Comparison between Carbohydrate Feedings before and during Exercise on Running Performance during a 30-km Treadmill Time Trial

in International Journal of Sport Nutrition and Exercise Metabolism
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The purpose of this study was to compare the effects of a carbohydrate-electrolyte solution, ingested during exercise, with the effects of a preexercise carbohydrate meal on endurance running performance. Ten endurance-trained males completed two 30-km treadmill runs. In one trial subjects consumed a placebo solution 4 hr before exercise and a carbohydrate-electrolyte solution immediately before exercise and every 5 km (C). In the other trial, subjects consumed a 4-hr preexercise high-carbohydrate meal and water immediately before exercise and every 5 km (M). Performance times were identical for M and C, and there was no difference in the self-selected speeds. Oxygen uptake, heart rates, perceived rate of exertion, and respiratory exchange ratios were also similar. However, blood glucose concentration was higher in C during the first 20 km of the 30-km run. In M, blood glucose concentration was maintained above 4.5 mmol · L1 throughout exercise. Thus, the two conditions produced the same 30-km treadmill running performance time.

The authors are with the Department of Physical Education, Sports Science and Recreation Management, Loughborough University, Loughborough, Leicestershire, LEI 1 3TU, UK. Address correspondence to C. Williams.