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The Abdominal Muscle Group


Updated June 02, 2014

Abdominal Muscles
Ed Snowshoe Collection/Digital Vision/Getty Images

Abdominal muscles are key for back support.  But did you know you have 6 of them?  Each abdominal muscle plays its own role in spinal support.  This article presents each of the ab muscles and describes how they affect your posture and back health.

What the Abdominal Muscles Are:

The abdominal muscles are a group of 6 muscles that extend from various places on the ribs to various places on the pelvis. They provide movement and support to the trunk, often called the core. They also assist in the breathing process.

Why Abdominal Muscles are Special:

Abdominal muscles are special because they provide postural support. They also play a role defining the form (with strength exercise). For example,the most superficial abdominal muscle, the rectus abdominus, gives the 6-pack ab effect when it is worked to a high degree of fitness. More structurally, the deeper and closer to the spine the particular abdominal muscle is, the more effect over body posture it will have, and this often contributes significantly to a healthy back.

The 6 Abdominal Muscles:

The six abdominal muscles all affect body posture. The deeper the muscle is located (i.e. the closer to the spine), the more powerful effect it will have, and therefore, the greater capacity it will have for creating and maintaining a healthy spine. From deep to superficial the abdominal muscles are:


Transversus Abdominis - The Deepest Ab Muscle:

The transverse abdominus muscle is the deepest of the 6 ab muscles. It can have a tremendous effect on body posture. You cannot touch this muscle from the outside. It wraps around the torso, creating an effect similar to a back support belt.

The Internal Oblique Muscles - Strong Effect on Posture:

The internal obliques are a pair of ab muscles, residing on each side of the torso. They are the next deepest, after the transversus. Just like the transversus, they affect body posture tremendously, only slightly less, because of their more superficial position. The internal obliques are involved in, among other things, rotation and lateral flexion of the spine.

External Obliques:

The external obliques are another pair of ab muscles that are located on either side of the torso. The external obliques are more superficial than the transversus and the internal obliques. Consequently the external obliques have less effect (but certainly not none) on body posture. Like the internal obliques, the external obliques are involved in, among other things, rotation and lateral flexion of the spine.

Rectus Abdominus:

The rectus abdominus muscle is the most superficial of the abdominal muscles. It and the external obliques affect body posture, just not as much as the deeper interal obliques and transversus. The rectus abdominis muscle is responsible for the 6-pack ab look in very fit people.

Spinal Action of the Abs:

Because muscles work in groups, we call the abdominal muscles spinal flexors. Their main job is to bend the spine forward, when contracting coencentrically. The back muscles counterbalance the action of the abs, and are called spinal extensors. What this means is that when the abdominals shorten to flex the spine, the back muscles are put on a stretch, and vice versa.

The Abs and Breathing:

The abdominals participate in the breathing process, especially during exhale, when they help force air out of the lungs by depressing the thorax.

Created on: November 27, 2005

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