It is an extremely important muscle that acts as a stabilizer for the entire lower back and core muscles.
Transversal means through and abdominis comes from the Latin word abdere which means to keep. From this, you get the idea that the abdominals, in general, work to “store” the contents (the digestive organs).
The transversus abdominis is one of the main stabilizing muscles of the lumbar spine nucleus. A transverse abdominal muscle is often weak and therefore one of the many reasons why people may experience low back pain.
The transversus abdominis muscle is a thin, sheet-like muscle that lies deep in the internal oblique.
The transversus abdominis muscle runs between the ribs and the hips, wrapping the trunk from front to back. The fibers of this muscle run horizontally, much like a backrest belt.
In this way, in addition to providing postural support, the transverse abdominal muscle helps to contain and support the organs located within the trunk.
Anatomy of the transverse abdominal muscle
In Victorian times, many women wore corsets to draw on their waists and make them appear smaller. In modern times, many people do endless sit-ups to get that desired figure.
In both eras, the same muscles are involved: the transverse abdominis. Located on each side of the torso, these muscles are actually called the “corset muscles” in Pilates exercises, and they play a key role in strengthening and stabilizing the core.
From the group of abdominal muscles we have:
- The transverse abdominis that wraps around the abdomen horizontally, predominantly below the level of the navel.
- The obliques that cross over the front of the belly like an ‘X’ in two large diagonal leaves.
- The rectus abdominis is the least efficient abdominal muscle, with a rope action in contraction that bends the upper body forward and runs vertically on either side of the midline.
There is a transverse abdominal muscle on each side of the body, and each wraps in a horizontal direction from back to front, where they are connected by a fascial lamina (thin strip of fibrous connective tissue) that allows the two muscles to act as one only.
The transverse abdominis is the deepest of the three anterolateral muscles of the abdominal wall.
All voluntary muscles have an origin and an insertion, and the transversus abdominis is no exception. In most cases, one end of the muscle (the origin) is still, while the other end (the insert) is moving.
The origin of a muscle is the point where it attaches to a bone that is fixed or immobile.
The origin is usually the end that is closest to the center of the body, a direction known as proximal. For example, the ankle is distal to the knee (meaning it is farther from the center of the body than the knee), and the wrist is distal to the elbow.
The transversus abdominis originates on the inner surface of the 7th to 12th costal cartilages with fibers interdigitated with the diaphragm muscle, which is the main muscle of respiration, and attaches to the inner surface of the six lower ribs.
In the posterior part, the transversus abdominis connects to the thoracolumbar fascia lateral to the quadratus lumbar.
In front, the transverse abdominal muscle connects to the front of the inside of the hip bone (on its inner surface), with the anterior two-thirds of the iliac crest.
The transverse muscle of the abdomen inserts into the xiphoid process, which is a small bone that hangs down from the bottom of the sternum, the linea alba, which is a tendon that runs vertically from the ribs to the pelvis and separates the right and left sides of the superficial rectus abdominis muscle and the pubic symphysis joint.
The part of the transverse abdomen, which originates from the costal cartilages, interdigitates with the junction of the diaphragm from the same place.
The fibers of the transversus abdominis pass transversely around the abdominal wall to the internal oblique muscle. Previously, they become aponeurotic.
The aponeurosis has two main attachments:
The rectum sheath
- Internal oblique aponeurosis fuses to insert in the linea alba.
- Above the arcuate line, it passes deep into the rectus abdominis, while below this line it passes superficially.
The pubic crest and pectineal line
The lower tendon fibers of the transverse joint are similar to the fibers of the internal oblique to form the conjoint tendon, which attaches to the pubic crest and pectineal line. This insertion is through the joint tendon.
It should be appreciated that the posterior border of the external oblique muscle is free, while the same borders of the internal oblique and the transverse abdominis are attached to the lumbar vertebrae through the lumbar fascia.
It is innervated by the branches of the following nerves.
- The five intercostal nerves.
- Nervio subcostal.
- Iliohypogastric nerve.
- Nervio ilioinguinal.
The five inferior intercostal and subcostal nerves represent the six inferior thoracic spinal nerves, while the iliohypogastric and ilioinguinal nerves represent the first lumbar spinal nerve.
Blood supply of the transverse abdominis
The transverse abdomen receives its blood supply from;
- Inferior posterior intercostal and subcostal arteries
- Upper and lower epigastric arteries.
- Superficial and deep circumflex arteries
- Posterior lumbar arteries
Functions of the transverse abdominis
The main function of the transversus abdominis is the maintenance of abdominal tone. It is the natural girdle that we all use. As is the case with all abdominal muscles, stabilization is a key function.
It also plays an important role in increasing intra-abdominal pressure.
But the functions of the transverse abdomen are multiple, among them we can refer:
Muscles such as the transversus abdominis support the abdominal wall, also known as the nucleus, and hold internal organs in place.
The transverse abdominal muscle also provides stability to the trunk and spine during movements involving the arms and legs, and the maintenance of posture.
Along with the obliques (muscles on the sides of the torso), the transverse muscles of the abdomen also support the bones of the spine when the body is in a squat or lean position.
They intervene in the movements of the trunk: flexion, extension, lateral flexion.
The contraction of these muscles is done voluntarily, which means that it can be controlled by the individual himself, and it has a corset effect on the abdomen by flattening and narrowing the muscles that pull at the waist.
These muscles support breathing by helping to pull the abdomen inward, forcing the air out of the lungs to make room for a new breath of fresh air.
The transverse abdominal muscle can also assist with exhalation by compressing the abdominal organs and increasing intra-abdominal pressure, which is necessary for functions such as urination, defecation, vomiting, and in the effort of vaginal delivery.
Other examples of daily use of this muscle include anything that involves deep breathing or having to use forced exhalation, such as playing a wind instrument.
Disadvantages with transverse abdominal muscle strengthening exercises
The idea that strengthening the transverse abdominal muscle was therapeutic and led to exercise regimens designed to specifically isolate this muscle.
However, it is simply not possible to work a single muscle in isolation. Nor is it possible to focus on strengthening a muscle in a highly integrated system of work, in the hope of improving its timing.
Excessive transverse abdominal muscle strengthening puts pressure on the lumbar spine segments and can increase lower back pain.
Deliberately pre-meditating each of your movements when starting the exercise also makes your back more tied and painfully stiff as time goes on.
Attempting to isolate the transverse muscle from the abdomen also increases pressure on the pelvic floor. This is a potent cause of stress incontinence so common in elite athletes.
Workouts of up to 400 sit-ups in one session are also implicated in respiratory problems (asthma, sleep apnea, and panic attacks) due to a tight upper abdomen that disables the downward excursion of the diaphragm.
Many of the core stability classes involve non-functional repetitive exercises, such as kneeling on all fours and lifting the arms and legs without allowing the trunk to move.
This type of formal exercise is unnatural and non-functional and has little to do with normal daily activity.
Strengthening the transverse abdominis
As mentioned earlier, in front, the transverse abdominal muscle joins the linea alba. The linea alba tends to lose its strength during pregnancy.
Strengthening the transverse abdominis muscle after the baby is born can be a good way to restore the integrity of the linea alba.
If the transverse muscles of the abdomen are weak, the abdominal wall will begin to bulge forward and the pelvis may turn forward and increase lordosis (inward curvature) in the spine.
This can result after pregnancy but can also be associated with weight gain or lack of exercise.
A recent study shows that weak muscles in the transverse muscle of the abdomen may be to blame for low back pain.
Therefore, strengthening the core muscles is supposed to make the spine more stable and less painful, although very few patients with low back pain show symptoms of “instability”, their problems are caused by too stiff lumbar spines.
Some research has shown that strengthening the transversus abdominis in people with low back pain makes the low back pain go away. This led to a flourishing industry of basic work and Pilates classes.
Deactivation of the transverse abdominal muscle
When the back hurts, the transversus abdominis can be turned off as an automatic mechanism for pain relief.
This is not an elective, brain-premeditated action, it is a simple brain reflex to avoid excessive compression of the lumbar segments and thus to reduce pain emanating from a painful spinal link.