This exercise is good for abdominal strength and endurance. It is safe and easy to do. The crunch is one of the most incorrectly performed exercises. This exercise works best when done slowly.
A workout mat is recommended. In the supine version of the stability ball crunch, the legs are elevated on the ball. This puts the lower back in the best position for this exercise. The hands can be placed just about anywhere: behind the head, across the chest, out to the side, etc. The main focus here is the abs. Once the hands are in place, simply contract the abdomen. As you do so, breathe out. The shoulder blades should come up no more than 3 inches off the floor. The "crunch" should be held for at least 2 or 3 seconds.
IMPORTANT: The head should always remain straight with the chin up. Look at the ceiling when you are performing this exercise. The back should always remain flat on the floor at all times.
Lie down with back flat. Elevate legs on ball. Position hands across chest.
Crunch the abs and hold for 2 - 3 seconds. Exhale.
Slowly return and repeat.