Temperature and Humidity, Effects on Exercise

Different environmental conditions, such as temperature and humidity, affect exercise tolerance and capacity in many ways. It is important for athletes to maintain their body temperature at or near 98.6 °F. Environmental conditions, in particular air temperature and humidity, determine the rate at which heat is lost or gained for the exercising athlete.

The body is able to regulate core temperature within a narrow range and must be able to manage heat transfer by convection, conduction, or evaporation. When the outside temperature is cooler than an athlete's body temperature, heat will be lost from the skin to the environment through conduction. The rate at which this heat is lost will be determined by the temperature difference between the environment and the athlete's body. Continual [Page 1455]replacement of the warmer air near the body by cooler air from the environment causes loss of heat from the body by means of convection. Convective heat loss is determined by the speed at which air flows across the body. Evaporation is the most effective way in which the body loses heat. However, with high humidity, sweat loss by evaporation is reduced.

At rest, athletes regulate their body temperature around 98.6 °F. Muscles produce more heat during exercise than at rest. The thermoregulation system of the body must compensate for this increase in heat production, and inability to do so could lead to hyperthermia. External factors such as extreme temperatures and humidity also contribute to the development of both hyperthermia and hypothermia.