Changes in core temperature and thermoeffector thresholds in exercise-trained rats.

Spontaneous running in a running wheel has emerged as an alternative method of exercise in small animals. The present study investigated how exercise training with a running wheel affects core temperature level and thermoeffector thresholds in rats. Female rats were allowed to run freely in the wheel for 6 months. Sedentary controls did not exercise during the same period. After the exercise training period, they were loosely restrained and their threshold core temperatures for tail skin vasodilation and cold-induced thermogenesis were determined by warming or cooling the animals by use of a chronically implanted intravenous thermode. Resting and threshold core temperatures of the exercise-trained rats were higher than those of the sedentary controls. The results suggest that in rat, exercise training with a running wheel shifts threshold temperatures for heat loss and heat production to high levels, which may result in a rise in core temperature level.