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Komar, John
- PublicationOpen AccessCan a good break shot determine the game outcome in 9-ball?This study aimed to quantify the break shot characteristics and identify their significance in predicting the game outcomes in 9-ball tournaments. The break shots of 275 frames (241 men’s, 34 women’s) of professional tournaments were analyzed from two aspects: (1) cue ball position, represented by the distance between the cue ball and the table center, and (2) ball distribution, indicated by the standard deviation of Voronoi cell areas determined from all remaining balls on the table. Spearman correlation and binary logistic regression were utilized to identify associations and to predict the frame outcomes, respectively. Results showed that the more balls falling into the pockets during the break, the more clustered the remaining balls (rs = 0.232, p < 0.001). The closer the cue ball ending toward the table center, the more balls potted in the visit immediately after the break (rs = −0.144, p = 0.027). Neither cue ball position nor ball distribution could predict table clearance or winning of a frame. In conclusion, pocketing more balls during the break is associated with more clustered balls remaining on the table. Parking the cue ball near the table center after the break can facilitate potting more balls immediately after.
WOS© Citations 4Scopus© Citations 6 253 143 - PublicationOpen AccessClustering analysis of movement kinematics in reinforcement learningReinforcement learning has been used as an experimental model of motor skill acquisition, where at times movements are successful and thus reinforced. One fundamental problem is to understand how humans select exploration over exploitation during learning. The decision could be influenced by factors such as task demands and reward availability. In this study, we applied a clustering algorithm to examine how a change in the accuracy requirements of a task affected the choice of exploration over exploitation. Participants made reaching movements to an unseen target using a planar robot arm and received reward after each successful movement. For one group of participants, the width of the hidden target decreased after every other training block. For a second group, it remained constant. The clustering algorithm was applied to the kinematic data to characterize motor learning on a trial-to-trial basis as a sequence of movements, each belonging to one of the identified clusters. By the end of learning, movement trajectories across all participants converged primarily to a single cluster with the greatest number of successful trials. Within this analysis framework, we defined exploration and exploitation as types of behaviour in which two successive trajectories belong to different or similar clusters, respectively. The frequency of each mode of behaviour was evaluated over the course learning. It was found that by reducing the target width, participants used a greater variety of different clusters and displayed more exploration than exploitation. Excessive exploration relative to exploitation was found to be detrimental to subsequent motor learning.
WOS© Citations 5Scopus© Citations 7 307 265 - PublicationOpen AccessAdaptive regulation in a stable performance environment: Trial-to-trial consistency in cue sports performanceThis study aimed to investigate individual trial-to-trial performance in three tests to define adaptive regulation as a key feature of expertise in nine-ball. Thirty-one male players were assigned into the low-skilled (n = 11), intermediate (n = 10), or high-skilled groups (n = 10). The power control, cue alignment, and angle tests were selected to assess participants’ ability to control the power applied in shots, strike the ball straight, and understand the ball paths, respectively. Error distance and correction of error distance were identified for each shot using 2D video analysis. Results of one-way analysis of variance showed that the high-skilled group performed better in two out of the three tests than the other two groups (p = .010 for the cue alignment test; p = .002 for the angle test). However, the adaptation effect represented by the decreased error distances across trials was not observed. Pearson correlation revealed only a few significant correlations between the error distance and its correction within each participant in all tests (p < .05), and hence, the hypothesis that “low correction happened after small error and vice versa” is not supported.
WOS© Citations 2 85 128 - PublicationOpen AccessFlexibility, stability, and adaptability of team playing style as key determinants of within-season performance in football(2022)
;He, Qixiang; The aim of this study was to examine the relationship between playing style variability and within-season team match performance outcomes. We examined 21,708 matches played in the top five leagues in Europe from the 2014/15 to 2019/20 season. Playing styles used by each team in each match were derived through a Gaussian-Mixture Model clustering of 31 match actions. The relationship between playing style choice and match outcome was also analysed using Multinomial Logistic Regression. However, team and opposition playing style predicted match outcome with low precision (39.78%). Measures of playing style variability, namely flexibility, stability, and adaptability, were derived using the coefficient of unalikeability, and relationship with performance outcomes were computed using Pearson’s correlation. Playing style flexibility was positively correlated with both offensive and defensive performance outcomes and win frequency (p < .01). Conversely, teams displaying higher playing style stability conceded less shots in the penalty box but demonstrated poorer offensive performance outcomes (p < .01). Playing style adaptability, indicative of high flexibility and stability, was positively associated with defensive performance outcomes and win frequency (p < .01). Our results indicate that playing style variability may be a significant indicator of team performance.117 172 - PublicationOpen AccessThe role of nonlinear pedagogy in supporting the design of modified games in junior sportsNonlinear 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.
WOS© Citations 9Scopus© Citations 19 94 320 - PublicationOpen AccessWhat data should be collected for a good handball expected goal model?Expected goal models (xG) are of great importance as they are the most accurate predictor of future performance of teams and players in the world of soccer. This metric can be modeled by machine learning, and the models developed consider an increasing number of attributes, which increases the cost of learning it. The use of xG is not widespread in handball, so the question of learning it for this sport arose, in particular which attributes are relevant for learning. Here, we used a wrapper approach to determine these relevant attributes and guide teams through the data collection stage.
Scopus© Citations 2 47 18 - PublicationOpen AccessThe 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.
WOS© Citations 2Scopus© Citations 7 64 206 - PublicationOpen AccessDevelopment of new 9-ball test protocols for assessing expertise in cue sportsBackground This study aimed to develop new test protocols for evaluating 9-ball expertise levels in cue sports players. Methods Thirty-one male 9-ball players at different playing levels were recruited (recreational group, n = 8; university team, n = 15; national team, n = 8). A 15-ball test was administered to indicate overall performance by counting the number of balls potted. Five skill tests (power control, cue alignment, angle, back spin, and top spin) were conducted to evaluate specific techniques by calculating error distances from pre-set targets using 2D video analysis. Results Intra-class correlation analyses revealed excellent intra-rater and inter-rater reliability in four out of five skill tests (ICC > 0.95). Significant between-group differences were found in 15-ball test performance (p < 0.001) and absolute error distances in the angle (p < 0.001), back spin (p = 0.006), and top spin tests (p = 0.045), with the recreational group performing worst while the national team performing best. Greater inter-trial variability was observed in recreational players than the more skilled players (p < 0.005). Conclusions In conclusion, the 9-ball test protocols were reliable and could successfully discriminate between different playing levels. Coaches and researchers may employ these protocols to identify errors, monitor training, and rank players.
WOS© Citations 3Scopus© Citations 6 121 160 - PublicationOpen AccessBetween exploitation and exploration of motor behaviours: Unpacking the constraints-led approach to foster natar learning in physical education
Introduction The constraints-led approach (CLA) and more generally a complex systems perspective on motor learning emphasizes the role of perceptual-motor exploration during learning in order to ensure the acquisition of a highly individualized, adapted and adaptable movement pattern. Recent studies have shown that human beings have a strong tendency to exploit already stable patterns rather than looking for new potentially more efficient patterns. In order to shape the amount of exploration, we implemented two learning designs based on a CLA where constraints were used to limit the boundaries of the perceptual-motor workspace of the learners. We sought to highlight how practitioners can play with the perceptual motor workspace boundaries in order to i) promote the use of exploratory behaviours and ii) guide the learner towards task-relevant functional areas.
Method For the experiment, twenty-four beginners in breaststroke swimming were allocated to three groups of learning: a control group receiving only the goal of the learning, an analogy group receiving the goal of learning accompanied by an analogy about “how to perform”, a pacer group receiving information on the goal of learning and the use of a metronome to continuously push them to “perform better”. Based on their assigned group, each learner then followed a learning protocol of 16 sessions with a 10*25m swimming distance per session with the goal of increasing the stroke length for a fixed swimming speed. Both performance (i.e., stroke length) and motor behaviour (i.e., arm-leg coordination) were collected for each session. The arm-leg coordination patterns were computed by the continuous relative phase between knee and elbow angles. Thereafter, a cluster analysis was performed on the coordination in order to get a qualitative label for every cycle performed during the entire process of learning. Based on the use of cluster analysis, an exploration/exploitation ratio was calculated and the increase in performance was determined based on the increase in stroke length.
Results and Discussion With reference to the exploration/exploitation ratio, our results showed that additional temporary constraints led learners to increase both the nature of their exploration and also the quantity of their exploration. In the meantime, the three groups showed an equivalent final performance enhancement. The aim of manipulating the constraints was not only to push the learner out of his comfort zone, but also to provide relevant information about “where” to explore during learning. For this purpose, the use of analogy appeared as the most relevant constraint to encourage the emergence of efficient behaviour. Interestingly the impact of the analogy was modified by adding the metronome, showing an interaction effect of both constraints. The group using the metronome exhibited different behaviours as compared to the analogy group and showed an increase in exploration during learning compared to the control group. However, although the metronome constantly pushed the learner to improve performance, it did not actually lead to a better improvement of performance when compared to the analogy group. The simple assumption that the constraints forced the learner to explore therefore does not seem a mandatory condition to promote an exploratory learning. Rather, the qualitative nature of the constraint seems the most relevant characteristic that can be manipulated to promote an exploratory learning by guiding the learner within the perceptual motor workspace.
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