The oblique muscles, located on the lateral sides of the abdomen, are a part of the core musculature. They contribute to a wide range of everyday movements and overall core strength by forming a supportive wall that connects the ribs to the pelvis. This structure stabilizes the trunk and facilitates motion.
Anatomy of the Oblique Muscles
The obliques consist of two primary layers: the external and internal obliques. The external oblique is the largest and most superficial layer, with fibers running diagonally downwards and forwards, like placing hands in front pockets. This muscle originates from the lower eight ribs and attaches to the iliac crest of the pelvis and the linea alba, a fibrous structure down the abdomen’s midline.
Beneath the external obliques are the internal obliques, which are smaller and thinner. Their fibers run opposite to the external obliques, coursing upwards and forwards. They originate from the thoracolumbar fascia (connective tissue on the lower back), the iliac crest, and the inguinal ligament, inserting on the lower ribs and the linea alba.
This layered, crisscross arrangement provides structural integrity to the abdominal wall. The aponeuroses (sheet-like tendons) of these muscles merge at the front of the abdomen to form the rectus sheath. This sheath encloses the rectus abdominis muscle, supporting the anterior abdominal wall.
Functions of the Oblique Muscles
The orientation of the oblique fibers allows for various movements and stabilizing actions, with a primary function being torso rotation. When the external oblique on one side contracts with the internal oblique on the opposite side, it produces a twisting motion. For example, rotating the torso to the left requires the right external oblique and the left internal oblique to work together.
These muscles are also responsible for lateral flexion, or bending the torso to the side. When the internal and external obliques on the same side contract, they pull the rib cage towards the hip, resulting in a side bend. This action is common in daily activities like leaning over to pick something up.
Beyond movement, the obliques play a role in core stabilization. They contract to create intra-abdominal pressure, which supports the spine and helps maintain posture during physical exertion like lifting heavy objects, protecting the lower back from injury. By compressing the abdominal contents, the obliques also assist in processes such as forced exhalation, coughing, and defecation.
Strengthening and Engaging the Obliques
Targeted exercises strengthen the obliques, improving core stability and rotational power. The side plank is an effective exercise that uses isometric contraction. To perform it, lie on your side propped up on one forearm with the elbow under the shoulder, and lift the hips until the body forms a straight line. Holding this position challenges the obliques on the supporting side to stabilize the trunk.
The Russian twist is another common exercise that targets the rotational function of the obliques. It is performed by sitting on the floor with knees bent and feet slightly elevated while leaning back to engage the core. From this position, the torso is twisted from side to side, often while holding a weight, which engages the obliques as they control the rotation.
The bicycle crunch is a dynamic exercise involving both torso rotation and flexion. Lying on the back with hands behind the head and knees bent, you alternate bringing the opposite elbow to the opposite knee in a pedaling motion. This movement requires the obliques to contract to lift the shoulder blade and rotate the torso with each repetition. Focusing on controlled movements is important for these exercises.