Core Muscles II: Rectus Abdominis

Jess Ennis six-pack

Our series of short articles on the core muscles began with the Transversus Abdominis. In this second article, we consider the Rectus Abdominis, the more well-known of the abdominal muscles and certainly the most visible (see image above of Jessica Ennis-Hill and the video below of Aidan Turner).  This article explains how the Rectus Abdominis works and why Pilates is such an effective of way of training it to function optimally.


The Rectus Abdominis consists of two parallel muscles running vertically on each side of the anterior wall of the human abdomen (see image below). They are separated by a mid-line band of white, fibrous connective tissue called the linea alba.  The rectus abdominis originates along the edge of the pubis bone and the pubic symphysis in the pelvis. Its insertions are the edges of the fifth, sixth and seventh ribs and the bottom part of the sternum (breast bone).

A sheath of connective tissue surrounds the rectus abdominis muscles and provides attachment points for the internal and external oblique or waist muscles (which we will look at in more detail in a future article in the core muscles series) that flank them on both sides.

Three bands of connective tissue run across the rectus abdominus, which separates it into eight distinct muscle “bellies”. In the abdomens of people with low body fat these “bellies” can be viewed externally and are commonly referred to as a “four, six, or eight pack,” depending on how many are visible; six is the most common.

Rectus Abdominis muscle


The Rectus Abdominis is an important postural muscle, responsible for flexing the lumbar spine. It helps to bring the rib cage up to where the pelvis is when the pelvis is fixed, e.g. as occurs when we do a Pilates ab curl, or brings the pelvis towards the rib cage (posterior pelvic tilt) when the rib cage is fixed, e.g. during a Pilates wheel or spine curl.

The Rectus Abdominis assists with breathing and plays an important role in respiration when forcefully exhaling. It also helps in protecting and maintaining the protect position of the internal organs, and in creating intra-abdominal pressure, such as when running or lifting heavy weights, or during forceful defecation or childbirth.


A weak Rectus Abdominus muscle causes us to slouch forward.  This results in the muscles of the lower back, the mid-back region towards the bottom of the rib cage, and the gluteal muscles over-working to compensate.

A more specific cause of Rectus Abdominis dysfunction is Diastasis Recti Abdominis. DRA is either a mid-line separation of more than 2.5 cm, or a bulging at the linea alba, occurring during exertion. This weakness results from the Rectus Abdominis being over-stretched during pregnancy.  This separation or bulging can cause an array of problems from poor posture to back and pelvic pain, hernias and pelvic floor dysfunctions.

Pilates to Train the Rectus Abdominis Muscles

At the heart of the Pilates Method is the breathing, the main objective of which is ensure the correct core muscles are engaged in the right way and at the right time in order to perform the exercises properly.  The inhale comes in through the nose and is a lateral breath into the sides of the rib-cage, NOT the belly.  This avoids the abdominal muscles doming or releasing.  The exhale is through the mouth and we suck the tummy right back towards the spine for the duration of the out-breath.  This actively engages the Rectus and Transversus Abdominis muscles.  The majority of the big movements in Pilates are on the exhale to ensure we have the correct support to execute them safely and well.

This sucking in of the tummy or navel-to-spine compression of the abdomen on the exhale is one of the reasons why Pilates is so effective at healing diastasis recti.  However, care needs to be taken in terms of the choice of Pilates exercises undertaken.  For this reason it is important to work with a Pilates teacher who has experience of dealing with this condition.

Pilates exercises to be avoided by those with DRA:

  • forward flexion of the upper torso, e.g. the ab curl
  • upper body rotation with reaching, e.g. the arm opening
  • extreme back extension/arching, e.g. the diamond press
  • upper body flexion with rotation, e.g. the scissors.

As a general exercise guide, any action that causes the stomach to bulge or protrude forward should not be practised by someone with DRA. It will not help to heal diastasis recti, in fact it often makes it worse. This should be the number one consideration when re-training the abdominal region. You should never feel pain or discomfort or any additional separation or bulging while exercising.  Any sports with rigorous sudden rotation of the trunk such as tennis, netball, hockey, etc should be avoided.

To close, here is Aidan Turner’s six-pack in action in an episode of the BBC drama serial, And Then There Were None.  The fact that he’s only wearing a towel is integral to the plot of course…the characters were looking for a missing weapon and wanted to be sure he wasn’t hiding a gun about his person…ahem!

Note: patience is required when watching the video…the scene starts after about 26 seconds…and then is repeated in case you missed it…cheesy grin…




Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s