Effect of condensed heat acclimation on thermophysiological adaptations, hypoxic cross-tolerance, exercise performance, and deacclimation.

IF 3.3 3区 医学 Q1 PHYSIOLOGY
Journal of applied physiology Pub Date : 2025-03-01 Epub Date: 2025-01-17 DOI:10.1152/japplphysiol.00775.2024
Charlotte E Stevens, Joseph T Costello, Michael J Tipton, Ella F Walker, Alex A M Gould, John S Young, Ben J Lee, Thomas B Williams, Fiona A Myers, Jo Corbett
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引用次数: 0

Abstract

Short duration heat acclimation (HA) (≤5 daily heat exposures) elicits incomplete adaptation compared with longer interventions, possibly due to the lower accumulated thermal "dose." It is unknown if matching thermal "dose" over a shorter timescale elicits comparable adaptation to a longer intervention. Using a parallel-groups design, we compared: 1) "condensed" HA (CHA; n = 17 males) consisting of 4 × 75 min·day-1 heat exposures [target rectal temperature (Trec) = 38.5 °C] for two consecutive days, with 2) "traditional" HA (THA; n = 15 males) consisting of 1 × 75 min·day-1 heat exposure (target Trec = 38.5°C) for eight consecutive days. Physiological responses to exercise heat stress, hypoxia, and normoxic exercise performance were evaluated pre- and postintervention. Thermal (Trec over final 45 min: CHA = 38.45 ± 0.17°C, THA = 38.53 ± 0.13°C, P = 0.126) and cardiovascular strain were not different during interventions, indicating similar thermal "dose," although CHA had lower sweating rate, higher starting Trec, and greater inflammation, gastrointestinal permeability, and renal stress (P < 0.05). However, CHA elicited an array of thermophysiological adaptations that did not differ from THA [reduced indices of peak thermal (e.g., Δ peak Trec CHA = -0.28 ± 0.26°C, THA = -0.36 ± 0.17°C, P = 0.303) and cardiovascular strain, inflammation, and renal stress; blood and plasma volume expansion; improved perceptual indices], although improvements in resting thermal strain (e.g., Δ resting Trec CHA = -0.14 ± 0.21°C, THA = -0.35 ± 0.29°C, P = 0.027) and sweating rate were less with CHA. Both interventions improved aspects of hypoxic tolerance, but effects on temperate normoxic exercise indices were limited. The diminished thermal strain was well-maintained over a 22-day decay period. In conclusion, CHA could represent a viable acclimation option for time-restricted young healthy males preparing for a hot, and possibly high-altitude, environment.NEW & NOTEWORTHY This study has shown, for the first time, that a novel condensed heat acclimation program can elicit an array of thermophysiological adaptations, many of which do not differ from traditional heat acclimation. These findings suggest that accumulated thermal "dose" is an important factor contributing to the adaptive responses to heat stress and that condensed heat acclimation may represent a viable option for time-restricted individuals (e.g., military personnel, firefighters, and athletes) preparing to enter a hot environment.

压缩热驯化对热生理适应、低氧交叉耐受性、运动表现和去驯化的影响。
与较长时间的干预相比,短时间的热驯化(每日热暴露≤5次)导致不完全适应,可能是由于较低的累积热“剂量”。目前尚不清楚在较短的时间尺度上匹配热“剂量”是否会引起对较长干预措施的可比适应。使用平行组设计,我们比较了:i)冷凝的HA (CHA;n=17名男性),包括4×75 min∙day-1热暴露(目标直肠温度(Trec)=38.5°C),连续2天;(二)“传统”HA;n=15名男性),包括1×75 min∙day-1热暴露(目标Trec=38.5°C),连续8天。在干预前和干预后对运动热应激、缺氧和常氧运动表现的生理反应进行评估。热(最后45分钟的Trec: CHA=38.45±0.17°C, THA=38.53±0.13°C, p=0.126)和心血管应变在干预期间没有差异,表明相似的热“剂量”,尽管CHA有较低的出汗率,较高的起始Trec,更大的炎症,胃肠道通透性和肾脏应激(p =0.126。, Δ Trec峰值CHA=- 0.28±0.26°C, THA=-0.36±0.17°C, p=0.303]和心血管应变、炎症和肾脏应激;血液和血浆容量扩张;虽然静息热应变(例如,Δ静息Trec CHA=-0.14±0.21°C, THA=- 0.35±0.29°C, p=0.027)和出汗率的改善较少。两种干预措施都改善了低氧耐受性,但对温带常氧运动指标的影响有限。衰减后的热应变在22天内保持良好。总之,CHA可以为时间有限的年轻健康雄性准备炎热的,可能是高海拔的环境提供一个可行的适应选择。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
6.00
自引率
9.10%
发文量
296
审稿时长
2-4 weeks
期刊介绍: The Journal of Applied Physiology publishes the highest quality original research and reviews that examine novel adaptive and integrative physiological mechanisms in humans and animals that advance the field. The journal encourages the submission of manuscripts that examine the acute and adaptive responses of various organs, tissues, cells and/or molecular pathways to environmental, physiological and/or pathophysiological stressors. As an applied physiology journal, topics of interest are not limited to a particular organ system. The journal, therefore, considers a wide array of integrative and translational research topics examining the mechanisms involved in disease processes and mitigation strategies, as well as the promotion of health and well-being throughout the lifespan. Priority is given to manuscripts that provide mechanistic insight deemed to exert an impact on the field.
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