Physiological Responses of Men and Women during Prolonged 40% Vo₂max Exercise at Different Ambient Temperatures

Abstract

Eight male and female physically active students performed bicycle ergometer exercises for 100min in cool(9.5*), neutral (22.0*) and hot (34.5*) environments. Relative humidity was 55-65% and air velocity was 20 cm/sec. Work load for each subject was based on 40% Vo2 max as determined in neutral environment. Heart rate (HR), systolic blood pressure (SBP), rectal temperature (Tre), pulmonary ventilation (Ve), oxygen uptake (Vo2) and sweat rate (SR) were measured during exercise.There were no sex differences in the magnitudes of HR and Tre increases in cool and neutral environments.However in hot environment, the final exercise HR and Tre for the males were significantly higher than those for the females. While SBP of male subjects tended to decrease after 80 min exercise in hot environment, this trend was not observed for female subjects. Significant increases in Ve during exercise in hot environment were only shown in male subjects, and the increases in Vo2 through the exercise time were more severe for the male than for the female subjects. The male had significantly more SR per degree increase in Tre than did the female subjects, indicating that evaporative cooling in the males was not as effective as in the females in the humid heat environment.