Posted by: tom.guerry (tom.guerry@kp.org) on Fri Feb 7 09:34:27 2003

Zig-

What do you think balance is ? How do you describe it ?

There are lots of buzz words/phrases around like dynamic balance and postural stability and postural integrity.What does this all mean?

I agree that most kids don't have it because they have never developed awareness of their proprioceptive and vestibular senses and can't control the muscles well that are necessary for "balanced" rotation.

Some "balance" hypotheses:

Jack has defined the rotational swing as a series of arcs,the hip/lower body turns(1 arc) with separation of the torso which turns to drive the tightly connected handpath(arc2) while postural adjustment sets the angle of the torso.The torque angle/x-factor is a measure of separation.The torso angle(bend at waist or what golfers call spine angle in coronal plane) and axis angle(lean back of body's rotational axis in vertical/saggital plane) determine the plane of the swing.The bat turning while the hands are still back and the body is separating("tht") is the 3rd/final arc.

One good way to teach balanced body rotation to a beginner is via Epstein's torque and numbers drills.Epstein describes the(whole body/hip/torso/4 limb/balance/weight) feel necessary to prevent "lunging" well.Jack describes this at a more fundamental level as weight shift being permissable in the early portion of the swing,but by the time of "launch"(2nd arc)the axis of rotation must be set/remain stable with no further forward weight shift(lunge).

From a motor learning perspective,this is very difficult/foreign for most kids.The complex motion is learned by "reducing degrees of freedom of movement"(as described by Nyman).So for example,you fix the bat on the back arm which controls a lot of upper body muscles as well as the shape of the 2nd arc(torso turn driving handpath) and final(3rd) bat arc.You can then focus on the first 2 arcs and their relationship and learn the feel of good balance which in this case includes transitioning to a stable axis/not lunging.

(as an aside,Jack's "tht" description includes the fact that the quick rotational swing requires the 3rd(bat/final) arc to be underway before "launch"/2nd arc starts and by which time the axis of rotation is set.)

Throughout the whole time this is happening,"balance" requires that the center of gravity of the body be dropping along the "target line".This is something that is almost impossible for the young hitter to sense/be aware of because they are pre-occupied with the complex task of getting the variuos body parts under control to just begin to learn how to rotate without lunging(turn body while keeping axis stable).However,as these beginning motions are mastered,the feel/sense of the weight and center of gravity and how it is carried becomes possible and essential.

In general,in hitting as well as in pitching and probably golf,there is never any need to take the center of gravity back wards.The early part("windup",etc.) of the motions has to do with getting the body sideways and flexed and into a stable/"balanced" configuration(hip cock) which permits feel and control of the center of gravity which should then "fall"(or be pushed precisely) into foot plant in the case of hitting to be harnessed to get the 2nd arc turning efficiently(this is different from the sequence in pitching).The back leg positioning and flex are keys to how this center of gravity movement is controlled(how you "sit" behind your axis).

Balance then is how the body is required to move to control the linear movement of the center of gravity until the body rotates around a stable axis from "launch" to contact.

Can you study this with your software?How frequently are motion readings taken(30 frames per secon,60,100,200,more) ?

Can you look for the relative timing of the arcs ? How does back leg action relate to "weight shift" ?

Have you studied realy quick hitters(Bonds is 4 frames from beginning of 2nd arc to contact,3rd arc already underway-hard to see exact motion landmarks)in all locations to see how they adjust ?

These things would seem important,while a hypothetical total swing model would be essential.