As you move, you contract and relax your muscles. When a muscle involuntarily contracts, it is called a spasm. When the spasm lasts a long time and the muscle can't relax, it becomes a cramp. Often you can see the hardening of the muscle that is cramped. Muscle cramps most often occur in the back and feet and can be unpredictable and painful. Fortunately, there are nutrients that help to reduce the occurrence of this uncomfortable cramping.