Wei Qi 衛氣
Yuan Qi 元氣 and Zong Qi 宗氣 come together and become Ying 营氣 and Wei Qi 衛氣. Ying Qi is the Qi that flows along the channels keeping the supply of nutrients, mainly from food and drink, reaching the organs. Wei Qi is protecting Qi and so is the Qi that protects us. It runs along outside the channels and also keeps us warm. It is like a body guard. Our Wei Qi tries to protect us and keep us safe from any negative Qi or viruses that come to attack us. So there are two parts to the Qi we develop. Ying Qi keeps us going through food and drink. Wei Qi keeps us warm, protects us from the outside, from attacks from the temperature, from germs and viruses. This all depends on how hot or cold the temperature is and also how strong the germs or virus. If our Wei Qi is stronger, then we are protected, if it is not strong enough and the temperature, germs or virus are stronger, then we will become sick.
Wei Qi follows a system as it flows along the channels of the body. In the day time the Wei Qi flows along the Yang channels 25 times. From this we can understand why the Yang channels are stronger during the day time, and need more Wei Qi. At night time, when we rest and sleep, the Wei Qi flows along the Yin channels to protect them and keep them warm.