A SIMPLE arm movement that most women can do is baffling men who are unable to copy.
Demonstrated by a couple on TikTok in a video viewed millions of times, it’s yet another viral trend that shows the bizarre differences in male and female anatomy.
TikTok @_byjemmieA couple claims a simple arm movement can only be performed by women. With her arms extended in front of her, Jemmie’s elbows are still touching[/caption] 
TikTok @_byjemmieBoyfriend Russ is unable to close the gap between his elbows – which the pair claim is standard for men[/caption]
In the clip, Jemmi, from San Diego, places her forearms and elbows together with her hands in fists.
She lowers her arms in front of her, so her palms would be facing up.
Her boyfriend Russ also attempts the move but is unable to do it as well.
The key difference is that Jemmi can keep her elbows together, while Russ can’t.
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The video, which says “only girls can do this…”, has been watched almost 2.5 million times as eager viewers try the trick out.
So what’s going on?
Women and male anatomy are different in dozens of ways. Some are blindingly obvious but others, such as this, are not so.
Justin from the Institute of Human Anatomy explains that gender differences that are not important to reproduction are called “secondary sex characteristics”.
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In a YouTube video titled “Women Have Weird Elbows”, he discusses the so-called “carrying angle”.
This is thought to be why women can do the simple arm trick while men cannot, MailOnline reported.
The carrying angle is the gap between the elbow and the body if you were to:
- Stand with your arms in front of you with your palms facing upward (supinated position)
- Extend your arms out and bring them to the side of your body. Your palms should be facing away from you
The gap that forms between your body and elbow is called the carrying angle.
It allows the arms to swing by the body without hitting the hips (which are wider than the shoulders).
For example, imagine you are walking home with very heavy shopping bags, and you are holding them at a slight angle from your body, with extended elbows.
Some people’s forearms come out at more of an angle than they might anticipate, Justin says.
Women are more likely to find this, and therefore have a larger carrying angle than males.
Normally a woman’s angle is 14° away from the body, while a man’s is 11°, according to Radiopaedia.org.
This may be because women have wider hips, and therefore need more space to swing their arms.
However, Justin noted some other theories too.
He explained that research has shown that the carrying angle is larger in shorter people, too, and women tend to be shorter than men.
Factors such as this could explain why some men will still be able to do the movement, while women cannot.
Research has shown that throwing athletes have a greater carrying angle.
And it may just be that can also determine whether you can do the arm movement trick.
It comes after a string of tasks have gone viral on TikTok showing women being able to do them while men cannot.
For example, to do the chair challenge – which women can do but men can’t:
- Stand up against the wall and take three footsteps back
- Place a chair in front of you, up against the wall
- Bend over the chair, creating a 90-degree angle with your body
- Place your head against the wall
- Lift the chair up to your chest, keeping your head against the wall
- Try to stand up straight, lifting the chair with you
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While women all over the social media platform showed off doing the task, men repetitively failed.
One school of thought blames the fact that men have a different centre of gravity – the point where a person’s total weight is concentrated – to women.
