Why does your body jerk as you fall asleep?

It’s something many of us experience on a regular basis without ever understanding why

Sleep is something we all do and all need, yet there is still a lot about sleep that can feel mysterious. No two people experience sleep in exactly the same way, and some of us have to deal with strange reactions and phenomena as we try to get some shut eye.

One such reaction is called a hypnic jerk or hypnagogic jerk, otherwise known as a ‘sleep start’. This is an involuntary muscle contraction that is usually experienced just as you are starting to fall asleep. Some are mild and hardly noticeable; others can be intense and alarming.

These muscle movements are called myoclonus — the same involuntary action which is responsible for hiccups. The strength of these jerks can vary significantly, and in some people can result in spasms strong enough to force them out of sleep.

In some cases, hypnic jerks can include symptoms such as rapid heartbeat, fast breathing, sweating, vivid dreams about falling, and a sensation of being about to fall down.

What causes hypnic jerks?

The majority of us will have experienced hypnic jerks at least once in our lifetimes. In fact, a 2016 study found that 60 to 70 percent of people experience sleep starts, usually just as they are beginning to fall asleep. The study also concluded that these jerks occur randomly and impact both men and women of all ages.

In most cases, there is no clear cause for hypnic jerks and they appear to occur in most people without any obvious explanation. However, there are certain theories about activities, actions and feelings which could make hypnic jerks more likely to appear.

These include exercising late in the evening, and practicing poor sleep habits such as irregular sleep patterns, sleep deprivation, late night screen time and more. These are all factors which can act as stimulants, making it more difficult for your brain to fully wind down.

Other stimulants which could contribute to the frequency of your hypnic jerks are caffeine, nicotine and emotional stimulants like stress and anxiety.

Here’s why you shouldn’t count sheep

Hypnic jerks aren’t the only mysterious area of sleep science. There is still a lot about sleep that raises questions, including disagreements over the best way to fall asleep.

One of the most classic techniques for drifting is to count sheep. This is designed to calm your mind and move your focus away from possible stresses. However, recent studies have found that this method could do more harm than good when it comes to falling asleep.

This is because, by counting sheep, you are effectively counting how long it has taken you to fall asleep. This invites further stress about not getting enough sleep, particularly if you have to be up early the following day.

What about sleep talking?

Just as some people experiencing hypnic jerks at night, so too do some people talk in their sleep. This is what is known as a type of parasomnia – or an unusual sleep behaviour.

The reasons why some people talk in their sleep are still mostly unknown, though it is thought to be harmless in the majority of cases. For some people, however, it can be the sign of an underlying sleep disorder such as REM sleep behaviour disorder, catathrenia, or sleep terrors.

Similarly to hypnic jerks, studies have found that around two thirds of people talk in their sleep to some degree. And, also like hypnic jerks, stress and anxiety could be a factor. Putting a healthy, consistent sleep routine into practice can help you experience a more restful night’s sleep.

A good night’s sleep requires a premium mattress. Explore the full range of Mammoth mattresses here on our website. Or check out the rest of our blog for more sleep news and tips.