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Tommy John Surgery and Pitch Velocity, Part II

After completing two studies comparing characteristics of pitchers headed toward Tommy John surgery with the league average pitcher, we look to the academic research arena for assistance on interpreting the results.

Rick Osentoski-USA TODAY Sports

Recently I introduced the most complete list of players who have undergone Tommy John surgery to reconstruct their UCLs in an effort to extend their professional baseball careers. With the list in hand, I investigated two characteristics of pitching in comparative studies between pitchers that were headed toward Tommy John surgery and the average major league pitcher. For both studies, two major confounding variables were controlled to help isolate the characteristics being studied. The controlled variables were pitching role (i.e. starter or reliever) and age.

Earlier this week, we looked at the first study involving pitch types and frequencies from a scientific research perspective.

Pitch Velocity

The second study targeted pitch velocities, and whether pitchers on the road to Tommy John surgery tended to throw their pitches any faster or slower than the average pitcher. The results in the table below show that on average they threw every major pitch type at a faster velocity than is typical for pitchers of their role and age.

Years Prior FBv SLv CTv CBv CHv SFv Sample Size
2 years prior 0.70 0.75 0.28 1.04 0.86 0.44 105
1 year prior 0.73 0.63 0.15 1.44 0.90 1.47 138
Year of TJS 0.62 0.49 0.85 0.82 0.76 0.47 110

Summary from Author

Based on these results, the best that I could say in the previous article was that the findings make some intuitive sense. With all else being equal, I can imagine throwing pitches harder would cause more strain on the arm.

To do much better than this, we consulted someone who is familiar with the latest academic research in the field of pitching biomechanics in an effort to determine whether these findings align and whether the differences are meaningful.

Question and Answer with Eric Post, Illinois State University

Q: Would you mind introducing yourself and describing your area of academic research?

A: My name is Eric Post and I am a graduate assistant and master’s student at Illinois State University. I work as the athletic trainer for the Illinois State baseball team and I am currently pursuing my master’s degree in athletic training. My area of interest for my master’s thesis is the correlation between peak fastball velocity and peak torque at the elbow and shoulder during pitching.

There have been studies examining the effects of increased velocity on injury and studies examining the effects of increased torque on injury, but only one to my knowledge that directly examined the relationship between velocity and torque. This study was performed with high school pitchers whose average fastball velocity was 71 miles per hour. My hope is to examine the correlation between these two variables in a more advanced population of pitchers (high level collegiate pitchers) with fastball velocities more comparable to those seen in professional pitchers.

Q: The results of the study showed that pitchers heading for Tommy John surgery tend to throw all pitch types at a higher velocity than the average pitcher in their peer group. Does this finding make sense given your own research and/or readings of biomechanics research papers?

This finding also makes sense based on the findings of biomechanical research. Hurd et al. (, 2012) analyzed 26 high school pitchers using 3-dimensional motion analysis and found a significant positive association between pitch velocity and elbow torque (more stress on the UCL).

In addition, Anz et al. ( used video biomechanical analysis and showed a significant correlation between higher elbow torque at the late-cocking stage of throwing and an increased risk of injury in a group of 23 professional baseball players. Putting the information from these two studies together, we have higher pitch velocity being shown to be associated with increased elbow torque and then increased elbow torque being associated with an increased risk of elbow injury.

But what about examining the relationship between pitch velocity and elbow injury more directly? Bushnell et al. ( used the data collected in the Anz et al. study mentioned above and followed the pitchers prospectively for three seasons. Nine of the 23 players developed an elbow injury, and this injured group had a significantly higher average fastball velocity (89.22 mph) than the 14 pitchers in the non-injured group (85.22 mph). Additionally, the Olsen et al. ( study referenced earlier examined risk factors between teenage pitchers with and without a history of shoulder or elbow injury and found that the elbow injury group threw with significantly higher fastball velocity (88.1 mph) compared to the non-injury group (82.7 mph).

So, there do seem to be associations between pitch velocity, elbow torque, and elbow injury. However, increased pitch velocity is an important aspect of performance, which is where using biomechanics may come into play in order to find pitching techniques that maintain velocity while reducing stress on the elbow.

Q: Would you say that the biomechanics research community is united in this viewpoint regarding pitch velocities? Are there other recent studies that have come to alternative conclusions?

Once again, as just a master’s student with an interest in the biomechanics of pitching I can’t speak for the biomechanics research community, but the research does appear to show associations between pitch velocity, elbow torque, and elbow injury risk. However, it must be noted that pitching is a very complex system with many variables.

There are many factors that contribute to elbow injury beyond simply increased velocity and elbow torque such as individual pitching mechanics, strength and conditioning, and pitching volume (per game and season). When examining the correlations between two variables (such as pitch velocity and elbow torque, or elbow torque and elbow injury), we must keep in mind that there may be confounding variables contributing to the associations seen in those studies.

Q: While pitchers heading toward Tommy John surgery tended to throw all pitches at a higher velocity, for almost all of the pitch types there was a slight drop in velocity in the year that the Tommy John surgery ended up taking place as compared to the year prior. Does this finding make sense given your own research and/or readings of biomechanics research papers?

I don’t personally know of any scientific research that has examined the relationship between a loss in velocity and elbow injury. This does not mean it doesn’t exist; I just have not come across it in my literature review. However, large decreases in control or velocity are often interpreted by health care professionals to be indicators of injury to the elbow or shoulder.

Q: Overall, in your opinion, are the results of this study consistent with your expectations with respect to pitch type, frequency and velocity as they pertain to elbow injuries and Tommy John surgery?

In my personal opinion, the directions of the deltas seen in this study make sense with what I would expect to see based on my review and interpretation of the current scientific literature.

Whether or not throwing one extra slider and fastball per hundred pitches (or about 30 extra of each for a starting pitcher over the course of a season, even less for a reliever) is significant enough of an increase to contribute to injury is impossible to say. However, the fact that pitches with higher velocity are being thrown more often by pitchers who sustain elbow injury is what I would expect based on my review of the research.


We have learned that there are published papers that arrived at conclusions that agree with the root of the findings from these two studies. This allows me perhaps to feel more comfortable that despite the relatively small deltas observed in the studies, there is more substantial evidence backing these findings.

I believe what Eric Post said to be true in that pitching is a complex system with many variables. I personally would expect that pitching mechanics are by far the biggest contributing factor to injury. Unfortunately, for the most part, a metric to capture such mechanics is not available for this entire group of pitchers. Given that many pitchers have a throwing motion that is not ideal, at this point other factors can cause an increased level of risk for injury. This is where I believe pitch type, frequency and velocity appear to play a role in elevating the risk of injury, which among other things could mean that one day a pitcher lands on the operating table for Tommy John surgery.

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You can follow Eric Post on Twitter @posteric. <a href="" class="twitter-follow-button" data-show-count="false">Follow @posteric</a>
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Sincere thanks to Eric Post for providing his time, effort and knowledge in answering these questions. Credit and thanks to Fangraphs for data upon which this analysis was based.