Infraspinatus muscle and teres muscle
 

The infraspinatus and teres minor rotate the head of the humerus outward (external, or lateral, rotation)
The primary motion of the infraspinatus is to externally rotate your humerus.

So more room in the thoracic outlet.

http://en.wikipedia.org/wiki/Infraspinatus_muscle
http://en.wikipedia.org/wiki/Teres_minor_muscle
http://www.ncpad.org/exercise/fact_s...6&section=2336
http://www.askthetrainer.com/rotator...exercises.html

Infraspinatus muscle atrophy in professional Baseball players (they got TOS sometimes)

http://cat.inist.fr/?aModele=afficheN&cpsidt=15523935



Do we need to strenghten these muscles ?

If there are triggerpoints or spasms or PAIN you would have to resolve those first.
It just causes more problems if you try to strengthen any muscle that has these issues happening.

So if you are feeling fairly normal with maybe just a little bit of tightness and a low pain level- 0-2 ??
then you could try slow gentle strengthening, but slow and easy to see how body responds.


When I was in PT for my then dx'd only as bilateral RSI - they didn't suggest any weights or bands for me until my pain & sx was down to a 1-2 .
For me they started with 1lb and a slow controlled lower/lifting with wrist over the edge of a table/stool and only to tolerance. And they asked about any pain level increases or sx increases before we continued on @ the next session.

They always asked how I felt before we started PT or added something new.

They said pain alone is a limiting factor - remove the pain and some muscle strength will return on it's own - but if someone has been in pain for a long time- then the muscles would be out of shape due to lack of use.

For traditional pt (upper trapzius, shoulder) maybe, but it seem harmless here no ?

" Finally, exercising the rotator cuff can lead to improved posture, as without exercise to the external rotator, the internal rotators can see a shortening, leading to tightness. This often manifests itself as rounded shoulders."

PT had me do the Lying Dumbbell External Rotation showed on this link -
http://www.askthetrainer.com/rotator...exercises.html

but i did it a lot slower than the video shows it. and only a 1 lb & 3 lb weight

but it was after the pain was reduced before we did anything like that