The Performance Effect of Early Versus Late Carbohydrate Feedings During Prolonged Exercise

Abstract

Ingesting carbohydrate during prolonged exercise can increase time to fatigue and improve time trial performance at the end of exercise. The purpose of this study was to determine how the timing of isoenergetic carbohydrate feedings during prolonged cycling affects performance in a subsequent 10 km cycling performance trial. Recreationally trained male cyclists (n = 8, age 34.5 ± 8.3 y, mass 80.0 ± 6.3 kg, 16.0 ± 3.8% body fat, VO2 peak 4.54 ± 0.42 L · min-1 ) completed four experimental trials consisting of cycling continuously for two hours at 60% of VO2 peak, followed immediately by a self-paced 10 km performance trial. Participants consumed 250 mL of beverage every 15 minutes during the two hour exercise. The four conditions included no carbohydrate ingestion (PP), early carbohydrate ingestion (CP), late carbohydrate ingestion (PC), or carbohydrate ingestion throughout (CC). A total of 60 g of carbohydrate was given in all trials except PP. Trials were completed in a randomized, counterbalanced order. 10 km performance trial time to completion was faster in trials CC (17.70 ± 0.52 min) and PC (17.60 ± 0.62 min) as compared to trial PP (18.13 ± 0.52 min, p = 0.028 and p = 0.007, respectively) while trial CP (17.85 ± 0.58 min) was not different from trial PP (p = 0.178) . Blood variables mirrored performance results. These data indicate that carbohydrate ingestion late during exercise (CC and PC) can improve subsequent 10 km time trial performance while early ingestion (CP) does not