Effects of free play or artificial rules on young soccer players' individual tactical behaviour: a one-by-one analysis.

This study assessed the effects of playing freely and introducing artificial rules on individual tactical behaviour during the team-possession game phase in two youth soccer categories. Thirty-two developmental players from U-14 and U-16 teams participated in the study, which consisted of four identical training sessions and two test sessions performed before and after the intervention. Each team was divided into two balanced groups, free-play and conditioned, that faced each other during three eight-a-side games (Gk + 7 vs 7 + Gk) in all training sessions. The free-play groups played freely, while the conditioned ones did so constrained by artificial rules. Individual tactical behaviour was assessed during a non-constrained eight-a-side match by the distance to centroid, spatial exploration index, their entropy measures, and the regularity of each player's displacement on the length and width of the pitch using a local positioning system. In addition to the average outcomes of all the players all together, the one-by-one analysis considered the mean values of each player to appraise individual responses. While the average outcomes of all the players in both groups and categories barely changed (Cohen's d ≤ small), with a very high inter-player variability, the one-by-one analysis revealed that the training intervention affected each player's tactical behaviour differently. Introducing artificial rules decreased and raised considerably (Cohen's d ≥ moderate) in-width and exploratory regularities of most U-14 and U-16 players, respectively. Therefore, assessing the training effects of game-based interventions from the individual to the whole team may provide unique and meaningful insight regarding the tactical competence of each player.

How Football Players' Age Affect Passing Patterns of Play According to Field Location.

This study aimed to characterize the passing patterns that support collective tactical behaviour in football players of different ages (U15, U17, and U19) in different field zones. Two hundred and twenty-eight male players, divided into U15, U17, and U19, participated in the study. Cluster analysis was used to group the passes into three sizes (short, medium, and long). The chi-square test was used to analyse the effect of player age on game-passing patterns in each field zone. The results revealed that long and medium passes were used more in areas close to the goals and short passes in the middle area of the field, concerning all ages (p < 0.001). Furthermore, the analysis of the relative distance between the ball carrier and the receiver indicated that older players (U17 and U19) used more distant players to pass the ball in medium and long passes. These results can help coaches design small-sided games according to the players' ages and adjust to the field's space and the numerical relationship, thus creating a greater transfer from training to competition.

Relationship between anaerobic work capacity and critical oxygenation in athletes / Relación entre la capacidad de trabajo anaeróbico y la oxigenación crítica en deportistas / Relação entre capacidade de trabalho anaeróbico e oxigenação crítica em atletas

Objective: Anaerobic work capacity (AWC) is understood as the maximum power that the athlete can withstand over time, conditioned by high intensityeffort and it is important to interpret it for the performance improvement. In addition, the muscle oxygen saturation (SmO2) provides information onmuscle metabolism and hemodynamics. Likewise, critical oxygenation (CO) is the highest metabolic rate that results in a fully oxidative energy supplythat reaches a stable state at the substrate level. The main problem is that SmO2 generally offers a traditional laboratory interpretation withoutapplication in field tests, Therefore, the purpose of this study is to provide the use of CO as an indicator of AWC performance in high intensity exercise. Methods: Twenty-two male rugby players participated. Peak torques during an isokinetic fatigue test and muscle oxygen consumption (mVO2) and SmO2in the vastus lateralis were measured. A correlation and multiple regression analysis were applied to find an explanatory prediction model of the AWC. Results: A greater SmO2 amplitude and CO would mean less anaerobic work (r = -0.58 and r=-0.63) and less force production. In addition, CO along withweight (kg) can explain the AWC by 64% during high intensity exercise. Conclusion: The measurement of critical oxygenation is associated with the AWC, so should be considered a performance factor. These parameters couldbe included in NIRS sensors to evaluate muscle metabolism.(AU)

Objetivo: La capacidad de trabajo anaeróbico (AWC) se entiende como la potencia máxima que el deportista puede soportar a lo largo del tiempo,condicionada por un esfuerzo de alta intensidad y es importante interpretarla para la mejora del rendimiento. Además, la saturación de oxígenomuscular (SmO2) proporciona información sobre el metabolismo muscular y la hemodinámica. Asimismo, la oxigenación crítica (OC) es la tasametabólica más alta que da como resultado un suministro de energía completamente oxidativo que alcanza un estado estable a nivel de sustrato. Elprincipal problema es que SmO2 generalmente ofrece una interpretación de laboratorio tradicional sin aplicación en pruebas de campo, por lo tanto, elpropósito de este estudio es proporcionar el uso de OC como indicador del rendimiento de AWC en ejercicio de alta intensidad. Métodos: Participaron 22 jugadores masculinos de rugby. Se midieron los picos máximos después de una prueba de fatiga isocinética y el consumo deoxígeno muscular (mVO2) y SmO2 en el musculo vasto lateral. Se aplicó un análisis de correlación y regresión múltiple para encontrar un modelo depredicción explicativo del AWC. Resultados: Una mayor amplitud de SmO2 y OC supondría un menor trabajo anaeróbico (r = -0,58 y r=-0,63) y una menor producción de fuerza. Además,el CO junto con el peso (kg) pueden explicar el AWC en un 64 % durante el ejercicio de alta intensidad. Conclusión: La medición de la oxigenación crítica está asociada a la AWC, por lo que debe considerarse un factor de rendimiento. Estos parámetrospodrían incluirse en sensores NIRS para valorar el metabolismo muscular.(AU)

Objetivo: A capacidade anaeróbica de trabalho (AWC) é entendida como a potência máxima que o atleta pode suportar ao longo do tempo, condicionadapor um esforço de alta intensidade, sendo importante interpretá-la para melhorar o desempenho. Além disso, a saturação muscular de oxigênio (SmO2)fornece informações sobre o metabolismo muscular e a hemodinâmica. Da mesma forma, a oxigenação crítica (OC) é a taxa metabólica mais alta queresulta em um suprimento de energia totalmente oxidativo atingindo um estado estável no nível do substrato. O principal problema é que o SmO2geralmente oferece uma interpretação laboratorial tradicional sem aplicação em testes de campo, portanto, o objetivo deste estudo é fornecer o uso doCO como indicador de desempenho de AWC em exercícios de alta intensidade. Métodos:Participaram 22 jogadores de rugby do sexo masculino. Foram medidos os picos máximos após um teste de fadiga isocinética e o consumo deoxigênio muscular (mVO2) e SmO2 no músculo vasto lateral. Uma análise de correlação e regressão múltipla foi aplicada para encontrar um modeloexplicativo de predição do AWC. Resultados: Uma maior amplitude de SmO2 e CO implicaria em menor trabalho anaeróbio (r = -0,58 er = -0,63) e menor produção de força. Além disso, oCO junto com o peso (kg) pode explicar a AWC em 64% durante o exercício de alta intensidade. Conclusão: A medida oxigenação crítica prevê AWC, portanto, deve ser considerada um fator de desempenho. Esses parâmetros podem ser incluídos emsensores NIRS para a medição do metabolismo muscular.(AU)

Effects of respiratory muscle training on respiratory efficiency and health-related quality of life in sedentary women with fibromyalgia: a randomised controlled trial.

OBJECTIVES: Fibromyalgia syndrome (FM) is a complex disease that is mainly characterised by chronic pain, fatigue, and sleep disturbances and may be precipitated or worsened by many stressors. The aim of this study was to examine the effects of respiratory muscle training (RMT) on respiratory efficiency and health-related quality of life (HRQoL) in women with FM. METHODS: A total of 30 women with FM were included in the intention to treat analyses: 15 were assigned to the RMT group and 15 to the control group. The intervention consisted of 12 weeks of RMT. The primary outcome was the change in pulmonary function assessed by global body plethysmography at 12 weeks compared with baseline. Secondary outcomes included changes of scores in HRQoL assessed by the Short Form 36 Health Survey-Portuguese version. RESULTS: The maximal inspiratory pressure (MIP) improved by 17.5% (p-value = .033), maximal expiratory pressure (MEP) improved 21.6% (p-value = 0.045) and maximum occlusion pressure (P0.1 max) increased 27.7% (p-value = 0.007). HRQoL improved in the dimensions of physical function, physical role, bodily pain and vitality (p-value <0.05). CONCLUSIONS: RMT results in a significant improvement of respiratory efficiency and HRQoL after 12 weeks. RMT could be an effective therapy to enhance respiratory function and quality of life in women with FM.

Amplifying the effects of adding extra players during association football game-based scenarios.

This study aimed to compare under-18 association football players' performance (age = 17.7±1.0 years; playing experience = 9.0 ± 3.2 years) when manipulating the number of teammates and opponents during football game-based practices. Time-motion, individual and tactical-related variables were monitored when manipulating conditions with different number of teammates and opponents (11vs11, No-Sup, No-Inf; 11vs12, Low-Sup, Low-Inf; 11vs13, Mod-Sup, Mod-Inf; and 11vs14, High-Sup, High-Inf). Results showed that adding teammates promoted increases in the longitudinal synchronization from No-Sup to Mod-Sup (Cohen's d with 95% of confidence intervals: 0.25 [0.12; 0.39]; p < .001) and High-Sup (0.61 [0.41; 0.82]; p < .001), while decreases in the distance to the nearest teammate, both in the offensive and defensive phases (p < .001 and p = .005, respectively). In addition, it was observed lower distance covered while running when playing in High-Sup compared to No-Sup (0.30 [-0.01; 0.61]; p = .002) during the defensive phase. Attacking in numerical inferiority promoted a higher variability in the distance to the nearest teammate from No-Inf to High-Inf (0.83 [0.27; 1.38]; p = .044), while decreasing the physical demands, specifically distance covered while running (-0.49 [-0.99; 0.01]; p = .039). In turn, defending, mainly in high-inferiority, increased the total distance covered compared to No-Inf (0.61 [0.30; 0.91]; p < .001) and led to a decrease in the distance to the nearest teammate (-0.90 [-1.35; -0.44]; p = .002). Overall, coaches may manipulate the number of teammates and opponents to promote distinct effects at the level of cooperation and opposition dynamical interactions.

Amplifying perceptual demands: How changes in the colour vests affect youth players performance during medium-sided games.

This study explored how manipulating the colour of training vests affects footballers' individual and collective performance during a Gk+6vs6+Gk medium-sided game. A total of 21 under-17 years old players were involved in three experimental conditions in a random order for a total of four days: i) CONTROL, two teams using two different colour vests; ii) SAME, both teams wearing blue vests; iii) MIXED, all 6 players per team wore different colour vests. Players' positional data was used to compute time-motion and tactical-related variables, while video analysis was used to collect technical variables. Further, these variables were synchronized with spatiotemporal data allowing to capture ball-related actions in a horizontal 2D plan. All variables were analysed from the offensive and defensive perspective. From the offensive perspective, players performed more and further shots to goal during the CONTROL than in SAME and MIXED (small effects) conditions, with a decreased distance to the nearest defender (small effects). While defending, results revealed lower distance to the nearest teammate (small effects) in the CONTROL than in the SAME and MIXED conditions, and higher team longitudinal synchronization (small effects). In addition, the CONTROL showed in general lower values of team width while defending than in the other 2 conditions. Overall, coaches may use the CONTROL condition to emphasize offensive performance and defensive behaviour over the longitudinal direction with increased physical demands. In turn, coaches may use the manipulation of players vests to emphasize defensive performance, as players seem to behave more cohesively under such scenarios.

Capturing and Quantifying Tactical Behaviors in Small-Sided and Conditioned Games in Soccer: A Systematic Review.

Purpose: To systematically describe and analyze the tracking systems, the variables, and the statistical methods used to evaluate the players and teams' tactical behavior in small-sided and conditioned games (SSCGs). Methods: A search was done in Web of Science, PubMed, Science Direct, and Scielo databases to identify manuscripts published between 2008 and 2019 that manipulated small-sided and conditioned games (SSCGs) and analyzed tactical behaviors of players and teams. Results: From 349 articles identified, 31 were selected for review. To collect positional data, the global positioning system (GPS), the local position measurement (LPM) system, and TACTO were identified as reliable tracking systems. Twenty-one positional variables were identified to evaluate tactical behaviors, grouped into five main categories: team balance, playing space, width and length of playing space, and interpersonal distance. Tactical behavior patterns were analyzed using approximate entropy, sample entropy, Shannon entropy, and patterns of coordination between players and teams were analyzed using relative phase and running correlation. Discussion: The tracking systems analyzed were reliable but revealed different advantages and disadvantages of their use. Authors should define the use of each tracking system based on their purpose and level of precision required for analysis. A great duplication was observed on the variables used with similar purposes of tactical analysis. The identification of the variables according to their purpose of analysis will allow a better understanding of their use in the future.

Development and validation of a continuous fall risk score in community-dwelling older people: an ecological approach.

BACKGROUND: Fall risk assessment in older people is of major importance for providing adequate preventive measures. Current predictive models are mainly focused on intrinsic risk factors and do not adjust for contextual exposure. The validity and utility of continuous risk scores have already been demonstrated in clinical practice in several diseases. In this study, we aimed to develop and validate an intrinsic-exposure continuous fall risk score (cFRs) for community-dwelling older people through standardized residuals. METHODS: Self-reported falls in the last year were recorded from 504 older persons (391 women: age 73.1 ± 6.5 years; 113 men: age 74.0 ± 6.1 years). Participants were categorized as occasional fallers (falls ≤1) or recurrent fallers (≥ 2 falls). The cFRs was derived for each participant by summing the standardized residuals (Z-scores) of the intrinsic fall risk factors and exposure factors. Receiver operating characteristic (ROC) analysis was used to determine the accuracy of the cFRs for identifying recurrent fallers. RESULTS: The cFRs varied according to the number of reported falls; it was lowest in the group with no falls (- 1.66 ± 2.59), higher in the group with one fall (0.05 ± 3.13, p < 0.001), and highest in the group with recurrent fallers (2.82 ± 3.94, p < 0.001). The cFRs cutoff level yielding the maximal sensitivity and specificity for identifying recurrent fallers was 1.14, with an area under the ROC curve of 0.790 (95% confidence interval: 0.746-0.833; p < 0.001). CONCLUSIONS: The cFRs was shown to be a valid dynamic multifactorial fall risk assessment tool for epidemiological analyses and clinical practice. Moreover, the potential for the cFRs to become a widely used approach regarding fall prevention in community-dwelling older people was demonstrated, since it involves a holistic intrinsic-exposure approach to the phenomena. Further investigation is required to validate the cFRs with other samples since it is a sample-specific tool.

Relative Age Effect in Physical Fitness of South Portugal Students between 10 and 18 Years Old.

Relative age is a phenomenon broadly studied in sport sciences. Youth sports participants born earlier in the selection year tend to present a maturational advantage over their peers. As it is also dependent on physical performance, older physical education students may also benefit from this effect in this school subject. The main goal of this manuscript was to determine whether the relative age effect is present within physical fitness outcomes of Portuguese children and adolescents. The physical-aerobic fitness, strength, flexibility and body composition of 885 students (490 females and 395 males) were collected and compared by quarters of birth, segmented by gender and age groups (10-12; 12-14; 14-16 and 16-18 years). The results reveal a moderate to small effect in physical fitness outcomes, with a trend for children and adolescents born in the early part of the year to present higher performance levels. These differences were more evident in ages closer to the physical maturational onset (12-14 y) and more apparent in male students. This physical fitness advantage may lead to a biased assessment and development of students born earlier in the year.

Can Tracking Data Help in Assessing Interpersonal Contact Exposure in Team Sports during the COVID-19 Pandemic?

During the COVID-19 pandemic, the temporary closure of physical activity and sports facilities, and the generalized cancellation or postponement of sports events have a massive impact on social and economic development. In this study, we explored the feasibility of using tracking data from a football match to assess interpersonal contact between individuals by calculating two measures of respiratory exposure. The dynamic tracking positioning of all players and referees during one international football match was analyzed. For each individual, two measures of respiratory exposure were calculated, based on the 2 m interpersonal distance recommendations for contact tracing for COVID-19 control. Overall, individuals spent a median of 0.12 mm:ss (IQR = 0.45 mm:ss) exposed to interpersonal contact of fewer than 2 m from others. The highest value of exposure was observed between two players of opposing teams (6.35 mm:ss). The results suggest that tracking data can be used to assess respiratory exposure to interpersonal contact in team sports, such as football. The measures of exposure calculated can be used to the prompt identification of high-risk contacts of COVID-19 cases during a match or a training session, but also the risk stratification of different sports and physical activities.

Different Marks in the Pitch Constraint Youth Players' Performances During Football Small-sided Games.

Purpose: This study aimed to compare players' performances when manipulating the external markings of the pitch during football small-sided games. Methods: Ten under-15 players performed a 5-a-side (plus goalkeepers) under three conditions: (i) Lines, the game was played in a pitch in which the external boundaries were painted with full lines; (ii) Dashed, the game was played in a pitch in which the external boundaries were painted with dashed lines; (iii) Corners, the game was played in a pitch were the external boundaries were delimited by one marker at each pitch corner. Players' positional data was used to compute tactical and time-motion variables. Also, technical analysis was comprised using video footage. Results: Results showed similar tactical, physical and technical performances between the Lines and Dashed conditions. In contrast, the Lines condition showed small higher effects than Corners scenario in the time spent synchronized in longitudinal and lateral displacements, game pace, total distance covered, distance covered while jogging, number successful dribbles and shots on target. The Lines scenario has also revealed a lower effective playing space, distance covered at walking and running and a lower number of passes (small effects) compared to Corners. Conclusions: These results highlight that these changes in informational perception constraints modify players movement behavior. Accordingly, pitches with more visible boundaries were likely to decrease team dispersion, which may optimize team synchrony and technical performances, while decreasing the distance covered at higher speeds. Coaches may use this information to modify the types of pitch external boundaries markings, exposing the players to different environmental information.

Reliability and construct validity of the stepping-forward affordance perception test for fall risk assessment in community-dwelling older adults.

Thus far, few studies have examined the estimation and actual performance of locomotor ability in older adults. To our knowledge, there are no studies examining the relationship between stepping-forward estimation versus ability and fall occurrence. The aim of this study was to develop and assess the reliability and validity of a new test for fall risk assessment in community-dwelling older adults. In total, 347 participants (73.1 ± 6.2 years; 266 women) were assessed for their perception of maximum distance for the stepping-forward and action boundary. The test was developed following the existing literature and expert opinions. The task showed strong internal consistency. Intraclass correlation ranged from 0.99 to 1 for intrarater agreement and from 0.83 to 0.97 for interrater agreement. Multivariate binary regression analysis models revealed an area under the curve (AUC) of 0.665 (95% CI: 0.608-0.723) for fallers and 0.728 (95% CI: 0.655-0.797) for recurrent fallers. The stepping-forward affordance perception test (SF-APT) was demonstrated to be accurate, reliable and valid for fall risk assessment. The results showed that a large estimated stepping-forward associated with an underestimated absolute error works as a protective mechanism for fallers and recurrent fallers in community-dwelling older adults. SF-APT is safe, quick, easy to administer, well accepted and reproducible for application in community or clinical settings by either clinical or nonclinical care professionals.

Towards the use of multidimensional performance indicators in football small-sided games: the effects of pitch orientation.

This study aimed to compare youth football players' performance during two small-sided games with different pitch orientation: i) 40x30m and ii) 30x40m formats. Twenty under-15 players (age = 14.1 ± 0.5 years) participated in nine GK+4vs4+GK situations in each format, with the duration of six minutes each. Positional data were collected using individual GPS units, and computed for tactical and physical performance indicators. The SSG were video recorded, using notational analysis for collecting technical indicators. A novel method that incorporates time dependent notational information with spatiotemporal data was used to compute multidimensional parameters. Standardised effect sizes and non-clinical magnitude-based inferences were used to compare formats. Results showed that players covered more distance at higher intensities, presented more passes and dribbles and were more synchronised in the longitudinal axis while playing in the 40x30m pitch. In the 30x40m pitch, results showed a lower distance between team centroids, higher number of shots, more lateral passes and a wider team positioning. Multidimensional indicators, as players position and distance to the closest defender while shooting, revealed a more constant distance between attacker and defender in the 40x30m pitch. These results highlight the importance of integrating information from different indicators for a contextually valid information.

Speed synchronization, physical workload and match-to-match performance variation of elite football players.

This study aimed to: (i) examine whether the speed synchronization and physical performance of an elite football team changed between the first and the second half, using match time blocks of 15-min, and (ii) explore the match-to-match variation of players' speed synchronization performance. Twenty-eight outfield elite footballers participated in 51 official matches. Positional data were gathered and used to calculate the total distance covered as a physical workload indicator. For all the outfield teammate dyad combinations (45 pairs), it was processed the percentage of time that players' speed was synchronized during walking, jogging and running using relative phase (Hilbert Transform). Also, the match-to-match variation of the players' speed synchronization, expressed in coefficient of variation was computed. The differences in the total distance covered from all players within the different match's time block periods revealed a moderate decrease in the distance covered in the last 15-min of the match compared to the first 15-min (-6.5; ±1.07%, most likely: change in means with 95% confidence limits). However, when compared the last minutes from both halves a small increase was observed (2.7; ±1.2%, likely) from first to second half. The synchronization of the players' speed displacements revealed small to moderate decreases in the % of synchronization in the second half periods for the jogging and running speed, while the opposite was found for the walking speed (~13 to 24% more, most likely). The playing position analysis for the walking zone showed similar trends between the groups, with small to moderate higher values in the second half, with the exception of [30'-45'] vs [75'-90'] in the midfielder's dyads and in [15'-30'] vs [60'-75'] match periods for forwards. Similar trend was found during the running speed, in which small to moderate higher synchronization was found during the first half periods, with the exception of [15'-30'] vs [60'-75'] and [30'-45'] vs [75'-90'] in midfielder's dyads. Regarding to the match-to-match variation of the players' speed synchronization, overall results showed small to moderate increases in coefficient of variation during jogging and running displacements from the beginning to the end of the match (32.1; ±13.2% increase in jogging and 26.2; ±10.5% in running, both comparisons most likely). The higher distance covered during most of the first half periods and the higher dyadic synchronization at high speeds might have limited players' performance in the second half. In addition, the decrease trend in speed synchronization during the second half periods might have resulted from accumulated muscular and mental fatigue towards the match. Within, the match-to-match variation in tactical-related variables increased across the match duration, with especial focus in the midfielder dyads. Dyadic speed synchronization might provide relevant information concerning the individual and collective performance.

Changes in Effective Playing Space when Considering Sub-Groups of 3 to 10 Players in Professional Soccer Matches.

Success in soccer is much dependent on how players and teams create and restrict space and time. In match situations, players constitute small sub-groups to improve their collective synchronization and achievement of specific goals. This study aimed to identify changes in the effective playing space (EPS, defined as the smallest polygonal area delimited by the peripheral outfield players) when considering sub-groups of 3 to 10 players. Twenty outfield professional players participated in this study. The EPS, its regularity pattern (measured by the approximate entropy), coefficient of variation and players' mean speed were calculated for sub-groups of 3, 4, 5, 6, 7, 8, 9 and 10 players, considering the smallest inter-player distance as the criterion. The EPS presented a most likely increase with a higher number of players, especially considering the transition from 3 to 4 players (~440% of variation, very large). As the EPS increased with the number of players, the correspondent regularity presented a trend of a most likely increase (from EPS3 vs. EPS4: ~25%, very large; to EPS9 vs. EPS10: ~11%, moderate). The mean speed results suggest that players may achieve different states of collective coordination, mainly between ~6 to 8 km.h-1. Overall, three different match scenarios should require additional attention when aiming to design more match transferable tasks: i) transition from EPS3 to EPS4; ii) transition from EPS4 up to EPS8; and iii) transition from EPS8 to EPS9. These results help to understand match self-organized behaviours and, consequently, allow to optimize task characteristics in practice sessions.

Accuracy of a Basketball Indoor Tracking System Based on Standard Bluetooth Low Energy Channels (NBN23®).

The present study aims to identify the accuracy of the NBN23® system, an indoor tracking system based on radio-frequency and standard Bluetooth Low Energy channels. Twelve capture tags were attached to a custom cart with fixed distances of 0.5, 1.0, 1.5, and 1.8 m. The cart was pushed along a predetermined course following the lines of a standard dimensions Basketball court. The course was performed at low speed (<10.0 km/h), medium speed (>10.0 km/h and <20.0 km/h) and high speed (>20.0 km/h). Root mean square error (RMSE) and percentage of variance accounted for (%VAF) were used as accuracy measures. The obtained data showed acceptable accuracy results for both RMSE and %VAF, despite the expected degree of error in position measurement at higher speeds. The RMSE for all the distances and velocities presented an average absolute error of 0.30 ± 0.13 cm with 90.61 ± 8.34 of %VAF, in line with most available systems, and considered acceptable for indoor sports. The processing of data with filter correction seemed to reduce the noise and promote a lower relative error, increasing the %VAF for each measured distance. Research using positional-derived variables in Basketball is still very scarce; thus, this independent test of the NBN23® tracking system provides accuracy details and opens up opportunities to develop new performance indicators that help to optimize training adaptations and performance.

Positional synchronization affects physical and physiological responses to preseason in professional football (soccer).

This study aimed to identify changes in tactical, physical and physiological performances in large-sided games during the preseason of elite footballers. Thirty professional football players participated in several GK+8vs.8+GK large-sided games across the first four weeks of the season. Players were monitored by GPS units and heart rate monitors to quantify physical, physiological and tactical performances. The variables were compared according to the preseason period, players' positioning and professional experience. The training situation promoted similar physiological responses during the first and the last training period. However, players were revealed to have higher levels of positional synchronization during the last preseason period, indicating an improved tactical performance. Tactical variables seem to reflect the improvement of players' performance during the preseason, measured in large-sided games situation, while affecting both physical and physiological demands. These results highlight the potential of positioning derived variables, concurrently to physical and physiological variables, for football training optimization.

Effects of Pitch Area-Restrictions on Tactical Behavior, Physical, and Physiological Performances in Soccer Large-Sided Games.

Gonçalves, B, Esteves, P, Folgado, H, Ric, A, Torrents, C, and Sampaio, J. Effects of pitch area-restrictions on tactical behavior, physical and physiological performances in soccer large-sided games. J Strength Cond Res 31(9): 2398-2408, 2017-The aim of this study was to identify how pitch area-restrictions affect the tactical behavior, physical, and physiological performances of players during soccer large-sided games. A 10 vs. 9 large-sided game was performed under 3 experimental conditions: (a) restricted-spacing, the pitch was divided into specific areas where players were assigned and they should not leave it; (b) contiguous-spacing, the pitch was divided into specific areas where the players were only allowed to move to a neighboring one; (c) free-spacing, the players had no restrictions in space occupation. The positional data were used to compute players' spatial exploration index and also the distance, coefficient of variation, approximate entropy, and frequency of near-in-phase displacements synchronization of players' dyads formed by the outfield teammates. Players' physical and physiological performances were assessed by the distance covered at different speed categories, game pace, and heart rate. Most likely higher values were found in players' spatial exploration index under free-spacing conditions. The synchronization between dyads' displacements showed higher values for contiguous-spacing and free-spacing conditions. In contrast, for the jogging and running intensity zones, restricted-spacing demanded a moderate effect and most likely decrease compared with other scenarios (∼20-50% to jogging and ∼60-90% to running). Overall, the effects of limiting players' spatial exploration greatly impaired the coadaptation between teammates' positioning while decreasing the physical and physiological performances. These results allow for a better understanding of players' decision-making process according to specific task rules and can be relevant to enrich practice task design, such that coaches acknowledge the differential effect by using specific pitch-position area restrictions.

Influence of additional players on collective tactical behavior in small-sided soccer games / Comportamento tático coletivo em Pequenos Jogos no Futebol: influência de jogadores adicionais

Abstract The aim of this study was to compare the collective tactical behavior between numerically balanced and unbalanced small-sided soccer games. Eighteen male soccer players (mean age 16.4 years) participated in the study. Polar coordinate analysis was performed using positional data obtained with a 15-Hz GPS device. Collective variables including length, width, centroid distance (average point between teammates), and length per width ratio (LPWratio) were collected. Data were analyzed using Friedman’s test. The results showed greater length and width values in 4vs.3 games, while a higher LPWratio was observed in 3vs.3+2 games compared to the other configurations. In games with an additional player (4vs.3), ball circulation and the increase in effective game space were alternatives to overcome the more concentrated defensive systems near the goal. On the other hand, 3vs.3+2 games allowed more actions in the length axis and a fast reach of the opponent’s goal.

Resumo Este estudo objetivou comparar o comportamento tático coletivo entre situações de Pequenos Jogos em igualdade e superioridade numérica. Participaram do estudo 18 jovens jogadores de futebol com idade média de 16,4 anos. A análise de coordenadas polares foi realizada a partir dos dados posicionais obtidos com equipamento de GPS de 15Hz. O comportamento tático foi acessado por meio das medidas de largura, profundidade, distância entre os centroides (ponto médio dos jogadores de uma equipe no campo de jogo) e razão profundidade/largura (LPWratio). Dados foram analisados por meio do teste de Friedman. Resultados apontaram para um aumento dos valores de largura e profundidade na configuração 4vs.3, enquanto o jogo 3vs.3+2 apresentou aumento do valor da razão profundidade/largura em relação às demais configurações. Nos jogos com jogador adicional no campo (4vs.3), a circulação da bola e ampliação do espaço efetivo de jogo foram alternativas para superar as defesas mais fechadas e próximas à própria baliza, enquanto a presença de jogadores adicionais de suporte (3vs.3+2) permitiu o rápido alcance à baliza adversária, incentivando o jogo em profundidade.

Programas de exercício na prevenção de lesões em jogadores de futebol: uma revisão sistemática / Exercise programs in the preventing injuries in football players: a systematic review / Programas de ejercicio en la prevención de lesiones en los jugadores de fútbol: una revisión sistemática

Dentre as lesões ocorridas em jogadores de futebol, as lesões dos isquiotibiais são as mais frequentes. Programas de exercício que previnam o seu aparecimento e diminuam a sua recorrência e severidade são de extrema importância para os fisioterapeutas, treinadores e jogadores. Conhecer as evidências científicas sobre a eficácia de programas de exercício na prevenção de lesões dos isquiotibiais, em jogadores de futebol masculino. Os estudos foram selecionados para revisão em diferentes bases de dados. Para avaliar a qualidade metodológica dos estudos e a força de evidência dos resultados utilizou-se a escala da Base de dados de Evidência em Fisioterapia (PEDro) e o sistema de classificação Melhor Síntese de Evidência, respectivamente. Os programas de exercício utilizados foram: força concêntrica e excêntrica; força excêntrica Nordic Hamstrings; The FIFA 11+; e elasticidade. As variáveis estudadas foram a incidência de lesões, a incidência de novas lesões, a recorrência de lesões, a severidade das lesões e o risco de lesão. O programa de força concêntrica e excêntrica e o programa de força excêntrica Nordic Hamstrings parecem ser os mais eficazes na redução da incidência das lesões e da incidência de novas lesões dos isquiotibiais, respetivamente (evidências limitadas). O programa de exercício de força excêntrica Nordic Hamstring não é eficaz na diminuição do risco de lesão (evidências limitada) e na melhoria da severidade das lesões (evidência moderada). O programa The FIFA 11+ não é eficaz na redução da incidência das lesões (evidência limitada). Há evidências contraditórias nas variáveis restantes.

Hamstrings injuries are one of the most frequent injuries in football players. Exercise programs leading to lower levels of injury, diminishing their recurrence and severity are extremely important for coaches, physical therapist and players. To recognize the scientific evidence of the effectiveness of exercise intervention programs in the prevention of hamstring injuries, in male football players. Different studies were selected for revision from several databases. To evaluate the methodological quality of these studies we used the Physiotherapy Evidence Database (PEDro) and determined the strength of the evidence using the best evidence synthesis grading system. The used exercise programs where based in concentric and eccentric strength, the eccentric strength exercise Nordic Hamstrings, The FIFA 11+, and flexibility exercises. The variables studied were: the incidence, the incidence of new injuries, recurrence of injuries, the severity, and the risk of injuries. The concentric and eccentric strength program and the Nordic Hamstrings program seem to be the most effective in reducing the incidence of injuries and the incidence of new injuries, respectively (limited evidence). The Nordic Hamstrings program does not reduce the risk of injuries (limited evidence) and does not improve the level of severity of the injuries (moderate evidence). The FIFA 11+program does not reduce the incidence of injuries (limited evidence). There are contradictory evidences on the other variables.

De entre las lesiones ocurridas en jugadores de fútbol, las lesiones de los isquiotibiales son las más frecuentes. Los programas de ejercicio que prevengan su aparición y disminuyan su recurrencia y severidad son de extrema importancia para los fisioterapeutas, entrenadores y jugadores. Conocer las evidencias científicas sobre la eficacia de programas de ejercicio en la prevención de lesiones de los isquiotibiales, en jugadores de fútbol masculino. Los estudios fueron seleccionados para revisión en diferentes bases de datos. Para evaluar la calidad metodológica de los estudios y la fuerza de evidencia de los resultados se utilizó la escala de Base de datos de evidencia en fisioterapia (PEDro) y el sistema de clasificación Mejor Síntesis de Evidencia, respectivamente. Los programas de ejercicio utilizados fueron: fuerza concéntrica y excéntrica; fuerza excéntrica Nordic Hamstrings; The FIFA 11+; y elasticidad. Las variables estudiadas fueron la incidencia de lesiones, la incidencia de nuevas lesiones, la recurrencia de lesiones, la severidad de las lesiones y el riesgo de lesión. El programa de fuerza concéntrica y excéntrica y el programa de fuerza excéntrica Nordic Hamstrings parecen ser los más eficaces en la reducción de la incidencia de las lesiones y de la incidencia de las nuevas lesiones de los isquiotibiales, respectivamente (evidencias limitadas). El programa de ejercicio de fuerza excéntrica Nordic Hamstrings no es eficaz en la disminución del riesgo de lesión (evidencias limitadas) y tampoco en la mejora de la severidad de las lesiones (evidencia moderada). El programa de The FIFA 11+ no es eficaz en la reducción de la incidencia de las lesiones (evidencia limitada). Hay evidencias contradictorias en las restantes variables.