Tag: injury

Falling for You: How to Reduce Fall Risks?

The majority of people know what a fall is and, in fact, many people have unfortunately experienced one or a few. But what would be a good definition for what a fall is? Simply put, a fall is something that happens when you lose your balance and cannot recover. Falls have the potential to ruin anyone’s day. For some, however, the risk is far more severe than that as falls are one of the leading factors in injury and death among the elderly population. This will continue to be a problem as the number of elderly people in the United States is expected to increase dramatically over the next fifty years.

Changes in bone mass for women and men, decreasing as a function of their age.
Graph of bone mass for men and women as they age (Wikimedia Commons)

There are a few reasons that make the elderly a more at-risk population. A major reason is the reduced reaction time that occurs as people age. Another reason is due to the reduction in bone density as people age. Additionally, some elderly people may suffer from disorders such as Parkinson’s Disease or other neurocognitive issues that cause diminished motor control, leading to more instability and a higher chance of falling. Parkinson’s Disease or (PD) is a nervous system disorder that affects both cognitive and motor functions. In PD patients, increased falling is often linked with cognitive decline according to this paper by Fasano, et al. While there is not much research on PD and falls, one benefit is that fall rate could be used as an early predictor of PD in individuals as injuries stemming from falls have the potential to be higher than normal for people even ten years before the onset of Parkinson’s Disease.

Chart with effects of Parkinson's Disease, split between motor and non-motor impairments
Effects of Parkinson’s Disease on the Body (Wikimedia Commons)

The best way to reduce fall risks is to prevent falls. A study by Hahn and Chou attempted to predict fall risk in individuals using a system similar to machine learning called a neural network to evaluate a group of subjects and place them into different groups based on level of fall risk. By categorizing the fall risk of individuals, one can know if they are likely to suffer from falls and can take appropriate measures to prevent them. The subjects of this study were split into two groups classified as healthy, with no preexisting conditions, and fallers, with self-reported issues. Each subject participated in three walking trials and different measurements were recorded including gait measurements, center of mass movement, and muscle response. The first distinction made was to classify each participant as either healthy or as a faller. After finding a baseline for healthy subjects, the participants were further classified by level of fall risk from very low risk to very high risk. This neural network had about ninety percent accuracy in separating healthy patients from ‘fallers’ and was successful in sorting by risk level.

Experimental setup of a trip recovery study
Illustration of Testing Setup for Recovering from Trips. Taken from Bieryla et al. (2007).

Another way to reduce the risk of falls is to reduce the severity of them. This study by Bieryla, et al. contained twelve healthy subjects and was designed to test the application of motor learning to reduce fall risk. It was conducted as a pretest/posttest study where the participants were divided into two groups: a control group and an experimental group. A first trial was performed where a trip was simulated using obstacles placed on a treadmill as shown in the figure. The participants were in a harness and were told to attempt to recover from the trip incident. The dummy obstacles were images that appeared to be obstacles and were used to ensure the validity of the results. After this first trial, the control group spent time walking on the treadmill while the experimental group underwent trip recovery training. The recovery training consisted of practicing stepping over an obstacle that resembled the motion of regaining balance after tripping. Then, a second trial was performed to see the effect of the recovery training. Overall, the results were positive and they showed beneficial effects of the trip recovery training.

Do Shoes Alter the Form and Function of Your Feet?

The underside of an individuals feet with the right foot barefoot and the left wearing a clear-soled shoe. It contrasts the shape of the foot when "free" and when constrained by a shoe. From https://jakewilliamschiro.com/2019/08/30/shoes-shaped-like-your-foot-or-feet-shaped-like-your-shoes/

Do Shoes Alter the Form and Function of Your Feet?

Have you ever worn a favorite pair of shoes much longer than you should’ve, only to experience an injury as a result? What if I told you that a large portion of modern footwear might increase your injury risk, even when brand new?

Our ancestors lived barefoot, yet most people wear shoes today. From an evolutionary standpoint, we did not evolve to be shod creatures. The effect of shoes on the growth and development of our feet is largely unknown. However, there are still some cultures that live barefoot that can be studied and used as a comparison. We must work to understand footwear’s influence on natural foot shape and function so that we might determine how footwear can be improved to foster healthy foot growth and function.

Living Barefoot

A barefoot population in Kenya was studied and compared to their shod counterparts. Controlling for other factors, the study found that the barefoot group was less likely to experience an injury to their lower limbs, was taller and had a lower BMI, and had greater foot strength and flexibility. The habitually shod group was found to have structurally different feet, particularly regarding their foot arch ratio.

Similarly, a barefoot population in India was studied and compared with their shod counterparts, along with another shod group from Belgium. The study found that the barefoot group had wider feet. As shown in Figure 1, it was found that more intrusive footwear resulted in more extreme foot pressure distributions. Therefore, the shod populations were found to have structurally, and thus functionally, altered feet. Interestingly, the results of the shod Indian subjects, who wore simpler shoes than the Western subjects, were found to be in a middle ground between the barefoot and Western groups.

Figure 1. Peak pressures for barefoot Indians, shod Indians, and Western groups, respectively (averaged over all trials). Pressure is expressed in a percentage relative to the average of the foot. Pressure distribution is most extreme in the western group and least extreme in the barefoot Indian group.
Figure 1. Peak pressures for barefoot Indians, shod Indians, and Western groups, respectively (averaged over all trials). Pressure is expressed in a percentage relative to the average of the foot.

These two studies demonstrate that a difference exists between individuals that wear shoes daily and those that do not. This difference manifests itself as a structural difference that can alter lower limb function and increase injury risk.

Mimicking Barefoot: Shoe Concepts

Shoes are necessary for many things, but these studies suggest that footwear that fails to respect natural foot shape and function affects the structure and biomechanical behavior of the foot. Therefore, multiple ideas for shoe concepts that attempt to mimic some aspect of being barefoot have been proposed. These concepts, which include Adidas “Feet You Wear,” Nike Free, and MBP Masai Barefoot Technology, attempt to mimic either the shape, kinematics, or feeling of being barefoot. Studies have found that all three of these techniques reduce injury or strengthen foot and ankle muscles to some degree.

Figure 2. The typical shape of a habitually unshod foot (top); Footprint of a teenager before (B) and after (A) six weeks of conventional shoe wear. The splay and width decrease of the foot after six weeks of wearing a shoe is significant.
Figure 2. The typical shape of a habitually unshod foot (top); Footprint of a teenager before (B) and after (A) six weeks of conventional shoe wear.

Footwear conditions significantly impact foot structure and function. First, understanding the natural form and function of the foot is necessary to inform future shoe developments. The impact of our current footwear can then be determined, enabling the development of better shoes. Improving our footwear can lead to better foot health, improved lower limb health, and decreased injury rates. Therefore, we must continue to work to understand the effect of footwear on foot health and development.

Do your Foot Arches make you more or less likely to be injured?

Picture showing what a flat foot, normal foot, and high arched foot and what the footprint looks like

Have you ever wondered how your arch type may affect your everyday life especially in physical activities such as running or playing sports? Well it turns out that without taking precautions, a higher arch or a flat foot may cause you to more likely be injured! People have all different types of arches, and each foot can be affected differently based on the type of arch.

Different arch types and properties of each (ShutterStock)

Arches are important because they provide impact absorption and stability in the push-off phase in walking or running. Usually there are patterns of types of injuries that may occur based on the type of arch a person has. The injuries may be similar for different types of activities, but the location of the injury may vary. Running is one of the most popular activities for Americans to do and it is estimated that about “one-half to two-thirds of runners will sustain an injury”. This is a very high number so it is important to understand some of the biomechanics behind why this may be happening.

An image showing the gait cycle of the leg swinging forward and stepping.
A man walking, showing the stages of the gait cycle (Taken by Kirker et al. 2016)

The dynamics of the foot cannot be studied without talking about the biomechanics of the leg as well. The main period that is studied to understand the biomechanics of the foot is called the gait cycle, which is the period of time for two steps to happen where the foot makes contact with a surface and the limb swings forward as shown in the image. When moving faster or running, the foot pronates (weight more on the inside of the foot) and supinates (weight more on the inside of the foot) differently and the pressure shifts medially.

Arch types affect where the pressure shifts on the foot. In the article by Rodgers, the collected research shows that high arches are more rigid, and there tends to be more pressure concentrated beneath the heel and forefoot. Low arches are usually associated with flexibility, where the pressure is spread out more including the area of the midfoot. The most common methods for determining the pressures in the feet are by having subjects stand on force plates and this was the method used by Rodgers.

An image showing the process of determining what arch type people have and choosing a shoe based on this arch type.

Various studies came to a few conclusions about injuries based on arch type. The types of injuries in people with high arches tend to be bone or lateral ankle injuries based on the biomechanics that most of the pressure on the foot is in the front and back of the foot mainly when running or walking. The injuries that usually occur to people with low arches tend to be related to soft tissues and knee pain because of how the pressure is more evenly distributed through the foot, especially in the middle of the foot. While many of the results conclude that there is a correlation with injury type and arch type, the main conclusion was that people with high or low arches generally have a higher risk of injury than people with normal arches. The most common injuries seen are overuse injuries and pain to the knee. Luckily, there is technology within shoes that is specifically designed to mimic pressures on a regular foot. Choosing the right shoe based on arch type is important to preventing injuries when doing strenuous activities!

Guide to finding the right shoe based on arch type (taken from Thomas 2019)

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.

Top Gun Trauma: the Effects of Ejecting From a Fighter Jet on the Spine

The need for speed places fighter pilots in electrifying yet dangerous situations. When things go wrong during flight, pilots must consider ejecting, a terrifying choice. Ejection is a last resort due to the large compressive forces and the high wind speeds that can cause many different serious injuries, including spinal injuries. Approximately 20-30% of people who survive ejection endure spinal fractures. Understanding the dangers of flight that servicemembers face increases awareness of the military lifestyle within the civilian population and is critical in finding solutions to lessen the severity of injury.

During ejection, the rocket-propelled ejection seat thrusts the pilot upward out of the aircraft. The pilot experiences around 18 g-forces (18 times your bodyweight)! The acceleration from the thrust of the seat, peaking at 140 to 160 m/sec2, compresses the spine vertically, loading the thoracic and lumbar spinal regions seen below. 

Anatomy of the spine
Photo from Patel et al., Pediatric Practice: Sports Medicine, 2009

The large rate of loading causes spinal fractures that can be either unstable and require surgery due to the movement of vertebrae or stable and treated with a brace. Thoracolumbar (lower back) fractures can be modeled using a variety of methods. One study applied axial loads of 5.2 kN (1,169 lbs) on two different spines from cadavers with a peak acceleration of around 20 g to simulate ejection. The resulting fractures for both specimens were on the L1 vertebrae, and one fracture was stable while the other was unstable. Another study constructed a drop tower and subjected 23 lumbar spines (T12-L5) to axial forces between 2.1 (472 lbs) and 7.3 kN (1,641 lbs) and accelerations between 8 and 23 g. Data analysis produced injury probability curves, which showed a 95% chance of injury with an acceleration of 20 g. The larger loads and accelerations also correlated with lower-level injuries (L4 and L5 vertebrae). 

One study modeled ejection using the finite element method, which can mathematically model the spine’s response to forces, and imaging software to investigate the effect of posture on spine injury severity. 

Software model of thoracolumbar spines in normal and relaxed postures.
Modified from Du et al., Int. J. Numer. Meth. Biomed. Engng., 2014

Thoracolumbar spines in normal and relaxed postures shown in the image above were simulated with an acceleration peak of 15 g for 0.2 sec. The relaxed posture correlates with increased stress on the endplate (the region between a vertebrae and an intervertebral disc), as the relaxed posture increases anterior flexion (forward bending) of the spine that is then increased by compression. Sitting straight up could help decrease the chance of injury during ejection. 

Ejection is a harsh reality that some pilots face. But as dangerous as ejecting is, ejection seats have a 92% survival rate, and sustaining a spinal injury is worth keeping your life. One B-1 Bomber crew member who ejected over the Indian Ocean said, “I lost a full inch in height.” It’s the price service members pay to dominate the skies and fly faster than the speed of sound. 

For more information, check out this retrospective study of French forces and this analysis of accident reports from the Royal Air Force

Work Smarter Not Harder!

We have all likely heard the saying, “Work smarter not harder.” While this is generally referenced in an academic setting, it is also very applicable in athletics! One of the benefits to being a runner is that it’s a sport people can participate in at any age and nearly anywhere. Unfortunately, however, anywhere from 65-80% of runners get injured in a given year. A large portion of these injuries are related to overuse.

Recovery

It’s a common misconception amongst runners that the harder you push during your runs, the faster you will be on race day. As a result, the majority or runners overdo their “easy” days. This leaves their legs fatigued and tired going into workouts and races. The majority of fitness is gained during a “workout” day, so overdoing easy days reduces your ability to push hard on workout days. To truly maximize their potential, an athlete must focus on their recovery. Recovery is a broad term that includes a variety of factors such as sleep quality, nutrition, and post run stretching and rehab exercises. Monitoring your heart rate is one way to manage your recovery, reduce overtraining, and limit bone stress injuries. 

Managing Heart Rate

Photograph of a smartwatch reading heart rate
Photo by Brooke Trossen

Heart rate monitors are used by runners to train smarter and ultimately race faster. Resting heart rate and heart rate recovery measurements are indications of how an athlete’s body is responding to stress and exercise long term. Heart rate measurements can be used to guide what the pace of a run should be. Heart rate measurements are commonly separated into five “zones.” On different days of the week and stages in a training cycle, a run should fall into the different zones. It may be beneficial for an athlete to also have a general idea of what their heart rate is at a given running pace. If their heart rate is more than 7 beats per minute above the usual rate, it may be a sign that the athlete has not fully recovered from their last training session and that they should continue with easy days until having another intense session. This is also important for runners since the weather conditions can greatly affect the difficulty of a run. Rather than having a goal pace for a given day, it is better to have a goal range of heart rates to make sure the run is best serving the athletes body. This will enable an athlete to get the appropriate effort in whether it is 70° and sunny or 30° with 20 mph winds.

Monitoring heart rate after exercise can also accurately indicate whether or not an athlete is fully recovered. It is important to note that your heart rate fluctuates, so it is more valuable to observe general trends than it is to overanalyze specific data points. A morning heart rate 5 beats per minute above your usual heart rate may be indicative that your body needs more rest or that you are getting sick. The image below shows a chart with ranges of resting heart rates depending on gender and age.

Chart of healthy resting heart rates for men and women with varying ages.
Photo by Jeremy on Agelessinvesting.com

Minimizing Bone Stress Injuries

Photograph of a stress reaction in the femur of a female runner
Photo by Brooke Trossen

Building a training plan with runs in a variety of zones will help limit overtraining and make the development of overuse injuries less likely. A bone stress injury (BSI) is defined as the inability of a bone to withstand repetitive loading. There are varying degrees of bone stress injuries from stress reactions to complete bone fracture. When performing repetitive motions such as running, micro-cracks form in your bone. These micro-cracks are actually healthy because loading your bones makes them stronger. In the process of remodeling, the micro-cracks are healed. Generally, additional remodeling units can be recruited in response to increase loads. The increase in remodeling units present, decreases the amount of bone mass. This results in a decrease in the ability for the bone to absorb energy and an increase in the number of cracks formed. When insufficient time is given for remodeling, the micro-cracks will begin to accumulate and stress reactions and fractures will form. A stress reaction in the right femur of a female runner is shown in the image above. The white highlights represent inflammation in the bone. 

Although overuse injuries are very common in runners, research shows that the use of heart rate monitors can help regulate recovery and positively influence training plans to limit overtraining. 

Ankle Sprains: An Epidemic in the World of Athletics

Have you ever been out running on a gorgeous fall day, only to have the run cut short by a painful misstep on a tree root covered by leaves? I have, and let me tell you – it’s awful! And even if you aren’t a runner, according to the Sports Medicine Research Manual, ankle sprains are a common, if not the most common, injury for sports involving lower body movements. Now, the solution to preventing this painful and annoying injury could be as simple as avoiding tree roots and uneven ground, but the real problem behind ankle sprains deals with the anatomy of the ankle.

The ankle is made up of many ligaments, bones, and muscles. However, when sprained, it is the ligaments that are mainly affected. Connecting bone to bone, ligaments are used to support and stabilize joints to prevent overextensions and other injuries. The weaker a ligament is, the easier it is to injure. There are three main lateral (outer) ligaments supporting the ankle joint that can become problematic: the anterior talofibular ligament, the calcaneofibular ligament and the posterior talofibular ligament. According to a study from Physiopedia, these lateral ligaments are weaker than those on the interior (medial) of the ankle, with the anterior talofibular ligament being the weakest.

An image depicting the various ligaments of the ankle, both lateral and medial.
Anatomy of the ankle, highlighting the lateral and medial ligaments

The next question that has to be asked is why are these ligaments so much weaker than other ones? The answer to this question is based on their physical make up. Ligaments are made of soft tissue that has various collagen fibers running parallel to each other throughout it. The more fibers there are, the more structure and rigidity there is. Think of the fibers as a rope: The rope can stretch to a certain point, but once it hits that point it will snap and break. But if you have a thicker rope (such as the medial ligaments), it becomes much harder to break.

The ligaments on the outer part of the ankle have fewer collagen fibers than those on the inside of the ankle. Thus, when the ankle is moved in an awkward position, it is more likely that the lateral ligaments will break.

Once you sprain your ankle, the focus turns to treatment. Treatment will differ slightly for every individual depending on the severity of the ankle sprain. The simplest way to treat a sprained ankle is to follow the RICE (Rest, Ice, Compression, Elevation) method. Other forms of treatment include taping the ankle or using a brace to restrict movement and to add support and extra stability. Wearing proper footwear is another way that one can prevent and help treat a sprained ankle, as certain shoes are specifically designed to help avoid such injuries. To prevent future ankle sprains, exercises are recommended to help strengthen and stabilize the joint and surrounding ligaments and muscles.

For more information on ankle anatomy and sprains, check out these articles on BOFAS and SPORTS-Health.

Pressurized Vessels Supporting the Spine: Structure and Function of Intervertebral Discs

Back in 1989, it was estimated that about 2.5 million U.S. workers suffered from low back pain, and low back pain has even been talked about as one of the largest causes of disability in the world. Intervertebral disc degeneration is one of the most common reasons for low back pain in adults. In order to understand how disc degeneration occurs and causes pain, it is important to examine the structure and function of discs in the back.

Computer generated image of a healthy lumbar spine
Vertebral Column: Obtained from Smart Servier Medical Art

Discs are structures that sit in between vertebrae in the spine (blue in the image). Their consistency has been compared to Jell-O and the seemingly mythical product called the waterbed. This consistency comes about because of the microstructure of the discs. The main structural component is collagen which not only surrounds the discs but also traverses across the fluid-filled center to give support. Collagen is found all over the body in places ranging from bones to eyes. There are many different types of collagen that are able to account for the softness of the cornea and the strength and stiffness of bones. In discs in the back, the collagen that traverses the middle is the same as that found in cartilage, while the collagen that makes up the outer layer is the same collagen found in skin and bones. This gives the discs a strong, thin outer layer surrounding the gel-like center, warranting the comparison to the waterbed.

Because of this structure, intervertebral discs provide support for the spine in compression. The spine can be compressed by activities as simple as carrying a backpack, sitting, or bending over. When these and other activities occur, the vertebrae press in on the discs, causing pressures from about 15 to 300 psi, or pounds per square inch, depending on the activity. For reference, the recommended tire pressure for a car is 30-35 psi and the pressure inside a champagne bottle is 60-90 psi.

As discs degenerate, either with age or trauma, they respond differently to the large compressive stress applied from the spine. With age, this change in response is most commonly attributed to the inside portion of the disc drying up and changing from a gel to a solid. Discs rely heavily on fluid flowing through their pores, and once they dry up, this no longer occurs. As loads are applied, instead of increasing pressure, degenerate discs can expand outward creating a phenomenon known as a bulging disc. While this is just one of the many medical problems a degenerate disc can cause, it is

Computer generated image of a lumbar spine with disc herniation.
Disc Herniation: Obtained from Smart Servier Medical Art

common and typically leads to an increase in pain. When the discs expand outwards, it reduces the space between the vertebrae causing irritation. If the discs expand far enough outward, they can leave the space between the vertebrae, entering the region where many nerves lie, potentially causing pain throughout the body.

Despite their odd consistency, intervertebral discs play an important role in the spine, sometimes pressurizing to more than 3 times that of a champagne bottle. Both injuries and natural degeneration leads to negative changes in the biomechanical properties of discs, causing an increase in back pain. If you are interested in learning how to take care of your discs, worried you have an injured disc, or simply want to learn more, I recommend going here.

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

The Weight of Combat: Are powered exoskeletons the solution to heavy combat loads?

Have you ever wondered how much weight a soldier carries in a combat zone?

Military servicemembers, particularly those in physically demanding roles such as infantry, are routinely required to carry heavy combat loads ranging from 25- to over 100-lbs. This load potentially includes weapons, ammunition, body armor, food, sleeping equipment, and other necessities for the mission. Consider that these loads are often carried for hours or even days at a time in both deployed and non-deployed environments and it becomes clear that these loads take a physical toll on those who bear them.

The physiological demands of these loads often lead to servicemember injury or discomfort both during and after their time in service. The most common musculoskeletal injuries resulting from carrying heavy combat loads include increased lower back pain and injuries to the knee, ankle, and spinal cord. Such injuries lead to acute and chronic effects over the servicemembers’ lifetimes, increased military healthcare costs, and decreased military readiness.

While it would be advantageous to decrease both the weight of the combat load as well as the frequency of weight-bearing events, the reality of modern warfare gives little hope to these suggestions. However, there is another solution: external, electrically powered exoskeletons to aid with carrying combat loads.

American defense and technology company Lockheed Martin is currently developing a prototype exoskeleton for military use – the ONYX exoskeleton. Two prior-service soldiers are shown performing common physical tasks under load – walking up a steep incline and walking up flights of stairs – while aided by the exoskeleton. Both soldiers involved in the test indicated a high level of comfort with the exoskeleton as well as improved weight-bearing ability using the ONYX exoskeleton. Check out the video to learn more:

Powered exoskeletons come with drawbacks, namely mobility/comfort issues and the need for a mobile, long-lasting power source. While the devices may perform well in a laboratory or controlled setting, reliability in the field will require durable materials and electronics. Additionally, while Lockheed-Martin’s ONYX exoskeleton is designed to reduce load on the wearer’s knees and quadriceps muscles, it gives no such support to the lower back or other parts of the body. This shift in load distribution throughout the body may have unintended consequences and potentially lead to further injury. A 2006 study by researchers at Loughborough University in the UK found that existing military load carriage systems result in gait and posture changes (head on neck angle, trunk angle, etc.) which lead to muscle tensions that increase one’s risk for injury.

A figure visualizing the angles made by the head, torso, and legs when walking
Image taken from Attwells et al., Ergonomics, 2006.

Thus, while there have been many improvements in robotic and soft electronics technology in recent years, powered exoskeletons have much to prove before they see time in service.

What do you think – are powered exoskeletons going to be commonplace on the battlefields of tomorrow, or are they a passing fad?

For more information, check out the following articles from the Army Times and Breaking Defense on the ONYX exoskeleton.