In Pilates lingo the core of the body is often referred to as a ‘girdle of strength’ or the ‘powerhouse.’ Corset is another seemingly outdated word often used to describe the core. In fact, I use both girdle and corset at times with my students. We find these words useful to help us visualize how, when the powerhouse muscles are strong and properly contracted, they work like a corset to wrap about the spine and keep it upright, as well as to protect the low back during our daily activities.

Illustration by: Ingrid MacDonald

By using the word corset, I do not mean to perpetuate the myth that the core is made up of only a few muscles located in the abdomen. Many muscles support the spine from the shoulders to the hips: front, back and on the sides. Indeed, Stuart McGill, Ph.D., (, a leading expert on low back disorders, believes that all trunk muscles play some role in stabilization.

The front and side of the ‘corset’ are the three abdominal muscles that work with small spinal muscles to make up the ‘powerhouse’. The outer level, rectus abdominis, is a superficial muscle group that runs vertically the length of the belly. These two muscles, one on each side of the midline, do not act directly on the spine, but are responsible for flexing the trunk by pulling the ribs toward the pelvis.  The deeper transversus abdominis (the ‘seat belt’ muscles, loosely located across the bikini line), is a muscle group that when contracted stabilizes the lumbar spine by narrowing the abdominal wall. It is associated with the prevention of chronic lower back pain. If you place your hands around your waist and cough, you will feel the transversus tighten. The third abdominal group are the external and internal obliques, often referred to as the body’s natural corset because of the way these sheet-like muscles crisscross the body. The obliques are responsible for side-bending and twisting of the spine.

The zipper on the back of the corset is multifidus–small, deep bundles that pass from vertebra to vertebra. Stuart McGill has identified multifidus and part of quadratus lumborum as key back stabilizers. These, as well as the small muscles that run up and down the back of the spine, called the ‘paraspinals’, can cause back spasms if they are not working properly, when bigger, more superficial muscles take over.

The bottom of the corset is the pelvic floor. Retraining weak pelvic floor muscles is important for men and women (see October 28th’s blog). Also key to the core are the buttock muscles or ‘glutes’, which are often misunderstood and/or neglected (for more on these, see my blogs on September 30th, October 7th, October 14th).

The shoulder area, also called the shoulder girdle, can be seen as another sort of core. Next week we will focus on the back of the upper body and what happened when Martha, my student in remission from ovarian cancer, finally returned to class.

Colleen Craig

Colleen Craig

Colleen is the author of Pilates on the Ball, Abs on the Ball, and Strength Training on the Ball, and the producer of the Pilates on the Ball DVD.

Disclaimer: The information and services provided in the blogs, videos, website and classes are provided with the understanding that Colleen Craig is not engaged in rendering legal, medical counselling or other professional services or advice.

We highly recommend that you watch the video first before attempting an exercise. Check with your doctor or health care practitioner to be sure these exercises are suitable for you. Pay attention to modifications and stop if there is any discomfort.

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