Abstract

Four trained young men, worked for 4 h/day at 40-50 of their maximum aerobic capacity for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Their thermal status was assessed using direct calorimetry. As a group, the men showed classical acclimatization responses, but there were marked individual differences. The calorimetric analysis revealed that reductions in strain were associated with minor changes in heat balance confined to the first and last hours of exposure. Events occurring within the first 4 days appeared to have little effect on body temperatures. Significcant decreases in body temperature took place only when sweat and evaporation rate increased. A 10 increase in evaporation rate was accompanied by a 30 increase in sweat rate and a 200 increaseinunevaporatedsweat; thus, there is a wasteful overproduction of sweat. By the 10th day skin temperature was confined to the level necessary to evaporate sufficient sweat to achieve thermal balance with a fully wet body surface. The efficiency of heart transport within the body did not change with acclimatization. Verf.-Referat