I pulled a muscle in my thigh yesterday. Somewhere during sex.
I noticed I tend to have sore muscles after a particuliarly rough sex session, but only if anal sex was involved. How odd.
It reminds me of a time I almost sprained my neck for good during a particuliarly acrobatic ex session, almost 10 years ago. Huge dick, water bed, standing up and enormous boobs : someone is going to regret this the next day.