Yang Extension

Shenmai, 申脉, combines 申, to extend, to unfold, and 脉 (脈), the vessel. The usual gloss relates it to its use: the point would treat a lack of flexibility in the sinews and vessels, hence the idea of stretching. The sources also mention a possible relationship of 申 to the system of the Earthly Branches (地支), without developing it with a citation, so it should not be given much weight.

Its importance lies in the Yangqiao, one of the Eight Extraordinary Vessels. The Zhenjiu Jiayi Jing (Systematic Classic of Acupuncture and Moxibustion) opens its entry with that affiliation: «申脈，陽蹺所生也», Shenmai is the place where the Yangqiao is born. That is why its alternate name is precisely 陽蹻. It is the opening point of that vessel, one of the eight confluent points (八脈交會穴), and its Xi-Cleft point is BL59, Fuyang.

The same work places it «在足外踝下陷者中，容爪甲許», in the depression below the lateral malleolus, where roughly a fingernail fits. Wang Bing also uses it as a reference for locating BL56, Chengjin.

The point also has a place in the tradition of spirits. The Qianjin Yaofang (Essential Formulas Worth a Thousand Gold) describes the fifth of Sun Simiao's thirteen points as «外踝下白肉際足太陽，名鬼路», below the lateral malleolus, at the border of the white flesh, of the foot Taiyang, called the “path of the spirits,” and the editorial note of the edition identifies it: «即申脈穴也», it is Shenmai.