In my first Marathon I ran the first half in about 1:38 and the second half in about 2:22. I hit the wall big time and suffered terrible cramps for 15 kilometers, having to stop and stretch every 100 meters or so. I was joined by another runner who was suffering from a similar fate (although he did eventually get a second wind and went on to finish ahead of me). He told me that this happened to him every year, which disheartened me and put me off the idea of running Marathons altogether. I thought, "What's the point? I'd be better off running a three-legged race or an egg-and-spoon race".
I looked into the subject a lot and discovered that there was no scientific evidence to back up the electrolyte imbalance idea. Instead, the best theory that is currently being touted is that they caused by a faulty reflex control of the motor nerve as a result of fatigue. Here I use the word "theory" in the following sense:
1. a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity. Synonyms: principle, law, doctrine.
2. a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact. Synonyms: idea, notion hypothesis, postulate. Antonyms: practice, verification, corroboration, substantiation.
Too often we hear the word "theory" and scoff, "Ah, so it's only the Theory of Evolution - it doesn't mean it's actually true." As a Mathematician, I am an admirer of the scientific method. A good theory is one that fits all available data and a really good theory is one that is able to (correctly) predict something you didn't know before. It is not necessary to like a theory for it to be a good one. And we don't like to be told that we set our sights too high or we didn't train enough.
In my experience, there are various forms of Grim Reaper that come for me when I have spent more than I have in my current account; muscle cramps are just one of these. The fact is that, over several years of consistent training for the distances at which I like to compete, I have been able to keep them more or less at bay. That doesn't mean to say I don't have my superstitious equivalents of a clove of garlic or a wooden stake to ward them off. I always take specially formulated salt tablets (SaltStick) in races longer than an hour and a half and I always compete with thigh and calf compression. I feel that these things help when, again, there is no scientific evidence to say so. On the other hand, there is no way I am going to risk it when there are few things more frustrating that can happen to you in a race.