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Lackner M, Grossmann F, Perret C, Flueck JL, Hertig-Godeschalk A. Chasing Gold: Heat Acclimation in Elite Handcyclists with Spinal Cord Injury. Int J Sports Med 2024; 45:733-738. [PMID: 38885662 DOI: 10.1055/a-2321-1832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
Thermoregulation is impaired in individuals with a spinal cord lesion (SCI), affecting sweat capacity, heat loss, and core temperature. This can be particularly problematic for athletes with SCI who exercise in hot and humid conditions, like those during the Tokyo 2020 Paralympic Games. Heat acclimation can support optimal preparation for exercise in such challenging environments, but evidence is limited in endurance athletes with SCI. We evaluated whether seven consecutive days of exercise in the heat would result in heat acclimation. Five elite para-cycling athletes with SCI participated (two females, three males, median (Q1-Q3) 35 (31-51) years, four with paraplegia and one with tetraplegia). All tests and training sessions were performed in a heat chamber (30°C and 75% relative humidity). A time-to-exhaustion test was performed on day 1 (pretest) and day 7 (posttest). On days 2-6, athletes trained daily for one hour at 50-60% of individual peak power (PPeak). Comparing pretest and posttest, all athletes increased their body mass loss (p=0.04), sweat rate (p=0.04), and time to exhaustion (p=0.04). Effects varied between athletes for core temperature and heart rate. All athletes appeared to benefit from our heat acclimation protocol, helping to optimize their preparation for the Tokyo 2020 Paralympic Games.
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Affiliation(s)
- Mike Lackner
- Sports Therapy, Swiss Paraplegic Centre, Nottwil, Switzerland
| | - Fabian Grossmann
- Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland
| | - Claudio Perret
- Neuro-Musculoskeletal Functioning and Mobility, Swiss Paraplegic Research, Nottwil, Switzerland
- Faculty of Health Sciences and Medicine, University of Lucerne, Luzern, Switzerland
| | - Joelle L Flueck
- Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland
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Deshayes TA, Sodabi DGA, Dubord M, Gagnon D. Shifting focus: Time to look beyond the classic physiological adaptations associated with human heat acclimation. Exp Physiol 2024; 109:335-349. [PMID: 37885125 PMCID: PMC10988689 DOI: 10.1113/ep091207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 10/12/2023] [Indexed: 10/28/2023]
Abstract
Planet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increases thermoeffector output (i.e., sweating and skin blood flow) and lowers cardiovascular strain (i.e., heart rate) during heat stress. However, the mechanisms mediating these adaptations remain understudied. Furthermore, several possible benefits of heat acclimation for other systems and functions involved in maintaining health and performance during heat stress remain to be elucidated. This review summarizes recent advances in human heat acclimation, with emphasis on recent studies that (1) advanced our understanding of the mechanisms mediating improved thermoeffector output and (2) investigated adaptations that go beyond those classically associated with heat acclimation. We highlight that these studies have contributed to a better understanding of the integrated physiological responses underlying human heat acclimation while leaving key unanswered questions that will need to be addressed in the future.
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Affiliation(s)
- Thomas A. Deshayes
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
| | - Dèwanou Gilles Arnaud Sodabi
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
| | - Marianne Dubord
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
| | - Daniel Gagnon
- Montreal Heart InstituteMontréalCanada
- School of Kinesiology and Exercise ScienceUniversité de MontréalMontréalCanada
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Ashworth E, Cotter J, Kilding A. Post-exercise, passive heat acclimation with sauna or hot-water immersion provide comparable adaptations to performance in the heat in a military context. ERGONOMICS 2023; 66:49-60. [PMID: 35332846 DOI: 10.1080/00140139.2022.2058096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
To mitigate the effects of heat during operations in hot environments, military personnel will likely benefit from heat acclimation (HA) conducted prior to deployment. Using post-exercise, passive heating, 25 participants completed a 5 d HA regime in sauna (70 °C, 18% RH) or hot-water immersion (HWI) (40 °C) for ≤40 min, preceded and followed by a heat stress test (1-h walking at 5 km.h-1 in 33 °C, 77% RH in military uniform (20 kg) before an incremental ramp to exhaustion). Fifteen completed both regimes in a randomised, cross-over manner. While performance did not significantly improve (+14%, [-1, 29], p = .079), beneficial adaptations were observed for mean exercising core temperature (-0.2 °C, [-0.2, -0.2], p <.001), skin temperature (-0.2 °C, [-0.2, -0.2], p = 035) and heart rate (-8 bpm, [-6, -10], p<.001) in both conditions. Post-exercise, passive HA of either modality may benefit military units operating in the heat.Practitioner summary: Strategies are required to prevent health and performance impairments during military operations upon arrival in hot environments. Using a randomised, cross-over design, participants completed five-day passive, post-exercise heat acclimation using sauna or hot-water immersion. Both regimes elicited beneficial albeit modest heat adaptations.Abbreviations: HA: heat acclimation; HST: heat stress test; HWI: hot-water immersion; RH: relative humidity.
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Affiliation(s)
- Edward Ashworth
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand
| | - James Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Andrew Kilding
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand
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Cramer MN, Gagnon D, Laitano O, Crandall CG. Human temperature regulation under heat stress in health, disease, and injury. Physiol Rev 2022; 102:1907-1989. [PMID: 35679471 PMCID: PMC9394784 DOI: 10.1152/physrev.00047.2021] [Citation(s) in RCA: 65] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 05/10/2022] [Accepted: 05/28/2022] [Indexed: 12/30/2022] Open
Abstract
The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.
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Affiliation(s)
- Matthew N Cramer
- Defence Research and Development Canada-Toronto Research Centre, Toronto, Ontario, Canada
| | - Daniel Gagnon
- Montreal Heart Institute and School of Kinesiology and Exercise Science, Université de Montréal, Montréal, Quebec, Canada
| | - Orlando Laitano
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
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Amano T, Fujii N, Kenny GP, Okamoto Y, Inoue Y, Kondo N. Effects of TEA-sensitive K + channel blockade on cholinergic and thermal sweating in endurance trained and untrained men. Exp Physiol 2022; 107:441-449. [PMID: 35340063 DOI: 10.1113/ep090251] [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: 11/30/2021] [Accepted: 03/23/2022] [Indexed: 11/08/2022]
Abstract
NEW & NOTEWORTHY What is the central question of this study? Does inhibition of K+ channels modulate the exercise-training-induced augmentation in cholinergic and thermal sweating? What is the main finding and its importance? Iontophoretic administration of tetraethylammonium, a K+ channel blocker, blunted sweating induced by a low dose (0.001%) of cholinergic agent pilocarpine, but not heat-induced sweating. However, no differences in the cholinergic sweating were observed between young endurance trained and untrained men. Thus, while K+ channels play a role in the regulation of eccrine sweating, they do not contribute to the increase in sweating commonly observed in endurance trained adults. Our findings provide important new insights into the mechanisms underlying the regulation of sweating by endurance conditioning. ABSTRACT We evaluated the hypothesis that the activation of K+ channels mediate the exercise-training-induced augmentation in cholinergic and thermal sweating. On separate days, 11 endurance trained and 10 untrained men participated in two experimental protocols. Prior to each protocol, we administered 2% tetraethylammonium (TEA, K+ channels blocker) and saline (Control) at forearm skin sites on both arms via transdermal iontophoresis. In protocol 1, a low (0.001%) and high (1%) doses of pilocarpine was administered at the TEA-treated and Control sites over a 60-min period. In protocol 2, participants were passively heated by immersing their lower limbs in hot water (43°C) until core (rectal) temperature (Tco ) increased by 0.8°C above resting levels. Administration of TEA attenuated cholinergic sweating (P = 0.001) during the initial 20-min after the treatment of low dose of pilocarpine only whilst the response was similar between the groups (P = 0.163). Cholinergic and thermal sweating were higher in trained relative to the untrained men (all P≤0.033). Thermal sweating reached ∼90% of the response at a Tco elevation of 0.8°C during initial 20-min of passive heating, which corresponds to the period wherein TEA attenuated cholinergic sweating in protocol 1. However, sweating did not differ between the Control and TEA sites in either group (P = 0.704). We showed that activation of K+ channels does not appear to mediate the elevated sweating response induced by a low dose of pilocarpine in trained men. We also demonstrated that K+ channels do not contribute to sweating during heat stress in either group. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Yumi Okamoto
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University, Osaka, Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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NAITO T, HARAMURA M, MURAISHI K, YAMAZAKI M, TAKAHASHI H. The impact of new evaluation method of short-term heat acclimation using salty taste recognition threshold. GAZZETTA MEDICA ITALIANA ARCHIVIO PER LE SCIENZE MEDICHE 2022. [DOI: 10.23736/s0393-3660.19.04252-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Kirby NV, Lucas SJE, Cable TG, Armstrong OJ, Weaver SR, Lucas RAI. Sex differences in adaptation to intermittent post-exercise sauna bathing in trained middle-distance runners. SPORTS MEDICINE-OPEN 2021; 7:51. [PMID: 34297227 PMCID: PMC8302716 DOI: 10.1186/s40798-021-00342-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/30/2021] [Indexed: 11/16/2022]
Abstract
Background The purpose of this study was to investigate the effect of sex on the efficacy of intermittent post-exercise sauna bathing to induce heat acclimation and improve markers of temperate exercise performance in trained athletes. Methods Twenty-six trained runners (16 female; mean ± SD, age 19 ± 1 years, V̇O2max F: 52.6 ± 6.9 mL⋅kg−1⋅min−1, M: 64.6 ± 2.4 mL⋅kg−1⋅min−1) performed a running heat tolerance test (30 min, 9 km⋅h−1/2% gradient, 40 °C/40%RH; HTT) and temperate (18 °C) exercise tests (maximal aerobic capacity [V̇O2max] and lactate profile) pre and post 3 weeks of normal exercise training plus 29 ± 1 min post-exercise sauna bathing (101–108 °C) 3 ± 1 times per week. Results Females and males exhibited similar reductions (interactions p > 0.05) in peak rectal temperature (− 0.3 °C; p < 0.001), skin temperature (− 0.9 °C; p < 0.001) and heart rate (− 9 beats·min−1; p = 0.001) during the HTT at post- vs pre-intervention. Only females exhibited an increase in active sweat glands on the forearm (measured via modified iodine technique; F: + 57%, p < 0.001; M: + 1%, p = 0.47). Conversely, only males increased forearm blood flow (measured via venous occlusion plethysmography; F: + 31%, p = 0.61; M: + 123%; p < 0.001). Females and males showed similar (interactions p > 0.05) improvements in V̇O2max (+ 5%; p = 0.02) and running speed at 4 mmol·L−1 blood lactate concentration (+ 0.4 km·h−1; p = 0.001). Conclusions Three weeks of post-exercise sauna bathing effectively induces heat acclimation in females and males, though possibly amid different thermoeffector adaptations. Post-exercise sauna bathing is also an effective ergogenic aid for both sexes. Supplementary Information The online version contains supplementary material available at 10.1186/s40798-021-00342-6.
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Affiliation(s)
- Nathalie V Kirby
- School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK. .,Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, K1N 6N5, Canada.
| | - Samuel J E Lucas
- School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Thomas G Cable
- School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,Loughborough University, Loughborough, UK
| | | | - Samuel R Weaver
- School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Rebekah A I Lucas
- School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
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Abstract
INTRODUCTION The aim of this study was to compare the effectiveness of exercise versus hot water immersion heat reacclimation (HRA) protocols. METHODS Twenty-four participants completed a heat stress test (HST; 33°C, 65% RH), which involved cycling at a power output equivalent to 1.5 W·kg-1 for 35 min whereby thermophysiological variables were measured. This was followed by a graded exercise test until exhaustion. HST1 was before a 10-d controlled hyperthermia (CH) heat acclimation (HA) protocol and HST2 immediately after. Participants completed HST3 after a 28-d decay period without heat exposure and were then separated into three groups to complete a 5-d HRA protocol: a control group (CH-CON, n = 8); a hot water immersion group (CH-HWI, n = 8), and a controlled hyperthermia group (CH-CH, n = 8). This was followed by HST4. RESULTS Compared with HST1, time to exhaustion and thermal comfort improved; resting rectal temperature (Tre), end of exercise Tre, and mean skin temperature (Tsk) were lower; and whole body sweat rate (WBSR) was greater in HST2 for all groups (P < 0.05). After a 28-d decay, only WBSR, time to exhaustion, and mean Tsk returned to pre-HA values. Of these decayed variables, only WBSR was reinstated after HRA; the improvement was observed in both the CH-CH and the CH-HWI groups (P < 0.05). CONCLUSION The data suggest that HRA protocol may not be necessary for cardiovascular and thermal adaptations within a 28-d decay period, as long as a 10-d CH-HA protocol has successfully induced these physiological adaptations. For sweat adaptations, a 5-d CH or HWI-HRA protocol can reinstate the lost adaptations.
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Affiliation(s)
- Nicola Gerrett
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, THE NETHERLANDS
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Alkemade P, Gerrett N, Eijsvogels TMH, Daanen HAM. Individual characteristics associated with the magnitude of heat acclimation adaptations. Eur J Appl Physiol 2021; 121:1593-1606. [PMID: 33646425 PMCID: PMC8144163 DOI: 10.1007/s00421-021-04626-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 02/05/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE The magnitude of heat acclimation (HA) adaptations varies largely among individuals, but it remains unclear what factors influence this variability. This study compared individual characteristics related to fitness status and body dimensions of low-, medium-, and high responders to HA. METHODS Twenty-four participants (9 female, 15 male; maximum oxygen uptake [[Formula: see text]O2peak,kg] 52 ± 9 mL kg-1 min-1) completed 10 daily controlled-hyperthermia HA sessions. Adaptations were evaluated by heat stress tests (HST; 35 min cycling 1.5 W kg-1; 33 °C, 65% relative humidity) pre- and post-HA. Low-, medium-, and high responder groups were determined based on tertiles (n = 8) of individual adaptations for resting rectal temperature (Tre), exercise-induced Tre rise (ΔTre), whole-body sweat rate (WBSR), and heart rate (HR). RESULTS Body dimensions (p > 0.3) and [Formula: see text]O2peak,kg (p > 0.052) did not differentiate low-, medium-, and high responders for resting Tre or ΔTre. High WBSR responders had a larger body mass and lower body surface area-to-mass ratio than low responders (83.0 ± 9.3 vs 67.5 ± 7.3 kg; 249 ± 12 vs 274 ± 15 cm2 kg-1, respectively; p < 0.005). Conversely, high HR responders had a smaller body mass than low responders (69.2 ± 6.8 vs 83.4 ± 9.4 kg; p = 0.02). [Formula: see text]O2peak,kg did not differ among levels of responsiveness for WBSR and HR (p > 0.3). CONCLUSION Individual body dimensions influenced the magnitude of sudomotor and cardiovascular adaptive responses, but did not differentiate Tre adaptations to HA. The influence of [Formula: see text]O2peak,kg on the magnitude of adaptations was limited.
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Affiliation(s)
- Puck Alkemade
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, 1081 HV, Amsterdam, The Netherlands.
| | - Nicola Gerrett
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, 1081 HV, Amsterdam, The Netherlands
| | - Thijs M H Eijsvogels
- Department of Physiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hein A M Daanen
- Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, 1081 HV, Amsterdam, The Netherlands
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Okamoto Y, Amano T. Effects of sex and menstrual cycle on sweating during isometric handgrip exercise and postexercise forearm occlusion. Exp Physiol 2021; 106:1508-1523. [PMID: 33899281 DOI: 10.1113/ep089464] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 04/20/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Do sex and menstrual cycle modulate sweating during isometric handgrip exercise and muscle metaboreceptor stimulation? What is the main finding and its importance? Sex modulates sweating during isometric handgrip exercise, as indicated by the lower sweat output per gland in women than in men, but not during muscle metaboreceptor stimulation. Sweat output per gland during isometric handgrip exercise and muscle metaboreceptor stimulation were lower in the mid-luteal phase than in the early follicular phase in women. Cholinergic sweat gland sensitivity might explain, in part, the individual variation of the response. Our results provide new insights regarding sex- and menstrual cycle-related modulation of the sweating response. ABSTRACT We investigated whether sex and menstrual cycle could modulate sweating during isometric handgrip (IH) exercise and muscle metaboreceptor stimulation. Twelve young, healthy women in the early follicular (EF) and mid-luteal (ML) phases and 14 men underwent two experimental sessions consisting of a 1.5 min IH exercise at 25 and 50% of maximal voluntary contraction (MVC) in a hot environment (35°C, relative humidity 50%) followed by 2 min forearm occlusion to stimulate muscle metaboreceptors. Sweat rates, the number of activated sweat glands and the sweat output per gland (SGO) on the forearm and chest were assessed. Pilocarpine-induced sweating was also assessed via transdermal iontophoresis to compare the responses with those of IH exercise and muscle metaboreceptor stimulation, based on correlation analysis. Sweat rates on the forearm and chest during IH exercise and muscle metaboreceptor stimulation did not differ between men and women in either menstrual cycle phase (all P ≥ 0.144). However, women in both phases showed lower SGO on the forearm and/or chest compared with men during IH exercise at 50% of MVC, with no differences in muscle metaboreceptor stimulation. Women in the ML phase had a lower forearm sweat rate during IH exercise at 50% of MVC (P = 0.015) and SGO during exercise and muscle metaboreceptor stimulation (main effect, both P ≤ 0.003) compared with those in the EF phase. Overall, sweat rate and SGO during IH exercise and muscle metaboreceptor stimulation were correlated with pilocarpine-induced responses (all P ≤ 0.064, r ≥ 0.303). We showed that sex and menstrual cycle modulate sudomotor activity during IH exercise and/or muscle metaboreceptor stimulation. Cholinergic sweat gland sensitivity might explain, in part, the individual variation of the response.
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Affiliation(s)
- Yumi Okamoto
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
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Périard JD, Eijsvogels TMH, Daanen HAM. Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies. Physiol Rev 2021; 101:1873-1979. [PMID: 33829868 DOI: 10.1152/physrev.00038.2020] [Citation(s) in RCA: 149] [Impact Index Per Article: 49.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.
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Affiliation(s)
- Julien D Périard
- University of Canberra Research Institute for Sport and Exercise, Bruce, Australia
| | - Thijs M H Eijsvogels
- Department of Physiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hein A M Daanen
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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Amano T, Fujii N, Kenny GP, Okamoto Y, Inoue Y, Kondo N. Effects of L-type voltage-gated Ca 2+ channel blockade on cholinergic and thermal sweating in habitually trained and untrained men. Am J Physiol Regul Integr Comp Physiol 2020; 319:R584-R591. [PMID: 32966123 DOI: 10.1152/ajpregu.00167.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We evaluated the hypothesis that the activation of L-type voltage-gated Ca2+ channels contributes to exercise training-induced augmentation in cholinergic sweating. On separate days, 10 habitually trained and 10 untrained men participated in two experimental protocols. Prior to each protocol, we administered 1% verapamil (Verapamil, L-type voltage-gated Ca2+ channel blocker) and saline (Control) at forearm skin sites on both arms via transdermal iontophoresis. In protocol 1, we administered low (0.001%) and high (1%) doses of pilocarpine at both the verapamil-treated and verapamil-untreated forearm sites. In protocol 2, participants were passively heated by immersing their limbs in hot water (43°C) until rectal temperature increased by 1.0°C above baseline resting levels. Sweat rate at all forearm sites was continuously measured throughout both protocols. Pilocarpine-induced sweating in Control was higher in trained than in untrained men for both the concentrations of pilocarpine (both P ≤ 0.001). Pilocarpine-induced sweating at the low-dose site was attenuated at the Verapamil versus the Control site in both the groups (both P ≤ 0.004), albeit the reduction was greater in trained as compared with in untrained men (P = 0.005). The verapamil-mediated reduction in sweating remained intact at the high-dose pilocarpine site in the untrained men (P = 0.004) but not the trained men (P = 0.180). Sweating did not differ between Control and Verapamil sites with increases in rectal temperature in both groups (interaction, P = 0.571). We show that activation of L-type voltage-gated Ca2+ channels modulates sweat production in habitually trained men induced by a low dose of pilocarpine. However, no effect on sweating was observed during passive heating in either group.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Yumi Okamoto
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University, Osaka, Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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Amano T, Fujii N, Kenny GP, Nishiyasu T, Inoue Y, Kondo N. The relative contribution of α- and β-adrenergic sweating during heat exposure and the influence of sex and training status. Exp Dermatol 2020; 29:1216-1224. [PMID: 33015872 DOI: 10.1111/exd.14208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/14/2020] [Accepted: 09/27/2020] [Indexed: 02/04/2023]
Abstract
While human eccrine sweat glands respond to adrenergic agonists, there remains a paucity of information on the factors modulating this response. Thus, we assessed the relative contribution of α- and β-adrenergic sweating during a heat exposure and as a function of individual factors of sex and training status. α- and β-adrenergic sweating was assessed in forty-eight healthy young men (n = 35) and women (n = 13) including endurance-trained (n = 12) and untrained men (n = 12) under non-heat exposure (temperate, 25°C; n = 17) and heat exposure (hot, 35°C; n = 48) conditions using transdermal iontophoresis of phenylephrine (α-adrenergic agonist) and salbutamol (β-adrenergic agonist) on the ventral forearm, respectively. Adrenergic sweating was also measured after iontophoretic administration of atropine (muscarinic receptor antagonist) or saline (control) to evaluate how changes in muscarinic receptor activity modulate the adrenergic response to a heat exposure (n = 12). α- and β-adrenergic sweating was augmented in hot compared with temperate conditions (both P ≤ .014), albeit the relative increase was greater in β (~5.4-fold)- as compared to α (~1.5-fold)-adrenergic-mediated sweating response. However, both α- and β-adrenergic sweating was abolished by atropinization (P = .001). Endurance-trained men showed an augmentation in α- (P = .043) but not β (P = .960)-adrenergic sweating as compared to untrained men. Finally, a greater α- and β-adrenergic sweating response (both P ≤ .001) was measured in habitually active men than in women. We show that heat exposure augments α-and β-adrenergic sweating differently via mechanisms associated with altered muscarinic receptor activity. Sex and training status modulate this response.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University, Osaka, Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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Gerrett N, Amano T, Inoue Y, Kondo N. The sweat glands' maximum ion reabsorption rates following heat acclimation in healthy older adults. Exp Physiol 2020; 106:302-315. [PMID: 33006218 DOI: 10.1113/ep088486] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 09/11/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question to this study? Do the sweat glands' maximum ion reabsorption rates increase following heat acclimation in healthy older individuals and is this associated with elevated aldosterone concentrations? What is the main finding and its importance? Sweat gland maximum ion reabsorption rates improved heterogeneously across body sites, which occurred without any changes in aldosterone concentration following a controlled hyperthermic heat acclimation protocol in healthy older individuals. ABSTRACT We examined whether the eccrine sweat glands' ion reabsorption rates improved following heat acclimation (HA) in older individuals. Ten healthy older adults (>65 years) completed a controlled hyperthermic (+0.9°C rectal temperature, Tre ) HA protocol for nine non-consecutive days. Participants completed a passive heat stress test (lower leg 42°C water submersion) pre-HA and post-HA to assess physiological regulation of sweat gland ion reabsorption at the chest, forearm and thigh. The maximum ion reabsorption rate was defined as the inflection point in the slope of the relation between galvanic skin conductance and sweat rate (SR). We explored the responses again after a 7-day decay. During passive heating, the Tb thresholds for sweat onset on the chest and forearm were lowered after HA (P < 0.05). However, sweat sensitivity (i.e. the slope), the SR at a given Tre and gross sweat loss did not improve after HA (P > 0.05). Any changes observed were lost during the decay. Pilocarpine-induced sudomotor responses to iontophoresis did not change after HA (P ≥ 0.801). Maximum ion reabsorption rate was only enhanced at the chest (P = 0.001) despite unaltered aldosterone concentration after HA. The data suggest that this adaptation is lost after 7 days' decay. The HA protocol employed in the present study induced partial adaptive sudomotor responses. Eccrine sweat gland ion reabsorption rates improved heterogeneously across the skin sites. It is likely that aldosterone secretion did not alter the chest sweat ion reabsorption rates observed in the older adults.
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Affiliation(s)
- Nicola Gerrett
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan.,Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University, Osaka, Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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15
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Klous L, de Ruiter C, Alkemade P, Daanen H, Gerrett N. Sweat rate and sweat composition following active or passive heat re-acclimation: A pilot study. Temperature (Austin) 2020; 8:90-104. [PMID: 33553508 PMCID: PMC7849678 DOI: 10.1080/23328940.2020.1826287] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The purpose of this study was to investigate local sweat rate (LSR) and sweat composition before and after active or passive heat re-acclimation (HRA). Fifteen participants completed four standardized heat stress tests (HST): before and after ten days of controlled hyperthermia (CH) heat acclimation (HA), and before and after five days of HRA. Each HST consisted of 35 min of cycling at 1.5W·kg−1 body mass (33°C and 65% relative humidity), followed by a graded exercise test. For HRA, participants were re-exposed to either CH (CH-CH, n = 6), hot water immersion (water temperature ~40°C for 40 min; CH-HWI, n = 5) or control (CH-CON, n = 4). LSR, sweat sodium, chloride, lactate and potassium concentrations were determined on the arm and back. LSR increased following HA (arm +18%; back +41%, P ≤ 0.03) and HRA (CH-CH: arm +31%; back +45%; CH-HWI: arm +65%; back +49%; CH-CON arm +11%; back +11%, P ≤ 0.021). Sweat sodium, chloride and lactate decreased following HA (arm 25–34; back 21–27%, P < 0.001) and HRA (CH-CH: arm 26–54%; back 20–43%; CH-HWI: arm 9–49%; back 13–29%; CH-CON: arm 1–3%, back 2–5%, P < 0.001). LSR increases on both skin sites were larger in CH-CH and CH-HWI than CH-CON (P ≤ 0.010), but CH-CH and CH-HWI were not different (P ≥ 0.148). Sweat sodium and chloride conservation was larger in CH-CH than CH-HWI and CH-CON on the arm and back, whilst CH-HWI and CH-CON were not different (P ≥ 0.265). These results suggest that active HRA leads to similar increases in LSR, but more conservation of sweat sodium and chloride than passive HRA. Abbreviations: ANOVA: Analysis of variance; ATP: Adenosine triphosphate; BSA (m2): Body surface area; CH: Controlled hyperthermia; CH-CH: Heat re-acclimation by controlled hyperthermia; CH-CON: Control group (no heat re-acclimation); CH-HWI: Heat re-acclimation by hot water immersion; CV (%): Coefficient of variation; dt (min): Duration of a stimulus; F: Female; GEE: Generalized estimating equations; HA: Heat acclimation; HRA : Heat re-acclimation; HST: Heat stress test; LSR (mg·cm−2·min−1) : Local sweat rate; LOD (mmol·L−1): Limit of detection; M: Male; mx (mg): Mass of x; RH (%): Relative humidity; RT: Recreationally trained; SA (cm2): Surface area; t (min): Time; T: Trained; Tsk (°C): Skin temperature; Tre (°C): Rectal temperature; USG : Urine specific gravity; VO2peak (mL·kg−1·min−1): Peak oxygen uptake; WBSL (L): Whole-body sweat loss; WBSR (L·h−1): Whole-body sweat rate
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Affiliation(s)
- Lisa Klous
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Cornelis de Ruiter
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Puck Alkemade
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Hein Daanen
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Nicola Gerrett
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
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Abstract
AbstractDisorders of sudomotor function are common and diverse in their presentations. Hyperhidrosis or hypohidrosis in generalized or regional neuroanatomical patterns can provide clues to neurologic localization and inform neurologic diagnosis. Conditions that impair sudomotor function include small fiber peripheral neuropathy, sudomotor neuropathy, myelopathy, α-synucleinopathies, autoimmune autonomic ganglionopathy, antibody-mediated hyperexcitability syndromes, and a host of medications. Particularly relevant to neurologic practice is the detection of postganglionic sudomotor deficits as a diagnostic marker of small fiber neuropathies. Extensive anhidrosis is important to recognize, as it not only correlates with symptoms of heat intolerance but may also place the patient at risk for heat stroke when under conditions of heat stress. Methods for assessing sudomotor dysfunction include the thermoregulatory sweat test, the quantitative sudomotor axon reflex test, silicone impressions, and the sympathetic skin response.
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17
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Amano T, Sekihara S, Fujii N, Kenny GP, Inoue Y, Kondo N. Does the iontophoretic application of bretylium tosylate modulate sweating during exercise in the heat in habitually trained and untrained men? Exp Physiol 2020; 105:1692-1699. [PMID: 32776611 DOI: 10.1113/ep088797] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/07/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Does the administration of the adrenergic presynaptic release inhibitor bretylium tosylate modulate sweating during exercise in the heat, and does this response differ between habitually trained and untrained men? What is the main finding and its importance? Iontophoretic administration of bretylium tosylate attenuates sweating during exercise in the heat in habitually trained and untrained men. However, a greater reduction occurred in trained men. The findings demonstrate a role for cutaneous adrenergic nerves in the regulation of eccrine sweating during exercise in the heat and highlight a need to advance our understanding of neural control of human eccrine sweat gland activity. ABSTRACT We recently reported an influence of cutaneous adrenergic nerves on eccrine sweat production in habitually trained men performing an incremental exercise bout in non-heat stress conditions. Based on an assumption that increasing heat stress induces cholinergic modulation of sweating, we evaluated the hypothesis that the contribution of cutaneous adrenergic nerves on sweating would be attenuated during exercise in the heat. Twenty young habitually trained and untrained men (n = 10/group) underwent three successive bouts of 15 min of light-, moderate- and vigorous-intensity cycling (equivalent to 30, 50, and 70% of peak oxygen uptake ( V ̇ O 2 peak ) respectively), each separated by a 15 min recovery while wearing a perfusion suit perfused with warm water (43°C). Sweat rate (ventilated capsule) was measured continuously at two bilateral forearm skin sites treated with 10 mm bretylium tosylate (an inhibitor of neurotransmitter release from adrenergic nerve terminals) and saline (control) via transdermal iontophoresis. A greater sweat rate was measured during vigorous exercise only in trained as compared to untrained men (P = 0.014). In both groups, sweating was reduced at the bretylium tosylate versus control sites, albeit the magnitude of reduction was greater in the trained men (P ≤ 0.024). These results suggest that cutaneous adrenergic nerves modulate sweating during exercise performed under a whole-body heat stress, albeit a more robust response occurs in trained men. While it is accepted that a cholinergic mechanism plays a primary role in the regulation of sweating during an exercise-heat stress, our findings highlight the need for additional studies aimed at understanding the neural control of human eccrine sweating.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Shin Sekihara
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University, Osaka, Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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18
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Choo HC, Peiffer JJ, Pang JWJ, Tan FHY, Aziz AR, Ihsan M, Lee JKW, Abbiss CR. Effect of regular precooling on adaptation to training in the heat. Eur J Appl Physiol 2020; 120:1143-1154. [PMID: 32232658 DOI: 10.1007/s00421-020-04353-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 03/18/2020] [Indexed: 11/28/2022]
Abstract
PURPOSE This study investigated whether regular precooling would help to maintain day-to-day training intensity and improve 20-km cycling time trial (TT) performed in the heat. Twenty males cycled for 10 day × 60 min at perceived exertion equivalent to 15 in the heat (35 °C, 50% relative humidity), preceded by no cooling (CON, n = 10) or 30-min water immersion at 22 °C (PRECOOL, n = 10). METHODS 19 participants (n = 9 and 10 for CON and PRECOOL, respectively) completed heat stress tests (25-min at 60% [Formula: see text] and 20-km TT) before and after heat acclimation. RESULTS Changes in mean power output (∆MPO, P = 0.024) and heart rate (∆HR, P = 0.029) during heat acclimation were lower for CON (∆MPO - 2.6 ± 8.1%, ∆HR - 7 ± 7 bpm), compared with PRECOOL (∆MPO + 2.9 ± 6.6%, ∆HR - 1 ± 8 bpm). HR during constant-paced cycling was decreased from the pre-acclimation test in both groups (P < 0.001). Only PRECOOL demonstrated lower rectal temperature (Tre) during constant-paced cycling (P = 0.002) and lower Tre threshold for sweating (P = 0.042). However, skin perfusion and total sweat output did not change in either CON or PRECOOL (all P > 0.05). MPO (P = 0.016) and finish time (P = 0.013) for the 20-km TT were improved in PRECOOL but did not change in CON (P = 0.052 for MPO, P = 0.140 for finish time). CONCLUSION Precooling maintains day-to-day training intensity and does not appear to attenuate adaptation to training in the heat.
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Affiliation(s)
- Hui C Choo
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, 270 Joondalup Dr, Joondalup, WA, 6027, Australia. .,Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, Singapore, 117593, Singapore.
| | - Jeremiah J Peiffer
- Discipline of Exercise Science, College of Science, Health, Engineering and Education, Murdoch University, 90 South St, Murdoch, WA, 6150, Australia
| | - Joel W J Pang
- Sport Science and Medicine Centre, Singapore Sport Institute, 3 Stadium Drive, Singapore, 397630, Singapore
| | - Frankie H Y Tan
- Sport Science and Medicine Centre, Singapore Sport Institute, 3 Stadium Drive, Singapore, 397630, Singapore.,Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, Singapore, 117593, Singapore
| | - Abdul Rashid Aziz
- Sport Science and Medicine Centre, Singapore Sport Institute, 3 Stadium Drive, Singapore, 397630, Singapore
| | - Mohammed Ihsan
- Research and Scientific Support, ASPETAR Orthopaedic and Sports Medicine Hospital, P.O. Box 29222, Doha, Qatar
| | - Jason K W Lee
- Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, Singapore, 117593, Singapore
| | - Chris R Abbiss
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, 270 Joondalup Dr, Joondalup, WA, 6027, Australia
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19
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Ravanelli N, Gagnon D, Imbeault P, Jay O. A retrospective analysis to determine if exercise training-induced thermoregulatory adaptations are mediated by increased fitness or heat acclimation. Exp Physiol 2020; 106:282-289. [PMID: 32118324 DOI: 10.1113/ep088385] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/28/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Are fitness-related improvements in thermoregulatory responses during uncompensable heat stress mediated by aerobic capacity V ̇ O 2 max or is it the partial heat acclimation associated with training? What is the main finding and its importance? During uncompensable heat stress, individuals with high and low V ̇ O 2 max displayed similar sweating and core temperature responses whereas exercise training in previously untrained individuals resulted in a greater sweat rate and a smaller rise in core temperature. These observations suggest that it is training, not V ̇ O 2 max per se, that mediates thermoregulatory improvements during uncompensable heat stress. ABSTRACT It remains unclear whether aerobic fitness, as defined by the maximum rate of oxygen consumption V ̇ O 2 max , independently improves heat dissipation in uncompensable environments, or whether the thermoregulatory adaptations associated with heat acclimation are due to repeated bouts of exercise-induced heat stress during regular aerobic training. The present analysis sought to determine if V ̇ O 2 max independently influences thermoregulatory sweating, maximum skin wettedness (ωmax ) and the change in rectal temperature (ΔTre ) during 60 min of exercise in an uncompensable environment (37.0 ± 0.8°C, 4.0 ± 0.2 kPa, 64 ± 3% relative humidity) at a fixed rate of heat production per unit mass (6 W kg-1 ). Retrospective analyses were performed on 22 participants (3 groups), aerobically unfit (UF; n = 7; V ̇ O 2 max : 41.7 ± 9.4 ml kg-1 min-1 ), aerobically fit (F; n = 7; V ̇ O 2 max : 55.6 ± 4.3 ml kg-1 min-1 ; P < 0.01) and aerobically unfit (n = 8) individuals, before (pre; V ̇ O 2 max : 45.8 ± 11.6 ml kg-1 min-1 ) and after (post; V ̇ O 2 max : 52.0 ± 11.1 ml kg-1 min-1 ; P < 0.001) an 8-week training intervention. ωmax was similar between UF (0.74 ± 0.09) and F (0.78 ± 0.08, P = 0.22). However, ωmax was greater post- (0.84 ± 0.08) compared to pre- (0.72 ± 0.06, P = 0.02) training. During exercise, mean local sweat rate (forearm and upper-back) was greater post- (1.24 ± 0.20 mg cm-2 min-1 ) compared to pre- (1.04 ± 0.25 mg cm-2 min-1 , P < 0.01) training, but similar between UF (0.94 ± 0.31 mg cm-2 min-1 , P = 0.90) and F (1.02 ± 0.30 mg cm-2 min-1 ). The ΔTre at 60 min of exercise was greater pre- (1.13 ± 0.16°C, P < 0.01) compared to post- (0.96 ± 0.14°C) training, but similar between UF (0.85 ± 0.29°C, P = 0.22) and F (0.95 ± 0.22°C). Taken together, aerobic training, not V ̇ O 2 max per se, confers an increased ωmax , greater sweat rate, and smaller rise in core temperature during uncompensable heat stress in fit individuals.
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Affiliation(s)
- Nicholas Ravanelli
- Cardiovascular Prevention and Rehabilitation Centre and Research Centre, Montreal Heart Institute, Montreal, QC, Canada.,Département de pharmacologie et physiologie, Université de Montréal, Montreal, QC, Canada
| | - Daniel Gagnon
- Cardiovascular Prevention and Rehabilitation Centre and Research Centre, Montreal Heart Institute, Montreal, QC, Canada.,Département de pharmacologie et physiologie, Université de Montréal, Montreal, QC, Canada
| | - Pascal Imbeault
- School of Human Kinetics, University of Ottawa, 200 Lees Ave, Ottawa, Canada
| | - Ollie Jay
- Thermal Ergonomics Laboratory, Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia.,Charles Perkins Centre, University of Sydney, Sydney, NSW, Australia
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20
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Barry H, Chaseling GK, Moreault S, Sauvageau C, Behzadi P, Gravel H, Ravanelli N, Gagnon D. Improved neural control of body temperature following heat acclimation in humans. J Physiol 2020; 598:1223-1234. [PMID: 32011734 DOI: 10.1113/jp279266] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/21/2020] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS With the advent of more frequent extreme heat events, adaptability to hot environments will be crucial for the survival of many species, including humans. However, the mechanisms that mediate human heat adaptation have remained elusive. We tested the hypothesis that heat acclimation improves the neural control of body temperature. Skin sympathetic nerve activity, comprising the efferent neural signal that activates heat loss thermoeffectors, was measured in healthy adults exposed to passive heat stress before and after a 7 day heat acclimation protocol. Heat acclimation reduced the activation threshold for skin sympathetic nerve activity, leading to an earlier activation of cutaneous vasodilatation and sweat production. These findings demonstrate that heat acclimation improves the neural control of body temperature in humans. ABSTRACT Heat acclimation improves autonomic temperature regulation in humans. However, the mechanisms that mediate human heat adaptation remain poorly understood. The present study tested the hypothesis that heat acclimation improves the neural control of body temperature. Body temperatures, skin sympathetic nerve activity, cutaneous vasodilatation, and sweat production were measured in 14 healthy adults (nine men and five women, aged 27 ± 5 years) during passive heat stress performed before and after a 7 day heat acclimation protocol. Heat acclimation increased whole-body sweat rate [+0.54 L h-1 (0.32, 0.75), P < 0.01] and reduced resting core temperature [-0.29°C (-0.40, -0.18), P < 0.01]. During passive heat stress, the change in mean body temperature required to activate skin sympathetic nerve activity was reduced [-0.21°C (-0.34, -0.08), P < 0.01] following heat acclimation. The earlier activation of skin sympathetic nerve activity resulted in lower activation thresholds for cutaneous vasodilatation [-0.18°C (-0.35, -0.01), P = 0.04] and local sweat rate [-0.13°C (-0.24, -0.01), P = 0.03]. These results demonstrate that heat acclimation leads to an earlier activation of the neural efferent outflow that activates the heat loss thermoeffectors of cutaneous vasodilatation and sweating.
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Affiliation(s)
- Hadiatou Barry
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Georgia K Chaseling
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Samuel Moreault
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Claudia Sauvageau
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Parya Behzadi
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Hugo Gravel
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Nicholas Ravanelli
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Daniel Gagnon
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Canada, Montréal, QC, Canada.,Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
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21
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Ely BR, Ely MR. Running in the Heat: Performance Consequences and Strategies to Prepare for Hot-Weather Racing. Strength Cond J 2020. [DOI: 10.1519/ssc.0000000000000484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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22
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Ely BR, Clayton ZS, McCurdy CE, Pfeiffer J, Needham KW, Comrada LN, Minson CT. Heat therapy improves glucose tolerance and adipose tissue insulin signaling in polycystic ovary syndrome. Am J Physiol Endocrinol Metab 2019; 317:E172-E182. [PMID: 31136202 PMCID: PMC7199222 DOI: 10.1152/ajpendo.00549.2018] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Polycystic ovary syndrome (PCOS) is associated with high rates of obesity and metabolic dysfunction. Repeated passive heat exposure (termed heat therapy) is a novel lifestyle intervention for improving health in obese women with PCOS. The purpose of this study was to examine changes in metabolic function in obese women with PCOS following heat therapy. Eighteen age- and BMI-matched obese women with PCOS (age: 27 ± 1 yr, BMI: 41.3 ± 1.1 kg/m-2) were assigned to heat therapy (HT) or time control (CON). HT participants underwent 30 one-hour hot tub sessions over 8-10 wk, while CON participants completed all testing but did not undergo heat therapy. Before (Pre), at the mid-point (Mid), and following (Post) 8-10 wk of heat therapy, metabolic health was assessed using a 2-h oral glucose tolerance test, a subcutaneous abdominal fat biopsy (Pre-Post only), and other blood markers relating to metabolic function. HT participants exhibited improved fasting glucose (Pre: 105 ± 3, Post: 89 ± 5mg/dl; P = 0.001), glucose area under the curve (AUC) (Pre: 18,698 ± 1,045, Post: 16,987 ± 1,017 mg·dl-1·min-1; P = 0.028) and insulin AUC (Pre: 126,924 ± 11,730, Post: 91,233 ± 14,429 IU l-1·min-1; P = 0.012). Adipocyte insulin signaling (p-AKT at Ser-473 with 1.2 nM insulin) increased in HT (Pre: 0.29 ± 0.14, Post: 0.93 ± 0.29 AU; P = 0.021). Additionally, serum testosterone declined in HT participants (Pre: 51 ± 7, Post: 34 ± 4 ng/dl; P = 0.033). No parameters changed over time in CON, and no change in BMI was observed in either group. HT substantially improved metabolic risk profile in obese women with PCOS. HT also reduced androgen excess and may improve PCOS symptomology.
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Affiliation(s)
- Brett R Ely
- Department of Human Physiology, University of Oregon , Eugene, Oregon
| | - Zachary S Clayton
- Department of Human Physiology, University of Oregon , Eugene, Oregon
| | - Carrie E McCurdy
- Department of Human Physiology, University of Oregon , Eugene, Oregon
| | - Joshua Pfeiffer
- PeaceHealth Medical Group, Oregon Bariatric Center , Springfield, Oregon
| | | | - Lindan N Comrada
- Department of Human Physiology, University of Oregon , Eugene, Oregon
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Amano T, Fujii N, Inoue Y, Kondo N. Cutaneous adrenergic nerve blockade attenuates sweating during incremental exercise in habitually trained men. J Appl Physiol (1985) 2018; 125:1041-1050. [PMID: 30024338 DOI: 10.1152/japplphysiol.00370.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
It remains unknown whether cutaneous adrenergic nerves functionally contribute to sweat production during exercise. This study examined whether cutaneous adrenergic nerve blockade attenuates sweating during incremental exercise, specifically in habitually trained individuals. Accordingly, 10 habitually trained and 10 untrained males (V̇o2max: 56.7 ± 5.4 and 38.9 ± 6.7 ml·kg-1·min-1, respectively; P < 0.001) performed incremental semirecumbent cycling (20 W/min) until exhaustion. Sweat rates (ventilated capsule) were measured at two bilateral forearm skin sites on which either 10 mM bretylium tosylate (BT) (an inhibitor of neurotransmitter release from sympathetic adrenergic nerve terminals) or saline (Control) was transdermally administered via iontophoresis. BT treatment delayed sweating onset in both groups (∼0.66 min; P = 0.001) and suppressed the sweat rate relative to the Control treatment at ≥70% relative total exercise time in trained individuals (each 10% increment; all P ≤ 0.009) but not in untrained counterparts ( P = 0.122, interaction between relative time × treatment). Changes in total sweat production at the BT site relative to the Control site were greater in trained individuals than in untrained counterparts (area under the curve, -0.86 ± 0.67 and -0.22 ± 0.39 mg/cm2, respectively; P = 0.023). In conclusion, we demonstrated that cutaneous adrenergic nerves do modulate sweating during incremental exercise, which appeared to be more apparent in habitually trained men (e.g., ≥70% maximum workload). Although our results indicated that habitual exercise training may augment neural adrenergic sweat production during incremental exercise, additional studies are required to confirm this possibility. NEW & NOTEWORTHY We demonstrated for the first time that cutaneous adrenergic nerves do modulate sweating during high-intensity exercise in humans (≥70% maximum workload). In addition, neural adrenergic sweating appeared to be greater in habitually trained individuals than in untrained counterparts, although further studies are necessary to confirm such a possibility. Nonetheless, the observations presented herein advance our understanding on human thermoregulation while providing new evidence for the neutral mediation of adrenergic sweating during exercise.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University , Niigata , Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba , Tsukuba City , Japan
| | - Yoshimitsu Inoue
- Laboratory for Human Performance Research, Osaka International University , Osaka , Japan
| | - Narihiko Kondo
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University , Kobe , Japan
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ELY BRETTR, BLANCHARD LAURIEA, STEELE JAREDR, FRANCISCO MICHAELA, CHEUVRONT SAMUELN, MINSON CHRISTOPHERT. Physiological Responses to Overdressing and Exercise-Heat Stress in Trained Runners. Med Sci Sports Exerc 2018; 50:1285-1296. [DOI: 10.1249/mss.0000000000001550] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Willmott AGB, Gibson OR, James CA, Hayes M, Maxwell NS. Physiological and perceptual responses to exercising in restrictive heat loss attire with use of an upper-body sauna suit in temperate and hot conditions. Temperature (Austin) 2018; 5:162-174. [PMID: 30377634 DOI: 10.1080/23328940.2018.1426949] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 01/08/2018] [Indexed: 10/18/2022] Open
Abstract
The aim of this experiment was to quantify physiological and perceptual responses to exercise with and without restrictive heat loss attire in hot and temperate conditions. Ten moderately-trained individuals (mass; 69.44±7.50 kg, body fat; 19.7±7.6%) cycled for 30-mins (15-mins at 2 W.kg-1 then 15-mins at 1 W.kg-1) under four experimental conditions; temperate (TEMP, 22°C/45%), hot (HOT, 45°C/20%) and, temperate (TEMPSUIT, 22°C/45%) and hot (HOTSUIT, 45°C/20%) whilst wearing an upper-body "sauna suit". Core temperature changes were higher (P<0.05) in TEMPSUIT (+1.7±0.4°C.hr-1), HOT (+1.9±0.5°C.hr-1) and HOTSUIT (+2.3±0.5°C.hr-1) than TEMP (+1.3±0.3°C.hr-1). Skin temperature was higher (P<0.05) in HOT (36.53±0.93°C) and HOTSUIT (37.68±0.68°C) than TEMP (33.50±1.77°C) and TEMPSUIT (33.41±0.70°C). Sweat rate was greater (P<0.05) in TEMPSUIT (0.89±0.24 L.hr-1), HOT (1.14±0.48 L.hr-1) and HOTSUIT (1.51±0.52 L.hr-1) than TEMP (0.56±0.27 L.hr-1). Peak heart rate was higher (P<0.05) in TEMPSUIT (155±23 b.min-1), HOT (163±18 b.min-1) and HOTSUIT (171±18 b.min-1) than TEMP (151±20 b.min-1). Thermal sensation and perceived exertion were greater (P<0.05) in TEMPSUIT (5.8±0.5 and 14±1), HOT (6.4±0.5 and 15±1) and HOTSUIT (7.1±0.5 and 16±1) than TEMP (5.3±0.5 and 14±1). Exercising in an upper-body sauna suit within temperate conditions induces a greater physiological strain and evokes larger sweat losses compared to exercising in the same conditions, without restricting heat loss. In hot conditions, wearing a sauna suit increases physiological and perceptual strain further, which may accelerate the stimuli for heat adaptation and improve HA efficiency.
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Affiliation(s)
| | - Oliver R Gibson
- Environmental Extremes Laboratory, University of Brighton, Eastbourne, UK.,Centre for Human Performance, Exercise and Rehabilitation, Brunel University London, Uxbridge, UK
| | - Carl A James
- Environmental Extremes Laboratory, University of Brighton, Eastbourne, UK.,National Sports Institute, Institut Sukan Negara, National Sport Complex, Bukit Jalil, 57000 Kuala Lumpur, Malaysia
| | - Mark Hayes
- Environmental Extremes Laboratory, University of Brighton, Eastbourne, UK
| | - Neil S Maxwell
- Environmental Extremes Laboratory, University of Brighton, Eastbourne, UK
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Post Junctional Sudomotor and Cutaneous Vascular Responses in Noninjured Skin Following Heat Acclimation in Burn Survivors. J Burn Care Res 2018; 38:e284-e292. [PMID: 27359190 DOI: 10.1097/bcr.0000000000000372] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Thermal tolerance is improved in burn survivors following 7 days of exercise heat acclimation. It is unknown whether post junctional sudomotor and/or cutaneous vascular adaptations in noninjured skin contribute to this improvement. Thirty-three burn survivors were stratified into moderately (17-40% BSA grafted, n = 19) and highly (>40% BSA grafted, n = 14) skin-grafted groups. Nine nonburned subjects served as controls. All subjects underwent a 7-day heat acclimation protocol, which improved thermal tolerance in all groups. Before and after this heat acclimation protocol, post junctional cutaneous vascular responses were assessed by administering increasing doses of sodium nitroprusside (SNP) and methacholine (MCh) using intradermal microdialysis in noninjured skin. MCh infusion was also used to assess post junctional responses in sudomotor function in noninjured skin. Cutaneous vascular responses to SNP and MCh were not different between pre- and post heat acclimation in either group of burn survivors (both P > .05). The maximal sweating rate to MCh increased post acclimation in the control group (0.41 ± 0.20 to 0.54 ± 0.21 mg·min·cm; P = .016) but was unchanged in both groups of burn survivors (both P > .05). The number of sweat glands activated during the highest dose of MCh was elevated in the >40% BSA-grafted group (49 ± 16 to 56 ± 18 glands·cm; P = .005) but was unchanged in control subjects and the <40% BSA-grafted group (both P > .05). Given that post junctional administration of MCh and SNP did not alter sweating or skin blood flow from noninjured skin of burn survivors, improved thermal tolerance in these individuals following heat acclimation is more likely a result of either an increased sweating efficiency or an increased neural drive for sweating.
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27
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Sauna exposure immediately prior to short-term heat acclimation accelerates phenotypic adaptation in females. J Sci Med Sport 2018; 21:190-195. [DOI: 10.1016/j.jsams.2017.06.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 06/21/2017] [Accepted: 06/27/2017] [Indexed: 01/10/2023]
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Abstract
In humans, sweating is the most powerful autonomic thermoeffector. The evaporation of sweat provides by far the greatest potential for heat loss and it represents the only means of heat loss when air temperature exceeds skin temperature. Sweat production results from the integration of afferent neural information from peripheral and central thermoreceptors which leads to an increase in skin sympathetic nerve activity. At the neuroglandular junction, acetylcholine is released and binds to muscarinic receptors which stimulate the secretion of a primary fluid by the secretory coil of eccrine glands. The primary fluid subsequently travels through a duct where ions are reabsorbed. The end result is the expulsion of hypotonic sweat on to the skin surface. Sweating increases in proportion with the intensity of the thermal challenge in an attempt of the body to attain heat balance and maintain a stable internal body temperature. The control of sweating can be modified by biophysical factors, heat acclimation, dehydration, and nonthermal factors. The purpose of this article is to review the role of sweating as a heat loss thermoeffector in humans.
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Francisco MA, Brunt VE, Jensen KN, Lorenzo S, Minson CT. Ten days of repeated local forearm heating does not affect cutaneous vascular function. J Appl Physiol (1985) 2017; 123:310-316. [PMID: 28473615 DOI: 10.1152/japplphysiol.00966.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 04/14/2017] [Accepted: 04/26/2017] [Indexed: 11/22/2022] Open
Abstract
The aim of the present study was to determine whether 10 days of repeated local heating could induce peripheral adaptations in the cutaneous vasculature and to investigate potential mechanisms of adaptation. We also assessed maximal forearm blood flow to determine whether repeated local heating affects maximal dilator capacity. Before and after 10 days of heat training consisting of 1-h exposures of the forearm to 42°C water or 32°C water (control) in the contralateral arm (randomized and counterbalanced), we assessed hyperemia to rapid local heating of the skin (n = 14 recreationally active young subjects). In addition, sequential doses of acetylcholine (ACh, 1 and 10 mM) were infused in a subset of subjects (n = 7) via microdialysis to study potential nonthermal microvascular adaptations following 10 days of repeated forearm heat training. Skin blood flow was assessed using laser-Doppler flowmetry, and cutaneous vascular conductance (CVC) was calculated as laser-Doppler red blood cell flux divided by mean arterial pressure. Maximal cutaneous vasodilation was achieved by heating the arm in a water-spray device for 45 min and assessed using venous occlusion plethysmography. Forearm vascular conductance (FVC) was calculated as forearm blood flow divided by mean arterial pressure. Repeated forearm heating did not increase plateau percent maximal CVC (CVCmax) responses to local heating (89 ± 3 vs. 89 ± 2% CVCmax, P = 0.19), 1 mM ACh (43 ± 9 vs. 53 ± 7% CVCmax, P = 0.76), or 10 mM ACh (61 ± 9 vs. 85 ± 7% CVCmax, P = 0.37, by 2-way repeated-measures ANOVA). There was a main effect of time at 10 mM ACh (P = 0.03). Maximal FVC remained unchanged (0.12 ± 0.02 vs. 0.14 ± 0.02 FVC, P = 0.30). No differences were observed in the control arm. Ten days of repeated forearm heating in recreationally active young adults did not improve the microvascular responsiveness to ACh or local heating.NEW & NOTEWORTHY We show for the first time that 10 days of repeated forearm heating is not sufficient to improve cutaneous vascular responsiveness in recreationally active young adults. In addition, this is the first study to investigate cutaneous cholinergic sensitivity and forearm blood flow following repeated local heat exposure. Our data add to the limited studies regarding repeated local heating of the cutaneous vasculature.
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Affiliation(s)
| | - Vienna E Brunt
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | | | - Santiago Lorenzo
- Lake Erie College of Osteopathic Medicine-Bradenton, Bradenton, Florida
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30
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Amano T, Fujii N, Louie JC, Meade RD, Kenny GP. Individual variations in nitric oxide synthase-dependent sweating in young and older males during exercise in the heat: role of aerobic power. Physiol Rep 2017; 5:5/6/e13208. [PMID: 28325791 PMCID: PMC5371569 DOI: 10.14814/phy2.13208] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Accepted: 02/22/2017] [Indexed: 11/24/2022] Open
Abstract
We evaluated the association between aerobic power (defined by peak oxygen consumption; VO2peak) and the contribution of nitric oxide synthase (NOS) to the sweating response in young and older individuals during exercise in the heat. Data from 44 young (24 ± 1 years) and 48 older (61 ± 2 years) males with mean VO2peak of 47.8 ± 2.4 (range, 28.0–62.3) and 39.1 ± 2.3 (range, 26.4–55.7) mLO2 kg−1 min−1, respectively, were compiled from our prior studies. Participants performed two 15‐ to 30‐min bouts of exercise at a fixed rate of metabolic heat production of 400 or 500 W, each separated by 15–20 min recovery in the heat (35°C, relative humidity of 20%). Forearm sweat rate (ventilated capsule technique) was measured at two skin sites that were continuously and simultaneously administered with lactated Ringers solution (Control) or 10 mmol/L NG‐nitro‐L‐arginine methyl ester (L‐NAME, nonselective NOS inhibitor) via intradermal microdialysis. Sweat rate during the final 5 min of each exercise bout was lower with L‐NAME compared to the Control in both groups (all P < 0.05). The magnitude of the attenuation in sweat rate induced by L‐NAME compared to the Control was not correlated with VO2peak (all P ≥ 0.46) while this attenuation was negatively correlated with the sweat rate at the Control in both groups and in both exercise bouts (all P < 0.01, R ≤ −0.43). These results suggest that NOS‐dependent sweating is not associated with aerobic power per se, while it becomes evident in individuals who produce larger sweat rates during exercise irrespective of age.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan.,Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Naoto Fujii
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada.,Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Jeffrey C Louie
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Robert D Meade
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada
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Trbovich MB, Kiratli JB, Price MJ. The effects of a heat acclimation protocol in persons with spinal cord injury. J Therm Biol 2016; 62:56-62. [DOI: 10.1016/j.jtherbio.2016.10.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 10/17/2016] [Indexed: 10/20/2022]
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32
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Cardiovascular adaptations supporting human exercise-heat acclimation. Auton Neurosci 2016; 196:52-62. [DOI: 10.1016/j.autneu.2016.02.002] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 01/29/2016] [Accepted: 02/04/2016] [Indexed: 11/22/2022]
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33
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Périard JD, Racinais S, Sawka MN. Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports. Scand J Med Sci Sports 2016; 25 Suppl 1:20-38. [PMID: 25943654 DOI: 10.1111/sms.12408] [Citation(s) in RCA: 318] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/13/2014] [Indexed: 11/29/2022]
Abstract
Exercise heat acclimation induces physiological adaptations that improve thermoregulation, attenuate physiological strain, reduce the risk of serious heat illness, and improve aerobic performance in warm-hot environments and potentially in temperate environments. The adaptations include improved sweating, improved skin blood flow, lowered body temperatures, reduced cardiovascular strain, improved fluid balance, altered metabolism, and enhanced cellular protection. The magnitudes of adaptations are determined by the intensity, duration, frequency, and number of heat exposures, as well as the environmental conditions (i.e., dry or humid heat). Evidence is emerging that controlled hyperthermia regimens where a target core temperature is maintained, enable more rapid and complete adaptations relative to the traditional constant work rate exercise heat acclimation regimens. Furthermore, inducing heat acclimation outdoors in a natural field setting may provide more specific adaptations based on direct exposure to the exact environmental and exercise conditions to be encountered during competition. This review initially examines the physiological adaptations associated with heat acclimation induction regimens, and subsequently emphasizes their application to competitive athletes and sports.
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Affiliation(s)
- J D Périard
- Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar
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Amano T, Inoue Y, Koga S, Nishiyasu T, Kondo N. Influence of exercise training with thigh compression on heat-loss responses. Scand J Med Sci Sports 2015; 25 Suppl 1:173-82. [PMID: 25943668 DOI: 10.1111/sms.12365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2014] [Indexed: 01/16/2023]
Abstract
We investigated the effect of thigh compression, which accelerates activation of central command and muscle metabo- and mechanoreceptors, on the adaptation of sweating and cutaneous vascular responses during exercise heat acclimation. Nine non-heat-acclimated male subjects were acclimated to heat (32 °C and 50% RH) while cycling [50% of maximum oxygen uptake ( V ˙ O 2 m a x )] 60 min/day for 7 days (control group). The experimental group (n = 9) conducted the same training while the proximal thighs were compressed by a cuff at 60 mmHg. V ˙ O 2 m a x , acetylcholine-induced forearm sweating rate (iontophoresis), and mean sweating and cutaneous vascular responses on the forehead, chest, and forearm (SRmean and CVCmean ) during passive heating were evaluated before and after training. Training significantly increased V ˙ O 2 m a x while did not affect acetylcholine-induced sweating rates in either group. Training significantly decreased Tb thresholds for SRmean and CVCmean during passive heating without the alternations of sensitivities in both groups. Although SRmean during passive heating at a given ΔTb was not improved in either group, CVCmean was significantly (P < 0.05) attenuated after exercise training only in experimental group. Our results indicate that thigh cuff compression during exercise heat acclimation does not influence adaptation of the sweating response but attenuate cutaneous vasodilation.
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Affiliation(s)
- T Amano
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
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Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales. J Therm Biol 2015; 49-50:55-65. [DOI: 10.1016/j.jtherbio.2015.02.005] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 02/11/2015] [Accepted: 02/11/2015] [Indexed: 11/18/2022]
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36
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Amano T, Koga S, Inoue Y, Nishiyasu T, Kondo N. Characteristics of sweating responses and peripheral sweat gland function during passive heating in sprinters. Eur J Appl Physiol 2013; 113:2067-75. [DOI: 10.1007/s00421-013-2641-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 04/04/2013] [Indexed: 05/27/2023]
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37
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Partial heat acclimation of athletes with spinal cord lesion. Eur J Appl Physiol 2012; 113:109-15. [PMID: 22592455 DOI: 10.1007/s00421-012-2417-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 05/02/2012] [Indexed: 10/28/2022]
Abstract
Heat acclimation (HA) can improve thermoregulatory stability in able-bodied athletes in part by an enhanced sweat response. Athletes with spinal cord lesion are unable to sweat below the lesion and it is unknown if they can HA. Five paralympic shooting athletes with spinal cord lesion completed seven consecutive days HA in hot conditions (33.4 ± 0.6 °C, 64.8 ± 3.7 %rh). Each HA session consisted of 20 min arm crank exercise at 50 % [Formula: see text] followed by 40 min rest, or simulated shooting. Aural temperature (T (aur)) was recorded throughout. Body mass was assessed before and after each session and a sweat collection swab was fixed to T12 of the spine. Fingertip whole blood was sampled at rest on days 1 and 7 for estimation of the change in plasma volume. Resting T (aur) declined from 36.3 ± 0.2 °C on day 1 to 36.0 ± 0.2 °C by day 6 (P < 0.05). During the HA sessions mean, T (aur) declined from 37.2 ± 0.2 °C on day 1, to 36.7 ± 0.3 °C on day 7 (P < 0.05). Plasma volume increased from day 1 by 1.5 ± 0.6 % on day 7 (P < 0.05). No sweat secretion was detected or changes in body mass observed from any participant. Repeated hyperthermia combined with limited evaporative heat loss was sufficient to increase plasma volume, probably by alterations in fluid regulatory hormones. In conclusion, we found that although no sweat response was observed, athletes with spinal cord lesion could partially HA.
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Castle P, Mackenzie RW, Maxwell N, Webborn AD, Watt PW. Heat acclimation improves intermittent sprinting in the heat but additional pre-cooling offers no further ergogenic effect. J Sports Sci 2011; 29:1125-34. [DOI: 10.1080/02640414.2011.583673] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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39
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Amano T, Ichinose M, Koga S, Inoue Y, Nishiyasu T, Kondo N. Sweating responses and the muscle metaboreflex under mildly hyperthermic conditions in sprinters and distance runners. J Appl Physiol (1985) 2011; 111:524-9. [PMID: 21659489 DOI: 10.1152/japplphysiol.00212.2011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To investigate the effects of different training methods on nonthermal sweating during activation of the muscle metaboreflex, we compared sweating responses during postexercise muscle occlusion in endurance runners, sprinters, and untrained men under mild hyperthermia (ambient temperature, 35°C; relative humidity, 50%). Ten endurance runners, nine sprinters, and ten untrained men (maximal oxygen uptakes: 57.5 ± 1.5, 49.3 ± 1.5, and 36.6 ± 1.6 ml·kg(-1)·min(-1), respectively; P < 0.05) performed an isometric handgrip exercise at 40% maximal voluntary contraction for 2 min, and then a pressure of 280 mmHg was applied to the forearm to occlude blood circulation for 2 min. The Δ change in mean arterial blood pressure between the resting level and the occlusion was significantly higher in sprinters than in untrained men (32.2 ± 4.4 vs. 17.3 ± 2.6 mmHg, respectively; P < 0.05); however, no difference was observed between distance runners and untrained men. The Δ mean sweating rate (averaged value of the forehead, chest, forearm, and thigh) during the occlusion was significantly higher in distance runners than in sprinters and untrained men (0.38 ± 0.07, 0.19 ± 0.03, and 0.11 ± 0.04 mg·cm(-2)·min(-1), respectively; P < 0.05) and did not differ between sprinters and untrained men. Our results suggest that the specificity of training modalities influences the sweating response during activation of the muscle metaboreflex. In addition, these results imply that a greater activation of the muscle metaboreflex does not cause a greater sweating response in sprinters.
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Affiliation(s)
- Tatsuro Amano
- Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, 3-11 Tsurukabuto, Nada-ku, Kobe 657-8501, Japan
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Lorenzo S, Minson CT. Heat acclimation improves cutaneous vascular function and sweating in trained cyclists. J Appl Physiol (1985) 2010; 109:1736-43. [PMID: 20864556 DOI: 10.1152/japplphysiol.00725.2010] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to explore heat acclimation effects on cutaneous vascular responses and sweating to local ACh infusions and local heating. We also sought to examine whether heat acclimation altered maximal skin blood flow. ACh (1, 10, and 100 mM) was infused in 20 highly trained cyclists via microdialysis before and after a 10-day heat acclimation program [two 45-min exercise bouts at 50% maximal O(2) uptake (Vo(2max)) in 40°C (n = 12)] or control conditions [two 45-min exercise bouts at 50% Vo(2max) in 13°C (n = 8)]. Skin blood flow was monitored via laser-Doppler flowmetry (LDF), and cutaneous vascular conductance (CVC) was calculated as LDF ÷ mean arterial pressure. Sweat rate was measured by resistance hygrometry. Maximal brachial artery blood flow (forearm blood flow) was obtained by heating the contralateral forearm in a water spray device and measured by Doppler ultrasound. Heat acclimation increased %CVC(max) responses to 1, 10, and 100 mM ACh (43.5 ± 3.4 vs. 52.6 ± 2.6% CVC(max), 67.7 ± 3.4 vs. 78.0 ± 3.0% CVC(max), and 81.0 ± 3.8 vs. 88.5 ± 1.1% CVC(max), respectively, all P < 0.05). Maximal forearm blood flow remained unchanged after heat acclimation (290.9 ± 12.7 vs. 269.9 ± 23.6 ml/min). The experimental group showed significant increases in sweating responses to 10 and 100 mM ACh (0.21 ± 0.03 vs. 0.31 ± 0.03 mg·cm(-2)·min(-1) and 0.45 ± 0.05 vs. 0.67 ± 0.06 mg·cm(-2)·min(-1), respectively, all P < 0.05), but not to 1 mM ACh (0.13 ± 0.02 vs. 0.18 ± 0.02 mg·cm(-2)·min(-1), P = 0.147). No differences in any of the variables were found in the control group. Heat acclimation in highly trained subjects induced local adaptations within the skin microcirculation and sweat gland apparatus. Furthermore, maximal skin blood flow was not altered by heat acclimation, demonstrating that the observed changes were attributable to improvement in cutaneous vascular function and not to structural changes that limit maximal vasodilator capacity.
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Affiliation(s)
- Santiago Lorenzo
- Department of Human Physiology, University of Oregon, Eugene, OR 97403-1240, USA
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