Our bodies are incredible. We ask them to walk, run, hang, swing, twist, and flip. All of these movements are brought about by
coordinated patterns of muscles firing to move joints into the appropriate positions at the appropriate time. Simple, right?
Touch your right shoulder with your right hand. If you are moving correctly, your shoulder should stay still as your hand comes up to your shoulder. In this case, you are stabilizing the proximal (meaning close to where the extremity meets the body) end of the biceps as the distal (meaning further from the body) end moves the forearm towards the shoulder. This illustrates the concept of ‘proximal stability’. This concept is played out throughout the body. As you trace each muscle back towards the center of the body you come back to an idea that we are all familiar with: core strength and stability.
If you have a “strong core” it means your core muscles are stronger than the other muscles that anchor to the boney structures of the spine, pelvis, and ribcage and are able to stabilize against their pull.
For the purposes of this post we will stick with detailing the abdominal muscles. However, the ‘core’ is made up of more than just the abs, and those other muscles are just as important! The primary muscles of the core consist of the abdominals, the pelvic floor, the lumbar spinal extensors/ stabilizers, and the diaphragm (more on these very important muscles in future posts).
There are four abdominal muscles. These muscles contribute to core stability in addition to side bending, rotation
and flexion (rounding) of the lumbar spine, as with a sit up.
The deepest muscle is the transversus abdominis (TA). It is a flat muscle that wraps around the body, originating from the lower 6 ribs, fascia (thick connective tissue) attached to the lumbar vertebrae, and the pelvis. Its muscle fibers run perpendicular to the spine. This means that when it contracts, the TA flattens the abdominals and compresses the organs adding stability and acting as your own personal weight belt.
On top of the TA is the internal oblique. Like the TA, the internal oblique attaches at the pelvis, the lumbar fascia, and the ribs. The fibers of the internal oblique run towards the center of the body on a diagonal upwards towards the head. This muscle aids with breathing and compression when both sides of the muscles fire together. When one side of the muscle fires, the internal oblique side bends and rotates the trunk.
Perpendicular to the internal oblique is the external oblique. This muscle runs from the rib cage diagonally down to the pelvis. Like the internal oblique this muscle aids in breathing and compression of the abdominal cavity in addition to some flexion and rotation.
The fourth muscle is probably the one that is most well-known. It is the ‘six-pack’ muscle, the rectus abdominis. The rectus runs down the length of the abdomen, from the center of the ribs down to the front of the pelvis. This muscle’s job is to curl the lower back into flexion. For us this can be pulling your knees to your chest to do a back tuck, or sitting up from a knee hang.
*Images generously provided by Thieme Publishing.
Below is a tutorial on how to engage your abdominals and three of my favorite exercises that emphasize core strength and stability for non-injured circus practitioners (if you are injured consult your local medical specialist).
Emily Scherb is a Doctor of Physical Therapy and owner of Pure Motion Physical Therapy in Seattle, WA. She has also been involved with circus for over 20 years as a student, performer, instructor, and now physical therapist. Emily works to educate circus performers on how their bodies work and how to use them most effectively to achieve their goals.