Cheuvront Samuel N, Carter Robert, Kolka Margaret A, Lieberman Harris R, Kellogg Mark D, Sawka Michael N
U. S. Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Kansas St., Natick, MA 01760-5007, USA.
J Appl Physiol (1985). 2004 Oct;97(4):1275-82. doi: 10.1152/japplphysiol.00357.2004.
The serotonin system may contribute to reduced human performance when hypohydrated in the heat. This study determined whether branched-chain amino acid (BCAA) supplementation could sustain exercise and cognitive performance in the heat (40 degrees C dry bulb, 20% relative humidity) when hypohydrated by 4% of body mass. Seven heat-acclimated men completed two experimental trials, each consisting of one preparation and one test day. On day 1, a low-carbohydrate diet was eaten and subjects performed exhaustive cycling (morning) and treadmill exercise in the heat (afternoon) to lower muscle glycogen and achieve the desired hypohydration level. On day 2, subjects consumed an isocaloric BCAA and carbohydrate (BC) or carbohydrate-only drink during exercise. Experimental trials included 60 min of cycle ergometry (50% peak oxygen uptake) followed by a 30-min time trial in the heat. A cognitive test battery was completed before and after exercise, and blood samples were taken. BC produced a 2.5-fold increase (P < 0.05) in plasma BCAA and lowered (P < 0.05) the ratios of total tryptophan to BCAA and large neutral amino acid. Blood prolactin, glucose, lactate, and osmolality were not different between trials but increased over time. Cardiovascular and thermoregulatory data were also similar between trials. BC did not alter time-trial performance, cognitive performance, mood, perceived exertion, or perceived thermal comfort. We conclude that BCAA does not alter exercise or cognitive performance in the heat when subjects are hypohydrated.
在炎热环境中处于低水合状态时，血清素系统可能会导致人体机能下降。本研究旨在确定补充支链氨基酸（BCAA）是否能在因体重减轻4%而处于低水合状态时，维持在炎热环境（干球温度40摄氏度，相对湿度20%）中的运动和认知表现。七名经过热适应的男性完成了两项实验试验，每项试验包括一天的准备期和一天的测试期。在第1天，受试者食用低碳水化合物饮食，并进行力竭性骑行（上午）和在炎热环境中的跑步机运动（下午），以降低肌肉糖原并达到所需的低水合水平。在第2天，受试者在运动期间饮用等热量的BCAA和碳水化合物（BC）饮料或仅含碳水化合物的饮料。实验试验包括60分钟的自行车测力计运动（峰值摄氧量的50%），随后在炎热环境中进行30分钟的计时赛。在运动前后完成一套认知测试，并采集血样。BC使血浆BCAA增加了2.5倍（P < 0.05），并降低了（P < 0.05）总色氨酸与BCAA以及大分子中性氨基酸的比值。各试验之间血催乳素、葡萄糖、乳酸和渗透压没有差异，但随时间增加。各试验之间的心血管和体温调节数据也相似。BC没有改变计时赛表现、认知表现、情绪、主观用力感觉或主观热舒适度。我们得出结论，当受试者处于低水合状态时，BCAA不会改变在炎热环境中的运动或认知表现。
