Hugo Folgado

Length, width and centroid distance as measures of teams tactical performance in youth football

Abstract Small-sided games are commonly used in training and teaching contexts of football. However, few studies have focused on the tactical implications of this type of drills. The aim of this study is to identify how tactical collective behaviour varies with age in different small-sided game formats. We investigated the in-game field position in three different age groups of youth football players [under-9 (n=10; age = 8.5±0.53), under-11 (n=10; age = 10.4±0.52) and under-13 (n=10; age = 12.7±0.48)], participating in two different small-sided game conditions (GK + 3×3 + GK and GK + 4×4 + GK). A team variable was created based on the players’ length per width ratio (lpwratio), and a match variable was calculated as the distance between the centroid of the two teams. Results show that team variable values were influenced by the age of the players, as younger teams tend to present a higher value of lpwratio in their dispersion on the pitch. The variability of this variable also showed a decrease for teams with older players, suggesting a more consistent application of the width (stretching and creating space) and concentration (compressing into a confined area) principles of play and reflecting a higher level of collective tactical behaviour. Match variable showed a larger centroid distance for the older age groups in comparison with the younger players in the GK + 3×3 + GK, while all age groups demonstrated similar large centroid distances in the GK + 4×4 + GK game format. These results suggest that length and width ratio and centroid distance are useful measures of tactical performance in small-sided games in youth football.

Competing with Lower Level Opponents Decreases Intra-Team Movement Synchronization and Time-Motion Demands during Pre-Season Soccer Matches

This study aimed to quantify the time-motion demands and intra-team movement synchronization during the pre-season matches of a professional soccer team according to the opposition level. Positional data from 20 players were captured during the first half of six pre-season matches of a Portuguese first league team. Time-motion demands were measured by the total distance covered and distance covered at different speed categories. Intra-team coordination was measured by calculating the relative phase of all pairs of outfield players. Afterwards, the percentage of time spent in the −30° to 30° bin (near-in-phase mode of coordination) was calculated for each dyad as a measure of space-time movement synchronization. Movement synchronization data were analyzed for the whole team, according to each dyad average speed and by groups of similar dyadic synchronization tendencies. Then, these data were compared according to the opponent team level (first league; second league; amateurs). Time-motion demands showed no differences in total distance covered per opposition levels, while matches opposing teams of superior level revealed more distance covered at very high intensity. Competing against superior level teams implied more time in synchronized behavior for the overall displacements and displacements at higher intensities. These findings suggest that playing against higher-level opponents (1st league teams) increased time-motion demands at high intensities in tandem with intra-team movement synchronization tendencies.

The Ecological Dynamics of 1v1 Sub-Phases in Association Football

This paper analyzes effects of different practice task constraints on heart rate (HR) variability during 4v4 smallsided football games. Participants were sixteen football players divided into two age groups (U13, Mean age: 12.4±0.5 yrs; U15: 14.6±0.5). The task consisted of a 4v4 sub-phase without goalkeepers, on a 25x15 m field, of 15 minutes duration with an active recovery period of 6 minutes between each condition. We recorded players’ heart rates using heart rate monitors (Polar Team System, Polar Electro, Kempele, Finland) as scoring mode was manipulated (line goal: scoring by dribbling past an extended line; double goal: scoring in either of two lateral goals; and central goal: scoring only in one goal). Subsequently, %HR reserve was calculated with the Karvonen formula. We performed a time-series analysis of HR for each individual in each condition. Mean data for intra-participant variability showed that autocorrelation function was associated with more short-range dependence processes in the “line goal” condition, compared to other conditions, demonstrating that the “line goal” constraint induced more randomness in HR response. Relative to inter-individual variability, line goal constraints demonstrated lower %CV and %RMSD (U13: 9% and 19%; U15: 10% and 19%) compared with double goal (U13: 12% and 21%; U15: 12% and 21%) and central goal (U13: 14% and 24%; U15: 13% and 24%) task constraints, respectively. Results suggested that line goal constraints imposed more randomness on cardiovascular stimulation of each individual and lower inter-individual variability than double goal and central goal constraints.

The effects of congested fixtures period on tactical and physical performance in elite football

Abstract The aim of this study was to examine the physical and tactical performances of a professional football team under congested and non-congested fixture periods. Six home matches of an English professional football team were analysed during competitive season (3 matches distancing three days from the previous fixture and 3 matches distancing six or more days from the previous fixture). Players’ physical performances were measured by the total distance covered and distance covered at different speed categories. Tactical performances were measured by the percentage of time of players’ movement synchronisation of lateral and longitudinal displacements. This variable was calculated considering all the possible pairs of outfield players, for the overall match and at different speed categories. Results showed no differences in the physical performance, although players’ spent more time synchronised during the non-congested fixtures compared to congested fixtures, both for lateral (41.26% to 38.51%, ES: −0.3, P < 0.001) and longitudinal displacements (77.22% to 74.48%, ES: −0.5, P < 0.001). These coordination differences were particularly evident at the lower speed categories and in dyads composed by positions that tend to be further apart during the match, typically central and wing positioned players. Tactical performance seems to be affected by fixtures distribution, with players’ spending more time synchronised during the non-congested fixtures. As players’ cover the same amount of distance at similar intensities in both fixtures distribution, this reduction of synchronisation may be associated with an increased perception of fatigue and consequent adaptation strategies.

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

ABSTRACT 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.

Exploring how movement synchronization is related to match outcome in elite professional football

ABSTRACT Purpose: This study aimed to explore whether the outcome of professional football matches is affected by changes in intra-team movement synchronization. Methods: Positional data from 77 players were collected during 4 matches of an English Premier League team, using the ProZone® tracking system. Intra-team movement synchronization was calculated using the relative phase of all possible pairing combinations of outfield teammates (dyads) and quantified by the overall percentage of time spent near-in-phase (−30º to 30º bin). Per each displacement axis, a 2 × 2 mixed-model analysis of variance (ANOVA) was used to compare the overall dyadic movement synchronization according to the team and the match final outcome. A two-way ANOVA was used to compare movement synchronization according to dyads’ on-field position (defensive or offensive) and match final outcome. Results: Despite individual dynamical trends during each match, the analysed team tended to exhibit lower movement synchronization when losing. Also, dyads with an emphasis in defensive roles seem to present a more synchronized behaviour during the match than dyads with more offensive roles. Conclusions: Findings suggest that movement synchronization may serve as a tactical performance indicator candidate, reflecting the dynamical interaction between teammates and opponents during the match.

Programas de exercício na prevenção de lesões em jogadores de futebol: uma revisão sistemática

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.Dentre as lesoes ocorridas em jogadores de futebol, as lesoes dos isquiotibiais sao as mais frequentes. Programas de exercicio que previnam o seu aparecimento e diminuam a sua recorrencia e severidade sao de extrema importância para os fisioterapeutas, treinadores e jogadores. Conhecer as evidencias cientificas sobre a eficacia de programas de exercicio na prevencao de lesoes dos isquiotibiais, em jogadores de futebol masculino. Os estudos foram selecionados para revisao em diferentes bases de dados. Para avaliar a qualidade metodologica dos estudos e a forca de evidencia dos resultados utilizou-se a escala da Base de dados de Evidencia em Fisioterapia (PEDro) e o sistema de classificacao Melhor Sintese de Evidencia, respectivamente. Os programas de exercicio utilizados foram: forca concentrica e excentrica; forca excentrica Nordic Hamstrings; The FIFA 11+; e elasticidade. As variaveis estudadas foram a incidencia de lesoes, a incidencia de novas lesoes, a recorrencia de lesoes, a severidade das lesoes e o risco de lesao. O programa de forca concentrica e excentrica e o programa de forca excentrica Nordic Hamstrings parecem ser os mais eficazes na reducao da incidencia das lesoes e da incidencia de novas lesoes dos isquiotibiais, respetivamente (evidencias limitadas). O programa de exercicio de forca excentrica Nordic Hamstring nao e eficaz na diminuicao do risco de lesao (evidencias limitada) e na melhoria da severidade das lesoes (evidencia moderada). O programa The FIFA 11+ nao e eficaz na reducao da incidencia das lesoes (evidencia limitada). Ha evidencias contraditorias nas variaveis restantes.

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.

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

Abstract 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.