Abstract

Tennis players have repeatedly been shown to present with signs of dehydration before training or competition. To date no study has investigated the role of post-exercise rehydration in tennis players. Therefore the aim of this study was to assess the efficacy of a post-training rehydration strategy on markers of hydration status in high-performance tennis players. Using a nonblinded randomised crossover design the participants (12 male elite tennis players; mean±SD; age 21±2 years, national ranking 13±8; range 2-25) completed their normal daily training and dietary routine followed by ad libitium consumption (CON) of a commercially available carbohydrate-electrolyte solution (Lucozade Sport Hydro Active PLUS; 4 g carbohydrate and 91 mg sodium per 100 ml) or 20 ml per kg body mass (EXP) of the same solution. An array of markers of hydration status were assessed after rest days (baseline) and each training and intervention day (CON, EXP) including but not limited to: urine osmolality (first morning void, freezing point depression method); total body water, intra and extracellular water (multifrequency bioelectrical impedance). All markers of hydration status were measured in the morning before any activity or meals and normalised as a percentage of baseline. A magnitude-based inferences approach1 was used to determine the main effect of the intervention on the markers of hydration status. The mean (±SD% normalised to baseline) in CON vs EXP for urine osmolality, total body water, extracellular and intracellular water were 104±25% vs 95±31%; 99±2% vs 100±2%; 100±2% vs 102±7% and 98±5% vs 100±2%. The probability of a beneficial or positive effect on these markers of hydration status was 87%, 67%, 84% and 59%, respectively. The probability of a harmful or negative effect was 2%, 3%, 8% and 4%, respectively. Therefore this post-exercise rehydration intervention has an unclear effect as the probability of a negative effect on these markers of hydration status was too great.