Ren meridian and Du meridian originally belonged to odd meridian and eight meridians. Because they have definite acupoints, doctors call them fourteen meridians together with the twelve meridians.

The second pulse of Ren Du originates from the Yin Hui point between the legs directly below the human body, and runs from the front of the body up to the pith point under the lip along the center. This meridian is Renmai. The Du Meridian, on the other hand, goes backwards along the spine from the point (some say Changqiang point), reaches the top of the head and goes forward between the eyes, reaching the gingival point of the oral maxilla. Ren meridian governs blood and Du meridian governs qi, which is the main meridian of human body. If Ren Du's two veins are connected, then the eight veins are connected; Eight veins are connected with hundreds of veins, which can further enhance physical fitness, strengthen tendons and bones and promote circulation. Ren-Du pulse is very important in TCM pulse diagnosis and Taoist health guidance. At the same time, because there are exaggerated descriptions in martial arts novels, for example, people with high martial arts can get through their own second pulse of Ren Du, and once the second pulse of Ren Du is opened, martial arts will advance by leaps and bounds, so it has become the most familiar name of one pulse.

Ren meridian and Du meridian originally belonged to odd meridian and eight meridians. Because they have definite acupoints, doctors call them fourteen meridians together with the twelve meridians. Ren pulse governs blood, which is the sea of yin pulse; Du meridian governs qi, and qi is the sea of yang pulse. In other words, Ren meridian and Du meridian respectively play a leading role in the six yin and six yang of twelve meridians. When the twelve meridians is full of qi and blood, it will overflow into Ren Du and Er Mai. On the contrary, if the Ren Du pulse has vitality, it will also circulate on the the twelve meridians, so it is said that "Ren Du pulse can be connected."

As for "opening the second pulse of Ren Du", it can be discussed from the perspective of Chinese medicine and Taoism. From the perspective of traditional Chinese medicine, we can understand the sequence of the twelve meridians and Ren Du from the narrative of Lingshu Qi Ying. The flow direction of meridians starts from the lung meridian and circulates to the liver meridian in turn; Then it enters the chest from the liver meridian, goes up to the top of the head through the forehead, goes down to the tail along the du meridian, passes through the yin organ and then passes through the ren meridian, and then flows back to the lung meridian. "Qi Ying" said: "What this Qi Ying does is often against his will. This is the natural law of Ren Du Qi running in human body described in medical classics. Understandably, as far as normal people are concerned, the second pulse of Ren Du is originally unblocked. Why should it be opened? From the Taoist point of view, the so-called "Tongren crossing" means going through three passes (tail, spine and jade pillow) and "Sunday" operation. The Taoist work Taiping Jing holds that the limit of human life is 120 years old. As long as we guide the training of Neidan, grasp the essence of heaven and earth from the "reverse" direction, condense the essence and improve the quality of life, we can challenge the limit of life.