Posted by: Jimmy () on Sat Jan 19 19:24:03 2008

> Hi All
>
> I will soon start a thread to discuss whether or not a batter�s linear momentum developed during his stride is a factor in generating hip and shoulder rotation. For this discussion, we need to clarify the difference between the term �weight shift� and �momentum.� The concept that �weight shift� develops power for the swing has been a long held �Truism.� However, the more I study the concept, the more reasons I find that it may qualify as another �Fallacy.�
>
> Webster�s definition of momentum: �Momentum, (p=mv) -- The quantity of motion of a moving object, equal to product of its mass and its velocity.�
>
> I think we can all agree that since a batter�s axis is tilted rearward in the launch position, he has more weight on the back-foot as he initiates his swing. We can further agree that during the swing, the batter�s weight on his back-foot becomes increasingly lighter so that by contact almost all of his weight is supported by the front-leg. -- Therefore, many would say that even with the �no stride� approach, there is a �back-to-front,� weight shift that provides power for the swing.
>
> I have problems with that conclusion. As an example: Suppose you are in your launch position and you just lift your back-foot off the ground. All your weight would now be on your front-foot. But, in which direction would your body tend to develop momentum? Obviously, you would tend to fall rearward.
>
> Therefore, in the �no-stride� approach, if there is no actual forward movement of mass, is there any forward momentum developed to power the swing? I think not, when the body (or center of mass) attains no forward linear velocity, there would be no forward momentum generated to do work. I realize I am challenging a sacred baseball truism. I do feel however, that it is necessary to make a distinction between the term �forward weight shift� and the actual generation of momentum for our upcoming discussion.
>
> In the video clip below, even though Bonds does stride a few inches forward with the lead-foot, the principles outlined above still hold true. I will also place a link to a post that explains why he does not fall rearward, as the weight on his back-foot becomes lighter.
>
> <a href="http://www.batspeed.com/media/Does_WS=momentum.wmv">Weight shift = Momentum?</a>
>
> <a href="http://www.batspeed.com/messageboard/113803.html">Gyro �Precession� Demo</a> --
>
> Jack Mankin

Hi Jack,

You state...""Therefore, in the �no-stride� approach, if there is no actual forward movement of mass, is there any forward momentum developed to power the swing?""

I'm sorry Jack, but even in a "no stride" load there is a shifting or transfer of weight from one foot to another. Just because the front foot doesn't leave the ground doesn't mean that there is no weight shift.

Any time that a mass is moving, that mass has momentum. A hitters body weight moving in a direction definitely produces momentum.

Jack, I would like to know what your definition of a load is and why it is needed.

Thanks,

Jimmy