This has never been a problem before, but I happened to work out my arms really hard since I'm taking all of next week off while I'm in Las Vegas. I decided to spank the monkey about half an hour after getting back, and about halfway through that happy process my left arm (yes, I'm righthanded but i use my left hand) completely cramped up. I spent the next five minutes flopping around on the floor (literally) trying not to scream out in agony and attract the attention of my sleeping parental units.