+1 on magnesium. I make sure to have some along DURING long rides and runs - in the form of Endurolytes or Zenergize, usually. I had enough experience on the bike before I started distance running, that I never even attempted anything over about 15-18 miles without Endurolytes.
Fit can be an issue too. I had terrible cramps in both my calves and tibiales anteriores when my saddle was too far forward. (I put it there before I knew any better because some guy thought it would help me sit farther back on the saddle - which was just too wedge-shaped for me.)
PS - calcium and magnesium ARE electrolytes.
Last edited by OakLeaf; 05-21-2011 at 02:00 PM.
Speed comes from what you put behind you. - Judi Ketteler