It's too easy to be contemptuous of sports in which we aren't interested. Rhythmic gymnastics must take gifts and dedication. Trampolinists must share many of the qualities of the divers and gymnasts. Asking "what is a sport?" is as useless as asking "what is art?" Personally I am prepared to admire anyone with the talent and persistence to become excellent at anything. If I don't enjoy watching them, that is my problem, not theirs.