Now I'm going to demonstrate how to do an ab crunch on an exercise ball. It's a little bit more challenging because with the ball you have to have a little more balance, you have to engage you core strength a little bit more before you progress to the exercise ball.
So I would start to master the ab crunch on the floor first. When you progress to the ball start out with your hands crossed in front of you. Notice that my spine and my torso are in an extension position to get that stretch in the abdominal region in the front. So your stretching your abdominals.
As you come up you hold that position for 1 or 2 counts and exhale. Come down again getting that nice stretch and that extension. Try to look straight above the head at the ceiling keeping the neck neutral and the chin neutral. Holding that for about 1 or 2 counts. So again, hold, exhale. You want to make it a little more challenging progress to hands behind the head. Same thing look straight ahead. That is the proper form how to do an ab crunch on an exercise ball.