Does anyone use an exercise ball in their workouts. I've ben doing a routine with the recumbent bike & upperbody weight workout. They are both great. I love them. I have been trying to add in a Abdominal workout but no matter what I do they all make my lower back and neck really sore. Not good since I run a home daycare and have to be able to pick up the kids. I got an exercise ball today - hoping that using it for an AB workout will take some pressure off my neck and lower back. Anyone have any experience with these things? Any tips?