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The external oblique muscle is one of the largest parts of the trunk area, extending from the lower half of the ribs down to the pelvis. It is the outermost of the three flat abdominal muscles of the lateral anterior abdomen. Each side of the body has an external oblique muscle, which together cover the sides of the abdominal area. The external oblique muscle helps rotate the trunk and pulls the chest downwards, which compresses the abdominal cavity. Strains or tears to the external oblique muscle can be debilitating and take several weeks to heal.
| Characteristics | Values |
|---|---|
| Location | External oblique muscles are located on each side of the rectus abdominis. Internal oblique muscles are underneath the external oblique muscles. |
| Function | The external oblique muscle pulls the chest downwards, compresses the abdominal cavity, and increases intra-abdominal pressure. It also performs ipsilateral side-bending and contralateral rotation. The internal oblique muscle functions similarly but rotates ipsilaterally. |
| Appearance | The external oblique muscle is broad, thin, and irregularly quadrilateral. |
| Composition | The external oblique muscle is supplied by the ventral branches of the lower six thoracoabdominal nerves and the subcostal nerve on each side. The cranial portion is supplied by the lower intercostal arteries, while the caudal portion is supplied by branches of the deep circumflex iliac artery or the iliolumbar artery. |
| Stabilization | The oblique muscles help stabilize the trunk and keep the body stable and balanced. |
| Support | The oblique muscles support the body and help force exhaled air out of the lungs. |
| Protection | The oblique muscles protect the spine. |
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What You'll Learn
External abdominal oblique muscle
The external abdominal oblique muscle is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. It is situated on the lateral and anterior parts of the abdomen, extending from the lower half of the ribs around and down to the pelvis. The external oblique is broad, thin, and irregularly quadrilateral, with its muscular portion occupying the side and its aponeurosis occupying the anterior wall of the abdomen. In most humans, the oblique is not visible due to subcutaneous fat deposits and the small size of the muscle.
The external abdominal oblique originates from the external surfaces of ribs 5–12, with its attaching fibres interdigitating with those of the serratus anterior and latissimus dorsi. This forms a zig-zag oblique line on the lateral side of the thorax. From here, the muscle fibres fan out towards the midline and inferior margins of the abdomen. The most posterior fibres course almost vertically, while the remainder passes anteromedially.
The upper two-thirds of the external abdominal oblique are supplied by the lower intercostal nerves T7–T11 and the subcostal nerve T12. The lower third is supplied by the iliohypogastric L1 from the lumbar plexus. The upper two-thirds receive blood supply from branches of the lower posterior intercostal and subcostal arteries, while the lower third receives blood supply from the deep circumflex iliac artery.
The external abdominal oblique has a variety of functions, including pulling the chest downwards and compressing the abdominal cavity, which increases intra-abdominal pressure. It also performs ipsilateral (same-side) side-bending and contralateral (opposite-side) rotation: the right external oblique would side-bend to the right and rotate to the left, and vice versa. The internal oblique muscle functions similarly, except it rotates ipsilaterally.
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Internal oblique muscle
The internal oblique muscle is one of the three layers of the lateral abdominal wall. It is found on the lateral side of the abdomen, underneath the external oblique muscle. It is a broad, thin muscular sheet, with fibres that are obliquely oriented, perpendicular to those of the external abdominal oblique.
The internal oblique muscle has multiple sites of origin, distributed along the anterolateral side of the trunk. The muscle fibres can be divided into the anterior, lateral and posterior fibres. Anterior fibres arise from the iliopectineal arch, passing inferomedially and arching over the inguinal canal. They then merge with the tendinous fibres of the transversus abdominis muscle to form the conjoint tendon. In males, some of these fibres extend into the spermatic cord and form the cremaster muscle.
Lateral fibres originate from the anterior two-thirds of the iliac crest, then diverge superiorly and medially. They extend into an aponeurosis that contributes to the formation of the rectus sheath, inserting at the linea alba. The rectus sheath largely encloses the rectus abdominis and pyramidalis muscles, as well as many neurovascular structures of the anterior abdominal wall. The lateral fibres of the internal oblique are continuous with the rectus sheath.
Posterior fibres originate from the posterior end of the iliac crest and the thoracolumbar fascia. They then ascend superolaterally and insert into the inferior borders and tips of the lower three or four ribs and their cartilages. Here, they merge with the internal intercostals.
The internal oblique muscle functions to increase intra-abdominal pressure, helping to maintain abdominal tension and movement of the trunk. It also acts as an accessory muscle of respiration, reducing the volume of the chest cavity during exhalation. When the internal obliques contract, they compress the organs of the abdomen, pushing them upwards into the diaphragm, which intrudes back into the chest cavity, reducing the volume of the lungs and producing an exhalation. This contraction also causes ipsilateral rotation and side-bending, working with the external oblique muscle of the opposite side to achieve this torsional movement of the trunk.
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Function and importance
The external abdominal oblique muscle is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. The muscle is situated on the lateral and anterior parts of the abdomen. It is broad, thin, and irregularly quadrilateral, with its muscular portion occupying the side and its aponeurosis the anterior wall of the abdomen. The external abdominal oblique is a paired muscle located on the lateral sides of the abdominal wall.
The internal obliques lie under the external obliques and are, therefore, the deeper muscles of the core. The internal obliques originate on the inguinal ligament, which runs from the anterior iliac spine to the pubic bone. They also originate on the anterior iliac crest. The external obliques, on the other hand, originate on the lower eight ribs. The internal obliques insert into the costal cartilages of the lower four ribs and the abdominal aponeurosis, which is a superficial sheet of connective tissue over the abdomen. They also insert into the linea alba, a fibrous band of connective tissue that runs from the xiphoid process to the pubic symphysis. The external obliques insert into the abdominal aponeurosis, the linea alba, the iliac crest, and the pubic bone.
The oblique muscles are important in supporting the body and helping to force exhaled air out of the lungs. They also provide stability to the rib cage and pelvis, assist in side bending the body, rotate the trunk, and assist in flexing the trunk forward. The abdominal muscles, in general, support the trunk, allow movement, and hold organs in place by regulating internal abdominal pressure. The external oblique muscle, in particular, pulls the chest downwards and compresses the abdominal cavity, increasing intra-abdominal pressure. This compression is useful in processes such as breathing, singing, and defecation. It also performs ipsilateral side-bending and contralateral rotation: the right external oblique would side-bend to the right and rotate to the left, and vice versa. The internal oblique muscle functions similarly, except it rotates ipsilaterally.
Because the oblique muscles play an integral role in everyday life, strain or injury to these muscles can be debilitating. For example, weak obliques can lead to an anteriorly tilted pelvis, which can contribute to back pain. Oblique strain is a common injury in baseball, particularly in pitchers.
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Oblique exercises
The obliques are a crucial group of muscles for supporting the body and providing stability to the ribcage and pelvis. They also help to force exhaled air out of the lungs and assist in side bending and rotating the trunk. The external obliques are the outermost abdominal muscles, while the internal obliques lie underneath and are the deeper core muscles.
Side Plank Hip Dips
Start in a side plank position with your forearm on the ground, ensuring your body is in a straight line from head to feet. Without rotating, slowly lower your hips a few inches toward the floor and then lift them back up to the starting position. Repeat for the desired number of reps. This exercise can be made more challenging by adding more resistance, increasing speed, or performing it with a staggered stance or on one knee.
Russian Twists
Lie face-up on the floor in a tabletop position with your knees bent at 90 degrees and stacked over your hips, shins parallel to the floor, and feet off the ground. Extend your arms up toward the ceiling directly above your shoulders, palms facing in. Gently press your lower back into the floor and engage your core. Simultaneously lower your left leg and right arm toward the floor, maintaining contact between your lower back and the floor. Return to the starting position and repeat on the other side.
Standing Oblique Crunches
Stand with your feet wider than shoulder-width apart and your toes pointed out. Bend your elbows and put your hands behind your head. Brace your core and bend sideways at the waist, bringing your left elbow toward your right knee. Return to the centre and repeat on the other side.
Windshield Wiper
Position yourself in front of a barbell in a landmine attachment and grab the end of the barbell with both hands overlapping. Keeping your arms extended, move the barbell to your right hip, twisting your torso to the right. Bend your knees slightly, keep your arms straight, and rotate your torso to the left, bringing the barbell up and over to the left hip. Pivot your feet to make this move smooth. Repeat, alternating sides until you reach the desired number of reps.
Wall Pelvic Tilt
Stand with your back against the wall with your feet about one foot in front of the wall and hip-width apart. Softened your knees so they are slightly bent. Gently perform a pelvic tilt with your glutes relaxed. Reach your arms forward and down so your upper back comes off the wall, but keep your lower back in contact with the wall. Inhale, pressing your arms back to the wall. Exhale, reaching your armpits forward. Perform four breaths and then repeat three times.
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Oblique strain and injury
The obliques are a group of abdominal muscles that support the body and help to force exhaled air out of the lungs. They also provide stability to the rib cage and pelvis, assist in side bending the body, rotate the trunk, and assist in flexing the trunk forward. There are two types of oblique muscles: external obliques and internal obliques. The external oblique is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. It is situated on the lateral and anterior parts of the abdomen. The internal oblique lies underneath the external oblique and covers the area between the ribs and pelvis on the sides.
Oblique strain or injury happens when the muscle is stretched or torn. This usually occurs due to sudden, forceful movements, overuse, or improper technique during physical activities. Oblique strains can occur on either side of the body and can be mild or serious. They are a common injury in sports such as baseball, cricket, hockey, and soccer, as well as in activities like golf and tennis. Oblique strains can be debilitating and cause pain and tenderness.
If you think you have an oblique strain, it is important to visit a healthcare provider. They will examine your stomach area and ask you to perform specific movements to determine which oblique muscle is injured. They will then advise you on the necessary course of treatment, which may include rest, physiotherapy exercises, and pain medication.
To prevent oblique strains, it is important to properly warm up before physical activity with dynamic stretches like trunk twists and side bends. Strengthening the core with exercises like Russian twists, side planks, and bicycle crunches can also help to build oblique strength. Maintaining good posture during daily activities and workouts can reduce unnecessary strain on the oblique muscles.
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Frequently asked questions
The obliques muscles are the internal and external abdominal muscles. They are two of the three layers that create our abdominal walls.
The internal obliques lie under the external obliques, so they are the core's deeper muscles. The external obliques are the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen.
The obliques muscles help support the body and force exhaled air out of the lungs. They also provide stability to the ribcage and pelvis, assist in side bending the body, rotate the trunk, and assist in flexing the trunk forward.
Oblique muscles can be strengthened through a variety of activities and motions such as side bending, rotation, and trunk flexion (which include exercises such as sit-ups).
