Roller Derby is a contact sport played by professional teams as well as amateur teams. It has turned into mostly a sport for women players. The rules vary between leagues, but usually two teams of five players each skate pack-style counter-clockwise around a thin track. The two positions in Roller Derby are blockers and jammers, and the pivots are blockers that set the initial pace at the start of the derby.
Jammers in Roller Derby try to get through the pack and the first one who does is the lead jammer. The lead jammer has the right to stop the jam, and the decision to do so is considered a strategic one. Points are scored when the jammers go through the pack a second time. Blockers do their best to stop the opposing jammers, but they also have to help their own jammers move through the pack by doing what is known as whipping. Whipping means pulling or pushing the jammers, and the jam is over either when it is called off by the lead jammer, or when a set period of time is reached, such as two minutes.
The sports entertainment style of Roller Derby has its roots in the Transcontinental Roller Derby that was started by film publicist Leo Seltzer in 1935. Pairs of skaters lapped around a track in 11 1/2 hours every day to try to skate the equivalent of the approximate distance between Los Angeles and New York City. Seltzer took his event to different cities and charged spectators admission. Eventually, the show turned into the sport we know today, as new rules and strategies kept being added.
The International Roller Speedway, sometimes called Roller-Catch, started touring Europe and the Philippines in 1937 — two years after Seltzer's event. Other roller teams started up in the 1960s, but Seltzer's Roller Derby, then run by Leo's son Jerry since the late 1950s, was the only one that was ever really popular. It lasted until 1973 when they closed it down, claiming high overhead costs. Attempts to bring the sport back were not really much of a success until the early 21st century when Roller Derby teams, mostly women's teams, began forming in many North American cities.