Fast-twitch muscle fibers (Type II) contract quickly and powerfully, enabling explosive efforts like sprints, jumps, and attacks. They fatigue faster but generate high force.
Type II fibers are of two types: IIa and IIx. IIa fibers assist in both power and endurance, whereas IIx fibers specialize in speed with less endurance. Fast-twitch fibers are extremely significant in activities such as sprinting and short explosions of effort, for example, cycling uphill or finishing a race in quick time. Plyometric exercises, short-distance sprinting, and heavy weightlifting are ways to strengthen these fibers. Even those athletes specializing in long endurance can benefit by improving their ability to change pace and execute significant movements.
