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The external oblique muscle is one of the outermost abdominal muscles, extending from the lower half of the ribs around and down to the pelvis. The internal oblique muscle lies underneath the external oblique muscle. The obliques are important for supporting the body and help to 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 strains are a common injury in sports such as baseball, tennis, football, and golf.
| Characteristics | Values |
|---|---|
| Number of abdominal oblique muscles | 2 |
| Names of the abdominal oblique muscles | External oblique, Internal oblique |
| Location of internal oblique muscle | Underneath the external oblique muscle |
| External oblique muscle | One of the outermost abdominal muscles |
| External oblique muscle origin | External surfaces of the fifth to twelfth ribs |
| External oblique insertion points | External oblique aponeurosis at the linea alba, the front of the iliac crest, and the pubic tubercle |
| Function of the external oblique muscle | Pulls the chest downwards, compresses the abdominal cavity, provides ipsilateral side-bending and contralateral rotation |
| Function of the internal oblique muscle | Ipsilateral rotation |
| Function of the oblique muscles | Provide trunk flexion and rotation, support the body, force exhaled air out of the lungs, provide stability to the ribcage and pelvis, assist in side bending the body, rotate the trunk, assist in flexing the trunk forward |
| Oblique muscle exercises | Side plank, pelvic tilt |
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What You'll Learn
External oblique muscle
The external oblique muscle, also known as 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 muscle is not visible due to subcutaneous fat deposits and its small size.
The external oblique muscle arises from eight fleshy digitations, originating from the external surfaces and inferior borders of the fifth to twelfth ribs (lower eight ribs). These digitations are arranged in an oblique line, with the upper digitations attached to the cartilages of the corresponding ribs and the lowest digitations attached to the apex of the cartilage of the last rib. The middle digitations are attached to the ribs at some distance from their cartilages. The attaching fibres interdigitate with those of the serratus anterior and latissimus dorsi, forming 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, with the most posterior fibres coursing vertically and the remainder passing anteromedially.
The external oblique muscle contributes to various trunk movements, including ambulatory motions such as walking or running. It functions to pull the chest downwards and compress the abdominal cavity, increasing 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 external oblique muscle is innervated by the anterior rami of the thoracic spinal nerves T7-T12, with the intercostal nerves T7-T11 supplying the uppermost part and the subcostal nerve T12 innervating the lower part. The muscle receives sensory innervation from the lumbar plexus via the iliohypogastric nerve (L1).
The blood supply to the external oblique muscle varies depending on the region. The upper two-thirds of the muscle receive blood from the branches of the lower posterior intercostal and subcostal arteries, while the lower third is supplied by the deep circumflex iliac artery. The external oblique muscle is also involved in bilateral contraction with the rectus abdominis and internal oblique muscles, flexing the trunk by drawing the pubis towards the xiphoid, as seen in crunches or sit-ups.
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Internal oblique muscle
The internal oblique muscle is found on the lateral side of the abdomen. It is a broad and thin muscular sheet, forming one of the three layers of the lateral abdominal wall, along with the external oblique on the outer side and transverse abdominis on the inner side. Its fibres are obliquely oriented, perpendicular to those of the external oblique.
The internal abdominal oblique has multiple sites of origin, which are distributed along the anterolateral side of the trunk. According to their origin, the muscle fibres can be divided into the anterior, lateral, and posterior fibres. Anterior fibres arise from a deeper structure known as 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 the anterior fibres extend into the spermatic cord and form the cremaster muscle.
Lateral fibres originate from the anterior two-thirds of the iliac crest and then diverge superiorly and medially. They extend into an aponeurosis that contributes to the formation of the rectus sheath and insert 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 abdominal 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, these fibres merge with the internal intercostals.
The internal oblique muscle functions to help maintain abdominal pressure and movements of the trunk, along with the other abdominal muscles. It acts as an accessory muscle of respiration, opposing the diaphragm and helping to reduce the volume of the chest cavity during exhalation. When the internal obliques contract, they compress the organs of the abdomen, pushing them up into the diaphragm, which intrudes back into the chest cavity, reducing lung volume and producing an exhalation. Its contraction also causes ipsilateral rotation and side-bending, as well as lateral flexion upon unilateral contraction.
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Function and definition
The external oblique muscle is one of the largest and outermost abdominal muscles, extending from the lower half of the ribs around and down to the pelvis. The external oblique 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 occupying the anterior wall of the abdomen. Each side of the body has an external oblique muscle. In most humans, the oblique is not visible due to subcutaneous fat deposits and the small size of the muscle.
The internal oblique muscle lies underneath the external oblique muscle. Together, the external and internal oblique muscles cover the sides of the abdominal area, with the internal obliques being much thinner and smaller than the external obliques. The internal oblique muscle functions similarly to the external oblique muscle, except it rotates ipsilaterally.
The external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases intra-abdominal pressure. 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 external oblique also supports the rotation of the spine.
The oblique muscles are important for supporting 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. The oblique muscles stabilize the pelvis, so if they are weak, it could lead to an anteriorly tilted pelvis, which can contribute to back pain.
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Oblique muscle pain
The obliques are the muscles that run down either side of the abdomen. There are two sets of oblique muscles: external and internal obliques. External obliques sit on the outer edge of the abdomen, and internal obliques sit directly next to them, closer to the core. These muscles work together when a person twists or rotates their body at the core.
Pain in the oblique muscles is often caused by a type of injury known as a "side strain". This injury is common in sports such as baseball and cricket, which require repetitive twisting and overarm movements. Oblique strains can also occur during everyday activities such as sweeping the floor or lifting objects from the ground. Other activities that can cause oblique muscle pain include rowing, raking leaves, persistent coughing, and sitting for long periods of time.
Conservative treatment often leads to a full recovery from oblique muscle pain within a few weeks. Treatment may include stretching, warming up, and cooling down when exercising. Applying an ice pack for up to 15 minutes may also help with muscle strains. It is important to learn the difference between a strain and a sprain.
To prevent oblique muscle strains, it is important to practice the correct techniques for a sport and work on conditioning. A balanced fitness regime that includes cardio, strength training, and flexibility work is recommended. Additionally, a full warm-up before exercise can reduce the risk of muscle strains.
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Oblique exercises
The abdominal external oblique muscle is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. The external oblique muscle is supplied by the ventral branches of the lower six thoraco-abdominal nerves and the subcostal nerve on each side. The internal oblique muscle lies just beneath the external oblique.
Twisting Crunches
Lie on your back with your knees bent and feet flat on the floor. Place your left hand behind your head, with your elbow pointing out to the side. Place your right hand flat on the floor, with your arm extended out at a diagonal from your body. Perform a crunch, bringing your left elbow toward your right knee. Repeat for the desired number of reps, then switch sides.
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 so your leg is extended, foot hovering off the floor, and your bicep is next to your ear. Maintain the contact between your lower back and the floor, resisting the urge to arch your back. If you can’t keep it on the floor, don’t lower your leg as far. Lift your right arm and left leg to return to the starting position, then repeat on the other side.
Side Plank Hip Dips
Start in a side plank position with your forearm, ensuring your body is in a straight line from head to feet. Without rotating forward or backward, slowly lower your hips a few inches toward the floor. Lift your hips up to return to the starting position. Repeat for the desired number of reps. To increase the difficulty, add more resistance, increase movement speed, or challenge your balance by staggering your stance or kneeling on one leg.
Standing Side 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 knee up and your elbow down simultaneously. Return to the centre and repeat on the other side.
Landmine 180
Position yourself in front of a barbell in a landmine attachment. 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 meet it. Bending the knees slightly and keeping your arms straight, rotate your torso, bringing the barbell up and over to the left hip. Pivot your feet to make this move smooth. Repeat, alternating sides until reaching the desired number of reps.
To prevent oblique muscle strain, it is important to warm up before exercising, stretch and cool down after exercising, and take rest days to avoid overexertion.
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Frequently asked questions
The external oblique muscle is one of the outermost abdominal muscles, extending from the lower half of the ribs around and down to the pelvis. The internal oblique muscle lies underneath the external oblique muscle.
The external oblique muscles cover the sides of the abdominal area. The internal obliques are underneath the external obliques on each side of the trunk.
The oblique muscles help to 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.
