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TYPE II (FAST-TWITCH) MUSCLE FIBRES

Powerful, fast-contracting fibres that fatigue quickly. Type IIa are trainable toward endurance; type IIx are pure sprint fibres.

Generate 2-3× more force than type I but fatigue in seconds to minutes. Masters cyclists lose type II fibres preferentially — one reason heavy strength training is essential after 40. You can't train type II with easy riding; heavy lifts and sprints are required.

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RELATED TERMS

Type I (Slow-Twitch) Muscle FibresAnaerobic CapacityW' (W-Prime / Anaerobic Work Capacity)
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