AZ's idea is flawed for many reasons. First of all, he relates the axis to the clubshaft. That would only make sense if the clubshaft and arms were in a straight line relationship, and if the arms rotated perpendicular to his "axis of rotation".
The only golfer who approaches that pattern is Moe Norman.
Moe stretched out his arms, and he also acquired a zero PA#3 angle by using a mid-palmar grip. That allowed his clubshaft and left arm to become in a near-straight line relationship.
However, nobody can swing like Moe!
The only person who mimics Moe's action is a hammer thrower
A hammer thrower rotates his arms and shoulders along the same plane of rotation that is perpendicular to the axis of the rotating torso.
Modern golfers, by contrast, choose to have a PA#3 angle at address, which allows then to hang their arms vertically at address. They then swing their arms on a different axis (more vertical) then they rotate their shoulders. They also choose to change planes during the downswing.
Garcia drops his club from the TSP to the hand plane in his downswing action.
The blue line is the TSP and it is perpendicular to the axis of rotation (red line). However, SG's clubshaft is on the hand plane (green line) and it is
not perpendicular to the axis of rotation.
This idea of an "axis of rotation" was already thought of by Luther Blacklock. He developed the idea of the optimum biomechanical swingplane (OBSP).
The idea came from the famous Da Vinci man.
Image 1 shows that idea where a line drawn through both arms passes across the spine at the level of the upper sternum. Image 2 shows a tilted man - mimicing a golfer's bent-over posture.
Image 3 shows the OBSP going through LB's (LB is dressed like Hogan) upper sternum. LB's idea is that the it is the clubhead, and not the clubshaft, that is on the OBSP (that passes through the upper sternum). That idea makes more sense than AZ's idea.
Image 4 shows how the upper sternum (black dot) and the clubhead are on the same horizontal plane when he stands erect, and that plane is perpendicular to his erect torso at the level of his upper sternum.
This idea gave rise to the Explanar - you can see LB standing in the Explanar, and note that his upper sternum is on the OBSP (Explanar loop).
In other words, when swinging on the OBSP, a golfer doesn't have to rotate the arms on the same rotational plane as the rotating shoulders.
I think that LB's idea is more rational than AZ's idea, but skilled professional golfers still choose to not swing on the OBSP. They choose to swing on a variety of planes eg. compare Furyk to Hogan to Garcia.
The same phenomenon applies to baseball pitchers - they throw overhand, underhand and horizontally (side-throw). Can one rationally argue that there is only one plane that baseball pitchers should be throwing - based on some
theoretical concept of biomechanical/mechanical efficiency?
Jeff.