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Biology

Muscle Fiber Types

Quick fact

Muscle fibers come in three main types: slow-twitch (Type I), fast-twitch oxidative (Type IIa), and fast-twitch glycolytic (Type IIx).

Why this is interesting

Did you know that your muscles aren't all the same? Some are built for long, steady effort, while others power explosive movements—like a sprint or a weight lift. What makes them so different?