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3Substitution is an essential tool for a coach to influence the match. Factors like the injury of a player, required tactical changes, or underperformance of a player initiates substitutions. This study aims to predict the physical performance of individual players in an early phase of the match to provide additional information to the coach for his decision on substitutions. Tracking data of individual players, except for goalkeepers, from 302 elite soccer matches of the Dutch ‘Eredivisie’ 2018–2019 season were used to enable the prediction of the individual physical performance. The players’ physical performance is expressed in the variables distance covered, distance in speed category, and energy expenditure in power category. The individualized normalized variables were used to build machine learning models that predict whether players will achieve 100%, 95%, or 90% of their average physical performance in a match. The tree-based algorithms Random Forest and Decision Tree were applied to build the models. A simple Naïve Bayes algorithm was used as the baseline model to support the superiority of the tree-based algorithms. The machine learning technique Random Forest combined with the variable energy expenditure in the power category was the most precise. The combination of Random Forest and energy expenditure in the power category resulted in precision in predicting performance and underperformance after 15 min in a match, and the values were 0.91, 0.88, and 0.92 for the thresholds 100%, 95%, and 90%, respectively. To conclude, it is possible to predict the physical performance of individual players in an early phase of the match. These findings offer opportunities to support coaches in making more informed decisions on player substitutions in elite soccer.
ARTIKEL
For almost 25 years, the goal of the RoboCup has been to build soccer robots capable of winning against the FIFA World Champion of 2050. To foster the participation of the next generation of roboticists, the RoboCupJunior competition takes place in parallel and provides a similar challenge of appropriate difficulty for high school students. RoboCupJunior has three main categories: Soccer, Rescue and OnStage. For the Soccer category, participants need to design, build and program a team of autonomous robots to play soccer against an opponent team of robots. The competition is physical in nature, since it assumes physical robots playing against one another. In 2020 and 2021, the COVID-19 pandemic has made it difficult for a competition of this type to take place, due to obvious restrictions on physical gatherings. To allow for some sort of participation, and inspired by positive experience of the larger RoboCup community, the Organizing Committee of RoboCupJunior Soccer has explored porting a portion of the challenge to a simulated environment. Many of the existing environments, however, are built for higher education/research teams competitions or research, making them complex to deploy and generally unsuitable for high school students. In this paper we present the development of SoccerSim, a simulated environment for RoboCupJunior Soccer, based on the Webots open-source robotics simulator. We also discuss how the participation of students was key for its development and present a summary of the competition rules. We further describe the case study of utilizing SoccerSim first as a testbed for a Demo competition, and later as part of RoboCup Worldwide 2021. The participation of more than 60 teams from over 20 countries suggests that SoccerSim provides an affordable alternative to physical robotics platforms, while being stable enough to support a diverse userbase. The experience of using SoccerSim at RoboCupJunior Worldwide 2021 suggests that a simulated environment significantly lowers the barrier to entry, as evidenced by the participation of many teams that have not participated before. To make it easy for similar competitions to take place in the future, we made the code of SoccerSim available as open-source, as well as the associated tooling required for using it in a tournament.
ARTIKEL
The objective of this study was to compose an objective and detailed notational analysis system for 3 vs. 2GK smallsided soccer games, in which three roles are examined: attacker with ball, attacker without ball and defender. The actions and the outcome of the actions were registered for each player and in each role. Players earn points for each action and outcome according to an a priori determined scheme. Performance scores for each role are calculated as the average number of points a participant earns per trial. This notation system was tested on 19 highly talented female soccer players and validity and reliability of the system were determined. In addition, practical applications were discussed and the most important items of the notation system were determined and using only these items, a simplified notation system was proposed. The notation system has high ecological validity and can discriminate the high and low categorized players, but further development is necessary to increase the reliability of the system.
ARTIKEL
Talent development programmes for professional soccer clubs aim to guide players towards professional level performance. We identify whether the intermittent endurance capacity of these players may have changed over time. Since the 2000/2001 competition season, the intermittent endurance capacity of players in the talent development programmes of two professional soccer clubs was measured annually. A total of 492 players participated, divided across seven age categories (under 13 (U13), U14, U15, U16, U17, U18, U19) and resulting in 953 measurements. Analyses of variance showed an improvement in intermittent endurance capacity from the 2000/2001 season to 2009/2010 of around 50% in all age groups (P < 0.05). A possible explanation is the increased quantity and quality of training over the years. When identifying, developing and selecting young players, scouts, trainers and coaches have to be aware that the current level of soccer and its underlying performance characteristics--such as intermittent endurance capacity--are improving over time. This factor may have consequences for current young players aiming to make it to the top 10 years from now.
ARTIKEL
The present study examined whether performance characteristics discriminated between selected and deselected players in talent development programmes. This examination was carried out in talented soccer players, aged 16-18 years using objective measurement instruments. Four domains of multidimensional performance characteristics (physiological, technical, tactical and psychological) were assessed by using a test battery consisting of soccer-specific field tests and questionnaires. Multivariate analyses of covariance revealed that the physiological characteristics peak and repeated shuttle sprint, the technical characteristics of peak and repeated shuttle dribble and the tactical characteristic of 'positioning and deciding', significantly differed between the selected (n=76) and deselected players (n=37), with selected players performing better (P<0.05). Discriminant function analysis showed that the combination of the technical characteristic 'peak dribbling', the tactical characteristic 'positioning and deciding' and the physiological characteristic of 'peak sprinting' classified 69% of talented players correctly. In conclusion, the decisions made by the investigated clubs to either select or deselect players in their talent development programme, whom were aged 16-18 years, were mostly discriminated by aspects of the players' technical, tactical and physiological skill performances. Sports research can play an essential role in investigating the club's perception of important performance characteristics in talented players.
ARTIKEL
The use of robots as educational tools provides a stimulating environment for students. Some robotics competitions focus on primary and secondary school aged children, and serve as motivation for students to get involved in educational robotics activities. Although very appealing, many students cannot participate on robotics competitions because they cannot afford robotics kits. Hence, several students have no access to educational robotics, especially on developing countries. To minimize this problem and contribute to education equality, we have created RoSoS Robot Soccer Simulator, in which students program virtual robots in a similar way that they would program their real ones. In this chapter we explain some technical details of RoSoS and discuss the implementation of a new league for the robotics competitions: Junior Soccer Simulation league (JSS). Because soccer is the most popular sport in the world, we believe JSS will be a strong motivator for students to get involved with robotics.
HOOFDSTUK
Abstract: OBJECTIVE: To describe characteristics of outdoor soccer injury and recovery among Dutch soccer players.
ARTIKEL
Young talented athletes that mature have an increased injury risk. Human movement scientist Alien van der Sluis studied soccer players of the talent development program of FC Groningen and tennis players of the talented development program of the Royal Dutch Lawn Tennis Federation (KNLTB).
The soccer players were followed for three years around their adolescent growth spurt. In the year of their growth spurt, players have more injuries compared to the year before or the year after, and they miss more training sessions and matches. A possible cause is the different rates in which bone tissue, muscle tissue and tendon tissue adapt to the growing body. More specific, players that grow more than 0.6 cm in one month, have an increased risk for injury in the next month. Moreover, players with a late growth spurt are relatively small compared to their peers, and this leads to more injuries compared to their ‘earlier mature’ counterparts.
Furthermore, tennis players high in risk-taking behavior (typical for puberty), have more injuries and players with better metacognitive skills such as monitoring, have less injuries. Players may be better capable of monitoring small physical complaints, which could help them to prevent themselves from having more severe injuries.
Van der Sluis concluded that during puberty, there are specific risk factors for injuries in talented athletes. Coaches and trainers should estimate the moment of the adolescent growth spurt, to take injury preventive measures at the right moment. Monthly monitoring of length, could help to predict an increased risk of injury in periods of intensive growth. At last, it is advised to provide feedback to players high in risk-taking and to educate athletes in monitoring their own training process.
PROMOTIEONDERZOEK EXTERN, AFSTUDEREN EXTERN
The aim of the study was to investigate whether an increased risk of injury occurrence can be determined through frequent anthropometric measurements in elite-standard youth soccer players. Over the course of one season, we followed 101 male elite-standard youth soccer players between 11 and 19 years of age. Height and body mass were monitored at monthly measurement intervals and fat percentage was assessed every 3 months by use of the sum of skinfold method. Growth in height (cm), alternations in body mass index (kg/m(2)), fat percentage and fat-free mass index (kg/m(2)) were calculated. Injuries were recorded in accordance with the recommendations of the FIFA Consensus Model for Injury Registration. Odds ratio scores and 95% confidence intervals were calculated using binary logistic regression analyses. The following anthropometric injury risk factors were identified: ≥ 0.6 centimeter growth per month (p=0.03; OR=1.63; 95% CI: 1.06-2.52), ≥ 0.3 kg/m(2) increase of body mass index value per month (p=0.03; OR=1.61; 95% CI: 1.04-2.49) and low fat percentage; i. e., < 7% for players aged 11-16 and < 5% for players over 16 years (p=0.01; OR=1.81; 95% CI: 1.18-2.76). Individual monitoring of anthropometrics provides useful information to determine increased risk of injury occurrence in elite-standard youth soccer.
ARTIKEL
Purpose
Young soccer players need excellent tactical skills to reach the top. Tactical behavior emerges through interactions between opposing teams. However, few studies have focused on on-field tactical behavior of teams with talented soccer players. Therefore, this study aimed to determine teams’ tactical behavior during small-sided games in two age categories, Under-17 and Under-19.
Methods
Positional data of thirty-nine elite-standard soccer players were collected during twenty-four small-sided games to calculate longitudinal and lateral inter-team distances, stretch indices and length per width ratios. Corresponding interaction patterns and game-to-game variability were also determined.
Results
Under-19 showed a significantly larger lateral stretch index and a significantly lower length per width ratio compared with Under-17. Furthermore, teams of both age groups showed similar large proportions of in-phase behavior. Variability of tactical performance measures within and between games was similar for Under-17 and Under-19.
Conclusions
Variability within games seems to be functional for attacking teams for creating goal-scoring opportunities. In conclusion, the main difference was that Under-19 adopted a wider pitch dispersion than Under-17, represented by a larger lateral stretch index and smaller length per width ratio. Coach instructions and training exercises should be directed at exploiting pitch width to increase the pursuit of goal-scoring.
ARTIKEL
