[Jeff]

12PB

You wrote-: "Jeff . . . Why should we pivot like that?"

Because there is no other way. What I mean is that if a human being does nothing more than rotate the pelvis 45 degrees by moving the right femoral head backwards/leftwards, and he lets his body/head move naturally/passively in an unrestricted manner, then he will end up with a reverse K posture. BM is exaggerating the upper body rightwards tilt motion.

In a human golfer, who consciously decides to keep his head stationary during the 45 degrees pelvic rotation movement, the natural movement of the upper torso becomes restricted and that is why the mid-upper thoracic spine becomes verticalized (when it would normally continue to spiral rightwards in a natural spiral arc).

Jeff.