Thermoregulatory responses to desert heat: age, race and sex

Sixty-nine whites (38 men and 31 women) aged 17 to 88 years and 48 blacks (19 men and 29 women) aged 17 to 61 years were studied. Each person walked in desert heat for 1 hour at a rate requiring 40% of aerobic capacity. Observations were recorded on their rectal temperature (Tre), skin temperature (Tsk), heart rate (HR), blood pressure, and sweat rate (SR). Older men and women of both races were able to complete their walks without any ill effects. Age, per se, did not significantly reduce elderly individuals' ability to tolerate the combined stress of dry heat and exercise. Men of both races had higher sweat rate and lower heart rate and rectal and skin temperature than women working at the same percentage of aerobic capacity. Success of thermoregulation at 40% of aerobic capacity of blacks and whites was equal, but in both races men thermoregulated more successful than women. Our data suggest that thermoregulatory capacity of humans under desert conditions differs between sexes and is not influenced significantly by age or race except for differences in aerobic capacity.