Beyond Mechanics: Understanding Movement as a Complex Emergent Phenomenon

For decades, the fields of physical therapy, sports science, and coaching have operated under a largely reductionist paradigm. We have often viewed the human body as a machine—a collection of parts that can be fixed, tuned, and optimized in isolation. However, a growing body of evidence and a shift toward dynamical systems theory suggest that this perspective may be incomplete.

To truly understand how we move, we must shift away from rigid classifications based on anatomical and physiological deviations from a perceived "normal" and instead focus on the interdependencies of the systems that comprise the human body (Glazier and Davids, 2009; Guccione, Neville and George, 2019).

This article explores the concept of movement systems, how movement patterns emerge through the interaction of complex constraints, and why "movement solutions" are more important than "ideal forms" in the world of coaching and rehabilitation.

Defining Movement Systems

The term "movement system" has evolved from a simple descriptive label to a well-defined construct for understanding human health and performance. Formally, it has been defined as the collection of systems—cardiovascular, pulmonary, endocrine, integumentary, nervous, and musculoskeletal—that interact to move the body or its component parts (APTA, 2018).

While this definition properly describe the physiological hardware involved, it often falls into the trap of seeming a rigid and nearly pleonastic description (i.e., the movement system is what moves us).

The real value in the concept lies not in a list of organs and tissues, but in understanding how these systems function in an integrated way to produce purposeful behavior. Based on this view, movement is not considered only as a physiological output; it is a phenotypic behavioral expression that changes dynamically over time (Guccione, Neville and George, 2019).

Integration of multiple, nonlinear inputs (ie, capabilities/resources, constraints) from which purposeful movement emerges (from Guccione, Neville and George, 2019)

Movement as an Emergent Phenomenon

One of the most critical shifts in modern movement science is the transition to considering movement as an emergent phenomenon. In a complex system, emergence occurs when a purposeful behavior—such as walking, reaching, or lifting—arises from the self-organizing interaction of multiple nonlinear inputs (Holt, Wagenaar and Saltzman, 2010).

This means movement is not a pre-programmed command sent from the brain to the muscles. Instead, it is a spontaneous behavior that emerges from the resolution of various constraints.

Constraints, in turn, are not necessarily limitations in a negative sense; rather, they are variables that regulate change by restricting the possibilities available for configuring a movement.

According to the framework popularized by Karl Newell (1986), these constraints fall into three primary categories: organismic, task, and environmental.

1. Organismic Constraints

These arise within the individual and include both structural and functional resources. To understand an individual's movement, a coach or therapist must ask whether the person possesses the structural support (integrity, alignment, load capacity) to perform the task. Other organismic constraints include:

• Ideation: Does the individual understand the movement and have the attention and motivation to perform it?

• Initiation: Can they generate enough force through activation and recruitment?

• Execution: Do they exhibit multisegmental actions without extraneous motion?

• Equilibrium: Can they stabilize after transitioning to a new posture?

• Allostasis and Sustainability: Does the system support appropriate thermoregulation and have the metabolic capacity to meet the energy demands?

2. Task Constraints

Task constraints are specific to the goal being performed. They include the composition of the task (its complexity or repetitiveness), the order or sequence required, and temporal characteristic (speed or volume expectations). A task might also impose a high cognitive load or a specific bioenergetic demand that exceeds the individual's current capacity. Finally, the proficiency or minimum skill threshold required to achieve a goal acts as a major constraint on how a movement pattern will shape itself.

3. Environmental Constraints

These are externally imposed by the conditions surrounding the performance environment. They include the physical location (is the body stable or in transport?), the predictability of the surroundings, and the geography or terrain. Even regulatory control—i.e. the rules or restrictions imposed on how a task must be executed—acts as an environmental constraint.

Movement, therefore, can be seen as a self-organizing resolution of these specific constraints to achieve a desired performance outcome (Davids et al., 2003).

The Role of Motor Variability and Movement Solutions

In traditional coaching circles, variability is often flagged as error—a sort of inability to hit an ideal and perfect technical model.

However, a dynamical systems approach completely overturns this view. In such a model, movement is described as an attempt to find a solution to a practical problem (like standing, walking, or grasping) embedded in a specific set of conditions (Shumway-Cook and Woollacott, 2012; Newell, 1986).

The Degrees of Freedom (DOF) Problem

Human movement involves a high number of Degrees of Freedom (DOF)—the independent coordinates (joints, muscles, motor units) required to describe the configuration of the system. A major challenge for movement systems is determining how to control these many variables.

• Novices often struggle with task constraints and may freeze or rigidly fix their DOF to simplify the movement (Sparrow and Newell, 1998).

• Skilled athletes, on the other hand, are adept at exploiting the high dimensionality of their own movement system. They can freeze or unfreeze DOF in the chain of movement based on the immediate demand, allowing for what has been defined as compensatory variability (Davids et al., 2003).

Bounded Variability

Because no two tasks or environments are exactly identical, there is no single ideal movement that can be applied across all conditions. Instead, there is a bandwidth of successful movement solutions that are highly variable. This is known as bounded variability (Guccione, Neville and George, 2019; Fetters, 2010).

Variability is not the consequence of a motor error; it is an attempt to self-organize in order to achieve a desired performance within an acceptable range.

In fact, having neither too much nor too little variability is desirable. Variability prevents the system from becoming too stable or "stuck," allowing the individual to find effective solutions in complex, ever-changing environments.

Redefining Optimal Movement

If there is no ideal form, how do we define optimal movement? Many traditional metrics rely on an external, abstract reference of what correct movement looks like. However, movement optimization is better considered from the perspective of the individual and the specific confluence of constraints they are facing at that moment.

Because constraints—such as fatigue, environmental changes, or task complexity—fluctuate continuously, the optimal pattern of coordination and control must also change accordingly (Glazier and Davids, 2009).

One key metric for movement optimization is movement economy. Adaptive patterns often emerge as a function of the organism's drive to minimize metabolic energy expenditure relative to the task and environment. Essentially, an optimized movement is a perpetual balancing act between the work done and the metabolic cost of that work.

Shifting Coaching and Clinical Practices

A complex systems approach has profound implications for how we coach and rehabilitate athletes. It forces a radical departure from narrow, impairment-based approaches.

From Diagnosis to Prognosis

Historically, practitioners have focused on diagnosis—identifying a static label for what is wrong with an organism's structure or function. But in a dynamical system, the state of the individual is far from equilibrium, and minute changes can result in nonlinear, disproportionate changes in how they move (Doll and Trueit, 2010).

Instead of looking for a static label, we should view initial examination findings as initial conditions.

Then the focus shifts from "What is the impairment?" to "What is likely to happen?".

This is a shift from diagnosis to prognosis. Coaching and intervention should be about predicting how an individual's behavioral repertoire will change over time in response to specific treatments or training (Croft et al., 2015).

Coaching as "Coaching Adaptation"

If movement is an emergent solution, then the role of the coach or therapist is not to fix a something dysfunctional, but to create the conditions for coaching adaptation.

This involves:

1. Identifying Key Constraints: recognizing which constraints (organismic, task, or environmental) are the most heavily "weighted" or influential in contributing to the current movement pattern

2. Manipulating Constraints: instead of giving verbal cues on how to move "correctly", a coach might change the task (i.e., changing the weight of a ball) or the environment (i.e., changing the surface) to encourage the athlete to self-organize into a more efficient solution

3. Encouraging Functional Variability: helping the athlete move from a rigid, "frozen" state to a more flexible one where they can exploit their degrees of freedom to solve problems

4. Leveraging History: understanding that a system's current behavior is influenced by its own history—its previous attempts at solutions and its phenotypic response to prior interventions.

The "Complex Web of Determinants"

Ultimately, physical therapists and coaches are working within a "complex web of determinants" (Philippe and Mansi, 1998). Every movement solution is highly individual.

When we make an exercise or therapeutic interventions, we aren't just correcting an isolated dysfunction; however, we are attempting to restore or improve the relationships between the interdependent components of the movement system.

The goal is to guide the system toward a state where the athlete has a wide range of movement repertoire to achieve successful outcomes across various tasks and environments. This requires ongoing assessment of dynamic interdependencies rather than a one-time "fix".

The transition toward a complex systems approach to human movement is more than just a change in terminology; it's a fundamental shift in how we perceive human capability.

By recognizing that movement emerges from an intricate interactions between organismic, task, and environmental constraints, we can move away from the frustration of trying to force every individual into a single "ideal" model.

For coaches and therapists, this means embracing motor variability as a positive and healthy sign of a highly functioning system rather than an error to be corrected.

It means shifting our focus from static anatomical deviations to the dynamic, nonlinear interdependencies of the body's different systems.

As soon as coaches recognize that their role is to facilitate self-organization and adaptation, we can better help athletes find their own optimal movement solutions, leading to improved performance, better health outcomes, and a deeper appreciation for the incredible complexity of the human body in motion.

In the next article i will explore how to practically distinguish safe movement solutions from abnormal movement limitations.

References

Croft, P. et al. (2015) 'The science of clinical practice: disease diagnosis or patient prognosis? Evidence about "what is likely to happen" should shape clinical practice', BMC Medicine, 30:13:20.

Davids, K, Glazier, P., Araujo, D. and Bartlett, R. (2003) 'Movement systems as dynamical systems: the functional role of variability and its implications for sports medicine', Sports Medicine, 33(4), pp. 245–260.

Doll, W. E. and Trueit, D. (2010) 'Complexity and the health care professions', Journal of Evaluation in Clinical Practice, 16(4), pp. 841–848.

Fetters, L. (2010) 'Perspective on variability in the development of human action', Physical Therapy, 90(12), pp. 1860–1867.

Glazier, P. S. and Davids, K. (2009) 'Constraints on the complete optimization of human motion', Sports Medicine, 39(1), pp. 15–28.

Guccione, A. A., Neville, B. T. and George, S. Z. (2019) 'Optimization of movement: a dynamical systems approach to movement systems as emergent phenomena', Physical Therapy, 99(1), pp. 3–9.

Holt, K. G., Wagenaar, R. O. and Saltzman, E. (2010) 'A dynamic systems/constraints approach to rehabilitation', Revista Brasileira de Fisioterapia, 14(6), pp. 446–463.

Philippe, P. and Mansi, O. (1998) 'Nonlinearity in the epidemiology of complex health and disease processes', Theoretical Medicine and Bioethics, 19(6), pp. 591–607.

Newell, K. M. (1986) 'Constraints on the development of coordination', in Wade, M. G. and Whiting, H. T. A. (ed.) Motor development in children: aspects of coordination and control. Dordrecht: Springer Netherlands

Shumway-Cook, A. and Woollacott, M. H. (2012) 'Control: translating research into clinical practice'. 4th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.

Sparrow, W. A. and Newell, K. M (1998) 'Metabolic energy expenditure and the regulation of movement economy', Psychonomic Bulletin & Review, 5, pp. 173–196.

Antonio Robustelli is the mastermind behind Omniathlete. He is an international high performance consultant and sought-after speaker in the area of Sport Science and Sports Medicine, working all over the world with individual athletes (including participation in the last 5 Olympics) as well as professional teams in soccer, basketball, rugby, baseball since 23 years. Currently serving as Faculty Member and Programme Leader at the National Institute of Sports in India (SAI-NSNIS).