Cable Crunches

Attach a rope handle to an overhead pulley and kneel down about 2 feet from the weight stack with the two ends of the rope handle in your hands about 3 inches above your head.
 
Simultaneously bend at the waist until your forehead nearly touches the floor and pull your hands down to the level of the top of your head.
 
Reverse the movement and return to the starting position.
 
The entire motion should be done in a smooth, controlled manner that lasts about 3 seconds, with the downward movement no faster than the upward.