THE EFFECT OF WATER DOUSING ON HEAT STRAIN AND PERFORMANCE DURING ENDURANCE RUNNING IN THE HEAT

Abstract

Water dousing (pouring water on the body) is an easy-to-implement cooling method while running due to the availability of water at race aid stations, and may decrease the risk of heat illness and improve performance. However, dousing has not been investigated in extended duration running (i.e., ≥10 km), a typical distance in both elite and community level events. AIMS: Assess the effect of water dousing on heat strain and performance during self-paced and fixed-intensity exercise in the heat. DESIGN: Crossover, block randomised controlled trial. 13 trained runners completed a 10 km time trial (TT) and 60 min fixed pace run (60% velocity of VO2max) in a 30°C, 47% relative humidity environment using either water dousing (DOUSE) or no dousing (CON). 10 km TT performance was faster in DOUSE compared to CON (44:11±6:14 vs. 44:38±6:03 min:s; p=0.033). Change in core temperature (Tc) was not different between groups during the TT (+0.02±0.33°C in DOUSE; p=0.853) or fixed pace run (+0.02±0.30°C; p=0.848). Change in mean skin temperature (Tsk) was lower in DOUSE during the TT (-1.80±0.63°C; p<0.001) and fixed pace run (-1.38±0.78°C; p<0.001). Heart rate (HR) was lower for DOUSE during the fixed pace run (-3.5±5.5 bpm; p=0.041) but not during the TT (-0.2±4.2 bpm; p=0.853). Thermal sensation was lower for DOUSE during the TT (-49.3±41.9 mm; p<0.001) and fixed pace run (-44.7±27.6 mm; p<0.001). Rating of perceived exertion (RPE) was not different between groups for the TT (-0.2±0.9; p=0.390) or fixed pace run (-0.2±1.0; p=0.480). Water dousing improves 10 km TT performance in the heat but does not mitigate a rise in Tc. The positive change in thermal perception (via lower skin temperature) likely drives this ergogenic effect.