Yes. Definitely not without some good medical knowledge!

Firstly it wasn't all of my weight I put on mi_guida at any time. I had either one foot on the ground and one on the back or a chair to put my hands on to take some of my weight. Usually both.

And I think the theory is it helps get the spine back into alignment. mi_guida knows all about it because she has a really messed up back so goes to a chiropractor regaularly. http://en.wikipedia.org/wiki/Chiropractice has info on the general stuff as well as links to "spinal adjustment" though it doesn't seem to be a greatly detailed article.