Theory of Using the Yi to Lead the Qi

The key is in the uniformity and fluidity of the breathing, the body’s relaxation and softness, the Yi's peace and calmness, and the spirit’s condensation and upraising.

Regulating the breathing means to regulate the breathing until it is smooth, abundant, uniform, and fluid. To regulate it, the Yi is the most important. When the Yi is strong, the circulation of the Qi is strong. When the Yi is peaceful, the Qi can be led smoothly. When the Yi is calm, the Qi can be uniform, smooth, and fluid.
Qi is bioelectricity. Yi is the electromotive force (EMF), i.e., electric potential difference. From Ohm's law, we know that:

V = I x R
V = Electric Potential Difference
I = Current
R = Resistance

From this, we can see that when the electromotive force is strong, the current will be abundant, and when the electromotive force is weak, the current will also be feeble. In addition, when the resistance is high, the current will be low, and when the resistance is low, the current will be high.
Consequently, when the Yi is strong, the Qi is strong, and when the Yi is weak, the Qi is weak. When the body is relaxed, the resistance is low, and the current is high. When the body is tense and stiff, the resistance is high, and the current is low.

調氣者，調氣之行順、沛、均、與勻。其調之，以意為先。意 強，氣沛。意寧，氣順。意平，氣均勻也。由今之科學上之瞭 解知，氣者，生化電也。意者，生化電流之電動勢(電位差) 也。由歐姆定律知:.. 

V=.I.x.R..

V:.電位差(電動勢) I:電流量

R:電阻..

由是可知，電動勢強，電量則沛;電動勢弱，電量則竭。不但 如此，電阻高，電量小;電阻低，電量大。因之，意強，氣 強;意弱，氣弱。身體鬆軟，電阻低，電流高。身體繃硬，電 阻高，電流低。..

The purposes of Qigong training are to increase the flow rate of the Qi's circulation (i.e., abundance of I) and also to improve the quality (i.e., efficiency) of the Qi's manifestation. From the formula, you can see that in order to increase I, you must increase V and also decrease R. In order to increase V, the Yi must be more concentrated. In addition, in order to decrease R, the body must be relaxed and soft.
This is the theory of Taijiquan: "relaxed physical movements with a concentrated mind." This is a way of "moving meditation."

The way of strengthening the Yi is through meditation training. The body relaxes through training the postures. Wu Yuxiang said: "Transport Qi as though through a pearl with a 'nine-curved hole'; not even the tiniest place won't be reached."
To reach the level of transporting Qi to everywhere as wished, the Gongfu of Yi's internal vision must be high and deep. Only if the Yi can reach everywhere in the body, can the Qi be led everywhere. This Gongfu must also be gained from training Qi in still meditation.

Furthermore, in order to gain the uniformity and fluidity in Qi circulation, the transportation of Qi must be soft and smooth. The key is in the uniformity and fluidity of the breathing, the body's relaxation and softness, the Yi's peace and calmness, and the spirit's condensation and upraising.

意之強，由靜坐練之。身之鬆軟，由練架得之。武禹襄云:〝 行氣如九曲珠，無微不到。〞為求氣之無所不到，意之內視功 夫必須高深。意之無所不到，才能導致氣之無所不到。此功夫 亦由靜坐煉氣中得之。再者，為求氣之均勻，氣之行必須柔 順。其要在於呼吸之均勻，在身體之鬆柔，在意之寧靜，在神 之內聚與上提。《大道靈源歌》曰:〝專氣致柔神久留，往來 真息自悠悠。〞此是神氣相合之道也。..

The Song of the Spiritual Origin of the Great Dao sings:
"Concentrate your attention to reach the Qi's softness,
The spirit will stay for a long time.
To and fro of the real breathing will also be natural."

This is the Dao of the unification of the spirit (Shen) and the Qi.

In order to increase the electric potential difference, you must first know how to increase the concentration of your Yi. The best way to increase concentration is through still meditation training. In addition, in order to reduce the resistance of the body, you must know how to relax and be soft in your movements.
When you are soft and relaxed, the Qi can flow smoothly without stagnation. In order to increase the efficiency of leading the Qi with the Yi, you must have a very sensitive inner feeling. The deeper the feeling, the more powerfully your mind can lead the Qi.

In addition, when Qi is flowing in your body, it should flow smoothly and feel natural, which allows you to relax continuously, which in turn makes the body more transparent to the Qi flow. It is known that when your breathing is smooth and correct, the Qi's circulation can be smooth and natural.
When you can regulate your mind and Qi until they are harmoniously coordinated with each other, and are coordinated with correct breathing, the Qi can be led effectively and efficiently.
This is one of the main goals in Taijiquan training.