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The oblique muscles refer to two abdominal muscles: the external and internal obliques. These muscles are responsible for trunk flexion and rotation, enabling side-to-side bending, torso rotation, and spinal flexion. The external oblique is the largest and outermost muscle, situated on the lateral and anterior parts of the abdomen, while the internal oblique lies underneath and is the deeper muscle. Both muscles contribute to the abdominal wall, with the external oblique covering the internal abdominal oblique, anterior halves of the ribs, and intercostal muscles.
| Characteristics | Values |
|---|---|
| Type | Two abdominal muscles: external and internal obliques |
| Appearance | Broad, thin, and irregularly quadrilateral |
| Location | Lateral and anterior parts of the abdomen |
| Visibility | Not visible in most humans |
| Function | Supports the body, helps force exhaled air out of the lungs, provides stability to the ribcage and pelvis, assists in side bending the body, rotates the trunk, and assists in flexing the trunk forward |
| Innervation | Anterior rami of the thoracic spinal nerves T7-T12 |
| Blood supply | Branches of the lower posterior intercostal and subcostal arteries, deep circumflex iliac artery |
| Common injuries | Oblique strain, particularly in baseball pitchers |
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What You'll Learn
External abdominal oblique muscle
The external abdominal oblique muscle is one of the outermost abdominal muscles, extending from the lower half of the ribs around and down to the pelvis. It is the largest and most superficial of the lateral abdominal muscles. It lies beneath the thoracic and abdominal skin, covering the internal abdominal oblique and anterior halves of the ribs and intercostal muscles.
The external abdominal oblique is a muscle of the abdominal wall that flexes the trunk anteriorly and laterally. Its muscular part contributes to the lateral part of the abdominal wall, while its aponeurotic part contributes to the anterior abdominal wall. The superior, medial and inferior margins of the muscle relate to their respective attachment points, while the posterior margin is free. The external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases intra-abdominal pressure as in a Valsalva manoeuvre. It also performs ipsilateral (same-side) side-bending and contralateral (opposite-side) rotation.
The external abdominal oblique originates from the external surfaces of ribs 5-12. 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. At the midclavicular line medially and spinoumbilical line inferiorly, the external abdominal oblique continues as an aponeurosis via which it inserts into the linea alba, pubic tubercle and anterior half of the iliac crest.
The upper two-thirds of the external abdominal oblique are supplied by lower intercostal nerves T7-T11 and 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 deep circumflex iliac artery supplies the inferior third of the muscle.
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Internal oblique muscle
The internal oblique muscle is a broad, thin muscular sheet found on the lateral side of the abdomen. It is one of the three layers of the lateral abdominal wall, with the external oblique on the outer side and the transverse abdominis on the inner side. The internal oblique muscle has multiple sites of origin, distributed along the anterolateral side of the trunk. Its fibres are oriented obliquely, perpendicular to those of the external abdominal oblique.
The internal oblique muscle has several functions. Firstly, 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 diaphragm contracts, it pulls the lower wall of the chest cavity down, increasing lung volume and filling the lungs with air. Conversely, when the internal oblique contracts, it compresses the abdominal organs, pushing them upwards into the diaphragm, which then intrudes into the chest cavity, reducing lung volume and producing an exhalation.
Secondly, the contraction of the internal oblique muscle causes ipsilateral rotation and side-bending. It works with the external oblique muscle of the opposite side to achieve this torsional movement of the trunk. For example, the right internal oblique and the left external oblique contract as the torso flexes and rotates to bring the left shoulder towards the right hip.
In males, some of the anterior fibres of the internal oblique extend into the spermatic cord and form the cremaster muscle. The 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 inserts at the linea alba. The posterior fibres originate from the posterior end of the iliac crest and the thoracolumbar fascia. They ascend superolaterally and insert into the inferior borders and tips of the lower three or four ribs and their cartilages, merging with the internal intercostals.
The internal oblique muscle is important for maintaining normal abdominal tension and increasing intra-abdominal pressure. Bilateral contraction of the internal oblique, along with the rectus abdominis and external oblique, flexes the trunk by drawing the pubis towards the xiphoid, as in crunches or sit-ups.
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Oblique muscle group
The oblique muscle group refers to two abdominal muscles: the external oblique and the internal oblique. These muscles provide trunk flexion and rotation, enabling side-to-side bending, torso rotation, and spinal flexion. The external oblique is the thickest and runs from the lower ribs to the iliac crest, while the internal oblique lies underneath and also originates at the iliac crest before reaching the pubic bone. The external oblique is the largest and most superficial of the lateral abdominal muscles, contributing to the lateral part of the abdominal wall. Its aponeurotic part contributes to the anterior abdominal wall and the anterior layer of the rectus sheath. The internal oblique has a similar function to the external oblique, except it rotates ipsilaterally.
The external oblique muscle is a paired muscle that runs outside ribs five to twelve down to the crest of the ilium bone. When the left side contracts, the right relaxes, allowing for ipsilateral flexion to the contracting side and contralateral rotation of the trunk. When both sides contract together, the external oblique works with the rectus abdominis and internal oblique muscles to flex the trunk forward, which also contributes to breathing. The external abdominal oblique 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 internal obliques originate on the inguinal ligament, which runs from the anterior iliac spine to the pubic bone, and also on the anterior iliac crest. They insert into the costal cartilages of the lower four ribs and the abdominal aponeurosis, a superficial sheet of connective tissue over the abdomen. They also insert into the linea alba, a fibrous band of connective tissue running from the xiphoid process to the pubic symphysis. The internal obliques assist with flexion and rotation to the contracting side.
The oblique muscles are important for supporting the body and forcing exhaled air out of the lungs. They also provide stability to the rib cage and pelvis, assist in side bending the body, and help to flex the trunk forward.
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Oblique strain
The obliques are a group of muscles located between the lower end of the rib cage and the upper part of the hips. They are known as the waist muscles and are responsible for controlling bending movements, such as bending over and twisting the torso. The oblique muscles also assist in breathing.
An oblique strain occurs when the oblique muscles are stretched too far or torn. This often happens in sports that require repetitive twisting and overarm movements, such as baseball or cricket. It can also occur during everyday activities such as rowing, raking leaves, chronic coughing, or even sitting for long periods. Oblique strains can cause pain and tenderness on the side of the nondominant arm, as well as limited range of motion and swelling.
To treat an oblique strain, it is important to rest and avoid activities that worsen the pain. Applying ice to the injured area for 15 to 20 minutes every few hours can help reduce swelling and pain, especially during the first few days after the injury. Manual therapy, including trigger point therapy and joint manipulation, can provide short-term pain relief and promote long-term healing. Therapeutic stretching is another beneficial treatment option for oblique strains, as it targets specific tight muscles and improves flexibility while reducing tension in the torso.
In addition to short-term pain relief, electrical stimulation and TENS (transcutaneous electrical neuromuscular stimulation) can be effective in accelerating recovery from oblique strains. These therapies target the nerves and muscles, disrupting and blocking pain signals while triggering healing processes in the muscle. A balanced fitness regime that includes cardio, strength training, and flexibility work can also help reduce the risk of oblique strains by improving conditioning and overall fitness.
To prevent oblique strains, athletes should practice correct techniques for their sport and focus on thorough conditioning. Stretching, warming up, and cooling down properly before and after exercise are crucial for preventing muscle strains. Additionally, introducing new moves and exercises slowly can help reduce the risk of injury.
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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. It is situated on the lateral and anterior parts of the abdomen, with its muscular portion occupying the side and its aponeurosis occupying the anterior wall of the abdomen.
The internal oblique muscle is located just beneath the external oblique muscle. The external oblique muscle pulls the chest downwards and compresses the abdominal cavity, increasing intra-abdominal pressure. It also performs ipsilateral side-bending and contralateral rotation.
To strengthen your oblique muscles, you can try the following exercises:
- Side planks: Lie on your side and prop your body up using your elbow and feet so that your body forms a straight line from your feet to your shoulders. For an added challenge, try adding beach scissors to the plank by bending and raising your legs in the air as if you're balancing glasses on your knees and ankles. Then, flex your upper body in a crunch motion, keeping your chin tucked in and your core scooped in. Exhale and reach one elbow toward your bent knee as you extend the other leg outward to a diagonal. Inhale as you switch sides, exhaling as you perform the movement on the other side.
- Windshield wipers: Hang from a bar and extend your legs. Use a barbell to work on power and explosiveness as well as your obliques. Position yourself in front of a barbell and grab the end with both hands overlapping. Keep your arms extended and move the barbell to your right hip, twisting your torso to meet it. Bend your knees slightly, keep your arms straight, and rotate your torso to bring the barbell up and over to the left hip. Pivot your feet to make the movement smooth. Repeat, alternating sides, until you've reached your desired number of reps.
- Russian twist: Sit on the floor with your knees bent and feet lifted slightly off the ground. Lean back at a 45-degree angle, keeping your knees bent. Clasp your hands together in front of your chest or put them on your hips. Twist your torso from side to side, touching the floor with your hands on each side of your body.
- Squat with side crunch: Take a wide stance with your toes pointed out. Sink into a squat position and lift your arms out to your sides with your elbows bent at a 90-degree angle. Staying in the squat position, bend to your side, bringing your right elbow toward your right knee. Return to the centre and crunch to the left.
- Crunches or sit-ups: Lie on your back with your knees bent and feet flat on the ground. Place your arms by your sides with your palms facing up or down, whichever you prefer. Inhale and use your core to lift your head and upper back off the ground.
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Frequently asked questions
The oblique muscles refer to two abdominal muscles: the external and internal obliques. These muscles provide trunk flexion and rotation.
The external oblique muscles are the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. They are broad, thin, and irregularly quadrilateral. They originate from the external surfaces of ribs 5-12 and run to the crest of the ilium bone.
The internal oblique muscles lie under the external oblique muscles, so they are the deeper muscles of the core. They originate at the front of the iliac crest and run to the pubic bone.
The oblique muscles 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.
