Erick Mead

In its most basic form it is seen in tai no henko (done properly) and in tenchinage. Two minutes. But then, I can teach you the rules of Go in two minutes, too, but I would not put money on it at that point...

Better, let me tell you, you try and see if it makes sense, then do tai no henko the same way, on your own. Take two pencils or chopsticks and a square of duct tape and tape them together with about a quarter inch of space between the ends, they should bend easily at the joint.

Now hold them in thumb and forefinger in each hand and (gently) try to lever one with the other. Though it will bend slightly at the hinge - it won't work well. Then gently push the two together so they are stable in compression. Now instead of levering, let the connection fail and it will hinge (suddenly) out and collapse. That is shear. The shear is now at the hinge instead of at your thumb and forefinger (where it was when you tried to lever it). In fact, if you are applying leverage when doing it you will not be able to make it fail properly.

After you play with it for a while you can make it fail in an arbitrary direction (up, down, in or out). If you pay attention to the means of doing this kid's game it begins with a slight displacement of a hinge closer to the core (usually the wrist) of the same kind as the displacement of the pencil hinge -- which is then moved to the pencil hinge. The shear is inherently rotational and this moment can be moved, like a wave, because it is a wave. If you ever did the "rubber pencil" trick you did the same thing by moving the center of rotation back and forth along the length of the rigid pencil.

Now, tai no henko is the same, engage the connection with the same slight but stable compression, and then make it fail in the same way by beginning the shear in the core, then feed that into the connection and follow the failure progressively.

Think of it more in terms of creating propagating structural failure -- not power. If you have concern about structural failure lacking necessary power -- stand in a building undergoing controlled demolition.

Yes, depends on the perspective I suppose. The bad shear is the one you missed ... but the other guy saw. If you see it you can make it keep failing the way it is already failing -- but so can he ... Since it can be shifted around in both structures, it is a very powerful multiplier. The problem is that the body is very, VERY concerned with avoiding misplaced shear because it can be so catastrophically destructive. Spinal reflexes (triggered by nikkyo, sankyo, yonkyo kotegaeshi) therefore are extraordinarily sensitive to the onset of potentially destructive torquing shears, and react structurally before conscious (cerebral) or even subconscious (cerebellar) action can be directed. Of course, we can "train the beast" -- learn to modulate the reflexes to counter or return the shear, by the same means of detection and action as are applied to us.