Posted by: dave p (cdpaetkau@telus.net) on Sat Feb 23 22:01:20 2008

HI Jack

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.

Dave