@Brett Jones
Thanks Brett, I'm in the San Francisco Bay Area.
@Steve Freides @Lew @mbasic
Lew, I'll give my best understanding of why the hip flexors (or any muscles opposite those which are the main drivers of a movement) are important. We've got enough experienced eyes on the thread that someone can step in an improve or correct. It's also central to why I started the thread so corrections in my understanding would be appreciated.
The antagonist muscle for a movement, in this case hipflexors for the squat serve (at least) two important functions.
1) Stability - By having muscles on both sides of the movement turned on you bias towards not moving. Then you can turn one up or down to start moving slowly. This is also useful because it reduces gravity's roll in the equation. While gravity itself is constant(for our purposes) the torque it causes at each joint is dependent on all the angles going on in the body at any given moment. By cranking up the force from muscles on both sides, we make this variable torque from gravity less of a perturbation.
2) Enhanced Strength - This happens two ways as I understand it. The first is through Irradiation, which I believe Pavel talks about in S&S. The idea is that the more signal going through the central nervous system the more efficient it is. So turning on any muscle unconnected to the motion you are attempting allows you to address the driving muscles more loud and clear - resulting in more strength. The second and more direct function is to allow the driving muscles to flex and store elastic energy on the away to the bottom of the squat, which you can then harvest as you drive out of the hole (assuming you don't stay in the bottom too long).
Now I believe I've also read in one or several of Pavel's books that antagonist muscle weakness, especially in relation to the muscles they must counter act can lead to reduced range of motion. This is related to the Idea that what we call "inflexibility" is not a hardware limitation, short muscles, but a software limitation enforced by the brain and central nervous system to keep us out of ranges of motion that we haven't demonstrated the ability to control. It's this reason that I think trouble in the pistol might be related to weak hipflexors.
Now this all gets back to my original question which I think maybe I failed present clearly. S&S has build a heck of a body for me, but it's a beautifully minimum dose and as far as I can see it doesn't hit the hip flexors at all. 1) Have weak hipflexors been a problem for people built through S&S commonly? 2) What tweak would one make to training to strengthen them?
@Anna C Apologies, I'll get to that video today.