Set the cable at the highest level on the machine using a rope attachment.
Grab onto the rope, kneel down and position your wrists on either side of your head. Begin with your hips back and slightly flexed.
While keeping your hips stationary, consciously flex your abs and crunch your elbows down toward your thighs until you feel a strong contraction in your abs.
Raise yourself back up following the same path until your spine is slightly hyper-extended, and then repeat.