Thermal Behavior Differs between Males and Females during Exercise and Recovery

Introduction This study tested the hypothesis that females rely on thermal behavior to a greater extent during and after exercise, relative to males. Methods In a 24°C ± 1°C; (45% ± 10% RH) environment, 10 males (M) and 10 females (F) (22 ± 2 yr) cycled for 60 min (metabolic heat production: M, 117 ± 18 W·m^-2; F, 129 ± 21 W·m^-2), followed by 60-min recovery. Mean skin and core temperatures, skin blood flow and local sweat rates were measured continually. Subjects controlled the temperature of their dorsal neck to perceived thermal comfort using a custom-made device. Neck device temperature provided an index of thermal behavior and mean body temperature provided an index of the stimulus for thermal behavior. Data were analyzed for total area under the curve for exercise and recovery time points. To further isolate the effect of exercise on thermal behavior during recovery, data were also analyzed the minute mean body temperature returned to preexercise levels within a subject. Results There were no sex differences in metabolic heat production (P = 0.71) or body temperatures (P ≥ 0.10) during exercise. Area under the curve for neck device temperature during exercise was greater for F (-98.4°C·min^-1 ± 33.6°C·min^-1 vs -64.5°C·min^-1 ± 47.8°C·min^-1, P = 0.04), but did not differ during recovery (F, 86.8°C·min^-1 ± 37.8°C·min^-1; M, 65.6°C·min^-1 ± 35.9°C·min^-1; P = 0.11). In M, mean skin (P = 0.90), core (P = 0.70) and neck device (P = 0.99) temperatures had recovered by the time that mean body temperature had returned to preexercise levels. However, in F, neck device temperature (P = 0.04) was reduced while core temperature remained elevated (P < 0.01). Conclusions Females use thermal behavior during exercise to a greater extent than M. During recovery, thermal behavior may compensate for elevated core temperatures in F despite mean body temperatures returning to preexercise levels.