Brief Answer:
Some information about what might be going on:

Detailed Answer:
Hello and welcome,

I doubt that the pain is from a chemical imbalance, such as an electrolyte imbalance (low potassium or magnesium) - otherwise it would be probable that you would have pain in other places as well. If you are on a water pill, that can deplete potassium though, in which case you should have a blood chemistry panel checked. Cholesterol lowering medicines (statins) can cause muscle aches too.

If there is swelling in the calf, then you should go in to be seen promptly as that can indicate a deep vein thrombosis (clot) and that is risky and needs attention.

But if neither of the above apply, then it might be a muscle cramp which might be prevented by stretching your feet, ankles, and legs prior to any vigorous activity.

I hope this information helps and gives you some ideas of what might be going on.

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Brief Answer:
A muscle strain or pull is possible.

Detailed Answer:
It is possible that it could be a muscle strain/pull. If it isn't hurting significantly, or the pain is controlled with the naproxen, rest and apply heat before use and ice after. Take the naproxen after eating food so that it doesn't cause problems with the stomach lining.

If your calf is hurting considerably, then do go in to see your doctor for evaluation, and possibly physical therapy exercises specific to the injured muscle (if it is an injured muscle) would help.

Another thing I am thinking can cause pain in one's calf is claudication (pain due to inadequate blood flow). Usually this type of pain starts during exercise, and you've made clear that it did not, so claudication is low on the list.

If the problem continues, please do go in and be examined in person.

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