Background

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat.

Objective

The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel.

Eligibility Criteria

Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6 weeks were included.

Data Sources

MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022.

Risk of Bias

A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias.

Data Synthesis

A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated.

Results

Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of − 0.19 °C [90% CrI: − 0.41 to 0.05, Pd = 91%] and − 6 beats·min⁻¹ [90% CrI: − 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by − 0.24 °C [90% CrI: − 0.67 to 0.20, Pd = 85%] and − 7 beats·min⁻¹ [90% CrI: − 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01 L·h⁻¹ [90% CrI: − 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation.

Conclusions

Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length.

PROSPERO Registration

CRD42022337761.

中文翻译：

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量化运动员和军事人员的运动热适应：系统回顾和荟萃分析

背景

运动员和军事人员通常需要在炎热和/或潮湿的环境中比赛和工作，在这些环境中，表现下降和劳力性热病风险增加的现象普遍存在。减少热应激不利影响的生理策略是适应高温。

客观的

这项系统评价的目的是量化搬迁到气候更炎热的地方对运动员和军事人员进行热适应的影响。

资格标准

其中包括调查热适应对未适应环境的运动员和军事人员通过重新安置到炎热气候< 6 周的影响的研究。

数据源

MEDLINE、SPORTDiscus、CINAHL Plus with Full Text 和 Scopus 的检索时间从最初到 2022 年 6 月。

偏见的风险

两位作者独立使用麦克马斯特批判性审查表的修改版本来评估偏倚风险。

数据综合

对五项结果指标进行了贝叶斯多级荟萃分析，包括静息核心温度和心率、热反应测试期间核心温度和心率的变化以及出汗率。湿球温度（WBGT）、每日训练持续时间和方案长度被用作预测变量。与后验均值和 90% 可信区间 (CrI) 一起，计算方向概率 (Pd)。

结果

其中包括来自 12 项独立研究的 18 篇文章。十四篇文章（九项研究）为荟萃分析提供了数据。在考虑 WBGT、每日训练持续时间和方案长度的同时，人群估计表明静息核心温度和心率降低了 − 0.19 °C [90% CrI：− 0.41 至 0.05，Pd = 91%] 和 − 6 次·分钟分别为⁻¹ [90% CrI：− 16 至 5，Pd = 83%]。此外，热反应测试期间核心温度和心率的上升减弱了− 0.24 °C [90% CrI：− 0.67 至 0.20，Pd = 85%] 和− 7 次·分钟⁻¹ [90% CrI： − 18 至 4，Pd = 87%]。出汗率的变化是相互矛盾的（0.01 L·h ⁻¹ [90% CrI：− 0.38 至 0.40，Pd = 53%]），主要是由于两项研究表明热适应后出汗率降低。

结论

搬迁到更炎热气候的运动员和军事人员的数据与静息核心温度和心率的降低一致，此外，在基于运动的热反应测试期间核心温度和心率的上升有所减弱。出汗率的增加也是可以实现的，这些适应的程度取决于 WBGT、每日训练持续时间和方案长度。

普洛斯彼罗注册

CRD42022337761。