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. ...
