Book 28, Question 80
What are fast-twitch and slow-twitch muscle fibers?
Muscles contain different kinds of fibers.
Fast-twitch fibers contract quickly and strongly but tire fast, which is great for sprinting and jumping. Slow-twitch fibers contract more gently, but they can keep working for a long time, which is important for distance running. Everyone has both types, in different mixes, and training can change how they work.