PREEXERCISE GLYCEROL HYDRATION IMPROVES CYCLING ENDURANCE TIME

The effects of glycerol ingestion (GEH) on hydration and subsequent cy cle ergometer submaximal load exercise were examined in well condition ed subjects. We hypothesized that GEH would reduce physiologic strain and increase endurance. The purpose of Study I (n = 11) was to determi ne if pre-exercise GEH (1.2 gm/kg glycerol in 26 ml/kg solution) compa red to pre-exercise placebo hydration (PH) (26 ml/kg of aspartame flav ored water) lowered heart rate (HR), lowered rectal temperature (T-c), and prolonged endurance time (ET) during submaximal load cycle ergome try. The purpose of Study II (n = 7) was to determine if the same pre- exercise regimen followed by carbohydrate oral replacement solution (O RS) during exercise also lowered HR, T-c, and prolonged ET. Both studi es were double-blind, randomized, crossover trials, performed at an am bient temperature of 23.5 - 24.5 degrees C, and humidity of 25 - 27%. Mean HR was lower by 2.8 +/- 0.4 beats/min (p = 0.05) after CEH in Stu dy I and by 4.4 +/- 1.1 beats/min (p = 0.01) in Study II. Endurance ti me was prolonged after GEH in Study I (93.8 +/- 14 min vs. 77.4 +/- 9 min, p = 0.049) and in Study 11 (123.4 +/- 17 min vs. 99.0 +/- 11 min, p = 0.03). Rectal temperature did not differ between hydration regime ns in both Study I and Study II. Thus, pre-exercise glycerol-enhanced hyperhydration lowers HR and prolongs ET even when combined with ORS d uring exercise. The regimens tested in this study could potentially be adapted for endurance activities.