Authentic or not, this chapter talks about all types of cool things: softening and strengthening 'tendons' (soft tissues; muscles; tendons; nerves; etc); gaining full range of motion in odd movement patterns; freeing the spine; freeing the breath; massaging the viscera - so the "..tissues will regain their dynamic buoyancy". Things that I am interesting in doing via the methods I have studied or made up (and am currently learning). People have obviously been fascinated by all things physical cultivation, since time immemorial.
I have always been attracted to, and fascinated by, various Daoist practices and philosophies (too much Monkey Magic and Kung Fu movies as a lad, perhaps..), so it is possibly surprising that I am only this year investigating qi gong/dao yin and other such things - and having a great time with them! I think they will blend very well with what I already know and practice, and it's great fun to have new methods to explore.
I've been having a great time playing with percussive style techniques on my ribcage and abdominal cavity; as well as trying to mobilize/relax/gain awareness of my viscera view bouncing up and down with different degrees of abdominal vacuum on (this I did not get taught by any one in particular; just figured it out by stuffing around - you could potential fuck something up if you do not have the body-awareness, so only try it if you take responsibility for your own body).
Training the viscera is something that is not mentioned too much is the western style training literature I have read; but, to me, is obviously an essential part of physical cultivation. Based on what I have figured out so far in my playing (and reading), I would say (IMHO) a decent amount of pain, dysfunction and ill health comes from mal-positioned, hypertonic and constricted organs.
One other aspect in the chapter that stood out to me was the part on 'marrow washing', which it described as a way of strengthening the bones via cleansing, regulating and then changing the bones shape. This piqued my interest.. I'll have to ask some of my Daoist lineage buddies about this sometime..
Anyhow, what I started to think about after this was what I knew that would strengthen bones. The most obvious being strength training (muscles and fascia contracting to stimulate bone growth and density via Wolfs Law - now 'Utah Paradigm of Bone Physiology!') and dynamic loading of them (jumping and impact absorption).
A less obvious one I want to run with a bit here, is putting spiral contract-relax/hold-relax (PNF) contractions through bones as a way of strengthening them - and effecting the fascia (periosteum) around them. What I feel when I get a good solid spiral contraction through, say my forearm, definitely feels like it's doing something positive (not very testable, I know).
Some of the Stretch Therapy wrist stretches are perfect for this set-up, and I have been using the stretch position to hold long and reasonably strong spiral contractions from them. These are not beginner/intermediate level contractions; I am talking about wringing out to those tissues (within parameter of no pain and/or wrist compression; just high level stretch sensation and muscular contraction); similar to wringing out a wet towel. It's not held for overly long, but over time you can get used to a high contraction stretch (be patient!).
I like the idea mentioned in the book about having strong but pliable/bendable bones (again with the bamboo analogy), rather than brittle or rigid. Just take a look at the statistics for life expectency post hip fracture..
I must re-read the 'Bone' chapter from Job's Body again, and go over the theory a bit more rigorously. Still, it is a fun thing to ponder. My gist for 'bone-training(™)' is to use high tension strength techniques (heavy weights; medium-high tension gymnastics holds; etc); plus dynamic recoil techniques (agility and jumping); plus impact techniques (heavy bag work); plus spiral 'wringing' long hold, multiple contraction Stretch Therapy style PNF contractions to change the bone make-up towards bamboo-dom. Cool?
On a side note, Bamboo is fucking awesome and should be planted everywhere (down median strips; in alley ways; etc) - noxious weed or not. It has many uses and fixes a fair amount of carbon sequestration. Plus it just looks awesome...(!) you feel like you are in a 70's kung fu movie when you walk passed it (at least I do)!