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F r e e S O A P n o t e s w i t h M a s s a g e B o o k f o r A B M P m e m b e r s : a b m p . u s / M a s s a g e b o o k 41 FUNCTIONAL ANATOMY education Iliocostalis By Christy Cael The iliocostalis is part of the erector spinae (erect means "upright" and spinae means "spine") group of muscles. The longissimus and spinalis are also part of this group. These muscles lie deep to the trapezius, latissimus dorsi, and rhomboids, and connect the sacrum, ilium, vertebral column, posterior ribs, and cranium. They provide broader stabilization and movement than the deeper transversospinalis group (rotatores and multifidi). Together, the erector spinae and transversospinalis groups maintain upright posture of the spine against gravity and position the vertebral column during movement. The iliocostalis is the most lateral of the erector spinae muscles. Its fibers run from inferior to superior and medial to lateral, extending from the vertebral column out to the ribs like the branches of a tree. This branching strategy provides better leverage over long distances and protects the muscle fibers from shearing damage under stress. (This is demonstrated when a multitrunked, frequently branching tree more successfully resists wind damage. Greater frequency and directional diversity of branching offers more flexible and resilient trees, as well as better, safer motion control in the trunk.) When activated, the iliocostalis extends a flexed or laterally flexed trunk and controls flexion and lateral flexion against gravity. The spinalis and longissimus—the other erector spinae muscles—lie more medial and relatively vertical on the posterior trunk compared to the iliocostalis. This directionality limits their contribution to lateral flexion and rotation as more complex movements of the trunk are attempted. Additionally, the iliocostalis is the only erector spinae muscle that contributes to breathing, due to its attachments on the posterior ribs. Dysfunctional breathing patterns may contribute to pain and tension in the iliocostalis. ILIOCOSTALIS Attachments • Origin: Posterior aspect of the sacrum, medial lip of the ilium, and posterior surface of ribs 1-12 • Insertion: Transverse processes of L1-3, posterior surface of ribs 1-6, and transverse processes of C4-7 Actions • Extends the vertebral column (bilateral action) • Laterally flexes the vertebral column (unilateral action) Innervation • Spinal nerves Iliocostalis

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