I just finished week 3 of C25K. For the past week or so, my feet have been cramping. Mostly up by the "knuckles" of my toes. Until today, it never started until *after* I was done running and had taken off my running shoes. Today it started almost from the beginning of my run, and was more at the back of my foot.
The odd things is, 15 years ago I was in synchronized swimming. I had to quit that because my toes cramp the moment my feet hit the water. Now it seems to be happening again, but with running.
Any suggestions? I eat a banana every day, so I don't think it's a potassium issue.
Possible and likely causes for cramps in runners are overexertion, underhydration, poor circulation, and electrolyte imbalance. Undernourishment is another, but I'm confident you know when you are starving.
Exertion is the easiest to rule out because you know whether or not you are pushing too hard, and you described toes cramping as soon as you hit the water.
Hydration is a umm, hot topic this time of year, and easy to underestimate as we dehydrate all day in air conditioned cars, stores, offices, and homes. Then we go crazy and exercise, sweating out water faster than we can possibly take it in. A dehydrated body lowers blood volume, which leads us to the third possibility...
Circulation problems often become evident in the distal extremities of fingers and toes. Cramping of these though, involves muscles that may be several inches away from the digits in question. There are other smaller muscles both under and over the foot bones that can cramp and deform the foot structure, something I've experienced after marathons or long training runs. I don't think I was experiencing a circulation problem at the time, so we'll move to the last item...
Electrolyte imbalance goes hand in hand with hydration, since water loss through the skin also takes with it the vital mineral salts we call electrolytes. Potassium is the poster child for these, since it has to be balanced internally (not in the diet) about 20x over sodium, of which the average diet contains way too much, but Potassium is not the only electrolyte people tend to be lacking in. Also important to muscle and heart function is Magnesium, which is deficient in roughly two-thirds of the population. Dietary Magnesium is present mostly in things like dark leafy greens and beans, which are not very high on most people's shopping lists.
While many people pay attention to another important mineral Calcium, they often forget that it should be balanced with about half the same amount of Magnesium intake in order to insure proper muscle and heart function. This is true whether or not Calcium is being taken as a supplement. Most vitamin and mineral supplements have to skimp on the minerals because they are so bulky and the pills can only be so large, so don't depend on the average multi to get you what you need of all the important electrolytes. A spinach salad and some bean burritos will be better insurance. BTW, Calcium tends to constipate, and Magnesium has the opposite effect. Don't say I didn't warn you...
Of the above, I would say hydration and electrolytes are the frequent flyers. By all means monitor the others, but stay on top of these two every day.