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  • Richard Ulm

FRC vs. DNS

Updated: Jan 29





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Recently, I had the chance to take Functional Range Conditioning, more commonly knows as FRC, right here in Columbus, Ohio. The course was taught by Josh Halbert and John Quint, both of whom were nice and engaging. I have long wanted to take this course for several reasons. First, I often get questions about FRC when I teach and feel obligated to be able to answer such inquiries intelligently. Second, as an instructor of Dynamic Neuromuscular Stabilization (aka, DNS), I often hear people say “FRC conflicts with DNS” or even ‘FRC hates DNS.” And finally, as a physician driven to continually evolve and improve, I am always looking for the next best thing. It was time to see what all the hype was about.


Just an FYI before we really dig in, this article is neither a recapitulation of FRC nor of DNS. It is also not an evaluation of FRC where I give it a thumbs up or a thumbs down. This is an analysis of FRC and its principles to see if and when these principles align with DNS and where they diverge. As with all information, if you want to learn more about FRC or DNS, I highly suggest that you take these courses for yourself.


What is FRC?

The Straw Man representation of FRC is that it’s just yoga for athletes. I have heard this on more than one occasion. The Steel Man representation of FRC that I can best construct is that it is a powerful system that seeks to simultaneously increase one’s active range of motion (AROM) and improve one’s joint control within this newly acquired range. The fundamental concept of FRC is to train each and every joint in the body to its maximal function, giving the athlete the best possibility of not only performing well but also reducing their risk of injury. This is accomplished by maximizing each joint’s available rang of motion (ROM) while simultaneously training “control” within this newly acquired ROM, primarily through alternating isometric contractions of the agonists and antagonist muscles in the end range position, which they call PAILs and RAILs. This muscle activation is important because once you have increased a joint’s ROM, there is a dangerously large gap between the Active End Range (AER) and newly acquired Passive End Range (PER). Increasing a joint’s ROM is a good thing; however, within this functional gap, if you will, joint control is not possible and injury is more likely. This is why it is so crucial to improve contraction capability within this range…to improve control, thereby, reducing risk of injury. To this end, in addition to PAILs and RAILs, FRC also uses a variety of other exercises to close this gap such as Positional Isometrics, Passive Range Holds, and what they call “Hovering”.


Once an athlete’s ROM is maximized and the control within this range is established, FRC focuses its efforts on increasing the athlete’s capacity for load (what I would call Load Tolerance or Tissue Tolerance). Unlike traditional strength training which trains the tissue predominantly within the mid-rang, FRC focuses on the end-range, where injury often occurs. The idea is based on the truth that injury happens when the load exceeds the tissue’s capacity (Load > Capacity = Injury | Page 4 of the FRC notes); so if there is a chance an athlete will get into a given position in their sport, than one needs to train this position to avoid injury.


The result of increasing an athlete’s ROM, joint-by-joint, and increasing each joint’s tissue capacity for load, is a more robust and resilient athlete, one which will have better capability of performing at a high level and one which has a better resistance against injury.   


Where does FRC converge with DNS principles?

While FRC places a strong emphasis on stretching tissue (more on this below), one of their main goals is to improve the athlete’s joint control. To achieve this they train isometric contractions of the agonist and antagonist muscles at the joint’s end range (that’s the PAILs & RAILs). These exercises may look nothing like the classic developmental exercises used in DNS, but the concept of improving control over one’s joints could not be more in line with DNS, they just go about it a different way.


A central goal of DNS, in my option THE most fundamental goal, is to train what we call Functional Joint Centration (FJC). FJC is a highly specific definition of joint control, or what I call Joint Position Management. FJC is the ability to precisely manage, or control as FRC might say, a joint’s position whether it is in motion or not, throughout its entire range of motion. With optimal joint position management, there is maximal efficiency of movement which reduces internal stress on the joints and improves both performance and longevity.


There are two hallmark characteristics of a functionally centrated joint: co-activation of the muscles around the joint and utilization of the minimum necessary muscular activity for the task. FJC requires having the ability to co-activate all muscles around the joint in a given position. This co-activation is necessary for precise joint position management. This is most easily achieved when the joint is in a mid-range position, which is why DNS tends to train there. However, it is essential that one can maintain FJC throughout the full AROM and so it must be trained. Because of diminishing force contraction capabilities, muscle co-activation becomes exponentially more challenging as the joint approaches end-range. DNS starts in a mid-range position to establish good quality muscle synergy (co-activation) and then progresses to the more extreme ranges of motion to ensure that the athlete has “control” (aka FJC) throughout the entire range of motion. [It is a misnomer often promulgated by FRC enthusiasts that DNS “only trains in a neutral position” or “only trains in a mid-range position”. I don’t know if this misnomer is an intentional straw-manning of DNS or is just a lack of understanding. Either way, the notion that DNS only trains in a neutral or mid-range position is not correct.] While DNS starts in a mid-range position and progresses toward the end-range position, FRC spends the vast majority of its time in the end-range position, either at active end-range using what they call Positional Isometrics & Hovering or at passive end-range using PAILs and RAILs or Passive Range Holds. Their goal is to improve what they call “control” of the joint at end-range, where muscle contraction becomes increasingly more challenging. To this end, the battery of exercises FRC deploys would couple beautifully with DNS because they train the ability to contract both the agonist and antagonist muscles at end-range, making co-activation, and therefore, FJC more likely in that position.


So while DNS trains predominantly in the mid-range position and FRC trains predominantly in the end-range position, they both seek to improve the athlete’s ability to “control” their joints or maintain what DNS calls Functional Joint Centration. It may not look like it, but on a fundamental level, it appears that the principles of DNS and FRC do align.


Where does FRC diverge with DNS principles?


Motor Programs

The first and most obvious way FRC diverges from DNS pertains to the existence of motor programs. FRC flat out denies the existence of motor programs whereas DNS is based on the concept that humans possess inborn motor programs which are the primitive basis for other more complex movements. Examples of such primitive motor programs would be: respiration, grasping, turning, crawling, squatting, & walking. For DNS, these motor programs are evoked or activated throughout development and are the reason why all healthy children learn to breathe, stabilize, turn, crawl, squat, walk, and run in the same order and with very similar patterns, no matter their upbringing or country of origin.


On this topic, FRC repeatedly hammered the idea that “no movement is ever performed exactly the same.” The keyword here is “exactly”. On page 6 of their notes, they say “Elite athletes are unable to reproduce invariant movement despite years of practice” and “‘THE’ movement doesn’t exist.” I think their logic is as follows: because no movement can ever be repeated exactly the same or without variance, no matter how much you practice or how hard you try, there cannot be a motor “program”. DNS would agree that no movement can be performed exactly the same (or invariantly)…down to the muscle fiber firing sequence. The variability in the sensory input and micro-changes in both the external and internal environments make exact replication of a movement utterly impossible. However, DNS does believe that there are general motor programs that influence movement. The brain of course has to modulate and accommodate each and every time a movement is performed, making exact replication of the movement simply impossible. “Repetition without repetition” as FRC quotes on page 6 of their notes.


DNS’ justification for the existence of inborn motor programs is the remarkable similarity with which all healthy humans mature (specifically neurologically & physiologically) during early development. Developing children acquire movements in the same order (e.g. they learn to turn before they can crawl, they develop ulnar grasp before they develop radial grasp, etc.) and they move with similar muscle synergy, not down the exact muscle fiber firing sequence but grossly speaking, quite similar.  This argument goes much deeper than the mere observation of a child’s movements. It goes deep down into neurology, all the way down to the spinal cord and sub-cortical levels. It’s not just that babies all move in similar ways; their nervous systems mature with remarkable similarity. You can map a child’s development/age by assessing their nervous system through performing a battery of tests called Primitive Reflexes and Postural Reactions. There is a non-coincidental similarity in the order which primitive reflexes (e.g. Crossed Extension Reflex, Grasping Reflex, Galant Reflex, etc.) disappear and there are consistently predictable changes in Postural Reactions (Horizontal Suspension test, Traction Test, etc.), all indicating a developing central nervous system with inborn motor programs driving the process.


From FRC’s  perspective, the best and most favorable explanation for the profound similarity in movement acquisition between developing children that I can construct is that we all have similar anatomy and what DNS interprets as a proof of inborn motor programs is really just the nervous systems of the individual humans trying to execute the movement(s) as efficiently as possible. Because we all have similar anatomy, and we are all seeking to execute movements as efficiently as possible, the movements will look similar. There are, however, no actual motor programs, certainly not inborn ones. Motor learning is simply the process of improving the efficiency of the movement for which we are training. Again, that’s my best guess on what the FRC explanation for the inexplicable consistency of movement between healthy children might be. I don’t know what their explanation of the predictable changes in Primitive Reflexes and Postural Reactions would be. I thought that question was too deep for the scope of the course.


While the existence of inborn motor programs is no doubt a point of divergence between FRC and DNS, pragmatically, it doesn’t matter. You can believe in the existence of inborn motor programs as DNS does or deny them all together like FRC and it will have zero effect on the efficacy of either system or on the utility of implementing FRC with DNS or DNS with FRC. It ends up being nothing more than a fun philosophical argument that has no actual impact in practice.


Emphasis: Structure vs. Neurology

Another way FRC diverges from DNS is that FRC emphasizes structure while DNS emphasizes neurology. No doubt, FRC is well aware of the roll neurology has on movement, after all they have a battery of exercises to improve joint “control”, but they constantly emphasize the importance of structural adaptation, force loading, increasing tissue capacity, etc. throughout the course. They hammer the importance of training the “internal system”, of improving the capacity of the “white stuff” to handle load, to cause permanent/structural adaptation, while never directly addressing the movement itself.


Evidence of FRC’s emphasis on structure can be seen in their hallmark exercises, PAILs & RAILs, which start off with a 2 minute sustained stretch so that one can stretch “through the neurology” to better load/train the structure. This is a fantastic idea, especially if the goal is to apply load to the connective tissue (or what they call the white stuff). In the course, we went through a multitude of exercises, all which started off with a long, sustained stretch so that we could better load the structure. This is not a crack on FRC, quite the contrary. I think this is a strength of FRC (pun intended), but it is no doubt a point divergence. DNS does not address structural adaptation directly as does FRC, but instead, focuses on the quality of the movement, on the efficiency of the movement, or the strategy with with which one moves to both reduce internal stress on the body and improve output (aka performance). The focus is not on the structure, but on the neurology.


To be crystal clear, I am not saying that FRC completely lacks an appreciation for the importance of neurology in movement, or that they never address neurology. However, it was blatantly obvious in the course and on various podcasts with Dr. Spina what the focus of FRC is and it was not on the neurology, it was on the structure. They do have a nice battery of exercises that address the neurology, but again the emphasis is on the tissue, on the white stuff, on training the joint, on improving tissues’ capacity for load, not on the neurology of the movement.


Again, the emphasis may differ between FRC and DNS, but they are compatible. One could use FRC to improve the robustness of the athlete’s structure and DNS to improve the neurological efficiency with which the athlete moves.


Approach: Isolationism vs. Integrationism

FRC takes a joint-by-joint approach to training (Isolationism) whereas DNS emphasizes integration of the individual parts (Integrationism). The general goal of FRC is to improve each joint’s overall function by increasing its AROM, the control the athlete has within this ROM, and its tissues’ capacity to handle load. Each and every one of their exercises are single joint exercises (or as close to a single joint exercise as can be managed). The assumption being if each joint has maximal function and robustness, than the athlete will be more capable to move well.


While FRC focuses their efforts on the individual joints, DNS emphasizes integration of each and every joint into the movement. The more efficiently the athlete is able to integrate each of the individual parts into the movements, the better they will be able to perform. Both emphasize “control”, but go about acquiring it in different ways. FRC focuses in improving local control (joint). DNS focuses on global control (movement). One is training the joint (FRC), the other is training the movement (DNS). I asked the lead instructor about FRC’s approach to improving movement he said “train the joint and the movement will figure itself out.” The assumption being that if you train the joints, the movement (quality) will automatically improve.


Once again, there is a difference in focus between these two systems, but they are not in conflict with each other. One could easily use FRC to improve a joint’s capability of moving well (its ROM, load tolerance, etc.) and then integrate that joint into the movement of focus using DNS.


Approach: Injury Prevention

The final way in which the principles of FRC and DNS diverge has to do with injury prevention, or at least the way each would go about this.

Remember, Load > Capacity = Injury. FRC and DNS each tackle this problem (equation) from different sides.


First, these systems converge slightly on the issue of injury prevention in that they seek to improve control. Improving control will reduce one’s risk of injury because it will minimize the number of instances when an athlete is in compromising and potentially injurious positions. FRC makes the assumption that training contractile capability at end-range will improve one’s control during the movement - in mid-range. (I’ll let that assumption ride for now and have to tackle the validity of that assumption in a subsequent article.) DNS, however, trains the actual control one has during the movement itself. FRC trains contractile capability at end range. DNS trains the actual movement itself. So, while they each seek to improve control via different methods - one trains joint/local control (FRC) and the other trains movement/global control - broadly speaking, they are similar in this regard. Where they differ is how they approach the injury equation.


FRC’s main focus to reduce risk of injury is by increasing the tissue’s load capacity, to improve the resiliency or robustness of the structure. This is accomplished through repeated loading of the tissue (infamously at end-range) to stimulate structural adaptation, thereby increasing the tissue’s load capacity. (Capacity >> Load = Prevention). The logic being, if there is a chance you will be in a given position, than you’d better train that position. Yes, that means training in really precarious positions like loaded lumbar flexion and knee valgus. I asked about this specifically and the instructors confirmed the FRC stance, that if there is a chance we will get into a position in sport than we should train there. There is a lot to unpack here. I am sure that FRC would most certainly progress the load to avoid injuring the tissue they are training, but the devil is most certainly in the details. For now, I’ll give FRC a pass on this issue. I want to remain focused on the way they seek to reduce risk of injury - by increasing the tissues’ capacity for load.


DNS, on the other hand seeks to reduce the load on the tissue by improving the efficiency with which the athlete moves. If you recall from above, the main goal of DNS is to train/restore Functional Joint Centration and one of the hallmark characteristics of FJC is using the minimum muscle activity (internal force) necessary for the task. By reducing the contractile force of the muscles executing the movement, you reduce the load transmitted through the tissue, or what one would call the Internal Stress. The total load going through the body/joint/tissue is a lot more than the magnitude of the external forces. It is the summation of the external forces (e.g. gravity, momentum, inertia, friction, etc.) and the internal forces (those produced by the muscles themselves). Most people forget that muscles contribute to stress on a joint/tissue; DNS, however, focus on it. Pavel Kolar, PT (founder of DNS) said to me years ago “It is more often the internal forces (those produced by the muscles themselves) that produce injury than the external ones.” Instead of focusing on the tissue’s ability to tolerate more load (Capacity >> Load = Prevention) as FRC does, DNS seeks to reduce the load on the tissue by decreasing the contractile force of the muscles executing the movement — by improving movement efficiency. The DNS equivalent of the FRC equation, therefore, would be Load << Capacity = Prevention.


Once again, there is no actual conflict, just a divergence in approach. DNS trains the movement (neurology) to reduce the load on the tissue; FRC trains the joint (structure) to improve the tissue’s capacity for load. Same goal, injury prevention, different approaches.


In the end…

Despite hearing otherwise from FRC enthusiast, I think these two systems can blend together beautifully. FRC improves the robustness of the body and improves the “potential” to movement well. It provides the clinician with a powerful battery of exercises to address local joint dysfunction. By increasing each joint’s ROM and their capacity to tolerate load, one can maximally train each joint to function optimally. DNS, on the other hand brings the increased potential (the result of FRC training) to fruition by addressing the movement directly, by improving the ability to integrate the joints into complex movement/sport. They may not look the same. They may not have the same focus. They may not use the same approach, but they go together quite well. They have differing, but complementary goals. FRC seeks to improve the potential to move well by training the joints, while DNS focuses on actually moving well - on the movement itself. Both are important for optimal performance and injury avoidance. So, there does not appear to be any incongruence between FRC and DNS, just a difference in emphasis and approach.


In review:

FRC spends most of its time in the end-range positions, whereas DNS spends most of its time in the mid-range position.

FRC trains the specific joints (joint-by-joint approach). DNS trains integration of all the joints.

FRC trains the individual joints to improve the movements (joint training). DNS trains the movements improve the joints (movement training).

FRC places more emphasis on structural adaptation. DNS places more emphasis on the muscle synergy, on the neurology, on the movement itself, on what they would call Functional Joint Centration.

FRC trains/increases the tissues' capacity in an end-range position to reduce injury. DNS reduces the contractile force produced by the muscles, thereby decreasing the load on the tissue, to reduce injury.

Both DNS and FRC seek to improve “control”. FRC does so by improving contraction capability at end-range, making the assumption that this will improve the movement itself. DNS does so by training the movement directly, within the active range or motion.


Dr. Richard Ulm


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