Latest research in football - week 33 - 2022

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases. 


Following studies were retrieved for this week:

#1 Anterior-Posterior and Inter-Limb Lower Body Strength Asymmetry in Soccer, Basketball, Futsal, and Volleyball Players

Reference: Medicina (Kaunas). 2022 Aug 10;58(8):1080. doi: 10.3390/medicina58081080.

Authors: Koulla Parpa, Marcos Michaelides

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Summary: The purpose of this study was twofold: (1) to examine strength asymmetries in elite athletes of different sports and (2) to examine the magnitude of asymmetries between elite and u18 athletes. A total of 254 athletes participated in this study. For the first purpose of the study, the group consisted of adult professional male basketball players (n = 30), elite male (n = 30) and female soccer players (n = 20), male futsal players (n = 30), elite male goalkeepers (n = 22), and professional female volleyball players (n = 20). For the second purpose, male youth goalkeepers (n = 22), youth female (n = 20) and male soccer players (n = 30), and youth male basketball players (n = 30) were compared to the adult athletes of the same sport. Asymmetries were measured utilizing a Humac Norm and Rehabilitation device. Testing included three maximal concentric flexion and extension repetitions at an angular speed of 60°/s. The differences in asymmetries were assessed using ANOVA followed by an LS means post-hoc analysis. An independent samples t-test was used to identify the differences between adult and youth players. It was indicated that none of the groups demonstrated asymmetries greater than 10%, other than the elite female soccer players and female volleyball players. Significant differences were demonstrated between youth and adult soccer players (males and females), with the adult groups demonstrating increased asymmetries. Special consideration should be given to female soccer players and volleyball players, as soccer and volleyball practice and competition at the professional level may induce greater lower -limb asymmetries. The isokinetic parameters can be useful for planning strength and conditioning interventions in order to reduce or prevent those imbalances. Additional unilateral and bilateral jumping testing is encouraged for the verification of imbalances.



#2 Grizzlies and gazelles: Duty factor is an effective measure for categorizing running style in English Premier League soccer players

References: Front Sports Act Living. 2022 Aug 9;4:939676. doi: 10.3389/fspor.2022.939676. eCollection 2022.

Authors: Brian Hanley, Catherine B Tucker, Liam Gallagher, Parag Parelkar, Liam Thomas, Rubén Crespo, Rob J Price

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Summary: English Premier League soccer players run at multiple speeds throughout a game. The aim of this study was to assess how well the duty factor, a dimensionless ratio based on temporal variables, described running styles in professional soccer players. A total of 25 players ran on an instrumented treadmill at 12, 16, and 20 km/h. Spatiotemporal and ground reaction force data were recorded for 30 s at each speed; video data (500 Hz) were collected to determine footstrike patterns. In addition to correlation analysis amongst the 25 players, two groups (both N = 9) of high and low duty factors were compared. The duty factor was negatively correlated with peak vertical force, center of mass (CM) vertical displacement, and leg stiffness (k leg) at all speeds (r ≥ -0.51, p ≤ 0.009). The low duty factor group had shorter contact times, longer flight times, higher peak vertical forces, greater CM vertical displacement, and higher k leg (p < 0.01). Among the high DF group players, eight were rearfoot strikers at all speeds, compared with three in the low group. The duty factor is an effective measure for categorizing soccer players as being on a continuum from terrestrial (high duty factor) to aerial (low duty factor) running styles, which we metaphorically refer to as "grizzlies" and "gazelles," respectively. Because the duty factor distinguishes running style, there are implications for the training regimens of grizzlies and gazelles in soccer, and exercises to improve performance should be developed based on the biomechanical advantages of each spontaneous running style.



#3 Reliability and Validity of the 30-15 Intermittent Field Test With and Without a Soccer Ball

References: Res Q Exerc Sport. 2022 Aug 26;1-10. doi: 10.1080/02701367.2022.2098230. Online ahead of print.

Authors: Kathleen M Paulsen, Brendon P McDermott, Aaron J Myers, Michelle Gray, Wen-Juo Lo, Matthew S Ganio

Summary: The purpose of this study was to examine the reliability and validity of the 30-15 Intermittent Field Test (30-15IFT) with and without a ball. Twenty-four collegiate female soccer players (19.46 ± 1.22 years; 167.01 ± 7.23 cm; 60.95 ± 7.84 kg) performed 1 trial of the Yo-Yo Intermittent Recovery (YYIR) test, 3 trials of the 30-15IFT, and 3 trials of the 30-15IFT with a ball (30-15IFT-B), separated by a minimum 48 hours. Maximal intermittent running velocity (VIFT), heart rate at exhaustion (HRpeak), and rating of perceived exertion (RPE) were collected. Intraclass correlation coefficients (ICCs) between trials demonstrated good reliability during the 30-15IFT in VIFT (ICC = 0.88) and HRpeak (ICC = 0.89), in addition to the 30-15IFT-B VIFT (ICC = 0.83) and HRpeak (ICC = 0.87). VIFT was significantly reduced in 30-15IFT-B (15.82 km h-1) compared to 30-15IFT (17.52 km h-1; p < .001), regardless of trial. HR and RPE were significantly greater in 30-15IFT compared to 30-15IFT-B (p < .05). Estimated maximal oxygen consumption (VO2max) YYIR and estimated VO2max of 30-15IFT and 30-15IFT-B was very strongly (r = 0.82) and strongly (r = 0.68) correlated. The 30-15IFT is considered valid and reliable and the 30-15IFT-B was reliable in female soccer players.



#4 Foot dominance and ball approach angle affect whole-body instep kick kinematics in soccer players

Reference: Sports Biomech. 2022 Aug 22;1-21. doi: 10.1080/14763141.2022.2110514. Online ahead of print.

Authors: Filippo Bertozzi, Rodrigo Rabello, Matteo Zago, Fabio Esposito, Chiarella Sforza

Summary: Past investigations provided limited information regarding instep kicking kinematics in soccer. It is unclear how foot dominance and ball approach angle impact whole-body kinematics and consequently the ball velocity. We aimed to analyse the effects of the ball approach angle and the foot used on the whole-body kinematics of soccer players performing an instep kick. Twenty-four soccer players performed maximal instep kicks, using the dominant and non-dominant feet, with the ball stationary or rolling from four different directions. Whole-body motion was recorded during the kicking action and kinematic time-series were extracted and resampled to 200 points equally divided into kicking and follow-through phases. 1-D statistical parametric mapping two-way ANOVA tested for the effect of ball condition and foot dominance. Ball approach angle affected most of the swinging and support limb variables and some upper body variables. Performance-related variables such as CoM, foot, and shank velocities were reduced when the ball approached posteriorly. The linear and angular velocities of the swinging limb, and CoM vertical position, were higher when kicking with dominant foot. Based on these findings, as a practical implication, coaches should vary ball approach angles and the foot used during kicking drills to improve technical effectiveness in various situations.



#5 Workload is associated with the occurrence of non-contact injuries in professional male soccer players: A pilot study

Reference: Front Psychol. 2022 Aug 4;13:925722. doi: 10.3389/fpsyg.2022.925722. eCollection 2022.

Authors: Hadi Nobari, Sara Mahmoudzadeh Khalili, Angel Denche Zamorano, Thomas G Bowman, Urs Granacher

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Summary: Injuries in professional soccer are a significant concern for teams, and they are caused amongst others by high training load. This cohort study describes the relationship between workload parameters and the occurrence of non-contact injuries, during weeks with high and low workload in professional soccer players throughout the season. Twenty-one professional soccer players aged 28.3 ± 3.9 yrs. who competed in the Iranian Persian Gulf Pro League participated in this 48-week study. The external load was monitored using global positioning system (GPS, GPSPORTS Systems Pty Ltd) and the type of injury was documented daily by the team's medical staff. Odds ratio (OR) and relative risk (RR) were calculated for non-contact injuries for high- and low-load weeks according to acute (AW), chronic (CW), acute to chronic workload ratio (ACWR), and AW variation (Δ-Acute) values. By using Poisson distribution, the interval between previous and new injuries were estimated. Overall, 12 non-contact injuries occurred during high load and 9 during low load weeks. Based on the variables ACWR and Δ-AW, there was a significantly increased risk of sustaining non-contact injuries (p < 0.05) during high-load weeks for ACWR (OR: 4.67), and Δ-AW (OR: 4.07). Finally, the expected time between injuries was significantly shorter in high load weeks for ACWR [1.25 vs. 3.33, rate ratio time (RRT)] and Δ-AW (1.33 vs. 3.45, RRT) respectively, compared to low load weeks. The risk of sustaining injuries was significantly larger during high workload weeks for ACWR, and Δ-AW compared with low workload weeks. The observed high OR in high load weeks indicate that there is a significant relationship between workload and occurrence of non-contact injuries. The predicted time to new injuries is shorter in high load weeks compared to low load weeks. Therefore, the frequency of injuries is higher during high load weeks for ACWR and Δ-AW. ACWR and Δ-AW appear to be good indicators for estimating the injury risk, and the time interval between injuries.



#6 Increased Risk of ACL Injury for Female but Not Male Soccer Players on Artificial Turf Versus Natural Grass: A Systematic Review and Meta-Analysis

Reference: Orthop J Sports Med. 2022 Aug 12;10(8):23259671221114353. doi: 10.1177/23259671221114353. eCollection 2022 Aug.

Authors: Michelle Xiao, Jacie L Lemos, Calvin E Hwang, Seth L Sherman, Marc R Safran, Geoffrey D Abrams

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Summary: Both natural grass (NG) and artificial turf (AT) are popular playing surfaces for soccer. Biomechanical studies have found increased frictional forces on AT that may lead to anterior cruciate ligament (ACL) injury. The increased risk of ACL injury during soccer in female participants may amplify this effect. To systematically review the literature for studies comparing ACL injury risk in soccer players on AT versus NG and to specifically determine whether there were differences in injury risk in male versus female players when considering the playing surface. A systematic review was performed using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Three databases were searched for studies with evidence level 1 to 3 that compared the incidence of ACL injuries on AT versus NG in soccer players. Data recorded included study characteristics, sex, competition level, exposure setting (games or practices), turf type, and ACL injury information. Study methodological quality was analyzed using the methodological index for non-randomized studies (MINORS) score, and incidence rate ratios (IRRs) were calculated. Included were 7 articles (3 studying professional soccer, 3 collegiate soccer, 1 youth-level soccer; 4 male cohorts, 2 female cohorts, and 1 male and female cohort; mean MINORS score, 20 ± 0.8). Pooled ACL injury IRRs demonstrated no significant differences in overall ACL injury risk when playing soccer on AT compared with NG (IRR = 0.57 [95% CI, 0.21-1.53]; P = .31). A significantly increased risk of ACL injury in games played on AT compared with NG was detected for female (IRR = 1.18 [95% CI, 1.05-1.31]; P = .004) but not for male players (IRR = 1.18 [95% CI, 0.97-1.42]; P = .09). Subgroup analyses showed no significant differences in injury risk for games (IRR = 1.07 [95% CI, 0.97-1.18]; P = .20) or practices (IRR = 0.21 [95% CI, 0.04-1.23]; P = .09). Findings indicated that female soccer players had a significantly higher risk of ACL injury when playing games on AT versus NG, whereas no significant difference was seen in male players. No differences were found for the combined male/female cohort or for soccer games or training sessions played on AT compared with NG.



#7 Motion Analysis of Football Kick Based on an IMU Sensor

Reference: Sensors (Basel). 2022 Aug 19;22(16):6244. doi: 10.3390/s22166244.

Authors: Chun Yu, Ting-Yuan Huang, Hsi-Pin Ma

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Summary: A greater variety of technologies are being applied in sports and health with the advancement of technology, but most optoelectronic systems have strict environmental restrictions and are usually costly. To visualize and perform quantitative analysis on the football kick, we introduce a 3D motion analysis system based on a six-axis inertial measurement unit (IMU) to reconstruct the motion trajectory, in the meantime analyzing the velocity and the highest point of the foot during the backswing. We build a signal processing system in MATLAB and standardize the experimental process, allowing users to reconstruct the foot trajectory and obtain information about the motion within a short time. This paper presents a system that directly analyzes the instep kicking motion rather than recognizing different motions or obtaining biomechanical parameters. For the instep kicking motion of path length around 3.63 m, the root mean square error (RMSE) is about 0.07 m. The RMSE of the foot velocity is 0.034 m/s, which is around 0.45% of the maximum velocity. For the maximum velocity of the foot and the highest point of the backswing, the error is approximately 4% and 2.8%, respectively. With less complex hardware, our experimental results achieve excellent velocity accuracy.



#8 Predictive Modeling of Injury Risk Based on Body Composition and Selected Physical Fitness Tests for Elite Football Players

Reference: J Clin Med. 2022 Aug 22;11(16):4923. doi: 10.3390/jcm11164923.

Authors: Francisco Martins, Krzysztof Przednowek, Cíntia França, Helder Lopes, Marcelo de Maio Nascimento, Hugo Sarmento, Adilson Marques, Andreas Ihle, Ricardo Henriques, Élvio Rúbio Gouveia

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Summary: Injuries are one of the most significant issues for elite football players. Consequently, elite football clubs have been consistently interested in having practical, interpretable, and usable models as decision-making support for technical staff. This study aimed to analyze predictive modeling of injury risk based on body composition variables and selected physical fitness tests for elite football players through a sports season. The sample comprised 36 male elite football players who competed in the First Portuguese Soccer League in the 2020/2021 season. The models were calculated based on 22 independent variables that included players' information, body composition, physical fitness, and one dependent variable, the number of injuries per season. In the net elastic analysis, the variables that best predicted injury risk were sectorial positions (defensive and forward), body height, sit-and-reach performance, 1 min number of push-ups, handgrip strength, and 35 m linear speed. This study considered multiple-input single-output regression-type models. The analysis showed that the most accurate model presented in this work generates an error of RMSE = 0.591. Our approach opens a novel perspective for injury prevention and training monitorization. Nevertheless, more studies are needed to identify risk factors associated with injury prediction in elite soccer players, as this is a rising topic that requires several analyses performed in different contexts.



#9 Injury Incidence Increases after COVID-19 Infection: A Case Study with a Male Professional Football Team

Reference: Int J Environ Res Public Health. 2022 Aug 18;19(16):10267. doi: 10.3390/ijerph191610267.

Authors: Antonio Maestro, David Varillas-Delgado, Esther Morencos, Jorge Gutiérrez-Hellín, Millán Aguilar-Navarro, Gonzalo Revuelta, Juan Del Coso

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Summary: The SARS-CoV-2 virus disease has caused numerous changes in sports routines in the last two years, showing the influence on an increase in sports injuries. The aim of this study was to prospectively analyze the incidence and characteristics of injuries in male professional football players diagnosed with COVID-19 when they return to play after recovering from this illness. Injury characteristics of professional male football players were recorded for the 2020-2021 season following the international consensus statement from the International Olympic Committee (IOC). SARS-CoV-2 infection in the football players was certified by PCR analysis. Injury epidemiology was compared in players infected by the SARS-CoV-2 virus before and after being diagnosed with COVID-19. 14 players (53.8%) were diagnosed with COVID-19 during 2020-2021 season and 12 (46.2%) were not infected (controls). Only three (21.4%) had suffered an injury before being diagnosed with COVID-19. Eleven players (78.6%) had injuries after being diagnosed with COVID-19 (p &lt; 0.001). Among the players diagnosed with COVID-19, injury incidence increased on their return to play after the infection (3.8 to 12.4 injuries/1000 h of exposure, p &lt; 0.001). Additionally, injury incidence during training (10.6 vs. 5.1 injuries/1000 h of exposure, p &lt; 0.001) and matches (56.3 vs. 17.6 injuries/1000 h of exposure, p &lt; 0.001) was ~two-fold higher on return to play after COVID-19 compared to controls (33.4 vs. 17.6 injuries/1000 h of exposure, respectively, p &lt; 0.001). Injury incidence in professional football players who had been infected by the SARS-CoV-2 virus significantly increased compared to the injury rates that these same players had prior to the illness. Additionally, the injury incidence was higher when compared to players who were not infected by the SARS-CoV-2 virus during the season, especially during matches.



#10 Biological Maturation Predicts Dynamic Balance and Lower Limb Power in Young Football Players

Reference: Biology (Basel). 2022 Aug 3;11(8):1167. doi: 10.3390/biology11081167.

Authors: Bartosz Wilczyński, Łukasz Radzimiński, Agnieszka Sobierajska-Rek, Karol de Tillier, Jakub Bracha, Katarzyna Zorena

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Summary: Biological maturation has an increasingly important role in youth sports. The aim of the study was to evaluate the relationship between dynamic balance and lower limb power and biological maturation in young football players. Seventy-two healthy, young male elite football players (age: 10 ± 2) participated in the study. Dynamic balance was assessed using a modified Star Excursion Balance Test (mSEBT). Power of the lower limbs was examined by a Countermovement Jump test (CMJ) and Single Leg Hop for Distance (SLHD). Furthermore, anthropometry and biological maturation (age, peak height velocity, and maturity offset) were assessed. There was a strong positive correlation between vertical jump (r = 0.75), distance long jump (r = 0.84), and biological maturation. A moderate positive correlation was found between dynamic balance (mSEBT COM, PL, and PM) and maturity offset. There was a significant association between mSEBT, CMJ, and SLHD (p &lt; 0.05). Moreover, maturity offset explained 75% of vertical jump and 74% of distance long jump performance, respectively, and 12% of dynamic balance. Biological maturation should be considered when assessing athletic performance, establishing rehabilitation, and sports training in youth football players.



#11 Clustering ball possession duration according to players' role in football small-sided games

Reference: PLoS One. 2022 Aug 25;17(8):e0273460. doi: 10.1371/journal.pone.0273460. eCollection 2022.

Authors: Diogo Coutinho, Bruno Gonçalves, Timo Laakso, Bruno Travassos

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Summary: This study aimed to explore which offensive variables best discriminate the ball possession duration according to players specific role (defenders, midfielders, attackers) during a Gk+3vs3+Gk football small-sided games. Fifteen under-15 players (age 13.2±1.0 years, playing experience 4.2±1.0 years) were grouped according to their positions (team of defenders, n = 5; team of midfielders, n = 7; team of attackers, n = 3). On each testing day (n = 3), each team performed one bout of 5-min against each team in a random order, accounting for a total of nine bouts in the following scenarios: i) defenders vs midfielders; ii) defenders vs attackers; iii) midfielders vs attackers. Based on video, a notational analysis process allowed to capture individual and collective actions. According to each playing position group, discriminant analysis was used to identify relevant variables that discriminate different ball possession sequences (short, medium, and long). The analysis revealed the existence of three clusters according to ball possession duration, classified as short sequence (~4 seconds), medium sequence (~10 seconds) and long sequence (~18 seconds). The number of touches per possession was the variable that discriminates the ball possession duration from all playing positions while passing actions were related to midfielders and attackers. In addition, different ball possessions sequences in the attackers were also discriminated by the number of players involved per possession. Accordingly, to increase the duration of the offensive phase during small-sided games, coaches should foster the players' ability to stay on the ball, as it may amplify their opportunities to maintain the ball possession. In addition, coaches may also include reward rules to encourage midfielders and attackers' passing actions and the number of attackers involved during the attack to promote longer ball possessions durations.



#12 The Influence of Weekly Sprint Volume and Maximal Velocity Exposures on Eccentric Hamstring Strength in Professional Football Players

Reference: Sports (Basel). 2022 Aug 19;10(8):125. doi: 10.3390/sports10080125.

Authors: Sunnan Shah, Kieran Collins, Lewis J Macgregor

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Summary: Hamstring strains are the most common moderate-major severity injuries in football. The majority of hamstring injuries occur during sprinting, with low eccentric hamstring strength being associated with an elevated risk. The aim was to examine the relationship between sprinting and eccentric hamstring strength by monitoring total weekly sprint distance and weekly efforts &gt; 90% and &gt;95% of maximum velocity. Fifty-eight professional male footballers were observed over one-and-a-half seasons. Players' running was monitored during training and matches using GPS, and eccentric hamstring strength was measured weekly. Weekly sprint distance (ρ = -0.13, p &lt; 0.01) and weekly efforts &gt;90% of maximum velocity (ρ = -0.08, p = 0.01) both displayed significant inverse relationships with the percentage change in eccentric hamstring strength; weekly efforts &gt;95% of maximum velocity showed no relationship with hamstring strength (ρ = -0.02, p = 0.45). Only weekly efforts &gt;90% of maximum velocity significantly influenced the mean percentage change in eccentric hamstring force, F(3,58) = 3.71, p = 0.01, with significant differences occurring when comparing 7-8 sprint efforts with 0-2 efforts (0.11%, p = 0.03) and 5-6 efforts (0.12%, p = 0.03). Eccentric hamstring strength levels significantly decrease when 7-8 weekly sprint efforts are completed at &gt;90% of maximum velocity. Monitoring weekly sprint loading at velocities &gt; 90% of maximum velocity may be valuable to help to reduce the risk of hamstring injuries in professional football.



#13 Modeling the Major Influencing Factor on Match Running Performance during the In-Season Phase in a Portuguese Professional Football Team

Reference: Sports (Basel). 2022 Aug 12;10(8):121. doi: 10.3390/sports10080121.

Authors: José E Teixeira, Luís Branquinho, Miguel Leal, Daniel A Marinho, Ricardo Ferraz, Tiago M Barbosa, António M Monteiro, Pedro Forte

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Summary: The aim of this study was two-fold: (1) to analyze the influence of season phase (i.e., the start of the in-season and mid-in-season) on match running performance in a Portuguese professional football team; (2) to determine and model the main factor influencing match running performance during the in-season in this specific football team. Eighteen matches were collected by an 18 Hz global positioning system (GPS) from a professional Portuguese football team during the start of the in-season and mid-in-season. The match running performance was analyzed according to season phases, presenting significant differences in total distance (TD) (tlowerbound = 4.71, p &lt; 0.001; tupperbound = -2.22, p = 0.002), average speed (AvS) (tlowerbound = 359.45, p &lt; 0.001; tupperbound = -359.87, p &lt; 0.001), and relative high speed running (rHSR) (tlowerbound = 13.10, p &lt; 0.001; tupperbound = -10.21, p &lt; 0.001). The logistic regression showed TD (β = -1.59, z = -2.84, p = 0.005) and AvS (β = 2.68, z = -2.84, p = 0.007) as the major factors influencing match running performance during seasonal variation. Sprints and accelerations showed no significance for predicting match running performance during the season phases (β = -0.05 to 1.07, z = -0.95 to 1.07, p = 0.29 to 0.72). Current research confirms that lower and upper bounds should be used to quantify seasonal differences on match running performance. TD and AvS were described as the main factors influencing match running performance during the in-season phase. Thus, it is important to highlight the pace and volume of the game to maximize match running performance.



#14 Low prevalence of relative age effects in Luxembourg's male and female youth football

Reference: PLoS One. 2022 Aug 23;17(8):e0273019.  doi: 10.1371/journal.pone.0273019. eCollection 2022.

Authors: Claude Simon, Fraser Carson, Irene Renate Faber, Thorben Hülsdünker

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Summary: The relative age effect (RAE) is a well-established phenomenon in football. However, while the majority of previous studies focussed on established football nations, it remains unclear if the constraint of a limited population of soccer players in smaller countries associated with less strict selection procedures may reduce the risk of RAE. This study aims to investigate the RAE in Luxembourg that follows an 'open-door' selection policy in youth football due to the limited pool of players. Birthdates from all licensed and actively playing Luxembourgish youth footballers including all players of the youth national teams (396 girls and 10981 boys) competing in the season 2018/2019 were analysed and categorised into birth quarters and semesters. To further investigate a performance dependence of the RAE in amateur leagues, success was determined based on the teams' rankings at the end of the season. Differences between observed and expected birthdate distributions were calculated across all licensed players and age groups, within the national teams, and for the top- and bottom-tier football teams using chi-square statistics. While a RAE was absent across all age groups (except U7), significant RAEs with high effect sizes were observed in the top-level and national teams. These findings contrast the substantial RAE effects in large football nations and suggest that open selection systems might reflect an environmental constraint that limit the prevalence of RAE in football. Further, this study indicates that a performance dependence of the RAE is not limited to high level football but already occurs on an amateur level.



#15 Femur 3D-DXA assessment in female football players, swimmers and sedentary controls

Reference: Int J Sports Med. 2022 Aug 22. doi: 10.1055/a-1928-9824. Online ahead of print.

Authors: Amineh Amani, Montse Bellver, Luis Del Rio, Joan Ramon Torrella, Antonia Lizarraga, Ludovic Humbert, Franchek Drobnic

Summary: Cortical and trabecular volumetric bone mineral density (vBMD), cortical thickness and surface BMD (sBMD, density-to-thickness ratio) were analysed in the proximal femur of elite female football players and artistic swimmers using a three-dimensional dual-energy X-ray absorptiometry (3D-DXA) new software, and compared to sedentary controls. Football players had significantly higher (p<0.05) vBMD (mg/cm3) in trabecular (263±44) and cortical femur (886±69) than artistic swimmers (224±43 and 844±89) and sedentary controls (215±51 and 841±85). Football players had also higher (p<0.05) cortical thickness (2.12±0.19 mm) and sBMD (188±22 mg/cm2) compared to artistic swimmers (1.85±0.15 and 156±21) and sedentary controls (1.87±0.16 and 158±23). Artistic swimmers did not show significant differences in any parameter analysed for 3D-DXA when compared to sedentary controls. The 3D-DXA modelling revealed statistical differences in cortical thickness and vBMD between female athletes engaged in weight-bearing (football) and non-weight bearing (swimming) sports and did not show differences between the non-weight bearing sport and the sedentary controls. 3D-DXA modelling could provide insight into bone remodelling in sports field, allowing to evaluate femoral trabecular and cortical strength from standard DXA scans.



#16 Heading and risk of injury situations for the head in professional German football: a video analysis of over 150,000 headers in 110,000 match minutes

Reference: Sci Med Footb. 2022 Aug 25;1-8. doi: 10.1080/24733938.2022.2114602. Online ahead of print.

Authors: Johannes Weber, Claus Reinsberger, Volker Krutsch, Robin Seiffert, Lorenz Huber, Volker Alt, Werner Krutsch

Summary: To provide detailed epidemiological data on situations with a propensity of head injuries due to heading in professional football. In a prospective cohort study including the four highest professional football leagues in Germany, headers carried out in 1244 official matches and critical situations (CI) with a potential risk for injuries over one season were assessed by video analysis and a standardised video protocol. Results: 154,766 headers in 111,960 match minutes were recorded (1.4 headings/min). Video analysis showed a mean of 6.2 headers per field player and match (SD: 2,9; min: 0; max: 19) in the entire study population with a peak in the third league (7.1 per player and match). Headers were predominantly carried out with the forehead (78.5%), and nearly two-thirds occurred during defence (64.3%). 49.9% of all headers occurred during tackling, of which 78.3% involved body contact with an opponent. Video analysis yielded 848 CI. 74.5% of all critical incidents occurred during heading duels as a part of tackling (odds ratio: 3.6, 95%-CI: 2.4-5.2), and 99.4% involved body contact (odds ratio: 5.9, 95%-CI: 2,8-12,7). This study is the first to provide detailed epidemiological data on heading and critical incidences with high risk for head injuries in professional football. Heading duels bear a high risk of head injury and thus represent a key target for prevention strategies. The impacts of headers should be critically investigated regarding neurological consequences in further studies, by including the mean heading rate per mal field player and match.



#17 Adherence to an injury prevention program in male amateur football players is affected by players' age, experience and perceptions

Reference: BMJ Open Sport Exerc Med. 2022 Aug 2;8(3):e001328. doi: 10.1136/bmjsem-2022-001328. eCollection 2022.

Authors: Peter Alexander van de Hoef, Michel S Brink, Jur J Brauers, Maarten van Smeden, Vincent Gouttebarge, Frank J G Backx

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Summary: Adherence to injury prevention programmes in football remains low, which is thought to drastically reduce the effects of injury prevention programmes. Reasons why (medical) staff and players implement injury prevention programmes, have been investigated, but player's characteristics and perceptions about these programmes might influence their adherence. Therefore, this study investigated the relationships between player's characteristics and adherence and between player's perceptions and adherence following an implemented injury prevention programme. Data from 98 of 221 football players from the intervention group of a cluster randomised controlled trial concerning hamstring injury prevention were analysed. Adherence was better among older and more experienced football players, and players considered the programme more useful, less intense, more functional and less time-consuming. Previous hamstring injuries, educational level, the programme's difficulty and intention to continue the exercises were not significantly associated with adherence. These player's characteristics and perceptions should be considered when implementing injury prevention programmes.



#18 A Review of Neuromuscular Training and Biomechanical Risk Factor Screening for ACL Injury Prevention Among Female Soccer Players

Reference: Bull Hosp Jt Dis. 2022 Sep;80(3):253-259.

Authors: Amelia Weingart, Nicole Rynecki, David Pereira

Summary: Anterior cruciate ligament (ACL) injuries are a highly prevalent and costly injury to treat, both financially and regarding its long-term detrimental effects on those injured. Adolescent female soccer players appear to be particularly vulnerable, possibly due to various biomechanical risk factors, such as knee valgus loading and imbalanced hamstrings-quadriceps (H/Q) ratio. Many studies support the benefits of generic neuromuscular training programs in mitigating this heightened injury risk. Despite this, ACL injuries remain pervasive within this population. This review aims to highlight the current tools available to assess athletes for biomechanical risk factors at an individual level, including three-dimensional motion analysis, the Landing Error Scoring System (LESS), and the Cutting Movement Assessment Score (CMAS). Utilization of these analyses could facilitate developing and implementing more individualized training programs, thereby identifying high-risk athletes, reducing sports-related ACL injuries, and lessening the economic burden of these injuries on both the patient and the health care system.



#19 Football in Times of COVID-19: A Recapitulation of Preventive Measures and Infection Control Policies Aiming at a Safe Game Environment

Reference: Int J Sports Physiol Perform. 2022 Aug 30;1-4. doi: 10.1123/ijspp.2022-0254. Online ahead of print.

Authors: Karim Chamari, Ismail Dergaa, Inigo Mujika, Yorck Olaf Schumacher, Montassar Tabben, Helmi Ben Saad

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Summary: Coronavirus disease 2019 (COVID-19) resulted in sporting event suspensions and cancellations, affecting competition calendars worldwide during 2020 and 2021. This challenged high-performance athletes' capacity to complete physical, technical, or tactical training during restricted movement measures (lockdown). With the Football World Cup organized in the last quarter of 2022, the past period of training and match disturbances challenged footballers concerning their performance and potential higher risk of injury at official matches' resumption. There has been considerable debate about the management of resuming professional football (soccer) during the COVID-19 pandemic. Governing bodies worldwide implemented measures to ensure a safe resumption of football. These precautionary measures aimed to protect the health of players, their support staff, and officials around the pitch and ensure the enjoyment of the event by spectators in the football stadiums. We have therefore narratively reviewed scientific papers about how football has resumed on the pitch and in the stands with special focus on the COVID-19 infection control strategies allowing footballers to perform again and supporters to enjoy the game after the 2020 global stop to sport.


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