External ObliqueExternal Abdominal Oblique

coreMusculus obliquus externus abdominis

The external oblique is the outermost of the abdominal side muscles, running downward and forward from the lower ribs. It rotates your trunk toward the opposite side.

External Oblique highlighted on an anatomical figure, from the front.
Where it sits, from the front.

The external oblique is the outer layer of the abdominal wall at the side, and the largest of the three flat abdominal muscles. It arises by fleshy slips from the outer surface of the lower eight ribs — interlocking there with the serratus anterior and the latissimus dorsi — and its fibres run downward and forward, ending partly on the hip bone and partly in a broad sheet of tendon that reaches the midline.

The direction of those fibres decides what it does. Because they run down and toward the front, the right external oblique turns the trunk to the left, and the left one turns it to the right. It always rotates you toward the opposite side.

Both sides working together bend the trunk forward, and one side alone bends it sideways toward itself. It also pulls the ribcage down and compresses the abdomen, which is part of how the midsection becomes rigid when you brace.

The lower border of its tendon sheet rolls under to form the inguinal ligament, the cord you can feel running from the front of the hip bone to the pubic bone. That is a piece of anatomy far better known than the muscle itself.

It is the oblique you can actually see. On a lean person, the visible finger-like ridges at the side of the abdomen below the ribs are its rib attachments, interlocking with the serratus anterior above them.

Training notes

It is trained by rotation away from its own side and by side bending toward it. A cable woodchop performed to the left is loading the right external oblique, along with the left internal oblique.

Because rotation always pairs an external oblique with the opposite internal oblique, every rotational set trains one of each, and doing both directions trains all four.

Its rib attachments are the reason ab work is often felt at the sides of the ribcage rather than in the abdomen proper. That is where the muscle actually starts.

It contributes heavily to bracing during heavy squats and deadlifts, working isometrically to compress the abdomen. That is real work, but it is not rotation, and it does not substitute for training the muscle through its range.

Anatomy

Origin
  • Outer surfaces of the fifth to twelfth ribs, interdigitating with serratus anterior and latissimus dorsi
Insertion
  • Anterior half of the iliac crest
  • The linea alba, through a broad aponeurosis
  • The pubic tubercle, via the inguinal ligament formed by the aponeurosis' lower border
Actions
  • Rotates the trunk to the opposite side
  • Bends the trunk sideways toward the same side
  • Flexes the trunk when both sides work together
  • Compresses the abdomen and raises the pressure inside it
Innervation
Anterior rami of T7–T12

Exercises

Antagonists

Synergists