I was getting pains in my shoulders. The doctor says it is because my shoulders curl. Not noticably but they do. I never noticed until the doctor pointed it out. He gave me some advice on how to train them to stay straighter. Using pillows at night to wall exercises. To even going for massages.
So i heard about these shoulder braces. That you can wear under your clothing and no one will notice. This will help train my shoulders to stay straight.
I looked on ebay and to my surprise there were shoulder braces for cheap! What did i have to lose? So i ordered one. One size fits all it said. I am not a big woman. Well this turned out to be tight and does the trick. But it was too tight and hurts around the under arm area. No matter how you adjust it. You can't udjust the underarm strap. Just the waist part of it.
I can't wear it during the day because i can't move well with it on. So i just wear it at night to bed. This way it can help with my shoulders and I don't end up in pain under my underarms from moving and it being so tight.
It works but hopefully it fits your underarms.