I wanna do rollerderby so bad

My parents wont let me do ‘fighting sports’ or whatever and also i feel like im copying someone when i say i want to. The friend i blocked i think im copying her but its like ive always wanted to do roller derby, the first time i was at a roller skate party my mom asked if i wanted to sign up for speed skating, and i really wanted to but at the same time i was in cheer or gymnastics. I still said yes and my mom was going to but she never did, and eventually i took interest in roller derby but im scared ti ask because in that sport u can shove people out the way so they might say no.