Weighted ball use as a method for pitchers to increase velocity is certainly a hot topic these days and a quick you tube search will provide you with enough videos of pitchers doing a wide variety of weighted ball drills to keep your heart content!  Likewise it seems like there is little regard given to extreme use of weighted baseballs and injury risk.  It’s like the old adage: “an apple a day keeps the doctor away,” has been applied to weighted baseball use for anyone and any team regardless of training age, pitching experience, physical ability, work capacity etc…. I’m am not at all bashing weighted baseball use, in fact I have weighted baseball’s in my facility from 3oz-12oz and plyocare balls in my facility up to 2lb, that we do use on occasion with certain athletes. Likewise research has shown that weighted balls do work to increase pitching velocity as well as have been shown to be relatively safe following simple protocols.  In fact, I published a post a while back discussing weighted ball use and youth pitchers:

Weighted baseball and youth pitchers

Where I feel the issue lies is the mad rush to follow the masses and chase that 100MPH plus run and gun throw on the radar gun even though we still have very limited research on using weighted baseballs at extremely high velocities or with extremely high intensity and/or volumes.  Weighted baseball programs are being implemented across the county among colleges and high schools at a rate I believe is too fast based on new research and what we still don’t know.

Mike Reinold just finished a very interesting study regarding weighted baseball use and the adaptations it causes.  The study was performed on high school baseball players for a 6 week duration.  The end results were a 2.6mph increase in velocity along with a 5 degree increase in external rotation range of motion and total range of motion (IR plus ER) in the dominant throwing arm. Both statistically significant compared to the control group.

Obviously the increase in throwing velocity is appealing.  However, the increase in shoulder external rotation of 5 degrees in just 6 weeks may be an issue to explore further with weighted ball use.   In part due to a recent study by Camp et al., just published in the August 2017 edition of the American Journal of Sports Medicine.  The Relationship of Throwing Arm Mechanics and Elbow Varus Torque

The authors placed a motus elbow sleeve on 81 professional pitchers and monitored them over the course of 82,000 total throws.  One finding of note was that an 8 degree increase in shoulder external rotation range of motion resulted in a 1-Nm increase in elbow varus torque. Any increase in elbow varus torque is not a good thing as too much elbow varus torque over time is a leading contributor to elbow injuries.  Medial Elbow Injury in Young Throwing Athletes In addition, excessive shoulder external rotation has also been shown to increase valgus stress on the elbow. Baseball pitching kinematics, joint loads, and injury prevention

Likewise, excessive shoulder external rotation produces greater tension on the biceps and labrum, a peel back mechanism that may result in a SLAP tear Baseball pitching kinematics, joint loads, and injury prevention

While we can’t say for certain if the duration of Mike Reinold’s study would have been longer than six weeks that a larger change in shoulder external rotation range of motion would have been present.  It’s still a point to consider because 5 degrees of ER gain is not far off from the 8 degrees of ER gain reported by Camp et al., that caused an increase in elbow varus torque. In addition, any gains in shoulder external rotation in an athlete  already displaying excessive shoulder external rotation range of motion may increase stress on the biceps and labrum.

Another study recently published by Glenn Fleisig and his fellow research staff at the American Sports Medicine Institute looked at differences in stress levels pitching 4,5,6 and 7oz balls from the mound and using a crow hop throw from flat ground.  The authors did report arm torque and forces increased as ball mass decreased.  However, the most interesting finding was all the flat ground crow hop throws resulted in greater shoulder internal rotation velocity and varus elbow torque compared to same weight pitches off the mound.

Biomechanics of weighted ball use

It’s becoming more and more common to include a variety of overload and underload (as low as 3 ounces) throws from a crow hop or from an all out sprint as part of weighted baseball programs.  Therein lies the unknown risk.  We know from Dr. Fleisig’s study, arm torque and forces increase as ball mass decreases.  We also know crow hop throws resulted in greater varus elbow torque than standard mound pitching.  We know from research that excessive elbow varus stress is a leading cause of elbow injuries.

What we don’t know is if greater stress results from throwing a baseball; be it overload or underload for extremely high velocity above those reached in a normal pitching situation while using a crow hop or full speed run and how much of that stress may be beneficial to create load tolerance versus how much stress is too much and will result in tissue breakdown.

Likewise, we know from one peer reviewed study (Reinold), shoulder external rotation range of motion has been shown to increase in a short amount of time as a result of weighted baseball use.  We also know shoulder external rotation increases of more than 8 degrees have been shown to result in a 1-Nm increase in elbow varus torque and excessive shoulder external rotation range of motion is a factor in SLAP tears and also increases elbow valgus stress.

What we don’t know was what caused the gain in shoulder external rotation in the Mike Reinold’s study.  Was it the use of heavier weighted baseballs; more overload resulting in more shoulder ER or was it the underload baseball; faster shoulder rotational velocities forcing greater ER? Nor do we know if those findings would be replicated in other studies or if ER gains would have been greater over a longer duration.

Mike Reinold did speculate the quick gain in ER came as a result of the supporting structures of the shoulder becoming looser, or more lax, thus creating anterior shoulder instability which in turn allowed for greater ER ranges of motion to be displayed.  If that is the case, that is an issue in and off  itself because anterior shoulder instability/joint laxity may contribute to shoulder injuries.

Kinetics of baseball pitching with implications about injury mechanisms 

Without a doubt, research exists showing weighted baseballs are able to be used safely and to increase velocity with conservative, structured programs.  However, those programs were implemented in a very controlled research setting.  Many programs are now being implemented across full college, high school and youth teams without the ability to properly control intensity, volume, recovery or even knowledge of shoulder/elbow biomechanics or injury mechanisms.  Likewise, baseball pitchers across a team will have many different shoulder and elbow adaptations as a result of their own throwing history.  Some of those adaptations may not warrant a weighted ball throwing program at all, yet some may benefit from it.  Finally, the potential results of a weighted baseball program, be it increased shoulder external rotation range of motion or even an increase in velocity may be more than that specific pitcher is physically prepared to handle at that point.

In conclusion, there is enough new research on weighted baseball use combined with what we already know about shoulder and elbow injury mechanisms and with what we still don’t know about high intensity throws at extreme velocities, extreme ball weights or over extended periods of time to urge caution when implementing a weighted baseball program.  They do work, but they are not without risk and there is still much to learn.