Tag Archives: shoulder

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 Shoulder: Super Joint or Super Hazard?

The shoulder joint is one of the most incredible joints in the human body.  Humans have been recorded throwing 100+ mph fastballs, pressing nearly 600lbs overhead, and performing incredible gymnastics moves. The shoulder is a ball-and-socket joint, and it is by far the most mobile joint in the human body.  But this great range of motion comes at the price of being the most unstable joint in the body.

The contact between the shoulder blade and the humerus (upper arm) is analogous to the contact between a golf ball and golf tee.  A golf ball is perched precariously on top of a tee, and can be removed from its resting place with very little force.  Thankfully, the shoulder joint is a bit more complex than a golf tee, giving it more stability.  However, it is still very weak in relation to the rest of the human body, as it is only held together by the four, small rotator cuff muscles, the glenoid labrum, the biceps tendon, and several ligaments.

graphic of a shoulder joint with muscles, tendons, and bones labelled
Image from Wikipedia

One of the most common shoulder injuries is a shoulder dislocation.   This injury occurs about 200,000 times per year.  This injury occurs most often in men in their 20s and in men and women above age 60.  The younger group sustains this injury most often from a violent incident, either from a sports injury or a motor vehicle accident.  The older age group sustains this injury mostly from non-violent injuries, such as falling.  This causes a tear in the labrum, resulting in future instability.

image showing the difference between a healthy labrum and a torn labrum
Image from Huang Orthopaedics

The labrum is a cartilaginous ridge around the joint that adds stability by creating a seal between the humerus and shoulder blade.  Returning to the golf ball analogy, the labrum is like a rubber ring around the top of the golf tee that helps keep the ball from falling off.  When this is torn, it does not often heal, as there is very little blood flow in the shoulder joint.  This tear remains and makes it more likely for future dislocations to occur.

This lack of stability can be addressed both surgically and non-surgically.  Non-surgically is generally the preferred, but less successful option.  It involves strengthening the shoulder muscles to make up for the lost stability of the labrum.  The rotator cuff muscles as well as other larger muscles are strengthened to compensate for the torn labrum.  While the muscles can help immensely with reducing instability, they cannot always entirely replace the labrum.  If this is the case, surgery can be done to re-attach the labrum and give the shoulder nearly all the stability that it had prior to the tear.

One example of someone who had this surgery and then returned to a near pre-injury level of function is Saints’ quarterback, Drew Brees. Brees suffered a torn labrum and had it repaired with twelve anchors. He then would return to the NFL and become one of the greatest quarterbacks of all time.  He was the MVP of Super Bowl XLIV and is a twelve-time Pro-Bowler.  A labral tear can be devastating, but as can be seen by Brees’ story, it can be overcome. So while the shoulder comes with its fair share of liabilities, it is still one of the most impressive joints in the body.

 

Sources and Further Reading:

The Story of Drew Brees and the ‘1 in 500 Injury’ That Couldn’t Stop His Historic Career

Mayo Clinic – Dislocated Shoulder

Huang Orthopaedics – Shoulder Dislocation and Instability

Teach Me Anatomy – The Shoulder Joint

PMC – Anterior Shoulder Dislocation

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.

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.