Smith, J. E., Zachwieja, J. J., Horswill, C. A., Pascoe, D. D., Passe, D., Ruby, B. C., & Stewart, L. K. (2010). Evidence of a carbohydrate dose and prolonged exercise performance relationship. Presentation 855 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

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This study investigated the relationship between carbohydrate ingestion rate and cycling time-trial performance to identify a range of carbohydrate ingestion rates that would enhance performance. Cyclists and triathletes (N = 5`), across four research sites, completed four exercise sessions consisting of a 2-hour constant load ride at 95% of the workload that elicited a blood lactate concentration of 4 mM. Twelve different beverages (three at each site) were tested providing Ss 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 grams of carbohydrate per hour during the constant load ride. A common placebo that was artificially sweetened, colored, and flavored and did not contain carbohydrate was tested at all four sites. The order of the beverage treatments was randomized at each site. Immediately following the constant load ride, Ss completed a computer simulated 20-km time-trial. Completion times were transformed into Z-scores to account for environmental and subject differences across sites.

Carbohydrate ingestion significantly improved performance. The most striking performance enhancement occurred at an ingestion rate between 60-80 grams if carbohydrate per hour.

Implication. A wide range of carbohydrate ingestion rates can benefit endurance exercise performance, with the greatest performance enhancement occurring with an ingestion rate between 60-80 grams of carbohydrate per hour.

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