Posted by: tom.guerry () on Sat Jul 1 16:19:30 2006

Jack-

This is where there may be a lot of overlapping complexity that is difficult to tease out.

I think perhaps the basic requirements are 1-that there needs to be momentum transfer
that requires proximal parts of the body to decelerate to efficiently accelerate the more
distal parts and the bat. 2 - the shoulder/arm/bat link as a distal link should have the
shoulders continue turning until contact 3-the axis of rotation needs to be "fixed" from
batherad launch to contact. It could "fix" in different places for different locations and/or
this axis can BOTH remain fixed in the sense of being stable (with accompanying
deceleration and reactive motions of proximal parts) AND could migrate as unloading
proceeds/bathead fires.

exactly how this "migration" transpires may be due primarily to load/resistance to
rotation/swing radius.

The lowest load to rotation will be with a short swing radius as for high inside location.

In this case, there is more forward weight shift, the axis is more upright, the hands stay in,
the hips and torso turn more/together and the timing of the shoulders so that they turn
just until contact/produce max bathead velocity right at contact is controlled by the hook
effect of the lead shoulder/handpath. This would be the equivalent of a more "centered" or
spinal axis. The lead shoulder will turn back to/past 105 degrees for example.

The highest load will be the low outside location.In this case, swing radius is long. The
axis remains leaned back, less weight shifts forward, the axis is set more early
(biomechanically, I suspect this has more to do with the back shoulder dropping which
stops forward weight shift and forces the body to set the axis to support a more
"extended" swing, earlier deceleration of proximal links/long swing radius/center of
rotation more forward/ some flex coming out of lead elbow going into contact, bat more
lined up with lead forearm at contact. but still shoulders turning until contact with max
bathead speed at contact.

To adjust for location, batters will vary the axis and they will also differ depending how
they learn to adjust for location.

Sorting this out/testing some of these speculations would require controlling lots of
variables for analyzing many swings/locations for many hitters.