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?
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.
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.
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.
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.
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.
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.
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.
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.
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?
Have you observed that someone around you has broken their arms or legs? Bone fracture is a complete or incomplete break of bone continuity. And it is very common in our daily lives that there are more than 3 million cases in the U.S. per year. Many events may cause bone fractures, such as falls, car accidents or sports injuries. So, do you know how long it takes for the fracture to heal?
Bone fracture healing is a repair process that consists of multiple stages. There are two types of repair: primary and secondary bone healing. Primary healing only occurs with the application of rigid internal fixation, for example, a compression plate. The rigid fixation provides absolute stability, and primary healing includes attempting to reconstruct the continuity between fracture fragments.
In contrast, secondary healing occurs when the fixation is not rigid. For secondary healing, there are four stages: inflammatory response, soft callus formation, hard callus formation, and bone remodeling. After the bone fracture, torn vessels form hematoma, which is localized bleeding outside of blood vessels within the fracture site and provides a foundation for the following stages. The inflammation begins immediately and continues until the cartilage or bone begins to form. During the inflammatory phase, stem cells migrate to the fracture site, form the granulation tissue (new connective tissue and microscopic blood vessels), and release growth factors that stimulate bone formation. This phase usually lasts 3-4 days and may last up to one week.
In the second week after the bone fracture, soft callus (cartilage) begins to form. At this stage, cells within periosteum (the membrane covers the outer surface of the bone) and granulation tissue begin to proliferate and differentiate into chondrocytes until they bind with each other. Chondrocytes are the cells found in cartilage connective tissue and constitute the “bridging callus”. In addition, the amount of newly formed cartilage is related to stability, that less stability leads to more cartilage. The formation of soft callus will be completed within the first three weeks after the fracture, which means this phase needs approximately two weeks to complete.
The following stage is hard callus formation, also known as endochondral ossification. It is a replacement of cartilage with bone. Mineralization of cartilage develops from the ends to the center of the fracture site. The trabecular bone would be formed from osteoblasts (cells that synthesize bone tissue) on the newly exposed mineralized surface. Finally, all the cartilage turns into trabecular bone and forms the “hard callus”. At the end of this phase, the injured bone will be able to recover sufficient strength and rigidity for rehabilitation exercise.
The final stage of secondary bone healing is bone remodeling. This phase starts 3-4 weeks after the bone fracture. Bone remodeling is a slow process that may last 6-9 years, which is 70% of the total healing time. In the remodeling, osteoclasts (cells that break down bone tissue) resorb the trabecular bone, and osteoblasts deposit compact bone. It is a process of equilibrium between resorption and formation, that the trabecular bone is replaced by compact bone, in order to recreate the bone to appropriate shape and adapt to mechanical loads and strain.
In clinical treatment, bone fracture usually takes 6-8 weeks to heal. However, it does not mean the bone is totally cured. When the doctor says the treatment is finished and it is fine to let the body free from the fixation, the bone actually is at the beginning of the final stage since the bone remodeling may take several years.
For more details of the bone fracture healing, please check the following video:
Can you imagine being the best player in the world at a certain sport and one day, aggravating an injury that not only put your athletic career in doubt, but also did not allow you to do normal daily activities? This is the challenge that faced Tiger Woods.
Tiger Woods is one of the greatest golfers to ever play the sport but has been plagued with back issues over the past few years that have prevented him from winning and also playing in golf tournaments. A golf swing applies a significant amount torque to one’s back. Repeating this motion as many times as Tiger has, through practice and tournaments since he began his career, caused him to have chronic back issues that had to be dealt with. In order to deal with these back issues, he had three back surgeries over the course of three years. After these, he was still unable to not only golf but also do daily activities without pain such as get out of bed, or play ball with his kids. Tiger was at a crossroads, and decided to get a spinal fusion surgery.
The spine has three regions: cervical, thoracic and lumbar. The cervical region is in the upper spine near the neck, the thoracic region is in the middle of the spine and the lumbar region is in the lower back. The lumbar region takes the majority of force in a golf swing and is where Tiger had his fusion done. In the spine, discs are in between each vertebra. The disc acts as a shock absorber and allows for slight mobility of the spine. Tiger had a severely narrowed disc in between two of his vertebrae in the lumbar region due to the previous three back surgeries he had. In order to be pain free, that disc had to be removed. This brought about the discussion of him receiving spinal fusion surgery.
Spinal fusion surgery is a process which removes the problematic disc from the spine and inserts a bone graft in place of the disc. A plate with screws is then placed in the vertebrae above and below the bone graft. The plate helps with the healing process and over time, it will heal as one unit. The essential goal of spinal fusion surgery is to take two vertebrae in your spine and make them act as one. When these two vertebrae become one through the surgery, it eliminates motion in between them and hopefully, removes the pain as well.
This spinal fusion surgery was a huge success for Tiger and allowed him to keep playing golf at a high level. Through his win at the 2019 Masters tournament, it’s safe to say that he has at least a few more years of winning tournaments and playing competitive golf before calling it a career.
Additional information and sources used can be found here and here.
Bones break, and broken bones need time to heal, or regrow. Fans of J.K. Rowling’s Harry Potter series are quite familiar with the concept of bone repair, as Harry is once required to drink a Skele-Gro potion to magically (and painfully) regrow his arm bones overnight. Now, as fantastic as it would be to completely fix broken bones in a few hours, modern medicine has not yet discovered that secret of the Wizarding World; however, several treatments have been developed in attempts to speed the rate of fracture repair as well as increase the comfort of the patient (take that, Skele-Gro).
For those unfamiliar with the process of bone repair, a quick overview is in order. In short, inflammation provides stability to a fractured area, and over the course of several weeks fibrous tissue forms a callus around the fracture which is eventually replaced by bone. The mechanical environment at the fracture site is influential in healing, with factors such as hormones, vitamins, minerals, diet, fluid flow, and physical and electrical stimuli affecting healing rates. With these factors in mind, engineers and scientists are attempting to speed bone regrowth.
Low-level laser therapy (LLLT) is one practice found to accelerate bone healing. A studypublished in Lasers in Medical Science revealed that LLLT stimulates bone cells in fracture areas which increases the rate of callus development. Tests performed on the broken tibial bones of two groups of white rabbits demonstrated that bone mineral density at fracture sites remained higher in the group receiving laser therapy than in the control group throughout healing.
However, post-mortem tests revealed that bones healed under LLLT endured significantly lower maximum stresses than intact bones or bones healed under normal conditions. This is a controversial result, as other studies have concluded opposite findings, so despite the enhanced growth resulting from LLLT, the authors of this study agree that additional experiments are necessary to satisfactorily settle this issue.
Surgical implants are another device used to facilitate bone healing. Most bone implants are made of titanium due to its lightness, durability, and biocompatibility. While these supports effectively immobilize and position bones for proper healing, some patients experience complications later on, largely due to stiffness differences between bone and titanium—resulting stress concentrations increase risk of fracture or implant loosening. Titanium foam implants coated in an organoapatite (OA) layer are a developing solution to this issue, described in detail in an Acta Biomaterialia article.
The porous surface of titanium foam, studied in vitro, substantially decreases implant stiffness, thus enabling stress to be more evenly shared between the foam and surrounding bone. Allowing bone ingrowth into the pores also reduces stress concentrations at the materials’ interface which helps alleviate risk of implant failure. Furthermore, the OA coating on the foam stimulates bonding between bone tissue and the implant, thereby increasing stability. The success of these studies suggest that titanium foam is ready for in vivo testing.
Check out this video on the advantages of titanium foam:
Although the results of these fracture repair treatments are still a far cry from those achieved with Skele-Gro, further research and development regarding bone regrowth may lead to significant advances in the very near future. Interested in learning more? Check out articles on other developing fracture treatment technologies hereand here.
A fall off of her horse in 2007 caused Claire Lomas to lose all function in her legs. In 2012, she completed the London Marathon, all 26.2 miles. Robotic exoskeletons can literally get people back on their feet shortly after a spinal cord injury occurs, but how exactly do these medical devices not only supplement but restore human performance? What does the future look like for robotic exoskeletons and those with paralysis?
There are approximately 300,000 people living with SCI in the United States, with 17,700 affected annually. So what exactly is a spinal cord injury? A spinal cord injury occurs when trauma, disease, or compression due to tumors causes damage to your spinal cord, which is responsible for your body’s motor functions (voluntary muscle movements), sensory functions (what you feel, such as temperature, pressure and pain), and autonomous functions (your heart beat, body temperature regulation, or digestion). Injuries are classified as complete or incomplete, with complete corresponding to a total loss of function or sensory feedback in areas of the body which are lower than the injury level.
Studies have shown that people with spinal cord injury, specifically individuals with paraplegia-paralysis who retain function of their upper limbs, prioritize walking as the main function they wish to regain. Robotic exoskeletons, which operate in collaboration with the user to reinforce and retrain certain functions, may be the answer to this pressing need. An exoskeleton facilitates untethered step repetitions and evenly redistributes the user’s weight to his or her core, minimizing stress on the user’s back, neck, and shoulder muscles. One study testing the exoskeleton from Ekso Bionics also showed an improvement in unassisted balance, since the device only initiates the next step if the user properly shifts his or her weight. Though primarily used for gait or mobility training in rehabilitation facilities, these devices are on their way to becoming everyday mobility aids for people with paralysis.
Rehabilitation for spinal cord injuries is long and tedious. Robotic exoskeletons enable patients to begin rehabilitation early after injury, which helps to prevent joint contracture (which is a limit in a joint’s range of motion, preserve muscle memory and strength, retain bone density, and ensure proper functioning of the digestive and respiratory systems). Humans are meant to be vertical and active, so just the act of standing reduces spasticity (perpetual muscle contraction) and pain, decreases the risk of pressure ulcers or osteoporosis from sitting or laying down for extended periods, and improves bowel and bladder functioning. Moreover, the ability to stand at eye-level and walk again reduces instances of depression.
Despite all of these benefits, current models aren’t perfect yet. The energy demand to operate the devices and consequential fatigue of the user limits long-term use, which restricts use outside of therapy. When people hear exoskeleton, images of Marvel’s Iron Man or soldiers carrying heavy packs come to mind. The advance of robotic exoskeletons may expand their use beyond rehabilitation facilities, allowing them to become integrated into everyday life.
The shoulder joint is one of the most incredible joints in the human body. Humans have been recorded throwing 100+ mph fastballs, pressing nearly 600lbs overhead, and performing incredible gymnastics moves. The shoulder is a ball-and-socket joint, and it is by far the most mobile joint in the human body. But this great range of motion comes at the price of being the most unstable joint in the body.
The contact between the shoulder blade and the humerus (upper arm) is analogous to the contact between a golf ball and golf tee. A golf ball is perched precariously on top of a tee, and can be removed from its resting place with very little force. Thankfully, the shoulder joint is a bit more complex than a golf tee, giving it more stability. However, it is still very weak in relation to the rest of the human body, as it is only held together by the four, small rotator cuff muscles, the glenoid labrum, the biceps tendon, and several ligaments.
One of the most common shoulder injuries is a shoulder dislocation. This injury occurs about 200,000 times per year. This injury occurs most often in men in their 20s and in men and women above age 60. The younger group sustains this injury most often from a violent incident, either from a sports injury or a motor vehicle accident. The older age group sustains this injury mostly from non-violent injuries, such as falling. This causes a tear in the labrum, resulting in future instability.
The labrum is a cartilaginous ridge around the joint that adds stability by creating a seal between the humerus and shoulder blade. Returning to the golf ball analogy, the labrum is like a rubber ring around the top of the golf tee that helps keep the ball from falling off. When this is torn, it does not often heal, as there is very little blood flow in the shoulder joint. This tear remains and makes it more likely for future dislocations to occur.
This lack of stability can be addressed both surgically and non-surgically. Non-surgically is generally the preferred, but less successful option. It involves strengthening the shoulder muscles to make up for the lost stability of the labrum. The rotator cuff muscles as well as other larger muscles are strengthened to compensate for the torn labrum. While the muscles can help immensely with reducing instability, they cannot always entirely replace the labrum. If this is the case, surgery can be done to re-attach the labrum and give the shoulder nearly all the stability that it had prior to the tear.
One example of someone who had this surgery and then returned to a near pre-injury level of function is Saints’ quarterback, Drew Brees. Brees suffered a torn labrum and had it repaired with twelve anchors. He then would return to the NFL and become one of the greatest quarterbacks of all time. He was the MVP of Super Bowl XLIV and is a twelve-time Pro-Bowler. A labral tear can be devastating, but as can be seen by Brees’ story, it can be overcome. So while the shoulder comes with its fair share of liabilities, it is still one of the most impressive joints in the body.