Core stability is a term used to describe the ability to control the position and movement of the central portion of the body.  When the core, or the trunk is stable, the body and extremities can work smoothly and effectively.  It requires maintaining a “center of power” by selectively using certain muscles, and learning to keep those muscles working while the rest of the body is moving.  Using these “core muscles” to maintain positions and postures also protects the spine from excessive or abnormal forces, and centralizes one’s power, allowing for smoother, more efficient, and coordinated activity.

What is “the core”?

When people think about the core, or do core exercises, they are usually doing exercises emphasizing the abdominal muscles.  The “six pack” muscles often get the most attention.  Core strength actually is rooted in the deepest abdominal muscle (the transverse abdominals), the muscles of the pelvic floor, and the deepest back extensors (the multifidus).  These three muscles grouped together are sometimes referred to as the “inner core”, “inner unit”, or “pelvic brace”.

 

If you think about the trunk as a barrel, these muscle groups would make up the top, bottom, sides, and back of the barrel.  In a healthy back these muscles would work together to stabilize the spine before we move our extremities.  Research has shown that when people experience low back pain, these “core” muscles often shut down and stop stabilizing the small movements of the spine.  This can cause pain and weakness to continue. 

 

Parts of the core:

1. The Transverse Abdominals:

The transverse abdominals are the largest, deepest abdominal muscles.  It makes up the sides, and parts of the front and back of your trunk.  This muscle forms a corset around the body and acts as your body’s natural back belt. It attaches to your ribs, pelvis, and dense soft tissue on the back.

 

Finding the Transverse Abdominals:  The transverse abdominals are the muscles that you contract if you are trying to put on a pair of tight jeans.  They pull your stomach and sides in toward your spine and upward toward your head.  Put your hands on your hips and draw your belly button toward your spine.  You should feel muscles tense under your fingers, these are the transverse abdominals.

2. The Pelvic Floor:

The pelvic floor is a group of muscles that are shaped like a hammock and form the floor of the pelvis.  The hammock extends from the tailbone to the pubic bone.  By contracting the pelvic floor, the three joints of your pelvis (two sacroiliac joints, one pubic joint) are stabilized.

 

Finding the Pelvic Floor:  The easiest way to find the pelvic floor is to contract the muscles that stop the flow of urine, or the muscles that keep you from passing gas.  Sit on a chair and try to lift the muscles of your pelvic floor away from the chair.  People commonly contract the muscles of the buttocks and upper leg by accident while learning to isolate the pelvic floor.  Do not let this happen, and remember to keep breathing. Make sure you are drawing the muscles up and in, don’t try to bear down or push while contracting.

 

3. The Multifidus:

The multifidus is a deep muscle that runs along each side of our spines.  The multifidus is the main muscle that stabilizes our spine at each spinal level against excess forward shear.

 

Finding the Multifidus:  Stand up with your feet shoulder width apart.  Put your hands on your back with your fingertips on either side of the spine.  Lean forward moving your weight from your heels to your toes.  As you lean forward, you should feel a trace of this muscle push into your fingertips.

 

Putting it all together…. The Pelvic Brace:

The pelvic brace refers to co-contraction of the pelvic floor muscles, the transverse abdominal muscles, and the multifidus. 

 

To perform the pelvic brace:

Lay down with your knees bent and take a belly (diaphragm) breath. Breathe out and lift your pelvic floor muscles as you tighten your transverse abdominals and your multifidus.  Avoid contraction of your buttocks, thighs, or “six-pack” abdominal muscles. Avoid tilting your pelvis and keep breathing. 

 

Once you can perform the pelvic brace easily, do this during other activities during your day including sitting at traffic lights, talking on the phone, lying down, waiting in line etc.

The co-contraction of these muscles is vital to regaining and maintaining spinal stabilization during activity.  The more complex the activity, the more demand on the core muscles.  For example:  when sitting in a chair your core muscles are working at a low level to maintain an upright posture.  When walking, the core muscles work harder to stabilize the spine as the arms and legs are moving to propel your body forward.  When running or playing sports, your core muscles must work even harder to stabilize your spine against even higher forces.  No matter what level of activity you are doing, your core muscles are vital to providing a stable base to move from.  If you do not have this strength and support with movement, injury is likely to occur. 

 

Now that you can do the pelvic brace, try to use it when doing your daily activities.  This is the beginning and most important part of a core exercise program.  Once you have mastered the pelvic brace, try adding harder exercises and movements.  When doing these exercises, ALWAYS start by contracting and maintaining your inner core contraction.  Good Luck!

 

 

References:

G.Jull, C.Richardson. Motor control problems in patients with spinal pain: A new direction for therapeutic exercise. Journal of Manipulative and Physiological Therapeutics, Volume 23, Issue 2, Pages 115-117.

 

Boyling, J., Jull. J. (2005)  Grieve's Modern Manual Therapy. The Vertebral Column, third edition. New York: Churchill Livingstone. 2005.

 

Lee, D. (1999) The Pelvic Girdle, Second Edition. New York: Churchill Livingstone.

 

Woods, N. SLIERS “Inner Core” patient education handout. Boise, Idaho. 2004.