Taijiquan possesses not only unique external features, but also precise internal requirements. The focus is on yi (mind intention), and qi (internal energy) and not just on li (unharnessed strength). The first criterion is using the yi to move qi, which in turn moves the body's jing (trained power). In other words, in Taiji, one practices and trains energy by trying to focus and concentrate the energy from the entire body in the performance of each action. By using the mind, qi and the physical body, one achieves the three harmonies, as well as the ability to utilize whole-body power.
Qi is not a mysterious and magical thing. The ancient Chinese related qi to fire. In the modern era it is often likened to an electric current. Although not a tangible organic substance, qi is one's energy or life force. This energy circulates through the pathway of meridians (jingluo) throughout the body. Qi is produced in an area located between the kidneys and stored in the dantian (energy centre) in the lower abdomen. From here, it is distributed to the different parts of the body. Although qi continuously circulates within the body, most people are unaware of its presence (just as one does not feel the flow of blood and the lymphatic fluids). The sensation or awareness of qi usually begins as warmth in the palms or tingling in the fingers. It is also manifested as a feeling of fullness. The sensation of fullness is gradually felt throughout the body, as if one were expanding outwards in all directions. There is also the sensation of warmth throughout the body. Certain rules need to be followed to stimulate, intensify and ensure the adequate circulation of qi. Only when one has cultivated abundant qi will it be able to "push through" the gateways and "saturate" (guan quang) every part of the body, bringing with it the benefits of good health and providing the basis for martial proficiency. This requires consistent training over a period of time.