Incorporating a medicine ball into your workouts is a great way to increase the difficulty while adding more strength. One nice thing about a medicine ball is that it is easily transportable so you don't necessarily need to be in a gym using weight machines in order to get your workout in.

Ab work is great using a medicine ball because it will add further resistance to typical crunches as well as providing more individual exercise options. To use it while doing crunches simply hold it out slightly in front of your face or for even more challenge right behind your head. As you crunch up still focus in on using your abdominal muscles to perform the action (while not using momentum from your arms).

Another great way to work the abs using this piece of equipment is to stand back to back with a partner. When you both are ready, start twisting from side to side and handing the ball of to each other as you do. Once on of you receives it you want to turn so you meet at the other side of your body and pass it off once again.

Try to do this action as fast as possible while still maintaining proper back alignment so you do not begin to suffer from back pain.