Breaking a skill down into component parts should make learning a complex task easier. The part training approach assumes the brain can rearrange individual motor stereotypes into a final complex motor
skill. However, modern neuroscience shows that the brain does not learn this way.^7,34 The brain is a processing system that converts sensory inputs to motor outputs.³⁵ It controls voluntary movements by formatting maps that contain dense neural signatures programmed in the central nervous system (CNS).^36,37,38 Counterintuitively, skills requiring a high degree of interlimb coordination are best learned by practice of the whole skill.^38,39,40,41 This has been demonstrated in a variety of disciplines—athletic, musical, or ergonomic.^{42,43,44,45,46}

The neurologic basis of skill acquisition depends on two different brain processes—an explicit domain (conscious) and an implicit domain (subconscious).⁴⁷ The explicit domain is concerned with the conscious goal, whereas the implicit domain is subconscious dealing with biomechanical and neurophysiologic properties such as limb trajectories and force generation. The implicit domain is developed by practice variability (thus whole rather than blocked) and becomes a subcortical automated movement pattern in expert performers.^48,49,50 The explicit domain is the focus of the early stages of motor learning through play and movement exploration.

According to Vaz et al,⁷ “Physical rehabilitation clinicians have (implicitly or explicitly) drawn much of their practice from theories of motor control.” She goes on, “Motor commands, reflexes and inhibition do not result in predictable movement outcomes independently of the context, that is, environmental constraints.” Vaz et al⁷ then debunk the following motor control myths:

The traditional approach in rehabilitation is typified by how children with cerebral palsy are trained with methods recapitulating a preprogrammed sequence of development.⁵¹ Yet, according to Vaz et al,⁷ “such approaches have been proven to be ineffective to improve functional activities thus leading numerous publications to recommend that clinicians abandon them in favor of other active rehabilitation approaches.”^51,52,53,54

The promise of training parts of skills to rebuild motor programs has a long history in motor control training.^{28,55,56,57,58,59} This has been based on the neuroscience tenet that “complex behavior can be described as a collection of simpler task processes … implemented in specialized brain systems” (p. 4S C).⁶⁰ However, using isolated motor control strategies to help rebuild basic life skills like getting up from a chair or walking are not highly effective.⁶¹ In contrast, as Vaz et al⁷ conclude, “Movement variability is essential for exploring the regularities in the dynamics of the individual and her or his environment.⁵” And that “research has shown that flexible, adaptive, healthy motor behavior is linked to optimal variability down to the fine temporal structure of movement details.^7,62,63,64

At times, breaking down tasks and using internally cued verbal instructions, hands-on passive modeling or active assistance can be useful in the learning process. At other times, a more hands-off approach or simply demonstration of a “monkey see monkey do” approach is preferred to provide an affordance for the learner to search for movement solutions independently. Blocking and randomizing could be done at either end of the spectrum (e.g., offering precise “prescriptions” to solve simple tasks or designing activities to enable discovery-based learning).

There is a balance between outcomes and physiology. The result of how high one jumps versus how kinematically one jumps. Because of the multitude of variables involved in complex performance
environments, our knowledge of the “tipping point” where risk of injury rises or sustainable performance gains can be achieved is unknown.

If the goals include PL, fitness, sustainable performance, and reduced injury risk, then a reasonable approach is to let movement coordination and control patterns be the guide (given clearly defined task objectives).

Vaz et al⁷ state that a pure neuroscience approach lacks “appreciation of the full implications of the context-dependency of functional movement, that is, of the fact that functional movement is goal directed and cannot be understood without serious consideration of the task at hand.” The heart of DST is that the individual, their environment, and the task being performed are all important and deserve consideration (Fig. 5.5). Separating the individual from their environment or context jeopardizes outcomes and transferability of “isolated” motor control strategies. This gets to the heart of why the ICF paradigm necessitated medical rehabilitation to evolve into functional rehabilitation.

It should be explicitly recognized that there are two perspectives of motor learning, which are not necessarily compatible. On the one hand, transfer of skill depends on the context of how it was learned, whereas on the other, learning occurs in the brain where “programs” are stored. In effect, there is a behavioral based view and an information processing (i.e., schema/motor program theory) perspective. The behavioral model involves motor development, control, and learning.³³ This paradigm contends that motor learning occurs in a variable ecologically valid environment. DST accepts both of these perspectives. Low (personal correspondence) draws from the work from Clark⁶⁵ and suggests that “we learn through the complex nature of perception and action—PERSACTION—we are not our brains … philosophically this could be seen as committing a mereological fallacy …. Learning can be seen as top down (e.g. drawing from prior experience). Behavioural responses—from a psychological perspective could be seen as top-down.”

This would explain why at the performance end of the spectrum there is a big gap between practice and competition. Skills often don’t transfer which is why the goal of practice is residual adaptation as opposed to “winning the exercise.”

Newell speaking of skill acquisition says, “The recovery of function entails persistence of a task relevant movement form(s) as reflected in the standard definitions of learning and practice in the traditions of the motor skill acquisition.”^68,69,70 Newell’s constraints-based DST paradigm was indebted to information theory in order to explain the dynamic nature of the variable relationship of the constraints between the individual, environment, and task (see Fig. 5.5).^71,72

DST highlights the “in the trenches” wisdom of coaches who achieved “buy in” for a drill after, for instance, a film session debrief following a loss. The drill would involve a gamification component and utilize environmental constraints (i.e., guardrails) that facilitate the needed motor learning. As an example let’s say a basketball team gave up too many open shots not because of lack of hustle or effort but failing to utilize a lateral shuffle step skill. The coach would get “buy in” with the video debrief. Then, suggest a drill where the offensive team doesn’t dribble and must shoot only after a set number of passes. The gamification component would be that the losing team has to run interval sprints. Clearly the defensive team is going to “buy in” to the lateral shuffle because it’s the most effective way to cover the court when the ball is moving through the air (pass) rather than on the ground (i.e., dribble). In this way, a coach motivates a behavior shift, which leads to skill acquisition in his or her players.

This is a prime example where motor learning is occurring without focusing on motor control. In this light, it becomes apparent why “correcting” faulty patterns becomes less cogent than designing an environment or task constraint, which challenges the relevant trait the individual needs for successful performance.

Teaching a person how to perform a skill in the office is valuable, but the real goal is to be better when participating in activities at home, work, or in recreation. This may be best achieved by constraints-based motor learning which utilizes altering the environment to create different challenges which the person has to problem-solve. In this way, motor learning is more likely to be transferable to real-life tasks. Otherwise a pure motor control approach which “corrects” faulty patterns may be “fool’s gold” by not being transferable.

Motor control is defined as “an area of science exploring how the nervous system interacts with the rest of the body and the environment in order to produce purposeful, coordinated movement.”⁷³ Latash’s definition represents a systems-oriented approach. It includes underlying neurocognitive, physiologic, and biomechanical mechanisms.

Motor control is a complex term with many varied opinions about what it means and how to apply it in practice. For instance, is it related to

For each, what do they actually mean and how should they be best addressed (Low)? Should shortening of hip flexors, which restrict hip hyperextension in the terminal propulsive phase of gait, be inhibited or stretched? Should the gluteals be cognitively activated or exercises introduced, which reactively potentiate them? Maybe the abdominal wall needs facilitation to create an ideal force converter for the hip? Possibly great toe flexion is inadequate, thus reducing the needed tensing of the plantar windlass mechanism kinetically linked to a high gear push off that hip hyperextension contributes to? Or, does it make more sense to practice vertical jumping, which is a task which nudges from an upstream perspective full hip extension. Or, maybe a dead lift, kettlebell swing, or broad (horizontal) jump could be used to use DST to focus on a task which involves an “attractor” state for complete hip extension.^33,74

There can be times when the raw materials or building blocks of movement (e.g., muscle strength, joint mobility) can be enhanced to enable specific training methods. Breaking complex patterns down into simple steps can help create the foundation for motor learning. Teaching a hip hinge is an example of a prerequisite for learning the dead lift teaching lifting mechanics. Notably, if ankle dorsiflexion is limited, ensuring a program to mobilize this joint is in place would give a person more options for safe, effective deep squats. This doesn’t mean optimizing ankle mobility will suddenly make a person a better squatter, but it is an upstream “hack,” which offers more optionality and affordance for successful performance and injury prevention.

According to Kraaijenhof,⁷⁶ “How a coach or trainer extrinsically creates a ‘nested’ learning environment conducive to skill acquisition is a foundational building block of performance enhancement. Motor control is a key component in both of these processes. Training motor control is a necessary, but frequently not sufficient, step since it must be transferable to the athlete’s activities and resilient to the stress and intricacies of performance. There are important neural and behavioral strategies related to how the nervous system learns, retains, and can apply new skills, which are vital to both growing and sustaining talent.”

Retention testing has shown that skill transfer is enhanced by environments that utilize contextual interference (CI; i.e., random practice) and on drill variations.^77,78,79,80 Early in the learning stages, blocked training may be preferable.^{74,81,82,83,84} This also has psychological benefit, so the athlete (and coach!) feels something is being accomplished. Moderately skilled learners benefit from a progressive increase in CI from a blocked to a random schedule.⁸⁵ It is hypothesized that training should start with blocked if the athlete is a child, the skill level is low, or the activity involves high-skill complexity.^86,87,88

When we speak of skill, the question of its quality is difficult to define operationally; it may be assessed on the basis of an efficiency or proficiency measure or on biomechanical loading parameters. What seems to be clear is that regardless of whether we are thinking about “whole vs. part” or “random vs. blocked,” the bottom line is that motor learning or skill acquisition occurs best in a nested environment where the anticipation, ramping up, and follow-up to a skill are included in the training.⁸⁹ The enemy of creating efficient, subcortical motor programs for newly acquired skills is task decomposition where a task is separated into smaller parts during practice.⁹⁰ Ecologic dynamics suggests that motor learning is facilitated by utilization of a nested task where perception-action coupling occurs.⁸⁹

Perception and action are linked in the ecologic approach where the individual and environment together determine human functioning. This is at the heart of the ICF pivot from medical to functional rehabilitation. According to Davids,⁸⁹ in a sports setting, … implies that learning design should emphasize keeping information and movements together to allow athletes to couple their actions to key information sources which are available in performance and practice environments.” This can be contrasted with a rehabilitation setting where, by virtue of the “rehab” setting, it is difficult to recreate the lived environment where disability occurs.

The modern ICF view of rehabilitation begins to resonate “at the interface between an individual’s set of capabilities—or effectivities—and the opportunities offered by the environment for realization of his or her goals—affordances, in ecological theory.”⁷ Successful functional performance is contingent on a good affordance-effectivity fit (see Fig. 53).^23,92,93 Why is a theory of perception and action essential to this process?

An example of a practice-training device (in common use in baseball or tennis) that is inconsistent with valid ecologic dynamic is a ball machine. This may provide a tennis or baseball hitter with information about ball flight but is limited by the absence of information about the pitcher’s or tennis opponent’s actions.

For the training or practice environment to be ecologically valid, it should replicate the performance environment in key areas so that perceptual inputs (visual, auditory, etc.) can be coupled to kinesthetic outputs of the individual.^89,94 One simple way to enhance ecologic validity of a training exercise is to make it dynamic instead of static, upright instead of recumbent, or triplanar instead or uniplanar. At the end of the day, we want practice to simulate performance in sport.

In what is termed “nonlinear pedagogy,” realistic performance simulations are created that present opportunities for athletes to discover their own performance solutions.^31,94,95,96 In more traditional approaches to coaching, detailed verbal instructions and “ready-made” repetitive practice are prescribed, whereas in nonlinear pedagogy, athletes are presented with problems to solve involving unique constraints designed by their coach.⁹⁷

Discovery versus rote practice in nonlinear pedagogy practice is seen as “… a process of searching a perceptual-motor landscape composed of interacting personal, task and environmental constraints…. instead of attempting to change athlete behavior through highly prescriptive instructions, which might short-circuit the discovery and exploration process of learning, the coach becomes a facilitator …” who designs training and learning tasks to bring about functional changes in behavior.⁸⁹

“The optimal pattern of coordination is determined by the interaction among constraints specified by the person, the environment, and the task.”³³ Optimal is a moving target that depends on the individual’s evolving goals and abilities.

An important irony is that while the goal is to achieve automated, efficient movement patterns, the stages by which one learns in practice are constantly recapitulated. Automatization in competition and performance is the peak our athletes (and musicians) strive to accomplish. However, in practice, cognitive and physical components are ideally both engaged in what is termed “deliberate practice.”⁹⁸ This is consistent with the premise that Fitts and Posners’⁹⁹ Stage Model for motor learning is not merely temporal, but even an elite athlete will learn a new skill via a recapitulation of all three stages as well (cognitive, developmental, and autonomous).

“Permanent gains in skilled performance capacity are only achieved when cognitive and physical training occur in tandem.¹⁰⁰ This is the concept of deliberate practice, which has been presented as a key determinant of elite performance.”¹⁰¹

Systems theory applied to neuroscience explains the nonlinear, non-reductionist way in which our brain learns. A combination of cognitive and physical effort is required to lay down a rich and varied neural matrix with a high concentration of synaptic connections bridging pattern recognition and movement automatization centers.^{102,103,104,105} Thus, expertise is achieved because a relevant “weak link” is identified. Then, it is challenged so that new “guardrails” for movements can be “wired.”

Studies have shown that if coaching instruction emphasizes the “correct” versus “incorrect” pattern that skill can be acquired more quickly. Paradoxically however, its retention actually suffers from this type of training which is called “blocked.”⁸⁰ A different form of training, called “random,” actually lets a person problem-solve with external feedback from a goal such as jumping as high as possible, or pointing a finger toward a target. As Pr McGill says, “The best cue is the one that achieves the desired outcome.” Let movement processes and outcomes be the guide to design and administer “practice.”

More often than not in life, movements are performed in unique rather than stereotypical ways because of changing environmental, tactical, or strategic contexts. In fact, our brain learns the process of how to adapt via exposure to novel or variable situations. So we should train with this in mind. “The concept of the human beings as complex dynamic systems changes the mechanical view of athletes and the adaptation process based on the computer metaphor. This change in paradigm affects training proposals stemming from classical training theories and leads to
a demand for its principles to be updated…The concept of the correct or right response has been fundamentally changed by the new paradigm. According to the research results obtained by applying DST to the study of human movement, the athlete does not need to know the solution of a new task beforehand.”¹⁰⁶

A challenging way to consider how we learn to control movement is that it depends heavily on exposure to learning opportunities as opposed to being told how to move. Todd Hargrove³⁰ says, “Movements are not ‘right’ or ‘wrong’ … it depends on the goal, the individual, the context … Teach movement by giving more choices and awareness, NOT by telling people how to move.” The famous movement therapist Moishe Feldenkrais went as far as saying “it is incorrect to correct.” This is an extreme example, but perhaps it is just as radical to think telling a person exactly what a movement pattern should look like will lead to an individual developing the skill to solve unpredictable motor challenges in the future. In fact, Wulf (2008) says, “Precise movement correction by strength coaches and PTs, for instance during trunk control exercises, are thus not so much a sign of professional expertise as a sign of ignorance about how movements are controlled. Well-intentioned but misapplied expertise can often by highly damaging.”¹⁰⁷

The bigger question is why are we using the trunk control exercise in the first place? Are we trying to teach someone an “optimal” exercise technique (winning the exercise), or trying to elicit a specific adaptation for a well-defined purpose (winning the adaptation)? For example, can a trunk control exercise be coached in a way that enhances positional awareness through direct perception? Or, can it be used to build basic muscle capacity in a deconditioned person, which could serve as the raw materials needed to enable him/her to solve more complex problems in “their way” through the techniques espoused in this quote?

Trunk control exercises, regardless of how they are administered, won’t magically transfer to different/more complex tasks without using specific techniques to facilitate transfer (e.g., CLA). But, for some, they can build awareness, change beliefs, improve motivation, etc., and prescriptive cueing could potentially facilitate this.

A final component in training is problem-solving. Most life activities involve decision-making in real time. If we “think” it slows us down and we are unable to react efficiently.¹⁰⁸ The movement challenges shown here utilize problem-solving and lend themselves to being reactive in nature because you and your partner move as a unit responding to each other. In the two examples shown here, the partner squat and single leg hinge, the goal is to maintain balance and tension while performing the movement. It’s best to figure out what works for you rather than thinking of tightening your abdominal or gluteal muscles.

Most pain complaints do not arise from a sudden traumatic injury, but rather they arise insidiously without a known antecedent even. McGill states, “There is a tendency among those reporting or describing the back injury to identify a single specific event as the cause of the damage, such as lifting a box and twisting. This description of low back injury is common, particularly among the occupational/medical community who are often required to identify a single event when filling out injury reporting forms. However, relatively few low back injuries occur from a single event. Rather, the culminating injury event was preceded by a history of excessive loading that gradually, but progressively, reduced the level of tolerance to tissue failure.¹⁰⁹ Thus, other scenarios in which subfailure loads can result in injury are probably more important. For example, the ultimate failure of a tissue (i.e., injury) can result from accumulated trauma produced either by repeated application of load (and failure from fatigue) or of a sustained load that is applied for long durations or repetitively applied (and failure from deformation and strain). Thus, the injury process may not always be associated with loads of high magnitude.”

Naturally it is not hard to see how a fracture, sprained ankle, or torn knee ligament occurs from sudden trauma (Fig. 5.6). Or even a bony stress injury from repetitive strain. However, LBP presents a mystery because the correlation of structural pathology and pain is tenuous.

Although biomechanists have been able to successfully explain how strenuous exertions cause specific low back tissue damage, explaining how injury occurs from tasks such as picking up a pencil from the floor has
been more challenging. Recent evidence suggests that such injuries are real and result from the spine buckling or exhibiting unstable behavior. But this buckling mechanism can occur during far more challenging exertions as well (Fig. 5.7).

A number of years ago we were investigating the mechanics of power-lifter spines while they lifted extremely heavy loads using video fluoroscopy to view their vertebrae in the sagittal plane. During their lifts, even though the lifters outwardly appeared to fully flex their spines, in fact their spines were 2 to 3 degrees per joint from full flexion, thus explaining how they could lift magnificent loads without sustaining injury—the risk of disc and ligamentous damage is greatly elevated when the spine is fully flexed (which the lifters skillfully avoided). We happened to capture one injury on the fluoroscopic motion film—the first such observation that we know of. During the injury incident, just as the semi squatting lifter had lifted the load approximately 10 cm off the floor, only the L2/L3 joint briefly rotated to the full flexion calibrated angle and exceeded it by one-half a degree, whereas all other lumbar joints maintained their static positions (not fully flexed).¹¹⁰ The spine buckled! Sophisticated modeling analysis revealed that buckling can occur from a motor control error in which a short and temporary reduction in activation to one, or more, of the intersegmental muscles would cause rotation of just a single joint so that passive or other tissues become irritated or possibly injured.¹¹¹

Adams and Dolan¹¹² have noted that passive tissues begin to damage with bending moments of 60 Nm—this occurs simply with the weight of the torso when bending over and a temporary loss of muscular support. This scenario is not an excessive task, but it is often reported to clinicians by patients as the event that caused their injury (i.e., picking up a pencil). However, reporting of such an event will not be found in the scientific literature. Medical personnel would not record this event because in many jurisdictions it would not be deemed a compensable injury—the medical report attributes the cause elsewhere.

In vitro, a ligamentous lumbar spine buckles under compressive loading at approximately 90 Newtons (approximately 20 lb) highlighting the critical role of the musculature to stiffen the spine against buckling (with the critical work and analysis of the passive tissues being performed by Crisco and Panjabi¹¹³).

Theories about bending with a neutral spine arise from this biomechanical perspective (Figs. 5.8 and 5.9).

The biomechanical hypothesis for LBP persistence independent of trauma is described thusly, so long as the patient has the behavioral tendency to routinely bend the spine to extremes, even when external loads are negligible, then perhaps the passive structures’ load tolerance decreases over time. The question remains for the “pure” biomechanical approach that we lack evidence that measurements of high frequency or poorly timed extreme spine bending patterns correlate either prospectively or even retrospectively with LBP. This is the same argument hoisted against claims that structural pathology “causes” LBP. We can ask does this work in concert with a “sensitized” patient such that in cases of persistent pain these mechanisms will be perpetuating factors prolonging the disability cycle? Or, can such “behavioral patterns” predispose one to LBP independent of psychosocial factors?

From the biomechanical evidence presented previously, it follows that it is not reasonable to recommend lifting heavy external loads (including mass and speed) with extremes of spinal flexion. However, most things are not black and white and in light of evidence that we now have, we have to admit that the abovementioned perspective is controversial.¹¹⁴ In short, there’s biomechanical and epidemiologic data that should be considered appropriately, in addition to load sharing concepts (see the next section). Note that a disc can be loaded without flexing it … it’s like a pressurized vessel … even with a neutral spine, the tissues experience deformations and thus can be mechano-stimulated. It is well known that different musculoskeletal tissues have different adaptive capabilities and different timescales of adaptation. The composition and organization of constituent materials influence the adaptive capabilities (in addition to other systemic factors, of course, such as nutrition, hormones).

According to McGill’s¹¹⁶ work, the structural tolerance of the spine system is affected by coordination and control. If we think of a structure like a bridge, it can collapse because the elements (building blocks) aren’t organized properly (spine-stiffening coordination and control patterns), not because the elements (e.g., ligaments) are faulty/weak. In this case, elements will fail because the bridge collapses, but the collapse was due to bad engineering, not bad manufacturing (of materials). According to Reeves and Cholewicki,¹¹⁷ McGill’s perspective is representative of a static stability situation (i.e., stability of equilibrium); however, the authors also discussed how stability theory applies to spinal mechanics and control in dynamic situations. In the latter approach, stability refers to the ability to establish and maintain the required spine motion trajectory to solve whole-body movement problems. They cited examples to show that too much spine stiffness (e.g., via superfluous trunk muscle co-activation) could impair global system performance (e.g., wholebody balance control). Both notions of static and dynamic spine stability suggest that spine system robustness and performance require that trunk muscles coordination patterns are appropriately “tuned” to meet task demands, which is a foundational principle of McGill’s biomechanical approach.

Spinal and whole-body stability are two distinct, but related, phenomena. Whole-body stability is the body’s ability to maintain equilibrium, especially after being subjected to external forces that temporarily destabilize it.¹¹⁸ Equilibrium is the ability to maintain the body’s center of mass over a stable base of support. Spine stability can more narrowly be defined as the ability of the spinal column or its components to resist buckling when undergoing load. Although the spine is likened to an inverted pendulum, and thus a highly unstable system (see Chapter 2, Fig. 2.2), this is not necessarily a negative characteristic. The body is a complex and adaptable system; for this to occur, we must balance the system at the edge of chaos.¹¹⁹ This “edge of chaos” can be thought of as the space between order and disorder and the constant dynamic interplay between the two. For adaptability to occur, the system needs to be able to produce a variety of behaviors. To create this variety of behaviors, the system needs to exhibit several degrees of freedom. However, there is a point of diminishing returns in relationship to variability.¹²⁰ Too much variability will lead to an uncontrolled system, whereas too little variability will lead to a system that is not flexible enough to handle perturbation.¹²⁰

Various forces such as stretch, compression, shear, or torsion can be involved in spinal stability. A classic model, according to Panjabi, posits that three subsystems work together to maintain spine stability.¹²¹ They are the central nervous subsystem (control), an osteoligamentous subsystem (passive), and a muscle subsystem (active) (see Chapter 2, Fig. 2.3). He states, “The neural subsystem receives information from the transducers, determines specific requirements for spinal stability, and causes the active subsystem to achieve the stability goal.” A contemporary view of connective tissue and ligamentous structures reveals there is an active component of connective tissue compared with the traditional view of passive restraint.¹²² Jaap van der Wall’s¹²² research has shown an “in-series” orientation of connective tissue that allows for a dynamic tuning of forces across joints to maintain integrity. Because of lack of favorable clinical effect, Panjabi’s spine stability model has been challenged in recent years.

Previous research has suggested that increased stiffness leads to increased spinal stability. This has created confusion for clinicians and exercise professionals alike. If a static definition of stability is used, then it would make sense to create as much stiffness as possible.¹¹⁷ Exercises would be engineered to increase spinal stiffness; this increase in stiffness would lead to improved stability.¹¹⁷ If a dynamic systems approach is taken to examine spinal stability, then stiffness is only one part of the equation. Feedback control and dampening must both be present when addressing stability from a dynamic perspective.¹²³ According to Srinivasan and Mattiassen’s¹²⁴ research, LBP leads to increased trunk stiffness, but too much stiffness decreases the ability to dampen movement. The increased stiffness decreases the amount of movement options available and this decrease in variability minimizes the system’s ability to adapt to changing environments.

Bergmark’s research is the first to look at the potential energy of the spine system.¹²⁵ This research defined spinal stability from a static perspective. There have been additional studies that have come to similar conclusions. A key finding of this original research was that stiffness was required for stability and a lack of stiffness could be attributed to possible injury.¹²⁵ Reeves asks the question, “is it always better to have a stiffer spine to reduce the risk of injury?” Reeves’s conclusion was in specific high load situations, that is, before a body check in hockey more stiffness is appropriate.¹²⁵ However, in situations where fine or precise motor control is important, less stiffness may be desirable. An example where less stiffness may be desirable can be seen in the investigation of skilled marksmen.^120,126 The conclusion was skilled shooters had increased accuracy and reduced errors when they allowed the arm to produce variable movements
compared with novice shooters who used a rigid arm to try to produce stability.^120,126 This also highlights the difference between end point variability and coordinative variability. In skilled marksmen, there is an increased amount of coordinative variability but a decreased amount of end point variability.¹²⁰ This has also been shown in cellists, where the novice cellist freezes his or her degrees of freedom to try and maintain control and coordination. This is in contrast to the expert who demonstrates a variable pattern of coordination, which improves task performance.¹²⁷ The body has redundant ways of accomplishing the same task.^73,128 This allows the body to be adaptable and give the person more options to optimize task performance. This is shown in the expert marksmen. Although there was increased variety in the way they achieved their goal, they were more consistent in achieving the end goal compared with novice marksmen.¹²⁰

When load management and load sharing concepts have been investigated simultaneously, it has been shown that load management is the more fundamental (Table 5.1).¹²⁹ However, based on the preceding text, it is evident that the load management and load sharing concepts are interrelated, at least at the level of low back structures. The way a performer coordinates and controls his or her movements will dictate how the mechanical loads are distributed internally among spinal structures. So, movement coordination and control patterns can be guided and shaped in training contexts to effectively regulate tissue loading via load distribution.

Should we “work-harden” the anterior cruciate ligament (ACL) in attempt to reduce ACL injuries, and/or should we (re)train people to avoid relying on the ACL as part of their habitual control strategies? How strong can we make the ACL, and how long would it take? How would we target it with sufficient specificity to progressively overload it?

Such an approach might in theory be easier to apply to a discreet structure like the Achilles tendon, but might be more difficult for more complex areas like the lumbar spine.

The blending of load science and motor control science results in well-coached movement, so tissues can respond/adapt as needed. This will lay down more/stronger tissue. From a motor control perspective, we want to optimize the efficiency of patterns to reduce stress/strain and recovery needs. These two approaches are distinct yet complementary windows blending both (a patterns view AND a parts perspective!!!).

The question of the safety of loading the spine in trunk flexion is but one example of the slippery slope of assuming in our definitions that we are comparing apples to apples.¹³⁰ Science is full of revolutions whereby paradigms are overturned—Copernican to Newtonian to Quantum. When a more powerful set of rules are discovered and elaborated, the knowledge transfer from discovery to dissemination to implementation may take decades or even a generation.¹³¹

In a nutshell, three crucial things must be known in order to ascertain risk—has the person suffered from a similar injury or pain in the past, what is the person’s physical demands, and what is the person’s physical capacity to handle those demands. A past history of similar complaint is the number one predictor of a future problem. Beyond that, a high demand combined with a capacity shortfall may lead to injury or pain. The key to increasing a person’s resilience is to increase functional integrity or capacity. Functional capacity must exceed the physiologic demands or stress of one’s sport or activities (Fig. 5.10). The surplus capacity will provide a stability margin of error, therefore reducing injury risk. Functional capacity as a concept is one which is built on a foundation of movement competency.

From the aforementioned, it would seem that tissue injury is related to pain severity. It would also seem that tissue pathology is related to pain severity. However, as outlined in Chapters 1, 2, 3, such a structural view or Bio perspective is grossly incomplete.

Degenerative changes to the spine, for example, are normal signs of aging and while they may correlate with symptoms, they are insufficient as a cause of pain or disability. The incidence of pathology is nearly 50% in asymptomatic people and does not even predict a higher future risk of disability (see Fig. 3.6).

Lewis and O’Sullivan¹³³ stated, “First, structural changes observed on imaging that are highly prevalent in pain free populations, such as rotator cuff tears, intervertebral disc degeneration, labral tears and cartilage changes, are ascribed to individuals as a diagnosis for their condition. In this context, this information may result in the individual believing that their body is damaged, fragile and in need of protection, resulting in a cascade of movement and activity avoidance behaviors and seeking interventions to correct the structural deficits. This trend has led to exponential increases in elective surgery rates and associated costs, while the efficacy of repairing (e.g., rotator cuff and medical meniscal tears), reshaping (e.g., subacromial decompression) or replacing (e.g., lumbar intervertebral discs) the structures considered to be at fault has been substantially challenged.”

Haven’t we all seen dozens, hundreds, or even thousands of patients who’ve been told the cause of their pain is spine degeneration, a herniated disc, or narrow spinal canal? Often they are told they have a compressed nerve when their symptoms are localized in the low back with no referred pain whatsoever! Inevitably, these patients are frustrated and don’t see how they can improve without recourse to surgery. To top it off, naturally no one has informed them of

According to Brukner and Khan,¹³⁴ “The critical concept is that pain is not a measure of tissue damage,
but an indicator of the brain’s conviction about the need to protect certain tissue.” Pain is a complex, subjective experience that may or may not depend on external stimuli (i.e., phantom or ghost pain). The chronic pain patient may have central sensitization just as an amputee can, but because they still have the limb, they are under the illusion that the pain is coming from the tissue. We should reconceptualize pain away from a binary construct of it being an input or output to the likelihood that it is both.

In this way, we can see that when we perform an MRI to rule out a tumor or infection, we are not performing it to find the “cause” of the pain. The same is true for impairment tests such as range of motion or isolated strength measures. Similarly, when we examine the function, motor control, movement patterns, “stability”, or biomechanics of our patient, how certain are we that what we find is a source of the trouble and not natural variability or healthy compensation?

When we find faults in structure, impairment, or function and symbolically tell a person that what we found is the cause of their pain or disability, in many ways we are providing a nocebo by increasing a person’s threat or taking away their self-confidence.

This author has always contended that there is a hierarchy such that identifying functional pathology has much less downside risk than identifying structural pathology because our interventions are (a) less invasive and (b) typically involve self-care and are thus empowering. However, it must be acknowledged that if a person thinks “something is wrong,” “out of alignment,” or “unstable,” they may maintain heightened pain hypervigilance, threat, and overprotection.

However, even if we don’t know the exact cause of pain and must acknowledge that to the patient, this can lead to distress, disillusionment, and despair.

So this is a bit of an enigma. How to bridge the gap between evidence-based practice, pain science, biomechanics, our theories and values as well as those of our patients.

An unfortunate message that is being promoted is one which takes away hope from patients.¹³⁵

Contrast this with this statement from Deyo and Weinstein,¹³⁶ “the emerging picture is that of a chronic problem with intermittent exacerbations, analogous to asthma, rather than an acute disease that can be cured.” In both quotes the concept of cure is being deemphasized. In the former, the emphasis is on learning to “live with their pain,” whereas in the latter, the pain will come and go “intermittent exacerbations.” According to Von Korff,¹³⁷ chronic back pain, like asthma or diabetes, may not have a cure, but with lifestyle adjustments and appropriate self-management control of symptoms, it can be achieved.

Rather than promising to cure disabling pain, it is more achievable to swerve to an emphasis on symptom control and tolerance, especially for a condition which, like the common cold, is likely to recur (over and over again). What we don’t want is to fearmonger by emphasizing false-positive structural pathologies that can only be corrected by surgery or to reduce
self-efficacy by explaining with certainty that potentially coincidental or compensatory functional pathologies are the clear cause of pain.¹³⁶

Complex systems theory (see Chapter 1) is an invaluable construct for managing nonlinear interacting phenomena such as pain, disability, and pathology (see Chapter 4 Figs. 4.7 and 4.8). Suggesting back pain is nonspecific is not a sign of ignorance, but rather a scientifically robust position given all the interacting variables swirling. According to Jarod Hall, “90% of back pain isn’t non-specific because there’s no specific tissue based input that is driving the experience. It’s non-specific because 90% of back pain is far too complex and multimodal to isolate down to any single factor, thinking, or simple tissue-based answer.”—Dr. Jarod Hall, PT, DPT, OCS

George EP Box¹³⁸ says, “Essentially, all models are wrong, but some are useful” This drives us to being systematic rather than forcing patients into our “system” or algorithm. Having a checklist is helpful for ruling out sinister disease processes, just as it makes surgery, or flying an airplane safe. “Uncertainty may be uncomfortable for some, it is nevertheless a critical first step…. Cast off the shackles that come with being bound to a regimented system of operating. Freedom permits exploration and allows practice to evolve over time.”¹³⁹ This is termed having an agile mind-set, which has been shown to be beneficial for navigating an uncertain, nonlinear landscape such as disabling back pain.

If we look at shoulder problems, we know—like LBP—most are persistent. Forty percent have symptoms at 1 year. There are many “labels” hypothesized to describe the condition.

According to Littlewood,¹⁴⁰ the most popular term subacromial impingement is outdated, unhelpful, and harmful.

Outdated because the common observation of a painful arc of motion led to a theory that decompressing surgery would resolve the mechanism of impingement. However, surgery is no better than structured exercise.¹⁴¹ Those who improve did not sustain the results long term.¹⁴² Therefore, it is not surprising that Beard¹⁴³ showed that placebo surgery was as effective as arthroscopic surgery. Because different treatments achieve similar results, the diagnostic label does not adequately explain the pain.