Magnesium, too. "Designer" sports drinks usually include some magnesium, but maybe not enough; convenient-store and homemade sports drinks usually don't have magnesium at all.

I started getting night leg cramps when the weather turned warm (even though I was hydrating with Heed, which does contain some Mg). I added 500 mg magnesium daily to the 3:2 calcium/magnesium supp I was already taking, and the cramps went away.

But then, I sweat. As I said last year - after a hard ride I like to jump in the pool to dry off.