Posted by: Shawn (mariner0324@yahoo.com) on Sun Jul 2 14:35:26 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.

Hi,

If rotation was around the spine, then there would be equal weight on the back foot. The weight would remain 50/50 on each leg/foot.

This doesn't happen, the weight doesn't remain 50/50. Instead the mass turns around the front hip and the weight goes against the front leg. It is true this is similar to a gate swinging, the entire mass turns.

I was the one that started the gate swinging, I heard it somewhere. I have a perfect clip of this happening. The front hip might move backwards but this doesn't mean the spine is the point of rotation. You could not get the entire mass into the swing by rotating 50/50. The weight would not transfer completely into the swing. It would be like taking half your mass out of the swing. Instead you would have a swing where 50% of weight remained on the back foot and it would not fully transfer into the swing.

The front hip needs to be the rotational point to fully get the mass into the swing. This also helps with creating leverage against the front leg, as all thew weight is transfered against it. Even the front knee acts as a rotational point for the swing itself.