Dose–Response of Dietary Carbohydrate Intake on Skeletal Muscle Glycogen, Gastrointestinal Comfort and Body Composition in Endurance‐Trained Individuals in Simulated Preparation for Competition

ABSTRACT High dietary carbohydrate (CHO) intake and reduced exercise training are recommended to optimize muscle glycogen stores pre‐endurance sports competition. However, the optimal CHO intake to support muscle glycogen synthesis and the dose–response of this relationship are still unknown in athletes who continue training pre‐competition. This study investigated the effects of different CHO intakes on muscle glycogen concentration. In a counterbalanced repeated measures design, 11 endurance‐trained participants (3 females, 8 males; age, 24 ± 5 years; body mass, 71.2 ± 12.0 kg; V̇ O 2max , 56 ± 6 mL kg −1 min −1 ) undertook 3 × 5 days of exercise and dietary control. During the final 48 h, participants ingested 6, 8 or 10 g kg −1 day −1 CHO prior to the assessment of muscle glycogen, gastrointestinal (GI) comfort and body composition. Muscle glycogen concentration was significantly higher following 10 vs. 6 and 8 g kg −1 day −1 (635.5 ± 78.0 vs. 460.9 ± 100.7 and 506.1 ± 124.0 mmol kg −1 dry mass, respectively, p < 0.03), with no difference between 6 and 8 g kg −1 day −1 ( p = 1.00). There was a strong positive correlation between relative CHO intake ( r = 0.71, p < 0.001) and skeletal muscle glycogen concentration. There was no effect of CHO intake on body mass ( p = 0.70) or GI symptoms ( p > 0.05), except fullness. In conclusion, there was a linear dose–response between dietary CHO intake and muscle glycogen in a protocol mimicking real‐world training and nutrition practices, as 10 g kg −1 day −1 achieved the highest muscle glycogen concentrations, with no detectable effect on body mass or GI symptoms, except increased fullness.