Neurobiological degeneracy: A key property for functional adaptations of perception and action to constraints

Towards an ecological dynamics theory of flow in sport

Flow is an optimal state of absorption that may be experienced in appropriately challenging and intrinsically motivating activities such as sports. Flow may be an important concept for understanding the emergence and role of sport in society, yet theoretical explanations of flow have had limited success explaining, predicting, and facilitating flow in sport. Here, we use the ecological dynamics framework, seeking to resolve foundational issues in an explanation of flow, building towards a theory of flow in sport. To address this challenge, we highlight the utility of ecological conceptualisations of experience, intention, skill, attention, information, and temporality, in explanations of flow experiences in sport, before discussing some novel empirical predictions motivated by the theory. We suggest that a multiscale ecological dynamics approach is well equipped to explore flow in performer-environment systems that display interaction-dominant dynamics and conclude by outlining avenues for future research created by an ecological dynamics theory of flow in sport.

The effect of experience on the perception of affordances for aperture crossing in cycling

To ride successfully and safely, cyclists must perceive and act on the affordances that are available in a given situation. This study investigated whether experience in perceiving and acting with respect to a person-plus-object system would influence whether and how a person choses to cross an aperture of different widths, especially in relation to their maximal action capabilities. We also explore whether the distribution of action modes reflects this effect. We examined the performance (i.e., the probability of successfully crossing the aperture) and the decision (i.e., the probability of attempting to cross the aperture) of 8 experienced cyclists and 16 occasional cyclists in an aperture crossing task. In term of performance, experienced cyclists demonstrated greater ability to cross narrower apertures than occasional cyclists, but there were no such differences when aperture width was scaled to maximal action capabilities. In term of decision, both experienced and occasional cyclists tended to over-estimate their abilities, but the experienced cyclists did so to a greater extent. Our findings indicate that experience improves the ability to perform more complex tasks due to utilizing a wider repertoire of actions, but not necessarily the ability to perceive and actualize (action-scaled) affordances.

Promoting Exploration During Learning: Effect of Imposed and Self-Controlled Practice Schedules on Learners' Behavioral Flexibility

Purpose: Enriching learners' motor repertoires in a complex pluri-articular task, such as climbing, could help learners' adaptation to various sets of task constraints. Promoting exploration with variable practice conditions is one solution recurrently proposed. However, recent studies have shown that a too elevated exploration-exploitation ratio during practice could impair learning. A proposed solution is to give learners some control over their practice schedule, which appeared to better respect the individual learning dynamic in comparison to the usual experimenter-imposed practice schedule. Thus, the aim of this study is to investigate whether giving learners the possibility of controlling when to confront to new climbing routes would result in greater flexibility in their motor repertoire compared to giving them an imposed schedule of climbing routes or a constant practice condition. Method: Participants were assigned to either a constant practice group (CPG), an imposed-variability group (IVG) or a self-controlled variability group (SVG) to carry out a climbing task. To assess participants' behavioral flexibility, a scanning procedure was conceived by manipulating the route design and the instructions. Results: Participants showed an initial lack of flexibility as they strongly relied on a single coordination pattern. At posttest and retention, the three groups more frequently used a new hand coordination pattern and more often showed coordination patterns associated with high climbing fluency. Results suggest that the individualized rate of exploration in the self-controlled practice condition may have helped the learners improve their flexibility, whereas forcing exploration did not seem more beneficial than constant practice in this complex pluri-articular task.

Qualitative age-related changes in fine motor skill performance among 3- to 6-year-old typically developing children

This study described intra-task fine motor skill components of the Manual Dexterity tasks (Posting Coins; PC, Threading Beads; TB, Drawing Trail; DT) of the Movement Assessment Battery for Children-2 Test for typically developing children and investigated age- and sex-related differences. Three- to six-year-old Dutch children (n = 182, Mage 4.5 ± 1.1 years, 51.1% boys) were observed with regard to intra-task fine motor skill components, and changes in intra-task components of the Manual Dexterity tasks were analyzed across age using of the Kruskal-Wallis test with post-hoc Mann-Whitney U tests, and differences between sexes using the Mann-Whitney U test. The following intra-task components were observed: grip type, manipulation, non-dominant or non-writing hand, grip position, posture, head, coin placement, placement of the bead on the lace tip and joint movement. Results showed that the younger children (3-year-olds) more frequently used a grasp with the full hand (PC, TB), more often put the coin on the container and sliding it in (PC), more often supported the side or top of the container (PC), used more bi-manual manipulation (transferring from hand-to-hand or hand, body or surface assist) (TB, DT), more frequently used primitive, too high grips, predominantly used their proximal joints, and did not support the paper (DT). This in comparison with more frequent use of three-point pinch, direct coin placement, grabbing the front or back of the container, in-hand-manipulation, mature grips and correct height, distal joint use and supporting the paper from the side or below by most 5- and 6-year-olds. Furthermore, most sex-related differences were found in the younger age-groups (3- and 4-year-olds) in the DT tasks with girls outperforming boys. Results from this study add to the knowledge on qualitative fine motor skill performance in a convenience sample of 3- to 6-year-old typically developing children. A limitation of the current study was the relatively small sample size of 6-year-old children. The strength of the current study is its novelty in providing qualitative descriptions of intra-task fine motor skill components in typically developing 3- to 6-year-old children.

A systematic review of perception of affordances for the person-plus-object system

Human behavior often involves the use of an object held by or attached to the body, which modifies the individual's action capabilities. Moreover, most everyday behaviors consist of sets of behaviors that are nested over multiple spatial and temporal scales, which require perceiving and acting on nested affordances for the person-plus-object system. This systematic review investigates how individuals attune to information about affordances involving the person-plus-object system and how they (re)calibrate their actions to relevant information. We analyzed 71 articles-34 on attunement and 37 on (re)calibration with healthy participants-that experimentally investigated the processes involved in the perception of affordances for the person-plus-object system (including attunement, calibration, and recalibration). With respect to attunement, objects attached to the body create a multiplicity of affordances for the person-plus-object system, and individuals learned (1) to detect information about affordances of (and for) the person-plus-object system in a task and (2) to choose whether, when, and how to exploit those affordances to perform that task. Concerning (re)calibration, individuals were able (1) to quickly scale their actions in relation to the (changed) action capabilities of the person-plus-object system and (2) to perceive multiple functionally equivalent ways to exploit the affordances of that system, and these abilities improved with practice. Perceiving affordances for the person-plus-object system involves learning to detect the information about such affordances (attunement) and the scaling of behaviors to such information (calibration). These processes imply a general ability to incorporate an object attached to the body into an integrated person-plus-object system.

Distinct clusters of movement entropy in children's exploration of a virtual reality balance beam

Although assessing motor competence is vital to advancing current understandings of motor development and its significance in various fields, no consensus exists on how the construct should be operationalised and measured. Existing approaches to assessing motor competence in children typically involve applying qualitative and/or quantitative scoring procedures in which children's performance is evaluated according to certain levels of assessment-specific task performance dependent upon predefined sets of instructions and procedures. Building upon ecological dynamics as a framework, different levels of motor competence can be identified in children's attempts to coordinate their degrees of freedom while trying to complete the interactive task and environmental constraints. Given the dynamic, nonlinear features of that coordinating process, assessments need to consider the inherit structure of inter- and intra-individual variability in patterns of movement. Against that background, we investigated 7-10-year-old children's (n = 58) whole-body joint kinematics as they freely explored a balance beam in a virtual reality playground. Specifically, we used exploratory cluster analysis to examine the discriminatory capability of utilising joint-specific sample entropy as a window into individual differences in movement coordination that emerged from children's exploration of the constraints embedded in the virtual task. Among the results, three clusters of children with distinct profiles of movement variability emerged, all of which showed heterogeneous levels of repeatability in joint movements in combination with the level of spatiotemporal exploration on the balance beam that could not be explained by between-cluster differences in age and gender distributions. Those findings suggest that entropy from whole-body movements can be used to cluster children into distinct groups with different profiles regarding the structure of movement variability, which can inform new understandings and the development of gross motor competence assessments for children.

Individual Muscle Contributions to the Acceleration of the Center of Mass During the Barbell Back Squat in Trained Female Subjects

ABSTRACT

Goodman, WW, Helms, E, and Graham, DF. Individual muscle contributions to the acceleration of the center of mass during the barbell back squat in trained female subjects. J Strength Cond Res 37(10): 1947-1954, 2023-The squat is used to enhance performance and rehabilitate the lower body. However, muscle forces and how muscles accelerate the center of mass (CoM) are not well understood. The purpose was to determine how lower extremity muscles contribute to the vertical acceleration of the CoM when squatting to parallel using 85% one-repetition maximum. Thirteen female subjects performed squats in a randomized fashion. Musculoskeletal modeling was used to obtain muscle forces and muscle-induced accelerations. The vasti, soleus, and gluteus maximus generated the largest upward accelerations of the CoM, whereas the muscles that produced the largest downward acceleration about the CoM were the hamstrings, iliopsoas, adductors, and tibialis anterior. Our findings indicate that a muscle's function is task and posture specific. That is, muscle function depends on both joint position and how an individual is interacting with the environment.

Reliability and Validity of Functional Grip Strength Measures Across Holds and Body Positions in Climbers: Associations With Skill and Climbing Performance

Purpose: In climbing, exceptional levels of fingertip strength across different holds and body positions are considered essential for performance. There is no commonly agreed upon way to measure such "grip strength variability." Furthermore, the accurate and reliable monitoring of strength is necessary to achieve safe, progressive improvement in strength. Therefore, this study aimed to develop reliability and criterion validity for assessment of grip strength across multiple holds and body positions. Methods: Twenty-two advanced toelite climbers (age = 28.5 ± 8.6 years) performed maximal voluntary isometric contractions on two occasions (for test-retest reliability). Conditions included two hold types (edge and sloper) tested in two postures (elbow flexion [90°] and self-preferred). Climbing performance was determined on two "difficulty" routes (difficulty increases with each hold): one route composed of only edges and another only of slopers. Results: Test-retest reliability was high (ICC between 0.94-0.99). Significant positive correlations were observed for the forces produced on the sloper test and climbing distance on the sloper route (r = 0.512,p < .05), and for the forces produced on the edge test and climbing distance on the edge route (ρ = 0.579, p < .01). Conclusion: These findings support reliability and validity of the method used to measure grip strength variability with different holds and body positions and suggest that improving strength across different grasping types supports adaptive climbing performance.

Beyond Nature Versus Nurture: the Emergence of Emotion

Affective science is stuck in a version of the nature-versus-nurture debate, with theorists arguing whether emotions are evolved adaptations or psychological constructions. We do not see these as mutually exclusive options. Many adaptive behaviors that humans have evolved to be good at, such as walking, emerge during development - not according to a genetically dictated program, but through interactions between the affordances of the body, brain, and environment. We suggest emotions are the same. As developing humans acquire increasingly complex goals and learn optimal strategies for pursuing those goals, they are inevitably pulled to particular brain-body-behavior states that maximize outcomes and self-reinforce via positive feedback loops. We call these recurring, self-organized states emotions. Emotions display many of the hallmark features of self-organized attractor states, such as hysteresis (prior events influence the current state), degeneracy (many configurations of the underlying variables can produce the same global state), and stability. Because most bodily, neural, and environmental affordances are shared by all humans - we all have cardiovascular systems, cerebral cortices, and caregivers who raised us - similar emotion states emerge in all of us. This perspective helps reconcile ideas that, at first glance, seem contradictory, such as emotion universality and neural degeneracy.

Bilateral human laryngeal motor cortex in perceptual decision of lexical tone and voicing of consonant

Speech perception is believed to recruit the left motor cortex. However, the exact role of the laryngeal subregion and its right counterpart in speech perception, as well as their temporal patterns of involvement remain unclear. To address these questions, we conducted a hypothesis-driven study, utilizing transcranial magnetic stimulation on the left or right dorsal laryngeal motor cortex (dLMC) when participants performed perceptual decision on Mandarin lexical tone or consonant (voicing contrast) presented with or without noise. We used psychometric function and hierarchical drift-diffusion model to disentangle perceptual sensitivity and dynamic decision-making parameters. Results showed that bilateral dLMCs were engaged with effector specificity, and this engagement was left-lateralized with right upregulation in noise. Furthermore, the dLMC contributed to various decision stages depending on the hemisphere and task difficulty. These findings substantially advance our understanding of the hemispherical lateralization and temporal dynamics of bilateral dLMC in sensorimotor integration during speech perceptual decision-making.

Biomechanics and the origins of human bipedal walking: The last 50 years

Motion analysis, as applied to evolutionary biomechanics, has experienced its own evolution over the last 50 years. Here we review how an ever-increasing fossil record, together with continuing advancements in biomechanics techniques, have shaped our understanding of the origin of upright bipedal walking. The original, and long-established hypothesis held by Lamarck (1809), Darwin (1859) and Keith (1934), amongst others, maintained that bipedality originated in an arboreal context. However, the first field studies of gorilla and chimpanzees from the 1960's, highlighted their so-called 'knucklewalking' quadrupedalism, leading scientists to assume, semi-automatically, that knucklewalking must have been the precursor to bipedality. It would not be until the discovery of skeletons of early human relatives Australopithecus afarensis and Australopithecus prometheus, and the inclusion of methods of analysis from computer science, biomechanics, sports science and medicine, that the knucklewalking hypothesis would be most robustly challenged. Their short, but human-like lower limbs and human-like hand indicated that knucklewalking was not part of our ancestral locomotor repertoire. Rather, most current research in evolutionary biomechanics agrees it was a combination of climbing and bipedalism, both in an arboreal context, which facilitated upright, terrestrial, bipedal walking over short distances.

Degeneracy in epilepsy: multiple routes to hyperexcitable brain circuits and their repair

Due to its complex and multifaceted nature, developing effective treatments for epilepsy is still a major challenge. To deal with this complexity we introduce the concept of degeneracy to the field of epilepsy research: the ability of disparate elements to cause an analogous function or malfunction. Here, we review examples of epilepsy-related degeneracy at multiple levels of brain organisation, ranging from the cellular to the network and systems level. Based on these insights, we outline new multiscale and population modelling approaches to disentangle the complex web of interactions underlying epilepsy and to design personalised multitarget therapies.

How do soccer players sprint from a tactical context? Observations of an English Premier League soccer team

The aim of this study was to quantify and tactically contextualise (i.e., phase of play and tactical outcome [TO]) sprints (≥7.0 m/s) of an English Premier League (EPL) soccer team during match-play. Videos of 901 sprints (10 matches) were evaluated using the Football Sprint Tactical-Context Classification System. Sprints occurred within a variety of phases of play (attacking/defensive organisation and transitions) and TOs, both out- and in-possession, with position-specific differences. Most sprints were completed out-possession (58%), with "closing down" the most observed TO (28%). In-possession, "run the channel" (25%) was the most observed TO. Centre backs predominantly performed "ball down the side" sprints (31%), whereas central midfielders mostly performed "covering" sprints (31%). Central forwards and wide midfielders mostly performed "closing down" (23% and 21%) and "run the channel" (23% and 16%) sprints when out- and in-possession, respectively. Full backs most frequently performed "recovery" and "overlap" runs (14% each). This study provides insights into the specific physical-tactical characteristics of sprints performed from an EPL soccer team. This information can be used to assist in the development of position-specific physical preparation programmes, and more ecologically valid and contextualised gamespeed and agility sprint drill construction to better reflect the demands of soccer.

The effect of nonlinear pedagogy on the acquisition of game skills in a territorial game

Introduction

Nonlinear Pedagogy (NP), underpinned by Ecological Dynamics, provides a suitable pedagogical approach for practitioners (e.g., Physical Educators, coaches) to encourage exploratory learning that is learner-centered even in Traditional Sporting Games (TSG) that could be represented by invasion or territorial-like games. NP involves the manipulation of constraints which form boundaries for interacting components to self-organize, facilitating the emergence of goal-directed behaviours. Key pedagogical principles relating to representativeness, manipulation of constraints, awareness of focus of attention instructions, task simplification and the functional role of noise can encourage exploratory learning that helps develop 21st century competencies. This is in contrast to a Linear Pedagogy (LP) approach that is more teacher-centered and focuses on repetition in practices to promote movement form consistency in enhancing the acquisition of movement skills. Little is known about the effectivity of NP in the learning and transfer of invasion games. The aims of this study were to: (a) determine the impact of NP on the teaching and learning of an invasion game in the Physical Education (PE) context; (b) examine the transferability of game skills to other games in the same game category (i.e., floorball as a territorial game in this study).

Methods

224 (between 12 to 13 years old) students underwent a 10-week intervention program to learn to play an invasion game (football) with either a NP or LP approach (i.e., repetitive and prescriptive drills).

Results

Performance outcome data were measured during Pre, Post, Retention, Transfer test 1 (larger playing area) and Transfer test 2 (floorball). Significant improvements in several performance outcome and game play measures in football was observed for the NP condition. Fewer improvements in the same measures were found for the LP condition.

Discussion

Evidence for transfer of learning for NP was not as strong as anticipated although there was still some potential for encouraging transfer of learning. The key findings from this study further challenge the "one-size fits all" philosophy in the teaching of PE. Both LP and NP approaches would have a role to play in supporting teaching and learning which could be context dependent.

Evaluating transfer prediction using machine learning for skill acquisition study under various practice conditions

Recent research highlighted the interest in 1) investigating the effect of variable practice on the dynamics of learning and 2) modeling the dynamics of motor skill learning to enhance understanding of individual pathways learners. Such modeling has not been suitable for predicting future performance, both in terms of retention and transfer to new tasks. The present study attempted to quantify, by means of a machine learning algorithm, the prediction of skill transfer for three practice conditions in a climbing task: constant practice (without any modifications applied during learning), imposed variable practice (with graded contextual modifications, i.e., the variants of the climbing route), and self-controlled variable practice (participants were given some control over their variant practice schedule). The proposed pipeline allowed us to measure the fitness of the test to the dataset, i.e., the ability of the dataset to be predictive of the skill transfer test. Behavioral data are difficult to model with statistical learning and tend to be 1) scarce (too modest data sample in comparison with the machine learning standards) and 2) flawed (data tend to contain voids in measurements). Despite these adversities, we were nevertheless able to develop a machine learning pipeline for behavioral data. The main findings demonstrate that the level of learning transfer varies, according to the type of practice that the dynamics pertain: we found that the self-controlled condition is more predictive of generalization ability in learners than the constant condition.

A classification of specific movement skills and patterns during sprinting in English Premier League soccer

The aim of this study was to quantify and contextualize sprinting actions (≥ 7.0 m/s) of English Premier League (EPL) soccer match-play with respect to the movement skills and patterns employed. Video footage (3.2.6, Premier League DVMS, ChyronHego) and raw video-based locomotor coordinates of 901 sprint efforts from 10 matches of an EPL soccer team (2017-2018), were evaluated using the Football Sprint Movement Classification System pertaining to transition, initiation, and actualisation of sprint movement skills and patterns. The results from a one-way ANOVA or independent t-test revealed that, generally, most sprinting actions begun from a linear initiation position compared to lateral or rear (63%, d = 5.0-5.3, p < 0.01), without a change of direction (COD) (48%, d = 4.9-5.6, p < 0.01) compared to lateral, front-back, back-front, and from forward travelling (linear and diagonal) transition movements (68%, d = 2.1-5.7, p < 0.01) compared to lateral or rear. Additionally, most sprints were initiated with a rolling acceleration (66%, d = 3.2, p < 0.01) compared to explosive acceleration, often performed with a degree of curvature (86%, d = 7.2, p < 0.01) compared to linear, with torso rotation (62%, d = 2.7, p < 0.01) compared to no rotation, and typically end with an action such as duelling with an opponent or involvement with the ball (49%). Additionally, the sprint movement characteristics proportions slightly differed across playing positions. Overall, this study confirms that sprints during EPL soccer matches are initiated from and performed with a variety of different movement skills and patterns in relation to different sport-specific outcomes. This data can be used to assist in the development of more effective physical preparation programmes, inform position-specific contextualized sprinting drills to achieve better specificity and potential transfer of training, while also informing speed testing protocols.

Front crawl swimming coordination: a systematic review

Several constraints, including environmental (e.g., aquatic resistance, temperature and viscosity), organismic (e.g., anthropometry, buoyancy) and task-related (e.g., imposed swim speed or stroke rate) impact motor coordination and swimming performance. As motor coordination requires structurally organising intra- and inter-limb coupling, the purpose of this review was to update the literature concerning coordination between the upper-limbs in front crawl swimming. We focused on the effects of biomechanical, physiological, and personal (gender, skill level, and age) factors on coordination and performance. In fact, it could be highlighted that upper-limbs coordination varies with organismic, task and environmental constraints, resulting in several available motor solutions that should be adopted according to how each swimmer deals with occurring constraints. As such, there is no ideal or optimal coordination pattern that youth, learners and less-skilled swimmers should imitate.

Why Sports Should Embrace Bilateral Asymmetry: A Narrative Review

(1) Background: Asymmetry is ubiquitous in nature and humans have well-established bilateral asymmetries in their structures and functions. However, there are (mostly unsubstantiated) claims that bilateral asymmetries may impair sports performance or increase injury risk. (2) Objective: To critically review the evidence of the occurrence and effects of asymmetry and sports performance. (3) Development: Asymmetry is prevalent across several sports regardless of age, gender, or competitive level, and can be verified even in apparently symmetric actions (e.g., running and rowing). Assessments of bilateral asymmetries are highly task-, metric-, individual-, and sport-specific; fluctuate significantly in time (in magnitude and, more importantly, in direction); and tend to be poorly correlated among themselves, as well as with general performance measures. Assessments of sports-specific performance is mostly lacking. Most studies assessing bilateral asymmetries do not actually assess the occurrence of injuries. While injuries tend to accentuate bilateral asymmetries, there is no evidence that pre-existing asymmetries increase injury risk. While training programs reduce certain bilateral asymmetries, there is no evidence that such reductions result in increased sport-specific performance or reduced injury risk. (4) Conclusions: Bilateral asymmetries are prevalent in sports, do not seem to impair performance, and there is no evidence that suggests that they increase injury risk.

Physical activity promoting teaching practices and children’s physical activity within physical education lessons underpinned by motor learning theory (SAMPLE-PE)

Purpose

Movement competence is a key outcome for primary physical education (PE) curricula. As movement development in children emerges through physical activity (PA), it is important to determine the extent of PA promotion within movement competence focused teaching pedagogies. Therefore, this study aimed to assess children’s moderate-to-vigorous PA (MVPA) and related teaching practices in primary PE within Linear pedagogy and Nonlinear pedagogy and to compare this to current practice within PE delivery in primary schools.

Methods

Participants (n = 162, 53% females, 5-6y) were recruited from 9 primary schools within the SAMPLE-PE cluster randomised controlled trial. Schools were randomly-allocated to one of three conditions: Linear pedagogy, Nonlinear pedagogy, or control. Nonlinear and Linear pedagogy intervention schools received a PE curriculum delivered by trained deliverers over 15 weeks, while control schools followed usual practice. Children’s MVPA was measured during 3 PE lessons (44 PE lessons in total) using an ActiGraph GT9X accelerometer worn on their non-dominant wrist. Differences between conditions for children’s MVPA were analysed using multilevel model analysis. Negative binomial models were used to analyse teaching practices data.

Results

No differences were found between Linear pedagogy, Nonlinear pedagogy and the control group for children’s MVPA levels during PE. Linear and Nonlinear interventions generally included higher percentages of MVPA promoting teaching practices (e.g., Motor Content) and lower MVPA reducing teaching practices (e.g., Management), compared to the control group. Teaching practices observed in Linear and Nonlinear interventions were in line with the respective pedagogical principles.

Conclusions

Linear and Nonlinear pedagogical approaches in PE do not negatively impact MVPA compared to usual practice. Nevertheless, practitioners may need to refine these pedagogical approaches to improve MVPA alongside movement competence.

Context-sensitive computational mechanistic explanation in cognitive neuroscience

Mainstream cognitive neuroscience aims to build mechanistic explanations of behavior by mapping abilities described at the organismal level via the subpersonal level of computation onto specific brain networks. We provide an integrative review of these commitments and their mismatch with empirical research findings. Context-dependent neural tuning, neural reuse, degeneracy, plasticity, functional recovery, and the neural correlates of enculturated skills each show that there is a lack of stable mappings between organismal, computational, and neural levels of analysis. We furthermore highlight recent research suggesting that task context at the organismal level determines the dynamic parcellation of functional components at the neural level. Such instability prevents the establishment of specific computational descriptions of neural function, which remains a central goal of many brain mappers - including those who are sympathetic to the notion of many-to-many mappings between organismal and neural levels. This between-level instability presents a deep epistemological challenge and requires a reorientation of methodological and theoretical commitments within cognitive neuroscience. We demonstrate the need for change to brain mapping efforts in the face of instability if cognitive neuroscience is to maintain its central goal of constructing computational mechanistic explanations of behavior; we show that such explanations must be contextual at all levels.

An Analysis of Lower Limb Coordination Variability in Unilateral Tasks in Healthy Adults: A Possible Prognostic Tool

Interlimb coordination variability analysis can shed light into the dynamics of higher order coordination and motor control. However, it is not clear how the interlimb coordination of people with no known injuries change in similar activities with increasing difficulty. This study aimed to ascertain if the interlimb coordination variability range and patterns of healthy participants change in different unilateral functional tasks with increasing complexity and whether leg dominance affects the interlimb coordination variability. In this cross-sectional study fourteen younger participants with no known injuries completed three repeated unilateral sit-to-stands (UniSTS), step-ups (SUs), and continuous-hops (Hops). Using four inertial sensors mounted on the lower legs and thighs, angular rotation of thighs and shanks were recorded. Using Hilbert transform, the phase angle of each segment and then the continuous relative phase (CRP) of the two segments were measured. The CRP is indicative of the interlimb coordination. Finally, the linear and the nonlinear shank-thigh coordination variability of each participant in each task was calculated. The results show that the linear shank-thigh coordination variability was significantly smaller in the SUs compared to both UniSTS and Hops in both legs. There were no significant differences found between the latter two tests in their linear coordination variability. However, Hops were found to have significantly larger nonlinear shank-thigh coordination variability compared to the SUs and the UniSTS. This can be due to larger vertical and horizontal forces required for the task and can reveal inadequate motor control during the movement. The combination of nonlinear and linear interlimb coordination variability can provide more insight into human movement as they measure different aspects of coordination variability. It was also seen that leg dominance does not affect the lower limb coordination variability in participants with no known injuries. The results should be tested in participants recovering from lower limb injuries.

The Ecological Dynamics Framework: An Innovative Approach to Performance in Extreme Environments: A Narrative Review

(1) Background: Uncertainty in extreme sports performance environments, such as climbing, provides considerable psycho-emotional and physiological demands, notably due to the many different environments in which climbing can be performed. This variety of environments, conditions of practice and engagement would challenge the acquisition of perceptual-motor skills; (2) Methods: To better understand how perceptual-motor skills are controlled and acquired in climbing, we proposed a narrative review anchored in the ecological dynamics theoretical framework and showed how this theoretical framework would support a nonlinear pedagogy to skill acquisition and to design safe learning and training situations that are representative of extreme performance contexts; (3) Results: We explained three theoretical pillars and we provide examples for design intervention following nonlinear pedagogy, notably (i) to set a constraint-led approach (in particular task constraint), (ii) to implement conditions of practice (constant vs. variable, imposed vs. self-controlled), (iii) to promote adaptive and creative behavioral variability during practice; (4) Conclusions: The challenge for the extreme sport practitioner is how to set up conditions of practice for efficient exploration in a manner that manages the dangers of performing in uncertain environments. Representing uncertainty within the relative safety of indoor settings may be one approach for preparing climbers for performance in extreme environments.

A Computational Neural Model for Mapping Degenerate Neural Architectures

Degeneracy in biological systems refers to a many-to-one mapping between physical structures and their functional (including psychological) outcomes. Despite the ubiquity of the phenomenon, traditional analytical tools for modeling degeneracy in neuroscience are extremely limited. In this study, we generated synthetic datasets to describe three situations of degeneracy in fMRI data to demonstrate the limitations of the current univariate approach. We describe a novel computational approach for the analysis referred to as neural topographic factor analysis (NTFA). NTFA is designed to capture variations in neural activity across task conditions and participants. The advantage of this discovery-oriented approach is to reveal whether and how experimental trials and participants cluster into task conditions and participant groups. We applied NTFA on simulated data, revealing the appropriate degeneracy assumption in all three situations and demonstrating NTFA's utility in uncovering degeneracy. Lastly, we discussed the importance of testing degeneracy in fMRI data and the implications of applying NTFA to do so.

Variation, mosaicism and degeneracy in the hominin foot

The fossil record is scarce and incomplete by nature. Animals and ecological processes devour soft tissue and important bony details over time and, when the dust settles, we are faced with a patchy record full of variation. Fossil taxa are usually defined by craniodental characteristics, so unless postcranial bones are found associated with a skull, assignment to taxon is unstable. Naming a locomotor category based on fossil bone morphology by analogy to living hominoids is not uncommon, and when no single locomotor label fits, postcrania are often described as exhibiting a 'mosaic' of traits. Here, we contend that the unavoidable variation that characterises the fossil record can be described far more rigorously based on extensive work in human neurobiology and neuroanatomy, movement sciences and motor control and biomechanics research. In neurobiology, degeneracy is a natural mechanism of adaptation allowing system elements that are structurally different to perform the same function. This concept differs from redundancy as understood in engineering, where the same function is performed by identical elements. Assuming degeneracy, structurally different elements are able to produce different outputs in a range of environmental contexts, favouring ecological robusticity by enabling adaptations. Furthermore, as degeneracy extends to genome level, genetic variation is sustained, so that genes which might benefit an organism in a different environment remain part of the genome, favouring species' evolvability.

Developing Players' Tactical Knowledge Using Combined Constraints-Led and Step-Game Approaches-A Longitudinal Action-Research Study

Purpose: Using an action-research design, this study examined the impact of combining concepts from two contemporary pedagogical approaches, the Constraints-led Approach (CLA) and Step-Game Approach (SGA), on the development of youth volleyballers' tactical knowledge, as expressed in performance, throughout a full competitive season. Method: Fifteen players and one coach participated in this study, which involved three action-research cycles, each including the processes of planning, acting and monitoring, reflecting, and fact-finding. The first author, who had the role of coach-researcher, collected data using a reflexive diary and field notes between September 2017 and June 2018, as well as eight semi-structured focus-group interviews. Data were analyzed using thematic analysis, in which inductive procedures deepened understanding of the development of the participants' tactical knowledge. Results: Findings suggested that combining CLA with SGA improved tactical knowledge in specific ways. Players progressed from a starting point where they were only able to describe game scenarios, and act without tactical criteria or considering contextual game constraints, to a point where their intentions during tactical actions were shaped by their ability to think strategically and guide their attention to recognize and interpret different constraints. Conclusions: Results suggested that the development of players' tactical knowledge benefited from a mutual integration of different, yet complementary, pedagogical approaches. By integrating SGA and CLA it was possible to enhance players' adaptable thinking using learning tasks involving the manipulation of meaningful constraints that afforded variable repetition and the resolution of tactical problems.

The Role of Nonlinear Pedagogy in Supporting the Design of Modified Games in Junior Sports

Nonlinear Pedagogy has been advocated as an approach that views acquisition of movement skills with a strong emphasis on exploratory behaviors and the development of individualized movement skills. Underpinned by Ecological Dynamics, Nonlinear Pedagogy provides key ideas on design principles to support a teaching and learning approach that accounts for dynamic interactions among constraints in the evolution of movement behaviors. In the context of junior sports, the manipulation of task constraints is central to how games can be re-designed for children to play that are age and body appropriate so that the games can still capture the key elements of representativeness as compared to the adult form of the game. Importantly, these games offer suitable affordances that promote sensible play that could be transferable to other contexts. In this paper, we provide an in-depth discussion on how Nonlinear Pedagogy is relevant in supporting the design and development of modified games in the context of junior sports. Practical implications are also provided to share how games can be modified for meaningful play to emerge.

Socio-Motor Improvisation in Schizophrenia: A Case-Control Study in a Sample of Stable Patients

Improvising is essential for human development and is one of the most important characteristics of being human. However, how mental illness affects improvisation remains largely unknown. In this study we focused on socio-motor improvisation in individuals with schizophrenia, one of the more debilitating mental disorder. This represents the ability to improvise gestures during an interaction to promote sustained communication and shared attention. Using a novel paradigm called the mirror game and recently introduced to study joint improvisation, we recorded hand motions of two people mirroring each other. Comparing Schizophrenia patients and healthy controls skills during the game, we found that improvisation was impaired in schizophrenia patients. Patients also exhibited significantly higher difficulties to being synchronized with someone they follow but not when they were leaders of the joint improvisation game. Considering the correlation between socio-motor synchronization and socio-motor improvisation, these results suggest that synchronization does not only promote affiliation but also improvisation, being therefore an interesting key factor to enhance social skills in a clinical context. Moreover, socio-motor improvisation abnormalities were not associated with executive functioning, one traditional underpinning of improvisation. Altogether, our results suggest that even if both mental illness and improvisation differ from normal thinking and behavior, they are not two sides of the same coin, providing a direct evidence that being able to improvise in individual situations is fundamentally different than being able to improvise in a social context.

Beyond animated skeletons: How can biomechanical feedback be used to enhance sports performance?

Biomechanical feedback technologies are becoming increasingly prevalent in elite athletic training environments but how the kinematic and kinetic data they produce can be best used to improve sports techniques and enhance sports performance is unclear. This paper draws on theoretical and empirical developments in the motor control, skill acquisition, and sports biomechanics literatures to offer practical guidance and strategic direction on this issue. It is argued that the information produced by biomechanical feedback technologies can only describe, with varying degrees of accuracy, what patterns of coordination and control are being adopted by the athlete but, crucially, it cannot prescribe how these patterns of coordination and control should be modified to enhance sports performance. As conventional statistical and theoretical modelling paradigms in applied sports biomechanics provide limited information about patterns of coordination and control, and do not permit the identification of athlete-specific optimum sports techniques, objective criteria on which to base technical modifications that will consistently lead to enhanced performance outcomes cannot reliably be established for individual athletes. Given these limitations, an alternative approach, which is harmonious with the tenets of dynamical systems theory and aligned with the pioneering insights of Bernstein (1967) on skill acquisition, is advocated. This approach involves using kinematic and kinetic data to channel the athlete's search towards their own unique 'optimum' pattern of coordination and control as they actively explore their perceptual-motor workspace during practice. This approach appears to be the most efficacious use of kinematic and kinetic data given current biomechanical knowledge about sports techniques and the apparent inability of existing biomechanical modelling approaches to accurately predict how technique changes will impact on performance outcomes for individual athletes.

Neurobiological tensegrity: The basis for understanding inter-individual variations in task performance?

Bernstein's (1996) levels of movement organization includes tonus, the muscular-contraction level that primes individual movement systems for (re)organizing coordination patterns. The hypothesis advanced is that the tonus architecture is a multi-fractal tensegrity system, deeply reliant on haptic perception for regulating movement of an individual actor in a specific environment. Further arguments have been proposed that the tensegrity-haptic system is implied in all neurobiological perception and -action. In this position statement we consider whether the musculoskeletal system can be conceptualized as a neurobiological tensegrity system, supporting each individual in co-adapting to many varied contexts of dynamic performance. Evidence for this position, revealed in investigations of judgments of object properties, perceived during manual hefting, is based on each participant's tensegrity. The implication is that the background organizational state of every individual is unique, given that no neurobiological architecture (musculo-skeletal components) is identical. The unique tensegrity of every organism is intimately related to individual differences, channeling individualized adaptations to constraints (task, environment, organismic), which change over different timescales. This neurobiological property assists transitions from one stable state of coordination to another which is needed in skill adaptation during performance. We conclude by discussing how tensegrity changes over time according to skill acquisition and learning.

Metastable attunement and real-life skilled behavior

In everyday situations, and particularly in some sport and working contexts, humans face an inherently unpredictable and uncertain environment. All sorts of unpredictable and unexpected things happen but typically people are able to skillfully adapt. In this paper, we address two key questions in cognitive science. First, how is an agent able to bring its previously learned skill to bear on a novel situation? Second, how can an agent be both sensitive to the particularity of a given situation, while remaining flexibly poised for many other possibilities for action? We will argue that both the sensitivity to novel situations and the sensitivity to a multiplicity of action possibilities are enabled by the property of skilled agency that we will call metastable attunement. We characterize a skilled agent's flexible interactions with a dynamically changing environment in terms of metastable dynamics in agent-environment systems. What we find in metastability is the realization of two competing tendencies: the tendency of the agent to express their intrinsic dynamics and the tendency to search for new possibilities. Metastably attuned agents are ready to engage with a multiplicity of affordances, allowing for a balance between stability and flexibility. On the one hand, agents are able to exploit affordances they are attuned to, while at the same time being ready to flexibly explore for other affordances. Metastable attunement allows agents to smoothly transition between these possible configurations so as to adapt their behaviour to what the particular situation requires. We go on to describe the role metastability plays in learning of new skills, and in skilful behaviour more generally. Finally, drawing upon work in art, architecture and sports science, we develop a number of perspectives on how to investigate metastable attunement in real life situations.

Scaling junior sport competition: A body-scaling approach?

The design of the junior sport competition environment plays a critical role in attracting and retaining children as life-long participants. Critically, however, the guidelines governing the design of junior sport are rarely scrutinized. With this in mind, our aim is to offer sports authorities a method to systematically assess the suitability of guidelines. The most popular junior ball sport competitions in Australia were assessed in relation to the scaling of task constraints and compared to children's corresponding physical maturation and/or performance measures. This assessment enabled the calculation of pi ratios, which were then used to categorise constraints as either (1) undersized, (2) appropriately sized or (3) oversized. Results revealed that most sports' ask children to play in oversized conditions, particularly in the under 9 to under 12 age groups and in boys' competitions. The task constraints that had the highest percentage of pi ratios appropriately sized were match duration and goal size. Comparatively, ball size and field length had the highest percentage of pi ratios classified as oversized. We contend that the systematic approach applied in this article should be used by sports authorities to understand the extent of scaling constraints in junior sport.

Exploring to learn and learning to explore

In respect to ecological psychology processes of attunement and calibration, this critical review focusses on how exploratory behaviors may contribute to skilled perception and action, with particular attention to sport. Based on the theoretical insights of Gibson (The senses considered as perceptual systems, Houghton Mifflin, Boston, 1966) and Reed (Encountering the world: Toward an ecological psychology, Oxford University Press, New York, 1996), exploratory and performatory actions have been differentiated in numerous experiments to study the perception of opportunities of action. The distinction between exploratory and performatory actions has informed the study of infant behavior in developmental psychology. In the current article, we highlight limitations with this distinction in the study of sports performers. We propose that a dynamic view of exploratory behavior would reveal how individuals develop exploratory activity that generates information about the fit between environmental properties and action capabilities. In this aim, practitioners should: (1) give learners the opportunity to safely develop exploratory behaviors even when they act outside their action boundary; and (2) guide learners to search for more reliable information to develop exploratory behaviors that would enhance the transfer of skills to various performance contexts.

Preferential Reaching and End-State Comfort: How Task Demands Influence Motor Planning

Various factors (e.g., hand preference, object properties) constrain reach-to-grasp in hemispace. With object use, end-state comfort (ESC) has been shown to supersede the preferential use of one hand at the midline. To assess how location, size, and orientation of objects (dowel, mallet, cup) influence preferred-hand use and ESC (N = 50; M_age = 20.83), three preferential reaching tasks were implemented. Object location influenced hand selection in all tasks, along with size (cups) and orientation (mallets). Object location and orientation influenced ESC, but only with dowels and mallets. When oriented away from the preferred hand in hemispace, there was a higher occurrence of non-preferred hand use to facilitate ESC. Overall, findings add to understanding of ESC and preferential reaching with varying task demands.

Facing Repeated Stressors in a Motor Task: Does it Enhance or Diminish Resilience?

The aim of the present research is to test whether resilience in a motor task enhances or diminishes when encountering stressors. We conducted a lateral movement task during which we induced stressors and tracked the movement accuracy of each participant over time. Stressors corresponded to organismic constraints (i.e., visual occlusion), task constraints (i.e., movement sensitivity), or both types of constraints in an alternating pattern. In order to determine resilience, we introduced a measure combining the strength of a stressor and the relaxation time. Across the three conditions, we found that resilience was enhanced rather than diminished over time. This supports the notion that stressors in the form of constraint alterations can be beneficial to human motor performance.

On the Issue of Developing Creative Players in Team Sports: A Systematic Review and Critique From a Functional Perspective

Driven by the practical goal of developing creative players, several approaches to training creativity have been proposed and underpinned by empirical studies in sport science. However, the scope of these studies encompasses various aspects, which have all been subsumed under the singular label of "creativity." Therefore, this systematic review aims to disentangle the pursued lines of thought in order to facilitate the derivation of well-grounded recommendations for sports practice. To this end, 38 studies are presented and characterized in terms of their underlying conceptualizations and measures of creativity. In most studies, creativity is conceptualized as a player's domain-specific divergent thinking (DT) ability, reflected by individual differences in the number, variety and originality of ideas he or she is able to generate in response to game situations. Empirical studies indicate that DT can be improved by practice. However, the critical assumption that an enhanced DT ability transfers to creative on-field actions has yet to be tested. On the basis of the reviewed literature, an alternative point of view is proposed. In line with a relational understanding of creativity and a functional approach to behavioral control, it is hypothesized that an enhanced repertoire of sensorimotor skills increases the probability for performing functional solutions that, within a specific social and cultural frame of reference, go beyond the expected and consequently appear creative to the observer. In the context of sports practice, the proposed conceptual re-orientation would then suggest, rather than seeking ways to improve players' DT ability, to target sensorimotor skills that allow players to perform a variety of task-solutions and thus to act less predictably to the opponent-or in other words, more creative.

Action capability constrains visuo-motor complexity during planning and performance in on-sight climbing

The capability to adapt to changing conditions is crucial for safe and successful performance in physical activities and sports. According to the affordance‐based control perspective, individuals act in such a way as to take into account the limits of their capability to act. However, it is not clear how strength interacts with skill in shaping performer‐environment interactions. We, therefore, determined whether fingertip strength influences patterns of gaze and climbing behavior on new routes of ever‐increasing difficulty. We expected that comparatively weaker climbers would show less complex behavior because of an inability to perceive and act. Stronger climbers would show more complex visuo‐motor behavior because more opportunities for action remain, even as route difficulty increases. For very strong climbers the route would not be challenging enough, and less complex patterns suffice. Twenty climbers, ranging from lower grade to elite level participated. Maximum fingertip strength was obtained. Participants previewed and then climbed two separate 3 m long traverses, gradually decreasing in edge depth. Gaze and hip positions were collected for subsequent computation of gaze transition entropy (during preview) and hip displacement entropy (during climbing). Data revealed statistically significant curvilinear relationships between both fingertip strength and gaze transition entropy, and fingertip strength, and hip displacement entropy. Visuo‐motor complexity is scaled by how close the individual must act relative to boundaries of what the environment affords and does not afford for action given the individual constraints. Future research should examine in greater detail relationships between action capabilities and functional movement variability.

Linking Tensegrity to Sports Team Collective Behaviors: Towards the Group-Tensegrity Hypothesis

Collective behaviors in sports teams emerge from the coordination between players formed from their perception of shared affordances. Recent studies based on the theoretical framework of ecological dynamics reported new analytical tools to capture collective behavior variables that describe team synergies. Here, we introduce a novel hypothesis based on the principles of tensegrity to describe collective behavior. Tensegrity principles operate in the human body at different size scales, from molecular to organism levels, in structures connected physically (biotensegrity). Thus, we propose that a group of individuals connected by information can exhibit synergies based on the same principles (group-tensegrity), and we provide an empirical example based on the dynamics of a volleyball team sub-phase of defense.

Analysis of the Variability of the Game Space in High Performance Football: Implementation of the Generalizability Theory

The analysis of variability in sport has shown significant growth in recent years. Also, the study of space management in the game field has not been object of research yet. The present study pretends to describe the variability in the use of strategic space in high performance football. To do this, the spatial management of the Spanish men’s soccer team when it is in possession of the ball has been analyzed, during its participation in the UEFA Euro 2012 championship. Specifically, 6861 events have been collected and analyzed. Different zoning of the field have been used, and the location of the ball has been recorded in each offensive action. Using the observational methodology as a methodological filter, two types of analysis have been carried out: first, a General Linear Model was implemented to know the variability of the strategic space. Models with two, three, four and five variables have been tested. In order to estimate the degree of accuracy and generalization of the data obtained, the Generalizability Theory was implemented. Next, and in order to estimate the degree of accuracy and generalization of the data obtained, the Generalizability Theory was implemented. The results showed that the model that produces greater variability and better explanation is the four-variable model (P = 0.019; r² = 0.838), with the inclusion of the variables match half, rival, move initiation zone and move conclusion zone. Next, an optimization plan was implemented to know the degree of generalization with the Rival, Start Zone (SZ) and Conclusion Zone (CZ) facets. The available results indicate that it is based on an adequate research design in terms of the number of observations. The results of the present study could have a double practical application. On the one hand, the inclusion of the game’s space management in training sessions will potentially conceal the true tactical intention. On the other hand, knowing the variability of the strategic space will allow to exploit areas of the optimal playing field to attack the rival team.

A multilevel hypernetworks approach to capture properties of team synergies at higher complexity levels

Previous work has sought to explain team coordination using insights from theories of synergy formation in collective systems. Under this theoretical rationale, players are conceptualised as independent degrees of freedom, whose interactions can become coupled to produce team synergies, guided by shared affordances. Previous conceptualisation from this perspective has identified key properties of synergies, the measurement of which can reveal important aspects of team dynamics. However, some team properties have been measured through implementation of a variety of methods, while others have only been loosely addressed. Here, we show how multilevel hypernetworks comprise an innovative methodological framework that can successfully capture key properties of synergies, clarifying conceptual issues concerning team collective behaviours based on team synergy formation. Therefore, this study investigated whether different synergy properties could be operationally related utilising hypernetworks. Thus, we constructed a multilevel model composed of three levels of analysis. Level N captured changes in tactical configurations of teams during competitive performance. While Team A changed from an initial 1-4-3-3 to a 1-4-4-2 tactical configuration, Team B altered the dynamics of the midfielders. At Level N + 1, the 2 vs. 1 (1 vs. 2) and 1 vs. 1 were the most frequently emerging simplices, both behind and ahead of the ball line for both competing teams. Level N + 2 allowed us to identify the prominent players (a6, a8, a12, a13) and their interactions, within and between simplices, before a goal was scored. These findings showed that different synergy properties can be assessed through hypernetworks, which can provide a coherent theoretical understanding of competitive team performance.

Designing Junior Sport to Maximize Potential: The Knowns, Unknowns, and Paradoxes of Scaling Sport

In this mini-review, we draw attention to an important yet relatively untapped topic in the developmental pathway - the design of junior sport so that it appropriately matches the functional capacities of children. Junior sport is a regular weekend activity for many children across the world, yet many will be required to prematurely play on a field or with equipment that is designed for adults. Herein lies an opportunity for sport administrators to nurture children's development in sport by appropriately manipulating the rules and dimensions of the game. The aim of this mini-review is to (1) draw attention to the value of scaling junior sport, (2) highlight paradoxes within the current scaling sport literature, and (3) emphasize a way forward for junior sport research. If we are genuine in our endeavor to tailor sports experiences for children, more sophisticated approaches to scaling those experiences are a must.

Influence of technique on upper body force and power production during medicine ball throws

This project examined the interrelationships between power production and upper body kinematics during a series of medicine ball push-press (MBP-P) throws. Twenty-five regular weight trainers (body mass = 86 ± 10 kg) performed a series of ballistic vertical MBP-P throws at loads representing 5% and 10% of their assessed 5RM bench press. Throws were performed lying supine on a force platform (1 kHz) with upper body kinematics assessed using standard infra-red motion capture techniques (0.5 kHz). Gross measures of performance and power production such as peak vertical ball velocity (Vel_peak), peak force (F_peak) and power (P_peak) were recorded during the propulsive phase of the movement. Comparative analyses indicated that despite significant reductions in Vel_peak from the 5% to 10% loads (P < 0.001), F_peak remained largely unchanged (P = 0.167). Analysis of inter-trial variability showed that the gross measures of performance and power were relatively stable (Coefficient of Variation [CV%] <13%), while most upper limb segmental kinematics varied considerably between trials (CV% up to 70%). This project highlights the complexity of the relationships between power production and upper body kinematics during light load ballistic MBP-P throwing. Additionally, it shows how trained athletes can achieve similar outcomes during ballistic movements using a variety of movement strategies.

Exploiting Bi-Directional Self-Organizing Tendencies in Team Sports: The Role of the Game Model and Tactical Principles of Play

Research has revealed how inherent self-organizing tendencies in athletes and sports teams can be exploited to facilitate emergence of dynamical patterns in synergy formation in sports teams. Here, we discuss how game models, and associated tactical principles of play, may be implemented to constrain co-existing global-to-local and local-to-global self-organization tendencies in team sports players during training and performance. Understanding how to harness the continuous interplay between these co-existing, bi-directional, and coordination tendencies is key to shaping system behaviors in sports training. Training programs are traditionally dominated by designs, which shape the self-organizing tendencies of players and teams at a global-to-local scale by coaches imposing a tactical/strategical plan with associated tactical principles of play. Nevertheless, recent research suggests that performers also need to be provided with opportunities to explore self-organizing tendencies that emerge at the local-to-global scale in training. This directional tendency in synergy formation can be facilitated by players being given opportunities to actively explore different adaptive and innovative performance solutions, coherent with principles of play circumscribed in an overarching game model. Developing methods (coaching sessions rooted on principles of dynamical systems theory that foment the development of such local-to-global relations) to exploit the continuous interplay between these co-existing tendencies within sports teams may promote more effective and efficient athlete skill training programs, in addition to enhancing performance.

Variability of upper body kinematics in a highly constrained task - sprint swimming

Before examining the effect of changing constraints on skill adaptation, it is useful to know the tolerable variability of a movement pattern for optimal performance. Tolerable variability may vary throughout the period of task performance as some parts of the movement pattern may be more important than others. The purpose of this study was to quantify the inter-trial variability of performance variables, and hand path as the task-relevant parameter, of skilled front crawl swimmers during 25 m sprints. It was hypothesised that the wrist paths would have smaller inter-trial variability during the below water phase than during the above water phase. Twelve skilled swimmers performed four 25 m front crawl sprints which were recorded by six phased locked video cameras for three-dimensional analysis. Standard deviations and time series repeatability (R ²) of the right and left wrist displacement were determined. On average, swimmers varied their sprint speed between trials by <1.5%. The spatio-temporal patterns of wrist paths varied by <3 cm in all directions (horizontal, vertical & lateral). There was no significant difference in inter-trial variability between above and below water phases. Swimmers increased wrist path consistency at the critical events of water entry in the horizontal and lateral directions and at exit for the horizontal direction. This study established levels of variability in spatio-temporal movement patterns of the paths of the wrist in sprint swimming and provided evidence that swimmers minimise variability for key events, in this case, the position of the wrists at water entry and exit.

Mapping collective variable and synergy dynamics to task outcome in a perceptual-motor skill

In complex adaptive systems approaches to perceptual-motor control the mapping between the different categories of task dynamics: namely, task outcome, collective variable, neuromuscular synergies and individual joint configurations is a central theoretical issue, that has been primarily studied in bimanual tasks. Here we report an investigation in the roller ball task of how the task goal and multiple degrees of freedom of the arm-hand complex affords degeneracy between the respective properties of the task dynamics. The relation of the candidate collective variable, namely, the synchrony of the inner ball to outer shell motion of the roller ball and its relation to the task goal (continued increasing in ball speed), was examined as a function of the initial ball speed acting as a control parameter. Within trial analysis revealed initial search behavior for synchrony of ball and shell motion that was longer in duration with initial lower ball speed conditions. In contrast, higher initial ball speed conditions reduced the search time for and enhanced the rate of stabilization of the synchrony of inner ball and outer shell motion-features that facilitated the continued increase of ball speed and the probability of task success. Participants adopted one of three wrist-elbow neuromuscular synergies to manipulate the roller ball, the distribution of which was not influenced by either initial ball speed or task outcome. The pattern of findings over the different properties of task analysis of the roller ball provides evidence for the distinct but complementary dynamics of searching to form, stabilize and exploit a collective variable that satisfies the task goal through a small redundant set of arm-hand synergy motions.