Roller derby bouts are made up of two 30-minute periods and each period consists of jams (or plays) that can last up to two minutes. In order to go hard in every jam you have to train your body to work at a high intensity for short periods of time, says Topless.

That's why skaters do lots of high-intensity interval training with bodyweight movements like jumping jacks and mountain climbers. Strength is crucial in any contact sport, so kettlebell training is a big part of their workouts, too. To build explosive power, Topless does plyometric exercises like box jumps and burpees. And they practice staying agile with footwork drills like the ones football and soccer players might do.

In addition to all that, many players cross train with running or fitness classes, says Topless.