Start: Use a light weight-perhaps one-third of what you'd work with on back squats-and go for speed and power Stay away from this one if you've had back problems. Set up for a back squat with the barbell resting on your traps. Then squat down quickly until your thighs are at a 45-degree angle with the floor.
Finish: Immediately change directions and push from your calves to straighten your body so explosively that your feet come off the floor a few inches. Land as softly as possible on your toes, then immediately descend back to the starting position as you shift your weight to your heels.