Posted by: tom.guerry (tom.guerry@kp.org) on Sun Jan 27 14:58:47 2008

Jack-

I think "shoulder rotation" makes sense in the context of a fairly purely "mechanical"
model of the swing.

In some cases such as interpreting teaching cues which try to convey "feel" as well as
motions/actions too complex/mysterious to fully objectively described, a more complex
model is necessary as a guide. So as I have said, I think of the swing as having the levels I
have mentioned, the mechanical, the biomechanical and the sequence of joint motions.

CHP and TORQUE is best mechanical model.

Biomechanical has to do with kinetic link and includes elastic and muscular force
production which develops x-factor/x-factor stretch and ability to adjust/match pitch.

Then there is a joint sequence which accomplishes these two requirements. That is where
thinking of shoulders as tilting becomes important Rotation is not a good enough
description because it does not describe the necessary adjustable resistance to create x-
factor stretch and plane matching.

The most revealing area of comparison is golf where emphasizing rotation fits with a
different kinetic link pattern where the shoulders turn the arms around the body while the
body turns. This works in golf with a still ball off the tee, but in hitting this would be a
shoulder action that ficre drag/prevents early batspeed and is traditionally described as
flawed "flying open"/pulling off the ball.

The mlb pattern is an adaptation resembling the other successful golf kinetic link pattern
which is the 2 plane golf swing where arms swing down as hips turn body with shoulders
responding to how these two different planes blend to create the plane of the swing. In
this patern shoulders have more of a rocking/tilting action as opposed to an action
turning action.

More purely mechanically speaking in terms of a more simplified model, "rotation" could
be an acceptable term, BUT there is the danger that you could oversimplify the swing if
the "tilt" nuance is lost. For example, Nyman's oversimplified analysis gave the appearance
that rotation alone could be used to model an mlb swing without THT.