WHAT IS ROLLER DERBY?
Roller derby is a full-contact sport played by two teams of five members roller skating counter-clockwise around a track. Roller derby is played by approximately 1,250 amateur leagues worldwide, mostly inside the United States. Game play consists of a series of short match-ups, called jams, in which both teams designate a jammer and compete to pass more opponents than the other team. Teams need to play both offense and defense simultaneously in order to allow their Jammer to score unhindered, while preventing the opposing Jammer from doing so. Wikipedia