Centre for Sport Research, Deakin University, 221 Burwood Highway, Burwood, VIC, 3125, Australia.
Deakin Biostatistics Unit, Faculty of Health, Deakin University, Burwood, VIC, Australia.
Sports Med. 2023 Jul;53(7):1395-1421. doi: 10.1007/s40279-023-01831-2. Epub 2023 May 24.
Heat adaptation regimes are used to prepare athletes for exercise in hot conditions to limit a decrement in exercise performance. However, the heat adaptation literature mostly focuses on males, and consequently, current heat adaptation guidelines may not be optimal for females when accounting for the biological and phenotypical differences between sexes.
We aimed to examine: (1) the effects of heat adaptation on physiological adaptations in females; (2) the impact of heat adaptation on performance test outcomes in the heat; and (3) the impact of various moderators, including duration (minutes and/or days), total heat dose (°Cmin), exercise intensity (kcalmin), total energy expended (kcal), frequency of heat exposures and training status on the physiological adaptations in the heat.
SPORTDiscus, MEDLINE Complete and Embase databases were searched to December 2022. Random-effects meta-analyses for resting and exercise core temperature, skin temperature, heart rate, sweat rate, plasma volume and performance tests in the heat were completed using Stata Statistical Software: Release 17. Sub-group meta-analyses were performed to explore the effect of duration, total heat dose, exercise intensity, total energy expended, frequency of heat exposure and training status on resting and exercise core temperature, skin temperature, heart rate and sweat rate. An explorative meta-regression was conducted to determine the effects of physiological adaptations on performance test outcomes in the heat following heat adaptation.
Thirty studies were included in the systematic review; 22 studies were meta-analysed. After heat adaptation, a reduction in resting core temperature (effect size [ES] = - 0.45; 95% confidence interval [CI] - 0.69, - 0.22; p < 0.001), exercise core temperature (ES = - 0.81; 95% CI - 1.01, - 0.60; p < 0.001), skin temperature (ES = - 0.64; 95% CI - 0.79, - 0.48; p < 0.001), heart rate (ES = - 0.60; 95% CI - 0.74, - 0.45; p < 0.001) and an increase in sweat rate (ES = 0.53; 95% CI 0.21, 0.85; p = 0.001) were identified in females. There was no change in plasma volume (ES = - 0.03; 95% CI - 0.31, 0.25; p = 0.835), whilst performance test outcomes were improved following heat adaptation (ES = 1.00; 95% CI 0.56, 1.45; p < 0.001). Across all moderators, physiological adaptations were more consistently observed following durations of 451-900 min and/or 8-14 days, exercise intensity ≥ 3.5 kcalmin, total energy expended ≥ 3038 kcal, consecutive (daily) frequency and total heat dose ≥ 23,000 °Cmin. The magnitude of change in performance test outcomes in the heat was associated with a reduction in heart rate following heat adaptation (standardised mean difference = - 10 beatsmin; 95% CI - 19, - 1; p = 0.031).
Heat adaptation regimes induce physiological adaptations beneficial to thermoregulation and performance test outcomes in the heat in females. Sport coaches and applied sport practitioners can utilise the framework developed in this review to design and implement heat adaptation strategies for females.
热适应方案被用于使运动员在热环境下进行运动，以限制运动表现的下降。然而，热适应文献主要集中在男性身上，因此，目前的热适应指南可能没有考虑到男女之间的生物学和表型差异，对女性并不完全适用。
我们旨在研究：（1）热适应对女性生理适应的影响；（2）热适应对热环境下运动测试结果的影响；（3）各种调节因素，包括时间（分钟和/或天数）、总热剂量（°Cmin）、运动强度（kcalmin）、总能量消耗（kcal）、热暴露频率和训练状态对热环境中生理适应的影响。
对 SPORTDiscus、MEDLINE Complete 和 Embase 数据库进行检索，截至 2022 年 12 月。使用 Stata 统计软件：版本 17 进行随机效应荟萃分析，用于静息和运动核心温度、皮肤温度、心率、出汗率、血浆容量和热环境下的运动测试。进行亚组荟萃分析，以探讨时间、总热剂量、运动强度、总能量消耗、热暴露频率和训练状态对静息和运动核心温度、皮肤温度、心率和出汗率的影响。进行探索性元回归分析，以确定热适应后生理适应对热环境下运动测试结果的影响。
本系统评价共纳入 30 项研究，其中 22 项进行了荟萃分析。热适应后，女性的静息核心温度（效应量 [ES] = -0.45；95%置信区间 [CI] = -0.69，-0.22；p < 0.001）、运动核心温度（ES = -0.81；95% CI = -1.01，-0.60；p < 0.001）、皮肤温度（ES = -0.64；95% CI = -0.79，-0.48；p < 0.001）、心率（ES = -0.60；95% CI = -0.74，-0.45；p < 0.001）和出汗率（ES = 0.53；95% CI = 0.21，0.85；p = 0.001）均有所降低。女性的血浆容量没有变化（ES = -0.03；95% CI = -0.31，0.25；p = 0.835），而运动测试结果在热适应后得到了改善（ES = 1.00；95% CI = 0.56，1.45；p < 0.001）。在所有调节因素中，持续时间为 451-900 分钟和/或 8-14 天、运动强度≥3.5 kcalmin、总能量消耗≥3038 kcal、连续（每日）频率和总热剂量≥23,000°Cmin 时，观察到的生理适应更为一致。热适应后运动测试结果的变化幅度与心率的降低有关（标准化均数差 = -10 次/min；95% CI = -19，-1；p = 0.031）。
热适应方案可诱导女性的生理适应，有利于热环境下的体温调节和运动测试结果。体育教练和应用体育从业者可以利用本综述中制定的框架，为女性设计和实施热适应策略。
