Bart--I've had them in my shoulders, triceps, biceps. Some for days, some for hours, some hit and run. It's nothing to worry about. I've written elsewhere that my son-in-law, who is 27 and a former college baseball player, mentioned in a very casual manner that he gets twitches in his shoulders that would last for "days on end" and then they're gone. He's not worried--apparently, he doesn't consult Google for his "health" concerns--and you shouldn't be worried, either.You're OK!!!Mark