The Therapy Ball is an important training tool at our clinic. The ball adds balance/coordination to simple exercises – making the exercises more life-like and forcing your body to learn control rather than just strength.
Lack of muscle control is believed to be one reason why many people suffer back injuries even with low stress tasks – improved control appears to reduce injury risk. Many floor exercises can be revised to add balance/coordination aspects with the addition of a therapy ball.
Here are some basic ball exercises.

The Crunch: The same crunch exercise you would do on the floor – contract the stomach muscles bringing your chest towards your hips. The ball reduces stability, making you work harder to balance. Position the ball higher on your back for less resistance, lower towards your hips for greater resistance. To increase the balance difficulty move your feet closer together.
Make sure to keep your chin tucked in. 15 repetitions.

Wall Ball Squat: An excellent exercise for the leg muscles. Strong legs help reduce stress on the lower back by improving lifting and bending postures.
Start with your legs extended in front. With the ball starting in your lower back slowly squat down until your thighs are horizontal. Rise back up slowly. Repeat 15 times.
For increased difficulty, move feet closer together (or try one foot!), or start the ball higher up your back and push into the ball as you stand back up.

Ball Superman: Strengthens the lower back muscles
Start, kneeling, with your feet against the wall, shoulder width apart, ball against your thighs. Lie over the ball and then push off the wall slowly. Stretch out keeping your back and legs in line. Hold for 10 seconds then roll back onto your knees. Repeat 10 times.
For increased difficulty move your feet closer together or extend your arms overhead.

The Ball Pushup: Same as a normal push-up – but the addition of the ball increases balance and varies positions.
Start with the ball under your thighs, balanced on your outstretched arms. Slowly lower yourself towards the floor, and then push back up again. Repeat 15 times.
Increase difficulty by moving the ball lower and lower down the legs, moving your hands closer together or adding forward/backward roll.