Cramps are common among healthy people, especially during or after vigorous exercise. Middle-aged and older people commonly have cramps after light exercise or during rest. Some people have leg cramps during sleep. These painful cramps usually affect the calf and foot muscles, causing the foot and toes to curl downward.
Cramps may be caused by inadequate blood flow to the muscles. For example, they may occur after eating, when blood flows primarily to the digestive tract rather than to the muscles. Low blood levels of electrolytes, such as potassium, can also cause cramps. Low potassium levels may result from use of some diuretics or from dehydration.