Two experiments were done at rest to examine gastric residue and secretion volume and electrolyte composition after ingestion of beverages of varying composition. In the first experiment the effects of two different sport drinks, one isotonic (7% carbohydrate, primarily sucrose) (I) and one hypertonic (18% carbohydrate, primarily maltodextrin) (H), and a control beverage (0.08 g.1−1 aspartame in water) (C) on titratable acid, pH, osmolality, gastric emptying and secretion volume, and Na+, K+, and Cl− content were measured. In a second experiment five solutions were tested all containing 150 g.1−1 maltodextrin, with 28 meq.1−1 Na+ (low Na), 140 meq.1−1 Na+ (high Na), 28 mcq.I-1 K+(K), or 140 meq.1-1 Na+ and 28 meq.1−1 K+(high NaK). Beverages H and C, and distilled water (W) were also tested. Samples were taken via a nasogastric tube. A dye dilution technique for serial sampling was employed to determine beverage and secretion volumes. After receiving a bolus of 8 ml.kg−1 body weight, samples of gastric residue were taken at 0, 10, 20, 30, 40, 60, and 80 min. Gastric secretion of Na*, K+, and Cl− was fairly constant despite large differences in beverage composition. Changes in gastric residue pH, titratable acid, osmolality, and electrolyte composition reflected the increasing proportion of the residue that was from gastric secretions. The effects of varying concentrations of Na+ and K+ (in a 150 g.1−1 maltodextrin solution) on gastric emptying were not significant. The high carbohydrate concentration and/or the large volume ingested may have overridden any effect of sodium or potassium. No differences were observed between W and C. Secretion was decreased in these two solutions versus all the others. Although nonsignificant, there was a trend for greater secretion in H versus the other carbohydrate containing solutions in experiment 2. This may be a result of the higher pH maintained after ingestion of this beverage.
©1993The American College of Sports Medicine