IMPROVEMENT IN EXOGENOUS CARBOHYDRATE OXIDATION IS NOT ACCOMPANIED BY ANY IMPROVEMENT IN PERFORMANCE
Tarpey, M. D., Roberts, J. D., Kass, L., & Tarpey, R. J. (June 2, 2010). Ingestion of maltodextrin, fructose, and protein during exercise: Influence on exogenous carbohydrate oxidation and performance. Presentation 1575 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.
This study determined whether combined ingestion of maltodextrin, fructose, and protein influences the rate of exogenous carbohydrate oxidation and exercise performance, compared to an isoenergetic maltodextrin and fructose beverage. Trained cyclists/triathletes (N = 7) performed four exercise trials. Each trial consisted of 150 minutes cycling at 50% maximum power output, followed by a 60 km time-trial performance test. One of four beverages was randomly assigned during each trial: (1) maltodextrin + fructose + protein, (2) maltodextrin + fructose, (3) maltodextrin alone, or (4) flavored water (Placebo). Exogenous carbohydrate oxidation was assessed via measurement of 13C content of expired air samples.
Peak exogenous carbohydrate oxidation rates, achieved during the final 30 minutes of steady state exercise, were approximately 45.2% higher with the ingestion of maltodextrin + fructose, and 44.3% higher with the maltodextrin + fructose + protein, both compared to maltodextrin alone. However, only the maltodextrin + fructose was significantly greater than the maltodextrin alone beverage. Similarly, average exogenous carbohydrate oxidation from 60-150 minutes of steady state exercise was significantly higher with the ingestion of maltodextrin + fructose compared to maltodextrin alone. There was no significant difference in peak or average exogenous carbohydrate oxidation between maltodextrin + fructose + protein and maltodextrin + fructose. Peak and average exogenous carbohydrate oxidation rates for all beverages were significantly greater than placebo. There was no significant difference in performance times between any of the beverages, despite maltodextrin + fructose ingestion resulting in the fastest mean time trial.
Implication. The ingestion of a maltodextrin + fructose beverage results in a significant increase in exogenous carbohydrate oxidation rate over maltodextrin alone. The inclusion of protein to a maltodextrin + fructose beverage offers no extra advantage. Performance times were not significantly different between any of the test beverages. [This is another instance of a physiological effect being achieved by an experimental manipulation, but that significant effect did not accompany any improvement in performance.]
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