ORIGIN

Anterior fibers: external surfaces of ribs 5 to 8, interdigitating with serratus anterior. Lateral fibers: external surfaces of 9th rib, interdigitating serratus anterior, and those ribs 10 to 12, interdigitating with lattissimus dorsi

 

INSERTION

Anterior Fibers: into a broad flat aponeurosis, terminating at the linea alba
Lateral fibers: into the anterior iliac spine and pubic tubercle, and into the external lip of the anterior half of the iliac crest

 

ACTION

Lumber flexion at both sides

Posterior pelvic rotation

Lumbar lateral flexion on both sides

Lateral pelvic rotation to both sides

 

INNERVATION

Intercostal nerves (T8-T12), iliohypogastric

nerve (T12, L1), and ilioinguinal nerve (L1)

 

PRIMARY JOINT

Lumbar spine

Thoracic spine

 

KEY STRENGTH TRAINING EXERCISES

Dumbbell side bends

Side jackknifes

 

NEW STRENGTH TRAINING EXERCISES

Plate twists

Side planks

 

COMMON INJURIES

Overuse

Straining/stiffness

Tear