For those of you who aren't familiar with the stability ball, it's like a big beach ball; you lay across it to exercise your abdominals and stretch your back. If you're serious about your game, you should buy one right away! I'm not kidding - every golfer should have a stability ball in his or her home.
Why am I so serious about this? Because the weakest and most injured area for most golfers is the lower back. Why? The golf swing puts tremendous stress on the back due to the torquing of the upper body over a stable lower body. If you're not strong and flexible in this area of your body, you'll get injured. It's as simple as that.
Why use the stability ball? The stability ball is ideal for training the core because it's unstable and its round surface allows for a greater range of motion. It forces you to use the stabilizer muscles of the body to stay on the ball. A fuller range of motion will recruit more muscle fibers. The more muscles fibers recruited, the fuller the development of those muscles.
The unstable nature of the ball requires you to stay alert and maintain a sense of equilibrium. That's very similar to your golf swing. This also removes any boredom from your routine.
Training aids are a huge business for the golf consumer. In my mind, the stability ball is one of the best and least expensive training aids out there. Being able to use it in the convenience of your home (or even when you travel) makes it an even better and more useful training aid.
There are several books that outline exercises that can be done on the ball. It's important for you to have an idea of what to do that will help your game - not hurt it. I use the stability ball in all of my training sessions, both in person and through my online golf fitness program. The results are staggering. Not only are golfers seeing big increases in driving distance and accuracy, but in a huge reduction in back injuries and strains.
For most golfers, back injuries are very common and most frustrating. What a great feeling to do a few exercises in the convenience of your home and see the results so quickly. What a nice return on investment. Go out and buy a stability ball - it'll be the best purchase you've made in a long time.