The effect of hot and cold drinks on thermoregulation, perception and performance: the role of the gut in thermoreception

Purpose. Hot compared to cold drinks alter sweating responses during very low intensity exercise in temperate conditions. The thermoregulatory, perceptual and performance effects of hot compared to cold drinks in hot, dry conditions during high-intensity exercise have not been examined. Method. Ten participants (mean ± SD characteristics age 25 ± 5 years, height 1.81 ± 0.07 m, body mass 73.5 ± 10.6 kg, maximal power output (PMax) 350 ± 41 W). completed two conditions where they drank four boluses (ingested at -9, 15, 30 & 45 minutes respectively) of 3.2 mL.kg-1 (~960 mL total) of either a COLD (5.3°C) or a HOT drink (49.0°C), which were contrasted to a no drink CONTROL. They cycled for 60-minutes (55% PMax in hot (34.4°C) dry (34% RH) ambient conditions followed by a test to exhaustion (TTE; 80% PMax). The thermoregulatory, performance and perceptual implications of drink temperature were measured. Results. TTE was worse in the CONTROL (170 ± 132 s) than the COLD drink (371 ± 272 s; p = .021) and HOT drink conditions (367 ± 301 s; p = .038) which were not different (p = .965). Sweat responses (i.e. reflex changes in mean skin temperature (Tmsk) and galvanic skin conductance) indicated transient reductions in sweating response after COLD drink ingestion. The COLD drink improved thermal comfort beyond the transient changes in sweating. Conclusion. Only COLD drink ingestion changed thermoregulation but improved perceptual response. Accordingly, we conclude a role for gut thermoreception in thermal perception during exercise in hot, dry conditions.