Dance Anatomy & Kinesiology

The Spine 83

External Oblique Abdominal Muscle

(Obliquus Externus Abdominis)

As its name suggests, the external oblique (L. obliquus,

slanting, deviation from the vertical or the horizontal) is the

more superficial of the oblique muscles and runs diagonally

downward from its lateral attachments toward its more medial

attachments. The line of pull of the fibers of this paired muscle

can be pictured as forming the letter “V” on the front of the

abdomen, with each oblique forming one side of the “V.” It’s

a thin and flat but relatively expansive muscle, covering the

abdomen from the rectus abdominis to the latissimus dorsi

(figure 3.13). Due to its lateral location and its diagonal line

of pull, the external oblique tends to produce spinal lateral

flexion to the same side or rotation to the opposite side. With

rotation of the spine with the pelvis stationary, it pulls the

lateral side of the rib cage downward and medially toward the

midline of the trunk such as in twisting the torso. However,

when the right and left external obliques contract together

(bilateral contraction), they produce spinal flexion and the

same type of movements as the rectus abdominis. With their

curved position around the side of the abdomen, these muscles

are also effectively positioned to help flatten the abdomen,

depress the lower rib cage, and maintain appropriate postural positioning of the torso and the pelvis.

Palpation: Curl up about 20° as just described for palpating the rectus abdominis, and then rotate

toward the left. You can palpate the contraction of the right external oblique by placing your fingertips

below the ribs and about 4 inches (10 centimeters) lateral to the navel (umbilicus).

FIGURE 3.13 The external oblique abdomi-

nal muscle (lateral view).

Attachments and Primary Actions of External Oblique Abdominal Muscle

Muscle Lateral attachment(s) Medial attachment(s) Primary action(s)

External oblique

(o-BLEEK)

Anterolateral aspect of lower

8 ribs

Anterior crest of ilium, crest of

pubis, and linea alba

Spinal flexion

Spinal lateral flexion (same)

Spinal rotation (opposite)

Attachments and Primary Actions of Internal Oblique Abdominal Muscle

Muscle Lateral attachment(s) Medial attachment(s) Primary action(s)

Internal oblique

(o-BLEEK)

Thoracolumbar fascia, anterior

2/3 of iliac crest, lateral

inguinal ligament

Ribs 9-12, cartilages of ribs

7-9, and linea alba

Spinal flexion

Spinal lateral flexion (same)

Spinal rotation (same)

Internal Oblique Abdominal Muscle (Obliquus Internus Abdominis)

As indicated by its name, the internal oblique is situated more deeply beneath the external oblique.

Like the external oblique it is a very flat muscle, and it forms the intermediate layer of the abdomi-

nal muscles. Its upper fibers run diagonally upward in a medial direction from its more lateral lower

attachments at approximately a 90° angle to the external oblique muscles as seen in figure 3.14 (its

lower fibers run more horizontally). When the internal oblique contracts it can produce lateral flexion

to the same side and rotation to the same side such as with side-bending, off-center facings, or spi-

raling movements of the torso in dance. With rotation with the pelvis stationary, it pulls the medial

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