Theoretical and Clinical Insights into KAI, HE, and SHU of the Six Channels

The Six Channels theory of 开（kāi, opening）, 阖（hé, closing）, and 枢（shū, pivot）was first proposed in the Suwen (Plain Questions), YinYang Lihe Lun Pian (Discourse on Yin–Yang Separation and Union), and it constitutes an important component of the theoretical system of the Huangdi Neijing (Yellow Emperor’s Inner Canon). This theory originates from the changes in the separation and union of the Yin–Yang Qi-numbers (气数) across the four seasons. Because the Qi-numbers of the three Yin and three Yang are unequal, each has its own exiting and entering, thereby reflecting the concrete forms of KAI, HE, and SHU. The process of seasonal Yin–Yang transformation is accomplished through the functional forms of KAI, HE, and SHU.

When applied to the Yin–Yang KAI, HE, and SHU of the human body, this constitutes a highly condensed summary of the functional state of Qi-transformation (气化) in the six channels. When Yin and Yang separate, there is KAI, HE, and SHU; when Yin and Yang unite (合), they become one Yin and one Yang. Separation and union of Yin and Yang both divide labour and cooperate: when separated, they are three; when united, they are one. KAI, HE, and SHU take as their material basis the biao–ben–zhongQi (标本中气) of the six channels, and take as their functional state the ascending–descending and exiting–entering of Qi movement (气机).

TaiYang is Old Yang and Great Yang; it guards the correct and defends against evil. Its Qi movement is KAI, and thereby it disseminates nutritive and defensive Qi (营卫) and ensures the free flow of body fluids. Yangming is Two Yangs united as brightness; it is rich in Qi and blood. Its Qi movement is HE, and it excels at storing capacity and receiving Yang, and at rotting and ripening water and grain (水谷). ShaoYang is newly born Yang, full of vitality; its Qi movement is SHU, and it governs the pivoting of Yin and Yang, connects exterior and interior, links upper and lower, and ensures the smooth flow of the Spleen and Stomach. TaiYin is Old Yin—mature, steady, and situated at the exterior of Yin; its Qi movement is KAI, and it governs transformation and transportation of refined essence, engenders nutritive Qi, and expels the old while taking in the new. JueYin is the point where two Yins mutually reach exhaustion; Yin Qi is at its peak. Its Qi movement is HE, and thus it governs the closing and restraint of Yin Qi, stores blood and houses the hun (魂), and contains it in order to generate Yang. ShaoYin is newly born Yin; Heart and Kidney dwell together, and water and fire are stored together. Its Qi movement is SHU, and it can bring about the mutual completion of water and fire and enable communication between Heart and Kidney. The theory of KAI, HE, and SHU in the three Yin and three Yang has important guiding significance for differentiation and treatment of six-channel disorders.

The normal and pathological states of the Six Channels’ KAI HE SHU

1. TaiYang corresponds to KAI

It governs the dissemination of nutritive and defensive Qi (Ying Wei营卫) and the free flow of body fluids.

When the TaiYang channel opens, defensive Qi moves and nutritive Qi moistens; the skin is moist and the interstices are well-filled; fluids are smoothly distributed and become sweat—what is meant by Sweat coming forth profusely is called Jin. When the TaiYang fu opens, Bladder Qi-transformation occurs, the Small Intestine receives and contains (受盛), the clear is excreted and the turbid is separated, and the two eliminations are unimpeded; thus when Qi-transformation occurs, it can be discharged (气化则能出矣). Therefore, when TaiYang expands and opens, nutritive and defensive Qi are harmonious, the skin and interstices are warm and moist, fluids circulate, exterior and interior are unblocked, and upper and lower are freely communicated; only then can upright Qi extend and resist external evil.

When abnormal, external evil invades, nutritive and defensive Qi are disharmonious, Qi-transformation is unfavourable, exterior and interior are obstructed, and urination is impeded. If KAI breaks down, then the flesh and joints are slack and sudden disease arises; therefore, for sudden disease, take it from TaiYang(开折则肉节渎而暴病起矣，故暴病者取之太阳).

2. Yangming corresponds to HE

It governs the storing and receiving of Yang Qi and the rotting and ripening of water and grain (水谷).

When the Yangming channel closes, Yang Qi gathers in abundance, warming the Zang–fu and the hundred bones, which is the meaning of Two Yangs united as brightness (两阳合明也). Wu Kun said: Yangming is in the interior; it receives and contains Yang Qi, and is called HE. Zhang Jiebin said: Yangming is HE, meaning that Yang Qi is stored within; it is the interior of the three Yang. When the Yangming fu closes, it receives and contains water and grain, transforms and generates Qi and blood, and conducts dross. As Wang Bing said, HE is that by which the authority to hold, restrain, and secure is grasped (阖者所以执禁固之权).

When abnormal, it may manifest as heat binding in the interior, with heat in both exterior and interior (热结在里，表里俱热), producing great heat; or as failure of conduction, with dry stool binding and accumulation, becoming fu-excess; or as insufficiency of Qi and blood, with sinews and flesh losing nourishment and giving rise to flaccidity disorders. If HE breaks down, Qi has nowhere to stop and rest, and flaccidity disorders arise; therefore, for flaccidity disorders, take it from Yangming (阖折则气无所止息而痿疾起矣，故痿疾者取之阳明).

3. ShaoYang corresponds to SHU

It governs pivoting of Yin and Yang, connection of exterior and interior, linking of upper and lower, and the free flow of the Spleen and Stomach.

The meaning of ShaoYang’s SHUhas two aspects. First, ShaoYang is the pivot of the three Yang, situated between TaiYang and Yangming, pivoting the channel Qi of the three Yang. Second, ShaoYang is the pivot of the six channels, situated between the three Yang and the three Yin, pivoting the Yin–Yang of exterior and interior. Moreover, ShaoYang governs fire; the Hand ShaoYang Sanjiao is also a passage for Qi and water. Therefore, under pathological conditions, ShaoYang disorders readily present with mixed patterns: combining with TaiYang, combining with Yangming, combining with the three Yin patterns, and also carrYing phlegm, dampness, water, Qi, fire, and so forth—this is all because ShaoYang governs the pivot mechanism.

In the Lingshu, Gen Jie (根结Root and Knot), it says: If SHU breaks down, then the ‘bone yao(骨繇) occurs and one is not stable upon the ground; therefore, for bone yao, take it from ShaoYang (枢折，即骨繇而不安于地。故骨繇者，取之少阳). Yao (繇) means shaking. Here bone does not refer to the human skeleton; rather, it refers to the framework that maintains the operation of the pivot axis, like the socket of a door hinge or the hinge that fixes the doorframe.

Therefore, bone shaking does not refer to flaccidity and disability of the sinews and bones with inability to walk; it refers to complex syndromes caused by looseness and wobbling of a door pivot, or by a door pivot tilting and about to fall. Hence the following text states: What is called bone yao is because it shakes (所谓骨繇者，摇故也), and bone yao is when the joints are lax and do not gather (骨繇者，节缓而不收也). This uses analogy to indicate that when ShaoYang is diseased, it is like disordered pivoting: KAI and HE fail to function properly; clinically the manifestations are necessarily complex and often mixed. Treatment should straighten out the root source and use simplicity to control complexity; therefore treatment should exhaust its root (当穷其本也).

4. TaiYin corresponds to KAI

It governs transformation and transportation of refined essence (精微), generation of nutritive Qi (营气), and expelling the old while taking in the new.

TaiYin can transform and operate nutritive Qi. The Lingshu, Ying Qi (Nutritive Qi), says: Therefore Qi emerges from TaiYin, pours into Hand Yangming… and again emerges from TaiYin. This is where nutritive Qi travels (故气从太阴出，注手阳明……复出太阴。此营气之所行也). Nutritive Qi circulates along the twelve channels, beginning with Hand TaiYin and also ending with Hand TaiYin. The Lingshu, Ben Shen (Root Spirit), says The Spleen stores nutritive (Qi) (脾藏营); the Lingshu, Yingwei Shenghui (Assemblage of Nutritive and Defensive), says Nutritive emerges from the middle jiao (营出于中焦). All state that the Foot TaiYin Spleen is the place where nutritive Qi is generated and transformed. It can be seen that TaiYin governs the generation and circulation of nutritive Qi in the human body, and this cannot be separated from TaiYin governs KAI (and guān, gate/closure) (太阴主开（关）): when it is closed, nutritive is transformed; when it is open, it is operated and circulated.

Therefore, when TaiYin’s opening/closing is abnormal, it can lead either to insufficient transformation and generation of nutritive Qi, or to sluggish circulation. The Suwen, Ci Jin Lun Pian (Treatise on Needling Prohibitions), says The Spleen acts as its envoy (脾为之使), indicating that the TaiYin Spleen can transport the refined essence of water and grain throughout the body—this is the principal manifestation of TaiYin governing KAI. When abnormal, the Spleen loses健运 (healthy transportation), ascending and descending are disordered, clear and turbid are mixed, and epigastric focal distension and diarrhoea arise. Therefore, if KAI breaks down, the granary has nothing to transport; ‘ge-dong’ (膈洞) occurs; for ge-dong, take it from TaiYin (故开折则仓廪无所输，膈洞，膈洞者取之太阴).

5. JueYin corresponds to HE

It governs closing and restraint of Yin Qi, containing and generating Yang Qi, and storing blood and housing the hun (魂).

The Suwen, Zhi Zhen Yao Da Lun Pian (Great Treatise on the Most Essential Truth), states that JueYin is the point where two Yins mutually reach exhaustion (两阴交尽), and further says: When two Yins mutually reach exhaustion, it is called you (幽) (两阴交尽谓之幽). You means confinement and restraint. JueYin is the exhaustion of the two Yins, TaiYin and ShaoYin, and therefore it can confine Yin Qi so as to facilitate the containment and generation of Yang Qi. Moreover, JueYin Liver-wood stores blood and governs ministerial fire; it is both the child of Kidney-water and the mother of Heart-fire, and the JueYin Pericardium governs joy and pleasure.

Therefore, JueYin governs HE, and can also coordinate water and fire to resist cold and heat. Although it is where the two Yins reach exhaustion, it is also where Yin is exhausted and Yang is generated. When abnormal, Yin and Yang are disordered, cold and heat are intermingled, Qi and blood are dysregulated, and the spirit-emotions are constrained: If HE breaks down, Qi is cut off and there is joy and sorrow; for sorrow, take it from JueYin (阖折则气绝而喜悲，悲者取之厥阴).

6. ShaoYin corresponds to SHU

It governs mutual completion of water and fire and communication between Heart and Kidney.

ShaoYin governs the Heart and Kidney: one Yin and one Yang, one water and one fire. Its channel Qi and Zang Qi pivot between TaiYin and JueYin. This important physiological basis is founded upon the generating and restraining, overacting and counteracting relationships among the Five Phases. ShaoYin Kidney-water can nourish JueYin Liver-wood. Under physiological conditions, through the pivoting function of the ShaoYin Kidney, essence-Qi is continuously conveyed to the JueYin Liver-wood, maintaining the Liver’s free coursing and its function of storing blood.

At the same time, Heart-fire can warm and generate Spleen-earth; therefore, under the pivoting function of the ShaoYin Heart, TaiYin Spleen-earth can be warmed and transformed without interruption, thereby strengthening transportation and transformation of water and grain into Qi and blood.

Therefore, under pathological conditions,especially when ShaoYin Heart–Kidney water–fire is abnormal—besides water and fire failing to aid each other with manifestations of Heart–Kidney not communicating, it can also lead to loss of governance in the pivot mechanism’s transport and transformation: either fire failing to warm earth, causing retching and diarrhoea and reversal cold of the limbs; or water failing to contain wood, causing dizziness, palpitations, and the body wanting to curl up. The Lingshu, Gen Jie, summarises this as the pivot mechanism being blocked; therefore, If SHU breaks down, the vessels become knotted and do not flow; for non-flowing, take it from ShaoYin (枢折则脉有所结而不通，不通者取之少阴).

The Lingshu, Gen Jie, discusses the pathological states of abnormal KAI, HE, and SHU, providing a theoretical basis for channel differentiation based on the functional attributes of KAI, HE, and SHU. According to the original text, sudden disease (暴病) is in TaiYang; flaccidity disorders (痿疾) are in Yangming; bone yao (骨繇) is in ShaoYang; Ge-dong (膈洞) is in TaiYin; Qi cut-off with joy/sorrow is in JueYin; and knotted vessels with non-flowing (脉结不通) is in ShaoYin. The key to channel differentiation lies in accurately understanding the characteristics of the disorders caused by the breakdown of KAI, HE, and SHU. Taking TaiYang governs KAI as an example: failure of the TaiYang KAI mechanism affects the dissemination of defensive Qi on the body surface, leading to impaired exterior defence and susceptibility to exterior patterns; or, due to dysfunction of TaiYang’s distribution of Qi and its flourishing at the exterior, there may appear skin symptoms such as dryness of the interstices, numbness, and loss of sensation. In internal medicine these are often differentiated as Lung-system disorders, but in acupuncture’s characteristic differentiation they are diagnosed as (Foot) TaiYang channel disease, and treated with back cupping along the channels, gua sha, and so forth, in order to open the Qi of TaiYang.

Zhang Jiebin, in Leijing, Zhujing Gen Jie Kaihe Bing Ci, said: What is called KAI, HE, and SHU is nothing more than the wish to clarify interior and exterior and thereby divide the methods of differentiation and treatment. The theory of KAI, HE, and SHU uses the components of a door as an analogy to explain the different characteristics and functions of the channels. To a certain extent, it reflects the distribution of channels across exterior–interior levels. In general, the three Yang are exterior and the three Yin are interior; in detail, each of the three Yin and three Yang has its own exterior–interior distinctions. Taking the three Yang channels as an example: TaiYang disease is in the skin and hair; Yangming disease is in the muscles; ShaoYang disease is in the fascia; each has its own region (太阳之病在皮毛，阳明之病在肌肉，少阳之病在筋膜，各有其部也, Lingshu Xuanjie, Gen Jie). It can be seen that the disorders caused by breakdown in the three Yang, following KAI, HE, and SHU, progressively deepen, yet all remain within skin, flesh, sinews, and bones; compared with the Zang–fu, they still belong to Yang within the human body and are closely related to Yang Qi function. The breakdown of the three Yin is also a gradual process: TaiYin KAI breakdown is in the Zang–fu; JueYin HE breakdown proceeds from Zang–fu Qi binding to affecting the emotions; ShaoYin SHU breakdown belongs to further binding of formless Qi that injures the formed blood vessels, leading to knotted vessels and non-flowing. If knotted vessels and non-flowing further develop, the disease moves from channels into collaterals and no longer belongs to the scope of channel differentiation.

Based on the relevant discussion in the Lingshu, Gen Jie, and modern physicians’ explanations, the exterior–interior level characteristics of the disorders caused by abnormal KAI, HE, and SHU, and their channel differentiation, are summarised in the following table.

Category (original term)	Examples of modern conditions	Level	开/阖/枢 breakdown	Channel diagnosis
Sudden disease (暴病)	Common cold, allergic asthma, acute stage of non-specific low back pain, etc.	Skin and hair	TaiYang KAI breakdown	Foot TaiYang channel
Flaccidity disorders (痿疾)	Myasthenia gravis, Guillain–Barré syndrome, multiple system atrophy, etc.	Muscles	Yangming HE breakdown	Foot Yangming channel
Bone yao (骨繇)	Knee osteoarthritis, ataxia, Parkinson’s disease, osteoporosis, etc.	Sinews and bones	ShaoYang SHU breakdown	Foot ShaoYang channel
Ge-dong (膈洞)	Upper gastrointestinal obstruction, reflux oesophagitis, diarrhoea, etc.	Zang–fu	TaiYin KAI breakdown	Foot TaiYin channel
Qi cut-off with joy/sorrow (气绝喜悲)	Depression, polycystic ovary syndrome, insomnia, etc.	Emotions	JueYin HE breakdown	Foot JueYin channel
Knotted vessels and non-flowing (脉结不通)	Diabetic complications, cardiac arrhythmia, etc.	Blood vessels	ShaoYin SHUbreakdown	Foot ShaoYin channel

The theory of KAI, HE, and SHU originates from changes in the Yin–Yang Qi-numbers across the four seasons. Heaven has the alternation of the four seasons and the rotation of day and night, morning and dusk; all things thereby grow and are stored, and thus have manifestations of KAI, HE, and SHU. Humans correspond to this, and thus there is separation and union of the three Yin and three Yang: when separated, there is KAI, HE, and SHU; when united, there is one Yin and one Yang—the three channels must not lose each other .