Effects of Acute Carbohydrate Supplementation on Endurance Performance: A Meta-Analysis

Abstract

Unlabelled Research on the performance effects of acute carbohydrate supplementation is comprehensive. Here we present the first meta-analytic review of this research. Methods Eighty-eight randomized crossover studies in which carbohydrate supplements were consumed with or without protein before and/or during exercise provided 155 estimates for performance effects in time-to-exhaustion tests or in time trials with or without a preload. For the mixed-model meta-analysis, all effects were converted into percentage changes in mean power in a non-preloaded time trial and weighted using percentage standard errors derived from exact p-values (in a minority of studies) or from estimated errors of measurement (in all other studies). Publication bias was assessed with a plot of t-values for the random-effect solutions versus standard errors. Probabilistic inferences were derived with reference to thresholds for small, moderate and large effects on performance of 0.5, 1.5 and 2.7%. Results Publication bias was reduced by excluding studies with a standard error >1.25%. In the remaining 73 studies and 122 estimates, the meta-analysed performance effects of carbohydrate supplements ranged from clear large improvements of ∼6% to clear moderate impairments of ∼2%. The best supplement inferred from the analysis consisted of a ∼3-10% carbohydrate-plus-protein drink providing ∼0.7 g/kg/h glucose polymers, ∼0.2 g/kg/h fructose and ∼0.2 g/kg/h protein. Substantial increases in the benefit of a s…