Art,
Is it possible to consider this by itself or do do have to take into account where the lead arm/club is (Lining up the club for impact) also?
Mike, two research references that could help you are (1) a series of papers on 'Hip Velocity" characteristics during the golf swing by Dr. H Gulgin, (starting with her thesis), and (2) "Three Dimensional Kinematic Model......instantaneous screw axis theory"A.S Vena, another interesting thesis.
From these, and other dynamic balance related research papers, I have concluded that every golfer, and in fact every swing produces an imbalance of forces during the downswing that must be minimized to result in an acceptable golf shot. Some of these significant imbalances are the centripetal forces that develop from the changing angular velocities of the pelvis, the torso the shoulder girdles, and of course the much published and understood 100 plus pounds along the driver shaft around club to ball contact. Since, with the exception of the rotation of the pelvis, all other centripetal forces are 'in front' of the golfer, the only chance to counter these disturbances is to develop pelvic centripetal forces that face backwards behind the golfer. In my opinion, that characteristic has a chance to develop ONLY if the predominant 'screw axis' of rotation, at least until ball contact is in the vicinity of the right hip joint. Of course this is very sensitive to body shape, weight distribution etc., but the lower body dynamic stability margins are enhanced with this pelvic axis in/near the right hip.
Hope this is clear, and helps, and to complete the answer to your question, this is needed during the entire downswing, and completely independent of and specific lead arm/club position etc. In summary, every golfer needs positive dynamic stability margin, especially from the lower body, or else natural, instinctive, involuntary reflex actions will over-ride the intentions of a good golf swing to satisfy the higher priority human body stability and survival dynamic requirements.
