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Re: Clips - hip & shoulder rotation

Posted by: tom.guerry (tom.guerry@kp.org) on Wed Oct 31 17:05:47 2007

Jack, thanks again for pursuing this.

I would first say that your characterization of my position is not what I have said, however, I appreciate your making the effort to summarize my position.

I did not say the shoulders did not transfer energy or momentum, I said what was important was how the shoulders functioned as part of the kinetic chain/link to control the direction and rate of stretch and unstretch of the torso which then drives unloading by momentum transfer and CHP/ball on string/pendulum type mechanics.

The stretch and fire of torso/shoulder turn is best characterized as Zig's company measures and describes it in terms of rate of separation/"x-factor/x-factor stretch".

More exactly, see >> my position as reflected in prior remarks<<

1 - Comments on teacherman's statements:

(A) “You see....the hips rotate. The shoulders do not.”

>> I would say BOTh the hips and shoulders turn with hips leading. A shared definition of "rotation" is probably the most difficult thing here. That could take a while to sort out bu t may not be necessary<<

(B) “Shoulder rotation occuring at the same time as hip rotation simply can not and does not work.

>> agree, it is probably not even humanly possible to lock the two together during turning<<

(C) “The hips and shoulders moving together in no way proves the existance of shoulder

>> I think the question is how the hips and shoulders move relative to one another, most importantly the "universal" (attributes common to high performers/setting them apart) sequence [and rate] of motions, which is most productively described in my opinion for purposes of factual discussion in terms of kinesiological joint motion sequence/proportion<<

2 - response to jack's question:

do you think that energy from hip rotation can be transferred to the bat without the shoulders moving (rotating or tilting)?

>>I think mechanically speaking, connection from firing of bathead once it gets out of arc of handpath to contact is via CHP/ball on string/double or multiple pendulum principles where the swing radius can not lengthen without disconnection/deceleration/loss of adequate timing.

Handle torque is important in controlling the connection as can be handpath hook via unshrugging (most similar to "horizontal aDduction of front scap) front shoulder.

The other EXTREMELY important factor is what is the bat connected to ?

It is connected via a kinetic chain where the most important energy source is coil of torso between hips and shoulders. The timing of coil/reversal/uncoil and the direction of this coil/stretch is essential.<<


With respect to the current annotated videos:

Jack, your video annotations are very similar to Williams overhead shots of himself and he was a pretty fair power hitter like Bonds and a pretty fair average hitter like Rose. See annotated picture in this thread, for example -


Determining the parameters of stretch and fire and the shoulders turn vs tilt is beyond the resolution of drawing lines on video. At the very least, motionanalysis is necessary and Zig's technology has already answered questions about the separation between shoulders and hips down to an error of 1 mm displacement:


"Let's assume you haven't seen it. For starters, the hitter takes a stance in any position (this position is random and stylistic and should not be considered the stance because it varies so much from each player). This position is comfortable and allows them them to prepare for the first phase of the swing (negative move) often referred to as loading, or wind up or whatever terminology you want to use. In this loading phase, which many of you call a backwards weight shift, the best athletes have a slight change in the position of the hips and shoulders, closing to a position of approximately 25 degrees of the hips and 40 degrees of the shoulders {X-Factor is now approximately 15} (This is accurate to 1mm)

The forward swing is then initiated at the ground with the application of force to the back foot. As force is applied to the back foot, it creates a linear shift of weight, at the same time, their is a release of rotational energy around (rotating) from the front foot up to the hip of the front leg (the heal of which has dropped during the linear/rotational shift, to provide a solid front side to hit against). At this point there is an X-factor stretch of approximately 12 degrees (x-factor stretch is an increase in the degree of separation between the hips and shoulders)."

-----In summary,

I believe when the hips fire (initiation/tht at launch superimposed over coil/rubberbandwinding already produced associated with earlier prelaunch tht), the shoulder action is controlled via handle torque (proprioception and force production) to resist turning open with hips by shoulders tilting more than turning so that as hips first fire, they turn faster than shoulders turn which means even as shoulders begin to be turned by hip turn, more/quick torso stretch is being created until a quick reversal/unloading is timed/synched with the center of mass of the bat being torqued out of the arc of the handpath promoting efficient hip DEceleration (prior to traditional bat pointing straight back/lag position) for the swing to be as quick and well timed and directed as possible (mlb pattern).

The videos you show are all consistent with my descriptions and Zig's measurements, but they are FAR less definitive/more open to widely variable interpretation than the motionanlysis data.


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