I've responded to a few posts telling people to supplement their diet with magnesium and potassium. So I figured that I should just share my personal experience here. I'm pretty sure that I was either magnesium- or potassium-deficient (or both) for years.
For years, I had this problem with sore calves. It's the kind of soreness that you get when you've had a bit too much to drink the day before (not everyone experiences post-excessive-drinking muscle soreness, but those of you who do would know what I'm talking about), except that I had it all the time. And when I drank too much, I'd be extra sore--not just my calves but my hamstrings and quads too. Anyway, in general, however, my calves would always be sore. It's not so bad that it interfered with any of my activities, but it was annoying as hell. It would go away for a couple hours after a run, which was one reason why I liked running so much.
I tried all kinds of stretches, massages, etc., and these things would help temporarily but did not make the soreness go away. Then three or four months ago I started experimenting with the ketogenic diet. As part of the diet, I started taking a magnesium supplement and gave myself salt licks of "light salt." Light salt is usually 50% sodium chloride and 50% potassium chloride. And the muscle soreness went away almost entirely. I'd say I experienced an 80-90% improvement. I mean, my calves are still tight and need to be stretched daily, but the really annoying soreness has gone away.
So all these years, my sore calves were caused by a mineral deficiency, and I had no idea. So, yeah, supplement with potassium and magnesium.