Expansion Breathing or Rotational Angular Breathing (RAB), established by Katharina Schroth, is the process whereby inhalation expands the rib cage and therefore opens the thorax and chest cavity, decreasing compressive areas and creating space for more inhalation.
When our body adjusts to asymmetries caused by excessive curves and malalignments, an altered breathing pattern is created which can feed further into spine curvature and vertebral rotation. The muscles along the vertebra and ribs closest to the breathing apparatus become imbalanced on opposing sides. Schroth Expansion Breathing or RAB teaches the patient to learn to change their breathing pattern by shortening the overstretched muscles on the outside of the curve (the convex side) of the spine and lengthening the muscles on the inside of the curve (the concave side), slowing the curve progression. Through deflexion, de-rotation, and elongation of the spine and rib cage, the body can return to a more ‘normal’ physiological position.

Inhalation naturally accompanies the expansion of your rib cage and can support your collapsed regions. As you increase your total air volume in your thorax in all directions, you are expanding the muscles between your ribs (intercostals) and in between your vertebra (your intervertebral musculature) as well as expanding your breathing apparatus (diaphragm), allowing for an opening and a reshaping of ribs that have adapted to vertebral rotation.