Great topic! May i add the immortal words of Arnold Scharzenegger, who, as a bodybuilder, knew quite a lot about pain XD: "As I went to sleep in my snug little room, I'd often feel one or another muscle that I'd traumatized that day jumping and twitching - just a side effect of a successful workout and very pleasing, because I knew those fibers would now recover and grow."
"Pain is merely weakness leaving the body!" ;)