Most people at one time or another have experienced leg cramping at one time or another. An athlete would appear to have more reason to have a cramp, but they are well schooled in the importance of getting enough water and warming up and stretching before exercise. They also train their muscles to be prepared for intense activity. For the average person, the cramp often comes when a muscle has been flexed for a long period or when in the midst of occasional exercise. Most cramps are a result of a lack of sodium that disrupts muscle cells. Most cramps only last a few minutes and will cease once the chemical imbalance has been restored. If a cramp lasts form ore than an hour, you should seek medical attention.