Latest research in football - week 13 - 2023

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 Successful Repair of M. obliquus Internus Abdominis Avulsion at the Iliac Crest-Operative Technique in Professional Soccer Players

Reference: Orthop Surg. 2023 Apr 11. doi: 10.1111/os.13699. Online ahead of print.

Authors: Heinz Lohrer, Andreas Höferlin

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Summary: Sports related injuries to the anterolateral abdominal wall have been described as side strain injuries or hip pointer. So far, only a few cases of avulsion injuries of the m. obliquus internus abdominis muscle from the iliac crest have been described. All were treated conservatively. The aim of this study is to present the surgical technique. This report presents three cases of professional soccer players who were treated surgically with transosseous reattachment to the iliac crest. These male players were 23, 25, and 29 years old. Two of them suffered a direct contusion and one an indirect injury. The diagnosis was suspected based on the patient's history and clinical examination and confirmed by MRI. In each case, the fibrocartilaginous layer of the m. obliquus internus was separated 2 cm from the iliac crest. All three players were operated by aponeurotic m. obliquus internus refixation to the lateral iliac crest (three transosseous drill holes). Return to play was 55, 60, and 122 days postoperatively. Functional limitations, symptoms, sports/recreational activities, and quality of life in terms of occupational, social, emotional, and lifestyle concerns were measured using the iHOT 12 instrument at 11.1 and 9.7 years postoperatively. Six weeks postoperatively, sport-specific training was started. After 2 to 4 months, all three patients were fully reintegrated into their elite sports and unrestricted sports ability was achieved. Long-term follow-up was performed using the German version of the iHOT-12 questionnaire and 92.7% and 99.9% were calculated for the two German speaking soccer players. Our cases demonstrate that transosseous suture reattachment was a successful procedure that allowed a safe and predictable return to sport. Full performance and excellent, long lasting treatment results were achieved.



#2 Prevalence and diagnostic significance of de-novo 12-lead ECG changes after COVID-19 infection in elite soccer players

Reference: Heart. 2023 Mar 27;heartjnl-2022-322211. doi: 10.1136/heartjnl-2022-322211. Online ahead of print.

Authors: Raghav T Bhatia, Aneil Malhotra, Hamish MacLachlan, Sabiha Gati, Sarandeep Marwaha, Nikhil Chatrath, Saad Fyyaz, Haroldo Aleixo, Samar Al-Turaihi, Aswin Babu, Joyee Basu, Paul Catterson, Robert Cooper, Joelle J N Daems, Harshil Dhutia, Filipe Ferrari, Juliette C van Hattum, Zafar Iqbal, Alexandros Kasiakogias, Antoinette Kenny, Tamim Khanbhai, Shafik Khoury, Chris Miles, David Oxborough, Kashif Quazi, Dhrubo Rakhit, Anushka Sharma, Amanda Varnava, Maria Teresa Tome Esteban, Gherardo Finocchiaro, Ricardo Stein, Harald T Jorstad, Michael Papadakis, Sanjay Sharma

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Summary: The efficacy of pre-COVID-19 and post-COVID-19 infection 12-lead ECGs for identifying athletes with myopericarditis has never been reported. We aimed to assess the prevalence and significance of de-novo ECG changes following COVID-19 infection. In this multicentre observational study, between March 2020 and May 2022, we evaluated consecutive athletes with COVID-19 infection. Athletes exhibiting de-novo ECG changes underwent cardiovascular magnetic resonance (CMR) scans. One club mandated CMR scans for all players (n=30) following COVID-19 infection, despite the absence of cardiac symptoms or de-novo ECG changes. 511 soccer players (median age 21 years, IQR 18-26 years) were included. 17 (3%) athletes demonstrated de-novo ECG changes, which included reduction in T-wave amplitude in the inferior and lateral leads (n=5), inferior leads (n=4) and lateral leads (n=4); inferior T-wave inversion (n=7); and ST-segment depression (n=2). 15 (88%) athletes with de-novo ECG changes revealed evidence of inflammatory cardiac sequelae. All 30 athletes who underwent a mandatory CMR scan had normal findings. Athletes revealing de-novo ECG changes had a higher prevalence of cardiac symptoms (71% vs 12%, p<0.0001) and longer median symptom duration (5 days, IQR 3-10) compared with athletes without de-novo ECG changes (2 days, IQR 1-3, p<0.001). Among athletes without cardiac symptoms, the additional yield of de-novo ECG changes to detect cardiac inflammation was 20%. 3% of athletes demonstrated de-novo ECG changes post COVID-19 infection, of which 88% were diagnosed with cardiac inflammation. Most affected athletes exhibited cardiac symptoms; however, de-novo ECG changes contributed to a diagnosis of cardiac inflammation in 20% of athletes without cardiac symptoms.



#3 Correlations Between Hamstring Muscle Architecture, Maturation, and Anthropometric Measures in Academy Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Apr 14;1-10. doi: 10.1123/ijspp.2022-0031. Online ahead of print.

Authors: Matthew Brown, Martin Buchheit, Mathieu Lacome, Karim Hader, Gaël Guilhem

Summary: Muscle architecture is associated with motor performance and muscle injury. While muscle architecture and knee-flexor eccentric strength change with growth, the influence of anthropometric measures on these properties is rarely considered. This study aimed to investigate the relationship between hamstring muscle architecture and knee-flexor eccentric strength with anthropometric measurements. Sixty male footballers (16.6 [1.05] y) from the U16, U17, and U19 teams of an elite soccer club were included in this study. Fascicle length, pennation angle, and muscle thickness of the biceps femoris long head (BFlh) and semimembranosus muscles were measured in both legs using ultrasound. Knee-flexor eccentric strength, height, body mass, leg length, femur length, and peak height velocity (PHV) were measured within 1 week of the ultrasound images. A stepwise regression and 1-way analysis of variance tests were used to evaluate the effects of age, maturity, and anthropometric measurements on muscle properties. Variance within BFlh and semimembranosus muscle thickness (r < .61), semimembranosus pennation angle (r < .58), and knee-flexor eccentric strength (r = .50) were highly related to body mass. We observed no significant correlations between muscle architecture and age (P > .29). However, moderately greater BFlh muscle thickness was shown for the post-PHV compared with the PHV group (effect size ± 90% CI: 0.72 ± 0.49). In conclusion, weak correlations between muscle architecture and anthropometric measurements suggest that other factors (ie, genetics, training regimen) influence muscle architecture. The moderate effect of maturity on BFlh muscle thickness strongly suggests post-PHV hypertrophy of the BFlh muscle. Our results confirmed previous findings that eccentric knee-flexor strength is influenced by body mass.



#4 External and internal training load comparison between sided-game drills in professional soccer

Reference: Front Sports Act Living. 2023 Apr 4;5:1150461. doi: 10.3389/fspor.2023.1150461. eCollection 2023.

Authors: Marco Beato, Kevin L de Keijzer, Andrew J Costin

Summary: This study aims to quantify and compare the external and internal training load demands of sided-game drills in professional team players during the competitive season. Twenty-four male professional soccer players of the same club were enrolled in this study. Drills were categorized as large-sided games (LSG): 10vs10 (84 × 60 m or 72 × 60 m), Hexagon possession 9vs9 + 3 (36 × 48 m), Possession gate 8vs8 + 2 (36 × 44 m), Possession 7vs7 + 3 (30 × 32 m) or as Small-sided games (SSG): 6vs6 (48 × 42 m), and Possession 6vs4 (30 × 60 m). A total of 7 drills and 279 individual data points were included in this analysis. Distance covered, high-speed running (HSR), and sprinting distance were all calculated in meters per minute (m.min-1) while total accelerations (>3 m.s-2) and total decelerations (- < 3 m.s-2) were calculated in number of actions per minute (n.min-1). All external load was measured with global navigation satellite systems (GNSS) STATSports Apex units. Players' internal load was quantified using their rating of perceived exertion (RPE). We found that distance covered (p < 0.01, large), HSR (p < 0.01, large), and sprinting distance (p < 0.01, large) changed between drills (e.g., greater in LSG formats), acceleration (p < 0.01, large) and deceleration (p < 0.01, large) demands were greater in smaller formats (e.g., SSG 6vs6, and Possession 6vs4), while RPE was lower in the Possession gate 8vs8 + 2 format (p < 0.01, large). This study found that sided-games can replicate and sometimes exceed some match-specific intensity parameters, however, HSR and sprinting were consistently lower compared to official matches.



#5 Development and Predictive Validation of the Brazilian Adductor Performance Test for Estimating the Chance of Hip Adductor Injuries in Elite Soccer Athletes

Reference: Int J Sports Physiol Perform. 2023 Apr 20;1-7. doi: 10.1123/ijspp.2022-0306. Online ahead of print.

Authors: Jeffeson Hildo Medeiros de Queiroz, João Paulo Frota, Filipe Abdala Dos Reis, Rodrigo Ribeiro de Oliveira

Summary: To develop and validate the Brazilian Adductor Performance Test (BAPT) for predicting hip adductor muscle injuries in elite soccer athletes. A total of 108 soccer athletes were assessed, followed up for 3 months, and evaluated for a history of adductor injury 6 months before BAPT evaluation. The Shapiro-Wilk test was used as the normality test. The Mann-Whitney U test was used to compare BAPT scores between injured and uninjured athletes. Binary logistic regression was performed to identify the athletes' chances of injury based on their BAPT scores. A receiver operating characteristic curve was used to determine the cutoff point for the number of repetitions in the BAPT and Spearman bivariate correlation and identify factors potentially related to the test score. Furthermore, the intraclass correlation coefficient was used to determine interexaminer agreement. The level of significance was set at 95%.The BAPT scores for hip adductor injury history did not differ significantly (P = .08). A significant deficit was identified in the BAPT scores of the injured athletes at the 3-month follow-up (P = .001). The cutoff point identified was 33 repetitions. Low BAPT scores increased the chance of injury by 20% (odds ratio, 1.20%; P = .001). The interexaminer agreement was .96 (P = .001). BAPT can be used to identify athletes most likely to sustain hip adductor muscle injuries, indirectly reducing the rate of this injury in soccer clubs.



#6 The influence of ball in/out of play and possession in elite soccer: Towards a more valid measure of physical intensity during competitive match-play

Reference: Eur J Sport Sci. 2023 Apr 20;1-23. doi: 10.1080/17461391.2023.2203120. Online ahead of print.

Authors: Benjamin W C Jerome, Michael Stoeckl, Ben Mackriell, Thomas Seidl, Christian W Dawson, Daniel T P Fong, Jonathan P Folland

Summary: The physical demands of soccer match-play have typically been assessed using a low-resolution whole match approach ignoring whether the ball is in or out of play (BIP/BOP) and during these periods which team has possession. This study investigated the effect of fundamental match structure variables (BIP/BOP, in/out of possession) on the physical demands, and especially intensity, of elite match-play. For 1083 matches from a major European league, whole match duration, and player physical tracking data, were divided into BIP/BOP, and in/out of possession periods throughout the match, using on-ball event data. These distinct phases were used to derive absolute (m) and rate (m·min-1) of distance covered in total and within six speed categories during BIP/BOP and in/out possession. The rate of distance covered, an index of physical intensity, was >2-fold greater during BIP vs BOP. Whole match total distance covered was confounded by BIP time and poorly associated with physical intensity during BIP (r=0.36). Whole match rates of distance covered substantially underestimated those during BIP, particularly for higher running speeds (∼-62%). Ball possession markedly effected physical intensity, with the rates of distance covered running (+31%), at high-speed (+30%) and in total (+7%) greater out than in possession. Whole match physical metrics underestimated the physical intensity during BIP, and thus the rate(s) of distance covered during BIP are recommended for accurate measurement of physical intensity in elite soccer. The greater demands of being out of possession supports a possession based tactical approach to minimise fatigue and its negative consequences.



#7 Effects of 6 weeks in-season flywheel squat resistance training on strength, vertical jump, change of direction and sprint performance in professional female soccer players

Reference: Biol Sport. 2023 Apr;40(2):521-529. doi: 10.5114/biolsport.2023.118022. Epub 2022 Jul 21.

Authors: Javier Pecci, Alejandro Muñoz-López, Paul A Jones, Borja Sañudo

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Summary: Flywheel resistance training devices (FRTD) is shown effective in improving strength, sprinting, jumping and changes of direction (COD) performance in male soccer players, however, this is not elucidated in female soccer players. We aimed to assess the effect of FRTD on these physical abilities in females soccer players. 24 professional female soccer players (age: 20.4 ± 2.6 years) were randomly assigned to a flywheel training group (FWTG) that trained twice a week for 6 weeks on a rotary inertia device with an initial volume of 3 sets of 6 repetitions and an inertia of 0,025 kg · m-2, increasing intensity and volume or a control group (CG) that did not performed any additional resistance training program. Concentric peak torque of the knee extensors (CONEXT) and flexors (CONFLEX), eccentric peak torque of the knee extensors (ECCEXT) and flexors (ECCFLEX) at 60° · s-1 on an isokinetic dynamometer, countermovement jump (CMJ) height, COD and 30-metres sprint were assessed. Significant time by group interactions were found in CONEXT (p = 0.002; η²p = 0.425), CONFLEX (p = 0.037; η²p = 0.22), ECCEXT (p = 0.002; η²p = 0.43) and ECCFLEX (p = 0.008; η²p = 0.334). No time by group effect was found in CMJ (p = 0.061; η²p = 0.182), COD (p = 0.067; η²p = 0.184) or sprint (p = 0.926; η²p = 4.979 · e-4). In conclusion, 6 weeks of flywheel squat training improved strength (especially eccentric strength) but not soccer-specific abilities such as jumping, changing of direction or sprinting in professional soccer players.



#8 Recovery time variation during sprint interval training impacts amateur soccer players adaptations - a pilot study

Reference: Biol Sport. 2023 Apr;40(2):417-424. doi: 10.5114/biolsport.2023.116008. Epub 2022 Jun 1.

Authors: Gürkan Diker, Abdulkerim Darendeli, Karim Chamari, Alexandre Dellal, Sürhat Müniroğlu, Sadi Ön, Hüseyin Özkamçı

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Summary: The objective of the present study was to investigate the selected performance adaptations of amateur soccer players to 2 different running-based sprint interval training (SIT) protocols with different recovery intervals and work-rest ratios (1:5 & 1:1). Twenty-three subjects (age 21.4 ± 1.1 years; height 175.4 ± 4.7 cm; body mass 69 ± 6.4 kg) participated in the study. Before the 6-weeks training period, participants completed 3-weeks of low-intensity training preparation. Subsequently, the pre-tests (anthropometric measurements, repeated sprint test [12 × 20-m with 30-s recovery intervals], Yo-YoIRT1 & Yo-YoIRT2 and treadmill VO2max test) were conducted. Thereafter, participants were randomly divided into 3 sub-groups (1 - SIT with 150 s recovery intervals [SIT150, n = 8]; 2 - SIT with 30 s recovery intervals [SIT30, n = 7]; and 3 - control group [CG, n = 8]). SIT150 and SIT30 training groups completed sprint interval training (2-days/week; 30-s all-out running, 6-10 repetition with 150 s recovery intervals for SIT150 and 30 s for SIT30 groups, respectively), a soccer match (1-day) and routine soccer training (3-days) per week. The CG attended only routine training sessions and the soccer-match (4-days). The study experiments and the trainings were conducted during off-season. Yo-YoIRT1, Yo-YoIRT2, and VO2max were significantly improved both in SIT30 and SIT150 (p < 0.05) groups. Yo-YoIRT1 and VO2max were also significantly improved in CG (p < 0.05). Both the SIT150 and SIT30 training were shown to improve Yo-YoIRT1, Yo-YoIRT2 and VO2max performance compared to the control group, nevertheless, SIT150 was more efficient in improving the Yo-YoIRT1, Yo-YoIRT2 than SIT30. The authors of this study suggest using SIT150 to induce more effective performance outputs in amateur soccer players.



#9 Is there any relationship between match running, technical-tactical performance, and team success in professional soccer? A longitudinal study in the first and second divisions of LaLiga

Reference: Biol Sport. 2023 Apr;40(2):587-594. doi: 10.5114/biolsport.2023.118021. Epub 2022 Sep 6.

Authors: José M Oliva-Lozano, Helena Martínez-Puertas, Víctor Fortes, Roberto López-Del Campo, Ricardo Resta, José M Muyor

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Summary: The aim of this study was to analyze the association between teams' success at the end of the season and match running, and technical-tactical performance in two professional soccer leagues. Match running, and technical-tactical performance data were collected during two consecutive seasons. A Factor Analysis was conducted to reduce the number of performance variables into a fewer number of factors. The scree plot with parallel analysis revealed that five factors should be retained. Then, a multiple linear regression analysis was performed to explain which variables and factors were more associated with teams' success at the end of the season. The main findings of this study were that factor 3, which was correlated with goals scored, possessions ending with a goal, shots on target, goals from set plays, goals from a direct free kick, offsides, and goals conceded, was the most important contributor to teams' success (β = 0.66). In addition, this study observed a significant interaction (p = 0.001) between the second division of LaLiga and factor 2, which correlated with total distance (TD), sprinting distance (SPD), and sprinting actions (SPA) when opponent team owns the ball, tackles, shots inside the box, and fouls received. This implies that factor 2 had a different effect on the total points at the end of the season depending on the league. However, factor 2 had no effect on the first division. In conclusion, technical-tactical performance variables were usually more closely linked to the team's success in both leagues than match running performance data. Regarding the technical-tactical performance, teams may focus on drills that promote goal situations, shooting accuracy, the total of shots performed in match play, and set pieces. However, defensive skills need to be reinforced considering the importance of goals conceded for team success in both divisions. When it comes to the match running performance, teams are encouraged to focus on offensive actions, in which they possess and run with the ball (especially at high speed) and defensive actions in which the players perform continuous and high-intensity physical efforts to prevent the opponents from scoring, avoid counterattacks, stay compact, and defend the area and goal.



#10 Factors affecting match running performance in elite soccer: Analysis of UEFA Champions League matches

Reference: Biol Sport. 2023 Apr;40(2):409-416. doi: 10.5114/biolsport.2023.116453. Epub 2022 Jun 1.

Authors: Toni Modric, Sime Versic, Marko Stojanovic, Paweł Chmura, Marcin Andrzejewski, Marek Konefał, Damir Sekulic

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Summary: This study aimed to examine the independent effect of different match-related factors on match running performance (MRP) in elite soccer. Players' MRPs (n = 244) were collected during UEFA Champions League (UCL) group stage matches in the 2020-21 season. All MRP data were collected by the semi-automatic optical system InStat Fitness (InStat Limited, Limerick, Republic of Ireland). Match-related factors included match outcome, team quality, match location, opponent quality and difference in team quality, while MRP included cumulative and relative measures of total distance (TD and R-TD), low-intensity running (LIR and R-LIR) (≤ 4 m/s), moderate-intensity running (MIR and R-MIR) (4-5.5 m/s) and high-intensity running (HIR and R-HIR) (≥ 5.5 m/s). Linear mixed models were used to examine the collective effect of match-related factors on MRPs when controlling for between-player, between-playing position and between-team variation. The main findings were that match outcome was associated with reduced HIR (d = -0.38, p = 0.04), match location was associated with increased TD, R-TD, LIR and R-LIR (d = 0.54-0.87, all p < 0.01), while team quality, opponent quality and difference in team quality were not associated with MRP. These results show that (i) winning UCL matches was not strongly influenced by players' physical performance, (ii) away UCL matches were characterized by a slower match pace and greater match volume, and (iii) players' physical performance was similar irrespective of playing either in or against high- or low-quality teams. The findings from this study may help soccer coaches to ensure optimal physical preparation of players in elite soccer.



#11 Effects of re-warm-up protocols on the physical performance of soccer players: A systematic review with meta-analysis

Reference: Biol Sport. 2023 Apr;40(2):335-344. doi: 10.5114/biolsport.2023.116013. Epub 2022 Jun 1.

Authors: Francisco Tomás González Fernández, Hugo Sarmento, Álvaro Infantes-Paniagua, Rodrigo Ramirez-Campillo, Sixto González-Víllora, Filipe Manuel Clemente

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Summary: This systematic review aimed to (1) identify and summarize studies that have examined the effects of re-warm-up (RWU) protocols on the physical performance of soccer players (vertical jump height and sprint time) and (2) establish a meta-comparison between performing a re-warm-up and not performing one regarding the outcomes of the aforementioned outcomes. A systematic review of EBSCO, PubMed, SciELO, SPORTDiscus, and Web of Science databases was performed on 12 January, 2021, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 892 studies initially identified, four studies were reviewed, and three of these were included in the present meta-analysis. Compared to a control condition, there was a moderate effect of RWU on vertical jump height (ES = 0.66; p = 0.001; I2 = 0.0%). However, compared to a control condition, there was a trivial effect of RWU on linear sprint time (ES = 0.19; p = 0.440; I2 = 38.4%). The nature of RWU enhances the performance of players with an emphasis on actions requiring vertical jumps. Therefore, the results provide essential information that soccer coaching staff can use to improve the performance of their teams. The limited number of studies available for the meta-analysis may have magnified the impact of heterogeneity on linear sprint time findings. More high-quality studies, with homogeneous study designs, may help to clarify the potential benefits of RWU for linear sprint time.



#12 Monitoring physical match performance relative to peak locomotor demands: implications for training professional soccer players

Reference: Biol Sport. 2023 Apr;40(2):553-560. doi: 10.5114/biolsport.2023.116450. Epub 2022 Jul 21.

Authors: José M Oliva-Lozano, Andrea Riboli, Víctor Fortes, José M Muyor

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Summary: This study aimed to analyse physical performance relative to peak locomotor demands of match play. Data were collected during 13 professional soccer matches. Initially, the 1-minute peak values were registered in each match, including the percentage of the total distance (TD), high-speed running distance (HSRD), sprinting distance (SPD), and high-metabolic load distance (HMLD), and a total of high-intensity accelerations and decelerations (Acc+Dec). Secondly, the time (measured in minutes) spent at different percentage ranges for the 1-minute peak values registered in each match was calculated. Thirdly, the physical performance required in the different percentage ranges for the 1-minute peak values were obtained. Finally, the time and physical performance required above the 90-minute average demands were calculated. The 90-minute average for all playing positions represented ~53% of the total distance (TD), ~23.4% of high-metabolic load distance (HMLD), ~16% of high-speed running distance (HSRD), ~11% of the total of high-intensity accelerations and decelerations (Acc+Dec), and ~6% of sprinting distance (SPD) for the 1-minute peak values. Likewise, statistically significant differences (p < 0.05) in the physical performance and time spent between specific percentage ranges for the 1-minute peak locomotor demands were also noted. In addition, all the variables reported that the physical performance required for above 90-minute average demands were significantly greater (p < 0.05) than the 90-minute average demands. Therefore, these findings may guide the prescription of training intensity by considering the physical performance relative to the peak locomotor demands of match play.



#13 Talent concentration and competitive imbalance in European soccer

Reference: Front Sports Act Living. 2023 Mar 30;5:1148122. doi: 10.3389/fspor.2023.1148122. eCollection 2023.

Authors: Bernd Frick, Tommy Kweku Quansah, Markus Lang

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Summary: While most of the available literature on competitive balance analyses its impact on ticket sales and TV audiences, less empirical research is available that examines the observable variation in competitive balance across leagues and over time. This paper studies the concentration of player talent and end-of-season league points to empirically assess whether leagues with a more equal distribution of player talent produce a more balanced competition than leagues with less equal distribution. The longitudinal data we use to estimate our empirical model comes from professional soccer leagues in twelve Western European countries from 2005/06 thru 2020/21, yielding 5,299 club-season observations. Our empirical analysis indicates that talent concentration in a league significantly and positively impacts points concentration in that league. However, in specifications controlling for year, country, and division, this impact is only weakly significant or insignificant, suggesting that talent concentration does not significantly affect competitive balance in that league. Additionally, our findings demonstrate that the relationship between talent and points concentration does not vary considerably across the European leagues or over time. Our results suggest that repeated participation in the UEFA Champions League, with its considerable monetary returns by (more or less) the same subset of teams, does not increase competitive imbalance in the respective national league. Thus, with relatively few additional regulatory interventions, the promotion and relegation system in the open European soccer leagues seems effective in ensuring a balanced competition.



#14 Differences in body composition, static balance, field test performance, and academic achievement in 10-12-year-old soccer players

Reference: Front Physiol. 2023 Mar 30;14:1150484. doi: 10.3389/fphys.2023.1150484. eCollection 2023.

Authors: Souhail Hermassi, Lawrence D Hayes, Thomas Bartels, René Schwesig

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Summary: This study aimed to compare 10-12-year-old Qatari male soccer players (n = 45) regarding different dimensions (anthropometric, academic and physical performance). Anthropometric parameters (body mass, fat percentage (%BF), body mass index (BMI)) academic achievement (mathematics and science grade point average [GPA]) and physical performance [Yo-Yo Intermittent Recovery Test (level 1), squat jumps (SJ), counter-movement jumps (CMJ), stork balance test, 10 and 15 m sprint tests, T-half test for change-of-direction (CoD) ability, hand-grip strength, medicine ball throw (MBT)] were measured. Schoolchild soccer players were divided into three groups: 12-year-old players (U12; n = 16), 11-year-old players (U11; n = 14), 10-year-old players (U10; n = 15). Apart from mathematics, Yo-Yo IR1 and 10 m sprint, all performance parameters showed significant age effects. The largest age-related difference was observed for 15 m sprint (p < 0.001). Both adjacent age groups displayed significant differences for 15 sprint (U10 vs. U11: p = 0.015; U11 vs. U12: p = 0.023). Concerning academic performance, a significant age effect was found for science (p < 0.001). There was a main age effect on academic performance difference between U10 and U11 (p = 0.007). Academic parameters did not correlate with any physical performance parameter or anthropometric parameter. The strongest correlations were detected for body height and agility T-half test (r = -0.686) and medicine ball throw (r = 0.637). The biological maturity was strongly correlated with handgrip strength (r = -0.635). Soccer coaches and physical education teachers can use these data as reference values for evaluation of school-aged soccer players, and for ascertaining specific training targets. Obviously, short sprinting ability and aerobic capacity are not functions of age and need a specific training for significant improvements.



#15 Virtual reality as a representative training environment for football referees

Reference: Hum Mov Sci. 2023 Apr 19;89:103091. doi: 10.1016/j.humov.2023.103091. Online ahead of print.

Authors: Tammie van Biemen, Daniel Müller, David L Mann

Summary: Visual experience plays an important role in facilitating referee decision-making. Video training can be used to train these perceptual-cognitive skills in discrete scenarios, for instance in foul situations in football, but is less suitable in other instances such as when seeking to make decisions in open-play scenarios due to a lack of representativeness. Recent technological advances enable the use of virtual reality (VR) to replicate game situations in a controlled and realistic manner. It is however not yet known how representative behaviour in VR would be of behaviour on-field in the natural environment. The aim of the study was therefore to examine the degree to which visual behaviour of football referees in virtual reality would reflect behaviour found when adjudicating matches on-field. Sub-elite football referees completed decision-making tasks in three experimental conditions: on-field (in a real match), in virtual reality and when observing video footage. Across the three environments we compared decision-making performance, visual behaviour (including search rate, fixation duration, and head movements) and the user experience of the referees. Results revealed that behaviour in the VR environment was indistinguishable from that on-field. In contrast, visual-motor behaviour when observing video footage was markedly different to that found on-field (and in VR). The results show that visual-motor behaviour in VR is representative of that found on-field and therefore suggests that VR offers promise as a representative training environment for sports officials to improve on-field performance in the natural environment.



#16 Comparison of the neuromuscular response to three different Turkish, semi-professional football training sessions typically used within the tactical periodization training model

Reference: Sci Rep. 2023 Apr 20;13(1):6467. doi: 10.1038/s41598-023-33630-0.

Authors: Joel M Garrett, Cedric Leduc, Zeki Akyildiz, Daniel J van den Hoek, Filipe Manuel Clemente, Mehmet Yildiz, Hadi Nobari

Summary: This study examined the neuromuscular responses to three typical football (soccer) training sessions and the reliability of peak speed (PS) measured during a submaximal running test (SRT) for identifying neuromuscular fatigue (NMF) status. Jump height (CMJH) and peak velocity (CMJPV) were collected from a CMJ test, while peak speed (PS) was collected during an SRT before and after each training session. Large effect size (ES) decreases were observed in each variable post-training (ES; - 1.42 to - 2.32). Significant differences (> 0.001) were detected between each football session's external load variables. Coefficients of variations were small (< 10%) with moderate (CMJPV; 0.53, PS; 0.44) and strong (CMJH; 0.72) intraclass correlation coefficients between pre-test measures. The demands of each football session aligned with the principles of tactical periodization and were sufficient to produce the fatigue necessary to elicit physiological adaptations. PS was also shown to be a viable measure of monitoring NMF status.



#17 Training Load Quantification in Women's Elite Football: A Season-Long Prospective Cohort Study

Reference: Int J Sports Physiol Perform. 2023 Apr 20;1-12. doi: 10.1123/ijspp.2022-0272. Online ahead of print.

Authors: Ulrik B Karlsson, Markus Vagle, Håvard Wiig, Live S Luteberget

Summary: The aim of this study was to investigate (1) if there are differences in training load and intensity between the different training days within a microcycle and (2) if training load and intensity within the different training days are stable over the course of a season. Data were collected over a full season from a team in the women's premier division in Norway. External load (total distance, high-speed-running distance, sprint distance, and the combined number of accelerations and decelerations [ACCDEC]) was assessed using a 10-Hz GPS system with a built-in accelerometer. Internal load was assessed through session rating of perceived exertion, which was multiplied with session duration (session rating of perceived exertion-load). Training days were classified in relation to their proximity to the upcoming match day (MD): MD - 4, MD - 3, MD - 2, and MD - 1. Contents on these days were standardized according to a weekly periodization model followed by the coaching staff. Differences between training days were analyzed using a linear mixed-effects model. All training days were significantly different from each other across multiple variables. ACCDEC values were highest on MD - 4 (147.5 [13.0] ACCDEC count), and all distance variables were highest on MD - 3. All measures of training load were significantly reduced from MD - 3 to MD - 2 (effect size [ES] = 1.0-4.1) and from MD - 2 to MD - 1 (ES = 1.6-4.3). A significant negative effect across the season was observed for session rating of perceived exertion-load and ACCDEC (ES = 0.8-2.1). These results provide evidence that elite female football teams can be successful in differentiating training load between training days when implementing a weekly periodization approach.


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