Robert John wrote:
Hopefully this'll take some of the guess work out of what I'm describing.
The following video shows the exercise being done, towards the end, the person on the left holds him down slightly, without exerting visible pressure.
I don't think the connection is at the shoulder, in fact I think the spine plays a more prominent role, and needs to be coordinated with the tanden. Its not "just" the tanden.
Its simply an exercise in understand what it means to "stand" and transmit your weight without committing it.
I see what you mean. Sorry I missed this earlier. Thanks for the video.
This actually helps me see something what Mike is so vaguely talking about, although it also confirms me further that he is wrong.
By reference to the front of his pants with the line of the mat just in front of them (but in background) you can see that the man on the right (apparently more skilled by the interaction), leans his hips forward just as he begins his push, but keeping his legs straight and his torso relatively steady. A straight leg pivot describes an arc, and if it is departing the center, it is headed downward, thus acclerating under force of gravity with no muscular input other that creating the topple.
So, while it seems "obvious" that like neither one has anything supporting their push, it is visually deceptive. The reaction to the push of the partners' arms is in fact absorbed by their own countering forward momentum, closely in rhythm. This is the closest I have seen to anything "springlike" but it is simply using that initiating forward momentum as the backstop for the backward reaction to the forward push.
AAANNDD most importantly
-- it is angular momentum created by gravity accleration from an intentionally perturbed balance system that commences the whole thing.