Mitchell, J. B., Costill, D. L., Houmard, J. A., Fink, W. J., Pascoe, D. D., & Pearson, D. R. (1989). Influence of carbohydrate dosage on exercise performance and glycogen metabolism. Journal of Applied Physiology, 67, 1843-1849.

Carbohydrate solutions of 0, 6, 12, and 18 g/100-ml were evaluated for effects on performance and muscle glycogen use. Trained male cyclists (N = 10) performed five 120-min trials on a cycle ergometer. The first 105 minutes were at 70% VO2max. The remaining 15 minutes was an all-out effort to measure work output. One trial was structured as 7 x 15-min intervals with 3-min rest intervals (workload 70% VO2max).

There were no differences between 0 or the two CHO-12 trials in glycogen use or depletion patterns. Blood glucose was significantly elevated in the 12 and 18 gm concentrations when compared to 0 gm. CHO-12 work output was also significantly higher than in the CHO-0 condition. This indicates that performance improvements may have resulted from maintenance of blood glucose. Intermittent exercise did not alter glycogen metabolism or performance.

Implication. Carbohydrate solutions of 12 g/100-ml increase cycling endurance performance in males when compared to a no-carbohydrate supplement condition.

Return to Table of Contents for this issue.