>>> Jack I do understand that a batter should stride with some flex in the front knee.what I find confusing is at the point of contact does extending the front knee turn the front shoulder back to the catcher ?,,or is it the other way around turning the frontshoulder back to the catcher extends the front knee thanks jerry <<<
I think your question could be addressed by asking, "Does rotating the shoulders cause the hips to rotate, or does the rotation of the hips aid in driving a more powerful shoulder rotation?" I posed this question because the same argument has been make regarding hip rotation. Some would say that it is the rotation of the hips that straightens the lead-leg.
I will place below a link to a post (with video) that discusses these questions.
What drives hip rotation?