Updated May 16, 2013.

The side or twist crunch is similar to a standard crunch with shoulders lifted from the ground and abdominals braced, except you twist the body to one side then the other in alternating crunches. With the medicine ball twist crunch, you hold a medicine ball at the chest and, as you lift, you swing the ball to one side and return. Here's how you do it.

1. Lie on a mat or surface suitable for doing floor exercises.

1. Select a medicine ball light enough to enable you to swing it to one side and return to starting position, yet heavy enough to make you work hard.
2. Lie on your back with your knees bent at about a 90-degree angle and your feet on the floor. You can hold the legs straight out, but keeping the knees flexed gives you more stability.
3. Hold the medicine ball at the chest. Brace the abdominal muscles.
4. Lift the shoulders as you would for a standard crunch, and swing the ball to one side at the same time. Return the ball to the chest as you lower your shoulders to the floor. You may need to lift the shoulders a little higher than you would in a standard floor crunch.
5. The ball should swing across the body to approximately the outside of the hip/thigh region. You can vary this position. As you lower the shoulders, bring the ball back to the chest position.

Find out more about weight training principles and exercise description if you need background information before you try this exercise.