EXpm. Compared with CONTROL, exercise training reduced serum concentrations of 20% of fasting lipid subfractions. EXpm reduced fasting cholesterol concentrations in three LDL subfractions by ⁓30%, while EXam only reduced concentration in the largest LDL particles by 19% (all q 0.05). Lipid subfraction profiles changed markedly after 5 days HFD in men with overweight/obesity. Both morning and evening exercise training impacted subfraction profiles compared with no exercise.

Erratum: Dysregulation of muscle lipid metabolism in rats selectively bred for low aerobic running capacity (American Journal of Physiology - Endocrinology and Metabolism (2007) 292, (E1631-E1636))

Publisher: American Physiological Society

Date: 12-2007

DOI: 10.1152/AJPENDO.ZH1-5190-CORR.2007

Effect of high-frequency resistance exercise on adaptive responses in skeletal muscle

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 12-2007

DOI: 10.1249/MSS.0B013E31815729B6

A new reliable laboratory test of endurance performance for road cyclists

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 12-1998

DOI: 10.1097/00005768-199812000-00014

Abstract: The purpose of this study was to devise and evaluate a laboratory test of cycling performance that simulates the variable power demands of competitive road racing. The test is a 100-km time trial interspersed with four 1-km and four 4-km sprints. On three occasions separated by 5-7 d, eight endurance-trained cyclists (peak oxygen uptake 5.0 +/- 0.7 L.min-1, peak power output 411 +/- 43 W, mean +/- SD) performed the test on their own bikes mounted on an air-braked Kingcycle ergometer. Subjects were free to regulate their power output but were asked to complete each sprint and the full distance as quickly as possible. The only feedback given to the cyclists during each test was elapsed distance. In the first test, time for the 100 km and mean times for the 1-km and 4-km sprints were 151:42 +/- 10:36, 1:16 +/- 0:06, and 5:31 +/- 0:16 min:s, respectively these times improved by 1.6-2.2% in the second test, but there was little further improvement in the third test (0.7 to -0.5%). The between-test correlation for 100-km time was 0.93 (95% CI 0.79 to 0.98), and the within-cyclist coefficient of variation was 1.7% (95% CI 1.1 to 2.5%). Mean sprint performance showed similar good reliability (within-subject variation and correlations for the 1-km and 4-km sprint times of 1.9%, 2.0%, 0.93, and 0.81, respectively). The high reliability of this laboratory test will make the test useful for research on performance of competitive road cyclists.

A Short-Term Ketogenic Diet Impairs Markers of Bone Health in Response to Exercise

Publisher: Frontiers Media SA

Date: 21-01-2020

DOI: 10.3389/FENDO.2019.00880

Impaired interval exercise responses in elite female cyclists at moderate simulated altitude

Publisher: American Physiological Society

Date: 11-2000

DOI: 10.1152/JAPPL.2000.89.5.1819

Abstract: The effect of hypoxia on the response to interval exercise was determined in eight elite female cyclists during two interval sessions: a sustained 3 × 10-min endurance set (5-min recovery) and a repeat sprint session comprising three sets of 6 × 15-s sprints (work-to-relief ratios were 1:3, 1:2, and 1:1 for the 1st, 2nd, and 3rd sets, respectively, with 3 min between each set). During exercise, cyclists selected their maximum power output and breathed either atmospheric air (normoxia, 20.93% O 2 ) or a hypoxic gas mix (hypoxia, 17.42% O 2 ). Power output was lower in hypoxia vs. normoxia throughout the endurance set (244 ± 18 vs. 226 ± 17, 234 ± 18 vs. 221 ± 25, and 235 ± 18 vs. 221 ± 25 W for 1st, 2nd, and 3rd sets, respectively P 0.05) but was lower only in the latter stages of the second and third sets of the sprints (452 ± 56 vs. 429 ± 49 and 403 ± 54 vs. 373 ± 43 W, respectively P 0.05). Hypoxia lowered blood O 2 saturation during the endurance set (92.9 ± 2.9 vs. 95.4 ± 1.5% P 0.05) but not during repeat sprints. We conclude that, when elite cyclists select their maximum exercise intensity, both sustained (10 min) and short-term (15 s) power are impaired during hypoxia, which simulated moderate (∼2,100 m) altitude.

Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis

Publisher: Wiley

Date: 05-04-2013

DOI: 10.1113/JPHYSIOL.2012.244897

Nutritional strategies to minimize fatigue during prolonged exercise: Fluid, electrolyte and energy replacement

Publisher: Informa UK Limited

Date: 1997

DOI: 10.1080/026404197367317

Abstract: While the presence of palatable (20 mmol l-1) concentrations of NaCl in drinks containing carbohydrate consumed during intense exercise would not be expected to promote absorption or significantly help maintain fluid balance, there is no doubt that athletes should ingest some from of carbohydrate (other than fructose) during moderate-intensity exercise lasting > 90 min. As only approximately 20 g of ingested carbohydrate is oxidized in the first hour of exercise, athletes should probably consume 100 ml every 10 min of a dilute (3-5 g 100 ml-1) carbohydrate solution and thereafter increase the carbohydrate concentration to approximately 10 g 100 ml-1 to match the peak (approximately 1 g min-1) rates of plasma glucose oxidation. Drinking more than those amounts of carbohydrate may increase muscle glycogen oxidation by attenuating the fall in plasma insulin concentration and thereby delaying fat mobilization, especially at relatively low (55% of peak oxygen consumption) intensity exercise. As carbohydrate ingestion does not slow the rate of glycogen utilization in working muscle, it is also advisable for endurance athletes to start exercise with an adequate supply of muscle glycogen, irrespective of whether or not they ingest carbohydrate during exercise. While carbohydrate ingestion 'spares' conversion of liver glycogen to plasma glucose and prevents hypoglycemia, it does not delay the fatigue associated with a low (approximately 20 mmol kg-1) glycogen content in working muscle. Conversely, increases in glycogen content of working muscle at the start of exercise have no effect on the rates of plasma glucose oxidation. Higher initial rates of glycogen utilization by active muscles in 'carbohydrate-loaded' subjects decrease the indirect oxidation (via lactate) of non-working muscle glycogen, rather than the conversion of liver glycogen to plasma glucose. Hence, athletes should ingest carbohydrate during endurance exercise even if they have 'carbohydrate-loaded' before exercise.

Aerobic training reverses high-fat diet-induced pro-inflammatory signalling in rat skeletal muscle

Publisher: Springer Science and Business Media LLC

Date: 02-07-2010

DOI: 10.1007/S00421-010-1559-7

Time-restricted eating improves measures of daily glycaemic control in people with type 2 diabetes

Publisher: Elsevier BV

Date: 03-2023

DOI: 10.1016/J.DIABRES.2023.110569

Exercise Plus Presleep Protein Ingestion Increases Overnight Muscle Connective Tissue Protein Synthesis Rates in Healthy Older Men

Publisher: Human Kinetics

Date: 05-2021

DOI: 10.1123/IJSNEM.2020-0222

Abstract: Protein ingestion and exercise stimulate myofibrillar protein synthesis rates. When combined, exercise further increases the postprandial rise in myofibrillar protein synthesis rates. It remains unclear whether protein ingestion with or without exercise also stimulates muscle connective tissue protein synthesis rates. The authors assessed the impact of presleep protein ingestion on overnight muscle connective tissue protein synthesis rates at rest and during recovery from resistance-type exercise in older men. Thirty-six healthy, older men were randomly assigned to ingest 40 g intrinsically L -[1- 13 C]-phenylalanine and L -[1- 13 C]-leucine-labeled casein protein (PRO, n = 12) or a nonprotein placebo (PLA, n = 12) before going to sleep. A third group performed a single bout of resistance-type exercise in the evening before ingesting 40 g intrinsically-labeled casein protein prior to sleep (EX+PRO, n = 12). Continuous intravenous infusions of L-[ ring- 2 H 5 ]-phenylalanine and L -[1- 13 C]-leucine were applied with blood and muscle tissue s les collected throughout overnight sleep. Presleep protein ingestion did not increase muscle connective tissue protein synthesis rates (0.049 ± 0.013 vs. 0.060 ± 0.024%/hr in PLA and PRO, respectively p = .73). Exercise plus protein ingestion resulted in greater overnight muscle connective tissue protein synthesis rates (0.095 ± 0.022%/hr) when compared with PLA and PRO ( p .01). Exercise increased the incorporation of dietary protein-derived amino acids into muscle connective tissue protein (0.036 ± 0.013 vs. 0.054 ± 0.009 mole percent excess in PRO vs. EX+PRO, respectively p .01). In conclusion, resistance-type exercise plus presleep protein ingestion increases overnight muscle connective tissue protein synthesis rates in older men. Exercise enhances the utilization of dietary protein-derived amino acids as precursors for de novo muscle connective tissue protein synthesis during overnight sleep.

Effects of 3 days of carbohydrate supplementation on muscle glycogen content and utilisation during a 1-h cycling performance

Publisher: Springer Science and Business Media LLC

Date: 05-1997

DOI: 10.1007/S004210050180

Abstract: This study compared the effects of supplementing the normal diets of six trained cyclists [maximal oxygen uptake (VO2max) 4.5 (0.36) l.min-1 values are mean (SD)] with additional carbohydrate (CHO) on muscle glycogen utilisation during a 1-h cycle time-trial (TT). Using a randomised crossover design, subjects consumed either their normal diet (NORM) for 3 days, which consisted of 426 (137) g.day-1 CHO [5.9 (1.4) g. kg-1 body mass (BM)], or additional CHO (SUPP) to increase their intake to 661 (76) g.day-1 [9.3 (0.7) g. kg-1 BM]. The SUPP diet elevated muscle glycogen content from 459 (83) to 565 (62) mmol.kg-1 dry weight (d.w.) (P < 0.05). However, despite the increased pre-exercise muscle glycogen stores, there was no difference in the distance cycled during the TT [40.41 (1.44) vs 40.18 (1.76) km for NORM and SUPP, respectively]. With NORM, muscle glycogen declined from 459 (83) to 175 (64) mmol.kg-1 d.w., whereas with SUPP the corresponding values were 565 (62) and 292 (113) mmol.kg-1 d.w. Accordingly, both muscle glycogen utilisation [277 (64) vs 273 (114) mmol.kg-1 d.w.] and total CHO oxidation [169 (20) vs 165 (30) g.h-1 for NORM and SUPP, respectively] were similar. Neither were there any differences in plasma glucose or lactate concentrations during the two experimental trials. Plasma glucose concentration averaged 5.5 (0.5) and 5.6 (0.6) mmol.l-1, while plasma lactate concentration averaged 4.4 (1.9) and 4.4 (2.3) mmol.l-1 for NORM and SUPP, respectively. The results of this study show that when well-trained subjects increase the CHO content of their diet for 3 days from 6 to 9 g.kg-1 BM there is only a modest increase in muscle glycogen content. Since supplementary CHO did not improve TT performance, we conclude that additional CHO provides no benefit to performance for athletes who compete in intense, continuous events lasting 1 h. Furthermore, the substantial muscle CHO reserves observed at the termination of exercise indicate that whole-muscle glycogen depletion does not determine fatigue at this exercise intensity and duration.

Effect of a carbohydrate mouth rinse on simulated cycling time-trial performance commenced in a fed or fasted state

Publisher: Canadian Science Publishing

Date: 02-2013

DOI: 10.1139/APNM-2012-0300

Abstract: It is presently unclear whether the reported ergogenic effect of a carbohydrate (CHO) mouth rinse on cycling time-trial performance is affected by the acute nutritional status of an in idual. Hence, the aim of this study was to investigate the effect of a CHO mouth rinse on a 60-min simulated cycling time-trial performance commenced in a fed or fasted state. Twelve competitive male cyclists each completed 4 experimental trials using a double-blinded Latin square design. Two trials were commenced 2 h after a meal that contained 2.5 g·kg −1 body mass of CHO (FED) and 2 after an overnight fast (FST). Prior to and after every 12.5% of total time during a performance ride, either a 10% maltodextrin (CHO) or a taste-matched placebo (PLB) solution was mouth rinsed for 10 s then immediately expectorated. There were significant main effects for both pre-ride nutritional status (FED vs. FST p 0.01) and CHO mouth rinse (CHO vs. PLB p 0.01) on power output with an interaction evident between the interventions (p 0.05). The CHO mouth rinse improved mean power to a greater extent after an overnight fast (282 vs. 273 W, 3.4% p 0.01) compared with a fed state (286 vs. 281 W, 1.8% p 0.05). We concluded that a CHO mouth rinse improved performance to a greater extent in a fasted compared with a fed state however, optimal performance was achieved in a fed state with the addition of a CHO mouth rinse.

Improved 2000-meter rowing performance in competitive oarswomen after caffeine ingestion

Publisher: Human Kinetics

Date: 12-2000

DOI: 10.1123/IJSNEM.10.4.464

Abstract: Eight competitive oarswomen (age, 22 ± 3 years mass, 64.4 ± 3.8 kg) performed three simulated 2,000-m time trials on a rowing ergometer. The trials, which were preceded by a 24-hour dietary and training control and 72 hours of caffeine abstinence, were condueted 1 hour after ingesting caffeine (6 or 9 mg kg ’ body mass) or placebo. Plasma free fatty acid concentrations before exercise were higher with caffeine than placebo (0.67 ± 0.34 vs. 0.72 ± 0.36 vs. 0.30±0.10 mM for 6 and 9 mg · kg −1 caffeine and placebo, respectively p .05). Performance lime improved 0.7% (95% confidence interval [Cf] 0 to 1.5%) with 6 mg kg −1 caffeine and 1.3$ (95% CI 0.5 to 2.0%) with 9 mg · kg −1 caffeine. The first 500 m of the 2,000 m was faster with the higher caffeine dose compared with placebo or the lower dose (1.53 ± 0.52 vs. 1.55 ± 0.62 and 1.56 ± 0.43 min p = .02). We concluded that caffeine produces a worthwhile enhancement of performance in a controlled laboratory setting, primarily by improving the first 500 m of a 2,000-m row.

No differences in muscle protein synthesis rates following ingestion of wheat protein, milk protein, and their protein blend in healthy, young males

Publisher: Cambridge University Press (CUP)

Date: 18-02-2021

DOI: 10.1017/S0007114521000635

Abstract: Plant-derived proteins have been suggested to have less anabolic properties when compared with animal-derived proteins. Whether blends of plant- and animal-derived proteins can compensate for their lesser anabolic potential has not been assessed. The present study compares post-prandial muscle protein synthesis rates following the ingestion of milk protein with wheat protein or a blend of wheat plus milk protein in healthy, young males. In a randomised, double-blind, parallel-group design, 36 males (23 ( sd 3) years) received a primed continuous L-[ring- 13 C 6 ]-phenylalanine infusion after which they ingested 30 g milk protein (MILK), 30 g wheat protein (WHEAT) or a 30 g blend combining 15 g wheat plus 15 g milk protein (WHEAT+MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent myofibrillar protein synthesis rates. Ingestion of protein increased myofibrillar protein synthesis rates in all treatments ( P 0·001). Post-prandial myofibrillar protein synthesis rates did not differ between MILK v . WHEAT (0·053 ( sd 0·013) v . 0·056 ( sd 0·012) %·h −1 , respectively t test P = 0·56) or between MILK v . WHEAT+MILK (0·053 ( sd 0·013) v . 0·059 ( sd 0·025) %·h −1 , respectively t test P = 0·46). In conclusion, ingestion of 30 g milk protein, 30 g wheat protein or a blend of 15 g wheat plus 15 g milk protein increases muscle protein synthesis rates in young males. Furthermore, muscle protein synthesis rates following the ingestion of 30 g milk protein do not differ from rates observed after ingesting 30 g wheat protein or a blend with 15 g milk plus 15 g wheat protein in healthy, young males.

Impaired High-Intensity Cycling Performance Time at Low Levels of Dehydration

Publisher: Georg Thieme Verlag KG

Date: 10-1994

DOI: 10.1055/S-2007-1021076

Abstract: On two separate occasions six trained subjects (peak oxygen consumption [VO2peak] 4.41/min) rode for 60 min at 70% of VO2peak and then to exhaustion at 90% of VO2peak to determine the effects of mild dehydration on high-intensity cycling performance time in the heat (32 degrees C, 60% relative humidity, wind speed 3 km/h). In one trial (F) subjects ingested a 400 ml bolus of 20 mmol/l NaCl immediately before, and then as repetitive 120 ml feedings every 10 min during the first 50 min of exercise. In the other trial they did not ingest fluid (NF) either before or during exercise. The order of testing was in a counter-balanced random sequence. For the first 60 min of exercise mean (+/- SD) VO2 (2.90 +/- 0.39 vs 2.93 +/- 0.38 l/min) and respiratory exchange ratio (RER 0.95 +/- 0.03 vs 0.94 +/- 0.04) values were similar between F and NF trials. However, weight loss was significantly reduced during F compared to NF (0.16 +/- 0.39 vs 1.30 +/- 0.22 kg p < 0.005) and high-intensity cycling time to exhaustion was significantly increased (9.8 +/- 3.9 vs 6.8 +/- 3.0 min p < 0.005). Increased cycling times to exhaustion in the F trial were not associated with any measurable differences in heart rate (HR), body temperature, respiratory gas exchange, leg muscle power over 5 sec, or the degree to which fluid ingestion reduced the level of dehydration within the group. Only the ratings of perceived exertion (RPE) and plasma anti diuretic hormone (ADH) concentrations were significantly increased in the NF trial compared to the F trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Gamma tocopherol supplementation prevents exercise induced coagulation and platelet aggregation

Publisher: Elsevier BV

Date: 02-2010

DOI: 10.1016/J.THROMRES.2009.11.015

Effects of Providing High-Fat versus High-Carbohydrate Meals on Daily and Postprandial Physical Activity and Glucose Patterns: a Randomised Controlled Trial

Publisher: MDPI AG

Date: 30-04-2018

DOI: 10.3390/NU10050557

Low intrinsic exercise capacity in rats predisposes to age-dependent cardiac remodeling independent of macrovascular function

Publisher: American Physiological Society

Date: 03-2013

DOI: 10.1152/AJPHEART.00638.2012

Abstract: Rats selectively bred for low (LCR) or high (HCR) intrinsic running capacity simultaneously present with contrasting risk factors for cardiovascular and metabolic disease. However, the impact of these phenotypes on left ventricular (LV) morphology and microvascular function, and their progression with aging, remains unresolved. We tested the hypothesis that the LCR phenotype induces progressive age-dependent LV remodeling and impairments in microvascular function, glucose utilization, and β-adrenergic responsiveness, compared with HCR. Hearts and vessels isolated from female LCR ( n = 22) or HCR ( n = 26) were studied at 12 and 35 wk. Nonselected N:NIH founder rats (11 wk) were also investigated ( n = 12). LCR had impaired glucose tolerance and elevated plasma insulin (but not glucose) and body-mass at 12 wk compared with HCR, with early LV remodeling. By 35 wk, LV prohypertrophic and glucose transporter GLUT4 gene expression were up- and downregulated, respectively. No differences in LV β-adrenoceptor expression or cAMP content between phenotypes were observed. Macrovascular endothelial function was predominantly nitric oxide (NO)-mediated in both phenotypes and remained intact in LCR for both age-groups. In contrast, mesenteric arteries microvascular endothelial function, which was impaired in LCR rats regardless of age. At 35 wk, endothelial-derived hyperpolarizing factor-mediated relaxation was impaired whereas the NO contribution to relaxation is intact. Furthermore, there was reduced β 2 -adrenoceptor responsiveness in both aorta and mesenteric LCR arteries. In conclusion, diminished intrinsic exercise capacity impairs systemic glucose tolerance and is accompanied by progressive development of LV remodeling. Impaired microvascular perfusion is a likely contributing factor to the cardiac phenotype.

Lower nocturnal blood glucose response to a potato-based mixed evening meal compared to rice in individuals with type 2 diabetes

Publisher: Elsevier BV

Date: 04-2021

DOI: 10.1016/J.CLNU.2020.09.049

University Of Toronto

Location: Canada

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Memorial University Of Newfoundland

Location: Canada

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Auckland Institute Of Technology

Location: New Zealand

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Brock University

Location: Canada

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Australian Catholic University

Location: Australia

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Sports Science Institute Of South Africa

Location: South Africa

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Ball State University

Location: United States of America

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Liverpool John Moores University

Location: United Kingdom of Great Britain and Northern Ireland

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Loughborough University

Location: United Kingdom of Great Britain and Northern Ireland

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RMIT University Bundoora Campus

Location: Australia

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University Of Cape Town

Location: South Africa

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Discovery Projects - Grant ID: DP0663862

Start Date: 2006

End Date: 12-2009

Amount: $200,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP100100010

Start Date: 02-2010

End Date: 12-2013

Amount: $324,851.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP200103542

Start Date: 2020

End Date: 12-2024

Amount: $493,000.00

Funder: Australian Research Council