PP13 The effects of food consumed with a sports drink or water on post-exercise rehydration

Abstract

Exercise performance may be impaired following reductions in body water amounting to approximately 2% body mass. Post-exercise rehydration is an important factor to consider when a subsequent bout of exercise is to be undertaken. Drink volume and composition are important considerations with regards to fluid retention after exercise. The aim of this study was to examine retention of a sports drink and water when consumed with food in the post-exercise period. Seven healthy participants (3 male, 4 female) aged 21–41 y were dehydrated by (mean ± SD) 1.6 ± 0.3% body mass by intermittent cycling in the heat (35.0 ± 0.9°C, 51 ± 7% relative humidity). Participants then consumed a volume equal to 150% body mass loss of a commercially available sports drink or water with a standard meal designed to provide 30% of estimated daily energy expenditure. The drink was consumed in four equal boluses over a period of one hour with the meal consumed with the final three boluses. Urine volume and osmolality were measured before and after exercise and at hourly intervals for three hours after completion of the rehydration period. No significant differences between trials were observed for percentage body mass loss (p = 0.405), sweat loss (p = 0.376) or drink volume (p = 0.371). Cumulative urine volume following rehydration amounted to 765 ± 223 ml and 630 ± 231 ml (p = 0.244) and percentage of drink volume retained amounted to 53 ± 13% and 59 ± 15% (p = 0.336) during the water and sports drink trials, respectively. No difference (p > 0.05) in net fluid balance was observed between trials. The results of this study indicate that there is no difference in post-exercise fluid retention between water and a sports drink when consumed with a meal. The addition of a meal during the post-exercise period is likely to reduce the rate of fluid absorption, resulting in reduced urine production. This may explain the lack of a significant difference between trials.