Tag Archives: athletes

The Dangers of Using Your Head: The Biomechanics of Sports-Related Concussions

Anyone that has ever had the misfortune of banging their head know how painful it can be, but does everyone understand just how dangerous it can be? Concussions occur when the brain hits the interior walls of the skull, either due to a direct blow or a sudden start or stop. These brain injuries most often result in confusion, headaches, and loss of memory but more severe injuries can cause vomiting, blurry vision, and loss of consciousness. In rare instances, they can even cause a brain bleed and result in death. Repeated concussions can lead to neurocognitive and neuropsychiatric changes later in life as well as increase a person’s risk of developing neurodegenerative diseases like Alzheimer’s.

So, who is at risk for concussions?

Athletes sustain 1.6-3.8 million concussions every year in the US. They are most common in contact sports such as soccer and hockey, but the largest contributor is American football. Players are constantly hitting or tackling each other in football, and each impact risks serious injury for both individuals.

How does it happen?

It all comes down to conservation of energy and momentum. Newton’s second law states that an object in motion tends to stay in motion while an object at rest tends to stay at rest, unless acted on by an outside force. When player 1 starts to run, he has a set energy and momentum based on his velocity (speed). Once he hits player 2, he either slows down, stops, or bounces off in the opposite direction. However, the initial energy and momentum that he had doesn’t just magically disappear, it needs to be conserved so it is transferred to player 2. This means that player two will start moving in the direction that player 1 was initially running. This is how billiards is played: the energy is transferred from the pool stick to the cue ball and then to the intended solid or stripe.

However, injury occurs when player 2 or his head cannot move. This may be because he hit the ground or another player or even simply because his neck stabilized his head, but regardless, that energy still needs to go somewhere. When the head stops, the brain keeps going until it collides with the inside of the skull.

Fortunately, not every hit results in a concussion. The brain is separated from the inside of the skull by cerebrospinal fluid that can protect it from collision to a certain degree, so not every impact reaches the injury threshold. What that injury threshold is has become the focus of many scientific studies.

Finding the injury threshold

The search for the injury threshold is a vital one that could help in the development of more effective helmets and rule changes to the game that could keep players safe. Three factors are believed to dictate this threshold: linear acceleration, angular acceleration, and location of the impact. The linear acceleration is what causes the collision with the skull, as previously described. The rotation of the cerebrum (the bulk of the brain) about the brain stem can cause strain and shearing within the upper brainstem and midbrain, which control responsiveness and alertness (causes the confusion symptoms). Finally, certain areas of the brain are more susceptible to injury- like the frontal lobe, temporal lobes, and brain stem since they are near bony protrusions– so the location of the impact can have a major influence in the injury threshold.

While there is still no set threshold, one study was conducted in which 25 helmet impacts from National Football League (NFL) games were reconstructed and the resulting helmet kinematics measured. The study found that the heads of concussed players reached peak accelerations of 94 (+/-) 28 g (acceleration due to gravity-9.8 m/s^2) and 6432 (+/-) 1813 radians/s^2. A separate study focused on the location of concussions of football players and that resulted from specified linear accelerations, as seen in Figure 1.

While there is still much that needs to be learned about sports-related concussions and their long term effects on athletes, scientists are well on their way to understanding the biomechanics that cause them. The next step is using that knowledge to create better protective headgear and a safer game.

Locations of concussions and their linear accelerations.
Back: Case 13-168.71 g (1 concussion)
Front: Case 12-157.5 g, Case 2- 63.84 g, Case 6- 99.74 g, Case 4- 84.07 g (4 concussions)
Right: Case 11-119.23 g, Case 8-102.39 g (2 concussions)
Top: Case 9-107.07 g, Case 1- 60.51 g, Case 7- 100.36 g, Case 10- 109.88 g , Case 5: 85.10 g, Case 3: 77.68 g (6 concussions)
Location of concussions and their linear accelerations. Modified from Neurosurgery

To learn more, check out these links!

https://pubmed.ncbi.nlm.nih.gov/23199422/

https://pubmed.ncbi.nlm.nih.gov/23299827/

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?

Look Strong, Be Strong, or Be Safe?: The Perils of a New Deadlifter

So, you’ve started deadlifting, but you’re not sure if you’re just weak, or if you’re going to break your spine, and there are plenty of “gym bros” slamming the weights, grunting, and walking around wearing equipment (wrist straps and back belts) that says “I’m literally too strong for my own body.” So, what do you do? Do you need to buy that stuff too?

This blog post will walk you through a biomechanical analysis of the deadlift while wearing supportive equipment, in the hopes of helping you face this daunting task.

First, let’s look at the proper form and muscles recruited in the Deadlift.  As can be seen in the graphic below, the lift begins on the ground in a hinged squat. From A to C, The gluteus maximus (butt), trapezius and lower erector spinae (long muscles that run alongside the spine) are primarily activated, whereas from C to D, the hip extensors and numerous smaller upper back muscles help to “lock out” the form, with the forearms supporting the load throughout.

Graphic of a side view of the proper deadlifting motion
Graphic Depicting Proper Form

The science of using wrist straps as discussed here.  Your forearms are significantly weaker than your gluteus and back, and as such, they will fail first. A comparison of different kinematic variables as a function of wrist straps and unsupported showed a higher activation in the back when using straps.  This means, when using wrist straps, you reduce the load on your forearms, which allows you to go heavier with weight.  In essence, it takes grip strength out of the lift.

Improper form, like arching your back, hips rising too early, leaning too far forward, or many other small inefficiencies can lead to concentrated shear stresses between the vertebrate in the back (not good), excessive reliance on small ligaments in lower back (not good), and high stress concentrations at the moment hinge (especially not good considering your lower back is a nerve junction between your sciatic and spinal nerves).  So how do you prevent this?

Many people instantly reach out to supportive equipment as their saving grace, but does this really prevent injury or does it just add a false sense of security to allow dangerous form? Studies by Thomas and Kingma both look at the effectiveness of weightlifting belts in protecting your spine in various loading conditions.  Although I encourage you to read them and discover their findings for yourself, they both reach generally the same conclusion.  Belts might help, by increasing Internal Abdominal Pressure (IAP) says Thomas, and by decreasing spinal load, tested by Kingma, however, any benefit is nominal.

As far as my suggestion goes, you should begin deadlifting at lower weights, without a belt or straps, until you get a feel for the form.  This will begin to increase your strength in the smaller muscles and form muscle memory required for heavier lifting.  Listen to your body. If a lift went well, and you think you can increase the wight without sacrificing form then go up in weight. Eventually, a weightlifting confidence will step in, and you’ll be able to determine for yourself which strength you want to strive for (grip strength, or bigger deadlift numbers).

If profane language is no issue for you, I STRONGLY encourage watching the YouTube video appended below. Eddie Hall, a now retired professional strongman, owns the record for the ONLY 500 kg Deadlift, and he most certainly knows what he’s talking about.

PS he trains without any supportive equipment, and safe to say he’s lifting heavier than you.

Continue reading Look Strong, Be Strong, or Be Safe?: The Perils of a New Deadlifter

What an Optimized Running Gait Can Do for You

Running is one of the oldest and most common forms of exercise, but there are many ways that running mechanics vary from person to person. Identifying the different running gaits is important so that their efficiencies and effects on the body can be analyzed. Injuries in runners are common and having an understanding of how different gaits apply stresses on the body differently can be used to educate runners on how to run in a way that will reduce the risk of injury.

Running with poor mechanics can lead to overuse injuries, which are more common than acute injuries in serious runners. The majority of these injuries occur in the leg either at or below the knee and include patellofemoral pain syndrome (PFPS) and medial tibial stress syndrome (shin splints). Running gait analysis can be used to identify the poor mechanics and the potential risks associated with the mechanics. Further studies have grouped the variations so that the effects of similar gaits can be identified. Extensive analysis has led to the identification of several potential variations in running gait.

A study at Shanghai Jiao Tong University‘s School of Mechanical Engineering determined the effects of step rate, trunk posture, and footstrike pattern on the impact experienced by the runner. Data was collected by instructing runners to run with specified gait characteristics. Sensors made used to make sure that the gait was correct and the impact forces on the running surface were measured. This study showed the lowest impact was experienced with a high step rate, a forefoot strike pattern, and an increased anterior lean angle. Limiting the impact reduces the effects of the loading. As a result, running with these gait characteristics reduces the risk of knee pain and stress fracture in the tibia.

Runner on treadmill with attached sensors following instructions to modify gait
from: Huang, Xia, Gang, Sulin, Cheunge, & Shulla, 2019

While the most important factor in this analysis is how forces are translated through the body, this is difficult to measure directly. The technology does not exist to measure these forces accurately and noninvasively. Since invasive techniques would not allow the person to run normally, indirect ways of measuring this data have been developed. One of these alternatives involves collecting kinematic data which can be used to calculate the forces and observe different gait patterns. They do this by recording high speed video of runners. Usually, photo reflective stickers or LEDs are fixed to critical points of motion so that the motion of these points relative to each other can be plotted and analyzed. This data can be used to develop algorithms that describe different gaits.

Running gait does not only affect risk of injury, but also efficiency. Kinematic studies have shown that as running speed increases, a runner’s gait changes to accommodate this change in speed. One change in the gait was the foot strike pattern changed from rear foot to forefoot. This motion shortens the gait cycle and increases the step rate. However, when the runners ran at their top speeds for an extended period of time, their mechanics broke down and some of the gait characteristics that increase injury risk became pronounced. Because of this tendency, incremental training with focus on proper mechanics is necessary to reduce injury risk.

 

 

 

The Spinal Fusion that Reignited a Legendary Career

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.

An image of the spine with the three regions labeled: cervical (upper region), thoracic (middle region), lumbar (lower region)
Taken from Wikimedia Commons

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 is an image of a spinal fusion surgery with screws helping to hold the vertebrae together
Image taken from Wikimedia Commons

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. 

 

What’s more important for athletes: training or genetics?

Usain Bolt, Michael Jordan, and Wayne Gretzky are arguably some of the greatest athletes of all time. You watch them on the television breaking record, winning titles or making impossible shots, and you can’t help to wonder, how are they that good? Do they use some secret training method, maybe even a special diet? Possibly, they are genetically gifted? Sports author David Epstein tackles this debate of training versus genetics in his book, “The Sports Gene”. Yes, athletes need to practice to become good, but some are just going to be naturally better than others. If you are 5’6” inches you are going to have to practice dunking a basketball a lot longer than someone who 6’6”. To see how some athletes are naturally better than others lets look at some talented athletes and see what makes them biomechanical specimens. First, we’ll look at Michael Phelps, an American swimmer who not only has multiple world records but also the most decorated Olympian of all time with 28 Olympic medals.

 

For swimmers, biomechanics have found the ideal body for performance. Body features that have been found helpful for swimming is a long torso and long arms.  The long torso reduces the drag on the swimmer and long arms allow for more powerful strokes. Michael Phelps’, who is 6’4”, has the torso proportions of someone who is 6’8” and the leg proportions of someone who is 5’9”, giving him an extremely high torso-to-leg ratio. Not only is Phelps’ torso long, but he also has a long wingspan, measured at 6’7”. Along with Phelps’ unreal proportions, his feet are another huge advantage when it comes to swimming. His size 14 feet help place more force into the water when he kicks. This is a benefit because 90% of a swimmer’s thrust comes from their feet. His ankles also hyperextend 15-degree when he kicks, creating more force. Biomechanically, Michael Phelps’s is a walking fish.

Modified from Hart Blenkinsop, Michael Phelps: The man who was built to be a swimmer 2014

You might be wondering, what would happen if you took someone who has trained to mastery and put them up against someone who is just perfectly gifted. David Epstein mentions this scenario in his book a battle between training and genetics. In the 2007 world high jump final, there are two jumpers left, Stefan Holm and Donald Thomas. Stefan Holm, has a personal best of 7’10.5”, only 2 inches off the world record. Holm has been training most of his life, since he was a child and even won the previous Olympic High Jump final. He is also 5’10” tall, which is very small for a high jumper. Donald Thomas, has a personal best of 7’8.5”. Thomas, on the other hand, is 6’3” and has been jumping for a little over a year and had started high jumping because of a bet with a friend. The two finish the completion and Thomas won clearing a 7’8.5” bar. Even though Holm’s technique was near perfect, Thomas just had the athletic edge. Being taller, Thomas already had a higher center of gravity meaning he had to travel less distance to get over the bar. Thomas also had much longer legs and Achilles tendon. This allows him to store and transfer much more energy into a jump. Thomas was just made to win.

 

For more information:

Michael Phelps: The man who was built to be a swimmer

Nature or Nurture?

Back Against the (John) Wall

What would you do if you went to the doctor expecting to get back to work, only to be told you might not ever be able to go back to work again?

According to ESPN, on February 4, John Wall visited his doctor regarding an infection in his heel after a previous operation. The doctor checked the infection, but upon further analysis, realized that Wall had suffered a partial Achilles tear. Unlike former teammate Boogie Cousins, he did not suffer the tear on the court, but at home. It was reported that while at home he fell and experienced extra discomfort in his heel. His doctor reported that he will undergo surgery and will likely rehab for the next 11 to 15 months.

Achilles Ache

The Achilles is a tendon (tissue that attaches muscle to bone) connecting the bottom of one’s calf to the back of the heel, as shown in Figure 1. It is famously named after the Greek hero whose only weakness was the back of his heel.

An Achilles tendon attached to the heel and calf (Soleus).
Figure 1: This shows the lower half of a human’s leg, where the Achilles tendon is attached to both the heel and calf (Soleus). Modified from Wikimedia Commons.

According to “The Achilles tendon: fundamental properties and mechanisms governing healing” by Freedman et al, the Achilles tendon is the strongest and largest tendon in the entire body, and can bear up to 3500N, or almost 800lb, before completely rupturing. This is a result of the materials that the Achilles is made of. The tendon is 90% collagen, which forms a structure full of fibers that are bound together by other molecules. The tendon is 2% elastin, which like the name suggests, adds some elastic, or stretchy, properties. The tendon is sometimes characterized as a viscoelastic material, meaning it has both viscous (slow to deform) and elastic properties. However, the Achilles is mostly elastic, allowing it to bear relatively high impacts and loads.

Healing the Heel

The Achilles, much like other tendons and ligaments, has interesting healing characteristics and procedures. There are two common recoveries for a tear in the Achilles: a surgery that stitches the ends of the tears together followed by rehabilitation, or a period of rest followed by rehabilitation. For a full tear, surgery is very common, as the torn tendon ends are not always spatially close enough for natural healing processes to occur. For a partial tear, a doctor in consultation with the patient will decide which of the two options will be best.

Experimental Excitement

While there is much more to study with regards to Achilles tear recovery, there is a lot of exciting research being performed on animal models. One study shows that stretching and compressing the Achilles at certain angles during recovery may lead to better long term health of the Achilles. Another study shows the efficacy of stem cell therapies. A third study shows the usefulness of incorporating a 3D printed structure to integrate the ends of torn Achilles. Essentially, this would connect each end with a scaffold that allows for the reintegration of the tendon. This is very similar to an experimental ACL reconstruction technique called BEAR. A video about BEAR can be seen below.

Although John Wall’s career may be in doubt, the future for effective therapies in treating Achilles related injuries is promising. This is exciting for the future, and hopefully will make for a better patient experience. To read more about the Achilles, click here or here.

What Happened to Markelle Fultz’s Shot?

What happened to Markelle Fultz? This is the question on the minds of many basketball fans who have watched a promising player slip into a sharp decline in his first two seasons in the NBA. The former 1st pick in the 2017 NBA draft was known in college for his ability to score; however, so far in his career, his shooting statistics have fallen dramatically as he seemingly forgot how to shoot the ball. A couple of painfully awkward shots can be seen below as Fultz tried new methods of shooting the basketball:

A few months ago, his difficulties were diagnosed as neurogenic thoracic outlet syndrome (TOS). But what is neurogenic TOS and how does it impact Fultz’s shot?

Male figure shown with location of thoracic outlet between the base of the neck, the clavicle and the arms.
White shaded area shows the position of the thoracic outlet on the body. From University of Washington School of Medicine in St. Louis.

A paper by neurosurgeons Jason Huang and Eric Zager of the University of Pennsylvania on TOS gives insight into Fultz’s diagnosed condition. The thoracic outlet is an intersection of nerves and blood vessels that run through the gaps between the base of the neck, the clavicle, and the arm. Neurogenic TOS occurs when there is compression of the brachial plexus, a bundle of nerves that run between the scalene muscles, the clavicle (or collarbone), and the subclavian arteries. When certain arm motions are performed, the space in the thoracic outlet can become smaller, leading to increased compression.

A picture shows the muscle, nerves, arteries, and bone that make up the thoracic outlet.
Representation of the thoracic outlet including the scalene muscles, the brachial plexus nerve bundle, the subclavian arteries, and the clavicle bone. From Huang and Zager, in Oxford Academic.

Particularly in men, it is common for the scalene muscles to cause TOS, and research has shown that it can happen through repetitive use or sports. There have been reports of baseball pitchers diagnosed with TOS because of the awkward arm motions from throwing the ball.  Often TOS is accompanied by a dull pain in the neck, shoulders and arm where affected, but is not sharp and is often characterized by discomfort, especially with overhead motions. This would explain why Fultz’s shooting motion could be uncomfortable and cause his brain to focus on the pain caused by the nerve compression.

 

So what is the treatment and what is Fultz’s timetable for return?

Sometimes for patients with TOS, surgery is an option, but not often for the type Fultz is likely experiencing, since they are tricky and carry high risk due to the presence of major nerves and arteries. Often a more conservative treatment is prescribed, and it seems as though Fultz is doing physical therapy. His initial timetable for return was listed at 3-6 weeks, but there is no indication of an immediate return, and there is little data to predict the length of recovery with physical therapy.

Because of the unpredictability of the treatment, the uncertainty surrounding Fultz seems to be just as thick with the diagnosis of TOS as it was before. However, the ability for Fultz to recover and relearn how to shoot will be imperative in determining whether he will return to his original form as an elite scorer or become one of the biggest busts in the history of the NBA.

 

Further reading on this topic can be found from The Washington University School of Medicine and In Street Clothes.