Posted by: Jeff M () on Fri Oct 27 18:16:37 2006

> Hi Jeff,
>
> I sense that my PFO geometric analysis and your dominant eye theory have reached a stalemate. That being said, let us move on to another topic (at least for now).
>
> I have read Setpro, which makes numerous references to pelvic loading. My question for you is simply this: what is pelvic loading and unloading? If I were to instruct a person how to load and unload his / her pelvis using precise terminology instead of cues, what terminology would I use.
>
> Remember, my intent here is gather and analyze information, rather than debate PFO endlessly. The debates will continue in the future--consider this a cease-fire. This is a good time for two scholars to learn from one another.
>
> Best,
> BHL, Erudition of Black Holes and Literature
> Knight1285@aol.com
>
> P.S. I will not debate you in the future on the grounds of physics, as you proved that my subject of expertise is Literature (Minor in Math and History), and yours is Science.

BHL- I would like to continue the “vision v PFO” aspects debate at a later time, but first let’s address the fact that there is no real load on the pelvis.
In general physics terms applied to the batspeed.com rotational baseball swing, we need to clear up terminologies before we get started. Loading can be more fully or better described as tensile loading since this application upon one’s torso will cause the torso to behave in an elastic manner. I think this is where many posters on batspeed get confused, since they don’t quite understand that each increment of load is accompanied by a proportional increment in extension, and when the load is removed, the torso or pelvic region returns exactly to its original size. That’s the main or critical flaw in the swing theory of many...how can the rotational body return to the exact start point! Continuing, however, once the load exceeds some threshold (the yield strength) the extension increases more rapidly than in the elastic region, and when the load is removed, some amount of the extension remains. So we’re really not talking about load by true description. So what does this mean and how do we get back on track with the baseball swing and your question. First of all forget about terms like load; instead look at lower body turn/coil - followed by the upper body coil to resistance, and then a universal unwinding effect which I believe is Jack’s rotational theory...could be wrong, but I don’t care. Staying on track as only I can manage, let’s visit plasticity, a property of a material that undergoes a non-reversible change of shape, in this case a response to an applied force. Plastic deformation occurs under shear stress, as opposed to lets say brittle fractures which occur under normal stress. One could look at Tom Gueery's rantings and draw a clear conclusion in this repect. In engineering, the transition from elastic behavior to plastic behavior is called yield. Perfect plasticity is a property of materials to undergo large shear deformation without any increase of shear stress. Microscopically, plasticity is a consequence of dislocations, similar to hitmans THT comments. There are several mathematical descriptions of plasticity, one of which is Hooke’s law or deformation theory where the stress tensor (of order d in d dimensions) is a function of the strain tensor. Although this description can be considered accurate when a small part of mater is subjected to increasing loading (such as strain loading), Hooke’s theory can not account for irreversibility. The more correct mathematical theory uses a set of non-linear, non-integratable equations to describe the set of changes on strain and stress with respect to a previous state and a small increase of deformation. Wow...could this be the answer to all the questions on batspeed.com? If I wasn’t so wrapped up in baseball I would rewrite the expressions now universally accepted as "gold" and change the curriculum in every major university. Base conclusion is relatively simple now that the terminology issues are addressed. Think coil BHL...versus load. Think uncoil versus unload, and remember the most important element in hitting a pitched baseball is sight. If you can’t see the ball you can’t hit it. But when you do see it, hit it and run.
Jeff M