Sports Medicine Research: In the Lab & In the Field: Are Swimmers Shoulder Motion Symmetrical? (Sports Med Res)
Friday, October 7, 2011

Are Swimmers Shoulder Motion Symmetrical?

Glenohumeral joint rotation range of motion in competitive swimmers.

Riemann BL, Witt J, Davies GJ. J Sports Sci. 2011 Aug;29(11):1191-9. Epub 2011 Jul 22.
http://www.ncbi.nlm.nih.gov/pubmed/21777164

Side to side shoulder ROM changes in overhead athletes is nothing new. Previous studies have noted that with repetitive overhead sporting activities, most notably baseball, we can expect to see an increase in dominant arm external rotation and a concomitant decrease in internal rotation. While this occurs in athletes performing unilateral UE activities, what isn't so clear is what type of shoulder ROM changes can be expected in individuals performing bilateral UE sporting activities. On the surface, it is tempting to believe that there will be equal ROM changes bilaterally. In this article Reimann et al. studied 144 competitive swimmers, aged between 12-61 years (broken down into age subcategories of youth, high school, college and master's). Recruitment was based on the following criteria: >1 year experience, >3 practice sessions/week and no recent history of shoulder pain or injury. The motions that were examined included ER, isolated 90/90 IR (glenohumeral IR only), composite IR (90/90 IR + scapular protraction) and the total arc of motion (ER+ composite IR). The authors investigated 3 different hypotheses. First they stated that there would be no difference between men and women. They found that all age groups except youth men and master's women had significant increases in dominant arm ER ROM. Of note, significant increases in non-dominant UE isolated IR, composite IR and total arc of motion were seen in the subjects regardless of age and gender. Secondly the authors believed that the dominant shoulder would have greater ROM in all directions than the non-dominant arm. Parts of the second hypothesis were supported, but a lack of significant dominant side ER ROM for youth men and master's women swimmers prevented the authors from being able to fully prove their hypothesis. These same swimmers (youth men & master's women) also had greater non-dominant isolated IR, composite IR and total arc of motion. Lastly, the authors believed that younger swimmers would have significantly more ROM than the older swimmers. This third hypothesis also was partially supported. The youth and high school swimmers exhibited significantly larger ROM values for composite IR when compared to college and master's-aged swimmers. They also had significantly greater total arc of motion values when compared against all other groups.

The authors believe that several factors may be influencing the results. First, in regards to dominant side ER increases, they state that this might be due to limb bias during activity of daily living. While the athlete is performing a bilateral UE sporting task, the repetitive and cumulative effects of their actions out of the water could be playing a role in the data that they obtained. Second, the authors theorize that the IR increases seen in the swimmers' non-dominant side could be related to the preferred side of breathing, which is often times their dominant arm side. They suggest that it may be plausible that more IR is needed on the non-dominant side in an effort to continue to propel the swimmers as their body rolls during breathing. Lastly, the authors believe that the greater ROM values seen in the younger subjects is potentially due to fewer years of repetitive training as well as inherent greater ROM values seen in a younger population. This study does a good job of clarifying what sports medicine professionals can reasonably expect to see when doing pre-participation screening for various healthy swimming populations. The next logical step would be to do a follow-up study examining ROM in an injured swimming population. What are your thoughts on this study? Are you surprised that there isn't more ROM uniformity between both UE's after participating in a task like swimming? What is your experience when examining a healthy swimmer? Are you looking critically at the athlete and taking into account age, gender and limb dominance when you examine them?

Written by: Mark Rice
Reviewed by: Stephen Thomas

5 comments:

Justin said...

I would be interested to see a comprehensive history for the subjects. Specifically, I would be curious to see what kind of other unilaterally dominant activities these people performed. For example, were any of these swimmers competitive baseball/softball or tennis players at any point because this could account for some of the unilateral dominance.

Mark A. Rice said...

Justin, thanks for reading. I love your thought process! While the study didn't really reveal the subjects comprehensive history, I believe that it something that should be accounted for during any upper extremity evaluation. As a clinician, when evaluating an athletes passive 90/90 ER and IR, I made certain to ask them if they ever played an upper extremity dominant sport in their youth, especially if I noticed a side to side disparity. If they answered yes, then I'd proceed to ask them what sport it was and how long they played it. By being able to get a more in-depth history on the patient, we as sports medicine professionals can then begin to understand that an increase/decrease in shoulder ROM isn't necessarily always pathological, but more a physiological adaptation to the individual's previous sporting demands.

With baseball being so pervasive in America, it should come as no surprise that many athletes at the college level have side to side ROM differences, even if they aren't playing baseball anymore. I can't begin to tell you how many athletes I've evaluated where that is the case.

Certainly, ROM changes can and will occur post-injury, but understanding and recognizing the difference between pathological and physiological changes during the evaluation process is key.

My advice for budding ATCs, PTs and other physical medicine specialists is: DIG DEEP! You might be surprised on what you'll discover during a patient history/evaluation.

John Goetschius, ATC said...

I think it would be interesting to see these measures further stratified by preferred competitive stroke of the swimmer. Would you expect a greater different in bilateral comparisons of internal rotation in freestyle swimmers and a greater difference of external rotation in backstroke swimmers? I feel the idea of breathing side plays a huge role in this bilateral difference, and in my experience differences in muscle tone can be noted just through visual examination of the upper back and extremities depending on the side the swimmer prefers to breath on. I shared the findings of this article to swimmers I have been working with to hear their subjective observations while swimming, and they stated they definitely notice differences in ROM and strength from one arm to the other.
As clinicians it raises the question, if we note a bilateral difference in a swimmer that is not causing symptoms should we try to correct the difference or leave it be as a normal consequence of the sport?

Mark A. Rice said...

John, thanks for reading and sharing with your athletes!!! I think delving further into the various strokes is absolutely something that needs to be considered as this research area is expanded. There is definitely a lot of work to still be done.

While swimmers do specify in certain strokes, what percentage of the time are they training for it? 30%? 40%? The front crawl is the most commonly utilized stroke by swimmers and that is why it was selected. If they are training backstroke, butterfly, there could conceivably be some changes, and there probably are, but I am of the mind the differences might not be all that pronounced due to the fact that they still spend the majority of their time training in the front crawl. I might be way off on that, but that's what SMR is all about, having a forum to provide new ideas and thought processes.

As far as what do we do with side to side differences, I think that is based upon the individual. Knowing what is normal for the athlete, and managing their ROM from that mindset I think is more important than trying to blanket the population. Case in point, managing baseball players and GIRD. The degree to which a player has it will dictate what efforts need to be made. Some may need more attention than others. With a preseason screen, we can determine such things.

Thanks for contributing.

Mark A. Rice said...

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