I've always been prone to Charlie horses, especially during my swimmer days. I'd get them so frequently and so badly in my calves and feet. I'd have to awkwardly swim to the side of the pool without drowning, somehow pull myself out, and then limp around until I worked it out. I still get them to this day and they still suck just as bad, though I'm usually not in a pool any more when they occur.
The other day, out of nowhere I got this crazy, sharp, tight pain in my right armpit. It made me gasp it hurt so bad. At first I didn't know what it was; then I recognized that all too familiar pain. The area by my armpit, where my chest muscle is stretched, was going into full on Charlie horse mode. Not cool!! How does one walk out a Charlie horse in one's armpit?! It's not scientifically possible!
The pain left as quickly as it came after a little stretch (and by stretch I just mean pulling my shoulders back), but it was quite an experience. Add Charlie horse to the side effects column of a double mastectomy.