Take position in the ab crunch machine with your feet under the ankle rolls and your palms gripping the handles above your shoulders. This is the starting position.
Commence the movement by contracting your abdominals and breathing out as you crunch down from the waist.
At the maximum contraction point, squeeze the abs hard before slowly reversing the torso back to the starting position, inhaling as you do. Do not let the weight stack come to rest at the starting position until the set is complete.