Ah ha...here I can help..... I suffer from fibromyalgia. My joints are in constant pain. Some days walking is just plain painful. BUT...I have noticed that the pain from my sessions with my Sir seemed to help. My most pain free time were after long sessions. I believe that is because of the natural endorphins released in the brain. They are our natural pain killers. It sounds weird, but the more fibro pain I was in, the more I needed the hard spankings, clamps, or rougher sex.