A Guide to the Core Muscles

The Core is composed of as many as 35 different muscle groups connecting into the pelvis from the spine and hip area. It is incorporated in almost every movement of the human body. Not only does a conditioned core make you look good, it is the main group of muscles that support you in an upright position. Your erect posture results from these three main muscle groups of the abdominal core:

Rectus Adomimus

Rectus Adominus

Commonly referred to as “abs” or “six-pack” or “washboard”, this flat muscle runs the entire length of the abdomen. It connects just under the pectoralis group on top and at the front of the pelvis on the bottom. Its main purpose is to hold in the internal organs and allow the spinal column to flex forward giving us the ability to bend forward at the waist.


Comprised of the external and internal obliques, these two muscle groups run the whole length of the chest from collarbone to the pelvis. Laterally they start on each side of the Rectus Adominus and wrap around the waist terminating midway down the spine to just above the buttocks (the gluteus maximus). As their name suggests, the internal obliques lie deeper underneath the external obliques.

Both obliques allow us to bend sideways and rotate our trunk in both directions. In addition, the obliques, like the rectus abdominus, also compress and hold the internal organs. The obliques are also responsible in assisting with digestion and are the muscles used when we forcibly exhale along with aiding with good erect posture.


The intercostals muscles run between the ribs and make up the wall of the chest cavity. As with many of the other muscle groups these too also break down into both internal and external.

External – This part of the intercostals are located on the outside of the ribs and function to increase the size of the thoracic cavity – the area from the neck to the diaphragm when contracted. They also assist with normal and forced inhalation.

Internal – The internal intercostals are located on the inside of the ribs and do just the opposite – they make the thoracic cavity smaller when contracted and assist with exhalation, both normal and forced.

Building Core Muscles

While there are dozens of exercises that can build up the abdominal core, these are the basics ones to start with:

Rectus Adominus – crunches or sit-ups
Obliques – side bends and decline oblique crunches
Intercoastals – trunk twists

The exercises include basic weight lifting to strengthen the hip muscles to isometric exercises for the back extensors, abdominals, and lateral trunk muscle.

While having a “six-pack” is the dream of many people, they are far more than for the attraction of the opposite sex. Not only do they serve to make the core more flexible, but also add stability to the posture.