GLUCOSE POLYMER INGESTION - EFFECT ON FLUID BALANCE AND GLYCEMIC STATE DURING A 4-D MARCH

The effect of glucose-polymer solution on physical performance has bee n extensively studied under controlled laboratory conditions. The pres ent study was conducted to investigate the influence of such beverages on fluid balance and on glycemic stare during a moderate, prolonged f ield exercise. Forty-eight endurance trained, male subjects participat ed in the study. The maneuver consisted of a 4-d march; 29, 39, 36, 30 km.d(-1), at a speed of 5-6 km.h(-1). The subjects covered a total di stance of 134 km al an estimated exercise intensity of similar to 40% VO2max, under hot climate conditions (ambient temperature, 32-41 degre es C; relative humidity, 60-14%). Subjects were randomly assigned to o ne of two groups: glucose polymer-electrolyte beverage (GP; N = 24) an d tap water (TW; N = 24). Each group was then divided into two subgrou ps consuming fluid ad libitum (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 mi in TWa and TWb; 5257 +/- 317 and 5253 +/- 216 mi in GPa and GPb, respectively). Weight loss, r eflecting 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 v olume 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 concentr ation changed from 143.0 +/- 0.1 and 143.0 +/- 0.2 mmol.l(-1) prior to the march on day 1, to 138.0 +/- 0.2 and 139.0 +/- 0.2 mmol.l(-1) fol lowing day 4 in the TW and GP groups, respectively. Serum osmolality c hanged 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 concen tration decreased in the range of up to -10 mg.dl(-1) on each day of m arch 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 conclud e that during prolonged, moderate exercise performed in a hot environm ent, similar hydration benefits were gained by drinking either tap wat er or glucose-polymer solution; yet, higher blood glucose levels were maintained when GP was consumed.