Introduction: Consuming a high-carbohydrate diet for a few days increases muscle glycogen stores (CHO loading). In practical settings, energy intake (EI) during CHO loading tends to exceed the habitual level in order to ingest the requisite carbohydrate amount (10-12 g/kg body mass [BM]/d, Burke et al.). However, few studies have been conducted on the effect of CHO loading with excess EI on body composition and performance. This study aimed to reveal the effects of 72-h CHO loading with excess EI on muscle glycogen concentration, body composition, and endurance performance. Methods: Eight subjects completed a glycogen-depletion session consisting of endurance and high-intensity intermittent exercise. For 72 h thereafter, the subjects consumed prescribed diets with 12 g/kg BM/d carbohydrate (energy 3686 ± 288 kcal/d, protein 77 ± 7 g/d, fat 33 ± 7 g/d, carbohydrate 770 ± 66 g/d), of which EI is exceeded the habitual diet (2089 ± 258 kcal/d, 73 ± 17 g/d, 65 ± 10 g/d, and 302 ± 51 g/d, respectively). Muscle glycogen concentration was assessed every 24 h after exercise by using 13C-magnetic resonance spectroscopy. A 3-compartment model of body composition (i.e., fat mass [FM], total body water [TBW], and fat-free dry solid [FFDS]) was assessed at baseline and 72 h after exercise by measuring body density and using the deuterium dilution technique. The endurance performance test requiring the accomplishment of individualized amount of work as fast as possible was completed at baseline and 72 h after exercise. Results: Muscle glycogen concentration linearly increased after exercise and reached 2.4- ± 0.8-fold the baseline value at 72 h after exercise (P < 0.001). BM, TBW, and FFDS significantly increased, but FM significantly decreased 72 h after exercise (P < 0.05). Endurance performance significantly improved 72 h after exercise (P < 0.001). Discussion: CHO loading for 72 h with excess EI increased BM, TBW, and FFDS. These changes were interpreted as increases in muscle glycogen and glycogen-binding water. FM decreased after CHO loading, despite the excess EI. In this study, the amount of carbohydrate intake was largely increased, but the amount of fat intake was reduced by 50% during CHO loading. Because de novo lipogenesis from carbohydrate is negligible before glycogen stores are saturated, reduction in FM may be induced by reduction in fat intake and glycogendepletion exercise-related lipolysis. The results of our body composition and performance analyses suggest that CHO loading with excess EI can help improve endurance performance.
© Copyright 2016 21st Annual Congress of the European College of Sport Science (ECSS), Vienna, 6. -9. July 2016. Veröffentlicht von University of Vienna. Alle Rechte vorbehalten.