Latest research in football - week 11 - 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 Ordering sequential competitions to reduce order relevance: Soccer penalty shootouts

Reference: PLoS One. 2020 Dec 30;15(12):e0243786. doi: 10.1371/journal.pone.0243786. eCollection 2020. 

Authors: Nils Rudi, Marcelo Olivares, Aditya Shetty

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Summary: In sequential competitions, the order in which teams take turns may have an impact on performance and the outcome. Previous studies with penalty shootouts have shown mixed evidence of a possible advantage for the first shooting team. This has led to some debate on whether a change in the rules of the game is needed. This work contributes to the debate by collecting an extensive dataset of shootouts which corroborates an advantage for the first shooter, albeit with a smaller effect than what has been documented in previous research. To evaluate the impact of alternative ordering of shots, we model shootouts as a probability network, calibrate it using the data from the traditional ordering, and use the model to conduct counterfactual analysis. Our results show that alternating the team that shoots first in each round would reduce the impact of ordering. These results were in part developed as supplement to field studies to support the International Football Association Board's (IFAB) consideration of changing the shooting order. 



#2 Defining the Normal Spectrum of Electrocardiographic and Left Ventricular Adaptations in Mixed-Race Male Adolescent Soccer Players 

Reference: Circulation. 2021 Jan 5;143(1):94-96. doi: 10.1161/CIRCULATIONAHA.120.049740. Epub 2020 Dec 30. 

Authors: Aneil Malhotra, David Oxborough, Prashant Rao, Gherardo Finocchiaro, Harshil Dhutia, Vivek Prasad, Chris Miller, Bernard Keavney, Michael Papadakis, Sanjay Sharma

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#3 Putting the player first: A method to analyse and develop expert players performance in professional soccer

Reference: J Sports Sci. 2020 Dec 31;1-13. doi: 10.1080/02640414.2020.1864103. Online ahead of print. 

Authors: Eileen Gleeson, Seamus Kelly

Summary: The purpose of this paper is to present a player-centred performance analysis method as an effective mechanism to enhance expert players' performance in professional soccer. Data were collected through an application of a developed performance analysis method and subsequent unstructured interviews to explore participants' experience of the applied methodology. Grounded by an enactive perspective of human activity, the applied methodology foregrounds the player's intrinsic experience and places the player at the centre of the analysis and interpretation process. The sample included thirty professional soccer players with professional playing experience ranging from 2 years to 19 years and representing three professional teams. Using an interpretive data analysis approach results were considered from a methodological perspective concerning the core functions of a performance analysis method. Categories regarding performance analysis and performance development were highlighted. Findings demonstrate that adopting a player-centred approach to performance analysis in professional soccer provides advancement of the understanding of the collective performance of the expert player and may increase the opportunity for sustained learning. 



#4 Salivary Immunoendocrine and Self-report Monitoring Profiles across an Elite-Level Professional Football Season 

Reference: Med Sci Sports Exerc. 2020 Dec 23;Publish Ahead of Print. doi: 10.1249/MSS.0000000000002553.

Authors: Matthew Springham, Sean Williams, Mark Waldron, Anthony J Strudwick, Chris Mclellan, Robert U Newton 

Summary: This investigation examined the longitudinal changes and inter-relationships of salivary and self-report monitoring measures across a professional football season. Measures were collected bi-weekly from 18 senior professional male players across a six-week pre-season and eight five-week in-season mesocycles and analysed using a linear mixed-effects model. Analysis identified a small (P=0.003) cross-season suppression of salivary immunoglobulin-A, small reductions to salivary α-amylase (P=0.047) and salivary cortisol (P=0.007), and trivial changes to salivary testosterone (P>0.05). The testosterone:cortisol ratio typically responded inversely to changes in player workload. Self-report measures of fatigue (P=0.030), sleep quality (P=0.003) and muscle soreness (P=0.005) improved (ES=small) across the first half of the season. Fatigue and sleep measures were most consistently related to hormonal measures (R2 = 0.43 to 0.45). For these relationships, increases in cortisol were associated with compromised self-report responses, whereas increases in testosterone:cortisol were associated with improved responses. Non-linear relationships were identified for fatigue with immunoglobulin-A (P=0.017; ES=trivial) and testosterone (P=0.012; ES=trivial); for sleep quality with testosterone (P<0.001; ES=trivial); for muscle soreness with testosterone (P=0.012; ES=trivial) and for the self-report inventory sum with testosterone (P=0.027; ES=trivial). For these relationships, self-report responses were optimal at mean immunoglobulin-A and testosterone levels and very low levels (-2 SD) exerted the most compromising effects. Players can experience a chronic cross-season suppression of mucosal immunity. Salivary immunoglobulin-A, testosterone, cortisol and testosterone:cortisol measures relate to self-report measures of fatigue, sleep quality and muscle soreness. In-season reductions in testosterone, cortisol and testosterone:cortisol or increases in cortisol among elite football players could be used to indicate the need for reduced workload, which might lead to improved wellbeing. 



#5 The incidence and characteristics of purposeful heading in male and female youth football (soccer) within Australia

Reference: J Sci Med Sport. 2020 Dec 26;S1440-2440(20)30865-3. doi: 10.1016/j.jsams.2020.12.010.

Authors: Kerry Peek, Teale Vella, Tim Meyer, Florian Beaudouin, Marnee McKay

Summary: The aim was too quantify the incidence and characteristics of purposeful headers and unintentional head impacts during male and female youth football (soccer) games in Australia. Ten match-videos (total n=110) per playing age (under 13-20 males; under 13-17 females) from the 2019 National Premier League season were coded for purposeful headers and unintentional head impacts. Total headers and head impacts as well as incidence rate (IR) per 1000 match-hours for different match characteristics were calculated. Purposeful headers accounted for 99% (n=4615, IR:1618) of total head impacts. The IR of purposeful headers per 1000 match-hours was highest for under-15 males (IR:2117) and under-17 females (IR:2090) followed by under-20 males (IR:1761). Midfielders completed the most headers in all female age groups (mean IR:713) and under 13-14 males (mean IR:891), with defenders completing the most headers in under 15-20 males (mean IR:760). Heading duels accounted for 16% of total headers with most headers performed during free play (68%), throw-ins (15%), free kicks (12%) and corner kicks (5%). Only 57 head impacts (IR:20) were coded as unintentional head impacts resulting from being struck by the ball or opponent body part with 4 (IR:1.4) requiring medical attention. Heading is a complex skill. Given the propensity of youth players of all ages to purposefully head the ball, consideration should be given to coaching heading technique based on specific game scenarios for their playing position and age group. The findings of this study can be used to inform heading guidelines. 



#6 Comparison of multidirectional jump performance and lower limb passive range of motion profile between soccer and basketball young players 

Reference: PLoS One. 2021 Jan 7;16(1):e0245277. doi: 10.1371/journal.pone.0245277. eCollection 2021. 

Authors: Marta Domínguez-Díez, Daniel Castillo, Javier Raya-González, Silvia Sánchez-Díaz, María Soto-Célix, Tara Rendo-Urteaga, Ángel Lago-Rodríguez

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Summary: This study was performed aimed at comparing multidirectional bilateral and unilateral jump performance and passive range of motion (ROM) of lower limbs between soccer and basketball young players and evaluating associations between inter-limb ROM asymmetry and bilateral jump performance. A total of 67 young male athletes participated in this study, who were classified as soccer (n = 40; 15.55 ± 1.5 y; 1.76 ± 0.12 m; 58.15 ± 10.82 kg; 19.84 ± 2.98 kg·m2) and basketball (n = 27; 15.7 ± 1.66 y; 1.76 ± 0.12 m; 62.33 ± 16.57 kg; 19.84 ± 2.98 kg·m2) players. Participants were asked to perform bilateral and unilateral multidirectional jumps, and passive ROM of hip (flexion, extension and abduction), knee (flexion) and ankle (dorsiflexion) joints was also assessed. Significant between-group differences were observed for hip extension with flexed knee ROM in dominant (soccer: 142.43 ± 7.74°; basketball: 148.63 ± 8.10°) and non-dominant (soccer: 144.38 ± 8.36°; basketball: 148.63 ± 6.45°) legs; hip flexion with flexed knee ROM in dominant (soccer: 13.26 ± 4.71°; basketball: 9.96 ± 3.42°) and non-dominant (soccer: 12.86 ± 4.55°; basketball: 9.70 ± 3.62°) legs; and for the ratio of hip abduction (soccer: 1.02 ± 0.08; basketball: 0.97 ± 0.11). However, no significant between-group differences were observed for bilateral and unilateral jump capacity, or for inter-limb asymmetries (dominant vs. non-dominant leg). Finally, no associations were observed between ROM ratio (dominant vs. non-dominant leg) and bilateral jump performance. These findings lead to the suggestion that differences on passive ROM values in young male athletes may be sport-specific. Additionally, there seems to be need for the implementation of training strategies specifically aimed at improving bilateral or unilateral jump ability, or at diminishing inter limb passive ROM differences in order to improve multidirectional jump performance for neither soccer nor basketball youth male players. 



#7 Improving Soccer Knowledge From Computerized Game Diagrams: Benefits of Sequential Instructional Arrows 

Reference: Percept Mot Skills. 2021 Jan 5;31512520983083. doi: 10.1177/0031512520983083.

Authors: Ghazi Rekik, Yosra Belkhir, Mohamed Jarraya

Summary: In this study, we used Cognitive Load Theory to examine the role of a sequential versus simultaneous presentation technique for learning tactical skills from computerized diagrams of soccer scenes with two levels of complexity. Young soccer players learned the evolution of soccer game systems from computer-based diagrams with three types of instructional arrows: simultaneous, sequential-without-tracing, and sequential-with-tracing. We randomly assigned participants to one of six experimental conditions (three arrow presentation methods by two levels of soccer scene complexity) and asked them to rate their invested mental efforts, complete a recall-reconstruction test, and indicate their attitudes, immediately after the learning phase. When diagram content complexity was low, the three types of arrow presentations had similar learning effects. However, when diagram content complexity was high, the two sequential means of presenting instructional arrows produced better learning outcomes (with a clear relative advantage for the sequential-with-tracing presentation). We also found that the sequential presentation of arrows elicited more positive player attitudes whatever the level of content complexity. Considering the better learning outcomes and improved player attitudes from sequential diagram presentations, soccer coaches should present computer-based instructional diagram arrows sequentially, rather than simultaneously. A sequential-with-tracing arrow presentation was particularly beneficial for learning complex team sport scenes. 



#8 The effect of a weekly flywheel resistance training session on elite U-16 soccer players' physical performance during the competitive season. A randomized controlled trial 

Reference: Res Sports Med. 2021 Jan 5;1-15. doi: 10.1080/15438627.2020.1870978. Online ahead of print. 

Authors: Javier Raya-González, Daniel Castillo, Kevin L de Keijzer, Marco Beato

Summary: This study investigated the effects of a weekly flywheel resistance training session over a 10-week period on U16 soccer players' physical performance with special attention to change of direction ability (e.g., deficit [CODdef]). Twenty elite young soccer players were assigned to an experimental (EG, n = 10) or control (CG, n = 10) group. Unilateral countermovement jumps with dominant (CMJd) and non-dominant (CMJnd) leg, 10, 20, and 30-m linear sprint test and change of direction sprint test in 5 + 5 (COD10) and 10 + 10 m (COD20) were performed before and after flywheel training period. Significant within-group differences were found in CG in COD10 (p = 0.01; effect size [ES] = large) and CODdef10 (p = 0.03; ES = small) with dominant leg, while differences in EG were observed in CMJ (p = 0.001-0.01; ES = moderate-large) and in all COD and CODdef variables (p = 0.001-0.04; ES = large). Between-groups analysis revealed differences in favour of the EG in CMJ (p = 0.03-0.05) and COD and CODdef variables (p = 0.001-0.05). These findings suggest a weekly flywheel training session is suitable for improving jumping and COD abilities in U16 elite soccer players in season. 



#9 Effectiveness of Plyometric and Eccentric Exercise for Jumping and Stability in Female Soccer Players-A Single-Blind, Randomized Controlled Pilot Study 

Reference: Int J Environ Res Public Health. 2021 Jan 3;18(1):294. doi: 10.3390/ijerph18010294. 

Authors: Guillermo Porrati-Paladino, Rubén Cuesta-Barriuso

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Summary: Hamstring muscle injury is common in female soccer players. Changes affecting eccentric strength, flexibility, and the quadriceps-hamstring contraction cycle are risk factors associated with this type of injury. Seventeen soccer players were randomized to two groups: experimental (plyometric and eccentric exercises without external loads) and control (eccentric exercises without external loads). Eighteen sessions were scheduled over 6 weeks. The exercise program included three plyometric exercises (single-leg squat and lunge, 180 jump, and broad jump stick landing) and three eccentric exercises (Nordic hamstring exercise, diver, and glider). Dependent variables were jumping height (My Jump 2.0 App) and anterior, posteromedial, and posterolateral lower limb stability (Y-Balance test). Following intervention, improvements were found in anterior and posteromedial stability (p = 0.04) in the experimental group. Posterolateral stability improved in athletes included in the control group (p = 0.02). There were differences in the repeated measures analysis for all variables, with no changes in group interaction (p > 0.05). Eccentric exercises, either combined with plyometric exercises or alone, can improve lower limb stability. No changes in jump height were noted in either group. There were no differences between the two groups in the variables studied. Future studies should analyze the effect of external loads on jumping stability and height in the performance of plyometric exercises. 



#10 Sustained Passing Performance of Elite and Subelite Female Soccer Players Following a Female Match-Specific Exercise Protocol

Reference: Int J Sports Physiol Perform. 2021 Jan 4;1-7. doi: 10.1123/ijspp.2020-0082. Online ahead of print. 

Authors: Mikayla J Lyons, Jennifer Conlon, Amy Perejmibida, Paola Chivers, Christopher Joyce 

Summary: This study examined the maintenance of passing performance following soccer-specific high-intensity intermittent exercise in elite (n = 9) and subelite (n = 11) Western Australian female soccer players (19.5 [2.5] y). A total of 20 participants completed the Loughborough Soccer Passing Test (LSPT) prior to, during, and following 90 minutes of a modified, female-specific, individualized exercise protocol (Loughborough Intermittent Shuttle Test [LIST]) to simulate 2 halves of a soccer match. Performance in the LSPT was calculated by adding "raw time" to the accumulated "penalty time" for each test. Elite players recorded greater distances (t58 = 4.671, P < .001, effect size [ES] = 1.21) and higher derived VO2max values (t58 = 4.715, P < .001, ES = 1.20) for the LIST exercise protocol over the subelite players. The total performance times for each LSPT were longer in the subelites in comparison with the elites, with a very large ES difference seen in post-LIST1 (t18 = -6.64, P < .001, ES = 2.99) and post-LIST2 (t18 = -9.143, P < .001, ES = 4.12). No between-groups differences were identified for "raw time" at any time point. Hence, all reported LSPT performance differences are attributed to "penalty time." These data suggest that elite players can sustain their passing performance more efficiently throughout match play that can subelite female soccer players. These findings may contribute to future talent-identification testing by helping to distinguish between elite- and subelite-level players through sustained passing performance. Coaches may also use this information to better inform best-practice training methods through modification of male soccer-specific high-intensity intermittent exercise to a female cohort. 



#11 Morning Priming Exercise Strategy to Enhance Afternoon Performance in Young Elite Soccer Players

Reference: Int J Sports Physiol Perform. 2021 Jan 5;1-8. doi: 10.1123/ijspp.2020-0094. Online ahead of print. 

Authors: Federico Donghi, Ermanno Rampinini, Andrea Bosio, Maurizio Fanchini, Domenico Carlomagno, Nicola A Maffiuletti 

Summary: The purpose was to compare the effects of different modalities of morning priming exercise on afternoon physical performance with the associated hormonal and psychophysiological responses in young soccer players. In a randomized counterbalanced crossover design, 12 young soccer players completed 3 different morning conditions on 3 different days: repeated-sprint running (6 × 40 m), easy exercise (4 × 12 fast half squats, 6 speed ladder drills, and 20-m sprints), and control (no exercise). Blood testosterone and cortisol concentrations were assessed upon arrival (approximately 8:30AM) and approximately 5 hours and 30 minutes later. Body temperature, self-reported mood, quadriceps neuromuscular function (maximal voluntary contraction, voluntary activation, rate of torque development, and twitch contractile properties), jump, and sprint performance were evaluated twice per day, while rating of perceived exertion, motivation, and the Yo-Yo Intermittent Recovery level 2 (IR2) tests were assessed once per day. Compared with the control, repeated-sprint running induced a possible positive effect on testosterone (+11.6%) but a possible to very likely negative effect on twitch contractile properties (-13.0%), jump height (-1.4%), and Yo-Yo IR2 (-7.1%). On the other hand, easy exercise had an unclear effect on testosterone (-3.3%), resulted in lower self-reported fatigue (-31.0%) and cortisol (-12.9%), and had a possible positive effect on the rate of torque development (+4.3%) and Yo-Yo IR2 (+6.5%) compared with the control. Players' testosterone levels were positively influenced by repeated-sprint running, but this did not translate into better physical function, as both muscular and endurance performance were reduced. Easy exercise seemed to be suitable to optimize the physical performance and psychophysiological state of young soccer players. 



#12 Monitoring Practices of Training Load and Biological Maturity in UK Soccer Academies 

Reference: Int J Sports Physiol Perform. 2021 Jan 5;1-12. doi: 10.1123/ijspp.2019-0624. Online ahead of print. 

Authors: Jamie Salter, Mark B A De Ste Croix, Jonathan D Hughes, Matthew Weston, Christopher Towlson 

Summary: Overuse injury risk increases during periods of accelerated growth, which can subsequently impact development in academy soccer, suggesting a need to quantify training exposure. Nonprescriptive development scheme legislation could lead to inconsistent approaches to monitoring maturity and training load. Therefore, this study aimed to communicate current practices of UK soccer academies toward biological maturity and training load. Forty-nine respondents completed an online survey representing support staff from male Premier League academies (n = 38) and female Regional Talent Clubs (n = 11). The survey included 16 questions covering maturity and training-load monitoring. Questions were multiple-choice or unipolar scaled (agreement 0-100) with a magnitude-based decision approach used for interpretation. Injury prevention was deemed highest importance for maturity (83.0 [5.3], mean [SD]) and training-load monitoring (80.0 [2.8]). There were large differences in methods adopted for maturity estimation and moderate differences for training-load monitoring between academies. Predictions of maturity were deemed comparatively low in importance for bio-banded (biological classification) training (61.0 [3.3]) and low for bio-banded competition (56.0 [1.8]) across academies. Few respondents reported maturity (42%) and training load (16%) to parent/guardians, and only 9% of medical staff were routinely provided this data. Although consistencies between academies exist, disparities in monitoring approaches are likely reflective of environment-specific resource and logistical constraints. Designating consistent and qualified responsibility to staff will help promote fidelity, feedback, and transparency to advise stakeholders of maturity-load relationships. Practitioners should consider biological categorization to manage load prescription to promote maturity-appropriate dose-responses and to help reduce the risk of noncontact injury. 



#13 Detrimental Effects of the Off-Season in Soccer Players: A Systematic Review and Meta-analysis 

Reference: Sports Med. 2021 Jan 5. doi: 10.1007/s40279-020-01407-4. Online ahead of print. 

Authors: Filipe Manuel Clemente, Rodrigo Ramirez-Campillo, Hugo Sarmento

Summary: The off-season period in soccer leads necessarily to changes in fitness status. However, there is a lack of systematization that allows identifying the magnitude of these changes in groups participating in off-season training programs compared with those subjected to training cessation. This systematic review with meta-analysis was conducted to assess the effects of training cessation in off-season training programs on men soccer players' body fat, maximal oxygen uptake (VO2max), yo-yo intermittent recovery test (YYIRT), vertical jump, sprinting time, and repeated-sprint ability. To qualify for inclusion in the systematic review, studies must have included: (1) a detraining period of ≥ 2 weeks; (2) controlled trials or cohorts of healthy men soccer players with no restriction on age; and (3) a pre-post training cessation or off-season training programs measure of body fat (%), VO2max (mL kg-1 min-1), YYIRT performance (meters), vertical jump (height), sprinting (time), and repeated-sprint ability (total time). The electronic search yielded 563 articles, and 12 were subsequently included. Significant (all p < 0.05) detrimental training cessation effects were noted for body fat (ES = 0.26), VO2max (ES = - 1.48), YYIRT (ES = - 0.46), vertical jump (ES = - 0.81), and repeated-sprint ability (ES = 0.68). Similarly, significant (all p < 0.05) detrimental off-season training programs effects were noted for body fat (ES = 0.26), VO2max (ES = - 0.48), vertical jump (ES = - 0.51), and sprinting time (ES = 0.86). When training cessation and off-season training programs effects were compared, greater detrimental effects were noted after training cessation for VO2max (p = 0.002) and repeated-sprint ability (p < 0.001). Detrimental effects on body composition and physical fitness were observed after both training cessation and off-season training programs. However, off-season training programs seem to ameliorate such detrimental effects on VO2max and repeated-sprint ability to some extent. The results presented here call for the implementation of more effective off-season training programs among male soccer players. 



#14 COVID-19-Related Restrictions and Quarantine COVID-19: Effects on Cardiovascular and Yo-Yo Test Performance in Professional Soccer Players 

Reference: Front Psychol. 2020 Dec 18;11:589543. doi: 10.3389/fpsyg.2020.589543. eCollection 2020. 

Authors: Lucas de Albuquerque Freire, Márcio Tannure, Márcio Sampaio, Maamer Slimani, Hela Znazen, Nicola Luigi Bragazzi, Esteban Aedo-Muñoz, Dany Alexis Sobarzo Soto, Ciro José Brito, Bianca Miarka 

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Summary: The present study aimed to verify the quarantine's effects during a serious viral outbreak on the cardiovascular and performance associated with the Yo-Yo test in a sample of professional soccer players. 20 high-level soccer players (n = 20; age: 26 ± 4 years-old; weight: 76.85 ± 6.7 kg; height: 179 ± 6 cm) participated in this study. The intermittent Yo-Yo test was performed pre- and post- COVID-19 quarantine in a random order. During each test, the soccer players' running performance outcomes were monitored using a portable 5-Hz GPS with a 100 Hz accelerometer and a paired t-test was conducted at a p-value of ≤ 0.05. The main results demonstrated significant differences between pre- versus post-COVID-19 quarantine in the following variables: relative distance (161.7 ± 5.9 > 141.1 ± 33.8 m/min), maximal speed (18.7 ± 0.9 > 18.2 ± 0.6 km/h), acceleration (60 ± 20 frequency > 52 ± 16 frequency), deceleration (34 ± 13 frequency > 27 ± 6 frequency), sprints > 19 km/h [0.8 (0.2;3)% >0.5 (0;0.5)%], and in high intensity running distance [16.48 (2.68;41.64)m > 0.827 (0.164;3.0)m]. We concluded that COVID-19-related restrictions and quarantine COVID-19 demonstrated adverse effects on professional soccer players' Yo-Yo tests performance. 


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