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