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There's no conclusive evidence that muscle fibers can transform from slow- to fast-twitch or vice versa. In other words, while you can improve at sprinting or other explosive movements, it may not be because you're converting muscle fiber types.
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Still, fast-twitch (type IIb) fibers can be converted into moderate fast-twitch (type IIa), or vice versa, through increases in endurance or resistance training. And keep in mind that fast-twitch muscle depletes with age considerably more than slow-twitch, so increasing muscle power is less feasible later in life.
Still, generally speaking, when muscles are forced to work differently and you get out of your comfort zone, you get a better workout. Keep mixing your workouts up to recruit all types of muscles fibers—and to fight dreaded gym boredom.