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Intercostal retractions occur when the muscles between the ribs pull inward. The movement is most often a sign that the person has a breathing problem. Intercostal retractions are a medical emergency.
1 The external intercostals are responsible for the elevation of the ribs and bending them more open, thus expanding the transverse dimensions of the thoracic cavity. 2  Internal intercostal muscles aid in forced expiration (quiet expiration is a passive process). External intercostal muscles aid in quiet and forced inhalation. 2  They originate on ribs 1-11 and have their insertion on ribs 2-12.