Hyperhydrating with glycerol: effects on thermoregulation, hydration and athletic performance during specific exergonic exercise in a warm-humid environment

Abstract

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We investigated the effects of hyperhydration with glycerol vs. water on athletic performance under hot-humid conditions (30% relative humidity and 36° C). During a 10-day acclimation period, 14 competitive male oarsmen performed 90 minutes of exercise at 260-W. On the eleventh day, athletes hydrated by consuming in 90 minutes a nutrient drink with or without glycerol. After hydration, athletes were tested three times with 250–400-W workloads in 30-W steps, at 15-min intervals. During the 250–400-W tests, athletes rehydrated with water (control and glycerol A groups) or with flavored glycerol solution (glycerol B group). Measurements of total extracellular body water (EBW) by bioelectric impedance analysis indicated a statistically significant increase in water retention (approximately 525 ml) and decreased lactate at aerobic threshold for the glycerol B group compared to the control and glycerol A groups following the exercise tests. The performance on the three 250–400-W tests was stable for glycerol B athletes but decreased for glycerol A and control groups. The 15-W difference observed at the aerobic threshold between glycerol B and control groups was estimated to translate into a 37-m competitive advantage during a 6-min Olympic rowing competition.