Abdominal Muscle Anatomy
Internal Obliques

Here's a more in-depth description of the internal obliques (int. obliques) for someone who really likes anatomy.

If you are not really familiar with anatomy, read the introduction to abdominal muscle anatomy.

The 4 main muscles of the front of your stomach are the rectus abdominus, the external obliques, the transverse abdominus and the internal oblique muscle.

The Int. Oblique Muscle originates (starts) on the thoracolumbar fascia, anterior two-thirds of the iliac crest, and lateral half of the inguinal ligament, and it inserts (finishes) on the inferior border of the 10-12th ribs, linea alba, and the pubis via the conjoint tendon.

It gets its nerve supply from the ventral rami of the inferior 6 thoracic nerves, the subcostal nerve, and the first lumbar nerve.

Its actions are to compress the abdominal contents to stabilize the spine, flex the spine (pull it forward like in crunches), rotate the trunk to the same side (ipsilateral rotation), and bend the spine to the side (lateral flexion).

Let's talk a little more about each action.

Actions of the Int. Oblique Muscle

#1 Compress the abdominal contents:

Every abdominal muscle will compress the abdominal contents. This helps with bracing the spine and keeping the pelvis and lower back stable.

For example, if someone were to act as if they were going to punch you in the stomach, you would tense up your abdominal muscles to brace yourself.

When you int. obliques contract they can help to brace your ribs, pelvis and lower back.

This is an important role for protecting against back pain.

#2 Flexion of the Spine:

Flexion simply means bending. When your int. obliques contract, they can pull your spine forward like in crunches or sit ups.

The obliques actually work really hard even when you are moving in a straight line.

The int. obliques are sometimes considered tonic muscles. All this means is that their primary role is stability and their secondary role is movement.

The int. obliques work really hard to help stabilize your spine in many directions and they will work during every ab exercise.

#3 Rotation to the Same Side (Ipsilateral Rotation):

Even though the int. obliques work during every ab exercise, you can emphasis the obliques when you add a twisting or rotation motion.

The internal oblique muscle rotates your body to the same side. What this means is that the internal oblique on the right side of your body will turn you so that you face towards the right and vice versa.

When you flex and rotate like in bicycle crunches or oblique crunches, the obliques work at maximum capacity.

The int. obliques rotate the body to the same side, so the ext. obliques on one side and the internal obliques on the other side work together when you twist or rotate your body.

#4 Side Bending (lateral flexion):

In addition to working at maximum capacity when you flex and rotate, you obliques also work at maximum capacity when you bend to the side, like in standing dumbbell side bends.

The obliques also work at maximum capacity when you perform
side crunches on a stability ball or side planks.

When you look at the actions of the internal obliques, it is easy to see why it is such an important core muscle.

It will work during every ab exercise, but remember that no ab exercise can magically melt fat from your love handle area. Spot reduction is the #1 ab myth.

Ab exercises help to strengthen your abs, not spot reduce fat.

I hope this gives you an even better understanding of abdominal anatomy.

If you're looking for ab exercises, check out the
Directory of Abdominal Exercises.

Take Care
Charles

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