Abstract

Twelve young women were randomly assigned to either a heat acclimatization (HA) or a training (TR) group. Both groups exercised on a treadmill at 50 V02max for a maximum of 60 min for 9 consecutive days, excluding weekends. Theenvironment for HA subjects was 48 degrees C, 10 rh; for the TR group, 23 degrees C, 45 rh. Data from pre and post tests conducted in each environment were used to isolate the contributions of exercise per se from the overall effects of heat acclimatization. Both groups improved significantly in V02max and in tolerance time in the 48 degrees C environment. However, the HA group had a greater improvement in tolerance time and also a greater increase in evaporative heat loss (Esk) and total sweat rate (SR). Exercise in 23 degrees C was most effective in decreasing heart rate (HR) and initial core temperature (Tre). Improvement for the TR group in variables generally associated with acclimatization effects, Tre, HR, Tsk, and Esk, averaged 45 of the change noted for the HA subjects. The increase in tolerance time of the TR subjects was 46 of that observed for the HA group. It was concluded that the unique contribution of the hot environment was related to the sweating mechanism, and that physical conditioning programs prior to heat acclimatization could mitigate some of the distress experienced by individuals early in the acclimatization procedure. Verf.-Referat