The hemodynamic and metabolic alterations associated with acute heat stress injury in marathon runners.

Studies of clinical, metabolic, and hemodynamic responses to heat stress in eight marathon runners have demonstrated several important differences from those observed in nonconditioned subjects. Three marathoners manifested a nonanhidrotic form of heat stroke, a phenomenon not observed in our Marine recruits. Five patients with heat exhaustion evidenced signs of severe mental confusion despite apparently adequate hemodynamic function. Heart rate was significantly lower in all eight marathoners in comparison to the 15 Marine recruits. This latter observation suggests that either selective regional shunting of blood or increased stroke volume index occurs in marathoners subject to heat stress.