Why don’t we fall out of bed while we sleep?

Why don't we fall out of bed while we sleep?

From the calmest of dreamers to the most agitated blanket puller, adults share the same nocturnal characteristic, characterized by not falling out of bed during sleep. You may have noticed by now that we don’t lie still during rest, snoring, snuggling, and even kicking. Why, then, do we remain in place and not fall out of bed?

  • What is sleep inertia, which makes us groggy in the morning?
  • There are at least 16 types of sleep, study finds

The ability not to fall, even, is independent of the size of the place where we sleep: it can be a very narrow air mattress for camping or a king size bed of the largest. It is very rare indeed that we wake up in a different place, inside the bed, from which we fell asleep initially. This happens because we have, even when we are asleep, body awareness, something that we can popularly call the sixth sense, but it has an official name — proprioception.

The sixth sense and sleep

This sense is less efficient in childhood, when we are still learning to perceive the world, and that is why little ones tend to fall out of bed more often than adults, even if it is rare. Despite the metaphysical association of the sixth sense in popular culture, placing premonition and clairvoyance abilities, its concept is very scientific, starting to be studied in the 19th century.

Over the centuries, we have come to better understand the importance of proprioception and, above all, our independence from it. To see it working live, do a test: close your eyes and touch the tip of your right elbow with your left index finger. Easy isn’t it? How did you know the position of these body parts with your eyes closed? Proprioception. It even allows you to know and describe the body’s current posture without having to see it. We know where every part of us is in space.

This perception is allowed by the neurophysiological signals of the receptors that we have in tendons, joints, skin and muscles, bringing to the brain information about the rotation of our joints, length and elongation of the muscles, skin flexion and any local alterations. Thus, we know where each part of the body is facing, where the joints move, how posture and balance are.

Other responsible

When we lose balance, proprioception is one of those responsible for helping us get back into the right balance so we don’t fall. The vestibular system, of the ears, is also related to this, as it allows us to know the inclination of the body, even with our eyes closed. It also helps us to know our acceleration in space, linked this time to the function of the eyes. This doesn’t help with not falling out of bed, however, since we are with our eyes closed and unconscious in our sleep.

We move less during sleep thanks to REM atonia. In this phase of sleep, the body increases the need for stimuli for us to move our limbs, so it is possible to dream and interact without the arms and legs responding, or we would go out walking every night, which only occurs in cases of sleepwalking. Nocturnal movements may occur when the stimuli are very strong, overcoming atony, but they usually do not go beyond weak kicking or slight displacement of the limbs.

The “body GPS” that proprioception gives us helps both in our movement and immobilization when we sleep, that is, we know when an arm or leg is about to fall off the bed, returning to position them correctly, even without realizing it. Our brain is equipped with many tools to ensure our safety, whether we consciously command them or not – thank it the next time you wake up in the same place you slept!

Source: BBC