What are some exercises I can do using an exercise ball?

What's the deal with those big bouncy balls taking up space around the gym? Stability balls (also called exercise balls, balance balls, Swiss balls, or fitness balls) are more than just fun to sit and bounce on-they're a great way to improve strength, cardio endurance, and balance. By tackling basic moves (like push-ups, squats, and planks) on an unstable surface, muscles get more bang for their buck. Stability balls are also great for getting back into shape after an injury because they can reduce muscle and spinal strain during certain movements.
To get the most from a bouncy fitness routine, make sure to choose the correct size stability ball. (Note: some moves below use a larger or smaller than normal ball. For most exercises, though, it's best to have correctly sized equipment.) Most balls come in three diameters based on the user's height: 55 cm for those between 4'11" and 5'4," 65 cm for people between 5'4" and 5'7," and 75 cm for tall drinks of water between 5'11" and 6'7." A good rule of thumb for finding the right fit: Sit on the ball and make sure the hips and knees are at right angles with the floor.
Reps and sets will depend on fitness levels, but for most of these exercises, we recommend doing 3 to 5 sets of 10 to 20 reps. After a few workouts, try bumping up the reps to really test that strength. Ready to go? These moves take the stability ball way beyond the basic crunch.

1. Overhead Ball Squat
Squat and Reach
Ready to use the arms and the legs? For this one, complete a traditional squat, while holding the stability ball with the arms extended overhead. Adding weight (nope, not quite light as air) while keeping the torso in an upright position engages the shoulders and deltoid muscles. Go for 10 to 15 reps of this bad boy.

2. Wall Squat
Put those quads to work with this power move. Stand about three feet from a wall with feet shoulder-width apart and the back to the wall. Place the ball between the lower back and the wall and squat down slowly until the legs form 90-degree angles at the knees. Use the ball to support the back as it rolls from the lower back to the shoulder blades. Slowly stand up again, and repeat for 10 to 15 reps.

3. Standing Ball Squeeze
If you embarrass easily, try this move at home. It may look funny, but it seriously works the hips, lower back, and inner thighs. Stand upright and place the ball between the legs, so the center is about even with the knees (it should not be touching the floor). Squat down until knees form 90-degree angles, squeezing the ball to stay balanced. Hold the position as long as possible, working up to 30 to 45 seconds per set. Note: For this move, consider using a ball that's not the perfect fit. A larger ball makes this move more difficult, while a smaller ball is a little easier on the thighs. Beginners can also use a chair or wall for help with balance.

4. Hamstring Curl
Hamstring Curl
Lie on the floor with arms extended perpendicular to the torso and lower calves and heels resting on the ball. Engaging the glutes and abs, lift the hips up from the floor. Use your outstretched arms for stability-you'll feel wobbly! Exhale and slowly bring the knees in towards the hips, so the feet are resting flat on top of the ball. Pause for a few seconds in this position and then inhale, straightening legs out again. Keep those hips up the whole time to get maximum gluteus maximus benefits. Aim for 10 to 12 reps of this total-body move.

5. Squat and Reach
Get the blood flowing with a slow and steady squat that works your arms and abs as well as legs. Hold the ball with straight arms so it's about level with the face. Squat down, bringing the ball all the way to the left side, just above the left foot. Hang tight in this position for three slow breaths, and then untwist the torso and return to standing before repeating on the other side. For the best results, keep that down in the squats and hold arms straight out in front of the torso. Try 10 to 15 reps of this twisty move to get the arms, core, and legs in tip-top shape.

6. Ball Lunge
Ready for the balance big leagues? While standing, place the ball behind the body and put one foot top-down on the top of the ball. Step the other foot out about six inches, and bend both knees in a deep lunge. Make sure the knee of the front foot does not go over the toes. (For the stability-challenged, a chair or railing can provide extra support.) This advanced move will test stability as well as strength, so shoot for 8 to 10 reps (or as many as you can do with proper form) on each side.

7. Reverse Extension
Last but certainly not least, time to work that. Start with your chest on the ball, with fingertips and toes resting on the floor. Roll forward so hands are under shoulders and hips are directly touching the ball. With the feet together and the core engaged, lift the legs straight from the floor until they are in line with the torso. Hold for a beat and then repeat. Try for 12 to 15 reps before heading back to solid ground.

Here is a list of over 40 exercises using an exercise ball with a description and picture of how to correctly execute each.

http://www.ball-exercises.com/exercises/index.html