Posted by: Jack Mankin (MrBatspeed@aol.com) on Sat Jan 19 09:18:18 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.

Weight shift = Momentum?

Gyro "Precession" Demo --

Jack Mankin