The role of salt and glucose replacement drinks in the marathon.

There is a large and growing body of scientific evidence that documents the benefits of ingesting salt and glucose (carbohydrates) during prolonged exercise. Those benefits include maintenance of cardiovascular function, enhanced carbohydrate oxidation, blunted decline in plasma sodium concentration and improved performance. The consumption of approximately 1g of carbohydrate per kilogram of bodyweight per hour appears sufficient to improve performance in prolonged exercise. Research also indicates that approximately 450mg of sodium per hour is the minimum amount required to maintain plasma volume and slow the decline in plasma sodium concentration that can accompany prolonged exercise in some runners. Adequate carbohydrate and electrolyte intake can be achieved by consuming a well formulated sports drink at regular intervals during exercise, in volumes designed to minimise dehydration. For marathon runners, this could range from approximately 400mL to >1.5L per hour, depending upon individual sweating rates.