Sports Medicine Research: In the Lab & In the Field: The Influence of Arm & Shoulder Position on 3 Clinical Tests for Subscapularis Injuries (Sports Med Res)
Monday, November 21, 2011

The Influence of Arm & Shoulder Position on 3 Clinical Tests for Subscapularis Injuries

The influence of arm and shoulder position on the bear-hug, belly-press, and lift-off tests: an electromyographic study.

Pennock AT, Pennington WW, Torry MR, Decker MJ, Vaishnav SB, Provencher MT, Millett PJ, Hackett TR. Am J Sports Med. 2011 Nov;39(11):2338-46. Epub 2011 Feb 7.

In the past, most rotator cuff tears involved the supraspinatus and infraspinatus muscles.  Therefore, most diagnostic and rehabilitative data involved techniques and exercises to focus on these muscles.  Increased awareness of subscapularis tears has lead to research that focuses on the causes, diagnosis, and treatments of subscapularis tears.  The belly-press, lift-off and bear-hug tests are used to identify subscapularis muscle injuries.  The belly-press and lift-off are the most commonly used tests with the belly-press being introduced most recently from Barth et al.  With variability existing between clinicians in regard to arm position with each test and the influence that pain and decreased mobility may cause in test performance, this study attempted to determine the optimal arm and shoulder position for evaluating subscapularis muscle function with each test and compare the efficacy of each clinical test in the isolation of the subscapularis muscle. This study included 20 healthy males aged 18-45 years old with no prior history of neck, shoulder or scapular pain. Electromyography (EMG; muscle activity) of 7 muscles (upper and lower divisions of the subscapularis, supraspinatus, infraspinatus, latissimus dorsi, teres major, triceps, pectoralis major) was monitored for each special test at varying arm positions. The participants were instructed in proper test performance and given adequate time to practice each test with an emphasis on arm positioning.  Muscle activity was recorded for each clinical test in the 3 positions for 3 trials, and lasting for 3 seconds each.  The reported ideal positions for each clinical test were as follows:  The bear-hug test was performed with the palm of the involved side on the AC joint of the contralateral shoulder, with the shoulder in 90° abduction.  The belly-press was performed with the palm of the involved side against the abdomen just below the level of the xyphiod process with the elbow in line with the trunk in the sagittal plane.  Finally, the lift-off test was performed with the arm of the involved shoulder behind the back with the dorsum of the hand just below the mid lumbar spine (L2-4).  Results indicated that regardless of arm and shoulder positioning, the upper and lower scapularis muscle activity was significantly greater than all other muscles.  Subscapularis muscle activity did not differ between tests.  No difference was noted between each division of the subscapularis muscle across any of the 3 positions for each test.   A difference in EMG activity was noted between the pectoralis major and triceps during the different clinical tests. 

This study shows that all 3 clinical tests are effective in testing the integrity of subscapularis muscle function.  It also demonstrates that patient arm position does not play a significant role in the activity of the subscapulris.  This is of particular importance in the presence of pain and decreased joint mobility which will not allow for testing in certain arm positions in a subset of injured patients.  It is common during a clinical examination of joint injury that pain and decreased mobility can limit the findings of special tests.  Most times this causes the clinician to defer the tests till pain and mobility issues have resolved.  This study shows that muscle integrity can still be determined despite these factors early in the examination process.  This would aide the clinician in terms of early diagnosis and intervention with treatment techniques.   Some limitations of this study include the limited amount of muscles chosen. There are several other muscles that are active during these tests that can compensate for the subscapularis and should be considered in the future.  In addition, it would have also been interesting to see if differences would have been noted with a longer hold time for each trial.  Future research should examine the variations of arm positioning for different special tests at the shoulder.  Have any clinicians already started to occasionally deviate from ideal test positions with joint examinations?

Written by:  Tom Martin
Reviewed by:  Stephen Thomas

Pennock AT, Pennington WW, Torry MR, Decker MJ, Vaishnav SB, Provencher MT, Millett PJ, & Hackett TR (2011). The influence of arm and shoulder position on the bear-hug, belly-press, and lift-off tests: an electromyographic study. The American Journal of Sports Medicine, 39 (11), 2338-46 PMID: 21300808

5 comments:

Jake Marshall ATC said...

Would some one be willing to explain what this means. It came from the abstract for the Barth et al. study.

"No statistically significant difference was found between the area under the receiver operating characteristic curve of the bear-hug test and that of the belly-press test in diagnosing a torn subscapularis. However, the areas under the receiver operating characteristic curve for both the bear-hug test and the belly-press test were significantly greater than those for the lift-off and Napoleon tests (P < .05)."

Thanks!

Stephen J. Thomas, PhD, ATC said...

Jake thanks for the comment. I actually had to look in the full text article to figure it out. From the article they state "Receiver operating characteristic (ROC) curves, which are graphic representations of corresponding sensitivity and specificity values." It is a graphical way of looking at sensitivity and specificity but also stats can be run on these to determine if the test had precision. I hope this helps.

Jeffrey B. Driban, PhD, ATC, CSCS said...

Jake you might find these links helpful...

http://www.medcalc.org/manual/roc-curves.php
http://en.wikipedia.org/wiki/Receiver_operating_characteristic

As Steve noted, it's a nice way to assess a diagnostic test or to determine cutoffs.

Ian Hix, ATC said...

This study brought up some good points that should not only be considered during evaluation, but rehabilitation as well. Traditionally, it has been emphasized that progression for strengthening with internal rotation should begin by the patient's side and progress to 90 degrees of abduction; however, this study states that EMG recorded the same amount of muscle activation across all three tests. Given this progression also normally reflects damage to other structures, i.e. labral tears, impingement, etc. Taking pain into account, I think a good question to consider would also be the position of the shoulder with subscapularis pathology. If each division of the subscapularis muscle exudes the same amount of muscle activation, should pain be present with all tests attempting to isolate the subscapularis? In other words, is one test as likely to rule in subscapularis pathology as the others, or should all three be used to better diagnose a subscapularis tear, or injury in general. Furthermore, a usual mechanism of injury isolating a subscapularis tear would be hyperextesion or external rotation of an abducted arm; therefore, I think future research should include diagnostic testing subscapularis tears emphasizing these these three tests.

Tom Martin said...

Thanks for the comments Ian

I agree that alot of evaluative techniques can be applied when developing a specific treatment plan for a patient/athlete. Progression of forces and joint positioning are vital components to any treatment progression.

In regards to this study, I feel it gives a clinician more choices when attmepting to identify subscap pathology. Not only is there variability in joint position for each test, but multiple tests that can be chosen from when looking into subscap injury. Adding this information to other components of an examination will only assist a clinician in diagnosis and treatment.

I agree that further research looking into subscap tears, especially with the testing format of this present study would give useful information. For instance, testing shoulders with diagnosed subscap pathology in variations of each test.

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