ABSTRACT
Male rats were trained to escape from radiant heat of infrared lamp (250W) by pressing a bar that turned a lamp off for 8 sec. To determine effects of repetitive exercise on this heat-escape behavior rats were either subjected to a 4-week physical training program in which they were forced to swim in agitating water of 36t or 38°C for 1 hour each day or were not trained (non-exercised controls) . After the program in 36°C water, the bar-pressing rate during the test period decreased markedly compared with that before the training period. Temperatures of the tail-skin and the environment in the test box increased to significantly higher levels in the trained rats than those before the training period, while the rectal temperature in the trained rats remained at the same level to that in the pretraining period. When a 4-week physical training program was completed in the same manner but using 38t water, no differences in the heat-escape activity and the extents of temperatures concurrently measured were obtained between those before and after the training period in the trained rats or controls.<BR>The significant reduction of heat-escape activity in rats with the repetitive exercise for 4-week in the 36t water is a result of adaptive changes in the autonomic thermoregulation due to the repetitive exercise itself.