Harmonizing & Building

The acupuncture textbook "Applied Channel Theory" by Wang Ju-yi provides one of the most detailed descriptions of the dynamics of Qi movement and transformation in the English language. It has made a big impact on my acupuncture technique and also clarified my understanding of how this applies to the internal arts.
Two forms of Qi that circulate through the body are the Wei (defensive) Qi and the Ying (nutritive) Qi. The Ying Qi moves through the channels, providing nourishment to the channels. The Wei Qi travels outside of the channels near the surface of the skin and protects the body. Breath and the Lung network governs the movement of the Wei qi, while the muscle - as an extention of what is known as the Spleen network in TCM - assist the movent of the Ying qi.
When movement and breath are co-ordinated, as with practicing internal arts, the Wei and Ying are harmonized. When these two types of qi are harmonized, the body is protected from external causes of disease. (In Chinese Medicine, this covers a range of diseases from acute, like the common cold, to chronic, like arthritis, to serious, such as stroke.)
When these two types of Qi are harmonized, they also allow the Channel Qi to be strong and nourish the internal organs. This happens when Essence (Jing) which is activated and dispersed throughout the body, is drawn back into the channels at the extremities by the harmonized flow of Ying and Wei.
With the internal organs strong, the body is protected by the other important cause of diseases - internal causes. This outward flow to the extremities by the Ying and Wei and the inward flow of the Channel Qi to the internal organs happens simultaneously and protects the body from both internal and external causes of disease.
This unifies Jing and Qi of the famous trio of Jing, Qi and Shen (Mind). What about the Mind?
When the body is resilient, it is better able to contain the Shen. The Shen can then become anchored and relaxed, which results in clarity of perception and judgement. While complex, it is important to remember that the coordination of breath and movement is the key.