Fluid Replacement During Sustained Activity in the Heat: Nutrient Solution vs.Water

摘要

Fluid replacement is essential for enabling thermoregulation in individualsworking for sustained periods in warm environments. During some military or industrial situations when individuals are encapsulated in chemical protective clothing in temperate as well as warm environments, relatively high sweating rates are elicited, often resulting in large losses of body fluids and electrolytes. For these individuals fluid intake is sometimes the only means of sustenance available. There are several physiological reasons why inadequate fluid and nutrient intake during sustained activity might reduce performance. First, inadequate fluid replacement causes hypohydration, which impairs thermoregulation and cardiovascular function. Hypohydration reduces the ability of the body to dissipate heat, which leads to elevated core temperature relative to euhydration, and thereby increases the risk of heat injury. Second, lack of food or nutrient supplement can lead to hypogylcemia, particularly when combined with physical exercise continued over many hours. Hypoglycemia, when accompanied by exercise-induced reductions in muscle glycogen, may result in muscle fatigue as well as impaired central nervous system function.