Dynamics of muscle glycogen increase in brachial and thigh muscles with carbohydrate loading

We investigated the changes in glycogen levels of the brachial and thigh muscles after 3 days of high carbohydrate intake without exercise.

Eleven healthy participants spent 3 days with a carbohydrate intake of 6 g/kg body mass/day (control period), followed by 3 days at 10 g/kg body mass/day (loading period). The glycogen levels in the triceps brachii and vastus lateralis plus intermedius muscles were evaluated noninvasively using ¹³C-magnetic resonance spectroscopy before and at 24 and 72 h of the loading period. Body composition and physical activity were also measured during the intervention period.

Body mass, fat free mass, and water volume significantly increased with 72 h of carbohydrate loading. Although the glycogen levels in both muscles were significantly elevated at 72 h of the loading period (brachial muscle 122.8 ± 29.2%, thigh muscle 122.5 ± 24.0%), there were no significant differences in the increase between the muscles. No significant correlation was observed in the changes between the two types of muscle (r = 0.073, P = 0.836).

Three days of carbohydrate loading (10 g/body mass/day) without exercise increased the glycogen levels by approximately 23% in both the upper arm and thigh muscles, suggesting that the changes were not always consistent between the muscles within each participant. These results should contribute to the development of nutritional strategies tailored to various sporting events involving different primary muscles.