Together with the back and chest muscles, the abdominal muscles form the muscular corset of the trunk. They enable various trunk movements, support breathing, protect the organs located in the abdominal cavity and also participate in excretion via the abdominal press. Among the most common pathologies are the strain and the hernia, as well as the herniated discs that often occur as a result of poor training condition of the abdominal muscles.
What are abdominal muscles?
The abdominal muscles or abdominal muscles (from Latin: abdomen = belly), together with the muscles of the back and chest, make up the trunk muscles. They are necessary to flex the trunk forward or to the side. In addition, they are used in all rotational movements of the trunk. They are involved in exhalation and support elimination via the abdominal press by increasing the pressure inside the abdomen through their contraction. Functioning abdominal muscles are of crucial importance for an upright and thus healthy posture. As a direct antagonist (counterpart) to the muscles of the back or spine, well-developed abdominal muscles prevent a hollow back and thus efficiently protect the intervertebral discs as well as the nerve structures emerging from the spinal canal. Unlike the muscles of the extremities of the arms and legs, the abdominal muscles originate on the skeleton and for this reason are counted as skeletal muscles.
Anatomy and structure
From an anatomical point of view, the abdominal muscles are divided into a superficial part and a deep-lying part. The superficial musculature forms the anterior and lateral abdominal wall. The anterior (also middle) abdominal muscles are the straight abdominal muscle (M. rectus abdominis) and the pyramidal muscle (M. pyramidalis), the lateral part consists of the transverse abdominal muscle (M. transversus abdominis) as well as – applied to the left and right respectively – the external and internal oblique abdominal muscles (M. obliquus externus and internus abdominis respectively). The lateral abdominal muscles end at the midline of the abdomen (median line) in tendon plates that together form a sheath in which the straight abdominal muscle lies. This line (also called rectus sheath) runs from the sternum down to the pubic symphysis. The low-lying part of the abdominal muscles is formed by the quadratic lumbar muscle (M. quadratus lumborum), some divisions also add the still M. iliopsoas.
Function and tasks
All abdominal muscles interact to ensure physiological and therefore healthy posture and an upright gait. In addition, they make an important contribution to the stable fixation and protection of the organs of the abdominal cavity. The main function of the straight abdominal muscle is to bend the trunk forward or – if the upper body remains in an unchanged position – to lift the legs. In addition, the muscle is involved in the abdominal press. A good training condition of the straight abdominal muscle is visually evident from the colloquial “six-pack”. The oblique abdominal muscles are particularly important for the main task of the abdominal muscles, which is to effectively brace the trunk and in this way protect the sensitive spine in particular from unilateral loads or external influences. The oblique portion is also needed when you want to turn the torso to the right or left or tilt it sideways. The oblique abdominal muscles also increase intra-abdominal pressure through their tension and are thus involved in the abdominal press. The transverse abdominal muscle supports the straightening of the pelvis and also shapes the waist. The task of the quadratic lumbar muscle, which belongs to the posterior abdominal wall, is to tilt the trunk sideways. In addition, it supports exhalation as well as inhalation via its stabilizing function.
Diseases and ailments
Among the frequent complaint patterns in the area of the abdominal muscles is the classic strain. Here, abrupt, non-physiological movements stretch the muscle fibers beyond the normal level. The smallest structures react with tears, which are sometimes experienced by the affected person as very painful during movement. Often, the recovery from an abdominal muscle strain is a comparatively long process, since the abdominal muscles are practically always in use in normal everyday life due to their holding and supporting function and for this reason can hardly be spared.Weak abdominal muscles can also promote the occurrence of an inguinal hernia, in which parts of the intestines bulge outward through a gap in the abdominal wall and usually have to be surgically put back in place. However, insufficiently trained abdominal muscles have the greatest relevance with regard to clinical pictures on the spine: Thus, a muscular imbalance – weak abdominal muscles and strong back extensors – can lead to a hollow back, which in the long run can damage the intervertebral discs as well as the nerves exiting the spinal canal. The classic herniated disc is therefore in many cases caused by an insufficient training condition of the abdominal muscles in conjunction with poor or one-sided posture. In concrete terms, this means that abdominal muscle training is one of the most important treatment pillars in conservative therapy.
