Meet Your Abs, the Abdominal Muscles

1
Rectus Abdominis

abdominal muscle
rectus abdominis, the "ripped abs" muscle. Photo © A.D.A.M.

Those of us interested in fitness love to talk abdominals. We throw around terms like great abs, six pack abs, flat abs and ripped abs all the time. But we are really talking about a specific set of muscles that have distinct functions yet work as a team.

Take this short tour of the abdominal muscles. Understanding how the abs are put together and how they help us move will help you get the most of the abdominal exercises that are part you workouts.

Rectus abdominis is the most famous abdominal muscle. It is the one responsible for the look of "ripped abs." A long muscle that runs down the front of the trunk, rectus abdominis starts at ribs 5 - 7 (count from top down) and the base of the sternum (breast bone), and runs all the way down to the top of the pubic bone. The fibers of the rectus abdominis are parallel to each other and contained in a sheath. They are attached to the sheath in three places creating little horizontal grooves. This is what gives the rectus abdominis a "6 pack" or "ripped" look when it is well developed.

The rectus abdominis is chiefly responsible for forward flexion (forward bending) of the trunk but it also helps compress the abdomen.

2
External Obliques

abdominal muscles
abs - external obliques. Gray's Anatomy, Wikimedia Commons

The external obliques form a wide band of muscle that runs down, along a diagonal, from ribs 5 - 12 to attach to ligaments near the top of the hip bones.

The external obliques are prime movers when it comes to side-bending and rotating the pelvis opposite the ribcage. They also help with compression and forward bending of the abdomen.
Next: the internal obliques.

3
Internal Obliques

abdominal muscle
Abs - Internal Obliques. Gray's Anatomy, WickimediaCommons

Under the external obliques, the fibers of the internal obliques run perpendicular to those of the external obliques, having numerous places where they attach (begin) and insert (end) along the way.

The internal obliques help with side-bending and rotation of the spine and rib cage. Like the external obliques, they aid compression and forward bending of the abdominal area.

The internal and external obliques work together in trunk rotation.

Learn about oblique workouts

Next: the transversus abdominis

4
Transversus Abdominis

abdominal muscle
Abs - Transversus Abdominis. Gray's Anatomy, WikimediaCommons

The transversus abdominus is made of a wide band of fibers that wrap horizontally around the middle of the body. It forms a supportive girdle for the trunk, making it an essential muscle of core stabilization. Pulling in the transversus abdominus results in a reduction of diameter of the abdomen. In other words, it gives you a waist.

In Pilates we take advantage of the abdominal compression and spinal flexion that the transversus abdominis provides.
Next: There is More to the Core

5
There's More to the Core

abdominal muscles
rectus abdominis - "ripped abs". Photo: Suza Scalora / Photodisc

While we focused on movements the ab muscles make for us, they also support the contents of the abdomen, support the spine, and help with breathing. It's also important to remember that the abdominal muscles work together. If one is to achieve a high level of functional fitness, working out with a balanced approach to toning the abs will be much more effective than over-working any one area, the rectus abdominis, for example.

The abdominal muscles are core muscles, but they are not the only muscles we refer to when we speak of core training or core strength. The core group also includes:

When it comes to developing a strong core with well toned abs, the Pilates method is unmatched. Explore over 100 sets of free Pilates exercise instructions here at pilates.about.com.


Sources:
Anatomy of Movement, Calais-Germain.
Pilates, Isacowitz.

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