Abdominal anatomy: discover all abdominal muscles, their function and how to train them

Abdominal anatomy: discover all abdominal muscles, their function and how to train them

It is important to know the anatomy of the abdomen, not only to know how to train the abs but also to protect your viscera. Many consider a flat stomach an aesthetic requirement, thus placing the abdominal muscles at the top of the list, as no other area gives the physique that athletic look.

But the fundamental role of the abdominal muscles is, first of all, linked to health and their functional aspect.

First, the abdominal muscles support and protect some of our body’s most important organs, such as the stomach, liver, and intestines.

Their function is to act as a natural anatomical belt that fixes the pelvis, stabilizes posture and supports the viscera. These muscles also perform an essential action in ensuring the link between the torso and the legs and are involved in the flexion and rotation of the spine.

Abdomen anatomy: learn to recognize abs

The abdominal walls, which extend from the chest to the pelvis and close the abdominal cavity, are made up of the abdominal muscles at their maximum thickness.

These muscles are divided into anterolateral and posterior, i.e. they occupy the anterior, lateral and posterior portions of the trunk.

The anterolateral muscles are represented by:

  • Rectus abdominis.
  • Pyramidal muscle.
  • External oblique.
  • Internal oblique.
  • Transversus abdominis.

The posterior muscles are represented by:

  • Square of the loins.
  • Big psoas.
  • Piccolo psoas.
  • Iliaco

If you are interested in the topic, discover our in-depth study on the psoas.

Abdominal anatomy: rectus abdominis muscle

It originates from the 5th to 6th costal cartilage and the xiphoid process of the sternum. It inserts low, at the level of the pelvis, in the pubic crest.

It is called an even muscular element, because there is a right portion and a left portion.

The rectums are separated only by the linea alba (or midline), which is a thin band of connective tissue, which extends lengthwise from below the breastbone to the pelvic bones.

Action of the rectus abdominis

The rectus abdominis has the task of lowering the ribs and flexing the chest on the pelvis: it is therefore expiratory and flexor of the chest.

Its contraction, with the increase in intra-abdominal pressure, favors urination, defecation, vomiting and facilitates childbirth.

Therefore, it is he who can form the famous and coveted “turtle”.

Upper and lower abs: they don’t exist

It’s important to dispel the myth of high and low abs.

Many people try to train them with different exercises, but the rectus abdominis is a unique muscle, there are no exercises for upper or lower abs.

Some exercises can train the upper muscles more effectively and others the lower rectus abdominis, but when you have a burning sensation during exercises it is only the recruitment of the fibers that are working.

Pyramidal muscle

It is a small muscle, flattened and elongated, located immediately in front of the rectus abdominis.

It takes its name from its pyramidal shape.

Action of the pyramidal muscle

This muscle allows you to stretch the linea alba, a structure located in the center of the rectus abdominis.

Abdominal anatomy: oblique abs

There are two of them: the internal oblique muscle and the external oblique muscle.

The external obliques are lateral to the rectus abdominis and are also superficially visible. They originate from the outer faces (surfaces) of the ribs 5th to 12th, which intertwine with the bundles of the serratus anterior muscle.

The direction of its fibers is from top to bottom and from back to front. They too are inserted at the level of the pelvis, more specifically on the iliac crest.

The internal obliques lie below the external obliques, arise from bony prominences in the pelvis, the anterior superior iliac spines, and fan out.

Oblique action

They help to twist the torso and flex the torso laterally.

It is often said that you have to work these two muscles to have a slim waist, but that’s not true!

If you are interested in the topic, discover our in-depth study on obliques.

Abdominal anatomy: transversus muscle

The transversus abdominis muscle, so named for the transverse direction of its muscle bundles, is covered by the internal oblique muscle.

It extends from the vertebral column to the linea alba.

It originates from the last 6 costal cartilages, from the thoracolumbar fascia covering the deep back muscles, from the iliac crest of the pelvis and from the inguinal ligament, running horizontally and inserting into the abdominal aponeurosis, forming the posterior sheath of the rectus abdominis .

It starts at the back of the torso, where it hooks up to all the vertebrae, and horizontally covers the entire abdomen.

By means of its bundles inserted on the ribs, it brings them closer to the median line, towards the center of the body, and thus contributes to narrowing the chest, facilitating expiration. Increases abdominal pressure and sends the diaphragm upwards, being its direct antagonist.

Transverse action

Its main function is to act on the abdominal viscera, participating in various actions, including:

  • Vomit.
  • Urination.
  • Defecation.
  • Part.
  • Cough.
  • Phonation.

It also contracts during efforts such as:

  • To lift.
  • Pull.
  • Push.

When it works it doesn’t make any movement, it simply contracts on itself without moving other muscles.

Consequently, it is the transverse muscle that you need to work to have a slim waist!

Abdominal anatomy: quadratus lumborum muscle

The quadratus lumborum is a flattened, quadrilateral muscle located on either side of the lumbar spine, between the iliac crest of the pelvis and the twelfth rib.

Square action

Its action is to stabilize the pelvic girdle and spine.

It is a muscle that is defined as “postural” given its involvement in maintaining postural attitudes.

It also intervenes in the inclination of the spine.

Anatomy addome: psoas grandus

It inserts on the medial surface of the lesser trochanter of the femur.


It is the thigh flexor muscle.

Piccolo psoas

It inserts on the iliopubic eminence of the hip bone.


Tenses the iliac fascia and flexes the trunk, helps to tilt the lumbar spine laterally, also tenses the fascia lata (muscle located in the anterolateral region of the thigh).

Abdomen anatomy: iliac muscle

It inserts on the undersurface of the lesser trochanter of the femur.


Participates in trunk flexion as well as flexing the thigh over the pelvis.

Abdominal anatomy: what is the abdominal core

The core is a set of muscles all in relation to each other, which form the center of gravity of the body.

It is the muscular corset of the body, it is the point from which the movement starts.

For this reason, having a trained core is equivalent to having a strong and resistant body, which moves easily.

If you are interested in the topic, discover our in-depth analysis on the core.

What are the core muscles

The muscles that make up the core are the deep muscles that protect and support the spine:

  • Rectus abdominis.
  • Oblique.
  • Transverse.
  • Square of the loins.
  • Gluteus maximus.
  • Gluteus medius.
  • Why it’s important to have a trained core

    A trained core means:

    • Flat stomach.
    • Open chest.
    • Correct physiological curves: cervical, dorsal and lumbar.
    • Reduced implementation of dysfunctional postural attitudes.
    • Good functioning of internal organs.
    • Possibility of making explosive efforts, involving energy and power on the whole body.
    • Excellent balance.
    • Ability to move quickly and with ease.

    The consequences of a weak core

    If your core isn’t trained, the first to suffer is the spine, which could assume unphysiological positions.

    The hypotonia of the abdominal muscles, which contribute to supporting the lumbar spine, could lead to a non-physiological accentuation of the lumbar curve, a logical premise for future low back pain.

    Weak abdominal muscles: the consequences

    Poorly trained abdominal muscles could lead to a weakness of the abdominal wall, a predisposing factor to the formation of abdominal hernias (the leakage of a bowel or part of it).

    Excessive weakening of the abdominal wall could also trigger a malfunction of the digestive system.

    In particular, the intestine could become “lazy”: constipation problems could thus arise and an unpleasant feeling of swelling in the abdomen could often be felt.

    Furthermore, the weakness of these structures could in some cases favor the formation of an abdominal diastasis.

    What is diastasis recti

    Abdominal diastasis consists of a separation of the muscle surfaces of the right and left portion of the rectus abdominis muscle, which widen excessively moving away from the midline.

    There are various causes: the first is pregnancy, due to its ability to determine a rapid and significant increase in abdominal volume which significantly stretches the rectus muscle.

    Find out what diastasis recti is and what to do about it.

    How to train your abs correctly

    The type of training for the abs has been a long-debated question, which must however be related to the posture of the subject.

    Each abs exercise must be designed taking into consideration the postural attitudes already present in the person. A tonic and hypertrophic abdomen will bring the pelvis into retroversion, flattening the lumbar lordosis.

    Hypotonic abdominal muscles, on the other hand, will be muscles that will not be able to control the pelvis, which will rotate anteriorly, therefore in anteversion, pulled by the hip flexors which will shorten more and more, also leading to back problems…

    About author

    My name is Angela Cannovale, I really enjoy helping people find happiness and feel good about themselves. I think that feeling good is important because it helps you do well in life. To me, being healthy is not just about lifting weights. It involves taking care of your body by doing things like stretching, warming up, eating healthy food, and getting enough rest and sleep. I love showing others what their bodies can do with a little bit of effort. My goal is to help you achieve a happy and balanced lifestyle that will keep you healthy in the future.
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