Ready, set, go! Type IIx fibers are your fastest, most powerful muscle cells. They give you big bursts of power, but they tire out quickly.
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Your muscles are made of long cells called muscle fibers. Type IIx fibers are the fastest kind in people.
They look pale, almost pinkish white. They have only a few mitochondria and fewer blood tubes around them. Instead, they keep lots of stored sugar fuel called glycogen (GLY-ko-jen).
Scroll up to the 3D model and press Squeeze!. Then press Cut it open to see all the yellow fuel dots.
Type IIx fibers burn their sugar fuel very fast, without needing much oxygen. That gives you super quick, super strong moves.
They help you sprint, jump high, and throw hard. But the fuel runs low fast, so they get tired in a short time.
Sprinters often have more fast-twitch fibers in their legs. Marathon runners often have more slow-twitch fibers.
By Peekaboo Kidz. A fun video for kids.
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