The middle of the day slump has hit and nap time is calling. Perhaps your bedtime is nearing, and you’re dozing off. No matter the scenario, you might get a startle as you drift off. If you’ve ever wondered why that is, yes, there is, in fact, a reason.
The twitch before sleeping is a hypnic jerk, and up to 70% of people experience them. You’re not alone. The good news? They’re also normal.
James K. Walsh, executive director and senior scientist at St. Luke’s Sleep Medicine and Research Center in St. Louis, told Today that the movements occur when muscles contract. This causes your limbs to jerk or twitch, waking you. The contractions typically happen between the state of sleep and wake and last only seconds.
Delving deeper, little research has been done on the actual cause of hypnic jerks as they’re considered harmless. However, there are theories.
Walsh said the body could be falling through mini-REM sessions. As this happens, your muscles relax and a dreaming state begins to set in. Brainwaves that occur in this stage of falling asleep (known as hypnagogia) resemble the same ones found during REM sleep. Because people experience erratic breathing, heart rate, and nervous system activity during REM, those same moments are happening in hypnagogia causing the twitches.
If you experience twitches before falling asleep, the phenomenon is completely normal (unless they inhibit your overall rest, in which case, see your physician).
For those who are simply looking to get better rest overall, there are things you can do to improve sleep.