Even after 30 years of experience as a physio shoulders are still the hardest to diagnose and treat. There are two key issues the problem is either structural( ie torn ligaments, joint subluxations, damaged tendons or tendon attachments or swollen bursa to name a few) or neuromuscular where the muscle action during movement dont keep the head of the humerus perfectly centred in its very shallo socket.


The former need correct diagnosis with the help of ultrasound or Wikipedia reference-linkMRI and the result will guide correct advice.

The latter respond to a carefully prescribed programme of exercises that correct the neuromuscular instability. the exercise that you illustrated on the 16th Nov 09 is likely jamming the humeral head upwards within the socket causing swelling in the ligament and or the bursa and Wikipedia reference-linkrotator cuff there this is a poor exercise

Another comment I will make is that where shoulders are concerned its better to describe the movement than using the muscle to describe your exercises and/or your symptoms

Are you getting any better??