Standing tall with your chest up (A), sink your hips back and bend at the knees, squatting down until the crease of your hips passes below your knee (B).
Standing tall with your chest up (A), sink your hips back and bend at the knees, squatting down until the crease of your hips passes below your knee (B). Drive back up explosively and repeat, try to keep your heels on the ground and torso upright.