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Glucose polymer ingestion—effect on fluid balance and glycemic state during a 4-d march

Medicine & Science in Sports & Exercise: March 1994

BURSTEIN, R., D. S. SEIDMAN, J. ALTER, D. MORAN, O. SHPILBERG, J. SHEMER, M. WIENER, and Y. EPSTEIN. Glucose polymer ingestion—effect on fluid balance and glycemic state during a 4-d march. Med. Sci. Sports Exerc., Vol. 26, No. 3, pp. 360–364, 1994. The effect of glucose-polymer solution on physical performance has been extensively studied under controlled laboratory conditions. The present study was conducted to investigate the influence of such beverages on fluid balance and on glycemic state during a moderate, prolonged field exercise. Forty-eight endurance trained, male subjects participated in the study. The maneuver consisted of a 4-d march; 29, 39, 36, 30 km·d-1, at a speed of 5–6 kmh-1. The subjects covered a total distance of 134 km at an estimated exercise intensity of ∼40% VO2max‘ under hot climate conditions (ambient temperature, 32–41°C; relative humidity, 60–14%). Subjects were randomly assigned to one of two groups: glucose polymer-electrolyte beverage (GP; N = 24) and tap water (TW; N = 24). Each group was then divided into two subgroups consuming fluid ad libium (TWa, GPa) or instructed to consume 900 ml·h-1 (TWb, GPb). The mean daily fluid consumption of all subgroups was similar (5252 ± 229 and 4640 ± 67 ml in TWa and TWb; 5257 ± 317 and 5253 ± 216 ml in GPa and GPb, respectively). Weight loss, reflecting the degree of dehydration, was 1.2 ± 0.1% and 1.9 ± 0.3% of initial body weight in TW and GP, respectively. On day 1, plasma volume changed by +0.4% and −1.8% in the TW and GP groups, respectively. On the days 2–4 changes in both groups were similar. Sodium concentration changed from 143.0 ± 0.1 and 143.0 ± 0.2 mmol·1-1 prior to the march on day 1, to 138.0 ± 0.2 and 139.0 ± 0.2 mmol·l-1 following day 4 in the TW and GP groups, respectively. Serum osmolality changed from 295 ± 1 and 294 ± 1 mOsm·kg-1 to 287 ± 1 and 286 ± 1 mOsm·kg-1 in the two groups, respectively. Blood glucose concentration decreased in the range of up to −10 mg·dl-1 on each day of march in subjects drinking TW and increased significantly (P > 0.01) in the range of up to +20 mg·dl-1, in subjects ingesting GP. We conclude that during prolonged, moderate exercise performed in a hot environment, similar hydration benefits were gained by drinking either tap water or glucose-polymer solution; yet, higher blood glucose levels were maintained when GP was consumed.

©1994The American College of Sports Medicine