Abstract

Since dehydration will impair exercise capacity, intake of fluid during exercise to offset sweat loss is important. Fluid intake should also provide substrates, usually carbohydrates. The availability of ingested fluids may be limited by gastric emptying or by intestinal absorption. Gastric emptying of liquids is slowed by the addition of carbohydrates in proportion to the carbohydrate concentration and osmolality of the solution. With increasing glucose concentration, the rate of fluid delivery to the small intestine is decreased, but the rate of glucose delivery is increased. Water absorption in the small intestine is a passive process and is stimulated by the active absorption of glucose and sodium. The optimum fluid for rehydration during exercise depends on intensity and duration of exercise, the environmental conditions, and the individual physiology of the athlete. There is no advantage in fluid intake during exercise of less than 30 min duration. The composition of fluids to be used will depend on the relative needs to replace water and to provide substrate. Where rehydration is a priority the solution should contain some glucose (20-30 g/l or glucose polymers) and should not exceed isotonicity (sodium content perhaps as much as 60 mmol/l). Where substrate provision is important, a concentrated solution, incorporating glucose polymers in concentrations of 150-200 g/l, is to be preferred. To minimize the limitation imposed by the rate of gastric emptying, frequent intake of small amounts of fluid is recommended. Verf.-Referat