You get into bed, fall fully asleep (or so you think) and you suddenly feel like you're falling. You jump and BOOM, you're awake, startled and can't fall back asleep.
If that happens to you, you're part of the 70 percent of people who experience something called hypnic jerks, or myoclonus.
"It's all really connected to your sleep cycle," physician Dr. Ian Smith explains.
There are four stages of sleep before you reach REM (rapid eye movement) stage — a.k.a. the dream stage — the doc explains.
STAGE 1: Beginning Stage/Light Sleep
STAGE 2: Brain Waves Start To Slow
STAGE 3: Brain Waves Become Very Slow
STAGE 4: Deep Sleep
"That cycle happens many times throughout the night," he continues. "It's not just one cycle."
And it's pretty easy to be woken up when you're in Stage 1.
"We're not 100 percent sure why [hypnic jerks] happen," Dr. Ian says, "but there are two theories."
THEORY NO. 1: When you're falling asleep, your body is starting to relax. Sometimes, if your body is having a hard time relaxing, you end up experiencing rigid contractions.
"Your brain is trying to send a message to your muscles to relax, because your brain doesn't want your muscles to react during your dreams," the doc explains. "That's one theory, your brain is trying to do that, but your body isn't relaxing fast enough."
THEORY NO. 2: When your body is trying to relax and you make a movement, your body thinks you're falling.
"Your body's response to falling is to get rigid," the doctor explains.
CAN I CONTROL HYPNIC JERKS?
Okay, this might not be the best news, but the doc says that consuming alcohol and caffeine at night could exacerbate the problem. "Some studies show they could increase the frequency," Dr. Ian explains.
Plus, "if you exercise too late," he continues, "your body has a harder time relaxing."