I think one of the most rewarding aspects of roller derby is now I WANT to commit to working out. I WANT to be a valued member of team. There are moments when I see my teammates and just feel really, really bad for the opposing team, and I want to be one of them.
It helps that even when you are having fun/suffering, you are building up riDICulous amounts of endurance. Its amazing what you can push your body to do.
Also, roller derby gives you a great ***. "Derby Booty" is an expression for a reason