Yang qi is the opposite of yin qi.  It refers to either the qi in the six intemal organs (gallbladder, stomach, large intestine, small intestine, urinary bladder and sanjiao), or defensive energy, or the upward, outward-moving invigorating qi.

1. When a disease lingers, it goes deep into the body and changes for the worse. When communication between the upper body and lower body is cut off, even a good physician will not be any help.
2. The accumulation of yang qi cause death for it will block communication. The treatment is to discharge.
3. If the patient is not treated in time or if the doctor is incompetent, he is in great danger.
4. In the daytime, yang qi mainly protects the exterior human body. At dawn, yang qi is active around the body.
5. Yang qi is strongest at noon.                                                                                                  
6. When the sun is going down in the west, yang qi around the human body begins to ebb and the open sweat pores begin to close.
7. So everybody should sleep at night to preserve yang qi. The skin and hair will close like a door and the tendons and bones will be undisturbed. Do not expose yoursef to fog and dew.
8. If you act contrary to the laws by which yang qi moves at these times, evil air will invade your body.
Also learn more in the article Acupuncture Single Points for prolonged labor.