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Body Size and Movement

John H. Challis

Humans of different sizes move in very similar ways despite the size difference. The principles of geometric scaling provide insight into the reasons for the similar movement patterns observed. In human locomotion, body size influences endurance running performance, with shorter body sizes being an advantage due to better heat exchange compared with their taller counterparts. Scaling can also show the equivalence of child gait with that of adults in terms of stride length and walking velocity. In humans, maximum jump height is independent of standing height, a scaling result which has been validated by examining jumps with mass added to the body. Finally, strength scales in proportion to body mass to the two-thirds power, which explains why shorter people have greater relative body strength compared with taller individuals. Geometric scaling reveals the underlying principles of many human movement forms.

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Brain Dynamics and Motor Behavior: A Case for Efficiency and Refinement for Superior Performance

Bradley D. Hatfield

The paper presents a theoretical perspective on brain activity that characterizes expert cognitive-motor performance grounded in neural and psychomotor efficiency. Evidence for the position is derived from several different measurement tools (EEG, ERPs, fMRI, EEG coherence) based on empirical studies of (1) expert-novice contrasts, (2) changes in the brain after practice, and (3) motor performance under conditions of mental stress. The impact of mental stress on brain processes during motor performance is then discussed followed by a model of the hypothesized central neural responses to emotion-eliciting events to explain resilience to stress and the ability to “perform under pressure” as observed in high-performing athletes. An overall explanation is offered of the cascade of events that link the perception of the environment in which the performance occurs to the peripheral process of motor unit recruitment and the resultant quality of movement. This integrative perspective on human performance considers multiple levels of explanation including the psychology of sport performance, cognitive-motor neuroscience, and basic biomechanics to understand the kinematic qualities of movement and the effort cost involved.

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Concussion: A Window Into Brain–Movement Relations in Motor Control

Michael Gay and Semyon Slobounov

Research into sports-related concussion (SRC) or brain injury has vastly expanded our knowledge of the connection between brain activity and behavioral outcomes. Historical examination of concussion reveals components of structural changes in the brain resulting from injury. A constellation of clinical symptoms is typically present following concussion for several days and weeks. However, the intersection of structural changes and clinical examination still remains elusive to medical professionals. With emerging technologies and modalities such as quantitative electroencephalography (EEG), functional magnetic resonance imaging (fMRI), virtual reality (VR), and the study of movement, we can better understand the brain–behavior relationship on clinical findings post-injury. Our advancement in SRC study using athletics provides a unique window into the advances in our ability to study this public health crisis. SRC also allows us to understand how athletics and exercise influence brain health. The evolution of SRC diagnosis, treatment, and management informs our current abilities in the study of the brain.

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Ecological Physics and the Perceptual Information That Supports Motor Control

Thomas A. Stoffregen

Ordinary behavior, such as walking, reading, and throwing, depends on real-time perceptual guidance. In this article, I discuss the nature of perceptual information that, in principle, might be sufficient for the guidance of movement to achieve behavioral goals. I argue that we achieve behavioral goals by controlling movements relative to multiple physical referents. Movement relative to different physical referents causes changes in the structure of different forms of ambient energy (e.g., light, sound) and, therefore, to changes in sensory stimulation. I claim that movement always is controlled simultaneously relative to multiple referents, such that no single form of ambient energy can, in principle, contain information that is sufficient for successful control. The needed perceptual information exists, I claim, solely in the global array, that is, in emergent, higher-order patterns that extend across different forms of ambient energy. I review formal and empirical examples, and discuss implications for kinesiology.

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The Embodied Origins of Infant Reaching: Implications for the Emergence of Eye-Hand Coordination

Daniela Corbetta, Rebecca F. Wiener, Sabrina L. Thurman, and Emalie McMahon

This article reviews the literature on infant reaching, from past to present, to recount how our understanding of the emergence and development of this early goal-directed behavior has changed over the decades. We show that the still widely-accepted view, which considers the emergence and development of infant reaching as occurring primarily under the control of vision, is no longer sustainable. Increasing evidence suggests that the developmental origins of infant reaching is embodied. We discuss the implications of this alternative view for the development of eye-hand coordination and we propose a new scenario stressing the importance of the infant body-centered sensorimotor experiences in the months prior to the emergence of reaching as a possible critical step for the formation of eye-hand coordination.

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Fractal Dynamics, Variability, and Coordination in Human Locomotion

Scott W. Ducharme and Richard E.A. van Emmerik

In human locomotion, the magnitude of gait variability is a strong predictor of fall risk and frailty due to aging and disease. Beyond variability magnitude, the past two decades have provided emerging alternative methodologies for studying biological variability. Specifically, coordination variability has been found to be critically important within a healthy, adaptive system. While many activities aim to minimize end-point variability, greater coordination variability indicates a more flexible system, and is greater in experts compared to novices, or healthy compared to diseased individuals. Finally, variability structure (i.e., fractal dynamics) may describe the overall adaptive capacity of the locomotor system. We provide empirical support that fractal dynamics are associated with step length symmetry during challenging split-belt treadmill walking. Individuals whose fractal scaling approached 1/f fractal scaling during constrained walking also exhibited the best gait adaptability performance. Importantly, this relation between fractality and gait adaptability was not observed in unperturbed preferred speed walking.

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Volume 7 (2018): Issue 1 (Feb 2018)

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Motor Patterns Acquired Early in Life, the Brain-Behavior Coalition, and the Importance of Context

Ryota Nishiyori and Beverly D. Ulrich

Our goal for this paper is to address changes in motor patterns that occur early in life. To do this, we begin by sharing first a brief set of exemplar patterns of movement that emerge prenatally and during the first year postnatally. We couch these descriptions in the hypotheses proposed to explain what has been observed, and emphasize, as well, the context in which they appear. We follow with some experimental studies developmental scientists have used to test these explanations. Subsequently, we address the brain-behavior collaboration that unfolds and supports skill acquisition across early development. We provide data to show that recent advances in brain-imaging technology enable researchers to monitor cortical activity as infants explore and learn functional skills in real time and over developmental time. This opens a new frontier to the scientific study of the early development of neuromotor control and can enhance both our basic science knowledge and our efforts to optimize positive clinical outcomes.

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Movement Forms, Function, and Skill

Karl M. Newell

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The Past and Future of Clock-Like Timing in Motor Performance

Howard N. Zelaznik

Over the past 18 years, Zelaznik and colleagues have promoted what is known as the event-emergent timing distinction. According to this framework, control of timing can be based upon a neurological clock-like process or upon an emergent process. I review the highlights of this research program that supports this distinction, then describe a new line of research that examines whether timing is a goal of the task or a consequence of other movement constraints. These results highlight the importance of goals in the control of timing.