Quadriceps
Calves, Glutes, Hamstrings, Core
Place box/bench behind you in rack.
Set bar in rack at upper chest height.
Assume front rack position (clean or cross-arm grip).
Lift bar off rack, step back, position feet shoulder-width in front of box.
Keep torso upright, elbows high.
Lower into squat until glutes gently touch box.
Maintain upright posture, don't relax fully on box.
Pause briefly.
Drive through heels to stand back up.
Repeat.