Roller derby

Roller derby is a roller skating contact sport played on an oval track by two teams of five skaters. It is played by approximately 1,250 amateur leagues worldwide, though it is most popular in the United States. A 60-minute roller derby game, or bout, is a series of two-minute timed jams. Each team, typically with a roster of 15, fields five skaters during each jam: one jammer, designated with a star on their helmet, and four blockers. During each jam, players skate counterclockwise on a circuit track. The jammer scores a point for each opposing blocker they lap. The blockers simultaneously defend by hindering the opposing jammer, while also playing offense by maneuvering to aid their own jammer. Because roller derby uses a penalty box, power jams, in which one team has a temporary numerical advantage after a foul, can have a major effect on scoring.