Latest research in football - week 31 - 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 Low-load strength resistance training with blood flow restriction compared with high-load strength resistance training on performance of professional soccer players: a randomized controlled trial

Reference: J Sports Med Phys Fitness.2023 Aug 3.  doi: 10.23736/S0022-4707.23.14974-7. Online ahead of print.

Authors: Christian Castilla-López, Natalia Romero-Franco

Summary: The aim of this study is to evaluate the effectiveness of low-load blood flow restriction strength resistance training (LL-BFR) compared to high load strength resistance training (HL) on performance of professional soccer players. Eighteen male players from National Soccer Professional League were randomly allocated into two groups: LL-BFR, who performed a 6-weeks strength training program with low load (20-35% of one-repetition maximum-[1RM]), or HL, who performed a 6-week resistance training program with high load (70-85% 1RM). Before and after, thigh girth, vertical jump, lower limb strength, vertical force-velocity profile (F-v), and 30-m sprint were evaluated. After the training program, both LL-BFR and HL induced significant increases compared to baseline in thigh girth (+3.3% for LL-BFR and +3.1% for HL) and maximal velocity during sprinting (+6.0 and +6.2%, respectively), without between-group differences. In reference to FV, only HL players improved imbalance (-54.4%), maximal theoretical force production (+10.4%) and decreased extension velocity (-20.5%) compared to baseline, without between-group differences. Only LL-BFR induced increases in maximum voluntary contraction of left hamstring compared to baseline (+13.8%), without between-group differences. No differences were shown for the rest of variables (P>0.05). Although LL-BFR may increase muscle circumference and sprint ability, these results are similar to those induced with HL in male professional soccer. In terms of F-v, only HL induced improvements, but these changes were not greater than those observed after LL-BFR.



#2 Blink-related EEG oscillations are neurophysiological indicators of subconcussive head impacts in female soccer players: a preliminary study

Reference: Front Hum Neurosci. 2023 Jul 19;17:1208498. doi: 10.3389/fnhum.2023.1208498. eCollection 2023.

Authors: Sahar Sattari, Rebecca Kenny, Careesa Chang Liu, Sujoy Ghosh Hajra, Guy A Dumont, Naznin Virji-Babul

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Summary: Repetitive subconcussive head impacts can lead to subtle neural changes and functional consequences on brain health. However, the objective assessment of these changes remains limited. Resting state blink-related oscillations (BROs), recently discovered neurological responses following spontaneous blinking, are explored in this study to evaluate changes in BRO responses in subconcussive head impacts. We collected 5-min resting-state electroencephalography (EEG) data from two cohorts of collegiate athletes who were engaged in contact sports (SC) or non-contact sports (HC). Video recordings of all on-field activities were conducted to determine the number of head impacts during games and practices in the SC group. In both groups, we were able to detect a BRO response. Following one season of games and practice, we found a strong association between the number of head impacts sustained by the SC group and increases in delta and beta spectral power post-blink. There was also a significant difference between the two groups in the morphology of BRO responses, including decreased peak-to-peak amplitude of response over left parietal channels and differences in spectral power in delta and alpha frequency range post-blink. Our preliminary results suggest that the BRO response may be a useful biomarker for detecting subtle neural changes resulting from repetitive head impacts. The clinical utility of this biomarker will need to be validated through further research with larger sample sizes, involving both male and female participants, using a longitudinal design.



#3 Fifth metatarsal strain distribution during cutting motions in soccer

Reference: Sports Biomech. 2023 Aug 2;1-17. doi: 10.1080/14763141.2023.2241839. Online ahead of print.

Authors: Yusuke Miyazaki, Rui Sugizaki, Miku Kawasaki, Takumi Nakagawa, Yasuaki Saho, Tomohiko Tateishi

Summary: The objective of this study was to determine the fifth metatarsal strain generation mechanism during cutting motions performed while playing soccer using a finite element foot model. Five collegiate soccer players performed the side-step cutting and the cross-step cutting motions to measure the three-dimensional foot kinematics, ground reaction force, and plantar pressure distribution. In addition, a finite-element model of a foot consisting of bony structures, ligaments, and skin was constructed from computed tomography images. Simulations were conducted to perform the cutting motions, using the measured foot motion and distributed load on the plantar surface as boundary conditions for the model. During the side-step cutting, the maximum principal strain on the fifth metatarsal was correlated to forefoot adduction angle during stepping out. For cross-step cutting, the maximum principal strain was correlated with plantar pressure at the distal end of the fifth metatarsal. Therefore, to prevent a fracture, it is necessary to take measures to reduce the lateral bending deformation of the forefoot while stepping out during side-step cutting and to reduce the plantar pressure on the distal end of the fifth metatarsal during cross-step cutting.



#4 SoccerNet: A Gated Recurrent Unit-based model to predict soccer match winners

Reference: PLoS One. 2023 Aug 1;18(8):e0288933. doi: 10.1371/journal.pone.0288933. eCollection 2023.

Authors: Jassim AlMulla, Mohammad Tariqul Islam, Hamada R H Al-Absi, Tanvir Alam

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Summary: Winning football matches is the major goal of all football clubs in the world. Football being the most popular game in the world, many studies have been conducted to analyze and predict match winners based on players' physical and technical performance. In this study, we analyzed the matches from the professional football league of Qatar Stars League (QSL) covering the matches held in the last ten seasons. We incorporated the highest number of professional matches from the last ten seasons covering from 2011 up to 2022 and proposed SoccerNet, a Gated Recurrent Unit (GRU)-based deep learning-based model to predict match winners with over 80% accuracy. We considered match- and player-related information captured by STATS platform in a time slot of 15 minutes. Then we analyzed players' performance at different positions on the field at different stages of the match. Our results indicated that in QSL, the defenders' role in matches is more dominant than midfielders and forwarders. Moreover, our analysis suggests that the last 15-30 minutes of match segments of the matches from QSL have a more significant impact on the match result than other match segments. To the best of our knowledge, the proposed model is the first DL-based model in predicting match winners from any professional football leagues in the Middle East and North Africa (MENA) region. We believe the results will support the coaching staff and team management for QSL in designing game strategies and improve the overall quality of performance of the players.



#5 Residual Deficits in Reactive Strength After Anterior Cruciate Ligament Reconstruction in Soccer Players

Reference: J Athl Train. 2023 May 1;58(5):423-429. doi: 10.4085/0169-20.

Authors: Paul J Read, William T Davies, Chris Bishop, Sean McAuliffe, Mathew G Wilson, Anthony N Turner

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Summary: Deficits in plyometric abilities are common after anterior cruciate ligament reconstruction (ACLR). Vertical rebound tasks may provide a targeted evaluation of knee function. The aim was to examine the utility of a vertical hop test for assessing function after ACLR and establishing factors associated with performance. Soccer players with a history of ACLR (n = 73) and matched control individuals (n = 195) participated in this study. The 10-second vertical hop test provided measures of jump height, the Reactive Strength Index (RSI), and asymmetry. We also examined possible predictors of hop performance, including single-legged vertical drop jump, isokinetic knee-extension strength, and the International Knee Documentation Committee questionnaire score. Between-limbs differences were identified only for the ACLR group, and asymmetry scores increased in those with a history of ACLR (P < .001) compared with the control group. The single-legged vertical drop jump, RSI, and knee-extension torque were significant predictors of 10-second hop height (R2 = 20.1%) and RSI (R2 = 47.1%). Vertical hop deficits were present after ACLR, even after participants completed a comprehensive rehabilitation program. This may have been due to reduced knee-extension and reactive strength. Vertical hop tests warrant inclusion as part of the return-to-sport test battery.



#6 The relationship between wellness and training and match load in professional male soccer players

Reference: PLoS One. 2023 Jul 31;18(7):e0289374. doi: 10.1371/journal.pone.0289374. eCollection 2023.

Authors: Rafael Franco Soares Oliveira, Rui Canário-Lemos, Rafael Peixoto, José Vilaça-Alves, Ryland Morgans, João Paulo Brito

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Summary: The aims of this study were to: (i) analyse the within-microcycle variations in professional soccer players; (ii) analyse the relationships between wellness and training and match load demands; (iii) analyse the relationships between match-day (MD) demands and wellness during the following day (MD+1); and (iv) analyse the relationships between MD and wellness during the day before match-play (MD-1). Thirteen professional soccer players (age: 24.85±3.13 years) were monitored daily over 16-weeks for wellness and training and match-play intensity. The daily wellness measures included fatigue, quality of sleep, muscle soreness, mood and stress using a 1-5 scale. Internal intensity was subjectively measured daily using the rating of perceived exertion (RPE) and the multiplication of RPE by session duration (s-RPE). While external intensity was quantified utilising high-speed running, sprinting, and acceleration and deceleration metrics. Data was analysed from each training session before (i.e., MD-5) or after the match (i.e., MD+1). Repeated measures ANOVA or Friedman ANOVA was used to analyse the aims (i) where Spearman correlation was applied to analyse the relationships between the aims (ii) and (iii) between sleep quality and training intensity. The main results for aim (i) showed that MD+1 presented the lowest values for wellness variables (p < 0.05). While MD-1 presented the lowest internal and external load values (for all variables), with MD presenting the highest values (p < 0.05). Regarding aim (ii), the main result showed significant large negative correlations between fatigue and s-RPE (r = -0.593; p = 0.033). Considering aim (iii), significant small to very large negative correlations were found for sleep quality, fatigue and muscle soreness with all internal and external variables (p < 0.05). Lastly, the main results for aim (iv) showed large negative correlations for fatigue and session duration; fatigue and s-RPE; muscle soreness and session duration; muscle soreness and s-RPE; and muscle soreness and decelerations (p < 0.05, for all). The main conclusions were that MD had an influence on wellness and internal and external training intensity, notably MD-1 and MD+1 were most affected. In this regard, a tendency of higher internal and external intensity on MD was associated with lower wellness measures of sleep quality, muscle soreness and fatigue on MD+1.



#7 Reliability and sensitivity to change of post-match physical performance measures in elite youth soccer players

Reference: Front Sports Act Living. 2023 Jul 13;5:1173621. doi: 10.3389/fspor.2023.1173621. eCollection 2023.

Authors: Alberto Franceschi, Mark A Robinson, Daniel Owens, Thomas Brownlee, Duccio Ferrari Bravo, Kevin Enright

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Summary: To effectively monitor post-match changes in physical performance, valid, reliable and practical measures which are sensitive to change are required. This study aimed to quantify test-retest reliability and sensitivity to change of a range of physical performance measures recorded during an isometric posterior chain (IPC) lower-limb muscle test and a countermovement jump (CMJ) test. Eighteen Italian Serie A academy soccer players performed three IPC repetitions per limb and five CMJ trials in 4 testing sessions. Test-retest reliability was evaluated between two testing sessions seven days apart using typical error of measurement, coefficient of variation and intraclass correlation coefficient. Sensitivity to change was assessed on two additional testing sessions performed before and immediately after a soccer match through Hedges' g effect size (g) and comparisons to typical error. Absolute reliability (coefficient of variations) ranged from 1.5 to 8.8%. IPC and CMJ measures demonstrated moderate to excellent relative reliability (intraclass correlation coefficients ranged from 0.70 to 0.98). A wide range of physical performance measures showed significant alterations post-match (p < 0.05; g: small to moderate). IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric forces (mean breaking force, mean deceleration force, peak force, force at zero velocity) and CMJ mean power measures had post-match changes greater than their typical variation, demonstrating acceptable sensitivity in detecting performance changes at post-match. IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric phase forces and CMJ mean power were found to be both reliable and sensitive to change, and thus may be appropriate for monitoring post-match neuromuscular performance in youth soccer population.



#8 What happens in the prefrontal cortex? Cognitive processing of novel and familiar stimuli in soccer: An exploratory fNIRS study

Reference: Eur J Sport Sci. 2023 Aug 3;1-11. doi: 10.1080/17461391.2023.2238699. Online ahead of print.

Authors: Lena F Schmaderer, Mathilda Meyer, Rüdiger Reer, Nils Schumacher

Summary: The importance of both general and sport-specific perceptual-cognitive abilities in soccer players has been investigated in several studies. Although these perceptual-cognitive skills could contribute significantly to soccer players' expertise, the underlying cortical mechanisms have not been clarified yet. Examining activity changes in the prefrontal cortex under different cognitive demands may help to better understand the underlying mechanisms of sports expertise. The aim of this study was to analyse the prefrontal activity of soccer experts during general and sport-specific cognitive tasks. For this purpose, 39 semi-professional soccer players performed four perceptual-cognitive tests, two of which assessed general cognition, the other two assessed sport-specific cognition. Since soccer is a movement-intensive sport, two tests were performed in motion. While performing cognitive tests, prefrontal activity was recorded using functional near-infrared spectroscopy (fNIRS) (NIRSport, NIRx Medical Technologies, USA). Differences of prefrontal activity in general and sport-specific cognitive tasks were analysed using paired t-tests. The results showed significant increases in prefrontal activity during general cognitive tests (novel stimuli) compared to sport-specific tests (familiar stimuli). The comparatively lower prefrontal activity change during sport-specific cognition might be due to learned automatisms of experts in this field. These results seem in line with previous findings on novel and automated cognition, "repetition suppression theory" and "neural efficiency theory". Furthermore, the different cortical processes could be caused by altered prefrontal structures of experts and might represent a decisive factor for expertise in team sports. However, further research is needed to clarify the prefrontal involvement on expertise in general and sport-specific cognition.



#9 The association between hip/groin pain and hip strength in football players: An exploratory analysis of the FORCe cohort

Reference: J Sci Med Sport. 2023 Jul 20;S1440-2440(23)00179-2. doi: 10.1016/j.jsams.2023.07.008.

Authors: C Bonello, M G King, K M Crossley, J J Heerey, M J Scholes, P Lawrenson, M A Girdwood, J L Kemp, A B Mosler, B F Mentiplay, A I Semciw

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Summary: The aim was to explore associations between peak hip strength in football players with hip/groin pain and healthy controls. Male and female sub-elite football players (soccer and Australian football) with hip/groin pain >6-month duration and players without hip/groin pain were recruited across Melbourne and Brisbane, Australia. Demographic information and two questionnaires; the Copenhagen Hip and Groin Outcome Score and the International Hip Outcome Tool 33 were collected. Hand-held dynamometry was used to measure isometric hip strength for flexion, extension, abduction, adduction, internal rotation, and external rotation. Linear mixed effects models were used to compare strength measures between groups. 190 football players with hip/groin pain (mean ± standard deviation age, 27.8 ± 6.3 years) and 64 controls (age, 27.3 ± 5.6 years) were included in this study. Of these, 291 symptomatic limbs and 128 control limbs were used for analyses. Symptomatic players had lower peak hip adduction (adjusted mean difference = -0.18: 95 % confidence interval -0.27 to -0.08, P : 0.001), external rotation (-0.06: 95 % confidence interval -0.09 to -0.02, P : 0.003), and internal rotation strength (-0.06: 95 % confidence interval -0.10 to -0.03, P : 0.001) compared to controls. A sport-specific interaction was observed for hip abduction strength. When separated by football code, abduction strength was lower in symptomatic Australian football players compared to their same sport peers (-0.20: 95 % confidence interval -0.33 to -0.06, P : 0.004), but not in symptomatic soccer players (-0.05: 95 % confidence interval -0.15 to 0.06, P : 0.382). Hip adduction, internal rotation, and external rotation strength appears lower in football players with hip/groin pain independent of sex and football code. Hip abduction strength was lower in symptomatic Australian football players but not in soccer players.



#10 Media Framing of Women's Football During the COVID-19 Pandemic

Reference: Commun Sport. 2023 Jun;11(3):592-615. doi: 10.1177/21674795211041024. Epub 2021 Dec 8.

Authors: Keith D Parry, Beth G Clarkson, Ali Bowes, Laura Grubb, David Rowe

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Summary: This article examines British media coverage of women's association football during the coronavirus (COVID-19) pandemic, to identify how the media framed the women's game and how these frames could shape the public perceptions of it. Through a database search of British-based news coverage of women's football, 100 news articles were identified in the first 6 months after the start of the pandemic. A thematic analysis was conducted, and five dominant frames were detected in the context of COVID-19: 1) financial precariousness of women's football; 2) the commercial prioritisation of men's football; 3) practical consideration of the sport (e.g., alterations to national and international competitions); 4) debating the future of women's football and 5) concern for players (e.g., welfare, uncertain working conditions). These frames depart from the past trivialisation and sexualisation of women's sport, demonstrate the increased visibility of women's football, and shift the narrative towards the elite stratum of the game. Most of this reporting was by women journalists, while men were shown to write less than women about women's football. This research advocates continued diversification of the sports journalism workforce to dissolve the hegemonic masculine culture that still largely dominates the industry.



#11 Return to Play After the Diagnosis of Reactive Arthritis in a Professional Football Player

Reference: Cureus. 2023 Jun 29;15(6):e41139. doi: 10.7759/cureus.41139. eCollection 2023 Jun.

Authors: Alexandre Fernandes, Pedro Cunha, Julio Pinto, Carlos Duarte, Alexandre Estaca, Tiago Pereira, Mónica Bettencourt, Miguel Reis E Silva, Susana Fernandes

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Summary: In professional football, most of the injuries are traumatic; however, these athletes may suffer from rheumatologic diseases, that may present as sports-related injuries. Reactive arthritis (ReA) is classified as a sub-group of the spondyloarthritis family and is relatively rare. In this article, we highlight the successful return to play (RTP) process after the ReA diagnosis in an elite football player in the Portuguese first league. The athlete was able to RTP four months and one week after the diagnosis, had no ReA recurrence nor re-injury >8 months after RTP, and is playing at an elite level.



#12 Players', Head Coaches', And Medical Personnels' Knowledge, Understandings and Perceptions of Injuries and Injury Prevention in Elite-Level Women's Football in Ireland

Reference: Sports Med Open. 2023 Jul 29;9(1):64. doi: 10.1186/s40798-023-00603-6.

Authors: Dan Horan, Seamus Kelly, Martin Hägglund, Catherine Blake, Mark Roe, Eamonn Delahunt

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Summary: To manage injuries effectively, players, head coaches, and medical personnel need to have excellent knowledge, attitudes, and behaviours in relation to the identification of risk factors for injuries, the implementation of injury prevention initiatives, as well as the implementation of effective injury management strategies. Understanding the injury context, whereby specific personal, environmental, and societal factors can influence the implementation of injury prevention initiatives and injury management strategies is critical to player welfare. To date, no qualitative research investigating the context of injuries, has been undertaken in elite-level women's football. The aim of our study was to explore the knowledge, attitudes, and behaviours of players, head coaches, and medical personnel in the Irish Women's National League (WNL) to injury prevention and injury management. We used qualitative research methods to explore the knowledge, attitudes, and behaviours of players, head coaches, and medical personnel in the Irish WNL to injury prevention and injury management. Semi-structured interviews were undertaken with 17 players, 8 medical personnel, and 7 head coaches in the Irish WNL. The data were analysed using thematic analysis. Our study is located within an interpretivist, constructivist research paradigm. The participants had incomplete knowledge of common injuries in elite-level football, and many held beliefs about risk factors for injuries, such as menstrual cycle stage, which lacked evidence to support them. Jumping and landing exercises were commonly used to reduce the risk of injuries but evidence-based injury prevention exercises and programmes such as the Nordic hamstring curl, Copenhagen adduction exercise, and the FIFA 11+ were rarely mentioned. Overall, there was dissatisfaction amongst players with their medical care and strength and conditioning (S & C) support, with resultant inadequate communication between players, head coaches, and medical personnel. Poor quality and availability of medical care and S & C support were considered to be a major obstacle in the effective implementation of injury risk reduction strategies and successful return-to-sport practices. More original research is required in elite-level women's football to explore injury risk factors, injury prevention initiatives, and contextual return-to-sport strategies, so that players, head coaches, and medical personnel can use evidence that is both up-to-date and specific to their environment.



#13 A Systematic Review of the Physical, Physiological, Nutritional and Anthropometric Profiles of Soccer Referees

Reference: Sports Med Open. 2023 Aug 10;9(1):72. doi: 10.1186/s40798-023-00610-7.

Authors: Diogo V Martinho, Adam Field, André Rebelo, Élvio R Gouveia, Hugo Sarmento

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Summary: The importance of soccer referees is widely accepted by international soccer organizations and governing bodies, although there is little research summarizing and appraising the literature on soccer referees. The aim of this study was to systematically review the information related to physical demands, nutrition and physiological profiling of soccer referees. Conforming with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searches of three electronic databases (Web of Sciences, PubMed and Scopus) were conducted on 24 April 2022. The following search terms were used: (Soccer OR football AND refer*) AND (physical OR physiolo* OR load* OR "body composition" OR "fat mass" OR "fat free mass" OR "body size" OR "nutrition*" OR "nutritional assessment" OR "nutritional intake" OR "macronutrient*" OR "micronutrient*"). The inclusion criteria of the manuscripts written in English were that articles with male and/or female soccer referees and included relevant data concerning performance, physical testing, nutrition, body composition, body size and/or physiology of soccer referees. The tools developed by the National Institute of Health were used to assess risk of bias according to the study design. In total, 110 manuscripts were included in the present review. Match activities of soccer referees and assistant referees are not comparable. Variation in performance is influenced by competitive level and competitive schedules. Additionally, match performance is often used to validate field protocols. The associations between match indicators and field protocols were not constant across the included studies, particularly in short-maximal tests. An age decline in physical performance was not conclusive. Body size did not discriminate between referees and assistant referees, as well as referees of different competitive levels. Few studies focused on nutritional guidelines among referees, particularly exercise energy expenditure. Energy intake was comparable across studies, but referees did not follow the daily dietary recommendations. Aerobic output was frequently assessed, and it was not comparable to the values for soccer players. Although there are decreases in the running profiles of older referees, they maintain the same distances from the ball, and thus, age per se should not be used to define participation at the international level. The assessment of physical fitness warrants future consideration given the levels of fatigue that are apparent at the end of matches. In order to attain ideal levels of body composition, future studies need to provide guidelines for daily energy expenditure and nutritional intake.



#14 Evolution of Tactics in Professional Soccer: An Analysis of Team Formations from 2012 to 2021 in the Spanish LaLiga

Reference: J Hum Kinet. 2023 Jul 15;87:207-216. doi: 10.5114/jhk/167468. eCollection 2023 Jul.

Authors: Joaquín González-Rodenas, Víctor Moreno-Pérez, Roberto López-Del Campo, Ricardo Resta, Juan Del Coso

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Summary: The aim of this investigation was to explore the evolution of team formations (TFs) in a top national professional soccer league. A comparative analysis of a total of 3420 matches was performed in 32 professional soccer teams that competed from the 2012/13 to the 2020/21 season in the Spanish LaLiga. The frequency distribution of TFs across seasons presented a statistically significant change (p < 0.001). A 4.2-3.1 TF was most common from 2012/13 to 2016/17, while a 4.4.2 TF was most used from 2017/18 to 2020/2021. TFs such as 4.3.3 and 4.5.1 showed a relatively stable trend over the seasons. Overall, there was a reduction of TFs with 5 midfielders and an increase in the frequency of 2-forward formations (p < 0.001). When the ranking of teams was considered, a 4.3.3 TF was implemented with higher frequency by the Champion and teams that qualified for the Champions League (p < 0.05). However, a 4.2-3.1 TF was most frequent for teams qualified for the UEFA Europa League or teams that got relegated to an inferior category (p < 0.05). These findings highlight that teams competing in LaLiga evolved from the implementation of very few TFs led by the 4.2-3.1 TF, towards a more diverse scenario with a greater variety of tactical positional structures.



#15 The decision-making in dribbling: a video analysis study of U10 soccer players' skills and coaches' quality evaluation

Reference: Front Psychol. 2023 Jul 24;14:1200208. doi: 10.3389/fpsyg.2023.1200208. eCollection 2023.

Authors: Enzo Iuliano, Valerio Bonavolontà, Dafne Ferrari, Nicola Bragazzi, Benito Capasso, Goran Kuvačić, Andrea De Giorgio

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Summary: Dribbling is an important soccer skill that, when effective, allows players to overcome opponents. It can provide a strong tactical advantage; for this reason, all of its components (sprint, speed, and ball control) are fundamental to the development of young players. Dribbling can also be considered a decision-making process, and due to its characteristics, it is not always easy to study ecologically. Using a video analysis study, this research aimed to determine whether dribbling skills, specifically dribbling choice (i.e., decision-making), were related to U10 soccer players' quality. Several outcomes measures, divided into three categories, were taken during video analyses: (i) measures related to the efficacy of dribbling skill; (ii) measures related to the ability of players without the ball to support the player in possession; and (iii) measures related to ball circulation. These data were retrospectively assessed to whether the coaches had formed the teams in training through an implicit knowledge of the players' dribbling skills. The percentage of accurate dribbling (that is, the ability to perform correct passes after a successful dribble) was found to be the variable that coaches may have implicitly used in creating the three groups differentiated by technical skills (p < 0.05). In fact, this percentage was 12.9%, 24.0%, and 48.1% for the groups with lower, average, and higher technical skills, respectively. Overall, the results demonstrate that dribbling accuracy has an important weight in the coach's evaluation of the technical skills level of young soccer players.


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