obliques

Obliques refers to the oblique muscles of the abdomen, a paired group on the lateral abdominal wall. The two main muscles are the external oblique and the internal oblique, which lie in layers with the transversus abdominis and rectus abdominis to form the abdominal wall. Their oblique fiber directions give them their name.

Anatomy and attachments: The external oblique originates from the outward-facing surfaces of the lower eight ribs (5–12) and inserts via an aponeurosis that contributes to the inguinal ligament, the linea alba, and the anterior iliac crest. The internal oblique originates from the thoracolumbar fascia, the anterior two-thirds of the iliac crest, and the lateral half of the inguinal ligament, inserting into the lower ribs (10–12), the linea alba, and the conjoint tendon at the pubic crest. The fibers of the external oblique run inferomedially, while those of the internal oblique run superomedially.

Innervation: The external oblique is supplied by the lower intercostal nerves (T7–T11) and the subcostal nerve (T12). The internal oblique receives innervation from the thoracoabdominal nerves (T6–T11) and from the iliohypogastric and ilioinguinal nerves (L1).

Function: Together with the transversus abdominis, the obliques compress and support the abdominal viscera, increase intra-abdominal pressure, and aid in forced expiration. Unilateral contraction rotates the trunk and contributes to lateral flexion, with opposing rotational effects for the external and internal components.

Clinical relevance: Oblique strains are common in athletes performing twisting or lateral movements. Weakness or injury of the obliques can contribute to abdominal or groin pain and may be involved in inguinal or abdominal wall hernias. Training and conditioning focus on rotational and side-bending strength and core stability.

Etymology: The term oblique derives from Latin obliquus, meaning slanting or at an angle.