Thermal Responses Under Different Exercise Intensity and Air Temperature

Abstract

This study examined the physiological and subjective thermal responses of the human body under moderate exercise intensity. Twenty subjects (10 males and 10 females) were exposed to four different air temperature conditions (15 °C, 20 °C, 25 °C, and 30 °C ) during a 30 minute constant-power cycling exercise at intensities set to 40% V̇O2 max, 50% V̇O2 max, 60% V̇O2 max, and 70% V̇O2 max. Physiological parameters (core temperature, skin temperature, metabolic rate, heart rate, and perspiration) and subjective thermal sensations were recorded from the subjects during the experiment. The results showed that the increase in exercise intensity had a significant effect on metabolism and heart rate. During the 30 min of exercise, exercise intensity significantly increased subjective thermal sensation while decreased thermal comfort and thermal acceptability. In terms of physiological parameters, skin temperature was influenced by both air temperature and exercise intensity. However, core body temperature was mainly influenced by exercise intensity. The thermal sensation and dissatisfaction rate predicted by the PMV (Predicted Mean Vote) model were no longer applicable in the exercise condition. The regression analysis of the comfort voting results showed that the upper limit of comfortable temperature (26.3 ℃, 23.3 ℃, 20.7 ℃, and 18 ℃) decreased with the increase of exercise intensity (40% V̇O2 max, 50% V̇O2 max, 60% V̇O2max, and 70% V̇O2 max).

Keywords: Thermal comfort, exercise, Metabolic rate, Thermal responses