The Internal and External Oblique Muscles

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What do the names of the external and internal oblique muscles, mean?

Internal Obliques

Internal Oblique Muscle

Internal Obliques

The name internal obliques refers to the location and shape of the muscle.

Internal means inside.

Oblique comes from the Latin word obliquus which means a slanting orientation.

The slanting direction refers to the direction of the fibers of this muscle.The fiber direction of the internal obliques is in the direction of reaching across your body. As in, if you place your hand on the opposite side of your abdomen, your fingers represent the direction of the fibers.

External Obliques

External Obliques

External Obliques

The name external obliques also refers to the location and shape of the muscle.

External means outside.

Oblique, as we just said, means a slanting orientation and refers to the muscle fiber direction.

The fiber direction of these muscles is like the direction of reaching into your pockets.

Where do the external and internal oblique muscles attach?

Origin

The internal obliques originate on the inguinal ligament (a ligament that runs from the anterior iliac spine to the pubic bone) and the anterior iliac crest.

The external obliques originate on the lower 8 ribs.

Insertion

The internal obliques insert onto the costal cartilages of the lower 4 ribs, the abdominal aponeurosis (a superficial sheet of connective tissue over the abdomen), and the linea alba. (The linea alba is a fibrous band of connective tissue that runs from the xiphoid process to the pubic symphysis.)

The external obliques insert onto the abdominal aponeurosis, the linea alba, the iliac crest, and the pubic bone.

What actions do the external and internal oblique muscles do?

In the case of these abdominal muscles, stabilization is a key function.
The internal obliques function bilaterally (both sides) to flex the trunk and compress its contents. They function unilaterally (one sided) to laterally flex the trunk and rotate it to the same side.

The external obliques function bilaterally to flex the trunk and compress its contents.
They function unilaterally to laterally flex the trunk and rotate the trunk to the opposite side.

Poses where the external and internal oblique muscles contract:

external and internal oblique muscles in navasana

If we look at a posture such as navasana, we see that all of the abdominals will be doing an isometric contraction in order to help stabilize the trunk and keep it rigid so that the hip flexors can do their work.


external and internal oblique muscles in Marichyasana C

As we twist right, the left side of the external oblique contracts with the right side of the internal obliques (they work together as synergists) when twisting.

Poses where the external and internal oblique muscles are lengthened:

external and internal oblique muscles in urdhva dhanurasana

In a posture such as urdhva dhanurasana, we can see a general lengthening of all of the abdominal muscles because the rib cage and the pelvis are required to move further apart, generally making more distance between origins and insertions.


external and internal oblique muscles in Marichyasana C

If we look at the twisting motion of marichyasana C as we twist to the right we are going to find the right side of the external obliques lengthening with the left side of the internal obliques.

yoga anatomy book cover

Many of the concepts in this article are discussed in:
Functional Anatomy of Yoga

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About David Keil

david keil yoga anatomyThis website is simply about delivering yoga anatomy to the yoga community in a simple and understandable way. It has always been about you, the reader, understanding the complexity and diversity of our own humanness as well as our anatomy.

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