ORCID Profile
0000-0002-2414-7539
Current Organisations
Bethel University
,
Deakin University
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Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 26-06-2019
DOI: 10.1249/MSS.0000000000002071
Abstract: The cumulative influence of sleep time on endurance performance remains unclear. This study examined the effects of three consecutive nights of both sleep extension (SE) and sleep restriction (SR) on endurance cycling performance. Endurance cyclists/triathletes ( n = 9) completed a counterbalanced crossover experiment with three conditions: SR, normal sleep (NS), and SE. Each condition comprised seven days/nights of data collection (−2, −1, D1, D2, D3, D4, and +1). Sleep was monitored using actigraphy throughout. Participants completed testing sessions on days D1–D4 that included an endurance time-trial (TT), mood, and psychomotor vigilance assessment. Perceived exertion (RPE) was monitored throughout each TT. Participants slept habitually before D1 however, time in bed was reduced by 30% (SR), remained normal (NS), or extended by 30% (SE) on nights D1, D2, and D3. Data were analyzed using generalized estimating equations. On nights D1, D2, and D3, total sleep time was longer ( P 0.001) in the SE condition (8.6 ± 1.0, 8.3 ± 0.6, and 8.2 ± 0.6 h, respectively) and shorter ( P 0.001) in the SR condition (4.7 ± 0.8, 4.8 ± 0.8, and 4.9 ± 0.4 h) compared with NS (7.1 ± 0.8, 6.5 ± 1.0, and 6.9 ± 0.7 h). Compared with NS, TT performance was slower ( P 0.02) on D3 of SR (58.8 ± 2.5 vs 60.4 ± 3.7 min) and faster ( P 0.02) on D4 of SE (58.7 ± 3.4 vs 56.8 ± 3.1 min). RPE was not different between or within conditions. Compared with NS, mood disturbance was higher, and psychomotor vigilance impaired, after SR. Compared with NS, psychomotor vigilance improved after SE. Sleep extension for three nights led to better maintenance of endurance performance compared with normal and restricted sleep. Sleep restriction impaired performance. Cumulative sleep time affects performance by altering the perceived exertion of a given exercise intensity. Endurance athletes should sleep h per night to optimize performance.
Publisher: Wiley
Date: 2003
DOI: 10.1046/J.1440-1681.2002.03794.X
Abstract: 1. Studies have shown that, in isolated skeletal muscles, maximum isometric force production (P o ) is dependent on muscle redox state. Endurance training increases the anti‐oxidant capacity of skeletal muscles, a factor that could impact on the force‐producing capacity following exogenous exposure to an oxidant. We tested the hypothesis that 12 weeks treadmill training would increase anti‐oxidant capacity in rat skeletal muscles and alter their response to exogenous oxidant exposure. 2. At the conclusion of the 12 week endurance‐training programme, soleus (slow‐twitch) muscles from trained rats had greater citrate synthase (CS) and catalase (CAT) activity compared with soleus muscles from untrained rats ( P 0.05). In contrast, CAT activity of extensor digitorum longus (EDL fast‐twitch) muscles from trained rats was not different to EDL muscles of untrained rats. The CS activity was lower in EDL muscles from trained compared with untrained rats ( P 0.05). 3. Equilibration with exogenous hydrogen peroxide (H 2 O 2 , 5 mmol/L) increased the P o of soleus muscles from untrained rats for the duration of treatment (30 min), whereas the P o of EDL muscles was affected biphasically, with a small increase initially (after 5 min), followed by a more marked decrease in P o (after 30 min). The H 2 O 2 ‐induced increase in P o of soleus muscles from trained rats was less than that in untrained rats ( P 0.05), but no differences were observed in the P o of EDL muscles following training. 4. The results indicate that 12 weeks endurance running training conferred adaptations in soleus but not EDL muscles. These adaptations were associated with an attenuation of the oxidant‐induced increase in P o of soleus muscles from trained compared with untrained rats. We conclude that endurance training‐adapted soleus muscles have a slightly altered redox–force relationship.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2002
DOI: 10.1097/00005768-200212000-00015
Abstract: Because it is believed that bone may respond to exercise differently at different ages, we compared bone responses in immature and mature rats after 12 wk of treadmill running. Twenty-two immature (5-wk-old) and 21 mature (17-wk-old) female Sprague Dawley rats were randomized into a running (trained, P = 10 immature, 9 mature) or a control group (controls, P = 12 immature, 12 mature) before sacrifice 12 wk later. Rats ran on a treadmill five times per week for 60-70 min at speeds up to 26 m.min. Both at baseline and after intervention, we measured total body, lumbar spine, and proximal femoral bone mineral, as well as total body soft tissue composition using dual-energy x-ray absorptiometry (DXA). After sacrificing the animals, we measured dynamic and static histomorphometry and three-point bending strength of the tibia. Running training was associated with greater differences in tibial subperiosteal area, cortical cross-sectional area, peak load, stiffness, and moment of inertia in immature and mature rats (P < 0.05). The trained rats had greater periosteal bone formation rates (P < 0.01) than controls, but there was no difference in tibial trabecular bone histomorphometry. Similar running-related gains were seen in DXA lumbar spine area (P = 0.04) and bone mineral content (BMC P = 0.03) at both ages. For total body bone area and BMC, the immature trained group increased significantly compared with controls (P < 0.05), whereas the mature trained group gained less than did controls (P < 0.01). In this model, where a similar physical training program was performed by immature and mature female rats, we demonstrated that both age groups were sensitive to loading and that bone strength gains appeared to result more from changes in bone geometry than from improved material properties.
Publisher: Wiley
Date: 04-01-2000
DOI: 10.1046/J.1440-1681.2000.03211.X
Abstract: 1. Osteoporosis is a major public health problem that is predicted to worsen over the next decade and preventative strategies that increase bone strength have become the focus of substantial research. 2. Although mechanical load is a primary factor in the acquisition and maintenance of skeletal tissue, the type of exercise used and when in life it is most effectively prescribed remain inconclusive. 3. The present study compared 10 weeks of resistance training in both young and mature female Sprague‐Dawley rats and measured bone density and body composition by dual energy X‐ray absorptiometry and biomechanical properties by three point bending tests of the tibia and femur. 4. No significant differences were observed for any of the bone parameters when comparing exercise and control groups at either age. This was despite using a comparable training protocol to that in humans and using loads of approximately 150% bodyweight. 5. The present study concludes that more intensive work programmes of resistance training or different outcome measures are required when using animal models for skeletal research.
Publisher: American Chemical Society (ACS)
Date: 05-03-2020
DOI: 10.26434/CHEMRXIV.11930031
Abstract: Psi4 is a free and open-source ab initio electronic structure program providing Hartree–Fock, density functional theory, many-body perturbation theory, configuration interaction, density cumulant theory, symmetry-adapted perturbation theory, and coupled-cluster theory. Most of the methods are quite efficient thanks to density fitting and multi-core parallelism. The program is a hybrid of C++ and Python, and calculations may be run with very simple text files or using the Python API, facilitating post-processing and complex workflows method developers also have access to most of Psi4’s core functionality via Python. Job specification may be passed using The Molecular Sciences Software Institute (MolSSI) QCSchema data format, facilitating interoperability. A rewrite of our top-level computation driver, and concomitant adoption of the MolSSI QCArchive Infrastructure project, make the latest version of Psi4 well suited to distributed computation of large numbers of independent tasks. The project has fostered the development of independent software components that may be reused in other quantum chemistry programs. / / /
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2012
Publisher: American Physiological Society
Date: 05-2019
DOI: 10.1152/AJPRENAL.00317.2018
Abstract: Patients with end-stage kidney disease on dialysis have increased mortality and reduced physical activity, contributing to impaired physical function. Although exercise programs have demonstrated a positive effect on physiological outcomes such as cardiovascular function and strength, there is a reduced focus on physical function. The aim of this review was to determine whether exercise programs improve objective measures of physical function indicative of activities of daily living for patients with end-stage kidney disease on dialysis. A systematic search of Medline, Embase, the Cochrane Central Register of Controlled Trials, and Cumulative Index to Nursing and Allied Health Literature identified 27 randomized control trials. Only randomized control trials using an exercise intervention or significant muscular activation in the intervention, a usual care, nonexercising control group, and at least one objective measure of physical function were included. Participants were ≥18 yr of age, with end-stage kidney disease, undergoing hemo- or peritoneal dialysis. Systematic review of the literature and quality assessment of the included studies used the Cochrane Collaboration’s tool for assessing risk bias. A meta-analysis was completed for the 6-min walk test. Data from 27 studies with 1,156 participants showed that exercise, regardless of modality, generally increased 6-min walk test distance, sit-to-stand time or repetitions, and grip strength as well as step and stair climb times or repetitions, dynamic mobility, and short physical performance battery scores. From the evidence available, exercise, regardless of modality, improved objective measures of physical function for end-stage kidney disease patients undergoing dialysis. It is acknowledged that further well-designed randomized control trials are required.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2011
Publisher: Wiley
Date: 06-2017
DOI: 10.14814/PHY2.13312
Publisher: Springer Science and Business Media LLC
Date: 08-2000
Abstract: Skeletal muscle mass in genetically obese (ob/ob) mice displays a reduced mass compared with their normal lean counterpart mice. However, the functional capacity of the available skeletal muscle mass in these animals has not yet been determined. To investigate the properties of skeletal muscle in ob/ob mice and determine the effects of leptin administration on skeletal muscle in these mice. Following 4 weeks of i.p. leptin administration (or control treatment) anaesthetized ob/ob and lean mice had their extensor digitorum longus and soleus muscles removed, and standard measures of isometric contractile properties and fatigability were performed. Histochemistry was used to determine fibre type proportions and in idual fibre areas of all muscles. Leptin had no effect on the morphology or function of ob/ob skeletal muscle despite reducing body mass in ob/ob mice. Force production was unaltered in obese mice. However, a significant prolongation of contraction and relaxation times were evident. Obese skeletal muscle was also more fatigue resistant. Fibre proportions displayed a more slow type profile in ob/ob skeletal muscle, and in conjunction with previous work a reduced ability to hypertrophy. Skeletal muscle from obese mice is morphologically and functionally different from lean mouse skeletal muscle. Obese muscle is very similar to skeletal muscle from aged mice, and the specific contractile properties examined appear to be determined by the fibre make-up of these muscles.
Publisher: Frontiers Media SA
Date: 03-02-2022
DOI: 10.3389/FPHYS.2022.837697
Abstract: Resistance-based blood flow restriction training (BFRT) improves skeletal muscle strength and size. Unlike heavy-load resistance training (HLRT), there is debate as to whether strength adaptations following BFRT interventions can be primarily attributed to concurrent muscle hypertrophy, as the magnitude of hypertrophy is often minor. The present study aimed to investigate the effect of 7 weeks of BFRT and HLRT on muscle strength and hypertrophy. The expression of protein growth markers from muscle biopsy s les was also measured. Male participants were allocated to moderately heavy-load training (HL n = 9), low-load BFRT (LL + BFR n = 8), or a control (CON n = 9) group to control for the effect of time. HL and LL + BFR completed 21 training sessions (3 d.week −1 ) comprising bilateral knee extension and knee flexion exercises (HL = 70% one-repetition maximum (1-RM), LL + BFR = 20% 1-RM + blood flow restriction). Bilateral knee extension and flexion 1-RM strength were assessed, and leg muscle CSA was measured via peripheral quantitative computed tomography. Protein growth markers were measured in vastus lateralis biopsy s les taken pre- and post the first and last training sessions. Biopsy s les were also taken from CON at the same time intervals as HL and LL + BFR. Knee extension 1-RM strength increased in HL (19%) and LL + BFR (19%) but not CON (2% p & 0.05). Knee flexion 1-RM strength increased similarly between all groups, as did muscle CSA (50% femur length HL = 2.2%, LL + BFR = 3.0%, CON = 2.1% TIME main effects). 4E-BP1 (Thr37/46) phosphorylation was lower in HL and LL + BFR immediately post-exercise compared with CON in both sessions ( p & 0.05). Expression of other growth markers was similar between groups ( p & 0.05). Overall, BFRT and HLRT improved muscle strength and size similarly, with comparable changes in intramuscular protein growth marker expression, both acutely and chronically, suggesting the activation of similar anabolic pathways. However, the low magnitude of muscle hypertrophy was not significantly different to the non-training control suggesting that strength adaptation following 7 weeks of BFRT is not driven by hypertrophy, but rather neurological adaptation.
Publisher: SAGE Publications
Date: 28-07-2020
Publisher: Frontiers Media SA
Date: 15-05-2019
Publisher: Springer Science and Business Media LLC
Date: 13-04-2010
DOI: 10.1007/S00421-010-1466-Y
Abstract: This study investigated cycling performance and oxygen uptake V(O)₂kinetics between upright and two commonly used recumbent (R) postures, 65 degrees R and 30 degrees R. On three occasions, ten young active males performed three bouts of high-intensity constant-load (85% peak-workload achieved during a graded test) cycling in one of the three randomly assigned postures (upright, 65 degrees R or 30 degrees R). The first bout was performed to fatigue and second and third bouts were limited to 7 min. A subset of seven subjects performed a final constant-load test to failure in the supine posture. Exercise time to failure was not altered when the body inclination was lowered from the upright (13.1 +/- 4.5 min) to 65 degrees R (10.5 +/- 2.7 min) and 30 degrees R (11.5 +/- 4.6 min) postures but it was significantly shorter in the supine posture (5.8 +/- 2.1 min) when compared with the three inclined postures. Resulting kinetic parameters from a tri-exponential analysis of breath-by-breath V(O)₂data during the first 7 min of exercise were also not different between the three inclined postures. However, inert gas rebreathing analysis of cardiac output revealed a greater cardiac output and stroke volume in both recumbent postures compared with the upright posture at 30 s into the exercise. These data suggest that increased cardiac function may counteract the reduction of hydrostatic pressure from upright approximately 25 mmHg to 65 degrees R approximately 22 mmHg and 30 degrees R approximately 18 mmHg such that perfusion of active muscle presumably remains largely unchanged, and also therefore, V(O)₂kinetics and performance during high-intensity cycling.
Publisher: Frontiers Media SA
Date: 30-04-2021
Publisher: Springer Science and Business Media LLC
Date: 18-09-2021
DOI: 10.1186/S12889-021-11595-X
Abstract: Awareness of the cumulative stress placed on first responders and tactical operators is required to manage acute fatigue, which can impair occupational performance, and may precipitate negative chronic health outcomes. The aim of this review was to investigate the utility of heart rate variability (HRV) to monitor stress and allostatic load among these populations. A systematic search of Academic Search Complete, MEDLINE complete, PsycINFO, SPORTDiscus and Scopus databases was conducted. Eligibility criteria: original peer reviewed research articles, written in English, published between 1985 and 2020, using human participants employed as a first responder or tactical operator, free from any psychological disorder. Of the 360 articles screened, 60 met the inclusion criteria and were included for full text assessment. Articles were classified based on single or repeated stressor exposure and the time of HRV assessment (baseline, during stressor, post stressor). Singular stressful events elicited a reduction in HRV from baseline to during the event. Stressors of greater magnitude reduced HRV for extended durations post stressor. Lower resting HRV was associated with lower situational awareness and impaired decision-making performance in marksmanship and navigation tasks. There were insufficient studies to evaluate the utility of HRV to assess allostatic load in repeated stressor contexts. A reduction in HRV occurred in response to acute physical and cognitive occupational stressors. A slower rate of recovery of HRV after the completion of acute occupational stressors appears to occur in response to stressors of greater magnitude. The association between lower HRV and lower decision-making performance poses as a useful tool but further investigations on within subject changes between these factors and their relationship is required. More research is required to investigate the suitability of HRV as a measure of allostatic load in repeated stress exposures for fatigue management in first responder and tactical operators.
Publisher: Frontiers Media SA
Date: 02-12-2015
Publisher: Frontiers Media SA
Date: 2021
Publisher: American Physiological Society
Date: 03-2020
DOI: 10.1152/AJPRENAL.00576.2019
Abstract: End-stage kidney disease is associated with reduced exercise capacity, muscle atrophy, and impaired muscle function. While these may be improved with exercise, single modalities of exercise do not traditionally elicit improvements across all required physiological domains. Blood flow-restricted exercise may improve all of these physiological domains with low intensities traditionally considered insufficient for these adaptions. Investigation of this technique appeals, but is yet to be evaluated, in patients undergoing dialysis. With the use of a progressive crossover design, 10 satellite patients undergoing hemodialysis underwent three exercise conditions over 2 wk: two bouts (10 min) of unrestricted cycling during two consecutive hemodialysis sessions ( condition 1), two bouts of cycling with blood flow restriction while off hemodialysis on 2 separate days ( condition 2), and two bouts of cycling with blood flow restriction during two hemodialysis sessions ( condition 3). Outcomes included hemodynamic responses (heart rate and blood pressure) throughout all sessions, participant-perceived exertion and discomfort on a Borg scale, and evaluation of ultrafiltration rates and dialysis adequacy (Kt/V) obtained post hoc. Hemodynamic responses were consistent regardless of condition. Significant increases in heart rate, systolic blood pressure, and mean arterial blood pressure ( P 0.05) were observed postexercise followed by a reduction in blood pressures during the 60-min recovery (12, 5, and 11 mmHg for systolic, diastolic, and mean arterial pressures, respectively). Blood pressures returned to predialysis ranges following the recovery period. Blood flow restriction did not affect ultrafiltration achieved or Kt/V. Hemodynamic safety and tolerability of blood flow restriction during aerobic exercise on hemodialysis is comparable to standard aerobic exercise.
Publisher: Springer Science and Business Media LLC
Date: 04-07-2015
DOI: 10.1007/S00421-015-3213-X
Abstract: Light-load blood flow restriction exercise (BFRE) may provide a novel training method to limit the effects of age-related muscle atrophy in older adults. Therefore, the purpose of this study was to compare the haemodynamic response to resistance and aerobic BFRE between young adults (YA n = 11 22 ± 1 years) and older adults (OA n = 13 69 ± 1 years). On two occasions, participants completed BFRE or control exercise (CON). One occasion was leg press (LP 20 % 1-RM) and the other was treadmill walking (TM 4 km h(-1)). Haemodynamic responses (HR, Q, SV and BP) were recorded during baseline and exercise. At baseline, YA and OA were different for some haemodynamic parameters (e.g. BP, SV). The relative responses to BFRE were similar between YA and OA. Blood pressures increased more with BFRE, and also for LP over TM. Q increased similarly for BFRE and CON (in both LP and TM), but with elevated HR and reduced SV (TM only). While BFR conferred slightly greater haemodynamic stress than CON, this was lower for walking than leg-press exercise. Given similar response magnitudes between YA and OA, these data support aerobic exercise being a more appropriate BFRE for prescription in older adults that may contribute to limiting the effects of age-related muscle atrophy.
Publisher: Springer Science and Business Media LLC
Date: 13-10-2005
DOI: 10.1007/S00421-005-0057-9
Abstract: The time sustained during a graded cycle exercise is approximately 10% longer in an upright compared with a supine posture. However, during constant-load cycling this effect is unknown. Therefore, we tested the postural effect on the performance of high-intensity constant-load cycling. Twenty-two active subjects (11 men, 11 women) performed two graded tests (one upright, one supine), and of those 22, 10 subjects (5 men, 5 women) performed three high-intensity constant-load tests (one upright, two supine). To test the postural effect on performance at the same absolute intensity, during the upright and one of the supine constant-load tests subjects cycled at 80% of the peak power output achieved during the upright graded test. To test the postural effect on performance at the same relative intensities, during the second supine test subjects cycled at 80% of the peak power output achieved during the supine graded test. Exercise time on the graded and absolute intensity constant-load tests for all subjects was greater (P<0.05) in the upright compared with supine posture (17.9+/-3.5 vs. 16.1+/-3.1 min for graded 13.2+/-8.7 vs. 5.2+/-1.9 min for constant-load). This postural effect at the same absolute intensity was larger in men (19.4+/-8.5 upright vs. 6.6+/-1.6 supine, P 0.05) and it was correlated (P<0.05) with both the difference in VO2 between positions during the first minute of exercise (r=0.67) and the height of the subjects (r=0.72). In conclusion, there is a very large postural effect on performance during constant-load cycling exercise and this effect is significantly larger in men than women.
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.JSAMS.2017.04.012
Abstract: The progressive age-related declines in muscle health and physical function in older adults are related to muscle size and strength. Walking with an applied blood flow restriction is an alternative to maintain muscle volume in older adults to increase the value for time spent walking. Therefore, the aim of this study was to examine the effect of adding blood flow restriction to low-intensity walking on clinical measures of physical function. Sedentary older men and women were randomised to either a low-intensity blood flow restriction walking group (BFRW n=10), or a non-blood flow restriction walking control group (CON n=9). Participants were assessed at baseline, three-weeks and six-weeks for the 30second sit to stand, six-minute walk test, timed up and go, and a modified Queen's College step test. While a rating of perceived exertion (RPE) for training sessions at baseline, three-weeks and six-weeks. BFRW typically resulted in a 2.5-4.5 fold greater improvement in performance on all measures of physical function compared with CON among these older adults. However, RPE was greater for BFRW at all time points (for baseline, three-weeks, six-weeks: 14±0 11±0 11±0) compared with CON (8±0 7±0 8±0), despite declining across the study for BFRW. The greater improvement in physical function with blood flow restriction demonstrates how this addition can increase the quality of simple walking exercise for populations that may be contraindicated to heavy-load resistance training.
Publisher: Oxford University Press (OUP)
Date: 02-2014
DOI: 10.1016/J.CROHNS.2013.07.006
Abstract: The association of fatigue with decreased physical performance and underlying mechanisms are poorly understood in Crohn's disease (CD). We aimed to measure and compare self-reported fatigue with skeletal muscle fatigue in CD subjects and healthy controls, and to identify associated factors that may be amenable to change. Demographic and clinical data were collected and fatigue assessed using the Fatigue Impact Scale (FIS) in 27 consecutive CD patients and 22 matched healthy controls. Circulating cytokines and growth factors were measured. The rate of quadriceps muscle fatigue was assessed using an isokinetic dynamometer as the decrement of force with 30 contractions performed over a 5-minute period. Compared with healthy controls, CD patients reported greater levels of fatigue (mean global FIS score 45.3 vs 10.5, physical dimension score 12.3 vs 2.7 respectively each p<0.01) and muscle fatigue (-5.2 vs -1.3 Nm min(-1) p<0.05). The two indices were correlated (r = -0.52 in CD p<0.01). Patients with CD had lower mean serum IGF-1 levels (16.1 vs 25.4 pmol/L, p<0.01) and higher oxidative stress (TBARS assay 4.3 vs 3.9 μM, p<0.05). On multivariate analysis, low serum vitamin D, IGF-1 and magnesium, and higher IL-6 levels were associated with increased muscle fatigue (all p ≤ 0.05). Subjects with CD had more muscle fatigue than matched healthy controls and this correlated well with self-reported fatigue. Of circulating factors that were independently associated with increased muscle fatigue, vitamin D, magnesium and IGF-1 could be targeted in future studies to reduce fatigue and improve physical performance.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2018
Publisher: Wiley
Date: 27-04-2020
DOI: 10.1111/SMS.13676
Publisher: Wiley
Date: 02-2017
DOI: 10.14814/PHY2.13142
Publisher: Springer Science and Business Media LLC
Date: 24-12-2015
Publisher: Elsevier BV
Date: 02-2023
DOI: 10.1016/J.APERGO.2022.103935
Abstract: The study aimed to determine if overnight heart rate variability (HRV) is reflective of workload and stress during military training. Measures of cognitive load, perceived exertion, physical activity, nocturnal HRV, cognitive performance and sleep were recorded for a 15-day assessment period in 32 combat engineers. The assessment period consisted of 4 phases, PRE, FIELD, BASE and RECOVERY that exposed trainees to periods of sleep deprivation and restriction. The FIELD phase was characterised by an increase in mood disturbance, perceived exertion, physical activity, HRV and a reduction in sleep quantity (p < 0.05). Measures of HRV returned to PRE-values quicker than subjective wellbeing responses. The combination of sleep duration (β = -0.002, F = 13.42, p < 0.001) and physical activity (metabolic equivalents, β = -0.483, F = 5.95, p = 0.017), the main stressors of the exercise, provided a significant effect in the best predictive model of HRV. The different recovery rates of HRV and subjective wellbeing suggest a different physiological and psychological response.
Publisher: American Chemical Society (ACS)
Date: 05-03-2020
DOI: 10.26434/CHEMRXIV.11930031.V1
Abstract: Psi4 is a free and open-source ab initio electronic structure program providing Hartree–Fock, density functional theory, many-body perturbation theory, configuration interaction, density cumulant theory, symmetry-adapted perturbation theory, and coupled-cluster theory. Most of the methods are quite efficient thanks to density fitting and multi-core parallelism. The program is a hybrid of C++ and Python, and calculations may be run with very simple text files or using the Python API, facilitating post-processing and complex workflows method developers also have access to most of Psi4’s core functionality via Python. Job specification may be passed using The Molecular Sciences Software Institute (MolSSI) QCSchema data format, facilitating interoperability. A rewrite of our top-level computation driver, and concomitant adoption of the MolSSI QCArchive Infrastructure project, make the latest version of Psi4 well suited to distributed computation of large numbers of independent tasks. The project has fostered the development of independent software components that may be reused in other quantum chemistry programs.
Publisher: Frontiers Media SA
Date: 22-10-2019
Publisher: Frontiers Media SA
Date: 21-08-2019
Publisher: Frontiers Media SA
Date: 10-09-2019
Publisher: Frontiers Media SA
Date: 25-10-2021
DOI: 10.3389/FSPOR.2021.738870
Abstract: Background: We investigated whether a brief cold water immersion between two cycling time trials (TT) improves the performance of the latter compared with passive and active recovery in normothermic conditions (~20°C). Methods: In Experiment 1 10 active participants (4 women) completed two 4-km TT (Ex1 and Ex2, each preceded by a 12 min moderate-intensity warm-up) separated by a 15 min recovery period consisting of: (a) passive rest (PAS) or (b) 5 min cold water immersion at 8°C (CWI-5). In Experiment 2 , 13 different active males completed the same Ex1 and Ex2 bouts separated by a 15 min recovery consisting of: (a) PAS, (b) 10 min cold water immersion at 8°C (CWI-10) or (c) 15 min of moderate-intensity active recovery (ACT). Results: In both experiments, the time to complete the 4-km TT-s was not different ( P & 0.05, ES = 0.1) among the trials neither in Ex1 ( Experiment 1 : PAS: 414 ± 39 s CWI-5: 410 ± 39 s Experiment 2 : PAS: 402 ± 41 s CWI-10: 404 ± 43 s ACT: 407 ± 41 s) nor Ex2 ( Experiment 1 : PAS: 432 ± 43 s CWI-5: 428 ± 47 s Experiment 2 : PAS: 418 ± 52 s CWI-10: 416 ± 57 s ACT: 421 ± 50 s). In addition, in all conditions, the time to complete the time trials was longer ( P & 0.05, ES = 0.4) in Ex2 than Ex1. Core temperature was lower ( P & 0.05) during the majority of Ex2 after CW-5 compared with passive rest ( Experiment 1 ) and after CWI-10 compared with PAS and ACT ( Experiment 2 ). Perceived exertion was also lower ( P & 0.05) at mid-point of Ex2 after CWI-5 compared with PAS ( Experiment 1 ) as well as overall lower during the CWI-10 compared with PAS and ACT conditions ( Experiment 2 ). Conclusion: A post-exercise 5–10 min cold water immersion does not influence subsequent 4-km TT performance in normothermia, despite evoking reductions in thermal strain.
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.PHYSBEH.2011.06.005
Abstract: Physical activity has been reported to improve cognitive function in humans and rodents, possibly via a brain-derived neurotrophic factor (BDNF)-regulated mechanism. In this study of human subjects, we have assessed the effects of acute and chronic exercise on performance of a face-name matching task, which recruits the hippoc us and associated structures of the medial temporal lobe, and the Stroop word-colour task, which does not, and have assessed circulating concentrations of BDNF and IGF-1 in parallel. The results show that a short period of high-intensity cycling results in enhancements in performance of the face-name matching, but not the Stroop, task. These changes in cognitive function were paralleled by increased concentration of BDNF, but not IGF-1, in the serum of exercising subjects. 3 weeks of cycling training had no effect on cardiovascular fitness, as assessed by VO2 scores, cognitive function, or serum BDNF concentration. Increases in fitness, cognitive function and serum BDNF response to acute exercise were observed following 5 weeks of aerobic training. These data indicate that both acute and chronic exercise improve medial temporal lobe function concomitant with increased concentrations of BDNF in the serum, suggesting a possible functional role for this neurotrophic factor in exercise-induced cognitive enhancement in humans.
Publisher: Frontiers Media SA
Date: 30-10-2020
Publisher: BMJ
Date: 14-09-2018
DOI: 10.1136/BJSPORTS-2018-099322
Abstract: To characterise the sleep of elite athletes and to identify factors associated with training and competition that negatively affect sleep. Prognosis systematic review. Three databases (PubMed, SCOPUS and SPORTDiscus) were searched from inception to 26 February 2018. Included studies objectively reported total sleep time (TST) and/or sleep efficiency (SE) in elite athletes. Studies were required to be observational or to include an observational trial. Fifty-four studies were included. During training, many studies reported athletes were unable to achieve TST (n=23/41) and/or SE (n=16/37) recommendations. On the night of competition, most studies reported athletes were unable to achieve TST (n=14/18) and/or SE (n=10/16) recommendations. TST was shorter (60 min) the night of competition compared with previous nights. SE was lower (1%) the night of competition compared with the previous night. TST was shorter the night of night competition (start ≥18:00 80 min) and day competition (20 min) compared with the previous night. SE was lower (3%–4%) the night of night competition but unchanged the night of day competition compared with previous nights. Early morning training (start :00), increases in training load ( %), late night/early morning travel departure times, eastward air travel and altitude ascent impaired sleep. Athletes were often unable to achieve sleep recommendations during training or competition periods. Sleep was impaired the night of competition compared with previous nights. Early morning training, increases in training load, travel departure times, jet lag and altitude can impair athletes’ sleep. CRD42017074367.
Publisher: Springer Science and Business Media LLC
Date: 11-09-2017
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-04-2022
DOI: 10.1249/MSS.0000000000002930
Abstract: Heart rate variability (HRV) has shown sensitivity to the acute stressors experienced by defense personnel. This study examines the suitability of overnight HRV as a repeated measure of allostatic load in defense personnel. Daily measures of sleep, cognitive load, and perceived exertion were reported for the 12-wk duration of basic military training (BMT) in 48 recruits. Physical activity, subjective well-being, and HRV were measured weekly. The natural log of the root mean square of successive differences of interbeat intervals (Ln RMSSD) and the Ln RMSSD to interbeat interval ratio (Ln RMSSD:RRi ratio) during predicted slow wave sleep were used for HRV. Physical performance was assessed via the 20-m shuttle run and maximal push-up test in weeks 2 and 8 of BMT with predicted V̇O 2 peak values calculated. Predicted V̇O 2 peak increased from 42.6 ± 4.5 to 48.0 ± 2.7 mL·kg −1 ·min −1 ( P 0.001). Ln RMSSD was elevated in weeks 7 and 10, and the Ln RMSSD:RRi ratio was elevated in week 10 above all other weeks ( P 0.05). An increase in perceived exertion ( F = 9.10, P = 0.003) and subjective fatigue ( F = 6.97, P = 0.009), as well as a reduction in V̇O 2 peak ( F = 7.95, P = 0.009), in idually predicted an increase in Ln RMSSD. The best predictive model of Ln RMSSD included perceived exertion ( F = 8.16, P = 0.005), subjective fatigue ( F = 8.49, P = 0.004), the number of awakenings during sleep ( F = 7.79, P = 0.006), and the change in V̇O 2 peak ( F = 19.110, P 0.001). HRV was predicted by subjective recruit responses to BMT workloads rather than objective measures of physical activity. Improvements in cardiorespiratory fitness depicted recruits who experienced enough stress to facilitate physiological adaptation, which was reflected by a reduction in HRV during BMT. Monitoring HRV and HRV in relation to interbeat interval length may provide a better tool for determining allostatic load than HRV alone.
Publisher: Springer Science and Business Media LLC
Date: 19-01-2018
DOI: 10.1007/S00421-018-3806-2
Abstract: We examined the concurrent characteristics of the remote development of strength and cross-sectional area (CSA) of upper body skeletal muscle in response to lower body resistance training performed with an applied blood flow restriction (BFR). Males allocated to an experimental BFR group (EXP n = 12) or a non-BFR control group (CON n = 12) completed 7-weeks of resistance training comprising three sets of unilateral bicep curls [50% 1-repetition maximum (1-RM)], then four sets of bilateral knee extension and flexion exercises (30% 1-RM). EXP performed leg exercises with an applied BFR (60% limb occlusion pressure). 1-RM strength was measured using bilateral leg exercises and unilateral bicep curls in both trained and untrained arms. Muscle CSA was measured via peripheral quantitative computed tomography in the dominant leg and both arms. 1-RM in the trained arm increased more in EXP (2.5 ± 0.4 kg mean ± SEM) than the contralateral untrained arm (0.8 ± 0.4 kg), and the trained arm of CON (0.6 ± 0.3 kg, P < 0.05). The increase in knee extension 1-RM was twofold that of CON (P 0.05), while untrained arm CSA did not change (P > 0.05). Lower limb BFR training increased trained arm strength more than the contralateral untrained arm, and the trained arm of controls. However, there was no additional effect on muscle CSA. These findings support evidence for a BFR training-derived remote strength transfer that may be relevant to populations with localised movement disorders.
Publisher: Informa UK Limited
Date: 07-2016
DOI: 10.1080/15438627.2016.1202828
Abstract: The purpose of the present study was to determine the efficacy of the multi-component training distress scale (MTDS), in monitoring swimmers prior to national competition. Twenty-one national-level adolescent swimmers completed eight weeks of testing. Once a week participants completed an 8 × 50 m sprint test, vertical jump test, sit-and-reach test, the MTDS and the Recovery-Stress Questionnaire for Athletes (REST-Q). All testing was incorporated into the swimmers' normal training programme. The REST-Q accounted for the following variances in performance: flexibility (14.6%, p = 0.009), power output (17.7%, p = 0.003), swimming speed (15.5%, p = 0.006) and swimming endurance (17.5%, p = 0.002). In comparison, the MTDS accounted for the following variances in performance: flexibility (12.1%, p = 0.095), power output (16.4%, p = 0.023), swimming speed (20.5%, p = 0.003) and swimming speed endurance (23.8%, p = 0.001). The findings of the current study suggest that both the REST-Q Sport and the MTDS have the capacity to predict performance on a range of fitness components associated with swimming.
Publisher: Informa UK Limited
Date: 16-09-2019
DOI: 10.1080/02640414.2019.1661561
Abstract: This study investigated effects of total sleep deprivation on self-paced endurance performance, and heart rate (HR) indices of athletes' "readiness to perform". Endurance athletes (n = 13) completed a crossover experiment comprising a normal sleep (NS) and sleep deprivation (SD) condition. Each required completion of an endurance time-trial (TT) on consecutive days (D1, D2) separated by normal sleep or total sleep deprivation. Finishing time, perceived exertion (RPE), mood, psychomotor vigilance (PVT), and HR responses were assessed. Time on D2 of SD was 10% slower than D2 of NS (64 ± 7 vs 59 ± 4 min, P < 0.01), and 11% slower than D1 of SD (58 ± 5 min, P < 0.01). Subjective to objective (RPE:mean HR) intensity ratio was higher on D2 of SD compared with D2 of NS and D1 of SD (P < 0.01). Mood disturbance and PVT mean response time increased on D2 of SD compared with D2 of NS and D1 of SD. Anaerobic threshold and change in TT time were correlated (R = -0.73, P < 0.01). Sleep helps to optimise endurance performance. Subjective to objective intensity ratios appear sensitive to effects of sleep on athletes' readiness. Research examining more subtle sleep manipulation is required.
Publisher: Wiley
Date: 23-07-2015
DOI: 10.1111/SMS.12297
Abstract: Light-load exercise training with blood flow restriction (BFR) increases muscle strength and size. However, the hemodynamics of BFR exercise appear elevated compared with non-BFR exercise. This questions the suitability of BFR in special/clinical populations. Nevertheless, hemodynamics of standard prescription protocols for BFR and traditional heavy-load exercise have not been compared. We investigated the hemodynamics of two common BFR exercise methods and two traditional resistance exercises. Twelve young males completed four unilateral elbow flexion exercise trials in a balanced, randomized crossover design: (a) heavy load [HL 80% one-repetition maximum (1-RM)] (b) light load (LL 20% 1-RM) and two other light-load trials with BFR applied (c) continuously at 80% resting systolic blood pressure (BFR-C) or (d) intermittently at 130% resting systolic blood pressure (BFR-I). Hemodynamics were measured at baseline, during exercise, and for 60-min post-exercise. Exercising heart rate, blood pressure, cardiac output, and rate-pressure product were significantly greater for HL and BFR-I compared with LL. The magnitude of hemodynamic stress for BFR-C was between that of HL and LL. These data show reduced hemodynamics for continuous low-pressure BFR exercise compared with intermittent high-pressure BFR in young healthy populations. BFR remains a potentially viable method to improve muscle mass and strength in special/clinical populations.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 27-10-2021
DOI: 10.1519/JSC.0000000000004157
Abstract: Roberts, SSH, Aisbett, B, Teo, W-P, and Warmington, S. Monitoring effects of sleep extension and restriction on endurance performance using heart rate indices. J Strength Cond Res 36(12): 3381–3389, 2022—Heart rate (HR) indices are useful for monitoring athlete fatigue or “readiness to perform.” This study examined whether HR indices are sensitive to changes in readiness following sleep restriction (SR) and sleep extension (SE). Nine athletes completed a crossover study with 3 conditions: SR, normal sleep (NS), and SE. Each condition required completion of an endurance time trial (TT) on 4 consecutive days (D1–D4). Athletes slept habitually before D1 however, time in bed was reduced by 30% (SR), remained normal (NS), or extended by 30% (SE), on subsequent nights (D1–D3). Daily resting HR and HR variability were recorded. The maximal rate of HR increase and HR recovery was determined from a constant-load test before TTs. Exercise intensity ratios incorporating mean HR, mean power (W), and perceived exertion (RPE) were recorded at steady state during constant-load tests (W:HR SS ) and during TTs (W:HR TT , RPE:HR TT ). Compared with D4 of NS, RPE:HR TT was lower on D4 of SE ( p = 0.008)—when TT performances were faster. Compared with D1 of SR, RPE:HR TT was higher on D3 and D4 of SR ( p 0.02). Moderate correlations were found between percentage changes in W:HR TT and changes in TT finishing time in SR ( r = −0.67, p = 0.049) and SE ( r = −0.69, p = 0.038) conditions. Intensity ratios incorporating mean HR seem sensitive to effects of sleep duration on athlete readiness to perform. When interpreting intensity ratios, practitioners should consider potential effects of prior sleep duration to determine whether sleep-promoting interventions are required (e.g., SE).
Publisher: Springer Science and Business Media LLC
Date: 06-10-2013
DOI: 10.1007/S00421-013-2737-1
Abstract: To examine the effects of four commonly used recovery treatments applied between two bouts of intense endurance cycling on the performance of the second bout in normothermia (~21 °C). Nine trained men completed two submaximal exhaustive cycling bouts (Ex1 and Ex2: 5 min at ~50 % [Formula: see text] peak, followed by 5 min at ~60 % [Formula: see text] peak and then ~80 % [Formula: see text] peak to failure) separated by 30 min of (a) cold water immersion at 15 °C (C15), (b) contrast water therapy alternating 2.5 min at 8 °C and 2.5 min at 40 °C (CT), (c) thermoneutral water immersion at 34 °C (T34) and (d) cycling at ~40 % [Formula: see text] peak (AR). Exercise performance, cardiovascular and metabolic responses during Ex1 were similar among all trials. However, time to failure (~80 % [Formula: see text] peak bout) during Ex2 was significantly (P < 0.05) longer in C15 (18.0 ± 1.6) than in CT (14.5 ± 1.5), T34 (12.4 ± 1.4) and AR (10.6 ± 1.0) and it was also longer (P < 0.05) in CT than AR. Core temperature and heart rate were significantly (P < 0.05) lower during the initial ~15 min of Ex2 during C15 compared with all other conditions but they reached similar levels at the end of Ex2. A 30 min period of C15 was more beneficial in maintaining intense submaximal cycling performance than CT, T34 and AR and CT was also more beneficial than T34 and AR. These effects were not mediated by the effect of water immersion per se, but by the continuous (C15) or intermittent (CT) temperature stimulus (cold) applied throughout the recovery.
Publisher: Elsevier BV
Date: 07-1996
DOI: 10.1016/S0143-4160(96)90052-4
Abstract: We have presented an assay for measuring the rate of sarcoplasmic reticulum (SR) Ca2+ uptake and Ca2+ release in skeletal muscle homogenates using the fluorescent Ca2+ probe Fura-2. Using this assay, we investigated the effects of an elevated temperature (40 degrees C) and lowered pH (6.8), two factors proposed to be involved in skeletal muscle fatigue, on SR Ca2+ uptake. The EDL muscle was found to have a higher rate of Ca2+ uptake than the soleus (34%). Exposure of the muscles to a raised temperature, but not a reduced pH, resulted in a reduction in the rate of Ca2+ uptake in both the EDL and soleus homogenates. This uptake process was blocked by cyclopiazonic acid (CPA) a specific inhibitor of the major transport protein of the sarcoplasmic reticulum, the Ca(2+)-ATPase. Calcium release was induced using AgNO3 after loading of the vesicles during the uptake process. It was found that AgNO3 was only effective in producing Ca2+ release in the EDL muscles. The soleus muscles did not release Ca2+ under varying [Mg2+] or with Hg2+ substitution for Ag+, suggesting that fast- and slow-twitch muscle fibres require different conditions for maximum Ca2+ release, or that different isoforms of the Ca2+ release channels are present in the different fibres.
Publisher: AIP Publishing
Date: 13-05-2020
DOI: 10.1063/5.0006002
Abstract: PSI4 is a free and open-source ab initio electronic structure program providing implementations of Hartree–Fock, density functional theory, many-body perturbation theory, configuration interaction, density cumulant theory, symmetry-adapted perturbation theory, and coupled-cluster theory. Most of the methods are quite efficient, thanks to density fitting and multi-core parallelism. The program is a hybrid of C++ and Python, and calculations may be run with very simple text files or using the Python API, facilitating post-processing and complex workflows method developers also have access to most of PSI4’s core functionalities via Python. Job specification may be passed using The Molecular Sciences Software Institute (MolSSI) QCSCHEMA data format, facilitating interoperability. A rewrite of our top-level computation driver, and concomitant adoption of the MolSSI QCARCHIVE INFRASTRUCTURE project, makes the latest version of PSI4 well suited to distributed computation of large numbers of independent tasks. The project has fostered the development of independent software components that may be reused in other quantum chemistry programs.
Publisher: BMJ
Date: 22-06-2017
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2017
DOI: 10.1519/JSC.0000000000001779
Abstract: Brandner, CR, and Warmington, SA. Delayed onset muscle soreness and perceived exertion after blood flow restriction exercise. J Strength Cond Res 31(11): 3101–3108, 2017—The purpose of this study was to determine the perceptual responses to resistance exercise with heavy loads (80% 1 repetition maximum [1RM]), light loads (20% 1RM), or light loads in combination with blood flow restriction (BFR). Despite the use of light loads, it has been suggested that the adoption of BFR resistance exercise may be limited because of increases in delayed onset muscle soreness (DOMS) and perceived exertion. Seventeen healthy untrained males participated in this balanced, randomized cross-over study. After 4 sets of elbow-flexion exercise, participants reported ratings of perceived exertion (RPE), with DOMS also recorded for 7 days after each trial. Delayed onset muscle soreness was significantly greater for low-pressure continuous BFR (until 48 hours postexercise) and high-pressure intermittent BFR (until 72 hours postexercise) than for traditional heavy-load resistance exercise and light-load resistance exercise. In addition, RPE was higher for heavy-load resistance exercise and high-pressure intermittent BFR than for low-pressure continuous BFR, with all trials greater than light-load resistance exercise. For practitioners working with untrained participants, this study provides evidence to suggest that to minimize the perception of effort and postexercise muscle soreness associated with BFR resistance exercise, continuous low-pressure application may be more preferential than intermittent high-pressure application. Importantly, these perceptual responses are relatively short-lived (∼2 days) and have previously been shown to subside after a few exercise sessions. Combined with smaller initial training volumes (set × repetitions), this may limit RPE and DOMS to strengthen uptake and adherence and assist in program progression for muscle hypertrophy and gains in strength.
Publisher: Wiley
Date: 08-01-2014
DOI: 10.1111/SMS.12169
Abstract: Sprint (high-intensity) exercise performance is reduced when immediately preceded by cold water immersion (CWI). We aimed to investigate whether this performance effect could be attenuated by combining an active recovery (arm exercise) with hip-level CWI, and whether this attenuation may be related to an effect on core temperature (Tcore ). Participants (n = 8) completed three Wingate tests before (Ex1) and after (Ex2) four different 30-min recovery interventions: CWI at 15 °C (CW15), arm exercise during CWI at 15 °C (CW15+AE), arm exercise during thermoneutral immersion at 34 °C (TW34+AE) and non-immersed arm exercise (AE). After AE and TW34+AE, performance during Ex2 was not different from Ex1 while after CW15+AE and CW15, performance was reduced by 4.9% and 7.6%, respectively. Arm exercise maintained Tcore during recovery in CW15+AE, while it declined to a larger extent upon commencement of Ex2 (-0.9 °C) when compared with CW15 (-0.6 °C). This suggests similar leg muscle cooling during recovery in CW15 and CW15+AE. Without any other significant effects (e.g., on blood lactate), these data suggest that the improvement in sprint performance following an active CWI recovery, over CWI alone, may be related to maintained Tcore and its effect on neurophysiological mechanisms that drive muscle activation, but not by reduced muscle cooling.
Publisher: Springer Science and Business Media LLC
Date: 05-11-2009
DOI: 10.1007/S00421-009-1254-8
Abstract: This study compared the rate of fatigue and lower limb EMG activities during high-intensity constant-load cycling in upright and supine postures. Eleven active males performed seven cycling exercise tests: one upright graded test, four fatigue tests (two upright, two supine) and two EMG tests (one upright, one supine). During the fatigue tests participants initially performed a 10 s all-out effort followed by a constant-load test with 10 s all-out bouts interspersed every minute. The load for the initial two fatigue tests was 80% of the peak power (PP) achieved during the graded test and these continued until failure. The remaining two fatigue tests were performed at 20% PP and were limited to the times achieved during the 80% PP tests. During the EMG tests subjects performed a 10 s all-out effort followed by a constant-load test to failure at 80% PP. Normalised EMG activities (% maximum, NEMG) were assessed in five lower limb muscles. Maximum power and maximum EMG activity prior to each fatigue and EMG test were unaffected by posture. The rate of fatigue at 80% PP was significantly higher during supine compared with upright posture (-68 +/- 14 vs. -26 +/- 6 W min(-1), respectively, P < 0.05) and the ergence of the fatigue responses occurred by the second minute of exercise. NEMG responses were significantly higher in the supine posture by 1-4 min of exercise. Results show that fatigue is significantly greater during supine compared with upright high-intensity cycling and this effect is accompanied by a reduced activation of musculature that is active during cycling.
Publisher: IEEE
Date: 06-2013
Publisher: Frontiers Media SA
Date: 13-08-2019
No related grants have been discovered for Stuart Warmington.