A doctor has explained why you sometimes get that horrible 'twitch' just before falling asleep.
You'll be all relaxed in bed, about to doze off, when your leg will randomly jerk like you're some sort of horse.
It's really annoying for us light sleepers out there who not only struggle to relax, but find it hard get through the whole night without being disturbed.
The sudden motion can make you panic, as if you were falling from a building or something.
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Well according to Dr Amir Khan (@doctoramirkhan), who appears regularly on ITV's Lorraine, there's actually 'nothing to worry about', as this is totally normal.
But why does it happen?
"Have you ever felt like you're falling just as you're nodding off?" the health expert said in one of his recent videos.
"That sudden jolt awake is actually called a hypnic jerk."
What is a hypnic jerk?
The Sleep foundation says hypnic jerks are 'involuntary muscle twitches that occur as you’re falling asleep'.
Dr Khan explained: "As you drift into sleep, your muscles relax, and sometimes your brain interprets that as falling. But it's a misinterpretation.
"So it sends a quick signal to your body to catch you, and that's why you twitch awake.
"Now, some scientists think that it's an ancient survival reflex, back to when we slept in trees. A sudden twitch might have stopped us from actually falling."
He said that hypnic jerks are 'harmless' and are more likely to happen when you're 'stressed, have caffeine late, or you're just super tired'.
"So next time it happens, don't panic, it's just your brain being quirky. Totally normal, totally harmless," he said.
Over in the comments, one person revealed: "My husband does this, he just about jumps out of bed."
"Yes I get this loads, I find it frightening xx," another shared.
The doctor also revealed in a follow-up video why we sometimes wake up in the middle of sleep with sleep paralysis.
"It’s scary, right? Well, that’s called sleep paralysis, and it happens when your brain wakes up before your body does," he said.
"During REM sleep, that’s the bit where you dream, your muscles are temporarily switched off, so, don’t act out your dreams. If you wake up whilst that’s still happening, you feel paralysed. Now sometimes people also feel pressure on their chest or see vivid hallucinations, shapes, shadows, even figures in the room.
"That’s because your brain is still half in dream mode, half awake."
Again, he says although it seems 'terrifying', the good news is that 'it's harmless'.
Sleep tight!
Anish Vij