Exercise balls, or stability balls, have been around for awhile but many people don't know what to do with them. The benefit of working out on a stability ball versus a weight-bench is the extra energy and muscles your body uses to keep still because the ball wants to roll around (with you on it, wee!). It's up to your core muscles to keep you balanced and stabilized, and therefore what was just for the upper-body becomes a whole-body exercise.

Good news for beginners -- stability balls are adjustable to difficulty level by how much you inflate them. If you're worried about rolling off and landing awkwardly on the floor, simply under-inflate your ball to a level that's more comfortable. Then you can add more air as you progress week by week.

Chris Freytag, with Prevention magazine, has created a stability ball workout adjustable from beginner to veteran, as well as some general pointers for people just getting started.