Actually they do come with warnings, but I'm just human enough to read them and ignore them. My ball rolled out from under me yesterday dumping me on the floor, hurting my shoulder. I'm nice and sore from it today. It sort of feels like a sprain. Can one sprain a shoulder? I'm thinking yes and if it isn't any better tomorrow I'll probably go to the doctor.
I had a wonderful workout on the ball otherwise, even getting back on it after my spill. It didnt' hurt immediately so I thought I wasn't hurt. My abs are a bit sore today too. ahhh! I know I worked out yesterday! Going to go run later this afternoon before the rain gets here again. April showers are supposed to bring May flowers so I better have some gorgeous flowers next month!