US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.
Med Sci Sports Exerc. 2009 Jun;41(6):1311-6. doi: 10.1249/MSS.0b013e3181988c14.
The impact of prior heat stress on subsequent aerobic exercise-heat performance has not been studied.
To determine whether prior heat stress degrades subsequent aerobic exercise performance in the heat.
Eighteen nonheat acclimated males were trained (four practice trials) on an aerobic exercise performance test in 22 degrees C and then divided into two (n = 8) groups. One group (EUHPH; (.)VO2peak = 44 +/- 7 mL x kg x min(-1)) was tested after 90 min of recovery (in 22 degrees C) from 3 h of intermittent light-intensity (<30% (.)VO2peak) exercise-heat (50 degrees C) stress, where sweat losses were matched with fluid intake (3.5 +/- 0.5 L) to maintain euhydration. The other group (EUH; (.)VO2peak = 45 +/- 5 mL x kg x min(-1)) was tested while euhydrated without prior exercise-heat stress. Aerobic performance was determined from a 30-min cycling preload (50% (.)VO2peak) followed by a 15-min time trial in 40 degrees C. Total work during the 15-min performance time trial in EUH and EUHPH was compared, as were the percent changes from the best practice trials.
Volunteers were euhydrated (plasma osmolality < 290 mOsm x kg(-1)) and normothermic before each exercise-heat trial. Heart rate and core temperature were not different (P > 0.05) between groups at any time point during exercise. Total work was not different (P > 0.05) at baseline or between EUH (150.5 +/- 28.3 kJ; 2.0 +/- 0.3 kJ x kg(-1)) and EUHPH (160.3 +/- 24.0 kJ; 1.8 +/- 0.2 kJ x kg(-1)). The percent change in total work relative to baseline was not different (P > 0.05) between EUH (-18.7% +/- 9.2%) and EUHPH (-15.0% +/- 7.8%).
If hydration and body temperatures recover, prior exercise-heat stress does not result in a greater degradation in aerobic time trial performance in the heat compared with heat exposure alone.
先前的热应激对随后的有氧运动-热性能的影响尚未研究。
确定先前的热应激是否会降低随后在热环境中的有氧运动表现。
18 名非热适应男性在 22°C 下进行了 4 次练习试验后，进行了有氧运动性能测试，然后分为两组（n=8）。一组（EUHPH；（.）VO2peak=44±7mL x kg x min(-1))在 3 小时间歇性低强度（<30%（.）VO2peak）运动-热（50°C）应激后 90 分钟恢复期间（在 22°C 下）进行测试，其中汗液损失与液体摄入相匹配（3.5±0.5L）以保持水合状态。另一组（EUH；（.）VO2peak=45±5mL x kg x min(-1))在没有先前运动-热应激的情况下保持水合状态进行测试。从 30 分钟的自行车预负荷（50%（.）VO2peak）开始，然后在 40°C 下进行 15 分钟的计时赛，确定有氧性能。比较 EUH 和 EUHPH 在 15 分钟性能时间试验中的总工作量，以及与最佳实践试验相比的百分比变化。
志愿者在每次运动-热试验前均保持水合状态（血浆渗透压<290mOsm x kg(-1))且体温正常。在运动过程中的任何时间点，两组的心率和核心体温均无差异（P>0.05）。基线或 EUH（150.5±28.3kJ；2.0±0.3kJ x kg(-1))和 EUHPH（160.3±24.0kJ；1.8±0.2kJ x kg(-1)))之间的总工作量无差异（P>0.05）。相对于基线，总工作量的百分比变化无差异（P>0.05）EUH（-18.7%±9.2%）和 EUHPH（-15.0%±7.8%）。
如果水合和体温恢复，与单独暴露在热环境中相比，先前的运动-热应激不会导致在热环境中进行的有氧运动时间试验性能更大的恶化。
