Changes in thermoregulatory functions of humans after scclimation to heat given daily at a fixed time.

本课题研究了受热暴露的人的体温调节功能，在整个实验过程中，志愿者的食物摄入和睡眠-觉醒周期都受到控制。实验一：在环境温度（Ta）为46 ℃的条件下，每天暴露4小时（14：00-18：00 h），观察受试者在27 ℃恒温条件下24 h的体温（Tcor）变化。热习服改变了Tcor的昼夜变化模式，实验2：受试者坐在Ta为28 ℃的椅子上，双腿浸泡在温水中，诱导出汗。在热适应前后，每天重复该程序两次，上午一次，下午一次。热习服缩短了热出汗的潜伏期，降低了出汗的阈值Tcor，结果表明，在人类中，每天固定时间的重复热暴露降低了Tcor，改变了受试者先前暴露于热的期间的体温调节功能。

The present project investigated thermoregulatory functions of humans subjected to heat exposure for several hours limited to a fixed time daily.The food ingestion and sleep-awake cycle of volunteers were controlled throughout the experiments. For heat accliamtion, the subjects were exposed to an ambient temperature (Ta) of 46ﾟC for 4 hrs (14 : 00-18 : 00 h) daliy.Experiment 1 : Core temperature (Tcor) of the subjects were measured for 24 h at a constant Ta of 27ﾟC with or without heat acclimation. The pattern of day-night variations of Tcor was altered by heat acclimation, i.e., the Tcor levels were maintained at low levels in the afternoon.Experiment 2 : The subjects were seated in a chair at Ta of 28ﾟC.Both legs were immersed in a warm water and sweating was induced. The procedure was repeated twice in the day, once in the morning and once in the afternoon, before and after heat acclimation. The latency for thermal sweating was shortented and the threshold Tcor for sweating was lowered by heat acclimation only in the afternoon.The results give evidence that in humans, repeated heat exposure limited to a fixed time daily lowers Tcor and alters thermoregulatory functions during the period when the subjects were previously exposed to heat.