MAGAL, M., M. J. WEBSTER, L. E. SISTRUNK, M. T. WHITEHEAD, R. K. EVANS, and J. C. BOYD. Comparison of Glycerol and Water Hydration Regimens on Tennis-Related Performance. Med. Sci. Sports Exerc., Vol. 35, No. 1, pp. 150-156, 2003.
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 ∼ 900 mL over the placebo (P) (P ≤ 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 ∼700 mL over the P trial (P ≤ 0.05). Although the magnitude of hypohydration was modest (<3%), sprint times were significantly slower after the EID (P ≤ 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 (∼2.7%) 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.