Overload Group

Is Long Toss with Weighted Baseballs Less Stressful on the Arm?

This article was written by Kyle Boddy, who is the head of the Research and Development department of Driveline Baseball. Kyle designed the study while Michael O’Connell helped collect the data.

This is the third of many research themed blog posts where we take a closer look at some of our in-house research. The objective is to share as much of the data as possible with you in order to encourage an earnest discussion amongst coaches on how to train healthier pitchers.

Weighted baseball and long toss use are popular in both amateur baseball and professional baseball organizations. Despite claims from coaches that weighted baseballs are not used in MLB, Driveline Baseball has served as consultants to multiple MLB organizations to help them roll out comprehensive weighted implement training programs. Furthermore, though many MLB teams employ a restrictive 90-120-150 foot throwing program, an increasingly larger number of MLB organizations participate in so-called “extreme” long toss as their de facto throwing program.

However, we’re here to take a look something beyond both of those programs: What if you long tossed with overload and underload weighted baseballs?

Study Design


We selected six (6) amateur baseball players – four of them with college experience, two with high school experience. All were currently training to throw as part of either a pitching preparation program or a position player throwing program. We instructed the athletes to warm-up in the same manner athletes in our programs prepare for a bullpen or long toss, including soft tissue work, Jaeger Sports J-Band programs, dynamic mobility drills, PlyoCare throwing patterning, and so forth. We had them throw regulation weight (5 oz) baseballs to tolerance until they were ready to start the data collection phase.

At this point we fitted the athlete with a MotusTHROW sensor (Motus Global) and form-fitting sleeve and had them make 1-3 test throws to ensure data was being accurately collected. We used the MotusTHROW sensor for this study because of its ease of use and quick results. At SaberSeminar 2016, Mike Reinold presented some interesting data from his ongoing weighted ball study, stating that the newest MotusTHROW sensor had intraclass correlation (ICC) values of 0.99 for valgus/varus torque vs. stress (newton-meters) between the American Sports Medicine Institute’s lab in Birmingham, AL and the MotusTHROW sensor itself. When I spoke to Dr. Glenn Fleisig (head of ASMI biomechanics research), he confirmed these values over the phone. Therefore, we can be pretty sure that the MotusTHROW sensor gives very close readings to the elbow torque values that ASMI publishes.

A few research articles worth looking into at this point:

  • Biomechanical comparison of baseball pitching and long-toss: implications for training and rehabilitation (Fleisig et al JOSPT 2011, web)
  • Computing muscle, ligament, and osseous contributions to the elbow varus moment during baseball pitching (Buffi et al Ann Biomed Eng 2015, web)
  • Correlation of Shoulder and Elbow Kinetics With Ball Velocity in Collegiate Baseball Pitchers  (Post et al J Athl Train 2015, web)
  • The Effect of Pitching Biomechanics on the Upper Extremity in Youth and Adolescent Baseball Pitchers (Davis et al ASJM 2009, web)
  • Baseball Pitching Biomechanics in Relation to Injury Risk and Performance (Fortenbaugh et al Sports Health 2009, web)

The gist of the above studies (and others widely cited) is that it is generally accepted that reducing elbow torque while improving ball velocity through optimizing kinematic (mechanical) parameters is a good goal. In other words, equivalent ball velocity at lower torques is a very desirable thing per most published biomechanical research on the pitching delivery. Dr. James Buffi’s research goes into a bit more detail on why simple elbow torque is not sufficient enough to predict injury with any reasonable error band, and while it is the position of Driveline Baseball to agree with this approach, measuring elbow torque accurately using the MotusTHROW sensor may provide Driveline Baseball and other coaches another set of data to analyze in the future.

Execution of Study

Each pitcher executed 20 high-arc long distance throws, simulated into the top of our throwing cage at about a 30-35 degree angle. Previous studies on long toss (Fleisig et al JOSPT 2011) may not have properly computed cosine angle error; to combat this, Driveline Baseball placed the radar gun (Stalker Sport 2, Plano, TX) directly in the line of the throwing vector to achieve the most accurate and precise results.

Cosine Effect

An example of cosine measurement error

Since our radar gun was elevated and placed directly in the “line of sight” of the baseball being thrown, no significant cosine angle error should be expected.

The grouping of the throws broke down as such:

  • 5 throws with regulation baseball (5 oz)
  • 5 throws with overload baseball (6 oz)
  • 5 throws with regulation baseball (5 oz)
  • 5 throws with underload baseball (4 oz)

PITCHER 4 IN OUR DATA THREW ONLY FOUR (4) REGULATION BASEBALLS IN THE THIRD PHASE. It is not expected this changed the values significantly at all.

This follows our standard regular-overload-regular-underload pattern that we’ve tested over the years.

For each throw, we recorded:

  • Ball velocity (MPH) – Stalker Sport 2
  • Elbow stress (newton-meters) – MotusTHROW
  • Arm speed (RPM) – MotusTHROW

We then averaged the velocities and stresses and computed the differences.

Hypothesis: Going into the study, we expected the overload throws to have a lower amount of elbow torque with lower velocity, and the underload throws to have a higher amount of elbow torque with higher velocity, all compared to the baseline regulation baseball throws.

Data Analysis / Results

All six pitchers completed the study with no pain, soreness, or missed readings with the MotusTHROW or the Stalker Sport 2 radar gun. Their results in chart form:

Overload Phase

Overload Phase

As expected, our Overload Phase had lower stresses recorded on the arm, and either reduced velocity or insignificantly higher velocities. What was surprising was the magnitude of the stress reduction with a 6 oz overload ball compared to a 5 oz regulation baseball!

Underload Phase

Underload Phase

Completely counter-intuitively, the Underload Phase had very large reductions in stress at the elbow, while the velocity changes were about what we expected.

Not a single pitcher showed increased stress when long tossing overload OR underload baseballs!Click To Tweet

This finding was shocking. Given the ICCs and sensitivity of the MotusTHROW compared to ASMI’s lab equipment, while we can’t definitively say that overload/underload weighted ball long toss is SAFER on the arm, the data absolutely does not support that weighted baseball throwing is MORE stressful on the arm. Further research will have to be done on these modalities using both the MotusTHROW and other equipment.

Improvements to this study may include:

  • A larger sample size of participants (larger n)
  • A more elite group of pitchers and throwers (professionals)
  • A larger sample of throws (more than 20)
  • Randomization of overload/underload throwing patterns

As always in these Primary Research articles, we’ve open sourced all of the data – please take a look at it and write your own articles based on the data!


Eugene Bleecker

That is pretty amazing! The overload results are what we would have expected as well but the underload results are very interesting. So my initial questions are:

Were the players throwing with max effort on the throws?

Was it a shuffle, pull down, crow hop?

While sitting here with our staff discussing it these were some initial questions. Also, sometimes when throwing an underload or overload ball there are mentality changes with the player executing the throws. Knowing they are throwing a heavier ball an athlete will sometimes prevent the arm from completely externally rotating. They do this in order to compensate for the weight because they don’t trust the throw. So, does it really decreases stress or is it because they aren’t throwing with the same effort/exact mechanical patterns they would use to throw a 5oz ball. Were these guys really letting it all hang out to provide completely accurate results?

How is it possible that a higher weight AND a lower weight both reduce stress?

Based on previous studies it is our understanding that throwing off a mound increases elbow varus torque and stress placed on the arm. If your results are accurate and throwing with overload and underload implements actually reduces stress placed on the elbow, wouldn’t it make sense to do more weighted ball work off of an actual mound. Won’t that translate results to the mound faster? Next study off of a mound por favor? We have the motus also. I will do the same testing here but I’d love to compare results. I have 2 coaches here that can still run it up to 92 but they are done so they could care less if they blow it out for the betterment of the community haha. We actually discussed doing a long toss program with weighted balls last year but with lack of data didn’t want to compromise anyone.

Kyle Boddy

It was near max-effort throws. They were indoors on an upwards angle so it’s tough to tell them to really air it out.

Shuffle/pull-down type throw with upwards angle.

Mentality could be a thing but velocities went up across the board especially for underload balls. So they were definitely giving it near-equivalent effort at the minimum.

Mound work is on the docket for sure!

Gary Young

Appreciate you letting us in on all this Kyle. Very helpful,

Kyle Boddy

Very welcome – thanks for reading!

Eugene Bleecker

I second that on the thanks for sharing. After I posted we discussed it more and realized that the output was the same due to the increased velocity readings with the lighter ball so effort must have been close to the same.

What are your initial thoughts on why there was a decrease in stress with both over and under? Is it just that we are so conditioned to the 5oz ball that we get into the protection mode with overload and because underload is lighter there is just less stress because of lower weight? I wonder what the results would be as you decreased the weight and at what weight would the stress levels spike.

Also, if you had a player with EXTREME external rotation resulting in poor acceleration what would your approach be? Assume much has been done and there have been results but we need to be more outside the box.

Kyle Boddy

Not sure about the theories. At this point I want to collect as much actionable data. In my opinion there are way too many untested theories out there, too many hours of pitching coaches talking about stuff they have zero proof of, and not enough people pulling together, collecting data, and answering the tough questions in an honest way. That’s what Driveline Baseball stands for now and I’m excited to continue to crank out tons of open data for everyone to take a look at and challenge everyone to pitch in as well!

Can You Reduce Pitching Elbow Stress Using a Sleeve? - Driveline Baseball

[…] Update 8/25/2016: Since the publication of this article we have found a high intraclass correlation (ICC) of 0.99 for valgus/varus torque vs. stress(newton-meters) measurement of the Motus. Specifically between the American Sports Medicine Institute’s (ASMI) lab in Birmingham, AL and the MotusTHROW sensor. We can therefore suggest that the MotusTHROW sensor gives very close readings to the elbow torque values that ASMI publishes. You can read more about this finding here […]

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