Biology
Pie Chart of Human Muscle Fiber Types (Average)
Last reviewed on 2026-05-22.
Biology — verifiable data, editable template
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The average sedentary adult's skeletal muscle is roughly 50% slow-twitch (Type I) and 50% fast-twitch (Types IIa and IIx combined). The ratio varies significantly between individuals and muscle groups.
The data
- Type I (slow-twitch) — 50 %
- Type IIa (fast oxidative) — 25 %
- Type IIx (fast glycolytic) — 25 %
Source
Standard exercise physiology references.
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