The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

and

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

(front and side)

abdominal wall In anatomy, the abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the anterolateral and posterior walls. There is a common set of layers covering and forming all the walls: the deepest being the vi ...

, deep to (layered below) the internal oblique muscle. It serves to compress and retain the contents of the abdomen as well as assist in

exhalation Exhalation (or expiration) is the flow of the breathing, breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing. This happens due to elastic properties of ...

Structure

The transverse abdominal, so called for the direction of its fibers, is the innermost of the flat muscles of the abdomen. It is positioned immediately deep to the internal oblique muscle. The transverse abdominal arises as fleshy fibers, from the lateral third of the

inguinal ligament The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may ...

, from the anterior three-fourths of the inner lip of the

iliac crest The crest of the ilium (or iliac crest) is the superior border of the wing of ilium and the superolateral margin of the greater pelvis. Structure The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the posterio ...

, from the inner surfaces of the cartilages of the lower six ribs, interdigitating with the diaphragm, and from the

thoracolumbar fascia The thoracolumbar fascia (lumbodorsal fascia or thoracodorsal fascia) is a complex, multilayer arrangement of fascial and aponeurotic layers forming a separation between the paraspinal muscles on one side, and the muscles of the posterior abdomina ...

. It ends anteriorly in a broad

aponeurosis An aponeurosis (; : aponeuroses) is a flattened tendon by which muscle attaches to bone or fascia. Aponeuroses exhibit an ordered arrangement of collagen fibres, thus attaining high tensile strength in a particular direction while being vulnerable ...

(the Spigelian fascia), the lower fibers of which curve inferomedially (medially and downward), and are inserted, together with those of the internal oblique muscle, into the crest of the pubis and pectineal line, forming the inguinal

conjoint tendon also known as superior tendon of abdominal cavity. The conjoint tendon (previously known as the inguinal aponeurotic falx) is a sheath of connective tissue formed from the lower part of the common aponeurosis of the abdominal internal oblique musc ...

also called the aponeurotic falx. In layman's terms, the muscle ends in the middle line of a person's abdomen. Throughout the rest of its extent the aponeurosis passes horizontally to the middle line, and is inserted into the linea alba; its upper three-fourths lie behind the rectus muscle and blend with the posterior lamella of the aponeurosis of the internal oblique; its lower fourth is in front of the

rectus abdominis The rectus abdominis muscle, () also known as the "abdominal muscle" or simply better known as the "abs", is a pair of segmented skeletal muscle on the ventral aspect of a person, person's abdomen. The paired muscle is separated at the midline b ...

Innervation

The transverse abdominal is innervated by the lower

intercostal nerves The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and dif ...

(thoracoabdominal, nerve roots T7-T11), as well as the

iliohypogastric nerve The iliohypogastric nerve is a nerve that originates from the lumbar plexus that supplies sensation to skin over the lateral gluteal and hypogastric regions and motor to the internal oblique muscles and transverse abdominal muscles. Structur ...

and the

ilioinguinal nerve The ilioinguinal nerve is a branch of the first lumbar nerve (L1). It separates from the first lumbar nerve along with the larger iliohypogastric nerve. It emerges from the lateral border of the psoas major just inferior to the iliohypogastric, ...

Function

The transverse abdominal helps to compress the ribs and viscera, providing thoracic and pelvic stability. It can contract during the

phase of

respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...

to force air out of the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

. The transverse abdominal also helps a pregnant person to deliver a child. Without a stable spine, one aided by proper contraction of the TVA, the nervous system fails to recruit the muscles in the extremities efficiently, and functional movements cannot be properly performed. The transverse abdominal and the segmental stabilizers (e.g. the

multifidi The multifidus (multifidus spinae; : ''multifidi'') muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. While very thin, t ...

) of the spine have evolved to work in tandem. It is true that the TVA is vital to

back The human back, also called the dorsum (: dorsa), is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck. It is the surface of the body opposite from the chest and the abdomen. The vertebral c ...

and

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber ...

health, the muscle also has the effect of pulling in what would otherwise be a protruding

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

(hence its nickname, the “corset muscle”). Training the

muscles alone will not and can not give one a "flat" belly; this effect is achieved only through training the TVA. Thus, to the extent that traditional

abdominal exercises Abdominal exercises are a type of strength exercise that affect the abdominal muscles (colloquially known as the stomach muscles or "abs"). Human abdominal consist of four muscles which are the rectus abdomens, internal oblique, external oblique, ...

(e.g. crunches) or more advanced abdominal exercises tend to "flatten" the belly, this is owed to the tangential training of the TVA inherent in such exercises. Recently, the transverse abdominal has become the subject of debate between biokineticists, kinesiologists, strength trainers, and physical therapists. The two positions on the muscle are (1) that the muscle is effective and capable of bracing the human core during extremely heavy lifts and (2) that it is not. Specifically, one recent systematic review has found that the baseline dysfunction of TVA cannot predict the clinical outcomes of low back pain. Similarly, another systematic review has revealed that the changes in TVA function or morphology after different nonsurgical treatments are unrelated to the improvement of pain intensity or low back pain related-disability. These findings have challenged the traditional emphasis of using TVA-targeted intervention to treat low back pain.

Exercise

The most well known method of strengthening the TVA is the vacuum exercise. The TVA also (involuntarily) contracts during many lifts; it is the body's natural weight-lifting belt, stabilizing the spine and pelvis during lifting movements. It has been estimated that the contraction of the TVA and other muscles reduces the vertical pressure on the intervertebral discs by as much as 40%. Failure to engage the TVA during higher intensity lifts is dangerous and encourages injury to the spine. The TVA acts as a girdle or corset by creating hoop tension around the midsection.

Additional images

File:Gray388.png, Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the lumbodorsal fascia. File:Gray390.png, Posterior surface of sternum and costal cartilages, showing Transversus thoracis. File:Gray398.png, The interfoveolar ligament, seen from in front. File:Gray399.svg, Diagram of sheath of Rectus. File:Gray400.png, Diagram of a transverse section through the anterior abdomina wall, below the linea semicircularis. File:Gray401.png, The abdominal inguinal ring. File:Gray531.png, The abdominal aorta and its branches.

References

External links

* - "Incision and reflection of the internal abdominal oblique muscle." * - "Anterior Abdominal Wall: The Transversus Abdominis Muscle" * - "Muscles and nerves of the posterior abdominal wall." * * * * {{Authority control Muscles of the torso