[BerntR]

For what it's worth I think the lever approach is insufficient in describing how Accumulator #4 works and how the Left Shoulder (and the right shoulder too) really powers the golf stroke. The lever III form doesn't account for pivot power.

If you assume that the Left Shoulder is the swing center I guess that a Lever III analysis should do, but the Left Shoulder is rotating around the center axis of the stroke. The left shoulder doesn't just deliver centripetal force that keeps the club in orbit. It is torqued around the swing axis and delivers Linear Force to the clubhead via the Left Hand.