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"T-Rex Arms" While Sleeping: Should You Be Worried?

In this article, we will take a close look at the phenomenon of "T-Rex arms" during sleep. We will understand whether this phenomenon is a cause for concern. We will also understand the wider science of arm movements during sleep, and the role of the nervous system in these movements.

Frederika Malichová

Author - Frederika Malichová

Neuroscientist at the University Of Cambridge.

Frederika used MediSearch to find sources for this blog.
MediSearch gives instant answers to medical questions based on 30 million scientific articles.

Observing T-Rex Arms During Sleep

While we don’t know exactly why we sometimes observe “T-Rex arms” while asleep, it is definitely not a sign of any arising condition.

While some people worry that "T-rex arms" are a sign of ADHD or even autism, these worries are not scientifically backed, as we discussed in our previous blogs.

Moving your arms while asleep is completely normal and should not worry you!

What Are T-Rex Arms In Humans?

The term “T-Rex arms” is not considered a medical, let alone scientific term. It is a colloquial expression used to describe a condition in which one’s arms are perceived to be disproportionately small compared to one’s body. It may also refer to bending your arms in such a way that the dinosaur Tyrannosaurus Rex did.

The term "T-Rex arms" originated from the forelimbs of the dinosaur Tyrannosaurus Rex, which were significantly smaller than its body.

In this context of shorter arms relative to the body, we can identify some medical conditions that lead to shorter arms, such as achondroplasia, which is a short-limbed dwarfism.

Please note that in any sense when we say “T-Rex arms”, we don’t suggest any structural, evolutionary, or functional similarities between the arms of the dinosaur and human arms. Human arms are used for much more complex situations [1, 2].

Do People Make Moves With Their Arms During Sleeping?

Yes, of course, we make movements with our arms during sleep. Although it varies from individual to individual, and some may not move during their sleep at all. This can depend on the sleep stage, age, but also on individual characteristics of the person.

In fact, a study found that around 68% of participants move their arms during the wakefulness stage of sleep, which is around the time we are just falling asleep or slowly waking up from sleep [3]. Another study also found that movements involving the neck, head, and upper limbs are often observed in various stages of sleep. For instance, during REM sleep, 93.8% of all respondents did such movements [4].

Age and BMI are also controlling factors for sleep movements. People aged 20-34 appear to move more than those aged above 34, including arm movements, and interestingly, obese people tend to do more movement while asleep than normal-weight people [5].

In conclusion, arm movements during sleep are quite common and can be influenced by various factors such as sleep stage, age, and individual characteristics.

However, research has shown that certain types of movements during sleep may be a predictor for developing neurodegenerative diseases in sleep.

For another interesting fact, try asking "Is there a link between "acting out in sleep" and Parkinson's disease?" in the above window.

What Are T-Rex Arms During Sleeping?

T-Rex arms during your sleep mean that your body is moving while you are asleep. The movement of the body can be due to various external factors and does not necessarily mean there is something wrong with you.

Can The Nervous System Affect Our Arms To Be Shaped As T-Rex Arms While Sleeping?

The nervous system plays a significant role in controlling our body's posture and muscle tone, including the positioning of our arms during sleep.

However, the specific phenomenon of our arms taking a T-rex-like shape while sleeping has not yet been addressed.

But do not worry, sleeping with oddly bent arms should not signal any condition. However, it may cause some problems. Let’s use Medisearch to help us understand what:

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