What is the Zone of Apposition?
The Zone of Apposition is defined as the area of attachment between the diaphragm directly behind the inner aspect of the lower chest wall and rib cage. This area is of great importance for proper diaphragm and breathing function, and depends largely on the anatomical positioning of the muscle to the rib cage.
In general, the ZOA constitutes about 40% of the rib cage at rest, and changes (decreases) with both passive (involuntary) and active breathing patterns as the diaphragm contracts and shortens. in short, the ribs are able to externally rotate (move up) or internally rotate (move down). When the ribs externally rotate, the diaphragm loses contact with the ribs, thus decreasing the ZOA, and restricting efficient breathing patterns, causing accessory respiratory muscle usage and inefficiency of the abdominal muscles.