Heart and lung work in the ribcage. If there is any tension in the ribcage, it takes more effort to breath and the heart has to beat harder to produce the same effect. When the ribcage is fluffy and relaxed, both organs have more space for their rhythmic movements and will be able to work under ideal conditions.
So, what can we do if we feel tension in the area of the ribcage? To loosen up and open the ribcage, the easiest way is to work with the arms. The muscles of the arms and their attachments spread out over the whole upper part of the back and the breast area. As outer muscular layer, they rest on the ribcage along with the shoulder blades.
Exercise to loosen the ribcage
Both hands are at head level, left and right, and slightly in front of the body. As we move the hands backwards, we build fists. – Our hands are now almost beside the head on both sides and are slowly tensed up. When the hands are moving backwards, we let the shoulder blades rotate freely. Thus, the ribcage closes itself in the back and at the same time it opens up in the front. Now, we move the fingers back to the front and open them. We let the fingers grow into all directions until we have big open hands. Then we move our hands back again and build fists (etc.). We tense up the whole body simultaneously with the change from open hand to fist.
When you feel comfortable with the exercise, you may add a slow turn of the head to address the deeper muscular layers as well.