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Are Weighted Baseball Velocity Programs Safe and Effective?

Weighted baseball velocity training programs continue to rise in popularity in baseball pitchers of all levels despite us not knowing why they may improve velocity, the long term effects on the body, or the most appropriate program to perform.

Unfortunately, it seems like the trend is towards more aggressive programs every day.

The following is a summary of the 2-year research project that we have just finished conducting at Champion PT and Performance.  Myself and Lenny Macrina teamed up with Dr. James Andrews and Dr. Glenn Fleisig of ASMI to design and conduct the first study to document the effects of a 6-week weighted baseball training program on pitching velocity, arm characteristics, and injury rates.

This may be the most important research project I have conducted to date.  Weighted baseball programs continue to rise in popularity while injury rates continue to soar in baseball.  This is completely unbiased scientific research that has been conducted with sound methodology.  I actually make a living rehabbing baseball injuries, so you can assure I am sincere when I say I want to decrease the amount of baseball injuries.

I simply want to advance the game of baseball.

The injuries we are seeing at the youth, high school, and collegiate level are heartbreaking.  Collegiate and minor league baseball pitchers are having their second Tommy John surgery, which have a low success rate.  When I first started working with baseball players, Tommy John surgeries were occurring in older baseball veterans, not youth.  The severity of injuries we are seeing are significant.  Never before in my 20 year career have I seen such an enormous amount of significant injuries in baseball players.

We have presented the findings of this study at numerous conferences so far, and the manuscript is currently submitted for publication in a scientific journal.  It is currently in the running for the 2018 Excellence in Research Award by the Sports Section of the APTA.

I’ve decided to publish an initial summary because I know many people are looking to start weighted baseball velocity programs this offseason.  The journal submission and publication process can takes months or even years to finally get the information published, and I did not want to delay any further.

 

We Still Don’t Know the Science Behind Weighted Baseball Velocity Programs

There has been a recent increased emphasis on pitch velocity within the amateur and professional levels of baseball.  According to Pitch/FX data, the average fastball velocity in MLB has gone up each year since tracking began in 2008, from 90.9 MPH to 93.2 MPH in 2017.  Previous studies have shown both a correlation between increased pitch velocity and increased elbow stress and elbow injury rates.   Thus, it is not surprising that injury rates continue to increase in a nearly linear fashion with increased average pitch velocity.

This emphasis on pitch velocity has resulted in the development of several velocity enhancement programs often marketed on the internet to baseball pitchers.  These have become increasingly popular with amateur baseball players looking to enhance their playing potential in the future.  One of the most popular forms of velocity enhancement programs utilize underweight and overweight weighted baseballs.

These programs have been theorized to enhance throwing mechanics, arm speed, and arm strength, resulting in enhanced pitch velocity, despite this not being validated scientifically.

Several studies have shown that weighted baseball training programs are effective at enhancing velocity, however, we still do not understand why or the long term effect of these programs.

Thus, the purpose of this study was to determine the effectiveness of a 6-week weighted baseball training program on enhancing pitch velocity while also quantifying the effects on biomechanical and physical characteristics of the shoulder and elbow.

 

How the Study Was Conducted

Youth baseball pitchers between the ages of 13 and 18 years old were recruited for the study.  To be clear, there was one 13 year old who turned 14 shortly after, who was in the control group and did not throw weighted balls.  The majority of subjects were ~16 years old.  We just reported how old they were in year, not the months, many were almost 16 years old.  If we were to have used the month, the mean would have been about 16 years old.  We choose to use high school aged pitchers because we wanted the study to look specifically at this population, as these are the baseball pitchers that are often looking to perform a weighted baseball program due to the aggressive amount of marketing online.

38 youth baseball pitchers with the mean age of 15 years old met these criteria and agreed to participate.  Subjects were randomly divided into a weighted baseball training group and a control group.

Upon enrollment in the study, baseline measurements of shoulder passive range of motion (PROM), elbow PROM, and shoulder strength were measured for each subject.  They then underwent baseline pitching performance testing while we recorded pitch velocity, elbow varus torque, and shoulder internal rotation velocity using the Motus M Sleeve.

After the baseline testing, both groups were allowed to participate in a supervised baseball offseason strength and conditioning program.  All subjects participated in a throwing program, but were not allowed to practice pitching off a mound.

The weighted baseball group performed a 6-week weighted ball throwing program in January and February of the baseball offseason.  Throwing was performed 3 times per week.   The 6-week program was developed to be similar, if not more conservative, than commonly marketed weighted baseball velocity programs available programs for baseball pitchers.  The volume, frequency, and weight of the balls used was less than many popular programs.

Over the course of the 6-week program, throws were performed from the knee, rocker, and run and gun positions.

weight baseball velocity program

Athletes were instructed to throw at 75%, 90%, and 100% of their full intensity depending on the week of the training program.  The intensity gradually ramped up over the course of the program.  Throws were performed from each position on each training session with a 2 ounce, 4 ounce, 6 ounce, 16 ounce, and 32 ounce ball.  One set with each weighted baseball was performed with the outlined repetitions below:

baseball weighted ball velocity program

 

Many of commented about throwing 2lb balls at full intensity run-and-gun.  Two things to realize about this:

  1. We choose to include this because this is being performed in our athletes
  2. Over the course of 6-weeks, there were 540 total throws, 18 of these were with 2lb balls at full intensity with run-and-guns.  This only represents 3% of the program.  We should not lose focus on the other 97%.

The control group performed an independent throwing program using standard regulation 5 oz baseballs and were not allowed to throw with any underload or overload balls.

All measurements were repeated after 6-weeks for both groups.  The subjects went on to pitch as normal through spring and summer baseball season.

Below is a summary of the major findings of the study.  The results were eye opening for me, personally.  I feel like we have discovered why weighted baseball training programs may work, and you could argue this isn’t for a good reason.

 

Pitch Velocity Increased, But Not in Everyone

After 6-weeks, the weighted baseball group showed a 3% increase of 2.2 MPH, from 67 MPH to 69 MPH.  The control group as a whole did not show a statistically significant increase in velocity.  However, we did note that:

  • 80% of the weighted baseball group improved velocity, and 12% showed a decrease in velocity
  • 67% of the control group also improved velocity, and 14% showed a decrease in velocity

Weighted baseball training on average does help increase velocity, however, not in everyone and some people actually go down.  Many people that did NOT perform the weighted ball program also increased velocity.

 

Shoulder External Rotation Increased, Likely in a Bad Way

There was a significant increase in almost 5 degrees of shoulder external rotation range of motion in the weighted ball group.

This rapid gain in external rotation occurred over a 6-week training program and did not occur in the control group.  I have previously published my results and reported that shoulder external rotation increased from pitching, however, reported only a 5 degree increase in external rotation in MLB pitchers over the course of an entire 8-month baseball season.

While we are not able to determine the exact cause of the increased pitch velocity, based on past studies it may be from the increased amount of shoulder external rotation observed following the weighted ball training program.  Previous biomechanical studies have shown that shoulder external rotation mobility correlates to both pitch velocity, as well as increased shoulder and elbow forces.

It is not known if such a rapid gain in external rotation following a 6-week weighted baseball training program is disadvantageous or challenges the static stabilizing structures of the shoulder.  However, previous research has shown that 78% of pitching injuries occur in athletes with greater amounts of shoulder rotational motion.

 

Weighted Baseballs Do Not Increase Shoulder Strength, They May Actually Inhibit Strength Gains

One of the more interesting findings to me was that external rotation rotator cuff strength actually went up in the control group and not the weighted baseball group.

During the 6-week period, subjects in both groups were allowed to perform a baseball-specific offseason strength and conditioning program.  Strengthening of the rotator cuff, particularly the external rotators, was a specific focus of this program and has been shown to increase pitching performance.  The control group showed a 13% increase in dominant shoulder ER strength, which we were thrilled about, while the training group showed no change.

It appears that not only do weighted ball training programs not help develop rotator cuff strength, as previously theorized, they may in fact inhibit strength gains and should be further investigated.

 

Weighted Baseballs Do Not Increase Arm Speed or Strength

There were no statistically significant differences in valgus stress or angular velocity of the arm in either group.

Arm strength, arm angular velocity, and arm stress were not statistically different following the training program.  This refutes the commonly reported theories that the effectiveness of weighted ball training programs can be attributed to the development of greater arm strength or arm speed.

 

24% of Pitchers Were Injured in the Weighted Ball Group

Potentially most important to the study was the finding that 24% of those in the training group either sustained an injury during the training program or in the following season, including two olecranon stress fractures, one partial ulnar collateral ligament injury, and one ulnar collateral ligament injury that surgical reconstruction was recommended.   This is the first study to document the injury rates associated with a 6-week weighted baseball training program.

No injuries were noted in the same time span within the control group.

It should also be noted again that the weighted ball program utilized in the current study is far less aggressive in regard to the weight of the balls used as well as the volume and frequency of throwing, in comparison to many commonly performed programs.

Of note, two players of the players that were injured both exhibited the greatest amount of increase in shoulder ER PROM of 10 and 11 degrees, making this appear to be related.

It is unclear how quickly athletes gain external rotation and whether it occurs at a safe rate, and future research should attempt to answer this question. While pitch velocity may be enhanced, injury risk may also be elevated when performing a weighted baseball training program.  Future studies should continue to assess the effects of different weighted ball training program on different age groups.  We still need to find the right dosage to maximize the effectiveness while reducing the injury risk.

 

Should You Perform a Weighted Baseball Velocity Program?

Based on the results of this study, it appears that weighted baseball training programs are effective at enhancing pitch velocity, but the question is, at what cost?

It is still unknown why velocity goes up.

Since arm strength and speed were not changed after the training program, and Dr. Glenn Fleisig of ASMI has shown no change in mechanics, the increased pitch velocity observed may be related to this gain in shoulder external rotation motion.

This is alarming to me, as I feel this may also at least partially explain the increase in injury rates.  This is not natural.

 

Who May Want to Perform a Weighted Baseball Program

Realistically throwing any baseball, even a standard 5 oz baseball, has an inherent amount of risk.  I, in fact, actually including weighted balls at times in both our rehabilitation programs and our Elite Pitching Performance Program at Champion.

However, we do them in a very controlled fashion with less volume, intensity, and weight.  We perform 4-7 oz throws with many of our athletes, however we have strict criteria to do so, that includes:

  • Full skeletal maturity
  • Efficient throwing mechanics
  • Baseline of strength and conditioning (usually a year or more of training)
  • Baseline of arm strength and dynamic stability (usually a year or more of training)

Essentially you need to be mature and developed enough to withstand the stress of these programs as well as justify the need to push the limits.  Weighted baseball programs should not be where you begin when developing pitching performance.  If you skip any of the above steps and jump straight to weighted baseballs, you are focusing on the frosting before you even baked the cake.

For you to use lighter balls, heavier balls, or aggressive run-and-gun drills, you need to be even more advanced.   Few will meet this criteria.

There are many people that are willing to accept the increased injury risk, especially older baseball pitchers that are trying to make it to the next level.  Weighted ball programs may be an effective option for you in this case, especially if you have maximized your throwing mechanics, strength and power development, and arm strength and dynamic stability.

Unfortunately, most baseball pitchers I meet have not done so.

 

Who Probably Should Not Perform Weighted Baseball Training

While some older baseball pitchers may be willing to accept this risk in an attempt to extend their career or take their game to the next level, it’s difficult to recommend most others perform an aggressive weighted baseball training program.

I’m not talking about warming up with a few light throws with a 6 oz ball, I’m talking about an aggressive several week- to month-long program with aggressive intensity using underload and overload balls.  These are the videos that are being sensationalized on Instagram so much.

Because it appears weighted baseball training programs are likely effective by pushing your physiological limits, they should be reserved for those that have maximized their potential and have again achieved our criteria of:

  • Full skeletal maturity
  • Efficient throwing mechanics
  • Baseline of strength and conditioning (usually a year or more of training)
  • Baseline of arm strength and dynamic stability (usually a year or more of training)

Basically, if you are still growing, have inefficient mechanics, haven’t been training in a weight room for a significant amount of time, and have never performed an arm care program, you’re not prepared to perform a weighted ball program.

Plus, I can show you several scientific studies that show different training programs and arm care programs can be just as effective, if not more, at gaining pitching velocity without the inherent risk.

We can’t just be jumping to the quick fix.

The problem I am seeing is that we are using weighted ball programs with everyone, regardless of age, mechanics, training level, and injury history.  This and the fact that we continue to try to push the limits and get more aggressive.  If a 16 oz ball works, than a 32 oz ball may be twice as effective.  This is simply unrealistic and unsafe to think this way.

More is not better.

I’ve talked about this before in my article, “Are Baseball Velocity Programs to Blame for the Rise in Pitching Injuries?”  We are overdosing.

I think the most scary trend I am seeing in baseball right now is the blind use of generic weighted baseball programs.  This includes people buying a random program on the internet, or worse, a baseball coach starting one generic program with all players on the team.

We’ve seen college teams with 4+ Tommy John surgeries with their players in one season, this was unheard of just a few short years ago.

We need to make the adjustment.

Weighted ball programs must be individualized, monitored, and implemented progressively.  If you can’t do this, you shouldn’t be using them.

Not everyone is appropriate for weighted baseball programs.  Many players that are currently performing a program probably shouldn’t be doing so, especially if they haven’t established a proper foundation of strength training, arm care, and physical maturity.  In fact, at Champion, we have found that stopping weighted ball programs in those that are not ready for this stress has resulted in an even bigger gain in velocity after we have focused on foundational strength training and arm care programs.

 

Call to Action to Everyone in Baseball

I need your help.

We need to get this information out there so we stop seeing so many injuries in baseball pitchers.  Baseball players, parents, coaches, and even rehabilitation and fitness specialists that work with baseball players need to understand the science behind weighted baseball training programs.

Yes, velocity goes up, but at what cost?

Based on this study, weighted baseball training does not change mechanics, increase arm speed, or increase arm strength.  In fact, they may inhibit strength gains.  They do stretch out your shoulder in a potentially disadvantageous way and lead to a 24% chance of injury.  1 in 4 players sustained an injury.  Are you willing to accept that risk?

Once you understand the science, you can make a more educated decision if using weighted baseballs is appropriate for you.  And if you do, how to safely and effectively choose to use these programs on the right players at the right times.

Please share this article with anyone that you feel shares our goal of advancing the game of baseball.  I feel that many baseball players, parents, and coaches simply are not aware of the science.   The more we can share the science, the better we can become.

We need to get better.  We need to accept the science.

 

 

Tunnel Vision: Making Every Pitch Look The Same

First and foremost – Velocity is STILL King, and for the foreseeable future, it will remain king. However, with the emphasis over the past ten years of throwing harder and harder, I feel that the art of pitching has been lost.

This article is for the reader that would like to get back to learning how to pitch and pitch effectively. One way to do this is to master the concept of “Effective Velocity.”

The Foundation of Effective Velocity

Before we get into the complex details, I want to start with the foundation of Effective Velocity, which is “pitch tunneling.” Pitch tunneling is rarely ever mentioned amongst other important aspects of training for pitchers, but every pitcher should instill this in their off-season training and put to use when they’re on the mound.

Pitching can be as simple or as complicated as you choose to make it.

It goes from as simple as the catcher setting up on the outside part of the plate, and you throwing the ball. Or, it can be as detailed as knowing which pitch to throw, in what situation and why.

Physically, the act of pitching is pretty complex. There are a lot of moving parts within the delivery that need to be moving in concert with each other. These parts all need to be synced in the correct order to ensure accuracy and maximum velocity (when necessary) of each pitch.

In the movie “Bull Durham,” Crash Davis (played by Kevin Costner), tells rookie pitcher, Nuke LaLoosh:

“Don’t think, it can only hurt the ball club.”

Baseball has traditionally struggled with its intellectuals, dismissing them as peculiar or eccentric. Think Barry Zito.

I want to make this clear – every pitcher, EVERY one of them, should be thinking along with their catcher and pitching coach, as to what pitch, what speed, and what location they should throw the ball.

Baseball has always been far more comfortable with its traditions; look at how long it took Major League Baseball to come around on instant replay! However, many MLB organizations are still in the pre-historic age when it comes to instituting new theories and philosophies – whether it is how they draft players, develop players, manage in-game situations, or their overall organizational philosophy.

In any competitive endeavor, the goal is to gain an advantage over your opponent, one that you can exploit. Pitchers have been trying to gain this vital inch on their adversary, the hitter, since the first pitch was thrown. The ultimate goal of any pitcher, when bringing the game down to pitch-by-pitch, is to miss the barrel.

Because of its complex nature, pitching has had it’s more than a fair share of theories. Most have fizzled out, proven just to be a flash in the pan. Think of how many gimmicky advertisements you see online or even on TV that guarantee this and that (Please do me a favor, run away as fast as you can from anyone that guarantee’s to add 10-15mph of velocity in 30 days – RUN).

However, one theory has taken MLB organizations by surprise with some traction on its research of more than 12,000 amateur at-bats, and more than 5 million pitches, a theory of design and level of success. The man that created this theory and the driving force behind its success is, Perry Husband.

Who is Perry Husband, you ask?

Perry Husband has more than ten years of research in the art of timing in the field of hitting, which has led to some amazing discoveries in what hitters can do, and more importantly, what they cannot do.

At CSU Northridge, he was co-captain of the NCAA Division II champs in 1984 and was named MVP of the College World Series. After two years in the pro ranks at the minor league level with the Minnesota Twins organization, he pursued a career as a PGA teaching apprentice in Southern California. After teaching golf for four years, Perry opened and operated The Baseball Academy for the better part of 17 years. He has written three books, “Downright Filthy Pitching,” “Downright Filthy Pitching: The Hitter’s Attention Theory,” and “Downright Filthy Pitching: The Science of Pitching Sequencing.”

What is Pitch Tunneling?

Husband’s theory on ‘Pitch Tunneling’ is centered on that every hitter must decide to swing no later than the first 20 ft. a pitch is in the air.

Business Insider Science produced an excellent video explaining this concept:

Now, I’m sure everyone reading this article will understand that pitchers throw fastballs, upwards of 60% throughout the duration of a game, therefore — the pitcher’s fastball trajectory will be the baseline that the hitter will read and react, in comparison with other pitches thrown.

To use this tidbit of information to our advantage, we need to train ourselves to have every pitch look the same for 20ft (or as close to this mark as possible). This will make it far more difficult for the hitter to get an early read on the trajectory, spin, velocity and location of the pitch.

Check out the video below of Yu Darvish and how all FIVE of his pitches are thrown consistently through the same tunnel, making him one of the most difficult pitchers to face in Major League Baseball.

 

According to Husband’s research, a normal strike zone, when extrapolated to 20 feet from a pitcher’s release point, measures 13 inches by 10 inches. This philosophy states that if a pitch passes through this tunnel of 13” x 10” not only will the pitch theoretically be a strike, but also be more difficult for the hitter to hit the pitch with 100% on time contact.

How to Improve Your Pitch Tunneling

So you may be asking, “how can I start training myself to throw all my pitches through the same tunnel?”

One of the easiest and the most cost-effective training methods is right in your pocket! The iPhone is a tremendous tool — it records video at 120 frames per second, allowing anyone to break down their mechanics and their pitches frame by frame!

I suggest recording from behind the pitcher’s head (preferably from above his throwing arm), also from behind the catcher (you can position the camera or iPhone in each batter’s box). Each angle provides valuable information to the pitcher when training; i.e. how each pitch will look to lefties and righties, its downward angle, and break of the pitch.

Now, I want to speak candidly here; this process will take time, especially with youth and high school-aged pitchers, because at this age level pitchers do not throw their off-speed pitches with the same intent and arm speed as their fastball (this is key!). Most youth/ high school aged pitchers will have their breaking balls “pop” out of their hand, making it easier for a hitter to recognize that an off-speed pitch is on the way. This is where arm speed is vital!

Success with this type of training is measured in building the neuro-pathways of the pitching delivery, throwing each pitch with the same intent, out of the same tunnel.

This will take hundreds, if not thousands of pitches thrown, over the course of tens of hours of training! It won’t come easy! But the success and results that will follow all of the hard work will make it well worth it.

By studying your pitching from the eye of the batter, you’ll be able to begin understanding how your pitch tunneling looks to the batter.

 

 

Why Building Muscle Mass Will Improve Your Pitching Velocity

Gaining pitching velocity is hard. I get it. It’s not easy, and it can feel overwhelming not knowing why you haven’t been making progress.  Here’s the thing: most high school and college pitchers don’t have the frame – and in particular, the muscle mass required to generate the elite velocity they are after.

Ready to invest 5 minutes? This article will open your eyes to the necessity of muscle mass – and strength – when it comes to maximizing your velocity development.

Why Building Muscle Mass Will Improve Your Pitching Velocity

A muscle’s size is directly proportional to its maximum contractile strength. Period. Excellent pitching velocity is a result of being able to transfer a large amount of force into the baseball as quickly as possible. To create the arm speed necessary to do this requires a coordinated set of mechanics that efficiently generates and transfers energy from the muscles of the lower body to the trunk, to the shoulder, elbow, wrist and ball. The more force (energy) that can be created, and perhaps more importantly -transferred, the harder you will throw.

Simple enough. What this means is that the most efficient mechanics in the world won’t lead to elite velocities if the pitcher in question is 120 pounds soaking wet!

While having poor mechanics that don’t efficiently transfer energy is a large reason many amateur pitchers don’t have impressive velocity, a bigger reason is that they simply aren’t very strong or powerful. In fact, pitchers tend to be some of the least physically prepared athletes out there, especially at the high school level and below.

 

What is Lean Body Mass?

I’m about to blow your mind.  Ready?  Lean body mass is a measure of how much non-fat mass an individual is carrying. In other words, if a 200 lb individual is 10% body fat, that means that his fat mass is ~20 lbs and his lean body mass is ~180 lbs.

Although lean body mass also includes other components such as bone, blood, organs, etc, these factors are more or less constant. Because directly measuring muscle mass requires very expensive equipment, lean body mass is actually a reasonably good way of measuring how much muscle somebody is carrying.

In other words, if you get bigger and it’s not all body fat? Congratulations, you just gained muscle mass.

But not all muscle mass is created equal – knowing where your personal deficiencies and limiting factors are helps determine the emphasis of your training and what parts of your body you will need to add the most mass.

The following chart shows how much lean mass players have in high school, college and professional baseball.

lean body mass in baseball
These massive jumps from high school to college ball, and college ball to the professional levels highlight how important lean body mass can be.

Some of these differences can be accounted for in terms of variance in height (taller people have more bone mass, for example, which counts towards lean body mass). However, there is a disproportionately large gap between levels, strongly suggesting that the differences are, in large part, due to muscle mass.

As you can see, these are just general correlations.

Big pitchers dont always throw hard, and small pitchers do sometimes throw exceptionally hard (though this is exceedingly rare, and “small” for a big leaguer is still about 170 or 180 lbs).

Exploiting This Information to Throw Gas

Realize that if you want to throw as hard as you are capable of, you’re going to have to build an appreciable amount of muscle mass and strength. Whatever your frame can hold, we want to come close to maxing that out.

We go into this in-depth in [eafl id=”1022″ name=”Building the 95 MPH Body” text=”Building the 95 MPH Body”], but for now here is a useful set of realistic guidelines we came up with to shoot for.

lean mass baseball guidelines

Find the row that corresponds to your height. For example, at 6’3”, I am about 215 lbs at 12% body fat. This puts me above the minimum target weight (~205 lbs at 12%), making it unlikely that my muscularity is a major limiting factor for velocity. Still, these tables predict as much as 12 lbs of lean body mass that could still be up for the taking.

If you need help calculating your lean body mass, you can download my free tool:

 

Do You Have What it Takes?

Building the 95 MPH BodyIf you’re a high school or college pitcher, and still 30 lbs away from the low end of these guidelines above, you have some work to do.

While things like height and arm length are out of your control, gaining as much lean body mass as your frame can hold is entirely within your control. Get as big and strong as you can while maintaining excellent movement quality. Shoot to be within the general weight range for MLB pitchers of your height.

It’s only one piece of the puzzle, but it’s one that many high school players are entirely overlooking.

For more information, check out our training program to build mass in baseball players, [eafl id=”1022″ name=”Building the 95 MPH Body” text=”Building the 95 MPH Body”].

 

 

Mass Equals Gas

Why Building Muscle Mass Will Improve Your Pitching Velocity

 

References

  1. Hoffman JR, Vazquez J, Pichardo N, Tenenbaum GJ. Anthropometric and 
performance comparisons in professional baseball players. J Strength Cond Res. 
2009;23(8):2173-8.
  2. Lehman G, Drinkwater EJ, and Behm DG. Correlation of throwing velocity to the results of lower body field tests in male college baseball players. J Strength Cond Res. 2013;27(4):902-8.
  3. Mangine GT, Hoffman JR, Fragala MS, Vazquez J, Krause MC, Gillett J et al. Effect of age on anthropometric and physical performance 
measures in professional baseball players. J Strength Cond Res. 2013;27(2):375-81.
  4. Mangine GT, Hoffman JR, Vazquez J, Pichardo N, Fragala MS, Stout JR. Predictors of Fielding Performance in Professional Baseball Players. Int J 
Sports Physiol Perform. 2013;8(5), 510-6.
  5. Nuttgen HG. Development of muscular strength and endurance. In 
Neuromuscular mechanisms for therapeutic and conditioning exercise, ed. pp.97-118. 
Baltimore: University Park Press. 
1976.
  6. Spaniol FJ. Baseball Athletic Test: A Baseball-Specific Test Battery. 
Strength Cond J. 2003;(31):479-491.
    Young A, Stokes M, Walker ICR. and Newham D. The relationship 
between quadriceps size and strength in normal young adults. Ann. rheum. 1981;40(619).