Just when you thought rehabbing pitchers was hard enough, a new injury has emerged in the throwing population

With Spring Training underway, baseball is officially back!  As a fan, I am more than excited.  As a medical professional and a PT who spends a lot of time treating the baseball population, I know my schedule is about to ramp up.  As Posner, et al (2011) found, April is the month with the highest injury rates for MLB players, with pitchers having a 34% higher injury than position players.  One of the injuries we are seeing more often than in years past in our professional pitchers are latissimus injuries.  For a lot of reasons, we will discuss below, it seems that latissimus injuries are being diagnosed more frequently than they were in decades past.  It was not until 2010 that the first lat repair surgery was performed on a professional baseball player, when Jake Peavy went under the knife.  Since then, many of the game’s biggest stars, including Stephen Strasburg, Fernando Rodriguez, Clayton Kershaw, Noah Syndergaard, and Cardinals top prospect Alex Reyes have sustained lat injuries.  In a systematic review of 30 professional baseball pitchers, Mehdi, Frangiamore, & Schickendantz (2016) found that the average time required to return to pitching was 99.8 days for the non-operative group and 140 days for the surgically treated group. As you can see, once you sustain a lat injury, the recovery is slow.

Because so few PT’s in the traditional clinic setting treat professional athletes on a regular basis, we created a massive two part blog for our audience to serve as an additional resource to develop a better understanding of the injury and implications for pitchers.  We hope you will enjoy!

In Part I, we will review latissimus anatomy and it’s involvement with pitching, theories for the increase in lat injuries for professional pitchers, and a brief review of the surgery.

In Part II, we will discuss common compensations for “lat dominant” athletes and demonstrate a few of our favorite functional exercises that specifically focus on addressing the common compensation patterns.

Anatomy

The latissimus dorsi is the largest and most powerful muscle in our backs, originating from the T7-L5 vertebrae (basically our bra straps to our belt line), the thoracolumbar fascia, iliac crest, the bottom 3-4 ribs, and the inferior aspect of our scapula.  The lats then insert on the intertubercular groove of the humerus. THAT’S A LOT OF ATTACHMENTS, LEADING TO A LOT OF MOVEMENT INFLUENCES. To make matters more complicated, the lats have a lot of variability in respect to its specific attachment sites.

The general functions of the lats include extension, adduction, cross body adduction, and internal rotation of the shoulder.  For many recreational lifters, the lats become the dominant muscle with all vertical and horizontal pulling movements such as rows, pull ups, and pull downs.

How are the Lats involved with Throwing?

For baseball pitchers, the lats are one of the most important muscles in developing arm speed, and therefore, increasing throwing velocity.  As Eric Cressey (2016) has previously stated, the lat “connects the lower body to the upper body to allow for force transfer that ultimately leads to arm speed and ball velocity”. The lats have several very specific and important functions in the pitching motion, including the following:

1. Initially, the lats work eccentrically during the cocking/lay back phase to control the shoulder external rotation occurring.
   1. When a muscle is working eccentrically, it is being lengthened under load. When a muscle is working concentrically, it is being shortened under load. For example, when you do a biceps curl, the curl portion of the movement is a concentric movement (shortening of biceps). As we slowly lower the weight, we are still using the biceps muscle eccentrically (lengthening of the biceps).
2. Next the lats transition from eccentrically lengthening (storing elastic potential energy) during the cocking/lay back phase to concentrically shortening (utilizing that stored energy to generate high arm speeds) during the arm acceleration phase.
3. Finally the lats continue working concentrically as the arm accelerates during throwing to release, acting as one of the major force generators during this phase. According to Fleisig, Andrews, Dillman, & Escamilla (1995), the throwing arm accelerates at over 7000 degrees per second, which is the fastest recorded human motion in sports (3).

The further the lay back phase, the more the elastic potential energy created by the lats, thereby providing more opportunities for increased velocity.  If you look at the picture below of Billy Wagner, one of the hardest throwing pitchers in the history of the game, you can appreciate the considerable amount of layback in his throwing shoulder, and it quickly makes sense how he became of the games hardest throwers. He generated vast amounts of elastic potential energy via the lats.

If the idea of elastic potential energy is still confusing, then check out this short video below which provides additional information.

What Does all that Energy Talk Mean Injury Wise?

Muscles and tendons, throughout the body, are most vulnerable to injury during the eccentric phase of movement (being lengthened).  When you add large loads to the eccentric phase, as seen when throwing a baseball, and then ask the muscle-tendon complex to transition from being maximally lengthened to concentrically contracted at high speeds , we are asking for trouble. As you can see, the demands on the lats are very high during the throwing phase.

To provide a better visualization of what happens when you overload a muscle/tendon during the eccentric phase, check out this video below (beware of language).  At the 30 second mark, you will see a lady (wearing the ironic “Today is the Day” shirt) take a quick step back with her left leg, leading to an eccentric stretch to the Achilles, followed by an attempt to quickly concentrically contract and shorten her Achilles. Unfortunately for her, she overloads the tissue, rupturing her Achilles (if you don’t mind the language, you can literally hear the pop happen).

Why the Increase in Lat Injuries?

Clearly, pitching places a lot of demands and stresses on the body, particularly the lats, but the question remains, why such sudden increases in lat specific injury risk?  The answer appears to be multi-factorial.  Below, I have listed some of the probable causes.

1. 1. Pitchers are throwing harder: From 2008-2017 the average 4-seam fastball increased from 90.9 mph to 93.2 mph. Additionally, in 2008, there were only 196 pitches thrown 100+ mph in the league for the entire season.  In 2017, there were over 1,000 pitches thrown 100+ mph for the league (Clair, 2018).  As throwing velocity increases, so do the stresses placed on the entire body as whole; furthermore, Gowan, et al (1987) showed that professional pitchers (harder throwers) have a much higher lat recruitment during the arm acceleration phase than amateurs.  Simply put, velocity is rising, and as velocity rises, so do the stresses placed on the lats.
   2. Pitching Year Around: Year around throwing is the root of all evil. At OSSPT, we tell our pitchers that the risks of year around throwing are analogous to the risks of smoking. Similar to how smoking is the top risk factor for many health conditions, year around throwing is the top risk factor for almost all throwing injuries.  As amateur pitchers constantly jump from school ball to travel ball, and then indoor lessons, they never allow their body to take a break, resulting in excessive cumulative stresses placed on the lats, and body as a whole.  Also, we know that as we throw throughout the year, our body undergoes some specific changes which further increase lat injury risk.  For example, we know that throughout the season, pitchers have a significant decrease in shoulder internal rotation, total motion, and elbow extension (Reinold, et al, 2008).  Also, Zeppieri et al (2015) showed that collegiate pitchers lose hip ROM and strength throughout the throwing season.  Besides simply reducing the amount of cumulative stresses placed on the body, we also must take time off from throwing to receive adequate rehab to regain strength and motion losses prior to the next season.
   3. The American Sports Medicine Institute has released throwing guidelines and recommends no overhead throwing of any kind for a minimum of 2-3 months per year(http://www.asmi.org)
      • Weighted Ball Programs: Because pitchers and performance coaches are constantly searching for ways to increase velocities, weighted balls have become the newest trend in baseball. Based on the literature from Reinold et al. (2018), a 6 week weighted ball throwing program led to a 3.3% increase in throwing velocity. A velocity jump like that could be the difference between AA ball or the majors.  All good news right? Not quite, Reinold et al. (2018) showed that the weighted ball group had a 4.3° degrees increase in external rotation, meaning more lay back, which may explain the velocity jump, but it also means increased eccentric loading for the lats as well. Not surprisingly, in the study, the weighted ball group also had a 24% injury rate, while the control group had no injuries during the 6 weeks period.  Although the usage of weighted balls appears to have some performance benefits, we are still uncertain of how to safely implement these throwing programs in regards to how often, how heavy should the weighted balls be, what ages are most appropriate, etc. Because of all the uncertainties surrounding weighted balls, we strongly recommend that you proceed cautiously when attempting a weighted ball program.
      • Lat Dominance/Faulty Training: We will discuss this in much more detail in Part II, along with providing some of the exercises we utilize to retrain our lat dominant throwing athletes.

Surgery

While most lat injuries are Grade I or II strains (partial tears), occasionally a throwing athlete will sustain a tear large enough that requires surgical intervention.  Dr. Anthony Romeo performed the first lat repair surgery on a MLB player and has become the pioneer of the lat repair surgery.  According to Dr. Romeo’s website,

“The latissimus dorsi repair is done by making an incision in the back of arm, near the armpit. The ruptured tendon is then located, and sutures are placed in the end of the torn tendon. Those sutures are then used to pull the tendon back up to the arm bone where the tendon ruptured. Small metallic anchors, called buttons, are then used to fix the tendon to the bone.” (https://www.romeoorthopaedics.com/surgeries/latissimus-dorsi-repair).

In the picture below, you can see OSSPT patient and San Francisco Giants prospect Caleb Simpson’s incision following his lat repair surgery.

To check out Part II, click here.

References

Clair, M. (2018, August 29). Are pitchers really throwing harder than ever? Retrieved from https://www.mlb.com/cut4/are-pitchers-really-throwing-harder-than-ever/c-292153594

Cressey, E. (2016, May 4). Pitching injuries: should lat strains even be happening? Retrieved from https://ericcressey.com/pitching-injuries-lat-strains

Cressey, E. (2018, July 9). 5 reasons for the increase in lat strains in baseball pitchers. Retrieved from https://ericcressey.com/5-reasons-lat-strains-baseball-pitchers

Fleisig, G. S., Andrews, J. R., Dillman, C. J., & Escamilla, R. F. (1995). Kinetics of baseball pitching with implications about injury mechanisms. The American Journal of Sports Medicine, 23(2), 233–239. https://doi.org/10.1177/036354659502300218

Gowan, I. D., Jobe, F. W., Tibone, J. E., Perry, J., & Moynes D. R. (1987). A Comparative Electromyographic Analysis of the Shoulder During Pitching. Professionals versus Amateur Pitchers. The American Journal of Sports Medicine, 15(6), 586-590.

Mehdi, S.K., Frangiamore, S.J., & Schickendantz, M.S. (2016). Latissimus dorsi and teres major injuries in major league baseball pitchers: a systematic review. American journal of orthopedics, 45(3), 163-167 .

Posner, M., Cameron, K., Wolf, J., Belmont, P.,  & Owens, B. (2011). Epidemiology of major league baseball injuries. The American Journal of Sports Medicine, 39(8), 1676-1680.

Reinold, M.M., Macrina, L. C., Fleisig, G. S., Aune, K., & Andrews, J. R. (2018). Effect of a 6-week weighted baseball throwing program on pitch velocity, pitching arm biomechanics, passive range of motion, and injury rates. Sports Health, 10(4), 327-333.

Reinold, M.M., Wilk, K.E., Macrina, L.C., Sheheane, C., Dun, S., Fleisig, G.S., Crenshaw, K., & Andrews, J.R. (2008). Changes in shoulder elbow passive range of motion after pitching in professional baseball players. American Journal of Sports Medicine, 36(3), 523-527.

Zeppieri, G., Lentz, T., Moser, M., & Farmer, K. (2015). Changes in hip range of motion and strength in collegiate baseball pitchers over the course of a competitive season: A pilot study. International Journal of Sports Physical Therapy. 10, 505-513.

https://www.physio-pedia.com/Throwing_Biomechanics (picture)