David Orange wrote:
Yes, tanren is the "core" of all the Japanese martial arts. But there is also something centrally unique to each of them, as to how they variously use that core to achieve their own peculiar affects. What is the difference, then, in aikido and sumo or jujutsu, judo, etc.? ... So my question remains, what, exactly, differentiates aikido from sumo/jujutsu/judo, since all are based on tanren, and how does the internal pressure model explain non-contact aiki?
First, non-contact aiki against an untrained opponent looks A LOT like full contact atemi. So much so, in fact, that it is.
"No touch" throws are, to my mind, distguishable only by uke's awareness of his own imminent peril. The techniques move into the same space regardless, the only question is whether uke is there at the time or not. It does not matter, either way. If he continues to belabor his hostility unawares, then all the imminent contingency is removed by his own ignorance and it becomes "suffered peril." QED.
As to distinguishing sumo, jujutsu, and aikido, I would, say that in practice they often look similar in result, but their principles in achieving that result are very different. All of them involve tanren to temper and strengthen the maintenance of and manipulation of dynamic balance. Their respective focus on the means used to display these effects are quite divergent, however.
I have made a serious attempt in the past few years to more rigorously grasp the physical mechanisms and modes of action underlying aiki. In in doing so, I have some better grasp on how it differs from other arts in some profound ways. Its manner of work, even where the ultimate result achieved is remarkable similar in form or appearance, is very differnt in both concept and action.
In doing so, I have also become critically aware of how little the physical mechnisms of human three diminsional balance are understood by scientists and scholars. There is much we now know NOT to be true, but much that still defies our closest approximate explanations.
Sumo principle is summed up for me in that deep kibadachi, leg lift and stomp that the sumo boys do at the beginning of each match. Sumo, as evidenced by the typical physique, is about manipulation of critically grounded inertia. Not to make light, but sumo uses ( to astonishing effect) the same physical principle as walking a refrigerator on its corners. Which, (to make light) is to all appearances, a regular aspect of stable training anyway, and to equally astonishing effect, I might add. ;-/}
Judo/jujutsu seems to me more intrerested in the manipulation of force couple principles -- the rotary push-pull combinations that isolate and manipulate planar momentum ( i.e --directly altering angular velocity) at critical junctures, in combination with eccentric shifts of existing rotation in the plane for the same purpose.
Aikido is much more about manipulations of constant acceleration potential moment (gravity), in conjunction with intermittent induced moments (attacks and techniques) to reorient the system of moments in its entirety, three dimensionally -- as opposed to adding to or diminishing from angular momentum (velocity) in what ever reference plane has been established by an attacking motion.
I have had some recurrent debates with Mike about this view of altering attacking dynamics in all three dimensions simultaneously versus the linear "six direction" "static spring" reaction model. It is not clear to me if this is the root or related to the "internal pressures" spoken of by others here. I do not find this "static spring" model very useful in my thinking. It certainly departs from what is known about the human balance and stability system.
Muscles of the legs do not seem act as static springs, but as active inputs according to some other mode of control. See: http://www.pubmedcentral.nih.gov/art...?artid=1456051
Leg muscles act paradoxically to the static spring model of ankle/ ground torque even for quiet standing. See : http://www.pubmedcentral.nih.gov/art...?artid=1456057
These studies primarily rely on the the plantar/ankle torque or center of pressure measuremtn, based on the simple (unsgemented) inverted pendulum model (wobbling pole). They focus on the plantar ankle ground troque as the measure of the support mechanism of simple balance.
Beyond that, and quite surprisingly, the mechanism and control modes of human balance remain remarkably poorly understood, although the vestibular and visual systems have been shown to have much less to do with it than is generally thought. . See http://bmj.bmjjournals.com/cgi/conte.../319/7220/1300
; And : http://www.pubmedcentral.nih.gov/art...?artid=1129077
A potentially more useful model may be a chaotic or stochastic (random) gyroscopic oscillation of a segmented inverted pendulum model focussed on the hip sway as active dampener/counterbalance, rather than on ankle/ground torque. SOme studies have sugested this is the normal rather than the extraordinary mode of balance. http://arxiv.org/abs/cond-mat/9908185
It is certaonly the focus of aikido training as a mode of balance.
Oscillating motions of this type, even chaotic motions, obey gyroscopic prinicples. I find many things in aiki techique that are not explained as easily by any other means, especially given the emphasis on spirals and circles in techniques. Nothing I have seen published contradicts it (but do contradict the static spring conception.) I am looking for any other work that may have been done along these lines using rotary or oscillalting hip dynamics dynamics as the studied balance model.
One study still using inverted pendulum model and the foot-center-of-pressure measure, tends to lead that way. Chaotic or stochastic processes are evident in the "random walk" orbit of the center of pressure measures of human balance sway. This shows that linear mechanical models are not likely to be very explanatory. http://arxiv.org/ftp/physics/papers/...ndom%20walk%22
Another shows evidence of cyclic muscular "kicks" (even in the ankle strategy scenario) to orbit a supercritically unstable center that would be typical of a driven gyroscopic oscillation system. See: http://www.pubmedcentral.nih.gov/art...?artid=1456055
Lots of room for traditional aiki concepts exist within contemporary physical understanding of the human dynamic support system we manipulate, but I am not sure that "pressures" or "springs" are good choices of physical or metaphorical models of aiki action.
There is some real room for aikido to make a useful addition to this body of knowledge for the benefit of more than just aikidoka. The rate of death of people over 80 from falls is NINE times that of their rate of death from car accidents. If we can contribute something to the understanding of the maintenance and recovery of good balance, or to aid in improving it where it is impaired, we can literally help save lives. If we aikidoka could get everyone we know, before the age of fifty, to learn proper ukemi, aikido would have been singularly worthwhile for that reason alone...