A sudden, unexpected tightening of one or more muscles, often in the legs. A charley horse is another name for a muscle cramp.
A charley horse is often due to long exercise or physical labor, especially in the heat. Dehydration, age, pregnancy, and certain medicines and illnesses also might cause muscle cramps.
A charley horse is harmless but can be very painful. It often awakens a person during the night. Muscle cramps happen mostly in leg muscles, most often in the calf. After the cramp eases, the area might be sore for hours or days.
Self-care measures can treat most muscle cramps. Massage the area to relieve cramping pain. Stretch and stay hydrated during exercise or work to help prevent a charley horse.