Latest research in football - week 12 - 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 The Development of a Return to Performance Pathway Involving A Professional Soccer Player Returning From A Multi-Structural Knee Injury: A Case Report

Reference: Int J Sports Phys Ther. 2023 Apr 2;18(2):450-466. doi: 10.26603/001c.73317. eCollection 2023.

Authors: Andrew Mitchell, Ollie Waite, Craig Holding, Matt Greig

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Summary: This case report describes a male professional soccer player returning to match play (English Championship League) following a medial meniscectomy that occurred during the course of rehabilitation after Anterior Cruciate Ligament (ACL) reconstruction. The player underwent a medial meniscectomy eight months into an ACL rehabilitation program and following 10 weeks of rehabilitation successfully returned to competitive first team match play. This report outlines description of the pathology, the rehabilitation progressions, and the sports specific performance requirements of the player as they progressed through the return to performance pathway (RTP). The RTP pathway included nine distinct phases with evidenced based criteria required to exit each phase. The first five phases were indoor as the player progressed from the medial meniscectomy, through the rehabilitation pathways to the "gym exit Phase". The gym exit Phase was assessed with multiple criteria: a) capacity; b) strength; c) isokinetic dynamometry (IKD); d) hop test battery; e) force plate jumps; and f) supine isometric hamstring rate of force (RFD) development qualities to evaluate the players readiness to start sport specific rehabilitation. The last four phases of the RTP pathway are designed to regain the maximal physical capabilities (plyometric and explosive qualities) in the gym and included the retraining of on-field sport specific qualities utilizing the 'control-chaos continuum.' The player successfully returned to team play in the ninth and final phase of the RTP pathway. The purpose of this case report was to outline a RTP for a professional soccer player who successfully restored specific injury criteria (strength, capacity and movement quality), physical capabilities (plyometric and explosive qualities). and on-field sport specific criteria utilizing the 'control-chaos continuum.'



#2 Prevention of sports-related concussion in soccer: a comprehensive review of the literature

Reference: Ann Med Surg (Lond). 2023 Mar 24;85(3):365-373. doi: 10.1097/MS9.0000000000000268. eCollection 2023 Mar.

Authors: Rr Suzy Indharty, Andre M P Siahaan, Rosarina, Martin Susanto, Steven Tandean, Marsal Risfandi

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Summary: Concussion is a common complaint among adult and adolescent athletes around the world and poses a safety risk in competitive, recreational, and noncontact sports. It is estimated that concussions occur at a rate of 0.5 per 1000 playing hours; however, the precision of this estimate is uncertain due to variations in the interpretation and reporting of concussions. Athletes with a history of concussions are more likely to sustain additional concussions, which can result in cognitive decline, depression, and early degenerative change. In order to lessen the likelihood of future difficulties, this study compiles the research on preventing sports-related concussion in soccer and presents a summary of the findings. We performed a literature search on PubMed, EBSCO (Elton B. Stephens Company), DOAJ (Directory of Open Access Journals), and Cochrane for the past 20 years. The search strategy was using Boolean terms based on any of the search terms of sports-related-concussion, soccer, and prevention. The studies were included based on inclusion and exclusion criteria. This research identified three systematic reviews, seven literature reviews, five cross-sectional studies, one randomized controlled trial, three prospective studies, and one retrospective study. As concussion prevention measures in soccer, several strategies can be implemented, including concussion education, rule/regulation changes, proper heading technique, behavioral skills training, vision training to improve sensory and anticipation, the use of supplements to prevent severe concussion and accelerate recovery, as well as prevention in youth sports and head impact detection. Good education, good technique, good training, and a good strengthening program can be implemented to prevent concussions in soccer. To determine the relationship between prevention and concussion, however, additional research is required.



#3 Skinfold thickness variation and associations with cardiorespiratory fitness in male soccer players of different ages

Reference: Eur Rev Med Pharmacol Sci. 2023 Mar;27(6):2200-2209. doi: 10.26355/eurrev_202303_31753.

Authors: P T Nikolaidis, K Weiss, B Knechtle

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Summary: The aim of the present study was to examine skinfold thickness (SKF) distribution in youth and adult male soccer players regarding cardiorespiratory fitness (CRF) and the role of age. Participants were youth [n=83, age 16.2 (1.0) years, mean (standard deviation)] and adult male soccer players [n=121, 23.2 (4.3) years], who were tested for SKF on 10 anatomical sites and Conconi test was used to assess velocity at maximal oxygen uptake (vVO2max). A between-within-subjects analysis of variance revealed a small interaction between the anatomical site and age group on SKF (p=0.006, η2=0.022), where adolescents had larger cheek (+0.7 mm; p=0.022; 95% confidence intervals - CI - 0.1, 1.3), triceps (+0.9 mm; p=0.017; 95% CI 0.2, 1.6) and calf (+0.9 mm; p=0.014; 95% CI 0.2, 1.5) SKF, while adults had larger chin (+0.5 mm; p=0.007; 95% CI 0.1, 0.8) SKF, and no difference was observed for the rest of the anatomical sites. No difference between adolescent and adult age groups was observed in average SKF (SKFavg) [9.0 (2.7) vs. 9.1 (2.5) mm; difference -0.1 mm; 95% CI, -0.8, 0.6; p=0.738]. Compared to adults, adolescents had a lower SKF coefficient of variation (SKFcv) [0.34 (0.10) vs. 0.37 (0.09); difference-0.03; 95% CI, -0.06, -0.01; p=0.020] and subscapular-to-triceps ration (STR) [1.08 (0.28) vs. 1.29 (0.37); difference-0.21; 95% CI, -0.31, -0.12; p<0.001]. The largest Pearson moment correlation coefficient between vVO2max and SKF was shown in the subscapular (r=-0.411; 95% CI, -0.537, -0.284; p<0.001) and the smallest in the patellar anatomical site (r=-0.221; 95% CI, -0.356, -0.085; p=0.002). In addition, vVO2max correlated moderately with SKFavg (r=-0.390; 95% CI, -0.517, -0.262; p<0.001) and SKFcv (r=-0.334; 95% CI, -0.464, -0.203; p<0.001). In summary, CRF was related to the thickness of specific SKF and the magnitude of thickness variation by the anatomical site (i.e., the smaller the variation, the better the CRF). Considering the relevance of specific SKF for CRF, their further use would be recommended for monitoring physical fitness in soccer players.



#4 Effects of a Short-Term Detraining Period on the Strength Deficit and Functional Performance of Highly Trained Soccer Players

Reference: J Strength Cond Res. 2023 Apr 3. doi: 10.1519/JSC.0000000000004496. Online ahead of print.

Authors: Irineu Loturco, Rafael Grazioli, Filipe Veeck, Fabio Y Nakamura, Martinho Inácio, Pedro Schons, Artur Preissler, Ronei S Pinto, Lucas A Pereira, Michael R McGuigan, Eduardo L Cadore

Summary: The aim of this study was to examine the effects of a 4-week detraining period on the neuromuscular performance of highly trained soccer players. Pre and post detraining, 18 adult soccer players (age: 27 ± 4.9 years; height: 180.2 ± 7.1 cm; body mass [BM]: 78.9 ± 7.6 kg) performed vertical jumps, 20-m linear sprints, curve sprint and change of direction speed tests, and a progressive loading test in the half-squat exercise with loads corresponding to 50, 100, and 150% of the players' BM to assess the peak-force (PF), mean power (MP), and strength-deficit (SDef). Pre and post differences in the variables of interest were analyzed using paired t-tests and effect sizes (ES). No significant changes were detected for vertical jumping height and sprint times. Higher PF at 50 and 100% BM and lower SDef were shown when comparing pre- and postassessments (ES = 0.66, 0.68, 0.55; p = 0.018, 0.016, and 0.046, respectively). The MP at 50 and 100% BM increased significantly after the detraining phase (ES = 0.56, 0.82; p = 0.049 and 0.007, respectively). The results indicate that these athletes were able to maintain and achieve satisfactory levels of performance after a short period of training cessation. Interestingly, some strength- and power-derived parameters improved significantly after short-term detraining, which may have important implications for training programs aimed at maximizing speed and power performance. It is recommended that coaches test their players not only at the beginning but also at the end of the season, to better evaluate variations in performance and thus create more efficient and tailored training strategies.



#5 Effects of FIFA 11 + warm-up program on kinematics and proprioception in adolescent soccer players: a parallelgroup randomized control trial

Reference: Sci Rep. 2023 Apr 4;13(1):5527. doi: 10.1038/s41598-023-32774-3.

Authors: Mohammadreza Seyedi, Mostafa Zarei, Abdolhamid Daneshjoo, Reza Rajabi, Elham Shirzad, Esmaeil Mozafaripour, Shadan Mohammadpour

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Summary: This study aimed to compare the effects of 8 weeks 11 + warm-up injury prevention program on kinematics and proprioception in adolescent male and female soccer players. Forty adolescent soccer players (20 males, 20 females) aged between 14-16 years old were randomly assigned into four groups. The experimental group performed the 11 + program for 8 weeks and the control group did their warm-up program. The kinematic variable in a cutting maneuver was measured using VICON motion analysis and ankle and knees' proprioception by joint position sense (JPS) was measured using a digital inclinometer. For kinematic variables only significant differences in knee valgus among females 11 + compared with female and male control groups were found (P < 0.05). Moreover, there were significant improvements in joint position sense variables in 11 + groups compared to control groups (P < 0.05). In conclusion, the 11 + program was proven to be a useful warm-up protocol in improving knee valgus and JPS among female and male adolescent soccer players. We suggest adding more training elements to the 11 + program that aimed to enhance the proper alignment of lower extremities which may consequently improve joint kinematics.



#6 Effect of interval and continuous small-sided games training on the bio-motor abilities of young soccer players: a comparative study

Reference: BMC Sports Sci Med Rehabil. 2023 Apr 4;15(1):51. doi: 10.1186/s13102-023-00664-w.

Authors: Farhad Daryanoosh, Hossein Alishavandi, Javad Nemati, Aref Basereh, Alireza Jowhari, Enayatollah Asad-Manesh, Rafael Oliveira, João Paulo Brito, Pablo Prieto-González, Tomás García-Calvo, Kayvan Khoramipour, Hadi Nobari

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Summary: The present study compared the effects of two different small-sided game (SSG) training methods, interval (ISSG) and continuous (CSSG) on the bio-motor abilities of young soccer players. Sixteen young soccer players (age: 19.5 ± 0.5 years; height: 177 ± 4.72 cm) were ranked based on the result of a running-based anaerobic sprint test (RAST) and randomly divided into two groups: CSSG (n = 8) and ISSG (n = 8). The training protocols were performed for eight weeks, three sessions per week. Participants were assessed twice (pre- and post-intervention) to estimate their anaerobic capacity with the RAST, aerobic capacity with Yo-Yo intermittent recovery test, body fat percentage with a bioimpedance analysis, speed with a 30-meter run test, and agility with the Illinois agility test. During the training session, the rating of the perceived exertion (RPE) and heart rate (mean and maximum) were recorded to assess the training load. In general, aerobic and anaerobic capacities improved after ISSG (p < 0.05, for all). The between-group analysis with repeated measures ANOVA revealed higher values for ISSG than CSSG groups post-intervention in anaerobic power (p = 0.042, ηp2 = 0.264). In addition, the independent t-test results indicated that ISSG presented lower values of mean heart rate (p = 0.023, effect size [ES] = 0.85) and RPE (p < 0.05, ES = 0.88) than CSSG. Moreover, higher values for maximum heart rate were revealed for ISSG than for the CSSG group (p = 0.004, ES = 0.85). In conclusion, the findings of this study suggests that ISSG can lead to better improvements in anaerobic power and aerobic capacity than CSSG. Additionally, the ISSG led to a lower mean heart rate and RPE than the CSSG. Therefore, coaches and trainers may want to consider incorporating ISSG into their training programs for young soccer players to enhance their bio-motor abilities.



#7 Ecological and Specific Evidence-Based Safe Return To Play After Anterior Cruciate Ligament Reconstruction In Soccer Players: A New International Paradigm

Reference: Int J Sports Phys Ther. 2023 Apr 2;18(2):526-540. doi: 10.26603/001c.73031. eCollection 2023.

Authors: Florian Forelli, Nicolas Le Coroller, Maxime Gaspar, Geoffrey Memain, Georgios Kakavas, Nicholas Miraglia, Patrice Marine, Pascal Maille, Timothy E Hewett, Alexandre Jm Rambaud

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Summary: Existing return to play (RTP) assessments have not demonstrated the ability to decrease risk of subsequent anterior cruciate ligament (ACL) injury after reconstruction (ACLR). RTP criteria are standardized and do not simulate the physical and cognitive activity required by the practice of sport. Most RTP criteria do not include an ecological approach. There are scientific algorithms as the "5 factor maximum model" that can identify risk profiles and help reduce the risk of a second anterior cruciate ligament injury. Nevertheless, these algorithms remain too standardized and do not include the situations experienced in games by soccer players. This is why it is important to integrate ecological situations specific to the environment of soccer players in order to evaluate players under conditions closest to their sporting activity, especially with high cognitive load. One should identify high risk players under two conditions: Clinical analyses commonly include assessments such as isokinetic testing, functional tests (hop tests, vertical force-velocity, profile), running, clinical assessments (range of motion and graft laxity), proprioception and balance (Star Excursion Balance Test modified, Y-Balance, stabilometry) and psychological parameters (kinesophobia, quality of life and fear of re-injury). Field testing usually includes game simulation, evaluation under dual-task conditions, fatigue and workload analysis, deceleration, timed-agility-test and horizontal force-velocity profiles. Although it seems important to evaluate strength, psychological variables and aerobic and anaerobic capacities, evaluation of neuromotor control in standard and ecological situations may be helpful for reducing the risk of injury after ACLR. This proposal for RTP testing after ACLR is supported by the scientific literature and attempts to approximate the physical and cognitive loads during a soccer match. Future scientific investigation will be required to demonstrate the validity of this approach.



#8 Expected goals in football: Improving model performance and demonstrating value

Reference: PLoS One. 2023 Apr 5;18(4):e0282295. doi: 10.1371/journal.pone.0282295. eCollection 2023.

Authors: James Mead, Anthony O'Hare, Paul McMenemy

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Summary: Recently, football has seen the creation of various novel, ubiquitous metrics used throughout clubs' analytics departments. These can influence many of their day-to-day operations ranging from financial decisions on player transfers, to evaluation of team performance. At the forefront of this scientific movement is the metric expected goals, a measure which allows analysts to quantify how likely a given shot is to result in a goal however, xG models have not until this point considered using important features, e.g., player/team ability and psychological effects, and is not widely trusted by everyone in the wider football community. This study aims to solve both these issues through the implementation of machine learning techniques by, modelling expected goals values using previously untested features and comparing the predictive ability of traditional statistics against this newly developed metric. Error values from the expected goals models built in this work were shown to be competitive with optimal values from other papers, and some of the features added in this study were revealed to have a significant impact on expected goals model outputs. Secondly, not only was expected goals found to be a superior predictor of a football team's future success when compared to traditional statistics, but also our results outperformed those collected from an industry leader in the same area.



#9 Effects of walking football on adherence, safety, quality of life and physical fitness in patients with prostate cancer: Findings from the PROSTATA_MOVE randomized controlled trial

Reference: Front Oncol. 2023 Mar 21;13:1129028. doi: 10.3389/fonc.2023.1129028. eCollection 2023.

Authors: Andreia Capela, Pedro Antunes, César André Coelho, Catarina Laranjeiro Garcia, Sandra Custódio, Rui Amorim, Telma Costa, Eduardo Vilela, Madalena Teixeira, Anabela Amarelo, Joana Silva, Ana Joaquim, Sofia Viamonte, João Brito, Alberto J Alves

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Summary: The aim was to analyze the feasibility and impact of a walking football (WF) program on quality of life (QoL), cardiorespiratory fitness (CRF), muscle strength, and balance program in men with prostate cancer under androgen deprivation therapy (ADT). Fifty patients with prostate cancer (stages IIb-IVb) under ADT were randomized to a 16-week WF program plus usual care (n=25) or usual care control group (n=25). The WF program consisted of three 90-minute sessions per week. Recruitment, withdrawal, adherence, enjoyment rate, and safety of the intervention were recorded throughout the study. Cardiorespiratory fitness was assessed before and after the interventions, while handgrip strength, lower limb muscle strength, static balance, and QoL were assessed before, during (week 8), and after (week 16) the interventions. Adverse events during sessions were also recorded. The WF group showed high levels of adherence (81.6 ± 15.9%) and enjoyment rate (4.5 ± 0.5 out of 5 points). In the intention-to-treat analysis, the WF group showed an improvement in chair sit-to-stand (p=0.035) compared to the control group. Within-group comparisons showed that handgrip strength in the dominant upper limb (p=0.024), maximal isometric muscle strength in the non-dominant lower limb (p=0.006), and balance in the dominant limb (p=0.009) improved over time in the WF group but not in the usual care group. The results obtained from the per-protocol analysis indicate that CRF improved significantly in the WF group as compared to the control group (p=0.035). Within-group analysis revealed that CRF (p=0.036), muscle strength in dominant (p=0.006) and non-dominant (p=0.001) lower limbs, and balance in the non-dominant lower limb (p=0.023) improved after 16 weeks of WF, but not in the control group. One major traumatic injury (muscle tear) was reported with a complete recovery before the end of the intervention. This study suggests that WF is feasible, safe, and enjoyable in patients with prostate cancer under hormonal therapy. Furthermore, patients who adhere to the WF program can expect cardiorespiratory fitness, muscle strength, and balance improvements.



#10 Are Football Players More Prone to Muscle Injury after COVID-19 Infection? The "Italian Injury Study" during the Serie a Championship

Reference: Int J Environ Res Public Health. 2023 Mar 15;20(6):5182. doi: 10.3390/ijerph20065182.

Authors: Alessandro Corsini, Andrea Bisciotti, Raffaele Canonico, Andrea Causarano, Riccardo Del Vescovo, Pierluigi Gatto, Paolo Gola, Massimo Iera, Stefano Mazzoni, Paolo Minafra, Gianni Nanni, Giulio Pasta, Ivo Pulcini, Stefano Salvatori, Marco Scorcu, Luca Stefanini, Fabio Tenore, Stefano Palermi, Maurizio Casasco, Stefano Calza

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Summary: Football was the first sport to resume competitions after the coronavirus disease 2019 (COVID-19) lockdown and promptly the hypothesis was raised of a potential relationship between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and musculoskeletal injuries in athletes. This study aimed to confirm the association between SARS-CoV-2 infection and muscle strain injury in a large population of elite football players and to investigate if the COVID-19 severity level could affect the risk of injury. A retrospective cohort study involving 15 Italian professional male football teams was performed during the Italian Serie A 2020-2021 season. Injuries and SARS-CoV-2 positivity data were collected by team doctors through an online database. Of the 433 included players, we observed 173 SARS-CoV-2 infections and 332 indirect muscle strains. COVID-19 episodes mostly belonged to severity level I and II. The injury risk significantly increased after a COVID-19 event, by 36% (HR = 1.36, CI95% 1.05; 1.77, p-value = 0.02). The injury burden demonstrated an 86% increase (ratio = 1.86, CI95% 1.21; 2.86, p-value = 0.005) in the COVID-19 severity level II/III versus players without a previous SARS-CoV-2 infection, while level I (asymptomatic) patients showed a similar average burden (ratio = 0.92, CI95% 0.54; 1.58, p-value = 0.77). A significantly higher proportion of muscle-tendon junction injuries (40.6% vs. 27.1%, difference = 13.5%, CI95% 0.002%; 26.9%, p-value = 0.047) was found when comparing level II/III versus Non-COVID-19. This study confirms the correlation between SARS-CoV-2 infection and indirect muscle injuries and highlights how the severity of the infection would represent an additional risk factor.



#11 Association between ACTN3 R577x and the physical performance of Chinese 13 to 15-year-old elite and sub-elite football players at different positions

Reference: Front Genet. 2023 Mar 10;14:1038075. doi: 10.3389/fgene.2023.1038075. eCollection 2023.

Authors: Shidong Yang, Wentao Lin, Mengmeng Jia, Haichun Chen

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Summary: The purpose of this study was to investigate the prevalence of ACTN3 polymorphisms in Chinese elite and sub-elite football players aged 13-15 years at different positions. Specifically we explored whether ACTN3 genotypes were linked with athletic performance of elite and sub-elite players at different positions. The RR genotype frequency of elite defenders (p = 0.018) and midfielders (p = 0.008) was significantly higher than that of sub-elite XX genotype in elite players. Furthermore, the R allele frequency of elite defenders (p = 0.003) and midfielders (p = 0.008) was significantly higher than that of sub-elite players. In all subjects, RR players performed faster and exhibited more explosive power than RX or XX players. RR, RX and XX elite players' 20 m/30 m sprint, 5 × 25-m repeated sprint ability (5 × 25 m RSA), and standing long jump were stronger than sub-elite players, but there was no significant different in aerobic endurance between elite and sub-elite players at different positions. In conclusion, there were significant differences in ACTN3 genotypes and alleles between elite and sub-elite players at different positions, and the RR genotype was significantly associated with power-related athletic performance in Chinese youth football players.



#12 "We're All the Same and We Love Football." Experiences of Players and Facilitators Regarding a Collaborative, Inclusive Football Program Between Academy and Special Olympics Footballers

Reference: Adapt Phys Activ Q. 2023 Mar 25;1-20. doi: 10.1123/apaq.2022-0139. Online ahead of print.

Authors: Melissa A Fothergill, Danna Baik, Hannah M Slater, Pamela L Graham

Summary: This study provides insight into an inclusive program between Special Olympics (SO) and academy football (soccer) players in the United Kingdom from the perspectives of players and facilitators. Qualitative focus groups were conducted across 30 participants (six facilitators, 14 Premier League academy players, and 10 SO players). Focus groups compared stakeholders' experiences of participating in a season-long inclusive football program. Three overarching higher order themes were generated, which highlighted positive outcomes from taking part. SO players provided endorsement for developing friendships and improving football skills, whereas academy players cited the positive impact that SO players had on their mood and motivation. Facilitators reflected on positive player outcomes and subsequent accomplishments. Overall, the findings indicated that this shared experience had psychosocial and football-specific benefits for everyone who participated. Facilitators indicated that these benefits could transition into everyday life but noted that there needs to be further considerations for future programs.



#13 Comparison of echocardiographic parameters of amputee football players with active football players and sedentary individuals

Reference: BMC Sports Sci Med Rehabil. 2023 Mar 24;15(1):41. doi: 10.1186/s13102-023-00651-1.

Authors: Ahmet Kurtoğlu, Ertuğrul Kurtoğlu, Nurettin Konar, Bekir Çar, Özgür Eken, Pablo Prieto-González, Hadi Nobari

Summary: The purpose of this study is to compare the echocardiographic (ECHO) parameters of amputee football players (AF) with those of athletes without a disability (football players) (FP), and sedentary individuals (SI). A total of 37 male participants (nAF = 12, nFP = 12, nSI = 13) were included in the study. All participants underwent a transthoracic echocardiographic examination. Aortic diameter in systole (ADs), aortic diameter in diastole (ADd), isovolumic contraction time (IVCT), isovolumic relaxation time (IVRT), left ventricular ejection fraction (LVEF), early (E) and late (A) wave velocities, myocardial systolic (S), early diastolic (E'), and late diastolic (A') myocardial rates, interventricular septal thickness (IVS), left ventricular end-diastolic diameter (LVDd) and left ventricular end-systole diameter (LVDs), left ventricular posterior wall thickness (LVPWd), left atrial diameter (LAD), and ascending aortic diameter (AAD) were measured. LVDd, E' were lower in AF than in FP. In contrast, LVDs, LVPWd, and A wave were higher in AF than in FP. When AF and SI groups were compared, ADs, LVPWd, A wave, IVRT, and S wave were higher in AF than in SI. ANOVA test showed a statistically significant difference between groups in LVPWd, A-wave, and E' wave. TTE data indicate that some parameters in AF differ from those observed in healthy individuals. The smaller LVEED diameter and higher PWT were found in AF. Although within normal limits, some ECHO parameters in the AF group differed from those without disability. Future studies should further investigate these differences using different and detailed measurement methods.



#14 Dictating play to the left wing: Does soccer make you more Democratic?

Reference: Front Sports Act Living. 2023 Mar 23;5:1004695. doi: 10.3389/fspor.2023.1004695. eCollection 2023.

Authors: Johan M Rewilak

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Summary: There is a correlation between soccer's popularity and states that traditionally vote Democrat in US elections. This has led to claims that where democrats lead, soccer follows. Yet, this relationship may not be entirely stable, as soccer may stimulate the Democratic party vote through its multicultural elements. Using the 1994 World Cup as a plausibly exogenous shock that positioned US soccer, we investigate whether US states that hosted the tournament increased their Democratic vote in future Presidential elections. A two-way fixed-effects estimator and a dynamic difference-in-difference estimator shows that if a US state was a 1994 World Cup host, it increased its Democratic vote share. However, when examining Major League Soccer franchises, this relationship breaks down but recovers when investigating the women's World Cup in 1999 and 2003. As the swing states of Florida and Georgia are hosting 2026 World Cup matches, the findings may hold key insights for the 2028 Presidential election.



#14 Soccer Players' Sleep Quality and Training Load Were Affected by the COVID-19 Lockdown: An International Survey

Reference: Int J Sports Physiol Perform. 2023 Apr 8;1-11. doi: 10.1123/ijspp.2022-0187. Online ahead of print.

Authors: Mohamed Romdhani, Jad Adrian Washif, Lee Taylor, Karim Chamari

Summary: The effect of the 2020 COVID-19 lockdown on athlete sleep and training behavior is documented, albeit without a worldwide soccer-specific focus. Soccer (football) players (N = 1639; 30 countries; age 22.5 [5.7] y; 81% ≤25 y; 56% male; 30% elite; 66% Muslim) answered a retrospective, cross-sectional questionnaire related to their behavioral habits before and during COVID-19 lockdown (survey period July to September 2020), including (1) Pittsburgh Sleep Quality Index PSQI, (2) Insomnia Severity Index (ISI), (3) bespoke questions about training behaviors, and (4) Muslim player focused sleep and training behavior questions. During lockdown (compared to prelockdown), PSQI (P < .001; moderate effect size [ES]) and ISI (P < .001; moderate ES) scores were higher in the overall sample and in elite versus nonelite (PSQI: P < .05; small ES and ISI: P < .001; small ES), >25 years versus ≤25 years (PSQI: P < .01; small ES and ISI: P < .001; moderate ES), females versus males (PSQI: P < .001; small ES), <1 month versus >1 month lockdown (PSQI: P < .05; small ES and ISI: P < .05; small ES), and players maintaining versus reducing training intensity (PSQI: P < .001; moderate ES and ISI: P < .001; small ES). Muslim players (41%) reported unfavorable sleep and/or training behaviors during Ramadan in lockdown compared to lockdown outside of Ramadan. Specific subgroups appear more vulnerable to lockdown effects, with training-intensity maintenance moderating negative effects relative to sleep. Policy and support (respectful of subgroup nuances) during lockdown-like challenges that facilitate training (including intensity) appear prudent, given their favorable relationship with sleep, mental health, and physical health, in the present data and elsewhere.



#15 Effects of Ramadan fasting on the diurnal variations of physical and cognitive performances at rest and after exercise in professional football players

References: Front Psychol. 2023 Mar 28;14:1148845. doi: 10.3389/fpsyg.2023.1148845. eCollection 2023.

Authors: Syrine Khemila, Mohamed Romdhani, Mohamed Amine Farjallah, Rihab Abid, Emna Bentouati, Mohamed Abdelkader Souissi, Salma Abedelmalek, Sergio Garbarino, Nizar Souissi

Summary: Ramadan fasting (RF) is characterized by daily abstinence from food and fluid intake from dawn to sunset. The understanding of the Ramadan effects on the diurnal variations of athletic and cognitive performance is crucial for practitioners, coach and researchers to prepare sport events and optimize performance. The aim of the present study was to reveal the effects of RF on the diurnal variation of physical and cognitive performances at rest and after exercise. In a randomized order, 11 male football players (age: 19.27 ± 0.9; height: 1.79 ± 0.04 cm; body mass: 70.49 ± 3.97 kg; BMI: 21.81 ± 1.59 kg/m2) completed a 30-s Wingate test [i.e., mean (MP) and peak powers (PP)] at 07:00, 17:00, and 21:00 h on five occasions: 1 week before Ramadan (BR); the second (R2); the third (R3); the fourth (R4) week of Ramadan; and 2 weeks after Ramadan (AR), with an in-between recovery period of ≥72 h. Simple (SRT) and choice (CRT) reaction times, mental rotation test (MRT) and selective attention (SA) test were measured before and after Wingate test. Rating of perceived exertion (RPE), body composition, dietary intake, profile of mood states (POMS) and Pittsburgh Sleep Quality Index (PSQI) were assessed over the five periods. Compared to BR, RF decreased MP at 17:00 h (p < 0.05, d = 1.18; p < 0.001, d = 2.21, respectively) and PP at 17:00 h (p < 0.05, d = 1.14; p < 0.001, d = 1.77, respectively) and 21:00 h (p < 0.01, d = 1.30; p < 0.001, d = 2.05, respectively) at R3 and R4. SRT (p < 0.001,d = 1.15; d = 1.32, respectively), number of correct answers (MRTE; p < 0.05, d = 1.27; d = 1.38, respectively) and SA (p < 0.01, d = 1.32; d = 1.64, respectively) increased during R2 and R3 in the evening before exercise compared to BR. Short term maximal exercise enhanced SRT (p < 0.01, d = 1.15; p < 0.001, d = 1.35, respectively), MRTE (p < 0.001, d = 2.01; d = 2.75 respectively) and SA (p < 0.05, d = 0.68; d = 1.18, respectively) during R2 and R3 in the evening. In comparison to BR, sleep latency and sleep duration increased during R3 (p < 0.001, d = 1.29; d = 1.74, respectively) and R4 (p < 0.001, d = 1.78; d = 2.19, respectively) and sleep quality increased in R2, R3 and R4 (p < 0.01, d = 1.60; p < 0.001, d = 1.93; d = 2.03, respectively). During RF, anaerobic and cognitive performances were unaffected in the morning but were impaired in the afternoon and evening. Short-term maximal exercise mitigates the negative effects of fasting on cognitive performance. Maximal exercise could thus partially counteract the effect of fasting on cognitive function.



#16 Osteomyelitis of the Pubis Treated by Masquelet Technique in a Football Player: A Case Report

Reference: J Orthop Case Rep. 2022 Dec;12(12):39-42. doi: 10.13107/jocr.2022.v12.i12.3456.

Authors: Hitomi Kitamura, Tomoaki Fukui, Keisuke Oe, Takehiko Matsushita, Ryosuke Kuroda, Takahiro Niikura

Summary: Osteomyelitis pubis is a rare disease that presents with fever, pubic or hip pain, pain during hip movement, and claudication to avoid pain. It most frequently affects young athletes involved in sports that require twisting and cutting, but its exact cause is unknown and no definite treatment has been established. We report a case of pubic osteomyelitis in a young football player who was treated using the Masquelet technique and antibiotics with a good clinical course. A 22-year-old male football player in a national-level university club team visited a nearby clinic complaining of high fever and mild pain in his bilateral hip joints. As a result of examination, we diagnosed osteomyelitis pubis and reconstructed the pubic symphysis by the Masquelet technique. In this case, the joint-like structure of the pubic symphysis was successfully reconstructed, and the patient was able to continue playing the sport. Three years and 3 months after surgery, he had no limitation of bilateral hip joint range of motion and did not display any symptoms while playing football. Masquelet technique could be a novel surgical method for managing osteomyelitis pubis, even in athletes.



#16 A framework of interpretable match results prediction in football with FIFA ratings and team formation

Reference: PLoS One. 2023 Apr 13;18(4):e0284318. doi: 10.1371/journal.pone.0284318. eCollection 2023.

Authors: Calvin C K Yeung, Rory Bunker, Keisuke Fujii

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Summary: While forecasting football match results has long been a popular topic, a practical model for football participants, such as coaches and players, has not been considered in great detail. In this study, we propose a generalized and interpretable machine learning model framework that only requires coaches' decisions and player quality features for forecasting. By further allowing the model to embed historical match statistics, features that consist of significant information, during the training process the model was practical and achieved both high performance and interpretability. Using five years of data (over 1,700 matches) from the English Premier League, our results show that our model was able to achieve high performance with an F1-score of 0.47, compared to the baseline betting odds prediction, which had an F1-score of 0.39. Moreover, our framework allows football teams to adapt for tactical decision-making, strength and weakness identification, formation and player selection, and transfer target validation. The framework in this study would have proven the feasibility of building a practical match result forecast framework and may serve to inspire future studies.



#17 Suggested improvements to the 11+ as identified by coaches, players, strength and conditioning staff and medical staff in New Zealand Football

Reference: BMJ Open Sport Exerc Med. 2023 Apr 4;9(2):e001463. doi: 10.1136/bmjsem-2022-001463. eCollection 2023.

Authors: Colleen Winstanley, Duncan Reid, Mark L Fulcher

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Summary: The aim of this study was to investigate the experience with the 11+, attitudes towards injury prevention, and potential improvements to the 11+ and the delivery of injury prevention strategies within football. A qualitative study design was used to investigate the views of four stakeholder groups (players, coaches, strength and conditioning staff and clinicians). Twenty-two adults participated (nine women; median age 35.5 years). Participants were purposively recruited and were based in New Zealand. They represented various levels of football, including different genders, ages and levels of play. Focus group interviews were conducted, which were recorded, transcribed and subject to thematic analysis. Four key themes were identified: understanding of the 11+ injury prevention warm-up, content of an ideal injury prevention programme, structure of the programme and education, adherence and dissemination. The study found that while participants appeared to have good awareness of the existing 11+ programme and an interest in injury prevention, adherence and enthusiasm towards the programme was limited. Participants highlighted a number of elements that may help shape the development of a new injury prevention strategy, including a desire to retain many of the elements of the 11+ and to have a proven programme. Participants wanted greater variety, more football-specific elements and to implement a new strategy throughout a session, rather than being seen as a stand-alone warm-up. Whether the intervention should also include strength-based exercises, or whether this should be promoted outside of a football training session, was less certain.



#18 "I hardly have a problem […] I have my period quite rarely too": Female football players' and their coaches' perceptions of barriers to communication on menstrual cycle

Reference: Front Sports Act Living. 2023 Mar 23;5:1127207. doi: 10.3389/fspor.2023.1127207. eCollection 2023.

Authors: Max Bergström, Malene Rosvold, Stig Arve Sæther

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Summary: Symptoms related to the menstrual cycle (MC) affect the performance level and health of female athletes in various ways. Previous research has reported MC symptoms such as pain, mood disturbance, reduced coordination and competition distraction as well as diminished performance levels and an increased injury risk among female elite athletes. Despite this, the coach-athlete communication related to the female hormonal cycle is limited. The aim of the present study was to explore the perceptions of MC communication in a group of junior elite football players and their male coaches in a case study of one youth football team in a specific club in Norway. The study used a qualitative approach with semi-structured interviews. In total, 8 female junior elite players (aged 16-20) from a Norwegian football team and 2 of their male coaches participated in the study. The data analysis revealed two main communication barriers: 1. interpersonal barriers (e.g., false assumptions about the coach/athletes and social discomfort) and 2. knowledge barriers (e.g., unaware/perceptions of insufficient knowledge levels). As the players seemed to be unaware of their insufficient MC knowledge (e.g., failed to see a connection between the MC and their health and performance level), the coaches perceived their knowledge as insufficient and coped mainly by outsourcing MC communication to female staff and apps. Hence, the MC communication was hindered by both the athletes and the coaches (e.g., mutual avoidance). In line with previous research, this study supports that there is a need for developing effective strategies to overcome the interpersonal barriers and knowledge gaps.



#19 The Importance of Crowd Support and Team Quality to Home Advantage in Brazilian Soccer League First Division

Reference: Percept Mot Skills. 2023 Apr 10;315125231169876. doi: 10.1177/00315125231169876.

Authors: Rodolfo A Dellagrana, Renan F H Nunes, Rodrigo L P Silva

Summary: Our aims in the present study were to analyze home advantage (HA) and number of goals scored in consideration of the presence or absence of crowd support and the influence of team quality during the last 11 seasons of the Brazilian Soccer League first division. We analyzed data from 4162 matches played in the Brazilian Soccer League in seasons 2012-2022 (3563 matches with an audience and 599 matches without an audience). We calculated HA by comparing the number of points won at home as a percentage of the total number of points gained, and we also recorded the number of goals scored by home and away teams. For analyses, we divided the teams based on home and away matches, with and without crowds, and we classified teams into three ability groups, based on the points scoring percentage of the team at the end of the season. There was a HA in all seasons analyzed (i.e., home teams won more than 50% of the total points won at home); but in matches in empty stadiums, the HA was reduced significantly, compared to matches with crowd support (66.6% with crowd vs. 57.2% without crowd, p < 0.05). The number of goals in all seasons was higher for home teams than for away teams; however, away teams scored more goals in empty stadiums than in stadiums with crowd support (p < 0.05). The HA was greater in matches with crowd support than in matches without crowd support (p < 0.01), independent of the team's ability level; but, top teams scored more goals than weaker teams (p < 0.01). In conclusion, in the Brazilian Soccer League, the HA and number of goals scored were affected by the presence or absent of an audience in the stadiums. While top teams scored more goals than weaker teams, the HA was lower without than with crowds, independent of team quality.



#20 Preparatory knee flexion movement facilitates faster sideways jumping execution in male collegiate soccer goalkeepers

Reference: Sports Biomech. 2023 Apr 10;1-15. doi: 10.1080/14763141.2023.2197876. Online ahead of print.

Authors: Masahiro Fujimoto, Masaomi Sato, Akinori Nagano, Mark W Rogers, Tadao Isaka

Summary: Preparatory lower-limb loading conditions may affect the jump-to-reach performance of soccer goalkeepers. This study investigated the effect of pre-jump lower-limb loading/unloading during bilateral knee flexion-extension movements on sideways jump-to-reach performance in 18 male collegiate soccer goalkeepers. Participants performed the two-choice (high and low targets) reaction-time single-leg jump-to-reach task under two conditions: without preparatory movements (no-prep) and with continuous alternating knee extension and flexion movements (prep). The 'go' cue was provided with different preparatory loading conditions during the pre-jump knee extension and flexion phases. Performance was assessed using three-dimensional kinematic data and ground reaction forces. A significant main effect of the preparatory condition was observed for the jump take-off time. Pairwise comparisons revealed that the jump take-off time was 3.4-4.4% faster when initiated during the knee flexion phase than the no-prep condition and the extension phase (p ≤ .028). Increasing lower-limb loading and downward body movement with knee flexion appeared to facilitate effective loading to take-off to reach the high target and faster downward-directed take-off to reach the low target, respectively. Pre-jump knee flexion movement could be utilised by soccer goalkeepers to facilitate faster take-off to maximise their chances of saving shots within the reach of single-leg side-jumping.



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