Latest research in football - week 27 - 2022

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


Following studies were retrieved for this week:

#1 The effect of bio-banding on technical and tactical indicators of talent identification in academy soccer players

Reference: Sci Med Footb. 2022 Aug;6(3):295-308. doi: 10.1080/24733938.2021.2013522. Epub 2021 Dec 19.

Authors: Christopher Towlson, Calum MacMaster, Bruno Gonçalves, Jaime Sampaio, John Toner, Niall MacFarlane, Steve Barrett, Ally Hamilton, Rory Jack, Frances Hunter, Amy Stringer, Tony Myers, Grant Abt

Summary: The aim of this study was to examine the effect of bio-banding on technical and tactical markers of talent identification in 11- to 14-year-old academy soccer players. Using a repeated measures design, 92 players were bio-banded using percentage of estimated adult stature attainment (week 1), maturity-offset (week 2) and a mixed-maturity method (week 3). All players contested five maturity (mis)matched small-sided games with technical and tactical variables measured. Data were analysed using a series of Bayesian hierarchical models, fitted with different response distributions and different random and fixed effect structures. Despite differences during maturity-matched bio-banding for post-peak height velocity players, very few tactical differences were evident during the remaining maturity-matched and mis-matched fixtures for both banding methods. In fact, the results showed no consistent differences across both banding methods for practitioner and video analysis-derived technical performance characteristics during maturity matched and mis-matched fixtures. Both bio-banding methods explained similar levels of variance across the measured variables. Maturity-matched bio-banding had some effect on both technical and tactical characteristics of players during maturity-matched bio-banded formats. That said, this trend remained during maturity mis-matched bio-banded formats which restricts the conclusions that can be made regarding the effectiveness of bio-banding to manipulate technical and tactical measures in academy soccer players.



#2 Mechanisms of injury for concussions in collegiate soccer: an NCAA/DoD CARE consortium study

Reference: Sci Med Footb. 2022 Aug;6(3):325-330. doi: 10.1080/24733938.2021.1991586. Epub 2021 Oct 13.

Authors: Thomas W Kaminski, Sara P D Chrisman, Joseph Glutting, Victoria Wahlquist, Shawn Eagle, Margot Putukian, Ryan Tierney, Steven P Broglio, Thomas W McAllister, Michael A McCrea, Paul F Pasquina, Anthony P Kontos, Care Site Investigators

Summary: The purpose of this study was to describe the mechanism of injury (MOI) and examine factors associated with greater risk for specific MOIs involving concussions in collegiate soccer players. Participants included 3,288 collegiate soccer players from 28 institutions across four competitive seasons, 2014-17. MOIs were documented for 262 soccer-related concussions during the study and placed into one of four categories: collisions, unintentional contact, aerial challenges, and others. 70% of the concussions occurred in DI soccer players. Collisions and unintentional contact were the MOIs that resulted in 66.5% of all concussions. DI and DIII soccer players sustained more concussions by unintentional contact versus collisions and aerial challenges when compared to their DII counterparts. Defenders were more likely than midfielders to sustain concussions by aerial challenges than collisions. As expected, the field players experienced more concussions as a result of collisions, unintentional contact, and aerial challenges when compared to goalkeepers. Future research should explore preventive strategies for decreasing collisions, especially during aerial challenges while heading the soccer ball, and unintentional contacts from errant balls in soccer in order to decrease concussion risk.



#3 A preliminary study of the reliability of soccer skill tests within a modified soccer match simulation protocol

Reference: Sci Med Footb. 2022 Aug;6(3):363-371. doi: 10.1080/24733938.2021.1972137. Epub 2021 Aug 31.

Authors: Paola Rodriguez-Giustiniani, Ian Rollo, Stuart D R Galloway

Summary: This study examined test-retest reliability of soccer-specific skills within a modified version of the soccer match simulation (SMS) protocol. Ten professional youth academy soccer players (18 ± 1 years) from the United Kingdom completed 30 minutes of the modified SMS on two occasions under standardised conditions. During each trial, participants performed 20-m dribbling, short passing (4.2-m), long passing (7.9-m), shooting skills, and 15-m sprints within four blocks of soccer specific activity. Collapsed normative data (mean (SD)) for trial 1 and trial 2 for dribbling speed was 2.7 (0.2) m/s, for sprint speed 5.9 (0.4) m/s, for short pass speed 11.1 (0.5) km/h, for long pass speed was 12.2 (0.5) km/h, and for shooting speed was 13.3 (0.4) km/h. Mean results from trial 1 and trial 2 were not different for all measures evaluated (P > 0.05). Good to excellent reliability (ICC 0.76-0.99) was observed for long and short passing speed, shooting speed, sprint speed, and long pass accuracy, with CVs typically < 5-10%. Moderate reliability (ICC 0.50-0.75) was observed for dribbling speed. Poor reliability (ICC <0.50) was observed for dribbling accuracy and shooting accuracy. The reliability of the modified version of the SMS protocol is promising for most of the skills assessed, with the exception of dribbling and shooting accuracy in this group of professional youth soccer players. The modified protocol is easy to implement within professional clubs without specialist equipment, but due to the limited sample size the reliability requires further confirmation in a larger sample.



#4 Maturity status influences perceived training load and neuromuscular performance during an academy soccer season

Reference: Res Sports Med. 2022 Jul 21;1-13. doi: 10.1080/15438627.2022.2102916. Online ahead of print.

Authors: Jamie Salter, Ross Julian, Stijn V Mentzel, Alastair Hamilton, Jonathan D Hughes, Mark De St Croix

Summary: Commonly we see large within-age-group variations in physique, including body mass, stature, and percentages of predicted adult height, which suggests that age-specified training loads are flawed. Aims were to investigate how maturation impacts training load and neuromuscular response within academy soccer and to provide recommendations for practitioners. Fifty-five male soccer players (age 14.5 ± 1.2 years; stature 172 ± 10 cm; body mass 59.8 ± 10 kg; 94.1 ± 1.8% predicted adult height) reported differential ratings of perceived exertion (AU) across a season. Neuromuscular performance (countermovement jump, reactive strength index, absolute and relative leg stiffness) was measured at three time points across the season. Perceived exertion and neuromuscular performance were examined using linear mixed modelling, supplemented with non-clinical magnitude-based decisions. Analysis indicates every 5% increase in maturity status results in players perceiving overall session intensity 6.9 AU lower and 13.9 AU lower for a 10% maturity shift. Both 5% and 10% changes in maturity most likely resulted in higher countermovement jump, with likely to very likely differences observed for RSI and ABS. Maturity substantially influences neuromuscular performance over the season. Therefore, maturity-specific load prescription may prevent significant within age-group differences in accumulated load, possibly reducing injury risk and/or burnout.



#5 Higher and lower caffeine consumers: exercise performance and biological responses during a simulated soccer-game protocol following caffeine ingestion

Reference: Eur J Nutr. 2022 Jul 20. doi: 10.1007/s00394-022-02955-3. Online ahead of print.

Authors: Andreas Apostolidis, Vassilis Mougios, Ilias Smilios, Marios Hadjicharalambous

Summary: Research on whether caffeine habituation reduces its ergogenicity is scarce and conflicting. The purpose of the present study was to examine the influence of habitual caffeine consumption on exercise performance and biological responses during a simulated soccer-game protocol following acute caffeine ingestion. Twenty professional male soccer players were categorized as higher (n = 9) or lower caffeine consumers (n = 11) after answering a validated questionnaire. Participants performed a simulated treadmill soccer-game protocol on treadmill following either caffeine (6 mg kg-1) or placebo ingestion, during which several variables were evaluated. Time to exhaustion, countermovement jump height, mean arterial pressure, heart rate, plasma glucose, and lactate were higher (P ≤ 0.001), while rating of perceived exertion (RPE) was lower (P = 0.002), following caffeine compared to placebo ingestion, with no differences between groups (P > 0.05). Plasma non-esterified fatty acids exhibited a higher response to caffeine in the higher vs lower caffeine consumers. Reaction time, plasma glycerol and epinephrine, carbohydrate and fat oxidation, and energy expenditure were not affected by caffeine (P > 0.05). Caffeine ingestion largely improved cardiovascular and neuromuscular performance, while reducing RPE, in both higher and lower caffeine consuming athletes during prolonged intermitted exercise to exhaustion.



#6 Relationship between sprint, jump, dynamic balance with the change of direction on young soccer players' performance

Reference: Sci Rep. 2022 Jul 18;12(1):12272. doi: 10.1038/s41598-022-16558-9.

Authors: Moisés Falces-Prieto, Francisco Tomás González-Fernández, Gabriel García-Delgado, Rui Silva, Hadi Nobari, Filipe Manuel Clemente

Summary: The aim of the present paper was to determine the relationship between linear sprinting and jump performance, dynamic balance and change of direction on young soccer players. Ninety-four healthy young highly trained male soccer players belonging to the same high-performance academy agreed to participate in the study [twenty-seven soccer players U16 (14.8 ± 0.4 years; height: 170.6 ± 5.6 cm; body mass 64.7 ± 8.4 kg)] and [sixty-seven soccer players U19 (16.6 ± 1.3 years; height: 173.7 ± 7.2 cm; body mass 66.7 ± 8.0 kg)]. Participants completed 3 testing sessions, 7 days apart. Data from a CMJ, Crossover Hop Test, 10-m sprint test, 505 COD tests and the 90° COD test were collected. Moderate correlations were found in some of the cases (r values were between 0.2 and 0.5 in all cases, being p < 0.05), indicating that linear sprinting, jumping performance and dynamic balance are influential factors in agility but are not the main limiting factor. The highest correlation was found between the cross-over hop test and the 505 COD test (r = 0.44; p < 0.001). The main evidence from the current study suggested that linear sprinting, jumping performance and dynamics balance are determinants of COD, namely explaining the variations in such a skill. The current study revealed that short-distance sprint and jumping performance significantly explain the variations of COD performance on young soccer players.



#7 Kinematic Differences Between the Dominant and Nondominant Legs During a Single-Leg Drop Vertical Jump in Female Soccer Players

Reference: Am J Sports Med. 2022 Jul 18;3635465221107388. doi: 10.1177/03635465221107388.

Authors: Yu Nakahira, Shuji Taketomi, Kohei Kawaguchi, Yuri Mizutani, Masato Hasegawa, Chie Ito, Emiko Uchiyama, Yosuke Ikegami, Sayaka Fujiwara, Ko Yamamoto, Yoshihiko Nakamura, Sakae Tanaka, Toru Ogata

Summary: In soccer, the roles of the dominant (kicking) and nondominant (supporting) legs are different. The kinematic differences between the actions of the dominant and nondominant legs in female soccer players are not clear. The purpose was to clarify the kinematic differences between dominant and nondominant legs during a single-leg drop vertical jump (DVJ) in female soccer players. A total of 64 female high school and college soccer players were included in this study. Participants performed a single-leg DVJ test utilizing video motion capture with artificial intelligence during the preseason period. This study assessed the knee flexion angles, knee valgus angles, hip flexion angles, and lower leg anterior inclination angle at 3 time points (initial contact, maximum flexion of the knee, and toe-off) and compared them between the dominant and nondominant legs. These angles were calculated from motion capture data and analyzed in 3 dimensions. A paired t test was used to analyze the differences between legs, and the significance level was set at P < .05. The knee valgus angle at initial contact was greater in the nondominant leg (mean ± SD, 0.8°± 5.2°) than the dominant leg (-0.9°± 4.9°) (P < .01). There were no differences between legs for any other angles at any of the time points. The kinematics of the dominant and nondominant legs of female soccer players in a single-leg DVJ differ in knee valgus angle. Leg dominance is associated with the risk of sports injuries. Kinematic differences between the dominant and nondominant legs may be a noteworthy factor in elucidating the mechanisms and risk of sports injury associated with leg dominance.



#8 Are Measurement Instruments Responsive to Assess Acute Responses to Load in High-Level Youth Soccer Players?

Reference: Front Sports Act Living. 2022 Jul 1;4:879858. doi: 10.3389/fspor.2022.879858. eCollection 2022.

Authors: Ludwig Ruf, Barry Drust, Paul Ehmann, Sabrina Skorski, Tim Meyer

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Summary: The aim of this study was to assess the short-term responsiveness of measurement instruments aiming at quantifying the acute psycho-physiological response to load in high-level adolescent soccer players. Data were collected from 16 high-level male youth soccer players from the Under 15 age group. Players were assessed on two occasions during the week: after 2 days of load accumulation ("high load") and after at least 48 h of rest. Measurements consisted of the Short Recovery and Stress Scale (SRSS), a countermovement jump (CMJ) and a sub-maximal run to assess exercise heart-rate (HRex) and heart-rate recovery (HRR60s). Training load was quantified using total distance and high-speed running distance to express external and sRPE training load to express internal load. It was expected that good instruments can distinguish reliably between high load and rest. Odd ratios (0.74-1.73) of rating one unit higher or lower were very low for athlete-reported ratings of stress and recovery of the SRSS. Standardized mean high load vs. rest differences for CMJ parameters were trivial to small (-0.31 to 0.34). The degree of evidence against the null hypothesis that changes are interchangeable ranged from p = 0.04 to p = 0.83. Moderate changes were observed for HRex (-0.62; 90% Cl -0.78 to -0.47; p = 3.24 × 10-9), while small changes were evident for HRR60s (0.45; 90% Cl 0.08-0.80; p = 0.04). Only small to moderate repeated-measures correlations were found between the accumulation of load and acute responses across all measurement instruments. The strongest relationships were observed between HRex and total distance (rm-r = -0.48; 90% Cl -0.76 to -0.25). Results suggest that most of the investigated measurement instruments to assess acute psycho-physiological responses in adolescent soccer players have limited short-term responsiveness. This questions their potential usefulness to detect meaningful changes and manage subsequent training load and program adequate recovery.



#9 Return to sports, functional outcomes, and recurrences after arthroscopic Bankart repair in soccer players

Reference: Shoulder Elbow. 2022 Jul;14(1 Suppl):16-20. doi: 10.1177/1758573220928926. Epub 2020 Jun 2.

Authors: Ignacio Pasqualini, Luciano A Rossi, Ignacio Tanoira, Maximiliano Ranalletta

Summary: There is a shortage of relevant reports about the results obtained after shoulder stabilization in soccer players. Therefore, this retrospective study aims to report return to sports, functional outcomes, and recurrences after arthroscopic Bankart repair in soccer players. A total of 156 soccer players were treated for anterior shoulder instability at a single institution between 2008 and 2017. The Rowe score and Athletic Shoulder Outcome Scoring System were used to assess functional outcomes. Return to sport and recurrence rates were also evaluated. The Rowe and Athletic Shoulder Outcome Scoring System scores showed statistical improvement after surgery (P < .001). Overall, 148 soccer players (94.8%) returned to sports, and 122 (78.2%) returned to the same level. The mean time to return to sport was 4.8 months. The recurrence rate was 5.2%. Soccer players who underwent an arthroscopic isolated Bankart repair for anterior glenohumeral instability have shown remarkable outcomes, with most of the patients returning to sports, and at the same level they had before surgery with a low rate of recurrence.



#10 A risk-reward assessment of passing decisions: comparison between positional roles using tracking data from professional men's soccer

Reference: Sci Med Footb. 2022 Aug;6(3):372-380. doi: 10.1080/24733938.2021.1944660. Epub 2021 Jun 27.

Authors: Floris Goes, Edgar Schwarz, Marije Elferink-Gemser, Koen Lemmink, Michel Brink

Summary: Performance assessment in professional soccer often focusses on notational assessment like assists or pass accuracy. However, rather than statistics, performance is more about making the best possible tactical decision, in the context of aplayer's positional role and the available options at the time. With the current paper, we aim to construct an improved model for the assessment of pass risk and reward across different positional roles, and validate that model by studying differences in decision-making between players with different positional roles. To achieve our aim, we collected position tracking data from an entire season of Dutch Eredivisie matches, containing 286.151 passes of 336 players. From that data, we derived several features on risk and reward, both for the pass that has been played, as well as for the pass options that were available at the time of passing. Our findings indicate that we could adequately model risk and reward, outperforming previously published models, and that there were large differences in decision-making between players with different positional roles. Our model can be used to assess player performance based on what could have happened, rather than solely based on what did happen in amatch.



#11 One of these things is not like the other: time to differentiate between relative age and biological maturity selection biases in soccer?

Reference: Sci Med Footb. 2022 Aug;6(3):273-276. doi: 10.1080/24733938.2021.1946133. Epub 2021 Jul 5.

Authors: Chris Towlson, Calum MacMaster, James Parr, Sean Cumming

Summary: Both maturity and relative age selection biases are entrenched within professional academy soccer programmes. Lay opinion, and that of some scholars, holds that relative age effects exist as a product of advanced biological maturity, that is relatively older players succeed as a consequence of the physical and athletic advantages afforded by earlier maturation. There is, however, a growing body of evidence to suggest that this is not the case, and that relative age and maturation should be considered and treated as independent constructs. The purpose was to avoid a disconnect between contemporary academic evidence and practitioner practice, the aim of this commentary is to provide a discussion of pre-existing and new evidence relating to maturity and relative age selection biases in soccer. It is hoped that this commentary will provide an overview of new insight regarding the differences between the two selection phenomena and enable practitioners who are responsible for the (de)selection of academy soccer players for talent development programmes to make more informed decisions regarding their retention/selection strategies.



#11 The effectiveness of 3D multiple object tracking training on decision-making in soccer

Reference: Sci Med Footb. 2022 Aug;6(3):355-362. doi: 10.1080/24733938.2021.1965201. Epub 2021 Aug 13.

Authors: Sebastian Harenberg, Zachary McCarver, Justin Worley, Dennis Murr, Justine Vosloo, Rumit Singh Kakar, Rob McCaffrey, Kim Dorsch, Oliver Höner

Summary: Soccer requires athletes to make quick decisions in dynamic environments. Several off-court technology-based interventions have been developed to train these perceptual cognitive skills. However, the evidence for training transfer using technologies to athletic performance has been sparse. Previous research found 3-dimensional multiple object tracking (3D MOT) training to cause a significant increase in quality of passing decision-making. Limitations to the research warrant further investigation of this association. The aim was to re-examine the effectiveness of 3D MOT on training decision-making. Thirty-one NCAA Division III soccer players (female n = 16) were randomized to 3D MOT training or a control task. The experimental group received 10 training sessions over a span of 4 weeks. The manipulation check indicated a significant training effect in 3D MOT performance for the intervention but not the control group (F(1,29) = 21.46, p < .001, np2 = .43). Non-significant changes with small effect sizes (np2 = .01-.03) in decision-making and measures of near-transfer were found. The findings challenge the association between 3D MOT training and increased quality of decision-making in soccer.



#12 Sport-related concussion return-to-play practices of medical team staff in elite football in the United Kingdom

Reference: Sci Med Footb. 2022 Aug;6(3):317-324. doi: 10.1080/24733938.2021.1983921. Epub 2021 Sep 28.

Authors: Craig Rosenbloom, Robin Chatterjee, Wing Chu, Daniel Broman, Katrine Okholm Kryger

Summary: This study explored sport-related concussion (SRC) return-to-play (RTP) behaviours and attitudes of medical team staff working in elite football in the United Kingdom. Usage and awareness of The Football Association (FA) guidelines, concussion education rates of players and coaching staff, and collection of baseline concussion assessments. Additionally, confidence in managing RTP post-SRC, perceived player under-reporting of symptoms, use of enhanced RTP pathways, and coaching pressure on RTP were investigated. A cross-sectional questionnaire study was distributed online by organisations including or representing medical staff working in elite football in the United Kingdom. A total of 112 responses were gathered. High awareness rates of the FA guidelines were found (96%) with variable rates of player and coaching staff concussion education. Baseline concussion assessments were collected by 80% of respondents with 93% feeling very confident or confident in managing the RTP of a player with a SRC. 60% rarely or never experienced coaching pressure around player RTP, and 24% felt players always or very often under-reported symptoms to expedite their return. 90% had a moderate to high confidence in the Sport Concussion Assessment Tool-5 (SCAT-5) as a RTP decision tool, and 66% always or very often used an enhanced RTP pathway. Confidence in managing player RTP post SRC and use of enhanced RTP pathways were high, as was confidence in the SCAT-5 as a RTP decision tool. Respondents raised concerns around player under-reporting of symptoms to accelerate RTP post-SRC, and perceived coaching pressure around decision making.



#13 Dealing with small samples in football research

Reference: Sci Med Footb. 2022 Aug;6(3):389-397. doi: 10.1080/24733938.2021.1978106. Epub 2021 Sep 14.

Authors: Anne Hecksteden, Ralf Kellner, Lars Donath

Summary: In football research, 'small' trials with low statistical power are common. On the elite level, the inherently low number of participants obviously conflicts with the relevance of even tiny effects. However, general characteristics of football also contribute (e.g. multifactorially influenced and/or complex outcomes). Importantly, small sample sizes are problematic regardless of the study outcome with issues ranging from inconclusive results and low precision to unrepeatable 'discoveries' and overestimation of effect sizes. Therefore, meeting the calculated, target sample size is the first priority. If a suboptimal sample size must be accepted, a range of tools can improve insights. To begin with, some general aspects of data collection and analysis become more important and should be optimally implemented (e.g. reliability of measures). Building on this foundation, specific amendments are available on the levels of data collection (e.g. aggregated single-subject designs) and data analysis (e.g. Bayesian methods). The present commentary aims to give an overview of selected, practical tools for dealing with small sample sizes in football research and provide recommendations for their application in scenarios typical for the field. Importantly, versatility and adaptability are mirrored by the need for utmost transparency including a predetermined (ideally preregistered) study plan. Collaboration or counselling with an expert statistician is strongly encouraged.



#14 A 7-min halftime jog mitigated the reduction in sprint performance for the initial 15-min of the second half in a simulated football match

Reference: PLoS One. 2022 Jul 19;17(7):e0270898. doi: 10.1371/journal.pone.0270898. eCollection 2022.

Authors: Sooil Bang, Jihong Park

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Summary: This study compared the effects of a 7-min shuttle jog during halftime to a control condition (seated rest) on subsequent athletic performance and lower-leg temperature in the second half. Eighteen male football players (22 years, 179 cm, 70 kg, 10 years of athletic career) randomly performed a 20-m shuttle jog (at an intensity of 70% of heart rate maximum) and a seated rest (sitting on a bench) during halftime in two separate sessions. A 5-min football simulation protocol consisting of football-specific activities (jumping, sprinting, kicking, passing, and dribbling at various intensities and distances) was repeated nine times to mimic the first and second half of a football match. Athletic performance (maximal vertical jump height, 20-m sprint time, and the Arrowhead agility test time) recorded during a 15-min period were averaged to represent each time point (first half: T1 to T3; second half: T4 to T6). Lower-leg skin and muscle (using the insulation disk technique) temperature was recorded before and after the first and second half. There was no condition effect over time in maximal vertical jump: F5,187 = 0.53, p = 0.75, Arrowhead agility test time: F5,187 = 1.25, p = 0.29, and lower-leg temperature (skin: F3,119 = 1.40, p = 0.25; muscle: F3,119 = 1.08, p = 0.36). The 20-m sprint time between conditions during the initial 15-min of the second half was different (condition × time: F5,187 = 2.42, p = 0.04) that subjects who performed the shuttle jog ran 0.09 sec faster (3.08 sec, p = 0.002, ES = 0.68), as compared with those who did the seated rest (3.17 sec). The results of our study confirmed that a decremental effect of the static rest on sprinting performance during the initial period of the second halftime can be attenuated by a halftime warm-up.



#15 Effects of an intervention programme designed to improve emotional intelligence and foster the use of coping strategies among professional female football players

Reference: Heliyon. 2022 Jul 5;8(7):e09860. doi: 10.1016/j.heliyon.2022.e09860. eCollection 2022 Jul.

Authors: Jon Berastegui-Martínez, Juan Carlos Lopez-Ubis

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Summary: The aim of the present study was to analyse the effects of a socioemotional competence development programme entitled 'Aurrera neskak' among professional female football players. Participants were 37 female footballers, of which 51% were assigned to the experimental group and 49% to the control group. A quasi-experimental design was used, with repeated pretest-posttest measures. The programme comprised 20 sessions, each lasting 90 min and focusing on four content areas: emotional awareness, personal autonomy, emotion regulation and team skills. The Trait Emotional Intelligence and the Sport Coping Approximation questionnaires were administered before and after the intervention. The results of the analyses reveal that, following the intervention, players perceived positive effects in terms of emotion expression and perception, used coping strategies such as emotional calming and behavioural risk more frequently, and mental withdrawal (a maladaptive strategy) less frequently, during competitions. The results were positive in that they attest to the both trainability of socioemotional competences and their influence on coping styles during competitions among professional female football players.



#16 Application of Deep Learning Technology in Strength Training of Football Players and Field Line Detection of Football Robots

Reference: Front Neurorobot. 2022 Jun 29;16:867028.  doi: 10.3389/fnbot.2022.867028. eCollection 2022.

Authors: Daliang Zhou, Gang Chen, Fei Xu

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Summary: The purpose of the study is to improve the performance of intelligent football training. Based on deep learning (DL), the training of football players and detection of football robots are analyzed. First, the research status of the training of football players and football robots is introduced, and the basic structure of the neuron model and convolutional neural network (CNN) and the mainstream framework of DL are mainly expounded. Second, combined with the spatial stream network, a CNN-based action recognition system is constructed in the context of artificial intelligence (AI). Finally, by the football robot, a field line detection model based on a fully convolutional network (FCN) is proposed, and the effective applicability of the system is evaluated. The results demonstrate that the recognition effect of the dual-stream network is the best, reaching 92.8%. The recognition rate of the timestream network is lower than that of the dual-stream network, and the maximum recognition rate is 88%. The spatial stream network has the lowest recognition rate of 86.5%. The processing power of the four different algorithms on the dataset is stronger than that of the ordinary video set. The recognition rate of the time-segmented dual-stream fusion network is the highest, which is second only to the designed network. The recognition rate of the basic dual-stream network is 88.6%, and the recognition rate of the 3D CNN is the lowest, which is 86.2%. Under the intelligent training system, the recognition accuracy rates of jumping, kicking, grabbing, and starting actions range to 97.6, 94.5, 92.5, and 89.8% respectively, which are slightly lower than other actions. The recognition accuracy rate of passing action is 91.3%, and the maximum upgrade rate of intelligent training is 25.7%. The pixel accuracy of the improved field line detection of the model and the mean intersection over union (MIoU) are both improved by 5%. Intelligent training systems and the field line detection of football robots are more feasible. The research provides a reference for the development of AI in the field of sports training.



#17 Video analysis of 100 matches in male semi-professional football reveals a heading rate of 5.7 headings per field player and match

Reference: BMC Sports Sci Med Rehabil. 2022 Jul 16;14(1):132. doi: 10.1186/s13102-022-00521-2.

Authors: Johannes Weber, Andreas Ernstberger, Claus Reinsberger, Daniel Popp, Michael Nerlich, Volker Alt, Werner Krutsch

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Summary: Heading is an integral part of football and frequent media reports and previous studies about potential danger of heading and head trauma in football fuelled discussions. Epidemiological data and video analyses regarding headings situation and associated head injuries are still missing in male adult professional football. In a prospective cohort study in the male fourth German football league, 100 official matches of the 2015-2016 season were assessed by video analysis and a standardized protocol. Heading situations and concomitant circumstances as well as incidents with a propensity of injury (critical incidents) were analyzed. Critical incidents (CI) and seasonal reported head injuries were cross-referenced. Overall, 11,514 headings were analysed in detail. Video analysis yielded a mean of 5.7 headings per player and match (SD: 1.2; range 0-15). Heading was predominantly performed with the frontal part of the head (76.8%), and nearly two thirds of all headings occurred during defending (65.8%). 71.0% of all headings occured during tacklings, of which 71.9% involved body contact with the opponent player. Video analysis yielded 31 CI on the head due to heading (incidence: 1.02 per 1000 h match exposure and player). 29 CI occurred during heading duels (odds ratio: 5.91), 30 CI with body contact (odds ratio: 28.8) and 6 CI with elbow contact (odds ratio: 6.13). Heading frequency in male semi-professional football could be determined with a rate of 5.7 headings per match and field player. Cross referencing CI and seasonal reported head injuries revealed a very low number of reported head injuries.



#18 Relative age effect among U14 football players in Portugal: do geographical location, team quality and playing position matter?

Reference: Sci Med Footb. 2022 Aug;6(3):285-294. doi: 10.1080/24733938.2021.1977840. Epub 2021 Sep 28.

Authors: Carlos Humberto Almeida, Anna Volossovitch

Summary: Relative age effect (RAE) has been found to be particularly pronounced between 13 and 15 years of age in male football. However, the extent to which the phenomenon varies within a country demands a more comprehensive approach. The purpose was to examine the effects of geographical location (north; centre-north; centre-south; south; islands), team quality (top-ranked; middle-ranked; bottom-ranked) and playing position (goalkeeper; defender; midfielder; forward) on the birthdate distribution (Q1: January-March; Q2: April-June; Q3: July-September; Q4: October-December) of U14 Portuguese players selected for the national inter-association tournament Lopes da Silva. A total of 2,693 players (mean age: 14.12 ± 0.38 years), selected by the 22 regional football associations for the last seven editions of the tournament (2013-2019), was included in the sample. Chi-square analysis showed a small-to-medium RAE in the U14 cohort compared to the general Portuguese male population (p < .01). Furthermore, the multinomial logistic regression model revealed that the probabilities of selecting Q1 players (vs. Q4) differed (p < .01) based on geographical location (increases of 76.3% in the north and 87.3% in the centre-north zone compared to the regional teams from islands) and team quality (increase of 94.6% in top-ranked compared to the bottom-ranked teams). The playing position did not affect the magnitude of RAE. Our findings confirm that besides being present in U14 Portuguese male football, the magnitude of RAE is influenced by demographic factors. This study also supports the notion that coaching staffs tend to choose players based on attributes associated with chronological age, seeking to achieve short-term competitive outcomes.



#19 Addressing head injury risk in youth football: are heading guidelines the answer?

Reference: Sci Med Footb. 2022 Aug;6(3):340-346. doi: 10.1080/24733938.2021.1967435. Epub 2021 Aug 18.

Authors: Alexander W Gilbert, Jesse M Bering, Lynley C Anderson

Summary: Recent findings of neurodegenerative pathology in former professional football players have once again called into question the role that "heading", a fundamental aspect of the game, plays in the onset of neurological disease. By introducing guidelines aimed at limiting heading among youth players, the United Kingdom recently joined the United States as the only two nations yet to implement heading regulation in response to growing concerns surrounding football's head injury burden. Evaluating the efficacy of risk mitigation strategies requires the continual reviewal of available evidence, however, youth heading guidelines have yet to undergo such an empirical evaluation. This review aims to address this absence by first discussing the literature informing heading-related health risk, followed by an assessment of the decision to limit youth heading in response to this research. The risk of injury due to heading remains highly uncertain, especially as it pertains to youth players for whom epidemiological data is severely lacking. However, consideration of policy making under conditions of scientific uncertainty, as well as intrinsic risk factors of acute head injury in children and adolescents, currently warrants a precautionary approach to youth heading regulation. Further research must be pursued to ensure that future risk management strategies remain grounded in evidence and enhance the safety of football for vulnerable individuals. While our understanding of the neurological outcomes of heading remains limited, the adoption of heading guidelines reflects an appropriate response to uncertain risk.



#20 Deep Learning-Based Football Player Detection in Videos

Reference: Comput Intell Neurosci. 2022 Jul 12;2022:3540642. doi: 10.1155/2022/3540642. eCollection 2022.

Authors: Tianyi Wang, Tongyan Li

Summary: The main task of football video analysis is to detect and track players. In this work, we propose a deep convolutional neural network-based football video analysis algorithm. This algorithm aims to detect the football player in real time. First, five convolution blocks were used to extract a feature map of football players with different spatial resolution. Then, features from different levels are combined together with weighted parameters to improve detection accuracy and adapt the model to input images with various resolutions and qualities. Moreover, this algorithm can be extended to a framework for detecting players in any other sports. The experimental results assure the effectiveness of our algorithm.



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