Empty Can vs Full Can
Empty Can vs Full Can
Written By: Paul Kochoa, PT, DPT, OCS, CGFI
Before I go into the explanation of what the title of this post means, we have to talk a little about the shoulder itself. The shoulder complex is made up of three bones: the clavicle, the scapula, and the humerus. The shoulder as a “ball and socket” joint, as it is commonly known, is actually just referring to the head of the humerus and the glenoid fossa. The head of the humerus bone glides and rotates in the socket of the scapula (the glenoid fossa), and in addition to the movement of the scapula and the clavicle, the three bones move in unison to create the normal movements of the shoulder.
The point of interest is the space underneath the acromion (the top part of the scapula). The space between the acromion and the head of the humerus is pretty small. There’s room for the bursa and supraspinatus tendon and other tendons to pass under there, but not for much else. This space is a prime spot for impingement (pinching of a tendon or other structure between two bones), if the movement between the humerus and the scapula are somehow compromised.
Another thing I want to point out, but is not indicated in the photo above, is the greater tuberosity of the humerus (in Latin: tuberculum majus). It’s the large bump on the left side of the humerus above, where the tendon of the supraspinatus ends. This bump, when the upper arm is in a certain position, can really close that space with the acromion, resulting in impingement (usually accompanied with pain).
So now that we’ve familiarized ourselves with some of the anatomical structures of the shoulder, let’s look at the “empty can” as demonstrated by this individual:
Notice the hand and arm position (thumb down, palm facing backwards, elbow pointing up), this places the arm/shoulder in internal rotation. This internal rotation, combined with raising the arm, results in the greater tuberosity of the humerus to narrow that space between it and the acromion. This is not a great position for the shoulder to be in, but sure, if you did this, you’d totally feel your shoulder burning, your muscles aching. I see this all the time in the gym.
Raising your arm to do lateral raises or upright rows with your palms down or worse with your thumbs down, creates an environment for impingement and pain. The fix would be to do the “full can”.
The “full can” position is the opposite of the empty can, the palm is facing forward, the thumb side of the hand is up, the elbow points down. This external rotation position allows that greater tuberosity to clear out from under the acromion and decreases the chance of impingement. Try this next time you’re in the gym.
There’s other positions that can cause impingement, but this is one of the most common ones. If you’re having shoulder pain, a physiotherapist at Professional Physical Therapy and Training can help you figure out the reason and help you fix it. Can you think of any other positions that can cause a shoulder impingement?Image courtesy of farconville / FreeDigitalPhotos.net