Effects Of Drinking And External Cooling On Low Intensity Exercise And Performance In Hot-Dry Environments

Abstract

Distance runners anecdotally claim the combination of drinking and externally cooling by pouring cold water over the body benefits physiological responses and exercise performance. Oral rehydration attenuates physiological stress, minimizes perceptual strain, and improves performance; limited available external cooling literature provides conflicting conclusions. PURPOSE: To examine independent and combined effects of cold water drinking and external cooling on physiological, perceptual, and performance variables in hot, dry environments. METHODS: Ten healthy male runners (age = 25 ± 4 y, mass = 75.8 ± 6.0 kg, height = 180 ± 8 cm, VO2max = 60.2 ± 5.4 ml·kg-1nim·-1, body fat = 11.1 ± 5.3%) completed four trials composed of walking 90 min at 30% VO2max followed by a 5 km time trial in hot, dry conditions (33 ± 1 °C, 29 ± 3% RH). Visits examined no intervention (CON), drinking (H), external cooling (E), and drinking plus external cooling (HE). Investigators measured core temperature, skin temperatures, heart rate, and environmental conditions every five minutes throughout trials. Perceptual measures (thirst, thermal sensation, and RPE) took place every ten minutes during the constant load exercise and ten minutes into the time trial. RESULTS: Drinking trials (H and HE) consistently lowered core temperature, heart rate, and thirst perception compared to non-drinking trials (CON and E) during the constant load exercise. Pouring trials (E and HE) consistently reduced heart rate, chest and thigh temperature, thermal sensation, and RPE compared to non-pouring trials (CON and H) during the constant load exercise. Performance exhibited no differences among trials (CON = 23.86 ± 4.57 min, H = 22.74 ± 3.20 min, E = 22.96 ± 3.11 min, HE = 22.64 ± 3.73 min). CONCLUSIONS: Pouring benefitted physiological and perceptual responses during low intensity exercise in hot, dry conditions but failed to influence high intensity exercise performance.