Burns, S. (2008). Physiological responses to glycerol ingestion and hyperhydration. ACSM 55th Annual Meeting Indianapolis, Presentation Number 1339.

This study determined 1) if glycerol induced hyperhydration could be maintained over four hours of moderate exercise through intermittent doses of glycerol, and 2) the effects glycerol induced hyperhydration has on plasma volume and core temperature. Male endurance trained cyclists (N = 8) served as Ss. After an initial bolus of water (21.4 ml/kg), Ss cycled for four bouts of 55-minute duration at 65% VO2max. Ss performed three different protocols: 1) An initial bolus of 1.0 g/kg glycerol, 2) an initial bolus of 1.0 g/kg glycerol plus intermittent doses of 0.5 g/kg glycerol each hour during exercise, and 3) water. Blood and urine were collected hourly to determine plasma volume and urine volume. Core temperature was monitored and recorded every 15 minutes.

Initial and intermittent glycerol reduced urine volume when compared to water ingestion during four hours of moderate exercise. The hyperhydrated condition led to significantly reduced core temperature. No differences were observed in retained fluids or plasma volume, between the ingestion protocols.

Implication. Intermittent glycerol ingestion during exercise reduces urine volume, producing a hyperhydrated condition. Glycerol is an effective hyperhydrating agent, therefore, capable of reducing physiological costs of exercise in the heat. Glycerol ingested prior to and during exercise also reduces core temperature during exercise.

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