Source: American Council on Exercise
If you watch sports on TV, at some point you’ve probably heard a commentator talk about an athlete having explosive or powerful muscles. For example, professional football player JJ Watt has received a lot of attention for his off-season conditioning program, which includes flipping a large truck tire. A sportscaster was recently discussing Watt’s training techniques and mentioned that Watt was working on his fast-twitch muscle fibers in an effort to become more explosive. At first this sounds kind of hokey—fast-twitch muscle fibers? Is that really a thing, and is it possible to do certain exercises that focus on one type of muscle fiber?
The answers, in short, are yes and yes.