GLYCEROL INGESTION IMPROVES PERFORMANCE IN THE HEAT

Murray, R. L., Perks, A., Lindy, M. R., & Mickleborough, T. D. (2004). Ingesting a pre-exercise glycerol solution improves endurance performance in a hot environment. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 1984.

This study determined if ingestion of a pre-exercise glycerol solution improved endurance time, body temperature (Tsk - mean skin; Tc - rectal), and heart rate during exercise in a hot environment. Males (N = 8) performed exercise to fatigue on a friction braked cycle ergometer at constant power output of 120W. Ambient temperatures were controlled at 35C 2C and subjects ingested either glycerol in solution with water (1.2 ml/kg to a total volume of 26 ml/kg) or an equal quantity of plain water (W) one hour pre-exercise. Heart rate, VO2 and temperature were measured continuously throughout exercise, sweat loss, evaporative water loss, and evaporative heat loss were measured at exhaustion.

Endurance time was significantly extended between for the glycerol condition when compared to the water condition. Heart rate was significantly lowered following glycerol ingestion at rest, at 20 minutes, and at 40 minutes but not at exhaustion. Significant differences were also seen in sweat loss, evaporative water loss, and evaporative heat loss. There was no significant variation across time for either measure of temperature.

Implication. Pre-exercise glycerol ingestion provides an effective means of improving endurance time and reducing heart rate during exercise in a hot environment, although no significant changes in body temperature were observed. Thermoregulatory heat and water loss increased as a result of the extended exercise time.

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