Hello, I went through your query, if the pain is on the calf muscles that is on the back of legs, common causes would be low potassium levels (due to dehydration, may be due to drinking or excess sweating), or due to low calcium. Drink plenty of water and fruit juice. Take some calcium supplements, to relieve pain. Other causes would be varicose vein, deep vein thrombosis, in that case consult a general surgeon.