Dear Tim,
1st Question -- shoulder stroke
The lead shoulder moves both down and back in the backstroke, in a vertical plane of motion (i.e., straight down at the balls of the lead foot and also straight along the line from the balls of the lead foot toward the balls of the rear foot). The rear shoulder in the backstroke moves up and forward over the same ground reference (balls of feet), in a reciprocating fashion.
In the forward stroke, the shoulders start from the top of the backstroke, where the lead shoulder is low and back, while the rear shoulder is high and forward in comparison to the level starting position of each shoulder. The shoulders retrace their paths back to level and then the stroke forward of this point is just like a back-stroke in reverse: the lead shoulder goes up and back while the rear shoulder goes down and forward.
If you held a plank in front of your neck with both arms and hands straight out, with the center of the plank even with your neck, and then rocked the shoulders back and thru in a vertical plane, the plank would spin back and then thru like a propeller, and the pivot point of the center of the plank would not move in space. The same motion would occur even if the plank's center were nailed to a wall, so long as the plank could spin on the nail's shaft. Watching the ends of the plank would show that the lead end both goes down and moves towards the middle line of the level plank (a vertical line on the wall thru the center of the plank) -- so that is both down and back at once.
If you amputated your ams at the shoulders but still made the identical physical motion as above, then you would have a good vertical-plane stroke going back and under.
2nd Question -- reverse pivot and weight shift
No, ideally, there is no reverse pivot with the weight shifting to the lead-side foot as the back stroke progresses. But this is an oversimplification, as good putting technique does not necessarily plan for the absence of any weight shift, but is sufficiently adaptable that it can expect and react correctly in case one occurs.
So long as the head's center of gravity remains centered in the same plane that includes the pivot and balance point of the shoulder frame's stroke in the base of the neck (a second center of gravity), and so long as the OTHER balance point in the lower abdomen also is in this plane that defines the balance line from feet to head, so that these three separate centers of gravity remain in alignment during the stroke back and thru in the left-right and front-back dimensions), the symmetrical distribution of the body's mass is preserved and there is no weight shift. As the lead shoulder mass curls down and under backwards, the same mass on the rear side curls up and over forwards; if the neck stays aimed square and the head's center does not slide left-right or front-back, it does not matter if the neck or head "rolls" with the shoulder frame, so far as the balance in the body and feet is concerned. The balance with respect to gravity remains undisturbed.
However, this is the ideal, and the golfer needs to deal with the reality. The reality is that the centers of gravity get coordinated in a complex interaction. The head's center of gravity tends to tilt to the lead-side in the backstroke, while the shoulder frame center of gravity tends to slide to the rear in the backstroke, and the center of gravity of the lower abdomen tends to follow the center of gravity in the base of the neck (headed to the rear in the backstroke). The actual weight distribution into the feet may well en up balanced or staying balanced even though these different centers of gravity do their little dance together, or maybe not. Freezing one section of the body probably causes reactive motion in another section, as in the full swing, where freezing the head in the backswing is seen as causing problems, not solving them. That's why I teach "putting from the top," in which the top balance of the head-neck-shoulder complex in motion is paramount over stillness in the lower body. If the effort to keep the top complex in balance during motion provokes reaction in the lower body, so be it. If head motion is needed to keep the neck and shouder frame centered and in balance during the stroke, so be it. The trick is to know what causes what, and then what to expect and what to do about it when it happens during a stroke.
I teach keeping the pivot of the stroke still-but-rotating by brain-body techniques of top-of-body management -- the eyes, the head, the neck over a reactible lower body ("reactible" is better than "reactive" because I may get lucky and move so that the lower body does not have to react) -- in a way that does not cramp the stroke motion. A focus on the weight in the feet is only subservient to this top-of-body balancing. If the weight shifts a little in a particular stroke, it probably should have, and was needed to keep the top-of-body closer to perfect balance. Intending to feel no weight shift in the feet during the stroke may be a good exercise to learn more about your body in motion, but I don't think it is a good idea when actually putting. In fact, one exercise I use in teahing is to make a stroke that keeps the neck still-but-rotating even though there is a nice, dancy weight shift in the feet from side to side. The point is to train the balance in the top, regardless of what is happening in the lower body.
I am separately responding to a question about the head in the stroke motion, and this response will include more detail about balance and movement at the top.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
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