Underground Secrets of Weighted Ball Training from an MLB Pitching Guru

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Muscle irradiation is likely a new term for you, but with an old definition, and we’re going to make a case of why it is the most important feature in weighted ball training.  It started back in the early 1900s with Sir Charles Sherrington, a Hall of Famer in neurophysiology, who used the word irradiation to define a concept where a maximally contracted muscle propagates tension to nearby muscles, facilitating an increase in force output. 

Simply speaking, you experience muscle irradiation every time you use a firm grip on the handles of your Crossover Symmetry Bands. By giving the handles a hard squeeze when doing your Arm Care exercises, you increase activation of the forearm muscles, but also increase recruitment of your posterior rotator cuff through irradiation (ref). If, instead, you performed your arm care without a fist or open hand (e.g., wrist cuffs, finger grip, etc.,) your shoulder force production would be significantly less in the movement.

You can read more about irradiation and the importance of having a firm grip on a handle for arm care exercises here.

arm care grip

Irradiation & Weighted Balls

You may have seen or heard of weighted ball holds, and just like most throwing-related training, it’s a contentious topic. With “holds,” the throwing athlete grips a plyocare ball maximally, activating the hand muscles, forearm flexors, and pronator teres, and then performs a full speed throw. The caveat is that the athlete does not let go of the ball, which increases time under tension in deceleration.  

It’s like the relationship between gripping bands for the shoulder, but it’s bumped up 10x when you accelerate your arm over 3000 degrees per second through the air.  

This type of training has a huge decelerative effect on the posterior rotator cuff’s coordination and reflex speed. Research has shown that weighted ball holds are more effective than bands in enhancing throwing velocity and strength. However, when combined with other forms of irradiation exercise, such as bands, the effects are likely much greater than isolation of either training approach (ref). 

muscle irradiation

Weighted Ball Analysis 

Some industry leaders have confused the point of these drills through their communication that the biomechanics of the weighted ball holds differ from regular baseball pitching deliveries and should be avoided due to differences in arm speeds. However, we have one pitching specialist in-house who sees the world differently regarding irradiation training for the throwing arm and the need to be data-led in the approach.

Before weighted ball training became a fad, our current Director of Performance, Jordan Oseguera, has been at the forefront of weighted ball training and has had firsthand experience seeing the benefits of muscle irradiation. Jordan is a former collegiate and professional pitching coach, and before joining the ArmCare team, he held the title of Pitching Analyst with the Los Angeles Angels.  

When Jordan was in charge of velocity enhancement programs for the Los Angeles Angels, he took a strong research approach. He initiated a program built on evidence-based coaching, detailing everything from throwing volumes, velocities, physiologic changes in jump profiles, orthopedic changes in shoulder rotation, rotator cuff, and grip strength. Still, to this day, research has yet to document these data on professional athletes. 


Customizing Weighted Balls

While much of the research on weighted balls is focused on the range of motion of the throwing arm, nobody has really investigated what different ball weights do for building arm strength—that is, nobody outside of himself. Using dynamometry and range of motion measures, Jordan formed a better understanding of how ball weights create adaptations in throwing athletes for shoulder strength, fixing imbalances, and building a more durable, robust, and competitive player on the field.  

To start, he posed an important question. He wondered, “Does every player benefit the same from weighted ball programs?”  

It seems that many programs are focused on volume and intensity and ramp those up steadily in the hopes that something will stick when it comes to gaining velocity. People will regularly advertise how much better a specific player or group of players became from doing their weighted ball program, but in his experience, from utilizing more than a dozen different variations of weighted ball programs, it was only a tiny percentage that saw any lasting results from the weighted ball training that carried over in the same season, or multiple seasons after engaging in velocity enhancement training.  

He also wanted to know why some players got better from weighted ball training, why some players became worse, and why so many players got hurt either in the process or within one season of participation. One common theme that Jordan found in players who improved with weighted balls was that they balanced out their shoulder strength between internal rotation (front side of the shoulder) and external rotation (backside of the shoulder), intending to get a 1:1 strength ratio between them. 

The athletes who showed this trait gained the most velocity, but they also maintained velocity throughout an entire professional season and stayed healthy. Conversely, the players that created a greater muscular imbalance in the shoulder either lost velocity or, worse, ended up missing time due to injury.

Strength vs. Length

This observation led to an initial hypothesis that he and other staff members had— heavyweight balls will build internal rotator cuff strength, and lightweight balls will build external rotator cuff strength. However, this thought seems to be opposite from what everyone has been thinking in the industry, as a heavier implement thrown is expected to increase external rotation range of motion and greater posterior cuff strength. 

Jordan and the accompanied staff thought, for every action, there is an equal and opposite reaction.  

(Forces & Loads w/ Pitching)

If the arm gets into greater layback because of the heavier implement, it also puts more time on tension when heading into the acceleration portion of the throwing motion. Therefore, Jordan believed that more layback with heavier weight should increase internal rotator cuff strength to accomplish the movement because the internal rotator cuff must decelerate increased layback over a greater amount of time. 

The team’s thought process was just the opposite for light balls. Light balls in their mind would need to recruit more ER strength faster through concentric external rotation to the maximum layback. Then as it accelerates forward, the faster arm speed will increase the force required by the posterior rotator cuff in deceleration after ball release.    

I know it seems hard to fathom, as we think heavier = stronger. But higher accelerations equate to more force! And physics tells us that a system can only accelerate what it can decelerate. Hence, the training seemed to be consistent in muscular recruitment effort on both sides of the throwing shoulder. 

The Data Led Approach to Weighted Balls

These scientific concepts had to be further validated to influence player development models. Jordan analyzed players recently released from other teams and brought into the new Angels system. As part of the player evaluation process, shoulder strength was rigorously tested before entering the weighted ball program and during its progression.  

He was able to separate these athletes into three groups:

  1. Athletes that lacked internal rotator cuff strength 
  2. Athletes that lack external rotator cuff strength
  3. Athletes that lack external rotation range of motion

From this, programs were prescribed differently. For example, some performed holds with specific weights of balls, others only threw with certain ball weights, and some performed a combination of both holding and throwing specific ball weights. Injury days amongst the weighted ball groups drastically decreased, and development rates significantly increased with improved pitching performance and accuracy. 

Essentially, the program accurately targeted what players specifically needed related to strength balance or stabilizing range of motion. In addition, the process laid out was data-led, as coaches, sports scientists, and sports medicine staff members worked tirelessly to observe, analyze and communicate changes in range of motion and dynamometry (force data) to customize strength training programs for each individual. 

No longer were programs thrown out to see what sticks. Instead, the evidence points to the specificity of training. Unfortunately, however, this type of practice is virtually non-existent in today’s remote velocity enhancement programs, especially when coaches are not with their athletes guiding them through the velocity enrichment training.

Right Training at the Right Time

Ultimately, the most impactful finding Jordan and his team identified was that holding the weighted ball with max intensity through the throwing program did wonders for the throwing arm.

It was found that holds were one of the quickest strength builders for a player’s arm on both sides of the shoulder. Jordan mentioned that holds became a norm when a player would begin to experience strength loss in the middle of the season, and again, specifically weighted ball holds were prescribed to quickly remediate strength over a short period (and in professional baseball, performance improvement must be urgent.)

Despite a quick turnaround in strength, athletes on the hold program saw a significant decrease in injured list days, and players were able to improve performance because they recovered better, meaning less soreness, less microdamage from throwing, and could get loose much faster for games—an essential attribute for relievers especially.

baseball-assessmentGains with Data Led Training

In bringing the conversation full circle, muscle irradiation through weighted ball holds can profoundly affect throwing arm strength and throwing velocity. However, if you do not understand your athletes’ strength and range of motion, you cannot be specific enough in your programming. As a result, instead of improving, players may lower performance and increase their risk of injury. 

Fortunately, the baseball world does not have to guess anymore, and programs do not have to be cookie-cutter, one-size-fits-all, as in reality, one size fits none..  

With ArmCare.com, testing strength and range of motion have never been easier, and if you are on a remote velocity enhancement program, the app provides vital data to your remote coach. The app is like having an advanced sports science team dedicated to measuring, tracking, and ensuring your strength is perfectly balanced and that your range of motion is fully supported through improved strength. 

Now everyone can afford to be specific in their training and understand when to increase or decrease demands based on strength and range of motion changes.

Like gripping bands and performing holds to enhance muscle irradiation and shoulder activation, leave nothing on the table when it comes to competition. And if you are truly serious about your personal development and performance goals, you can unlock your full potential by using the Arm Care platform to help customize your training program.

If you have questions or comments about this blog, please feel free to email us at support@armcare.com


1. Fleisig GS, Diffendaffer AZ, Aune KT, Ivey B, Laughlin WA. Biomechanical analysis of weighted-ball exercises for baseball pitchers. Sports Health. 2017;9(3):210-215.

2. Garner S, Wicke J, Legreaux S, Chianciano B. Effects of deceleration-focused exercise strategies on shoulder range of motion and throwing velocity in baseball and softball athletes. Sport Biomech. Published online 2019.

3. Hoogenboom BJ, Schultz A, Dekkinga H, Huyser KL, Miller EM. Comparison of EMG Activation in Shoulder Girdle Musculature During Open-and Closed-Handed Grip External Rotation Elastic Resistance Exercise: An Observational Cohort Study. J Perform Heal Res. 2019;3(1):8-18.

4. Reinold MM, Macrina LC, Fleisig GS, Aune K, Andrews JR. Effect of a 6-week weighted baseball throwing program on pitch velocity, pitching arm biomechanics, passive range of motion, and injury rates. Sports Health. 2018;10(4):327-333.


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