Adjust the back pad so that the knees are aligned with the axis of rotation on the machine. Extend knees to straighten the legs and place the back of the lower legs on the ankle pads. Lock down the knee bar and sit tall. (Note: knee bar should be above the knee, not below). Engage abdominals and pull navel in to stabilize the core. Maintain a neutral (flat to normal) spine. Exhale and curl your heels down and back toward your glutes by flexing your knees. Pause then slowly raise your heels out and up by extending the knees. (Note: do not let knees fully extend until the end of the exercise). Repeat.