Cold water immersion after exercise-induced hyperthermia

Abstract

Cold water immersion (CWI) is the most effective known cooling treatment against exercise-induced hyperthermia. However, sex differences related to body composition (i.e. body fat, muscle mass, surface area, etc.) may affect core cooling rates in hyperthermic males and females. Purpose. To determine sex related differences in core cooling rates during CWI after exercise-induced hyperthermia. Methods. Ten male (M) and nine female (F) participants matched for body surface area to mass ratio took part in this study. Participants exercised at 65% V˙O2max at an ambient temperature of 40°C until rectal temperature (Tre) increased to 39.5°C. Following exercise, subjects were immersed in a 2°C circulated water bath until Tre decreased to 37.5°C. Results. Females had a significantly greater core cooling rate compared to males. This was paralleled by a lower skin temperature and a shorter time to reach the exit criterion. Conclusion. We conclude that previously hyperthermic females have a 1.7 times greater Tre cooling rate compared to males. We attribute this difference to a smaller lean body mass (expressed by the body-surface-area-to-lean-body-mass ratio) in females compared to males.