In the Womb: Alive and Kicking

For a pregnant woman, it can be a thrilling moment when her baby kicks for the first time. Women have described the feeling as a flutter, a tumble, or a gentle thud. However, these movements are not only exciting because they are unpredictable but because they indicate healthy fetal development. 

Although a pregnant woman may not feel her baby’s kicks and punches until 18 to 25 weeks of pregnancy, fetal movement may begin as early as seven weeks and science shows that it is crucial in the development of joints and bones. In fact, a lack of fetal movement can be a sign of abnormal musculoskeletal development and other poor birth outcomes. In the last decade, scientists have begun to wonder how mechanical factors have positive or negative effects on a baby in utero. 

MRI scan animation of developing fetuses
An animation composes of MRI scans of fetal movement during various stages of development. (Image: © Stefaan W. Verbruggen, et al./Journal of the Royal Society)

In particular, researchers Stefaan Verbruggen and Niamh Nowlan at Imperial College in London decided to take a deeper look at the mechanics of these fetal movements through several different studies. As it turns out, neonates can throw a pretty strong punch. In one experiment, researchers saw that fetal kicks can incur an impact of 6 lbs at 20 weeks, 10 lbs at 30 weeks, and less than 4 lbs beyond 30 weeks of pregnancy. The force of fetal kicks decrease after 30 weeks due to the limited amount of space for the baby to move. 

In addition, the force of fetal kicking was also observed in three different neonatal positions: typical (head-first), breech (feet first), and twin fetuses. These studies revealed that twin fetuses can exert the same amount of kick force and motion as a healthy singleton fetus in the typical head-first position. However, fetuses in the breech position showed significantly lower kick forces and lower stress and strain in their hip and knee joints. This discovery might explain why babies in the breech position have the highest probability of being born with hip problems.

simulated strain concentrations in a fetal leg
Simulation of principal strain which indicates that strain increases with gestational age for fetuses in the head first position.  Modified from Verbruggen et al., 2018.

 In another study, three mothers volunteered to have their wombs monitored via MRI so that the researchers could observe the geometry, force, and frequency of fetal motion. It was found that fetal muscles are able to produce nearly 40 times more force than the kick itself. The magnitude of force exerted by these muscles confirms the importance of fetal kicks for proper growth of the hip and knee joints. This information is helping scientists and doctors connect the dots between neonatal environment and newborn joint abnormalities.

Interested in learning more? Check out some of the new technology being developed to further this study!

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

Using K-Motion Technology to Achieve the Perfect Baseball Swing

The question on every baseball player’s mind is: besides more practice, how can I improve my batting skills?

Most people would assume it comes down to practice and strength training, but according to Joe Lemire, a sports reporter at SportTechie, the answer actually lies in the biomechanics of the swing. An in-depth description of the intricacies of the biomechanics that are involved in a baseball swing can be found in David Fortenbaugh’s dissertation here.

A photo of a baseball player mid-swing, making contact with the ball in a game.
Photo by Chris Chow on Unsplash

Many professional baseball teams and some training facilities, including Driveline Baseball in Seattle, have turned to using a K-Motion vest to record and analyze different aspects of a baseball swing. This wearable technology started as an analysis for golf swings, but the technology has now been implemented in baseball. Initial installations of this technology were much more expensive and not portable, but engineers have found ways to translate these technologies into wearable devices that can be used in more natural situations.

Prior methods of swing analysis left many unanswered questions and didn’t provide athletes with proper information for improvement. The K-Motion vest collects data on the speed and bend in a player’s torso and pelvis, and the rotation of their body. The portability of the vest allows for it to be used in game-like scenarios and provide useful information. The data that can be extracted from the K-Motion vest can be used to fix mechanical flaws in a player’s swing.

A photo of a man wearing the K-Motion vest, showing that a sensor sits on the top of the spine and at the tailbone.
Photo from Lemire, SportTechie 2018 (Courtesy of K-Motion)

The K-Vest uses four different sensors to measure the rotational velocities of the torso, hips, lead arm, and bottom hand. The four sensors are placed above the elbow on the lead arm, on the back of the lead hand, on the tailbone, and on top of the thoracic spine. The velocities are compiled into a graph, and the peak velocity of each sensor can be analyzed to track the transfer of energy throughout the swing. Through use of the K-Vest, they have found that to elevate one’s hitting ability comes down to the transfer of energy from pelvis and torso rotation to their arms and wrists.

In order to fix the mechanics of a swing, the system has to obtain an understanding of what a good swing is by compiling data from a variety of professional players. On the graph produced with each swing, the range for pro hitters is displayed to give the user an idea of how they compare. Some more information about the kinematic analysis of the data can be found here.

An example of the data that the user receives from the system and how it can be used to improve a player’s swing can be seen in this video:

Though already proven useful in baseball and golf, people are finding that it can also be useful in volleyball, running, skiing, and other forms of physical activity. The use of this technology has become much more common as professional players have found the feedback to be constructive.

For more information about this technology, check out K-Motion’s website, and see here how it’s being used in golf.

Why Not Running Could Lead to Bad Bone Health

Is staying active and fit enough to avoid bone loss? Maintaining high bone mineral density (BMD) is important for preventing osteoporosis, fractures, and other conditions associated with bad bone health. However, high-impact sports that often involve running or jumping might be necessary in order to preserve and improve BMD among athletes of all ages. Low-impact sports (such as cycling) as well as weight training may not be enough to maintain high BMD and avoid associated health risks.

Among senior athletes, a 2005 study examined BMD among those competing in the Senior Olympics [1]. They concluded that competing in high-impact sports (basketball, running, volleyball, track and field, and triathlon) correlated with a higher BMD compared to low-impact sports (including cycling, race walking, and swimming), among other factors such as younger age and absence of obesity. Similar results were found in a Norwegian study comparing elite cyclists and runners, as cyclists—despite heavy weights programs as part of their training—were shown to have lower BMD than runners [2].

On the other hand, a study comparing younger men and women showed BMD increases as a result of resistance training, but only among men in the spine and neck. Women showed no significant BMD increase [3].

Bone mass changes with age, peaking for both genders at around 30-40 years old.
Modified from Wikimedia Commons

In light of unsubstantial data to support resistance training as a method to increase BMD, why do many articles online praise weight training as the perfect way to promote healthy bones? Online articles with catchy titles claim that “resistance training is really the best way to maintain and enhance total-body bone strength” and it “increases bone mineral density,” but either provide no sources or cite research that showed no significant increase in BMD [4] [5] [6] [7]. Promoting weight training as the perfect solution to late-in-life bone problems sounds wonderful, but formal research concerning its effects on BMD is as best contested and inconsistent. It is not a blanket solution for those looking to improve bone health through staying fit, and should not be used as the only supplement to other low-impact sports such as cycling or swimming.

Running is among high-impact sports that can promote bone health
Modified from Wikimedia Commons

Ultimately, it seems as though staying fit through low-impact sports and weight training might put an athlete at risk for low BMD and associated health risks. Regular participation in high-impact sports (such as running, basketball, and volleyball) has been shown to correlate with higher BMD across different age groups and athletic skill levels [1] [2]. Even though cycling and weight training might cover all the bases from cardiovascular and strength fitness standpoints, bone health requires more impact than just staying fit.

For further reading on the relationship between running and bone health and how other factors play a role, look at Runner’s World’s article.

 

[1] Leigey D, Irrgang J, Francis K, Cohen P, Wright V. Participation in High-Impact Sports Predicts Bone Mineral Density in Senior Olympic Athletes. Sage: Sports Health. 2009. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445153/]

[2] Andersen OK, Clarsen B, Garthe I, Morland M, Stensrud T. Bone health in elite Norwegian endurance cyclists and runners: a cross-sectional study. BMJ Open Sport & Exercise Medicine. 2018. [https://bmjopensem.bmj.com/content/4/1/e000449]

[3] Almstedt HC, Canepa JA, Ramirez DA, Shoepe TC. Changes in bone mineral density in response to 24 weeks of resistance training in college-age men and women. Journal of Strength and Conditioning Research. 2011. [https://www.ncbi.nlm.nih.gov/pubmed/20647940]

[4] Heid, M. (2017, June 6). Why Weight Training Is Ridiculously Good For You. Retrieved from http://time.com/4803697/bodybuilding-strength-training/

[5] (2018, February 2). 10 Health Benefits of Strength Training That Are Backed by Science. Retrieved from https://www.myoleanfitness.com/health-benefits-of-strength-training/

[6] Nelson ME, Fiatarone MA, Morganti CM, Trice I, Greenberg RA, Evans WJ. Effects of high-intensity strength training on multiple risk factors for osteoporotic fractures. A randomized controlled trial. JAMA. 1994. [https://www.ncbi.nlm.nih.gov/pubmed/7990242]

[7] Going SB, Laudermilk M. Osteoporosis and Strength Training. American Journal of Lifestyle Medicine. 2009. [https://journals.sagepub.com/doi/abs/10.1177/1559827609334979]

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.

Hell for your Heels: Plantar Fasciitis and Heel Spurs

Heel and foot pain are somewhat universal issues, impacting people of all different sizes and activity levels. This type of pain can be seen in obese people, who have increased strain on their feet and heels. This pain can limit their mobility, and even discourage healthy amounts of exercise.  It is also common to extremely active people, such as runners or sports players. This type of pain can prevent a person from participating in the athletics that they work so hard to compete in. I experienced a great deal of heel pain during high school, which made it difficult for me to play sports such as soccer, basketball, and track and field. This was an issue I had to deal with throughout high school, however I never understood what caused this pain that kept me on the sidelines at times.

Image showing the plantar fascia ligament and where inflammation is common
Image from Energize Health

By far the most common cause of heel pain is damage to the plantar fascia. The plantar fascia is a ligament connecting the ball of the foot to the heel bone, critical for stability and power in human locomotion. Damage to this ligament is caused by 2 main factors: weight and use. Increased weight, especially over a short period of time, significantly increases the load experienced by the plantar fascia. This increased load pushes the ligament past its yield load and causes tears in the ligament, weakening its mechanical abilities and causing pain. Another important contributor to this ligament’s damage is its workload. Active athletes and runners push this ligament to its limit by regularly undergoing periods of high-intensity loading, causing fatigue failure. In my case, a combination of these two factors caused damage to my plantar fascia: a large growth spurt combined with regular athletics overloaded this ligament, causing damage.

Artist's rendition of the medical conditions plantar fasciitis, where the ligament is damaged and swollen, and heel spurs, where abnormal bone growth is seen to to ligament damage.
Image from 2019 Harvard Health Publishing

This damage to the plantar fascia relates to two resulting conditions: plantar fasciitis and heel spurs. Plantar fasciitis is the swelling of the plantar fascia ligament. This inflammation is caused by the tears and damage as previously discussed, causing sharp pains to the bottom of the foot and heel. Tears in the ligament typically occur at the connection of the bone and ligament. Certain factors can make a person more susceptible to this condition, such as having flat feet or wearing footwear with poor support. In both cases, the plantar fascia is loaded poorly, causing the painful inflammation. There are conflicting studies as to how this condition relates to heel spurs and heel pain.

Heel spurs are calcium deposits located around the connection of the plantar fascia to the heel bone, which cause abnormal bone growth in the area. Heel spurs are caused by prolonged loading and damage to the foot muscle and plantar ligament. Heel spurs are often seen as a result of plantar fasciitis, however the two aren’t mutually exclusive. Heel spurs are found in patients without any evidence of heel pain, raising doubts about how they are directly related. Some studies argue that the heel spurs themselves cause pain, while others contest that they develop in response to plantar fasciitis, the true source of the pain.

These conditions are typically first treated through non-invasive methods. These strategies include specific stretches, targeted exercising, a reduction in workload, and weight loss (if safe). These treatment methods help to improve the mechanical properties of the ligament, making it stronger, less stiff, and less fatigued. Dr. Jarocki from Michigan Medicine gives a thorough and concise summary of the causes of heel pain, as well as some exercises that can help to alleviate this pain.

If these fail, invasive surgery can be required. Surgery can be used to repair the ligament itself or to remove the heel spur. The controversy over the relationship between heel spurs and pain has important implications for the effectiveness of this type of surgery.

Sources and Additional Information:

https://www.health.harvard.edu/a_to_z/heel-pain-a-to-z

https://www.sciencedirect.com/science/article/pii/S1067251601800715

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3309235/

https://www.sciencedirect.com/science/article/pii/S1067251609800653

Tearing and repairing the meniscus

How does someone go from being the youngest NBA MVP one year to barely making headlines the next? Ask Derrick Rose. After being named the youngest MVP in the NBA, Derrick Rose tears his ACL the next year and then tears his right meniscus twice in the span of three years. Knee injuries have not been kind to Derick Rose, but how does one tear their meniscus and how does it get repaired?

The meniscus is shown in Figure 1.

Showcases the location of the meniscus in the knee. Gives the user an image of how the meniscus works, and where it is located.
Figure 1

According to Sports Health, the meniscus is a type of cartilage that provides cushioning between the bones in the knee. The meniscus main role is to absorb shock and the impact on the leg and knee when it is in motion. It allows for stability and smooth motion between the joints.

In a game of basketball, one of the biggest sports in the United States, there is plenty of running, jumping to shoot the ball into the basket, jumping up to catch a rebound, and doing sharp cuts during the game to shake off a defender. All these movements cause high loading on the knee, and if there is an over-rotation on the knee during these movements, then it can cause a tear in the meniscus. The video below shows when Derrick Rose tore his meniscus.

In the video, it shows Derrick Rose doing a relatively easy movement, he plants his foot in order to change direction to chase after the ball. It is a non-contact movement, but due to an awkward landing on his foot, he gets injured and misses games for the rest of the season.

When the meniscus is torn, there are two options in terms of healing the tear. The options are getting the meniscus removed or getting it repaired. Both options have their own recovery time. If you get the meniscus removed, then the recovery time would be from four to six weeks. However, there are setbacks to getting the meniscus removed such as leading to early arthritis. If the meniscus is repaired, then the timetable to return to play is around six months. According to USA Today , he chose to get the meniscus repaired in order to not have future complications around his knee, which is why he had to sit out for the rest of the season. Going this route also gave Derrick Rose the chance to return to his playing form before injury. According to Stein, 96.2% of athletes that undergo meniscal repair go to pre-injury level of activity after the repair, which is good news for Derick Rose.

However, Derrick Rose tore his meniscus again the following season in 2015. He would then have surgery to remove the damaged part of the meniscus and would return in a couple of weeks. This would then be his third surgery to repair his knee, and his surgeries must have an effect on his playing performance. After these surgeries, the world waits to see if Derrick Rose can reach MVP status again during his career. It would be tragic to see that these knee injuries would ruin someone’s career.

Sources and Additional readings:

General information about the meniscus

Meniscal Injuries in the NBA

Injuries in the WNBA

What is Tommy John surgery?

Baseball card of Tommy John for the Los Angeles Dodgers
From Zellner, “A History and Overview of Tommy John Surgery,” Orthopedic & Sports Medicine Specialists

In July of 1974, Tommy John, pitcher for the Los Angeles Dodgers, felt a twinge in his throwing arm, and could no longer pitch. Dr. Frank Jobe tried a new kind of surgery on John’s elbow, and after missing only one season, Tommy John returned to the mound in 1976 and continued pitching until 1989.

How?

The surgery which bears Tommy John’s name is by now a common buzzword in the baseball community. Over 500 professional and hundreds of lower level players have received this treatment, but even the most avid fan may still be unsure what it means.

Tommy John surgery is the colloquial name for surgery on the Ulnar Collateral Ligament (UCL). This ligament is vital to the elbow, especially in the throwing motion. Injury to the UCL accrues over time; fraying and eventual tearing occurs after repeated and vigorous use. Baseball pitchers, throwing around 100 times per game and at speeds upwards of 100 mph, put themselves in danger of UCL injury.

Location of the Ulnar Collateral Ligament in the human arm, shown on a baseball pitcher.
Image from Wikimedia Commons.
Tendons in the elbow joint, with the Ulnar Collateral Ligament marked
Image from Wikimedia Commons

What can be done when a player injures his or her UCL?

Prior to 1974, not much. Ice and rest, the most common suggestions, would do little to improve serious UCL damage. A “dead arm” spelled the end of a player’s career. Dr. Jobe would change that. 

Jobe removed part of a tendon from Tommy John’s non-pitching forearm and grafted it into place in the elbow. John’s recovery required daily physical therapy before slowly starting to throw again.

Since Jobe’s pioneer surgery on Tommy John, most patients undergo a similar kind of reconstruction procedure. A tendon from either the forearm (palmaris longus) or the hamstring (gracilis), is looped through holes drilled in the humerus and ulna, the bones of the upper arm and inner side of the forearm. In some modern cases, the hope is to repair the UCL with a brace that lets it heal itself rather than total replacement. This allows for faster recovery time because the new blood vessels that have to form in traditional ligament replacement are unnecessary. In either case, athletes recovering from UCL surgery, a procedure which itself takes less than two hours, typically require at least a year to restore elbow stability, function, and strength.

Some misconceptions about Tommy John surgery exist. One 2015 study found that nearly 20% of those surveyed believe the surgery increases pitch speed. However, increase in pitch speed may be affected more by the extensive rehabilitation process rather than the new tendon itself.

The study also found that more than a third of coaches and more than a quarter of high school and collegiate athletes believe the surgery to be valuable for a player without an injured elbow. This perception of Tommy John surgery makes it seem like a superhuman kind of enhancement, as if out of The Rookie of the Year, or worse, it becomes like a performance enhancing drug. In reality, a replacement UCL at best replicates normal elbow behavior. A procedure capable of creating a superhero might be attractive, but for now, Tommy John surgery just helps players get back in the game.

 

For further information:

 

How Many MLB Players Have Had Tommy John Surgery?