T’ai chi is a moving Qigong. Each posture is said to send the ch’i to various parts of the body in order of importance. Each movement is said to activate the twelve main acupuncture meridians and thus give the whole body a healthy workout. T’ai chi is mainly preventive but will cure many diseases or body disorders over a long period of time. Usually I will either send a sick
person to our acupuncturist or treat the ailment with a more specific Qigong exercise to have a more immediate effect. Then I give T'ai chi to stop the disease coming back.

The way in which Tai-chi postures work to heal the body is to cause the ch’i to travel along certain acupuncture meridians to perform certain work. This work is to do with the martial art of T'ai chi.
If we imagine that we are performing certain martial techniques, for instance pushing someone over, and if we have understood the criteria for the practice of T'ai chi, the ch’i or energy will flow along the meridians in order to reach its goal of pushing.

Before the ch’i has reached its goal it must pass through certain organs and is able to heal those organs as it passes. What we do is fool the mind into doing a task when there really isn’t a task to be done. If we really had to push someone over then we would create tension in order to do it, and the ch’i would be blocked. After many years of practice we learn to work and still have the ch’i flow to all parts. This is because T'ai chi has a rather unique training method to teach us to perform tasks while still remaining relaxed. This exercise is called toi-sau or pushing hands. It involves two people using certain pushing and defending techniques to try and push without using brute force (tension) and to defend themselves without using tension. In this way the ch
’i is turned into jing, a sort of purified ch’i which can be used for work.

From - Buddhist Meditation - Contemplation of the Mind

Around our bodies we have channels called meridians through which energy flows, something like the vessels through which the blood flows. All eastern philosophies of health talk of such a flow. The Indians talk of prana, the Japanese call it ki, the Chinese call it ch’i, we call it electricity or life-force. The fact that it exists is not the question for most western scientists now know of such a force. What is not known is how to keep a plentiful supply and how to keep the channels open.
What is needed is some way to train the mind not to allow tension to affect us. Whether the tension is psychological or physical it has the same effect on the body’s energy. If the body’s energy flow is interrupted or slowed down our natural healing systems are unable to cope with normal external attacks.
Tension, more than anything else, affects the flow of ch’i by closing the channels. Through the miracle of television cameras we can actually see the stomach contracting and unable to digest when the person is placed under stress or even thinks about being angry. The same things happen to the acupuncture meridians; they contract, allowing only a small amount of ch’i to flow to all
parts of body. This can be used to great advantage by a trained martial artist; it is possible to strike certain parts of the body when the most ch’i is flowing through that area, to cause immediate great tension, thus closing the meridian. After some time, perhaps days, the meridian slowly closes completely and the recipient of the blow dies. This is sometimes called the delayed
death touch or ‘dim-mak’. However, it is said that this practice takes around three lifetimes to learn so not many ever come to such a level.
There is a small gland at the base of the neck running to the sternum. It is called the thymus gland, and in Chinese medicine is said to control the flow of ch’i as well as its physical function of producing anti-bodies. The first gland to be affected by stress is the thymus. The energy system of the body is affected immediately and if left unchecked will lead to the destruction of the body’s energy system.
We do gain some relief from stress through sleep, but most of us counteract the benefit by sleeping on soft mattresses and watching television and eating before retiring. We need sleep to recharge our batteries; if we are using energy for digestion or for processing thoughts, we aren’t using it to recharge.
If we can find a way to stop stress from affecting us we are on the way to defeating the main cause of disease. We need to develop a calm mind, not always an easy thing to do. Meditation is completely foreign to most westerners, but Chinese exercises do not seem so strange because we are using the body to gain a mind effect.