It seems easy, girls with ribbon, ball or hoola hoop, in their pretty little dresses, dancing around. 
But in reality even the easiest element of their sport is barely possible to do by someone without special training. 
Some of these girls spend 25+ hours a week in the gym training and when there is no school, they may train up to 50 hours a week. 
They do stretch until they cannot hold back their tears, then they wipe the tears and go on with the training. They are so flexible that sometimes they can give themselves a black eye with the heel of their foot by swinging it across their back and over their head. They can throw a ball as good as a basketball player and can handle clubs like a circus performer, they can group, fall and roll like a wrestler and can do a Jean Claude Van Damme trick with splits between chairs better than anyone else.
In the past other athletes have attempted to do a rhythmic routine (as a part of a TV show) and failed. Here's a video of one of Australian leading Juniors. 
This 15 year old really makes it look easy.