Practitioners over the centuries have been speculating what Bone Marrow cleansing (or in modern terminology: Bone Marrow nei-gung) was. I shall join this bandwagon here, always bear in mind that the whole subject is at best speculative in nature!
According to modern scientific studies, the best form of exercise to promote bone-health is weight lifting. Through weight lifting, bones are locked into a strong structure end-to-end, and pressure is exerted along the length of the bones by transmission of force along the bone structure through its end-to-end solid arrangement.
My contention is that Bone Marrow nei-gung has to work in similar way. According to the existing short text of "the art of Bone Marrow Cleansing" (洗髓經）, one has to practice "the art of Tendon Changing" (易筋經) before practicing the Bone Marrow part. Actually it is similar to required prior practice of Asana before all the way to Dhyana (meditation) in Yoga. In other words, an aligned body structure is an essential foundation of serous meditation.
In some stage during deep meditation, massive chi will be generated. In such situation, a practitioner's extension muscles will "cry out" for extension. If a practitioner can stay focused and manage to stay stationery, the force will revert back and act on the bone structure itself, pushing the structure centrally from all terminal points (like the finger tips). The result is similar to doing weight lifting with it beneficial result of conditioning and nourishing the bones.
Needless to say, I'm not the first one to put forward this view. It can be found in the Chinese original text of the famous Taoist Yoga translated by Charles Luk. One of master (author) Zhao's students wrote in a forward to the text that Zhao's practice is the same as "the art of Bone Marrow Cleansing" (洗髓經）: Lost in Zen Buddhism but preserved in Taoist Meditation (Neidan)!
And in the internal martial art literature, I noticed one similar training on bone structure compression in a book by Yu YongNian (于永年), one of the best student of Master Wang XianZhai (王芗斋), in the form of an advanced practice in Combat stance zhan zhuang.
|The art of Bone Marrow Cleansing -洗髓經|