Start: Set a bench lengthwise in front of the weight stack, and set a sturdy platform between the bench and the low pulley. Attach the straight bar to the low pulley. Grab the bar and sit up straight at the end of the bench facing the pulley. Rest your forearms on your thighs and hold the bar just above your knees. Set the balls of your feet on the platform, and lower your heels as far as you can.
Finish: Push from the balls of your feet, raising your heels as high as you can. Pause, then slowly return to the starting position.