Category Archives: 2021 Spring

A striking difference: How combat sports affect bone density

We have all seen it before, whether it is in Hollywood depictions, or watching competitors in the Ultimate Fighting Championship, there is always a sense of awe when watching humans strike and break surfaces with astounding force. Whether it is breaking bricks, a baseball bat or their opponents, the physiological phenomena that allows these athletes to perform such feats results from years of dedicated practice and study. By continuously placing their bodies under immense stresses and impacts, the actual composition and density of the athlete’s bones adapt to provide increased strength and durability. In practice this is done by repetitively striking a hard surface, such as a wooden planks, or a punching bad, with increasing force for a prolonged period of time. Although the practice of bone hardening has roots as ancient as the martial arts themselves, the scientific study of the phenomena has only occurred in the past few decades. So how do these athletes develop exceptionally strong bones?

Taekwon-Do Grandmaster Rhee Ki Ha breaking a solid concrete block with a punch
Courtesy of: Oakville Today

One of the most important aspects of bone hardening is increasing bone mineral density by continuously loading and unloading bones, as well as contracting the surrounding muscles consistently and for a prolonged period of time. It is particularly interesting to study how the typical bone mass gain that occurs during the adolescents is affected by sports that are high-impact and place great stress on one’s bones. Studies show that adolescents who participate in combat martial arts had significantly higher bone material density in their hands, arms, and legs than comparable adolescents who did not. Since the development of bone mass and structure is most significant during adolescence, the potential to increase the bone mineral density is greatest during this time.

However, as with most things there is a Ying to every Yang in the world of increasing the bone mineral density. The difficult and complex movements required to “harden” one’s bones make the athlete more susceptible to sustain a severe injury in training or competition. As it is typical to experience pain throughout the process of developing bone material density, the development and progression or micro-fractures and injuries can be ignored or mistakenly thought of as typical training pains. This results in there being a fine line between strengthening bone and causing injury to oneself.

Anderson Silva after suffering a gruesome leg injury.
Courtesy of: Lanna MMA

There are other benefits to increasing one’s bone mineral density outside the realm of combat sports. By engaging in high-impact activities during one’s adolescence into adulthood, one can decrease the risk of developing osteoporosis by having increased their bone mineral density. This further supports the reasoning to stay active and healthy to ensure a longer and healthier life.

Whether it is breaking boards to entertain sports, or fighting on the world’s premier combat stage, having strong and healthy bones is an essential aspect of being an athlete in high-impact combat sports. This is achieved through generating increased bone mineral density and is the result from years of dedicated practice and time. All in all, the difference it makes is rather striking.

Curing Cancer: a Giant Problem with a Nano- Solution

What if scientists could treat cancer without the extreme side effects of chemotherapy? Could scientists create a tiny way to cure a giant health crisis? Nanoparticle drug delivery systems could be the answer to our prayers.

Image of nanoparticles (small red circles) in a rat brain that has a tumor (green string-like material)
Nano-particles (red) in rat brain with tumor (green). Image taken from Washington Post.

Almost everyone knows a friend or family member who has had cancer and suffered through chemotherapy to recover. Currently, chemotherapy for treating cancer causes extreme side effects. For years, scientists have been researching methods to mitigate the adverse effects of treating cancers with the hope of one day creating a cure.

Delivering therapeutic drugs via nanoparticles (NP) are currently used in some FDA approved cancer treatments. Nanoparticles are extremely small–on the scale of the cells in our body. This is even smaller than a strand of hair on your head. Their size makes them ideal candidates for transporting drugs to tumors without damaging healthy tissue . In theory, NPs could hold drugs inside them, travel through our blood (ignoring healthy cells) and deposit the drugs right into the tumor.  However, there is a lot of research and improvements to be made before NPs can live up to their full potential. One of the largest unknowns in the study of NPs is their mechanical properties and how these properties interact with the body.

How does our body automatically know how to function without us telling it? Our body has biological sensors which govern our bodily functions in response to the world around us. For example, to prevent unwanted particles that may enter our bloodstream from getting to our brain or lungs, we have filters (like the spleen) that prevent them from passing through. Blood cells are soft, so they can squeeze through biological filters that dirt or stiffer blood cells could not pass through. To reach cancer cells, NPs must pass through these filters.

Stiffness is a mechanical property that measures how much an object moves when it is pushed on. Greater stiffness corresponds to larger applied forces.  For example, a piece of wood is stiff but a pillow is soft because it is easier to dent a pillow than to dent wood. To deliver NPs to the tumor through blood, the NPs have to get through the biological filters as they flow through the blood.

Image of blood cells squeezing through cell walls. Imagine a trying to push a pillow through a narrow opening. The blood cells (pillow) deform to pass through.
Blood cells squeeze through spleen walls, which acts as a filter for foreign objects in the bloodstream. Image taken from Zhang, et. al.

To allow passage through these filters, the NP’s mechanical properties must mimic blood. Scientists have performed tests on NPs with various stiffnesses and found that the soft NPs (like blood) were more likely to be allowed through the biological filters, whereas the stiffer (harder) NPs were blocked. If the NPs are blocked, they cannot travel through the blood streams to reach the tumor and are thus ineffective in treating the diseased cells.

The NPs (represented by the red circles) travel further into the tumor (blue and irregular shaped) than the stiff NPs do, allowing for more effective drug delivery. Image adapted from Hui, et. al.

Furthermore, soft NPs have been shown to penetrate deeper into tumor cells. The soft NPs can deform, allowing them to maneuver through the gaps between tumor cells (intercellular spaces). The deeper the NPs travel into the tumor, the more effective the drug treatment will be in attacking cancerous cells.

Nanoparticles hold the potential to revolutionize cancer treatment and prevention. By optimizing the mechanical properties of NPs, they could automatically release drugs in the presence of the tumors in response to their biological environment without delivering drugs to other cells. Further development of nanoparticle drug delivery methods may one day lead to a cure that will save loved ones’ lives. 

Staying airborne: How bird wings are built for aerodynamic and efficient flight

Flight is a concept that has, until relatively recently in history, eluded humanity. However, birds have been successfully flying for approximately 130 million years, proving themselves to be a physical marvel of the natural world. And while our means of flight have historically been crude in design and performance, nature provides an elegant, efficient solution to get creatures off of the ground. Rüppell’s griffon vultures have been recorded flying as high as 37,000 ft, while some species of shorebirds have been recorded flying as far as from Alaska to New Zealand over eight days without stopping. But how exactly do birds seem to effortlessly overcome gravity so effectively? And perhaps more importantly, how might we apply these answers to improve manmade aircraft?

Morphology

Obviously, the exact aerodynamics and physical characteristics of birds will vary from species to species, but there are still underlying similarities that enable birds to fly. A bird’s wing consists of a shoulder, elbow, and wrist joint which establish the wing’s basic shape and allow a range of motion. Covering the wing are structures called primary, secondary, and coverts, which are all groups of feathers that provide lift and stabilize flight. Feathers consist of flexible fibers attached to a center shaft, called the rachis. Overtime, the rachis will become damaged from fatigue and large instances of stress. As a result, birds will molt and regrow their feathers on a regular basis. 

A diagram of the structure of a bird wing
Picture by marcosbseguren on Wikimedia Commons

Generally, a bird’s body will be adapted to either gliding flight, in which the wings flap very infrequently, or active flight, in which the wings flap nearly constantly. For gliding birds, such as the ocean dwelling albatross, the wings will extend far away from the body, and prioritize both wing and feather surface area over flexibility. Additionally, these wings will have a thick leading edge, and will be much straighter. However for fast, agile birds, such as falcons, the opposite is true. Consequently, agility is sacrificed for energy efficiency. In both cases, the rachis will change shape and rigidity, becoming larger and stiffer for gliding flight and smaller and more flexible for agile flight. 

Aerodynamics

One of the most unique aerodynamic characteristics of birds is that nearly all of their lift and thrust is exclusively generated by their wings, as opposed to aircraft that implement both wings and engines. This provides, among other things, near instantaneous control of both flight direction and speed. In other words, this gives birds an advantage when hunting, escaping from predators, and maneuvering through a landscape. 

To aid in the generation of thrust and lift during flight, birds will change their wing shape through a process called active morphing. During flight, the wing will be bent inwards and twisted up during the upstroke, and extended and straightened during the downstroke. As a result, this minimizes drag while maximizing thrust and, consequently, energy efficiency. This can aid in anything from traveling farther distances to hunting prey.

An osprey folding its wings in while catching a fish
Photo by Paul VanDerWerf on Wikimedia Commons

Applications

Initially, these principles may seem difficult to realistically utilize in aircraft. After all, we are limited by the materials available and the size that aircraft must reach. However, small steps could be taken to improve the energy efficiency and responsiveness of aircraft. For example, wing shape, material flexibility, surface finish, and moving joints could all be explored. In fact, research at MIT is currently being conducted on flexible wings made of scale-like modular structures. If experiments like this are successful, it could show that aircraft designs inspired by nature may be the future of the world of aeronautics.

Innovative plant: How does the dandelion drift its seeds?

How far do you think a dandelion seed can drift from its base plant?

The Common Dandelion (Taraxacum officinale) primarily relies on wind flow to scatter its seeds. The dandelion seed has a fluffy structure that enables it to hold the most prolonged wind-based dispersal record. Commonly the seeds land 2 meters away from their mother plant. Still, in windy, dry weather favored by the dandelion, the seeds can fly up to 30 kilometers and even far (150 kilometers in some conditions). The vital point in this extraordinary adventure of the dandelion is flying with a constant velocity and having a short descent time, which means it should stay stable in the air for a relatively long time.

A study tried to illuminate the mystery behind the dandelion seeds’ ability to stay aloft in the air. Researchers attempted to mimic the dandelion flight using similarly structured silicon disks in a wind tunnel that simulated the airflow around the pappus. Pappus, the flying seed of the dandelion, consists of radially oriented filaments, each interacting with other adjacent ones, resulting in a reduction in the airflow. They compared the flight of natural seeds collected from one plant with several silicon disks with different porosities.

Dandelion seeds and silicon disks in wind tunnel
Wind tunnel experiment, modified from Cathal Cummins & et al. 2018
vortex ring above pappus
Pappus & separated vortex ring, modified from Madeleine Seale & et al. 2019

Their results showed that when pappus separates into the air,  it forms an air bubble detached from its surface above it. This air bubble, known as a vortex, is unique to the dandelion seed. When the pappus is released in the air, it takes some time to reach a steady point, in which the vortex becomes symmetrical. An important feature affecting this symmetry is the porosity of the pappus, defined by the number of filaments and their dimension in each pappus— generally, the more the porosity, the steadier the flight. The best porosity for a stable vortex ring is greater than 84.97%, and the vortex ring begins to separate as the porosity falls below 77.42%. The experiment also indicated that the vortex is axisymmetric in low velocities, but it begins to lose its symmetry as the Reynolds increases.

Pappus with water drops on it
Pappus in moisture, photo by enfantnocta

This phenomenal plant has evolved techniques for mass germination, even in the absence of wind! Pappus’s hairy structure enables it to attach to an animal’s skin and soil particles, assuring the dandelion to have enough seed dispersion during the flowering season. More interestingly, the dandelion is known to have an informed dispersal in response to environmental fluctuations. When the plant experiences root herbivory, it intensifies the seed dispersal. The flight distance may vary from meters to kilometers to assure good germination in the absence of threatening conditions. Imagine a rainy day; the moist weather condition makes the pappus’ bristles come close together, reducing the possibility of separating from the plant. The moisture makes the current spot a suitable choice to stay. So even the detached seeds prefer to fall close to their base plant. 

It worth mentioning that this remarkable plant also inspired areas of science. In their study of Mars exploration, researchers presented a primary model of a dandelion-inspired rover. Considering the harsh environmental condition on Mars, other excavators find the wind flow as an obstacle that results in damaged parts and incomplete missions. In contrast, the new dandelion-shaped rovers use the wind flow as an accelerating point to explore locations on Mars that other robots couldn’t access.

Dandelion-shaped Mars rovers
Dandelion-shaped rovers ,modified from Michelle Sherman & et al. 2020

COVID-19 Vaccines: Helping You Combat One Spike Protein at a Time

COVID-19 vaccinations reduce the risk of infection and have the potential to ensure life returns to normal. Everywhere you turn someone is talking about which vaccine they have received: Pfizer, Moderna, Janssen, AstraZeneca… But what is the difference? How do the different types of COVID-19 vaccinations protect us? And does it matter which vaccine you receive?

COVID-19 vaccine comparison chart illustrating Pfizer and Moderna are RNA vaccines and Janssen and AstraZeneca are viral vector vaccines.
COVID-19 Vaccine Comparison. Photo by BBC News on Wikimedia Commons.

To start off, it is important to understand how coronavirus enters our cells: spike protein. Spike proteins are visually the spikes protruding from the spherical coronavirus and what bind to our cells to transmit the RNA virus (a code for COVID-19), enveloped inside the coronavirus, to our cell’s cytoplasm (the area inside a cell excluding the nucleus). The spike proteins fuse to our cell membrane (the outside of the cell) and are the target for researchers and vaccine developers.

Image of SARS-CoV-2 with red spike protein protruding from the spherical coronavirus.
SARS-CoV-2 (red spike proteins). Photo by Alissa Eckert, MS; Dan Higgins, MAM on Wikimedia Commons.

There are various types of vaccines that stop the spike proteins from fusing to our cell membrane, however, the two main types of vaccines used in the United States are mRNA vaccines and viral vector vaccines. Pfizer and Moderna are mRNA vaccines, while Janssen and AstraZeneca are viral vector vaccines. Both types of vaccines have the same goal: create antibodies to bind to spike proteins to block the spikes from attaching to and infecting healthy cells.  

The Pfizer and Moderna vaccines use messenger RNA technology to deliver genetic code to our cells to instruct how to make the SARS-CoV-2 spike protein. mRNA is very fragile thus it is encapsulated in something called lipid nanoparticles (LNPs) in order to reach the cell. LNPs increase translatability and stability to ensure mRNA’s delivery to the cell. When the mRNA vaccine is delivered to our cell it breaks free of the LNPs. 

Diagram of mRNA with LNPs.
mRNA and LNPs. Photo by Andreas M. Reichmuth, Matthias A. Oberli, Ana Jaklenec, Robert Langer, and Daniel Blankschtein, “mRNA vaccine delivery using lipid nanoparticles,” NCBI, PMID: 27075952.

After the mRNA is released from the LNPs, the cell begins making spike proteins. The spike proteins then trigger an immune response to begin producing antibodies. Ultimately, the antibodies latch onto the coronavirus’s spikes making the virus unable to latch onto other cells.

The Janssen and AstraZeneca vaccines incorporate viral vector vaccine technology. The viral vector is a genetic code that creates an instruction manual for human cells to produce the SARS-CoV-2 spike protein transported into the body by a harmless virus called an adenovirus. The adenovirus acts as the delivery system for this important DNA code and helps the body to trigger an immune response. 

The vector vaccine attaches onto proteins on the cell’s surface and the adenovirus is pulled into the cell. The main difference between the mRNA vaccine and the viral vector vaccine is that the DNA in the adenovirus of the viral vector vaccine must travel into the cell’s nucleus in order to be transcribed whereas the mRNA vaccine remains in the cytoplasm throughout the process. From there viral vector vaccine acts very similar to mRNA vaccines—once the DNA is transcribed into mRNA, the mRNA leaves the nucleus and the cell begins assembling spike proteins.

Further research is being completed to determine exactly how COVID-19 vaccines enter the cell. However, endocytosis is thought to be the answer based on previous vaccine knowledge. Endocytosis is a cellular process in which something is brought into the cell by engulfing it in a vesicle (small fluid bubble). In mRNA vaccines, the LNPs take advantage of the natural process of endocytosis. The LNPs are engulfed in a bubble, triggering a reaction that allows the nanoparticle to enter the cell and eventually release the mRNA.

Image depicting endocytosis in COVID-19 vaccines.
Endocytosis in COVID-19 vaccines. Photo by Oleg O. Glebov, “Understanding SARS‐CoV‐2 endocytosis for COVID‐19 drug repurposing,” NCBI, PMID: 32428379.

Overall, both the mRNA and viral vector vaccinations are great options each with their own unique design to produce antibodies and stop coronavirus from latching onto our cells.

Doses of the Pfizer COVID-19 vaccine.
Doses of the COVID-19 vaccine are seen at Walter Reed National Military Medical Center, Bethesda, Md., Dec. 14, 2020. Photo by Lisa Ferdinando on Wikimedia Commons.

Ditching the shoes: Minimalist trend or natural advantage?

The discussion of returning to minimalist ways, namely walking or running barefoot, is a question that rises in many circles, from new parents to elite runners. For example, parents are told to let children learn to walk barefoot, as studies have shown early use of footwear can lead to feet deformities and can alter natural gait, which is especially important when learning to walk. Likewise, many avid and elite runners have shown interest in barefoot running (or minimalist running shoes), as some are convinced that the forefront strike (FFS or also known as NRFS – non rear foot strike), more commonly used during barefoot running, lowers the loading rate on the foot and minimizes injuries from the repeated stress that occurs in the feet during running. 

Diagram illustrating four phases of foot contact with the ground for forefront strike and rear foot strike patterns
Forefront strike (top) and rear foot strike (bottom). Modified from Daniel E. Lieberman et al., Springer Nature 2010

In general, walking or running barefoot yields more frequent steps, a smaller stride length and a slower velocity (most noticeable while running). Barefoot running is thought to reduce some of the injuries many runners are prone to, such as shin splints, stress fractures or plantar fasciitis. Additionally, the stiff fit of modern shoes limits the width and spreading of feet in the natural walking or running motion. However, barefoot running also comes with a cost, with injuries in the achilles region more prevalent. 

A study in the Gait & Posture journal examined foot motion in children and found modern commercial footwear does have a large impact on gait, especially in regards to range of motions of different muscles and joints in the foot, likely due to the stiffness of shoes. More flexible shoes, similar to minimalist running shoes, were found to have a smaller impact on foot motion in reference to bare feet, but still had a significant difference in regards to the added support in the arch area. 

The common belief that barefoot motion lowers the impact on the body has been questioned by a recent research study from Southern Methodist University. The findings indicated that while running barefoot with a forefront strike, the feet strike the ground at a more pronounced angle which generates a longer contact time, thus decreasing the loading rate and allowing the muscles in the back of the feet and legs (especially the Achilles) to absorb some of the loading stress. When humans adapted to running in shoes, especially shoes with thick cushioning, the landing switched to a rear foot strike that allows the heel cushioning to absorb some of the loading stress, resulting in a fairly equal loading rate for both cases. The heel cushioning, with a flatter angle of contact, also allows for decreased impact time with the ground surface, which is why higher running speeds are achieved with footwear. 

barefoot person walking outdoors during the day
Photo by ‏🌸🙌 في عین الله on Unsplash

While the advice to encourage barefoot walking in young children certainly makes sense as they continue to grow and learn to control their bodies, the choice to use shoes or go barefoot for older children and adults remains an individual preference. There is no significant difference in the stresses the body experiences, but the footwear choice does influence the likelihood of certain, which is important for runners with past injuries to consider.

For more information, check out this extensive technical review of studies on barefoot vs. footwear mechanics or this video from Exercising Health comparing running shoes with minimalistic barefoot shoes.

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.