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Rotator Cuff EMG During Daily Activities

Posted Jul 12 2010 3:00am

DSC01454A frequent topic of discussion on this site involves the postoperative guidelines following rotator cuff repair.  We have had many discussions about the contrast in preference between early rehabilitation and conservative rehabilitation among clinicians.  Obviously, if you have read some of my past posts and publications (check out here and here ), you know that I have always preferred to start immediate rehabilitation and have had pretty good success.

However, many, many clinicians are still progressing conservatively, even delaying the initiation of range of motion for 2 months and strengthening exercises for 3+ months!  The common justification is to avoid deleterious forces on the repair in attempt to minimize failure of the repair.  A few studies have been published showing that anywhere from 25-75% of rotator cuff repairs are torn again 1-2 years after repair.

That is why a recent study in JOSPT was of interest to me.  The study quantified the EMG activity of the infraspinatus, supraspinatus, and deltoid musculature during the pendulum exercises and three activities of daily living – typing, drinking from a glass, and brushing your teeth.  These are all activities that our rotator cuff repair patients are performing and an exercise, the pendulum, that I would say most physicians are comfortable allowing early in the rehabilitation process.

 

Results

The results of the study were very interesting, highlights include:

  • Pendulums were broken down into 4 groups and compared.  These included large circles and small circles as well as performed passively (correctly) or actively (incorrectly).
  • Large circles in general created higher EMG activity of all muscles involved.
  • Large circles performed actively produced the highest amount of supraspinatus EMG activity – about 19% MVIC
  • Small circles produced less than 10% MVIC of the deltoid and supraspinatus, and under 15% MVIC of the infraspinatus
  • Typing had relatively low EMG activity with 12% MVIC infraspinatus and 7.5% MVIC supraspinatus
  • Brushing your teeth showed 20% MVIC of the infraspinatus
  • Drinking from a glass showed over 18% MVIC of the infraspinatus and 21% MVIC of the supraspinatus

image image

 

Clinical Implications

There are a few major points I took away from this study

  1. Pendulums should be performed using small, rather than large, circles.  Furthermore, it is important to instruct the patient in proper technique, using the body to sway the shoulder passively rather than actively perform circles.  We have all seen patients just actively twirl the arm around.  This was never the true intent of the pendulum exercises.  It’s true form should be passive.  Here is a good example:
  2. Some common ADL’s, including brushing your teeth and drink from a glass, show higher EMG activity than pendulums.
  3. Furthermore, if you combine this information with past studies by McCann (CORR ’93) and Dockery (Ortho ‘98), these common ADL’s also have higher EMG activity than passive and active assisted range of motion exercises.  Thus, it again appears that we have more information to justify the use of early range of motion exercises following rotator cuff repair.

Interesting information.  How many people have physicians that will allow pendulums but will not let you start passive range of motion early after rotator cuff repair?

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