Posted by: tom.guerry (tom.guerry@kp.org) on Mon Nov 7 11:34:14 2005

Jim-

Good stuff !!! I have many stray thoughts I will try to round up for you a little.

####see comments below#####
>
> Jack,
>
> I did not mean to imply that rotation is a series of disjointed steps. I am talking about the body’s process of initiating movement beginning from the stance.
>
> I have seen some coaches actually teach placing the batter in a rigid looking stance with their “weight back” resembling what the body should look like at the beginning of rotation, and then having them suddenly rotate to swing. I know this is not your approach.
>

####Agree, "pre-loading" is bad.See especially Ted Williams SCIENCE OF HITTING,section on mechanics (HIPS:Where the action is). After some "rhythmic pre-swing activity" (Lau Sr. term) the swing itself needs to have a back and forth rhythm of "positive and negative move" (Don Slaught) to be effective.#########


> The body cannot efficiently accelerate its parts in this manner. Acceleration must build. It takes time and coordination for muscle groups to accomplish this. It doesn’t take much time (fractions of a second), but it certainly can’t occur instantly. This process gets well under way during the time it takes to go from stance to heel plant or the beginning of actual rotation. The visual image this process produces can be described as fluid motion.
>
> After heel plant we are past “hip slide”, but acceleration continues to build as rotation takes over. Angular momentum amplifies kinetic energy the muscles have produced. The energy is transmitted through the upper body, arms, hands, and bat to the ball.


#########The missing element that explains how to discuss this is, in my opinion, the "up/down" or "tilt" (adjustment) to "match the swing plane" to the pitch (Epstein).

See,for example,Sosa clips at youthbaseball. There are a number of front and side clips there with high and low ball.

Notice for low ball:

http://www.youthbaseballcoaching.com/mpg/sosa_sammy1.mpeg

Much deeper squat (I would not call this "bend at waist"),lead arm lower against chest,hands lower (I think of back hand/top hand as being level setter).

Notice for high ball:

http://www.youthbaseballcoaching.com/mpg/Sosa06.mpeg

Less squat,lead arm up off chest,hands high (Williams might call this levelling out swing to get on top of high ball)

In both cases,the hips do NOT slide after front foot down, BUT the head continues forward which helps with ongoing coil/final setting of axis.

When the shoulders are more level.this is a lower load (lower resistance to rotation) type situation and the torso is stretched well by higher lead arm and the torso turns more to contact.

When the shoulders "tilt" so hands and back shoulder are lower,this is a high load situation and the unloading is driven by deeper/more pronounced "sit-get out of chair" or "down/up" or "bow-arch" type action.

#########


> I think of batting as an overall two step process. The first step is a linear phase (being discussed here) and the second step is the rotation phase.

##### I agree there are 2 phases,what makes it complicated is that they overlap and vary depending on adjustment.Jack describes the inside/out adjustment well.Epstein describes the up/down adjustment well which is the one more involved with weight shift timing as degree of axis lean/tilt is set and sequential loading/unloading is supported.

The up/down adjustment results in/works by tilting of the plane that the bathead fires out in -- with a flatter plane for high hard one and more tilted plane for dropping trajectory. The more tilted plane will swing the bathead more up through the ball with more "extension" ("L" out of back elbow without disconnecting) at contact/maxvelocity/escape velocity.##########
>
> Getting back to the “hip slide’ discussion, in an earlier post I presented the following:
>
> “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?”

######I think it may be more a matter of having a firm surface with traction than gravity,but that would be for a hard science type to figure out.Always good to learn how to "use the ground".#######
>
> I believe when we see “hip slide” or “positive linear hip movement” or whatever you want to call it, we may actually be seeing the body in the process of converting some of the force of gravity to kinetic energy. If this is the case, it may explain the need for a tilted axis of rotation. Or maybe it’s more accurate to say that the tilted axis is the result. That is, “the correct swing causes a tilted axis” rather than “the tilted axis causes a correct swing”.

###I think this hip leading/rubberband winding/rotating into toe touch/sitting to hit phase is the loading/unloading of the hips middle out to create good coil dynamics and drive the uncoiling####
>
> Gravity pulls objects toward the center of the earth. The human body constantly resists this downward force with its own upward force. If this potential energy is momentarily converted to kinetic energy, movement has to occur in some direction. To me it is logical that what we see during the “hip slide” could be the process of the body attempting to direct some of this energy into the swing.


### Also nice to have that boost from the "down/up" stretch receptor reflex as well as harnessing elastic properties of soft tissue#####
>
> The primary source of energy, of course, comes from the body’s muscles. But if my ideas are correct, gravity could be providing a source of extra energy. It could certainly be a good explanation of why sometimes a batter swings as hard as he can, makes good contact and creates an average hit, while other times an easy swing sends a line drive over the scoreboard.
>
> Do you (or anyone) have thoughts on this?

#######I think its more a matter of good mechanics that use the ground well than actual acceleration due to gravity/drop, but if mechanical sequence is good, Does it matter ? #####
>
> Jim