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Annual Meeting Abstracts: D-32 – Free Communication/Poster: Supplements and Ergogenic Aids

Metabolic and Performance Effects of Raisins Versus Sports Gel as Preexercise Feedings in Cyclists

Kern, Mark; Heslin, Christopher J.; Rezende, Robert S.

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Medicine & Science in Sports & Exercise: May 2004 - Volume 36 - Issue 5 - p S174
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Previous research has suggested that carbohydrate sources resulting in varied glycemic responses may differentially alter metabolism and endurance performance. PURPOSE: To determine the differences in metabolism and cycling performance after consumption of raisins (a moderate to low glycemic index food) versus a commercial sports gel (a high glycemic index food). METHODS: Eight endurance-trained cyclists (30 ± 5 years of age), including four men and four women, completed two feeding/performance trials in random order. Participants were fed 1g carbohydrate/kg body weight from either raisins or sports gel 45 min prior to exercise on an electronically braked cycle ergometer for 45 min at 75% VO2 max. Immediately thereafter, participants completed a 15 min performance trial in which total power output (kj) was determined. Blood was collected prior to the exercise bout, as well as after the 45th min of exercise, to determine serum concentrations of glucose, free fatty acids (FFA), triglycerides, lactate, and beta-hydroxy-butyrate (BHB). RESULTS: Performance was not different (p>0.05) between the raisin (189.5 ± 69.9 kJ) and gel (188.0 ± 64.8 kJ) trials. Prior to exercise, serum concentrations of fuel substrates did not differ between the two trials. After exercise, FFA concentration increased (+0.2 ± 0.1 mEq/l) significantly (p<0.05) during the raisin trial only. No other differences in blood-borne substrates were detected between the trials. Participants reported no difference in gastrointestinal symptoms between the two trials. CONCLUSION: Overall, only minor differences in metabolism and no difference in performance were detected between the feeding trials. Raisins cost approximately 1/5 of the cost of sports gels and have a higher nutrient content; thus, for exercise similar to that used in the study, raisins may be the better alternative. Supported by a grant from the California Raisin Marketing Board.

©2004The American College of Sports Medicine