POSITION YOURSELF FOR THE LIFT
1) Set your stance. You should set your stance as wide as possible, with your knees pushed out to the sides and your feet pointing straight ahead or slightly outward. Using a wide stance when squatting will place greater stress on the posterior chain (glutes, hips, hamstrings, and back) where it belongs, not on the quads (it’s a common misconception that the quads are really important for squatting maximal weights).
2) Set yourself to the bar. Get under the bar, push your neck into your traps, and position the bar in the groove of the upper back (not above the traps). Pulling your shoulder blades together may help you maintain the proper position of the bar. With a wide-hand monkey grip on the bar, pull the bar tightly into your traps, while pulling your elbows up and under to engage the lats (do not flare your elbows out).
3) Set your core. Now that your upper back is tight and you are positioned for the lift, you’ll need to tighten your midsection. Expand your abdomen (not your chest) by taking a deep breath through the diaphragm, pulling as much air as possible into your abdomen by pushing your belly into your lifting belt. In order for the power from your lower body to be maximally transferred to the bar, your abdominal muscles must be tight throughout the entire lift. This will also stabilize and support the lower back. If your core isn’t tight, there will be unnecessary dissipation of kinetic energy through the core, in addition to the inherent loss of kinetic energy resulting from the collision that occurs when you sit down on the box. This will translate to an overall reduction in kinetic energy and stored stretch reflex that contributes to your ability to explode off the box as you initiate the concentric phase of the lift.
4) Lift the bar from the rack. With the core as tight as possible, lift the bar out of the rack by arching your upper back, lifting your chest up as you drive your head back, then pushing the bar up evenly with your legs. You should also be forcing your knees out to the sides and pushing out on the sides of your shoes, never downward, as though you are trying to spread the floor apart. This is to further activate the hips. You are now ready to descend into the eccentric phase of the lift.
THE ECCENTRIC PHASE— DESCENDING ONTO THE BOX
The eccentric phase begins by breaking the hips first, not the knees. You do this by pushing the glutes and hips rearward (then follow with the head) as you push your feet and knees out, thus forcing you to sit back (not down, or your quads will dominate). This is the only way to activate your hips and glutes to their full potential, to ensure maximum involvement of the posterior chain. By sitting back, rather than down, you place the glutes and hamstrings in a highly desirable stretched position. While descending to the box, continue to keep your head and chest high, maintain a tightly arched back, and be sure your core is as tight as possible by keeping your abs pushed out until you are sitting on the box.