Posted by: Jack Mankin (MrBatspeed@aol.com) on Tue Nov 1 12:25:10 2005

Whenever a discussion of swing mechanics arises, the term “weight shift” is sure to play an active role. It is said to be a basic component of the swing. And yet, there appears to be no clear consensus of what constitutes a “weight shift.”

In the past, batting authorities like Lau Sr. and Adair (“The Physics of Baseball”) contended that an aggressive forward shift of the batter’s weight was necessary to generate energy for the swing. They believed that the body moving forward developed linear kinetic energy that would be transferred into bat speed as the body and hands slowed to a stop (“Crack of the Whip”).

However, video analysis later showed that the forward shift of the batter’s weight ceased prior to the swing being initiated and the batter actually rotated about a stationary axis. This means that during the swing, there is no linear momentum (or kinetic energy) available to be transferred to power the whip theory.

Since video analysis discredited the earlier version of how “weight shift” was transferred into bat speed, many new theories arose in our discussions on this board. The most prominent was the theory that the linear momentum attained during the stride was transferred into rotational momentum when linear movement ceased.

However, once again, video analysis showed that some great hitters had no forward movement of the body during the stride – they simply picked up and replaced the lead-foot without moving forward. And, some like Bagwell, take a negative stride. Now, some claim that it is the downward (or upward) shift of weight as a batter “sits to hit” that is important. Some claim that weight shift contributes to a “loading and unloading process” (also undefined) regardless of how much or which direction weight is shifted.

Therefore, I think we can all agree that for the sake of clarity in our discussions of “weight shift”, we need a clear definition of the writer’s interruption of the term. --- Because I think this is an important subject, I am placing below the last post from an October thread (http://www.batspeed.com/messageboard/23699.html ) on this topic for further discussion.

Jack Mankin
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Re: Re: Re: Re: Re: Re: Re: Epstein - lead-arm

Posted by: Jack Mankin (MrBatspeed@aol.com) on Sun Oct 30 13:48:54 2005


(Shawn)
>>> I do not see where you have gotten Jack and I are being any less then fair to each other.

I have a problem with Jack saying that a weight shift doesn't contribute to power.

The clip he provided is a poor example to use or try to rebute weight shift. I have clip of Vlad that show his weight shift rather well.

The stride is part of the force production and isn't a useless timing device. Anyone who has remotely studied hitting knows that the weight shift back is the begining of force production, beginning of the swing process. During the "stride" there is both a weight shift back (loading) and a weight shift forward (positive move). The unloading starts as the stride ends, and when the swing begins (bat moves forward). Just because the bat doesn't begin forward until toe touch, doesn't mean that is the start of force production. This is rather basic biomechanics.

If there was no weight shift into the swing, the weight would remain on the back foot. And everyone know this is not the case in a high level swing.

I'm sorry but you simply do not understand the agruement or the swing.

If Jack doesn't believe that weight shift contibutes to power is one thing, to deny it's existence is completely different. Jack does not deny it's existence, he merely doesn't understand how it's used in the swing. He is so wrapped up in an unmoveable axis that he doesn't see how the weight shift is used in the swing. <<<

Hi Shawn

I have never said weight shift (body moving forward) does not exist. I said its existence occurs prior to rotation and the swing. You stated that a clip showing a close-up of Guerrero ( http://www.youthbaseballcoaching.com/mpg/Guerrero01.mpeg ) from the hips-up is a poor example to discuss weight shift. It would then appear your version of weight shift depends more on what occurs below the hips. If the upper body is equally involved, please point it out in the Guerrero clip.

It would help if you clarified your definition of “weight shift.” Must the upper body move for there to be a weight shift? Or, is it more dependent on which leg is supporting the weight at different points of the swing?

Jack Mankin