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The Full Can Exercise as the Recommended Exercise for Strengthening the Supraspinatus While Minimizing Impingement

Tino, Dustin ATC, CSCS; Hillis, Cameron ATC, CSCS

Strength and Conditioning Journal: October 2010 - Volume 32 - Issue 5 - p 33-35
doi: 10.1519/SSC.0b013e3181d54721
Columns: Flexibility and Rehab Tips

THE PURPOSE OF THIS COLUMN IS TO SHOW THAT CURRENT RESEARCH SUPPORTS THE USE OF THE FULL CAN EXERCISE OVER THE EMPTY CAN IN STRENGTHENING THE SUPRASPINATUS EFFECTIVELY WITHOUT INCREASING IMPINGEMENT BY LIMITING REDUCTION OF THE SUBACROMIAL SPACE.

Pine Crest School, Fort Lauderdale, Florida

Figure

Figure

Helen M. Binkley, PhD, ATC, CSCS,*D; NSCA-CPT,*D

Column Editor

Dustin Tino

is the assistant athletic trainer at Pine Crest High School.

Cameron Hillis

is the head athletic trainer at Pine Crest High School.

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INTRODUCTION

The rotator cuff consists of the supraspinatus, infraspinatus, terres minor, and the subscapularis muscles. The supraspinatus provides stability of the humerus in the glenoid fossa and aids in abduction along with the deltoid (5,11). The supraspinatus is vulnerable to impingement from mechanical compression when the supraspinatus tendon is compressed between the coracoacromial arch and the greater tuberosity of the humerus during abduction and flexion (2). The subacromial space (area inferior to the coracoacromial arch) is decreased when the humerus migrates superiorly from either weakness (18) or injury to the rotator cuff (4,10,14,17,21). Strengthening the supraspinatus to improve shoulder stability while limiting impingement are prominent issues in athletes who use overhead motions.

With the importance of the supraspinatus in providing stability and its vulnerability to impingement, it is important to choose appropriate strengthening exercises. Initially, it was believed that the “empty can” (EC) exercise was the most favorable exercise for strengthening the supraspinatus during rehabilitation (6,20). The EC is performed by elevating the arm 90 degrees in the scapular plane (30 degrees anterior to the frontal plane) while maintaining shoulder internal rotation. However, athletes and patients reported pain in their shoulder during the EC. The pain associated with the EC has been attributed to the mechanical compression and impingement from the reduction of the subacromial space (7). The concern over the pain associated with the EC leads researchers, strength professionals, and therapists to the search for alternative exercises that will activate the supraspinatus muscle effectively and minimizes the detrimental effects seen with the EC. The EC has been modified by performing elevation in external rotation instead of the internal rotation with the EC. Performing abduction in the scapular plane with the shoulder in ER has been labeled as the “full can” (FC). It is our contention that current research supports that the FC strengthens the supraspinatus effectively without increasing mechanical compression and impingement by limiting reduction of the subacromial space. The FC should be the preferred exercise for strengthening the supraspinatus over the EC.

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EMPTY CAN VERSUS FULL CAN

When the EC is performed, there is an excess of middle deltoid activity in comparison of the FC (13,22). This excess amount of deltoid activation in comparison with the supraspinatus activity leads to superior humeral head migration and a decrease in subacromial space (12). The position of the scapula also can produce subacromial impingement. When the scapula is protracted, it rotates internally and tips anteriorly, decreasing the subacromial space (15). The EC produces more scapular internal rotation and anterior tippingleading to a decrease in subacromial space verse the FC (19). Shoulder internal rotation during the EC was thought to maximize the supraspinatus activity by increasing tension of the muscle (9). However, when the FC and EC have been analyzed, the FC has performed similar in electromyographic testing (7,13,22) and magnetic resonance imaging (16) for supraspinatus activity.

One of the modifications of the FC is the prone full-can exercise. This is performed by horizontal abduction at 100 degrees while maintaining external rotation in the prone position. Early research showed that the prone FC was superior to its standing counter parts in activation of the rotator cuff muscles (1). However, present studies show that the prone FC performed similar (13) or less (16) for supraspinatus muscle activity than the EC and FC. There was also increased activity of the middle deltoid verse the FC (13) leading to humeral head superior migration and a decrease in subacromial space.

Another modification proposed is by performing the EC with just 60 degrees of elevation (9) in the scapular plane. The EC produces a superior resultant force on the humeral head at 30 and 60 degrees of elevation that can lead to the superior migration that causes impingement (11). Even at just 30 and 60 degrees of elevation, there is a significant internal rotation and anterior tipping with the EC when compared with the FC (19).

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FULL CAN TECHNIQUE

The FC exercise is performed by elevating the arm in the scapular plane with the thumb pointed up to indirectly produce the desired shoulder external rotation (Figure 1). The arm is elevated to 90 degrees before being lowered. The athlete is instructed to retract the scapular before arm elevation and maintain it throughout the exercise to maintain optimal subacromial space as well as reinforcing activation of the scapular stabilizers. Maintaining a retracted scapula during arm elevation produces more force than when the scapula is protracted, proving the importance of the scapular stabilizers in providing a stable foundation for the arm (8). The athlete or patient should be observed from the back to detect any scapular winging during the exercise. Scapular strength deficiencies need to be addressed to allow optimal shoulder function. The FC should be performed to improve muscular endurance and strength because of the demands of the rotator cuff in overhead sports and to prevent the humeral head from migrating superiorly from fatigue during activities (3,18). Typically, 10-15 repetitions are performed for 2-3 sets with 3-5 lb of resistance to satisfy these goals. When working with an injured shoulder, the resistance should be reduced until they can produce the exercise pain free. The FC can be performed by holding a dumbbell or with an elastic band by holding the ends and standing on the band (Figure 2).

Figure 1

Figure 1

Figure 2

Figure 2

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CONCLUSION

The FC is superior to the EC or the modified versions mentioned. The present research supports the use of the FC as the recommended exercise for strengthening the supraspinatus and maximizing the subacromial space (7,12,13,16,19,22).

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