
Iliocostalis Lumborum O, I, A
Origin: The iliolumbar fascia, the posterior medial lip of the iliac crest, the lateral crest of the sacrum, and the spinous processes of T11 to L5
Insertion: Inferior borders of the angles of the lower six or seven ribs
Actions: Extension and lateral flexion of the thoracic spine, extension and lateral flexion of the lumbar spine
Innervation: Dorsal primary rami of T11 to L5
Blood Supply: Intercostal and lumbar arteries
Primary Actions of the Iliocostalis Lumborum
1. Extension of the thoracic spine when acting bilaterally
Agonists:
-
Iliocostalis cervicis
-
Iliocostalis thoracis
-
Longissimus cervicis
-
Longissimus thoracis
-
Spinalis thoracis
-
Semispinalis cervicis
-
Semispinalis thoracis
Antagonists:
-
Rectus Abdominis
2. Lateral flexion of the thoracic spine when acting unilaterally
Agonists:
-
Iliocostalis cervicis
-
Iliocostalis thoracis
-
Longissimus cervicis
-
Longissimus thoracis
-
External Oblique
-
Internal Oblique
Antagonists: Same muscles on contralateral side
-
Iliocostalis cervicis
-
Iliocostalis thoracis
-
Longissimus cervicis
-
Longissimus thoracis
-
External Oblique
-
Internal Oblique
3. Extension of the lumbar spine when acting bilaterally
Agonists:
-
Longissimus thoracis
-
Spinalis thoracis
Antagonists:
-
Rectus Abdominis
4. Lateral flexion of the lumbar spine when acting unilaterally
Agonists:
-
Longissimus thoracis
-
Psoas major
-
Quadratus lumborum
-
External oblique
-
Internal oblique
Antagonists: Same muscles on contralateral side
-
Longissimus thoracis
-
Psoas major
-
Quadratus lumborum
-
External oblique
-
Internal oblique
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