Voluntary fluid intake and core temperature responses in adolescent tennis players: sports beverage versus water

Objective: To examine differences in ad libitum fluid intake, comparing a 6% carbohydrate/electrolyte drink (CHO-E) and water, and associated differences in core temperature and other selected physiological and perceptual responses in adolescent athletes during tennis training in the heat. Methods: Fourteen healthy, fit, young tennis players ( nine male; five female; mean (SD) age 15.1 (1.4) years; weight 60.6 (8.3) kg; height 172.8 (8.6) cm) completed two 120 minute tennis specific training sessions on separate days (randomised, crossover design) in a warm environment ( wet bulb globe temperature: CHO-E, 79.3 ( 2.6) degrees F; water, 79.9 (2.2) degrees F; p > 0.05). Results: There were no significant differences (p < 0.05) between the trials with respect to fluid intake, urine volume, fluid retention, sweat loss, perceived exertion, thirst, or gastrointestinal discomfort. However, there was a difference (p < 0.05) in the percentage body weight change after training (CHO-E, -0.5 (0.7)%; water, -0.9 (0.6)%). Urine specific gravity before training (CHO-E, 1.024 (0.006); water, 1.025 (0.005)) did not correlate significantly (p < 0.05) with any of these measurements or with core body temperature. In examining the main effect for trial, the CHO-E trial showed a significantly lower (p < 0.001) mean body temperature (irrespective of measurement time) than the water trial. However, the mean body temperature in each trial was not associated (p < 0.05) with fluid intake, fluid retention, sweat loss, or percentage body weight change. Conclusion: Ad libitum consumption of a CHO-E drink may be more effective than water in minimising fluid deficits and mean core temperature responses during tennis and other similar training in adolescent athletes.