HEAT EXCHANGES OF MAN IN THE DESERT

Abstract

Measurements were made on 7 men during rest and during exercise at Boulder City, Nevada, in summer (mean air temp. 35[degree]C, rel. humidity 12%), of heat lost by evaporation, heat accumulated (from rectal and surface temps.), heat produced, and heat gained by radiation. The latter was 140 Calories per hr. in direct sunlight, this being the difference of heat losses by evaporation in sun and in shade. During exercise the heat loss by evaporation exceeded the heat production. Recovery from exercise required 1 to 1 1/2 hr. to dissipate the heat accumulated. Pulse rates and systolic arterial pressure increased with rates of heat loss. Changes in the circulation and in the rates of sweating indicated that acclimatizations were significant factors in enduring high temps. Individual differences suggested that not all persons are equally able to preserve heat balances.