Parametric Acceleration  IV

Parametric acceleration occurs for clubhead pull along the centripetal force vector. Hence rotation is required. A golfer reduced to the most elementary form can be viewed as having two axes of rotation, a 'vertical' and a 'horizontal' axis. This is schematically indicated in Fig1. The vector sum (green) determines the swing plane, which is perpendicular to this resultant vector. For sure the situation is rather schematized but it is simple and straightforward.

Miura's parametric acceleration is associated with the rotation about the horizontal axis of rotation, (blue). But there is also a rotation about a vertical axis (red). A golfer swinging in-to-out or even out to the target is prone to increase his swing radius about the vertical axis. But swinging tightly to the left through impact can have the opposite effect, i.e., reducing the effective swing radius of the clubhead and increasing its speed.

Mandrin