Echanges thermiques et fonction thermoregulatrice de l'home, en altitude

Abstract

Summary. The study deals with aspects of the temperature regulation in men native to or transplanted into a high altitude environment, at rest or exercising. In a previous study, the effects of a moderate internal heat thermal heat strain (25 min. of sub-maximal exercise, 53 W.m-2) were compared in highlanders and lowlanders at high altitude. Core temperature increases similarly in both groups whereas mean skin temperature increases in highlanders and decreases in lowlanders. The energy balance calculated from partitional calorimetry shows a heat storage in both groups but the evaporative heat loss was higher and the radiant convective losses lower in the unacclimated group. Thus the thermoregulatory processes allow achievement of the same thermal equilibrium but through different heat dissipating mechanisms. In the unacclimatized subjects, altitude seems to affect the set value of sweating but the gain of the sweating drive depends on the ambient temperature.