>> ron: very difficult tricks, yes. >> dr. mary ann roberts: yes, very difficult tricks and if they fall to the floor and hit their head, then they are going to be in serious difficulty. >> ron: yeah, because females today, their athleticism is amazing and they're working very hard and becoming stronger and they're going to have the same kinds of injuries that any man would have too. >> dr. mary ann roberts: oh yes. >> dr. richard roberts: they're breaking into sports like hockey and wrestling that have been traditionally male dominated as well. >> ron: we have to take another break. we'll talk about the book pour too and how you collaborated