• What is the "Core"?
• What is the importance of the Core?
• What are the best exercises to strengthen my Core?
• Testing for Core Weakness

What is the "Core"?

The core muscles are those that include the abdominal and low back musculature.  These include:

1) Deep lumbar stabilizers
2) Abdominal muscles
3) Muscles of the lower and and middle back
4) Hip muscles

What is the importance of the Core?
The core is important because it provides lumbopelvic stability as well as generating force for movement.   When the spine is stripped of muscle and left to rely only on passive support (bones and ligaments), it will collapse under just 20 lb of load.  Just submaximal levels of strength from the core musculature have been shown to be effective in adequate spine stabilization for average daily tasks.   Stability for the lumbopelvic region has also been shown to be crucial for whole-body stability while producing external forces (ie. throwing a ball). 

Stability

The muscles that are most important in providing stability for the lumbopelvic region are divided into primary and secondary groups:

Primary include: the transverse abdominis (indicated by the red arrows on the picture below) and multifidi.

Secondary include:  Internal oblique, medial fibers of the external oblique, quadratus lumborum, diaphram, pelvic floor muscles, iliocostalis and longissimus (lumbar portions).




Movement
The muscles important to the global movement of the lumbopelvic region include:  Rectus abdominis, lateral fibers of the external oblique, psas major, erector spinae and iliocostalis (thoracic region).


Testing for Core Weakness

Aside from being in a lab with high tech equipment, the next best way to test your core is via the Sahrmann Core Stability Test (see below) given by a training specialst.  It is a series of movements while maintaining lumbopelvic stability.  The tester will be using a pressure cuff under your back to determing if there is any rocking of the pelvis either forward or backward by watching for a pressure change.  You can try a rough test at home by placing your hands under your low back and feeling for any change in pressure while attempting the stated positions.  Take note, do you hold your breath while performing low back and abdominal exercises?  Do you attempt to flatten your back with abdominal exercises? 




The old thought was to perform a pelvic tilt (flatten your back) when performing exercises.  Think about it? When do we flatten our backs in standing?  The only population who should be focusing on this position are those who have spinal stenosis.  All of the rest of us should be focusing on maintaining a neutral or "natural" curve while performing our core exercises.  The neutral curve is the best way to co-contract the transverse abdominus, multifidi and internal obliques which are important muscles in spine stabilization.

Faries, M and Greenwood, M, Strength and Conditioning Journal Vol 29:2; 10-25
Gamble, P, Strength and Conditioning Journal, Vol 29:1;58-68

What are the best exercises to strengthen my Core?

The best abdominal and oblique exercises are (in order best to least recruitment):

Greatest recruitment
1)  Ab slide (the wheel on the floor) rolling both straight and curved  and the Torso Track.  

Intermediate recruitment
2)  Crunch (normal and oblique)
3)Bent knee sit up (back coming all the way up off of the floor)
4) SAM- super abdominal machine
5) Ab roller- crunch and oblique

Least recruitment
6) Ab twister (crunch and oblique)
7)  Ab rocker (crunch and oblique)
8)  Ab doer (crunch and oblique)
9)  Side Bridge
Escamilla, R et al. Journal of Orthopaedic and Sports Therapy, Feb 2006
Youdas, J et al.  The Journal of Strength and Conditioning Research, Nov 2008