Thermal and Cardiovascular Strain from Hypohydration: Influence of Exercise Intensity

This study determined the effects of exercise intensity on the physiologic (thermal and cardiovascular) strain induced from hypohydration during heat stress. We hypothesized that the added thermal and cardiovascular strain induced by hypohydration would be greater during high intensity than low intensity exercise. Nine heat-acclimated men completed a matrix of nine trials: three exercise intensities, 25%, 45% and 65% VO2 max; and three hydration levels, euhydration and hypohydration at 3% and 5% body weight loss (BWL). During each trial, subjects attempted 50 min of treadmill exercise in a hot room (30 degrees C db, 50% rh) while body temperatures and cardiac output were measured. Hypohydration was achieved by exercise and fluid restriction the day preceding the trials. Core temperature increased (P