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From Mike Tyson to George Foreman, many of the world's most famous boxers are known for their powerful uppercut punches.
Now, scientists have revealed why the move so regularly knocks boxers out cold, with an experiment on eggs.
Egg yolks are bathed in liquid egg white and are surrounded by a hard shell - a similar layout to our brains, which are bathed in cerebrospinal fluid inside a hard skull.
Through their experiment, the researchers found that egg yolks can be broken without cracking the shell when hit side-on, indicating that our brains can also be damaged, without cracking the skull.
The findings may help to explain why boxers tend to faint if they're hit on the chin.
© Provided by Daily MailWhen the egg was hit directly (row A), the egg yolk was not damaged. However, when the egg was hit from the side (rows B and C) - known as rotational impact - there was 'tremendous' yolk deformation. In particular, decelerational rotational impact was found to deform the egg yolk (row C)
WHAT IS ROTATIONAL IMPACT?
Two types of impacts can be imposed on the container, whether it's an eggshell or the skull.
A translational impact is one that hits the container directly.
A rotational impact occurs when the outer container is accelerated or decelerated rotating.
The latter arises naturally in sports when helmets are not round.
In the study, researchers from Villanova University in Pennsylvania looked at whether it was possible to break or deform an egg yolk, without breaking the eggshell.
Professor Qianhong Wu, a professor in Mechanical Engineering and lead author of the study, said: 'Critical thinking, along with simple experiments within the kitchen, led to a series of systematic studies to examine the mechanisms that cause egg yolk deformation.'
Using an egg scrambler, the team showed that rotational force could easily break the egg yolk and make it mix with the egg white, without cracking the outer shell.
Surprisingly, the experiment revealed that when the egg was hit directly, the egg yolk was not damaged.
However, when the egg was hit from the side - known as a rotational impact - there was 'tremendous' yolk deformation.
Professor Qianhong Wu, a professor in Mechanical Engineering and lead author of the study, explained: 'We suspect that rotational, especially decelerational rotational, impact is more harmful to brain matter.
© Provided by Daily MailThe findings indicate that straight-on punches are less likely to knock boxers out than rotating punches, such as uppercuts to the chin. In this image, Japanese Olympic gold medalist Ryota Murata (R) connects with a left uppercut against Gunnar Jackson (L) of New Zealand
'The large deformation of brain matter during this process induces the stretch of neurons and causes the damage.'
The findings indicate that straight-on punches are less likely to knock boxers out than rotating punches, such as uppercuts to the chin.
'Considering the chin is the farthest point from the neck, hitting on the chin could cause the highest rotational acceleration/deceleration of the head,' Professor Wu said.
While it remains unclear exactly how the brain is injured in concussions, the researchers hope the findings will help to shed light on the intricate biomechanics of the brain.
Professor Wu added: 'We hope to apply the lessons learned from it to the study of brain biomechanics as well as other physical processes that involve soft capsules in a liquid environment, such as red blood cells.'
Worryingly, up to 90 per cent of boxers suffer some form of brain injury during their career, according to the American Association of Neurological Sciences.
© Provided by Daily MailWhile it remains unclear exactly how the brain is injured in concussions, the researchers hope the findings will help to shed light on the intricate biomechanics of the brain. In this image, Ray Joval (R)lands a right uppercut to the head of Rodriguies Moungo (L)
It explained: ' There are boxers with minimal involvement and those that are so severely affected that they require institutional care.
'There are some boxers with varying degrees of speech difficulty, stiffness, unsteadiness, memory loss, and inappropriate behaviour.
'In several studies, 15-40 percent of ex-boxers have been found to have symptoms of chronic brain injury. Most of these boxers have mild symptoms.
'Recent studies have shown that most professional boxers (even those without symptoms) have some degree of brain damage.'
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