During my volunteer work as a physical therapist I took note that the exercise ball had a lot of practical uses and realized with some imagination it certainly can, and was being put to use as a valuable and fun piece of exercise equipment. I recently bought one for myself to practice and experiment with. It kind of makes you feel like a kid playing with a big ball and I think I’m going to have fun with this. Some of the exercises take quite a bit of balance and dexterity and I feel learning them well and adding in a few tricks will provide a fun way to introduce it to future patients. (And the added bonus of working on my own 6-pack ) There is a lot one can do toward working especially on his core, a lot for legs, or even entire body, and it’s also good for developing all the little stabilizing muscles which help provide better balance. They only cost $15-$20 and that often includes a pump and instructional DVD. You can virtually do it anywhere in your home and I’ve found I like messing with it while watching TV. There are some general guidelines when going to purchase a ball such as when sitting on it your legs should bent at 90 degrees, but this is not set in stone: 4'6”–5’0”...........45cm ball (18 in) 4'11"-5'7"..........55cm ball (22 in) 5'8"-5'11"..........65cm ball (26 in) 6' and taller.......75cm ball (30 in) The ones I looked at were undersized so I bought the 75cm one. It had a band to put around it for sizing when blowing it up but was getting overly hard before getting to the maximum size. I’m going to check out some other brands and also get different sizes because it is more practical to have a few more sizes available for different exercises. Scroll down for a few basic exercises which have been animated: http://www.abs-exercise-advice.com/free-fitness-ball-exercise.html#plank There are many more exercises to learn and do which can isolate different parts of the body. Add in some dumbbells or tubes and the versatility is almost limitless!