Abstract

This study examined the effects of hypohydration on plasma volume and red cell volume during rest in a comfortable and exercise in a hot-dry environment. Six male and six female volunteers completed two test sessions following a 10-day heat acclimation. One test session was completed when subjects were euhydrated and the other when subjects were hypohydrated. The test sessions consisted of rest for 30 min in a 20 degrees C antechamber, followed by two 25-min bouts of treadmill walking in the heat, with 10 min of rest. No signifi cant differences were found between the genders for the examined variables. At rest, hypohydration elicited a 5 decrease in plasma volume with smaller than 1 change in red cell volume. During exercise, plasma volume increaed by 4 when subjects were euhydrated and decreased by 4 when subjects were hypohydrated. These percent changes in plasma volume values were significantly different between the euhydration and hypohydration tests. Although red cell volume remained fairly constant during the euhydration test, these values were signifikantly lower when hypohydrated during exercise. We conclude that hydration level alters vascular fluid shifts during exercise in a hot environment; Hemodilution occurs when euhydrated and hemo concentration when hypohydrated. Verf.-Referat