In a previous blog post, I introduced this topic. In this post, I plan to go in more detail on how I implemented underload balls in a youth throwing clinic, why I did so, and my findings.
I would suggest reading my previous blog post on this topic before jumping into this one. You can find it here.
Lets recap why I wanted to implement underload balls into this 8-week clinic with Guelph Minor Baseball.
A couple months back I found a study done by Glenn S. Fleisig entitled Kinematics and Kinetics of Youth Baseball Pitching with Standard and Lightweight Balls. This article confirmed a theory I have had for a long time - that youth baseball players should probably be throwing a lighter ball.
The study showed reduced stress on the elbow and increased throwing velocity when using the underload ball, a 4oz ball to be precise. This is pretty easy to understand - a regulation 5oz ball for an 11-year-old is much heavier for them than the same ball being used by an MLB pitcher.
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 look at underload balls, we can see they get closer to the body weight percentage that an adult experiences.
.01875lbs (3oz) / 60 pounds = .003125% body weight
.025lbs (4oz) / 60 pounds = .004166% body weight
The study also suggests that the use of underload balls could help a youth pitcher develop more arm speed while maintaining good mechanics.
Now in terms of how I went about implementing underload balls.
In week 1 of the clinic, we did some initial baseline testing. After long tossing with regulation baseballs each player threw 5oz and 3oz balls with a shuffle throw and I recorded the results.
Aside: the reason I chose to focus on testing 3oz was that it is closer to the body weight percentage that a 200lb man would utilize. Simply, a one-ounce difference in ball weight is not that significant.
As expected most players threw the 3oz faster than the 5oz. On average kids threw the 3oz ball 3.25mph harder (n=42). The hardest throws were 55mph (5oz) and 59mph (3oz).
Over the next three weeks, we used underload plyo balls for drill work. During this drill work, I noticed a couple things:
1. The kids liked using the lighter balls.
The fact that they were able to throw the ball harder and hear a louder thump off the mats created some positive feedback.
2. Increased intent
Building off the previous point, the kids seemed encouraged by the lighter weight. When throwing the 5oz balls they were more apprehensive to throw hard - put the 3oz ball in their hands and it became easier to get them to dial up their intensity.
3. Ball weight/size fits their hand size better
The underload plyos fit in their hands much better. Most players had to use their whole hand to grip a regulation baseball, but with a plyo ball, they were able to remove a finger or two and get closer to a prototypical fastball grip.
This was mostly due to the plyo balls being squishy. They were able to contort the ball to fit their hand better without putting much thought into it.
The underload weight also seemed to loosen their grip on the ball. When using a regular ball many had the ball deep into their hands and a lot of tension/flexion in their forearm.
This observation leads me to question if we should not only reduce the ball weight for younger ages but also reduce the ball size. This is where legitimate research would have to be done and see if there are noticeable kinematic/kinetic differences based on ball size.
Could the difference in grip and forearm tension with the 5oz be leading to increased stress on the elbow?
Week 5 Retesting
In week 1 the average kid threw the 3oz ball 3.25mph harder than the 5oz - this average increased to 4.21 in week 5 (n=41). The average 5oz throw was 45.6 up from 42.5, 3oz increased to 49.81 from 45.75.
This shows us that kids improved more with the 3oz than the 5oz. Almost an entire mph more. This could possibly because of increased familiarity with an underload ball from performing drill work almost exclusively with underload.
But I would not jump so far to say that it is entirely because of this. Building off the hypothesis of Fleisig - I believe increased mechanical efficiency is also to play for this jump in 3oz velo.
In other words: thanks to the prolonged use of a more appropriate ball weight kids threw harder - and they gained more velocity on their 3oz throw than their 5oz throw because their movements are more efficient with the lighter weight.
Week 8 Retesting
The average 3oz ball was thrown 3.89mph harder than the 5oz - this is a decrease from week 5 - but an overall increase from week 1. The average 5oz throw was recorded at 47.27 while the 3oz was recorded at 51.17. This is an increase of 1.67, and 1.35mph respectively. N = 41.
This tells us that my observations from the week 5 data may have been off. This time around we are not encountered by a larger increase to the 3oz. We will have to compare data from week 1 to week 8 and see if the same correlation exists.
From week 1 to week 8 the average kid increased their 5oz throw by 4.77, while also increasing their 3oz throw by 5.41.
If we exclude player 1 - who was the only kid to show significant regression from weeks 1 to 8 - the numbers are: 5.29 for 5oz and 5.92 for 3oz.
Again, we see the correlation I noted with week 5's data - a bigger improvement in 3oz velocity compared to 5oz velocity. A difference of 0.64mph or 0.62 if we exclude player 1. While it is entirely possible this is simply from increased familiarity with the underload ball - I would argue that their mechanical efficiency was increased while using the 3oz ball which netted them more of a velocity increase week to week than when using the 5oz ball.
More numbers:
The hardest thrown 5oz ball in week 8 was 61mph compared to in week 1 of 55. The hardest 3oz in week 8 was 67 while week 1 was 59.
Both 3oz records were held by the same athlete - that is a pretty nuts increase - and a good player to look at for how this whole experiment of underload training went.
Athlete 27 came in at week 1 with 5oz throws of 54 and 53mph, and 3oz throws of 59 58. In week 5 he threw the 5oz 59mph twice, and the 3oz 64mph and 63mph. And in week 8 he threw the 5oz 60, 58, 61, 59mph - while throwing the 3oz 62,67,61 and 64mph.
Data Limitations
45 total players participated in this clinic - 9 players ended up missing a day of testing throughout this process - some missing multiple testing days. Because of this inconsistency in A. the number of players participating and B. the quality of player missing could skew the data in on direction or another.
The other limitation to the data collected would be the number of throws recorded due to time. In weeks 1 and 5 only 2 throws of each ball weight were recorded - in week 8 some players (a little less than half) had 4 of each recorded.
"Findings"
I must say I am pretty surprised at the development of some of these players over an 8 week period. We cannot take much from just this one case study. However, I think it is safe to say that creating an environment for kids to trust themselves, albeit let themselves loose - enough to throw with max intent is key.
If there is anything I learned from this, it is that underload balls can help to facilitate that environment for younger players by giving them increased confidence and possibly decrease legitimate physical limitations because of ball weight.
Concluding Thoughts + Questions
This has been a fun topic to write about. If there is anything I have accomplished with this, I want to raise awareness and possibly add a bit of validity to the idea that we should be using underload balls with our youth players.
The full google spreadsheet with the data is available here - if there is anything in the data I overlooked please do not hesitate to let me know.
After writing about this topic and working with underload balls at the youth level first hand, a couple of questions have crossed my mind:
1. should we not only decrease the ball weight - but also decrease the ball size?
2. At what age are kids physically able to handle the 5oz ball?
3. Should even physically advanced 10-12 year be using an underload ball? Is there a good way to test their physical readiness/lack off for a 5oz ball?
Over the next couple of years, I hope to tackle these questions and find potential answers.
I am always happy to answer questions and discuss this topic with anyone and can be reached through email: lennon@richardsbaseball.com or via Twitter: @RichardsBSB, or Instagram: @Richardsbaseball