Sand Bag Box squat:
This lift is very similar to the barbell box squat. The box that you are using should have you sit so your legs are just below your knees. After placing the bag across your back shelf, slowly lower yourself in the squatting motion. Keep your back tight and eyes forward throughout the entire lift. Sit totally down on the box, relieving the weight from your feet. After unloading your legs quickly stand back up in proper squatting motion.