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  • Writer's pictureLennon Richards

Introducing: Documenting the 8-Week Use of Underload Balls with Youth Throwers


For the last 8 weeks, I have been running a throwing clinic with youth athletes alongside Guelph Minor Baseball. This group of 8-12 year-olds are house-league caliber players - house-league is what we call rec ball here in Canada.


Going into the clinic I wanted to test out the use of underload balls with youth throwers. Based on the research and findings of Glenn S. Fleisig and his article Kinematics and Kinetics of Youth Baseball Pitching with Standard and Lightweight Balls I knew there was merit to having kids use a lighter ball to not only reduce their risk of injury but also instill better motor patterns for their long-term development.


You can find the copy of Fleisig's study here. Basically, he found that when using a lighter ball participants velocity increased and elbow varus torque decreased. These findings suggest that a reduction in ball weight could lead to fewer arm injuries because of the reduced stress put on the arm.



"Of particular note was decreased elbow varus torque produced with the 4 oz baseball. This parameter is important because of the alarming increase in the number of ulnar collateral ligament reconstructions (‘Tommy John surgeries’) in adolescent pitchers (Petty et al., 2004) and the fact that elbow varus torque has been described as the load that stresses the UCL (Fleisig et al., 1995; Sabick et al., 2004)."


The researchers hypothesized that because of this decrease stress on the elbow and increase in velocity that the mechanics of the pitchers became more efficient when using the lighter ball - setting them up for better movement patterns long-term.


"Another potential benefit of the lightweight ball is helping the young pitcher develop arm speed while still maintaining good arm mechanics."

Lastly, when asked subjective questions about the two ball weights, participants responded more positively to the 4oz weight. 68% stated they preferred the feel of the 4oz ball compared to the 5oz. 65% felt they threw the 4oz ball faster - and 55% felt they were more accurate with the 4oz.



Most other major sports use a lighter ball at the younger ages: Football, Basketball, and even Hockey have adopted lighter implements for their youth leagues.


I have been thinking about this topic for some time:


Why do an MLB pitcher and an 8-year-old use the same ball?


Think about it like this. For a 200 pound man, a 5-ounce ball is .00156% of his body weight. The same ball is .00520% of body weight for a 60-pound child. That means that the 5-ounce ball for the youth thrower is equivalent to the 200-pound man throwing a ball over 1 1/2 pounds.


If we take the same approach to calculating the body weight percentage of a 3oz and 4oz ball we find that they become closer to the percentage that the 200 pound man uses.


.01875lbs (3oz) / 60 pounds = .003125% body weight


.025lbs (4oz) / 60 pounds = .004166% body weight


Both balls are still "heavier" than what the 200-pound man uses - but significantly lighter than the 5oz. A 40% decrease in body weight percentage for the 60-pound child going from the 5oz ball to a 3oz ball - to be precise.


Knowing this I wanted to test the use of underload balls with youth and put this research into practice and see some of the effects on participants velocity, mechanics and accuracy when using a lighter ball.


The first week of the clinic I had all players throw 5oz and 3oz balls and record their velocity. As you would expect most threw the 3oz harder. On average kids threw the 3oz ball 3.25mph harder (n=42). With the hardest thrown 3oz ball at 59, and the hardest thrown 5oz at 55. Throws were recorded using a Pocket Radar and performed using a shuffle throw.


Over the next couple of weeks at the clinic, we used plyocare balls for all throwing drill work. We used 5.5oz, 5oz, 4oz, and 3.5oz plyos. Each week players would long-toss with regulation baseballs and then perform drill work with plyocare balls - the majority of the drill work was done with underload balls, either 4oz or 3.5oz plyos. Every player performed a variety of drills like quick picks, rocker throws, step-backs - etc.


Just by observing the kids during their drill work it is obvious that they move better with the lighter balls. Most kids are able to get more external rotation, with the weakest kids showing fewer signs of "pushing" the ball.


This is by no means meant to be a scientific study - I simply wanted to see the implications and applications of the research for myself. And thus far I have been pleasantly surprised by how well the underload balls are used by the players. I plan to continue to explore me with this and hope that there is new research being done in this field.


There still needs to be more research and testing done with what a lighter ball may mean for fielding, catching and hitting - but in terms of throwing the benefits are clear.


In the next couple of weeks I will share the data from retesting during Weeks 5 and Weeks 8 of the clinic - and go more in depth about how I used underload plyo balls and what I observed.


I will end with this - based on the research already presented, my own application, and some common sense - there is no reason that younger baseball players should not be using a lighter ball for throwing.






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