Heat Acclimatization

Heat acclimatization is the set of physiological adaptations that develops after repeated exposure to a hot environment. These adaptations reduce the physiological strain produced by subsequent heat exposure, particularly during physical activity, and improve the body's ability to regulate temperature and maintain cardiovascular function in the heat .^1,2

Important adaptations include an earlier and more effective sweating response, improved fluid and electrolyte regulation, greater cardiovascular stability, and expansion of plasma volume. As acclimatization develops, the same amount of exercise in the heat can generally be performed with a lower heart rate and lower core temperature than before adaptation .^1,2

Heat acclimatization develops progressively with repeated heat exposure rather than after a single encounter with hot conditions. Many thermoregulatory and cardiovascular changes appear during the first several days, while further adaptation can continue over roughly one to two weeks. The magnitude and rate of adaptation vary between individuals and depend partly on the intensity and duration of heat exposure and prior acclimatization or fitness status .^1,2

In exercise physiology, heat acclimatization is often distinguished from heat acclimation according to the conditions in which adaptation occurs. Acclimatization usually refers to adaptation produced by exposure to natural environmental heat, whereas acclimation generally refers to similar adaptations produced under controlled conditions, such as an environmental chamber. The underlying physiological adaptations substantially overlap .¹