Anatomy of the abdominal muscles

The abdominal muscles comprise four distinct pairs of muscles, located on both the left and right sides of the midline at the level of the navel. These muscles play a crucial role in maintaining posture and facilitating movement of the trunk and pelvis. Additionally, they help position the abdominal organs and are actively engaged during activities such as (forceful) exhalation, straining, coughing, and sneezing.

The abdominal muscles can be divided into:

• Rectus abdominis (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)

Rectus abdominis

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

When the rectus abdominis contracts, the pelvis and rib cage move towards each other. The pelvis tilts backwards, flattening the buttocks somewhat and rounding the lower back. These abdominal muscles therefore work hard during abdominal exercises such as a sit-up or crunch. If these muscles are weak, you often see that people have an increased arch in the lower back (lordosis).

More towards the side, 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 fibres. They attach to the lower ribs, a large tendinous sheet on the back, and the pelvic brim.

Contracting 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 reduces. The abdominal organs therefore move more downwards and/or upwards. 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 forwards and upwards to the ribs. When the internal oblique abdominal muscles contract, the pelvis is pulled upwards sideways towards the ribs. They also help to rotate the trunk.

External oblique abdominal muscles

In the most superficial layer lie the external oblique abdominal muscles (m. obliquus externus abdominis). They lie almost at right angles to the internal oblique abdominal muscles and therefore rotate the trunk the other way. In addition, like the rectus abdominis, they draw the pelvis and ribs towards each other.

Tendinous sheet (aponeurosis)

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

However, weak spots can be present in this line where a rupture (hernia) can occur. Part of the organs then bulges through the abdominal wall to the outside. This is then visible as a lump on the abdomen.

Abdominal exercises

Many people would like a flatter abdomen or a nice 'six-pack'. To get this, 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. The abdominal muscles only truly become visible at a low body fat percentage. 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, for example due to a postural problem or back problems.

Exercises
A good exercise programme 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.