At this point, the pilot gets the plane in the "dirtiest" configuration possible, i.e. the airplane is fully configured for landing at the slowest possible speed; flaps fully extended, speed brakes deployed, gear down. By now, the plane is on dat glideslope and dropping agressively. The speed brakes disrupt the lift over the wing creating turbulent air and the aircraft begins to shake, as though it's really struggling to stay in the air.