In terms of motor control and motor development, the literature suggests that the dynamic systems theory is the most accurate
depiction of how the central nervous system both develops motor skills and continues to adapt motor control through life. In this article we will take a deep dive into the dynamic systems theory of motor control by answering the following questions: Who developed the dynamic systems theory of motor control? What is the dynamic systems theory of motor control? What critical factors
distinguishes the dynamic systems theory from other theories of motor control and development? Throughout the article we’ll also discuss how concepts of the dynamic systems theory could be practically integrated into an orthopedic and sports medicine practice. We will be using both evidence based practice and evidence based experience to share these interventional options. For those of you interested in pain neuroscience education (PNE), later in this article we
discuss how we might be able to blend PNE and the dynamic systems theory into our practice. Back in the early 1900s Nicolai Bernstein, a Russian scientist, looked at the nervous system in a whole new way. He not only asked questions about the organism, but about the organism in a continuously changing environment. Bernstein seemed very interested in how the organism itself could influence the brain and how
the task and the environment itself could influence the properties of movement. Bernstein proposed the following questions: How does the mechanical body influence the motor control processes? How do the initial conditions of the task &/or environment affect the properties of movement? Let’s keep in mind that, previously, in terms of motor control most scientists seemed to only be
concerned with either the biomechanical and sensorimotor systems without much acknowledgement as to how they influence one another or could be influenced by the environment or the task In Berstein’s mind “coordinating movement is the process of mastering the redundant degrees of freedom of the moving organism.” He also believed that: “You can’t understand the neural control of movement without understanding the characteristics of the system you are
moving and the internal and external forces acting on the body.” (Bernstein, 1967) To paraphrase Berstein here, it is the characteristics of both the internal forces, musculoskeletal and neurological systems (along with the other systems), and the external forces: gravity, environment, and the task, that one must understand before really understanding the neural control of movement. Bernstein realized that the mechanical system (our bodies) leaves us with a significant problem when it comes to controlling movement, called the “Degrees of Freedom '' problem. Think of “degrees of freedom” as the number of joints in the body (well over 300) multiplied by the sum of all of the available ranges of motion at each joint, which for most joints includes 3 planes of motion. The dynamic systems theory’s main objective seems be targeted at better understanding how
the central nervous system solves the degrees of freedom problem and how this can help rehabilitation professionals offer better solutions to movement problems. An example of the degrees of freedom problem is thinking about a child trying to intricately cut a pattern into a piece of paper. If the child’s spine is not supported by a back rest, think of all the proximal joints and degrees of freedom that have to be controlled in order to give the elbow, wrist, and hand the leverage and
stability to cut the paper a certain way. If you stop and think about it, this level of control is amazing given that the human body is the most complex dynamic system on the planet with respect to degrees of freedom. Bernstein seemed to be obsessed with figuring out: “How does the movement system go about solving this degrees of freedom problem?” Something to keep in mind is that since Bernstein was by trade a physical
scientist and philosopher who was also interested in movement. To answer his own questions about movement, he seemed to use his knowledge in physical dynamics and synergistics in nature. With that in mind, another question Bernstein proposed was: “How do the patterns and organization we see in nature come into being from odorless constituent parts?” A question that gave birth to a fundamental principle unique to the dynamic systems theory
called the “self-organizing principle” which we’ll dive into in the next section. Bernstein proposed four principle based concepts to solve the degrees of freedom problem: Synergies The Self Organizing Principle A Non-Linear System vs A
Linear System Movement Variability The perspective brought to each of these can be seen as the critical factors unique to the Dynamic Systems theory. Let’s break down each one of these concepts. First up, Synergies The concept of muscle synergy is not new, however the dynamic systems model goes a bit deeper than just “muscle” synergy. We’ll first start with
Bernstein’s original perspective, and finish with how the term “synergy” is being thought of in the current motor control literature. Bernstein figured that muscle synergies were a rational idea for solving the degrees of freedom problem. To him, muscle synergies were controlled via a hierarchical system (he seemed to have adopted some perspective from the Neurodevelopment model of motor control) in that the higher levels of the CNS activate lower level neurons which then activate chains
of muscles that are wired and fire together to perform a functional task like, locomotion. If we looked at motor control and degrees of freedom like a business, muscle synergies can be seen as an automation strategy for productivity. In other words, this is a clever strategy to organize the CNS in a way that simplifies and unites various degrees of freedom toward a common goal, similar to having various departments in an organization. Berstein saw three categories of stereotypical muscle synergies working as a functional unit to help automate human function: 1. Respiratory Synergies 2. Postural Synergies 3. Locomotor Synergies Doesn’t it make sense that the nervous system would find and create a way to automate the 3 pillars for human survival, that is breathing, being upright, and walking? Wouldn’t it also make sense if these synergies were controlled by subcortical areas of the CNS, reflex motor control, to allow our conscious mind to focus on other tasks? This thought process really ties in concepts from the reflex motor control model sparked by Dr. Sherrington which is discussed in this article HERE as it relates to applying traction & approximation into your practice. Luckily for us, we also have the option of consciously controlling these three pillars of function. Can you imagine if we had to think about all the components of breathing, staying upright, and walking all the time? I’m not sure we would survive let alone be productive. As the neurologist Dr. Charles Beevor once said “The brain does not know muscles, only movements.” Dr. Beevor’s quote highlights the nervous systems’ tendency to create synergies and movements for the sake of automation and efficiency. It seems to me that the concept of synergy has been taken too far and out of context in recent years as there are many who have belittled the importance of screening, assessing, and treating isolated joints and muscles. I don’t believe those who recommended movement synergies like Dr. Beevor and Berstein were suggesting that individual muscles and joints no longer matter. Keep in mind at this time the main approach to movement was the reductionist approach of training joints and muscles in isolation because that was all that was known. The brain organizing the movement system via synergies and whole patterns was a paradigm shift at that time. However, the innovators of this insight did not seem to abandon the fact that if isolated biomechanical function was absent, the synergy was compromised. This seems to boil down to a fundamental principle that says independence is a prerequisite to interdependence. How can we expect a bunch of joints to work together interdependently without first meeting their independent criteria for basic mobility & motor control? Just because we now know that the brain communicates better in patterns doesn’t mean isolated joint function no longer matters. If we want to optimize movement patterns we also have to optimize isolated joint function. Interestingly, one of the “debates'' you'll come across if you read more about synergies is that some argue that the idea of synergies “constricts' ' movement to only certain patterns, not allowing for variation. This is a very linear way of thinking about synergies. A more liberating and adaptable definition for synergy was recently proposed by Latash and Anson in 2006 as well as Latash et al in 2007 as they coined the term “The Principle of Motor Abundance”. This principle states that synergies are not used by the nervous system to eliminate redundant degrees of freedom, but instead to foster adaptable and stable performance of motor tasks. So rather than seeing a synergy as allowing for certain movement patterns while restricting others, think of a synergy as providing a blueprint of various possibilities within a given “degree of freedom window” while still allowing for alternatives and variations to accomplish the task at hand. In their paper titled “Motor control Theories and Their Application” Latash ML et al suggest:
In other words, when an individual is given a specific intent with a task, i.e touch this target with your finger, they found that those who demonstrate motor skill acquisition and hit the target every time had more variability in how they got there. So the joint angles of the elbow, wrist, and shoulder along with the muscle activation patterns had a lot of variation. This challenges that clinical approach of teaching someone a new movement with very strict “rules” so as to get them to move the “exact” same way every rep to accomplish a task. For example, think of how many letters there are in the alphabet to create a word or express a sentence. Although there are rules in the english language, every word typically has a synonym which allows us to express what we’re thinking in various ways; this is the beauty and art of language. Similarly, this is the “newer” way we’re starting to look at synergies with respect to movement. Muscle synergies allow for “movement synonyms'' or the same pairing of muscles activated in many different ways to accomplish a similar task. 
1) Organizes sharing of a task among a set of elemental variables i.e higher order neurons, lower level neurons (motor units), muscles and joints and 2) Ensures co-variation among connective tissue in order to stabilize performance variables i.e the center of gravity within the base of support for postural control. Thus synergies allow for both stability against perturbations and flexibility to solve concurrent tasks (Latash et al. 2007; Newell et al 1984). This co-variation among connective tissue could provide a way of minimizing ‘repetitive stress’ injuries, by allowing for a wider distribution of mechanical force through connective tissue by having various synergies to accomplish the same task or goal as shown in the image below. To help conceptualize this new definition of synergy even further lets use a series of images. In the first image below we see that one muscle can be a part of three different synergies all of which accomplish the same task.
So our understanding of synergy has expanded way beyond the myopic perspective of just chains of muscles. Latash’s new definition of synergy seems to suggest that we encapsulate higher order neurons, lower level neurons (subcortical/spinal cord level), various connective tissue options, as well as the specific task at hand into our understanding of a synergy.
Thus there has to be a level of adaptability and co-variation within the system to stabilize performance variables so that the client can maintain their center of gravity within their base of support in order to hit the target each time and execute the task. Note the potential integration of the reflex model, hierarchical model, and the dynamic systems model in this example. Although this is a stretch, if we ask the client to coordinate lifting the front leg with each rep we could consider the reciprocal support and stepping function in half kneeling as a reflex manifestation of a central pattern generator (CPG) from the motor program model. This new perspective of synergies and the principle of abundance seems to be more complete in that it acknowledges the necessity for adaptable movement strategies within a changing environment. Thus the three functional synergies that Berstein proposed that could solve the degrees of freedom problem: 1. Respiratory Synergies 2. Postural Synergies 3. Locomotor Synergies The use of these synergies could be a very reliable way to control the many degrees of freedom the body has to offer while providing an abundance of variations within these three synergies. Keeping in mind the environment, task, and the synergy of abundance may help shift us away from the idea of definitive “right” vs “wrong” movement patterns &/or postures but rather towards the idea of coaching variability within a normal range that accomplishes a desired task in a specific environment. In this way we could walk, breath, and hold ourselves upright in many different ways without having to think about it (reflex model) while interacting with our environment and using our conscious minds for other tasks. The Neurodevelopment Model (Hierarchical Model) + The Dynamic Systems ModelHow does the neurodevelopmental model relate to the dynamic systems model? To me its just as productive to discuss similarities between motor control models as it is to discuss what distinguishes them from one another. One way to ‘marry’ these models is by considering the relationship between our base of support (BOS) and our center of gravity (COG), in response to postural variations with the intent of solving the degrees of freedom problem. Using this cognitive framework can provide a simple yet systematic way of progressing or regressing movement, making an exercise more or less challenging. If it's not helpful for you to think about the developmental milestones in terms of progression and regression of movement (hierarchical mindset) then shift your focus to the following 3 variables:
As laid out in the chart below, the lower level postures have the largest BOS, the lowest COG, and the least number of joints to have to control, thus the least degrees of freedom.
Lower level postures would be considered any variations of the supine, prone, or side lying positions. This makes lower level postures a logical place to start with beginners whether you’re using the hierarchical mindset or the dynamic systems mindset. As you progress to middle level or transitional postures, such as various prone on elbows, quadruped, and kneeling, the BOS gets smaller while the COG moves away from the ground. This of course increases the risk of falling given the added degrees of freedom, which overall increase the demand of postural control, making the task a bit more challenging. Finally, we have higher level postures which include various foot positions like symmetrical stance, asymmetrical or split stance, single leg stance, and every variation in between. At this point the BOS is pretty small with a relatively high COG, thus the most degrees of freedom and joints to control, highest demand for postural control, and the highest risk for falling. If thinking about the developmental milestones of a baby does helps you think through progressions and regressions then you can add the BOS/COG relationship as an alternative educational tool to help educate your clients and a treatment planning tool to help you problem solve cases. So that was a break down of the first of Bernstein’s proposed concepts to solve the degrees of freedom problem:
Next lets discuss the second concept: The Self Organizing PrincipleHere is a very interesting twist that the dynamic systems’ theory proposes in terms of how the body deals with “the degrees of freedom '' problem. Fair warning this principle is one of the hardest to understand at first. Remember, Bernstein was a physical scientist who was also interested in movement, so he came at trying to figure out movement in a very unique and “unorthodox” way. To bring back one of Bernstein’s question we brought ups earlier:
Take for example water going from a liquid to solid ice or turning into gas. This is the principle in nature called “self-organization” which is a fundamental principle of any dynamic system. The self organizational principle states that when a system of individual parts come together, its elements behave collectively in an ordered way. There aren't always higher centers sending out instructions to achieve coordination. Thus Berstein was curious if we really needed higher CNS commands given this natural principle. So if we acknowledge the human movement system as a dynamic system, could the self-organization principle apply to human movement? Is there a possibility that movement can be formulated by the constituent parts orchestrating among themselves without “higher order instructions” from higher order “motor programs” within the CNS? It seems easier to fully understanding this phenomenon by, again, integrating concepts from Sherrington and the reflex model (i.e the action potential threshold) discussed HERE. It’s important to keep in mind the the sensorimotor system seems to have been evolutionarily designed to reflexively respond to signals from the environment via various sensory receptors without the need for conscious activity as a survival mechanism. In his book, Focus, Daniel Goleman calls this reflex activity ‘bottom-up’ circuitry. In terms of speed, subcortical neural pathways (reflex pathways) can conduct electricity a lot faster than the “top-down” circuitry (cerebral cortex). Thus the bottom up circuitry’s millisecond firing speeds in conjunction with the organization of synergies seems to be a clever way of dynamically organizing so many degrees of freedom. Two other questions to consider:
2. What if we combined the reflex model of motor control and CPGs as a way of rationalizing the self organizing principle? Let’s use a visual to conceptualize this. The image to the right attempts to show a close up of the ‘cross section’ of the anterior horn of the spinal cord with the odorless chaos that is the cluster of alpha motor neurons, inhibitory interneurons, and facillitory interneurons. I acknowledge that this thought process is a stretch, but please humor me for a minute. Could one say that this cluster of cells somewhat resembles the cluster of molecules of a solid or liquid state in nature? So, as the image demonstrates, the question now becomes:
The self organizing principle that Bernstein proposed could be the intersection of the reflex model, his concept of synergies, and CPGs from the motor program model. The combination of these concepts highlights a potential option that the motor control system has to automate the degrees of freedom problem. So that was a break down of the second of Bernstein’s proposed concepts to solve the degrees of freedom problem:
Next lets discuss the third concept: A Non-Linear System vs. A Linear SystemLet’s take this “degrees of freedom” problem even deeper, shall we? Warning, this concept really highlights Bernstein’s perspective as a physicist, which brings us back to basic mathematical concepts. Linear Model: Y = mx + b Output (Y) is proportional to its input (X) Let’s start with a ‘clean’ linear model. A linear model is where the output is proportional to its inputs. The linear model can be represented by the equation Y = MX + B and the graph to the right. The linear model can be thought of as representing reductionist explanations of movement using biomechanical or kinesiological logic. For example, if we know where the bicep tendon inserts and the distance from its insertion to the joint’s axis of rotation, we know that when the bicep contracts the elbow will flex and we can calculate the torque imposed on the elbow joint. Basically when you insert a value for X (input) you know what you’re going to get for Y (output). This linear/biomechanical perspective is necessary and has served as a valuable tool in advancing our understanding of movement. However when it comes to studying neuroscience and motor control mechanisms, it seems to be more appropriate to use a non-linear model. Unfortunately, this equation is not as simple and ‘clean’, yet it seems to be a better representation of the relationship between inputs and outputs that comprises the sensorimotor system. For the record I have no idea if the graph below represents that chaotic nonlinear equation, I’m not that good at math. A Non-Linear Model The point here is that with a non-linear model the output is not proportional to its inputs (Harbourne & Stergiou, 2009). Some have used the phrase, “The whole is greater than the sum of its parts.” A pragmatic example of this is when we observed a client who has adequate range of motion and isolated joint control yet they can’t seem to organize a movement pattern like a lunge. You could say it's because this person is just not coordinated, but that is exactly what motor control and the non-linear model highlights - there is a lot more processing going on than just adding up the biomechanical parts. So when we discuss motor control, we have to get comfortable with more abstract thinking and more ambiguity compared to the biomechanical model. This transition can be quite difficult and uncomfortable at first, but if you can embrace the struggle it is worth it. And please don’t get caught in the cognitive trap of thinking that you have to choose between the non-linear and the linear model. The idea is to have both cognitive skill sets readily available to you, in addition to the various other motor control models, so that you have the mental agility to tackle a variety of clinical movement puzzles. The Non-linear model Redefines PostureIn 2003 and 2009 Harbourne R and Stergiou N published two interesting articles. The article in 2009 was titled Movement variability and the use of nonlinear tools: principles to guide physical therapist practice. The article in 2003 was titled Nonlinear analysis of the development of sitting postural control. This brings up a very interesting discussion in terms of posture that I’ve been having with myself, my mentors, and other professionals for years now. For centuries, in our industry of physical rehabilitation we have placed posture in distinct binary categories of having either ‘good’ or ‘bad’ posture. We have associated ‘good’ posture with aligning the joints to minimize tension and force on the musculoskeletal system. But is ‘good’ posture really defined as proper alignment or stacking of the joints? Clinically, we’re recognizing a pattern of people who demonstrate and are obsessed with ‘good posture’ coming to us in the clinic with similar problems. Could this strict mindset of defining ‘good posture’ as proper alignment be perpetuating a new problem? Many of us seem to think so. The motor control science behind the dynamic systems theory, the nonlinear model, and ergonomics supports our suspicions and helps us to potentially redefine posture for the health of our communities. Both science and clinical experience suggest that we completely abandon the terms ‘good’ and ‘bad’ posture in absence of considering both the environment and the task at hand. Posture is a dynamic entity, and needs to have a profound level of variability throughout our day so that we can accommodate various tasks, thrive in various environments, and minimize redundant stressors. Similar to how we’ve upgraded the term “Synergy” to include higher order neurons and the task, its about time that we upgrade our myopic view of posture. It's the mindless stagnation of posture that needs to be demonised, not mis-alignment of posture. Posture is a living breathing moving entity, it's not a 12 story apartment building that needs to be perfectly aligned at all times. The literature consistently suggests that the more postural variability we have throughout the day, including intermittent slumping and flexing, the less correlation we're seeing with the reports of repetitive stress injuries especially in the workplace. An image and concept that I found works really well with educating clients is “The Postural Continuum”. My clients have found it helpful to visualize where they tend to ‘live’ on this continuum. I will then explain to them that the more time we spend across The Postural Continuum throughout the day, the better off our joints will be. So let's stop communicating to our friends, family, and clients that “you have ‘good posture’ and you have ‘bad posture’”. Let’s stop arbitrarily communicating the direct causation of ‘bad posture’ being the reason that someone is in pain. But wait, couldn’t it be that someone’s neck or shoulder hurts because they are always slumping at their desk? And if we have them sit with ‘better’ posture and their pain goes away doesn’t that indicate that we’re on to something? This is a valid point however this rationale only considers the short term resolution of pain and does not take into account the longevity of the client and their musculoskeletal health. The magic of longevity here is in the communication with the client so as not to have them walk away with a strong mental associate of ‘slump sitting equals pain and suffering’. We can simply educate them that they are only expressing one postural option, using the “Postural Continuum”, and they need to sit upright and stop exhausting the option of flexion. Now they still get the same message to sit more upright which may improve short term pain but they will not also walk away with a subconscious fear of slumping. Now instead of this client trying to consciously always stay in extension to avoid pain, they realize that it was the mindless stagnation of posture, which forces them to be more mindful of postural variability. I’ll provide two simple client stories to further help with clinical application. Katie’s Posture StoryKatie came in reporting a vague, dull aching shoulder/neck pain. Long story short she was very proud of the fact that she always has ‘good posture’ and never catches herself slumping anymore. I praised her diligence and mindfulness regarding her movement health while also educating her of the fact that her body ‘forgot’ how to flex. She was essentially stuck in extension, and in my opinion it was perpetuated by her belief that flexion was ‘bad’ for you. I gave her a quick lesson about this new definition of posture and the importance of variability and avoiding stagnation instead of always seeking to align our joints. In the before & after picture on the left below, you’ll notice that Katie is less extended in the ‘after’ photo. This was not the result of fancy manual therapy or an advanced corrective exercise, this was simply the result of giving Katie permission to relax her chest and shoulders after educating her that flexion is not the enemy. It was a paradigm shift that resulted from a self care education lesson on posture. “Wow that actually feels better” as she relaxed her sternum. The resting discomfort she was constantly feeling quickly dissipated. Through our 4 week treatment plan we-re-taught Katie how to express flexion at her upper thoracic spine through various manual therapy and self care strategies. She even reported that reminding herself that it was ok to relax her chest throughout the day took time and “mindset reconditioning”. Katie regained her ability to flexion her upper thoracic spine after 3-4 sessions within a 4 weeks period. Based on my past failures to help clients similar to Katie, only using manual therapy and exercise, I believe that if I didn’t address the mindset of “flexion and slumping is bad for you”, I wouldn’t have been able to help Katie given that she is a nurse who works 12 hour shifts. The message I kept reminding her was
Jay’s Posture StoryJay came in for an evaluation reporting back pain after only 20-30 minutes of meditation in the seated cross legged posture. He told me that he typically likes to sit and meditate for an hour at a time so this back pain was really bothering him. I asked him to show me how he sits. I then asked him to talk me through how he thinks he needs to sit. Jay said, “Well I typically sit on a mat on the floor like this and I do my best to stack my head over my shoulders and over my hips. I also keep my chest up so that I don’t slump and round my shoulders, but I feel like I’m fighting to keep my chest up. It's almost like something is holding me back.” What I noticed was that Jay was working unnaturally hard to keep his chest up, you could see the struggle and tension in his facial muscles. He did not look like he could relax. So I asked him “why is it so important for you to keep your chest up like that?” Jay responded “I’m trying not to slump because I was told that it wasn’t good to slump.” I gave Jay the same education I gave Katie, and gave him permission to relax his chest (specifically sternum) and play with various positions of his sternum to find what felt relaxed yet natural. The image above is where he reported to be at ease, yet he reported feeling like he was extremely slumped forward, which I’ve found to be a very typical proprioceptive response when taking people out of an extreme habitual position. So I took a picture and showed him that he was actually still fairly stacked yet relaxed. I could tell that Jay was a bit skeptical of the fact that I was telling him that flexion and slumping wasn’t the enemy, yet stagnation of any posture was. I’m very used to this skepticism and welcome it because for many people it’s the first time they’ve heard this, so I present it as an ‘experiment’ rather than a hard fact which seems to help clients open to the suggestion. Six days later Jay emailed me:
Previously I would’ve only addressed Jay’s thoracic spine mobility limitations, but I’m noticing that addressing this ‘bad posture’ mindset first, along with movement limitations, is demonstrating profound short term and long term results for many people. People are also reporting more peace of mind as they don’t feel “guilty” when they catch themselves slumping from time to time. In my mind this helps people go from a sympathetic to a parasympathetic state or from tension to relaxation. One client reported:
The bottom line here is that if we want to optimize someone's joint health, let’s ask them to express a multitude of postures throughout the day without having to demonize one posture or the other. Remember, we have to consider the task when we talk about posture, since posture after all is a synergy. This new thought process of posture lines up well with the fact that variability is inherent in all biological systems to optimize health. Let’s free people of this outdated mindset that posture is a binary entity and either ‘good’ or ‘bad’ because it's very clear that this mindset is not helping our communities foster longevity. A Nonlinear System vs. A Linear System ContinuedAs we discussed previously, in a non-linear model the output (desired outcome) is not proportional to the inputs. The non-linear model also suggests that new behavior can emerge due to a critical change in one of the system’s “control parameters”. A control parameter is a variable that regulates change in the behavior of the entire system. So, in the non-linear model theory, we could change one variable in the movement system, i.e a joint’s mobility or someone’s belief system, and as long as we bring that variable to what they call “a critical value” we can change the movement system all together without even touching the other variables. So if ‘Y’ is the desired outcome, a behavior or the global movement. And if ‘X’ is the control parameter, a belief about posture, mobility, or motor control. Applying this concept to Katie and Jay’s posture stories, we seemed to have created a critical change in their belief (a control parameter) about posture (X), thus leveraging change and allowing for a new less rigid movement behavior to emerge which helped them both to alleviate some discomfort. Let’s shift from a belief to an actual movement example. Let’s talk about helping someone lunge easier by improving their ankle dorsiflexion. Let’s say a client is really struggling with lunging. So a fluid lunge pattern is the desired global movement ‘Y’. So what are the component parts, control parameters ‘X’, that require us to lunge appropriately? To just name a few we need ankle mobility, hip mobility, knee stability, and hip stability. Let’s say all of these control parameters are suboptimal because we’re coaching a 45 year old male and he is stiff everywhere. Also his balance is not that great. So do we go into a stress response because there's all these variables that we have to change in order for him to successfully lunge? Or can we shift our mindset to the dynamic systems theory and the nonlinear system perspective knowing that all we have to do is create a critical change in just one of the control parameters. Let’s say that you are a lethal weapon when it comes to treating ankle mobility restrictions, so let's pick ankle mobility to apply our mobility techniques. Let's say you take his ankle mobility from -5 degrees of dorsiflexion to 5 degrees of dorsiflexion. Now all of a sudden a new movement behavior emerges and he can perform a respectable lunge, and you look like a magician. We see this situation clinically resolving knee pain and in a fitness setting improving squats and lunges quite often. This “non-linear” concept is a brilliant way of helping us potentially explain what we’re seeing with a spontaneous improvement in the squat &/or lunge pattern without much additional coaching to warrant such a change. Pavel Tsatsouline, at StrongFirst®, calls this the “What The Hell Effect” (WTHE) where focusing on one physical variable completely changes a seemingly unrelated variable or physical quality. The beautiful thing about a neuromuscular rehab approach that acknowledges and applies the dynamic systems model, specifically this non-linear perspective, is that being presented with a lot of control parameters (joints) that are not perfect doesn't bother you or stress you out as a practitioner. The reason is because you appreciate that if you can just make a critical change in one of the “low hanging fruit” control parameters, you can create a new behavior and create patient buying in a shorter period of time. So whether it's a belief, a mobility limitation, or a motor control limitation acknowledging the fact that the body is a nonlinear system can create resilience in both you and your clients’ mind. This mindset reignites a sense of hope that at one point may have been hopelessness. In my opinion this is a huge paradigm shift for us in the movement industry. The Non-Linear Model & VelocityAnother example of a control parameter, other than mobility or a belief is velocity. If you have had the privilege to observe brilliant track or martial coaches at work, you will sometimes see them using speed as a control parameter to alter movement behavior by manipulating the tone, speed, the intonation of their voice. Whether it's jumping, sprinting, swinging kettlebells, or martial arts, listen to the coach’s tone of voice and the speed in which they deliver their verbal cues. For example I once got to observe a track coach cuing up one of his athletes with phrases like
I also got to observe a master martial artist coach an athlete during punching and kicking drills and cueing
Without obsessing over biomechanics or individual muscles, I watched these brilliant coaches change these athletes’ movement behavior right before my eyes with a lot less frustration compared to what I may have done a couple years back as I used to obsess and micromanage all the parts. This is another example of how bringing a control parameter, velocity, to a critical value via verbal cues can help change the entire dynamic system and facilitate a new behavior to emerge. According to Daniel Coyle, author of The Talent Code, playing with speed is something that great coaches do to facilitate “deep practice” and learning. What a great example of the nonlinear systems’ perspective applied to motor control and a practical coaching strategy. Through insights gained from synergies, the principle of abundance, the self-organization principle, and the nonlinear system’s thought process we’re starting to get a glimpse at how Bernstein’s mind was wrestling with some of his original questions of
That was a break down of Bernstein’s third concept to solve the degrees of freedom problem:
Now let’s get into the fourth and final principle that Bernstein proposed: Movement VariabilityThis seems to be one of the most popular concept in terms of the dynamic systems theory in the rehabilitation industry today. Remember, solving the degrees of freedom problem was Bernstein’s main focus and the principle of movement variability or having various movement options was, in his mind, a critical one. The concept of variability seems to be totally different compared to how variability is seen in other motor control models such as the motor program model. Remember back to our discussion of how variability from “correct posture” is seen as a mistake or an error from a motor program perspective. In the motor program model it is assumed that through the process of skill acquisition “errors” and variability will decrease with practice. In contrast, the dynamic systems model sees variability as a critical component to optimize function. Variability allows for adaptive strategies in a changing environment and task. In support of this thought process, Stergiou et al 2006 found that motor skill acquisition includes variations that occur normally in motor performance across multiple repetitions of the same task. So contrary to popular belief as we get better at a motor task there seems to be more variability, not less, in the neuronal discharge patterns being recorded from the CNS. I am by no means dismissing the utility of the motor program model’s mindset here as I do believe there is a time and place for strict movement rules as we will discuss later. However, having this liberating “variability” perspective of the dynamic system’s model allows us to open up to other movement possibilities while still keeping our clients safe. I like to use the analogy of a food menu at a restaurant. With the classic perspective of the motor program model the menu can be quite restrictive and boring with limited options. However with the dynamic systems model, the food menu can provide a very interesting variety of options allowing us to mix and match appetizers, entrees, and desserts to create a very different yet engaging dining experience with each visit. It seems that, once again, variability plays a key role in the health of our movement system, similar to the correlation between the neuro-cardiac biomarker of Heart rate Variability (HRV) and our adaptability to stress. More variability in heart rate seems to be indicative of an adaptable autonomic nervous system. Likewise, variability in movement seems to be indicative of an adaptable movement system in an ever changing environment. Movement and postural variability, as discussed previously, is also proving to be an extremely cost effective strategy in reducing the incidence of repetitive stress problems as is seen with too little variability (aka rigidity). Not only is movement variability proving to create resilience in the body but for the mind as well. Keep in mind that just like too little variability (rigidity) is not optimal too much variability (aka instability) is also not optimal. There seems to be a sweet spot when it comes to variability (optimum variability) that we as coaches need to find for each client which highlights the art of our craft as therapists and coaches. For an even deeper dive into movement variability I would recommend Regina T. Harbourne and Nicholas Stergiou’s article: “Movement Variability and the Use of Nonlinear Tools: Principles to Guide Physical Therapist Practice” Movement Variability, Pain Neuroscience Education, and Our Word ChoicesLets elaborate on the “right vs wrong” perspective that the motor program model can perpetuate. When coaches believe that variations are “errors” rather than a desirable outcome, they will tend to gravitate toward therapeutic strategies with the intent to minimize variations and coach their clients to move in a “correct”, “optimal”, “stable”, and “safe” movement pattern. If we’re not mindful, this inner belief can often give the client an indirect message of “right” vs. “wrong” movement. In extreme cases, from my experience, some clients may extrapolate this belief to “this movement is bad for me and will hurt me” vs “this movement is good for me, will keep me pain-free, and prevent injury”. The newer science of psychoneuroimmunology highlights the importance of mindset and its role in recovery and performance. Psychoneuroimmunology strongly suggests that a belief can change our physiology and drive us into either a sympathetic (tension) or parasympathetic (relaxation) state. Thus this science continues to suggest that we, as health and fitness professionals, should be extremely mindful of our word choices because the belief of right vs wrong movement seems to be promoting quite a bit of fear-avoidance behavior which can often become more debilitating than a physical limitation itself. As health care providers we have to remember the Hippocratic oath of “do no harm” and realize that some of our language may have been perpetuating harm to our communities. We have to own that and change. As proposed by Vlaeyen in 2000, the diagram below, in my opinion, demonstrates how a strict allegiance towards a motor program model can affect our coaching style and word choices which can lead a client down two very different paths, one being recovery (right side of the model) and the other being the perpetuation of dependency, frustration, and fear (left side of the model). This is very similar to what we previously discussed in terms of “the non-linear model redefining posture”. Please excuse the redundancy here but I believe that addressing this concept from various angles has helped me personally digest and apply the concept to my clients and I hope this does the same for you. I’d like to offer an example by comparing and contrasting a classic motor program model vs dynamic system’s model narrative to highlight this concept. Let’s again use the example of a flexion and load intolerant low back. Here is a classic motor program narrative that I have personally used in the past:
Let’s reflect on how this motor program narrative and these word choices can lead to catastrophization and fear-avoidance behavior for Bob. Let’s say he is an entrepreneur and he's working in an office, sitting at a desk for seven to nine hours a day with a 30-minute commute each way. His current lifestyle exposes him to A LOT of flexion. Now a professional is telling him that flexing his spine is going to inhibit his recovery. What if, in Bob's mind, all he can think of is how his current lifestyle has to be completely changed and if not he has to live with pain. Might this induce fear and a stream of negative thoughts in his mind? Now let's take a dynamic systems narrative to the same situation:
Vlaeyen’s Model 2000 This narrative demonstrates that with a dynamic systems mindset we don't have to give the direct message of right vs wrong or good vs bad. This is just an example of how our belief systems in motor control can dramatically change our narratives and therefore the beliefs of our clients. Getting creative with our narratives can help us guide our clients to the right side of Vlaeyen’s model. So although we're still confronting a load sensitive and flexion intolerant spine, we immediately plant the seed of how we're going to avoid these positions while maintaining productivity standards without demonizing flexion itself. I think it is imperative that we foresee the client’s concerns based on the context of their life to confront any fears they have about their recovery process. You can get creative here and replace “flexion” with whatever position or movement the client is sensitive to. This ties in the belief of coaching the whole person and knowing the client’s profession and interests so you can use metaphors that resonate with them and what they already know. The bottom line is to migrate away from the idea and the message of “this position/posture/movement is bad for you and this one is good for you”. Let’s start to replace the feeling of hopelessness with hope. Let’s replace a fragile mindset with a resilient mindset. This core belief highlights that aging is not the enemy, yet stagnation, mindlessness, and a lack of movement is. With that said, I’d like to emphasize that we don't have to jump into one model and completely ignore the other. In other words, we don’t have to “pick sides” when it comes to motor control models. There are certain cases when the motor program model is quintessential for recovery because when people are actually hurt, you can't just let them haphazardly move without any “rules” or guidelines. In the case of back pain, I resort to the biomechanical model I learned during my OMT training with Martin Langas as well as Professor Stuart McGill’s approach. As demonstrated above, we can still present a motor program / biomechanical model within the framework of both pain science and the dynamic systems model using the principle of variability as our guide. Something to note, given the seductive nature of the movement variability concept, it will often attract those who don’t like structure and “rules”. Keep in mind that there is a sweet spot to variability.Too much variability is known as instability and too little variability is rigidity. In my opinion, variability can often times get taken too far, which can promote delusional thinking or denial of the fact that there is, in fact, a sensitivity going on at a tissue level. This can often leads to very little strategy and guidelines communicated to the client, resulting in no behavior change. In my experience, this ultimately can lead to the other end of the fear-avoidance behavior continuum, that being denial, delusion, and a perpetual pain experience (represented by my addition to Vlaeyen’s model in the bottom right of the image). This denial leads to the thought of “we just need to move because pain is just an output of the brain anyway”. My response to this thought process is, typically, peripheral sensitization precedes central sensitization with pain neuroscience education, something my pain science mentor Stephen Schmidt taught me in Vallejo, CA. I have intellectually and physically lost so many clients in the past because I inappropriately jumped into pain science education with central sensitization concepts before educating about tissue level peripheral sensitization. I didn’t realize I was doing this until I reflected back on what Stephen taught me and realized I was not meeting my clients where they were at. We have to realize that the majority of our clients have no clue or any reference regarding the abstract concepts of neuroscience like the “smudging of the homunculus”, the overriding fear-memory of the amygdala, and the CNS perception of threat’s influence on up-regulating peripheral receptors in the dorsal root ganglion. We have to meet our clients where they are at from an intellectual standpoint, especially in the beginning, so we are not saying things that are too different from what they are hearing from their doctors and other health care professionals. Starting at peripheral sensitization education and relating it to movements and postures their bodies demonstrate sensitivity to in both the objective exam and linking it to the subjective history is a powerful tool. This is what has helped me reconcile the biomechanical/motor program model with the dynamic systems and pain neuroscience model. In my opinion, in terms of motor control & movement variability, the dynamic systems theory and the new literature regarding Pain Neuroscience Education (PNE) compliment each other very well. So just because the motor program model seems to have perpetuated a “right vs wrong” approach in the past doesn’t mean we can’t reframe the approach with the variability principle from the dynamic systems model to open a whole new set of possibilities and approaches that can truly help to liberate us and our clients. The concept of movement variability offers a challenging question:
When variability is seen as a critical element of optimal & adaptable function, coaches will naturally start encouraging clients to explore and investigate a variety of movement patterns that will lead to success in achieving performance goals (Harbourne & Stergiou 2009). This belief honors the idea of “play” and how controlled chaos can open new window of opportunities for our clients. The belief that “movement variability” is optimal, creates an open space that allows for various movement options and believing that reflexes and experiential instincts from practice will kick in when our environment throws us a curveball. Lessons from Movement Variability: Clinical Case StoryBefore we move on I’d like to share a clinical story that highlights an important lesson to be learned regarding movement variability. I can vividly remember two clients I had that came to me in the clinic with back pain while I was first learning and excited about this variability concept. These clients both demonstrated textbook flexion intolerant load sensitive discogenic back pain as defined by the biomechanical model, specifically Prof Stuart McGill and Freddy Kaltenbourne. One client had a mild level of sciatic nerve tension that we identified via the slump test on her right side. The other client showed no signs of nerve tension sensitivity, just localized low back pain specifically with flexion in loaded postures. I decided to try out this movement variability concept and “steer away” from McGill’s recommended framework because in my mind “variability was now key for motor control”. I coached both clients very “loosely” allowing them to just explore squats, lunges, and getting up from the floor. Both clients seemed to be having a lot of fun and immediately after the session both clients reported feeling pretty good, “looser” and actually better than when they walked in! I was convinced that I unlocked another key to back pain. I saw both of these clients a couple of days later and the client who presented with mild nerve tension came back reporting full-blown sciatica just hours after our previous session. The other client had a 75% increase in back pain the night of our session. To be honest, I felt humiliated, embarrassed, and immediately came down from my high horse. If you’re familiar with treating this type of acute/subacute low back pain you know that it can sometimes be like playing with fire based on how sensitive the symptoms can be. I literally envisioned Prof. McGill and my orthopedic mentor Martin Langaas scolding me as the young grasshopper that I was. I put my tail between my legs and had to have two very difficult back to back discussions with my clients about load management, graded exposure, pain science, and the McGill protocol we were now going to initiate. The difficult lesson I learned here is that we have to be extremely careful when we are coaching those who are truly hurt using the variability principle. A big mistake I made in addition to just letting both clients haphazardly explore movement variability without any “rules”, is that I did not measure the volume of squats, lunges, and floor recoveries which would’ve made my “graded exposure” discussion a lot easier. It is now my opinion that if we are going to initiate a movement variability experiment with clients experiencing pain, we have to be extremely keen and modest with the volume. It’s very easy to keep going when we are having so much fun, but we have to know when to stop, document the volume/load, and listen to how the client felt for the next 24-48 hours to ensure appropriate dosage. It is extremely easy to over-treat these clients especially if they are fitness enthusiasts. There is a time and place for variability and there is a time and place for strict movement rules and a defined intention based on biomechanical principles. These two clients taught me these three lessons very quickly and in a very aggressive manner because it was clear that I hurt them, and that's the bottom line. If we choose to learn from our mistakes and actually share that with each other, I think that can go a lot further than just sharing our success stories. I didn't learn how to apply movement variability to my practice by just healing people and making people better. There are actually more stories where I unintentionally hurt people because I just didn't understand the pragmatic applications of this concept. Regardless of the outcome, we can learn something and apply that lesson to the next situation.
I hope this story helps you really take a second to reflect before you take movement variability into these clinical scenarios. I hope this reminds you to be a little bit more humble, a little more cautious, and a little less arrogant than I once was. Movement Variability and The Hip HingeWhen we are teaching someone the deadlift or the hip hinge we can utilize variability in a way that alters the load application, the environment, or the task itself. For example, in the picture on the far left we have a very constrained task. I'm asking the client to both maintain three points of contact with the dowel and posteriorly weight shift via a hip hinge into a band that is trying to pull his hips forward and throw him off balance. This forces him to instinctively use a hip balance strategy i.e hip hinge. In the next picture we’ve removed the constraints of the stick and the band, giving him more ‘degrees of freedom’ to demonstrate the pattern on his own. That freedom in and of itself can be considered variability under the umbrella of acceptable technique because the load application is altered by not having a band trying to pull him forward. Once he’s got that down we can alter the load application again by using a barbell, a sand bag, 2 kettlebells instead of just one, or have him lift the weight at his side (‘suitcase’ lift). Thus when progressing a flexion intolerant spine back to weight training we can integrate variability while still utilizing the principles of biomechanical leverage and good old-fashioned technique of lifting and strength training. I think it's time that we as an industry appreciate that the dynamic systems model, movement variability, pain science, and biomechanical principles can all live under the same clinical roof without a hostile attack toward each other. Just be sure to acknowledge that the concept of variability needs to still be anchored by the natural principles of biomechanics, tissue tolerance, progression, motor learning, and common sense. I wish someone told me this before I unintentionally hurt those two clients with back pain. Now when that clinical pattern walks in the door, I know I won’t make that mistake again. Movement Variability, Martial Arts, and other movement practicesIf all this talk about movement variability has left you craving more of it and you find yourself trying to force it into your strength training because that’s all you’ve been exposed to, I have definitely been there and know the feeling. That is one of the main reasons I started exploring various martial art systems years ago. If you’re serious about increasing your exposure to movement variability, I highly recommend you step out of your comfort zone and explore other movement practices. So many other systems can provide you with the variability that you're looking for like various forms of martial arts (Bagua chung, Tai Chi, Qigong, Kung Fu, Udo, Jujitsu, different forms of weapons training like Samurai sword). These systems have an overwhelming amount of variability AND structure built into them that is extremely engaging and liberating; it's amazing! If martial arts isn’t appealing, you could also explore rock climbing, the MovNat system, Feldenkrais, or various forms of dance, and so many more. Exploring other movement practices will add variety to your physical routines, but experimentation is the key because finding something you love and look forward to is proving to be a key to longevity and aging like a fine wine. My Tai Chi Sifu (Master), offered me a refreshing perspective that helped me see movement variability in a new light while blending the other motor control models. He says that there are many schools of eastern martial arts and most of them are very strict with form and joint position in the early stages of their training. Sifu, would always say
How refreshing is this perspective outside of a martial application? Couldn’t we bring this same insight to movement with respect to life and our environment? When does life offer us any guarantees? What I observed is that after Sifu sees competence with the basics, he would then coach to “spar” lightly with varying speeds to see what reflexively comes out as a form of defense. What a brilliant integration of the concepts of the motor program theory of getting a movement “correct” yet then moving on to a variety of options, allowing deviation from the “correct” movement and allowing reflex motor control to emerge. What a refreshing martial perspective that progresses away from pure “form” and opening to reflex variability based on reality, protective instincts, and a controlled environmental threat, i.e a fist coming at your face. To me, so far, the blending of the motor program model and the dynamic systems model highlight how valuable it is to learn the rules like an expert so you can eventually break them like an artist. Side note, one of my favorite hand-eye coordination and variability training toys, other than nun-chucks of course, is the boxer’s reflex ball. The Dynamic Systems Model, Mobility, and The Sensorimotor SystemLet’s start by analyzing the mechanical system as one of the internal variables that Bernstein referred to back at the beginning of this article. To paraphrase Bernstein:
According to this theory and the principles of the sensorimotor system, movement is not determined solely by output of the CNS (As proposed by previous perspectives back in Bernstein’s time). Movement is an output (behavior) that is the result of a filtering/processing of afferent inputs from the mechanical system - our joints and musculoskeletal system. In other words the afferent input that the CNS receives from the body is dependent on the stimulation of mechanoreceptors and proprioceptors within our joints and tissues. This afferent information provides the CNS with “in the moment” feedback regarding the body’s current position in space, known to many as proprioceptive awareness. Thus the mechanical system, the body, acts like a filter for the sensorimotor system. The only way to optimize the afferent inputs from these joints’ mechanoreceptors is to ensure a competent level of mobility because movement is what stimulates these proprioceptors (i.e mechanoreceptors). If you again think back to the beginning of this article, this concept helps to answer one of Bernstein’s original questions: How does the mechanical body influence the motor control processes? So if a joint doesn’t have acceptable mobility then the joints’ mechanoreceptors are simply not activated or depolarized. This leaves the CNS with inadequate information about the joints’ current position in space, which ultimately alters optimal, adaptable, and reflexive motor control. The CNS then has to take that afferent information (or lack thereof) and compare it to:
Keep in mind this all happens in milliseconds and at speeds that the conscious mind could never physiologically keep up with. In the motor learning and motor control literature, the diagram to the bottom right is a visual representation of what they call a “closed loop system” which can help explain the critical relationship between tissue mobility and proprioceptive sensory feedback to the CNS. In the diagram the “movement control center”, the brain, sends out movement instructions to the “movement effectors”, muscles and joints. Luckily, in a closed loop system, the muscles and joints provide the command center with sensory feedback in regards to the success of the original movement command in the current environment. Now think back to our discussion in the non-linear model and how we can think of a control parameter as mobility or a perception/belief. Keep in mind that this sensory feedback can encompass any of the sensory modalities (vision, auditory, beliefs/perceptions, mechanical/proprioceptive) as a means of communicating back to the control center to alter behavior. Without this sensory feedback we would have something called an “open loop system” which looks like the image below. This system is set in its ways and essentially can’t adapt to change because feedback isn’t a part of the control process. The open loop system reminds me of someone who just tells people what to do without ever asking for feedback on how to improve, the opposite of ‘open minded’. Visualize having the worst boss, now make it worse and that's an open loop system. In a constantly changing environment you can see how this system can not thrive without the ability to adapt, refine, and alter the original movement plan. Let’s use a theoretical example, imagine if you were about to kick a soccer ball on the field and you anticipated that the ground was flat and level. All of a sudden you plant your foot and the ground is not level, there is a mini pothole. If you had the subtalar mobility to pick up on the unlevel ground, the mechanoreceptors and proprioceptors in your subtalar joint would depolarize and reflexively notify (via sensory afferents) the CNS saying something along the lines of
The CNS could then reflexively make the appropriate motor adjustments to adequately plant and stabilize the foot, allowing the athlete to “stick it” and successfully strike the ball to make the play. Now let’s use that same scenario, yet this time you don’t have adequate subtalar mobility. The subtalar mechanoreceptors and proprioceptors can’t depolarize without adequate movement in the joint thus the CNS can’t get that reflex feedback about the subtalar’s current position in space and thus the unleveled ground. So the original motor command is allowed to play out which could lead to either missing the ball completely, missing the goal, a terrible pass, or an injury. For the record, a stiff ankle doesn’t guarantee an injury, this is not a causal relationship, but rather strong correlation that allows us to communicate and manage risk. This inability to adapt and react is what we typically see with balance reactions as people lose their mobility. There seems to be strong correlation between lack of ankle mobility and a loss of ankle balance reactions especially in older population. In my time in the martial arts community, I’ve had the privilege to meet several instructors who are a lot older than me yet demonstrate more mobility and have better balance than me. This has been a true inspiration for me because they have demonstrated that it is possible to age with grace because they’ve made mobility a serious priority in their lives not because they somehow found the “fountain of youth” but because they put in the work. On the other end of the spectrum I witness those who are older than me demonstrate the opposite of graceful aging who clearly demonstrate the opposite relationship with mobility. How then can we blame that on aging? I think it makes more sense to observe and learn from the behaviors of those who exemplify longevity and ask ourselves how we can integrate that into what we’re already doing and learn more about what we’re not doing. These questions are what eventually lead me to the Chinese martial arts and getting certified as a mobility specialist according to Dr. Andreo Spina and Functional Range Conditioning (FRCms). For me, one of the takeaway from the dynamic system’s theory:
The paradigm shift here for me was that mobility is equally as important for the sensorimotor and biomechanical system. For the biomechanical system we can look at it through the lens of optimizing joint play and the roll/glide arthrokinematics that help reduce excess joint compressive/shear forces. So if you consider yourself an orthopedic manual therapist, most of us have been trained to think in terms of mobilization to optimize arthrokinematics and thus osteokinematics of a joint. But there isn’t as much talk in terms of mobilizing with a sensorimotor intent, with the exception for grade 1 and 2 mobilizations to induce relaxation and decrease pain perception. But I don’t think mobilizations with a sensorimotor intent gets enough love and attention in orthopedic manual therapy in order to optimize motor control and the ease of movement. I believe it is very important to explicitly define this intention prior to initiating manual mobilization because a biomechanical intent tends to be associated with more force application compared to a sensorimotor intent. Unnecessary force in the absence of a true mobility restriction can lead to undesired post treatment side effects (i.e pain, soreness, headache with cervical mobilization). To be clear we still don’t know how the CNS processes the inputs it receives from peripheral joints. All we can say with confidence is that input comes in, gets processed, and we get a movement behavioral output. And there seems to be a strong correlation between adequate joint mobility, reflex balance reactions, motor skill acquisition, and adaptability in a changing environment. An “Ah-Ha” Moment at a Functional Range Release SeminarIt was the Friday of Labor Day weekend early September in Boston back in 2014. It was kind of nice because Boston was a ghost town and I was really excited for Day 1 of the FR Release seminar to begin. We were sitting in a lab room at Northeastern University, and in the middle of his lecture Dr. Andreo Spina, asked an actionable question that triggered a paradigm shift for me.
Dr. Spina then goes on to say:
In my opinion, this offers a logical and very actionable answer to Bernstein’s original question:
Thus, Spina suggests that we take a step back from obsessing over whole patterns before we have checked that the parts (joints) involved in the respective pattern are even communicating to the CNS in the first place. Basically we need to ask if the parts are clearing prerequisite mobility standards (i.e Can the joints communicate to the CNS?) To go deeper, Dr. Aaron Swanson PT, DPT, CSCS wrote one of my favorite articles that summarizes Dr. Andreo Spina’s Functional Range Release course. Parts vs. Patterns?On the surface it seems like Spina’s “parts-focused” approach contradicts many movement pattern based approaches (i.e FMS & PNF) out there. However I don’t see it that way and I’d like to offer a different perspective. When you go deep into each of these leaders’ thought processes, you’ll realize that most agree on a lot of foundational principles and concepts because the great ones acknowledge that the CNS is the king and a primary target tissues in both rehab & training. Take for example both Dr. Herman Kabat (PNF) and Gray Cook (FMS). Although their approach start with appraising patterns, checking the parts is an integral part of both their systems (From my experienced as a resident in Vallejo, CA and an assistant instructor for the Selective Functional Movement Assessment). I personally think the confusion can be traced back to the inception of the rehabilitation industry. Before the hierarchical (neurodevelopmental) and reflex motor control models’ births, the focus seemed to be on understanding isolate muscle and joint function from a pure reductionist mindset of biomechanics and kinesiology without any consideration of The Central Nervous System. A lot of that mentality unfortunately continues on today. But if you think about it, we had to start somewhere! Starting with understanding parts good place to start when trying to understand movement. But rehabilitation leaders like Kabat, Bobath, Vladimir Janda, Karl Lewit, and more recently Gray Cook, propose starting with appraising movement patterns and moving beyond just the biomechanical parts, while not neglecting their importance. However just like any “trend” we will always have extremists blindly following the leaders and defending “their approach” aggressively without a full understanding of the other perspective, which unfortunately seems to dilute the originators’ brilliance. Thus in the recent years there seemed to have been an unnecessary shift away from respecting isolated parts given the seductive nature of whole movement patterns. Coming back to Spina’s perspective. In my opinion, Spina’s emphasis on the parts, i.e joint health and joint mobility, couldn’t have come at a better time to bring the pendulum back to respecting isolated parts just as much as we respect patterns. Yet instead of just having a myopic biomechanical focus on the parts, Spina has us seeing the mobility of the parts through the lens of the CNS. We can see that the mobility of the parts are the filters that deliver critical sensory feedback to the CNS to optimize reflex motor control and movement health. A side effect is preserving the health
and longevity of our joints or what Spina likes to call our “meat-wagon”. Dynamic systems theory and using variable velocity to promote “Deep Practice”Another practical application of the dynamic systems model is the use of variable velocity to coach movement. When it comes to motor learning, using variable repetition to reinforce motor learning and independence is critical. The dynamic systems theory highlights that variable velocity is an important contributor to the dynamics of movement. This in, my opinion, could be considered its own principle. Previously we discussed velocity, in the non-linear model section, as a control parameter (X) to change a movement behavior (Y). In his book The Talent Code, Daniel Coyle highlights the importance of playing with various speeds during “deep practice” as a critical contributor to “mylinating” new neural pathways and motor learning. Coyle’s concept correlates well with how the dynamic systems theory highlights velocity as a vital control parameter to create a critical change in movement behavior. In rehabilitation, we are conditioned to have our patients and clients move slowly in order to be safe, which is wise in the early phases of an injury. However eventually there needs to be some form speed variation given the task. In regards to motor control, motor learning and the histology of connective tissue, there is a very interesting interaction between speed, fascia, and the production of momentum that can help clients learn to move with a greater sense of ease and freedom. According to connective tissue experts, various master martial artists I’ve talked to, and Thomas Myers’s work some of the best ways to build resilience in our connective tissue and fascia is either:
There is also a large amount of research suggesting that, in addition to building aerobic capacity, progressively training short explosive movements may increase mitochondrial density in our fast twitch muscle fibers. Mitochondrial density in our fast twitch muscle fibers has been linked to successful aging and longevity. Think of velocity in this context as a relative speed instead of absolute speed. For example after going through a Tai Chi movement, we might then go to a normal or faster speed that might seem normal and then immediately go back to very slow. What’s interesting is that varying the speed seems to welcome the idea of “controlled chaos” when it comes to movement and it allows the client to more quickly develop their own internal “feel” for the movement. As one Tai Chi coach once said to me:
The dynamic systems theory has de-emphasized the notion of commands from the CNS in controlling movement and has sought physical explanations that may contribute to movement characteristics as well (Perry, 1998). To me this perspective is extremely refreshing, however, just because we have a new perspective does not mean we need to throw out the science and perspectives brought forth by the discovery of other motor control models. Various perspectives should foster mental flexibility when thinking about the control mechanisms of movement and how we can utilize these paradigm shifts clinically and in the gym with our patients and clients to empower them and optimize their quality of life. Dynamic Systems Model says “Movement is an Emerging Property”Another important takeaway from the dynamic systems theory is that movement is an emerging property. As Shumway-Cook and Woollacott explain it in their book Motor Control: Translating Research into Clinical Practice:
Think of these elements as either:
If a joint can’t do what a movement pattern is requiring, then the system will self organize to move around the limitation. Thus, shifts and alterations of movement behavior can often be explained by physical limitations rather than just neural structures & neuromuscular control. So when someone performs a squat and their foot and knee collapses in, should we be quick to assume that the glutes and the hip’s external rotators aren’t firing? Or should we also consider that this person may not have the adequate ankle dorsiflexion or hip rotational mobility to perform the movement? Would it make sense to quickly check for prerequisite mobility before making a bold assumption about the hip’s neuromuscular control and influence on the knee and foot? I think oftentimes we’re conditioned to make blank assumptions about people’s movements without first asking ourselves the right questions. The dynamic systems model offers a unique set of questions to ask ourselves before jumping to conclusions. A simple question can be: “Before I judge their motor output, what does their input look like?” Questions like this may lead us to even better questions and guide our thought processes throughout screening, assessment, and intervention Limitations of The Dynamic Systems TheoryOne could argue that the dynamic system theory is more “complete” compared to the previously proposed models of motor control since it takes into account both internal influences (musculoskeletal & neurological) as well as external influences (environment & task) on movement. However, as Shumway-Cook and Woollacott mention in their book “Motor Control”, one of the biggest limitations of this model is that some of the dynamic systems’ “camps” give mathematical formulas and principles of biomechanics and physics a more dominant role in describing motor control than the actual nervous system itself. This way of looking at movement, may make the dynamic systems model more attractive to biomedical engineers compared to Physical Therapists, Chiropractors, Athletic Trainers, and Performance coaches. Although understanding the application of this model to clinical practice can present as a bigger cognitive barrier at first, I think it is up to us as professionals to take the extra step to explore indirect evidence by further studying the internal variables (sensorimotor, biomechanical, neuro-cardio-respiratory, psychoneuroimmunology) and external variables (environment/task) that influence the nervous system’s control of movement. I feel as though the paradigm shifts this model has to offer has the potential to take the rehabilitation and physical training world to the next level. Leaders like Nicolai Bernstein, Dr. Andreo Spinae, and Moshe Feldenkrais have opened up the floodgates for applying the dynamic systems model to real people and I think we could all benefit from listening and trying to practically apply what they have to say to further help our clients. References
Which of the following describe four key aspects that reflect the dynamic systems theory of development?Recently, Karen Adolph and Justine Hoch (2019) described four key aspects that reflect the dynamic systems theory of motor development: (1) embodied, (2) embedded, (3) encultur- ated, and (4) enabling. Motor Development Is Embodied. Opportunities for motor behavior involve the current status of a child's body.
Who is associated with the dynamic system view of how people develop their motor skills?THE DYNAMIC SYSTEMS VIEW Developmentalist Arnold Gesell (1934) thought his painstaking observations had revealed how people develop their motor skills. He had discovered that infants and children develop rolling, sitting, standing, and other motor skills in a fixed order and within specific time frames.
Which of the following statements about income following divorce is true quizlet?Which of the following statements about income following divorce is true? Income usually increases dramatically following divorce for mothers with child custody, whereas income for fathers with custody does not.
Which of the following reflexes greatly diminish or disappear by the fourth month of life choose every correct answer multiple select question?The answer is C: 4 months. The sucking reflex in an infant will disappear and become a voluntary function at about 4 months of age. 6. In a 3-month-old infant you assess the Babinski Reflex.
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According to the dynamic systems theory, which of the following statements is true?
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