I agree. I can't move like they can either, nor can I handle the bouncing/jumping aspects. Modify the moves to a variation you can do and try to keep the pace as best you can. This goes for ANY workout video you encounter, not just the dance ones. There will always be some (if not many) moves that will be too difficult for you to do at that moment. Do the best you can, with modifications if necessary, and you'll eventually build up the muscle needed to perform the moves as directed.