About This Lesson
Have you ever been lying in bed, about to fall fast asleep when your leg jerks suddenly, snapping you awake? Well, those twitches, or jerks are called hypnagogic myoclonus, or hypnic jerks. They are normally caused by sudden muscle contractions, but they also can result from brief lapses of contraction in a normally active muscle. Typically, hypnic jerks are a normal part of a body’s transition from alert and awake, into sleep. Scientists don’t know for sure why they happen, but there are at least two hypotheses.
