Schleh Michael W, Ruby Brent C, Dumke Charles L
Department of Health and Human Performance, Montana Center for Work Physiology and Exercise Metabolism, University of Montana, Missoula, MT, United States.
Department of Health and Human Performance, Montana Center for Work Physiology and Exercise Metabolism, University of Montana, Missoula, MT, United States.
J Therm Biol. 2018 Dec;78:227-234. doi: 10.1016/j.jtherbio.2018.10.004. Epub 2018 Oct 19.
Heat acclimation lowers physiological strain when exercising in the heat, and may be enhanced by promoting dehydration during acclimation. The purpose was to compare fluid intake during heat acclimation by promoting dehydration (DEH=0.5 mL kg 15 min, 2.4% dehydration per acclimation session) compared to euhydration (EUH=2.0 mL kg 15 min, ~1.4% dehydration per acclimation session) following four heat acclimation bouts on thermal strain, and exercise performance. Thirteen males completed 90 min heat stress tests (HST) at 50% VO (40 °C, 30%RH) before and after three 90 min heat acclimation trials, involving consecutive bouts with 4-fold less fluid (DEH) or EUH. DEH and EUH trials were separated by 48 h and assigned in a random crossover design separated by a 5 week washout. Wildland firefighter (WLFF) Nomex: shirt, pants, and a cotton T-shirt baselayer were worn. Peak core temperature (T) from the HST significantly decreased following both DEH (39.5 ± 0.1-39.0 ± 0.1 °C: P < 0.001) and EUH acclimation (39.5 ± 0.1-38.9 ± 0.1 °C: P < 0.001). HR, RPE, physiological strain index (PSI), and total work (J) completed in a graded exercise test to exhaustion were improved (P < 0.001) in effect for acclimation, but not different when comparing DEH or EUH fluid delivery. SBF was unchanged (P = 0.313). Sweat rate increased greater following DEH (1.52 ± 0.06-1.89 ± 0.09 L h) compared to EUH acclimation (1.57 ± 0.06-1.79 ± 0.08 L h: P = 0.015). Resting plasma volume increased in effect for acclimation (P = 0.002). Aldosterone decreased in effect for acclimation (P < 0.001) at rest and following exercise, and total protein was unaffected (P = 0.83). In conclusion, short-term heat acclimation (360 min) attenuates heat stress, and improves exercise capacity in the heat, and was not impaired nor improved by promoting DEH during acclimation.
热适应可降低在高温环境下运动时的生理应激，并且在适应过程中通过促进脱水可能会增强这种效果。目的是比较在热适应过程中，通过促进脱水（DEH = 0.5毫升/千克体重，每适应训练时段约2.4%脱水）与正常水合状态（EUH = 2.0毫升/千克体重，每适应训练时段约1.4%脱水）后的液体摄入量，以及它们对热应激和运动表现的影响。13名男性在进行三次90分钟的热适应试验前后，在50%最大摄氧量（40°C，30%相对湿度）条件下完成了90分钟的热应激测试（HST），试验包括连续时段摄入液体量减少4倍的（DEH）或正常水合状态（EUH）的情况。DEH和EUH试验间隔48小时，并采用随机交叉设计，中间有5周的洗脱期。穿着野外消防员（WLFF）诺梅克斯服装：衬衫、裤子和一件棉质T恤打底衫。热应激测试中的核心体温峰值（T）在DEH适应（39.5±0.1 - 39.0±0.1°C：P < 0.001）和EUH适应（39.5±0.1 - 38.9±0.1°C：P < 0.001）后均显著降低。在渐增负荷运动试验至疲劳过程中完成的心率（HR）、主观用力程度（RPE）、生理应激指数（PSI）和总功（J），因适应而得到改善（P < 0.001），但在比较DEH或EUH的液体摄入时并无差异。皮肤血流量（SBF）未改变（P = 0.313）。与EUH适应（1.57±0.06 - 1.79±0.08升/小时）相比，DEH后出汗率增加幅度更大（1.52±0.06 - 1.89±0.09升/小时：P = 0.015）。静息血浆量因适应而增加（P = 0.002）。醛固酮在静息和运动后因适应而降低（P < 0.001），总蛋白未受影响（P = 0.83）。总之，短期热适应（约360分钟）可减轻热应激，并提高在高温环境下的运动能力，在适应过程中促进脱水既未损害也未改善这一效果。
