"A muscle cramp is a sudden and involuntary contraction of one or more of your muscles. If you've ever been awakened in the night or stopped in your tracks by a sudden charley horse, you know that muscle cramps can cause excruciating pain. Though generally harmless, muscle cramps can make it temporarily impossible to use the affected muscle.
Long periods of exercise or physical labor, particularly in hot weather, may lead to muscle cramps. Some medications and certain medical conditions also may cause muscle cramps. You can usually treat muscle cramps at home with self-care measures."
For more information: