If you have a hunched back or rounded shoulders, make sure to focus on stretching the muscles around your collarbones, in addition to those in your shoulders and back.
Rounded shoulders mean that the muscles around your collarbones are also constantly in a contracted state.
Extend one arm straight out to the side, then bend it at a 90-degree angle.
Lower your arm slightly (to an angle of 45–60 degrees) while keeping the elbow bent, and place the section between your elbow and wrist against a pillar or the corner of a wall.
From this position, rotate your body away from the pillar or wall to stretch the area beneath your collarbone and the upper part of your pectoralis major (chest muscle).
Additionally, if you position your arm parallel to the floor, you can stretch your entire chest area; if you raise your arm slightly above that parallel position, you can stretch your side (flank) area.
