In Chinese medicine, Qi is the fundamental substance responsible for movement, the essential life force of the body. It is the medium that links all events with each other, transcending time and space because patterns are formed that persist beyond their moment of origin. Qi is fundamental to Chinese understanding of health, disease and medical treatment. Without Qi, Moisture and Blood stagnate, coagulate and cease circulating.
In the Chinese cultural tradition no distinction is made between matter and energy, so Qi could be understood as matter on the verge of becoming energy, or energy at the point of materializing -- although traditionally the approach is functional and concerned with what it does. Its functions include: acting as a source of all movement in the body, as well as accompanying it; protecting the body; acting as the source of harmonious transformation in the body; governing retention of the body's substances and organs; warming the body. In Japanese, Qi is called ki and in yoga it is called prana. Wilhelm Reich called it 'orgone energy'; Russian experiments with life force, called 'bioplasma', led to the development of Kirlian photography which makes the energy field of living organisms visible.
Just as the Earth is comprised of land, ocean and atmosphere, so the body is organized as Blood, Moisture and Qi. Blood governs tissue, the material form of the body. Moisture governs the internal environment, the body's inner ocean. Qi governs the shape and activity of the body and its process of forming and organizing itself. Qi is the motive force that establishes respiration. This enables the Qi of the air to enter the body. The essence of food is also a form of Qi. When the Qi of food and the Qi of air enter the body, they become one entity known as "pure" or 'righteous" Qi. Air Qi represents the immaterial motivating aspect of Qi and Food Qi the material or constructing aspect.
Qi has many aspects; good health depends on the presence and action of five Qi which are associated with different parts and functions of the body: Organ Qi ( zang-fu-zhi-Qi), Meridian Qi (Jing-luo-zhi-Qi), nutritive Qi (yong-Qi), protective (defensive) Qi (wei-Qi) and ancestral Qi (Qi of the chest (zong-Qi) or essential energy). Both nutritive Qi and protective Qi are transformations of ancestral Qi. The guardians of ancestral Qi (or congenital Qi) are the Kidney. Patterns of Qi disharmony are therefore very numerous. There are two major patterns of disharmony associated with Qi: deficient Qi (affecting the whole body, as in the case of lethargy) and stagnant Qi (as in the case of aches and pains).
Every Organ has its own Qi. If this Qi is deficient or stagnant, this can result in disharmonies of the Organ. Deficient Lung Qi may predispose a person to catching colds, for example. Meridian Qi is Qi moving along the Meridians throughout the body. Blockages can result in deficient Qi to the Organs and symptoms of stagnant Qi. Nutritive Qi moves the Blood through the Blood Vessels to nourish the body. Protective Qi is what combats external pernicious influences, such as weather, pathogenic organisms or pollutants, and corresponding somewhat in western medicine to the immune system. Qi of the chest, or ancestral Qi, moves the breath, the Lung and the Heart.