Variations in cumulative workload and anaerobic power in adolescent elite male football players: associations with biological maturation.

BACKGROUND: It is considered that the maturity condition of young football players is related to their physical performance during short high-intensity efforts dependent on anaerobic power ability. Hence, the aim was to determine possible relationships between maturity status and training intensity by measuring the footballer´s peak height velocity (PHV), maturity offset and anaerobic power. METHODS: Seventeen youth male players of different playing positions participated in the study and performed tests at three different stages of the season (early-, mid- and end-season) All the anthropometric parameters and biomarkers related to maturation were controlled during the season. The training intensity and load was monitored and the anaerobic power of the players was assessed by a running-based anaerobic sprint test (RAST). RESULTS: The analysis of all the recorded data revealed a positive relationship between PHV and anaerobic power in the early- and end-season stages (p < 0.05). Maturity offset and anaerobic power (mean RAST) showed an absolute correlation in early- and end -season stages (r: - 0.39 to 0.91). The multiple linear regression analysis revealed that min RAST was the best predictor for both PHV and maturity offset. The analysis of the training intensity and workloads showed a positive effect on the performance in the fitness test (p < 0.05). Additionally, players experienced less fatigue at the end-season stage than at the early-season. CONCLUSIONS: The results show that coaches might benefit from monitoring training loads and the maturity status of the players in order to enhance their physical performance during the season.

Effects of a Neuromuscular Warm-Up Program in Youth Female Soccer Players.

The protective effects of different warm-up injury prevention routines in youth female soccer players have been demonstrated in the literature, however, there is a paucity of information regarding the effects that these kinds of programs have on soccer-specific physical performance variables. The purpose of this study was to assess the effectiveness of a 12-week neuromuscular warm-up program on physical performance in youth female soccer players. Players (age: 13.94 ± 0.82 years) were divided into two groups. One group performed a neuromuscular activation program (n = 21) twice per week whereas the other group (control, n = 17) continued with their habitual warm-up routine for the same duration. Both groups of players performed strength, jumping and balance tests before and after the intervention period. Substantially greater improvements were detected in the mean velocity for the squat (p < 0.001; Effect Size = 0.95) and the hip thrust (p < 0.001; Effect Size = 0.51) in the experimental group in comparison to the control group. In addition, after the intervention period players in the experimental group showed an increase in the jumping height in the unloaded double-leg and single-leg counter-movement jumps (p = 0.003-0.012; Effect Size = 0.42-0.46). The results of this study provide evidence that a 12-week neuromuscular warm-up program can be effective to improve different physical performance variables in youth female soccer players.

Relationships between Strength and Step Frequency with Fatigue Index in Repeated Sprint Ability.

Force-velocity profile (FVP) and repeated-sprint ability (RSA) tests are indicators of physical capacities in most team sport players. The purpose of this study was to examine the stride kinematics during a repeated-sprint ability (RSA) test and to analyze the relationship between Bosco's force-velocity profile (FVP) and RSA performance in elite female field hockey players. Thirteen elite-female players performed both RSA (six 30 m maximal sprints) and jumping (CMJ weighted and body weight) tests. Sprinting time fatigue indexes during a 30 m RSA test were correlated with step frequency fatigue indexes (r > 0.7; p < 0.01). CMJ50 showed a large relationship with sprint time fatigue indexes. FV50 showed a very large relationship with sprint time fatigue indexes (r > 0.7; p < 0.01), and a large relationship with the step frequency fatigue indexes (r > 0.5; p < 0.05). This study highlighted two possible ways to improve fatigue indexes in RSA, with the aim of maximizing the distances covered at high-intensities during the matches: (a) strength training and (b) focusing on step frequency during speed training.

Spatiotemporal Comparisons Between Elite and High-Level 60 m Hurdlers.

Despite the existence of literature on the athletics hurdles event, no previous studies have examined the kinematic behavior of athletes during the race. The aims of the present research were (1) to compare the spatiotemporal parameters of elite and high-level hurdlers (men and women) in the approach run, hurdles-unit and run-in phases and (2) to relate these parameters to the 60 m end race results. Split times, step lengths, step widths, step times, contact times and flight times were calculated for the 60 m hurdlers (n = 110) who participated in the 44th Spanish Indoor Championship and in the 12th IAAF World Indoor Championship. Both men and women elite-level hurdlers obtained shorter split times than high-level hurdlers in the approach run (δ 0.14 ± 0.01 and 0.18 ± 0.02 s, respectively), the hurdles-unit (δ 0.11 ± 0.01 and 0.13 ± 0.01 s, respectively) and the run-in (δ 0.10 ± 0.01 and 0.20 ± 0.02 s, respectively) race phases. Elite-level men athletes also presented lower step lengths in the approach run phase (δ 0.01 ± 0.00 m), greater take-off distances (δ 0.10 ± 0.03 m) and shorter landing distances (δ 0.17 ± 0.05 m) than high-level athletes, although elite-level women hurdlers only showed longer landing step length (δ 0.07 ± 0.02 m) than high-level athletes. Finally, in the run-in phase, elite-level hurdlers had longer step lengths than high-level hurdlers (men: δ 0.09 ± 0.03 m; women: δ 0.11 ± 0.03 m). Step times, contact times and flight times were also different between both levels of performance in most of the race phases. Correlational analysis with the race result showed large (r > 0.5), very large (r > 0.7), or nearly perfect (r > 0.9) relationships for most of the mentioned kinematic parameters. These results indicate that elite-level athletes were faster than high-level in the three phases of the 60 m hurdles event, specifically in some new spatiotemporal parameters (e.g. step length in the run-in phase) as well as others already studied. Accordingly, coaches and athletes should implement their training programs to have an impact on these key variables.

Physical Demands of Top-Class Soccer Friendly Matches in Relation to a Playing Position Using Global Positioning System Technology.

The aim of this study was to examine the physical demands imposed on professional soccer players during 11-a-side friendly matches in relation to their playing position, using global positioning system (GPS) technology. One hundred and eleven match performances of a Spanish "La Liga" team during the 2010-11 and 2011-12 pre-seasons were selected for analysis. The activities of the players were monitored using GPS technology with a sampling frequency of 1 Hz. Total distance covered, distance in different speed categories, accelerations, and heart rate responses were analyzed in relation to five different playing positions: central defenders (n=23), full-backs (n=20), central midfielders (n=22), wide midfielders (n=26), and forwards (n=20). Distance covered during a match averaged 10.8 km, with wide and central midfielders covering the greatest total distance. Specifically, wide midfielders covered the greatest distances by very high-intensity running (>19.8 km·h-1) and central midfielders by jogging and running (7.2-19.7 km·h-1). On the other hand, central defenders covered the least total distance and at high intensity, although carried out more (p<0.05-0.01) accelerations than forwards, wide midfielders, and fullbacks. The work rate profile of the players obtained with the GPS was very similar to that obtained with semi-automatic image technologies. However, when comparing results from this study with data available in the literature, important differences were detected in the amount of distance covered by sprinting, which suggests that caution should be taken when comparing data obtained with the GPS with other motion analysis systems, especially regarding high-intensity activities.

Effects of different swimming race constraints on turning movements.

The aim of this study was to investigate the effects of different swimming race constraints on the evolution of turn parameters. One hundred and fifty-eight national and regional level 200-m (meters) male swimming performances were video-analyzed using the individualized-distance model in the Open Comunidad de Madrid tournament. Turn (p<.001, ES=0.36) and underwater distances (p<.001, ES=0.38) as well as turn velocity (p<.001, ES=0.69) significantly dropped throughout the race, although stroke velocity and underwater velocity were maintained in the last lap of the race (p>.05). Higher expertise swimmers obtained faster average velocities and longer distances in all the turn phases (p<.001, ES=0.59), except the approach distance. In addition, national level swimmers showed the ability to maintain most of the turn parameters throughout the race, which assisted them in improving average velocity at the end of races. Therefore, the variations in the turning movements of a swimming race were expertise-related and focused on optimizing average velocity. Turning skills should be included in the swimming race action plan.

A new procedure for race analysis in swimming based on individual distance measurements.

The aim of this study was to develop a new application based on the "individual distances" method to analyse swimming races, and to compare it with the traditional "fixed distances" method. One hundred and seventy-nine national level 100 m (four strokes) performances obtained from the 2008 "Open Comunidad de Madrid" (Spain) were analysed using a two-dimensional Direct Linear Transformation (2D-DLT) video analysis system. Average velocities in all race segments (P < 0.001) were faster using the "individual distances" method than when employing the "fixed distances" method. Specifically, start and turn times were shorter (P < 0.001) while free swimming times were longer (P < 0.001) when using the "individual distances" method. Correlations between methods were moderate to high, but several gender and stroke groups showed poor to no correlation, especially during the start and turn segments. Differences between methods were higher in some groups (female swimmers and freestyle stroke) where the start and turn distances were shorter. Measurements with the 2D-DLT technique provide distances and times employed during the race segments, which do not completely agree with times at fixed distances. Therefore, when evaluating swimming races, a combination of the individual and fixed distances methods should be used.

Effect of positioning on the accuracy of decision making of association football top-class referees and assistant referees during competitive matches.

The aim of this study was to examine the effect of positioning on the correctness of decision making of top-class referees and assistant referees during international games. Match analyses were carried out during the Fédération Internationale de Football Association (FIFA) Confederations Cup 2009 and 380 foul play incidents and 165 offside situations were examined. The error percentage for the referees when indicating the incidents averaged 14%. The lowest error percentage occurred in the central area of the field, where the collaboration of the assistant referee is limited, and was achieved when indicating the incidents from a distance of 11-15 m, whereas this percentage peaked (23%) in the last 15-min match period. The error rate for the assistant referees was 13%. Distance of the assistant referee to the offside line did not have an impact on the quality of the offside decision. The risk of making incorrect decisions was reduced when the assistant referees viewed the offside situations from an angle between 46 and 60°. Incorrect offside decisions occurred twice as often in the second as in the first half of the games. Perceptual-cognitive training sessions specific to the requirements of the game should be implemented in the weekly schedule of football officials to reduce the overall error rate.

Injury incidence in a spanish sub-elite professional football team: a prospective study during four consecutive seasons.

The aim of this study was to investigate the injury incidence and injury characteristics of a Spanish sub-elite professional football team during four consecutive seasons. A team was followed prospectively from the season 2003-2004 to 2006-2007 and individual player exposure and time loss injuries were recorded during all club training sessions and matches. A total of 313 time-loss injuries were recorded. The mean injury incidence was 10.9 injuries/1000 hours (5.2 injuries/1000 training hours and 44.1 injuries/1000 match hours). The injury incidence during competitive matches was higher (p < 0.001) than in friendly matches (55.8 vs. 22.6 injuries/1000 hours). The incidence of major injuries (>28 days absence) was 0.4 injuries/1000 hours. The thigh was the most commonly (35%) injured region and caused 29% of all competitive match absence. Muscle injuries in the four main groups of the lower limbs (hamstrings, adductors, quadriceps and calf muscles) caused 43% of competitive match unavailability. The results of this study show that the risk to sustain a major injury in the course of the season was low for sub- elite footballers in comparison to elite players. Thigh strains were the first cause of absence in competition due to injury. Key pointsThe incidence of major injuries (absence greater than 4 weeks) was lower in a Spanish sub-elite football team than in elite European teams.The risk of sustaining an injury was 2.5 fold higher (p < 0.001) in official than in friendly matches.Lower limb muscular (hamstrings, quadriceps, hip adductors and calf muscles) and joint (knee and ankle) injuries were the main causes of match unavailability.

The application of biomechanics to penalty corner drag-flick training: a case study.

The penalty corner is one of the most important game situations in field hockey with one third of all goals resulting from this tactical situation. The aim of this study was to develop and apply a training method, based on previous studies, to improve the drag- flick skill on a young top-class field hockey player. A young top-class player exercised three times per week using specific drills over a four week period. A VICON optoelectronic system (Oxford Metrics, Oxford, UK) was employed to capture twenty drag-flicks, with six cameras sampling at 250 Hz, prior and after the training period. In order to analyze pre- and post-test differences a dependent t-test was carried out. Angular velocities and the kinematic sequence were similar to previous studies. The player improved (albeit not significantly) the angular velocity of the stick. The player increased front foot to the ball at T1 (p < 0.01) and the drag-flick distances. The range of motion from the front leg decreased from T1 to T6 after the training period (p < 0.01). The specific training sessions conducted with the player improved some features of this particular skill. This article shows how technical knowledge can help with the design of training programs and whether some drills are more effective than others. Key pointsThis article adds information about the drag-flick kinematics.This article adds information about how to train the drag-flick.The drag-flick is the most efficient technique shooting for goal after a penalty corner.

Biomechanical analysis of the penalty-corner drag-flick of elite male and female hockey players.

The aim of this study was to analyse the kinematic sequencing in the penalty-corner drag-flicks of elite male and female field hockey players of international calibre. Thirteen participants (one skilled male drag-flicker and six male and six female elite players) participated in the study. An optoelectronic motion analysis system was used to capture the drag-flicks with six cameras, sampling at 250 Hz. Select ground reaction force parameters were obtained from a force platform which registered the last support of the front foot. Twenty trials were captured from each subject. Both player groups showed significantly (p < 0.05) smaller ball velocity at release, peak angular velocity of the pelvis, and negative and positive peak angular velocities of the stick than the skilled subject. Normalised ground reaction forces of the gender groups were also smaller than that of the skilled drag-flicker. By comparing these players we established that the cues of the skill level are a wide stance, a whipping action (rapid back lift) of the stick followed by an explosive sequential movement of the pelvis, upper trunk and stick.

Rendimiento físico del arbitraje de fútbol en función del nivel de la competición / Physical match perfomance of soccer referees ans assistant in relation to the level of competition

El objetivo de este trabajo fue examinar el rendimiento físico de árbitros y árbitros asistentes de élite en dos niveles distintos de competición en el fútbol: partidos de juveniles (Mundial sub-17 2003) y de categoría sénior (Copa de las Confederaciones 2005). El análisis de la participación cinemática de los jueces en 21 partidos oficiales se llevó acabo empleando un sistema de análisis biomecánico en dos dimensiones. La respuesta de la frecuencia cardíaca (FC) se registró mediante el uso de pulsómetros tanto en árbitros (n = 22) como en árbitros asistentes (n = 42). La distancia recorrida durante los partidos fue mayor en el Mundial sub-17 tanto para los árbitros (p < 0,05) como para los árbitros asistentes (p < 0,01), principalmente por el mayor volumen de acciones realizadas a una baja y a una media intensidad. Por el contrario, ambos grupos de jueces emplearon más tiempo (p < 0,001) realizando esfuerzos a la máxima intensidad (>18 km/h) al arbitrar en los partidos con futbolistas de categoría sénior. La FC med de los árbitros durante los partidos, expresada en función de la FC máx individual, fue superior en la Copa de las Confederaciones, debido al incremento del volumen de tiempo empleado entre el 86 y el 95% de la FC máx. Los resultados de este estudio demuestran cómo las exigencias físicas que deben soportar los árbitros y árbitros asistentes aumentan conformelo hace el nivel de los futbolistas que intervienen en los partidos. En concreto, la cantidad de ejercicio realizado a la máxima intensidad parece ser la variable de rendimiento físico que mejor discrimina el nivel de la competición (AU)

The aim of this study was to examine the physical match performance of top-class football referees and assistant referees at two different competitive standards: youth(2003 U-17 World Cup) and senior (2005 Confederations Cup) level. Match analyses were carried out in 21 games by means of a bidimensional photogrammetric system. The heart rate was measured with the use heart rate monitors in referees (n = 22) and assistant referees (n = 42). Total distance covered by the officials was higher in the U-17 World Cup both for the referees (p < 0.05) and the assistant referees (p < 0.01) principally due to the superior amount of low- and medium- intensity activities performed. On the other hand, both groups of officials performed more (p < 0.001) maximal-intensity activities, that is, sprinting (>18 km/h) during the senior matches. The mean match heart rate of the referees, expressed as a percentaje of the individual HR max was higher in the Confederations Cup, as referees spent more time execising at intensities between 86-95% HR max. The results of this study show that the physical requirements of officiating are competitive-level dependent. The amount of maximal-intensity activities seem to be the best physical performance variable to discriminate between different standards of match play (AU)

Activity profile of top-class association football referees in relation to fitness-test performance and match standard.

The aim of this study was to examine the kinematic activity profiles, cardiovascular responses and physical fitness of top-class football referees (n=11) during the FIFA Confederations Cup 2005. Computerised match-analyses (n=9) were performed with a two-dimensional photogrammetric video system, and the cardiovascular demand imposed on the referees (n=12) was measured using heart rate recordings. Total distance covered was 10,218, s=643 m of which 3531, s=510 m was covered at high intensities (>3.6 m.s(-1)). Both total distance covered (r2=0.59; P=0.02) and high-intensity activities (r2=0.44; P=0.05) were related to the distance covered by the ball in the same match. The referees ran at high speed 37% further (P=0.01) in the actual tournament than during under-17 top-level officiating. After the 5-min interval during which high-speed running peaked, in the following 5 min the performance was reduced by 19% (P=0.01) in relation to the mean of the game. Mean heart rate was 161, s=9 b.min(-1) (86, s=3% of maximal heart rate (HRmax)). Mean heart rate (expressed as percentage of HRmax) was related in part (r2=0.36; P<0.01) to the number of high-intensity activities performed in the same 5-min interval. The results of this study show that: (1) kinematic activity profiles of top-class referees can be influenced by the distance covered by the ball; (2) the amount of high-speed running (>5 m.s(-1)) best describes the physical performance of referees; (3) heart rate recording can be a useful tool to determine the most intense periods of a match and (4) the new fitness tests adopted by FIFA were poor predictors of match activities.

Analysis of the kinematical demands imposed on top-class assistant referees during competitive soccer matches.

The aim of this study was to describe the kinematical demands placed on soccer assistant referees during the 2003 U-17 World Championship, and to examine the relationship between the results in the fitness tests adopted by FIFA and match activities. Twenty-two international-level assistant referees were observed during 12 matches and computerized analysis of match activities was performed using a two-dimensional photogrammetric video analysis system based on DLT (direct lineal transformation) algorithms. Before the start of the tournament, the assistant referees completed a 2 x 50-m sprint test and a 12-minute run test. Assistant referees covered on average 6137 +/- 539 m during the matches, with 20% of the total distance covered at high velocities (speeds faster than 13 km x h(-1)). During the second half, time spent standing still increased (P < 0.01) and distance covered jogging (P < 0.05), cruising (P < 0.01) and moving sideways (P < 0.001) decreased. The score in the 12-minute run test showed a low correlation with the entire match distance (r = 0.24; P > 0.05) and with the time spent exercising at a high intensity (r = 0.35; P > 0.05). The 50-m sprint time was not significantly correlated (r = -0.38; P > 0.05) with time spent within the high-intensity activities category. The results of this study demonstrate that assistant referees experience unique kinematical demands during soccer officiating and that the score in the battery of fitness tests adopted by FIFA was not correlated to match activities.

Activity profile of top-class association football referees in relation to performance in selected physical tests.

The aims of the present study were (1) to analyse the physical demands of top-class referees and (2) to compare their official FIFA fitness test results with physical performance during a match. The work rate profiles of 11 international referees were assessed during 12 competitive matches at the 2003 FIFA Under-17 World Cup and then analysed using a bi-dimensional photogrammetric video analysis system based on direct lineal transformation (DLT) algorithms. In the first 15 min of matches, the referees were more active, performing more high-intensity exercise (P < 0.01) than in the first 15 min of the second half. During the second half of matches, the referees covered a shorter distance (P < 0.01), spent more time standing still (P < 0.05), and covered less ground cruising (P < 0.05), sprinting (P < 0.05), and moving backwards (P < 0.001) than in the first half. Also in the second 45 min, the distance of referees from infringements increased (P < 0.05) in the left attacking zone of the filed. There was also a decrease (P < 0.05) in performance in the period following the most high-intensity activity, compared with the mean for the 90 min. Time spent performing high-intensity activities during a match was not related to performance in the 12-min run (r(2) = 0.30; P < 0.05), the 200-m sprint (r(2) = 0.05; P < 0.05), or the 50-m sprint (r(2) = 0.001; P < 0.05). The results of this study show that: (1) top-class referees experienced fatigue at different stages of the match, and (2) the typical field tests used by FIFA (two 50-m and 200-m sprints, followed by a 12-min run) are not correlated with match activities.

Evaluación del rendimiento físico de los árbitros y árbitros asistentes durante la competición en el fútbol / Evaluation of the physical match performance of association football referees and assistant referees

El objetivo de este estudio fue evaluar el esfuerzo físico realizado por los árbitros y árbitros asistentes de fútbol durante partidos de competición oficial. Para analizar la participación cinemática en el juego (distancia recorrida, velocidad de los desplazamientos, etc.) se filmaron 12 partidos del Campeonato del Mundo sub-17 del año 2003 y se analizaron con un sistema fotogramétrico bidimensional. Para determinar la carga fisiológica se monitorizó la respuesta de la frecuencia cardiaca mediante el empleo de pulsómetros en árbitros (n=10) y árbitros asistentes (n=20) y se expresó en relación a la frecuencia cardiaca máxima (FCmáx) individual. Los árbitros recorrieron una distancia superior (p<0.001) a la de los árbitros asistentes durante los partidos: 11,1 vs 6,1 km. El patrón de esfuerzos también fue distinto entre ambos grupos de jueces ya que los árbitros invirtieron más tiempo (p<0.001) andando, trotando, corriendo y esprintando mientras que los árbitros asistentes permanecieron más tiempo (p<0.001) parados durante los partidos. Los valores relativos de frecuencia cardiaca media también fueron más altos (p<0.001) en los árbitros (83 vs 77% de la FC máx) debido principalmente al ejercitarse durante un período temporal superior (p<0.01) con intensidades que superaban el 85% de la FC máx mientras que fueron los árbitros asistentes los que emplearon más tiempo (p<0.01) en esfuerzos entre el 66 y75% de la FC máx. Los resultados de este estudio sugieren que los árbitros y árbitros asistentes deben ser considerados como dos poblaciones independientes de deportistas y sus programas de entrenamiento deberían prescribirse específicamente según las demandas experimentadas durante el juego (AU)

The aim of this study was to compare the physical demands placed on association football referees and assistant referees during competitive matches. To examine the kinematical demands, 12 matches from the 2003 FIFA U-17 World Championship were filmed and analysed with a bi-dimensional photogrammetric video-system. To determine the physiological workload, the heart rate of referees (n=10) and assistant referees (n=20) was monitored using heart rate monitors and expressed as a percentage of the maximal heart rate (HRmax). The physical and physiological load imposed on referees when officiating exceeded the requirements of assistant refereeing. The referees covered more distance(p<0.001) than the assistant referees during the matches: 11.1 vs 6.1 km and showed a different work-rate profile as they spent more time (p<0.001) walking, jogging, cruising and sprinting whereas assistant referees spent more time(p<0.001) standing still. The relative mean heart rate values were also superior (p<0.001) in referees (83 vs 77% HRmax) principally because they appeared to spend more time (p<0.01) at intensities exceeding 85% HRmax, while assistant referees performed mostly (p<0.01) between 66 and 75% HRmax. The results of this study suggest that referees and assistant referees should be considered as independent populations of sportsmen and their training regimens should be specifically prescribed according to the physical demands experienced during match-play (AU)