text: what causes leg cramps during sleep?   also known as rest cramps. especially in older adults, cramps at rest (often during the night) are very common. rest cramps may be experienced at any age, however, including during childhood. while not life-threatening, night cramps can be very disruptive of sleep and otherwise quite disturbing. they sometimes recur frequently (that is, many times a night, and/or many nights each week) and are very painful. the actual cause of night cramps is unknown. sometimes, such cramps seem to be initiated by making a movement that shortens the muscle, which then cramps. an example is pointing the toe down while lying in bed, which shortens the calf muscle, a common site of cramps.