I have been getting pain in my shoulder when doing certain exercises at the gym

The pain seems to go away after a few reps

I think it’s a problem with a tendon, it’s behind the deltoid muscle and goes down my upper arm about half way

Sounds like one of my current problems…

I get the pain in my biceps tendon, but the physio reckons its pain transference and actually the problem is an impingement in the Supraspinatus tendon. He has this guide on his website:

http://injuryactive.com/339/

Following a thorough assessment it is sometimes very hard to identify the exact injury without imaging/investigations. A lot of the time we therefore categorise the injury under the term “sub acromial impingement” (SAI). SAI can be caused by a number of structures being compromised in the subacromial space (this is the space shown by the red circle in the picture above, between the humerus (arm) and the acromion (top of the shoulder which forms the end of the shoulder blade). SAI is the most common shoulder injury I see in my clinic.

Treatment protocol is rest (avoid pain at all costs) and lots of work with bands to strengthen the scap muscles, mainly internal and external rotation exercises.