Tagged: throwing velocity

You need stronger legs to Pitch than we thought!!!

We all know that you need strong legs to pitch but a new study, which isn’t even published yet, is telling us that they need to be stronger than we originally thought.

Broxton needs his tree trunk legs to handle his big frame and produce his big fastball

Jonathan Broxton, now with the Royals, needs his big tree trunk legs to handle his big frame (6’4″ – 295lbs) and produce his big fastball.

As always I will break down the geeky science then provide you with some practical applications that you can use to improve your game.

The study:

Lower-Extremtiy Ground Reaction Forces in Collegiate Baseball Pitchers

Authors: John A. Guido, Jr and Sherry L. Werner.

Before we get into the nitty-gritty details of this study let’s do background work.

Ground reaction forces are basically the amount of force that is exerted back to your body from the ground which is equal and opposite to the amount of force that you put into the ground.  During a jump you push your feet into the ground and this force is redirected back up allowing you to get off the ground – the more force you put into the ground the higher you will jump.  But if you want to be able to jump higher than you can now you need to get stronger so that you can put more force into the ground.

Ground reaction forces are measured in different directions.  If you jump straight up you will be exerting vertical ground reaction forces.  If you are running the majority of the forces being produced will be horizontal and when you need to slow down you will need to apply whats known as anterior or braking forces.

What this study did:  This current study used 14 college baseball pitchers who were on average 175lbs and 5’10” and threw 78mph.  They had each pitcher throw 10 fastball strikes from a mound with a force plate built into it in order to measure the amount of force being put into the ground.  They also filmed each pitcher during their deliver to figure out exactly when these forces where being produced during their delivery.

This current study did not measure the forces being produced by the back leg like the one that MacWillams performed back in 1998. If you want to learn more about the MacWillams study which concluded that more force being produced by the back leg translated into more throwing velocity check out this article that I wrote back 2010.

https://lehmansbaseball.wordpress.com/2010/12/20/ground-reaction-forces-of-pitching/

What they found out: The main finding of this study were that the ground reaction forces in an anterior or braking direction where approximately 245% of body weight whereas the MacWillams study only reported these forces to be equal to about 72% of body weight!!

This is a huge difference.  The reason for this discrepancy might be that the pitchers in the current study threw harder and where bigger than in MacWillams study which did not report either.  One of the main reasons the authors decided to perform this study was that there was only one previous study which measured in baseball players and it is a good thing they did.

Gagne’s front leg is about the apply the brakes!!!

The anterior or braking forces are very important to throwing velocity from a pitching mechanics point of view because it stops the forward momentum created by the back leg allowing the energy to be transferred from a strong and stable position.  If you land and your front leg continues to move forward you won’t be able to transfer energy as efficiently and what’s known as an energy leak will occur.

Energy leaks are bad – you want to transfer as much energy as possible from the lower body to the upper body as possible in order to throw gas.

The authors did state in the abstract that “a correlation between braking force and ball velocity was evident.”

Here is an another article I wrote discussing the importance of front leg strength.  Basically it states that pitchers who landed with their front leg bent/flexed and continued to bend/flex throughout the rest of the delivery didn’t throw as hard as those pitchers who had the strength to land with a bent/flexed leg and then straighten/extend this front leg throughout the pitching motion.

https://lehmansbaseball.wordpress.com/2011/02/28/the-stride-leg/

This video of Justin Verlander demonstrates his great front leg action allowing him to efficiently transfer energy and strike out hitters.

In regards to vertical ground reaction forces this current study reported forces of approximately 200% of body weight while the MacWillams study reported only 150%.  The vertical forces are important because we need to transfer this energy up the kinetic chain.

What you can do: The authors of this study were nice enough to provide an exercise which they thought might be beneficial to help players get strong enough to handle the forces needed to achieve higher throwing velocity.

The exercise they suggest is basically a lunge where you start standing tall and balanced on one leg.  You then fall forward and catch yourself with the opposite leg and immediately try to push yourself back up the starting position.  The way they describe this exercise is much like a plyometric exercise where you try to minimize the amount of time your front foot stays on the ground.  The speed and velocity that you push yourself back up is very important and when that begins to slow down you stop.

However this exercise can also be done with weights which will allow to work on absorbing more force but you won’t be able to push yourself back up as explosively.  Both have their place on what is known as the strength velocity curve.  Ideally you focus on the weighted version during the off-season in the weight room and then use that strength you’ve built up to make the plyometric version even more explosive.

Stick to reps between 4-10 per side with both the plyometric and weighted version for 3-5 sets.  Even though you always land on the same leg when you throw it is very important to do the same amount of reps for both legs.  In fact it might even be a better idea to do more reps on the leg you don’t land on (right leg or righties) because of the fact that you do so much landing on the other leg every time you pitch or throw.

Where is an example of basic forward lunge.

Graeme Lehman, MSc, CSCS

Jogging Kills Your Power – Studies You Should Know About

Baseball is a game of POWER, power pitchers and power hitters dominate the game and get the attention of coaches, scouts and fans.  Every play in baseball lasts only a few seconds and the two main actions, swing and throwing, requires less than a second.  Despite these facts endurance training has been emphasised for years which is especially true for pitchers who have been made to run countless about of poles.

The big question is why would you do endurance training if your sport requires nothing but short bursts of power?

The warning should be that running on the warning track for too long will kill your power outputWarning – running on the warning track for too long will

Kill your Power Output!!!!

Enter today’s study that you should know about:

NONCOMPATIBILITY OF POWER AND ENDURANCE TRAINING AMONG COLLEGE BASEBALL PLAYERS

Authors: Matthew R. Rhea,  Jeff R. Oliverson, Greg Marshall, Mark D. Peterson, Joseph G. Kenn and Fernado Naclerio Ayllo’n.

What did they want to find out?

They wanted to find how lower body power in baseball player was affected throughout a season with either endurance or sprint based metabolic/conditioning work.

Lower body power is a great thing to have in baseball and pretty much any other sport in the world.  In another study the Texas Rangers organization tested all of their players from “A” ball all the way up to the Big Leaguers and showed that lower body power levels climbed higher and higher with each level of competition.  To find out other differences between the minor league and the big league players check out the rest of the article here.

https://lehmansbaseball.wordpress.com/2010/12/20/do-you-have-big-league-skills/

How did they find out?

They split 16 college baseball players into two groups.  While both groups performed the exact same in-season weight training program 2-3 days per week they differed in how they performed their conditioning.  One group performed sprints (10-30 reps, 15-60 meters, 10-60 sec rest) while the other group performed approximately 45 minutes of jogging or cycle 3 days per week.

Lower body power was measured before and after the season.   To measure lower body power these authors used a TENDO FiTROdyne  Powerlizer.  This device measures jump height but also takes into consideration body weight.

Body weight is an important component of power because if two guys can both jump 24 inches off the ground the guy who weighs more needs to produce more power to get 24 inches off the ground.

At 307lbs with a 35 1/2 inch vertical Ndamukong Suh of the Detroit Lions is a very very powerful athlete

At 307lbs with a 35 1/2 inch vertical Ndamukong Suh of the Detroit Lions is a very powerful athlete

Why Use the Vertical Jump?

The vertical jump is standard test for lower body power in the world of exercise physiology.  While a baseball player’s ability to jump vertically is not stressed it does still indicate a level of athleticism and power.  The study that I performed found that vertical jump height does not significantly correlate with throwing velocity but I would say it doesn’t hurt to have a guy that can jump high.  If nothing else it indicates a good strength to weight ratio.

If you want to measure your own power get a calculator and find out how high your vertical jump is in centimeters (your vertical in inches/2.54) and how heavy you are in kilograms (your weight in pounds X 2.2) and follow the equations below for your peak and average power in watts with the Harman Formula.

Peak power (W) = (61.9 x jump height (cm)) + (36.0 x body mass (kg)) + 1,822

If you want to compare yourself to the pro ball players in this other study that I mentioned here are their numbers.  The big league players in the Rangers organization had average verticals of nearly 72 cm and weighed 101.2 kg which gave them a peak power of 11542 watts.  Compare this to the “A” ball players who were 92kg with verticals of 70 cm which produced peak power of 10823 watts.

For the record Ndamukong Suh’s peak power is 12427 watts!!!  Someone who weighs 100kg (220lbs) would need to jump a freaky 45 inches to produce as much power.

What did they find out?

From the beginning to the end of the season the group that performed endurance training saw their power levels drop an average of 39.5 watts.  This isn’t a huge drop and it is understandable how at the end of the season your body might not be what is was at the start of the season.   However the sprint group saw an average increase of 210.6 watts!!!

The results really come down to a principle in exercise physiology called specificity.  This principal states that the training program needs to be sport specific.  Obviously the most specific thing to throwing or hitting a baseball would be throwing or hitting a baseball but our bodies can only handle so much of these actions so we need to find a means of conditioning that DOES NOT hurt our ability to produce power.

What this means

Whenever you exercise you are training your body to get better at that particular action.  So if you run long distances your body is going to make the adaptations necessary to get better at this type of training by improving your ability to use the slow twitch muscles rather than the fast twitch muscles.

Slow twitch muscles are made for endurance and as a result they have very poor power production while fast twitch muscles are great for short powerful bursts but bad for endurance.  Although baseball games can last a long time there is approximately 13 seconds between pitches which is more than enough time for those fast twitch muscles to recover.

Check out the picture below of an endurance runner versus a sprinter.  Which body would you say is better for throwing hard?

I’m going with the guy on the right

Take Home Message

Running is great for baseball players but the type of running you do is going to have a huge effect on how your body is going to respond.

Instead of conditioning with long distance running try:

  • running sprints like they did in this study
  • perform circuits of exercises likes lunges, pushups and rows
  • push a sled or a car (be sure its in neutral and a safe environment)
  • try interval poles where you alternate between jogging, sprinting and walking

It’s a very expensive piece of exercise equipment

but you might already have one 

Until next time Stay Powerful

Graeme Lehman

Pitching 8 months a Year Might not be a Great Idea – Studies you should know about

The study in question today comes from the Dr. Andrews lab in the American Sports Medicine Institute in Birmingham, Alabama.

Risk Factors for Shoulder and Elbow Injuries in

Adolescent Baseball Pitchers

By: Samuel J. Olsen II, MD, Glenn S. Fleisig,* PhD, Shouchen Dun, MS, Jeremy Loftice, and James R. Andrews, MD

What did they want to find out?

If the pitching practices of adolescent (14-20yrs) pitchers that DON’T have any history of arm injury are different then adolescent pitchers that DO have a history of arm problems.

The goal here is to identify common factors that most pitchers with injuries have in common and compare to no injured throwers in order to find out which ones may contribute to arm problems which nobody wants.

How did they find out?

They had pitchers both injured and uninjured (90 and 45 respectivly)  fill out a detailed questionnaire that asked them questions like:

  • How tall and heavy are you?
  • How many innings do you pitch?
  • How many months out of the year do you pitch?
  • Your coach cares most about?  the game, the season or your career?
  • Do you exercise for baseball?
  • Do you ice and/or stretch after you throw?
  • If you come out of the game as a pitcher do you stay in and go to another position?
  • Out of 10 pitches how many are fastballs, breaking balls, change ups?
  • Do you use anti-inflammatory drugs?
  • How old were you when you started to shave?

And many, many more questions like this.

What they found out?

The significant differences between the groups were that the injured group pitched more months per year, games each year, innings per game, pitches per game, pitches per year and warm up pitches before game.  The injured group was also 4cm taller and 5kg heavier on average – there was no age differences between the groups.  The injured group averaged 88mph while the uninjured group threw 83mph.

Let’s look at some of these factors more closely.

1.       Height and Weight

While the two groups were very similar in terms of age the injured group was on average 4cm taller and 5kg heavier.  At younger ages most pitchers lack the strength needed to handle the forces that come with throwing a baseball as hard as you can so it is no surprise that heavier and taller pitchers have more injuries because they need even more strength.

If you’re tall for your age great!! This height will come in handy when you get older and stronger so make sure that your arm is in good shape to take advantage of your long limbs in the years to come.  For coaches and parents out there make sure the taller and heavier pitchers don’t over do it.

As far as weight goes it can be a good thing because it can add to the total amount of force that you generate and deliver to the ball, CC Sabathia maybe?

With added weight comes the need for added strength otherwise the extra mass will work against you.  Any weight that you want to add should come in the form of muscle and not junk food.

CC can be big because he is strong – big without strength is called fat

2.       How much, how often and how hard should you throw?

It really comes as no surprise that pitchers who threw more often get hurt but we need to throw in order to get better.  We need to find out how much pitching there needs to be.

One factor that jumped out was the members of the injured group that needed surgery (I would classify this injured) pitched competitively for about eight months a year while the non-injured group averaged only five and half months.

Maybe playing on three different teams might not be the greatest idea.

It should be noted that the injured group reported average velocities of 88mph compared to 83mph in the uninjured group.  While these numbers may not be completely accurate because I am sure that any adolescent pitcher is going to inflate their velocity numbers but at least both group most likely exaggerated their numbers equally.  It’s just like basketball players and their vertical jumps, football player’s and their forty times or men in general with their bench press totals.  Take them with a grain of salt until you see them.

Now hard throwers obviously have to deal with the higher forces needed to reach these higher velocities which can place them a higher risk of injury.  Think of Joel Zumaya’s arm problems compared to the fact that Jamie Moyer is still throwing in his 40’s.

But hard throwers are more likely to pitch more often since every teams likes to put their hardest throwers up on the bump.   Hard throwers are also more likely to go participate in “Showcases” in  order to be recruited for higher levels of baseball.  While great for exposure these “Showcases” may be doing more harm then good by getting pitchers to max out their arms trying to impress scouts and coaches by throwing as hard as possible in hopes to impress.

These “Showcases” can be especially damaging when they are held during what is typically the off-season.  This not only adds more competitive pitching months to the yearly total but has the pitcher going from a state of no throwing to going all out in order to get that scholarship.  Trying to go from zero to hero like this is bad news.

If you’re good enough and play organized baseball in the summer scouts will find you so don’t worry about firing up the old pitching arm in winter to go pay someone to go show them what you got.

3. Use of Anti-Inflammatory Drugs

Again this one is not a shocker.  If you need to pop a couple of Aleve’s before you pitch to numb the pain that you know is coming you might what to get your arm checked out.

The first step is admitting that you have a problem

Hopefully you can put this information to good use and help prevent arm injuries from occurring in the first place.

Graeme Lehman, MSc, CSCS

Studies You Should Know About – Factors for Increased Velocity

The name of the study: Comparison of Kinematic and Temporal Parameters Between Different Pitch Velocity Groups

Overview:  This research split up their subjects into either high or low velocity throwers based on their…. you guessed it –  throwing velocity.  They then analysed their mechanics to determine what were the main differences between the two groups in order to find out what allows certain pitchers to throw harder than others.  This is a landmark study since they discovered some great information to pass along to anyone who wishes to throw harder and if you are reading this you are probably interested in throwing harder or you know someone who wants to increase their throwing velocity.

The authors: Tomoyuki Matsuo, Rafael F. Escamilla, Glenn S. Fleisig, Steven W. Barrentine, and James R. Andrews (that same Dr. Andrews that performs Tommy John surgery on all the big name guys)

Where to find it: Journal of Applied Biomechanics 2001; 17: 1-13

What they did:  They looked at 127 healthy college and professional pitchers and had them throw in their lab with a bunch of reflective markers on specific points of their body in order to determine joint angles and body positions (kinematics parameters).  They also used a high-speed camera to determine exactly when each pitcher got to certain joint angles like maximal external rotation during their deliveries (temporal parameters).

Of the 127 subjects 29 were classified as hard throwers because they could achieve speeds of 38 meters per second (m/sec) which is 85 mph while 23 were classified as slow throwers that topped out at 34.2 m/sec (76.5 mph).

Below are the main differences (aka significant factors) between the slow and hard throwers were:

1 – Physical differences – the hard throwers were signficantly taller (5cm) and had longer arms (4cm).   This is just a matter of physics – being taller and having longer arms can allow you to throw harder but it doesn’t guarantee it.  If fact having longer limbs means that you have to strong enough to control those long legs and arms.  If you aren’t strong enough you will lose potential energy that you could have transmitted into that baseball.  They call this an energy leak.

2- Maximum Shoulder External Rotation:  the hard throwing group was able to get their arms back into 179 degrees of rotation whereas the slow group could only get 166.3 degrees.

Greater amounts of external rotation allows you to throw harder because you generate more of a stretch reflex in your internal rotators which act like springs allowing your arm to rotate forward at an incredibly fast rate.  Another reason why more external rotation allows you to throw harder is that you are creating a bigger range of motion which means that you have more time to add force.  Your muscles take time to build up force so by creating a bigger range of motion you give yourself a little bit of extra time to add an MPH or two.

3 – The lead knee:  this was the major finding of this study and I go into greater detail in this article about the front leg:

https://lehmansbaseball.wordpress.com/2011/02/28/the-stride-leg/

What they found here was that the lower velocity group showed greater amounts of knee flexion (bending your leg at the knee) from between the time their front foot landed until they released the ball.  The high velocity group did they opposite where their front legs extended (straightening your leg at the knee).

In the discussion portion of the reasearch paper the authors talk about how the front leg braces and stabilizes which enhances the ability of the trunk to rotate more effectively forward over the front leg.  If the front leg collapses this creates a major energy leak and slows down your fastball big time.

Watch the video below of the newest Texas Ranger Darvish Yu throw back when he was pitching in the Japanese league.  This guy throws hard and watch his front leg brace to the point where he hops backwards after releasing the ball.

Another study (Escamilla et al. 1998) showed that in collegiate pitchers began to extend their front leg just before the shoulders started to get into their externally rotated position and kept extending until the point of ball release.

Check out 2011’s best pitcher Justin Verlander and his front leg in this video

That front leg bracing enables you to transfer all that energy you build up from your lower half and transmit it up through your upper body.

This next video does a great job of slowing things down to show how that front leg stiffens up.

4- Forward trunk tilt at instant of ball release – this one is a by product of strong front leg.  A stiff and strong front leg enable you tilt your upper body to a greater degree than a weak and sloppy one.  The high velocity group had a forward trunk tilt of 36.7 degress while the slower throwing group were more upright with a trunk tilt of only 28.6 degrees.

Having a greater degree of trunk tilt allows you to hold onto the ball longer which again allows you to build up more force than someone who has to let go of the ball earlier because their standing more upright.  When you couple this with more shoulder external rotation you really get to add some extra force to that baseball.

Forward trunk tilt also enables you to let go of the baseball closer to the plate which is always a good thing because it gives the hitter less time to decide whether or not they should take a swing or not.  This may not add any MPH’s to the radar gun but it make it seem faster to the hitter which is what really matters.

Below are some examples of some great trunk tilts upon ball release from one of the hardest throwers ever and one of the best pitchers ever (in his prime).

One of the hardest throwers ever - Chapman

One of the best ever - Pedro Martinez

I hope you found this information useful and the simple fact that you know these things are important will allow you to at least be aware of how far back your arm gets into external rotation, what your front leg does and how much trunk tilt you have upon release.

As far as the body height and arm length go be sure to pick the right parents and eat your Wheaties!!

Graeme Lehman, MSc, CSCS

The “X-Factor” to Increasing Velocity

The “X Factor” might be secret for tapping into a major source of power which can be translated into high throwing velocities.  If this sounds like something that you might be interested in keep reading.

Before we jump into what exactly this “X Factor” is and how to use it let’s do a quick review of the two biggest sources of power you need to throw gas.

1. Linear power – momentum

Linear (straight line) power comes from a pitcher driving down the mound with hip leading the way followed by an explosive drive off from the back leg towards the target.  This is sometimes referred to as momentum. My thesis discovered a positive correlation between an athlete’s ability to jump laterally and high throwing velocity which proves this need for linear power. I will cover this in more detail in another post.

Back leg drive creates linear power

2  Rotational power – torque

Once a pitchers front foot lands they can start adding in the rotational forces of the hips, trunk, shoulders and the arm to deliver the ball.  The sum of these forces when sequenced correctly is greater than individual parts.  This is often referred to as torque.

The top of the Jays rotation showing off his rotational power

X-Factor

This rotational force is where we find the “X Factor”.  I came across this “X Factor” term from reading a study on golf which used it to describe the hip and shoulder separation which they concluded was a major factor for producing high rotational velocities that translated into longer drives.  Any athlete that plays a rotational sport can benefit from learning about and maximizing their ability to separate their hips and their shoulders.

The hip and shoulder separation is arguably the most important part of the pitching motion to produce high velocities.  I remember reading a Tom House book where he stressed its importance by stating that most of his guys could achieve about 80% (going by memory here) of their normal throwing velocity by throwing from their knees.  Throwing from your knees eliminates nearly all linear velocity and isolates the rotational forces that contribute to throwing velocity.

To get the most out of your rotational power you need to have proper sequencing where your hips rotate before your shoulders which creates this separation between the two – this would be the X-Factor.

Elastic Energy

The reason why hip and shoulder separation can create so much torque and energy is due to what’s known as elastic energy.  When the hips are open and the shoulders are closed the trunk that connects the two is essentially being twisted like a dish cloth.  When this twisting occurs the muscles of the trunk are being stretched and begin to store elastic energy.  All this stored energy ends up getting released once the shoulders begin to rotate towards the target.  The more we can separate the two the more energy we can store and release.  But when there’s no separation everything ends up rotating at the same time which reduces velocity and increases the time a hitter has to decide if he should lay off or drill it into the parking lot.

Separation = Elastic Energy

How to separate?

Just knowing about this important factor allows you to watch for it when you review video of yourself at which point you can focus on this aspect of throwing. Throwing from your knees is a great way to focus on the rotational component but it doesn’t really mimic true pitching from our feet.

A better drill in my opinion would be one where we get the pitcher into a stride position then have them rock back and forth a couple with the hips closed before rotating them forward while focusing on keeping the shoulders back  and storing elastic energy in the trunk.

But what if you can’t separate?

Coaches often get frustrated when a player cannot do what they are telling them no matter how many times they describe exactly what to do.  In this case a player may not have the ability to separate the hips and shoulders due to tightness and a lack of mobility.

It’s all in the Hips

The hips need to be both strong and mobile.  It’s easy to understand why we need strong hips in order to generate both linear and rotational power but you can’t forget about mobility.  If the hips are tight  they won’t be able to rotate as much as you would like to which will end up reducing your ability to separate.  If your hips are too tight your shoulders will rotate with your hips and you will lose out on any potential elastic energy you could have created in your trunk.

Prove It!!

There was a study by Dr. Andrew Robb who is a chiropractor in Toronto that looked at how hip mobility affected both mechanics and velocity.  Dr. Robb completed a fellowship at the prestigious American Sports Institute in Birmingham Alabama – this place might sound familiar because it is where the legendary Dr. Andrews works.  Other members of this study include some big names in the world of baseball research like Dr’s. Glenn Fleisig and Kevin Wilk.  Based on all these factors you can rest assured that this is a great study and will have some pretty good information for those out there looking for ways of improving throwing velocity.

Here is a quote from this study – translation is below:

“During the arm-cocking phase, total arc of motion Abduction & Adduction of the dominant hip was positively correlated with trunk separation velocity. This relationship would suggest that larger ranges in the dominant hip facilitate greater angular velocity of the pelvis as this is the leg that initiates the forward momentum of the pitching motion. Presumably, having more range would permit greater kinetic energy production, ultimately producing greater ball and angular velocity. Of the total arc of motion (Abduction + Adduction), only Abduction in the dominant hip was found to have a positive correlation with trunk separation velocity.”

Translation:

The range of motion of your dominant hip (same hip as your throwing arm) will enable you to not only take a longer stride which enables you to build more linear velocity but also allow your hips to rotate more.  More range of motion allows for more time for energy to be built up while also allowing your shoulders to stay back.  This is especially true when looking at your ability to abduct your hip.

What is Hip Abduction?

If you were to stand up and lift your dominant leg to the side away from your body this would be abduction.  Your range of motion to abduct your hip however is limited by the tightness of your adductors.

How do I Increase my Hip Abduction?

Here are a couple of methods that you can use to increase your hip mobility although you could always seek the help of a qualified professional (chiropractor or physiotherapists) who can properly assess your range of motion.

If you want to do it yourself your best bet is to do some soft tissue work (aka massage) then stretch.

Here are a couple of links to videos that show you how to do some soft tissue work on your adductors

http://www.youtube.com/watch?v=Z9K4yLcJQ0w

http://www.youtube.com/watch?v=vkVg1dEmjwE

Half Kneeling Stretch

Be sure to keep a curve in the small of your back and rock back and forth.

 Wall Stretch

This one looks funny but you can stay in this position for a while to let those tight muscles relax.

Stay strong and stay loose.

Graeme Lehman, MSc, CSCS

References

1. Joseph Myers, Scott Lephart, Yung-Shen Tsai, Timothy Sell, James Smoliga & John Jolly (2008): The role of upper torso and pelvis rotation in driving performance during the golf swing, Journal of Sports Sciences, 26:2, 181-188

2. Andrew J. Robb, Glenn Fleisig, Kevin Wilk, Leonard Macrina, Becky Boltz, and Jason Pajaczkowskiy (2011): Passive Ranges of Motion of the Hips and Their Relationship With Pitching Biomechanics and Ball Velocity in Professional Baseball Pitchers Investigation performed at the American Sports Medicine Institute, Birmingham, Alabama. Am J Sports Med 2010 38: 2487