Well-being fluctuations and injuries during an entire season in male professional soccer players: an observational study.

This study aimed to describe and relate the well-being perception and injury incidence of soccer players in an entire soccer season. For 37 weeks, twenty-eight male professional soccer players (25.2 ± 4.3 years old; 22.8 ± 1.4 kg/m2) daily scored (from 1: bad; to 5: perfect) well-being perception (fatigue, sleep, muscle soreness, stress and mood and Hooper Index (HI) as general status). Injuries were also registered. Results showed that players had the lowest well-being perception during Preseason (in terms of HI, fatigue, muscle soreness and stress), being lower than EarlySeason (ps < 0.05, ds > 1.0) and/or InSeason (ps < 0.05, ds > 1.0). The injury incidence was 8.3 ± 9.2/1000 h, being always higher in training compared to competition (35.0 vs 11.1/1000 h). A lower stress perception (worse) correlated with a higher rate of new injuries during PreSeason (r = -0.84), while a greater muscle soreness and fatigue correlated with the new injuries occurring in the following week during the whole season (r = -0.38 and r = -0.39, respectively). As a conclusion, the well-being perception of professional soccer players was especially low during Preseason, with fatigue, muscle soreness and stress as the most affected items that correlated with injury incidence.

Influence of leg axis alignment on MRI T2* mapping of the knee in young professional soccer players.

BACKGROUND: Investigation of the association between leg axis alignment and biochemical MRI in young professional soccer players in order to identify a potential influence of the leg axis on cartilage regions at risk. METHODS: Sixteen professional soccer players (21 ± 3 years) underwent static and dynamic leg axis analysis via radiation free DIERS formetric 4 D as well as 3-T MRI examination of both knees. Quantitative T2* mapping of the knee cartilage was performed and T2* values were evaluated as 144 regions of interest. Subgroup analysis was performed in players with severe varus alignment (> 6°). RESULTS: Analysis of the leg axis geometry revealed a mean static alignment of 6.6° ± 2.5 varus and a mean dynamic alignment of 5.1° ± 2.6 varus. Quantitative T2* mapping showed significantly increased T2* values in the superficial cartilage layer compared to the deeper region (p < 0.001) as well as a significant increase in relaxation times in the femoral cartilage from anterior to intermediate to posterior (p < 0.001). Combination of both methods revealed a significant correlation for the degree of varus alignment and the femoral, posterior, deep region of the medial knee compartment (r = 0.4; p = 0.03). If severe varus alignment was present this region showed a significant increase in relaxation time compared to players with a less pronounced leg axis deviation (p = 0.003). CONCLUSION: This study demonstrates that varus alignment in young soccer players is associated with elevated T2* relaxation times in the deep cartilage layer of the medial, posterior, femoral compartment and might therefore be a contributing factor in the early pathogenesis of manifest cartilage lesions. Therefore, these findings should be considered in the development of preventive training programs.

Using video docuseries to explore male professional football head coaches' well-being experiences throughout a season.

Football coaches have disclosed how their work environment is unpredictable and demanding, comprising a multitude of stressors which can impede well-being. Additionally, the masculine culture within football often promotes suppression of voice, causing internalisation of thoughts and isolation. Due to professional football head coaches being a seldom-heard group, little is known about how they experience well-being within their given context (i.e., ecological niche). The present study utilised football docuseries and a bioecological framework to explore how four male professional head coaches experienced well-being whilst working in one of the top European football leagues (Premier League, La Liga). Four docuseries were sampled and resulted in the analysis of 31 episodes (Mduration = 46.6 min, SD = 4.5 min). The study implemented an adapted interpretative phenomenological analysis approach to illuminate convergences and divergences in contextual accounts. These accounts resulted in five group experiential themes: 'I belong to the game'; 'he belongs to the game'; 'you need the right people around you'; 'it's difficult to describe the manager without describing the person'; and 'people are trying to stab you'. The findings indicate that football coaches may experience identity conflicts and become deeply absorbed in their work. This impacts not only their well-being but also their family's, who they often turn to for social support. Consequently, by unveiling nuanced challenges to coaches' well-being, organisations may be better informed to offer more aligned and bespoke well-being support systems.

Exposure assessment for repeated sub-concussive head impacts in soccer: The HEalth and Ageing Data IN the Game of football (HEADING) study.

The purpose of this paper was to develop exposure estimates for repetitive sub-concussive head impacts (RSHI) for use in epidemiological analyses. We used a questionnaire to collect lifetime history of heading and other head contacts associated with training and playing football from 159 former footballers all members of the English professional football association. We used linear mixed effect regression with player as the random effect, to model the number of headers, blows to the head and head-to-head impacts as a function of potential exposure affecting factors, which were treated as the fixed effects. Exposure affecting factors included playing position, league, context of play (game vs training) and decade of play. Age at time of response to the questionnaire was also included in the models. In model results, playing position was important, with RSHIs being highest among defenders and lowest among goalkeepers. Players headed the ball more during games than in training, and when playing in amateur or youth leagues compared with semi-professional or professional leagues. The average number of reported head impacts declined linearly throughout the observation period (1949-2015). The derived final model for headers explained 43%, 9% and 36% of the between player, within player and total variance in exposure, respectively with good precision and predictive performance. These findings are generally in agreement with previously published results pointing towards the models forming a valid method for estimating exposure to RSHI among former footballers although some further external validation is still warranted.

Effects of eccentric-emphasized leg curl intervention on muscle strength imbalance markers in professional soccer players during pre-season.

BACKGROUND: The effects of strength training on muscle strength imbalance are unclear in professional soccer players. As a result, this study examined the effects of an 8-week strength training program comprising eccentric-emphasized prone leg curl adjusted according to the individual strength imbalance status. METHODS: Ten professional soccer players (26.0 ± 3.6 yrs) participated in the study. Players who had a ≥ 10% contralateral imbalance in knee flexors eccentric peak torque (n = 6) performed two additional repetitions per set in the low-strength limb (high-volume, HV) compared to the high-strength limb (low-volume, LV). Isokinetic concentric knee extension and concentric and eccentric knee flexion peak torque (PT) and derived contralateral imbalances and conventional and functional hamstring-to-quadriceps ratios (H:Q) were assessed at baseline and after 8 weeks. Differences at baseline were assessed using paired-sample T-tests, and a two-way (limb x time) repeated measures analysis of covariance (ANCOVA) for changes over time. RESULTS: A significant improvement in the eccentric knee flexion PT was observed in both limbs after 8 weeks (P < 0.05), with greater effects observed in the HV limb (25.0 N m, 95% CI: 15.1-34.9 N m). Significant decreases were also observed in the contralateral imbalances from concentric knee extension and flexion and eccentric knee flexion PT (P < 0.05). Differences were not observed in concentric knee extension and flexion PT (P > 0.05). CONCLUSIONS: A short-term eccentric-emphasized leg curl intervention adjusted by the initial knee flexors eccentric strength was an efficient method to improve knee flexors strength imbalance in professional soccer players.

The impact of COVID-19 lockdown on soccer positional and physical demands in the Spanish La Liga.

The present study aimed to analyse the playing surface area, dispersion and distance covered of professional football teams comparing the pre-lockdown and post-lockdown periods. Positional and match physical demands data were collected from all matches played in the First Spanish Division (n = 760) during season 2019/2020. Pre-lockdown (1st-27th matchday) and post-lockdown periods (28th-38th matchday) were compared. Variables related to team-level spatial (i.e., convex hull, team width and team length) and physical performance (i.e., total distance and high-speed running distance) were analysed using an optical tracking system (i.e., ChyronHego). In addition, these variables were concerned with respect to the match location contextual variable. Linear mixed models were used to examine the difference between the pre-lockdown and post-lockdown periods following a hierarchical structure considering players, matches and teams. The results revealed that the pandemic lockdown affected the teams' performance when comparing the periods before and after lockdown, showing a general decrease in the average values of the spatial and physical variables measured. The current data could assist practitioners in making informed decisions in order to design and improve training plans for similar situations in which teams return to competition after an unusual period with no training.

How Does Ball Possession Affect the Physical Demands in Spanish LaLiga? A Multilevel Approach.

Purpose: Using a multilevel approach, this study analyzed the relationship between ball possession and distance covered at different speed sections: total distance (TD), distance covered between 14.1-21 km·h-1 (MIRD), 21.1-24 km·h-1 (HIRD), and > 24.1 km·h-1 (VHIRD). Methods: The sample included 1,520 matches played by 80 Spanish professional soccer teams across four consecutive LaLiga seasons (from 2015/2016 to 2018/2019). Two observations were collected per match, one from each team, resulting in a total of 2,950 records (760 per season). Data were collected using Mediacoach®. Results: At match level (i.e., grand-mean centered), ball possession negatively predicted all distances covered. At team level (i.e., group-mean centered), ball possession negatively predicted total distance covered and distance covered between 14.1-21 km·h-1. Furthermore, cross-level interactions (Match X Team) in ball possession negatively predicted all distances covered at speeds above 14.1 km·h-1. Specifically, in high-possession teams, the negative relationship between match ball possession and distances traveled at all speed ranges above 14.1 km·h-1 was stronger than in teams with medium or low possession. Conversely, match ball possession was positively related todistance covered at low intensities, and negatively related at high intensities in low-possession teams. Conclusion: These findings show practitioners and researchers that the distances covered at different speed ranges depend on technical-tactical parameters such as ball possession.

Monitoring Internal Training Intensity Correlated with Neuromuscular and Well-Being Status in Croatian Professional Soccer Players during Five Weeks of the Pre-Season Training Phase.

This study aimed to investigate the changes in internal training intensity, well-being, and countermovement jump (CMJ) performance and to determine their relationship across five weeks of the pre-season training phase in professional soccer players. A total of 22 professional male soccer players (age = 21.7 ± 4 years, body height = 185.9 ± 6.3 cm, body weight = 79 ± 6.3 kg, BMI = 22.8 ± 1.4 kg·m−2; VO2max = 52.9 ± 3.2) from the Croatian Second League voluntary participated in this study. The players spent 2230 ± 117 min in 32 technical/tactical and strength/conditioning training sessions, mostly at the low intensity zone (61%), and played 8 friendly matches at a high intensity (>90%). A one-way repeated measure of analysis ANOVA revealed a significant difference between weeks in CMJ performance (F(1,22) = 11.8, p < 0.001), with CMJ height in weeks 4 and 5 being likely to very likely higher than that noted in week 1. Moreover, significant differences between weeks were found in all internal training intensity measures (average [F(1,22) = 74.8, p < 0.001] and accumulated weekly internal training intensity [F(1,22) = 55.4, p < 0.001], training monotony [F(1,22) = 23.9, p < 0.001], and training strain [F(1,22) = 34.5, p < 0.001]). Likewise, differences were observed for wellness status categories (fatigue [F(1,22) = 4.3, p = 0.003], sleep [F(1,22) = 7.1, p < 0.001], DOMS [F(1,22) = 5.7, p < 0.001], stress [F(1,22) = 15.6, p < 0.001]), mood [F(1,22) = 12.7, p < 0.001], and overall well-being status score (F(1,22) = 13.2, p < 0.001). Correlation analysis showed large negative correlations between average weekly internal training intensity and fatigue (r = −0.63, p = 0.002), DOMS (r = −0.61, p = 0.003), and WBI (r = −0.53, p = 0.011). Additionally, fatigue was significantly associated (large negative correlation) with accumulated weekly internal training intensity (r = −0.51, p = 0.014) and training strain (r = −0.61, p = 0.003). Small, but non-significant, correlations were found between CMJ performance and wellness status measures. These findings highlight the utility and simplicity of monitoring tools to improve athletes' performance.

COVID-19 in European Soccer: A Public 2-Year Comparison of COVID-19 Case Management and Case Characteristics between the 1st Bundesliga, La Liga, Serie A and the Premier League.

To evaluate the extent and characteristics of COVID-19 cases in relation to environmental COVID-19 incidences in the four best European soccer leagues (Bundesliga, Premier League, Serie A and La Liga) from the first of January 2020 until the end of January 2022. Methods: A retrospective evaluation of all publicly available COVID-19 cases in the studied cohorts was performed. The 14-day case incidences from epidemiological national data were used as reference values. The leagues studied are the Bundesliga (Germany), Premier League (Great Britain), Serie A (Italy) and La Liga (Spain). For all cases, the duration of time loss and date of case notification were recorded. Results: League-specific mean time loss due to disease or quarantine per COVID-19 case differs significantly between La Liga (11.45; ±5.21 days) and the other leagues studied (Bundesliga 20.41; ±33.87; p 0.0242; Premier League 17.12; ±10.39; p 0.0001; Serie A 17.61; ±12.71; p < 0.0001). A positive correlation between 14-day national incidence with COVID-19 disease occurrence in soccer leagues was found for all leagues studied. The correlations were strong in the Bundesliga (r 0.5911; CI 0.4249−0.7187; p < 0.0001), Serie A (r 0.5979; CI 0.4336−0.7238; p < 0.0001) and La Liga (r 0.5251; CI 0.3432−0.6690; p < 0.0001). A moderate correlation was found for the Premier League (r 0.3308; CI 0.1147−0.5169; p 0.0026). Odds ratios for altered environmental case risk in the cohorts studied could be calculated for four different national COVID-19 incidence levels (<50/100.000 to >500/100.000). A trend towards shorter COVID-19 case duration in the second half of 2021 was shown for all leagues studied. Conclusions: There was a significantly lower mean time-loss caused by a COVID-19 infection for cases occurred in La Liga compared with the other three leagues studied. For all four leagues studied, a positive, significant correlation of national environmental COVID-19 incidence level and the incidence of COVID-19 cases in the cohort of a football league was found.

Análisis biomecánico comparativo de recepción a media altura entre jugadores profesionales y amateurs de fútbol / Análise biomecânica comparativa da captura em meia altura entre jogadores profissionais e amadores de futebol / Comparative biomechanical analysis of mid-height reception between professional and amateur soccer players

RESUMEN El fútbol es un deporte de varias acciones motrices, donde la recepción del balón se clasifica como una acción de control a diferentes alturas, velocidades y ángulos. El jugador debe tener la capacidad de receptar el balón para poder generar una acción diferente: un pase, tiro o driblar; su optimización implica mayores probabilidades de rendimiento técnico-táctico. En tal sentido, se planteó como objetivo de la investigación analizar biomecánicamente la técnica de la recepción a media altura en futbolistas profesionales y amateurs a partir de video análisis como método de medición. La investigación fue descriptiva-explicativa de orden correlacional, se analizan cuatro variables del movimiento motriz (D: distancia Recorrida; AM: aceleración máxima; VM: velocidad máxima y AF: amplitud de la articulación femorotibial) a través de video-análisis con Kinovea. Se estudiaron a cinco jugadores profesionales (grupo 1) y 15 de nivel amateur (grupo 2). Los futbolistas de nivel amateur presentaron una mayor media en todas las variables estudiadas, "D" (grupo 1: 72.17cm; grupo 2: 101.27cm; p=0.001), "AM" (grupo 1: 61.84m/s2; grupo 2: 101.73m/s2; p=0.000), "VM" (grupo 1: 8.18m/s; grupo 2: 12.55m/s; p=0.000) y "AF" (grupo 1: 62.6°; grupo 2: 75.2°; p=0.002), lo cual se comporta significativamente diferentes en todos los casos. El análisis biomecánico realizado a futbolistas profesionales y amateurs, en la técnica de recepción del balón a media altura, concluye que en los jugadores amateur requieren un mayor perfeccionamiento técnico, independientemente de su experiencia en competencias.

RESUMO O futebol é um esporte de várias ações motoras, onde a recepção da bola é classificada como uma ação de controle em diferentes alturas, velocidades e ângulos. O jogador deve ter a capacidade de receber a bola para poder gerar uma ação diferente: um passe, um chute ou um drible; sua otimização implica em maiores probabilidades de desempenho técnico-tático. Neste sentido, o objetivo da pesquisa era analisar biomecanicamente a técnica de recepção em meia altura em jogadores profissionais e amadores de futebol utilizando a análise de vídeo como método de medição. A pesquisa foi descritiva-explicativa de ordem correlacional, quatro variáveis de movimento motor (D: distância coberta; MA: aceleração máxima; MV: velocidade máxima e FA: amplitude da articulação femorotibial) foram analisadas através de vídeo-análise com Kinovea. Foram estudados cinco jogadores profissionais (grupo 1) e 15 jogadores amadores (grupo 2). Os jogadores de futebol de nível amador apresentaram uma média maior em todas as variáveis estudadas, "D" (grupo 1: 72,17cm; grupo 2: 101,27cm; p=0,001), "AM" (grupo 1: 61,84m/s2; grupo 2: 101. 73m/s2; p=0,000), "VM" (grupo 1: 8,18m/s2; grupo 2: 12,55m/s; p=0,000) e "AF" (grupo 1: 62,6°; grupo 2: 75,2°; p=0,002), que se comportam de forma significativamente diferente em todos os casos. A análise biomecânica realizada sobre jogadores profissionais e amadores de futebol, na técnica de recepção de bola em altura média, conclui que os jogadores amadores requerem um maior aperfeiçoamento técnico, independentemente de sua experiência em competições.

ABSTRACT Soccer is a sport of various motor actions, where the reception of the ball is classified as a control action at different heights, speeds and angles. The player must have the ability to receive the ball in order to generate a different action: a pass, shot or dribble; its optimization implies greater probabilities of technical-tactical performance. In this sense, the objective of the research was to biomechanically analyze the mid-height reception technique in professional and amateur soccer players using video analysis as a measurement method. The research was descriptive-explanatory of correlational order, four variables of the motor movement (D: distance covered; AM: maximum acceleration; VM: maximum speed and AF: amplitude of the femorotibial joint) are analyzed through video-analysis with Kinovea . Five professional players (group 1) and 15 amateur players (group 2) were studied. The amateur soccer players presented a higher mean in all the variables studied, "D" (group 1: 72.17cm; group 2: 101.27cm; p=0.001), "AM" (group 1: 61.84m/s 2 ; group 2: 101.73m/s 2 ; p=0.000), "VM" (group 1: 8.18m/s; group 2: 12.55m/s; p=0.000) and "AF" (group 1: 62.6°; group 2 : 75.2°; p=0.002), which behaves significantly different in all cases. The biomechanical analysis carried out on professional and amateur soccer players, in the technique of receiving the ball at mid-height, concludes that amateur players require greater technical improvement, regardless of their experience in competitions.

Effects of COVID-19 Lockdown on Physical Performance, Sleep Quality, and Health-Related Quality of Life in Professional Youth Soccer Players.

Background: In March 2020, the COVID-19 outbreak led to the declaration of a pandemic. The accompanying restrictions on public life caused a change in the training routines of athletes worldwide. The present study aimed to investigate the effects of a 13-week supervised home training program on physical performance, sleep quality, and health-related quality of life in professional youth soccer players during the first COVID-19 lockdown in Germany. Methods: Eight professional soccer players (age range 16-19; height: 1.81 ± 0.07 m; body weight: 72.05 ± 6.96 kg) from a Bundesliga team in Germany participated in this study. During the lockdown, they trained 5-6 days per week with home-based training plans and were monitored via tracking apps and video training. To determine the effects of home training, measurements were taken before (March 2020) and after (June 2020) the home training period. Bioelectrical impedance analysis was used to determine body composition, and an isokinetic strength test and a treadmill step test, including lactate measurements, were used to measure physical performance. Two questionnaires were responded to in order to assess health-related quality of life [Short-Form 36 Health Survey (SF-36)] and sleep quality (Pittsburgh Sleep Quality Index). Results: When comparing measurements before and after the home training period, we observed significant increases in the following variables: body weight (72.05 ± 6.96 kg vs. 73.50 ± 6.68 kg, p = 0.034), fat mass (11.99 ± 3.13 % vs. 13.98 ± 3.92 %, p = 0.030), body mass index (22.04 ± 0.85 kg/m2 vs. 22.49 ± 0.92 kg/m2, p = 0.049), and mental health component summary score (MCS) of the questionnaire SF-36 (53.95 ± 3.47 vs. 58.33 ± 4.50, p = 0.044). Scores on the general health (77.88 ± 14.56 vs. 89.75 ± 13.76, p = 0.025) and mental health (81.50 ± 9.30 vs. 90.00 ± 11.71, p = 0.018) subscales of the SF-36 also increased significantly. Conclusion: The COVID-19 lockdown led to an increase in body composition parameters and showed an improvement in the MCS and scores on the general and mental health subscales of the SF-36. Physical performance and sleep quality could be maintained during the home training period. These observations may help trainers for future training planning during longer interruptions in soccer training.

The Effect of the Video Assistant Referee System Implementation on Match Physical Demands in the Spanish LaLiga.

The present study aimed to analyze the influence of the Video Assistant Referee (VAR) on match physical demands in the top Spanish professional football league. Match physical demand data from all the matches for two seasons (2017/2018 and 2018/2019) in the First Spanish Division (n = 1454) were recorded using an optical tracking system (ChyronHego®). Total distance, relative total distance covered per minute, distance covered between 14-21 km·h-1, distance covered between 21-24 km·h-1, and distance covered at more than 24 km·h-1 were analyzed; also, the number of sprints between 21-24 km·h-1 and more than 24 km·h-1 were taken into consideration. The times the VAR intervened in matches were also taken into account. Results showed that total distance and relative total distance significantly decreased in seasons with VAR compared to seasons without VAR. Finally, distance covered between 21-24 km·h-1, distance covered at more than 24 km·h-1, and the number of high-intensity efforts between 21-24 km·h-1 and more than 24 km·h-1 increased in seasons with VAR compared to seasons without VAR, but the differences were nonsignificant. Thus, these findings help practitioners to better understand the effects of the VAR system on professional football physical performance and to identify strategies to reproduce competition demands.

Quantifying technical actions in professional soccer using foot-mounted inertial measurement units.

OBJECTIVES: This study aimed to (i) establish the concurrent validity and intra-unit reliability of a foot-mounted inertial measurement unit for monitoring soccer technical actions, (ii) quantify the within-microcycle inter-positional differences in the technical actions of professional soccer training, and (iii) determine the influence of drill category on the technical actions of professional soccer training. METHODS: Twenty-one professional soccer players' technical performance data (ball touches, releases, ball touches per minute, releases per minute), collected during training sessions throughout twenty-four weekly microcycles, were analysed using general linear modelling. RESULTS: The inertial measurement unit exhibited good concurrent validity (PA = 95.1% - 100.0%) and intra-unit reliability (PA = 95.9% - 96.9%, CV = 1.4% - 2.9%) when compared with retrospective video analyses. The most ball touches (X‾ = 218.0) and releases (X‾ = 110.8) were observed on MD - 1, with MD - 5 eliciting the highest frequency of ball touches (X‾ = 3.8) and releases (X‾ = 1.7) per minute. Central midfielders performed the most ball touches (X‾ = 221.9), releases (X‾ = 108.3), ball touches per minute (X‾ = 3.4) and releases per minute (X‾ = 1.6). Small-sided games evoked more ball touches (X‾diff = 1.5) and releases per minute (X‾diff = 0.1) than previously reported in match-play. The fewest ball touches (X‾ = 1.2) and releases per minute (X‾ = 0.5) were observed during tactical drills. CONCLUSION: The results of this study provide a novel understanding of the within-microcycle, inter-positional and drill category differences in the technical actions performed by professional players during training.

Incidence of Injury for Professional Soccer Players in the United States: A 6-Year Prospective Study of Major League Soccer.

Background: Despite an abundance of injury research focusing on European professional soccer athletes, there are limited injury data on professional soccer players in the United States. Purpose: To describe the epidemiology of injury across multiple years in Major League Soccer (MLS) players. Study Design: Descriptive epidemiology study. Methods: A web-based health management platform was used to prospectively collect injury data from all MLS teams between 2014 and 2019. An injury was defined as an incident that required medical attention and was recorded into the health management platform anytime over the course of the 2014-2019 seasons. Injuries and exposure data were recorded in training and match settings to calculate injury incidence. Results: A total of 9713 injuries were recorded between 2014 and 2019. A mean 1.1 injuries per year per player were identified, with midfielders sustaining the largest number of injuries. The most common injuries were hamstring strains (12.3%), ankle sprains (8.5%), and adductor strains (7.6%). The mean time missed per injury was 15.8 days, with 44.2% of injuries resulting in no days missed. Overall injury incidence was 8.7 per 1000 hours of exposure, declining over the course of the investigation, with a 4.1-times greater mean incidence during matches (14.0/1000 h) than training (3.4/1000 h). Conclusion: Between 2014 and 2019, the most commonly reported injuries in MLS players were hamstring strains, ankle sprains, and adductor strains. Injury incidence during matches was 4.1 times greater when compared with training, while overall injury incidence was found to decline during the course of the study period.

Semi-quantitative magnetic resonance imaging scoring of the knee detects previous injuries in professional soccer players.

PURPOSE: The medical examination ("medical") is an important procedure in professional soccer since it has high economic relevance. In addition to clinical tests, magnetic resonance imaging (MRI) is used to assess joint health. In the present study, the reliability of semiquantitative knee MRI during the "medical" in professional soccer was tested, and its relationship with clinical data and days missed due to knee injury was observed. METHODS: In this cross-sectional study, between 2012 and 2019, 69 newly assigned players (age 18-35 years) from a professional soccer club underwent MRI (3.0 T) of both knee joints during their "medical". Reported knee injuries and previously missed days due to injury were obtained from player anamnesis and the "transfermarkt.com" database. Based on the established "Whole-Organ Magnetic Resonance Imaging Score" (WORMS), two independent radiologists graded the MRI results. Further evaluation was based on the mean score of both knees. RESULTS: The mean WORMS for all subjects was 13.9 (median 10.5, range 0-61). Players with previous injuries had significantly higher scores than players without reported injuries (22.1 ± 17.7 vs. 8.9 ± 4.4, p < 0.002). Three outliers (previously undetected injuries) in the group of players without reported injuries were observed (6.7%). The WORMS was significantly correlated with a prior knee injury (r: 0.424, p < 0.0001) and days missed due to injury (r: 0.489, p < 0.001). Age was correlated with the WORMS (r: 0.386, p < 0.001). In a linear regression model, prior injury was the only significant predictor of a high WORMS (p = 0.001). The WORMS was a significant predictor of days missed due to injury (p < 0.0002) and prior injury (sensitivity: 78%, specificity: 91%, p = 0.006). The intraclass correlation coefficient was excellent (0.89). CONCLUSION: Semiquantitative knee MRI for WORMS determination during the soccer "medical" is a robust and reliable method. Prior injury, even in players without documented trauma, was detected by the WORMS, and previously missed days due to injury were correlated with the semiquantitative MR knee score. LEVEL OF EVIDENCE: Level III.

In-season head-coach changes have positive short- and long-term effects on team perfor-mance in men's soccer-evidence from the Premier League, Bundesliga, and La Liga.

The study investigated effects of in-season head-coach changes (HCC) on the subsequent team performance in men's English, German, and Spanish premier soccer leagues. A pre-post matched-controls design involved 149 HCC-teams and 3,960 games in 2010-19. Analyses (paired t-test, repeated-measurement ANOVA) revealed five central findings. 1. An HCC was preceded by a spell of under-performance, with a particular performance collapse in the two last pre-HCC rounds. 2. Performance showed an instant, strong improvement in the first post-HCC game. 3. The performance remained increased up to 16 post-HCC rounds. 4. Post-HCC performance also exceeded teams' initial baseline performance earlier before the HCC. Accordingly, the summed performance through 8, 12, and 16 post-HCC rounds exceeded the performance through 8, 12, and 16 pre-HCC rounds (0.92 < Cohen's d < 1.17). 5. HCC-teams' pre-post performance development differed from matched non-HCC control teams. In sum, the present evidence suggests positive short, medium, and long-term HCC effects at the highest professional soccer level. Theoretical hypotheses discussed in the literature - the "common-sense," "ritual-scapegoating," "vicious-circle," and "mean-reversion" hypotheses - are partly inconsistent with the present evidence. However, the evidence is fully consistent with a new hypothesis introduced here: the hypothesis of relief from a coach's performance-suppressing factor (RCPSF).

Physical activity on mental wellbeing in senior English Premier League soccer players during the COVID-19 pandemic and the lockdown.

The COVID-19 pandemic and the subsequent lockdown created new stressors that could potentially attenuate mental wellbeing (MW) in athletes, who are already susceptible to poor MW. This study aims to describe fluctuations to MW during "lockdown" and subsequent "return to sport" protocols, in comparison to the normal "in-season" in professional soccer. Twenty-five English Premier League (EPL) soccer players completed the Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS) every two weeks, during the 2019/2020 season, and every week during "lockdown" and "return to training" for 28 weeks. The duration of each physical activity (PA) session completed was recorded. No significant differences were found for MW between time points (In-season, lockdown, return to training and the restart) (51.5 ± 5.6 vs. 50.7 ± 4.8 vs. 50.8 ± 5.7 vs. 50.7 ± 5.6 (p > 0.05)) respectively. Individually, differences were identified; in-season weekly session duration (243 ± 38 min) was higher than during lockdown (180 ± 62 min) (p < 0.05). During lockdown, weekly MW scores were related to the previous 7-day number of sessions (r = 0.151) and active min (r = 0.142) (p < 0.05). Furthermore, participants that exercised >250 min in lockdown, had higher MW scores (52.46 ± 4.65) than <250 min (50.35 ± 6.55) (p < 0.05). MW responses to lockdown were best understood on an individual basis. Additionally, PA only had a measurable effect on MW when >250 min. Further, stressors imposed upon players during an EPL season, are potentially greater than those inflicted by the lockdown. Implications for monitoring MW in EPL soccer players and the potential inclusion of an in-season break are discussed.Highlights Mental Wellbeing Responses, as measured by the Warwick-Edinburgh Mental Wellbeing scale did not change significantly at a group level across the four phases of the season. However, on an individual level changes were evident.There was a decline in the trend of wellbeing scores during in-season, return to training and the restart, but an increase in wellbeing scores during lockdown.Physical Activity had a measurable effect on wellbeing, when physical activity was >250 min during lockdown.These findings highlight the need for individual monitoring of wellbeing and longitudinal monitoring in sport to identify decline in wellbeing and implement intervention. In addition, the prescription of physical activity >250 min per week during lockdown in trained athletes may promote positive mental health.

The Influence of Time Winning and Time Losing on Position-Specific Match Physical Demands in the Top One Spanish Soccer League.

The aim of the present study was to analyze the influence of time winning and time losing on position-specific match physical demands with and without ball possession in the top Spanish professional soccer league. All matches played in the First Spanish soccer league over four consecutive seasons (from 2015/16 to 2018/19) were recorded using an optical tracking system (i.e., ChyronHego), and the data were analyzed via Mediacoach®. Total distance (TD), and TD > 21 km·h-1 covered with and without ball possession were analyzed using a Linear Mixed Model, taking into account the contextual variables time winning and losing. Results showed that TD and TD > 21 km·h-1 covered by central midfielders (0.01 and 0.005 m/min, respectively), wide midfielders (0.02 and 0.01 m/min, respectively), and forwards (0.03 and 0.02 m/min, respectively) significantly increased while winning (p < 0.05). By contrast, TD and TD > 21 km·h-1 covered by central defenders (0.01 and 0.008 m/min, respectively) and wide defenders (0.06 and 0.008 m/min, respectively) significantly increased while losing (p < 0.05). In addition, for each minute that teams were winning, total distance with ball possession (TDWP) decreased, while, for each minute that teams were losing, TDWP increased. Instead, TDWP > 21 km·h-1 obtained opposite results. Total distance without ball possession increased when teams were winning, and decreased when teams were losing. Therefore, the evolution of scoreline significantly influences tactical-technical and physical demands on soccer matches.

Sleep Quality in Chilean Professional Soccer Players.

Recent research has shown that good sleep quality has a positive effect on physical performance. However, sleep quality in Chilean professional soccer players is unknown. The purpose of this study was to determine sleep quality in Chilean professional soccer players. It was a cross-sectional, explanatory study with observable variables. The sample consisted of 94 Chilean male soccer players belonging to four professional clubs. The main variable was the Sleep Quality Index, evaluated through the Pittsburgh questionnaire (Spanish version). After estimating sleep quality individually, the four professional soccer clubs' comparison was performed through a one-factor ANOVA. The Pearson test was used to relate the questionnaire variables; the significance level was p < 0.05. In the global analysis of the Pittsburgh Sleep Quality Index, a value of 4.75 ± 2.29 on a scale of 0-21 was observed, with no significant differences between the clubs evaluated (p > 0.05). Based on the results obtained, Chilean male professional soccer players present good sleep quality. However, the high values of "sleep latency" and "sleep disturbances" are indicators that should be worked on by the multidisciplinary team of each professional club. They should develop strategies to improve sleep hygiene, encourage good sleep, and fall asleep efficiently.

Hamstring and Quadriceps Muscle Strength in Youth to Senior Elite Soccer: A Cross-Sectional Study Including 125 Players.

PURPOSE: Increasing age, high quadriceps strength, and low hamstring muscle strength are associated with hamstring strain injury in soccer. The authors investigated the age-related variation in maximal hamstring and quadriceps strength in male elite soccer players from under-13 (U-13) to the senior level. METHODS: A total of 125 elite soccer players were included from a Danish professional soccer club and associated youth academy (first tier; U-13, n = 19; U-14, n = 16; U-15, n = 19; U-17, n = 24; U-19, n = 17; and senior, n = 30). Maximal voluntary isometric force was assessed for the hamstrings at 15° knee joint angle and for the quadriceps at 60° knee joint angle (0° = full extension) using an external-fixated handheld dynamometer. Hamstring-to-quadriceps strength (H:Q) ratio and hamstring and quadriceps maximal voluntary isometric force levels were compared across age groups (U-13 to senior). RESULTS: Senior players showed 18% to 26% lower H:Q ratio compared with all younger age groups (P ≤ .026). Specific H:Q ratios (mean [95% confidence interval]) were as follows: senior, 0.45 (0.42-0.48); U-19, 0.61 (0.55-0.66); U-17, 0.56 (0.51-0.60); U-15, 0.59 (0.54-0.64); U-14, 0.54 (0.50-0.59); and U-13, 0.57 (0.51-0.62). Hamstring strength increased from U-13 to U-19 with a significant drop from U-19 to the senior level (P = .048), whereas quadriceps strength increased gradually from U-13 to senior level. CONCLUSION: Elite senior soccer players demonstrate lower H:Q ratio compared with youth players, which is driven by lower hamstring strength at the senior level compared with the U-19 level combined with a higher quadriceps strength. This discrepancy in hamstring and quadriceps strength capacity may place senior-level players at increased risk of hamstring muscle strain injuries.