Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity. It can happen when you hold or pick up something, or when you stretch or exercise with weights.

Though many people experience muscle twitching, it's often incorrectly identified as a muscle spasm. While both are involuntary contractions of a muscle, muscle spasms and muscle twitching aren't ...

Muscle cramps are sudden, involuntary contractions that can cause sharp, intense pain lasting from a few seconds to several minutes. They often strike during exercise, dehydration, or even while ...

Clonus reflex is a set of rhythmic, involuntary muscle movements. It is a neurological condition that affects the nerve cells that control muscle movements. Damage to the nerves, as in clonus, causes ...