Sleeping should be one of the most relaxing moments of the day. We put ourselves to bed, we feel always more comfortable and lose the connection with the world around us to abandon ourselves into the arms of Morpheus. But sometimes, just before falling completely asleep, we have the sensation of falling and feel a sort of spasmodic movement.
It is a small gasp, as when we walk and put our foot wrongly because we misjudged the distance. Although it’s a normal phenomenon, many people are scared or even experience a panic attack. In fact, in extreme cases, when the hypnic jerk is very violent and fast, the person wakes up completely and can no longer fall asleep.
The hypnic jerk: A legacy of our ancestors?
The feeling of falling while we sleep is part of what is known as “hypnic jerk” and in some cases may also be accompanied by visual hallucination, which makes it even more baffling. It is estimated that 70% of people feel often this sensation when it’s about to fall asleep, although many do not remember it.
Usually a spasm occurs when muscles, usually in the legs, contract very quickly and unintentionally, something similar to what happens when we’re shoved or suffer a muscle spasm.
One of the theories that attempt to explain this phenomenon refers to the evolutionary point of view. According to this perspective, the movements and sensations that cause the rude awakening would help us monitor our environment for the last time, to ensure that we are definitely safe. That way helps us avoid falling asleep in a dangerous place, simply because we were overwhelmed by fatigue.
In addition, according to evolutionists, the hypnic jerk served our ancestors also to confirm that they had chosen a stable position to sleep. In practice, it was an ancestral mechanism to make sure they have selected a sufficiently strong and stable point of support before falling asleep completely.
But in recent times, thanks to progress in neuroscience, another theory appeared that attempts to find the explanation of the hypnic jerk in the brain.
The brain never disconnect permanently
Neuroscientists, on their side, believe that these movements simply point out that our physiological system is giving up to sleep. In fact, when we sleep, as a precaution, it is produced a paralysis in our body, called “sleep paralysis”. During REM sleep, which is the deepest, when we dream, the brain is “disconnected” from the main muscle groups, so we can not imitate the movements we do while dreming and avoid to harm ourselves.
In this regard, the sensation of falling and those jerky movements would be a signal that we are moving from the active muscle control to a state of total relaxation.
But there are some factors that can increase the chance to experience the hypnic jerk or have a more intense feeling of it.
– When we don’t sleep regularly or go to bed too tired.
– When we consume an excessive amounts of stimulants such as coffee and tea, especially in the evening, and do intense physical activity always in the evening.
– When are interferences of external stimuli such as lights and sounds while we are about to enter the deepest stage of sleep.
In all these cases, sleep is interrupted, it develops an irregular pattern that implies that the organism enters the REM stage before being prepared, and this can cause an hypnic contraction or the sensation of falling into the void. In fact, it was seen that the hypnic jerk is more common when the person falls quickly asleep. In practice, our body falls asleep so quickly that the brain is not able to follow the pace and go through the different stages of sleep, so that there is a sort of “short circuit”.
Finally, it should be clear that while the hypnic jerk is a natural phenomenon of sleep, which usually decreases with age, it can still become annoying for both the person who suffers it and those sleeping next. In these cases it is advisable to consult a sleep specialist as the cause may be another disorder such as sleep apnea or restless legs syndrome.