Carbohydrate intake before and during exercise helps save energy in specific muscle fiber types

Preexercise glycogen content was higher in type IIa fibers (9.1 +/- 1 x 10(-2) optical density (OD)/microm(2)) compared to type I fibers (8.0 +/- 1 x 10(-2) OD/microm(2)).

• Type IIa muscle fibers showed a significant decrease in glycogen content during fasting, from 9.6 +/- 1 x 10(-2) OD/microm(2) to 4.5 +/- 1 x 10(-2) OD/microm(2).
• No significant change in glycogen content was observed in type IIa fibers during carbohydrate intake (P = 0.29).
• Type I fibers experienced a similar decrease in glycogen content during both carbohydrate and fasting conditions.
• The combination of carbohydrate intake before and during exercise is associated with glycogen sparing in type IIa muscle fibers.

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