[Pentegarn]

In the states, women's roller derby is a sport. Inasmuch as it has rules and a scoring system.

As best as my memory will allow, I will try to explain what I remember of it.

The teams roller skate in laps. I believe each team has a 'jammer'. Her job is to lap the opponents team. Each team takes timed turns on offense. The team gets a point every time the jammer laps the opposing team. The opposing team can block the jammer in a limited way by trying to use their body to get in the jammers way. There is no shoving, striking, or (and this is where I may be off on the rules a lot) use of elbows or forearms. I believe the jammer has a small team to protect her, while the opposing team has enforcer like women who are supposed to knock her down legally. Though you will need to check your league policy to see what is or is not legal in that regard.