A Muscle Spasm vs Muscle Twitch

A muscle spasm, or muscle cramp, is an involuntary contraction of a muscle.  Muscle spasms occur suddenly, usually resolve quickly, and are often painful.  A muscle spasm is different than a muscle twitch.  A muscle twitch, or fasciculation, is an uncontrolled fine movement of a small segment of a larger muscle that can be seen under the skin.  Spasms may occur when a muscle is overused and tired, particularly if it is overstretched or if it has been held in the same position for a prolonged period of time.  In effect, the muscle cell runs out of energy and fluid and becomes hyperexcitable and then develops a forceful contraction.  This spasm may involve part of a muscle, the whole muscle, or even adjacent muscles.