For the past few weeks I have been experiencing extremely painful cramps in my legs and feet. Occassionaly, both calves and feet at the same time. Sometimes I'm able to walk them off but not when both limb are affected. I've tried hot packs and massage, neither are really effective. Sometimes they last for over an hour and usually they occur in the middle of the night and wake me up. Does anyone know what the cause is? Any suggestions to relieve them?