That inflated exercise ball you bought a few years back can be used for more than just sit-ups and extra seating. In fact, exercises done on a stability ball can be more beneficial than similar variations incorporating machines. According to fitness trainer Marie Bodine, ball exercises allow for more than one muscle group to be worked at once. "They force you to focus on balance and stability as well as strengthening," she says. "When you're hooked into a machine you don't get to use your balance. This means you'll get strong in certain muscle groups, but your stabilizing muscles will remain weak. One benefit of stabilizing exercises is that they help you to avoid trips, falls and slips by increasing your reaction time."

Pump up your workout routine by following these step-by-step instructions for five of Marie's most effective ball exercises.

A. When you do this exercise you want to feel like you're squeezing your shoulder blades together. Start with your arms in an open position and your feet spread apart with toes on the floor. You want your arms to be slightly bent.

B. Raise your arms so that they're almost parallel with your shoulders. You don't want to feel like you're lifting with your hands, you want to feel that you're actually squeezing your back so that your arms rise. Repeat this exercise until you feel you can't do it anymore. You want this to be challenging. Concentrate on keeping your shoulders down and raising your arms together to squeeze your back.