Exercise in the heat: Factors limiting exercise capacity and methods for improving heat tolerance

Citation

Galloway SD, Shirreffs SM, Leiper JB & Maughan RJ (1997) Exercise in the heat: Factors limiting exercise capacity and methods for improving heat tolerance. Sports Exercise and Injury, 3 (1), pp. 19-24.

Abstract
Performance of prolonged exercise is impaired when the ambient temperature is high. The reason for reduced performance in the heat is not clear but a number of possible factors have been identified: a failure of thermoregulation and the subsequent hyperthermia; hypohydration and the resultant circulatory collapse; and changes in muscle metabolism leading to greater carbohydrate depletion have all been addressed as possible factors reducing exercise tolerance in the heat. Heat acclimation and fluid replacement are two methods of improving tolerance to heat and these have been studied extensively over the past 50-60 years. Although improvements in exercise tolerance have been observed with both acclimation and fluid replacement, neither can fully restore exercise capacity to that obtainable in a cool environment. Heat acclimation can result in large improvements in thermoregulation and cardiovascular stability during exercise; but the benefits of acclimation are lost if dehydration occurs. Fluid replacement has frequently been observed to be of benefit during exercise in the heat especially following a period of heat acclimation when sweating rates can reach very high levels: although ingestion of plain water can improve performance, carbohydrate/electrolyte solutions are generally more effective. Other ways of improving heat tolerance such as pre-cooling and hyperhydration have been examined, but to date there is little evidence for any large benefits from these practices.

Keywords
acclimatization; article; carbohydrate metabolism; dehydration; environmental temperature; exercise; exercise tolerance; fluid therapy; heat; heat tolerance; human; hyperthermia; muscle metabolism; priority journal; shock; sweating; thermoregulation

Journal
Sports Exercise and Injury: Volume 3, Issue 1