Mike Sigman wrote:
Oooh! Video analysis. I like this game. First of all, I may not have to explain it by that means becasue what he is doing is fairly low energy and he may be doing what you suggest in terms of direct resistance or without much in the way of tenkan principle (which seems so from the video).
I never said that what you are talking about is utter foolishness, or unrelated, just that it does not not seem wise practice in the context of aikido. Irimi/tenkan is inherently rotational -- I just found some mechanics to describe what it does, so far with fair consistency so -- let's see now ...
I can't see his whole body in the first couple cuts since he is cut off at the waist, so I begin with the first cut where he is being pushed from the rear. In this case, the "front" foot for irimi purposes is the one toward the push (from the rear) and it is clear that he shifts the weight in irimi fashion toward that leg nearest the attacking force, and the leg away is clearly lightened almost to the point it comes off the ground. In other words the same Taijuuido weight transfer I described earlier, just going backwards into it, instead of forwards into it. His black clothing makes it impossible to see if or how he turns or disposes his hips in the shift. Tenkan does not seem to be terribly involved, certainly not in the integrated way it combines with the irimi in aikido. Although he does use limb and torso rotations in the vertical plane to generate these forces.
The knee push is a straight forward irimi shift as I described, he just does not follow through. The side hip push is clearly weighting to the irimi side, too.
The single outstretched hand push is an irimi movement and the leg weighting and arm motions seem to be coordinated as I would expect an irimi to be, although with the "front leg" straight on it is hard to guage the shift directly toward the camera with the darkness of his pants.
The front hip push (parallel stance) is more of a sway back and "pop the pelvic bowstring" dynamic. Same with the parallel stance rear hip. If there is a turn on those I cannot see it because of his dark clothing. Definitely rotating the torso and legs in opposed rotation in the vertical plane forward or back at the hips in coordinated fashion That seems directly resistant, however, and does not answer to anything I would recognize as aikido movement. The side knee push is related to these in principle, but again, it too, seems directly resistant.
The double hand pushes are much more like typical kokyu tanden ho, but without any hip preference, the pushes go around his center and cancel one another out so there is no resistance in the way of Master Sum's direct forward entry. I have done this "frontal entry" with kokyu tanden ho both seated and standing also (granted, with far less constrained movement, and more rotary motion of the arms), although my ukes are generally not THAT compliant. But it is a training demo so exagerration of real action is alright to make it more evident.
That's what I see. Everything in the video seems consistent with irmi principle but not with non-resistant application of force. The irimi seems to use the vector offsets that Mike has talked about, so there is a certain component of resistance in all of these. The parallel stance front and rear hip pushes, and the side knee push I would not characterize as related to aikido even on the irimi principle.
All of it seems to have virtually no aspect of tenkan to it, and very little tangential connections to receive forces, except for the double arm push, perhaps. Since I see very little tenkan-type movements (other than that of the arms in the kokyu tanden motions), this does not surprise me. The mechanics that I have worked out would suggest that the tenkan element of the irimi/tenkan principle does the heavy lifting in converting incoming force from one plane or orientation by perpendicular or tangential inputs once a connection is made. Irimi puts one in a place to make or continue that necessary connection.
I would also make the point that Master Sum seems more to be generating force by the weight shifts rather than than using the force applied to him, which is a legitimate distinction between the arts. Generating force is not the same as resisting an incoming force, although it may, of course, be used to do so.