I'm not an athlete. I don't climb mountains or run marathons. The most working out I do these days is Rhythm Boxing and fake Tennis on my Wii. But I do know something about pushing the body past it's limits, of doing things that according to basic rules of biology, I shouldn't be doing. Much of BSDM is about going beyond those places (mentally, emotionally, psychologically) of reason and seeing just how far we can go before we break.