Posted by: Jack Mankin (MrBatspeed@aol.com) on Wed Aug 20 11:29:28 2008

>>> Thanks for the video. We see things slightly different. IMO the forwrd "linear" momentum is stopped, especially when you stop the video at foot plant. The forward momentum is not gone it continues in the rear hip. I do agree that the axis of rotation IS NOT the front leg, but rather the rear hip.

I'll use foot plant in this video as my point of reference as you did. The rear hip is loaded it is pulled in or back towards the first base dugout and the lead hip is starting to ever so slightly open. As the frames advance you see the lead hip open more, as the rear hip starts to unload, driving forward to replace the front hip. The lead leg continues to straighten driving the lead hip back and out of the way.

Why I don't believe the base of the spine is the axis of rotation. If this was the case then the rear hip would have to go out towards the plate and then around the spine, like a revolving door, I do not see this. What I do see is the lead hip clearing the way and the rear hip driving more "linear" in the direction of contact. Of course it will be "rotational" because the front leg as blocked any forward slide of the hips and weight shift. Therefore, I have come to the conclusion that the rear hip is the "pivot" point of the bodies rotation. The spine does not stay stationary, like a rod stuck in the ground, but it will actually move out of the way also.<<<

Hi Graylon

Just to clarify a few points for our discussion. (1) Do you agree that the head and neck should remain still during rotation? (2) If you agree, then would not the shoulders be rotating under the head like a revolving door? (3) If you agree, this means the shoulders rotate about the top of the spine - like a revolving door. What mechanical advantage do you find in the hips having a different axis of rotation than the shoulders – the spine?

Jack Mankin