Weak Core

The concept of “core” strength and it’s role in back pain and rehabilitative exercise programs emerged from research carried out in the early 1990s. The popularity of core stability training soared as this research made its way into the practice patterns of clinicians and trainers throughout the 1990s and into the 2000s. The message that has long since been propagated is two fold:

  1. that a weak core predisposes one to lower back injury and pain
  2. that the resolution of back pain is contingent upon strengthening of the core

We now know that there is more to back pain than what is implied by these two propositions… things just aren’t that black and white. The utility of the core stability concept is also hampered by inconsistencies in the operational definitions of the “core” across and within health and fitness professions. Some will define “the core” as it was initially described in the research by Paul Hodges. That being the canister formed by the diaphragm, transversus abdominus and the pelvic floor. Others will describe “the core” as including all the trunk muscles, hip and buttocks muscles.

We can’t really say that a “weak core” causes back problems, or that we need to “work on the core” to fix back problems, because we can’t even agree on what we mean when we talk about “the core”. And even if we could agree on a definition, back pain is a really complex phenomenon. Reaching agreement on what constitutes a “weak” versus a “strong” core, and then linking that to one’s back pain in a cause / effect manner would be very challenging.

So where to from here? 

The one thing we can be pretty sure about is that exercise helps people with back pain. So I think it makes sense for back pain sufferers to engage in an exercise program of some sort. The specific type of exercise one chooses to engage in really boils down to personal preference. The research is generally equivocal when it comes to asking the question “which type of exercise is the best for back pain?”

I guess we could say that “core exercises” are a type of exercise for back pain. Since there are varied definitions of what constitutes “the core”, we see different types of “core training emerging in the exercise rehabilitation scene. The different types of core training sit on a spectrum ranging from very specific, targeted transversus abdmominus training, to more global trunk, hips and buttocks training. In this post we’ll take a look at the two types of core training that sit at each end of this spectrum.

Specific training of the transversus abdominus

The exercise programs that have been developed to train the transversus abdominus (and other groups such as lumbar multifidus, horizontal fibres of internal oblique) in isolation, perhaps with the assistance of real time ultrasound, provide patients with a novel perspective for understanding the role of motor output in their back pain. I think there is value in the process of learning how to be more aware of what it feels like to contract some groups of muscles near the spine, but not others. People with lower back pain are often very sensitive and reactive to movement or loading of the spine. I suspect that the gentle, small amplitude, low effort movements that characterise specific transversus abdominus training sharpen one’s awareness of movement in the lower back and helps restore normal sensitivity to movement in the lower back.

I tend to prescribe this type of exercise to back pain patients who are still in an acute or perhaps just into subacute phase following a recent episode of low back pain. I think it’s important to reiterate though, that I don’t think the benefit lies within “strengthening” of any particular muscle group. Rather, I argue that when this type of careful, conscious movement helps with symptoms, it has helped because the movement brought about a reduction in protective tensioning of the trunk musculature. Very often, my focus for the acutely painful lower back patient, is gentle, very low load active movement of the spinal segments in multiple planes, without any particular attention to which muscle is “on” or which is “off”.

As a patient becomes less symptomatic with a course of treatment, or with the natural course of recovery following injury, I like to progress the extent to which we load the spine while the patient attempts to control movement in the lower back or limbs. Again, early in the process, this more about normalizing the sensitivity of the nerve pathways in and around the lower back than it is with any particular strength gains. It is quite normal for a patient to reports “feeling stronger” from these exercises, but I attribute this to feeling associated with having shifted out of a “protective” holding pattern.

Higher load and Higher Intensity Exercises

Typically, when a trainer defines “the core” as including all the trunk, hip and buttocks muscles, their “core” workouts tend to be more intense and involve greater loading than the more specific transversus abdominus protocols. Some examples of exercise that spring to mind include, “planks” or “bridges”. There really aren’t many limitations on a “core exercise” when the definition of the core is so broadly framed… under such a broad definition, one could argue that running is a core exercise.

I think these types of higher load, higher intensity exercises are useful for patients who have moved beyond the subacute phase of an episode of back pain. Once a patient is at this point in their rehabilitation, I think we are able to load the system enough to see some measurable changes in “strength” and functional measures that relate specifically to the patients goals, occupation or recreational activities. Putting in place a plan to systematically increase the intensity, frequency or duration of load on a patient’s lower back is a good idea in my books. The key is to make sure that the load parameters are appropriate for the specific patient.

The Core of the problem

Whether or not all these exercises should be described as “core” exercises is really a matter of semantics. I tend to suspect that those who argue very strongly for a very narrow, or a very broad definition of what constitutes “the core”, usually have a vested interest in having it defined in a particular way. I tend to take a view that the terms core stability, core strength, weak core, etc etc have been so loosely defined and reinvented so broadly and so often, for so long that none of them mean anything in particular. For example, one can only know what the term “core stability” means to a particular physio or trainer by asking a bunch of questions to clarify what it means to them.

So I tend to steer away from describing any exercises I prescribe as being specifically directed at “the core”. It doesn’t make sense to propagate confusion and misunderstanding among my patients. It makes far more sense to me to frame any prescribed exercises in terms of the patient’s activity limitations, and the mechanism by which the prescribed exercise is thought to assist that limitation.

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