You’re dozing off, about to fall asleep, when suddenly your body jerks.
Have you ever been startled awake like that?
Sometimes it comes with a sensation of falling from a height, or of your body jolting right at the border between dreams and reality.
You might worry that something is wrong with your body, but this is a physiological phenomenon known as a hypnic jerk (hypnic myoclonus), and it happens in healthy people too.
The Jerk Happens Just as You Fall Asleep
A hypnic jerk is a sudden, involuntary muscle contraction that occurs during the transition from wakefulness to sleep.
Sometimes only an arm or leg moves; other times the whole body moves dramatically.
Medical literature reports that around 60-70% of the general population experiences this at sleep onset, so it is by no means unusual.
In other words, a jerk once or twice does not, on its own, mean that anything is wrong with your body.
Why Does the Body Move the Moment We Fall Asleep?
In fact, the detailed mechanism behind hypnic jerks is still not fully understood.
As we begin to fall asleep, the brain shifts from wakefulness to sleep, and the body’s muscles gradually relax.
It is thought that temporary changes in nervous system and muscle activity during this transition lead to a sudden muscle contraction.
Another theory holds that the brain interprets the feeling of the body relaxing as “falling” and contracts the muscles in response, but this is only one hypothesis, not an established mechanism.
Do Hypnic Jerks Increase When You’re Tired?
Hypnic jerks can happen to anyone, but some factors have been suggested as possibly making them more frequent.
Typical examples include:
• lack of sleep
• severe fatigue
• stress and anxiety
• stimulants such as caffeine
• intense exercise before bed
and so on.
For example, your sleep is cut short by a busy work schedule, you keep drinking coffee into the evening, and you work or exercise right up until bedtime.
If that kind of lifestyle continues, you may notice these jerks before sleep more often.
Usually, There’s No Need to Worry Too Much
An occasional jerk as you fall asleep is, in most cases, considered a physiological phenomenon that doesn’t require treatment.
However, if you experience things like
“It repeats many times a night and I can’t sleep,”
“My body moves on its own frequently during the day, too,” or
“It’s clearly happening more often than before,”
and it persists to the point of affecting your sleep or daily life, there may be a cause other than hypnic jerks, so we recommend consulting a medical professional.
If the Jerks Increase, Use It as a Cue to Review Your Sleep Habits
Hypnic jerks can’t be definitively called a “sign of fatigue” from your body.
Still, because links with lack of sleep, stress and caffeine have been suggested, if you feel they’ve increased lately, it can be a good opportunity to look back on your daily routine.
It’s also important to create time to shift gently from wakefulness into sleep, for example by dimming the lights a little before bed, stepping away from your smartphone and cutting back on caffeine from the evening onward.
At La HEAD, we slowly care for not only the head but also the neck, shoulders and arms, in a calm, fully private room.
If your busy days leave your mind and body tense right up until you fall asleep, why not make a conscious effort to set aside time to do nothing and simply let go?
If you’re looking for a head massage or dry head spa in Shinjuku, we would love to welcome you at La HEAD.
We look forward to your visit.