Is Your Can Emtpy or Full?

In this monthly series of articles, Mike will discuss the science and practice of physical training for Water Polo.  Strength, flexibility, Water Polo science, rehab and other areas of interest with respect to the physical development of the Water Polo athlete will be covered.

Most Water Polo players will experience some kind of shoulder injury or dysfunction at some point in their career. In conjunction with that comes some knowledge of the “rotator cuff” (RC) to the point where these two words have become part of the lingo of most if not all Water Polo coaches and athletes. But of all the rotator cuff (RC) exercises out there, which ones are the best suited for Water Polo and which are less then desirable.

With the increased knowledge of the human body comes the realization that what was done in the past wasn't always the best option. You will see in this article some exercises that you are very familiar with that have become part of the trash heap while others are receiving very high approval from researchers and rehab clinicians.

In this article I will discuss the following key points:

Rotator Cuff Function

There are four muscles that make up the rotator cuff (Subscapularis, Infraspinatus, Supraspinatus & Teres Minor). When you look at these muscles it is quite obvious that they are rather small when compared to some of the bigger prime movers of the shoulder.

The function of them is usually categorized as either Humeral (shoulder) internal or external rotators but probably more important is the function of keeping the head of the Humerus centrally located in the Glenoid Fossa (or cavity).

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But it's not that simple ... or is it?

You also need to consider that the body works as a whole not as isolated parts, the RC muscles are no different. Since they all originate on the Scapulae (shoulder blade), the position of the shoulder blade will greatly impact how well the RC muscles are able to perform their job. As seen in my last 2 articles, “Stretching the Shoulders for a BIGGER ShotPart I & Part II”; the position of the Thoracic Spine will affect the range of motion of the shoulder. It just so happens that the position of the Scapulae also is greatly influenced by the Thoracic Spine.

What does this mean?

Obviously we need to consider the position of the Thoracic Spine but also the muscles that attach from the Scapulae to the spine. These muscles are primarily the upper, middle & lower Traps and the Rhomboids.

If this is starting to get confusing, don't worry. In this article I will just focus on the RC muscles but you do need to consider the effect of the Scapulae and Thoracic Spine when performing these exercises. What this ultimately comes down to is that your posture (or set up) when doing these exercises is critical. Basically, you want to sit or stand tall with your shoulders down and slightly back, imagine you have a string attached to the top of your head and it is pulling you up towards the ceiling.

sitting bent over

The polar opposite of the posture or set up
you want to use when training your shoulders.

Performing your RC exercises with good or near perfect posture will also train all those muscles that hold you in that good tall posture. Remember your body does not work in isolation.

Best and the Worst

I will start with the most recent villain in the world of shoulder rehab which has to be the “Empty Can” exercise, which is commonly used to target the Infraspinatus.   


"Thumbs Down on the “Empty Can”

The problem with this exercise is actually quite simple. When you maximally internally rotate your Humerus (shoulder) the subacromial 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. The “empty can” movement is actually a common provocative test used by doctor's and clinicians when diagnosing shoulder injuries.


So, from a bio-mechanical perspective, the “empty can” is not a very good option for improving shoulder health. Researchers and rehab clinicians have been aware of this problem with the “empty can” exercise for a few years. With this awareness has come some recent research studies which have looked at EMG analysis of various exercise options for training the RC muscles.

Electromyography (EMG): A diagnostic test that records the electrical activity of muscles. In the test, small electrodes are placed on or in the skin; the patterns of electrical activity are projected on a screen or over loudspeaker. This procedure is used to test for muscle disorders, including muscular dystrophy.

What has been found is that although the “empty can” exercise is good for activating the Infraspinatus (one of the RC muscles) it also activates the Deltoid to a high degree. One of the other exercise options that have been looked at is the “full can” position which is the same as the “empty can” but with the thumbs up. Again, from an EMG stand point not bad but it also has a very high degree of deltoid involvement although from a bio-mechanical perspective it has a much lower risk of causing shoulder impingement type symptoms.

The best exercises seem to involve some kind of “full can” or external rotation in a prone (lying on stomach) position when using free weights or standing using a cable or tubing as resistance. These exercises activate the RC muscles to a high degree while at the same time not over stimulating the the surrounding bigger muscles. Some of the research also shows the below exercises also activate the Infraspinatus muscle (another reason not to do the “empty can” exercise).

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(Above pictures from: Boettcher et al. 2009)

What about the Subscapularis ... Internal Rotation?

So far I have only talked about the external rotator cuff muscles, but what about internal rotation (i.e. Subscapularis). Well there is a very good reason why I have not discussed it up to this point.

The specific repetitive activity of water polo, like baseball pitching, emphasizes adduction and internal rotation. This study used the Cybex II to evaluate the isokinetic strength of the rotator cuff in elite water polo players and in a group of control subjects. The water polo players were significantly stronger than the controls. Of greater importance was the confirmation of imbalances in the rotator cuff force couples of adduction/abduction and external/internal rotation. These changes are similar to those reported for pitchers. The adductors in the water polo group had gained in relative strength resulting in an increase in the adduction/abduction ratio to about 2:1. The internal rotators had gained in relative strength resulting in a decrease in the external/internal ratio to about 0.6:1. For both force couples the differences are more apparent at a slow speed. Side-to-side differences were not significant.

(McMaster et al. 1991)

All this means is that Water Polo players are much stronger with internal rotation and therefore need more strengthening of the shoulder external rotators to balance out the whole shoulder complex. This actually goes hand in hand with my recommendation of doing more pulling then pushing exercises.

So, the best exercises for the Water Polo athlete's rotator cuff has external rotation as a component of the movement performed anywhere from a neutral humeral position to approximately 90 degrees.

The video below is an example of a good dumbbell external rotator cuff exercise with a small twist. Watch the video to see what that twist is.

Training the Other Function

Remember that “other” function of the RC muscles, keeping the head of the Humerus centrally located in the Glenoid Fossa (or cavity). This function is actually quite easily trained by performing closed chain exercises like various push ups, pull ups and one of the best in my opinion the Turkish Get Up (TGU). I wrote about the TGU in an earlier article.

Below are two exercises that really challenge your shoulder stability and are great for training the RC muscles.


The shoulders are the most common joint injured in Water Polo players. The RC muscles perform three main functions, internally and externally rotate the Humerus and to stabilize (or centralize) the head of the Humerus in the Glenoid Fossa.

With the exercises shown in this article, you now have the beginnings of a good tool box of drills to aid in strengthening all the different functions of the RC muscles and actually when done with “perfect” posture it will also train all the other synergistic muscles appropriately (remember the body never works in completes isolation and everything is related some how).

I will open a thread on the message board in the category “Physical Training with Mike Reid” with the title of this article. Please leave your comments, questions, suggestions, experiences, ... on the message board.

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

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

McMaster WC, Long SC, Caiozzo VJ. Isokinetic Torque Imbalances in the Rotator Cuff of the Elite Water Polo Player. Am J Sports Med. 1991 Jan-Feb;19(1):72-5

Reinold MM, Escamilla RF, Wilk K. Current Concepts in the Scientific and Clinical Rationale Behind Exercises for Glenohumeral and Scapulothoracic Musculature. Journal of Orthopaedic & Sports Physical Therapy 2009; 39 (2)

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 Entire Article for Free here.

Wagner P. A Comprehensive Approach to Shoulder-Complex Maintenance. Strength & Conditioning Journal 2003; 25 (3): p 65–70

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