Whether it all started out as fight prep for a movie role (here’s looking at you, Ryan Gosling) or real-life self defense (sorry about those bullies, Ryan Phillipe!), celebrities can’t seem to get enough mixed martial arts these days. And we can’t say we blame them.

MMA isn’t just a killer total-body workout that ups your physical toughness, but it makes you mentally tough as well. It teaches disclipline. It builds confidence. It helps you stay calm in the face of chaos. (That sounds like a pretty good Hollywood survival strategy, doesn't it?)

So here, 13 stars who can kick your butt, yet keep their cool doing it. Click through—and get ready for a surprise or two.