Posted by: ray porco () on Thu Sep 15 19:35:19 2005

phil,

Thanks.

“…at what point during shoulder rotation do you feel the arms should swing away from the body…?

For me, easier to answer “what is the meaning of life?”

I will attempt to answer why it is a hard question. And why the answer is individual. And how you can spot the dynamics in your son. And how he can “feel” it, to recognize it. Please bear with me.

Stand with your feet shoulder width apart with your hands at you sides. Have a mental image as though you were viewing yourself from overhead. Now turn your hips to the left and rotate you shoulders at the same rate that you rotate your hips (as if moving in unison). Then restart, and this time rotate the hips to the left without moving your shoulders. This is a demonstration of two extreme conditions. There are many points in between, in which the shoulders can vary their start time (lag behind) in relation to the hip turn start time.

Next.
From the same standing position, reach your left arm across your chest and place your left hand on your right shoulder. Now without releasing your left hand, rotate your shoulders to the left ( no disconnection). Restart, and this time do not rotate your shoulders, but do allow your left hand to release and permit your shoulder joint to rotate, allowing the upper arm to move to the left.

Next.
----------Well, the same can be done for the elbow joint, and for the wrist joint.

What the self demonstration hopefully demonstrates is for you and your son to visually see and physically feel the near infinite permutations/combinations of rotational torques that can result by changing the timing and degree of unhinging/releasing of each the hips, torso, shoulders, elbow, and wrist.

A sequence of releases that can be altered to alter timing and location.

Google “Interaction Torques”. (be forewarned to put your thinking cap on)

From a post I made awhile back (at another site) re: “interaction torques”.
>>>THE MELDING OF MIND AND MOVEMENT.
At random:
one important role of the cerebellum is to adjust the motor output controlling a given part of the body to compensate for mechanical effects caused by movement of other body parts (interaction torques).
cerebellum controls timing and amplitude scaling in the agonist and antagonist muscle groups
constraints of task complicate timing and amplitude in single joint movements
multi-joint movements (multiple degrees of freedom) complicate further
single joint movements are involved in multi-joint tasks but the movements are not controlled separately. If several elemental single-joint commands were executed simultaneously, a normal multi-joint movement would not be generated; instead, a very disorganized movement would arise.
inter-segmental "interaction torques" link movement of one segment to another segment
muscles acting at a joint produce torque and combine this torque with interaction torques (generated by movement of linked joints) to produce the correct amount of torque to accomplish task (anticipatory response). Adjustments are made with inter-segmental interaction torques.
anticipatory responses at joints are independent but related.<<<

Some links:

http://www.ptjournal.org/Jun97/Bastian.cfm

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10805697&dopt=Abstract

http://www.annalsnyas.org/cgi/content/abstract/978/1/16

Further.

You liken a fault (?) in your son’s swing to some up-loaded clips (?). It would be both unfair and foolish of me to formulate an opinion without seeing at least a video clip.
But…
If you don’t want to, or can’t post a clip, then I can give you my suggestion on viewing and analyzing.
It’s important to note that all of the body (including mind and vision) is incorporated (when hitting) to accomplish one goal --- combining the greatest speed of the “sweet spot” of the bat with the greatest accuracy, to maximally drive the ball. The “sweet spot” is the extension of our body. It is only fitting that that is where we start our analysis. Focus on that particular part of the bat first. With the software that I own, I am able to plot a path (frame by frame @ 60 fps) of the “sweet spot”, I then compare each frame to the one preceding and following. I relate the movement of the sweet spot to what body part/parts caused the movement and relative location in space. And then I physically imitate the action, to feel it. Noting location, direction, and change. This is extreme tasking, but it is your son.

Why I am not more specific with my answer/opinion is that I do not fully comprehend your thoughts, which are certainly clear to you (i.e., “I was viewing some of the up-loaded clips and it seems to me that in many of the swings the bat appears to be pulled laterally, away from the line of the pitch, by the shoulders instead of the barrel swinging into the ball.” I think Jack would call this a linear movement, I would bet. I can’t comment because I may be interpreting you incorrectly. If you can refer to a specific clip …

One last…
This really all does tie in with “timing” and “start of the swing”. The physical adjustment to the pitch. When you change the timing, degree, and sequencing of unhinging, you are adjusting to the speed, location, and movement of the pitch. For further discussion, see:

http://s6.invisionfree.com/Hitting/index.php?showtopic=184&view=findpost&p=2949193

http://s6.invisionfree.com/Hitting/index.php?showtopic=184&view=findpost&p=2949463

http://s6.invisionfree.com/Hitting/index.php?showtopic=184&view=findpost&p=2952532