Thermoregulation during exercise in relation to sex and age

Summary The thermoregulatory responses to 1 h exercise of 14 male (age range 18–65 year) and 7 female (age range 18–46 year) athletes and 4 (3 and 1 ) non-athletic subjects have been investigated in a moderate environment (T _db=21 C, T _wb=15 C and rh<50%) and analysed in relation to age, sex, and maximum aerobic power output (VO₂ max).The maximal sweat loss (M _{sw max}) under the given conditions was closely related (r=+0.90) to VO_{2 max} and for a given relative work load (%VO_{2 max}), rectal (T _re) and mean skin (¯T _sk) temperatures was the same in all subjects.Sweat loss (004d _sw) was linearly related to total heat production (H) and to peripheral tissue heat conductance (K) and if expressed in relative terms (%M _{sw max}) was linearly related to T _re. For a given T _re relative sweat rate was identical in the groups studied. From these results it would seem that during exercise T _re rises to meet the requirements of heat dissipation by establishing a thermal gradient from core to skin and stimulating sweating in proportion to maximal capacity of the system. Thus provided the thermal responses to work were standardised using the appropriate physiological variables, there was no evidence to be found for differences in thermoregulatory function which could be ascribed to sex or age.