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 Ultimate 2-for-1: the Power of Contralateral Strength Training

For the competitive athlete, injury often means loss. Loss of playing time, loss of skill development, and most importantly, loss of training time. These are all unfortunate consequence of getting a bone or tissue injury requiring a long-term healing prognosis. Injuries can be so devastating because the road to recovery is often times an arduous two-step process. First, the athlete must wait for their broken bones, torn ligaments, or pulled muscles to naturally heal. During this time, the athlete’s injured limb is likely immobilized in a cast or brace, leaving the resulting muscle to slowly atrophy as the body tries to heal itself. As a result, an athlete must spend the second part of their recovery process re-training the weakened muscles in the immobilized limb to return to full-strength. What if there was a way to heal and train the body at the same time? This is the power of a neurophysiological phenomenon known as “contralateral strength training.”

First observed in 1894, this phenomenon describes the increase in strength seen in an untrained limb of the body after strength training the opposite limb. For example, performing strength training exercises using the left arm has been shown to also induce an increase in strength in the right arm without working out the right arm at all. This effect can be seen in all different muscle groups in the body, in both males and females, and in people of all different ages. Researchers have hypothesized that high-force contractions used in resistance strength training can have a “spillover” effect on the neurons controlling the opposite limb. These neural circuits can carry motor output signals from the trained muscle to the untrained contralateral muscles which works to increase the electrical activity of the untrained muscle and effectively activate the muscle as if it were being trained as well. The video from the YouTube channel “House of Hypertrophy” helps illustrate this effect.

This video is from the YouTube channel “House of Hypertrophy” and helps illustrate the contralateral strength training phenomenon.

Harnessing the power of this neurophysiological phenomenon is key to injury recovery especially when one limb is immobilized for an extended period of time. It’s not just for competitive athletes either. Anybody with an injury can take advantage of contralateral strength training to dramatically speed up injury recovery. This can be especially useful for the elderly population where maintaining balance is an important factor of injury rehab. Imagine being able to maintain the strength and mobility of an elderly patient’s leg after a common surgery such as a knee replacement. Although the leg will be immobilized by a brace or a cast to keep the knee stable after surgery, it could be possible to prevent the muscles from atrophying by simply training the opposite leg with effective physical therapies. This could mean the difference between a smooth recovery versus one where the patient faces serious balance and stability issues as a result of a weakened limb that was immobilized in a cast for weeks to months at a time. Whether it be for injury recovery or specialized strength training, contralateral strength training has an amazing 2-for-1 effect in which the body’s own neural mechanisms allows both homologous muscles to experience the effect of a single unilateral training.

A Second Chance: Robotic Exoskeletons May Be the Future of Mobility for Patients with Spinal Cord Injuries

No one ever imagines themselves getting seriously injured. Accidents do happen though, like car crashes and unexpected sports injuries. These events can drastically change a person’s life, leaving them unable to perform simple daily tasks without assistance, such as walking. One injury that can radically impact a person’s life is a spinal cord injury. There are approximately a quarter of a million people in the United States with spinal cord injuries, and that number grows by 12,500 each year.

The spine is the center of support in the body. It adds structure and facilitates movement. Its other extremely important job is to protect the spinal cord, which is a column of nerves that runs down the length of the neck and back. The spinal cord is part of the nervous system, and it acts as a messenger, taking orders from the brain and relaying these messages to the rest of the body, telling the muscles what to do. If the spinal cord is injured, the messages can’t be delivered properly. This often results in a loss of mobility.

Diagram of the central and peripheral nervous system showing how the spinal cord connects the brain to nerves that run throughout the body
From OpenStax Anatomy and Physiology on Wikimedia Commons

Most people don’t think about the mechanics involved in the simple act of walking. However, in order to walk, various joints such as the hip, knee, and ankle need to work together, rotating and bearing loads to allow for movement. When your foot hits the ground, the ground imparts a force through the foot which is translated up through the lower extremities to the spine. When a spinal cord injury occurs, the brain is unable to communicate with our muscles which inhibits this load bearing and the resulting movement.

Studies have shown that powered exoskeletons have numerous benefits for patients with spinal cord injuries to help with walking and mobility. These powered exoskeletons are built in various ways to bear loads and encourage movement, and a review of different exoskeletons, along with other rehabilitation devices, discusses differences in design and control of the systems. For example, to allow for control of movement, one exoskeleton was built with motors located at the joints while another was designed with a braking system at the joints.

Photo of the Indego powered exoskeleton
Indego Exoskeleton – From Indego.com

One study researched mobility outcomes for patients with injuries that varied in severity and location on the spine. Some patients were paraplegic, which means their lower extremities were paralyzed, and some patients were tetraplegic/quadriplegic, which means the paralysis affected both their lower and upper extremities. Also, some patients had complete spinal cord injuries, which means all feeling was lost below the injury, while others had incomplete spinal cord injuries, which means they had some feeling and some ability to control movement below the injury. This study showed that powered exoskeletons, specifically the Indego exoskeleton, could help a patient move in both indoor and outdoor settings, and there is potential for patients with paraplegia caused by injuries to the lower spine to use this device to allow greater ease of mobility in public spaces. For patients with more severe injuries, such as those with quadriplegia, the powered exoskeleton allowed for slower movement with supervision and occasional assistance from a therapist. These patients also needed assistance with putting on and removing the device. Therefore, the powered exoskeleton won’t help patients with more severe injuries move on their own in public settings, but it was excellent for exercise and rehabilitation.

These exoskeletons are also proven to be safe and feasible. Patients with complete spinal cord injuries did not report discomfort or injury, and they were able to use a powered exoskeleton more easily than previous rehabilitation technology.

Powered exoskeletons may be the future of movement for those who thought they would never walk again. This further reading contains examples of paraplegics who walked using a powered exoskeleton. Another man even walked marathons using one of these devices:

From Freethink on YouTube

There are limitations on these devices, but the robotics field is swiftly evolving, and the technology is giving patients something they never thought they would have: a second chance.

Which is more stable, washing machines or birds? The answer might surprise you

What do birds and washing machines have in common? Shockingly, it’s not the ability to wash clothes. Rather, most birds and washing machines are great examples of vibration isolation systems.

Now that’s cool and all – but what is a vibration isolation system?

Better known as a mass-spring-damper system, vibration isolators are generally a mechanical or industrial mechanism that can reduce the amount of vibrational energy produced by a system. Vibration isolators are incredibly important; studies show “undesirable vibrations” can shorten a machine’s service life and even permanently damage the machine and those using it. Considering this, engineers are constantly improving upon current vibration control systems, and are now looking to birds for inspiration.

But why birds? Well, to understand this, let’s consider a bird as a simple mass-spring-damper system.

Avian vibration isolation system represented as mass-spring-damper-system
Simple approximation of avian vibration isolation system as mass-spring-damper system. Taken from the 2015 study: ‘The role of passive avian head stabilization in flapping flight.”

First, visualize vibrations as an oscillating force stemming from the bird’s body moving back-and-forth. Vibrational forces can be generated by the flapping of wings, unexpected gusts, and/or movement of legs. Now, if we continue up from the body to the neck, we can see where avian skeletal and muscular structure really begins to “show off its feathers.”

Characterized as a multi-layered structure, the avian neck contains many sections of “hollow” bones, connected by surrounding muscles. The structural units (muscles and bones) of the avian neck have properties of both springs and dampers, optimizing them for vibration isolation.

Simplified representation of multi-layered neck as spring-damper structure

For starters, we see the muscles largely act as springs. Springs have the unique ability to move a body with its vibrations. This behavior is present in the muscles connected to the bone segments, in that they are capable of instantaneously compressing, elongating and twisting in response to rapid changes in the body’s movement. This elastic response prevents not only the head, but the whole bird, from shaking when bombarded when vibrations from any form of movement.

Simplified visualization of multi-layered spring-damper structure. The transparent grey portion represents the hollow bone, which is connected by the black lines, or strong spring-like muscles. The empty space between each unit would consist of the softer, damper-like muscle. Taken from the 2021 study: “A novel dynamics stabilization and vibration isolation structure inspired by the role of avian neck.”

Alternatively, the muscles, primarily those not connected to bone, can act as dampers. Effective dampers are similarly identified by the ability to move with vibrations; however, they can dissipate some of the vibrational energy as heat, or store energy until relaxed. The interior muscles are capable of slowly deforming (changing shape) if exposed to steady vibrations, allowing for dissipation of excessive vibrational energy.

But hey, what about those bones?

The avian neck has nearly three times the number of bone sections than most mammals, on top of muscles entirely surrounding the neck. This drastically increases the bird’s flexibility, helping it maneuver through sharp positional changes, thereby further limiting the effect of vibrational forces.

Finally, what makes the avian vibration isolator truly superior is its passive activation. As engineers at Shanghai Jiao Tong University point out, manmade passive vibration isolators fall short because they require sensors and input energy to adjust for “shocks and random vibrations.” As previously explained, the multi-layered neck is well equipped to handle random oscillations, yet, more importantly, the bird’s neck muscles can passively change position to brace for incoming vibrations.

A recent study from Stanford University proved this concept by recording a whooper swan’s reaction to different strength gusts. They found that swan’s neck adjusted to protect the head, and that even when the flapping doubled, the movement of the head reduced by a quarter. Finally, it is important to note that passive activation is not limited to the sky; researchers have found that mainly terrestrial birds like chickens and pigeons have a similar neck structure and system for maintaining stability and clear vision.

Overall, continuing to study the avian vibration isolation system could prove very beneficial for many different applications. For a more in-depth look at the current work out, check-out the studies referenced throughout the article. Otherwise, enjoy watching this chicken work its body control magic!

Mercedes-Benz “Chicken” Magic Body Control Advertisement, highlighting the chicken’s amazing head stabilization ability.

Why We Need to Re-Evaluate the RACIALIZED History of Spirometry

One of the leading indicators of good health is adequate lung capacity. Lung capacity, as defined by Bajaj and Delgado is the volume of air in the lungs upon the maximum effort of inspiration. For an average healthy adult, that is about 5.5 liters of air. But how do we measure our lung capacity? A spirometer is the answer. Even though the device has undergone multiple revisions since it was first invented in the 1840s, it has not deviated away from its original purpose of measuring lung capacity.

Luckily, the function of a spirometer is very intuitive to understand. One type of spirometer, called the pneumotachograph spirometer, measures the amount of air a person exhales and inhales in a second. Here is a quick run through of how that happens. The pneumotachograph spirometer typically consists of a tube, a flowmeter and a sensor. The tube is responsible for converting the information gathered by the sensor to an electric signal. The information carried by the signal is then displayed using a spirogram, a graph with flow rate (volume per second) plotted against inhaled air volume (meters cubed). Based on the characteristics of the graph, the health personnel conducting the test can then analyze the lung capacity of the subject.

Basic set-up of a spirometer test Source:Wikipedia

What are some lung conditions that a spirometer can help us diagnose? It can help us diagnose Asthma, determine if our airways have become narrowed or if our lungs are congested by mucus (pulmonary fibrosis). Another condition on the list of diagnosis is cystic fibrosis, a rare chronic condition that alters  the function of body parts such as the lung and liver by producing mucus. Our vital capacities can be compromised for different reasons eventually causing the aforementioned defects in our health. Some of the reasons are partly hereditary(such as cystic fibrosis) but most of these are caused by external factors such as smoking and exposure to polluted air. Other factors cited in early medical studies include race, gender and age.

The difference in lung capacity between white people and colored people has been a widely accepted phenomenon. For a long time the broader medical community believed that lung capacity difference was innate. As a result, “race corrections” are applied on the spirometer results in an attempt to get a more accurate value. The correction factor shrinks the benchmark for standard lung capacity of black people by 10% and Asian people by 4% to 6%.

This obviously calls into question who the system designated as the benchmark of health and normalcy – the white population. The “race correction” doesn’t acknowledge the intersections of socio-economic status, exposure to cleaner air, or sex. These are all factors that can largely influence well-being including but not limited to lung capacity.

Why does this matter? It matters because race correction could result in the deprivation of the necessary medical attention that needs to be given to colored communities. It also overlooks the intersectionality of their experiences that exist in the spheres of social class, environmental factors, and lived experiences. Thus, we need to question how race correction was installed in the first place. Was it a pure speculation? Was it devised as a result of segregative policies? Or did it have an empirical basis? That is why it is important to put the spirometer in a historical context and reevaluate the implicit biases with which it was designed.

References and Further Readings:

Braun, Lundy. “Race, ethnicity and lung function: A brief history.” Canadian journal of respiratory therapy : CJRT = Revue canadienne de la therapie respiratoire : RCTR vol. 51,4 (2015): 99-101. Link

Haynes, Jeffrey M. “Basic spirometry testing and interpretation for the primary care provider.” Canadian journal of respiratory therapy : CJRT = Revue canadienne de la therapie respiratoire : RCTR vol. 54,4 (2018): 10.29390/cjrt-2018-017. doi:10.29390/cjrt-2018-017

Braun, Lundy. Breathing Race Into the Machine: The Surprising Career of the Spirometer from Plantation to Genetics. N.p., University of Minnesota Press, 2014. Link

González, Jorge:Spirometer Demo with Freescale Microcontrollers, NXP, 2012.
A brief history of the spirometer

Prof. Klapperich et al.

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/

Nine Brains Are Better Than One: An Octopus’ Nervous System

Picture this: Earth has made its first contact with an extraterrestrial species, and, as to be expected, their anatomy and nervous system are entirely different from our own. Rather than having a single brain where all sensory information and motor controls are processed, they have nine brains. Rather than having a rigid skeleton, they have compact arrays of muscle tissue that stiffen and soften when they move, and their many limbs have an infinite number of degrees of freedom. Oh, and they can only breath underwater, too.

What was just described isn’t an alien at all, but actually the complex anatomy belonging to a common octopus, otherwise known as Octopus Vulgaris, and there is a lot we can learn from it. So how does an octopus fully control all eight of its flexible limbs? The answer lies in its partially de-centralized nervous system. When most people think of a nervous system, they think of a single brain sending out messages to move our arms and legs, then gathering information back to process everything we touch, see or hear. For an octopus, though, this process is much more complicated.

Independent Thinkers

Each arm of an octopus is able to control itself semi-independently from the central brain. An octopus has about 500 million neurons in its body, two-thirds of which are distributed amongst its limbs. This means that there are about 40 million neurons in each tentacle. That’s more than two times the number of neurons the average frog has in its entire body! An experiment conducted by German Sumbre et al. showed that even when a disconnected arm was electrically stimulated, it would still move in the same basic patterns of a tentacle being controlled naturally by an octopus. The arm even adapted its movement patterns the same way a still-connected tentacle did when the arm’s environment and initial posture were changed.

There are two columns of images. The left shows an octopus outstretching its arm over the course of 920 seconds. An arrow tracks the movement of a bend in the arm that travels along the arm until it is fully stretched out. The right column shows a single, detached octopus arm outstretching over a similar time frame. The single tentacle follows a similar movement pattern as the original octopus' arm. Another arrow also follows a similar bend that travels along the single arm as it stretches out.
An experiment shows that an electrically stimulated octopus arm (right), when detached from its central nervous system , will still move in the same basic patterns as an arm naturally controlled by an octopus (left). Image modified from G. Sumbre, Science Magazine.

Master Delegaters

So how does this partially de-centralized nervous system work? The octopus does, in fact, have a central brain located between its eyes containing about 180 million neurons. This is the part of the nervous system that determines what the octopus wants or needs, such as if it needs to search for food. These are sent as messages through groupings of neurons. Commands like “search for food” are then received by each of the tentacles, who all have their own smaller, independent brains. With these commands in mind, each tentacle gathers its own sensory and position data, processes it, and then issues its own commands on how to move by stiffening or relaxing different parts of the arm, all without consulting the central brain upstairs. As the tentacle moves, it keeps collecting and processing sensory information, and any relevant information, such as the location of food, gets sent back to the central brain to make larger decisions.

Beyond the Octopus

There is still a lot left unknown about how exactly an octopus’ nervous system functions. However, new and upcoming fields such as soft robotics and artificial intelligence are starting to look towards the opportunity for innovation that octopuses present. Learn more about how the anatomy of an octopus is being applied to science and technology here and here!

Further Reading

Sources

Sumbre, G. “Control of Octopus Arm Extension by a Peripheral Motor Program.” Science, vol. 293, no. 5536, Sept. 2001, pp. 1845–48. DOI.org (Crossref), doi:10.1126/science.1060976.

Zullo, L., Eichenstein, H., Maiole, F. et al. Motor control pathways in the nervous system of Octopus vulgaris arm. J Comp Physiol A 205, 271–279 (2019). https://doi.org/10.1007/s00359-019-01332-6

Levy, Guy, et al. “Arm Coordination in Octopus Crawling Involves Unique Motor Control Strategies.” Current Biology, vol. 25, no. 9, May 2015, pp. 1195–200. DOI.org (Crossref), doi:10.1016/j.cub.2015.02.064.

Attention Deficit Handwriting Details: The Effects of ADHD on Handwriting

Imagine you’re in college and struggling to focus during a boring lecture with a monotone professor. Now imagine that same struggle, but every little thing around you is a distraction making it difficult to focus on everyday tasks, not just the boring ones. Individuals with Attention Deficit Hyperactive Disorder (ADHD) battle this inability to focus constantly. Yet for individuals with ADHD, about 1 in 20 children (basically a lot of children), the struggle does not stop there: these individuals who struggle to focus often exhibit fine motor coordination impairments as well.

It just so happens, writing requires fine-motor coordination. Even with computers and evolving technology, writing is a necessary skill used by most individuals throughout their lifetime. It is well-known that when taking notes, you are more likely to retain information when writing notes as opposed to typing them. We have to write when we take exams (hopefully more so once the pandemic is over because I am tired of computer glitches during online exams). We write to communicate different ideas to each other, or even to communicate ideas to future self that we wish to remember.

Writing is still a necessary part of our everyday life, yet when this writing is difficult to read, its effectiveness diminishes. Imagine finally being able to focus enough during that boring class to take notes but not being able to read them. Imagine taking a timed exam but wasting this limited time to ensure the handwritten answers are legible. When compared, the handwriting of most individuals with ADHD is worse than individuals without this disorder.

There are three subtypes of ADHD: individuals are primarily hyperactive, primarily inattentive, or combined type (both hyperactive and inattentive). Individuals with ADHD who are primarily hyperactive are more likely to write faster with shorter strokes and to write more efficiently. On the other hand, individuals with ADHD who are primarily inattentive write with inconsistent letter sizes and spacing between the letters, along with diminished legibility. These individuals will exhibit this inconsistency in their writing due to a greater variability in stroke sizes.

Image of the handwriting with inconsistent letter sizes and spacing. There are 6 letters circled out of 10 letters. The letters are circled because they are illegible and it is difficult to know what the letters are supposed to be. The four letters not circled are: t, v, x, y.
Image of the handwriting with inconsistent letter sizes and spacing, along with illegibility of letters circled.
Source: https://doi.org/10.1177/0883073807309244


Individuals with combined type ADHD experience an inner battle between hyperactivity and inattentiveness, resulting in faster, more efficient writing at the expense of accuracy and legibility of their handwriting. Interestingly, these individuals on Methylphenidate, a stimulant used to treat ADHD symptoms, tend to write in the complete opposite fashion: the quality of their handwriting improves while the speed diminishes. Since the illegibility of the combined type ADHD individual’s handwriting is affected by their inattentiveness, the improved handwriting quality is due to the increased focus provided by this stimulant.

It is believed that the handwriting of primarily inattentive and combined typed individuals are the results of a form of Dysmetria. Dysmetria is a lack of coordination between movements, which would result in the irregular handwriting due to an under or overshoot of the desired writing size. These individuals are unable to process the information that they receive fast enough to generate the desired response.

While primarily hyperactive individuals tend to write faster and more efficiently, their handwriting does not necessarily differ from individuals without ADHD. On the other hand, the difference in quality of handwriting in individuals with ADHD compared to individuals without is more prominent in those with primarily inattentive or combined typed ADHD. There are many individuals out there who struggle with ADHD and are at a disadvantage because of this. Accommodations for individuals with ADHD should go beyond accommodating inattentiveness and hyperactivity since difficulties are only the root of them problem that stem into more obstacles such as reduced writing quality.

Sources

Rebecca A. Langmaid, Nicole Papadopoulos, Beth P. Johnson, James G. Phillips, Nicole J. Rinehart. Handwriting in Children With ADHD. Journal of Attention Disorders. https://doi.org/10.1177/1087054711434154. Original Research.

Marie Brossard-Racine, Michael Shevell, Laurie Snider, Stacey Ageronioti Bélanger, Marilyse Julien, Annette Majnemer. Persistent Handwriting Difficulties in Children With ADHD After Treatment With Stimulant Medication. Journal of Attention Disorders. https://doi.org/10.1177/1087054712461936. Original Research

Javier Fenollar-Cortes, Ana Gallego-Martinez, Luis J. Fuentes. The Role of Inattention and Hyperactivity/Impulsivity in the Fine Motor Coordination in Children with ADHD. Research in Developmental Disabilities. https://doi.org/10.1016/j.ridd.2017.08.003. Original Research.

“Whirlybirds, helicopters, and Maple seeds”

Photo by Annette Meyer on Pixabay – Samaras of a Japanese Maple, with the seeds inside.

As Maple trees shed their fruits, it is hard not to be captivated by the view and stare in admiration. The free fall of maple seeds is simply graceful. Commonly referred to as helicopters, samaras are the fruit of Maple trees. Inside of each fruit one can find seeds that are used by the parent plant to produce new ones. The nickname helicopter refers to the similarity that exists between its motion as it falls to the ground and that of a helicopter. Indeed, a remarkable aspect of the samaras is the behavior they display as they fall. As the fruit of the Maple seed descends to the ground, it performs a rotating motion that mimics the rotor blade of helicopters in unpowered descent, a behavior that has intrigued scientists and has been the subject of many studies. The auto-gyration motion and flight mechanics of the samaras have been observed in order to explain why and how the fruit rotates on itself as it leaves the tree.

Importance of understanding the whirling motion of Samaras:

The use of seeds to produce new plants is called seed dispersal. Since trees are unable to move, they rely on different means for the dispersal of their seeds, such as the wind, water, animal, or human beings. Samaras being carried away by the wind are an example of wind dispersal. Seed dispersal is important for the survival of species. It allows the plant to spread in its environment. By allowing the seeds to fall at great distances from the parent plant, decreases the chances of interference of the growth of new plants with the development of the parent plant and allows it to colonize new environments. Studying the flight of samaras helps understand how this process can be enhanced. However, not only does it help with seed dispersal, but it may also have applications that can help advance the field of aviation and the conception of flying devices. (Sang Joon Lee et Al. 2014)

Flight Mechanics:

There are two principal categories of seeds that have the ability to use oncoming winds to travel away from the parent plant, pappose seeds, and winged seeds. Maple seeds fall within the second one. As the name indicates, winged seeds tend to have appendages that resemble wings and act as such. While pappose seeds use draft force to maintain their flight, winged seeds rely on lift force. While they share common traits, not all winged seeds rotate. The rotation of samaras is due to the location of its center of gravity which is found near the terminal end of the wings. The wings of the seeds of the Maple tree generate a stable leading-edge vortex (LEV) which accounts for the lift force slowing down the descent. Note that an LEV is a type of airflow that is halfway between a steady and a turbulent flow. Upon being detached from the tree and is released into the air, the very shape of the wing initiates the stable vortex. The mechanism used by samaras has been identified to be similar to the LEVs of insects such as flower flies. 

Packing a punch: Does strength indicate boxing performance?

Every sport has a different “ideal” body type, which is largely dictated by the muscle groups it focuses on training. Swimmers prioritize developing the muscles in their shoulders and backs, which allows them to propel themselves through the water with their arms. On the other hand, runners prioritize the hamstrings and quads in their legs, which allows them to generate greater force when pushing off of the ground. So, what is the ideal body type for boxing? Strength is clearly important when punching an opponent, but is it even the most important factor in boxing performance? Should either upper- or lower-body strength be prioritized over the other?

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Photo by Bradley Popkin for Men’s Journal.

The overall goal in boxing is to either knock out your opponent with a single punch or land more punches in the scoring area than your opponent. One of the best ways to achieve the latter is by wearing down your opponent with powerful strikes to reduce their ability to retaliate. Therefore, hitting your opponent, and hitting them hard, is crucial within the sport of boxing. 

First, let’s take a look at upper-body strength. Boxers execute punches by using muscular force to accelerate their arms, so it is easy to assume that arm strength is the most important factor in punch performance. However, this may not be the case. One of the most common upper-body strength exercises is the bench press, and research has shown that there is no significant correlation between the maximum weight a boxer can bench press and the force they deliver in a punch. While this may be surprising, the relationship between upper-body strength and punching actually comes down to speed rather than force. Based on data from both professional and elite amateur boxers, the maximum speed at which a boxer can bench press is indicative of improved punch performance. More specifically, professional boxers showed a strong relationship between the maximum velocity of their bench press and maximum punch velocity of their rear, or dominant, arm. 

If upper-body strength does not indicate punch force, then does lower-body strength? A study of amateur boxers found a positive correlation between maximum punch force and lower-body strength measures, including countermovement jump (see video below) and isometric midthigh pull. In contrast to the upper-body exercises, the maximum force generated in lower-body exercises is more important for increasing maximum punch force than the speed at which the exercise is completed.

Plot of countermovement jump force in Newtons versus punch force in Newtons. The data has a correlation of 0.683 and a p-value of less than 0.001. Plot of isometric midthigh pull force in Newtons versus punch force in Newtons. The data has a correlation of 0.680 and a p-value of less than 0.001.
Plots showing a strong, positive correlation between punch force and the lower-body strength exercises, countermovement jump, CMJ, (left) and isometric midthigh pull, IMTP, (right). Adapted from “Relationships Between Punch Impact Force and Upper- and Lower-Body Muscular Strength and Power in Highly Trained Amateur Boxers” by Emily C. Dunn, et al.
Video of how to execute the countermovement jump test by Training & Testing.
Kinetic Chain: Force is generated from the floor and transferred from foot to fist. Leg force, hip and torso rotation are key. Arrows show movement of force from foot, through the body, to fist.
Graphic of Kinetic Chain in a boxer from Boxing News.

When executing a punch, a boxer gains forward momentum by pushing off of the ground with their legs. Through a kinetic chain, force moves through a boxer’s body from the floor to the foot, then through the legs and torso, and finally, to the arm and hand. This phenomenon is what explains why lower-body force is crucial to a boxer’s maximum punch force. 

So, what does this all mean? How should boxers train in order to improve their punching performance? Most importantly, boxers should focus on their lower-body strength, as it is the most direct indicator of maximum punch force. While lower-body strength should be a primary training goal, exercising muscles within the upper-body, specifically while focusing on the speed of the movements, will also likely improve overall punch performance. We now know that developing strength is clearly beneficial in improving a boxer’s punch; however, brute force alone does not win a fight. Boxers should develop correct boxing technique through methods such as those suggested in this article, which will allow them to implement their new strength in the most effective manner.    

For additional information on the impact of strength on athletic performance click here and here.