All Glossary Terms
Anatomy
Type II Muscle Fiber (Fast-Twitch)
Muscle fibers optimized for power and speed but fatigue quickly.
Type II (fast-twitch) muscle fibers generate high force quickly but fatigue rapidly. Type IIa fibers have some oxidative capacity; Type IIx are purely glycolytic. Sprinters and power athletes have higher proportions of Type II fibers. Heavy and explosive training preferentially develops Type II fibers. Fiber type is largely genetic but trainable.
Examples
- Used for sprinting, jumping, lifting
- Dominant in sprinters, powerlifters
- Type IIa and Type IIx subtypes