Important stabilizers (not highlighted): Erector Spinae, Rectus Abdominis, Obliques, Anterior and Lateral Deltoid, Clavicular (Upper) Pectoralis Major, Levator Scapulae
Mechanics: Compound
Force: Push
Starting position
Stand in front of a box or bench with a barbell on the front of your shoulders and your hands crossed over the barbell to keep it stable.
Spread your feet so that they are positioned a little wider than shoulder width (i.e. wider than with a regular barbell front squat).
Point your feet and knees out diagonally in the same direction.
Execution
Keeping your torso upright, inhale as you slowly squat by first pushing your hips backward and then your knees outward.
Stop and hold for one second when your butt touches the box. Do not sit on the box and rock backwards.
Exhale as your spring back upward without rocking forward.
Repeat for the prescribed number of repetitions.
Comments and tips
Control the movement all the way down to the box. Do not sit on the box and rock backwards, as this leads to compression of the spine; just pause.
When you spring upward, drive through your heels, and do not rock forward.
Keep your shins vertical and your knees out.
Keep your feet and knees pointing in the same direction, and your feet flat on the floor.
For safety, use a power cage, with the safety pins set at an appropriate height to prevent injuries.
The purpose of using the box in the barbell front box squat is to eliminate the stretch reflex, which occurs at the bottom of the squat and aids in the concentric (ascending) phase of the repetition. Eliminating the stretch reflex makes the exercise more difficult and therefore allows you to use less weight to overload the front squat movement pattern.
By eliminating the stretch reflex, the barbell front box squat allows experienced squatters to improve their front squat strength, which carries over to their barbell front squat.
As less weight can be used with the barbell front box squat, the exercise is also suitable for people with knee problems.
The barbell front box squat (or any type of box squat for that matter) is not suitable for beginners, who first have to learn how to squat.
If you don’t have a box, use a bench.
The height of the box or bench should allow you to descend until your thighs are at least parallel with the floor.