Influence of slow versus fast ramp exercise-induced hyperthermia on core cooling rates during ice-water immersion

Identifying potential factors which may alter the efficacy of cooling treatments is critical for the treatment of exertional heat stroke victims. Current evidence strongly supports the use of cold water immersion as the most potent method for rapidly reducing body core temperature. However, it is unclear if differences in the level of cardiovascular strain following exercise-induced hyperthermia may influence this response. PURPOSE: To compare core cooling rates during 2\ub0C ice-water immersion of subjects rendered hyperthermic by either a low (Slow heating, SH) or moderate (Fast heating, FH) exercise intensity performed in the heat. METHODS: On 2 separate days, seven subjects (5 males, 2 females) either walked (4 mph, 2% grade, SH) or ran (7.5 mph, 2% grade, FH) on a treadmill until rectal temperature (Tre) increased to 39.5\ub0C. After exercise, the subjects were immersed to the clavicles in a circulated water bath controlled at 2\ub0C until Tre returned to 38.0\ub0C. Heart rate, mean arterial pressure (MAP) and blood plasma volume were assessed during baseline rest and prior to ice-water immersion.Peer reviewed: YesNRC publication: N