" Back leg is is not the cause but is the effect of other body movement." Of course. And I have done a number of posts here explaining this in some detail, i.e., the "kick back" is a "resultant" that is a function of certain postural/rotational dynamics and also pitch location.
I'll add that the players talking on the clip is a typical ex. of "the action-perception gap", i.e., what you may THINK [verbalize] about your swing is vastly different from what you ACTUALLY are doing to create a high level swing.
As I have said many times as regards hitting expertise there are 3 modes so to speak: "Doing it, understanding it, teaching it." Elite players are--typically--ONLY expert in "doing it."
Why the gap? One explanation can possibly be found in Howard Gardner's bk. "Multiple Intelligences." This link has a chart about his theory:
Note the upper right box that shows musical/kinesthetic intelligence. The argument [simply put] is that kinesthetic intelligence is a function of tacit [non-verbal] awareness/experience.
This type of intelligence is not really a function of logical reasoning but is derived by non-verbal/internal feedback via movement aims/goals/intentions etc.
Gardner's argument is that there IS a genetic component to these classifications [broadening the "g factor" theory of intelligence]. I agree with this basic argument, i.e., SOME people are very likely born with a POTENTIALLY greater ability to LEARN -via internal feedback.
As I have tried to explain this, some, I think, have a more "refined or heightened" kinesthetic awareness when they are practicing movement goals [relative to others].
This greater genetic capability, can, over time [ via practice/experience/feedback], CAN--POTENTIALLY-- yield greater performance [relative to those who have an average or below kinesthetic awareness].
So, to get back to my original point about an explanation of the typical action-perception gap, I think an argument can be made that elite level hitters likely are born with this greater kinesthetic capability.
How much? To what degree? I don't know [and no one else does either!] Is it ALL of 'em? Almost certainly NOT!
As regards the long standing question as regards the "genetics vs. environment debate", my favorite quote comes from a geneticist I saw yrs. ago[can't remember the name]:
" I can guarantee you, it's 100% genetics......and 100% environment." A very good summary of the very complex interaction of the two components of human development!!
And I'll add one more point [self-serving but I think accurate]: Much of my instruction is very much a function of my very good understanding as to how to create practice methods that......
.....are designed to facilitate, within the athlete, how to develop, over time, a much more "refined kinesthetic self", so to speak. Certainly I spent a good deal of time on this question of kinesthetic development.
More thoughts on the genetics vs. environment question. Going back [about 20 yrs] to when I first considered working as a hitting instructor. I had a very basic question: Can you actually teach hitters? It was my first question. And why would it not be?
After all, I grew up in an age wherein we learned via what I have described as "disorganized baseball." Meaning that there were ZERO select teams. Nor were their these people called "hitting instructors." Nor was there yr. round baseball.
If for know other reasons [in Tx.] back then no football coach would allow good looking young athletes to NOT play football. HALE No!!
As a guy who has spent much of my life either trying to create high level movement or trying to teach it, I marvel at the tremendous capability of Simon Biles. I consider it a supreme honor to even watch her!
The very obvious degree of lift she creates in this last phase at the end is tremendous. But note at the start the horizontal displacement [think broad jump].Tremendous physical capability!
One comment in this feed said along the lines of .."she may be the greatest athlete in our lifetime." Not a bad argument in that she can move in ways that NO ONE can actually do at this time.
What exactly does this "getting on plane" actually mean in the context on non-elite level hitters? And what are the exact kinds of joint articulations of the back arm/shoulder are involved?
Based on long experience/observation of non-elite hitters [starting at tee ball], it means the following:
I can still remember [circa the 1970's] seeing the uncontrollable sobbing of some Latin guys getting released at the end of spring training. Never saw any Americans react this way. Why?
Because growing up where they did, they fully well knew the very stark contrast between the opportunities they might have here, vs. where they had been and now had to return to.
In a somewhat relative context, some of my most favorite guys to talk to about this country are cab drivers in big cities like New York. Asking them what they think about this country almost always yields an interesting insight.
As some likely know, I recently talked about some aspects of Ohtani's hip action e.g., hip displacement via eccentric [twisting action] loading causing a "forward by turning," Actions synonymous with "Paul's "pelvic loading." I want to add to what he says here.
I think he is certainly empirically correct in saying that for most elite level hitters, the degree of "separation" between the hip and shoulder rotation [unload] is minimal.
To say it another way, the differential between the hips starting to rotate and the shoulders starting to rotate is minimal. [I will add here that, yes, there is some degree of variability among hitters as regards this differential, e.g, Harper opens the hips more than Trout].
Last night I searched in vain [about 2 hrs. on my website] for an academic meta-analysis on implicit vs. explicit learning. I'm going to keep looking. But in the meantime here's a pretty good article about this [from a practical/teaching perspective].
An excerpt: "On the other side of the spectrum many self-taught athletes will often attempt to learn everything implicitly. The issue here is that without constructive feedback on the initial stages of learning bad habits will become permanent patterns in an athletes movement."
And: " Since you don’t know what you don’t know, you won’t be able to make the minor corrections necessary to continue to make improvements over the long term."