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Gordon RJFH, Moss JN, Castelli F, Reeve T, Diss CE, Tyler CJ, Tillin NA. Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production. Eur J Appl Physiol 2023; 123:1067-1080. [PMID: 36637508 PMCID: PMC10119217 DOI: 10.1007/s00421-022-05127-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 12/23/2022] [Indexed: 01/14/2023]
Abstract
PURPOSE This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. METHODS Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions. RESULTS Acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P < 0.05), increased evoked torques (P < 0.05), and shortened contraction and relaxation rates (P < 0.05). HA lowered resting rectal temperature and heart rate after 10 days (P < 0.05), and increased sweating rate after 5 and 10 days (P < 0.05), no differences were observed between 5 and 10 days. The hyperthermia-induced reduction in twitch half-relaxation was attenuated after 5 and 10 days of HA, but there were no other effects on neuromuscular function either in normothermic or hyperthermic conditions. CONCLUSION HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions.
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Affiliation(s)
- Ralph Joseph Frederick Hills Gordon
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK. .,Faculty of Science and Engineering, School of Psychology & Sport Science, Anglia Ruskin University, East Road, Cambridge, CB1 1PT, UK.
| | - Jodie Natasha Moss
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK
| | - Federico Castelli
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK
| | - Thomas Reeve
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK
| | - Ceri Elen Diss
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK
| | - Christopher James Tyler
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK
| | - Neale Anthony Tillin
- School of Life and Health Life Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, England, UK
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Liu S, Wen D, Feng C, Yu C, Gu Z, Wang L, Zhang Z, Li W, Wu S, Liu Y, Duan C, Zhuang R, Xue L. Alteration of gut microbiota after heat acclimation may reduce organ damage by regulating immune factors during heat stress. Front Microbiol 2023; 14:1114233. [PMID: 36910226 PMCID: PMC9995595 DOI: 10.3389/fmicb.2023.1114233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 02/06/2023] [Indexed: 02/25/2023] Open
Abstract
Introduction Heat-related illnesses can lead to morbidity, which are anticipated to increase frequency with predictions of increased global surface temperatures and extreme weather events. Although heat acclimation training (HAT) could prevent heat-related diseases, the mechanisms underlying HAT-promoting beneficial changes in organ function, immunity, and gut microbes remain unclear. Methods In the current study, we recruited 32 healthy young soldiers and randomly divided them into 4 teams to conduct HATs for 10 days: the equipment-assisted training team at high temperature (HE); the equipment-assisted training team under normal hot weather (NE); the high-intensity interval training team at high temperature (HIIT), and the control team without training. A standard heat tolerance test (HTT) was conducted before (HTT-1st) and after (HTT-2nd) the training to judge whether the participants met the heat acclimation (HA) criteria. Results We found that the participants in both HE and NE teams had significantly higher acclimation rates (HA/total population) than whom in the HIIT team. The effects of HAT on the participants of the HE team outperformed that of the NE team. In the HA group, the differences of physiological indicators and plasma organ damage biomarkers (ALT, ALP, creatinine, LDH, α-HBDH and cholinesterase) before and after HTT-2nd were significantly reduced to those during HTT-1st, but the differences of immune factors (IL-10, IL-6, CXCL2, CCL4, CCL5, and CCL11) elevated. The composition, metabolism, and pathogenicity of gut microbes changed significantly, with a decreased proportion of potentially pathogenic bacteria (Escherichia-Shigella and Lactococcus) and increased probiotics (Dorea, Blautia, and Lactobacillus) in the HA group. Training for a longer time in a high temperature and humidity showed beneficial effects for intestinal probiotics. Conclusion These findings revealed that pathogenic gut bacteria decrease while probiotics increase following HA, with elevated immune factors and reduced organ damage during heat stress, thereby improving the body's heat adaption.
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Affiliation(s)
- Shanshou Liu
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Dongqing Wen
- Air Force Medical Center, Fourth Military Medical University, Beijing, China
| | - Chongyang Feng
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Chaoping Yu
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Zhao Gu
- Air Force Medical Center, Fourth Military Medical University, Beijing, China
| | - Liping Wang
- Air Force Medical Center, Fourth Military Medical University, Beijing, China
| | - Zhixiang Zhang
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Wenpeng Li
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Shuwen Wu
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Yitian Liu
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Chujun Duan
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Ran Zhuang
- Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Lihao Xue
- Air Force Medical Center, Fourth Military Medical University, Beijing, China
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Osborne JO, Minett GM, Stewart IB, Trost S, Drovandi C, Costello JT, Pavey TG, Borg DN. Evidence that heat acclimation training may alter sleep and incidental activity. Eur J Sport Sci 2022:1-10. [PMID: 36106465 DOI: 10.1080/17461391.2022.2124386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
This randomized cross-over study tested the hypothesis that heat acclimation training would detrimentally affect sleep variables and alter incidental physical activity compared to a thermoneutral training control condition. Eight recreationally trained males (V̇O2peak 49±4.9 mL.kg-1.min-1) completed two separate interventions separated by at least 31 days: 5 consecutive day training blocks of moderate-intensity cycling (60 min·day-1 at 50% peak power output) in a hot (34.9±0.7 °C and 53±4 % relative humidity) and a temperate (22.2±2.6 °C; 65±8 % relative humidity) environment. Wrist-mounted accelerometers were worn continuously for the length of the training blocks and recorded physical activity, sleep quality and quantity. Data were analysed in a Bayesian framework, with the results presented as the posterior probability that a coefficient was greater or less than zero. Compared to the temperate training environment, heat acclimation impaired sleep efficiency (Pr β<0 = .979) and wake on sleep onset (Pr β>0 = .917). Daily sedentary time was, on average, 35 min longer (Pr β>0 = .973) and light physical activity time 18 min shorter (Pr β>0 = .960) during the heat acclimation period. No differences were observed between conditions in sleep duration, subjective sleep quality, or moderate or vigorous physical activity. These findings may suggest that athletes and coaches need to be cognisant that heat acclimation training may alter sleep quality and increase sedentary behaviour.HighlightsFive consecutive days of heat training negatively affected some objective measures of sleep quality and incidental physical activity in recreationally trained athletes.Athletes and coaches need to be aware of the potential unintended consequences of using heat acclimation on sleep behaviours.
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Affiliation(s)
- John O Osborne
- School of Sport Sciences, UiT The Arctic University of Norway, Tromsø, Norway
- School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia
| | - Geoffrey M Minett
- School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia
| | - Ian B Stewart
- School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia
| | - Stewart Trost
- School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia
- School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia
| | - Christopher Drovandi
- School of Mathematical Sciences, Queensland University of Technology, Brisbane, Australia
- Centre for Data Science, Queensland University of Technology, Brisbane, Australia
| | - Joseph T Costello
- Extreme Environments Laboratory, School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, United Kingdom
| | - Toby G Pavey
- School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia
| | - David N Borg
- Australian Centre for Health Services Innovation and Centre for Healthcare Transformation, School of Public Health and Social Work, Queensland University of Technology, Brisbane, Australia
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Fennel ZJ, Amorim FT, Deyhle MR, Hafen PS, Mermier CM. The Heat Shock Connection: Skeletal Muscle Hypertrophy and Atrophy. Am J Physiol Regul Integr Comp Physiol 2022; 323:R133-R148. [PMID: 35536704 DOI: 10.1152/ajpregu.00048.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Skeletal muscle is an integral tissue system that plays a crucial role in the physical function of all vertebrates and is a key target for maintaining or improving health and performance across the lifespan. Based largely on cellular and animal models, there is some evidence that various forms of heat stress with or without resistance exercise may enhance skeletal muscle growth or reduce its loss. It is not clear whether these stimuli are similarly effective in humans or meaningful in comparison to exercise alone across various heating methodologies. Furthermore, the magnitude by which heat stress may influence whole body thermoregulatory responses and the connection to skeletal muscle adaptation remains ambiguous. Finally, the underlying mechanisms, which may include interaction between relevant heat shock proteins and intracellular hypertrophy and atrophy related factors, remain unclear. In this narrative mini-review we examine the relevant literature regarding heat stress alone or in combination with resistance exercise emphasizing skeletal muscle hypertrophy and atrophy across cellular and animal models, as well as human investigations. Additionally, we present working mechanistic theories for heat shock protein mediated signaling effects regarding hypertrophy and atrophy related signaling processes. Importantly, continued research is necessary to determine the practical effects and mechanisms of heat stress with and without resistance exercise on skeletal muscle function via growth and maintenance.
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Affiliation(s)
| | | | | | - Paul Samuel Hafen
- Department of Health, Exercise, and Sport Sciences, University of New Mexico, Albuquerque, NM, United States.,Indiana University School of Medicine Department of Anatomy, Cell Biology, and Physiology; Indiana Center for Musculoskeletal Health, Indianapolis, IN, United States
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