Skeletal muscle cramp

A skeletal muscle cramp is a sudden, involuntary, painful contraction of one or more skeletal muscles that temporarily resists voluntary relaxation.

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Motor neuron: A nerve cell that sends signals to control muscle fibers. Excessive motor-neuron activity is central to the leading explanation for many cramps.
Skeletal muscle: Striated muscle tissue, usually attached to bones, that is generally controlled voluntarily. Cramps in this concept occur in this muscle type, not smooth or cardiac muscle.
Exercise-associated muscle cramp: A painful involuntary muscle contraction occurring during or shortly after physical activity. Exercise-associated cramps are a common setting in which fatigue and altered neuromuscular control matter.
Muscle strain: An injury caused by overstretching or tearing muscle fibers or their tendons. A strain can cause pain and tightness, but it is tissue injury rather than a transient involuntary contraction.
Exercise-associated muscle cramp theories: Competing explanations for exercise-related cramps, including altered neuromuscular control and fluid or electrolyte loss. The debate shows why one cause cannot account for every exercise-associated cramp.
Neuromuscular junction: The synapse where a motor neuron communicates with a muscle fiber. Signals crossing this junction initiate the contractions that cramps prolong.
Muscle fiber: A single elongated muscle cell containing contractile machinery. A cramp involves involuntary contraction in fibers recruited within an affected muscle.
Nocturnal leg cramps: Sudden painful contractions of leg muscles that occur during sleep or while resting in bed. They are a frequent form of skeletal muscle cramp with distinct effects on sleep.
Delayed onset muscle soreness: Muscle soreness and tenderness that develop hours after unfamiliar or strenuous exercise. Its delayed, persistent soreness differs from the sudden contraction of a cramp.
Neuromuscular fatigue: A decline in the nervous system’s and muscles’ ability to sustain force during activity. Fatigue is a leading proposed trigger for cramps during strenuous or prolonged exercise.