Cool Kai, thanks. I've had a similar experience of tension rising from the core when doing breathing exercises with similar feelings of pleasure. (Man, I need to start regular practice again, I've fallen out of it recently. My girl's also started doing a pilates/yoga workout that I'm going to join in with her on. Need to keep in shape during the swordfighting off-season. ^__^)
The basic reflexes have sunk in tho, and I can drop the breath down to the Centre pretty easily during day to day activity.
RAW calls this 5th circuit Neuro-Somatic feedback. I like the term Kinesthetic intelligence, but haven't heard of the multiple-intelligence theory. Where did you pick that up?
Also, the 'rushing up' feeling corresponds to how Kundalini is described in Tantra.
Do you have a breathing count pattern that you use? And how long do you usually practice? (You mentioned rushing it this last time.) I've used a 4-2-4-2 (inhale-relax-exhale-relax) pretty successfully when sitting Zazen, and this produces a mild euphoric high. I've also used it while walking to ignore extreme weather in the cold (my core had been shivering throwing off my breathing pattern, so I focused on integrating the count/breath with my walking, and the shivering stopped pretty quickly). Then I realized that while I could still feel the cold, it wasn't effecting my muscles anymore. Probably similar to what wgeorgew described.
Ok, now for some citations. The book is 'Aikido and the Dynamic Sphere' by A. Westbrook and O. Ratti. This book also has some extremely good illustrations. Oooh, I found a some animated gifs taken from the text: http://www.aikido-otago.com/images.html
::Edit:: .gif broke, linked to the page with all of them.
~hara: the Centre of existence, abdominal and otherwise
~ki: centralized, coordinated energy, considered as the energy of life itself
Westward from the Orient have come many tales of strange forms of power -of strength like that of "massed wind or water" sweeping everything away before it. This power has been called by many names, but the one that appears most often in these accounts, especially in Japan, is ki and the seat of that power is the hara, or Centre.
Almost all of the martial arts at some point in their development mention this power and the various means by which it may be developed. It is held to be "Intrinsic Energy" or "Inner Energy" and possessed by everyone although developed consciously by only a few.
The seat of this energy, the hara, or Centre, is a point approximately two inches below the navel. This corresponds roughly to the physical balance point of a man's anatomy which we in the West call his centre of gravity.
In aikido, the emphasis upon this balance point and this Inner Energy (as differentiated from purely physical, muscular energy) is the very core and lodestone of the method.
We are faced with certain difficulties in attempting to explain and define this power according to generally accepted Western terminology. It is mental as opposed to physical and yet more than mental in the restricted, Occidental sense of "mental power" -although Western psychology does speak of "will power," the "will to live," etc., all aspects of attitudes and mental impulses which, while unsubstantial can nevertheless produce physical results.
By far the most serious obstacle to any discussion of the particular strength referred to in aikido as ki is the strict division which Western terminology usually makes between what is mental and what is physical -between the mind and the body. But of what use is the mind and its reasoning, directing powers without the body to act and carry out its decisions? And of what use is the body without any over-all conscious control and direction? The mind and the body are not separate entities; the mind is part of and contained within the body. The closer the unity of mind and body -the fusion of these two functions (direction and action) -seems to come closest to an acceptable Western explanation of the strange strength which aikidoists call ki.
What do we mean, exactly, by this "fusion" of mind and body? Well, if you have ever tried unsuccessfully to open a tiny baby's tightly closed fist, you will have encountered and example of this fusion. The baby is relaxed and obviously not straining to resist you -he may not even seem to be aware of you -but that little fist remains closed. Since a baby responds instinctively to its environment, there is hardly any seperation between perception and reaction, or between the mental and the physical. But as we grow older and develop our rational powers, we find, especially in Western cultures, a widening of the ga between mind and body, a noticeable hesitation between decision and action. It is as if the mind is to review, decide, and then leave the body to carry out the physical activity, depending solely upon the muscle power which can be generated.
But if this gap can be bridged, the result will be a closer unity of mind and body, with the strength, decision, and direction of the mind flowing directly and without interruption through all the channels and into all the recesses of the body.
It might be possible to link the idea of the hara, or Centre, more closely to what Westerners know as a man's center of gravity -the spot where his weight reaches its concentration and balance, achieving equilibrium between the central and upper anatomy above and the supporting architecture of his hips and legs below. Mr. Tohei especially warns again and again that you cannot "keep one point" or stay centralized (and thus be able to extend and utilize your ki, or Inner Energy) unless you keep your balance.
Aikido begins, in fact, with the fundamental assumption that every human being possesses this ki: this vital force which when concentrated in a single unified stream can be extended and channeled into a practically irresistible action of defense, into a technique.
The general doctrine of the martial arts also enlarges at great length upon the basic differences between the "hard" for of ki and the "soft" form. Hard ki appears to be sharp and concentrated to a dangerous point of fusion resembling the edge or point of a Japanese blade. As such, when used in combat (whether offensively or defensively), it will cut through the physical target against which it is being directed. It is predominantly straight (direct) although there are circular forms of hard ki (theory of slashing extension). The very concentration of this form of ki usually requires that a single anatomical weapon, i.e., arm, leg, foot, elbow, etc., be employed to deliver the force of the concentrated energy.
Soft ki, by contrast, appears to be evenly diffused, irradiating, and expanding like a huge globe to envelop the target completely or spin tangentially against it. Here again we have the image of "massed wind or water."
This form of energy does not cut though the target, it sweeps it away in a tangential, circular pattern that sends that target spinning in full centrifugal unbalance or extends and stretches it elastically in the desired direction. The diffusive nature of this soft ki implies necessarily a typically circular form of extension as well as the employment of the whole body to produce it.
In aikido, soft ki is the desired form, and according to Master Uyeshiba, it should be employed within the framework of the natural laws of creation. Aikido does not, in other words, advocate the employment of intrinsic or total energy in a way which breaks those laws by seriously injuring or destroying another man.
Finally, this intrinsic energy is permanent in the sense that, like the Centre, its extension is "turned on" at all times, not only during combat. This requisite implies that the energy developed progressively through the specialized exercises of abdominal breathing and mental concentration in the Centre, extended consciously at first, will become a part of your personality -a way of being -through regular and properly motivated practice of the art of aikido.
Okaaay. Now for the SECRET. Lol.
The easiest place to internally feel your own pulse is where the abdominal aorta splits into the two iliac arteries which continue down into the legs as the femoral arteries.
This is where the blood pressure is the highest as it runs into a divided channel. As you can see, this point lies just at or below the navel and level with the tops of the hip bones, just at or above the area called the Hara. Masters use this as a point to concentrate on. By feeling the pulse internally and loosing yourself in the rhythm, you can achieve a trance state with one-point concentration in the correct area.
This is easy to do while sitting Zazen, less easy to do with walking meditation, and even tougher at the beginning of combat where your senses are screaming for you to pay attention to the external environment. Find the silence after the inhalation phase as the chi is pooled into your Hara/Dan Tien and you should feel an almost audible thump-thump-thump. Cultivating the awareness of this area should assist in centering your concentration there when you really need it.