Elevation in set point for body temperature regulation after prolonged exercise.

1. In nine healthy men, after prolonged exercise (approximately 37 km walk and 2.5 km ascent and descent in 9 hr) deep body temperature at rest stabilized at a higher level than in the absence of previous exercise.2. The increase, approximately 0.36 degrees C, was recorded at both oral and rectal sites. It persisted while the subjects rested in warm and in cool surroundings, and disappeared about 11 hr after the end of exercise.3. The increase in body temperature after exercise was accompanied by a similar increase in the body temperature at which sweating started during body heating.4. After exercise the subjects' metabolic response to cold air (13.6 degrees C) was normal or increased in spite of the elevation in body temperature.5. Blood glucose concentration was never lower than 3.1 mM during these experiments.6. The temperature changes are most easily explained by mild pyrexia due to the release of endogenous pyrogen associated with minor tissue damage.