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The abdominal muscles

This is an excerpt from Vital Core Training by Leslee Bender & Leslee Bender.

There are five main muscles in the abdomen: The two vertical muscles, rectus abdominis and pyramidalis (located under the rectus abdominis), are located toward the middle of the body, and the three flat muscles, the external obliques, internal obliques, and transversus abdominis, are stacked on top of each other and situated toward the sides of the trunk (figure 2.1).

Pyramidalis

This vertical muscle is small and shaped like a triangle. It’s located very low in the pelvis under the rectus abdominis and helps maintain internal abdominal pressure. The pyramidalis is frequently thought of as the lower abs, but in actuality, the pyramidalis and the rectus abdominis work in conjunction and cannot be isolated when training.

Rectus Abdominis

This pair of muscles goes down the middle of the abdomen from the ribs to the front of the pelvis and may form what looks like a “six-pack” when someone has a lean body. They hold the internal organs in place and provide stability during all body movements. These muscles flex the spine when supine and decelerate extension when leaning back. When the small ball is placed behind the back, the rectus abdominis muscles provide extension rather than just flexion against gravity.

External Obliques

The external obliques are a pair of large, flat muscles, one on each side of the rectus abdominis. They run from the lower half of the ribs around and down to the pelvis. They are the outermost of the three types of flat muscles and cover the internal obliques and the anterior ribs. The external obliques allow the trunk to rotate and extend.

Internal Obliques

The internal obliques are a pair of muscles on top of the external obliques, just inside the hip bones. Like the external obliques, they are located on the sides of the rectus abdominis, running from the sides of the trunk toward the middle. They work with the external oblique muscles to allow the trunk to rotate.

Transversus Abdominis

Located near the spinal column and deeper than the other muscles, the transversus abdominis muscle wraps around the lower part of the torso and is known as the body’s corset. It influences respiration but does not create movement such as flexion or extension. During muscle contraction, the fibers are pulled toward the center of the body, tightening the pelvic floor and organs toward one another and creating balance relative to the core. Training the core correctly increases muscle strength, which, combined with good posture and alignment, will improve posture and help relieve pressure on the spine, which may, in turn, lead to less pain.

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