Comparison of glycerol and water hydration regimens on tennis-related performance

Purpose: To compare glycerol and water hyperhydration and rehydration on tennis related skill and agility performance. Methods: Eleven male subjects completed two counter-balanced, double-blind trials. Each trial consisted of three phases: 1) hyperhydration with or without glycerol (1.0 g(.)kg(-1)) over 150 min, 2) 120 min of exercise-induced dehydration (EID), and 3) rehydration with or without glycerol (0.5 g(.)kg(-1)) over 90 min. After each phase, subjects performed 5- and 10-m sprint tests, a repeated-effort agility test, and tennis skill tests. Results: Glycerol (G) hyperhydration significantly increased fluid retention by similar to 900 mL over the placebo (P) (P less than or equal to 0.05). After EID, body weight was reduced in both groups but was not significantly different between groups (G: -2.71 +/- 0.08, P: -2.67 +/- 0.09%). At the end of the rehydration phase, PV was significantly greater in the G trial than in the P trial, and the G trial resulted in a significantly greater fluid retention of similar to700 mL over the P trial (P less than or equal to 0.05). Although the magnitude of hypohydration was modest (<3%), sprint times were significantly slower after the EID (P less than or equal to 0.05) compared with post hyperhydration and post rehydration but were not significantly different between trials. No significant difference existed between groups and across time for the repeated effort agility tests and groundstrokes and serve tests. Conclusion: The data demonstrate that relatively modest hypohydration (similar to2.7%) as a result of EID, significantly slows 5- and 10-m sprint times. Furthermore, although the glycerol hydration regimen provided a better hydration status than the placebo hydration regimen, no performance benefits were observed.