What it is: A variation of traditional Pilates that calls for people to bang drumsticks and jump around to loud rock music.

Why it became popular: Give anyone—literally, anyone—a set of drumsticks and they'll immediately start pretending to play the drums and moving around all over the place. We've all seen actual drummers do it so many times that we're naturally inclined to do it, too. But now, people can do it and get a workout at the same time with Pound, which requires quite a bit of movement. But that movement is made easy by the drumsticks that people are given, as well as the music that's played during Pound classes. Rocking out has never looked or felt this good before.