Shoulder exercise rant, “Empty Can” (EC) exercise

One of my D1 baseball players recently came into the training center today after his first workout with the team strength and conditioning coach and told me about an exercise that got me steamed! (Honestly the whole workout he described was seriously lacking, but this really stuck out). The particular shoulder exercise was the “Empty Can” (EC) exercise. Now I should say the empty can has long been a basis in physical therapy circles when it comes to shoulder rehabilitation. Dr Frank Jobe (the Dr. who performed the first Tommy John surgery in 1974), a well known shoulder specialist, was the first to come up with this exercise. Since then it has become widely known as an isolation exercise for the supraspinatus, even though recent research has show otherwise (3,4,5).

Well with the little history lesson over I wanted to get back to my main concern which was the fact that the strength coach was having the baseball players perform the EC exercise with their arm elevation above a 60 degree angle. (All the way overhead for that matter). Now I have to say I am not a fan of the EC but if you’re going to do them, you need to stay below 60 degrees to prevent impingement of the rotator cuff tendon (2) between its insertion on the greater tuberosity of the humerus and the acromion process.

So why don't I like the EC exercise? Well, according to a study by Reinold et al, the EMG activity of the supraspinatus in the empty can (thumbs down) vs. the full can (thumbs up) is the same. The difference lies in the activity of the deltoid. The empty can produces high levels of activity in the middle deltoid when compared to the full can. So why is this problem? The strong pull of the deltoid pulls the head of the humerus superiorly. It overpowers the supraspinatus and rotator cuff muscles that act to depress and stabilize the head of the humerus. It basically creates forced impingement. Mmmm...Not a good thing for an athlete!

Mike Reinold states in his article, “If the deltoid overpowers the supraspinatus, the rotator cuff cannot keep the humeral head centered within the glenoid fossa and superior migration occurs. Superior humeral head migration = impingement. Not good, and that is why it hurts. There are numerous other anatomical and biomechanical reasons to not use the empty can exercise, but if the full can has the same EMG activity I don’t see the controversy.” Yep, thats why I read his stuff!! (BTW, Mike Reinold is the Head Athletic Trainer and Assistant Director of Medical Services of the Boston Red Sox Baseball Club, check him out at http://www.mikereinold.com/)

Ok, back the the science stuff.....the full can (thumbs up) offers the same benefits for the supraspinatus but produces much less surrounding musculature activity in the deltoid. This allows the humerus to stay nice and comfy in the glenoid fossa in a neutral position. By not forcefully internally rotating the humerus, we don’t re-create impingement in the sub-acromial space. Along with internally rotating an abducted arm we can also get scapular protraction, and anterior tilt. The combination decreases the sub-acromial space resulting in the possibility of more impingement.

The problem with this exercise is simple. When you maximally internally rotate your Humerus (shoulder) the sub-acromial space is greatly decreased when compared to a neutral or externally rotated position. So, when you raise your arm towards shoulder height or higher you are most likely going to impinge the Infraspinatus tendon or other tissues.

Now that you know I’m not a fan of the EC exercise, but you chose to do them yourself you should perform them with proper technique. This requires individuals to internally rotate their shoulder as a means of increasing tension and maximizing activation of the supraspinatus. When raising the arm overhead in the scapular plane, the humerus is required to externally rotate at approximately 60 degrees to prevent impingement of the rotator cuff tendon (2) between its insertion on the greater tuberosity of the humerus and the acromion process. Internal rotation of the arm as required during the EC technique provides a means to improve activation of the supraspinatus, however it prevents the necessary external rotation required to raise the arm overhead without impingement.

Individuals who exceed 60 degrees of elevation during the EC may place themselves at risk for shoulder impingement (1,2). This risk may be avoided by strict adherence to proper form, particularly by avoiding arm elevation above the 60 degree angle. Although the EC may be prescribed for an individual with a shoulder disorder, those previously diagnosed with shoulder impingement have a tendency towards worsening their condition when performing movements similar to the EC, therefore the risk of impingement may outweigh the benefit.

Brian Van Hook, MS, CSCS
Van Hook Sports Performance Las Vegas, NV


References

1. Norkin CC and Levangie PK. Joint Structure and Function. A Comprehensive Analysis. Philadelphia: F.A. Davis Company, 1992. pp. 207–238.

2. Brossmann J, Preidler KW, Pedowitz RA, White LM, Trudell D, and Resnick D. Shoulder impingement syndrome: Influence of shoulder position on rotator cuff impingement—an anatomic study. AJR Am J Roentgenol 167: 1511–1515, 1996.

3. Boettcher CE, Ginn KA & Cathers I. Which is the Optimal Exercise to Strengthen Supraspinatus? Medicine & Science in Sports & Exercise 2009; March: p 1979-1983

4. Escamilla RF, Yamashiro K, Paulos L & James R. Andrews JR. Shoulder Muscle Activity and Function in Common Shoulder Rehabilitation Exercises. Sports Med 2009; 39 (8): 663-685

5. Reinold MM, Macrina LC, Wilk KE, Fleisig GS, Dun S, Barrentine SW, Ellerbusch SW, Andrews JR. Electromyographic Analysis of the Supraspinatus & Deltoid Muscles During 3 Common Rehabilitation Exercises. Journal of Athletic Training 2007;42(4):464–469. (Download full research article in PDF format)

6. The Empty Can Exercise: Considerations for Strengthening the Supraspinatus Strength & Conditioning Journal: April 2009 - Volume 31 - Issue 2 - pp 38-40