STARTING POSITION:
You need to place a bench behind the Smith machine. Adjust the bar to the height that best suits your height and select the appropriate plates amount to put them on the machine. Step under the bar and hold it with the back of your shoulders. Make sure the bar is on your muscles and not pressing your bones Grab the bar with your hands, your palms should facing forward. Spread your feet at shoulder width apart. Place the dorsum of your right foot behind you on the bench and the left foot in front of you. Contract your pelvic floor and core. Lift the bar just a little and twist your hands to un-rack the bar.
MOVEMENT:
Bending your knees, slowly lower your body down until your right knee almost touches the floor while you inhale. Make sure to keep your right shin perpendicular to the floor avoiding the rise of the heel. Pushing mainly from the heel, return to the starting position while you exhale. Make sure you don't move your torso backwards while you perform the exercise. Repeat the movement for the specified amount of repetitions and then repeat with the other leg.
TIPS: While your are doing the exercise, move only the legs, make sure you don't move any other part of your body. Make sure your knee does not move toward the midline of your body.