Parcell, A. C., Ray, M. M., Moss, K. A., Sharp, R. L., & King, D. S. (1996). Addition of soluble dietary fiber to pre-exercise carbohydrate feedings: Effects on substrate availability and endurance performance. Medicine and Science in Exercise and Sports, 28(5), Supplement abstract 534.

Soluble fiber reduces the plasma glucose and insulin changes after an oral glucose load by reducing the rate of intestinal absorption of glucose. Moderation of insulin changes after a pre-exercise carbohydrate (CHO) feeding may provide additional fuel sources for exercise in the form of plasma glucose and free fatty acids. The effects of soluble fiber combined with a pre-exercise CHO feeding on substrate availability and endurance performance in college males (N = 8) was investigated. Ss were exercised on a cycle ergometer, an activity for which they were untrained.

Results indicated no effect of the combination of fiber ingestion with CHO feeding on plasma glucose or glycogen use. It is possible that the untrained status of the Ss contributed to the absence of effect as well as the method of fiber presentation (capsule form).

Implication. In untrained individuals, soluble dietary fiber when combined with CHO feeding has no effect on performance. This is another instance where considering research on untrained individuals may lead to erroneous generalizations to trained individuals.

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