Voluntary dehydration in man

The effects singly and in combination of heat, exercise, and hypohydration upon voluntary dehydration were studied in four acclimated, physically fit, young men. Voluntary dehydration is the delay in complete rehydration following water loss. Hypohydration refers to the state of decreased water content while the osmotic concentration of the body is maintained. Ad libitum drinking during the heat experiments was 146% greater than it was in the cool experiments. Hypohydration increased drinking 109% over the corresponding hydration experiment, exercise increased water intake 41% over resting. Hypohydration and exercise were less effective than heat in stimulating drinking. During the 4-hr experimental periods, the subjects did not or could not drink enough to compensate for the water lost. Regardless of the magnitude of the water deficit at the beginning of the recovery periods, the rates of rehydration were the same. The more stressful the experiment, the greater the water consumption and, in general, the longer it took to regain the lost water. water balance; heat; exercise; drinking; hypohydration Submitted on September 8, 1964