Thread by @SteveEnglishbey

I recently received a msg asking about a recent tweet as regards the back leg flexion action. An action, I argued CAN help facilitate ["free up" as I sometimes say] the hip rotation.

To the clips I showed already let me add 2 more:

A Bonds clip:
englishbeyhitting.com/videoclips/bon…

and a Hamilton clip [2008 HR Derby]

englishbeyhitting.com/videoclips/bon…

As regards the action of the back leg ,both are similar in that both show a good deal of knee flexion AS the lead heel starts to go into foot plant.

Now, the questions sent were: "..do we rotate around the femur? And do we actively force the knee down to support the move or is it a result of the rotation? "

As regards rotation "around the femur" I would say that yes, the muscle actions occurring within the pelvic girdle are the main components causing hip rotation.

The next question: "Do we force the knee down or is it a result of rotation?" This is a very good question--especially from a teaching standpoint.

I will say this: The hip rotation CAN create a "pulling effect" [my term] on the back knee --such that it causes a "passive" reaction [knee flexion]. BUT.

Having said this, I will also say that the back knee flexion CAN be a somewhat "active" torque [and this can be combined with a subtle adduction torque of the hip to knee segment [Bonds looks like he does this I think]

Based on both empirical and physiological considerations, relatively subtle flexion/ adduction torques in the back leg region CAN work synergistically, to help the back hip region rotate.

Note here that in neither ex. is the back leg/foot INTERNALLY rotating, i.e., "squishing the bug." THAT kind of action will NOT CAUSE or help facilitate actual pelvic girdle muscle action [hip rotation].

Nor will back knee flexion or back leg adduction---IN AND OF ITSELF --CAUSE torques in the pelvic girdle region [hip action in the transverse plane].

So, all of the above is really consistent with my argument that the legs ---in the context of elite level hitters---do not CAUSE hip rotation. But they can [and do] create muscle actions [either passively or more actively] that help facilitate rotation.

@threadreaderapp unroll

Correcting my mistake from last night:
Here's Hamilton [2008 HR derby clip]: