Ch'i or Ki
Ch'i (Chinese) or Ki (Japanese) is the internal force in our bodies, the manifestation of our spirit. It comes from the Taoism, and the universe, or our center (which is our center of balance). And the idea in Martial Arts and Eastern Medicine is that if it is out of balance, you must balance it. And if you're balanced, you can harness it to do things things you might think are impossible.
It varies from a very useful visualization tool (mind over matter), to mechanical techniques (physics), to supernatural force, that George Lucas borrowed for Star Wars. It is real, and can be demonstrated: it just doesn't always mean what people think it means.
Where it comes from?
The source of this power is the Tan Tien (Chinese) or Hara (Japanese). This Tan Tien is located about 3" below the navel, and in the center of our bodies. Not so coincidentally this is also where the center of balance for the average human is. The name comes from the idea of "center", and represents our center; center of the spirit, soul, power, and balance. There is a physical center, and a center of balance -- so describing that as a "spot" (Tan Tien) is a convenient construct for understanding.
The Chinese and the Japanese Cultures are very into superstitions and mysticism (the Japanese a little less than the Chinese) - of course so are occidentals.
While it is convenient to dismiss superstitions and gobbledygook , we should not do so too quickly. Many superstitions have other intents -- like "not talking ill of the dead" is a way of letting our anger go and not dwelling on the past (or bad). Not walking under a ladder is a good way to avoid having things dropped on top of us. Chinese Feng-Shui (how to arrange living spaces), has some good things for the psyche like visual balance and humans are just less relaxed with their back to a door or passageway. So sometimes the behaviors are significant, even if the cause of the superstition itself may be less than accurate.
There is a physical center of balance -- pretending that it is something more may have its benefits. You may not believe in an "power" running through your body, or a spirit/soul. You may not believe in the Tao - the power of nature existing everywhere (Christians might call this "the holy ghost"). Placebo's are beneficial. And faith healers do help people beyond pure placebo effect. Visualization in martial arts and sports does cause an increase in performance. So think it before you dismiss it.
In the case of Acupuncture, accupressure, shiatsu massage, and other oriental medicine, the body is not as broken down into component parts as much as it is looked at interlocked systems, and balanced as a whole. In Oriental medicine there are pressure points or trigger point that stimulate different systems, and by balancing the energies (Yin and Yang) in these systems you can tune the whole. These energies (Yin and Yang) collectively are the Ch'i or Ki in our body, and it is this flow of life force through our body that keeps us healthy. There is another force that runs through all things in nature (and is nature itself), this is partly an explanation of the Tao (or Taoism).
Westerners tend to be more deconstructive -- always trying to break things down into its component parts rather than understanding the system. Then later we try to look at all those component parts and see how they relate to the whole (reconstruction). They are different ways to look at the world. The more I have tried to understand the Oriental perspectives, the more I have learned about myself. But that sounds suspiciously oriental in its holistic outlook.
In the oriental medicines, they have designated systems or organs in our bodies that scientifically don't exist (as defined). Yet, stimulating these nonexistent organs (systems) gets the desired results anyway. So while western medicine and science can disprove the existence of organs like the preheater, etc., manipulating that construct still gets the desired results in many cases. So surprisingly, even if the construct is wrong (inaccurate), it does not mean that the results will be wrong. Ancients though that the sky was painted on, and spinning above us as a ceiling -- yet they still accurately mapped the constellations and predicted many astrological events. Even Western medicine also doesn't always agree with itself -- as in Chiropractors, etc., but their are many that have received the real and physical benefits of these "charlatans". As time progresses the scientific community is learning that there are results that can not always be explained. The Chinese and to a lesser extend the Japanese are a mystical people. Many Orientals have chosen to define these results with a mystical definition, and though all the definitions might not be accurate, results are results.
First without Chi: Stand upright. Extend your dominant arm out, palm up (but in a fist). Have your partner put the back of your fist on top of their shoulder, and they can rest both hands at the crook of your elbow. With every muscle in your arm tense, when they slowly pull down, they will be able to bend your arm.
Next with Chi: Stand upright. Extend your dominant arm out (on their shoulder), fingers extended, hand vertical (palm to the side), close your eyes and relax. Say, "go". Stay relaxed (only resist whatever force they're pressing on you). And as they push down, imagine your arm is steel rod extending in the distance, or a hose with energy flowing from the earth out through it. Imagine they can not bend or budge it. If you're both doing it right, they'll be unable to bend your arm. (Or at least it'll be MUCH harder).
What happened Easterers call Chi, Westerners would call body mechanics, technique and visualization. But it doesn't matter if you believe in their explanation or not, we just proved it though demonstration.
The more scientific definition of Ch'i is based on some interesting facts. We (humans) have an amazingly complex electrochemical and electromagnetic system in our bodies (nervous system). By training our brains and bodies to utilize our nervous system and muscles to their full potential, and using technique, visualization and proper use of energy, we are able to do incredible feats.
Since we don't understand the full effects of this electrical, chemical or magnetic energy, we don't understand its limitation. But we do know things like positive attitude helps healing, and stress causes fatigue and disease (mental and physical). We know that visualization and "psyching yourself out" can help or hurt performance. We know that people in times of severe distress can do things like lift far more than we think they should... and others of us, can tap into that, and artificially induce that state at will.
So the feats of Ch'i that are seen as "magic" are not impossible, just not fully understood.
I have demonstrated Ch'i to people (and still do), but I don't think it is magic. Some Ch'i demonstrations are parlor tricks to persuade people to have more faith in Ch'i, and thus their own abilities as they progress. But there's a large percentage of Chi demonstrates that are technique and something else. Using visualization, timing, coordination, training and body mechanics I can hit harder than other non-martial artist or do other "tricks". I explain it in constructs that I understand (physics, training, timing, visualization) -- many others just describe it as a good use of Ch'i. There are elements to this "power" that I do not understand -- but understanding it is not necessary for utilizing it. Just like a complete understanding of astrophysics was not necessary for ancients to create calendars and predict the seasons, phases of the moon, or track the planets.
These articles came from a book (student guide) I wrote on Martial Arts in the 1980's.