Oral rehydration vs. external cooling in male distance runners in a hot, dry environment

Distance runners anecdotally claim benefits from the combined use of cold water to drink and externally cool with to attenuate the rise in core body temperature. Therefore, the purpose of this study was to examine the independent and combined effects of oral rehydration and external cooling with cold water on physiological, perceptual, and performance variables in a hot, dry environment. Nine healthy male runners (age = 25 +/- 4 y, mass = 76.2 +/- 6.2 kg, height == 180 +/- 8 cm, VO2max = 59.4 +/- 5.1 ml·kg-1min-1, body fat = 10.6 +/- 5.4%) participated in this randomized repeated measures design study. Each subject completed four bouts of a 90 min walk at 30% VO 2max followed by a 5 km time trial in a hot, dry environment (33 +/- 1°C, 29 +/- 3% RH). Each visit examined the effects of either no fluid consumption (CON), drinking (H), external cooling (E), or drinking and external cooling (HE). The findings of this study showed pouring benefitted physiological and perceptual responses during low intensity exercise since 1) pouring trials (E and 11E) showed lower skin temperatures than non-pouring trials (CON and H), 2) drinking and pouring decreased thermal perception as compared to CON and H, and 3) pouring trials (E and HE) decreased RPE as compared to CON. Despite these findings, which suggest performance improvements, high intensity performance was not affected by drinking or pouring. Future research should investigate the effects of the combination of cold water drinking and pouring on low intensity exercise in the heat to determine possible performance benefits.