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Background: Street football can be understood as the most natural way to learn football and it can be a great starting point to develop perceptual, decisional, tactical and motor skills. Importantly, players involved in Street football may develop a strong emotional bond to the game through their experiences playing in an informal setting and eventually this could support their participation in a more structured playing environment. However, nowadays, talented children have reduced opportunities to play the game in this informal environment and instead, are mostly experiencing the game through their participation in organised settings such as in youth football clubs and academies. Importantly, such structured and formal environments afford the children a more rigid and less representative learning environment, which could potentially inhibit the development of creativity and adaptability among these young players. Purpose: The current paper aims to discuss the importance of Street football to players' development and the role of a Nonlinear Pedagogy (NLP) framework to support the design of a player-centred and game-based approach that can contribute to enhance learning of creative and adaptive behaviours in football. Discussion: Pedagogical principles of NLP (representative learning design, information-movement couplings, manipulation of constraints, exploratory learning and reducing conscious control of movement) underpinned by concepts from Ecological Dynamics and working through pedagogical channels (instruction, feedback and practice) can facilitate the design of representative training tasks to enhance learning. NLP emphasises a learner-centred approach and highlights the critical role that the practitioner plays as a facilitator in providing learners with meaningful practice that leads to effective transfer of game-play behaviours. Street football affords features that capture some of the above key pedagogical principles and presents a suitable platform to support the acquisition of game-play behaviour that is meaningful for the individual learner. Conclusions: Through a recognition of the current need to design a football learning environments that capture key elements of Street football, we highlight the relevance of NLP as a pedagogical framework to underpin a learner-centred and game-based approach, supporting practitioners with a set of pedagogical principles. Thus, we propose that through this representative learning environment we can enhance learning in football and contribute to the development of intelligent and creative players.

Purpose: This study aimed to investigate if player tactical skill level and age category influence team performance and player exploratory behavior in tasks with different difficulty levels. Method: In total, 48 youth male soccer players participated in the study (U15, n = 24, mean age = 13.06 [plus or minus] 1.53 years; U17, n = 24, mean age = 16.89 [plus or minus] 0.11 years). Player tactical skills were evaluated through the System of Tactical Assessment in Soccer (FUT-SAT), allowing them to be organized into three groups according to tactical efficiency: Higher tactical skill level (Group 01), Intermediate tactical skill level (Group 02), and Lower tactical skill level (Group 03). Next, Group 01 and Group 03 of both categories performed six Small-Sided and Conditioned Games (SSCG) each, namely three High difficulty SSCGs and three Low difficulty SSCGs. Team performance and players' exploratory behavior were analyzed through the Offensive Sequences Characterization System and Lag Sequential Analysis, respectively. Results: We found that team performance and players' exploratory behavior were influenced both by the age and tactical skill level of the players, as well as by task difficulty level. Conclusion: Therefore, in an attempt to improve player performance, practitioners must carefully manipulate key task constraints to adapt training task difficulty levels to player age and tactical skill level.

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aimed to identify the most frequent behavioural, structural and interactional variables that induced three types of penetrative passing that generated goal-scoring chances in elite soccer. Following restrict inclusion criteria (each and every type of pass that disrupts the opposition's last defensive line), 134 attacking sequences from UEFA Euro 2016, 2017 FIFA Confederations Cup, and 2018 FIFA World Cup, were sampled. The PePas observational instrument - which integrates previous validated criteria - was used to analyse the penetrative passes. Moreover, the proportion z-test was performed to verify whether the proportions of tactical and technical behaviours differed from the others (α = .05). The results showed that ball control and running with the ball were the most frequent behaviours before the short penetrative pass preceded by an individual action, and the short pass was the most frequent behaviour that preceded the short penetrative pass preceded by a collective action. All tacticaltechnical behaviours occurred in an interactional context of no pressure and mostly in the pitch's central paths. Further, ball control was significantly different from the other categories in the long penetrative pass preceded by an individual action. We suggest that coaches consider replicating scenarios with no pressure of the defence and include activities that encourage tactical-technical behaviours such as running with the ball and quick exchange of passes with one and two touches. [ABSTRACT FROM AUTHOR]

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We aimed to investigate if social networks measures can be used as indicators of training tasks' adjustment level to soccer players' tactical skills. Twenty-four U17 male soccer players (16.89 ± 0.11 years) participated in this study. The System of Tactical Assessment in Football (FUT-SAT) was used to identify players' tactical level and to organize them into three groups: Higher tactical level (Group 01), Intermediate tactical level (Group 02) and Lower tactical level (Group 03). Then, the players performed three High difficulty Small-Sided and Conditioned Games (HD-SSCG) and three Low difficulty Small-Sided and Conditioned Games (LD-SSCG). Teams' interaction patterns and players' prominence were analysed based on macro (Density – D and Clustering coefficient – CC) and micro networks (Indegree, Outdegree, Total links and Eigenvector) measures. We found that Group 01 presented higher D (p =.004 and ES = 1.189) and CC (p =.004 and ES =.785) at HD-SSCG than Group 03, whereas Group 03 presented higher values of D (p =.003 and ES = 1.200) and CC (p =.037 and ES = 1.180) at LD-SSCG than Group 01. When training tasks difficulty were adjusted to players' tactical level, teams played more collectively and players were more actively engaged in ball circulation. We concluded that macro and micro networks measures can be applied in training context as indicators of training tasks adjustment to players' tactical level. [ABSTRACT FROM AUTHOR]

Research in sport pedagogy and its applied recommendations are still characterized by a contrast between the different learning theories from psychology. Traditional theories and their corresponding approaches to the specific case of teaching and learning "how to play [team sports like soccer]" are subject to compatibilities and incompatibilities. We discuss how behaviorism as an approach to teaching the game shows more incompatibilities with the nature of tactical actions when compared to constructivism. As coaches strive to teach the game and make their players and team perform, we argue that teaching the game requires teaching approaches that will help develop their way to play (i.e., tactical behavior) without taking away their autonomy and adaptiveness. The teaching-learning-training process for playing the game should then be conducted to harmonize the characteristics of the contents, the context, and the individual(s) at hand. We provide two illustrated examples and portray how the recommended approaches fit key contents of the game that are observed in the tactical behavior. We finally argue that the coherent design of games provides minimal conditions to teaching approaches, and that such a design should be a priority when elaborating the learning activities along the player development process. As a conclusion, the interactionist theory is the one that best serves the teaching of the game and the development of tactical behavior. We therefore defend that its principles can help coaches tailor their own strategy to teach the game with the many tools. [ABSTRACT FROM AUTHOR]

This study aimed to investigate: i) how Small-Sided and Conditioned Games based on different representation and exaggeration modification strategies, from the Teaching Games for Understanding pedagogical principles, affected team performance and exploratory behaviour; and ii) how teams and players of different ages and skill levels were affected by the use of these different modification strategies. In total, forty-eight youth male soccer players participated in the study (U15, n = 24 mean age = 13.06 ± 1.53 years; U17, n = 24 mean age = 16.89 ± 0.11 years). In both categories, players were organized into three groups according to their tactical efficiency level (Group 01 = High Skilled Players (HSP), Group 02 = Intermediate Skilled Players (ISP), and Group 03 = Low Skilled Players (LSP)). The HSP and LSP groups performed two types of Gk+4vs4+Gk Small-Sided and Conditioned Games (SSCGs) based on different representation and exaggeration modification strategies. The first type of SSCGs was modified by structural constraints (Structural SSCG) and the second type was modified by rule manipulation (Manipulation SSCG). Team performance and exploratory behaviour were analysed through the Offensive Sequences Characterization System and Lag Sequential Analysis, respectively. SSCG modification strategies affected differently tactical performance and exploratory behaviour of teams composed of players of different skill levels. It was found that SSCG modification strategy through rule manipulation provided players and teams with a higher level of difficulty, compromising their performance and inhibiting exploratory behaviour. This information is crucial to practitioners wishing to apply more appropriate pedagogical strategies to improve a specific tactical problem using a player-centred and game-based approach. [ABSTRACT FROM AUTHOR]

The aim of this article was to systematically review the methods adopted to collect and interpret external training load (ETL) using microtechnology incorporating global positioning system (GPS). The main deficiencies identified concerned the non-collection of match ETL, and the non-consideration of potential confounders (e.g. playing position, fitness level, starting status or session content). Also, complementary training (individual/reconditioning) and pre-match warm-up were rarely quantified. To provide a full picture of the training demands, ETL was commonly complemented by internal training load monitoring with the rating of perceived exertion predominantly adopted instead of heart rate recordings. Continuous data collection and interpretation of ETL data in professional football vary widely between observational studies, possibly reflecting the actual procedures adopted in practical settings. Evidence about continuous ETL monitoring in female players, and female as well as male goalkeepers is lacking. [ABSTRACT FROM AUTHOR]

Researchers in soccer match analysis have been using limited procedures to express the dynamics of the game and mainly focus on the attack. Therefore, the aims of this paper were to detect the successful teams' ball recovery defensive patterns of play and study the influence of tactical modelling, halves, match status, opponent quality and stage competition on those patterns. The sample consisted of 1323 situations of defensive ball possession of the semi-finalist teams from the 2014 FIFA World Cup play-offs, which was collected by a valid and reliable observational instrument (Soccer-Defence). The Kruskal-Wallis H, Mann-Whitney U, Chi-square, Z-, multinomial logistic regression tests and sequential analysis (p <.05; z > 1.96) were used accordingly to test the differences and associations among and within teams of tactical modelling, tactical-technical behaviours and contextual variables to ball recovery. We found that among teams ball recovery differed in duration; H(3) = 14.958, p =.002. Germany were more likely to perform ball recovery by the goalkeeper than Argentina (p =.04; OR = 0.47) or the Netherlands (p <.05; OR = 0.50). Nevertheless, Brazil was the least likely to concede a shot off goal. Teams facing lower-ranked opponents were 0.63 times less likely to perform ball recovery by interception (p <.001). Additionally, sequential analysis illustrated that teams varied between central and lateral high-pressure zones before ball recovery in lower zones of the field. Finally, coaches could use such findings to design training exercises, create their own style of play, and set strategies. [ABSTRACT FROM AUTHOR]

Purpose. Small-sided games (SS G) with floaters are frequently adopted during the training process of soccer players. However, no study has previously investigated how the rules imposed to these additional players impact the physical, tactical, and physiological responses of the regular players. This study aimed to analyse the influence of the number of floaters on players' tactical behaviour, physical demands, and physiological responses in soccer SS Gs and to compare these variables between players with different positional statuses. Methods. Overall, 32 U-13 (n = 16) and U-14 (n = 16) players participated in this study, performing four 4-minute 3 vs. 3 SS Gs in both 1-floater and 2-floater formats. The frequency of core tactical principles, time-motion variables, and heart rate were used to describe the game multifactorial phenomenon. Results. Results showed an increased number of tactical actions of delays, defensive coverage, and width and length without ball actions in the 2-floater SS G without differences in physical demands or physiological response. Midfielders presented higher frequencies of penetration and offensive coverage, and lower frequencies of actions of width and length without the ball. There were also higher physical and physiological responses in midfielders. Conclusions. In conclusion, the 2-floater 3 vs. 3 format may be an important pedagogical strategy to promote a higher ball circulation pattern during SS Gs. Midfielders are the most demanded players tactically, physically, and physiologically in 3 vs. 3 SS Gs with floaters. [ABSTRACT FROM AUTHOR]

Understanding team behaviours in sports performance requires understanding the interdependencies established between their levels of complexity (micro-meso-macro). Previously, most studies examined interactions emerging at micro- and macro-levels, thus neglecting those emerging at a meso-level (reveals connections between player and team levels, depicted by the emergence of coordination in specific sub-groups of players–simplices during performance). We addressed this issue using the multilevel hypernetworks approach, adopting a cluster-phase method, to record player-simplice synchronies in two performance conditions where the number, size and location of goals were manipulated (first-condition: 6 × 6 + 4 mini-goals; second-condition: Gk + 6 × 6 + Gk). We investigated meso-level coordination tendencies, as a function of ball-possession (attacking/defending), field-direction (longitudinal/lateral) and teams (Team A/Team B). Generally, large synergistic relations and more stable patterns were observed in the longitudinal direction of the field than the lateral direction for both teams, and for both game phases in the first condition. The second condition displayed higher synchronies and more stable patterns in the lateral direction than the longitudinal plane for both teams, and for both game phases. Results suggest: (i) usefulness of hypernetworks in assessing synchronisation of teams at a meso-level; (ii) coaches may consider manipulating these task constraints to develop levels of local synchronies within teams. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate how team's tactical behavior varies within and between age categories in different Small-Sided and Conditioned Games' configurations and conditions. Twenty non-elite youth male soccer players (U15, n = 10, mean age = 13.5 ± 1.2 years; U17, n = 10, mean age = 16.3 ± 0.5 years) were selected. Thirty-six Small-Sided and Conditioned Games (SSCG) were played in both categories, namely three Representative SSCG (R-SSCG), three Maintaining Ball Possession Games (MBPG) and three Progression to Target Games (PTG) performed for each configuration (Gk+3vs3+Gk and Gk+4vs4+Gk). Teams' tactical behavior was analyzed based on simple and composite performance indicators, as well as through Lag Sequential Analysis. Rules manipulation and SSCG configurations influenced teams' tactical behavior on both categories, but in different ways. Teams composed by younger players presented greater difficulties in MBPG played in smaller games configuration, while Gk+4vs4+Gk configuration can be used to enhance teams' tactical performance of younger players in R-SSCG and MBPG conditions. Moreover, increasing rules manipulations appeared to negatively impact on teams' exploratory behavior. Therefore, practitioners should carefully manipulate key constraints to adapt task demands to players' age category and training session's goals in order to enhance tactical performance. [ABSTRACT FROM AUTHOR]

The research about soccer defensive phase shows many limitations regarding the procedures and operational definitions. The aims of this paper are to create an observational instrument based on Dynamic Systems concepts and evidence sufficient content validity to adequately and reliably recode defensive soccer behaviours. For these, a five-stage development process for validity was followed: (1) an initial literature review, instrument development, observation training; (2) adapting an existing systematic observational instrument; (3) pilot study with non-experts; (4) content validity with experts (coaches and researchers) and (5) inter- and intra-observer reliability. Using Aiken's V coefficient and its cut-off value to determine validity content, consensus was found (V > 0.67, n = 32, p < 0.05) for all items answered by participants in pilot study and for almost all subjects in the experts' study (V > 0.69, n = 12, p < 0.05). Also, Cohen's Kappa shows inter- and intra-reliability values of 0.87 and 0.90, respectively. The final model, entitled Theoretical Dynamic Model of Soccer Defence, and the observational instrument, named Soccer-Defence, with 14 criteria and category systems, and 106 categories, seems to be suitable for analysing the defensive process in soccer and could be used to find strengths or weaknesses of tactical–technical defensive patterns of play and to help coaches to better prepare their teams. [ABSTRACT FROM AUTHOR]

We examined the influence of competitive standard of the opponent on activity profile and fatigue during preseason friendly soccer matches. Time motion analysis was performed in a male professional soccer team (N = 14) during six friendly games played against professional, semi-professional and amateur-level opponents (PL, SPL and AL). The reference team covered higher acceleration distance, acceleration and deceleration > 2 m· s−2 distance against PL than AL (ES = 0.77 to 0.91). Acceleration and deceleration distance > 2 m· s−2 was also higher (ES = 0.66 to 0.84) against SPL than AL. Greater decreases in total distance, distance> 16 km· h−1 and > 22 km· h−1, total acceleration and deceleration, acceleration and deceleration distance > 2 m· s−2 (ES = 0.84 to 2.20) were also observed during PL compared to AL opponent. Playing against a stronger opponent seems to be more physically demanding, with special emphasis on events related with change of velocity (accelerations and decelerations). Declines in physical performance appear more evident against a higher opponent. [ABSTRACT FROM AUTHOR]

Copyright of Anales de Psicología is the property of Servicio de Publicaciones de la Universidad de Murcia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aims of this study were (i) to characterise the acceleration demands of two different formats of small-sided game (SSG), i.e., 4v4 + goalkeepers (4v4 + GK) and 8v8 + goalkeepers (8v8 + GK); (ii) to analyse the correlation between performance in power-based tests and acceleration-based physical loading during the two different SSG formats and (iii) to analyse the neuromuscular-induced fatigue. Eighteen adult male footballers participated in the study (20.7 ± 1.0 years, 178 ± 5 cm and 71.4 ± 2.1 kg). Baseline measurements were obtained from countermovement jumps, 15 s repeated jumps and 5 and 15 m sprints. A total of 36 min was analysed for each SSG (4v4 + GK: two sets of 3 × 6 min, and 8v8 + GK: 2 × 18 min). Heart rate, blood lactate, perceived exertion and movement pattern (GPS) were analysed. Distances covered by very-high-intensity activities and very-high-speed running were lower in 4v4 + GK than in 8v8 + GK (effect sizes (ES) = −0.69 ± 0.67 and −1.04 ± 0.67, respectively; very likely), while accelerations and decelerations were higher in 4v4 + GK than in 8v8 + GK (ES = 1.13–1.52; almost certainly). Blood lactate concentrations were higher (ES = 1.40 ± 0.58; almost certainly) and players perceived themselves to be more tired (ES = 0.80–2.31; almost certainly) after 4v4 + GK than after 8v8 + GK. Sprint ability in 5 and 15 m tests decreased (ES = 0.87 ± 0.58 and 0.89 ± 0.58, respectively; almost certainly) only after 4v4 + GK. This SSG format appeared more demanding in relation to repetitions and fatigue development of muscle power-based actions than 8v8 + GK. It may therefore be logical to use the former type of SSG to target development of power-related football actions. [ABSTRACT FROM PUBLISHER]

The effect of altered game formats on team performances during soccer practice can be harnessed by coaches to stimulate specific tactical behaviours. The aim of the present study was to analyse the influence of using (i) small goals [SG], (ii) goalkeepers [7G] and (iii) floaters [7GF] on the dispersion, shape and available space of teams during small-sided games (SSGs). Twenty-four male soccer players were distributed into four teams composed of five players, two goalkeepers and two floaters that performed six SSG bouts of 6 min, interspersed with 6 min of passive recovery. Offensive and defensive phases were also analysed separately in order to verify the preservation of basic principles of attacking (teams more stretched to create free space) and defending (teams more compact to tie-up space) during SSGs. The variables used to characterize the collective behaviour were: length [L], width [W], team shape [Sh], and team separateness [TS]. Results revealed that the teams showed different collective behaviours depending on SSG format and a playing phase: a) L and W were higher in attack than in defence in all SSGs; b) team shapes were more elongated in defence in all SSGs except SG; c) the space separating players from their closest opponents (TS) was shorter in 7G; and d) SG and 7GF elicited greater defensive openness due to increased team width. The results suggest that manipulating task constraints, such as goal size, presence or absence of goalkeepers and floaters can be harnessed by coaches to shape distinct team tactical behaviours in SSGs while preserving the basic principles of attacking and defending. [ABSTRACT FROM AUTHOR]

Soccer research has traditionally focused on technical and tactical aspects of team play, but few studies have analyzed motor skills in individual actions, such as goal scoring. The objective of this study was to investigate how Lionel Messi, one of the world's top soccer players, uses his motor skills and laterality in individual attacking actions resulting in a goal. We analyzed 103 goals scored by Messi between over a decade in three competitions: La Liga (n = 74), Copa del Rey (n = 8), and the UEFA Champions League (n = 21). We used an ad-hoc observation instrument (OSMOS-soccer player) comprising 10 criteria and 50 categories; polar coordinate analysis, a powerful data reduction technique, revealed significant associations for body part and orientation, foot contact zone, turn direction, and locomotion. No significant associations were observed for pitch area or interaction with opponents. Our analysis confirms significant associations between different aspects of motor skill use by Messi immediately before scoring, namely use of lower limbs, foot contact zones, turn direction, use of wings, and orientation of body to move toward the goal. Studies of motor skills in soccer could shed light on the qualities that make certain players unique. [ABSTRACT FROM AUTHOR]

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Copyright of Brazilian Journal of Kineanthropometry & Human Performance is the property of Brazilian Journal of Kineanthropometry & Human Performance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Brazilian Journal of Kineanthropometry & Human Performance is the property of Brazilian Journal of Kineanthropometry & Human Performance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this systematic review was to identify and synthesize the available information regarding longitudinal data addressing young soccer players' motor performance changes. Following the Preferred Reporting Items for Systematic and Meta-analyses (PRISMA) statement, literature searches were performed in three databases: PubMed, ISI Web of Science and SCOPUS. The following descriptors were used: football, soccer, youth, young, player, athlete, physical performance, motor performance, longitudinal. The inclusion criteria were original articles in English with longitudinal data of young males (aged 10–18 years), with the aim to investigate motor performance serial changes. The initial search returned 211 records, and the final sample comprised 32 papers. These papers covered the European continent, and used mixed and pure longitudinal design with variation in sample size and age range. The reviewed studies tended to use different tests to assess the motor performance and aimed to identify changes in motor performance in several ways. In general, they indicated motor performance improvements with age, with a marked influence of biological maturity, body composition, and training stimuli. This review highlights the need for coaches and stakeholders to consider players' motor performance over time whilst considering biological maturation, biological characteristics, and training stimuli. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Soccer Science / Revista Brasileira de Futebol is the property of Revista Brasileira de Futebol and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aimed to investigate: i) how Small-Sided and Conditioned Games based on different representation and exaggeration modification strategies, from the Teaching Games for Understanding pedagogical principles, affected team performance and exploratory behaviour; and ii) how teams and players of different ages and skill levels were affected by the use of these different modification strategies. In total, forty-eight youth male soccer players participated in the study (U15, n = 24 mean age = 13.06 ± 1.53 years; U17, n = 24 mean age = 16.89 ± 0.11 years). In both categories, players were organized into three groups according to their tactical efficiency level (Group 01 = High Skilled Players (HSP), Group 02 = Intermediate Skilled Players (ISP), and Group 03 = Low Skilled Players (LSP)). The HSP and LSP groups performed two types of Gk+4vs4+Gk Small-Sided and Conditioned Games (SSCGs) based on different representation and exaggeration modification strategies. The first type of SSCGs was modified by structural constraints (Structural SSCG) and the second type was modified by rule manipulation (Manipulation SSCG). Team performance and exploratory behaviour were analysed through the Offensive Sequences Characterization System and Lag Sequential Analysis, respectively. SSCG modification strategies affected differently tactical performance and exploratory behaviour of teams composed of players of different skill levels. It was found that SSCG modification strategy through rule manipulation provided players and teams with a higher level of difficulty, compromising their performance and inhibiting exploratory behaviour. This information is crucial to practitioners wishing to apply more appropriate pedagogical strategies to improve a specific tactical problem using a player-centred and game-based approach., (© 2020 João Cláudio Machado, Daniel Barreira, Israel Teoldo, Jaime Serra-Olivares, Alberto Góes, Alcides José Scaglia, published by Sciendo.)

Background: In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason., Methods: Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers)., Results: Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3%). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59)., Conclusions: During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.

Introduction: Soccer training and completion is conventionally practiced on natural grass (NG) or artificial turf (AT). Recently, AT pitches for training/competition, and of unstable surfaces for injury prevention training has increased. Therefore, soccer players are frequently exposed to variations in pitch surface during either training or competition. These ground changes may impact physical and physiological responses, adaptations as well as the injury. The aim of this review was to summarize the acute physical and physiological responses, chronic adaptations, and injury risk associated with exercising on different pitch surfaces in soccer., Evidence Acquisition: Eligible studies were published in English, had pitch surface as an independent variable, and had physical, physiological or epidemiological information as outcome variables. Specific data extracted from the articles included the training response, training adaptations or injury outcomes according to different pitch surfaces. A total of 224 studies were retrieved from a literature search., Evidence Synthesis: Twenty articles met the inclusion criteria: 9 for acute physical and physiological responses, 2 for training adaptations and 9 for injury assessment. The literature lacks consistent evidence regarding the effects of pitch surface on performance and health outcomes in soccer players. However, it seems that occasionally switching training surfaces seems a valuable strategy for focusing on specific musculoskeletal queries and enhancing players' fitness. For instance, sand training may be occasionally proposed as complementary training strategy, given the recruitment of additional musculature probably not involved on firmer surfaces, but the possible training-induced adaptations of non-conventional soccer surfaces (e.g., sand) might potentially result into a negative transfer on AT or NG., Conclusions: Since the specific physical demands of soccer can differ between surfaces, coaches should resort to the use of non-traditional surfaces with parsimony, emphasizing the specific surface-related motor tasks, normally observed on natural grass or artificial turf. Further studies are required to better understand the physiological effects induced by systematic surface-specific training, or switching between pitch surfaces.

Background: The use of sand has been suggested as fitness-enhancing surface in field-based team sports. However, concerns have arisen in regard whether physical responses associated to sand training are sport-specific. We compared physical and technical demands during small-sided soccer games (4 vs. 4 + goalkeeper; SSGs) played on artificial turf and on sand., Methods: Movement patterns, rating of perceived exertion (RPE) and technical parameters were obtained from eight adult male soccerers (20.1±1.0 years, 176±4 cm and 70.1±2.0 kg) using Global Positioning Systems, Visual Analogue Scale questionnaires, and notational analysis., Results: High-intensity actions (high intensity running, high intensity activities), low changes of speed, as well as peak and average speed were higher on artificial turf (P<0.05; effect sizes (ES) 0.41 to 0.82). In contrast, time spent by jogging as well as high and maximum changes of speed was higher on sand (P<0.05; ES: 0.59 to 0.82). Moreover, players perceived more demanding to play on sand (P<0.05; ES=0.72). Rating of successful actions was higher during turf SSGs than sand SSGs (P<0.05; ES: 0.44 to 0.73), whereas actions requiring lifting the ball were higher on sand (P<0.05; ES: 0.47 to 0.50)., Conclusions: The use of sand can be considered as complemental to on-turf soccer training, when the training goal is to tax lower limb muscle strength or to require high-ball situations. Nonetheless, sand training is not appropriate when the achievement of maximal speed is desired. Further research should clarify the suitability of sand training within soccer conditioning programs.