Building your fast-twitch muscle fibers can help you get stronger and faster. This type of muscle fiber is responsible for the fast, explosive movements used in activities like sprinting, jumping, and ...

Your body is made up of two kinds of muscle fibers: slow twitch (type 1) muscles, and "fast twitch" (type 2) muscles. "Slow-twitch muscles are the ones in charge of long endurance challenge—so they ...