The abdominal muscles more commonly known as abs or six pack for short located on the front lower half of the human torso. Four core muscle groups make up the the Abdominal muscles as we know them and they are as follows;
- Rectus Abdominal
- Exernal Obliques
- Internal Obliques and
- Transverse Abdominals
These muscles combine to provide different important functions for our bodies such as providing movement, postural support to the trunk, protecting the inner organs and assisting in the breathing process. The abdominal muscles work very closely with the muscles of the back to assist in these functions and they play a very important role in defining the form (posture) of our body.
Rectus Abdominal
The Rectus Abdominal is a long superficial muscle extending vertically on each side of the human abdomen from the lower rib cage down to the pubic bone. There are two parallel muscles separated into 4 smaller paired compartments by the Linea Alba, giving it the commonly referred to name of the six pack due mainly to the fact the lower two compartments are close to the pubic bone and therefore not visible. The origin point of attachment of the Rectus Abdominal Muscle is the Pubic Crest and the Pubic Symphysis. The insertion point of attachment of the Rectus Abdominis is the xiphoid process and the costal cartlages of the 5th to 7th ribs. The main function of the Rectus Abdominis Muscle is flexion of the trunk, in other words the bending of one’s spine/back forward. The lower muscle fibbers also contribute to the flexion of the hips or tilting the hips forward. In addition to these functions the Rectus Abdominis plays a large role in breathing as it is the muscle used when forcefully expelling air from you lungs and assist in keeping internal organs in place.
External Oblique
The External Oblique muscles are the largest and most superficial of all the abdominal muscles. The opposite to the internal Oblique muscle, they extend downwards and inwards and are the strongest of all the abdominal muscles. The origin points are the anterlateral boarders of the lower 8 ribs and the insertion points are the outer anterior half of the Iliac Crest, the Pubic Crest and Tubercle and the aponeurosis of the anterior rectus sheath. Working closely with the internal oblique muscles, the main function of the external oblique muscles are to abduct and rotate the trunk, support the abdominal wall, assist the lungs with forced expiration as well as aiding in raising the intra-abdominal pressure by flexion of the trunk (pulling the chest downwards).
Internal Obliques
The internal Oblique muscles is found lying in-between the external Oblique and Transversus abdominis. The origin attachment point of the the internal oblique muscle is the anterior two thirds of the iliac crest, the lateral two thirds of the inguinal ligament and the lumbar fascia. The insertion attachment points are the costal cartilages of ribs 8 to 12 and the aponeurosis of the rectus sheath and a conjoint tendon to the Pubic crest. Working closely with the external oblique muscles the internal oblique muscles function to abduct and rotate the trunk, to abduct and rotate the trunk, supporting the posterior wall of the inguinal canal, assist the lungs with forced expiration as well as aiding in raising the intra-abdominal pressure.
Transversus Abdominis
The Transverse Abdominis is a flat triangular muscle the deepest of the abdominal muscles, and as the name suggests it horizontally from the front to the back of the abdomen. Unlike the other muscles of the abdomen, the Transversus Abdominis function is not primarily for postural support but rather an important muscle to aid in our breathing especially forced exhalation, compressing the ribs and viscera assisting in providing and pelvic stability and during pregnancy assisting women in the delivery of their baby.
The Transversus Abdominis lies underneath the inner oblique and has multiple origin and insertion attachment points with the origin points being the Costal Margin, lumbar fascia, anterior two thirds of iliac crest and lateral half of inguinal ligament. The Insertion attachment points are Aponeurosis of posterior and anterior rectus sheath and conjoint tendon to pubic crest and pectineal line.
