Meyer F, Bar-Or O, MacDougall D, Heigenhauser G J
Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada.
Med Sci Sports Exerc. 1995 Jun;27(6):882-7.
Twelve 9- to 12-year-old children (6 boys, 6 girls) performed four exercise-in-heat (35 degrees C, 45% RH) trials which differed in the composition of the fluids they drank. In each trial, subjects cycled for one 20-min and two 15-min bouts at 50% peak VO2 with 10-min rest periods in between. In a fourth bout, they cycled at 90% peak VO2 until exhaustion. Drinks had the same grape flavor and were assigned in a double-blind design and in a Latin-square order. Subjects drank 7 ml.kg-1.h-1 to keep them euhydrated. Three of the drinks had 6% carbohydrates (CHO), with different [Na+]: 0, 8.8, 18.5 mmol.l-1 and one drink had neither CHO nor Na+ (WATER). Among drink trials, there were no differences in the increase in rectal temperature, HR, or performance time to exhaustion. Despite the larger Na+ deficit induced by the Na(+)-free drinks compared with the Na+ drinks (11.8 +/- 1.4 vs 5.7 +/- 0.9 mmol.h-1), neither plasma [Na+] nor osmolality were affected. These results suggest that electrolyte, as in the above conditions, did not affect electrolyte balance, thermoregulatory responses, or aerobic performance of children exercising in the heat. The greater Na+ deficit induced by ion-free drinks was of minor biological importance.
12名9至12岁的儿童（6名男孩，6名女孩）进行了四项热环境（35摄氏度，相对湿度45%）下的运动试验，他们饮用的液体成分不同。在每项试验中，受试者以50%的最大摄氧量进行一次20分钟和两次15分钟的骑行，中间有10分钟的休息时间。在第四次骑行中，他们以90%的最大摄氧量骑行直至 exhaustion。饮料具有相同的葡萄口味，采用双盲设计并按拉丁方顺序分配。受试者每小时饮用7毫升·千克-1以保持身体水分平衡。其中三种饮料含有6%的碳水化合物（CHO），[Na+] 不同：0、8.8、18.5毫摩尔·升-1，一种饮料既不含CHO也不含Na+（水）。在不同饮料试验中，直肠温度升高、心率或疲劳表现时间没有差异。尽管与含Na+饮料相比，无Na+饮料导致的Na+ 缺失更大（11.8±1.4对5.7±0.9毫摩尔·小时-1），但血浆[Na+]和渗透压均未受影响。这些结果表明，在上述条件下，电解质不会影响热环境中运动儿童的电解质平衡、体温调节反应或有氧运动表现。无离子饮料导致的更大Na+ 缺失在生物学上的重要性较小。
