Absent any extreme methods (such as jumping off the roof) is it possible to twist, tweak, or otherwise manipulate your own neck or back so hard that your spine breaks, leaving you paralyzed?
I don’t know of any instances where someone has deliberately set out to do this and succeeded. It would seem to be possible in the case of chiropractic-style neck-cracking, which is a rare but well-documented complication of this procedure. I’d think one could manipulate one’s own neck forcefully, more easily than the back.*
Chiros don’t seem too eager to promote the idea of self-manipulation (though I’ve seen a book marketed on the Internet by a chiro that includes this modality). Even someone claiming to be an M.D. has gotten into the act (doesn’t the accompanying photo make you want to try out his ideas?).
*note - forceful neck manipulation of any kind, by yourself or others, is a bad idea whose risks far exceed any potential benefit.
You mean twisting it using your own muscles only? I’ll often sit in a chair, grab the back of it, and twist my torso to pop my back. So far, no problems and I use most of my strength. I pop my neck too. Usually I just lean it to the side quickly, but sometimes I use my hands too. Never broken anything, but I have pinched nerves on a few occasions. I think breaking your neck would be a lot more possible as you have a thin neck instead of a thick body resisting the twisting.
I’d be surprised if one could do it with voluntary muscle contractions, but from what I understand, the muscles are indeed capable of doing the job with involuntary contractions, as when induced by advanced tetanus infection or a TAZER.
And just to be clear, simply breaking one’s spine does not in and of itself paralyze you; many, many people suffer spinal fractures without incurring permament paralysis. The relevant injury is to the spinal cord, or to the nerves that exit through channels in the spine. That’s often associated with spinal fractures, but not always.
Even if you could get beyond the in-built neurological reflexes that prevent you from doing so, I don’t think the muscles have the mechanical leverage to stress the spine that much as the spine provides the foundation for the muscles mechanical advantage.