Greg Dea and Rod Harris: Core Stability and Core Strength Are Not the Same
Greg Dea and Rod Harris: Core Stability and Core Strength Are Not the Same
The current paradigm in training is to add strength to everything because when things are strong, they should work well. It’s commonly thought that tissues and cells should be strong as opposed to the idea of having an ability to express strength or capacity, which is totally different.
However, core stability and core strength is not the same thing. Being strong doesn’t imply the ability or the behavior to be stable.
And stable is not even all that desirable if you think of stable as just “being still.” We could call that static stability, but there’s another element of dynamic stability—the ability to control motion in one plane while resisting it in others. That occurs with every movement, and the variations in the context of life suggest that we’re going to have a different behavior of how stable or how controlled we are through the trunk…and it’s rarely going to be a demand for high strength.
Sequencing and timing are two concepts that relate to motor control. In the literature, there’s about 10 times as much motor control research as there is strength and conditioning research. It’s challenging to bring that down to a simple paradigm, and yet it’s been done beautifully by Richard Schmidt and Tim Lee in their book, Motor Control and Learning.
The authors talk about three elements consistent with a central pattern generator, or in their words, “a general movement pattern.” When we refer to a GMP, we mean generalized movement pattern or general movement pattern, which is synonymous with a centralized pattern generator. These are fundamental movement software programs written in the central nervous system that underpin a wide variety of movements.
Muscles don’t remember movement. They have a genetic ability to respond to the movement patterns and the stimuli generated from the central nervous system. If you’ve previously been exposed to the stimuli, you will respond quicker when re-exposed to it. That’s the muscle having a genetic adaptation. There’s an epigenetic adaptation to respond to stimulus, but muscle don’t “remember” movement. That comes from the central nervous system.
In fact, there’s research proving that muscles don’t actually have memory. We shouldn’t be talking about muscle memory, but instead about motor memory before considering strength and adding capacity.
There are three things that make up a general movement pattern. The first element is that there’s relatively invariable sequencing, which means a particular muscle will activate first, followed by another muscle, followed by another. That’s the sequence of each pattern of movement; it doesn’t change even with subtle variations of movement.
With a generalized motor pattern, you could add more speed to it or add more amplitude, but it doesn’t actually change the sequencing of the muscles, and it doesn’t change the timing—how long the muscle stays under contraction.
The second component of the GMP or central pattern generator (CPG) is that there’s relatively invariable timing. A muscle will stay active for a particular time, followed by the second muscle in the sequence and it will stay active for a particular period of time, and it may be two-thirds shorter or four-tenths faster or longer.
And then the third element is that there’s a relatively invariable distribution of forces between each of these muscles. This means if that muscle was to activate with an amplitude of one, the one that’s following it may have an amplitude that’s 40% greater. It’ll be a stronger contraction relative to that one, and the one following it could be 70% of the first.
When you run that movement pattern against force—an external force, for example—the whole 1.4, 0.7 relationship amplitudes up. The ratios stay the same; that relative force distribution is the same. To summarize the three components, we have sequencing, timing and relative force distribution.
Clinically, that’s impossible to detect, and yet our field has—many times—attempted to do so with an alarming lack of success. It’s not reliable, has no validity and isn’t transferrable. In other words, even if we’re good enough to detect this as clinicians, does that actually help the person motor learn? We’re going to argue that it doesn’t. When our patients leave the controlled environment of the clinic, can they actually replicate the learnings? The motor learning research clearly says no.
Let’s look at an example. A person is lying prone, and because you’ve read some research that says that the lumbar multifidus is a segmental stabilizer and it should be a primary activator before limb movement, you palpate the lumbar multifidus or erector spinae. You palpate the glute max and the hamstring. And you ask the person to perform hip extension. Theoretically, you should get a segmental proximal stabilization first, followed by distal mobilization.
This would include lumbar multifidus activating first, because the glute max has a little SIJ stabilization, which is proximal. And then the hamstring should activate to hip extension with glute max. If you palpate that, you’d have some pretty wicked skills to be able to detect what goes first, how long after, and which fires to the right amount.
Let’s just say you can do it. Is that useful for the person? What are you actually teaching the patient to do? You’re teaching the person to isolate how to extend the hip when in a prone position, which changes instantly when moving into a different position.
Typically, our profession has said, “Let’s jump to trying to get that person to activate the multifidus better.”
And so again, you’ve missed the problem. If you said that the timing, sequence and force distribution is off, is that because there’s an underlying pain changing motor control?
Or does the person have a mobility restriction making it impossible to get good hip extension? In this case, the compensation might be lumbar extension, which causes a massive erector spinae component. In that scenario, you’ve missed pain; you’ve missed the mobility restriction and its inputs problem. And you’re measuring outputs using a faulty technique.
Motor control is complex. It’s been simplified down to three things, and even those are too complex to be able to clinically assess.
So…we changed that a few years back, instead saying, do you know how to encapsulate what timing, sequencing and force distribution looks like? To do that, you should know what a CPG looks like within a bandwidth of variation. But you should know that if that movement pattern goes outside that variation, we consider that to be beyond the realm of a normal CPG.
That takes some training. Luckily, you don’t have to reinvent that.
Now, that still requires you to make a call, and here’s what turns out: CPG, or GMP that has appropriately minimum levels of competency of sequencing, timing and force distribution. How does that look in two words?
Clean and easy.
It’s clean because the sequence flows; it’s easy because there’s no excessive effort or loss of control that requires more effort. Clean and easy.
Once that movement pattern falls outside the bandwidth of acceptable or normal CPG, it changes from clean and easy to the opposite. The opposite of clean is dirty and difficult. Movement can be viewed as being clean and easy or dirty and difficult, and we step in to correct when it becomes dirty and difficult.
Let’s just give you an example of two, like two people doing a squat. If someone pings a really good squat, people will still argue about how to make that look better. In other words, they ignore the performance bandwidth because they’re trying to give someone what they want to do, rather than what that person needs.
And the other thing that happens is if you get someone who has a really poor squat, everyone can pick the poor movement.
When we’re talking clean and easy and dirty and difficult, it’s with training and some parameters. We find everyone can work out very quickly and consistently what’s clean and easy and what’s dirty and difficult.
Now let’s circle back to core strength. Many people think it’s essential that we have a strong core, and what we’re saying is…no. There’s only one circumstance where you need strong muscles or tissue behaving in a way that resists very high force, which is called a high threshold strategy.
And there’s only one category, and that is when you need to develop immeasurable energy to resist an immovable force, for example if you’re a front rower in a rugby match. You have a 120-kilogram person running fast at you. The force is immeasurable and you need to be an immovable object. You need to generate extraordinary stiffness and strength throughout the entire body.
That’s a high threshold strategy. That’s where you need to bring everything up to maximum outputs.
For control of movement against load, not just control of movement without load, you don’t need that high threshold strategy. You need reflexive control as perturbations disturb you—a reflex control. Typically, you wouldn’t do that consciously. That’s a reflex-driven activity.
Now, reflexes are done beneath the level of consciousness. You can’t initiate a reflex with conscious thought.
In other words, if I have to think about contracting my core before I pick up a pen off the ground, it’s too late—something’s already gone wrong. And the instant you get distracted, you can’t do that. Training conscious core control is not required. It’s useful in block training to begin with, but then we need to go to random and unconscious control.
Core control is the underpinning of athletic endeavors and performance and behaviors—not core strength, unless you need to be an immovable object against an immeasurable force.
Core control is reflex driven, not conscious driven.
Input from the mechanoreceptors supports reflexes, modulated by a central nervous system that tracks up and down the spinal cord. Effectively, you need a very healthy input from the periphery into the central nervous system so the CNS can detect it. Then it sufficiently processes it.
It has to detect movement exquisitely quickly and needs to stabilize against that or allow it to occur in a controlled fashion. That happens so quickly that you can’t generate a thought in response. That reflex is not trained by doing conscious exercise; it’s trained by removing any barriers to that input loop happening.
Leave the best computer alone in the universe to do what it does fantastically, which is to sufficiently process this in a way that we could never coach. Get out of its way by taking away pain, toxins, ill health, mobility restrictions and then create a circumstance through exercise that challenges the person’s ability to use that reflex.
We can’t see that proprioceptive input going on. However, we can see sufficient processing of inputs through the movement pattern and we see it through the output. With some guidance and parameters, it’s very quick to determine what looks good within a performance bandwidth and what looks bad.
Clean and easy, dirty and difficult.
We use that output to measure what’s happening because we can’t measure the inputs. We can’t even see how the process is occurring—we can just see the result of the processing. It’s very complex, but we can simplify it down to “clean and easy,” “dirty and difficult.”
We look at the outputs to tell us whether the central nervous system is sufficiently processing inputs, and if it’s not, we have the systematic processes to say, “We need to change inputs.”
That’s the essence of performance physical therapy.
And then the greatest essence of rehabilitation and coaching is to cue this processing so it gets organized in a way to regain that output. If you don’t have the skills to do, that’s okay. But don’t try to add capacity to a motor control problem, because at best it’s going to be fairly useless because it’s still a performance roadblock. At worst it can actually create potential injuries and pain.
Most of the time, the idea of core strength is wrong. Core motor control is the correct terminology.
This would lead you into the most appropriate pathway, which is get timing and sequencing and relative force production right before you add strength to the tissues. Get all the building blocks right first. Capacity comes last.
There are three benefits of getting those right:
- Enhanced performance
- Improved efficiency
- And, potentially, improved safety.
And those are the only three reasons that you should step if you find someone is outside the parameters. Once you’ve made a decision that a person is outside the realms of normal variation, and has slipped into a dirty and difficult movement pattern, your choice to change that is for three reasons.
If you don’t change it, the likelihood of success is lower…much lower.
If you don’t change it, that person has to work harder to replicate this movement over and over again. That’s called efficiency.
And the third is that it increases the use of resources through efficiency, which may bring on a fatigue onset earlier.
And could be a risk factor for injury.
These people tend to be the least robust athletes who are drawing more resources. If you just get them fitter, it teaches them to compensate, not necessarily to be better. If they come up against someone who doesn’t need to compensate but has just as much capacity, it’s going to be a problem—the non-compensator will run rings around them.
And there’s one more thing we need to add that’s important, because the motor control research is incredibly clear on this. If we give somebody a poor movement pattern, it’s stored in the nervous system; you can never get rid of it.
You can either be part of the problem or you can be part of the solution. You can help people establish good movement patterns, or you can be part of the problem and either allow someone to maintain a poor movement problem or indeed, if you don’t know how to do this properly, you can actually create a worse movement pattern.
And that’s stored forever. It doesn’t go away. You’re charging people to make them worse.
More from the OTP experts on movement mistakes and how you can fix them:
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