Make sure to find a PT who has experience with TOS. I had two tough PT programs that made my symptoms pressively worse. Thankfully, my third PT knew what she was doing. Beware weights and rubber bands. The focus should be on stretching the fascia. Building muscle, which they will tell you will better your posture and give the area stability/less strain, may actually increase the muscle mass of the scalenes which can put more pressure on the nerves and/or blood vessels affected by compression in the brachial plexus.