A muscle spasm, known as a "charlie horse," lasts from a few seconds to 15 minutes or more. Some muscle spasms recur multiple times before subsiding completely and may bring soreness for hours afterwards.
The involuntary muscle contractions are typical in the front and back of the upper thigh and the back of the lower thigh, though spasms in the hands, arms, feet, rib cage and abdomen are also common.
Muscle fatigue, dehydration, heat and electrolyte depletion are causes of muscle spasms. Extreme physical activity beyond one's capability, especially among those over 40, can lead to muscle spasms. Some athletes also experience muscle spasms as a result of extended workouts.