ORCID Profile
0000-0002-2642-7083
Current Organisations
Griffith University
,
UT Southwestern Medical Center
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Publisher: American Physiological Society
Date: 10-2018
DOI: 10.1152/AJPREGU.00132.2018
Abstract: Heart failure (HF) patients are susceptible to heat strain during exercise, secondary to blunted skin blood flow (SkBF) responses, which may be explained by impaired nitric oxide (NO)-dependent vasodilation. Folic acid improves vascular endothelial function and SkBF through NO-dependent mechanisms in healthy older in iduals and patients with cardiovascular disease. We examined the effect of folic acid supplementation (5 mg/day for 6 wk) on vascular function [brachial artery flow-mediated dilation (FMD)] and SkBF responses [cutaneous vascular conductance (CVC)] during 60 min of exercise at a fixed metabolic heat production (300 Ẇ Hprod ) in a 30°C environment in 10 patients with HF (New York Heart Association Class I–II) and 10 healthy controls (CON). Serum folic acid concentration increased in HF [preintervention (pre): 1.4 ± 0.2 postintervention (post): 8.9 ± 6.7 ng/ml, P = 0.01] and CON (pre: 1.3 ± 0.6 post: 5.2 ± 4.9 ng/ml, P = 0.03). FMD improved by 2.1 ± 1.3% in HF ( P 0.01), but no change was observed in CON postintervention ( P = 0.20). During exercise, the external workload performed on the cycle ergometer to attain the fixed level of heat production for exercise was similar between groups (HF: 60 ± 13 CON: 65 ± 20 external workload, P = 0.52). Increases in CVC during exercise were similar in HF (pre: 0.89 ± 0.43 post: 0.83 ± 0.45 au/mmHg, P = 0.80) and CON (pre: 2.01 ± 0.79 post: 2.03 ± 0.72 au/mmHg, P = 0.73), although the values were consistently lower in HF for both pre- and postintervention measurement intervals ( P 0.05). These findings demonstrate that folic acid improves vascular endothelial function in patients with HF but does not enhance SkBF during exercise at a fixed metabolic heat production in a warm environment.
Publisher: Wiley
Date: 06-12-2016
DOI: 10.1113/EP085423
Publisher: Informa UK Limited
Date: 26-04-2020
Publisher: Elsevier BV
Date: 03-2020
Publisher: American Thoracic Society
Date: 07-2021
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2019
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-06-2020
DOI: 10.1249/MSS.0000000000002336
Abstract: Regional heterogeneity of the human heart plays an important role in left ventricular (LV) and right ventricular (RV) function and may contribute to enhanced myocardial efficiency in the athlete’s heart. This study comprehensively characterized regional and transmural myocardial tissue deformation (strain) in recreationally active (RA) and endurance-trained (ET) men to determine if regional nonuniformity evolves alongside morphological adaptations associated with endurance training. Echocardiography was used to measure LV and RV global, regional (apical, mid, basal) and transmural (endocardial, epicardial) longitudinal strain in 30 endurance-trained (ET) (age, 31 ± 2 yr body mass index, 23.1 ± 0.5 kg·m −2 V˙O 2peak , 60.2 ± 6.5 mL·kg −1 ·min −1 ) and 30 RA (age: 29 ± 2 yr body mass index, 23.4 ± 0.4 kg·m −2 V˙O 2peak : 42.6 ± 4.6 mL·kg −1 ·min −1 ). Nonuniformity was characterized using apex-to-base and transmural (endocardial-to-epicardial) strain gradients. Global longitudinal strain was similar in ET and RA in the left (−17.4% ± 0.4% vs −17.8% ± 0.5%, P = 0.662) and right ventricle (−25.8% ± 0.8% vs 26.4% ± 1.0%, P = 0.717). The apex-to-base strain gradient was greater in ET than RA in the left (−6.5% ± 0.7% vs −2.7% ± 0.8%, P = 0.001) and right ventricle (−9.6% ± 1.8% vs −3.0% ± 1.6%, P = 0.010). The LV transmural strain gradient was greater than RV in both groups, but similar in ET and RA (−4.7% ± 0.2% vs −4.7% ± 0.2%, P = 0.850), whereas RV transmural strain gradient was greater in ET than RA (−3.4% ± 0.3% vs −1.6% ± 0.4%, P = 0.003). RV apex-to-base and transmural strain gradients correlated with RV end-diastolic area ( R = 0.536 & 0.555, respectively, P 0.01) and V˙O 2peak ( R = 0.415 & 0.677, respectively, P 0.01). Transmural nonuniformity is more pronounced in the left ventricle than the RV free wall however, RV functional nonuniformity develops markedly after endurance training. Differences in myocardial architecture and exercise-induced wall stress in the left and right ventricles are possible explanations for the marked functional nonuniformity throughout the myocardium and in response to endurance exercise training.
Publisher: American Physiological Society
Date: 2022
DOI: 10.1152/JAPPLPHYSIOL.00474.2021
Abstract: [Formula: see text] provides a better estimate of [Formula: see text] than PJ CO 2 at peak exercise, and V D /V T[ET] provides a better estimate of V D /V T[art] than V D /V T[J] at peak exercise. Although we reported significant correlations, we did not find an identity between [Formula: see text] and estimates of [Formula: see text], nor did we find an identity between V D /V T[art] and estimates of V D /V T[art] . Thus, caution should be taken and estimates of [Formula: see text] and V D /V T should only be used if s ling arterial blood during CPET is not feasible.
Publisher: American Physiological Society
Date: 04-2023
DOI: 10.1152/JAPPLPHYSIOL.00597.2022
Abstract: Exercise in the heat increases the slope of the relation between minute ventilation and carbon dioxide elimination (V̇ E /V̇co 2 slope) in young healthy adults. An indispensable role for skin temperature in modulating the ventilatory response to exercise is noted, contradicting common belief that internal/core temperature acts independently as a controller of ventilation during hyperthermia.
Publisher: American Physiological Society
Date: 08-2021
DOI: 10.1152/JAPPLPHYSIOL.00133.2021
Abstract: It is unclear whether obesity in combination with sex influences the dysanapsis ratio (DR). These data indicate that DR is unaltered in adults with obesity and is greater in women than in men but similar between sexes when matched for lung volume. We also report a significant difference between predicted and measured static recoil pressure. Thus, we caution against predicting static recoil pressure in the calculation of DR.
Publisher: Georg Thieme Verlag KG
Date: 13-12-2019
DOI: 10.1055/A-0732-5621
Abstract: We examined the accuracy of Smart Socks – a device that measures foot pressure during gait for detecting step-count across various walking speeds. Thirty-six participants (17 men 19 women) wore Smart Socks (Sock), a pedometer (Pedometer), and a smartphone with a commercially available Phone Application (Phone) pedometer to measure step-count during 3-min of treadmill or over-ground walking at 1.3, 2.2, 3.0, 3.8, and 4.7 km/h. Steps were compared to a gold-standard tally-counter (Count), collected by independent assessors. All devices (Sock, Pedometer, and Phone) underestimated step-count when compared to Count at 1.3 km/h (p .05) however, Sock (27±18%) demonstrated a lower percent error compared to Phone (40±28%) and Pedometer (98±5%) (both p .01). At 2.2 km/h, Sock was not different compared to Count (Sock: 213±39 Count: 229±24 steps, p=0.25) however, both Phone (271±55 steps) and Pedometer (169±166 steps) were different compared to Count (p .05). At 3.0 km/h, both Sock (258±30 steps) and Pedometer (254±45 steps) were similar to Count (267±22 steps) (p .05) however, Phone (291±28 steps) overestimated step-count (p .01). All devices (Sock, Pedometer, and Phone) were similar to Count at 3.8, and 4.7 km/h (p .05). These findings demonstrate that Smart Socks are more accurate than pedometers used in the present study for detecting step-count during treadmill or over-ground ambulation at slower walking speeds.
Publisher: American Physiological Society
Date: 03-2022
DOI: 10.1152/JAPPLPHYSIOL.00786.2021
Abstract: Calculating VD/VT with and without correcting for VDM yields quantitively and qualitatively different results, which could have an important impact on the interpretation of V/Q mismatch in HFpEF. The finding that V/Q mismatch and gas exchange efficiency worsened, as reflected by an increase in VD/VT VDM during exercise, has not been previously demonstrated in HFpEF. Thus, further studies are needed to investigate the mechanisms explaining the increase in VD/VT VDM during exercise in patients with HFpEF.
Publisher: American Physiological Society
Date: 2021
DOI: 10.1152/AJPHEART.00427.2020
Abstract: High-intensity endurance exercise elicits acute cardiac imbalances that may be an important stimulus for adaptive cardiac remodeling. This study highlights that following a bout of high-intensity exercise that is typical of routine day-to-day cycling training, exercise-induced autonomic, biochemical, and functional cardiac imbalances are attenuated in middle-aged relative to young well-trained cyclists. These findings suggest that aging may alter exercise-induced stress stimulus response that initiates cardiac remodeling in Athlete’s Heart.
Publisher: American Physiological Society
Date: 05-2020
Publisher: Wiley
Date: 17-07-2022
DOI: 10.1113/EP090309
Abstract: What is the central question of the study? What are the sex differences in ventilatory responses during exercise in adults with obesity? What is the main finding and its importance? Tidal volume and expiratory flows are lower in females when compared with males at higher levels of ventilation despite small increases in end‐expiratory lung volumes. Since dyspnoea on exertion is a frequent complaint, particularly in females with obesity, careful attention should be paid to unpleasant respiratory symptoms and mechanical ventilatory constraints while prescribing exercise. Obesity is associated with altered ventilatory responses, which may be exacerbated in females due to the functional consequences of sex‐related morphological differences in the respiratory system. This study examined sex differences in ventilatory responses during exercise in adults with obesity. Healthy adults with obesity ( n = 73 48 females) underwent pulmonary function testing, underwater weighing, magnetic resonance imaging (MRI), a graded exercise test to exhaustion, and two constant work rate exercise tests one at a fixed work rate (60 W for females and 105 W for males) and one at a relative intensity (50% of peak oxygen uptake, ). Metabolic, respiratory and perceptual responses were assessed during exercise. Compared with males, females used a smaller proportion of their ventilatory capacity at peak exercise (69.13 ± 14.49 vs. 77.41 ± 17.06% maximum voluntary ventilation, P = 0.0374). Females also utilized a smaller proportion of their forced vital capacity (FVC) at peak exercise (tidal volume: 48.51 ± 9.29 vs. 54.12 ± 10.43%FVC, P = 0.0218). End‐expiratory lung volumes were 2–4% higher in females compared with males during exercise ( P 0.05), while end‐inspiratory lung volumes were similar. Since the males were initiating inspiration from a lower lung volume, they experienced greater expiratory flow limitation during exercise. Ratings of perceived breathlessness during exercise were similar between females and males at comparable levels of ventilation. In summary, sex differences in the manifestations of obesity‐related mechanical ventilatory constraints were observed. Since dyspnoea on exertion is a common complaint in patients with obesity, particularly in females, exercise prescriptions should be tailored with the goal of minimizing unpleasant respiratory sensations.
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.CARDFAIL.2017.04.003
Abstract: Upon heat exposure, the thermoregulatory system evokes reflex increases in sweating and skin blood flow responses to facilitate heat dissipation and maintain heat balance to prevent the continuing rise in core temperature. These heat dissipating responses are mediated primarily by autonomic and cardiovascular adjustments which, if attenuated, may compromise thermoregulatory control. In patients with heart failure (HF), the neurohumoral and cardiovascular dysfunction that underpins this condition may potentially impair thermoregulatory responses and, consequently, place these patients at a greater risk of heat-related illness. The aim of this review is to describe thermoregulatory mechanisms and the factors that may increase the risk of heat-related illness in patients with HF. An understanding of the mechanisms responsible for impaired thermoregulatory control in HF patients is of particular importance, given the current and projected increase in frequency and intensity of heat waves, as well as the promotion of regular exercise as a therapeutic modality. Furthermore, novel therapeutic strategies that may improve thermoregulatory control in HF, and the clinical relevance of this work in this population will be discussed.
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.RESP.2018.07.008
Abstract: We measured pulmonary gas exchange during six minute walk test (6MWT) in patients with idiopathic (IPAH) and congenital heart disease-related pulmonary hypertension (CHDPH), and determined the relationship between the degree of desaturation and changes in minute ventilation to carbon dioxide production V˙
Publisher: Elsevier BV
Date: 08-2020
Publisher: Hindawi Limited
Date: 02-08-2018
DOI: 10.1155/2018/8306154
Abstract: Climate change is predicted to bring about a greater variability in weather patterns with an increase in extreme weather events such as sustained heat waves. This change may have a direct impact on population health since heat waves can exceed the physiological limit of compensability of vulnerable in iduals. Indeed, many clinical reports suggest that in iduals over the age of 60 years are consistently the most vulnerable, experiencing significantly greater adverse heat-related health outcomes than any other age cohort during environmental heat exposure. There is now evidence that aging is associated with an attenuated physiological ability to dissipate heat and that the risk of heat-related illness in these in iduals is elevated, particularly when performing physical activity in the heat. The purpose of this review is to discuss mechanisms of thermoregulatory control and the factors that may increase the risk of heat-related illness in older in iduals. An understanding of the mechanisms responsible for impaired thermoregulation in this population is of particular importance, given the current and projected increase in frequency and intensity of heat waves, as well as the promotion of regular exercise as a means of improving health-related quality of life and morbidity and mortality. As such, the clinical implications of this work in this population will be discussed.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2018
Publisher: American Physiological Society
Date: 26-10-2023
Publisher: Wiley
Date: 05-2022
DOI: 10.14814/PHY2.15264
Publisher: Elsevier BV
Date: 03-2021
Publisher: Wiley
Date: 11-2016
DOI: 10.14814/PHY2.13022
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 31-01-2023
DOI: 10.1161/CIRCULATIONAHA.122.061828
Abstract: Exercise intolerance is a defining characteristic of heart failure with preserved ejection fraction (HFpEF). A marked rise in pulmonary capillary wedge pressure (PCWP) during exertion is pathognomonic for HFpEF and is thought to be a key cause of exercise intolerance. If true, acutely lowering PCWP should improve exercise capacity. To test this hypothesis, we evaluated peak exercise capacity with and without nitroglycerin to acutely lower PCWP during exercise in patients with HFpEF. Thirty patients with HFpEF (70±6 years of age 63% female) underwent 2 bouts of upright, seated cycle exercise dosed with sublingual nitroglycerin or placebo control every 15 minutes in a single-blind, randomized, crossover design. PCWP (right heart catheterization), oxygen uptake (breath × breath gas exchange), and cardiac output (direct Fick) were assessed at rest, 20 Watts (W), and peak exercise during both placebo and nitroglycerin conditions. PCWP increased from 8±4 to 35±9 mm Hg from rest to peak exercise with placebo. With nitroglycerin, there was a graded decrease in PCWP compared with placebo at rest (–1±2 mm Hg), 20W (–5±5 mm Hg), and peak exercise (–7±6 mm Hg drug × exercise stage P =0.004). Nitroglycerin did not affect oxygen uptake at rest, 20W, or peak (placebo, 1.34±0.48 versus nitroglycerin, 1.32±0.46 L/min drug × exercise P =0.984). Compared with placebo, nitroglycerin lowered stroke volume at rest (–8±13 mL) and 20W (–7±11 mL), but not peak exercise (0±10 mL). Sublingual nitroglycerin lowered PCWP during submaximal and maximal exercise. Despite reduction in PCWP, peak oxygen uptake was not changed. These results suggest that acute reductions in PCWP are insufficient to improve exercise capacity, and further argue that high PCWP during exercise is not by itself a limiting factor for exercise performance in patients with HFpEF. URL: www.clinicaltrials.gov Unique identifier: NCT04068844.
No related grants have been discovered for Bryce Balmain.