Position yourself for this exercise by standing in a power rack with a box behind you. The box should be at an appropriate height so as to allow you to squat to a depth where your upper thighs are parallel to the floor. Step underneath a loaded barbell and place it across the backs of your shoulders. Squeeze your shoulder blades together and rotate your elbows forward, like you are trying to bend the barbell across your upper back. Now, take the barbell off of the rack and position yourself in front of the box to perform the movement. A wider starting stance (wider than shoulder width) ensures that you are targeting the hamstrings for this exercise. You should be looking directly forward. To execute the exercise, push your knees and butt backwards in order to begin your descent. Focus on sitting back with your hips until you are fully seated on the box. Ensure that, even when you are sitting down, you do not let go of any tension in your lower or upper back. The moment you let go of this tension, the box squat becomes an unsafe exercise. Pause briefly when sitting before driving through your heels and pushing your knees out to drive your body off of the box until you are once again standing upright. Repeat for the prescribed number of repetitions.