All skeletal muscles are composed of a blend of fast-twitch (Type IIb), slow-twitch (Type I), and intermediate muscle fibers (Type IIa). The fast-twitch and slow-twitch muscle fibers have different characteristics
Fast-twitch muscle fibers are larger, have less blood flow, have more immediate fuel sources, have larger nerves, and can contract more rapidly and with more force than slow-twitch fibers.
The intermediate fibers are more like fast-twitch fibers but, like slow-twitch fibers, have more blood flow.
