Every now and then I get these killer leg cramps in my sleep. My calf muscle will tighten so much that I spring to wakefulness. The calf is so tight that you could break a board across it and feels like it wants to rip from my leg. It can hurt so bad as to bring tears to my eyes. The biggest challenge is riding it out without waking others in my bed. I am helpless to voluntarily relax the muscle. The only thing that can be done is grip it firmly, apply pressure and massage. Pointing the toes and relaxing the foot then repeating that motion sometimes helps. The calf will be tender all day.
According to the secondary causes, I appear to be in the late stages of pregnancy.