In traditional Chinese medicine, the life energy, qì, is present in all the internal organs, as it allows them to function. It also flows with a circadian rhythm that allows it to become relatively abundant in one of any of the 12 organs distinguished by Chinese medicine physiology at any given time. When the qì is abundant in an organ, the organ is most capable of performing its designated function, and a pathology of the organ can also be exaggerated. The period for which the qì is predominant in each organ lasts for two hours, and the flow cycle follows the order set in the accompanying table.
If you are roughly aware of the relative positions of the channel meridians, that connect to the internal organs and can be stimulated using acupuncture, as they extend to the upper and lower limbs, you can actually quite easily recall the order of the circadian flow of qì.
Imagine you are standing upright, with your arms by your, and your palms facing inwards. There are three channel traversing each the medial aspect of your arm, the lateral aspect of your arm, the medial aspect of your leg, and the lateral aspect of your leg. These groups of three channels can be further distinguished as one channel being relatively anterior, another relatively central, and the third being posterior, in each instance. Note that although the liver channel runs anterior to the spleen channel on the most distal region of the interior aspect of the lower limb, it crosses posteriorly to the spleen channel little more than half way up the lower leg, and should be considered as the central, rather than anterior channel on the medial lower limb for the purpose of this exercise.
The circadian rhythm of qì always follows from an organ connected to a channel on the medial upper limb, to an organ connected to a channel on the lateral upper limb, to an organ connected to a channel on the lateral lower limb, to an organ connected to a channel on the medial lower limb. You could imagine such a cycle proceeding like a loop, in a sideward direction, or along a frontal plane: out, down, in and up.
From 3am to 11am, this loop specifically proceeds through the anterior channels on each of the four aspects: medial upper limb (lung), then lateral upper limb (large intestine), then lateral lower limb (stomach) and then medial lower limb (spleen). From 11am to 7pm it similarly proceeds through the posterior channels of each aspect, in the same order, and from 7pm to 3am to proceeds via the central channel of the four aspects.
The yīn-yáng zàng-fǔ organ pairings are also grouped according to the circadian rhythm of qì: 11pm to 3am as wood, 3am to 7am as metal, 7am to 11am as earth, 11am to 3pm as fire, 3pm to 7pm as water and 7pm to 11pm as ministerial fire.
- Chad Ryan, August 2017, updated October 2021