This exercise uses the weight of a cable machine to assist in a abs crunch.
Steps
Attach a rope to a high cable pulley. Place a bench in front of cable weight stack. Grasp the rope on over your shoulders and sit with your back towards the stack. With your feet firmly on the floor and keeping your hips steady, flex at the waist bringing your elbows towards your knees. Return to the starting position.
Tips
Perform this exercise in a slow controlled manner.