Latest research in football - week 52 - 2020

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 Effect of Playing Position, Match Half, and Match Day on the Trunk Inclination, G-Forces, and Locomotor Efficiency Experienced by Elite Soccer Players in Match Play
Reference: Sensors (Basel). 2020 Oct 14;20(20):E5814. doi: 10.3390/s20205814.
Authors: José M Oliva-Lozano, Elisa F Maraver, Víctor Fortes, José M Muyor
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Summary: The rapid growth of wearable sensors has allowed the analysis of trunk kinematics during the match, which is necessary for having a better understanding of the postural demands of soccer players. However, some contextual variables may have an impact on the physical demands of the players. This study aimed to analyze the effect of three contextual variables (playing position, match half, and match day) on the sagittal trunk inclination, G-forces, and locomotor efficiency experienced by soccer players in match play. Then, wearable sensors were used to collect the trunk kinematics during 13 matches. Firstly, positional differences were found on the trunk inclination (p = 0.01) and the G-forces experienced by the players (p < 0.001). For example, the greatest and lowest trunk inclination was found for FW (~34.01°) and FB (~28.85°) while the greatest and lowest G-forces were found for WMF (1.16 G) and CD (1.12 G), respectively. However, there were no positional differences in the locomotor efficiency (p = 0.10). Secondly, the match half had a significant effect on the trunk inclination (p = 0.01) and the G-forces experienced by the players (p < 0.001) with significantly lower values observed during the second half. No differences between halves were found on the locomotor efficiency for any playing position (p = 0.41). Finally, no significant effect of match day on any variable was observed. This investigation is one of the first steps towards enhancing the understanding of trunk kinematics from elite soccer players. The positional differences found on the trunk inclination and G-forces imply that the development of position-specific training drills considering the postural demands is necessary to prepare the players not only for the physical demands but also for successful performance in the field of regard. The resistance to fatigue needs to be trained given the differences between halves.

#2 The use of a running power-meter for performance analysis in five-a-side football
Reference: Gait Posture. 2020 Sep 30;83:35-43. doi: 10.1016/j.gaitpost.2020.09.028. Online ahead of print.
Authors: Paul W Macdermid, Tom Pearce, Andrew Foskett
Summary: Power output considers all movement aspects of the game of football and could have meaningful impact for teams. The aim was to assess inter-reliability of ten power meters designed for running; and as a descriptor of individual and team performance during a five-a-side football match. The work aimed to assess inter-device reliability of running power-meters combined with data analysis from intermittent running, along with descriptives of player work rate, gait and team performance during a small-sided game of football. 10 different running power meters inter-reliability were on a treadmill at 8, 10, 12, and 16 km h-1 for 60 s in a random order. Football players (N = 10) performed the Yo-Yo ET1 with the running power meters to determine participants' endurance capability, while assessing the ability to record metrics of gait and power output during intermittent running. Following a period of 7-days participants took part in a 20 min small-sided game of football wearing the running power meters to provide descriptors of work and gait. Good inter-device reliability for the power meters (CV 1.67, range 1.51-1.94 %) during continuous treadmill running were found. Overall mean ± SD results for Yo-Yo ET1 power output 263 ± 36W, power:weight 3.59 ± 0.34W∙kg-1 significantly (p < 0.05) increased with successive stages, while ground-contact time 234 ± 17 ms, and vertical oscillation 90.7 ± 27 mm did not change (p > 0.05). Descriptive analysis of the small-sided game presented mean ± SD absolute and relative power outputs of 148 ± 44W and 1.98 ± 0.53W∙kg-1, equating to 54 ± 21 %Wmax and 74 ± 5%HRmax. Characteristics of gait included cadence 125 ± 22 rpm, ground contact time 266 ± 19 ms, and vertical oscillation 76.7 ± 7 mm. The winning team worked relatively harder than the losing team (53.3 ± 0.7 %Wmax vs 46.7 ± 0.4 %Wmax, p < 0.0001) with more time (398 s vs 141 s) spent above 70 %Wmax.

#3 Attitudes, beliefs and factors influencing football coaches' adherence to the 11+ injury prevention programme
Reference: BMJ Open Sport Exerc Med. 2020 Sep 24;6(1):e000830. doi: 10.1136/bmjsem-2020-000830. eCollection 2020.
Authors: Julie Shamlaye, Luboš Tomšovský, Mark L Fulcher
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Summary: The purpose was to explore football coaches' beliefs and attitudes about injury prevention and the 11+ injury prevention programme, and to investigate factors that may influence adherence to the 11+ injury prevention programme. A total of 538 football coaches who had completed an injury prevention education workshop were invited to participate in a web-based nationwide survey. The survey questions explored beliefs and attitudes about injury prevention and the 11+ injury prevention programme, self-reported adherence to the 11+ programme, as well as perceived barriers and facilitators to the use of the 11+ programme. There were 158 respondents. The majority believe that injury prevention is part of their coaching role (94%) that a structured warm-up is an important part of their team's preparation for training and games (96%), and that the 11+ is effective (92%). While most respondents (95%) use the 11+, modifications are common. Participants with greater coaching experience are more likely to use the programme. Time constraints are the main barriers to adherence, while knowing that the programme enhances performance is seen as a major facilitator. Coaches who attended an injury prevention workshop have positive attitudes towards injury prevention and the 11+ programme. However, coaches with less coaching experience may be less likely to use the 11+ and could therefore be the target population for future education workshops. Promoting the performance enhancing effects of the 11+ and encouraging modifications could improve acceptability and adherence.

#4 Mechanisms explaining the birthplace effect for male elite football players
Reference: J Sports Sci. 2020 Oct 21;1-7. doi: 10.1080/02640414.2020.1835237. Online ahead of print.
Authors: Michiel H H van Nieuwstadt, Marjolijn Das, Marije T Elferink-Gemser
Summary: Earlier research shows that wide regional variations exist in the success of athletes' talent development but is divided with respect to the role of urbanity: both low and high urbanity have been identified as settings that contribute to the presence of talent hotspots. In this article, we intend to provide more insight into the role of urbanity in talent development in Dutch football. We used public data on the regional background of male elite players (N = 825) and combined this with public data on municipal characteristics from Statistics Netherlands and other sources: urbanity, football participation, instructional resources and population composition effects (migration background and income of inhabitants). Linear regression analysis showed that football participation, the proportion of non-western migrants and median income predict "talent yield", i.e., the proportion of young people that reach an elite level in a municipality. Urbanity does not have an independent influence when the proportion of non-western migrants in the municipality is taken into account. The presence of instructional resources does not have an independent influence. The results suggest that characteristics of the built environment, such as indoor and outdoor play opportunities, may be less influential in talent development than previously assumed.

#5 Short-Term Effect of Ankle Eversion Taping on Bilateral Acute Ankle Inversion Sprains in an Amateur College Football Goalkeeper: A Case Report
Reference: Healthcare (Basel). 2020 Oct 15;8(4):E403. doi: 10.3390/healthcare8040403.
Authors: Jung-Hoon Lee
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Summary: This case study aimed to investigate the short-term effects of ankle eversion taping (AET) using kinesiology tape on bilateral acute ankle inversion sprains in an amateur college soccer goalkeeper. Ankle eversion taping was applied for two weeks (average 16 h/day) on a 24-year-old goalkeeper with bilateral grade 2 acute ankle inversion sprain with swelling (left ankle more severe) during a soccer match. The subject had a foot ankle outcome score (FAOS) of 41%; visual analog scale (VAS) scores of 5/10 and 7/10 for the right and left ankles, respectively; patient-specific functional and pain scale (PSFS) score of 12/50; and limited range of motion of the ankle. The swelling disappeared after AET in both ankles. In the weight-bearing lunge test, the right and left ankle distances increased from 2 cm to 12 cm, and from 0 cm to 12 cm, respectively. The FAOS improved from 20% to 97%, while the PSFS score improved from 12/50 to 50/50. The VAS scores decreased to 0/10 for both ankles. AET is a potential clinical treatment method for acute ankle inversion sprain with swelling.

#6 How Successful Are the Teams of the European Football Elite off the Field?-CSR Activities of the Premier League and the Primera División
Reference: Int J Environ Res Public Health. 2020 Oct 16;17(20):7534. doi: 10.3390/ijerph17207534.
Authors: Kinga Ráthonyi-Ódor, Éva Bácsné Bába, Anetta Müller, Zoltán Bács, Gergely Ráthonyi
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Summary: In the past two decades the sports sector has turned its attention to understanding the idea of sustainability, particularly to the practical steps related to this. The purpose of this study is to investigate the nature of CSR (corporate social responsibility) activities carried out by teams playing in the Premier League and the Primera División in the 2018/2019 season, and how these CSR actions serve environmental protection and society, manifesting the concept of sustainable development. We applied comparative analysis based on secondary databases. We examined the available reports regarding all the 40 teams, focusing on information about their CSR aspirations and related academic research results, and we worked out specific criteria to evaluate environmentally and socially related CSR activities. Arsenal and Real Madrid were chosen to show good practices that can serve as examples for the other members of the sports sector. At Premier League clubs, the practical application of the CSR activities has been intensively developed. Clubs share detailed statistical information about their actions, while some of the clubs even publish their future plans. The quantity and detail of the information found with Primera División clubs is rather varied. Some clubs introduce their CSR activities in full detail; however, in the case of most clubs, the accessible information is rather superficial and lacks any exact descriptions. The findings clearly show that the sports world is consciously shifting towards the realization of sustainable development, which requires a comprehensive reconnection of sporting society and an increase in awareness in order to achieve the efficient and successful integration of CSR activities into sport.

#8 The sound of silence in association football: Home advantage and referee bias decrease in matches played without spectators
Reference: Eur J Sport Sci. 2020 Nov 1;1-21. doi: 10.1080/17461391.2020.1845814. Online ahead of print.
Authors: Fabrizio Sors, Michele Grassi, Tiziano Agostini, Mauro Murgia
Summary: Home advantage and referee bias are two well-documented phenomena in professional sports, especially in association football. Among the various factors determining them, the crowd noise is considered as one of the most relevant; yet, the majority of previous studies could not isolate its contribution. The possibility to study the effects of crowd noise - or, better, of its absence - in an ecological context was given by the matches played behind closed doors due to the COVID-19 pandemic. The aim of the present study was to investigate whether home advantage and referee bias still occur (and to what extent) during matches played in absence of spectators. In particular, the focus was on the first and second divisions of the top four countries in the UEFA ranking, for a total of 841 matches behind closed doors. The hypothesis was that, if these phenomena are largely due to the effect of crowd noise, the absence of spectators should reduce their occurrence. Various parameters for each of the two phenomena were considered, and the analyses revealed a reduction of home advantage and the absence of referee bias. The results bring further support to the claim that, among all the factors contributing to home advantage and referee bias, crowd noise has a relevant role. Thus, spectators can significantly contribute to determine the dynamics and the outcomes of professional football matches.

#9 Special Issue on Concussion Biomechanics in Football
Reference: Ann Biomed Eng. 2020 Nov 3. doi: 10.1007/s10439-020-02653-3. Online ahead of print.
Authors: Bethany Rowson, Stefan M Duma
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#10 Athlete workloads during collegiate women's soccer practice: Implications for return-to-play
Reference: J Athl Train. 2020 Nov 5. doi: 10.4085/205-20. Online ahead of print.
Authors: Natalie Kupperman, Alexandra F DeJong, Peter Alston, Jay Hertel, Susan A Saliba
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Summary: Athlete monitoring using wearable technology is often incorporated with soccer athletes. While evaluations have tracked global outcomes across soccer seasons, there is little information on athlete loads during individual practice drills. Understanding these demands is important for athletic trainers for return-to-play decision-making. The objective was to provide descriptive information on total distance, total playerload (PL), distance per minute, and PL per minute for practice drill structures and game-play by player position among female soccer athletes across a competitive season. Thirty-two female college soccer players (20±1 years) participated in this study. Athletes wore a single GPS and triaxial accelerometer unit during all practices and games in a single soccer season. Individual practice drills were labeled by the team's strength and conditioning coach, and binned into physical, technical and tactical skills, and small- and large-sided competition drill structures. Descriptive analyses were used to assess the median total distance, total PL, distance per minute, and PL per minute by drill structure and player position (defenders, midfielders, forwards/strikers) during practices and games. Small- and large-sided competitive drills imposed the greatest percentage of workload across all measures for each position (~20% of total practice), followed by physical drills. When comparing technical and tactical, technical skills required athletes to cover the greatest distance (technical: ~17%; tactical: ~15%), tactical skills required higher play intensity during practices across all positions (technical: ~18%; tactical: ~13%). Defenders had the highest median PL outcomes of all positions during practices. Different practice drill types imposed varying levels of demands on female soccer athletes, which simulated game play. Athletic trainers and other clinicians may use this information for formulating objective return-to-play guidelines for injured collegiate women's soccer players.

#11 The relationship between Isometric Mid-Thigh Pull variables and athletic performance measures: empirical study of english professional soccer players and meta-analysis of extant literature
Reference: J Sports Med Phys Fitness. 2020 Nov 4. doi: 10.23736/S0022-4707.20.11205-2. Online ahead of print.
Authors: Liam Mason, Andrew Kirkland, James Steele, James Wright
Summary: There is currently limited evidence available to support the use of the isometric mid thigh pull (IMTP) within professional soccer. The aim of this study was to analyse the association between IMTP variables, with common markers of athletic performance capability. Eleven professional development soccer players (age: 20 ± 2 years, stature: 1.82 ± 0.10 m, mass: 76.4 ± 12.8 kg) performed IMTP, 5 m and 10 m accelerations, maximal sprint speed (MSS), countermovement jump (CMJ), and the 505 change of direction test (COD). Relative and absolute Peak force (PF) and force at 50, 100, 150 and 200 ms values were measured during the IMTP. Relative F150, F200, PF displayed large to very large correlations with MSS (r = 0.51, r = 0.66, and r = 0.76 respectively), while absolute PF also displayed a large correlation with MSS (r = 0.57). Relative and absolute PF showed large correlations with CMJ height (r = 0.54 and r = 0.55 respectively). Relative F150 and F200 highlighted large correlations with COD ability (r = -0.68 and r = -0.60 respectively). Relative F200 and PF had a large negative correlation with 10m acceleration (r = -0.55 and r = -0.53 respectively). This study provides an important contribution to knowledge within the area of IMTP testing in professional soccer by evidencing the prominence of the isometric force generating capacity as an underpinning factor in relation to athletic capability.

#12 Effects of Strength vs. Plyometric Training on Change of Direction Performance in Experienced Soccer Players
Reference: Sports (Basel). 2020 Oct 30;8(11):E144. doi: 10.3390/sports8110144.
Authors: Håvard Guldteig Rædergård, Hallvard Nygaard Falch, Roland van den Tillaar
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Summary: The purpose of this study was to compare how 6 weeks of strength- vs. plyometric training, which were matched upon direction of motion and workload, influences change of direction (COD) performance. Twenty-one experienced male soccer players (age: 22.2 ± 2.7) were pair-matched into a strength- (n = 10) and a plyometric (n = 11) training group. CODs of 45°, 90°, 135° and 180° performed from either a 4 m or 20 m approach distance were compared before and after intervention. Results showed no significant difference between groups. Significant effects were only found within the plyometric training group (-3.2% to -4.6%) in 90°, 135° and 180° CODs from 4 m and a 180° COD from a 20 m approach distance. Individual changes in COD performances showed that with the 4 m approach at least 55% and 81% of the strength and plyometric training group, respectively, improved COD performance, while with the 20 m approach at least 66% of both groups improved performance. This study showed that the plyometric training program can improve most CODs, with angles over 90°, although this is dependent on the distance approaching the COD. Considering the limited time of implementing physical conditioning, in addition to regular soccer practice in most soccer environments, the current plyometric training program can be advantageous in improving CODs at maximal intensity.

#13 Purposeful Heading in Youth Soccer: A Review
Reference: Sports Med. 2020 Nov 3. doi: 10.1007/s40279-020-01376-8. Online ahead of print.
Authors: Victoria E Wahlquist, Thomas W Kaminski
Summary: Recent public concern over the short- and long-term effects of repetitive head impacts (RHI) associated with purposeful heading in soccer has led researchers to study a multitude of variables related to this important aspect of the game. Of particular interests are the effects of soccer heading in the youth population (≤ 13 years old) whose brains are undergoing rapid development. We conducted a review on youth soccer heading that includes purposeful heading frequency, head impact biomechanics, head injuries, clinical outcomes, and modifying factors. We have concluded that youth soccer players head the ball at a low frequency that typically increases with age and with a finding that boys head the ball more often than girls do. Interestingly, although girls head the ball less frequently than boys do, they tend to sustain higher head impact magnitudes. Head injuries are more likely to occur in girls versus boys and during games because of contact with another player. Clinical outcome measures of concussion are often utilized to study the effects of soccer heading, in both field and laboratory environments. Immediately following soccer heading, youth often report having a headache and demonstrate some deficits in balance measures. Modifying factors that may benefit soccer players participating in purposeful heading activities include stronger neck musculature, wearing headgear, and the use of mouthguards. Research involving youth soccer players needs to be expanded and funded appropriately to better understand the consequences of RHI in both the short and long term.

#14 Relationships Between Training Workload Parameters with Variations in Anaerobic Power and Change of Direction Status in Elite Youth Soccer Players
Reference: Int J Environ Res Public Health. 2020 Oct 29;17(21):E7934. doi: 10.3390/ijerph17217934.
Authors: Hadi Nobari, Luis Felipe Tubagi Polito, Filipe Manuel Clemente, Jorge Pérez-Gómez, Mina Ahmadi, Miguel Ángel Garcia-Gordillo, Ana Filipa Silva, Jose Carmelo Adsuar
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Summary: The purpose of this study was to test the relationships between training workload (WL) parameters with variations in anaerobic power and change of direction (COD) in under-16 soccer players. Twenty-three elite players under 16 years were daily monitored for their WL across 20 weeks during the competition soccer season. Additionally, players were assessed three times for anthropometric, body composition, COD, and anaerobic power. A correlational analysis between the mean differences between assessments and accumulated WL parameters were conducted. Moreover, a regression analysis was executed to explain the variations in the percentage of change in fitness levels considering the accumulated WL parameters and peak height velocity. The accumulated daily loads during one week showed a large and a moderate correlation with peak power and COD at different periods of the season. Regression analysis showed no significant predictions for COD (F(12, 10) = 1.2, p = 0.41) prediction, acute load (F(12, 10) = 0.63, p = 0.78), or chronic load (F(12, 10) = 0.59, p = 0.81). In conclusion, it may be assumed that the values of the chronic workload and the accumulated training monotony can be used to better explain the physical capacities of young soccer players, suggesting the importance of psychophysiological instruments to identify the effects of the training process in this population.

#15 Coronavirus Disease-19 Quarantine Is More Detrimental Than Traditional Off-Season on Physical Conditioning of Professional Soccer Players
Reference: J Strength Cond Res. 2020 Oct 30. doi: 10.1519/JSC.0000000000003890. Online ahead of print.
Authors: Rafael Grazioli, Irineu Loturco, Bruno M Baroni, Gabriel S Oliveira, Vasyl Saciura, Everton Vanoni, Rafael Dias, Filipe Veeck, Ronei S Pinto, Eduardo L Cadore
Summary: Beyond the severe health crisis, the coronavirus disease 2019 has also affected the high-performance sports scenario. In soccer, practitioners are concerned about the effects of long-term detraining on players' conditioning, and caution is required when activities return. This study assessed body composition, jump and sprint performance, hamstring eccentric strength, and intermittent cardiorespiratory fitness of 23 male professional soccer players who returned to training activities after 63 days of quarantine. The results were compared with their physical condition assessed before a pre-season phase as soon as they returned to training after a regular 24-day off-season period. In comparison with after off-season assessments, the quarantine induced significant increases in body mass, body fat mass, 10- and 20-m sprint times as well as decreases in countermovement jump height (p < 0.05). There were no significant changes in hamstring eccentric strength, squat jump height, and cardiorespiratory fitness (p > 0.05). In summary, we showed that 63 days of quarantine impaired several physical performance measures compared with regular off-season in soccer players. Given the present results, special attention should be given to body composition-related and speed power-related capabilities after long-term detraining in professional soccer.

#16 Monitoring Training Load in Soccer: The ROMEI Model
Reference: J Strength Cond Res. 2020 Oct 30. doi: 10.1519/JSC.0000000000003875. Online ahead of print.
Authors: Marco Montini, Jacopo E Rocchi
Summary: For a training organization, monitoring training load (TL) is of paramount importance. Despite this, a conclusive response on such topic is yet to be reported. The aims of this study were to investigate the relationship between TL indicators and to propose a new method for monitoring TL response and physical fitness. Twenty professional soccer players were retrospectively evaluated. The first phase of data analysis included 34 in-season training sessions. Subsequently, three microcycles (T1-T2-T3) of pre-season training were processed. A regression model was used to examine the relationships between internal TL (session rating of perceived exertion [s-RPE]) and external TL (energy expenditure, EE). The standard error of the regression equation was used to propose a new model called "ROMEI" (Relation of Ongoing Monitored Exercise in Individual). The level of statistical significance was set at p < 0.05. During the competitive season and the pre-season training camp, the average TL values were 65.8 ± 22 and 58.2 ± 22 minutes; 336 ± 204 and 228 ± 101 AU of s-RPE; and 29 ± 13 and 25 ± 9 kJ kJ of EE, respectively. In the competitive season, the collective and average individual correlation coefficients between s-RPE and EE were r = 0.888 and r = 0.892 ± 0.05, respectively. Considering slope values (m) of the regression line, data highlighted a significant increase of +34.4 ± 15.9% in T2 vs. T3 (p < 0.001) and +38.2 ± 15.2% in T1 vs. T3 (p < 0.001). Data shown in this investigation support the use of an individualized analysis to better understand the TL administered to soccer players rather than a collective analysis. This may be accomplished with the proposed ROMEI model.

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