Anatomy of Abdominal Muscles and How They Work

The most common body goal that people set out for themselves is, without a doubt, weight loss. More precisely, you want to lose belly fat and tone abdominal muscles. It takes more to achieve this than making adjustments to your diet and exercising regularly. Getting educated about abdominal muscles, their anatomy and how they work is also important. Why? Knowing more about your abdominals and how they function helps you make wiser decisions to reach your goal successfully. Keep reading to learn more about different types of abdominal muscles and how they work.

Rectus abdominis

Rectus abdominis is the most well-known and prominent abdominal muscle. It is a long, flat, paired muscle located in the front of the abdomen. The muscle starts at the pubic bone and ends at sternum or the breastbone. The rectus abdominis is divided into two equal halves by the linea alba, a strong tendinous sheath. The linea alba is a long, white line which you can see in the photo below. Besides the long, vertical line, there are also three horizontal white lines which divide this muscle. Thanks to these white lines, athletes as well as other people who train regularly have the clearly defined abdominal area or six-pack.

The role of this muscle is to help flex the spinal column, narrowing the space between pelvis and ribs like when you’re doing crunches. Rectus abdominis facilitates breathing and helps in respiration, especially during forced exhalation after a workout. Side bending motions activate the muscle and stabilise the trunk during movements which involve the extremities and head.

To keep this muscle activated, make sure you do these exercises:


External obliques

The external oblique muscle is the largest part of the trunk area. Each side of your body has an external oblique muscle. They are situated on each side of the rectus abdominis. The external oblique muscle poses as one of the outermost muscles in the abdominal area extending from the lower half of the ribs around and down to the pelvis, as you can see in the photo below.

The lowest part of the muscle connects to the top corner of the pelvis, the bottom-front of the pelvis or the pubis, and the linea alba. Basically, external obliques cover the sides of the abdominal area. These muscles have multiple functions such as allowing flexion of the spine, torso rotation, sideways bending, and compression of the abdomen.

To keep these muscles activated, you should do the following exercises:

Barbell: Standing side bend, seated side bend, standing twist, seated twist.


Dumbell: Standing side bend, Roman chair side bend, standing overhead side bend,  Russian twist.


Cable: Standing side crunch, seated side crunch, kneeling twist, standing lift.


Machine: Lying twist, seated side crunch

Side Plank


Internal obliques

Internal obliques are located just below the external obliques. Basically, internal and external obliques are at right angles to each other. The muscle starts at the lumbar fascia which is the connective tissue covering the lower back, continues to the outer portion of the inguinal ligament located at the bottom outer edge of the pelvis, and extends to the back of the iliac crest or the upper-outside area of the pelvis. Internal obliques end at the bottom edge of the rib cage.

Together with external obliques, internal obliques participate in flexing the spinal column, trunk rotation, sideways bending, and compression of the abdomen. Since both groups of muscles are aligned at right angles to each other, they are referred to as opposite-side rotators. For example, when the trunk rotates to the right, the external oblique fibres on the left activate the movement and vice versa. Internal obliques also support the abdominal wall and assist in forced respiration.

To activate these muscles, you should do the following exercises: Bicycle crunches, reverse twist, side crunches, standing side bends.

Transversus abdominis

Transversus abdominis is a thin sheet-like muscle located deep in the internal obliques. The muscle is situated in the deepest level of abdominal muscles. It wraps around your torso from ribs to the pelvis and from front to back. Muscle fibers of transversus abdominis run horizontally. We can compare them to the weight belt or a corset.

The primary function of this muscle is the maintenance of abdominal tone, but it also participates in increasing the intra-abdominal pressure. Unlike other groups of muscles, transversus abdominis doesn’t move the spine or pelvis, but it does help with breathing and respiration. It facilitates forceful expiration of air from the lungs, thus stabilising the spine and it compresses the internal organs.

To keep this muscle activated, do these exercises: Abdominal hollowing, Plank, Supine leg extension, Glute bridge, Quadruped lifts, Russian twist.

Hip flexors

Hip flexors bring the thigh and trunk of the body closer together. You use these muscles in daily activities such as walking, bending over, stepping up, and so on. Although they don’t belong to the group of abdominal muscles, it’s important to discuss them since they facilitate movements during ab exercises. Hip flexors comprise of different muscles like:

  • Psoas major
  • Iliacus
  • Rectus femoris
  • Pectineus
  • Sartorius

The primary function of hip flexors is to help the hip joints move properly in full range. For example, they help you draw your leg to the torso as well as moving them side to side or backward.

To activate these muscles, strengthen and stretch them, here are the exercises you should do: Seated butterfly stretch, pigeon pose, weighted hip extension, bridge, runner’s lunges, pendulum, skater squats.

The abdominal area comprises of different groups of muscles that require different exercises to stay active, strong, and help you reach your body goal. If your workout plan doesn’t include exercises that activate these muscles, make sure you include them or ask your fitness trainer about the training program to target these muscle groups.

Please Note: Before following exercise routines or changing your fitness regime, please consult a certified fitness professional. Always talk with a medical practitioner before following dietary advice or taking supplements.

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