Position a Smith machine bar a couple feet off of the ground. Ensure that it is resting on the safeties. After loading the bar to an appropriate weight, lie underneath the bar. Place the middle of your feet on the bar, tucking your knees to your chest. This will be your starting position. Begin the movement by driving through your feet to move the bar upward, extending the hips and knees. Do not lock out your knees. At the top of the motion, pause briefly before returning to the starting position.