[Jeff]

The delivery path the hands take during the downswing depends on many factors (eg. kinetic sequencing pattern, amount of movement of the left shoulder socket leftwards during the earl/mid downswing, degree of secondary axis tilt, position of the hands at the start of the downswing, and aiming point variations).

The Iron Byron golf machine's peripheral hinge point (hand arc) has a circular path because its central arm is suspended from a fulcrum point that is fixed in space. However, human golfers produce an U-shaped hand arc because the left shoulder socket moves leftwards during the downswing and because the arms can be pulled down towards an aiming point ahead of the ball. The shape of the U-shaped hand arc is therefore individual golfer dependent.

Here is Sergio Garcia's hand arc - you can see that he has a straightish top U-section and a more rounded lower curve (with a smaller radius) and that combination results in a late release.



Here is Anthony Kim's U-shaped handarc. It is more rounded and it results in an earlier release - random release.



A rounded arc predisposes to club release because the pull on the grip is at an angle to the longitudinal axis of the clubshaft. A straight line pull (along the longitudinal axis of the clubshaft) doesn't predispose to release of PA#2. The second factor affecting the release is hand speed at the exact moment when the hands are going through a tight curve. Sergio Garcia has a late release because his hand arc is nearly-straight in the early/mid downswing and therefore there is no centrifugal force operant during that time period. Then his hands undergo a sharp curve-to-the-left movement at the exact moment when his hand speed is maximal - and that induces a very fast, but late, release. His hand speed is maximal at that time point because he has a perfect kinetic sequence.

Jeff.