Temperature regulation; effects of sweat loss during prolonged exercise.

Prolonged exercise leads to thermal dehydration which interferes with circulatory as well as thermoregulatory functions, due to the reduction of the volume of the circulating blood and the increased osmolality of the body fluids. The effect of the reduced filling of the vascular system is counteracted by an increase in heart rate and a peripheral vasoconstriction. The resulting reduction in skin perfusion and heat transfer leads to a higher than normal core temperature during exercise. The sweating mechanism is inhibited by hyperosmolality. This, too, results in an extra rise in exercise temperature plateau.