Why Are There so Many Different Versions of Yi Jin Jing & Xi Sui Jing?
The “Muscle-Tendon Changing Classic” (易筋經 Yì Jīn Jīng), or “Sinew Changing Classic”, refers to a text that, according to legend, is attributed to Da Mo (Bodhidharma), a semi-legendary Buddhist monk of the 5th or 6th century who is often credited with transmitting Buddhism to China. Purportedly Da Mo taught these exercises to monks of the Shaolin Monastery whose bodies were weak. The monks used Yi Jin Jing as a method of cultivating the body, mind and spirit to create a stronger, more flexible body that could then be used as vehicle for spiritual cultivation. Also according to legend, the practice of Yi Jin Jing led to the development of Shaolin Gung Fu. Some sources say that before the Song Dynasty (960-1279), Yin Jin Jing was only taught to Shaolin Temple monks, and only in the Ming (1368-1644) and Qing (1644-1911) Dynasties did it become popular and branch out into several styles. 
Purportedly Da Mo kept the two sets of writings in his meditation cave in the Shaolin Temple: the Muscle-Changing Classic, a method for changing and renewing tendons and sinews, and the Marrow Washing Classic (Xǐ Suǐ Jīng 洗髓經), a method for cleansing and washing the marrow (thereby renewing the body’s Essence (Jing). During a renovation of a cave wall, the two scriptures were discovered. According to Shaolin sources, Yi Jin Jing/Xi Sui Jing were originally secret practices of the Shaolin Temple, that only later become known to the public. This viewpoint has largely been debunked by modern scholars. There is also some disagreement on whether these two practices are in fact the same practice, two connected practices, or two entirely separate practices.
Today one can find many different versions of the Yi Jin Jing and Xi Sui Jing. Some stake the claim of being the “original” version directly passed down from Da Mo. “Original” is fuzzy word here, as the texts considered to explain these “original” methods date from the 16th century (Ming Dynasty) and not from the 5th or 6th century when Bodhidharma was thought to have lived. The Yi Jin Jing/Xi Sui Jing “text” seems to be a series of fragments that outline principles of internal training and does not discuss specific exercises. Therefore anyone, including myself, who purports to do the “real” Yi Jin Jing and Xi Sui Jing, or to completely understand what was in the original text is really relying on later interpretations, rewritings and compilations that were constructed centuries later – in that sense all of us who practice Yi Jin Jing are interpreting the principles that have been passed down through the centuries and basing that interpretation to some degree on how past generations have interpreted and commented on the text.
The earliest mention of the Yi Jin Jing is attributed to Zhang Jun Fang in the Song Dynasty (960-1279), while the earliest account of the modern 12 movement exercises is included in the Illustrations of Internal Exercise compiled by Pan Wei in 1858 in the Qing Dynasty. To further complicate matters, there is a version of Yi Jin Jing taught in Taiwan that contains 18 movements rather than 12, and yet other versions that contain 24 movements. In addition, various versions of the Yi Jin Jing have been passed down by Daoist sects, who see the Yi Jin Jing as a method of self-cultivation and transcendence, and martial arts groups, who employ the Yi Jin Jing to strengthen the body and develop power.
The textual history of the Yi Jin Jing/Xi Sui Jing is very complicated. Early extant works on the Yi Jin Jing/Xi Sui Jing are fragmented and those fragments do not contain illustrations. Although the text is attributed to Da Mo, most scholars think that the Yi Jin Jing/Xi Sui Jing was compiled in the early 17th century. According to Meir Shahar, the “text” is a product of late Ming syncretism. This version of the Yi Jin Jing/Xi Sui Jing is attributed to Zongheng (宗衡), who was known as was Zining Daoren (紫凝道人) or “Purple Concretion Dao Person.” A “Dao Person” would usually be a Daoist priest, but this title may also have designated a Buddhist monk. Indeed, some Buddhist sources feel that these methods come from Buddhism and are part of Chan Buddhist practices (Zen). Because of the interweaving of Daoism and Buddhism at different periods in Chinese history, it is difficult to trace the source of these methods as they come down to us today.
The Da Mo origin story of the Yi Jin Jing has been discredited by some historians, including Tang Hao, Xu Zhen and Matsuda Ryuchi. This argument is summarized by modern historian Lin Boyuan in his Zhongguo wushu shi:
As for the “Yi Jin Jing” (Muscle Change Classic), a spurious text attributed to Bodhidharma and included in the legend of his transmitting martial arts at the temple, it was written in the Ming dynasty, in 1624, by the Daoist priest Zining of Mt. Tiantai, and falsely attributed to Bodhidharma. Forged prefaces, attributed to the Tang general Li Jing and the Southern Song general Niu Gao were written. They say that, after Bodhidharma faced the wall for nine years at Shaolin temple, he left behind an iron chest; when the monks opened this chest they found the two books “Xi Sui Jing” (Marrow Washing Classic) and “Yi Jin Jing” within. The first book was taken by his disciple Huike, and disappeared; as for the second, “the monks selfishly coveted it, practicing the skills therein, falling into heterodox ways, and losing the correct purpose of cultivating the Real. The Shaolin monks have made some fame for themselves through their fighting skill; this is all due to having obtained this manuscript.” Based on this, Bodhidharma was claimed to be the ancestor of Shaolin martial arts. This manuscript is full of errors, absurdities and fantastic claims; it cannot be taken as a legitimate source.
According to researcher Matsuda Ryuchi, the oldest available copy of the Yi Jin Jing was published in 1827. However, the composition of the text itself has been dated to 1624. Therefore the two oldest written and illustrated Yi Jin Jing exercise routines are from Chen Yi’s “A Collection of Annals” published in 1624 during the Ming Dynasty, and Wang Zu Yuan’s 12 Posture moving exercise published in Internal Work Illustrated (內功圖說 Nei Gong Tu Shuo) in 1882. This work is purportedly a reprint of a similarly titled book by a Qing Dynasty official named Pan Wei. These manuals contain the illustrations of the “ancient” Yi Ji Jing Exercises that are often reproduced in modern manuals.
Given the tendency of past masters to be secretive, and the cultural tendency of Chinese teachers to relate self-cultivation practices to a famous person or a famous training method, it is no surprise that there is such confusion. It is impossible to say that one version or another is original and impossible to know what Bodhidharma taught the monks back in the sixth century, or even if he actually existed.
Keeping all this in mind, the Yi Jin Jing 12-Posture Exercise series that is most commonly practiced today is not mentioned in the fragments of the Yi Jin Jing that survive and it probably developed later from Yi Jin Jing theory. This exercise series is often associated with Buddhism, Buddhist meditation practices and Shaolin Kung Fu. Other versions of the Yi Jin Jing 12-Posture Exercises, Massaging/Patting ad Xi Sui Jing are said to originate with Daoist self-cultivation methods, and some teachers like to delineate the specific differences between Daoist and Buddhist versions. There are also different Yi Jin Jing and Xi Sui Jing methods that have been passed down orally through martial arts, Daoist and Qi Gong lineages. Although almost all employ similar theories about internal and external training, how these theories actually manifest in training can be quite a bit different.
As mentioned earlier, there are also 24-exercise, 18-exercise and 12-exercise versions of the Yi Jin Jing moving exercises. Some people perform these exercises with obvious external tension (in fact I originally learned them that way). Others (myself included) have found that this more “external” approach does not yield the desired results. Often the Yi Jin Jing exercises are practiced without the Massage/Patting and Marrow Washing elements, which are considered by some to a crucial aspect of the Yi Jin Jing training method. There are at least 20 different versions of Yin Jin Jing exercises that can be identified today. Some involve dynamic moving exercises, while others utilize discrete contractions of the hand and arms that are generated internally while rising up on the toes and heels.
Some practitioners say that the Twelve (0r 18 or 24) Yi Jin Jing exercises are not effective, and because they were not part of the original fragments – therefore they are not worth doing, and that really the Yi Jin Jing is speaking generally about internal training in general and not in specific. By this logic, which seems based on questionable manuscripts, any Qi Gong set could be criticized as being inauthentic and not worth doing. Yet certain groups of exercises have withstood the test of time and the association with the various Yi Jin Ying exercise series (as it comes down to us today) with the “original text” should not be dismissed without proper investigation. The individual exercises and practices taught within the Yi Jin Jing/Xi Sui Jing tradition, can be quite subtle (if performed properly) and have been clearly calculated to have very specific effects that are in line with Yi Jin Jing/Xi Sui Jing, particularly when combined with the Massaging/Patting and Marrow Washing practices, which together seem designed to create an interlocking triad of cascading internal effects.
Marrow Washing (Xi Sui Jing), is itself a big conundrum, because although “washing the marrow” is often referred to in various texts and by various practitioners there are rarely specific practical instructions or even agreement on how to “wash” the marrow, or even what this phrase actually means. Some authors refer to the Yi Jin Jing 12 exercise series as “marrow washing,” and others refer to a type of Buddhist meditation as Marrow Washing. Still others say that one must do the Yi Jin Jing Practice first as it is a preparation for the more advanced Marrow Washing practice. Given the convergence and interweaving of Daoist and Buddhist practices that occurred in China’s long history, the task of sifting through all of these various view points and opinions out becomes very difficult, if not impossible.
Several versions of Marrow Washing are loosely associated with the Buddhist/Daoist meditation practices sometimes called “Sitting and Forgetting,” or “Sitting in Stillness.” Other versions fuse “Bone Breathing” and “Brain Cleansing” exercises with meditation and Tu Na (“taking in the new and spitting out the old”) breathing exercises in which one visualizes breathing fresh Qi into the bones and expelling dead or negative Qi out.
Several famous teachers of Bone Marrow Nei Gong and Marrow Washing advocate a much more complex regimen of stimulating the sex glands, both manually (massage) and by hanging a weight from the sex organs (women practitioners grip a stone or metal “egg” with the vagina, the stone/egg can also be attached to a weight). These practices are combined with beating the meridians and sections of the torso with a metal flail and bags of smooth stones. In internal martial arts these methods are traditionally associated with Iron Shirt training, which allows one to take powerful blows to the body without harm. They do not have a direct association with Marrow Washing, although clearly the bones and marrow are strongly stimulated by this type of training.
An interesting version of “Marrow Washing” taught by both Shaolin and Daoist practitioners involves sitting in a cross-leg or lotus position while holding a series of different postures with the arms and torso, while stilling the mind and regulating the breath. These exercises are also found in Illustrated Supplement to the Internal Exercises of the Yi Jin Jing compiled by Zhou Shuguan in the Qing Dynasty. The author explains that in his youth he tended to get sick, so he did exercises to improve his constitution. In autumn 1893 he by chance met a monk named Kong Wu (“Emptiness and Understanding”), at the Tonghui temple in Ziyang. He followed Kong Wu’s teaching him for a master and followed his teachings. At the moment of their parting the monk gave him a book called Illustrated Supplement to the Internal Exercises of the Yi Jin Jing, composed of 6 volumes. Zhou Shuguan later revised and published his book, which contains “Supplemental Yi Jin Jing Exercises.” These exercises effectively combine elements of Marrow Washing and Muscle Tendon Change in a series of seated meditation practices that open the meridians and circulate Qi to the internal organs and through the Macrocosmic and Microcosmic orbits. They are quite effective as supplements to the 12 Exercise Yi Jin Jing Set, the Ba Gua Marrow Washing (mentioned below), and the Yi Jin Jing Massaging/Patting practices.
Ba Gua Marrow Washing is yet another version of Marrow Washing passed down through Ba Gua Zhang lineages. Ba Gua Marrow Washing uses posture, breath and visualization as well as Daoist saliva swallowing methods to circulate blood and fluids to the bones, membranes and marrow and nourish the tissues with Jing (essence). This method then employs An Mo self-massage techniques as a “closing” method to further circulate Qi blood and fluids and guide them to the bones, marrow and the internal membranes.
Ultimately there is probably not one “correct” or “orthodox” way of performing the Yi Jin Jing, because a lot depends on how you understand, think about and actually perform the exercises. The main question that is important is: Does the method one is practicing deliver the promised results? Are the tendons and muscles actually changed and are the marrow, brain function and immune system enhanced by the exercises? This requires practicing precisely, with an ongoing investigative intent.
 Ibid, p. 248-249.
 “Yi Jin Jing” The Classics of Changing Tendons: 中国武功经典：易筋经 (100 Books of Ancient China Classics Book 23). China Kungfu and Yi Jin Jing. Compiled by the Chinese Health Qi Gong Association (Beijing: Foreign Language Press, 2007) p.3.
 Yi Jin Jing. Compiled by the Chinese Health Qi Gong Association (Beijing: Foreign Language Press, 2007) p.3.
 Zhang Z. [Textual research on the illustrations in ancient versions of Yi jin jing (Classic of Changing Tendon)]. Zhonghua Yi Shi Za Zhi. 2015 Sep;45(5):299-305. Chinese. PMID: 26813095.
 Shahar, M. 2008, The Shaolin Monastery: History, Religion, and the Chinese Martial Arts (Honolulu: University of Hawai’i Press, 2008) pp. 160–5.
 Hsu, Elizabeth. The Iconography of Time: What the Visualisation of Efficacious Movement (Shi 勢) Tells Us about the Composition of the Yijin Jing 易筋經 (Canon for Supple Sinews)
 Lin, Boyuan (1996), Zhōngguó wǔshù shǐ 中國武術史, Taipei 臺北: Wǔzhōu chūbǎnshè 五洲出版社 – https://encyclopediaofbuddhism.org/wiki/Bodhidharma#CITEREFLin1996
 Willian C. C. Hu. Research Refutes Indian origin of I-chin ching (Black Belt Inc: Black Belt Magazine December 1965 Vol. 3 No. 2) pp.48-50