Search

Combining biomechanics and motor control, the aim of this study was to investigate the limit cycle dynamics during the high bar longswing across the UK elite gymnastics pathway age groupings. Senior, junior and development gymnasts (N = 30) performed three sets of eight consecutive longswings on the high bar. The centre of mass motion was examined through Poincaré plots and recurrence quantification analysis exploring the limit cycle dynamics of the longswing. Close to one-dimensional limit cycles were displayed for the senior (correlation dimension (CD) = 1.17 ±.08), junior (CD = 1.26 ±.08) and development gymnasts (CD = 1.33 ±.14). Senior elite gymnasts displayed increased recurrence characteristics in addition to longer longswing duration (p <.01) and lower radial angular velocity of the mass centre (p <.01). All groups of gymnasts had highly recurrent and predictable limit cycle characteristics. The findings of this research support the postulation that the further practice, experience and individual development associated with the senior gymnasts contribute to the refinement of the longswing from a nonlinear dynamics perspective. These findings support the idea of functional task decomposition informing the understanding of skill and influencing coaches' decisions around skill development and physical preparation. [ABSTRACT FROM AUTHOR]

The present study investigated the transversal rotation of body and its relation to the horizontal movement for expert shooters and novices in a pistol aiming task. Participants stood on a force plate with an air pistol and aimed it to the centre of a target, positioned 1.4 m above the floor and 10 m away from the force plate, for 30 s as accurately as possible. The results revealed that the novice group showed greater transversal body variability represented by the free moment (FM) than the expert group. Correlation analysis showed that there is tight coupling between the FM and centre of pressure both in the anterior–posterior and medio-lateral directions for the expert group while only strong coupling of that in the anterior–posterior direction for the novice group. The findings suggest that FM is a critical factor to accurately aim the pistol on the target and there is a different postural strategy, in terms of the body motion in the transversal and horizontal space, as a function of skill level to realise success in the pistol aiming task. [ABSTRACT FROM AUTHOR]

The experiment reported was designed to investigate the interaction of information and force variability on the evolving search strategy, specifically testing the hypothesis of convergence to tolerant regions. Participants were required to produce proportional bimanual isometric force output over three days of practice, with no prespecified force target and where performance was more tolerant to force variability at higher forces. The duration of intermittent visual feedback was manipulated to test the effects of information and force variability on the search process and the resulting sensitivity to tolerant regions of the task space. The findings showed that just under half of the participants exploited more tolerant regions and that this was predicted by the initial force conditions. Different characterizations of the individual search patterns were also predicted by inherent force-dependent variability and initial force conditions. Visual intermittency feedback did not affect the time-dependent properties of the search process but did influence the within-trial variability. Our findings suggest that the attraction to tolerant regions needs to be considered within the interactions of the different categories of constraints on the search process. [ABSTRACT FROM AUTHOR]

Chronological age classifies elite male gymnasts into developmental performance classifications: senior (18+ years), junior (14–18 years) and development (8–14 years). Here, we examine the influence of age and experience on the biomechanics of the high bar longswing across classifications. Joint angular kinematics and kinetics were obtained from 30 gymnasts performing three sets each of eight consecutive longswings. Differences between groups and relations between age, experience and key biomechanical variables were correlated. Kinetic variables and range of motion of the hip and knee were highest for development gymnasts. In all age groups, a dominant shoulder kinetic contribution was found, although circle location of the peak joint kinetics occurred earliest for junior gymnasts. Hip work contributed more prominently in development gymnasts. Age and experience were positively correlated to an increase in peak shoulder moments and powers and negatively correlated to peak hip and knee moments. The findings reveal that age and experience combine to influence the functional phase, joint kinematics and relative joint kinetic contribution, particularly with the senior group demonstrating a shoulder dominant technique. Changes in musculoskeletal loading across the age groups suggest that factors such as relative strength and practice may have influenced this joint mode transition of the longswing. [ABSTRACT FROM AUTHOR]

This paper outlines a framework for strength training as a dynamical model of perceptual-motor learning. We show, with emphasis on fixed-point attractor dynamics, that strength training can be mapped to the general dynamical principles of motor learning that arise from the constraints on action, including the distribution of practice/training. The time scales of the respective dynamics of performance change (increment and decrement) in discrete strength training and motor learning tasks reveal superposition of exponential functions in fixed-point dynamics, but distinctive attractor and parameter dynamics in oscillatory limit cycle and more continuous tasks, together with unique timescales to process influences (including practice, learning, strength, fitness, fatigue, warm-up decrement). Increments and decrements of strength can be viewed within a dynamical model of change in motor performance that reflects the integration of practice and training processes at multiple levels of learning and skill development. [ABSTRACT FROM AUTHOR]

Human movement takes place in both space and time so that measures of movement accuracy in space are made with respect to time, and vice-versa providing a foundation to the proposal of the complementarity of spatial and temporal error in aiming movements. We examined this hypothesis in both the standard Fitts and Peterson discrete movement speed-accuracy protocol that requires moving to stop within a fixed spatial target (distance (D) with target bandwidth (WD) in an emergent movement time (T) and, also in the reciprocal and novel space-time protocol introduced here that required moving for a fixed temporal target goal T with bandwidth of WT with an emergent D. Experiment 1 examined a range of D conditions (45, 100, 180, 280, and 405 mm with bandwidth WD ±5 mm) within the Fitts' Law discrete spatial accuracy protocol to provide compatible spacetime boundary conditions for the reciprocal spacetime protocol in Experiment 2 that examined the effect of target time (T − 250, 460, 670, and 880 ms each with bandwidth WT ±50 ms) on the emergent D. The findings showed that the spatial and temporal error profiles in Experiment 2 were consistent with exchanging D and T in Fitts' Law Equation. This provides evidence for the reciprocal nature of the spacetime error functions in Fitts' type movement aiming protocols and is compatible with the reciprocal profiles of spatial and temporal errors in other classes of movement aiming tasks. [ABSTRACT FROM AUTHOR]

Constraints on practice can benefit motor learning by guiding the learner towards efficient coordination patterns, but can also narrow the potential solution space of coordination and control. The aim of this paper was to investigate whether narrowing the solution space through more restrictive task constraints limits the expression of potential exploratory behaviours during the learning process, identified using Drifting Markov Models. In a breaststroke swimming task, the change in interlimb coordination of 7 learners practicing for 16 lessons over 2 months was analysed to quantify motor exploration and identify periods of metastable regimes of coordination. Results showed that the observed exploratory dynamics were highly individual both in terms of range of exploration and in the patterns of search. The more restrictive task constraints did not impair the amount of exploration but rather channelled the exploration around a few selected patterns. In addition, restraining the nature of the exploratory process increased the inter-individual differences of the learning rate. Although manipulating the task constraints during learning can help learners to escape from the behavioural consequences of their intrinsic dynamics, maintaining a broad solution space for a diversity of coordination patterns to emerge was key to fostering effective exploration of individual coordination solutions. [ABSTRACT FROM AUTHOR]

Constraints on practice can benefit motor learning by guiding the learner towards efficient coordination patterns, but can also narrow the potential solution space of coordination and control. The aim of this paper was to investigate whether narrowing the solution space through more restrictive task constraints limits the expression of potential exploratory behaviours during the learning process, identified using Drifting Markov Models. In a breaststroke swimming task, the change in interlimb coordination of 7 learners practicing for 16 lessons over 2 months was analysed to quantify motor exploration and identify periods of metastable regimes of coordination. Results showed that the observed exploratory dynamics were highly individual both in terms of range of exploration and in the patterns of search. The more restrictive task constraints did not impair the amount of exploration but rather channelled the exploration around a few selected patterns. In addition, restraining the nature of the exploratory process increased the inter-individual differences of the learning rate. Although manipulating the task constraints during learning can help learners to escape from the behavioural consequences of their intrinsic dynamics, maintaining a broad solution space for a diversity of coordination patterns to emerge was key to fostering effective exploration of individual coordination solutions. [ABSTRACT FROM AUTHOR]

Movement variability has been postulated to afford perception of the perceptual motor workspace and to be directly linked to improved performance. Here, we investigated how instructions mediate the search process and the relation between performance outcome and movement variability. We used a novel bimanual force tracking task where zero error was achieved via proportional output between the hands. Participants were either instructed or not as to how to coordinate their force output to achieve this goal, but the goal to minimize error was explained to all participants. The provision of instructions restricted the overall area of the task space that was searched. Moreover, the time dependent properties of the search were influenced; where instructions increased the likelihood that participants would produce a higher force level over practice. Multiple regression revealed that variability was positively correlated with performance outcome, but the strength of this relation was dependent on instructions and individual search strategies. The findings are consistent with the view that information through instructions shapes individual emergent perceptual-motor search strategies that in turn mediate how movement variability relates to performance outcome. [ABSTRACT FROM AUTHOR]

The preservation of static balance in both upright- and hand-stance is maintained by the projection of center of mass (CM) motion within the region of stability at the respective base of support. This study investigated, from a degrees of freedom (DF) perspective, whether the stability of the CM in both upright- and hand-stances was predicted by the respective dispersion and time-dependent regularity of joint (upright stance—ankle, knee, hip, shoulder, neck; hand stance—wrist, elbow, shoulder, neck) angle and position. Full body three-dimensional (3D) kinematic data were collected on 10 advanced level junior female gymnasts during 30 s floor upright- and hand-stands. For both stances the amount of the dispersion of joint angle and sway motion was higher than that of the CM and center of pressure (CP) with an inverse relation to time-dependent irregularity (SampEn). In upright-standing the variability of neck motion in the anterior–posterior direction was significantly greater than that of most joints consistent with the role of vision in the control of quiet upright posture. The findings support the proposition that there are both task specific and general properties to the global CM control strategy in the balance of upright- and hand-standing induced by the different active skeletal-muscular organization and the degeneracy revealed in the multiple distributional variability patterns of the joint angle and position in 3D. [ABSTRACT FROM AUTHOR]

This paper examines the influence of task and skill level constraints on the generality of proximal–distal control for within-limb movement coordination. Analysis and synthesis of the experimental findings leads to the proposition that proximal–distal is one of several within-limb patterns of coordination, including: the reverse distal–proximal sequence, simultaneous activation of segments, and other sequence variations of this. The probability of particular patterns occurring is induced by task constraints and skill level of the individual, together with their evolving biomechanical consequences, including: open/closed chain, absorption/propulsion of force, magnitude of momentum, and accuracy/timing. We develop the theoretical perspective that classes of task constraints induce particular types of neuromechanical organization to within-arm or within-leg segment coordination. In this task constraint framework, proximal–distal within-limb organization is a particular rather than a general case for within-limb coordination. The limitations of anatomically-based accounts of directional change for within-limb organization are discussed with reference to a general functional degrees of freedom task constraint framework for movement coordination and control. [ABSTRACT FROM AUTHOR]

There is a long-held view that discrete movements aimed to a target are composed of a sequence of movement units (sub-movements) that have different roles in motor control (e.g., initial impulse, error correction and movement termination) depending on the task constraints (e.g., spatial-temporal requirements). Here we report findings from the manipulation of vision/no-vision on the prevalence and type of sub-movements in discrete movement tasks over a range of space-time task criteria. The presence of vison resulted in longer movement times compared to the no-vision counterpart in time-matching tasks. A similar vision effect was observed in the highest Index of Difficulty for time-minimization tasks. Conditions that resulted/required longer movement times demonstrated more pre-velocity-peak and post-velocity-peak types of sub-movements whereas short movement times increased the likelihood of overshooting sub-movements. The present study results are consistent with the idea that movement time is the variable associated with changes in sub-movement profiles. [ABSTRACT FROM AUTHOR]

In this paper we examine the role of instructional strategies as constraints within a discovery learning framework for the teaching of open skill team ball games to elementary school-aged children. The cohesive and adaptive integration of constraints (individual, environment, and task) by practitioners of movement and physical activity (instructor, teacher, coach) is proposed as the pathway to exploiting the effectiveness of guided discovery learning. The qualitative analysis of the practical instantiations of this framework by expert teachers is examined with respect to the learning of open skill team invasion games (e.g., basketball, soccer). The primary constraints to action in this learning-teaching developmental framework are coordinated so as to keep the self-organization of skill development (movement pattern and tactics) continually evolving, while preserving the child's motivation and enjoyment for the expanding repertoire and performance capacity of his/her perceptual-motor skills. In this open skill and elementary school age-related context, generality and specificity are both necessary and complementary in the expression of task, skill and practice influences on motor learning and performance. [ABSTRACT FROM AUTHOR]

This paper is Part II of a study of the effects of practice on young adult novice gymnasts learning the movement coordination pattern of the longswing. The focus was the early stage of learning a critical component of the longswing, namely: through joint motion to inject mechanical energy into the upswing segment effectively to complete the longswing circle. Twenty-five novice male gymnasts received expert instruction while practicing two sessions a week for 3 weeks between a pre- and a post-practice assessment test trial. Seven novices completed a full circle by the end of Test 4. Completion of the longswing was positively related to the angular velocity generated in the gravity driven free fall of the initial segment and the greater rate of energy input in the upward segment. A successful performance in terms of the emergent movement pattern requires coordination of the onset, rate and level of energy input to counterbalance the negative influence of gravity on the second half upwards segment. The development of the complete longswing through the emergence of the collective variable dynamics (Paper 1) and biomechanical energetics of the gymnast (Paper 2) informs coaches, scientists and clinicians regarding task decomposition and learning the longswing. [ABSTRACT FROM AUTHOR]

We studied novice gymnasts (N = 25) learning to form the longswing movement coordination pattern. The focus was the emerging behavioural organisation of centre of mass (CM) dynamics and the relative phase of the bar–CM angular motion. Seven novices learned a complete longswing by the end of the study, 8 novices showed no improvement in proportion of circle completed, and the remainder produced modest but persistent increments of final swing height without achieving a full circle. The radial angular velocity generated in the free fall phase and the circle location of bar-CM relative phase progressively and predominantly predicted circle completion. Bar-CM relative phase produced a consistent qualitative relation within- and between-subjects characteristic of a collective variable with the bar leading the CM on the initial downward antiphase segment and the CM leading on the upward antiphase segment. The ratio of these phases was related by the last practice session to degree of circle completion. The findings showed strong individual differences in the effect of practice on the early steps of learning the movement coordination where the progressive emergence of the longswing circle is driven by exploiting the positive- and minimising the negative-influence of gravity on the bar–CM coordination dynamics (candidate collective variable). [ABSTRACT FROM AUTHOR]

The goal of present experiment was to test whether different speed-accuracy paradigms outcomes (time minimization and time matching) were due to different temporal and spatial task constraints. Fifteen participants twice performed 100 trials of time minimization and time matching tasks with the yoked temporal and spatial requirements (criterion time and target width). The results showed that performing an aiming movement under the same spatial and temporal constraints resulted in similar outcomes with distributional properties (skewness and kurtosis) being slightly affected by practice effects. There was a trade-off in the information entropy for space and time (temporal information entropy decreased as spatial information entropy increased) with practice. Nevertheless, the joint space-time entropy of outcome did not change across tasks and conditions-revealing a common level of space-time entropy between these two categories of aiming tasks. These findings support the hypothesis that under the same spatial and temporal constraints the movement speed-accuracy function shares the same properties independent of task category. [ABSTRACT FROM AUTHOR]

In this paper we review studies that have identified collective variables (order parameters) in movement coordination, control and skill with emphasis on whole-body multiple joint degree of freedom (DF) tasks. Collective variables of a dynamical system have been proposed formally and informally from a diverse set of perceptual-motor tasks, from which we emphasize: bimanual coordination, locomotion (pedalo, walking, running, bicycle riding), roller ball task, static (quiet standing) and dynamic (moving on a ski-simulator) balance, grasping, and juggling. Several types of candidate collective variables have been identified, including: relative phase, frequency ratio, number of hands active in grasping, synchrony, learning rate and relative timing. There is a strong influence of the task goal in determining the collective variable that can be body or environment relative. The emergence of the task relevant collective variable is typically in the early stage of skill learning where subjects through practice adapt movement organization to realize a never previously produced movement coordination pattern. Throughout, the paper elaborates on open theoretical, experimental and analysis issues for collective variables in the context of task constraints and Bernstein's (1967) view of skill acquisition as learning to master redundant DF. [ABSTRACT FROM AUTHOR]

This study investigated overarm throwing technique at different developmental ages in children from the perspective of three distinct, though potentially complementary, approaches to motor skill acquisition. Children at 6, 10, and 14 years of age (N = 18), completed dominant overarm throws during which whole-body kinematic data were collected. Firstly, application of Newell's ([1985]. Coordination, control and skill. In Advances in Psychology (Vol. 27, pp. 295–317). North-Holland.) stages of learning identified three distinct age-related coupling modes between forward motion of the centre-of-mass (CoM) and the wrist, which demonstrated a greater range of couplings for older children. Secondly, in line with Bernstein's ([1967]. The coordination and regulation of movement. London: Pergamon Press.) hypothesis of freezing before freeing degrees of freedom, a significantly smaller range of motion (ROM) at the ankle and knee joints, but greater ROM at the hip and upper limb joints was found for the 6 year old group compared to the 10 and 14 year old groups. Thirdly, based on the components model (Roberton & Halverson [1984]. Developing children-their changing movement: A guide for teachers. Lea & Febiger.), the overarm throws demonstrated by 6 year olds were characterised as primitive to intermediate, where 10 and 14 year old's throws were characterised by the penultimate action level for each component. Characteristics of CoM-wrist coupling more clearly identify children's age-related technique and highlight the importance of posture-ball release dynamics. The posture-ball dynamics were supported by changes in ROM and the components model, revealing the complementary nature of the three approaches to the analysis of age-related differences in overarm throwing action. [ABSTRACT FROM AUTHOR]

Information entropy of the joint spatial and temporal (space-time) probability of discrete movement outcome was investigated in two experiments as a function of different movement strategies (space-time, space, and time instructional emphases), task goals (point-aiming and target-aiming) and movement speed-accuracy constraints. The variance of the movement spatial and temporal errors was reduced by instructional emphasis on the respective spatial or temporal dimension, but increased on the other dimension. The space-time entropy was lower in targetaiming task than the point-aiming task but did not differ between instructional emphases. However, the joint probabilistic measure of spatial and temporal entropy showed that spatial error is traded for timing error in tasks with space-time criteria and that the pattern of movement error depends on the dimension of the measurement process. The unified entropy measure of movement outcome in space-time reveals a new relation for the speed-accuracy function. [ABSTRACT FROM AUTHOR]

This paper provides reflections on the progress to date and current status of research in kinesiology. The accompanying overview articles in this special issue of Kinesiology Review show that the contemporary disciplinary/professional foci of kinesiology remain, by and large, the same as the initial research and teaching structures of 50 years ago, as outlined in the inaugural overviews. Nevertheless, within this prevailing disciplinary/professional structure, there have been many new developments in movement-related research, including the juxtaposition of novel alignments and integrations of certain specializations of kinesiology. There is general consensus that the quality and quantity of research in kinesiology have advanced substantially, albeit unevenly, on multiple fronts, both within and between the areas of specialization. The research agenda in kinesiology has benefitted from the growing realization of the centrality of human movement and physical activity in contributing to a healthy lifestyle for individuals and societies. [ABSTRACT FROM AUTHOR]

This study examined the specificity hypothesis by examining the association between two specific motor competence test batteries [Movement Assessment Battery for Children (MABC) and Test of Motor Competence (TMC)] in a sample of young children. In addition, we explored the factorial structure of the MABC and TMC. A total of 80 children participated in the study (38 girls and 42 boys) with a mean chronological age of 7.9 years (SD 0.55). The correlation between total score MABC and total z-score TMC was r = 0.46. In general, low pair-wise correlations (r 2 < 0.20) between the different motor tasks were found. The highest correlation was between the placing bricks and building bricks r = 0.45 (TMC); the stork balance and jumping in squares r = 0.45 (MABC). These low pair-wise relations of items are consistent with findings from younger and older children's age-related motor competence test batteries. Principal components analysis (PCA) showed that the 1st component accommodated 25% of the variance and was dominated in the top five variable weightings by items of the MABC test; whereas the 2nd component accommodated 12% of the variance with the higher weightings all from the TMC test. The findings provide evidence with children for specificity rather than generality in learning motor skills a viewpoint that has predominantly been driven by adult learning studies. The PCA revealed that the MABC and TMC are testing different properties of children's motor competence though in both cases the variance accounted for is relatively modest, but generally higher than the motor item pair-wise correlation. [ABSTRACT FROM AUTHOR]

The experiment was set up to investigate the inter- and intrafoot coordination dynamics of postural control on balance boards. A frequency domain principal component analysis (PCA) was applied on 4 center of pressure (COP) time series collected from two force platforms to reveal their contributions to postural stability. The orientation of support played a more significant role than its width in channeling the foot coordination dynamics. When the support was oriented along the AP-challenging direction, the 4 COPs revealed a parallel contribution to the 1st principal component (PC1) indicating an interdependence of the foot coordination in both directions. When the support was positioned along the ML-challenging direction, the COPs in the AP direction showed larger weightings to PC1 implying an interfoot coordination. These findings provide evidence that COP coordination operates in adaptive ways to sustain postural stability in light of changing support constraints to standing. [ABSTRACT FROM AUTHOR]

The experiment was set up to investigate the inter- and intrafoot coordination dynamics of postural control on balance boards. A frequency domain principal component analysis (PCA) was applied on 4 center of pressure (COP) time series collected from two force platforms to reveal their contributions to postural stability. The orientation of support played a more significant role than its width in channeling the foot coordination dynamics. When the support was oriented along the AP-challenging direction, the 4 COPs revealed a parallel contribution to the 1st principal component (PC1) indicating an interdependence of the foot coordination in both directions. When the support was positioned along the ML-challenging direction, the COPs in the AP direction showed larger weightings to PC1 implying an interfoot coordination. These findings provide evidence that COP coordination operates in adaptive ways to sustain postural stability in light of changing support constraints to standing. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify motor control solutions associated with the ability to maintain handstand balance. Using a novel approach, we investigated the dynamical interactions between centre of pressure (CoP) and centre of mass (CoM) motion. A gymnastics cohort was divided into a 'less skilled' group, who held handstands for 4–6 s, and a 'more skilled' group, who held handstands in excess of 10 s. CoP–CoM causality was investigated in anterior–posterior (AP) and medio-lateral (ML) directions, in addition to time–space, time–frequency and Hurst Exponent (H) analyses. Lower AP CoP to CoM causal drive and lower H values (> 0.6) indicated the more skilled gymnasts were less reliant on CoP mechanics to drive CoM motion. More skilled performance demonstrated greater adaptability through use of reactive, as opposed to anticipatory, control strategies. Skilled performers additionally exploited mechanical advantages in ML (e.g. a wider base of support), compared to the less skilled athletes. A multiple regression analysis revealed H and frequency domain measures to be better predictors of handstand balance duration than time–space domain measures. The study findings highlight the advantage of an adaptable motor control system with a directional profile, and provide new insight into the clear, measurable footprint of CoP on the dynamics of CoM. [ABSTRACT FROM AUTHOR]

Recent studies have shown more than one time scale of change in the movement dynamics of practice. Here, we decompose the drift and diffusion dynamics in adaptation to performing discrete aiming movements with different space-time constraints. Participants performed aiming movements on a graphics drawing board to a point target at 5 different space-time weightings on the task outcome. The drift was stronger the shorter the time constraint whereas noise was U-shaped across the space-time conditions. The drift and diffusion of adaptation in discrete aiming movements varied as a function of the space-time constraints on performance outcome and the spatial, temporal, or space-time measure of performance outcome. The findings support the postulation that the time scale of movement adaptation is task dependent. [ABSTRACT FROM AUTHOR]

A hallmark of skilled motor performance is behavioral flexibility – i.e., experts can not only produce a movement pattern to reliably and efficiently achieve a given task outcome, but also possess the ability to change that movement pattern to fit a new context. In this perspective article, we briefly highlight the factors that are critical to understanding behavioral flexibility, and its connection to movement variability, stability, and learning. We then address how practice strategies should be developed from a motor learning standpoint to enhance behavioral flexibility. Finally, we highlight some important future avenues of work that are needed to advance our understanding of behavioral flexibility. We use examples from sport as a context to highlight these issues, especially in regard to elite performance and development. [ABSTRACT FROM AUTHOR]

A review and synthesis of the literature on the learning and development of motor skills supports the postulation that whether a motor skill can be deemed fundamental is dependent on the collective presence of three conditions: (i) uniqueness to the movement pattern and/or outcome; (ii) near universality of the functional outcome in the healthy population; (iii) capacity to act as an antecedent influence supporting generalization to a large and broad set of perceptual-motor skills. Within this framework, it is proposed that the infant motor development sequence underpinning upright posture (e.g., sitting, bipedal standing), locomotion (e.g., walking, running), and object-interaction (e.g., grasping) represents the minimum set of fundamental motor skills from which all other skills evolve with over the lifespan. This position is in contrast to the views of many students of motor development and learning who describe numerous skills that typically emerge in the ∼2- to 18-year-old range as fundamental but do not meet the criteria outlined here to be fundamental. It is proposed that these be labeled as core developmental activities having a more restricted but still practically relevant influence on the acquisition of and generalization to other motor skills. [ABSTRACT FROM AUTHOR]

Human physiological signals are inherently rhythmic and have a hallmark feature in that even distant intrasignal measurements are related to each other. This relationship is termed long-range correlation and has been recognized as an indicator of the optimal state of the observed physiological systems, among which the locomotor system. Loss of long-range correlations has been found as a result of aging as well as disease, which can be evaluated with detrended fluctuation analysis (DFA). Recently, DFA and the scaling exponent α have been employed for understanding the degeneration of temporal regulation of human walking biorhythms in, for example, Parkinson disease (PD). However, heterogeneous evidence on scaling exponent α values reported in the literature across different population groups has put into question what constitutes a healthy physiological pattern. Therefore, the purpose of this systematic review was to investigate the functional thresholds of scaling exponent α in young vs. older adults, as well as between patients with PD and age-matched asymptomatic controls. Aging and PD exhibited a negative effect size (i.e., led to decreased long-range correlations) of −0.20 and −0.53, respectively. Our meta-analysis based on 14 studies provides evidence that a mean scaling exponent α threshold of 0.86 [2 standard error (0.76, 0.96)] is able to optimally discriminate temporal organization of stride interval between young and old, whereas 0.82 (0.72, 0.92) differentiates patients with PD and age-matched asymptomatic controls. The optimal thresholds presented in this review together with the consensus guidelines for using DFA might allow a more sensitive and reliable application of this metric for understanding human walking physiology than has been achieved to date. [ABSTRACT FROM AUTHOR]

A case study visualisation approach to examining the coordination and variability of multiple interacting segments is presented using a whole-body gymnastic skill as the task example. One elite male gymnast performed 10 trials of 10 longswings whilst three-dimensional locations of joint centres were tracked using a motion analysis system. Segment angles were used to define coupling between the arms and trunk, trunk and thighs and thighs and shanks. Rectified continuous relative phase profiles for each interacting couple for 80 longswings were produced. Graphical representations of coordination couplings are presented that include the traditional single coupling, followed by the relational dynamics of two couplings and finally three couplings simultaneously plotted. This method highlights the power of visualisation of movement dynamics and identifies properties of the global interacting segmental couplings that a more formal analysis may not reveal. Visualisation precedes and informs the appropriate qualitative and quantitative analysis of the dynamics. [ABSTRACT FROM AUTHOR]

To execute a motor solution to a given task, individuals search through the space of movement possibilities guided by information that arises from the interaction with task and environment. Through this search, individuals seek to avoid inappropriate solutions through local minima in the task space. The processes that lead to some but not all individuals avoiding local minima and finding solutions is not yet understood. Based on the tenets of ecological psychology for perception and action, we examined in two experiments the hypothesis that the incapacity to differentiate errors (performance of an inappropriate solution) from inherent variability would interfere with the perception of properties of the task space and result in a longer time performing an inappropriate solution for the task before exploration of other solutions. Inherent variability was shown to be a direct predictor of the changes in the search strategies. Also, we found that the specifics of the search patterns could predict the performance in the task. Thus, the pattern of motion through the task space affords perception of specific properties of this space guiding individuals in the evolving dynamics of exploration or exploitation. [ABSTRACT FROM AUTHOR]

In this study, two force platforms were synchronized to investigate the coordination of the right and left foot center of pressure (COP(R) and COP(L)) and its relation to the COP(NET) in the control of 5 upright postures with and without visual information. The results revealed that the standard deviation (SD) of COP(L), COP(R), and COP(NET) progressively increased in the more challenging staggered and tandem stances, respectively, and to a lesser degree with the absence of visual information. Circular analysis of the relative phase of COP(L) and COP(R) revealed that the coupling pattern and variability were dependent on postural stances and the availability of vision. A negative correlation between the variability of the relative phase of the two feet COPs and the SD of the COP(NET) in the anterior-posterior (AP) direction was evident most strongly in the no vision conditions. Thus, the asymmetry of the mechanical constraints on the feet as a function of stance organize the coordination patterns of the feet COPs while the degree of adaptive variation between the feet COPs is dependent on both the mechanical constraints and the availability of vision. [ABSTRACT FROM AUTHOR]

This study investigated the asymmetry of bilateral interference in relation to the relative difference of force amplitude between hands and the hand dominance. In Experiment 1, one hand produced a fixed constant force of 5% maximum voluntary contraction (MVC) while the other hand produced different constant forces of 5%, 20%, and 50% MVC in blocked conditions. Asymmetric interference in force amplitude alone was evident in that the hand producing the fixed low force showed a stronger interference than the hand performing the higher force. Asymmetric interference in hand dominance was also found in that more interference was observed when the nondominant left hand produced the higher force, a finding that does not support the hemisphere specialization hypothesis. Experiment 2 was performed to rule out the fixed force level interpretation compared with the low force level account and the fixed force was set at 50% MVC. The results were consistent with the findings in Experiment 1 showing asymmetric interference with force amplitude rather than with fixed force level. The findings revealed that without a timing constraint the task demand associated with force amplitude alone can induce the asymmetric bilateral interference. The external task asymmetry and intrinsic asymmetry of the organism interact and influence the bimanual force coordination and control patterns. [ABSTRACT FROM AUTHOR]

In this study, two force platforms were synchronized to investigate the coordination of the right and left foot center of pressure (COPR and COPL) and its relation to the COPNET in the control of 5 upright postures with and without visual information. The results revealed that the standard deviation (SD) of COPL, COPR, and COPNET progressively increased in the more challenging staggered and tandem stances, respectively, and to a lesser degree with the absence of visual information. Circular analysis of the relative phase of COPL and COPR revealed that the coupling pattern and variability were dependent on postural stances and the availability of vision. A negative correlation between the variability of the relative phase of the two feet COPs and the SD of the COPNET in the anterior-posterior (AP) direction was evident most strongly in the no vision conditions. Thus, the asymmetry of the mechanical constraints on the feet as a function of stance organize the coordination patterns of the feet COPs while the degree of adaptive variation between the feet COPs is dependent on both the mechanical constraints and the availability of vision. [ABSTRACT FROM AUTHOR]

This study investigated the asymmetry of bilateral interference in relation to the relative difference of force amplitude between hands and the hand dominance. In Experiment 1, one hand produced a fixed constant force of 5% maximum voluntary contraction (MVC) while the other hand produced different constant forces of 5%, 20%, and 50% MVC in blocked conditions. Asymmetric interference in force amplitude alone was evident in that the hand producing the fixed low force showed a stronger interference than the hand performing the higher force. Asymmetric interference in hand dominance was also found in that more interference was observed when the nondominant left hand produced the higher force, a finding that does not support the hemisphere specialization hypothesis. Experiment 2 was performed to rule out the fixed force level interpretation compared with the low force level account and the fixed force was set at 50% MVC. The results were consistent with the findings in Experiment 1 showing asymmetric interference with force amplitude rather than with fixed force level. The findings revealed that without a timing constraint the task demand associated with force amplitude alone can induce the asymmetric bilateral interference. The external task asymmetry and intrinsic asymmetry of the organism interact and influence the bimanual force coordination and control patterns. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the mechanisms contributing to the different scaling functions between force and force variability in continuous and discrete isometric forces. Muscle forces were simulated with the Fuglevand et al. (1993) model of motor unit recruitment and rate coding, and a range of recruitment and firing properties were manipulated. The influence of time-to-peak force on the discrete force variability was also examined. The results revealed that the peak firing rate, the synchrony between motoneurons, and the recruitment range contributed to the different variability functions in continuous and discrete forces. The shorter time-to-peak force led to higher variability in the peak force. The findings show that the model can produce the distinct properties of the force variability scaling functions in continuous and discrete forces. The simulation results provide preliminary insight into the neuromuscular mechanisms of the different force variability functions in continuous and discrete isometric forces. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the mechanisms contributing to the different scaling functions between force and force variability in continuous and discrete isometric forces. Muscle forces were simulated with the Fuglevand et al. (1993) model of motor unit recruitment and rate coding, and a range of recruitment and firing properties were manipulated. The influence of time-to-peak force on the discrete force variability was also examined. The results revealed that the peak firing rate, the synchrony between motoneurons, and the recruitment range contributed to the different variability functions in continuous and discrete forces. The shorter time-to-peak force led to higher variability in the peak force. The findings show that the model can produce the distinct properties of the force variability scaling functions in continuous and discrete forces. The simulation results provide preliminary insight into the neuromuscular mechanisms of the different force variability functions in continuous and discrete isometric forces. [ABSTRACT FROM AUTHOR]

Fitness and skill are embedded constructs that have been the primary foci of the field of physical education. The emphasis of one of these constructs over the other is a matter of context that cannot, given their embedding, lead to the exclusivity of one in the education of and through the physical (Williams, 1930), particularly as we seek to develop more efficacious school based systems of physical education that transcend into a lifespan perspective for the individual. The NASPE national standards for physical education and sport provide a broad, integrated, and age-related plan for fitness and skill within physical education but the degree to which the goals of this plan are actually realized in schools is in question. It is proposed that a lifespan agenda for fitness and skill will be more appropriately and effectively realized by emphasizing and exploiting in practice: a) a balanced and integrated approach to the knowing how and knowing that of physical education; b) the macro level constructs associated with physical activity, such as joy, meaning and values; and c) the time scales of influence to movement and physical activity in an integrated healthy lifestyle. [ABSTRACT FROM AUTHOR]

Studies of bimanual coordination have typically estimated the stability of coordination patterns through the use of the circular standard deviation of relative phase. The interpretation of this statistic depends upon the assumption of a von Mises distribution. The present study tested this assumption by examining the distributional properties of relative phase in three bimanual coordination patterns. There were significant deviations from the von Mises distribution due to differences in the kurtosis of distributions. The kurtosis depended upon the relative phase pattern performed, with leptokurtic distributions occurring in the in-phase and antiphase patterns and platykurtic distributions occurring in the 30° pattern. Thus, the distributional assumptions needed to validly and reliably use the standard deviation are not necessarily present in relative phase data though they are qualitatively consistent with the landscape properties of the intrinsic dynamics. [ABSTRACT FROM AUTHOR]

This paper presents the stochastic modeling of isometric force variability in the steady-state time series recorded from the index finger of young adults in the act of attempting to hold different levels of constant force. The isometric force time series were examined by assuming that the stochastic (random) models were linear. System identification techniques were employed to estimate the parameters of each linear model. Once the models were parameterized, the values of the estimated parameters were compared to determine if a single linear time-invariant model was applicable across the entire isometric force range. Although the overall random models were found to be nonlinear functions of the target force level, within a fixed target level, linear modeling provided adequate estimates of the underlying processes thus enabling the use of well-known linear system identification algorithms. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of how the field of kinesiology can exploit the advantages of multiple agendas while minimizing the disadvantages. Agendas here are the scholarly themes that help organize the field of study explicitly or implicitly and that give emphases to it with respect to its content and impact in society. The issue of multiple agendas is discussed with respect to the core knowledge dimensions of physical activity: namely, lifespan development, interdisciplinary knowledge, and the professions of physical activity. The selection of programmatic emphases within dimensions and their interpretation are critical to determining the relative degrees of coherence and fragmentation of a department and the field of study at large. [ABSTRACT FROM AUTHOR]

The study reported had three purposes, namely, to analyze the effect of aging (cohort groups 20-29, 60-69, 70-79, and 80-89 years of age), step length, and self-efficacy on the time to reacquire stability after the execution of a step. The analysis of force-platform data showed that the time to reacquire a stable posture after taking a step increased with increments of age. Correlation analysis showed that older adults were less confident in their ability to complete daily activities without falling or losing balance and that participants with lower levels of balance-related efficacy required a longer time to reacquire stability. These findings provide evidence that aging imposes temporal limitations in the regaining of postural stability that are related to individuals' perceptions of balance and falls efficacy. [ABSTRACT FROM AUTHOR]

The experiment reported examined: (a) the role of the geometrical body scaled informational invariant for the transition of human grip configurations; (b) whether the same invariant can be scaled considering also the force applied during the grasp phase; and (c) how the temporal duration of the grasp and displacement phases of prehension are scaled to the object properties of size and mass. Adult subjects performed a series of trials in reaching, grasping, and displacing spheres that varied in size and mass. The grip transitions were described by the body scaled relation: [formula: see text] where L(s) and M(s) are, respectively, the diameter and the mass of the spheres grasped and L(h) and M(h) are the length and the mass of the hand. The impulse during the grasp phase was linearly related with the mass of the spheres within each density. The temporal durations of the grasp and displacement components were scaled coherently to the object properties. These findings provide support to the hypothesis that the grasp and displacement components of prehension are organized coherently within a single action. [ABSTRACT FROM AUTHOR]

Examines the inter-digit individuation and force variability in the precision grip of young, elderly, and Parkinson's disease participants. Assessment on force variability using the standard deviation; Relation between force variability and inter-digit individuation; Increment of force variability with the force level.

The relation between limb stiffness and postural tremor in the upper arm was investigated during a pointing task. The task goal was to minimize the amount of motion (tremor) at the index finger under levels of increasing limb stiffness. This study investigated the influence of increasing limb stiffness on the pattern of intra- and interlimb dynamics. The frequency profile of the tremor for all limb segments across all conditions displayed two peaks, one between 2-4 Hz and another between 8-12 Hz. A third, higher frequency component (20-22 Hz) was present in the index finger. Increasing limb stiffness through voluntary co-contraction of antagonistic muscle pairs effectively constrained the segments of the upper limb to increasingly operate as a single biomechanical degree of freedom. Higher levels of limb stiffness typically led to an increase in the frequency and power of the 2-4 and 8-12 Hz peaks. There was also a decrease in the frequency of the 20-22 Hz component of finger tremor. The act of reducing the effective degrees of freedom in joint space through voluntarily stiffening of the upper limbs also resulted in decreased performance as determined by an increase in finger tremor. In the preferred, natural level of limb stiffness, specific intralimb segment relations were observed but there was no significant interlimb coupling. The intralimb segment correlations were characterized by compensatory (out of phase) coupling between the upper arm/forearm and hand/index finger segment pairs of each limb that were organized about the action of the wrist joint. Increasing the degree of limb stiffness led to a decrease in the level of intralimb coupling. The findings suggest that the most efficient mechanism for reducing tremor at the periphery is that of compensatory coupling between relevant intralimb segments with a low level of limb stiffness. [ABSTRACT FROM AUTHOR]

Smeets and Brenner provide a very clear and useful statement of the work that has been stimulated by Jeannerod's 1984 paper but seem more concerned about the viability of model fitting than model assumptions. The theoretical and practical limitations of viewing "grasping as nothing more than pointing" are noted. We reemphasize the importance in prehension of the union of the hand with the object in the act of realizing a task goal. [ABSTRACT FROM AUTHOR]

In this paper we re-visit and elaborate-on the theoretical framework of learning as searching within the perceptual-motor workspace for a solution to the task. The central focus is the nature of search strategies to locate and create stable equilibrium regions in the perceptual-motor workspace and how these strategies relate to the emergent movement forms in the acquisition of coordination, control, and skill. In the ecological theory of perception and action, the enhanced stability of performance occurs through the attunement of the perceptual systems to the task dynamics together with modifications of action as task and intrinsic dynamics cooperate and/or compete. Thus, through practice in this search process, individuals adapt to the pick-up of task relevant perceptual variables and change their movement form according to the stability of the performed action and its outcome in relation to the task demands. Contemporary experimental findings have revealed features of the search process given the interaction of individual intrinsic dynamics in the context of task requirements and principles that drive the change – e.g., exploitation of more tolerant task-space solutions and emergence of compensatory mechanisms. Finally, we outline how the search strategy framework relates to traditional learning-related phenomena: including the dynamical pathways of learning, learning curves, factors of learning, individuality, motor development, and sport and rehabilitation interventions. [ABSTRACT FROM AUTHOR]

Many experiments have shown independence of the index finger dynamics under bilateral postural tremor protocols. Here we investigated in young adults the dynamics of bilateral multidirectional postural tremor and forearm muscle activity under the progressively fatiguing conditions supporting an external weight to the point of induced postural failure. When no loads were applied, tremor in the vertical (VT) and mediolateral (ML) directions was similar with prominent peaks within 2- to 4-Hz and 8- to 12-Hz bandwidths. Contrastingly tremor in the anterior-posterior (AP) direction was characterized by a single peak between 0 and 2 Hz. Although no tremor coupling occurred cross limbs, strong within-limb coupling was found between ML and VT directions when no loads were applied (coherence range: 0.77-0.85), implying that these oscillations are related and likely derived from mechanical sources. Applying an external load to the index finger(s) led to significant increases in the amplitude of VT tremor and EMG activity within that limb but also caused increases in tremor directions not aligned with the gravitational vector (AP and ML). Significant increases in VT and ML tremor and EMG activity in the contralateral (unloaded) limb were also found when a single index finger was loaded; however, this bilateral increase did not align with increases in interlimb coupling (coherence <0.21). The effects of fatigue caused by prolonged loading were widespread, affecting tremor and muscle activity in both limbs through a combination of neural and mechanical mechanisms. The single- and dual-limb loading to fatigue increased neural overflow but not tremor coupling between the index fingers. [ABSTRACT FROM AUTHOR]

We investigated the coordination of balance and propulsion processes in learning to ride a unicycle through a principal component analysis (PCA) of the nature and number of functional degrees of freedom (DOF) in the movement coordination patterns. Six participants practiced unicycle riding on an indoor track for 28 sessions over separate days. The movement time and performance outcomes were recorded for each trial and body segment kinematics were collected from the first and every succeeding 4th session. The first appearance of no-hand-support performance varied across participants from the 5th practice session to the 22nd session. The PCA showed that initially in practice the 39 kinematic time series could be represented by 6–9 components that were reduced over practice to 4–7 components. The loadings of the PCA that reflected balance and propulsion processes became more coupled as a function of successfully riding the unicycle. The findings support the proposition that learning to ride the unicycle is a process of making the system more controllable by coordinating balance and propulsion while mastering the redundant DOF. [ABSTRACT FROM AUTHOR]

We examine the proposition that information availability and postural facilitation—usually viewed as opposing views in postural control—are intertwined with the effects of one being related to the other. If that is the case, a single control parameter (precision demands) would capture the changes in postural control relating information and postural facilitation. Using the dynamical systems approach, we investigated whether, manipulating touch requirements as to increase precision demands, would induce quantitative and qualitative changes in postural dynamics. Additionally, we tested whether the COM-COP coupling reflects the qualitative dynamics of the system. Seventeen participants were instructed to maintain quiet standing while maintaining or not a light finger force with either precision or no precision. Standard deviation (SD) of the COP decreased with the precision demands and the correlation dimension (CD) of COP showed higher values for the touch conditions. Participants showed reduced synchronization of COP–COM coupling; following changes in CD. These results point out the integrated nature of information availability, task requirements, and the emergent postural organization reflected in COP–COM coupling. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]