Latest research in football - week 23 - 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 mid-season coach turnover on running match performance and match outcome in professional soccer players

Reference: Sci Rep. 2022 Jun 23;12(1):10680. doi: 10.1038/s41598-022-14996-z.

Authors: Łukasz Radzimiński, Alexis Padrón-Cabo, Toni Modric, Marcin Andrzejewski, Sime Versic, Paweł Chmura, Damir Sekulic, Marek Konefał

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Summary: The aim of this research was to examine the physical match performance and match outcome before and after coach turnover in professional soccer teams compared with a control group containing coaches working continuously for 3 consecutive seasons. Analysed data included 325 performances of teams led by dismissed coaches (DC), 313 of teams led by new coaches (NC), and 580 of teams led by unchanged coaches (UnC). Variables, such as average number of collected points, total distance (TD), total distance per minute (TD/min), high-speed running (HSR), sprinting and number of high-intensity runs (NHIR), were analysed in the last 15 games of DC and 15 matches of NC. These periods were divided into 3 blocks out of 5 matches (5-match blocks). NC collected a significantly higher number of points than DC (p = 0.015), whereas average points collected by UNC were significantly greater than DC (p < 0.001 and NC (p = 0.012). TD and TD/min for DC were significantly lower (p < 0.001) compared with both NC and UnC, whereas significant differences in HSR (p = 0.003) and NHIR (p = 0.03) were identified between DC and NC. The current study reported that mid-season coach turnover may result in short-term improvement in team results and physical match performance. However, this effect disappears after a period of approximately 5 games.



#2 Evolution of determinant factors of maximal sprinting and repeated sprint ability in women soccer players

Reference: Sci Rep. 2022 Jun 23;12(1):10633. doi: 10.1038/s41598-022-13241-x.

Authors: Francisco Tomás González-Fernández, Olalla García-Taibo, Moisés Vila, Hadi Nobari, Filipe Manuel Clemente

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Summary: The present study aimed to determine the influence of force-power-velocity, vertical and horizontal jumps, and repeated sprint ability on the sprinting performance of adult women soccer players. Eighteen women soccer players from one team participating in the first female national Spanish soccer league were analyzed. Fitness assessments were performed twice in a period of three months. The following assessments were made to reach the aim of the study: (1) anthropometric measures, (2) CMJ (0%, 20% and 40%), (3) hop test (dominant and nondominant leg), (4) linear sprinting at 30 m and (5) RSA test. The main evidence of this study revealed the meaningful contribution of lower-limb power (vertical and horizontal jump), maximal sprint and peak power on sprinting time performance, while stride frequency was meaningfully explained by vertical jump and maximal sprinting. In fact, positive moderate and large correlations were found between Time and CMJ, CMJ 20%, CMJ 40%, Hop Test Dominant and Non-dominant, and Pmax and MS of Force-Power-Velocity (r = - 0.73, p = 0.001; r = - 0.68, p = 0.002; r = - 0.51, p = 0.03; r = - 0.64, p = 0.004; r = - 0.57, p = 0.013; r = - 0.78, p = 0.001, and r = - 0.83, p = 0.001, respectively). In sum, peak power, maximal speed, and lower-limb power (in vertical and horizontal jumps) were significant determinants of sprinting performance (time), while vertical jump was the determinant of stride frequency. In addition, our findings suggest that potentiation and explosive vertical power could be the emphasis for sustaining the stride frequency of women soccer players, while sprinting performance should be supported by strong acceleration and maximal velocity sustained by both vertical and horizontal force and concentric and eccentric strength and power.



#3 Programming Plyometric-Jump Training in Soccer: A Review

Reference: Sports (Basel). 2022 Jun 10;10(6):94. doi: 10.3390/sports10060094.

Authors: Rodrigo Ramirez-Campillo, Jason Moran, Jon L Oliver, Jason S Pedley, Rhodri S Lloyd, Urs Granacher

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Summary: The aim of this review was to describe and summarize the scientific literature on programming parameters related to jump or plyometric training in male and female soccer players of different ages and fitness levels. A literature search was conducted in the electronic databases PubMed, Web of Science and Scopus using keywords related to the main topic of this study (e.g., "ballistic" and "plyometric"). According to the PICOS framework, the population for the review was restricted to soccer players, involved in jump or plyometric training. Among 7556 identified studies, 90 were eligible for inclusion. Only 12 studies were found for females. Most studies (n = 52) were conducted with youth male players. Moreover, only 35 studies determined the effectiveness of a given jump training programming factor. Based on the limited available research, it seems that a dose of 7 weeks (1-2 sessions per week), with ~80 jumps (specific of combined types) per session, using near-maximal or maximal intensity, with adequate recovery between repetitions (&lt;15 s), sets (≥30 s) and sessions (≥24-48 h), using progressive overload and taper strategies, using appropriate surfaces (e.g., grass), and applied in a well-rested state, when combined with other training methods, would increase the outcome of effective and safe plyometric-jump training interventions aimed at improving soccer players physical fitness. In conclusion, jump training is an effective and easy-to-administer training approach for youth, adult, male and female soccer players. However, optimal programming for plyometric-jump training in soccer is yet to be determined in future research.



#4 The Association between Multidirectional Speed Performance, Dynamic Balance and Chronological Age in Young Soccer Players

Reference: J Funct Morphol Kinesiol. 2022 May 24;7(2):41. doi: 10.3390/jfmk7020041.

Authors: Giordano Scinicarelli, Christoph Offerhaus, Boris Feodoroff, Ingo Froböse, Christiane Wilke

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Summary: The ability to maintain a stable single-leg balance stance during a fast change of direction movement is a fundamental aspect both for improving sport-specific skills and for prevention strategies. The aim of this cross-sectional study was to investigate the associations between multidirectional speed performance (MDS), dynamic balance performance (DBP), and chronological age in young and uninjured soccer players. In addition, it was examined whether chronological age and balance can predict variance in speed performance. One-hundred forty-six young male soccer players (age range 11-19) performed the y-balance test (YBT) and the lower extremity functional test (LEFT). Descriptive statistics, Pearson correlation, and multiple regression analysis were executed. The analyses were carried out on the further variables: for the DBP, the YBT composite score % (CS dominant leg/CS non-dominant leg) and limb symmetry index % (LSI) were used; for the MDS, the LEFT time in seconds (s) was used. Findings revealed LEFT scores to have a significant association with chronological age (p = 0.000), CS dominant (p = 0.019) and LSI (p = 0.044) of the YBT. In addition, CS dominant and chronological age explained the variance of the LEFT by 44%, regardless of LSI. To conclude, MDS revealed a strong association with DBP of the dominant side but a small association with LSI. In addition, a small association was found between quick LEFT times and older players. Finally, MDS variance can be predicted from DBP of the dominant side and chronological age in young soccer players. The tests used in this study could be useful screening tools for the detection of performance deficits, the implementation of prevention training programs, and the optimization of selection strategies in soccer academies.



#5 The effect of eight weeks beetroot juice supplement on aerobic, anaerobic power, and field performance of soccer players

Reference: Res Sports Med. 2022 Jun 21;1-13. doi: 10.1080/15438627.2022.2090250. Online ahead of print.

Authors: Vahid Giv, Mohsen Aminaei, Rohullah Nikoei

Summary: The purpose of the study investigated the effect of eight weeks of soccer training with beetroot juice supplement on aerobic power, anaerobic power, and field performance of soccer players. This is experimental research, by the control group in pre and post-test. The statistical population was male soccer players. Forty subjects were randomly divided into four groups including the exercise group (EX) the exercise group with beetroot juice supplement (EX&BRJS) the beetroot juice supplement group (BRJS), and the control group (C). Aerobic power, anaerobic threshold, and respiratory exchange ratio, measured by the gas analyser (Cosmed), anaerobic power (peak, mean power), and fatigue index, by Wingate cycle test (Monark, 839), and field performance by (Bangsbo, field test performance). The statistical methods include the Kolmogorov-Smirnov, Levin, covariance (ANCOVA), and pair comparison with Bonferroni test. The results showed eight weeks' of soccer training with beetroot juice supplement, significantly changed aerobic power, respiratory exchange ratio, anaerobic threshold, anaerobic power, field performance, and fatigue index (P ≤ 0.05). Additionally, in all variables, the paired comparison showed that the EX&BRJS group progressed more than all other condition groups. The soccer athletes may use beetroot juice supplements along with soccer exercises to improve aerobic and anaerobic power and field performance.



#6 The effects of different small-sided games configurations on heart rate, rating of perceived exertion, and running demands in professional soccer players

Reference: Eur J Sport Sci. 2022 Jun 20;1-26. doi: 10.1080/17461391.2022.2092427. Online ahead of print.

Authors: Petrus Gantois, Francisco Piqueras-Sanchiz, Miguel José Ferreira Andrade Cid, José Pino-Ortega, Daniel Castillo, Fábio Yuzo Nakamura

Summary: We aimed to compare the effects of different small-sided games (SSG) configurations on heart rate (HR), rating of perceived exertion (RPE), and running demands in soccer players. Twelve outfield male soccer players (U18) participated in this randomized cross-over design study. Players performed three SSG in different "fixed" and "dynamic" pitch sizes (3v3 in large (SSGL) and small (SSGS) fixed area; or 3v3 in dynamic dimensions [SSGD]), with 4x4 minutes interspersed by 2 minutes of rest. HR measures (maximum [HRmax], average [HRavg], and percentage of maximum [%HRmax]), RPE, and running demands were collected across the SGG sessions. The following running activities - total distance covered (TD), distance covered (DC) at 6-12 km·h-1, ≥ 12-18 km·h-1, and >18 km·h-1, peak running speed, acceleration (ACC) and deceleration (DEC) at 1-2 m·s-2 and 2-3 m·s-2, player load, and high metabolic load distance (HMLD) - were recorded by an inertial measurement unit devices. SSGL displayed higher HRavg, %HRmax, and RPE values than SSGS (p < 0.05). SSGL resulted in higher TD, DC at 6-12 km·h-1, ≥ 12-18 km·h-1, > 18 km·h-1, and higher peak speed than SSGS and SSGD (p < 0.05). Moreover, SSGD presented higher TD and DC at 6-12 km·h-1 and ≥ 12-18 km·h-1 than SSGS (p < 0.05). In contrast, SSGD and SSGS showed higher number of ACC and DEC at 1-2 m·s-2 than SSGL (p < 0.05). In conclusion, the pitch size and playing area of the SSG can be manipulated to promote desired physiological and physical demands in young soccer players.



#7 Acute Effects of Partial Range of Motion Resistance Training and Increases in Blood Lactate Impact Accuracy of Penalty Kicks in Soccer Players

Reference: Biomed Res Int. 2022 Jun 8;2022:4769560.  doi: 10.1155/2022/4769560. eCollection 2022.

Authors: Mariusz Ozimek, Tadeusz Ambroży, Tatiana Krasavina, Irina Lazareva, Christina Popova, Łukasz Rydzik, Vitaly Rybakov, Konstantin Gurevich, Stefane Dias, Brian Binkley, Rokaya Mikhailenko, Alexander Tsymbal, Emilian Zadarko, Victoria Zaborova

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Summary: The purpose of this investigation was to assess the acute effects of partial range of motion (pROM) exercises, on the accuracy of soccer penalty kicks on goal. This method limits the joint from moving through the complete length of a motion, creates an occlusion effect, and thus causes the type 1 muscle fibers to work anaerobically. Thirty-six soccer players, with 5-8 years of soccer playing experience, were pretested for accuracy then retested (rtt = 0.92) and divided into random groups from the Associação Banco do Brasil Futebol Clube-Group A, Paraná Futebol Clube-Group P, and Coritiba Futebol Clube-Group C. Groups were composed of 12 people performing full range of motion (fROM) exercises or pROM exercises. Both groups performed 5 sets of back squats at 50% of body weight in sets of 40 seconds with metronome tempo of 56 bpm for an average of 10-12 repetitions per 40-second set. Blood samples were collected post-warm-up, after the 3rd set, and following the 5th set for both groups, within 3-5 minutes of cessation of exercise. Athletes performing fROM exercises showed increased blood lactate from 2.69 ± 0.2 to 4.0 ± 1.2 mmol/L (p < 0.05), and in pROM, blood lactate increased from 2.48 ± 0.42 to 10.29 ± 1.3 mmol/L (p < 0.001). In fROM, accuracy decreased from 42.96 ± 13.39% to 41.37 ± 17.25% (p > 0.1), a slight decrease, while in the pROM groups, accuracy decreased from 45.42 ± 14.93% to 24.53 ± 10.2% (p < 0.001). The calculations demonstrating average percentages of accuracy are presented in the tables. These findings support that pROM exercises significantly increase blood lactate resulting in a reduction in soccer kick accuracy. This decrease in accuracy directly correlates to the accumulation of lactic acid and hydrogen ions (H+) and demonstrates that pROM strength training should not be utilized prior to a sport-specific session in order to avoid interference with the development of special skills.



#8 Injuries During Return to Sport After the COVID-19 Lockdown: An Epidemiologic Study of Italian Professional Soccer Players

Reference: Orthop J Sports Med. 2022 Jun 14;10(6):23259671221101612. doi: 10.1177/23259671221101612. eCollection 2022 Jun.

Authors: Daniele Mazza, Alessandro Annibaldi, Giorgio Princi, Leopoldo Arioli, Fabio Marzilli, Edoardo Monaco, Andrea Ferretti

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Summary: The injury rate in professional soccer players may be influenced by match frequency. The purpose was to assess how changes in match frequency that occurred because of coronavirus disease 2019 (COVID-19) influenced training and match injuries in the Italian Serie A league. Three phases in the Serie A league, each 41 days long, were evaluated: phase A was the beginning of the 2019-2020 season; phase B was a period after the COVID-19 lockdown was lifted, when the remaining matches of the season were played with greater frequency; and phase C was the beginning of the 2020-2021 season. All male professional soccer players who were injured during the 3 phases were included. Player age, height, position, injury history, and return to play (RTP) were retrieved from a publicly available website. Training- and match-related injuries during each of the 3 phases were collected and compared. Moreover, match injuries that occurred after the lockdown phase (phase B), in which there were 12 days designated for playing matches ("match-days"), were compared with injuries in the first 12 match-days of phases A and C. When comparing 41-day periods, we observed the injury burden (per 1000 exposure-hours) was significantly lower in phase B (278.99 days absent) than in phase A (425.4 days absent; P < .05) and phase C (484.76 days absent; P < .05). A longer mean RTP period was recorded in phase A than in phase B (44.6 vs 23.1 days; P < .05). Regarding 12-match day periods (81 days in phase A, 41 days in phase B, and 89 days in phase C), there was a significantly higher match injury rate (0.56 vs 0.39 injuries/1000 exposure-hours; P < .05) and incidence (11.8% vs 9.3%; P < .05) in phase B than in phase A and a longer mean RTP period in phase A than in phase B (41.8 vs 23.1 days; P < .05). Finally, the rate and incidence of training-related injuries were significantly higher in phase B (4.6 injuries/1000 exposure-hours and 6.5, respectively) than in phase A (1.41 injuries/1000 exposure-hours and 2.04, respectively) (P < .05). Both training- and match-related injuries were greater during the abbreviated period after the COVID-19 lockdown. These may be linked to the greater match frequency of that period.



#9 Does Technical Match Performance in Professional Soccer Depend on the Positional Role or the Individuality of the Player?

Reference: Front Psychol. 2022 May 31;13:813206. doi: 10.3389/fpsyg.2022.813206. eCollection 2022.

Authors: Leon Forcher, Leander Forcher, Sascha Härtel, Darko Jekauc, Hagen Wäsche, Alexander Woll, Timo Gross, Stefan Altmann

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Summary: The aim of the study was to examine the impact of the positional role and the individuality on the technical match performance in professional soccer players. From official match data of the Bundesliga season 2018/19, technical performance [short (<10 m)/medium (10-30 m)/long (>30 m) passes, dribblings, ball possessions] of all players who played during the season were analyzed (normative data). Five playing positions (center back, full back, central midfielder, wide midfielder and forward) were distinguished. As the contextual factor tactical formation is known to influence match performance, this parameter was controlled for. Further, those players who played at minimum four games in at least two different playing positions were included in the study sample (n = 13). The technical match performance of the players was analyzed in relation to the normative data regarding the extent to which the players either adapted or maintained their performance when changing the playing position. When switching playing positions, positional role could explain 3-6% of the variance in short passes and ball possessions and 27-44% of the variance in dribblings, medium passes, and long passes. Moreover, we observed large interindividual differences in the extent to which a player changed, adapted, or maintained his performance. In detail, five players clearly adapted their technical performance when changing playing positions, while five players maintained their performance. Coaches can use these findings to better understand the technical match performance of single players and further, to estimate the impact of a change in the positional role on the technical performance of the respective player.



#10 Reliability of a soccer player based on the bivariate Rayleigh distribution with right censored and ignorable missing data

Reference: J Appl Stat. 2020 Feb 4;48(2):285-300. doi: 10.1080/02664763.2020.1723504. eCollection 2021.

Authors: Fayyaz Bahari, Safar Parsi, Mojtaba Ganjali

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Summary: In this paper, we study the performance of a soccer player based on analysing an incomplete data set. To achieve this aim, we fit the bivariate Rayleigh distribution to the soccer dataset by the maximum likelihood method. In this way, the missing data and right censoring problems, that usually happen in such studies, are considered. Our aim is to inference about the performance of a soccer player by considering the stress and strength components. The first goal of the player of interest in a match is assumed as the stress component and the second goal of the match is assumed as the strength component. We propose some methods to overcome incomplete data problem and we use these methods to inference about the performance of a soccer player.



#11 Discovering associations between players' performance indicators and matches' results in the European Soccer Leagues

Reference: J Appl Stat. 2020 May 28;48(9):1696-1711.  doi: 10.1080/02664763.2020.1772210. eCollection 2021.

Authors: Maurizio Carpita, Silvia Golia

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Summary: The application of data mining techniques and statistical analysis to the sports field has received increasing attention in the last decade. One of the most famous sports in the world is soccer, and the present work deals with it, using data from the 2009/2010 season to the 2015/2016 season from nine European leagues extracted from the Kaggle European Soccer database. Overall performance indicators of the four roles in a soccer team (forward, midfielder, defender and goalkeeper) for home and away teams are used to investigate the relationships between them and the results of matches, and to predict the wins of the home team. The model used to answer both these demands is the Bayesian Network. This study shows that this model can be very useful for mining the relations between players' performance indicators and for improving knowledge of the game strategies applied by coaches in different leagues. Moreover, it is shown that the ability to predict match results of the proposed Bayesian Network is roughly the same as that of the Naive Bayes model.



#12 Amplifying the effects of adding extra players during association football game-based scenarios

Reference: PLoS One. 2022 Jun 24;17(6):e0270052. doi: 10.1371/journal.pone.0270052. eCollection 2022.

Authors: Diogo Coutinho, Bruno Gonçalves, Hugo Folgado, Bruno Travassos, Sara Santos, Jaime Sampaio

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Summary: This study aimed to compare under-18 association football players' performance (age = 17.7±1.0 years; playing experience = 9.0 ± 3.2 years) when manipulating the number of teammates and opponents during football game-based practices. Time-motion, individual and tactical-related variables were monitored when manipulating conditions with different number of teammates and opponents (11vs11, No-Sup, No-Inf; 11vs12, Low-Sup, Low-Inf; 11vs13, Mod-Sup, Mod-Inf; and 11vs14, High-Sup, High-Inf). Results showed that adding teammates promoted increases in the longitudinal synchronization from No-Sup to Mod-Sup (Cohen's d with 95% of confidence intervals: 0.25 [0.12; 0.39]; p < .001) and High-Sup (0.61 [0.41; 0.82]; p < .001), while decreases in the distance to the nearest teammate, both in the offensive and defensive phases (p < .001 and p = .005, respectively). In addition, it was observed lower distance covered while running when playing in High-Sup compared to No-Sup (0.30 [-0.01; 0.61]; p = .002) during the defensive phase. Attacking in numerical inferiority promoted a higher variability in the distance to the nearest teammate from No-Inf to High-Inf (0.83 [0.27; 1.38]; p = .044), while decreasing the physical demands, specifically distance covered while running (-0.49 [-0.99; 0.01]; p = .039). In turn, defending, mainly in high-inferiority, increased the total distance covered compared to No-Inf (0.61 [0.30; 0.91]; p < .001) and led to a decrease in the distance to the nearest teammate (-0.90 [-1.35; -0.44]; p = .002). Overall, coaches may manipulate the number of teammates and opponents to promote distinct effects at the level of cooperation and opposition dynamical interactions.



#13 The Application of Artificial Intelligence in Football Risk Prediction

Reference: Comput Intell Neurosci. 2022 Jun 13;2022:6996134.  doi: 10.1155/2022/6996134. eCollection 2022.

Authors: Jinyu Qiao

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Summary: Football is the most popular sports in the World, with an estimated global following of 4.0 billion fans worldwide. Football draws attention from people of various age groups. The result of the game only decides the performance of the team and individual players. The player has to train smarter to avoid a career-ending injury. Sports have also entered into the new era of artificial intelligence as any industry. Artificial intelligence (AI) in football acts like a teammate to the players and also plays the role of an assistant coach. The coach uses artificial intelligence and incorporates it into the traditional way of training. The Football Associations have already implemented sensors to collect data in the form of technologies such as Video Assistant Referee and Goal Line Technology. Additionally, the quality of the players and the coaches is improved with smart technological implementation. This technology itself incorporates the utilization of smart technologies for data acquisition using sensor networks and an intelligent data analysis. The proposed algorithm is compared with the fuzzy logic model (FLM) and found that it is 7.2% of higher risk predication by the proposed model than the existing.



#14 Recommencement of football competition with spectators during the active phase of the COVID-19 pandemic in a Middle Eastern country

Reference: BMC Sports Sci Med Rehabil. 2022 Jun 20;14(1):112. doi: 10.1186/s13102-022-00504-3.

Authors: Naushad Ahmad Khan, AbdulWahab Abubaker Al Musleh, Sameer Abdurahiman, Mohammad Asim, Ayman El-Menyar, Hassan Al-Thani

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Summary: With the global spread of COVID-19 infection caused by the severe acute respiratory syndrome coronavirus-2 virus (SARS-CoV-2), all the national and international sports events were ceased early in 2020. The sport activities have been reinstated since then, albeit without spectators. However, several governments have established a variety of risk-mitigation measures to gradually reintroduce the spectators to stadiums. We aimed to evaluate the implementation of a strict health protocol to ensure the resumption of professional football with spectators and to access its effectiveness in limiting the spread of COVID-19 infections within the community. This was a retrospective, observational study involving football players, match officials, local organizing committee members, working in close coordination, and over 16,000 spectators in the state of Qatar. We examined data from the Amir Cup final (December 18th, 2020), which was played under a strict protocol that included extensive reverse transcription-Polymerase chain reaction (RT-PCR) testing for players and match officials, as well as the utility of COVID-19 rapid antigen and antibody testings as screening tools for spectators to ensure their safe return to the stadiums. In addition, we reviewed the guidelines and protocols that were put in place to organize Qatar's Amir Cup Football Final, which drew over 16,000 spectators in the stadium. A total of 16,171 spectators undertook rapid antigen and antibody tests for the Amir cup final (from December16-December18, 2020). Fifteen Spectators (n = 15) returned with a positive result for COVID-19 infection during the final event (positivity rate = 0.12%). All players underwent RT-PCR testing 48 h before the match. None of the players tested positive for COVID-19 infections. 1311 individuals reported having symptoms related to COVID-19 post final of Amir Cup. These spectators were tested for COVID-19 RT-PCR with an overall positivity rate (positive/reactive) to be 0.42% (69/16171). This report shows a meagre incidence rate of COVID-19 infections during and post-Amir Cup football final. Based on the low infectivity rate reported during and post the Amir Cup, we propose that supervised and controlled resumption of football matches with spectators can be carried out safely following a strict testing and tracing protocol. Similar infection control policies can be replicated with a higher number of spectators.



#15 Effects of Walking Football During Ramadan Fasting on Heart Rate Variability and Physical Fitness in Healthy Middle-Aged Males

Reference: Am J Mens Health. May-Jun 2022;16(3):15579883221103418. doi: 10.1177/15579883221103418.

Authors: Noureddine Kammoun, Sami Hidouri, Amine Ghram, Achraf Ammar, Liwa Masmoudi, Tarak Driss, Beat Knechtle, Katja Weiss, Omar Hammouda, Mehdi Chlif

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Summary: This study aimed to investigate the effect of a walking football (WF) program during Ramadan fasting (RF) on heart rate variability (HRV) indices, body composition, and physical fitness in middle-aged males. Thirty-one healthy sedentary men were randomized to WF (n = 18) and control (n = 13) groups. Both groups participated in RF. The WF group were involved in a training program (small-sided games) of three sessions a week during RF. The time and frequency domains of HRV, body composition, handgrip, lumbar strength, Modified Agility Test (MAT), and 6-minute walk test (6MWT) were measured before Ramadan (BR), during Ramadan (DR), and after Ramadan (AR). We reported that RF has significantly altered some parameters of HRV DR; the mean HR decreased while the mean RR, LF, and HF increased. WF had a significant effect on HRV and mean HR DR compared with BR and AR decreased while mean RR, HF and LF increased. DR, body mass decreased in both groups, while body mass index (BMI) decreased and lean mass increased only in WF group. Lower body mass and BMI levels were reported AR only in WF group. Physical capacity improved AR, compared with BR, only in the WF group with longer distance in 6MWT, shorter time(s) in MAT, and higher lumbar strength levels. We conclude that RF increases parasympathetic system activity. WF practice during RF is safe and might improve body composition, physical fitness, autonomic cardiac function, and physical fitness in middle-aged males.



#16 Football Game Video Analysis Method with Deep Learning

Reference: Comput Intell Neurosci. 2022 Jun 8;2022:3284156. doi: 10.1155/2022/3284156. eCollection 2022.

Authors: Nian Liu, Lu Liu, Zengjun Sun

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Summary: Football is a beloved sport, and its wide audience makes football video one of the most analytically valuable types of video. Researchers have achieved certain research results in football video content analysis. How to locate interesting event clips from a complete long video is an urgent issue to be addressed in football game video analysis. The granularity of sports event detection results with traditional machine learning is relatively coarse, and the types of events that can be detected are limited. In recent years, deep learning has made good progress in the research of video single-person events and action detection, but there are few achievements in the detection of sports video events. In response to this problem, this work uses a deep learning method to build an event detection model to detect events contained in football videos. The whole model is divided into two stages, in which the first stage is utilized to generate candidate event fragments. It divides the football video to be detected into a sequence of frames of a certain length and scans using a sliding window. Multiple frame sequences within a sliding window form a segment, and each segment is a prediction unit. The frame sequence features within the segment are obtained through a three-dimensional convolutional neural network, which is used as the input of each time point of the bidirectional recurrent neural network and further integrated to generate the event prediction of the segment. The second stage is to further process the above results to remove all segments predicted as nonevents. The thresholds are set according to the detection effect of various events to filter out event fragments with higher probability values, obtain the start and end positions of the events through merging, classify and mark them, and finally output complete event fragments. This work has carried out comprehensive and systematic experiments to verify correctness of the proposed method.



#17 Quantifying the Effectiveness of Defensive Playing Styles in the Chinese Football Super League

Reference: Front Psychol. 2022 Jun 2;13:899199. doi: 10.3389/fpsyg.2022.899199. eCollection 2022.

Authors: Lingfeng Ruan, Huanmin Ge, Yanfei Shen, Zhiqiang Pu, Shouxin Zong, Yixiong Cui

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Summary: Establishing and illustrating a predictive and prescriptive model of playing styles that football teams adopt during matches is a key step toward describing and measuring the effectiveness of styles of play. The current study aimed to identify and measure the effectiveness of different defensive playing styles for professional football teams considering the opponent's expected goal. Event data of all 1,120 matches played in the Chinese Football Super League (CSL) from the 2016 to 2020 seasons were collected, with fifteen defense-related performance variables being extracted. The PCA model (KMO = 0.76) output eight factors that represented 7 different styles of play (factor 6 and 8 represent one style of play) and explained 85.17% of the total variance. An expected goal (xG) model was built using data related to 27,852 shots. Finally, the xG of the opponent was calculated in the multivariate regression model, outputting five factors that (p < 0.05) explained 41.6% of the total variance in the xG of the opponent and receiving a dangerous situation (factor 7) was the most apparent style (31.3%). Finally, the predicted model with defensive styles correlated with actual xG of the opponent at r = 0.62 using the 2020 season as testing data which showed that the predicted xG was correlated moderately with the actual. The result indicated that if the team strengthened the defense closed to the own goal, high intensity confrontation, and defense of goalkeeper, meanwhile making less errors and receiving less dangerous situations, the xG of the opponent would be greatly reduced.



#18 The Effects of Physiological Demands on Visual Search Behaviours During 2 vs. 1 + GK Game Situations in Football: An in-situ Approach

Reference: Front Psychol. 2022 May 30;13:885765. doi: 10.3389/fpsyg.2022.885765. eCollection 2022.

Authors: Filipe Casanova, Pedro T Esteves, Maickel Bach Padilha, João Ribeiro, Andrew Mark Williams, Júlio Garganta

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Summary: We examined the effect of physiological workload on gaze behaviour during defensive performance in 2 vs. 1 +goalkeeper game situations in football. Twenty-two players were assigned to either a high- or low-performing group based on a validated measure of tactical performance. A total of 12 game sequences (trials) were presented under high- and low-workload conditions. At the end of each sequence, participants were asked to indicate their perceived exertion using the Rating Scale of Mental Effort and the Borg Scale. The low- and high-workload conditions were defined when the players achieved 60 and 90% of their maximal heart rate, respectively, as per their performance in the Yo-Yo Intermittent Recovery Test. Visual search behaviours were recorded using Tobii Pro eye-movement registration glasses. Players reported higher rates of perceived exertion on the high- compared to low-workload condition. Participants in the low-performing group increased their average fixation duration and decreased the number of fixations and number of fixation locations from the low- to high-workload conditions. The low- and high-performing groups displayed different visual search strategies with regards the areas of interest fixated upon. Participants in the high-performing group focused on the SpaceFrontPlayer, followed by Ball, and AnotherOpponent. The low-performing group spent more time focusing on the SpaceFrontPlayer and SpacePlayer than Ball and AnotherOpponent. It appears that physiological workload and tactical expertise interact in constraining visual search behaviours in football players. Coaches and practitioners should consider ways to manipulate individual and task constraints while attending to the close interplay between physiological workload, visual behaviour, and tactical performance during practise.



#19 Head acceleration event exposure and cognitive and functional outcomes: a comparison of multiple football seasons

Reference: Res Sports Med. 2022 Jun 16;1-10. doi: 10.1080/15438627.2022.2090249. Online ahead of print.

Authors: Alexa E Walter, James R Wilkes, Madeleine Scaramuzzo, Tesa Johns-Bostick, Scott Lynch, Wayne Sebastianelli, Peter Seidenberg, Tim Bream, Semyon M Slobounov

Summary: Athletes in contact sports are exposed to repetitive impacts as an inherent part of sport. There is concern over the accumulative effect; however, much is still unknown regarding their short-term effects. This study investigated impact accumulation and outcomes over three seasons (2015, 2017, 2019) in NCAA Football Bowl Subdivision players. Impacts were recorded using helmet accelerometers, and virtual reality testing (VR) was done across the season. Incidence rates for impacts (total; ≥25 G to <80 G; ≥80 G) all significantly differed by season (p < 0.05). VR scores changed across the seasons, specifically significant decreases in spatial memory (p < 0.05) in 2015, significant changes in balance and spatial memory (p < 0.05) in 2017, and no significant changes in 2019. Linear regressions predicting VR change score by impact incidence rate were nonsignificant. Monitoring exposure to impacts and changes in outcomes is useful; however, results are fluid, and many factors could indirectly have protective effects on athletes.



#20 Bayesian change-point modelling of the effects of 3-points-for-a-win rule in football

Reference: J Appl Stat. 2019 Jul 2;47(2):248-264. doi: 10.1080/02664763.2019.1635572. eCollection 2020.

Authors: Gebrenegus Ghilagaber, Parfait Munezero

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Summary: We examine the effects of the 3-points-for-a-win (3pfaw) rule in the football world. Data that form the basis of our analyses come from seven leagues around the world (Albania, Brazil, England, Germany, Poland, Romania, and Scotland) and consist of mean goals and proportions of decided matches over a period of about six years before- and about seven years after the introduction of the rule in the respective leagues. Bayesian change-point analyses and Shiryaev-Roberts tests show that the rule had no effects on the mean goals but, indeed, had increasing effects on the proportions of decided matches in most of the leagues studied. This, in turn, implies that while the rule has given teams the incentive to aim at winning matches, such aim was not achieved by scoring excess goals. Instead, it was achieved by scoring enough goals in order to win and, at the same time, defending enough in order not to lose. Our results are in accordance with recent findings on comparing the values of attack and defense - that, in top-level football, not conceding a goal is more valuable than scoring a single goal.



#20 A systematic review of match-play characteristics in women's soccer

Reference: PLoS One. 2022 Jun 30;17(6):e0268334. doi: 10.1371/journal.pone.0268334. eCollection 2022.

Authors: Alice Harkness-Armstrong, Kevin Till, Naomi Datson, Naomi Myhill, Stacey Emmonds

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Summary: This review aimed to (1) systematically review the scientific literature evaluating the match-play characteristics of women's soccer, (2) determine the methods adopted to quantify match-play characteristics of women's soccer, and (3) present the physical, technical and tactical characteristics of women's soccer match-play across age-groups, playing standards and playing positions. A systematic search of electronic databases was conducted in May 2021; keywords relating to the population, soccer and match-play characteristics were used. Studies which quantified physical, technical or tactical performance of women's soccer players during match-play were included. Excluded studies included adapted match-play formats and training studies. Sixty-nine studies met the eligibility criteria. Studies predominantly quantified match-play characteristics of senior international (n = 27) and domestic (n = 30) women's soccer match-play, with only seven studies reporting youth match-play characteristics. Physical (n = 47), technical (n = 26) and tactical characteristics (n = 2) were reported as whole-match (n = 65), half-match (n = 21), segmental (n = 17) or peak (n = 8) characteristics. Beyond age-groups, playing standard, and playing position, fourteen studies quantified the impact of contextual factors, such as environment or match outcome, on match-play characteristics. Distance was the most commonly reported variable (n = 43), as outfield women's soccer players covered a total distance of 5480-11160 m during match-play. This systematic review highlights that physical match-performance increases between age-groups and playing standards, and differs between playing positions. However, further research is warranted to understand potential differences in technical and tactical match-performance. Coaches and practitioners can use the evidence presented within this review to inform population-specific practices, however, they should be mindful of important methodological limitations within the literature (e.g. inconsistent velocity and acceleration/deceleration thresholds). Future research should attempt to integrate physical, technical and tactical characteristics as opposed to quantifying characteristics in isolation, to gain a deeper and more holistic insight into match-performance.



#21 DNA Soccer-Ball Framework Templated Liposome Formation with Precisely Regulated Nucleation Seeds

Reference: ACS Nano. 2022 Jul 1. doi: 10.1021/acsnano.2c03575. Online ahead of print.

Authors: Yunyun Xu, Qian Shi, Kui Huang, Yang Yang

Summary: A soccer-ball-shaped three-dimensional DNA origami framework was assembled to serve as an exoskeleton and to direct liposome growth inside. With up to 90 available inner modification sites, cholesterol moieties were introduced as nucleation seeds, and the vesicle templating efficiency was systematically investigated with precisely regulated seed numbers and arrangements. We confirmed that a nonsaturated optimum number (n = 30) of nucleation seeds with relatively even spatial distribution was essential for achieving well-templated and highly uniform liposomes. The seed arrangement principles and effects and the liposome formation mechanisms are thoroughly discussed. The revealed key factors in the design and optimization of 3D DNA nanoframes for functional liposome production could benefit the fields of nanotechnology and molecular medicine.


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