Bone Breathing
While many parts of Bone Marrow Nei Kung are truly advanced, challenging, and risky (and should not be attempted without the close guidance of a teacher) - bone breathing is an aspect that can be safely and very beneficially practiced by the beginning student. There's no need to miss out on this simple, gentle - yet profound - technique because of (justifiable) jitters over other parts of BMNK.
Approached in this moderate way, no techniques (no hanging of weights, no special aggressive genital massage) are used to bring extra jing up into the blood stream: Simply work with the ambient energy that you normally have in your body (plus any external energies that you draw in through the practice).
Bone Breathing: Sexual Energy and Lumbar
Marrow-Washing through Ming Men
All of the classics talk about the importance of ming men.
Not surprisingly, I find that compressing sexual energy into the marrow of the
lumbar vertebrae - up through ming men - to be key. Simple bone breathing
works well for this. That is, breathing in external chi, spiraling it
around the lumbar vertebrae (either one at a time or in larger portions) and
compressing that spiral into the vertabral marrow with your yi, intent.
(There may be incidental contraction of local muscles, which is fine, but this
is done primarily with yi.) Super important to get the chi into the marrow
of the vertebrae, not simply rushing up the spine willy-nilly. Once this
is done up through ming men a pulsing occurs that includes ming men, the
kidneys, sexual essence, the external chi from air... That pulsing propels the
sexual energy through the marrow of not only the spine but through the whole
skeletal system. In my opinion, if you were to take up bone breathing in
no other area, this would be it.
related essays
turtle breathing
sacrum breathing

bone breathe, spiral and compress,
deeply into the vertebral body
Reading References
1. Bone Marrow Nei Kung book.
2. Iron Shirt Chi Kung III video #V58.
3. Qigong: The Secret of Youth - Da Mo's Muscle/Tendon Changing and Marrow/Brain Washing Classics by Dr. Yang, Jwing-Ming
Caution: If you are sick, you should be cautious about practicing any chi kung (see general disclaimer), and especially cautious of any marrow washing practices during illness. You don't want to do anything to drive an illness condition deeper into your body.