I dunno if any of you has ever seen one before. But they just rolled one into the gym I go to for the attendant to sit on. I immediately thought the claim would be that it works your core while you sit on your ass. So I did a little search, and here is the claim.
Looking for an alternative to the traditonal desk chair? Many have found the simple (and inexpensive!) solution is an Exercise Ball (aka Swiss ball, balance ball, fitness ball). Exercise Ball sitting encourages better posture as well as motion in the low back and pelvis. Try the number one burst resistant ball in USA - FitBall. The Ball Chair, Sit-A-Round Ball Chair and the ErgoChair egg shaped ball chair are just elaborations on the theme - adding wheels, height adjustments and backrests.
So, now you can get fit by just ‘sitting’ on a Swiss Ball?
Think I’ll place my order today.