Latest research in football - week 17 - 2021

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 Talent Development Environments in Football: Comparing the Top-Five and Bottom-Five-Ranked Football Academies in Norway 

Reference: Int J Environ Res Public Health. 2021 Feb 1;18(3):1321. doi: 10.3390/ijerph18031321. 

Authors: Kristian Gangsø, Nils Petter Aspvik, Ingar Mehus, Rune Høigaard, Stig Arve Sæther

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Summary: The aim of this study was to examine junior-elite football players' perception of their talent development environment by comparing clubs ranked as the top-five and bottom-five in the 2017 Norwegian academy classification. In total, 92 male junior-elite football players recruited from under-19 teams from five professional football club academies took part in the study. The Talent Development Environment Questionnaire (TDEQ-5; Martindale et al. 2010) was used to measure the players' perceptions of their team environment. The subscale long-term development focus and support network had the highest score and indicated that they perceived that the environment was high quality with respect to those factors. Players from the top-five-ranked clubs perceived their development environments to be significantly more positive with respect to holistic quality preparation, alignment of expectations, communication and, compared to players from the bottom-five-ranked clubs. The players' perceptions of the talent development environment seem to be in alignment of the academy classification undertaken by the Norwegian top football association. 



#2 A Longitudinal Exploration of Match Running Performance during a Football Match in the Spanish La Liga: A Four-Season Study 

Reference: Int J Environ Res Public Health. 2021 Jan 28;18(3):1133. doi: 10.3390/ijerph18031133. 

Authors: Eduard Pons, José Carlos Ponce-Bordón, Jesús Díaz-García, Roberto López Del Campo, Ricardo Resta, Xavier Peirau, Tomas García-Calvo

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Summary: This study aimed to analyze and compare the match running performance during official matches across four seasons (2015/2016-2018/2019) in the top two professional leagues of Spanish football. Match running performance data were collected from all matches in the First Spanish Division (Santander; n = 1520) and Second Spanish Division (Smartbank; n = 1848), using the Mediacoach® System. Total distance and distances of 14-21 km·h-1, 21-24 km·h-1, and more than 24 km·h-1, and the number of sprints between 21 and 24 km·h-1 and more than 24 km·h-1 were analyzed. The results showed higher total distances in the First Spanish Division than in the Second Spanish Division (p < 0.001) in all the variables analyzed. Regarding the evolution of both leagues, physical demands decreased more in the First Spanish Division than in the Second Spanish Division. The results showed a decrease in total distance and an increase in the high-intensity distances and number of sprints performed, although a clearer trend is perceived in the First Spanish Division (p < 0.001; p < 0.01, respectively). Knowledge about the evolution of match running performance allows practitioners to manage the training load according to the competition demands to improve players' performances and reduce the injury rate. 



#3 Comparison of Goal Scoring Patterns in "The Big Five" European Football Leagues 

Reference: Front Psychol. 2021 Jan 13;11:619304. doi: 10.3389/fpsyg.2020.619304. eCollection 2020. 

Authors: Chunhua Li, Yangqing Zhao

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Summary: The objective of the study was to compare goal scoring patterns among the "Big Five" European football leagues during the 2009/2010-2018/2019 seasons. A total of 18 pattern dimensions related to the offense pattern, the shooting situation and the scoring time period were evaluated. Kruskal-Wallis analyses revealed significant pattern differences among the five leagues. The Spanish La Liga showed a greater proportion of goals from throw-ins. The English Premier League had a higher tendency to score from corner kicks. The German Bundesliga had the greatest number of goals from counterattacks and indirect free kicks, and the Italian Serie A had the greatest proportion of penalties. Ligue 1's scoring ability is weaker than that of the other leagues, especially Bundesliga. The Bundesliga had an overwhelming advantage in goals scored on big chances with assists, while the Premier League had an advantage in goals scored with assists that were not from big chances. However, the differences among the five leagues in the mean goals scored in the last 15 min and the goals from elaborate attacks and direct free kicks were not statistically significant. These results provide a valuable addition to the knowledge of different goal patterns of each league and allow us to better understand the differences among the leagues. 



#4 Professional football clubs and empirical evidence from the COVID-19 crisis: Time for sport entrepreneurship? 

Reference: Technol Forecast Soc Change. 2021 Apr;165:120572. doi: 10.1016/j.techfore.2021.120572. Epub 2021 Jan 13. 

Authors: Jonas Hammerschmidt, Susanne Durst, Sascha Kraus, Kaisu Puumalainen

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Summary: The coronavirus disease (COVID-19) has spread worldwide in a short period and has developed into one of the biggest public health issues of the last decade. The actions initiated by governments to minimize person-to-person contact have also severely affected professional football clubs (PFCs) in the season 2019/20. Given the role of football in Europe, football clubs gained massive public and political attention during the COVID-19 crisis. Based on an exploratory multiple case study approach involving PFCs from five European football leagues, this study investigates the responses of these clubs to the COVID-19 pandemic. The findings show the relevance of solidarity with certain stakeholders during the pandemic, but also reveal the fragility of PFCs due to their financial structure and underdeveloped managerial and entrepreneurial strategies to cope with the crisis. This study contributes theoretically and empirically to the literature on the entrepreneurial behavior and crisis management of elite sport organizations and illustrates a holistic map of a dense, high solidary stakeholder network. 



#5 Exertional heat illness risk factors and physiological responses of youth football players

Reference: J Sport Health Sci. 2021 Jan;10(1):91-98. doi: 10.1016/j.jshs.2019.03.002. Epub 2019 Mar 7. 

Authors: Susan W Yeargin, John J Dickinson, Dawn M Emerson, Jessica Koller, Toni M Torres-McGehee, Zachary Y Kerr

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Summary: The aim was to determine which intrinsic and extrinsic exertional heat illness (EHI) risk factors exist in youth American football players and observe perceptual and physiological responses of players during events (games and practices). Cross-sectional cohort study observing 63 youth football players, varying in position. Independent variables were league (weight-restricted (WR, n = 27) and age-restricted (AR, n = 36)) and event type. Dependent variables were anthropometrics, work-to-rest ratio, and wet bulb globe temperature. Descriptive variables included preparticipation examination and uniform configuration. A subset of 16 players participated in physiological variables (heart rate and gastrointestinal temperature). Data collection occurred on 7 AR and 8 WR nonconsecutive practices and the first 3 games of the season. Mean values for anthropometric variables were higher (p < 0.05) in the AR league than the WR league. Work time (χ2 (1,111) = 4.232; p = 0.039) and rest time (χ2 (1,111) = 43.41; p < 0.001) were significantly greater for games, but ratios were significantly higher for practices (χ2 (1,111) = 40.62; p < 0.001). The majority of events (77%) observed were in black and red flag wet bulb globe temperature risk categories. A total of 57% of the players had a preparticipation examination, and up to 82% of events observed were in full uniforms. Individual gastrointestinal temperature and heart rate responses ranged widely and no players reached critical thresholds. Extrinsic (disproportionate work ratios, environmental conditions) and intrinsic (higher body mass index) EHI risk factors exist in youth football. Certain risk factors may be influenced by event and league type. National youth football organizations need to create thorough guidelines that address EHI risk factors for local leagues to adopt. 



#6 Analysis of Burnout and Psychosocial Factors in Grassroot Football Referees 

Reference: Int J Environ Res Public Health. 2021 Jan 27;18(3):1111. doi: 10.3390/ijerph18031111. 

Authors: Natalia Orviz-Martínez, María Botey-Fullat, Sergio Arce-García

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Summary: The aim of this paper is to analyze the interrelationships between the burnout and different psychosocial variables to which the grassroots football referee is exposed, in particular, associated with the influence of the environment and the level of verbal and physical aggression. To this end, a questionnaire was developed, consisting of items from the Maslach Burnout Inventory-General Survey(MBI-GS) and various self-constructed items designed to find out these psychosocial variables. First, a study of the structure of the form was carried out. Second, a structural equation model was designed in order to test the causal relationship between the variables under consideration. The results obtained point to the validity of the proposed theoretical model. It is recommended to initiate training programs for this group aimed at strengthening personal coping and social support strategies, which can help minimize the evolution of this syndrome. 



#7 Heart Rate Variability and Physical Demands of In-Season Youth Elite Soccer Players

Reference: Int J Environ Res Public Health. 2021 Feb 3;18(4):1391. doi: 10.3390/ijerph18041391. 

Authors: Javier Sánchez-Sánchez, Javier Botella, Jose Luis Felipe Hernández, Manuel León, Víctor Paredes-Hernández, Enrique Colino, Leonor Gallardo, Jorge García-Unanue

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Summary: Monitoring fatigue and performance is important for adjusting training loads in soccer. Therefore, knowing the status of the player when applying a training stimulus is key to optimizing the players' development. This study aims to evaluate the interaction between internal and external load, during training and matches, in an elite youth soccer team. Seventeen youth players of the highest Spanish category were monitored with GPS devices during training and matches, as well as recording their nocturnal heart rate variability (HRV). We employed a linear mixed model to assess the physical demands between training and matches, and to compare the HRV variables. A higher total distance (+2993.35-5746.56 m; ES = 1.4), distance at high intensity (+641.24-1907 m; ES = 1.5), sprint distance (+350.46-795.05 m; ES = 2.1), number of sprints (+18.38-41.58; ES = 1.9), and number of repeated sprints (+5.91-15.30; ES = 1.7) (all p < 0.001), but not in the number of accelerations, were reported during the matches when compared to the training sessions during the 11 weeks. The analysis of the HRV variables showed no significant differences between the accumulated values during a training week, providing similar results pre-match or post-match (p > 0.05). The LF/HFRATIO showed a negative influence on the total distance ran, distance at high intensity, distance in sprint, number of sprints, and repeated sprint. RRMEAN was positively related to the sprint number. The results of the present study suggest that nocturnal HRV variables are not different between pre-match and post-match. Furthermore, it suggests that LF/HFRATIO and RRMEAN during pre-match can determine the external load that the player will be able to complete during the match. 



#8 Relative Age Effect in Elite German Soccer: Influence of Gender and Competition Level

Reference: Front Psychol. 2021 Jan 7;11:587023. doi: 10.3389/fpsyg.2020.587023. eCollection 2020. 

Authors: Martin Götze, Matthias W Hoppe 

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Summary: The relative age effect (RAE) is associated with (dis)advantages in competitive sports. While the RAE in elite male soccer reveals a skewed birthdate distribution in relation to a certain cut-off date, research of RAE in elite female soccer is affected by small number of samples and conflicting results. The purpose of this study was to investigate the RAE in elite adult German soccer regarding gender and competition level. The sample comprised 680 female and 1,083 male players of the two top German leagues during the 2019/20 season and German national teams (A-Team to Under 19). Differences between the observed and expected birthdate distributions were analyzed using chi-square statistics and effect sizes followed by calculating odds ratios. Results showed a statistically significant RAE with small effect size across all players included for both genders (female players: P < 0.001, W = 0.16, male players: P < 0.001, W = 0.23). The identified RAE was based on an over-representation of players born at the beginning of the year. According to gender and competition level, RAEs were more pronounced in German male soccer. While significant RAEs were found among males in the first two leagues (first league: P < 0.001, W = 0.19, second league: P < 0.001, W = 0.26), the RAE of females was more pronounced in the second league (first league: P = 0.080, W = 0.16, second league: P = 0.002, W = 0.20). The analysis of RAE regarding the national teams revealed a statistically significant RAE with large effect size for only the youngest investigated age group of male players (Under 19: P = 0.022, W = 0.52). Our data show an RAE in female and male German adult soccer, which could be accompanied by a loss of valuable elite players during the youth phase of the career. Consequently, the pool of talented players at the adult level would be limited. 



#9 Feasibility Study of an Educational Intervention to Improve Water Intake in Adolescent Soccer Players: A Two-Arm, Non-Randomized Controlled Cluster Trial

Reference: Int J Environ Res Public Health. 2021 Feb 2;18(3):1339. doi: 10.3390/ijerph18031339. 

Authors: Rubén Martín-Payo, María Del Mar Fernández-Álvarez, Edurne Zabaleta-Del-Olmo, Rebeca García-García, Xana González-Méndez, Sergio Carrasco-Santos

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Summary: This study aimed to assess the feasibility of an educational intervention on hydration behavior in adolescent soccer players. A pilot study of a two-arm, non-randomized controlled cluster trial was conducted. A total of 316 players aged 13-16 agreed to participate. The response variables were the players' participation in the intervention, their perception of the knowledge acquired, the usefulness and the overall assessment of the intervention. Hydration patterns and acquisition of knowledge on hydration behavior were also assessed. The intervention involved two elements: posters and a web app. A total of 259 adolescents completed the study (intervention group (IG) = 131; control group (CG) = 128). 80.6% of the players responded to the survey assessing the feasibility of the intervention. The mean number of correct answers regarding behavior was significantly higher in the IG (3.54; SD = 1.162) than in the CG (2.64; SD = 1.174) (p < 0.001). The water consumption pattern at all the clubs was ad libitum. Of the players, 10% did not drink any water at all during the game. In conclusion, this intervention has been shown to be feasible for implementation with adolescent soccer players. It suggests that hydration guidelines should be informed by personal factors and that ad libitum water consumption should be avoided. 



#10 The Impact of Covid-19 on Women's Experiences of and Through Football in Buenos Aires

Reference: Front Sports Act Living. 2021 Jan 18;2:624055. doi: 10.3389/fspor.2020.624055. eCollection 2020. 

Authors: Juliana Román Lozano, Mónica Santino, David Wood

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Summary: This research report explores the impact of Covid-19 on women's football in Buenos Aires. The suspension of all forms of football in Argentina as part of the country's hard lockdown measures threatens to undo significant gains made in women's football in recent years. By focussing on the experiences of key actors in a feminist Civil Society Organization (CSO) and a newly professional women's team, respectively, we examine what the pandemic has meant for women's football and for women football players at different levels of the game. We also consider the potential impact of the current situation on the future of women's football in Argentina, representative of wider social advances for women in the country. 



#11 Measuring Sports' Perceived Benefits and Aggression-Related Risks: Karate vs. Football

Reference: Front Psychol. 2021 Jan 18;11:625219. doi: 10.3389/fpsyg.2020.625219. eCollection 2020. 

Authors: Teresa Limpo, Sid Tadrist

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Summary: Little is known about people's perceived benefits and risks of sports, despite their role in shaping people's intentions to engage in them. Here, we developed and tested a scale to measure perceived physical, emotional, cognitive, and social benefits as well as aggression-related risks of karate and football. Additionally, we compared these perceptions within and between these two sports, as well as among undergraduates with current/former participation in different types of physical activity (viz., martial artists, team sports players, participants in other types of physical activity, and non-participants). After a literature review, we created a 5-factor scale with 20 items administered to 184 undergraduates, along with questions about physical activity participation. After removing five items, confirmatory factor analyses supported the factor structure of the scale. Factor loadings and reliability indices were acceptable, though less than desirable results were found concerning the average variance extracted of all benefits dimensions and the reliability of the social benefits dimension. Analyses of variance showed that: (a) physical benefits were seen as the salient outcomes of karate and football, though martial artists perceived karate's physical, emotional, and social benefits to the same extent; (b) in comparison to football, karate was perceived to bring more emotional and cognitive benefits and to entail less aggressiveness risks; (c) karate and football perceptions varied as a function of participant's involvement in physical activity. This study presents a promising instrument to gather information on people's perceptions about karate and football, which can be used to foster people's engagement in them. 



#12 Anthropometric and musculoskeletal gender differences in young soccer players

Reference: J Sports Med Phys Fitness. 2021 Feb 8. doi: 10.23736/S0022-4707.21.11617-2. Online ahead of print. 

Authors: Shuji Taketomi, Kohei Kawaguchi, Yuri Mizutani, Ryota Yamagami, Shin Sameshima, Seira Takei, Kenichi Kono, Hiroshi Inui, Sakae Tanaka, Nobuhiko Haga

Summary: This study aimed to clarify potential gender differences across a comprehensive set of anthropometric and musculoskeletal characteristics within a young soccer player population. This study included 227 (121 males and 106 females with mean ages of 19.0 and 17.5 years, respectively) young elite soccer players. Anthropometric measurements were obtained. In addition, general joint laxity tests assessing the wrist, elbow, shoulder, trunk, hip, knee, and ankle were performed. Muscle flexibility tests were performed on the iliopsoas, quadriceps femoris, hamstring, gastrocnemius, and soleus muscles. Moreover, isometric knee extension and flexion strength and isometric hip abduction strength were measured. Single- and double-leg balance tests were also performed. Male soccer players were taller, heavier, and had lower fat mass and percent body fat, and greater skeletal muscle mass and body minerals than female soccer players. Female soccer players had significantly greater laxity in all tests for general joint laxity. Female soccer players demonstrated significantly better hamstring and soleus flexibility than male soccer players but worse iliopsoas flexibility. Consequently, no significant differences were noticed in the quadriceps and gastrocnemius muscles between the male and female soccer players. However, female soccer players demonstrated significantly weaker knee extension and flexion and hip abduction. The hamstring- quadriceps ratio was significantly lower in female soccer players. Although no significant difference exists in the center of pressure excursion in the double-leg balance test between male and female soccer players, female soccer players displayed a significantly lower center of pressure excursion in the single-leg balance test. Young male and female soccer players demonstrate significantly different anthropometric and musculoskeletal profiles. 



#13 Processing visual information in elite junior soccer players: Effects of chronological age and training experience on visual perception, attention, and decision making 

Reference: Eur J Sport Sci. 2021 Feb 8;1-28. doi: 10.1080/17461391.2021.1887366. Online ahead of print. 

Authors: Stefanie Klatt, Nicholas J Smeeton

Summary: Processing information in peripheral vision is an important perceptual-cognitive skill in team sports. The relative contribution of various perceptual-cognitive skills to expertise in sports throughout adolescence has not been investigated in detail yet. The current study examined the effects of chronological age and training experience on perception, attention, and decision making in young soccer players. Sixty-five elite youth players were required to judge different game situations in a decision-making task involving both perceptual (object detection) and attentional (postural feature recognition) skills to perceive player configurations in the visual periphery. In general, performance decreased in the decision-making and feature-recognition tasks with increasing use of peripheral visual field, but not in the object-detection task. Superior performances were found for under 18 years old players compared to under 16 years old players especially in their attentional skills. Higher training experience affected decision-making and attentional performance. Overall, the findings provide insights and implications for training perceptual-cognitive skills in team sports. 



#14 Hand, Wrist, and Forearm Injuries in Male Professional Soccer Players: A Prospective Cohort Study of 558 Team-Seasons From 2001-2002 to 2018-2019 

Reference: Orthop J Sports Med. 2021 Jan 25;9(1):2325967120977091. doi: 10.1177/2325967120977091. eCollection 2021 Jan. 

Authors: Jonny K Andersson, Håkan Bengtsson, Markus Waldén, Jón Karlsson, Jan Ekstrand

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Summary: The literature on upper extremity injuries in professional soccer players is scarce, and further insight into the onset and cause of these injuries as well as potential differences between goalkeepers and outfield players is important. The purpose was to investigate the epidemiology of hand, wrist, and forearm injuries in male professional soccer players between 2001 and 2019. Between the 2001-2002 and 2018-2019 seasons, 120 European male soccer teams were followed prospectively for a varying number of seasons (558 team-seasons in total). Time-loss injuries and player-exposures to training sessions and matches were recorded on an individual basis in 6754 unique players. Injury incidence was reported as the number of injuries per 1000 player-hours, and between-group differences were analyzed using Z statistics and rate ratios (RRs) with 95% CIs. Between-group differences in layoff time were analyzed. In total, 25,462 injuries were recorded, with 238 (0.9%) of these affecting the hand (71.4%; n = 170), wrist (16.8%; n = 40), and forearm (11.8%; n = 28), producing an incidence of 0.065 injuries per 1000 hours. A majority of the injuries were traumatic with an acute onset (98.7%; n = 235). Fractures were the most common injuries recorded (58.8%; n = 140), often involving the metacarpal bones (25.2%; n = 60) and phalanges (10.1%; n = 24). The injury incidence was significantly higher for goalkeepers (115 injuries; 0.265 per 1000 hours) compared with outfield players (123 injuries; 0.038 per 1000 hours) (RR, 7.0 [95% CI, 5.4-9.0]). Goalkeepers also had a significantly longer mean layoff time than outfield players (23 ± 27 vs 15 ± 27 days; P = .016). Injuries to the hand, wrist, and forearm constituted less than 1% of all time-loss injuries in male professional soccer players. Fractures were most common and constituted more than half of all injuries. Goalkeepers had a 7-fold higher incidence and an over 1-week longer mean layoff time compared with outfield players. 



#15 Effects of Complex Training on Sprint, Jump, and Change of Direction Ability of Soccer Players: A Systematic Review and Meta-Analysis 

Reference: Front Psychol. 2021 Jan 22;11:627869. doi: 10.3389/fpsyg.2020.627869. eCollection 2020. 

Authors: Rohit K Thapa, Danny Lum, Jason Moran, Rodrigo Ramirez-Campillo

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Summary: The aim of this meta-analysis was to evaluate the effects of complex training (CT) on sprint, jump, and change of direction (COD) ability among soccer players. After an electronic search, 10 peer-reviewed articles were considered in the meta-analysis. The athletes included in this meta-analysis were amateur to professional level male soccer players (age range, 14-23 years). These studies incorporated CT in soccer players who were compared to a control group. Significant moderate to large improvements were observed in the CT group [sprint: standard mean difference (SMD) = 0.92-1.91; jump: SMD = 0.96-1.58; COD: SMD = 0.97-1.49] when compared to control groups. Subgroup analysis were also conducted based on age, duration, and competitive level. The beneficial effects of CT were greater in players <18 vs. ≥18 years (linear sprinting; SMD = 2.01 vs. -0.13), after ≥8 vs. <8 weeks (jumping and COD; SMD = 1.55-2.01 vs. 0.31-0.64, respectively) and among professional vs. amateur players (linear sprinting and with COD; SMD = 1.53-1.58 vs. 0.08-0.63, respectively). In conclusion, regular soccer training programs may be supplemented with CT to improve sprint, jump, and COD performance. A longer duration of CT (≥8 weeks) seems to be optimal in improving the physical abilities of soccer players. Professional players and <18 years players may benefit more from CT program. 


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