Was doing a gig yesterday, and toward the end of it my left hand cramped up between the thumb and forefinger for a few moments, so I had to stop playing and relax, shake it out, then resume. It did it off and on for the next ten minutes or so. I recovered and finished the set. The difference between this gig and others is that this time I was standing up, also I was playing a different guitar, a slim body electric. I noticed that forming chords with my thumb seemed to be the origin of the cramps.
The keyboardist and drummer told me afterward that there's an infallible cure for cramps: potassium. They've had cramps, and said that eating a banana beforehand worked like a charm. Taking potassium in pill form could also work, banana is just better tasting. Anybody have experience with this cure? Any other cures?