Tag Archives: concussion

Why is heading the ball so dangerous for youth soccer players?

young girl attempting to head an incoming soccer ball
Photo by Carson Ganci on THE42

I received my first concussion while playing soccer at 15 when I was knocked out by a ball that was “accidentally” punted directly into the side of the head. It seemed to me like this was one of the few, rare ways to get a concussion from the sport – an unlikely occurrence combined with an unusually aggressive impact. I was proven wrong, however, after I received two more concussions just from heading the ball – a frequently used technique involving seemingly mild impact forces. I have since come to discover that concussions, particularly due to heading the ball, are a huge problem for youth soccer players: currently, in the United States, youth soccer players aren’t allowed to start heading the ball until age 11 in an effort to reduce the risk of concussions. But how do headers cause so many youth concussions, especially when the speed of play is so much lower than for adults?

Physical vulnerability to concussion mechanics

illustration showing a head impacting a an object with arrows decribing the movement of the skull and the brain towards the object just before impact
Illustration of the movement of the skull and brain just before impact with an object. Upon impact, the movement of the skull decreases rapidly while the movement of the brain has a delayed response. Original image created for Wikipedia

In most sports, concussions are commonly caused by rapid acceleration/deceleration of the head that causes the exterior of the brain to crash into the interior wall of the skull, which is suddenly accelerating in a different direction. When headers are performed in soccer, this rapid acceleration is caused by impact with the ball, and the risk of concussion depends on both the acceleration of the head and the duration of the impact. The acceleration of the brain can be modeled by Newton’s Second Law (F = ma) for a given impact force F, and the resulting acceleration depends on the effective mass of the players head m, which depends on both the strength and weight of the players head and neck as well as their relative movement compared to the ball (which boils down to technique). This means that a major portion of the risk of concussion relies on the size, strength, and technical ability of the player, all of which have an inverse relationship with player age. So while the relative speed of play and impact forces may seem lower for youth players that can’t run as fast or strike the ball as hard as their adult counterparts, these factors are offset by their relative physical vulnerability.

Issues with injury recognition and response

Another factor contributing to the threat of concussions for youth players is their relatively low ability to recognise and respond appropriately to a brain injury when one occurs. Between 2008 and 2012, researchers observing elite female players aged 11 to 14 for 414 player-seasons (288 athletes were observed for a single season and 63 were observed for two seasons) discovered that 59 concussions occurred, with headers being the most frequent cause at 30.5%. In addition to this injury frequency, it was found that over half of these middle-school-aged athletes continued to play with symptoms after receiving a concussion. This is an additional a logistical problem for youth players, for as age decreases, athletes on average have less access to on-hand, qualified medical personnel and less of an ability to self-diagnose and respond appropriately to injury, putting them at increased risk for long term damage.

The Dangers of Using Your Head: The Biomechanics of Sports-Related Concussions

Anyone that has ever had the misfortune of banging their head know how painful it can be, but does everyone understand just how dangerous it can be? Concussions occur when the brain hits the interior walls of the skull, either due to a direct blow or a sudden start or stop. These brain injuries most often result in confusion, headaches, and loss of memory but more severe injuries can cause vomiting, blurry vision, and loss of consciousness. In rare instances, they can even cause a brain bleed and result in death. Repeated concussions can lead to neurocognitive and neuropsychiatric changes later in life as well as increase a person’s risk of developing neurodegenerative diseases like Alzheimer’s.

So, who is at risk for concussions?

Athletes sustain 1.6-3.8 million concussions every year in the US. They are most common in contact sports such as soccer and hockey, but the largest contributor is American football. Players are constantly hitting or tackling each other in football, and each impact risks serious injury for both individuals.

How does it happen?

It all comes down to conservation of energy and momentum. Newton’s second law states that an object in motion tends to stay in motion while an object at rest tends to stay at rest, unless acted on by an outside force. When player 1 starts to run, he has a set energy and momentum based on his velocity (speed). Once he hits player 2, he either slows down, stops, or bounces off in the opposite direction. However, the initial energy and momentum that he had doesn’t just magically disappear, it needs to be conserved so it is transferred to player 2. This means that player two will start moving in the direction that player 1 was initially running. This is how billiards is played: the energy is transferred from the pool stick to the cue ball and then to the intended solid or stripe.

However, injury occurs when player 2 or his head cannot move. This may be because he hit the ground or another player or even simply because his neck stabilized his head, but regardless, that energy still needs to go somewhere. When the head stops, the brain keeps going until it collides with the inside of the skull.

Fortunately, not every hit results in a concussion. The brain is separated from the inside of the skull by cerebrospinal fluid that can protect it from collision to a certain degree, so not every impact reaches the injury threshold. What that injury threshold is has become the focus of many scientific studies.

Finding the injury threshold

The search for the injury threshold is a vital one that could help in the development of more effective helmets and rule changes to the game that could keep players safe. Three factors are believed to dictate this threshold: linear acceleration, angular acceleration, and location of the impact. The linear acceleration is what causes the collision with the skull, as previously described. The rotation of the cerebrum (the bulk of the brain) about the brain stem can cause strain and shearing within the upper brainstem and midbrain, which control responsiveness and alertness (causes the confusion symptoms). Finally, certain areas of the brain are more susceptible to injury- like the frontal lobe, temporal lobes, and brain stem since they are near bony protrusions– so the location of the impact can have a major influence in the injury threshold.

While there is still no set threshold, one study was conducted in which 25 helmet impacts from National Football League (NFL) games were reconstructed and the resulting helmet kinematics measured. The study found that the heads of concussed players reached peak accelerations of 94 (+/-) 28 g (acceleration due to gravity-9.8 m/s^2) and 6432 (+/-) 1813 radians/s^2. A separate study focused on the location of concussions of football players and that resulted from specified linear accelerations, as seen in Figure 1.

While there is still much that needs to be learned about sports-related concussions and their long term effects on athletes, scientists are well on their way to understanding the biomechanics that cause them. The next step is using that knowledge to create better protective headgear and a safer game.

Locations of concussions and their linear accelerations.
Back: Case 13-168.71 g (1 concussion)
Front: Case 12-157.5 g, Case 2- 63.84 g, Case 6- 99.74 g, Case 4- 84.07 g (4 concussions)
Right: Case 11-119.23 g, Case 8-102.39 g (2 concussions)
Top: Case 9-107.07 g, Case 1- 60.51 g, Case 7- 100.36 g, Case 10- 109.88 g , Case 5: 85.10 g, Case 3: 77.68 g (6 concussions)
Location of concussions and their linear accelerations. Modified from Neurosurgery

To learn more, check out these links!

https://pubmed.ncbi.nlm.nih.gov/23199422/

https://pubmed.ncbi.nlm.nih.gov/23299827/

Attempting to “Knock Out” the Causes of Concussions

This image displays a human head experiencing impact to the forehead region.
This image is licensed under CC BY-SA 3.0 .

Approximately every 15 seconds, a traumatic brain injury occurs in the U.S. A concussion is a form of mild traumatic brain injury produced by a contact or inertial force to the head (or neck) area. A concussion causes the brain to rapidly move around inside the skull, harming natural brain function. According to the Brain Injury Research Institute, roughly 1.6 to 3.8 million concussions occur each year in the U.S., resulting from both recreation and sports related incidents. In fact, brain injuries cause more deaths than any other sports injury.

The high incidence of concussions has made the injury subject to several biomechanical studies in recent years. Kinematic, or motion-based, parameters of the head are used as common indicators to predict brain injury as they are suggestive of the brain’s response to force. Early efforts focused on the linear acceleration of the head during concussion as the primary prediction factor of the injury. The peak linear acceleration of the head is correlated to the peak pressure within the brain, and an increase in pressure within the brain can cause neurological damage. Modern sports protection equipment, including ice hockey helmets, maintain performance standards based on the peak linear acceleration experienced by the head during impact. However, linear acceleration does not entirely reflect the risk of concussion and rotational acceleration of the head must be considered. A shear force acts in a parallel direction to a surface or cross section. Shear forces and subsequent strains in the brain are correlated to peak rotational acceleration of the head. Brain tissue is one of the softest bodily materials and deforms quickly to shear forces. Therefore, rotational acceleration of the head is a common catalyst of severe concussion.

This image presents two human skull and brain combinations. The left skull has red horizontal arrows pointing to the brain to depict the linear acceleration of the head during a concussion. The right skull has red arrows acting in a circular manner around the head to represent rotational acceleration acting on the brain during concussion
This image is licensed under the Creative Commons Attribution 2.5 Generic License. Changes were made to the image in the form of text and red arrows.

A 2015 study introduces the addition of the brain deformation metric maximum principal stress (MPA) in order to aid in connecting kinematics and injury during concussion prediction.  The study used Hybrid III crash test dummy head forms to examine the result of varying forms and severities of impact. Each head form was equipped with nine single-axis accelerometers to study the acceleration of the head and hyperelastic models were used to study brain tissue deformation.

The results of the study revealed the existence of significant correlations between linear acceleration, rotational acceleration and maximum principal stress of brain matter, emphasizing the importance of considering several kinematic parameters in predictive concussion studies. Results of the study exemplified the magnitude of accelerations experienced by the head during concussion: the head forms experienced an average linear acceleration of approximately 40.62g and an average rotational acceleration of approximately 3388 rad/s2, which is equal to about  539 rev/s2. The extent of brain injury is revealed through the immensity of the accelerations experienced during impact.

This image presents a side view of the skull that presents all organs as semi-transparent, enabling viewers to effectively see the inner-workings of the head.
“Years in the making: How the risk for Alzheimer’s disease can be reduced.” (2018)

When determining the probability of concussion, it is limiting to utilize just one parameter. Instead, several parameters and the relationship between each must be considered. Additionally, factors like sex-specific characteristics and under-reporting of injury have been proven to affect the severity of brain injury through study.  While brain injury can never be fully avoided, these studies can help to make equipment more protective and reduce injury.

Interested in reading more?

Neuroscience, Biomechanics & the Risk of Concussion in Developing Brains

Additional Sources:

Biomechanics of Concussion

Brain Injury Prediction

Concussion in Female Collegiate Athletes

How much wood can a woodpecker peck? The Science Behind a Woodpecker’s Anatomy

Woodpecker anatomy: showing the location of the tongue
Diagram showing the tongue of a woodpecker, obtained from “BirdWatchingDaily.com”

Have you ever wondered how a woodpecker is capable of banging its head against a tree so furiously without seriously injuring itself? The impact of a woodpecker’s beak with a tree can exceed speeds of up to 6 meters per second and occur over 12,000 times a day.These kinds of numbers are what allow woodpeckers to smash through trees to get to those tasty bugs that live inside.

How is this possible you may ask? Scientists have studied the anatomy of a woodpecker and have come across an extraordinary discovery: the tongue of a woodpecker wraps completely around its neck before exiting the mouth, constricting the blood flow to and from the brain. This increases the amount of blood volume in the skull, making it, and its precious cargo, filled to the brim with fluid. This creates an effect known as “slosh mitigation”, where an object that is completely enclosed by an incompressible fluid becomes protected from an outside force due to the constant stabilization of pressure within the enclosed system. Thus, the harsh vibrations translated throughout the skull of the woodpecker are mitigated by a cushioning effect induced by the increased volume of blood in the brain. Ever notice how a snow globe always has a little pocket of air sitting on top of the water? Without it, there would be no pressure changes, and the flakes of snow would be restrained from ever creating that magical snowy blizzard we all love.

This incredible discovery is not just a fascinating fact you can pull out to impress your friends. In fact, companies have begun applying the science behind a woodpecker’s anatomy to the sports arena. A company by the name of Q30 Innovations has been on a mission to curb the estimated 3.8 million concussion occurrences every year. Their latest product, the Q Collar, features a tightly fitted neck brace that applies a mild compression to the jugular in the neck, thus creating the “slosh mitigation” effect on the brain. The Q-Collar has already been put to the test, showing positive results on football players and hockey players. Their latest test showed the effects of wearing the Q-Collar for a high school girls soccer team, whose total head impacts were collected via an accelerometer throughout the entire season. Half the team was selected to wear the Q-Collar, and at the end of the season, the accelerometers of both groups reported similar levels of head impact, both in quantity and severity. However, it was shown the group wearing the Q-Collar required less brain activity to complete a concussion protocol than those of the control group. This shows that despite any of the girls having a reported concussion, the high impact loads exhibited on the brain during the season were enough to prohibit the brain from performing at its optimal level.

Want to learn more about breakthrough technologies covering the challenges of concussions? Learn more at Q30 Innovations.

 

References:

  1. “Do Woodpeckers Get Concussions?”http://explorecuriocity.org/Explore/ArticleId/6734/do-woodpeckers-get-concussions.aspx
  2. “Response of Woodpecker’s Head during Pecking Process Simulated by Material Point Method” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4406624/
  3. “What is a Concussion?” http://www.protectthebrain.org/Brain-Injury-Research/What-is-a-Concussion-.aspx
  4. “Q-Collar tests produce positive results in protecting girl soccer players from concussions” https://www.news5cleveland.com/news/health/q-collar-tests-produce-positive-results-in-protecting-girl-soccer-players-from-concussions

Will Removing Headgear Make Boxing Safer?

Our brains are made of a very soft material but luckily our skulls provide the brain protection from the outside world. However, during violent movements the brain is free to move inside the skull and collide with the skull. This impact can cause injury to the brain, known as a concussion, that can lead to various symptoms depending on severity. A 2014 paper by McIntosh et al. researched the biomechanics of concussions for Australian football players. Their research showed that a linear acceleration of 88.5 g to the head results in a 75% likelihood of a concussion. A g is the unit of acceleration and a single g is equivalent to the force of gravity at the Earth’s surface.

A very serious long-term effect of brain injury is Chronic Traumatic Encephalopathy known as CTE. Additional reading on CTE can be found here. Proper care must be taken to ensure the long-term health of contact sport athletes. Some contact sports utilize protective equipment such as helmets or mouth guards. However, the world of amateur boxing went a very different route to prevent brain injuries. An article by the New York Times reviews the International Boxing Association’s (A.I.B.A.) decision to remove headgear from international, male boxing competitions. In 2016, Olympic boxers entered the ring without headgear for the first time since 1984 according to the article. Apparently, this seemingly counterintuitive decision makes boxing safer. A cross-sectional study by the A.I.B.A. Medical Commission found there were more stoppages, caused by hard hits to the head, in fights with headgear. In fact, the data suggests that boxing without headgear lowers the chance of a stopped fight by 43%.

The A.I.B.A. claims that headgear did little to prevent brain injuries, however, there is counter research that refutes the A.I.B.A.’s claim. For example, a study by McIntosh and Patton researched the capability of A.I.B.A.-approved headgear to protect against injury. A glove was mounted to a driver and a Hybrid III head was used to record the head accelerations at different contact points and speeds. According to this study, head accelerations were significantly reduced by the headgear.

Boxing glove on piston delivering punch to a crash test dummy head
Modified from McIntosh & Patton, British Journal of Sports Medicine 2015

Headgear by no means prevents all concussions, for example, when the glove speed reached 8.34 m/s in the previously mentioned McIntosh and Patton study. Without headgear, the head experienced 133 g from a punch to the side of the head and 131 g from a punch to the front center of the head. With headgear, the head experienced 86 g from the lateral punch and 88 g from a punch to the front center of the head. The results showed there is a chance those with headgear could develop a concussion. However, without headgear, a concussion is guaranteed.

Headgear will not prevent all concussions but it can significantly decrease the chances of getting one. At some point, the force will surpass the protective capability of the headgear. Both sides of the argument present interesting and compelling data. In short, boxing is a contact sport. There will most likely always be a chance the athletes could develop brain injury.  In order to ensure the safety of the athletes, it is important to make decisions based on their health with definitive proof it protects them. The video below shows different sides to the debate.