Posted on 14 Dec 2010 17:30
By Paul Hemsworth
As most of you know, the world of core stabilization has yielded as much attention as Paris Hilton buying a new Chihuahua. The difference: core stabilization warrants most of the attention it gets. I say "most" because as with many catchy terms in the fitness industry, it can be abused with the content that goes into defining these terms. However, for the sake of this article I am going to review what I feel to be the more logical techniques that are involved in stabilizing that snake-like structure we call the spine.
What is Core Stabilization?
That's the million dollar question isn't it? If you asked 100 different sport scientists that question, you would get 100 different answers. To me, core stabilization is the ability to create uncompromising stiffness around the spine as to not allow any "energy leaks" during various static or dynamic tasks. You may agree or disagree with me on that definition, but the bottom line is this: Whether you are an elite athlete, construction worker, or receptionist, chances are you will probably go through some sort of back pain in your life. So throw the 6-pack talk out the window for now and start thinking about the spine. If we can ensure the athlete is a column of strength with no loose kinks in the chain, then we can ensure optimal power with minimal force loads on the spine.
First, let's look at the anatomy.
Internal & External Obliques (IO & EO): Involved in flexion, as their forces are redirected to the rectus abominis (RA) to enhance the flexor potential. They are involved in lateral bending, twisting, and stabilization of the lumbar spine (McGill, 1991a, 1991b, 1992; Juker, McGill, and Kropf, 1998). Lastly, they are involved in active expiration (Henke et al., 1988).
Transverse Abdominis: Rotates thorax from side to side, increases interthoracic pressure, and is involved in defecation, urination, childbirth. The TA is also an anticipatory muscle.
Rectus Abdominis (RA): The major flexor of the trunk. It forms a continuous hoop around the spine by transferring the forces from the obliques. The upper and lower RA are activated together and at similar rates during flexion (Lehman & McGill, 2001): So throw your "upper and lower abdominal exercises" out the window.
Rotatores: Have a high number of muscle spindles and thus serve more as a spinal positioner than a rotator of the spine (Nitz & Peck, 1986). They are most active when trying to resist the rotation of the spine that the obliques and latissimus are likely causing.
Longissimus & Iliocostalis: Have thoracic and lumbar components. These are the major back extensors.
Multifidus: Extension of the spine but only through the correcting of spinal joints that are enduring stress. Line of action actually contributes to shearing forces of superior vertebrae.
Quadratus Lumborum (QL): Bilateral support wall or stabilizer for the lumbar spine. The QL is active during flexion, extension, and lateral bending of the spine and maybe one of the few muscles that doesn't turn off during the flexion/relaxation phenomenon.
Psoas: Major hip flexor. May assist in some stabilization due to its orientation (Origin is T12-L5).
Core Stabilization Mechanisms
Abdominal Hollowing vs. Abdominal Bracing.
The abdominal hollowing technique was essentially developed from a group of Australian sport scientists (Richardson et al. 1999). This "Queensland group" determined that the transverse abdiminis (TA) and multifidus (MT) muscles in particular, were very important muscles for motor patterning. They found that following injury to the back, the TA and MT underwent motor disturbances that had profound effects on the motor patterning of the body. Because further injury would just add to these effects leading to a chronic state of poor patterning and pain, the Queensland group argued that only specific abdominal activation techniques could break this poor programming. Thus was born the abdominal hollowing technique: This technique involves the drawing in of the abdomen in an attempt to isolate the TA, while relaxing the surrounding musculature (RA, IO, EO).
The abdominal bracing technique was primarily developed - or more appropriately, coined - by Canadian biomechanist Stuart McGill. This technique involves the co-activation of all the muscles surrounding the spine (RA, IO, EO, TA, MT, Latissimus, QL, and the extensors) in an attempt to create 360 degrees of stability. While bracing, the individual doesn't draw in or push out, but rather "braces" or widens the trunk. If you think about what you would do if someone was to punch you in the stomach: You would set or brace for the punch and effectively create stability all the way around the spine. (For more on abdominal bracing, see Ultimate Back Fitness & Performance by Stuart McGill).
To Brace or Hollow: That is the question.
Much of the data that came out of the Queensland research was misinterpreted. Because they were working with injured individuals with malfunctioning motor patterns, the techniques they came up with were an attempt to disrupt the faulty patterns and educate the patients on abdominal control. Moreover, the TA anticipates trunk, upper and lower limb movement as well as protects the spine (Hodges, 1999). This anticipatory and protective function can be lost with acute or chronic low back pain. However, many clinicians took this information and regarded the techniques as a way of creating optimal core stability during various tasks. Thus, abdominal hollowing seems to be the preferred choice of many physiotherapists, strength coaches, chiropractors and kinesiologists for core stabilization.
Enter Stuart McGill! Not dismissing the importance of these muscles in their role as intra-abdominal pressure creators and stabilizers, McGill and others have since argued that this is simply not enough to endure tasks of even moderate intensity. Furthermore, during athletic events, unpredictable forces from all directions occur in almost any sport. Specifically, if a posterior perturbation - or unsuspected push from behind - occurs on the spine (lets say a defensive stiff-arm as you lean into a defender in basketball), abdominal hollowing produces the same resistance to the force that no activation does and results in an increase in spinal flexion (vs. 43% reduction of spinal flexion when bracing is used) (Vera-Garcia et al. 2007). As kettlebell lifter and educator Brett Jones says, if you took a cardboard box on its side and loaded it from the top, the box would crumble. Just ask Human Motion's Cliff Harvey what would have happened if he drew his stomach in while attempting world record lifts in weightlifting: He too would have crumbled. Furthermore, it is almost certain that if you try to contract only the TA, you will have activity in the IO and EO as well.
When the muscles surrounding the spine co-contract, they create a stiffness that is greater than the sum of the individual muscle stiffness (McGill, 2006). Thus, during the hollowing procedure, you are actually inhibiting the potential for optimal stiffness, ultimately limiting performance. You would think that in order to brace properly and ensure "superstiffness" that you would need to have an all out contraction during most activities. However, this doesn't seem to be the case as the first 25% of a maximal abdominal contraction creates sufficient stiffness for most activities (Brown & McGill, 2005). During 1RM lifts such as Cliff's world record attempts however, a maximum voluntary contraction (MVC) of all the surrounding musculature is necessary to withstand the massive force.
Let's hug it out: We are dealing with apples and oranges
There seems to be a lack of understanding as to the different techniques used between physios and strength coaches for core stabilization and activation. When a patient is seeing a physio, they are exactly that - a patient. Most of the time they are coming from an injury and have consequently obtained faulty patterns within their muscle sequencing. On the other hand, they could have had years of overuse injuries or poor gait biomechanics that has led to muscular imbalances. Thus, abdominal hollowing seems to be the technique of choice to help create that control that probably was never there even before the "injury" brought them to rehab. THIS IS PERFECTLY FINE. This is our group of apples. Our group of oranges are either these same patients coming from physio or our uninjured group of individuals who need to get stronger. Once these individuals are able to withstand heavier forces and are loaded up with weights, abdominal hollowing is no longer sufficient to lift this kind of weight, while sparing the spine. Thus, the abdominal brace must be taught. Herein lies the problem. We are constantly nagging each other (various health care practitioners) about the different techniques used. We need to remember that it is the needs of the client/patient that is our primary concern. WE NEED TO EDUCATE AND PREPARE THEM FOR THE NEXT STEP. Physios: Inform the patient that if they are an athlete or they are going to be lifting weights in the future, they will have to learn both techniques. Strength coaches: Actually integrate both techniques into your training. Isolate then integrate. It is a great way to allow the client to achieve initial success (abdominal hollowing) and then allow them to see the big picture of lifting heavier loads (abdominal bracing).
An integrated team approach can produce great success for the athlete, however, all members need to be on the same page even if their philosophies differ. Work with each other to produce the best results for the client/patient. Your athlete will ultimately be stronger, safer, and less confused in the process!
- Brown, & McGill . (2005). Muscle force-stiffness characteristics influence joint stability: A spine example. Clinical Biomechanics, 20(9), 917.
- Henke, Sharratt, Pegelow, & Dempsey, (1988). Regulation of end-expiratory lung volume during exercise. Journal of Applied Physiology, 64(1), 135.
- Hodges (1999). Is there a role for transversus abdominis in lumbo-pelvic stability? Manual Therapy, 4(2), 74.
- Juker, Mcgill, & Kropf, (1998). Quantitative intramuscular myoelectric activity of lumbar portions of psoas and the abdominal wall during a wide variety of tasks. Medicine and Science in Sports and Exercise, 30(2), 301.
- Lehman & McGill, (2001). Quantification of the differences in electromyographic activity magnitude between the upper and lower portions of the rectus abdominis muscle during selected trunk exercises. Physical Therapy, 81(5), 1096.
- McGill, (1991a). Electromyographic activity of the abdominal and low back musculature during the generation of isometric and dynamic axial trunk torque: Implications for lumbar mechanics. Journal of Orthopaedic Research, 9(1), 91.
- McGill, (1991b). Kinetic potential of the lumbar trunk musculature about three orthogonal orthopaedic axes in extreme postures. Spine, 16(7), 809.
- McGill, (1992). A myoelectrically based dynamic 3-D model to predict loads on lumbar spine tissues during lateral bending. Journal of Biomechanics, 25(4): 395.
- McGill, (2006). Ultimate back fitness and performance. Waterloo, ON: Backfitpro Inc.
- Nitz & Peck, (1986). Comparison of muscle spindle concentrations in large and small human epaxial muscles acting in parallel combinations. The American Surgeon, 52(5), 273.
- Richardson, Jull, Hodges, & Hides, (1999). Therapeutic exercise for spinal segmental stabilization in low back pain. Edinburgh, Scotland: Chruchill Livingstone.
- Vera-Garcia, Elvira, Brown, & McGill (2007). Effects of abdominal stabilization maneuvers on the control of spine motion and stability against sudden trunk perturbations. Journal of Electromyography and Kinesiology, 17(5), 556.
Paul is a strength and conditioning coach from Thunder Bay Ontario where he works at Trainer's Edge Gym. He is a certified strength and conditioning specialist with the NSCA as well as a certified exercise physiologist with CSEP. Check out Paul's strength training and conditioning blog.
This page created 14 Dec 2010 17:30
Last updated 17 Jul 2016 00:18