One of 11 pairs of muscles lying between the ribs. The fibres run downward and posteriorly, and are deeper than the external intercostals. Each muscle has its origin on the inferior border of the rib above and its insertion on the superior border of the rib below. The internal intercostals take part in expiration by drawing the ribs together and depressing the rib cage, and may work as antagonists to the external intercostals, but opinion is divided on this.
Subjects: Sports and Exercise Medicine.