I thought I would add here that first rib mobilisation has been something I have been doing to myself for the past 4 or 5 days now.

I will link folks to the video I followed so that others can see the technique used.

Athletic Thoracic Outlet (TOS) | Feat. Kelly Starrett | Ep. 257 | MobilityWOD - YouTube

In this video he used a PVC pipe and a towel. For me I use a broomstick, and I cut a + into a tennis ball and stuck in on the broomstick. What I like to do BEFORE doing the first rib mobilisation is either take a hot shower to loosen up the muscle fibers or use moist heat on the neck and trap area to loosen up the fibers as well. Then follow the directions in the video. What I can say is that it is uncomfortable to do. Are you going to feel 100% better instantly? No. But you might find that if you do this regularly you might retrain that rib to work properly.

Some folks here have been dealing with TOS for years. You aren't going to fix it in 5 minutes, the first rib may not even be your problem, it could be pec minor, and a host of other issues. It is good to loosen up every possible area of compression before as well as mobilise the first rib. I try to do this twice a day right now to keep my rib moving normally. One in the morning and once at night.

I have kind of realised that when my first rib originally got stuck in the upward position, it caused some weird pain in my armpit. To avoid that pain I started shrugging my shoulders up because relaxing them felt tight and uncomfortable. By shrugging for hours all day every day my traps, my pec minor, started to compensate for shoulder movements. This, in my opinion causes the degradation of proper scapular movement. From here you also get tight, shortened scalenes (hypertonic) because the rib is constantly elevated. Now you're in a world of trouble.

So, start getting to work loosening up those soft tissues. I recommend a good PT, massage therapist or chiro, to loosen you up. Some of them may be able to do the first rib mobilisation for you as well!