My calf muscle was cramping during races; usually while going up a hill. It wasn't something that was painful or even noticeable if it weren't for all of the runners who started passing me while it cramped. My solution was to stretch it multiple times a day. It was almost healed when, while not paying attention, I smashed my knee into my daughter's car. The next day, my calf muscle would cramp whenever my leg was bent at 90 degrees. It also seemed that my shins, quads and hamstring were part of the problem. So, using the stick and foam roller while also stretching multiple times a day since last February, when I smashed my knee, has me running faster than last year without my calf cramping. Wearing much lighter racing flats has also helped.
Switching worn trainers for new (same model) also helped. Quite often, when a muscle has lost flexibility, it take a long time to heal.