Fitness fads come and go -- remember the thighmaster? -- but if you want a well-rounded workout, then embrace the fitness ball. It's no secret that exercise balls are a great way to add variety to your workout and improve strength in your core and lower body. But working out on a large, bouncy object might be intimidating for beginning exercisers. The key is to find the right size for your height. A ball that's 55 cm in diameter works best for those who are 5'4" or shorter. If you're 5'5"-5'11", try a 65-cm ball, and if you're taller than that, then a 75-cm ball will work. Exercise balls put any workout you do in an unstable environment, forcing your bottom half to contract to keep you stable. So if you're doing a chest press or curls, then your lower body is working as well, thereby increasing the work you're doing.
You can do abs work, flexibility work or yoga, and simply sit around on the ball. Use the ball instead of a chair, and you'll strengthen your core without even having to think about it. If you want to get a little more advanced, then the best sources of instruction are DVDs or online demonstrations. Inflated exercise balls are not to be confused with medicine balls, which are smaller, weighted balls used for strength training and can contribute to a great, fun workout. Both balls got their start in physical therapy and rehabilitation, but you can incorporate them to increase strength.