YOUNGSTOWN, Ohio (WYTV) – You’re just about to drift off into a deep sleep when suddenly your body jerks and you’re awake.
What is that twitch?
This body movement, also known as a sleep start, is what doctors and scientists call a hypnic jerk.
They are completely normal.
We aren’t sure why they happen, but scientists have a few theories.
One says your brain becomes confused as your muscles relax when you drift off to sleep. Just for a moment, your brain thinks you’re falling.
In response, the brain causes your muscles to tense up so you “catch yourself” before you fall down. The spasms are an ancient reflex — we’re falling out of a tree, so we have to react.
Some people report hypnic jerks come with hallucinations, dreams, the sensation of falling, bright lights or loud noises coming from inside the head.
60 to 70 percent of us have them, maybe every night, and if they don’t fully wake us up, we don’t remember them.
Too much caffeine, vigorous exercise, stress or lack of sleep can bring them on.
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