Why is it that when you're almost alseep, you flinch really hard?

Factual Questions
1

So this happened to me the other night, i was almost asleep and i had this vision of my falling of a bike on a curb and i flinched really hard and woke up…why does this happen?

2

I have always wondered as well. My guess would be it’s just a simple matter of your mind is wandering, so if it envisions a situation that would call for curling up for protection or a reflex reaction then your body jolts up in defense. As far as i know your motor functions arn’t disabled until you are actually asleep.

3

I have had the exact same thing occur, repeatedly. Only fall off of a skateboard (despite me never having ridden one before, nor do I have any desire to). It’s quite startling for a few seconds.

4

This happens to me regularly. I’m just about to fall asleep, then I dream a football is about to hit me in the face, and I flinch so hard my whole body lifts a few inches off the bed.

5

Twitching in your sleep has been discussed before…

Incidentally, I see I misspelt “myoclonic” in that thread. More on myoclonic twitches:
http://www.ninds.nih.gov/health_and_medical/pubs/myoclonus_doc.htm

It’s interesting that people are reporting the twitch while dreaming of flinch-inducing incidents. Whenever I’ve experienced it, I was just falling asleep and can’t recall dreaming anything at the time.

6

Two relevant colums from Cecil:

Why does my body jerk when I’m falling asleep?"
Why do we twitch while falling asleep?

7

I always feel that the bed is tilting, before I flinch.

Hmm. I think I may have imparted that piece of info in an earlier thread…

8

There is medication that will stop the myoclonic twitches happening. A few years ago I was in hospital with a broken leg. Every time one of the stupid twitches happened in that leg the resulting pain was excruciating and I would come fully awake, every time I began to drop off again another twitch. I don’t mind saying I was nearly in tears with frustration and tiredness when I called for the nurse. I actually didn’t think there would be anything she could do and was so relieved when she got the doctor to prescribe something and it worked. I don’t know what it was, perhaps someone could enlighten us, but I guess it’s not something they would prescribe under normal circumstances.