Purpose: One limitation shared by all published carbohydrate-loading regimens is that 2-6 d are required for the attainment of supranormal muscle glycogen levels. Because high rates of glycogen resynthesis are reported during recovery from exercise of near-maximal intensity and that these rates could in theory allow muscle to attain supranormal glycogen levels in less than 24 h, the purpose of this study was to examine whether a combination of a short bout of high-intensity exercise with 1 d of a high-carbohydrate intake offers the basis for an improved carbohydrate-loading regimen.
Methods: Seven endurance-trained athletes cycled for 150 s at 130% VO2peak followed by 30 s of all-out cycling. During the following 24 h, each subject was asked to ingest 12 g.kg-1 of lean body mass (the equivalent of 10.3 g.kg-1 body mass) of high-carbohydrate foods with a high glycemic index.
Results: Muscle glycogen increased from preloading levels (+/- SE) of 109.1 +/- 8.2 to 198.2 +/- 13.1 mmol.kg-1 wet weight within only 24 h, these levels being comparable to or higher than those reported by others over a 2- to 6-d regimen. Densitometric analysis of muscle sections stained with periodic acid-Schiff not only corroborated these findings but also indicated that after 24 h of high-carbohydrate intake, glycogen stores reached similar levels in Type I, IIa, and IIb muscle fibers.
Conclusion: This study shows that a combination of a short-term bout of high-intensity exercise followed by a high-carbohydrate intake enables athletes to attain supranormal muscle glycogen levels within only 24 h.