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Imagine that you're relaxed and drifting off to sleep when suddenly an arm or leg twitches and you have the sensation of falling out of bed. If this has happened to you, you've experienced what sleep specialists call a hypnic jerk or sleep start. Sleep starts happen in normal, healthy people and don't ordinarily require any medical treatment. However, certain medical conditions can make you jump in your sleep and should be evaluated by your physician.
Sleep paralysis is a condition in which someone about to fall asleep, or just upon waking from sleep, realizes that they are unable to move or speak, but can still breathe and move their eyes. I like to call this half-asleep/half-awake stage the twilight stage.leep paralysis is a condition in which someone about to fall asleep, or just upon waking from sleep, realizes that they are unable to move or speak, but can still breathe and move their eyes. I like to call this half-asleep/half-awake stage the twilight stage.