Tag Archives: elbow

Staying airborne: How bird wings are built for aerodynamic and efficient flight

Flight is a concept that has, until relatively recently in history, eluded humanity. However, birds have been successfully flying for approximately 130 million years, proving themselves to be a physical marvel of the natural world. And while our means of flight have historically been crude in design and performance, nature provides an elegant, efficient solution to get creatures off of the ground. Rüppell’s griffon vultures have been recorded flying as high as 37,000 ft, while some species of shorebirds have been recorded flying as far as from Alaska to New Zealand over eight days without stopping. But how exactly do birds seem to effortlessly overcome gravity so effectively? And perhaps more importantly, how might we apply these answers to improve manmade aircraft?

Morphology

Obviously, the exact aerodynamics and physical characteristics of birds will vary from species to species, but there are still underlying similarities that enable birds to fly. A bird’s wing consists of a shoulder, elbow, and wrist joint which establish the wing’s basic shape and allow a range of motion. Covering the wing are structures called primary, secondary, and coverts, which are all groups of feathers that provide lift and stabilize flight. Feathers consist of flexible fibers attached to a center shaft, called the rachis. Overtime, the rachis will become damaged from fatigue and large instances of stress. As a result, birds will molt and regrow their feathers on a regular basis. 

A diagram of the structure of a bird wing
Picture by marcosbseguren on Wikimedia Commons

Generally, a bird’s body will be adapted to either gliding flight, in which the wings flap very infrequently, or active flight, in which the wings flap nearly constantly. For gliding birds, such as the ocean dwelling albatross, the wings will extend far away from the body, and prioritize both wing and feather surface area over flexibility. Additionally, these wings will have a thick leading edge, and will be much straighter. However for fast, agile birds, such as falcons, the opposite is true. Consequently, agility is sacrificed for energy efficiency. In both cases, the rachis will change shape and rigidity, becoming larger and stiffer for gliding flight and smaller and more flexible for agile flight. 

Aerodynamics

One of the most unique aerodynamic characteristics of birds is that nearly all of their lift and thrust is exclusively generated by their wings, as opposed to aircraft that implement both wings and engines. This provides, among other things, near instantaneous control of both flight direction and speed. In other words, this gives birds an advantage when hunting, escaping from predators, and maneuvering through a landscape. 

To aid in the generation of thrust and lift during flight, birds will change their wing shape through a process called active morphing. During flight, the wing will be bent inwards and twisted up during the upstroke, and extended and straightened during the downstroke. As a result, this minimizes drag while maximizing thrust and, consequently, energy efficiency. This can aid in anything from traveling farther distances to hunting prey.

An osprey folding its wings in while catching a fish
Photo by Paul VanDerWerf on Wikimedia Commons

Applications

Initially, these principles may seem difficult to realistically utilize in aircraft. After all, we are limited by the materials available and the size that aircraft must reach. However, small steps could be taken to improve the energy efficiency and responsiveness of aircraft. For example, wing shape, material flexibility, surface finish, and moving joints could all be explored. In fact, research at MIT is currently being conducted on flexible wings made of scale-like modular structures. If experiments like this are successful, it could show that aircraft designs inspired by nature may be the future of the world of aeronautics.

Punch like a nerd: Utilizing Biomechanics in Boxing Form

Why we punch and how we do it

You and I are living creatures. Every living creature on Earth has some means of self-preservation, and while society and technology have advanced humans far beyond the norms of the animal kingdom, deep down at our core is the self-preserving instinct known as “fight or flight”. When the moment arises that flight is not possible, that unarmed self-defense is the only option, a human will most likely throw a punch. Unless you are trained in a combat sport or a style of self-defense, that punch will likely be inefficient and ineffective. I’m here to break down, with biomechanics, the most effective way to throw that punch.

This diagram shows 4 main punches in boxing. This blog will focus mainly on the cross, hook, and uppercut. Photo from neilarey.com

In boxing, that sport that deals with punching a good bit, there are three main types of punches: straight (jab/cross), hook, and uppercut. As pictured above, the three motions have varying paths traveled by the fist and they engage different muscles in different ways.

“Hold on a minute, why not throw a karate chop or a big ol’ open hand slap?” A study was done to answer this question, where untrained men and women hit a target with an open hand, a karate chop and a closed fist. For each of the techniques they calculated the effective mass, which measures the impact the target experiences. The results showed that while the open hand slap and karate chop had similar effective masses, the closed fist punch had an effective mass that was more than double the other techniques. So, unless you’re a black belt in karate with a mean karate chop, let’s stick to punching if the need arises.

Which punch to utilize

Now that you have decided that the first step is to clench your fist and rear up for a punch, how exactly do you do that? Biomechanical studies have shown for low-level boxers the cross, which is a straight punch with the dominant hand, generates noticeably more punching force. When elite level boxers such as Olympic athletes are observed, however, all three techniques produce extremely similar punching forces. This suggests that for the average untrained human, the most effective and efficient punch to use is going to be the cross.

While it is not the most scientific diagram, this graphic gives some biomechanically sound tips on how to throw an effective straight cross. Photo from The Art of Manliness.

But why is the straight cross generating more force in amateur boxers, and how can elite boxers generate high forces with the other techniques? It’s all answered by biomechanics.

Each punch is unique in how force is generated due to the motion of our bodies and the muscles each motion uses. For example, elite level boxers generate much more of their punching force from extension of their back leg and the extension of their elbow when throwing the cross. This is similar to how a baseball pitcher generates force by driving off the mound with their back leg in their throwing motion. When throwing hooks and uppercuts, elite boxers tend to utilize their hip rotation much more than lower-level boxers, who rely on their shoulder motion. All of this leads to the fact that while you’re throwing your fist at a target, most of the power comes from your waist and legs, so mixing a leg day into your workout schedule could be beneficial.

Sources and Further Reading

The Benchmark of Upper Body Strength: Injury Prevention During the Bench Press

Who wouldn’t want to look like Captain America? This common desire to attain a strong Herculean physique, either for athletics or aesthetics, has led many ambitious men and women to weightlifting. An egotistical motivation puts these people at risk of injury, however, as they sacrifice proper form to achieve their next personal best. The bench press is one example of an effective but potentially dangerous lift.

This upper body exercise requires an individual to lie flat on a bench while repeatedly lowering and pressing a straight bar loaded with weights on each end. The hands evenly grip the bar slightly wider than shoulder width apart with the feet remaining flat on the ground and the arms fully extended. During the eccentric (or lowering) phase, the bar is brought in contact with the lower chest. The bar is then pressed up until the arms are once again fully extended (concentric phase).

Recreational weightlifters commonly use a wider grip on the bar, believing that this will increase activation of the chest muscles and allow them to mimic Terry Crew’s version of the Old Spice Man. One study performed on 12 powerlifters, however, found that the prominent muscles used during the lift, such as the pectoralis major, triceps brachii, and anterior deltoids (i.e. chest, triceps, and shoulders), experienced similar electromyographic activity despite varying hand spacing.

Diagram of a human upper body muscular system.
Image by OpenStax from Wikimedia Commons.

Although hand spacing does not significantly affect muscular activity, it can lead to injury. A review of several studies on the effects of hand grip found that a grip width greater than 1.5 times biacromial width, or shoulder width, naturally resulted in shoulder abduction, or rotation away from the body’s centerline, greater than 45°. As this angle increases, shoulder torque increases, causing potential injuries. For instance, the inferior glenohumeral ligament, a ligament restricting translational motion in the anterior direction at the shoulder’s ball and socket joint, may tear as abduction increases, causing instability at that joint. Repetitive cycles with this wider grip may also cause acromioclavicular joint (AC Joint) osteolysis – chronic destruction of the bone tissue at the joint between the clavicle and acromion.

Diagram of shoulder joint.
Image by OpenStax College – Anatomy & Physiology from Wikimedia Commons.

Aside from a wide grip, injuries also commonly stem from over-training and using excessive weight. Research on 18 male college students demonstrated that repeating the bench press motion with high frequency until failure resulted in a significant increase in the medial and lateral force exerted on the elbow joint, which could result in injury over time. Furthermore, performing the bench press with heavier loads could result in a sudden rupture of the pectoralis major. At the bottom of the eccentric phase as the bar touches the chest, the muscle fibers are simultaneously lengthening while also contracting, which increases the risk of muscle tear in this region.

Unlike Captain America, people cannot instantly acquire strength or build muscle. Muscular development and improving one’s bench press require time, patience, and proper form. To learn more about injury prevention or variations of the bench press, check out the video below or read these papers by Bruce Algra and JM Muyor.

Sources can be found below:

The Affect of Grip Width on Bench Press Performance and Risk of Injury

The Effects of Bench Press Variations in Competitive Athletes on Muscle Activity and Performance

Elbow Joint Fatigue and Bench-Press Training

An In-Depth Analysis of the Bench Press

 

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.

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?

What Makes Someone More Likely to Tear Their UCL?

It takes a lot to make a professional athlete collapse to the ground during a game. After throwing a pitch on September 14, 2019, Toronto Blue Jays pitcher Tim Mayza knelt on the side of the mound while clutching his arm, expecting the worst. The next day, MRI revealed that what he had feared: Mayza had torn his Ulnar Collateral Ligament (UCL).

player following through after throwing baseball
Photo by Keith Johnston on Unsplash

Because of UCL reconstruction, or Tommy John, surgery, this injury is no longer the career death-sentence that it once was, but there is still a long road ahead for Mayza. He probably will not pitch in a game again until 2021. Sadly, this injury is only becoming more and more common among MLB pitchers. In the 1990s, there were 33 reported cases of UCL tears by MLB pitchers. In the 2000s, this number more than tripled to 101. From 2010 to the beginning of the 2015 MLB season, 113 UCL reconstruction surgeries had already been conducted. It has become so common that surgeons have called it an epidemic, and researchers in the US and abroad are attempting to find a way to combat this increase.

Digital image of elbow joint, with a small, red tear in the UCL
Orthopaedic and Neurosurgery Specialists, 2019

The UCL connects the ulna and humerus at the elbow joint, and its purpose is to stabilize the arm. During the overhead pitching motion, the body rotates in order to accelerate the arm and ball quickly, putting a large amount of stress on the UCL. In fact, according to a study by the American Sports Medicine Institute, the torque, or twisting force, experienced by the UCL during pitching is very close to the maximum load that the UCL can sustain.

Recently, many studies have investigated factors that could make pitchers more susceptible to UCL injuries, with a hope of identifying ways to prevent them. One of the biggest findings has been the correlation between UCL tears and pitch velocity. According to a study from the Rush University Medical Center, there is a steady increase in the frequency of UCL tears as max velocity increases. This makes intuitive sense, as more torque would be required to accelerate a baseball to the higher velocities. While this finding does have a very strong correlation, it does not help the players avoid injuries. Pitchers are unlikely reduce their velocity because it would also decrease their effectiveness, so another answer must be found.

The University of Michigan conducted another study, and found that, in addition to velocity, the number of rest days between appearances decreased by just under a full day for pitchers who later needed Tommy John surgery. While this does not seem like a large number, starting pitchers typically only receive 4 days of rest between starts, so the extra .8 days is equivalent to a 20% increase in rest time.

Because of these findings, the MLB has increased the max roster size from 25 to 26 for the 2020 season, with the hope that teams will use the extra player to reduce the frequency that each pitcher is used. In addition, pitch counts in Little League Baseball have had a positive effect on youth injuries. This can be explored further here. This discovery has already made a tangible impact on Major League Baseball, and hopefully more findings will reduce the rate of UCL tears in the future.

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

Striking Out the Myths behind the Curveball

Anybody who has played baseball growing up was probably told “Don’t start throwing a curveball until you are ‘X’ years old.” That “X” in there for the age was normally around fifteen or sixteen years old depending on who you asked. When an eager, young ball player responded with “Why,” it was normally answered by “Because you will hurt your elbow and shoulder.” No sixth or seventh grade kid is really going to question that statement beyond asking another adult, and subsequently getting the same answer. Likewise, no youth baseball coach has really put in the effort to research whether or not learning to throw a curveball is detrimental health of young athletes.

A study was recently conducted by professionals at Elite Sports Medicine at Connecticut Children’s Medical Center to find out the answer. The study was aimed to analyze the shoulder and elbow joints of several teenage pitchers as they threw multiple fastballs and curveballs. They were specifically looking at the moments put on the elbow and shoulder and comparing those between pitches. A moment is a measure of a force on an object and the distance away from the object the force is being applied, mostly resulting in rotation. A moment can also be thought of as torque.

This image shows the grip and wrist position for a curveball
From McGraw, How to Play Baseball, a Manual for Boys

After warming up, the athletes selected for the study had reflective markers placed on their body. These markers assisted in gathering information for “3-Dimensional motion analysis”. This analysis allows the researchers to record “kinematic and kinetic data for the upper extremities, lower extremities, thorax, and pelvis” for both the fastball and the curveball. The researchers found that the moments in the shoulder and in the elbow are lower when throwing a curveball compared to a fastball. This means that the rotational force put on the joints is actually less severe in a curveball than a fastball. The only thing found that is more intense in a curveball than a fastball is the force on the wrist ulnar, which is used when making the motion trying to touch the wrist to the pinky finger. The wrist and forearm motion and forces were the only significant differences between the two pitches.

From this data it is easy to see that the reason for not learning curveballs at a young age has nothing to do with shoulder and elbow injury. There may be a reason related to wrist injury, but that is yet to be explored. A fastball is actually harder on the joints than a curveball. For whatever reason, youth coaches have always preached not to throw curveballs until you absolutely need to. They may have their reasons, but science has shown that it is not realistic to blame injuries.

For further reading on this topic, please see these articles from Driveline Baseball, The New York Times, and Sports Illustrated.