late response but maybe someone will read this. david Butler's book as Bob mentioned, is excellent but a lot of his stuff is empirical. However if no-one has anything better...I have had, as mentioned in another episode, v ery good results that could be arguably M/S in origin, except for tell tale LINES of pain and localised pain patches. I think it must be partly biochemical as well as mechanical but have no objective means of showing it to be.