The Yijin Jing (simplified Chinese: 易筋经; traditional Chinese: 易筋經; pinyin: Yìjīn Jīng; Wade–Giles: I Chin Ching; lit. 'Muscle/Tendon Change Classic', 'or "Sinews Transformation's Classic"') is a manual of Daoyin exercises, a series of mental and bodily exercises to cultivate jing (essence) and direct and refine qi, the internal energy of the body according to traditional Chinese medicine.
According to legend, the Yijin Jing was said to be left behind by Bodhidharma after his departure from the Shaolin Monastery, and discovered within his grave (or hidden in the walls of the temple) years after he left (or died). It was accompanied by another text, the Xisui Jing, which was passed to a student of Bodhidharma's, but has not survived to the present day. The monks of Shaolin supposedly practiced the exercises within the text but lost the true purpose of the document; Lin Boyuan recounts that they "selfishly coveted it, practicing the skills therein, falling into heterodox ways, and losing the correct purpose of cultivating the Way. The Shaolin monks have made some fame for themselves through their fighting skill; this is all due to having obtained this manuscript."
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