The curl-up strengthens your stomach muscles.

Here's how to do it.

Start by lying on your back with your knees bent and your feet flat on the floor.

Cross your arms over your chest.

Now slowly tighten your belly muscles and raise your shoulder blades off the floor.

Keep your head in line with your body. Don't press your chin to your chest.

Hold this for 1 or 2 seconds, and then slowly lower yourself back down to the floor.

Do this 8 to 12 times.

Remember, if an exercise makes you feel worse, stop doing it.