Body Fatness, Body Core Temperature, and Heat Loss During Moderate-Intensity Exercise

Limbaugh JD, Wimer GS, Long LH, Baird WH. Body fatness, body core temperature, and heat loss during moderate-intensity exercise. Aviat Space Environ Med 2013; 84:1153–8.Purpose: This study examined the influence of body fatness on body core temperature and heat loss responses during moderate-intensity exercise. Methods: Nine men with lower body fat and eight men with higher body fat, matched for aerobic fitness, completed 1 h of recumbent cycling at the same absolute intensity in a warm environment (30°C, 40% RH). Percent body fat was measured by hydrostatic weighing, using oxygen dilution to determine residual volume. Esophageal temperature (T_es), mean skin temperature (<inline-graphic xlink:href="1153inf1.gif"/>), and local sweat rate (<inline-graphic xlink:href="1153inf2.gif"/>_sw) were measured at rest and continuously during exercise while forearm blood flow (FBF) was measured at rest and every 10 min during exercise. Results: The lower body fat and higher body fat groups were successfully matched for aerobic fitness, removing the influence of body fatness, given that <inline-graphic xlink:href="1153inf3.gif"/>o_2peak was 50.72 ± 7.34 and 50.43 ± 5.01 ml · kg LBM⁻¹ · min⁻¹, respectively. When compared to lower body fat individuals, % body fat, body surface area (A_D), and body mass were higher and A_D/mass was lower in higher body fat individuals. T_es, <inline-graphic xlink:href="1153inf1.gif"/>, FBF, <inline-graphic xlink:href="1153inf2.gif"/>_sw, and the slope of <inline-graphic xlink:href="1153inf2.gif"/>_sw:T_es were not different between groups. Metabolic heat production was similar between the lower body fat (299.7 ± 40.5 W · m⁻²) and higher body fat (288.1 ± 30.6 W · m⁻²) subjects, respectively. Dry and evaporative heat loss, as well as heat storage during exercise, were not different between groups. Conclusion: These data suggest that there is no effect of body fatness on body core temperature or heat loss responses during moderate-intensity exercise in a warm environment.