From my forty years of Tai Chi practice. It seems to me that Tai Chi is a form of muscular therapy. At the beginner level, Tai Chi starts with muscles relaxed in slow motion and the breathing improves. As time goes by, the breathing is getting more deeper and less shallower. Unfortunately, most people just ignore the most important breathing part. The deep breathing part has a lot to do with muscle control in the body. It is because muscle contraction requires energy. Where does the energy come from? Well, it comes from the foods we eat and the oxygen we breathe.
If the practice of Tai Chi was done properly, one would take a deep, slow and long breath along with the first move. Then, exhale on the next movement. The muscle cells will use the oxygen which stored in the tissues and decompose the glucose into ATP energy for contraction. After the deep inhalation on the first move, it will provide enough energy for the muscles to perform the movement. Then, next is to exhale the carbon dioxide waste from the cell respiration process. However, there is still enough oxygen left in the body for the next movement during the exhalation. The breathing cycle repeats throughout the whole Tai Chi practice. By the time the practice was done, there will be more oxygen provided for the body to perform its function throughout the day. Literal speaking.
The slow motion in Tai Chi practice is only use the oxygen slowly while a greater amount was breathed in. Thus the body will never be lack of oxygen or hypoxia. As compare to sprint, the runner gets tired in few minutes due the the depletion of oxygen to sustain the reproduction of the vital energy.
The vital energy works the same way for all the internal organs in the body. Two third of the body is oxygen. If ample of oxygen was provided to maintain the two third level inside the body, the internal function of the body will be performed to its peak at all times.
The slow movements and breathing in Tai Chi practice will keep the cell respiration active. If the deep breathing method was performed continuously through the day, even not practicing Tai Chi, the body will be very healthy and function to its peak at all times. One will feel a lot stronger, more alert and more sensitive in the five senses. Indeed, the desire in the sexual department becomes a most noticeable factor.