Since taijiquan is an internal qigong martial style, correct posture is essential. Incorrect postures can cause many problems: a tight posture can stagnate the internal qi circulation, wrong postures may expose your vital points to attack, and floating shoulders and elbows will break the jing and reduce jing storage.

Taiji students are generally taught to make the postures large at first. This helps the beginner to relax, makes it easier to see and feel the movements, and also helps him to sense the qi flow. Furthermore, because large postures are more expanded and relaxed, the qi flow can be smoother. Large-posture taiji was emphasized by Yang, Cheng-fu (楊澄甫) and has been popularly accepted as the best taiji practice for health.

Large postures also make it easier to train jing. It is more difficult to learn jing with small postures because the moves are smaller and quicker, and they require subtler sensing jing. Large postures build the defensive circle larger and longer than small postures, which allows you more time to sense the enemy's jing and react. It is best to first master the large circles, and only then to make the circles smaller and increase your speed. Thus, the poem, "Thirteen Postures: Comprehending External and Internal Training," states: "First look to expanding, then look to compacting, then you approach perfection."

In addition, when you begin taiji, you should first train with low postures and then gradually get higher. When you first start taiji, you cannot build your root by leading your qi to the bubbling well point (yongquan, K-1, 湧泉) on the soles of your feet. Without this firm foundation, you will tend to float and your jing will be weak. To remedy this problem, you should first train with low postures (though not so low as to make you tense), which will give you a root even without qi, and simultaneously develop your qi circulation. Only when you have accomplished grand circulation and the qi can reach the bubbling well can you use it to build the internal root. This is done by visualizing the qi flowing through your feet and extending into the ground like the roots of a tree.

At this time, you may start using higher postures and relaxing your leg muscles. This will facilitate the qi flow, which in turn will help you to relax even more. In the higher levels of taijiquan, muscle usage is reduced to the minimum, and all the muscles are soft and relaxed. When this stage is reached, qi is being used efficiently and is the predominant factor in the jing. Usually it takes more than thirty years of correct training to reach this level. Train according to your level of skill—start with the larger and lower postures, and only move to the smaller and higher postures as your skill increases.

To summarize: build your qi both externally and internally, and circulate it through the entire body. After the internal qi can reach the limbs, use this qi to support your jing. Gradually de-emphasize the use of the muscles, and rely more and more on using the mind to guide the qi to lead the body. Train the postures from large to small, low to high, slow to fast, and easy to hard. First build the defensive circle large; then make it smaller. For maximum jing, strengthen the root, develop power in the legs, balance your yi and qi, exercise control through the waist, and express your will through your hands.

Now, let us discuss the general rules of posture:

Hands and Wrists
The most common hand forms used in Yang Style bare hand practice are the taiji palm and the taiji fist. The open palm hand form is done in two ways, depending on the style one is practicing. In one style, the little finger is pulled slightly back while the thumb is pressed forward. The hand should be cupped. The other open palm hand form is similar to the first, except that the thumb is pulled back slightly instead of pushed forward. Here the hands should be shaped as if you were holding a basketball with the palms, without the thumbs and little fingers touching the ball. In Yang Style Taijiquan this hand form is called tile hand (wa shou, 瓦手) because it is curved like a Chinese roof tile. In both hand forms, the thumbs and little fingers are slightly tensed to restrict the qi flow to these fingers and increase the flow to the middle fingers and palms.

The open palm hand form is classified as a yang hand in taiji. When palms are used to attack, the fingers are loosely extended and the wrists settled (dropped slightly) in order to allow the jing to reach the palms and exit easily. It is said: "Settle the wrists, extend the fingers" (appendix A-10).

The taiji fist should be formed as if you were holding a ping-pong ball lightly in the center of the hand. When striking, the fist closes momentarily, but the fingers and palms are kept relaxed to allow the qi to circulate. The fist hand form guides the energy back to the palm and is classified as a yin hand in taiji.

Elbows and Shoulders
The taiji classics say: "Sink the shoulders, drop the elbows."  There are several reasons for this. First, it allows the elbows and shoulders to be loose and the muscles relaxed. Second, dropping the elbows seals several vital cavities, such as the armpits. Third, when the elbows and shoulders are sunk, jing can be effectively stored in the postures, as well as emitted naturally from the waist without being broken. Fourth, dropped elbows and shoulders help to keep the postures stable and the mind more centered.

Head
The head should be upright. It is said: "An insubstantial energy leads the head (upward)."  When your head is upright and feels suspended from above, your center will be firm and the spirit of vitality will be raised up. In addition, the eyes and mind should concentrate. It is said: "The eye gazes with concentrated spirit."

Chest
It is said: "Hold the chest in, arc the back." Remember that yi leads the qi, so whenever you inhale, pull your chest in and arc your back to store jing in the posture, and visualize as vividly as possible that you are storing yi and qi.

Waist, Hips, and Thighs
The waist and hips are particularly important in taiji martial applications. The waist is the steering wheel that is used to direct the neutralization of the enemy's attack and the emission of jing. The waist must be relaxed and the hips should be as if sitting, so that the pelvis is level and the lower back straight. This will let your movements be agile and alive. As you move, your waist should generally stay the same distance from the floor—unnecessary up and down movement will disturb your root.

The dan tian in the abdomen is the source of qi. It must be stimulated in order to fill it up with qi so that the abdomen is tight like a drum. However, the muscles in this area must be relaxed in order to pass the qi you have generated in the dan tian down to the sea bottom cavity, and then up the spine and out to the hands. The hips and thighs connect the waist to the legs, where the jing is generated. In order to pass this jing to the waist, the hips and thighs must be relaxed and stable; otherwise, the jing will be broken and the qi stagnant. In addition, if the hips and thighs are tight, the qi generated in the dan tian will have difficulty reaching the legs. Thus, it is said: "Relax your waist and relax your thighs."

Legs, Knees, and Feet
The legs and knees must be loose and alive. Then you can generate jing from the tendons and sinews. The muscles should not be tensed, for this will obstruct the generation of jing. However, the legs and knees cannot be completely loose and relaxed. They must be slightly tensed in order to keep your foundation stable. You should look loose but not be loose, look relaxed but not be relaxed.

When your weight is on the front foot, the rear leg should not be straightened, but should have a slight bend, and the front knee should generally not go past the front toe. The exception to this is when you are emitting jing. In this case, the knee may momentarily go past the toe, but should immediately pull back, and the rear leg may momentarily straighten, but should immediately bend again.

In taiji, the weight is almost never distributed evenly on both legs. Rather, it is always more on one foot than the other, and it is always shifting from one foot to the other. Once you learn to use the muscles and tendons in your legs correctly, and learn the exchange of substantial and insubstantial, you will not lose your root, and will be able to generate jing efficiently. Thus, it is said: "The knees look relaxed, but are not relaxed."

The feet are the root of all the postures and the source of mobility. The feet must firmly stick to the ground. It is said: "Soles touch the ground" (or "Feet flat on the ground." In order to do this, your yi must be directed into the ground and the qi must be able to reach the bubbling well cavity. It takes a great deal of practice to develop a good root, but gradually you will grasp the trick and your root will grow deeper and deeper.

Conclusion

The entire body must be relaxed, centered, stable, and comfortable, and should not lean forward or backward, nor tilt to either side. It is said: "Postures should not be too little or too much [i.e., neither insufficient nor excessive]. They [the postures] should seek to be centered and upright." Every form must be continuous, smooth, and uniform; then the spirit will be calm, the yi concentrated, and the qi will flow smoothly and naturally.

Also: "Every form of every posture follows smoothly; no forcing, no opposition, the entire body is comfortable. Each form is smooth."  Chang, San-feng's Taijiquan Treatise says: "No part should be defective, no part should be deficient or excessive, no part should be disconnected." Yi, qi, jing, the postures, top and bottom, inside and outside, front and back, all must act as one unit. When you reach this level, you will no doubt be a real taiji expert.

The above is an excerpt from Tai Chi Chuan Martial Power by Dr. Yang, Jwing-Ming