Tag: other sports

Ski Racing: Where Champions are Made on the Course and in the Lab

If you have ever watched the winter Olympics, you have probably watched in awe as the alpine ski racers flew down the course. Years of training to perfect technique and build strength are essential for any athlete trying to compete with the best, but in a sport where hundredths of a second can separate first and second place, racers are always looking for ways to shave time. Understanding the forces that slow them down and their relationship to body positioning gives these athletes a competitive advantage.

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How to Optimize Biomechanics Forces of Olympic Giant Slalom Skiers

            Do you ever wonder what differentiates a casual skier from an Olympic level skier? The distinction lies in the immense forces these Olympic skiers’ output as they naturally transition from incredibly high speeds to sharp turns on the icy slopes. The four famous alpine skiing events held at the Winter Olympics are the slalom, giant slalom, downhill, and super-G events. In these events the human body is pushed to its limit with skiers experiencing forces of up to 2000N during turns through closely spaced poles and gates. Which is the equivalent of a 440-pound weight laying on top of you. These forces are integral in achieving faster times, better technique, and winning Olympic gold. How can these forces and techniques be optimized for the best possible ski run?

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Which Body Mechanics Help You Jump Higher?

Vertical jumping is an essential aspect of many sports. In volleyball and basketball, for example, jumping higher than your opponent gives you a significant competitive advantage. Volleyball players need to be able to block and spike, while basketball players need to be able to rebound well and finish tough shots over opponents. Most athletes know the basics of jumping, but few know what specific body mechanisms contribute to jump height. This article will discuss four key elements to vertical jump height:

  • Squat depth
  • Non-extension movements
  • Arm swing
  • Toe flexor strength

Understanding the mechanics behind each of these elements can help guide athletes in training regimens to better increase jump height.

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Why is heading the ball so dangerous for youth soccer players?

young girl attempting to head an incoming soccer ball
Photo by Carson Ganci on THE42

I received my first concussion while playing soccer at 15 when I was knocked out by a ball that was “accidentally” punted directly into the side of the head. It seemed to me like this was one of the few, rare ways to get a concussion from the sport – an unlikely occurrence combined with an unusually aggressive impact. I was proven wrong, however, after I received two more concussions just from heading the ball – a frequently used technique involving seemingly mild impact forces. I have since come to discover that concussions, particularly due to heading the ball, are a huge problem for youth soccer players: currently, in the United States, youth soccer players aren’t allowed to start heading the ball until age 11 in an effort to reduce the risk of concussions. But how do headers cause so many youth concussions, especially when the speed of play is so much lower than for adults?

Physical vulnerability to concussion mechanics

illustration showing a head impacting a an object with arrows decribing the movement of the skull and the brain towards the object just before impact
Illustration of the movement of the skull and brain just before impact with an object. Upon impact, the movement of the skull decreases rapidly while the movement of the brain has a delayed response. Original image created for Wikipedia

In most sports, concussions are commonly caused by rapid acceleration/deceleration of the head that causes the exterior of the brain to crash into the interior wall of the skull, which is suddenly accelerating in a different direction. When headers are performed in soccer, this rapid acceleration is caused by impact with the ball, and the risk of concussion depends on both the acceleration of the head and the duration of the impact. The acceleration of the brain can be modeled by Newton’s Second Law (F = ma) for a given impact force F, and the resulting acceleration depends on the effective mass of the players head m, which depends on both the strength and weight of the players head and neck as well as their relative movement compared to the ball (which boils down to technique). This means that a major portion of the risk of concussion relies on the size, strength, and technical ability of the player, all of which have an inverse relationship with player age. So while the relative speed of play and impact forces may seem lower for youth players that can’t run as fast or strike the ball as hard as their adult counterparts, these factors are offset by their relative physical vulnerability.

Issues with injury recognition and response

Another factor contributing to the threat of concussions for youth players is their relatively low ability to recognise and respond appropriately to a brain injury when one occurs. Between 2008 and 2012, researchers observing elite female players aged 11 to 14 for 414 player-seasons (288 athletes were observed for a single season and 63 were observed for two seasons) discovered that 59 concussions occurred, with headers being the most frequent cause at 30.5%. In addition to this injury frequency, it was found that over half of these middle-school-aged athletes continued to play with symptoms after receiving a concussion. This is an additional a logistical problem for youth players, for as age decreases, athletes on average have less access to on-hand, qualified medical personnel and less of an ability to self-diagnose and respond appropriately to injury, putting them at increased risk for long term damage.

Oops I Did It Again: The Biomechanics Behind Repetitive Ankle Injuries

Ankle injuries – either sprains or fractures – are one of the most common sports traumas plaguing the US today. Sprains are overextensions or tears in ligaments.  Fractures, on the other hand, are broken bones.

Here, we will focus on sprains of which there are three grades. To help visualise a sprain, think of a Fruit By the Foot (the gummy fruit snack you may have eaten as a child). A Grade 1 sprain involves stretching like if you were to pull on either end of the fruit rope and small tears start to develop along the middle. A Grade 2 sprain develops when the tear is larger and originates from a side; a grade 3 sprain is a complete tear into two pieces.

A Little Background

The ankle joint, also known as the talocrural joint is a synovial hinge joint that mainly moves in dorsiflexion and plantarflexion 1. If you were sitting on the ground with both legs extended in front of you, dorsiflexion is the movement of your foot upwards toward your shin, and plantarflexion is the action associated with pointing your toes moving away from your body.

Video Explanation of Ankle Movements in Dorsiflexion and Plantarflexion

Sprains & Pains

The most common type of ligament injury are lateral ankle sprains or inversion sprains where the ankle joint over rotates in the outward direction, especially an inversion while in plantarflexion 2. Exercises that include running, jumping, and/or cutting put the athlete’s ankle at high risk for sprains. This is especially seen in soccer, football, basketball and volleyball players.

Depiction of ankle position with an inversion sprain. Light purple items are bones and have rectangular callouts, while red items are ligaments with circular call outs. Labeled items include: Tibia, Fibula, Talus, Cuboid, and Calcaneus bones as well as the ATFL, PTFL, and CFL (ligaments).
Figure 1 – Left Foot/Ankle in an over-rotation with main bones (in square callouts) and ligaments (in circle callouts) identified

Figure 1 above shows an ankle in the common and compromising position of an inversion sprain. The circled ATFL, PTFL, and CFL are ligaments in the joint, namely the Anterior Talo-Fibular ligament, the Posterior Talo-fibular ligament, and the Calcaneofibular ligament respectively. Additionally, the boxed call outs are bones in the foot.

Numbers show that close to 70% of patients that had experienced a lateral ankle sprain in the past repeated the same injury to their ankle1.

What is the medical explanation behind repeated ankle injuries?

One study by Doherty et al. followed emergency room visits for ankle injuries and found that 40% of patients with ankle sprains had to seek medical treatment for another ankle injury within the year. Yet, another statistic found that over half of people who experience ankle sprains don’t even go to a hospital.

Ankle sprains are sometimes deemed as a “walk-off injury“, or one that hurts momentarily but just needs a few minutes before resuming activity. However, many people suffer from prevalent and reoccurring ankle sprains. Officially dubbed Chronic Ankle Instability or Sprained Ankle Syndrome, this condition is characterised by a host of symptoms including pain, swelling, perceived and actual instability, balance issues, and joint weakness. Chronic Ankle Instability, or CAI more commonly, can also cause a decrease in physical activity, changes to walking or running form, onset arthritis, and problems with knees and hips due to overcompensation1.

The tried-and-true course of action to prevent CAI is efficient rehabilitation. A study showed that if the patient recovers fast enough, the body won’t change movement patterns.

Problem: Altered Movement Patterns

The changing of movement patterns in the ankle joint, or arthrokinematics1 is one of the main factors that contributes to CAI. The brain, like a protective mama bear, trains the body to operate (walk, run, jump) in a different manner to protect the strained ligaments. Over time, muscle memory kicks in and the compensation for ankle mobility becomes your new normal. This adoption of an incorrect form of walking, running, jumping, etc. can backfire and translate to repeated ankle injuries. This muscle memory has been identified as a neurosignature2 from Melzack’s neuromatrix of pain theory; however, this pain theory also describes how elimination of the pain, stress, or chronic symptoms associated with an ankle sprain can prevent reoccurrence – elimination, that is, through efficient rehab.

Solution: Efficient Rehabilitation

A quick recovery can be achieved through various muscle strengthening exercises from a licensed physical therapist or “ankle disk training,” which basically consists of a flat board mounted on a semi-circle. By standing on this unbalanced board, stability can be practiced as well as specific ligament targeting to build muscle. A more serious solution of ankle surgery showed a 90% success rate of mediating mechanical instability, but this is not a widely-practiced nor traditional treatment plan for CAI3. In fact, ankle taping and/or lace-up 3 bracing when exercising proved most helpful in preventing over rotations of the lateral ligaments.

Big Air: The mechanics of SKIERS and snowboarders landing after jumps

Snowboarder getting big air off a jump
Photo by Jörg Angeli on Unsplash

Have you ever watched the X-Games or Olympics or any other skiing or snowboarding competition and marveled at the sheer heights that the athletes achieve? Depending on the type of jump the skier goes off, they can reach heights of up to 50 feet off the ground [1]. How exactly do the skiers land what are essentially free falls from such heights? Supposedly “survivable injuries” occur from falling heights above the “critical threshold” of 20-25 feet, so how do these athletes land from heights of up to double this [2]?

First, let’s talk about the limits of the human body and falling. The critical fall height threshold, or the height at which injuries from falling start happening, is defined as “> 20 feet (6 meters)” by the American College of Surgeons Committee on Trauma [2]. This means that “survivable injuries” happen when people fall from the “critical threshold of a falling height of 20-25 feet” [2]. These athletes are falling from heights of up to double this, meaning that they should be sustaining some type of injury, yet they will do multiple runs and emerge completely fine. How is this?

To answer this question, we need to understand the design of the jumps that they are going off. Despite ramps for ski and snowboarding competitions typically being “purpose-built to fit their particular venues,” or built for the specific competition and run they will be used for, the ones that lead to athletes getting big air all share the same general structure, which is displayed below [3].

Diagram of typical ski and snowboarding jump layout

It starts with the inrun, a long, straight drop that allows the athletes to accelerate, and then the “kick,” or the actual jump itself that launches the athletes into the air, and last is the landing ramp, another section that is essentially the same as the inrun where the athletes land [3].

The most important part of the jumps, and the part that allows the athletes to land safely is the landing ramp. The landing ramps downhill slope allows the athletes landing to “convert” their downward momentum from falling into forwards momentum, which spares them the “ruinous impact of a multi-story fall” [3]. The fall impact in situations like this is quantified by physicists as “equivalent fall height,” because “when a snowboarder [or skier] lands at an angle and keeps moving down a slope, the impact is equivalent to falling from a much lower height” [4]. This is the case because gravitational energy gets transformed into “forward-moving energy,” leaving a smaller impact to be absorbed by the knees [4].

Jump designers and builders have become very adept at making the jumps for competitions very safe by using this concept of “equivalent fall height.” It has reached a point that the park and pipe contest director for the International Ski Federation (FIS), Roberto Moresi, stated in an email to Scientific American that “A good jump is when landing, they barely feel the impact,” meaning that through the design of the jump a fall of 50 feet can lead to a nearly imperceptible impact [4].

Sources:

[1] https://www.usskiandsnowboard.org/news/aerial-skiing-101

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3212924/

[3]https://www.wired.com/story/big-engineering-big-air-olympics/

[4]https://www.scientificamerican.com/article/olympic-big-air-snowboarders-use-physics-to-their-advantage/

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

Biomechanics of Pitching: Pushing Limits on the Shoulder and Elbow

Aroldis Chapman of the New York Yankees holds the Guinness World Record for the fastest recorded baseball pitch at 105.1 MPH; a record that has held for almost a decade. Why has no one been able to top his record? — An answer to this question may be found in the biomechanical limits of the human shoulder and elbow during the throwing motion.

As a little background on the subject, the throwing motion can be broken down into six separate phases: windup, stride, arm cocking, arm acceleration, arm deceleration, and follow-through as can be seen below.

Images depicting the six phases of the throwing motion.
Image from the www.physio-pedia.com article “Throwing Biomechanics”

Of the six phases only two are the main instances of injury: the arm cocking phase and the arm deceleration phase.

Injury can occur in the labrum and rotator cuff in the shoulder, as well as in the ulnar collateral ligament (UCL) in the elbow during the throwing motion. In pitchers the stresses are at their extremes due to the unique positions the arm reaches, thus leading to a higher chance of failure in the muscles and ligaments of the arm.

Torques and forces on the shoulder and elbow at the end of the arm cocking phase.
Image from The American Journal of Sports Medicine article “Kinematics of Baseball Pitching with Implications About Injury Mechanisms” by Fleisig et al.

At the end of the arm cocking phase, the arm is in a position of 160° to 180° from the horizontal and puts the arm in the position to accelerate the ball forward. According to one study, extreme torques of 64 N-m and 67 N-m are applied at the elbow and shoulder, specifically loading the rotator cuff and the UCL. Furthermore, the anterior (forward) force at the shoulder of 310 N loads the labrum in such a way that may cause it to tear. The feeling of these loads is equivalent to holding 60 lbs in your hand in the position shown on the right!

Force and position of the shoulder and elbow during the arm deceleration phase.
Image from The American Journal of Sports Medicine article “Kinematics of Baseball Pitching with Implications About Injury Mechanisms” by Fleisig et al.

During the arm deceleration phase the arm is in a position of 64° from the horizontal and the shoulder resists the extreme speed and acceleration it just endured. An article showed that during the deceleration phase the arm experiences angular velocities in the shoulder of almost 7,000 degrees/sec making it one of the fastest known human motions. That is about 1,200 RPM which is comparable to the rotational speed of some car engines during cruise control, while traveling at about 50 MPH! Additionally, the rotator cuff and the labrum take the brunt of the 1090 N (245 lbs) compressive force needed to slow down the arm and it is enacted in just an instant!

According to one article, the limiting factor on pitch speed is that the force pitchers apply to their UCL is at the limit of what makes it tear. This means that attempting to throw any faster would result in the UCL tearing! In summary, pushing to gain more MPH on the fastball would mean even higher loads and thus more demand from the shoulder and elbow despite already being at their limits.

All in all,  biomechanical data shows that limits in the rotator cuff, labrum, and especially the UCL explain why  Aroldis Chapman’s record has been preserved for almost a decade and why the chances of throwing any faster are almost impossible. However, in the world of sports, limits and impossibilities are just waiting to be broken.

 

Sources and Additional Reading:

“Fastest Baseball Pitch (Male)” https://www.guinnessworldrecords.com/world-records/fastest-baseball-pitch-(male)/

“Kinematics of Baseball Pitching With Implications About Injury Mechanisms” https://journals.sagepub.com/doi/pdf/10.1177/036354659502300218

“Biomechanics of baseball pitching: A preliminary report” https://journals.sagepub.com/doi/pdf/10.1177/036354658501300402

“Why It’s Almost Impossible For Fastballs to Get Any Faster” https://www.wired.com/story/why-its-almost-impossible-for-fastballs-to-get-any-faster/

“Throwing Biomechanics” https://www.physio-pedia.com/Throwing_Biomechanics

“Your car’s engine rpm at highway cruising speeds” https://www.team-bhp.com/forum/technical-stuff/171572-your-cars-engine-rpm-highway-cruising-speeds.html

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?