Posted by: Jim (jwelborn@lexcominc.net) on Mon Dec 19 21:44:04 2005

> If the upper body action that Jack M describes IS happening and I believe that it is, then a shift is necessary just to keep overall balanced or counter balance the upper body arm and hand action and shoulder loading that is occuring on the back side of the core. You must balance the scales or you will stay back too much and spin or the inertia of the bat will pull you farther back at launch.
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> The stride is momentum to counter balance and /or to uncoil the hips harder.
>



Dave P & donny & all

The resistance afforded by the “firm front side” is but part of the chain of events that creates rotational movement in the core. I believe linear hip slide does provide movement that is channeled into rotation by the front leg. But it is not the only source of rotational core movement or even the major source. The muscles of the legs (front and back) and core (lower and upper) all combine to generate rotation that continues to accelerate after all linear movement has ceased. The hip slide is not necessarily related to stride. Some batters have no stride. But all pro clips I have seen through this site and elsewhere show some degree of hip slide (some more than others). From the start of positive linear movement to the onset of hip rotation, the hips practically always move further than the head. This establishes the backward leaning axis of rotation that is necessary for balance, even in no striders.

The back leg also has a role in creating rotation. As the foot pushes the back leg forward off the toes, the knee will rotate inward slightly (sometimes referred to as the back knee driving forward). This slight inward roll of the back leg along with the firing of the lower body core muscles has the effect of inducing rotation in the back hip. Immediately following the back foot push, the foot and leg are momentarily relaxed and allowed to be pulled forward by the rotating core. If this does not happen, the result is a power robbing, “bug squashing” drag on rotation.

The hips do not always rotate through contact. In fact, their rotation has either stopped or in the process of decelerating by contact. What is happening in a good rotational swing is the upper body is accelerating its rotation off of the rotating hips. As the upper body accelerates, the hips are reaching their limit of rotation and must decelerate both because of their physical limits and their reaction to upper body acceleration. This upper body rotation is what is actually driving a powerful swing (assuming there is good connection between the body and the bat).

The hips and upper body do not rotate as a rigid unit. The hips can almost always be seen beginning their rotation slightly before the upper body (1 or 2 video frames). The upper body then always continues rotating past the point where the hips have stopped. If the upper body stops rotation with the hips, you have a linear swing.

Jim

> While the speed of the shift or transfer is small, the weight of the player is large so....mass times assleration must be considered.
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> I agree that a large noticable shift is not necessary. Balance is a dynamic move that can move weight if necessary to maintain the center point WHILE loading and launching take place. So maybe your both correct. It is not a step to hit but a shift to maintain the balance point relative to the load and launch