Ever tried the stretch in the photo?
I used to tell my clients to use this type of movement to help them 'stretch' their chest in order to get their shoulders back in to position (Think rounding shoulders).
BUT (and there is ALWAYS a but!) quite often stretching this way does not help a huge amount (and that's talking from 14 years experience). What in fact happens quite often is that the nerve in the arm is under tension already, as a consequence the muscles around the shoulder aim to protect it and go in to a low grade spasm (meaning you can't feel it) so that you can't stretch it any further and potentially 'damage' the nerve.
But now everything feels 'tight' and so we stretch and stretch. After all, that's what you do when something feels tight isn’t it?
Well not always. In this instance, the stretch in the photo is only going to put more pressure on the nerve and so cause the muscles around it to tighten even further. And the more you stretch the more protective the body becomes. Now if you're stretching in this way and are feeling any tingling then it's a sure sign that you're affecting the nerves. STOP. Stretching them further isn't going to help and will in fact cause more harm than good. You need to figure out WHY the shoulder feels 'tight' or why you feel your shoulders are rounding.
I wish so much that I could tell you that if you do X, Y and Z then it will fix it but I can't. Every single person that I assess is different. But what I can tell you is that where the issue is the cause is not.