Effects of oral rehydration and external cooling on physiology, perception, and performance in hot, dry climates.

Only limited research evaluates possible benefits of combined drinking and external cooling (by pouring cold water over the body) during exercise. Therefore, this study examined cold water drinking and external cooling on physiological, perceptual, and performance variables in hot, dry environments. Ten male runners completed four trials of walking 90 min at 30% VO(2max) followed by running a 5-km time trial in 33 ± 1 °C and 30 ± 4% relative humidity. Trials examined no intervention (CON), oral rehydration (OR), external cooling (EC), and oral rehydration plus external cooling (OR + EC). Investigators measured rectal temperature, skin temperatures, heart rate, thirst, thermal sensation, and ratings of perceived exertion (RPE). Oral rehydration (OR and OR + EC) significantly lowered heart rate (P < 0.001) and thirst (P < 0.001) compared with nondrinking (CON and EC) during low-intensity exercise. External cooling (EC and OR + EC) significantly reduced chest and thigh temperature (P < 0.001), thermal sensation (P < 0.001), and RPE (P = 0.041) compared with non-external cooling (CON and OR) during low-intensity exercise. Performance exhibited no differences (CON = 23.86 ± 4.57 min, OR = 22.74 ± 3.20 min, EC = 22.96 ± 3.11 min, OR + EC = 22.64 ± 3.73 min, P = 0.379). Independent of OR, pouring cold water on the body benefited skin temperature, thermal sensation, and RPE during low-intensity exercise in hot, dry conditions but failed to influence high-intensity performance.