Muscle cramps, including muscles of the feet, can result from a deficiency in potassium, calcium or magnesium. Other causes of muscle cramps include muscle overuse, nerve compression and insufficient blood flow to the extremities.
For muscles to function optimally, they require an adequate supply of oxygen and vital minerals. Potassium absorbed from the diet gets stored inside muscle cells. Potassium molecules are exchanged for sodium ions on the outside of the cell. After entering the body, potassium works by balancing sodium levels and allowing contracted muscles to relax. When potassium levels fall too low, muscles become stuck in the contacted position and are unable to relax.
A deficiency in calcium causes muscle cramps by preventing contraction. The movement of calcium molecules into the cell allows muscles to contract. When calcium levels fall too low, muscles become stuck in the relaxed state and are unable to contract.
Muscle cramps also develop when a muscle is unable to get an adequate supply of oxygen. For some individuals, the arteries carrying blood to the lower extremities narrow during exercise. The narrowing causes cramp-like pains in the muscles experiencing the blood shortage. This change in the arteries is temporary and normalizes when the exercise stops.