Origin: Lateral 2/3 of the inquinal ligament and the anterior 1/3 of the middle (or intermediate) line of the iliac crest

Insertion: Crest of the pubis and the linea alba by its aponeurosis

Isolated function: 
-Assists in concentric acceleration of flexion of the spine
-Assists in concentric acceleration of ipsilateral rotation

Integrated function: 
-Assists in eccentric deceleration of spinal extension
-Assists in eccentric deceleration of contralateral rotation
-Assists synergistically with the transverse abdominis, deep erector spinae and multifidi to create a posterior shear force at L5-S1
-Assists synergistically with the transversis abdominis to provide rotational and translational stability to the lumbar spine secondary to its attachment to the thoracolumbar fascia

Nerve Supply:  Ventral rami of T7-12 and iliohypogastric and ilioinquinal nerves, L1.