In Traditional Chinese Medicine, Midnight-noon Ebb-flow theory is also called Zi Wu Liu Zhu (子午流注). The flowing and ebbing of Qi and Xue along different meridians (Jingluo) is believed to be related to the designated days and hours in terms of the heavenly stems and earthly branches(天干地支).
Zi (midnight) and Wu (midday) reflect the growth and decline of Yin and Yang. In reference to the 24 hour cycle, in the Zi time (23-1) the Yin Qi reachers its most extreme. After that the Yin Qi begins to decline and the Yang Qi starts to increase. At the Wu time the Yang Qi is at its most extreme, after that it begins to decline, and the Yin Qi starts to increase. Thus the Zi and Wu represent the pivotal points of the growth and decline of the day and night, and Yin and Yang.
The original meaning of "Liu Zhu" (ebb and flow) is the circulation of the water system. It's dissipating and it's gathering together. Zi Wu Liu Zhu describes the circulation of Qi and Xue in the Jing Mai. It explains that the physiological functions of the body will follow the diurnal rhythm and vary according to the changing of time.
In the Yuan Dynasty, Hua Bo Ren said "The Jing Mai serve as pathways for Qi and Xue and so circulate the Yin and Yang and nourish the whole body. Starting in the Middle Jiao and form there pouring into the Hand Tai Yin and Hand Yang Ming, the Qi belongs to the 'Ping Dan' time, like the dew drops that fall at dawn. The Qi flows day and night, reaches the end and then starts again."
Ping Dan time here refers to the Yin time (the 3rd of the Earthly Branches, 3-5am).
- In the Yin time (3rd) the Qi and Xue will exit the Middle Jiao and flow and pour into the Hand Tai Yin Lung channel.
- In the Mao time (4th), Qi and Xue will flow and pour into the Hang Yang Ming Large Intestine channel.
- In the Chen time (5th), iQi and Xue will flow and pour into the Foot Yang Ming Stomach channel.
- In the Ji time (6th), Qi and Xue will flow and pour into the Foot Tai Yin Spleen channel.
- In the Wu time (7th), Qi and Xue will flow and pour into the Hand Shao Yin Heart channel.
- In the Wei time (8th), Qi and Xue will flow and pour into the Hand Tai Tang Small Intestine channel.
- In the Shen time (9th), Qi and Xue will flow and pour into the Foot Tai Yang Bladder channel.
- In the You time (10th), Qi and Xue will flow and pour into the Foot Shao Yin Kidney channel.
- In the Shu time (11th), Qi and Xue will flow and pour into the Hand Yue Yin Pericardium channel.
- In the Hai time (12th), Qi and Xue will flow and pour into the Hand Shao Yang Sanjiao channel.
- In the Zi time (1st), Qi and Xue will flow and pour into the Foot Shao Yang Gall Bladder channel.
- In the Chou time (2rd), Qi and Xue will flow and pour into the Foot Jue Yin Liver channel.
- And then Qi and Xue will return to the Lung channel.
The Qi and Xue flow in every channel for a period of two hours, and just like the tides of the sea, will ebb and flow, reaching a high point followed by a low point, entering every channel at its time of fullness, and leaving it at the time of emptiness.
Zi Wu Liu Zhu in Traditional Chinese Medicine can help in diagnosis, in prevention of disease, and especially to choose the most auspicious time to treat the patient. Because of this, in the past few years a new direction in the study of medicine has evolved—when to select the treatment time. Many scholars outside China have performed trials investigating left heart failure due to hypertension. It has been found it mostly occurs between 11pm-1am. When patient is given a suitable amount of vasodilators and a small amount of diuretics at 10 pm, this can prevent left heart failure.