[BerntR]

The left shoulder joint is IMO very significant in powering the swing. Its offset to the swing center means that it produces linear force and therefore swing speed by simply pulling the arm. I'm not referring to the shoulder throw enabled by pp#4, but the continous pull from the shoulder throughout the stroke.

There is some serious lag between the left shoulder and the left arm at the top. And also some serious lag pressure in the shoulder joint throughout the downstroke if the alignments allows it. The rigidity of the shoulders has a similar effect as a very sturdy pp# pressure point and totally dictates it to keep up with the pivot. No matter what resistance it faces during release and impact.

The "lag pressure point" in the left shoulder joint enables a throw-out action of the whole lever assembly. And it doesn't require pp#4 assistance to work either. The shoulder joint delivers power from the pivot to the ball. Just like any other power package.

But the left shoulder movement and location is geometrically misfit - too flat and above the inclined plane. So the shoulder needs help. If the left shoulder were left alone to power the club it would possibly pull the club outside the inclined plane. When the swinger rotates pp#3 to the aft of the clubshaft he will promote a downwoard directed force from pp#3 in the down stroke. More downward than the "from behind" pressure in a hitting stroke. This downward force will to a certain extent balance out and redirect the outward tendency produced by the left shoulder. Some of us use hip tilt, sequenced release, plane shift, pressure point rotation and basically any legal trick in the book to conter-balance the outward biased delivery from the left shoulder.

If we were to vote for an accumulator no#5 my vote would probably go to the left shoulder joint. Can't live with it, can't live without it.