How Muscles Work and Protect a Pitcher’s Elbow

Let’s talk about muscles. Muscles are the motors of the body. They are the components that generate movement. They can also absorb dangerous forces to protect more vulnerable tissues, like ligaments, and this is especially important for baseball pitchers.

Before I dive in, if you missed part one or two of the three part introduction to my views on the biomechanics of pitching, here’s a short summary.

I disagree with using the total elbow load as an approximation of the load on the ulnar collateral ligament (UCL). Therefore, I believe using the total load as an indicator of elbow injury risk is flawed.

One of the biggest drawbacks to using the total joint load is that it provides no information about the underlying muscles. This is why I account for the muscles, in addition to the ligaments and bones, when I analyze the biomechanics of a pitching motion using computational modeling techniques.

Now that you’re caught up, let’s focus on the muscles.

A muscle originates on one part of the body, at a location called its origin. It then crosses one or more joints and inserts on a different body part, at a location called its insertion. The body part of origin is typically the larger body part. When a muscle is excited by the nervous system, it contracts and attempts to shorten. In doing so, it exerts a pulling force at the origin and insertion. The pulling force causes the connected body parts to attempt to rotate about the encompassed joints in directions that shorten the muscle.

One of the most vital properties of muscle is the force-velocity property. Due to this property, the pulling force exerted by a muscle depends on the speed with which it is changing length. When a muscle is contracting and shortening quickly, it cannot generate much pulling force. This is called a concentric contraction. In contrast, when a muscle is lengthening but also excited by the nervous system (i.e. attempting to contract), it can generate a lot of pulling force. This is called an eccentric contraction. A stationary contraction, when the muscle is not changing length, is called an isometric contraction.

Force-Velocity Curve

Figure from Millard et al. 2013 [1]. The vertical axis shows the multiplier by which the force exerted by a muscle is decreased or increased depending on contraction type.

An eccentric contraction occurs when an outside force is applied to a muscle that is greater than the maximum internal pulling force it can generate in its current condition. The maximum internal pulling force is governed by the muscle’s structure, its current level of excitation from the nervous system, and several other physiological factors. As seen in the figure, a muscle can actually produce more force during lengthening than it can when it is either shortening or stationary.

(A great reference for the previous paragraphs is this textbook from Dr. Rick Lieber [2].)

Our bodies often use eccentric contractions to decelerate body parts after periods of rapid acceleration, which is exactly what happens in the forearm during pitching.

Other examples of concentric, isometric, and eccentric contractions can be seen when a person is doing pull-ups. When the person is pulling up to the bar, his or her biceps muscles are concentrically contracting. When the person is holding at a steady position, the muscles are isometrically contracting. And finally, when the person is slowly lowering himself or herself down from the bar and controlling the descent, the biceps are eccentrically contracting.


Understanding muscle force production under all conditions is critical to analyzing and improving pitching mechanics, especially at the elbow. All of the muscles that cross this joint make essential contributions using all different types of muscle contractions.

And in baseball pitching circles, one group of elbow muscles gets more attention than the rest: the flexor-pronator muscles.

This muscle group gets more attention with good reason – studies have shown that muscle contractions in this group can relieve loading on the UCL [3-5]. Lesser loading on the UCL likely reduces the risk for a UCL tear and Tommy John surgery. Accordingly, injuries in this muscle group likely increase UCL loading during pitching and therefore may increase UCL injury risk.

The flexor-pronator muscles are able to protect the UCL because they reside in similar locations to the UCL on the body [6]. Both the muscles and the ligament originate on the inside (the medial side) of the bone of the upper arm (the humerus). Thus, when the muscles are contracting, they are likely absorbing force that would otherwise be damaging the UCL.

The UCL originates on the humerus and then simply crosses the elbow joint to insert on the medial bone of the forearm (the ulna). However, the paths of the flexor-pronator muscles from origin to insertion are far more complex. In this muscle group, there are four muscles (FDS, FCR, FCU, and PT) that collectively cross the elbow, forearm, wrist, and even finger joints.

Try placing your left hand on the inside of your right elbow and then making a tight fist with your right hand. You will feel the movement of the tendons of your flexor-pronator muscle group with your left hand when you squeeze your right hand.

Because of the complexity of the flexor-pronator muscle paths, we cannot look at one arm joint or posture in isolation when we’re trying to analyze a pitcher’s elbow injury risk. Motions at the elbow, forearm, wrist, and even fingers all impact the outputs of the flexor-pronator muscles and their collective ability to protect the UCL. Depending on a pitcher’s mechanics and nervous system excitation patterns, the muscles can either be contracting concentrically, eccentrically, or even isometrically at any point in the pitching motion.

Therefore, an understanding of how a pitcher’s muscles are acting during his specific motion is imperative to assessing risk and prescribing effective training regimens.

This is exactly what I do in my biomechanical analysis approach [7]. I use a computational musculoskeletal model of the human body to compute and describe muscle actions, and then assess injury risk based on the results. From looking at the muscle actions, strategies can be devised that target the most important muscles in the most effective ways possible.

In the high school, college, and professional pitching motions I’ve analyzed, I’ve observed both concentric and eccentric contraction patterns in the flexor-pronator muscles during time periods of increased UCL injury risk. Different contraction patterns require different training techniques.

I do not agree with forcing a pitcher to conform to exact “ideal” mechanics. I do believe there should be mechanical guidelines, but I think it is essential to let a pitcher’s individual anatomy and muscle physiology guide his precise mechanical approach. Look at Greg Maddux. Look at Randy Johnson. Look at Pedro Martinez. Pitching success comes in all shapes and sizes.

Dr. James H. Buffi has a degree in mechanical engineering from the University of Notre Dame and a PhD in biomedical engineering from Northwestern University. His doctoral dissertation was called, “Using Biomechanical Modeling and Simulation to Calculate Potential Muscle Contributions to the Elbow Varus Moment during Baseball Pitching.”  He has also been a visiting scholar in the National Center for Simulation in Rehabilitation Research at Stanford University as well as a visiting researcher at Massachusetts General Hospital. You can follow @jameshbuffi on twitter.


  1. Millard, M., et al., Flexing Computational Muscle: Modeling and Simulation of Musculotendon Dynamics. Journal of Biomechanical Engineering-Transactions of the Asme, 2013. 135(2).
  2. Lieber, R.L., Skeletal muscle structure, function & plasticity : the physiological basis of rehabilitation. 3rd ed. 2009, Philadelphia: Lippincott Williams & Wilkins.
  3. Lin, F., et al., Muscle contribution to elbow joint valgus stability. Journal of Shoulder and Elbow Surgery, 2007. 16(6): p. 795-802.
  4. Seiber, K., et al., The role of the elbow musculature, forearm rotation, and elbow flexion in elbow stability: an in vitro study. Journal of Shoulder and Elbow Surgery, 2009. 18(2): p. 260-8.
  5. Udall, J.H., et al., Effects of flexor-pronator muscle loading on valgus stability of the elbow with an intact, stretched, and resected medial ulnar collateral ligament. Journal of Shoulder and Elbow Surgery, 2009. 18(5): p. 773-778.
  6. Davidson, P.A., et al., Functional-Anatomy of the Flexor Pronator Muscle Group in Relation to the Medial Collateral Ligament of the Elbow. American Journal of Sports Medicine, 1995. 23(2): p. 245-250.
  7. Buffi, J.H., et al., Computing Muscle, Ligament, and Osseous Contributions to the Elbow Varus Moment During Baseball Pitching. Ann Biomed Eng, 2014.

A More Forward Approach to Understanding Pitching Biomechanics

This is part two of three of the initial guest posts by Dr. James Buffi. Part one was titled Challenges with Typical Biomechanical Analyses of Pitching.

It is impossible to figure out if a specific player scored a run in a baseball game just by looking at the final box score. This is essentially what typical biomechanical analyses of pitching try to do. They attempt to infer the underlying outcome for the UCL from macroscopic surface-level observations of net elbow loading.

As stated in my previous post, the total elbow load is not nearly enough information to determine the underlying ligament load.

Most of these typical biomechanical analyses can be classified as inverse dynamic analyses. The word “inverse” refers to the order in which calculations are performed relative to the way the body actually creates motion. In an inverse dynamic analysis, the total joint loads are recorded and calculated first. The loads on individual joint structures and muscles are then computed second. This directly contrasts the way the human body actually creates motion.

In the human body, the muscles are generally activated first by the brain. A motion then occurs second, as a result of the activation. When an analysis of a motion is performed by working “forward” from neural command, to muscle output, to joint loading, and then to the motion, it is called a forward dynamic analysis. In a forward analysis, a motion is analyzed in the same way the body creates it, as opposed to the inverse approach, in which the analysis starts with the end result and works backwards.

Forward Dynamics

Referring back to the example I used in my first post, let’s again consider the situation in which two teams of 15 people are playing a game of tug-of-war. To perform an inverse analysis of the game, the total load on the rope is measured first, and then the loads supported by individual players are estimated second from the total rope load.

In contrast, to perform a forward analysis of tug-of-war, one would start by determining the loads supported by individual players, and then calculate the total rope load that results. The forward analysis better represents the observed process. It does not require approximating a method for working backwards from the load on the rope to the underlying loads supported by specific individuals.

When I perform a biomechanical analysis of a pitcher, I use a more forward approach. I go straight to the muscles and ligaments. To be clear, I do not perform a forward dynamic analysis in the purest sense, because my approach still begins with the recording of the pitching motion rather than the neural command. However, I do not calculate the total joint loading as an intermediate step. I compute the actions of the muscles and ligaments directly from the pitcher’s motion using knowledge of musculoskeletal anatomy and neural activation patterns. I am able to accomplish this with computational, physics-based, musculoskeletal-modeling techniques.

The development of my computational approach began while I was working toward my PhD. I used a computer model of the human body and a well-defined algorithm [1] to compute muscle forces that generated a recorded pitching motion. The algorithm included an embedded forward dynamic analysis. The specific computer model I used was developed from bone, muscle, and ligament geometry measurements taken in cadavers, as well as strength measurements taken in living subjects [2, 3].

Pitching Timeline

In 2014, I published an academic article using my modeling approach [4]. In this study, titled “Computing Muscle, Ligament, and Osseous Contributions to the Elbow Varus Moment During Baseball Pitching,” I created a computer simulation of a high school pitcher’s throwing motion. I then used the simulation to investigate how individual muscles can affect UCL loading. I also investigated how changes in muscle output can either relieve or exacerbate the load on the UCL.

My simulation results supported what many people have postulated over the years: muscles have the ability to substantially influence the load on the UCL [5-7]. As expected, my simulation results showed that the forearm flexor-pronator muscles have the capacity to generate considerable protective elbow forces. Surprisingly, due to the subject’s specific posture at the time of maximum elbow loading in his pitching motion, I also found that the triceps muscles were able to protect the subject’s UCL. This may not hold for every pitcher, but it is definitely worth exploring.

Additionally, when I increased the outputs of all the subject’s muscles in a simulation (as one could theoretically do using a well-defined training regimen), I was able to eliminate the simulated load on the subject’s modeled UCL.

This is an awesome result. It implies that pitchers can protect their elbows through muscle training. It implies that changes to throwing mechanics are not always necessary for injury prevention. However, it is important to understand that it only occurred in one simulation of one motion with certain muscles isolated. More work is needed before this result can be applied in the training room or on the practice field. The potential to get this work done is just one of the many reasons why I am excited to work with Kyle Boddy here at Driveline. He believes in using scientific evidence to support advanced training techniques.

The most important outcome of my 2014 study, which became the crux of my doctoral dissertation, is that I developed a framework for subject-specific muscle-driven analyses of pitching. This means that I can now record a specific pitcher’s throwing motion and give him a legitimate analysis of what is going on with his muscles and ligaments, in a way that has never been done before.

In fact, this more forward approach is already generating new and exciting research outcomes. Using this approach, I have observed notable differences between the muscle and ligament actions of previously injured and non-injured pitchers (which I hope to publish within the next year). If I am able to develop tests that detect specific differences such as these, there is great potential to identify injury-prone pitchers before they get injured. Furthermore, there is the potential to design training programs that compensate for observed differences and protect vulnerable muscles and ligaments.

The current state of baseball speaks volumes. Elbow injury rates are so severe that teams feel like they are running out of options. Certain teams are even seriously considering six-man rotations. Now I think it’s time for baseball to embrace a more forward approach to pitching injury prevention.

Dr. James H. Buffi has a degree in mechanical engineering from the University of Notre Dame and a PhD in biomedical engineering from Northwestern University. His doctoral dissertation was called, “Using Biomechanical Modeling and Simulation to Calculate Potential Muscle Contributions to the Elbow Varus Moment during Baseball Pitching.”  He has also been a visiting scholar in the National Center for Simulation in Rehabilitation Research at Stanford University as well as a visiting researcher at Massachusetts General Hospital. You can follow @jameshbuffi on twitter.


  1. Thelen, D.G., F.C. Anderson, and S.L. Delp, Generating dynamic simulations of movement using computed muscle control. Journal of Biomechanics, 2003. 36(3): p. 321-328.
  2. Holzbaur, K.R.S., et al., Moment-generating capacity of upper limb muscles in healthy adults. Journal of Biomechanics, 2007. 40(11): p. 2442-2449.
  3. Holzbaur, K.R.S., et al., Upper limb muscle volumes in adult subjects. Journal of Biomechanics, 2007. 40(4): p. 742-749.
  4. Buffi, J.H., et al., Computing Muscle, Ligament, and Osseous Contributions to the Elbow Varus Moment During Baseball Pitching. Ann Biomed Eng, 2014.
  5. Lin, F., et al., Muscle contribution to elbow joint valgus stability. Journal of Shoulder and Elbow Surgery, 2007. 16(6): p. 795-802.
  6. Seiber, K., et al., The role of the elbow musculature, forearm rotation, and elbow flexion in elbow stability: an in vitro study. Journal of Shoulder and Elbow Surgery, 2009. 18(2): p. 260-8.
  7. Udall, J.H., et al., Effects of flexor-pronator muscle loading on valgus stability of the elbow with an intact, stretched, and resected medial ulnar collateral ligament. Journal of Shoulder and Elbow Surgery, 2009. 18(5): p. 773-778.

Keeping Pitching Simple – Setting Artificial Ceilings for Your Athletes

At the 2015 ABCA Convention, the overarching message from pitching coaches and attendees alike was the idea that things need to be “kept simple.” That going into deep detail was ultimately very confusing and hard to understand, and not necessary – after all, pitching effectively simply involves throwing strikes, locating well, having a good pitch selection, and keeping the hitter off balance. What could be more difficult than that?

Let’s back up. I think most people would agree that sprinting is a much simpler activity than pitching – it’s mostly in a single plane, it doesn’t require a second party that is reacting to what you’re doing, it’s generally easier to train for, etc. As we all know, Usain Bolt is one of the best sprinters in the world and of all-time:

Usain Bolt

Unfortunately, sprinting turns out to be quite a bit difficult to understand – according to lead researchers in the field like Dr. Frans Bosch:

“It’s very early stages in understanding,” he says. “It could be many, many years still before we know more. If you look at a very important development in science over the last 15 years called dynamic systems theory and complex theory, we have learned that the answers to our questions are actually further away than ever before. We’re probably not getting closer to the answer, we’re just getting closer to asking the right questions.”

Pitching is heavily triplanar (sagittal, frontal, and transverse planes of movement) and tough to analyze using video without multiple cameras – often synchronized to get actual joint kinematics and kinetics through deeper analysis. If an Olympic sport that has been researched to death isn’t even close to getting the final answers, how can we hope to “simplify” pitching for our instructors and coaches?

A pitching coordinator who was recently at my facility for a week made probably one of the smartest comments I’ve ever heard in my life. He was talking to a group of us including me, two college pitchers, and two pro pitchers who train at my facility. When the topic of pitchability came up, he said: “We honestly don’t know a damn thing about how to get guys out. Or really how to throw strikes.” This is a guy who has been a pro coach for 10+ years in multiple organizations, and he’s absolutely correct. If we knew how to teach throwing strikes and getting guys out, everyone would have sniper-like command and would never walk hitters – and offense would be even more abysmal than it is in today’s MLB game. It is no different with velocity – if it was easy to teach velocity, then everyone would throw 90+ MPH. Instead, you have coaches claiming: “It’s impossible to develop velocity, and that should not come before ‘proper’ pitching mechanics anyway” as a safe valve for their own ignorance.

Your Job is NOT to Make it Simple for Yourself – But for Your Athlete

I’m not saying you should explain complex mechanical concepts to your 12 year old pitchers; we don’t do that, either. We’ve designed specific drills and underload/overload training mechanisms to help train those concepts without our verbal instruction, however, since verbal discussion of complex mechanical movements is largely useless outside of an education setting. You absolutely need to make the athlete feel and understand what is going on without verbally terrorizing him (kudos to Brent Strom for the phrase), but to take that attitude yourself is to deny the very reality that throwing hard and throwing strikes and increasing spin rates and staying healthy and, and, and…. are all REALLY hard problems that are as of yet, totally unsolved.

We’re getting better at asking the right questions, but to simplify your approach and ignore the deeper pool of research – like the 261 pages in Hacking the Kinetic Chain hopes to detail – then you’re only doing yourself and your athletes a huge disservice by setting an artificial ceiling on them. It’s impossible to get better if you aren’t interested in delving into the unknown; experiment and research as much as possible to turn over all the rocks you can.

Control Problems on the Mound? It’s Not Always “Mental.”

How many times have you heard these lines?

  • “It’s a mental issue.”
  • “He has the yips.”
  • “He lost the ability to throw strikes.”
  • “It’s all in his head.”
  • “He’s mentally weak.”

They’re catch-all phrases that hope to capture the essence of why a pitcher like Daniel Bard can put up these kinds of insane runs:

It’s generally assumed that pitchers like Bard simply lose it mentally and can’t throw strikes because of some ephemeral issue that no one can pinpoint. Let me state for the record that this kind of thing DOES happen, but very often it’s actually an underlying physiological issue, not a mental/psychological one (or at least one rooted in those areas). Daniel Bard can still throw 95+ MPH – just like a handful of my pro clients who were throwing at their top velocities despite spraying the ball all over the place. None of them reported pain, soreness, or weakness – so it couldn’t be physical, right?

Unfortunately, that’s not how it always works.

First, let’s take a closer look at just how hard it is to throw strikes.

A Matter of Timing

Throwing a five ounce baseball with raised seams to a catcher at a target of your choosing is not exactly the easiest thing to do, yet the actual physics-to-performance marriage goes largely unexamined. Here’s two slow-motion videos shot from the side and overhead to capture the two main planes that the arm’s trajectory is on (capturing internal rotation, elbow extension, and trunk rotation). Aaron West is on the left, Taiki Green is on the right.

Aaron West vs. Taiki Green

The distal wrist of the pitching arm (and therefore, the ball) is on a weird curvilinear path around the body that is very individual to the pitcher in question. However, for simplicity’s sake to understand the basic geometry behind throwing strikes, we’ll make the arm path a simple circle below:

Tangent Arc

Imagine the black circle is the arm path and the blue line with points A and B is the ball’s trajectory. This is a line drawn tangent to the arc, and this is how a ball is thrown from the arm path. A line drawn tangent to a circle has only one point of intersection (inflection point).

So, now that the basic geometry lesson is over, here’s how it relates to throwing a baseball at a target – a baseball is ejected from the hand at a “release point” that has just one point of intersection with the hand (the moment of separation between the baseball and the hand, usually the middle finger). Now imagine that the circle above is rotating at something like 4500 degrees per second (internal rotation) but is also being deformed at up to 2500 degrees per second by increasing the radius of the circle (elbow extension), and you have a good idea of just how difficult it is to “repeat” your mechanics. (Take a look at an interactive display – change the point on the circle just slightly, and see how much the tangent line deviates.)

Actually, when you think of it that way, how is it even possible to repeat your mechanics? How is it possible that professional pitchers can hit their target on a somewhat regular basis? Mathematically, it seems to require superhuman reaction speeds and timing ability.

Physiologically, the body is one hell of a weapon.

Proprioception is Everything

Your body has the ability to automatically and unconsciously sense and control motor units in a complex way to perform incredibly difficult tasks – like ballistically ejecting an object at 90+ MPH towards a target with some degree of precision. Your body uses a set of levers (bones), pulleys (muscles, tendons, ligaments), and a central processing unit (brain, nerves installed in the muscles) to coordinate everything together to make minute changes that are impossible to consciously repeat. This is the genesis of the so-called “10,000 hour rule” as made popular by Outliers, and the MUCH better book by Geoff Colvin, Talent is Overrated.

Proprioception is the sense of the relative position of various body parts in relation to one another, usually while they are being moved. This is a generally automatic function of the body – you don’t think about firing the muscles of the upper leg in relation to the lower leg while you’re walking, nor do you think about expanding your chest manually when you breathe. When the body is damaged, there may be a temporary loss of proprioception, but the feedback given to the nervous system generally makes quick adaptations and allows for quick recovery.

For healthy pitchers, this is why we do a lot of overload/underload training using wrist weights, PlyoCare balls, and Driveline Elite Weighted Baseballs. By forcing the body to adapt to new stimuli through similar ranges of motion (and with vastly different ballistic profiles), the motor units of the pitching arm become more efficient.

However, for injured pitchers, it’s a completely different story – and that includes both pitchers who were previously injured and are now healthy in addition to pitchers who are injured but display no symptoms of injury.

Rebuilding Proprioception Through Rehabilitation – Early Intervention is Key

Rehabilitation of previously injured pitchers is far more complex than sending them to physical therapy after surgery and “returning to function” based on strength and skill tests. A pitcher who has had UCL graft/replacement (Tommy John surgery) will now have holes drilled in his arm plus a brand new tendon in place of the original ligament, not to mention severe cuts to the pronator/flexor mass that were required to get to the connective tissue in the first place.

Tommy John

Retraining the pitcher’s proprioceptive ability is similar to what we do with our healthy pitchers, though the focus is generally more on partial and constraint movements that get backchained into the full throwing motion. By using overloaded drills to help force the body to feel the proper movement patterns to more safely generate velocity, we can start the primary programming of the interval throwing program off with an accelerated pace. It is critical that when the athlete starts interval throwing that he immediately starts these simple and safe drills, because the minute a pitcher picks up a baseball, he will revert to primary programming – even if that programming is detrimental to his arm’s health. Furthermore, primary programming is not always applicable, because leftover proprioceptive sense believes the ligament is in one place, the forearm flexors have sufficient strength, the biceps work in a certain way…

Get where I’m going with this? Is it any wonder that a pitcher who seems “healthy” after surgery has ridiculous control problems? It may partially be due to psychological fear of getting on a mound and “cutting loose,” but often it is due to proprioceptive failure. Remapping the proprioceptive senses is incredibly important, and one that is often lost in the physical therapy world. Even if the PT uses Bosu Balls or other unstable surfaces to work on proprioceptive sense, these are not sport-specific and have little to no carryover to ballistic training.

Rebuilding and Regaining Control

For athletes who have microtears in their ligaments or otherwise damaged tissues that they cannot feel – ligaments have poor blood supply and innervation – this can have a serious negative impact on their ability to throw strikes. The proprioceptive mapping of how to throw strikes may be on one setting but cannot adequately adjust to the new situation of slightly damaged tissue that presents no symptoms to the central nervous system. This is why pitchers who have destabilization of the elbow tend to display control/command issues well before their UCL ruptures, even if their velocity does not significantly drop in the process.

Close monitoring of these markers should be done by all professional teams, and athletes themselves should integrate proprioceptive remapping exercises into their training.

The next time you think your favorite pitcher has simply “lost his marbles” and has developed “Steve Blass disease,” consider that maybe he has a serious injury that is simply asymptomatic. Just because he doesn’t feel pain doesn’t mean he’s not hurt – and that’s one of the most frustrating things any athlete can go through.