Delayed muscle relaxation after contraction is called?

• A. Spasticity
• B. Rigidity
• C. Fasciculation
• D. Myotonia

Answer: (D)

Delayed muscle relaxation after contraction is called myotonia. It occurs when muscle fibers take longer to return to their resting length after a voluntary contraction, causing a transient stiffness that lingers after the effort ends. This arises from membrane or ion channel abnormalities in the muscle that delay repolarization, so the relaxed state is slowed. Clinically you can see grip or percussion myotonia, where the hand remains stiff briefly after a firm grip or after tapping a muscle. This stands in contrast to spasticity (increased tone that is velocity-dependent and tied to upper motor neuron lesions), rigidity (constant increased tone not dependent on movement), and fasciculation (involuntary muscle fiber twitches). Myotonia is a hallmark feature in myotonic dystrophy and related disorders, reflecting the delayed relaxation after contraction.