Posted by: Jack Mankin (MrBatspeed@aol.com) on Tue Aug 23 18:41:32 2005

>>> Re: "weight back" Jack Mankin Fri Aug 19 18:59:56 2005

Hi Grc

Good questions. I also would find it helpful to have a clear definition of “weight shift.” If the batter takes a short stride but the center of his body mass remains stationary (zero forward velocity) through rotation, was there a forward weight transfer? Since momentum is the product of mass with velocity, there would be no momentum to transfer if the velocity is zero. – Or, is “weight shift” just to indicate which leg is most responsible for supporting the body’s weight at different points of the swing?

Jack Manklin
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No one else has a definition of “weight shift”?

Do you have one Jack? <<<

Hi Ray

As I pointed out above, for a “weight shift” to occur that produces linear momentum, the center of mass (the spine) must attain velocity. So I would define “weight shift” as “forward axis movement.”

It is obvious that a “forward axis movement” does take place in the stride of many hitters. Where I run into a problem is with those (Chris Yeager for one) that maintain that this momentum is used to rotate the back-side around a posted lead-side – like a door swinging on hinges. If the back-side did in fact rotate around the lead-shoulder - like a door swinging on hinges – then the spine would also be rotating forward.

Since the average shoulder width is about 20 inches, the spine, neck and head would need to rotate forward about 10 inches from initiation to contact – if the body rotated around a posted lead-side – like a door swinging on hinges. However, in all my studies, forward “weight shift” ceases (linear momentum approaches zero) before rotation begins. The spine, neck and head remain fairly stationary while the shoulders rotate more evenly around them – more like a “revolving door.”

If some one can show clips of good hitters that rotate their head 10 inches forward during rotation (not the stride), I will retract my objections to the - like a door swinging on hinges – theory.

Jack Mankin