Posts

A New Exercise for Strength and Stability of the Shoulder

The PronatorThere is not doubt that we need a strong and stable shoulder to maximize performance.  I recently started playing with a new device called The Pronator.  It’s a device designed to strengthen the forearm musculature.  Honestly, this little thing is a fantastic device for grip and forearm strength, but I also started using it with my shoulder exercises and think this may be a game changer!

Take a look at the video below.

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I see this very similar to performing bottom-up kettlebell exercises.  By having an offset weight, you need to work the shoulder in 3D to stabilize and move at the same time.  Pretty cool.  It essentially allows you to:

  • Develop stability in one plane of motion and strength in another
  • Train the cuff to fire and stabilize while moving the scapula

The product is brand new and very affordable at only $55.   I don’t often tell my audience that they need to buy a product, but I really think everyone should have this one.  I like it that much!

 

Laxity Does Not Mean Instability

Several years ago, when Eric Cressey and I released Optimal Shoulder Performance, I discussed the Beighton Laxity Scale and how I use it to determine the amount of laxity that individuals may possess.  This is just one of the many factors that go into how I design my rehabilitation and performance programs, as an individual’s amount of laxity influences program design.

Since then, I have started to hear comments from people that their clients may have Ehlers-Danlos syndromeLoeys-Dietz syndrome or Marfan syndrome because of their Beighton score.

 

Laxity is Normal

Beighton Scale Laxity InstabilityIf you Google “Beighton Score,” you see that this is a scale often used to diagnose the above hypermobility syndromes, however each has their own specific features.  A Beighton score is not the only factor involved, and actually is probably not the most important finding in any of these syndromes.

Laxity is not a syndrome, in fact, laxity is normal.

We all have a certain degree of laxity, you’ve probably seen many people along this spectrum from the really tight to the really loose.  A high Beighton score does not indicate that they have a syndrome or problem, it just helps determine where they sit in the laxity spectrum.

 

Laxity Does Not Mean Instability

While joint laxity is normal, a high amount of laxity does not necessarily mean you have instability.  Stability is a combination of the function of your static and dynamic stabilizing systems.  Instability is when you have an issue with either (or both) of the static and dynamic stabilizers.  Functional stability is the ability to dynamically stabilize a joint during functional activities to allow proper control and movement.  This is the basis behind our entire Functional Stability Training programs.

Check out this video of my friend Sam’s Beighton score.

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As you can see, Sam has a high Beighton score and a lot of joint laxity.  But Sam can deadlift over 2x her body weight.  That is laxity combined with functional stability.  She doesn’t have any problems because she can control her laxity.

Don’t automatically assume a lot of laxity is a bad thing, in fact many professional athletes possess a high amount of laxity.  Remember laxity is normal, does not mean instability, does not mean you have a clinical syndrome, and something you can control with the right program.

 

 

Base of Support and Core Stability

I work with with a lot of youth athletes, especially baseball players.  I am often amazed at how some of our younger athletes have such poor movement skills.  Many are 6 inches away from touching their toes!  I’m sure this is a trend this is not going away as our society spends more and more time staring at our iPhones and less on long term athletic development.

The body is great at compensating and finding the path of least resistance.  Here is a quick tip that you can apply to many different exercises to enhance core stability.

 

Base of Support

When the core and entire lumbopelvic region has poor motor control and stability, especially in the transverse and frontal planes, a way the body likes to compensate is by widening the base of support.  Here is an example of a young athlete performing a medicine ball chest pass.  Notice his base of support in the first photo.  This was his natural set up position.

Base of Support

 

By widening his base of support, he can likely generate more power during the exercise by making it more stable in general.  However, in a training environment, I want to assure that we develop both power and control.

By narrowing his base of support, as you can see in the second photo, he has to stabilize his core during the exercise and work on developing power while controlling the force of the ball.  This is going to have a more functional carry over into his sport.

Building athletes isn’t always just about strength and power, it’s also about movement quality and control.  Watch for compensations at the base of support for signs of poor lumbopelvic and core stability.

 

 

A New Exercise for Shoulder, Scapula, and Core Control

Today’s post in a guest post from my friend Tad Sayce, who is a strength coach in the Boston area that specializes in swimmers.  Tad shares a great exercise video that works shoulder, scapula, and core control.  I’m a big fan of “big bang for your buck” exercises that promote strength and stability in one exercise, which is something we talk a lot about in Functional Stability Training.  Tad came up with one that I am going start trying with my athletes.

Band Resisted Horizontal Abduction with a Press

As a former competitive swimmer, I can closely relate to the overhead athlete and the complications that can arise at the shoulder. As a strength and conditioning coach working predominately with swimmers, I am constantly looking to improve the durability of the shoulder. It is widely accepted that the shoulder operates at maximum efficiency in the presence of a stable base at the core. While I am a believer in the use of isolated exercises, today’s focus will be that of a more integrated effort. The video below demonstrates an exercise that facilitates shoulder, scapular and core activation: Band Resisted Horizontal Abduction with a Press. 

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As the name implies, the exercise combines resisted horizontal abduction with an anti-rotation press. It is encouraged to first master each exercise in isolation before attempting to combine them. This exercise is great for educating athletes about proper scapular movement, and also demonstrating the ability to maintain position in the presence of increasing tension. I particularly like this exercise because it incorporates both dynamic and static efforts. I typically program this exercise for sets of 5 holding for 5 seconds, or sets of 8 holding for 2 seconds.

About Tad Sayce

tad-sayceTad Sayce, Head Coach and Owner of Sayco Performance Athletics, located in Waltham, MA. Tad is a Strength and Conditioning specialist with a strong interest in the sport of swimming. Formerly, Tad was a competitive swimmer in the Big 10 Conference and Olympic Trials qualifier, as well as a USA Swimming club coach.  For more information please visit www.saycoperformance.com.

Functional Stability Training for the Upper Body

My latest educational program with Eric Cressey, Functional Stability Training for the Upper Body, is now available!  

FST for the Upper Body is the third program in out Functional Stability Training system, adding to the popular Core and Lower Body programs.  When Eric and I started to brainstorm what we wanted to teach with these programs, we wanted to share our approaches to rehabilitation and performance training, but more importantly how we integrate the two together.  This makes the FST products a great resource for any rehabilitation, fitness, or performance specialist.

 

Functional Stability Training for the Upper Body

Functional Stability Training for the Upper BodyIn order to function properly, our body needs to be strong and mobile, but control and stabilization of this mobility is often less than optimal.  Unfortunately, stabilization is often overlooked in the design of rehabilitation and performance programs.  Traditional program design relies too much on mobilizing what is tight and strengthening what is weak.  We are missing the boat on stabilization and it’s effect on enhancing optimal movement patterns.

Proper function of the upper extremities is complicated and requires the arm to work in conjunction with the scapula, thorax, cervical spine, and core to provide mobility, strength, and power to the entire body.  Any deficits in stability throughout the body’s kinetic chain can lead to injury, dysfunction, and a decrease in performance in the upper body.  FST for the Upper Body aims to help formulate rehabilitation and training programs designed to optimize how the upper body functions.

By addressing alignment, strength, mobility, and dynamic motor control, you can maximize your rehabilitation and training programs to reach optimal performance.

Think about a few of these:

  • Can the lumbopelvic and thoracic regions impact shoulder function?
  • Can the cervical spine impact the elbow?
  • Can scapular position decrease shoulder performance?

The answer to all of these questions is ABSOLUTELY!  Functional Stability Training for the Upper Body discusses all this and more, showing you exactly how you can assess and correct issues within the kinetic chain to optimize stability and performance of the upper extremity.

Here is an outline of the presentations and lab demonstrations that we perform.  Eric and I combine presentations with real life examples so you can see how we both manage specific individuals based on our assessments.  You get to see Eric and I at work together working with people:

  • How posture and position influence upper extremity function
  • Understanding and managing joint hypermobility
  • Understanding the elbow: functional anatomy, common injuries, and conditions
  • Elbow injuries: evaluation and management
  • Assessment and management of thoracic mobility restrictions
  • Assessment and management of muscles imbalances of the shoulder and scapula
  • Assessment and management of scapular position
  • Assessment and management of elbow epicondylitis

 

Optimal Shoulder Performance

For those that are familiar with Eric and I’s other education program Optimal Shoulder Performance, Functional Stability Training for the Upper Body takes this information to the next level by showing how we integrate the entire body to optimize upper body function.  

FST for the Upper Body integrates the concepts learned from FST for the Core and FST for the Lower Body, and serves as the sequel to their previous educational program, Optimal Shoulder Performance.  FST for the Upper Body is perfect as a stand alone program, but also builds off Optimal Shoulder Performance to help take your knowledge to the next level.  Putting the information from all of these products together will give you a complete understanding of how we approach our integration of rehabilitation and performance.

We had great reviews from the live filming of this program:

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Special Sale Price This Week Only

Functional Stability Training for the Upper Body is available now and is on sale for $20 off to celebrate the launch.  

If you haven’t purchased any of the other FST products in the past, you can get all three FST programs for the Upper Body, Core, and Lower Body together in one bundle and save another $20.

These special sale prices are for this week only and end Sunday May 18th at midnight EST.  Click below to learn more and order before this sale price ends!

 

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7 Reasons Why Corrective Exercises May Not Always Work

The latest webinar recording for Inner Circle members on Why Corrective Exercises Don’t Always Work is now available below.

Why Corrective Exercises Don’t Always Work

corrective exerciseThis month’s Inner Circle webinar discussed Why Corrective Exercises Don’t Always Work.  I felt like this was an important webinar to discuss the fact that correct exercises aren’t perfect.  In fact, many times they are ineffective.  In order to best use corrective exercises, you first need to understand why they sometimes do not work. In this webinar, I will discuss:

  • What exactly are corrective exercises?
  • Do corrective exercises always work?
  • 7 reasons why corrective exercises may not always work
  • What you can do to maximize the effectiveness of your corrective exercises

 

To access the webinar, please be sure you are logged in and are a member f the Inner Circle program.  If you are currently logged in, you will see the webinars below.  If not, please log in below and then scroll down to the “webinar archives” section.  If you are not a member, learn more and subscribe to Mike Reinold’s Inner Circle program.

Inner Circle Log in:

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A Simple Dynamic Stability Exercise for the Leg [Video Demo]

This week’s post is a video demonstration of a simple way to integrate reactive neuromuscular training (RNT) into your programming to enhance dynamic stabilization of the lower extremity.

Reactive Neuromuscular Training for Dynamic Stabilization of the Lower ExtremityIn this video, I show a client that has an ankle sprain.  While going through her rehabilitation, it became clear that she also needed balance training to really work her ankle, knee, and hip to stabilize during functional tasks.

To perform this exercise, you simple need a large resistance band (which are great from many stretching, strengthening, and stability exercises – here are the ones I use).  Loop the band around a rack or other object and step within the loop.  Place the band just above your knee.

I show a few exercise ideas in the video, progressing from simple balance, to unstable surfaces, to incorporating functional movements.  By using the band, you can emphasize training the bodu’s ability to stabilize in the frontal and transverse planes while performing a sagittal plane exercise.  This is essential to optimal function and a big key to my Functional Stability Training program.

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Groin Injuries in Hockey Players

Today’s guest post on Groin Injuries in Hockey Players is from Peter Nelson.  Peter is currently working in collegiate hockey and has shown great interest in understanding why groin injuries are so common and what we can do about it.  Peter does a great job thinking outside the box and taking a look at the bigger picture.  Thanks Peter, great article, I’ll add some of my own comments at the end.

 

Groin Injuries in Hockey Players: An All-Too-Common Problem With a Not-So-Commonly Known Solution

going injuries in hockey playersBeing a former competitive hockey player (admittedly not a very good one—fourth line for life!) and working predominately with hockey players in a strength and conditioning capacity for the last few years, it has become clear to me that hockey players and groin injuries go together like the artist formerly known as Ron Artest and his psychiatrist.  Gold star if you get the reference.   (photo by David Shane)

 

Examining the Prevalence of Groin Injuries Among Hockey Players

While this relationship exists at almost all levels of the game, it has been particularly well documented in elite players.  Several studies have been conducted to assess the prevalence of this specific injury at the professional level.  The results have been consistent, and they are troubling.

A 1978 study by Sim et al. concluded that “ice hockey players are at high risk for noncontact musculoskeletal injuries because of the excessive force generated during the acceleration and deceleration phases of skating.”

A 1997 study by Molsa et al. reported that 43% of muscle strains in elite Finnish hockey players were involving the groin region.

A 1999 study by Emery et al. found that “the impact of groin and abdominal strain injury at an elite level of play in hockey is significant and increasing.”  According to their data, the rate of groin/abdominal strains in the NHL increased from about 13 injuries per 100 players per year during the 1991-1992 season to almost 20 injuries per 100 players per year during the 1996-1997 season.  Furthermore, the recurrence rate was 23.5%, meaning that injuries of this nature went on to plague a significant percentage of players for an extended period of time.

More recently, a study by Tyler et al. found that out of 9 NHL players evaluated, all of whom had suffered from groin injuries, four had sustained multiple strains.

 

The Long and Short of Groin Injuries: Muscular Imbalances in Athletes

With the strong correlation between hockey players and groin injuries established, it becomes important to understand why this is the case.  Many would be quick to attribute it to the violent nature of the sport, but research indicates that this is unfounded.  The study by Emery et al. found that upwards of 90% of all groin injuries were non-contact in nature.  Others posit that strains are due to the muscles involved being too short and lacking flexibility.

Sports physicians, physiotherapists, and strength coaches who fall under this category often prescribe stretching of the groin musculature to remedy the issue.  The study by Tyler et al., however, found that preseason flexibility of the hip adductors, the primary muscles that make up the groin region, did not differ between NHL players who went on to sustain groin strains and those who did not.  This indicates that stretching of the groin is probably not an effective approach toward preventing or treating this type of injury.

What the Tyler et al. study did find was that preseason hip adduction strength of the players who sustained groin injuries was 18% lower than that of the healthy players.  They also found that adduction strength was 95% of abduction strength in the uninjured players, compared to only 78% in the injured players.  This suggests that a muscular imbalance between the weak adductors and the relatively strong abductors plays a large role in groin issues.  The Sim et al. study also supports this view, suggesting that “in ice hockey players, adductor strains may be caused by the eccentric force of the adductors attempting to decelerate the leg during a stride.”  The researchers further went on to state that “a strength imbalance between the propulsive muscles and stabilizing muscles has been proposed as a mechanism for adductor muscle strains in athletes.”

 

Detective Work: Delving Deeper to Identify the Root of the Problem

The logical conclusion then should be that the solution is to strengthen the adductors and stretch the abductors, right?  Well, yes, but a more in-depth look at the problem is necessary to determine exactly why this imbalance is present in the first place, that way we can most effectively remedy the issue.  As a sports physician, physical therapist, or strength coach, you are not truly solving the problem unless you address the root cause.

In order to identify the root cause, it is important to first consider three main concepts.  First, it is imperative to understand the biomechanics of skating.  This brief excerpt from the study by Sim et al. sums it up very well:

“During the powerful skating stride the hip extensors and abductors are the prime movers, while the hip flexors and adductors act to stabilize the hip and decelerate the limb.”

 

Janda Lower Body Cross SyndromeThe second concept to understand is that these specific movement patterns have a profound effect on the relative strength—and consequently length—of the muscles involved.  Because hockey players, like most athletes, spend so much time in extension, the spinal erectors become extremely tight.  The same is true of the hip flexors, which become tight due to the constant forward lean seen in an “athletic stance” as well as the strength required to overcome the aforementioned eccentric force needed to slow down the leg in the recovery phase of a skating stride.

Consequently, since the hip flexors pull the pelvis down from the front and the spinal erectors pull the pelvis up from the back, the pelvis becomes tilted anteriorly.  This lengthens the hamstrings, putting them at a leverage advantage and forcing them to take on more of the load in extending the hips than the glutes.  The glutes then become relatively weak, as does the anterior core.  The end result is a player with what Janda called “lower-crossed syndrome”, illustrated below, who is at risk for both low back and hamstring injuries.

How does this play into groin injuries?  In order to make that connection, you need to understand the third concept, which is a central tenet of the Postural Restoration Institute (PRI): while muscles are often prime movers in a single plane, they must actually be considered as having an effect on movement in all three planes—sagittal, frontal, and transverse.

The perfect example of this is the hip extensors.  While the hip extensors are mostly responsible for movement generated in the sagittal plane, these same muscles—most notably the gluteus maximus—function as external rotators and abductors.  This is relevant to hockey because the nature of a skating stride requires players to have strong abductors—they are prime movers in this movement—as well as spend a lot of time in external rotation.  This tightens both the external rotators and abductors and pulls the hips into chronic external rotation and abduction, or in other words causes them to become “flared”.  Adductor muscles like the adductor magnus, which also contribute to internal rotation, become lengthened and, like the hamstrings in the sagittal plane, are put at risk for injury.  This clearly fits the theory of a muscle imbalance as the potential contributor to groin injuries, and it becomes clear from the analysis above that pelvic alignment is important in understanding the root cause of this imbalance.

It also makes it apparent that stretching the groin is not only ineffective; it can actually feed right into the problem!

 

Shifting Into Neutral: Correcting Pelvic Positioning

That brings us to the million-dollar question: how do we fix it?  After coming to the understanding that groin issues are caused by pelvic misalignment in all three planes of movement, you can see why I suggested that strengthening the internal rotators and stretching the external rotators is not a comprehensive solution to the problem.  We must address muscular imbalances with the triplanar perspective in order to effectively prevent injuries of this nature.

The first plan of attack should be to rectify the imbalances in the sagittal plane.  The reason being is simply that extension limits rotation, and since I already explained that hockey players—and athletes in general—tend to live in chronic extension, it makes sense to resolve that problem first in order to maximize the effectiveness of attempts at repositioning an athlete in the other two planes.  I group the frontal plane with the transverse plane, even though I am talking about rotation being limited, because there is significant overlap between the prime movers in abduction/adduction and internal/external rotation.

Addressing the imbalances in the sagittal plane is fairly straightforward.  I like the approach Mike Robertson takes in identifying two “force couples”.  The posterior force couple consists of the anterior core and the posterior chain (primarily the glutes and hamstrings), and these two will be weak in athletes living in extension, as I previously mentioned.  Hammering the glutes and hamstrings with exercises like hip thrusts (demonstrated by Bret Contreras below) and Romanian Deadlifts, respectively, will strengthen the posterior chain and tilt the hips posteriorly by pulling them down from the back, the net result being a more neutral alignment since the athlete was in anterior tilt to begin with.  With the anterior core, it is important to note that it is the internal obliques, external obliques, and transverse abdominis that are usually weak, as opposed to the rectus abdominis.  Strengthening these muscles will tilt the hips posteriorly by pulling them up from the front, also resulting in a more neutral alignment.

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The anterior force couple consists of the spinal erectors and the hip flexors, and these two will be tight.  Stretching the hip flexors is crucial; this can be accomplished with stretches like the Bench Hip Flexor Stretch, illustrated by Tony Gentilcore.  Self-myofascial release can also be useful.

groin injuries

With the Bench Hip Flexor Stretch, the harder the athlete squeezes the glutes and extends at the hips, the greater the stretch on the rectus femoris.  Be careful, however, not to allow the athlete to extend at the lumbar spine, as this reinforces the incorrect movement pattern we are trying to move away from.

Stretching the spinal erectors can be accomplished with “prayer position”-type stretches.  Self-myofascial release with a lacrosse ball peanut can also be effective.  In working with Head Strength Coach Rob McLean and the Pennsylvania State University Men’s Ice Hockey team, we tend to use exercises with movement patterns that inhibit the paraspinals while also activating the anterior core, such as the exercise from the Postural Restoration Institute shown below, demonstrated by Kevin Neeld.

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In this case, we are killing two birds with one stone in strengthening the weak muscles and teaching the athletes to inhibit the tight muscles (notice how Kevin’s back is rounded; this helps to inhibit the spinal erectors) at the same time.  You can also see that in the video there is a ball between Kevin’s knees—this is to activate the internal rotators/adductors, which I will discuss next.

Addressing the frontal and transverse planes when it comes to fixing pelvic alignment is overlooked too often.  Again, we want to strengthen the internal rotators and adductors—the muscles might largely overlap but it is important to pattern both movements individually—and stretch the external rotators and abductors.  For internal/external rotation, med ball crushes is a good one to strengthen internal rotation (note that this exercise can also pattern the adduction movement, depending on how it is performed), and knee-to-knee mobilization is good for both activating the internal rotators and stretching the external rotators.  Any exercises that target the semimembranosus (the most medial hamstring muscle) will also help strengthen the internal rotation movement.  An easy modification to an already great exercise, which I mentioned earlier, that will help in this regard is having athletes internally rotate the legs during the hip thrust.  Here at Penn State we have started doing band-resisted hip thrusts with internal rotation, and Coach McLean and I both like how it hits the internal rotators.  Considering that it also strengthens the posterior chain, you’re really killing two birds with one stone in repositioning the pelvis with this small tweak.

There are also a number of good exercises for patterning and strengthening the adduction movement.  Adductor Side Bridges, demonstrated below by Kevin Neeld, are great in this regard.

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The adductor pullback exercise from PRI, demonstrated below also by Kevin Neeld, is another good one.

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We have our players perform the adductor pullback exercise only on the left side (so they would be lying on their right side, as Kevin is in the video) to address the left AIC alignment that I mentioned earlier.  Doing the opposite by lying on your left side and shifting your right hip forward and externally rotating it (since the right leg tends to be internally rotated) also helps correct this particular alignment.

 

Conclusion

Simply put, pelvic positioning is an important piece in preventing groin injuries, which affect athletes in all sports, but are especially a problem amongst hockey players.  The three main concepts to remember in assessing pelvic positioning in any athlete are 1) understanding the biomechanics of the sport, 2) identifying the effects these movements have on the muscles involved, and 3) considering muscles as contributors to movement in all three planes, even if they are not prime movers in one or more of those planes.  These concepts can be applied in order to identify imbalances in an athlete and the effects they have on the position of the pelvis. Once this is accomplished, a program can be designed so that the imbalances can be corrected and the pelvis returned to neutral.  After all, neutral is where we want our athletes to be, as that puts them at the lowest risk for injury.  And any reputable strength coach knows that keeping athletes healthy is the primary objective in any program.  You can’t translate gains in strength and power to the playing field if you’re stuck on the sidelines.

 

Mike’s Thoughts

I think Peter did a great job with this article, highlighting the need to start thinking about alignment and triplanar function of the body.  These are often missed in our critical thinking.  The only thing I would add to this great article is that the real goal of working to enhance alignment is to then allow you to train the body in better neutrality.  We may not function in neutral, but you don’t want to be stuck in our poor alignment.  You want to be able to get out of your asymmetry when needed.

Every athlete I have worked with that is “stuck” in their asymmetry is prone to recurrent injuries.  We’ve all had them, right?  The person that just keeps straining their groin, or hamstring, etc.  Take a step back and think of the 3 principles that Peter summarizes in his conclusion.

If you like information like this, I’ve discussed concepts like triplanar training of the glutes.  These are some of the fundamental principles in my Functional Stability Training of the Lower Body program with Eric Cressey.  We discuss a lot of concepts related to alignment, triplanar function of the body, and training the body in 3D.

Functional Stability Training for the Lower Body

About the Author

Peter Nelson is a Strength and Conditioning Staff Intern with the Pennsylvania State University Men’s Ice Hockey Team.  He graduated in 2012 from Phillips Academy Andover, and is currently a sophomore at Penn State’s University Park Campus.  Peter is a former competitive hockey player, having played for Andover’s Varsity Hockey Team for three years in Division 1 of the New England Prep School Ice Hockey Association.  While he no longer plays competitively, his longtime involvement in sports has driven his interest in research fields such as nutrition and strength and conditioning.  He has previously interned at NIKE SPARQ-affiliated Athletic Evolution in Woburn, MA.  Peter is greatly looking forward to continuing to work under Head Strength and Conditioning Coach Robert McLean of the Penn State Men’s Hockey Team and continuing his education in pursuing a career in the health and fitness realm.

Note: I’d like to thank Coach Rob McLean, Head Strength and Conditioning Coach for the Pennsylvania State University Men’s Ice Hockey Team, for taking me under his wing and introducing me to and helping me understand important concepts like those presented by the Postural Restoration Institute.  Much of this article reflects what I have learned over the course of the past year while working with him and the hockey team as an intern.  I sincerely appreciate the opportunity.

 

Referenses

  • Sim FH, Simonet WT, Melton LJ III, et al: Ice hockey injuries. Am J SportsMed 15: 30–40, 1987.
  • Molsa J, Airaksinen O, Näsman O, Torstila I. Ice hockey injuries in Finland: a prospective epidemiologic study. Am J Sports Med. 1997;25(4):495-499.
  • Emery CA, Meeuwisse WH, Powell JW. Groin and abdominal strain injuries in the National Hockey League.. Clin J Sport Med. 1999;9(3):151-156.
  • Tyler TF, Nicholas SJ, Campbell RJ, McHugh MP. The association of hip strength and flexibility on the incidence of groin strains in professional ice hockey players. Am J Sports Med. 2001;29(2):124-128.
  • Robertson, Mike. March 3, 2007. “Hips Don’t Lie: Fixing Your Force Couples.T Nation.

 

 

 

 

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