The science behind why your body jerks when you fall asleep

Have you ever gone to sleep at night and dreamt that you were falling? Then suddenly, your body jerks, and you are startled awake. An experience like this can be somewhat unsettling, but if it’s happened to you, you’re not alone. This strange occurrence is called a hypnic jerk, and a 2016 study found that sixty to seventy percent of people experience them [1].

The Stages of Sleep

Before getting into the cause of these hypnic jerks, let’s first do a refresher on the stages of sleep:

Stage One

This is what happens when you first start nodding off. This short period lasts several minutes. During this time your heartbeat, breathing, and eye movements slow, and your muscles relax with occasional twitches. Your brainwaves also begin to slow from their wakefulness patterns.