What is core stability? What is its relation to back pain? How should the core be trained?
We asked our audience these questions and more in arguably the largest survey of its kind.
The answers might surprise you.
Since we received responses from clinicians, coaches, fitness enthusiasts, and everyone in-between, the goal of this blog isn’t to single anybody out or prove anyone wrong. Instead, I want to highlight the vast variability in answers and attempt to provide a balanced perspective.
Looking for rehab or performance programs? Check out our store here!
Anatomically Speaking, What Is The Core?
As expected, there was no consensus.
Some people were unsure:
- “I have always considered it to be groups of muscles working together in the lower abdomen region on the front and sides, but being asked like this I realise I don’t actually know at all!”
- “…for a long time I had no idea because people who are more into exercise than me had me thinking it was some mystical force that you should know how to ‘activate’ on demand when they say so, without any explanation on what it is.”
Some respondents were skeptical. One person stated that it’s a “junk term” while another let me know that it’s a “stupid question.”
Others took a more measured approach:
- “It’s highly context dependent.”
- “A poorly defined concept… As such there’s a lack of definition, but the common narrative appears to equate the core with the abdominal muscles.”
With that being said, there were commonalities with muscles listed, such as the transversus abdominis (TA), internal and external obliques, rectus abdominis, pelvic floor, diaphragm, multifidi, and others.
Altogether, I noticed 3 general trends with the explanations:
- One focused on the low back and abdominal region
- The second encompassed the entire area between the pelvis and rib cage
- The third included muscles of the hips and shoulders
This is what makes defining the “core” so challenging.
For example, many individuals use planks to train their core. What happens if their shoulders fatigue first? Is it more of a shoulder exercise or a core exercise?
Since the serratus anterior attaches from the rib cage to the shoulder blade, is it considered a core muscle? How about the pecs and lats which attach to the arm?
Unsurprisingly, there’s no standardized definition found within the research either. Even a 2014 study interviewing 15 experts in the field couldn’t get them to agree upon what muscles make up the core.
So, what is the core?
There’s no straightforward answer, but I think there are 3 ways to approach the topic:
- Clearly define how you’re representing the word when bringing it up in discussion and ask for clarification when someone else does
- Understand and appreciate that it will always be a vague, nonspecific term. Or…
- Ditch the term completely
What Is The Role of The Core?
Although a consensus about what makes up the core was lacking, there was considerable agreement regarding its function.
Similarities included words like stability, support, balance, posture, and protection.
One person said “to create and resist movement” which was a common theme.
Someone else considered other functions, stating that it “helps with processes of breathing, digestion, and coughing too.”
Given that I think this will be the least debated question, I’ll concede to the fitness enthusiast who provided the most thorough explanation: “Depends on context. Generally speaking, some of it relates to performing or resisting movement (be it flexion, extension, rotation, lateral flexion…), and some to other functions, like respiration (well I guess it also involves movement), continence (same), protecting internal organs etc. Really hard to say if we don’t settle on a specific definition of the core. :)”
What Is Core Stability?
There were strong opinions for this question:
- “An overused term based on a poor study regarding low back pain and TA activation.”
- “A fictional cause of low back pain.”
- “A made up concept that when detected allows people to charge for core stabalising exercises.”
Recurring trends were related to rigidity, alignment, control, and the transfer of forces from the lower body to upper body.
Strength was also often used synonymously for stability, and the timing of muscle contractions seemed important.
- “Sufficient strength to avoid unnecessary (maybe injurious) movements of the core.”
- “Strong and appropriately activated musculature”
- “Symmetrical activation and utilization of the above listed muscles during movement or isometric holds”
Expectedly, maintaining a neutral spine was a common theme. However, some people expressed doubts.
- “The flawed idea that the lumbar spine is inherently unstable and that resisting any deviation from a ‘neutral’ spinal position (if there is such a thing) by active contraction of the abdominal muscles is essential for minimising lumbar injuries.”
- “One’s ability to keep the spine and abdomen in a neutral position during dynamic movements (even though we know that isn’t possible or necessary)”
I didn’t ask what people thought “neutral spine” meant because that could be a blog in itself. From my understanding, how “neutral spine” is described in research is significantly different from how most trainers and gym-goers would describe it.
When the phrase is used, I imagine many people would visualize a “flat back” during a deadlift or squat that perhaps represents the midpoint between maximum lumbar flexion and extension.
Despite what our eyes are telling us or what cueing we might employ, the low back flexes substantially during these movements even with relatively low loads. Therefore, “neutral spine” is another concept that’s recognized as relatively ambiguous.
Back to the question at hand – What is “core stability”?
Just like there is no agreement on the exact meaning of the “core,” the term “core stability” has been subject to different interpretations throughout the years, many of which have been influenced by the early work of Bergmark and Panjabi.
Their research helped give rise to the notion that the TA is the primary contributor to core stability, owing to its role in assisting with intervertebral stiffness. However, further research revealed that the TA does not work in isolation, and that bracing all the core muscles is more effective in resisting unwanted movements than attempting to isolate the TA through abdominal hollowing.
It’s easy to see how this then paved the way for the popularity of the McGill Big 3: the bird dog, side plank, and isometric curl-up.
However, there is no proven best method and I find it difficult to apply any model of core stability confidently when we’ve yet to establish universal definitions of “core” and “stability.”
And how is core stability viewed as it relates to different, context-dependent tasks, such as:
- Consciously bracing for a 1-rep max deadlift?
- Unconsciously increasing trunk stiffness and maintaining balance while carrying heavy bags of groceries up the stairs?
- The powerful swing of a baseball bat or a punch in boxing?
- Or the coordinated limb movements while remaining upright and stable during walking?
We can try to conceptualize core stability as the coordinated and often automatic effort to generate, resist, manage, and/or transfer forces in response to the demands of a particular task, amid constantly changing conditions, but that’s about as vague of a definition as any.
How Should Core Stability Be Measured?
Once again, some people were unsure while others didn’t even believe it possible.
Some individuals had a more nuanced viewpoint:
- “Measuring is goal specific.”
- “Not one answer is applicable. Different movement tasks require different core stability requirements. A strongman competitor requires different activation than a gymnast or a soccer player.”
Others took a more standardized approach:
- “Core stability should be measured by increasing strength on specific lifts that target multiple functions of the core musculature. Including muscular endurance with things like timed planks.”
- “Through dynamic and static movements which may be loaded or performed for time/reps”
Hopefully you can appreciate that it’s challenging to answer this question because we’re trying to create a pyramid of cards built on previously unclear definitions and loose interpretations. The further we dive into the questions, the more unstable the structure becomes. Pun intended.
Here’s a framework taken from Reeves et al in 2019:
“In general terms, stability is tested by applying a small perturbation to a system of interest and observing the new behavior. If the new behavior is approximately the same as the old, then the system is stable (eg, a ball in a valley returning to the undisturbed position). If the disturbed behavior differs significantly from the old behavior, then the system is unstable (eg, a ball on a hill rolling away following a perturbation).”
This is difficult to conceptualize and apply in a clinical setting or gym environment, which is why standardized testing is inconsistent and lacking. Therefore, as you might predict, experts have not been able to agree on assessment techniques for core stability.
There are standard measures available that use reference normative values, such as isometric endurance times for the trunk extensors, flexors, and lateral musculature.
However, as already mentioned, the function of the core will vary between walking, sprinting, throwing, jumping, squatting, pressing, etc., and there isn’t always a quantifiable transfer from isolated core training to other exercises, activities, or sports.
What Is The Relationship Between Core Stability and Back Pain?
Now that we’ve built this unstable pyramid of cards, we’re trying to see how well it holds up to a pile of bricks placed on top.
Let’s explore some of the answers to the question.
- “If hip flexors overwork in trying to compensate for the lack of stability caused by other weak muscles or if hip flexors are weak, that can cause back issues.”
- “Back pain is a very complex condition and might happen for many reasons, core stability in some cases, can aid to reduce back pain and provide people a sense of control and stability in their activities of daily living.”
- “One study a long time ago spoke nonsense and the rest is history”
- “Obsessing about core stability or tilt of the lower back is not useful. It will put you in a mindset where you obsess over controlling every aspect of your body, and that is impossible.”
As you can see, diverse answers emerged.
Some people pointed to the research:
- “As per Peter O’Sullivan’s research, there isn’t one!”
- “There is no relationship between core stability and back pain according to the literature I’m aware of. Take for example the article ‘The myth of core stability’ by Eyal Lederman from 2008. But I’m open to change my mind.”
Peter O’Sullivan, who is considered one of the foremost leaders in the field, used to be a strong proponent of core stability through specific muscle activation. After years of research and clinical practice, he now champions the idea that a large proportion of individuals with low back pain would actually benefit from relaxing the “core” muscles.
Eyal Lederman single-handedly wrote two of the most well-known papers pushing back against the belief that core stability is related to low back pain in papers titled “The myth of core stability” and “The fall of the postural-structural-biomechanical model in manual and physical therapies: exemplified by lower back pain.”
Some individuals appeared to not dismiss the idea completely:
- “Many people with back pain do have a weak core, but a weak core is not causal for low back pain.”
- “Motor control and muscle strength probably are a factor for back pain, but there are a ton of other factors probably equally or more important.”
- “There is no valid relation. The clinical experience though shows that there is a relation. Better core stability provides less back pain.”
If research tends to show no significant association between low back pain and core stability, why do some clinicians and patients notice improvements in symptoms after prescribing or performing core exercises?
I don’t think anyone would argue that targeted “core” exercises can help someone’s low back pain improve, even Peter O’Sullivan and Eyal Lederman, but I think it’s important to always consider alternative explanations.
Can someone’s low back pain be associated with a change in endurance or strength? Maybe, but it’s usually a chicken-or-egg scenario. Research from over a decade ago has demonstrated that people can improve from spine stabilization exercises despite no related changes in abdominal function.
If someone’s low back pain improves immediately after doing a side plank or bird dog, is it because they had an immediate change in strength? Probably not, but we know exercise can be analgesic, especially if that person holds strong beliefs or expectations.
Exercise is also a great way to improve confidence and help prepare you for activities meaningful to you.
Regardless of how we define “core” exercises, I think they can be a great component of any rehab or performance program except when people are led to believe 1 of 3 things:
- That they’re fragile and therefore need to brace their core all day long
- That they must perform core exercises daily to improve symptoms and prevent injury
- That certain exercises are superior for pain
Intentionally bracing your core should be reserved for specific tasks, such as deadlifting or heavy squatting, not walking around the block or getting up from a chair. Most movements should be thoughtless and fearless.
You wouldn’t clench your fists all day, so why would you do the same with your core? This is why Peter O’Sullivan suggests that people frequently benefit from letting their cores relax.
And since I see it most often recommended for the curl-up, side plank, and bird dog, I just want to reiterate that there’s absolutely nothing to suggest that these exercises need to be done daily or that they are superior for treating pain or preventing injury.
How Should The Core Be Trained?
Thankfully, there was a lot of agreement here with the “how”:
- “It depends on the patient and his/her goals. In general: following the same guidelines we use for training other parts of the body. I.e. progressive overload, recovery etc.”
- “Just like any other muscle. Adequate resistance, reps and intensity based on scheme. We need raw strength, power, endurance, and motor control here. Traditionally I think we see a lot of motor control and endurance.”
- “Depends on the task you are training for, but essentially similar to any other muscle group where there is some degree of resistance, at a high enough intensity, and a repeated exposure to the activity to elicit the adaptations we are hoping for.”
And here’s a longer answer with a similar theme that discusses more of the “what”:
- “Depends on the definition of the core. And even then there isn’t just one “correct” way to train the core. I believe there’s a value to train core “directly”, both through isometric and isotonic exercises (this means all sorts of things: planks, medicine ball rotational throws, Jefferson curls, back extensions, ab wheel rollouts, bird dogs, there are so many options). The core will also be trained through “big lifts”, like squats, pull-ups, deadlifts etc… And what about endurance training?… And obviously some unilateral stuff, like unilateral OHP… So perhaps moving in various planes of motion, using a variety of loads, and a variety of modalities. Movement is good.”
Someone even brought up swimming and rollerblading.
I agree with all of these responses.
Exercises such as deadlifts, barbell hip thrusts, pull-ups, and push-ups are effective in activating multiple muscles, including the abdominals, erector spinae, multifidus, and TA. Rather than focusing solely on individual muscles, the body works to accomplish specific tasks, and many compound lifts require the trunk to establish a stable and rigid base by increasing intra-abdominal pressure and co-activating the surrounding musculature.
Behm et al in 2010 even suggest that “For fitness and health conscious individuals and athletes at all levels (i.e., recreational to elite), ground-based free weight lifts (e.g., back squats, deadlifts, Olympic lifts, and lifts that involve trunk rotation) should form the foundation of exercises to train the core musculature.” Plus, these movements allow for easily implementing progressive overload and monitoring long-term progress.
If desired, certain exercises can be modified to place a greater emphasis on the abdominal or low back musculature. For example, the Z Press is a popular alternative to the traditional standing overhead press as its intended purpose is to eliminate leg drive and increase the demand on the midsection.
Incorrectly, the resulting narrative is that performing compound lifts on unstable surfaces must be even better.
This is not the case. In a separate 2010 paper by Behm et al, the authors state that “…unstable devices should not be utilized when hypertrophy, absolute strength, or power is the primary training goal, as force generation, power output and movement velocity are impaired and may be insufficient to stimulate the desired adaptations.”
Unilateral, multi-joint exercises that create asymmetrical loads can also be implemented, like a half kneeling overhead press or single arm dumbbell press. There are inevitably trade-offs to consider though, including the potential reduction in the maximum load that can be used. It’s impossible to provide a framework for what’s “optimal,” so it’s likely easier to perform a combination of bilateral and unilateral exercises.
Similar to how people do biceps and triceps exercises in addition to their compound pushing and pulling movements, isolated “core” training (if we want to call it that) can be done with the goal of maximizing the strength, hypertrophy, range of motion, control, etc. of the “core” musculature. I’ll touch on this more in the next section.
The last thing to consider is task-specific training. Although it’s plausible to assume that core training has a notable impact on athletic performance, there is not enough evidence to confirm this. Conventional resistance training can be employed to improve physical fitness and athletic performance by promoting desirable adaptations, such as enhanced strength and power. However, Willardson in 2004 recommends that “The optimal method to promote increases in balance, proprioception, and core stability for any given sports skill is to practice the skill itself on the same surface on which the skill is performed during competition.”
Practical Application of Training The Core
How do you practically apply this information to train the core?
Firstly, it’s necessary to point out that many gym-goers and athletes get by with only performing compound lifts and task-specific activities or movements, which is completely fine. However, I’m going to focus on how isolated exercises might fit into a rehab or training routine. And I’m using the term “isolated” loosely here as aspects of the lower and upper body will be contributing to these movements. Plus, no muscles act in isolation.
Core training is often based on the primary movements of the spine: flexion, extension, rotation, and side bending.
It is then usually further categorized into static and dynamic exercises, also referred to as isometric and isotonic exercises.
I’ll throw up 2 charts on screen that demonstrate these categorizations depending on the main motion being produced or resisted.
If you’re confused by the isometric chart, I’ll try to explain.
A forearm plank is classified as an “anti-extension” based exercise because if you weren’t trying to resist gravity, your low back would sink toward the floor resulting in lumbar extension.
Therefore, despite the trunk flexors being activated during the exercise, it is considered an anti-extension maneuver. You are working your flexors to resist lumbar extension.
Obviously this framework isn’t perfect, especially for movements that involve multiple planes of motion, but the simplicity can be useful for programming and discussions with others.
If you’re designing a rehab program, core exercises can be performed for a variety of purposes, such as reducing fear, increasing confidence, improving symptoms, and enhancing function. For example, if you’ve become fearful of bending your spine, but there are no contraindications for why you shouldn’t be able to bend your spine, you might gradually incorporate flexion-based exercises into your regular routine to increase your overall confidence with the movement.
On the other hand, if you notice you have pain when you sit for more than 2 hours, it’s totally acceptable to throw in a few sets of isometric bird-dogs if they make you feel better. They’re one way to get you moving and exploring a different position of your spine. Going for a 10 minute walk would be another option in this scenario.
If you’re implementing core exercises with the intention of rounding out a comprehensive training program, there are tons of strategies you can try. Here’s a few examples:
- You could use certain exercises to target specific goals, such as cable crunches at the end of your workouts twice per week to enhance hypertrophy of your rectus abdominis.
- You could also use specific exercises to target weak points in your lifts, such as reverse hyperextensions to improve low back strength and endurance for deadlifts or other similar movements.
- A possible contrasting method is to combine a hollow body hold, which emphasizes the trunk flexor muscles, with the deadlift, an exercise that primarily targets the trunk extensors. It’s worth noting that these two exercises do not have to be performed as a superset.
- If your workout mainly focuses on sagittal plane lifts or machine-based movements that don’t challenge the trunk muscles much, such as seated leg extensions, adding rotational exercises like med ball throws can be used to introduce more variability into your routine.
There are so many options, but they don’t have to be overly complicated. And remember, training the core (or whatever we want to call it) should follow similar principles as other regions of the body with respect to manipulating and progressing variables such as sets, reps, hold times, weight, speed, etc.
This blog has gotten too long, so I’ll end my rambling here.
Looking for rehab or performance programs? Check out our store here!
Did you know you DON’T need to “fix” anterior pelvic tilt? Learn more!
Thanks for reading. Check out the video and please leave any questions or comments below.
