Qi is our human mobility energy and the intentional feeling of Yi is an inspiring energy. Both are required in our normal life, we can't live with one without the other. The stockpile of Qi resides in the meridians and requires Yi to amplify it for physical action.
Qi is the optimal power for an internal martial artist. It is potential energy fuel that is easily ignited into explosive force for a quick punch or kick. The Feeling Yi triggers the Qi, which in turn generates the Willpower of Shen, the power of the spiritual Soul (or immortal Soul).
To generate the power of mastery, we think and feel it (Yi), we will it, and we create a huge amount of fuel to ignite Qi like gasoline to produce an explosive force. Shen contributes a massive amount of oxygen which combines with the "human fuel" of Qi to ignite a super explosive force.
Therefore, a devoted martial artist's body strength is supported and sustained by the resilient Willpower of Shen and Feeling Yi from the brain. Feeling Yi is the best generator of Qi for physical action. The source of the connection between the three (Yi, Qi, and Shen) is the best human treasury. These three essential elements are the central emphasis and application of Chinese martial artists. In addition, they constitute the basis for human productivity, enabling us to accomplish our daily obligations to society.
Millions of people throughout the world have been living long, productive lives from the daily practice of Tai Chi Chuan. The Brain Aerobics of Tai Chi Chuan is a great contribution to our well-being, making the brain strong and healthy. What is good for the brain is good for the body.