Begin by positioning yourself underneath a Smith Machine barbell. Make sure the bar is across your upper traps and not your neck. Stand with one foot on the floor and another foot on a bench or box. Brace your core and keep your chest up as you drive all your weight through your elevated leg until it's fully extended. All the while exhaling as you do so. Slowly return to the start position by bending at the knee and driving the hips back, inhaling as you do so. Repeat all the required reps on one leg before changing to the other.