The main symptom of a muscle cramp or spasm is pain in the muscle. The muscle itself is tender to the touch. In most cases a person is unable to continue using the affected muscle due to the pain. The exact cause of muscle cramps is not well understood. They can occur in any muscle at any time.
Cramps occur most often in the muscles of the leg or foot.
They usually occur while playing sports, exercising, or lying in bed. The calf muscle in the back of the lower leg is a common place for nighttime cramps. These often occur after vigorous exercise. Tight muscles are more likely to cramp than flexible muscles that have been stretched. A low level of physical fitness increases the risk of muscle cramps.