Assume a comfortable standing position, with a short box positioned next to you. This will be your starting position. Quickly dip into a quarter squat to initiate the stretch reflex, and immediately reverse direction to jump up and to the side. Bring your knees high enough to ensure your feet have good clearance over the box. Land on the center of the box, using your legs to absorb the impact. Carefully jump down to the other side of the box, and continue going back and forth for several repetitions.