Posted by: Jim (jwelborn@lexcominc.net) on Thu Nov 3 19:29:23 2005

> Hi Tom
>
> I have always found a dialog with a gentleman to be enjoyable and constructive. And, as I found from our past discussions, our differences are more a matter of definition than principle. I will give my conclusions regarding our discussion of “weight shift” for your comments.
>
> It appears the term “weight shift” can be used in two different forms. One form would generate linear momentum (or kinetic energy) and would therefore require linear movement of body mass. This form would occur when a batter shifts weight rearward to “load” or during the stride as the batter shifts the center of mass forward to a new balance point.
>
> The second form that would constitute a “weight shift” would not require a linear movement of the center of mass and therefore would not generate linear momentum. This form would occur during the swing as the body rotates about a fixed axis. At the start of rotation, more weight is supported by the rear leg. As the body rotates to contact, the responsibility for supporting the weight is shifted to the lead-leg
>
> Those are my conclusions
>
> Jack Mankin


Hi All,

This has been an interesting thread. I would like to throw some things into the discussion.

First, it seems to me that to initiate the swing and accelerate the bat with maximum force, the muscles of the body must be given the opportunity to sequentially fire. All of the muscles cannot instantly fire at the time and yield a powerful, controllable swing. If they could, then rotation could start directly from a static body position. A negative move, leading into a positive linear move, leading into rotation, allows the muscles of the body to fire in sequence at the correct time and build acceleration. I have watched a ton of pro clips (including Bonds), and some sort of negative movement can be detected in every one. Sometimes it is very slight and many times it is actually relative to positive movement (occurring at the same time).

Another thing I have noticed is that in every clip, during the positive move prior to rotation, the hips ALWAYS move forward farther than the head. This move is, of course, what provides the backward tilt to the rotation axis. This move is not necessarily a function of the stride. In two of my clips, Jim Edmonds and Mike Sweeney both have no stride at all. Yet both had positive linear hip movement measuring almost a foot.

Finally, I am curious about a possible energy source that I have never seen in any swing discussions. That is gravity. I have noticed that during rotation at contact and slightly beyond, batters with great swings appear to be very light on their feet. The rear heel is up dragging the toe. The front foot torques around seemingly on the heel (perhaps the true bottom end of the axis of rotation???). The batter’s weight for a brief instant appears to not be bearing totally on the ground. Have the dynamic forces of rotation captured some of the potential energy of gravity, converted it to kinetic energy, and transmitted it to the bat? Could this be an explanation of how the batter sent the ball over the fence with what is described as a seemingly effortless swing?

What do you think?

JW