1. Qi

Before any scientific investigation of Qi, the concept of Qi and its properties in Chinese philosophy must be known, in order to judge how closely any modern scientific interpretation fits.

Qi is a fundamental concept or terminology in traditional Chinese medicine (TCM) with multiple levels of meanings. If you read enough in TCM, you would find that TCM seems to use “qi” to describe almost all invisible forces that affect human lives and health. More specifically, Qi can devote the invisible forces both outside and inside the human body in many different ways (1). We will introduce some of these uses here as we lay out the some basic background of qi in Chinese philosophy and culture.

Qi might be first discussed by Chinese philosophers (2). Huai Nan Zi, a Daoist book around 122 B.C., states that the Dao originated from Emptiness and Emptiness produced the universe. The universe produced Qi,– Here it was most likely referred to qi energy outside of body.

Zhang Zai (1020-1077) said that the Great Void consists of Qi. Qi condenses to become the myriad of things. He clearly understood the concept of the matter-energy continuum, in the sense of modern physics, even though these ideas were conceived centuries later. He also saw the indestructibility of matter-energy as revealed by his statement “Qi in dispersion is substance and so is it in condensation”. Since Qi forms myriad of things implies that Qi must also involve information, in modern terminology. He also said that every birth is a condensation and every death a dispersal of Qi. Thus, just as “Qi” is the energetic foundation of the universe, it is also the physical and spiritual substratum of human life. Zhu Xi (1131-1200) confirmed that Qi condensing can form beings and the conservation of energy, when he stated: “When dispersing Qi makes the Great Void, only regaining its original misty feature, but not perishing; when condensing it becomes the origin of all beings”.

From these classic discussions, we should say that a modern scientific explanation of Qi must involve aspects of matter, energy, and information, which remind us the new finding in physics, the “hidden dimension.”

This universal Qi, postulated by Chinese philosophers, will be denoted by “Qi” to differentiate from its usage in Chinese medicine, which will be denoted by Qi (without quotation).

TCM has been using concept of Qi primarily in two senses. The first use is in abbreviation of function or condition. Qi is used to describe the complex of functional activities of any organ. For example, Heart-Qi, is not a refined substance in the Heart, but indicates the complex of the Heart’s functional activities, such as, governing the Blood, controlling the Blood vessels, etc. Thus, there is Liver-Qi, Heart-Qi, Lung-Qi, etc. In the sense, it is also used to indicate disorders of the organ’s function or body’s disorder – for example, “Qi Bi” (Qi constipation) and “Qi Liu” (Qi tumor). These abbreviations will not be discussed in more details here, but Qi as an actual refined substance will.

The second use of Qi is vital energy, which stems from the Chinese character for Qi (气). Qi can be decomposed into two radicals, which stand for “vapor, steam or gas” and (uncooked) “rice” or grain. In the second case, it is the energy or life-resource within the grain that is called “qi”, not the material or chemical part itself. This is evidence by the fact that rice could lose its taste and “gain qi” after being offered as oblation to the soul. This usage implies that Qi can be used as immaterial as vapor and as dense and material as rice. It also implies that Qi could be just subtle substance (vapor) produced from a coarse one (rice), just as cooking rice produces steam. Thus, sinologists generally agree that Qi is matter-energy in the sense of modern physics.

Natural energies, which are not tangible or visible are particular specializations of this use of “Qi” – for example, Seasonal Qi, Heavely Qi , Earthly Qi and Food Qi. Other examples are environmental factors or forces that may affect human health, such as cold, dampness, dryness, etc.

Just as “Qi” is the energetic foundation of the universe, it is also the physical and spiritual substratum of human life. In Chinese medicine, the terminology employed depends on the state of the energy-matter. Energetic material, ranging from less dense to denser, is termed: Spirit (Shen 神), Energy (Qi 气), Essence (Jing 精), Blood (Xue 血), Body Fluids (Jin Ye 津液), Marrow (Sui 髓), and Bone (Gu 骨).

The three most important energetic substances for the function of the body are Jing, Qi and Shen, representing different stages or phases of life phenomenon. These are known as the “Three Treasures” or “San Bao” (三宝).

2. Jing

In order to understand concept of Qi, we need briefly discuss another related TCM concept “Jing”. Jing is usually translated as “Essence”. The Chinese character implies that it is a refined substance derived from a coarser one. In many senses, Jing could be the internal sources or structure base of Qi. Jing itself can be divided into different types or be looked from different angles. If Qi is used in the sense of function, Jing would be understood as the physiological structure. If Qi is considered as vital energy, then Jing would be the physiological systems that support the energy.

For example, endocrine system is frequently referred as “jing” in TCM. Keep it in mind that there are disagreements on what can be called Jing, what can not. Basically there are three different types of Jing discussed in TCM books.

Prenatal Jing (Pre-Heaven Essence)

At conception, the Prenatal Jing passes from the parents to the embryo. This essence, together with nourishment derived from the Kidneys of the mother, nourishes the embryo and fetus during pregnancy. It is the only kind of essence present in the fetus.

Prenatal Jing determines basic constitution, strength, vitality, and so individual uniqueness. Since Prenatal Jing is inherited from the parents, it is very difficult to influence in later life. Some say the quality and quantity of Prenatal Jing cannot be altered. The way to conserve Prenatal Jing is by striving for balance in all life activities – moderation in diet, work/rest, and sexual activity. Irregularity or excess in these areas wastes Prenatal Jing. Certain exercises help conserve Prenatal Jing, such as Tai Chi and Qigong. Tortoise breathing may positively influence it.

Postnatal Jing (Post-Heaven Essence)

After birth, the infant starts to eat, drink, and breathe on its own. The Spleen and Stomach then extract and refine Qi from the food and drink and the Lung gets Qi from the air. Postnatal Jing is the complex of essences thus refined and extracted. It is the material basis for the functional activity of the body’s internal organs and metabolism. The Kidneys store any surplus Jing to be released when required.

Postnatal Jing is continually being used by the body and replenished by food and drink. The Prenatal Jing is enriched and functions optimally only through the action of the Postnatal Jing. Without the function of the Prenatal Jing, the Postnatal Jing cannot be transformed into Qi.

Kidney Jing

Kidney Jing plays important role in physiology. It arises from both Prenatal and Postnatal Jing. Is hereditary, like Prenatal Jing and determines ones constitution. However, it is partly replenished by the Postnatal Jing.

Kidney essence is stored in the Kidneys, but has fluid-like nature and circulates all over the body, especially in the Eight Ancestral (Extraordinary) Vessels. Kidney Essence is said to have the following functions:

(i) It is the basis for growth, development, sexual maturation, and reproduction. — It moves in long, slow developmental cycles (men’s Essence flows in 8-year cycles; women’s in 7-years) and presides over the major phases of development in life.

In childhood, Kidney Jing controls growth of bones, teeth, hair, brain development and sexual maturation. When Kidney Jing is weak, there may be poor bone and teeth development, stunted growth, and mental retardation.

In puberty, Kidney Jing controls reproductive function and fertility, and normal development into adulthood. Developmental problems that can occur at this time, such as amenorrhea, are often related to weak Kidney Jing.

Conception and pregnancy are guided and controlled by Kidney Jing. When Kidney Jing is weak, signs such as infertility, chronic miscarriage and other such problems may occur.

Kidney Jing declines naturally, finally producing the characteristic signs of aging, such as: hair/teeth loss, impairment of memory, etc.

(ii) Kidney Jing is the basis for Kidney Qi — Jing is fluid-like and therefore more Yin and so can be considered as an aspect of Kidney Yin. It forms the material basis for Kidney Yin to produce of Kidney Qi. Kidney Yin is warmed by Kidney Yang and the heat from the Gate of Vitality (Ming Men) to produce Kidney Qi. However, Kidney Jing is necessary before this transformation can occur.

Kidney Qi can become deficient with age producing signs such as: aching and weakness of the loins and knees, weak bladder, frequent, clear or dripping urination, thin and profuse leukorrhagia..

(iii) Kidney Jing produces Marrow — Marrow produces bone marrow, the brain, and fills the spinal cord. Marrow in Chinese medicine has no exact equivalent in Western Medicine).

The Brain in TCM is called the “Sea of Marrow”. Therefore if Kidney Jing is weak, the brain may be undernourished, leading to poor memory or concentration, dizziness, a feeling of emptiness in the head, etc.

(iv) Kidney Jing determines our Constitution — Protection from exterior pathogens depends largely on the strength the Defensive (Wei Qi), discussed below. However, the state of Kidney Jing also influences our strength and resistance. If the Essence is “wasted” or poorly stored, the person may have lowered immunity to exogenous pathogenic influences and constantly be ill with colds, allergies, etc.

(v) Essence and Qi are the material foundation for Shen (Mind) — This postulate is used in Chinese medicine because Jing, Qi and Shen represent three different states of the condensation of “Qi”, from coarse, to rarified, to subtle and immaterial, respectively. If Jing and Qi are healthy and plentiful, the Mind will be happy. If both Jing and Qi are deficient, the Mind will suffer.

3. Different Types of Qi

To help students of TCM to understand “qi,” modern TCM books started to define different “qi” one way or other. These exploratory definitions discussed below may inspire us to think about the concept of Qi more carefully and comprehensively, they may also create new problem or confusing in understanding the true meaning of qi and its applications in TCM. However, as long as we keep it in mind that qi is more a multi-meaning or multi-component concept than a specific matter, energy or function, we would be less likely to deviate from the original meaning of qi.

Some TCM books have classified the life-force energy according to its location and function in the body (2, 3). Here are some examples of the definitions of various qi for us to start thinking this abstract concept in a more concrete way:

Prenatal Qi (Yuan Qi)

Yuan Qi is said to be Essence in the form of Qi. Yuan Qi has its root in the Kidneys and spread throughout the body by the San Jiao (Triple Burner). It is the foundation of all the Yin and Yang energies of the body. Yuan Qi, like Prenatal Jing, is hereditary, fixed in quantity, but nourished by Postnatal Jing.

Yuan Qi is the dynamic force that motivates the functional activity of internal organs, and is the foundation of vitality. It circulates through the body in the channels, relying on the transporting system of the San Jiao (Triple Burner). It is the basis of Kidney Qi, and dwells between the two Kidneys, at the Gate of Vitality (Ming Men). It facilitates transformation of Qi described below, and participates in producing Blood. It emerges and stays at the 12 Source points.

Center Qi (Zhong Qi)

Energy generated from the Spleen and Stomach, whose function is to transport the Qi from food into the chest where it is combined with the Heart’s and Lungs’ Qi.

Food Qi (Gu Qi)

Food entering the Stomach is first “rotted and ripened”; then transformed into a usable form by the Spleen. The energy derived from this food essence is divided into Pure Yang Qi and Impure Yin Qi by the Spleen. The Pure Yang Qi is sent upward to the chest by the Center Qi via the Middle Burner. First, it goes to the Lungs where it combines with the

Heavenly Qi to form Gathering (Zong) Qi. Then, it is transported to the Heart, where it unites with the Yuan Qi form the Kidneys to produce Blood. The turbid Yin Qi of Gu Qi is sent down by the Spleen via the Middle Burner to the Lower Burner to be further refined and excreted.

Clear Yang Qi (Qing Qi)

This is the pure energy form the Gu Qi sent by the Spleen to the Upper Burner and chest via the Middle Burner.

Turbid Yin Qi (Zhou Qi)

This is the impure energetic essence of Gu Qi transported by the Spleen via the Middle Burner to the Lower Burner to be further refined and excreted.

Gathering Qi (Zong Qi)

This is also called Chest Qi (Xiong Qi), Big Qi Da Qi) and “ Big Qi of the Chest”. The Spleen sends the pure energetic essence of Gu Qi up to the Lungs, where (with the help of Yuan Qi and Kidney Qi) it combines with air and transforms into Zong Qi.

Zong Qi nourishes the Heart and Lungs. It enhances and promotes the Lungs in controlling Qi and respiration and the Heart’s function of governing the Blood and Blood Vessels. If Zong Qi (Gathering Qi) is weak, the extremities, especially the hands, will be weak or cold.

Zong Qi gathers in the throat and influences speech (which is under control of the Heart) and the strength of voice (under control of Lungs). The strength of Zong Qi can also be determined form the voice – weak (strong) voice, weak (strong) Zong Qi. It is easily affected by emotional problems, such as grief and sadness, which disperse the energy in the chest and weaken the Lungs.

The Lungs and Kidney mutually assist each other via Zong Qi and Yuan Qi. Zong Qi flows downward to aid the Kidneys while Yuan Qi flows upward to aid in respiration (and the formation of Zong Qi). The chest area where Zong Qi collects is called the “Sea of Qi”. Zong Qi and the Sea of Qi are controlled by Shanzhong (Ren-17). Gathering Qi is also treated by the Heart and Lung Channels and breathing exercises.

True Qi (Zhen Qi)

Zong Qi originates in the Lungs. It is transformed into Zhen Qi with the catalytic action of Yuan Qi. Zhen Qi is the last stage in the transformation and refinement of Qi. It is the Qi that circulates in the channels and also outside the body and nourishes the organs. Zhen Qi has two different forms, Ying Qi and Wei Qi.

Ying Qi (Nutritive Qi)

Ying Qi nourishes the internal organs and the whole body. It spends two hours in each channel, moving through all twelve channels in a twenty four hour period (termed the Horary Cycle). During these periods, the corresponding organs are nourished and maintained by the Ying Qi.

It is closely related to Blood, and flows with Blood in the vessels as well in the channels. Ying Qi is the Qi that is activated by insertion of an acupuncture needle. It is closely related to the emotions, since it can be directed by thought.

Wei Qi (Protective Qi)

Wei Qi is fast moving, “slippery” and more Yang than Nutritive Qi. It flows primarily under the skin and in between the muscles, especially in the Tendino-Muscular meridians. Wei Qi protects the body from attack by exogenous pathogenic factors such as, harsh weather conditions, microorganisms, harmful emotions, and evil spiritual forces. For example, a deficiency of Wei Qi can make someone prone to frequent colds.

There are also three Wei Qi energy fields extending several feet from the body. All energetic forms of the body, including organs, blood vessels, nervous system, etc., can be accessed and treated through these fields.

• Wei Qi warms, moistens, and aids in nourishing skin and muscles. For example, a person with a deficiency of Defensive Qi will tend to feel easily cold.

• Wei Qi adjusts the opening and closing of pores; thus, regulating sweating and the body temperature. It is controlled by the Lungs, which regulates its circulation. The Lungs also disseminate fluids to moisten the skin and muscles. These fluids mix with Wei Qi. Perspiration function depends on the Lungs ability to circulate Wei Qi and fluids to the exterior. A weakness of Lung Qi may cause a weakness of Wei Qi, and lead to susceptibility to frequent colds.

• Deficient Wei Qi can lead to spontaneous sweating. When an exogenous pathogen (e.g., Wind-Cold) invades the Exterior, the pathogen can block the pores, inhibiting the function of the Wei Qi, and blocking sweating. The treatment is to restore the Lungs’ function of dispersing, strengthen the Wei Qi and produce sweating. Sweating therapy is often used in the early stages of a Wind-Cold pathogenic invasion.

• Defensive Qi has its root in the Lower Burner (Kidneys). It is nourished by the Middle Burner (Stomach and Spleen) and is spread outwards by the Upper Burner (Lungs).

• Wei Qi has a complex circulation pattern, of 50 cycles during a 24 hour period, 25 times in the day and 25 at night. In the daytime, Wei Qi circulates in the Exterior, but at night it goes into the Interior and circulates in the Yin Organs. From midnight to noon, the Wei Qi is exterior, and is at its maximum strength at noon. From noon to midnight, the Wei Qi gradually withdraws into the Interior, to protect the Yin Organs.

• It is said that sleeping under an open window at night gives exogenous pathogens a better chance for attack than during the daytime, since the Exterior of the body is less well protected. Hence, it is easier to catch a cold at night than in the daytime.

• Wei Qi can become thicker and extends farther out during Qigong practice. Therefore, it may take longer to move inward at night, causing some Qigong practitioners to have difficulty falling asleep after evening practice.

Upright Qi (Zheng Qi)

Upright Qi is also known as Righteous Qi. This is not another type of Qi but a general term to indicate the various Qi protecting the body from invasion by Xie Qi.

Postnatal Qi (Hou Tian Zhi Qi)

Energy derived from food and drink (from Earth) and air (from Heaven) which are cultivated after birth. Postnatal Qi depends on Prenatal Qi for development. Both form the foundation for the body’s vital energy.

Organ Qi (Zang and Fu Qi)

This is the energy responsible for the functioning of the internal organs. The Yang-Fu, hollow bowels, produce Qi and Blood from food and drink. The Yin-Zang, solid viscera, store vital substances. Each organ has its own energy corresponding to one of the Five-Element energies, which respond to the universal and environmental energy fields. Thinking, feeling, metabolism and hormones can influence the Organ Qi.


1. Wiseman N. English-Chinese Chinese-English Dictionary of Chinese Medicine. Hunan, China: Hunan Publish of Science and Technology. 1996.


3. Johnson, J. A. Chinese Medical Qigong Therapy. International Institute for Medical Qigong, Pacific Grove, 2000.

Author's Bio: 

Dr. Eisen is a retired scientist who created mathematical models in cancer chemotherapy and epilepsy. He has studied and written articles on Qigong, Yoga and martial arts and Chinese medicine. See


Dr. Chen is an associate professor in the Center for Integrative Medicine and Department of Psychiatry at the University of Maryland School of Medicine. Dr. Chen is a NIH-funded investigator conducting survey research on adolescent substance abuse, and conducting clinical studies investigating the clinical feasibility and efficacy of Chinese energy therapy for treating osteoarthritis and addiction. With intensive training in research methodology and statistics, Dr. Chen has had extensive experience in designing and implementing various research projects, including clinical trials, and has long been interested in the scientific study of qigong and its medical applications. As long-time practitioner of qigong, Dr. Chen has observed many unexplained successes in qigong healing, and is willing to subject this ancient therapy to serious scientific examination. His major research interests include research methodology, epidemiology of substance abuse, and health applications of energy therapy and mind-body integrative medicine. Dr. Chen is among the few scientists who have both first-hand knowledge of qigong practice and active involvement in scientific research of Qigong in the U.S. His research includes both verification of qi energy through laboratory detectors, and medical application of qigong therapy in clinical settings. He has been involved in clinical trials to examine the feasibility and efficacy of adding qigong therapy in treating heroin and cocaine addiction, as well as osteoarthritis, fibromyalgia, cancer and chronic pain. He is currently working on NIH- and foundation-funded research projects on the application of bio-energy therapy and self-help methods in the treatment of addiction, arthritis, cancer and other health problems.