At the top of the swing, the golf club remains at a fixed angle to his arms (since his wrists are angled). But at the bottom of the swing, the golf club begins to "release" and the angle between it and his arms begins to increase rapidly (since his wrists are now uncorked), and as a result the club moves radically towards the 'external. At the bottom of the swing the golf club is almost perfectly parallel to his arms. This is where contact with the ball occurs. Part of the physics of a golf swing (from the golfer's perspective), means finding the release point (wrist uncorking) so that in the bottom position, where the player's hands are directly over the ball, the golf club both in the vertical position parallel to the arms. This will maximize club head speed at impact and result in maximum distance