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Rapid carbohydrate loading after a short bout of near maximal-intensity exercise


Medicine & Science in Sports & Exercise: June 2002 - Volume 34 - Issue 6 - p 980-986
BASIC SCIENCES: Original Investigations

FAIRCHILD, T. J., S. FLETCHER, P. STEELE, C. GOODMAN, B. DAWSON, and P. A. FOURNIER. Rapid carbohydrate loading after a short bout of near maximal-intensity exercise. Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 980–986, 2002.

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% V̇O2peak 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.

Department of Human Movement and Exercise Science, The University of Western Australia, Crawley, Western Australia, AUSTRALIA

Submitted for publication June 2001.

Accepted for publication November 2001.

©2002The American College of Sports Medicine