The Effect Of Drink Temperature On Sweating Response And Performance During Exercise In The Heat

Abstract

Drink temperature disproportionately influences sweating rate and volume during low intensity exercise in temperate conditions that permit full sweat evaporation. Specifically, cold drinks may reduce sweat production and hot drinks are thought to increase it by stimulation of a gut thermoreceptor. Consequently, cold drinks may have a negative influence on thermoregulatory responses during exercise in the heat. PURPOSE: The effect of drink temperature has yet to be examined on the sweat response, thermoregulation and performance in hot, dry conditions using an ecologically valid protocol with measurement of regional sweating responses. METHODS: Ten trained cyclists completed three trials prior to and during which they ingested 3.2 mL.kg-1 of a COLD (5.3 ± 1.7 °C) or HOT drink (49.0 ± 1.9 °C), which was contrasted to a no drink CONTROL. They cycled in hot, dry conditions (34.5 ± 0.6 °C & 22 ± 1% RH) for 60-minutes at 55% of pre-determined maximal power output (Pmax) and then completed a test to exhaustion at 80% Pmax. Thermal (rectal temperature Trec, 8-site skin temperature Tmsk) and local sweat rate responses (absorbent sweat pad & galvanic skin conductance GSC) were recorded. TTE duration indicated the performance effect. Comparisons were made using ANOVA. Data are displayed as mean [SD]. RESULTS: Participant’s TTE performance was significantly worse in the CONTROL (170 [132] s) condition (p<0.05) than the COLD (371 [272] s) and HOT drink (367 [301] s) conditions which did not differ. Throughout the fixed intensity exercise period, local sweat responses at the bicep and upper back were not different (p>0.05) between any of the test conditions (e.g. grand mean [SD] Bicep GSC CONTROL 15.2 [8.0] μS, HOT 17.3 [8.0] μS & COLD 14.0 [6.0] μS). Temperature responses were higher (p<0.05) in the CONTROL than both drink conditions at the core (Trec, CONTROL 38.3 [0.5] °C, COLD 38.0 [0.5] °C, HOT 38.1 [0.5] °C) but not the skin (CONTROL 34.5 [0.2] °C, COLD 34.5 [0.3] °C, HOT 34.6 [0.3] °C). CONCLUSION: Drink temperature did not influence performance, temperature responses or regional sweat responses during high-intensity exercise in hot, dry conditions. Consumption of fluid, irrespective of its temperature, provided a benefit to exercise performance in the heat in contrast to not drinking. Supported by European Hydration Institute Grant.