The stability ball will strengthen your core, and you can do strength training while sitting on it. And because rubber is hot and sweaty to sit on, you will be motivated to get up and move more and not just sit around for hours doing just one thing! So lose your comfort chair and get moving!!
You can do balance moves on it, and sit ups, just about anything! Its a no excuses workout! No impact for persons with joint problems! It will train you to sit up properly and your back will love you for it!! Just Do It!!