Anatomy of the abdominal muscles

The abdominal muscles consist of no fewer than 4 different pairs of muscles. These muscles are located on the left and right sides of the midline at the level of the navel. The abdominal muscles contribute to posture and the movement of the trunk and pelvis. They also influence the position of the abdominal organs and are active during (forceful) exhalation, straining, coughing, and sneezing.

The abdominal muscles can be divided into:

• Straight abdominal muscles (musculus rectus abdominis)
• Transverse abdominal muscles (musculus transversus abdominis)
• Internal oblique abdominal muscles (musculus obliquus internus abdominis)
• External oblique abdominal muscles (musculus obliquus externus abdominis)

Straight abdominal muscles

At the front are the straight abdominal muscles (m. rectus abdominis). The straight abdominal muscles run in two bands to the left and right of the midline from top to bottom. At the top they attach to the breastbone and at the bottom they are connected to the pubic bone. The muscle fibers of the straight abdominal muscles are interrupted in several places by tendon tissue. This creates the characteristic block pattern or 'six-pack' that many people strive for.

When the straight abdominal muscles contract, the pelvis and rib cage move toward each other. The pelvis tilts backward, flattening the buttocks somewhat and rounding the lower back. These abdominal muscles therefore work hard during ab exercises such as a sit-up or crunch. If these muscles are weak, you often see people having an increased arch in the lower back (lordosis).

More toward the sides, the oblique and transverse abdominal muscles lie in 3 layers on top of each other.

Transverse abdominal muscles

The transverse abdominal muscles (m. transversus abdominis) form the deepest layer of abdominal muscles with more or less horizontally running muscle fibers. They attach to the lower ribs, a large tendon sheet on the back, and the pelvic brim.

Contraction of the transverse abdominal muscles does not really move the trunk but mainly affects the position of the abdominal organs. When you contract these abdominal muscles, the circumference of the waist decreases. The abdominal organs then move farther downward and/or upward. In this, the transverse abdominal muscles are supported by the other 3 abdominal muscles.

Internal oblique abdominal muscles

In the middle layer we find the internal oblique abdominal muscles (m. obliquus internus abdominis). These run from the pelvic brim diagonally forward and upward to the ribs. When the internal oblique abdominal muscles contract, the pelvis is pulled upward sideways toward the ribs. They also help rotate the trunk.

External oblique abdominal muscles

In the most superficial layer lie the external oblique abdominal muscles (m. obliquus externus abdominis). They are almost perpendicular to the internal obliques and therefore rotate the trunk the other way. In addition, like the straight abdominal muscles, they draw the pelvis and the ribs toward each other.

Tendon sheet (aponeurosis)

At the front of the abdomen, the tendon fibers of the abdominal muscles from the left and right sides come together. There they form a large tendon sheet or aponeurosis. They cross and overlap each other strongly there, creating a kind of braided structure. This is capable of transmitting a great deal of force. In the middle, the overlap is greatest and a connective tissue line has formed. Because tendon and connective tissue appear white, we call this the linea alba or white line.

Nevertheless, weak spots may be present in this line where a rupture (hernia) can occur. A portion of the organs then bulges outward through the abdominal wall. This is then seen as a bulge on the abdomen.

Abdominal exercises

Many people would like a flatter abdomen or a nice 'six-pack'. To get those, they train the abdominal muscles. There are many different exercises for this. But not all exercises necessarily produce a flatter abdomen or slimmer waist. It is often also necessary to do other forms of training, such as running or cycling, to lose weight and achieve the desired figure.

In addition, a good diet plays a major role. Only with a low fat percentage do the abdominal muscles actually become visible. To get a general impression of whether you have a healthy weight, you can calculate your BMI.

Another reason to do abdominal exercises is to prevent or reduce physical complaints due to, for example, a postural problem or back pain.

Exercises
A good training program for the abdominal muscles consists of different exercises in which you train all the abdominal muscles. The correct execution of these exercises is very important.