Posted by: Jack Mankin (MrBatspeed@aol.com) on Sun Feb 24 00:39:22 2008

Your lines in your overhead of Pete do not line up to the same place on the front shoulder as they did for the rear shoulder. The contact line for the front shoulder was off as it began at the rear of the shoulder blade not the shoulder socket.

The overhead of video is also not exactly overhead of the hitter but to the rear of the hitter which makes the lines not accurate.

The only way you can do this properly is if you use a sensor system that actually measures the rotation of each shoulder not a video which is always an estimation.

I will refer to the skelatal system and attachments of the shoulder joint and its movement about the axis of the spine. The ball and socket joint of the shoulder rotates but the shoulder girdle (the attachment for the shoulder joint on both sides of the spine) move together as one unit. For each motion there is an equal and opposite motion that balances the body or else the body would be out of balance. <<<

Hi Dave

You state, “The only way you can do this properly is if you use a sensor system that actually measures the rotation of each shoulder not a video which is always an estimation.”

I have run the test you describe with the Motion Studies Computer mentioned in the post below. Two of the sensors were placed at each shoulder socket. We received about the same data as I showed in the clip.

Jack Mankin
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Posted by: Jack Mankin (MrBatspeed@aol.com) on Thu Mar 6 00:43:59 2003

Hi Zig

I am aware of the hard work and dedication you put into your project and you are to be commended for it. During 1996-7, we ran a similar study at the U of CA (San Bernardino) using their newly acquired Motion Study computer with 4 position motion detectors, pressure sensors and high-speed cameras. Sensor points (looked like miniature Ping-Pong balls) were placed at each joint of the batter's body and the linear velocity and angular displacement rate for any limb (or joint) at any point of the swing could be analyzed.

Zig, I am sure the data from our study would confirm the findings you just presented. After analyzing your data, does a batting principle emerge that has not been published or discussed on this and other sites? With the pool of batters we had to work with, I could not find predictable correlation’s between the angular rate of the various sensor points and bat speed development.

Jack Mankin