Posted by: tom.guerry (tom.guerry@kp.org) on Mon Jun 25 09:37:37 2001

Joe-

Good question.
Transfer of momentum is a very non-intuitive concept,but is the main energy source for batspeed/power.More in depth info describing how the body does this for both pitching and hitting is at:

http://setpro.com/NEWWEB/mmax02.htm

and

http://setpro.com/NEWWEB/best%20of%20max00.htm

Since momentum transfer is so nonintuitive,this is an area where being familiar with underlying principles is important to keep coaches from stuggling i vain against the underlying physical principles.

It is also most important to point out that the transfer mechanics are different in hitting and throwing as Jack has elucidated.In both throwing and hitting the body generates power in the turning torso the same way.In pitching,this is used to whip the arm.In hitting,you have a two handed grip on a long heavy object.The bat needs to be torqued to extension without allowing the hands to get away from the body's center of rotation,or the chain of momentum transfer will be broken.

Mike Marshall tries to put the momentum transfer principle simply describing it as resembling the bullwhip:"The bullwhip analogy refers to the sequential action of the various body segments that apply force,then stop and snap slightly backward to add momentum to the next body part." Remember,this refers to pitching,not hitting where transfer from torso to bat is different.However,in both cases,you should be able to observe the "reactive torque" of the slightly backward snapping of body parts when momentum is being transferred.

Momentum is transferred from the hip to the shoulder by the untwisting of the coiled trunk that happens when the hip opens before the shouders rotate-the "dynamic" part of hip rotation-see first link above.When the untwist proceeds up from the hip to the top of the spine,the back foot drags(opposite reaction from hip down) as a sign that momentum is being transferred upward from the hip.This momentum transfer continues as the bathead is torqued out of the arc of the hand path-see second link.Next,the hands can extend away from the bodies axis of rotation once the bathead is nearly fully extended causing a "second" wave of momentum transfer which dramatically slows torso turn then twists the hips and leg in the opposite direction causing the back hip to fall back and the back heel to turn(until now back foot has been up on toe with some drag behind front foot).

One of the main problems kids have is they try to swing with the arms.This extends the handpath away from the torso and transfers the "second wave" before the first ever had a chance.So you don't see the back foot get on the toe and drag,you just see the back foot roll over or squish the bug.This gives an "arm swing" that does not have the energy of the lower body and that swings in a variable plane that differs from the plane of the torso turn.