Thermal Behavior Does not Differ Between Sexes During and Following High Intensity Aerobic Exercise

Abstract

Females utilize thermal behavior more than males during low intensity aerobic exercise. Core temperature is elevated during high vs. low intensity aerobic exercise because of greater heat production. Thus, thermal behavior is greater during high intensity exercise because of the heightened stimulus to behave. It is unknown if sex modulates thermal behavior during high intensity exercise. PURPOSE: Test the hypothesis that thermal behavior differs between males and females during high intensity exercise and recovery. METHODS: 10 males (M) and 10 females (F) (23±3y) underwent 30 min of cycling exercise at a power output that elicited 80±5% (F) and 78±4% (M) of VO2peak (P=0.28) followed by 120 min seated recovery in a 27±1°C, 21±2% relative humidity environment. Subjects were instructed to maintain a thermally comfortable neck temperature throughout using a custom-made neck device. Neck device temperature provided an index of thermal behavior. Mean skin (10 site) and core (intestinal) temperatures, mean skin wettedness (8 site), neck device temperature, skin blood flow (laser Doppler) and local sweat rate (ventilated capsule) were measured continually. RESULTS: There were no sex differences in heat production during exercise (F: 399±68, M: 429±62 W/m2, P=0.39). During exercise, core and mean skin temperatures, skin wettedness, skin blood flow and local sweat rate increased, while neck device temperature decreased (all P<0.01). There were no sex differences in core (F: 37.7±0.2, M: 37.9±0.3°C, P> 0.50), mean skin (F: 32.6±0.3, M: 32.6±0.3°C, P>0.99) or neck device (F: 12.1±10.6, M: 11.9±10.2°C, P>0.25) temperatures, mean skin wettedness (at 30 min: F: 0.50±0.06, M: 0.53±0.04 au, P>0.99), skin blood flow (F: 163±50, M: 172±36 PU, P>0.99) or local sweat rate (F: 0.72±0.20, M: 0.85±0.27 mg/cm2/min, P>0.33) during exercise (data reported at 30 min). During recovery, core and mean skin temperatures, mean skin wettedness, skin blood flow and local sweat rate decreased, and neck device temperature increased back towards pre-exercise levels (all P<0.01). There were no differences in the dynamics of these changes between sexes (all P>0.16). CONCLUSIONS: Thermal behavior during and following high intensity aerobic exercise does not differ between males and females. This study was funded by lululemon athletica inc.