When most Americans hear the words -roller derby- today, they think of the kitschy sport once popular on weekend television during the seventies and eighties. Originally an endurance competition where skaters traveled the equivalent of a trip between Los Angeles and New York, derby gradually evolved into a violent contact sport often involving fake fighting. But after nearly dying out in the nineties, derby has been making a comeback. From a mere handful of leagues in the United States just a few years ago, there are now more than 17,000 skaters in more than 400 leagues around the world, with...