STARTING POSITION:
Select the appropriate resistance on the weight stack. Get on your knees. There should be a cable with a rope that is attached to a high pulley. Grab it and pull it to place your hands in front of your head.
MOVEMENT:
Using your abdominal muscles, curl your spine and move your elbows toward your hips. Exhale during the movement. Return to the starting position in a smooth movement while you inhale. The moving weights should not touch the rest of the stack.
TIPS: The exercise key is quality over quantity. The trick is to perform the exercise using proper form.