Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.
Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee.
Am J Physiol Regul Integr Comp Physiol. 2020 Jul 1;319(1):R114-R122. doi: 10.1152/ajpregu.00048.2020. Epub 2020 May 20.
Exercise-heat acclimation (EHA) induces adaptations that improve tolerance to heat exposure. Whether adaptations from EHA can also alter responses to hypobaric hypoxia (HH) conditions remains unclear. This study assessed whether EHA can alter time-trial performance and/or incidence of acute mountain sickness (AMS) during HH exposure. Thirteen sea-level (SL) resident men [SL peak oxygen consumption (V̇o) 3.19 ± 0.43 L/min] completed steady-state exercise, followed by a 15-min cycle time trial and assessment of AMS before (HH1; 3,500 m) and after (HH2) an 8-day EHA protocol [120 min; 5 km/h; 2% incline; 40°C and 40% relative humidity (RH)]. EHA induced lower heart rate (HR) and core temperature and plasma volume expansion. Time-trial performance was not different between HH1 and HH2 after 2 h (106.3 ± 23.8 vs. 101.4 ± 23.0 kJ, = 0.71) or 24 h (107.3 ± 23.4 vs. 106.3 ± 20.8 kJ, > 0.9). From HH1 to HH2, HR and oxygen saturation, at the end of steady-state exercise and time-trial tests at 2 h and 24 h, were not different ( > 0.05). Three of 13 volunteers developed AMS during HH1 but not during HH2, whereas a fourth volunteer only developed AMS during HH2. Heat shock protein 70 was not different from HH1 to HH2 at SL [1.9 ± 0.7 vs. 1.8 ± 0.6 normalized integrated intensities (NII), = 0.97] or after 23 h (1.8 ± 0.4 vs. 1.7 ± 0.5 NII, = 0.78) at HH. Our results indicate that this EHA protocol had little to no effect-neither beneficial nor detrimental-on exercise performance in HH. EHA may reduce AMS in those who initially developed AMS; however, studies at higher elevations, having higher incidence rates, are needed to confirm our findings.
运动-热适应（EHA）可诱导适应性改变，从而提高对热暴露的耐受性。EHA 引起的适应性改变是否也能改变对低氧（HH）环境的反应尚不清楚。本研究评估了 EHA 是否会改变 HH 暴露期间的计时赛表现和/或急性高原病（AMS）的发生率。13 名海平面（SL）居民男性[SL 峰值摄氧量（V̇o）3.19±0.43 L/min]完成稳态运动后，进行 15 分钟的自行车计时赛，并在 EHA 方案[120 分钟；5 公里/小时；2%坡度；40°C 和 40%相对湿度（RH）]前后（HH1，3500 m；HH2）评估 AMS。EHA 引起的心率（HR）和核心温度较低，血浆容量扩张。在 2 小时（106.3±23.8 与 101.4±23.0 kJ， = 0.71）或 24 小时（107.3±23.4 与 106.3±20.8 kJ， > 0.9）后，HH1 和 HH2 之间的计时赛表现无差异。从 HH1 到 HH2，稳态运动和计时赛测试结束时的 HR 和氧饱和度在 2 小时和 24 小时均无差异（ > 0.05）。13 名志愿者中有 3 名在 HH1 期间发生 AMS，但在 HH2 期间未发生，而第 4 名志愿者仅在 HH2 期间发生 AMS。HH1 时，热休克蛋白 70（HSP70）在 SL 与 HH2 之间无差异[1.9±0.7 与 1.8±0.6 归一化积分强度（NII）， = 0.97]，HH2 后 23 小时时也无差异[1.8±0.4 与 1.7±0.5 NII， = 0.78]。我们的结果表明，该 EHA 方案对 HH 下的运动表现几乎没有影响（既没有益处，也没有坏处）。EHA 可能会减少最初发生 AMS 的患者的 AMS；然而，还需要在海拔较高、发病率较高的地方进行研究，以证实我们的发现。
