The works of Susie Bright, a.k.a. Susie Sexpert, are excellent primers for fisting. I believe the best books of hers on the subject are: Susie Bright’s Virtual Sex World, and her first collection of essays on lesbian sex.
Fisting, from the reading I’ve done, started out primarily as a lesbian thing, moved into the gay male community, and then moved into the straight community to a point.
It can be done safely, and there is pleasure involved. We’re talking big fun here. But, it’s not for everyone. But… it’s not just for breakfast anymore either.
Nitrate is not a muscle relaxant, but an artery relaxant. It is used by heart patients to relax the coronary arteries. As a “popper” it relaxes the blood vessels in the penis so that blood flows more freely in there. Kaposi’s sarcoma, as far as I know, has only been found in those with AIDS, as an opportunistic infection. Well, not only, but it is very rare otherwise.
It is indeed also a smooth muscle relaxant. It very quickly allows one to relax the anal sphincter, without the normal foreplay.
So they do relax the arterial wall muscles, which are also smooth. Amyl nitrate was used to reduce the blood pressure of angina and heart disease suffers before they discovered nitroglycerine.
I’ve tried them, but not for anal sex. They’re supposed to make orgasms more intense, but I found that they just make my heart race, my head spin, and my dick limp. Yes, limp.
And yes, the association of Kaposi’s sarcoma to poppers was done in the early days of HIV and AIDS discovery, when there was a large segment of the scientific population looking to blame AIDS on something other than HIV infection. More objective studies contradict the initial results, and some even go so far as to accuse the initial researchers of exactly this kind of bias.
Nonetheless, poppers are harsh on your lungs, and not good for you at all… one person I spoke to who used them frequently said that using three poppers made him feel the next day as if he had smoked a whole pack of cigarettes.