Sit on the machine with your back against the cushion and adjust the machine you are using so that your knees are at a 90 degree angle at the starting position.
Raise the weight by extending your knees outward, then lower your leg to the starting position. Both movements should be done in a slow, controlled motion.
Begin by standing in front of a sturdy box or bench that is about knee-height, holding a barbell across your upper back and shoulders, using an overhand grip.
Place your right foot on the box and push through the heel to lift your body up and onto the box.