Thursday, July 24, 2008

Three Types of Skeletal Muscle

Skeletal muscle can be slow twitch or type I or red, or fast twitch or type II white muscle fiber muscles.
Slow twitch muscles contract slower, contain more mitochondria, and use more oxygen than fast twitch muscles. The slow twitch muscle are fatigue resistant and their fibers are smaller in diameter compared to those of fast twitch muscles. Fast twitch muscle fibers are divided into IIA and IIb types. Type IIa fibers are called fast twitch oxidative because they have more mitochondria than Type IIb, or fast-twitch glycolytic muscles. Most bodybuilders have fast twitch white muscle fibers, while top marathoners have mostly slow twitch red muscle fibers. It is possible to change fast twitch type II to slow twitch type IIa muscle fiber.

For the past several blog posts, I have not created exercise programs. Look to past posts or search by muscle group, and you will find them!

Disclaimer: None of the above information can be taken as a substitute for advice from a medical professional, such as a physician.

My third book, Pocket Guide to Fitness, is available on,, and If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories.

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