Posted by: Jim (jwelborn@lexcominc.net) on Fri Nov 11 21:09:40 2005

> >>> From moving your lead leg off of the ground to the toe touch position, are your hips internally or externally rotating? Also, what happens after the toe touch at the hip, internal or external rotation? I've been debating with someone about this. <<<
>
> Hi Mike
>
> First, I think we need to clarify my interruptions of “internally” and “externally” rotation. For the purpose of this discussion, I will refer to “internally” rotation of the hips as generated from the contraction of muscles of the upper-thighs and lower back. By “externally,” I will mean hip rotation that is generated from torque applied as the hip joints are driven in opposite directions.
>
> Most of the best hitters have little-to-no hip rotation (internally or externally generated) during the stride until after toe touch.
>
> In order to keep my post as short as possible, I will address “what happens after the toe touch” with a few of my thoughts.
> (1) I have found that batters that predominately use “internally” rotation of the hips, stride to a straighter front-leg.
> (2) Since there is less extension from the lead-leg, their back-hip rotates around a more posted lead-hip.
> (3) This could be referred to as “swinging like a gate on hinges” – lower axis moves forward (“Back to Center”).
> (4) An example -- http://www.youthbaseballcoaching.com/mpg/Chipper01.mpeg
> (5) #
> (6) Batters that predominately use “externally” generated rotation, stride to a well-flexed lead-leg.
> (7) They use the extension of the lead-leg to drive the lead-hip-joint rearward as “internally” generated rotation drives the back-hip forward.
> (8) This could be referred to as “rotating evenly about a fixed axis” ( like a revolving door)
> (9) Examples -- http://www.youthbaseballcoaching.com/mpg/bagwell1.mpeg
> http://www.youthbaseballcoaching.com/mpg/bonds600.mpeg
>
> Many batters may fall somewhere in between predominately “externally or internally” generted.
>
> Jack Mankin


Some thoughts on external vs. internal hip rotation.

The straighter the front leg is at heel plant (more rotation generated internally), the closer the axis of rotation at hip level will be to the front leg. Therefore the more flex in the knee (more rotation generated externally), the closer the axis will move toward the spine. Is either style really any better than the other in its affect on rotation potential? Both create lower body torque.

Upper body rotation builds off of lower body rotation. This is evidenced by the fact that the hips cease rotation about the time contact is made (or slightly after). The upper body seems to accelerate off the lower body, continuing rotation into the follow-through. This upper body acceleration would tend to decelerate the rotation of the hips beginning slightly before contact.

The axis of rotation at shoulder level seems to always be the spine regardless of internal or external style. It is at the shoulder level where rotational forces are ultimately transmitted to the bat through the arms.

Under no circumstances would one want the axis of rotation at hip level to be anywhere between the spine and the back leg (squash the bug). If this is the case, corrections need to be made. But as long as the student is not striding onto a totally stiff post I would not be too concerned, assuming upper body rotation is good.

Jim