Posted by: Jim (jwelborn@lexcominc.net) on Mon Jun 27 08:09:50 2005

> > Jack-
> >
> > Thanks for the ongoing discussion.
> >
> > I would think from the frame of reference that there is sequential rotation of body parts to transfer momentum that there might be different axes based on what has decelerated and what is accelerated.The hips might rotate around a spinal/central axis then decelerate as the torso stretches/coils then "rotates" (uncoils/unloads) around a higher more forward axis, then the lead arm and bat would rotate aorund a higher more forward axis prior to escape velocity of the bathead at contact.
> >
> > If you take a Sosa clip,see sosa-sammy3 for example,notice that the head will continue forward well after handpath "initiation",even after front heel down,THEN the head stops its forward progress and the chin tucks (batting helmet visor tips down slightly) to stabilize a more forward axis for transfer/transformation of torso momentum into the bat as head goes up and then back a little.While head goes back,belt buckle stays forward.
>
> Jack you say,
>
> "You stated earlier that “the desired rotation as more around the front hip.” – If that were true, it would mean the spine would also be rotating forward around the front hip. However, the head (at the top of the spine) remains almost motionless. For the head to remain still means the shoulders must be rotating around the spine – not the front hip."
>
> Rotation happens around the front hip. Anyone can look at the Bagwell clip and see this. The front leg action happens second to the start of rotation (backside). In this case where/when seperation is created, start of rotation.
>
> I looked at several swings and the front hip always appears to be the rotational point for the mass. You say the spine must be rotating forward is this was true. Well they do swing the gate, mass rotates around the front hip.
>
> I see the front hip as the rotational point for numerous reasons.



Hi All,

Some thoughts on this discussion.

At ground level at the moment of contact, the axis of rotation must go through the heel of the front foot because the heel is firmly in contact with the ground. At shoulder level, the axis is through the spine allowing rotation through the center of mass of the upper body. If the axis is straight, at hip level it cannot go through the middle of the spine. It must be slightly off center (through the front hip joint?).

If this is true, the "gate swing" analogy from the hips down would be a good one, especially when searching for ways to communicate this technical stuff to 14 year olds. It would also lend support to the theory that the back foot should come up on the toes and tend to drag forward at the moment of contact rather than the back foot simply spinning.

I believe the only way the axis of rotation could follow the entire spine is if it bends. It clearly should not bend. When we tackle hitting mechanics problems in our young players, one of the first goals is to eliminate a bending axis of rotation. We can immediately see power increase with correct body alignment during rotation.

When done correctly, the positive linear move that occurs prior to rotation puts the body in the correct position to achieve a straight axis of rotation. It also creates some momentum that is channeled into rotation as the actual swing is initiated.

Jim