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

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 degrees 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 ((T) over bar (sk)), and local sweat rate (m(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 Vo(2peak) was 50.72 +/- 7.34 and 50.43 +/- 5.01 ml center dot kg LBM-1 center dot min(-1), respectively. When compared to lower body fat individuals, % body fat, body surface area (AD), and body mass were higher and A(D)/mass was lower in higher body fat individuals. T-es, (T) over bar (sk), FBF, m(sw), and the slope of m(sw):Tes were not different between groups. Metabolic heat production was similar between the lower body fat (299.7 +/- 40.5 W center dot m(-2)) and higher body fat (288.1 +/- 30.6 W center dot 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.