The effects of glycerol ingestion (GEH) on hydration and subsequent cycle ergometer
submaximal load exercise were examined in well conditioned subjects. We hypothesized
that GEH would reduce physiologic strain and increase endurance. The purpose of Study
I (n = 11) was to determine if pre-exercise GEH (1.2 gm/kg glycerol in 26 ml/kg solution)
compared to pre-exercise placebo hydration (PH) (26 ml/kg of aspartame flavored water)
lowered heart rate (HR), lowered rectal temperature (Tc ), and prolonged endurance time (ET) during submaximal load cycle er-gometry. The
purpose of Study II (n = 7) was to determine if the same pre-exercise regimen followed
by carbohydrate oral replacement solution (ORS) during exercise also lowered HR, Tc , and prolonged ET. Both studies were double-blind, randomized, crossover trials,
performed at an ambient temperature of 23.5 -24.5 °C, and humidity of 25 - 27 %. Mean
HR was lower by 2.8 ± 0.4 beats/min (p = 0.05) after GEH in Study I and by 4.4 ± 1.1
beats/min (p = 0.01) in Study II. Endurance time was prolonged after GEH in Study
I (93.8 ± 14 min vs. 77.4 ± 9 min, p = 0.049) and in Study II (123.4 ± 17 min vs.
99.0 ± 11 min, p = 0.03). Rectal temperature did not differ between hydration regimens
in both Study I and Study II. Thus, pre-exercise glycerol-enhanced hyper hydration
lowers HR and prolongs ET even when combined with ORS during exercise. The regimens
tested in this study could potentially be adapted for endurance activities.
Key words
Hyperhydration - endurance exercise - heart rate
