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All Muscles Are Not Created Equal      

Athletic Feet of Runner Positioned at Starting Block

Born That Way

Some people are born with more fast-twitch muscle fiber than others, and that's a big part of what makes some people so much faster than others.

Muscles are made of two kinds of fibers--fast twitch and slow twitch.

Slow-twitch fibers use energy aerobically and can work for long periods of time before getting tired. They contract more slowly, but can keep going without burning themselves out.

Fast-Twitch vs. Slow-Twitch

Slow-twitch fibers have a lot of myoglobin, a protein that helps transfer oxygen into the mitochondria, the power houses of the cell that produce cellular energy.

So marathon runners must have a lot of slow-twitch muscle fibers, and sprinters must have a lot of fast-twitch muscle fiber.

Fast-twitch fibers consume energy quickly and are good for short, powerful bursts of movement such as sprinting and jumping. World-class sprinters typically have about 80% fast-twitch muscle fiber.

And of course they train incredibly hard to develop their natural gifts. Olympic gold is not won by muscle fiber alone. But it certainly helps.

Read More:

"Fast and Slow Twitch Muscle Fibers" (


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