Latest research in football - week 1 - 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 Evaluation of soccer players under the Moneyball concept
Reference: J Sports Sci. 2019 Dec 26:1-27. doi: 10.1080/02640414.2019.1702280. [Epub ahead of print]
Authors: Gavião LO, Sant'Anna AP, Alves Lima GB, de Almada Garcia PA
Summary: The recruitment of athletes with limited resources is a global problem in professional sports. In US Major League Baseball, the experience of the Oakland Athletics' general manager in the last decade turned his "Moneyball" model into a synonym of quantitative analysis in the transfer market of baseball players. His strategy focused on hiring players with outstanding technical skills but relatively low market value. This study adapted this model to the framework of a multiple criteria decision aid (MCDA), by selecting undervalued players who have complementary abilities. The novelty here refers to the joint use of four algorithms explored by the composition of probabilistic preferences (CPP) (i.e., ranking, classification, dynamic evaluation and regularity analysis) and their application to soccer player performance evaluation. The new model analysed the recent transfer of a left-back soccer player to Europe. The results indicated 12 opportunities for better investment, among 32 left and right-back players considered. Two years later, the value of the same player was considerably lower. He played only five matches in the 2018-2019 season, without scoring or providing any assists. On the other hand, the players better classified by the CPP-MB model presented higher performances and market values.

#2 Treatment of Anterior Cruciate Ligament Injuries in Professional Soccer Players by Orthopedic Surgeons
Reference: Rev Bras Ortop (Sao Paulo). 2019 Dec;54(6):703-708. doi: 10.1055/s-0039-1697017. Epub 2019 Dec 13.
Authors: Arliani GG, Pereira VL, Leão RG, Lara PS, Ejnisman B, Cohen M
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Summary: The purpose was to describe the treatment provided by specialists for ACL lesions in professional soccer players. A cross-sectional study in which orthopedic surgeons affiliated to soccer teams competing in the Brazilian Soccer Championship answered a questionnaire about the treatment of ACL injuries in professional soccer players. The specialists wait between one to four weeks after the ACL injury to perform the surgical treatment. They use a single incision and single-bundle reconstruction, assisted by arthroscopy, femoral tunnel drilling by an accessory medial portal, and quadruple flexor tendon autografts or patellar tendon autografts. After three to four months, the players are allowed to run in a straight line; after four to six months, they begin to practice exercises with the ball without contact with other athletes; and, after six to eight months, they return to play. The main parameter used to determine the return to play is the isokinetic strength test. The specialists estimate that more than 90% of elite soccer players return to playing professionally after an ACL reconstruction, and 60 to 90% return to play at their prior or at a greater level of performance. The present article successfully describes the main surgical practices and post-surgery management adopted by specialists in this highly-specific population of patients.

#3 Improvements in Match-Related Physical Performance of Professional Soccer Players After the Application of an on-Field Training Program for Hamstring Injury Rehabilitation
Reference: J Sport Rehabil. 2019 Dec 22:1. doi: 10.1123/jsr.2019-0033. [Epub ahead of print]
Authors: Jiménez-Rubio S, Navandar A, Rivilla-García J, Paredes-Hernández V, Gómez-Ruano MÁ.
Summary: Although there are multiple, validated return-to-play programs following hamstring strain injuries, no studies have evaluated their changes in match performance parameters. The aim of this study was twofold as follows: (1) to determine the changes in match-based physical performance parameters in professional soccer players before and after sustaining a hamstring strain injury and undergoing a soccer-specific rehabilitation program and (2) to observe the progress of these performance parameters 6 to 10 weeks after the player returned from injury. Nineteen players suffering a hamstring strain injury from 2 male professional teams playing in the Spanish professional football league (La Liga) were followed during the 2015-2016, 2016-2017, and 2017-2018 seasons. The intervention was a participation in on-field training program following a hamstring injury. Match global positioning system data were collected in the following stages: prior to injury (PRE), after return to play (RTP), program, and 6 to 10 weeks following RTP (C2). Peak velocities and distances ran at sprint velocities showed most likely improvements in C2 versus PRE, and very likely improvements in RTP versus PRE. The distances ran at high and very high intensities, the average velocity, and work-to-rest ratio showed very likely improvements in C2 versus RTP and likely improvements in RTP versus PRE. Likely improvements were observed for all variables in C2 versus RTP. The authors' results showed an improvement of physical performance during competitive match after RTP, compared with PRE. There was a steady progression in the progress, and in 8 months following RTP, there was no injury reported in the players. The current findings may indicate that the hamstring muscle complex not only recovered completely from the injury but could also withstand a greater training and match load reducing the risk of reinjury.

#4 Seasonal variation in neuromuscular control in young male soccer players
Reference: Phys Ther Sport. 2019 Dec 16;42:33-39. doi: 10.1016/j.ptsp.2019.12.006. [Epub ahead of print]
Authors: Lloyd RS, Oliver JL, Myer GD, De Ste Croix M, Read PJ
Summary: Determine how lower limb neuromuscular control changes over the course of a competitive soccer season. 43 male youth soccer players (age 13.1 ± 2.2 yr; height 160.1 ± 15.7 cm; body mass 49.4 ± 14.3 kg; maturity offset 0.2 ± 1.9 yr) participated in this study.  Pre-, mid- and end of season assessments of peak landing forces during single leg 75% horizontal hop and stick (75%HOP) and a single leg countermovement jump (SLCMJ), single leg hop for distance (SLHD), knee valgus during the tuck jump assessment (TJA) and inter-limb symmetries. Hop distance increased significantly. Absolute peak landing forces in the left leg during the SLCMJ and 75%HOP increased significantly, with significant increases also present in the same leg for SLCMJ relative peak landing force. TJA knee valgus score was reduced in the right leg, but remained at a 'moderate' level in the left knee. Neuromuscular control, as evidenced by increased absolute and relative peak landing forces, appears to reduce over the course of a competitive season. Young soccer players should engage in neuromuscular training throughout the season to offset any decrements in neuromuscular control and to facilitate appropriate landing strategies.

#5 Normalized Hip and Knee Strength in Two Age Groups of Adolescent Female Soccer Players
Reference: J Strength Cond Res. 2019 Dec 20. doi: 10.1519/JSC.0000000000003420. [Epub ahead of print]
Authors: Hannon JP, Wang-Price S, Garrison JC, Goto S, Bothwell JM, Bush CA
Summary: Limb symmetry strength measures are used for clinical decision-making considering when an athlete is ready to return to sport after anterior cruciate ligament (ACL) injuries. However, changes in bilateral muscle strength occur after ACL injury resulting in potentially altered limb symmetry calculations. Adolescent female soccer players are at increased risk of sustaining ACL injuries. Published age and sex-matched strength values in this population may be of benefit to clinicians to improve clinical decision-making. The purpose of this study was to establish normative hip and knee strength data of both the dominant and nondominant limbs in adolescent female soccer players. Sixty-four female soccer players (ages 10-18) were enrolled in this study. Subjects were divided by age into 2 groups (group 1: 10-14 years; group 2: 15-18 years). Subjects underwent Biodex isokinetic strength testing at 60°·s and 180°·s to assess quadriceps and hamstring strength. Isometric hip strength (abduction and external rotation) was measured using a hand-held dynamometer. No significant differences were found between groups on either limb in regards to quadriceps or hamstring strength. No significant differences were found between groups on either limb for hip external rotation strength. Significant differences in hip abduction strength were found between groups on the dominant (group 1: 0.21 ± 0.04; group 2: 0.18 ± 0.04; p = 0.014) and nondominant (group 1: 0.21 ± 0.05; group 2: 0.18 ± 0.05; p = 0.019) limbs. The results of this study shed light on normative strength values for a high-risk injury population.

#6 Effects of Ramadan Fasting on Recovery Following a Simulated Soccer Match in Professional Soccer Players: A Pilot Study
Reference: Front Physiol. 2019 Dec 6;10:1480. doi: 10.3389/fphys.2019.01480. eCollection 2019.
Authors: Bouzid MA, Abaïdia AE, Bouchiba M, Ghattassi K, Daab W, Engel FA, Chtourou H
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Summary: Assessing the effects of Ramadan fasting on recovery following a soccer match simulation. Eight elite soccer players (age: 21.0 ± 0.4 years) performed a modified Loughborough Intermittent Shuttle Test protocol (LISTmod) on two occasions: 1 week before (BR) and during the fourth week of Ramadan (End-R). At BR and End-R, soccer players performed squat jump, countermovement jump, maximal voluntary contraction, and 20 m sprint, and creatine kinase, uric acid, and subjective ratings (feelings scale, quality of sleep, fatigue, muscle soreness and stress) were assessed at baseline and 0, 24, 48, and 72 h following LISTmod. Following LISTmod, performance in squat jump (48 and 72 h) (p < 0.05), countermovement jump (48 and 72 h), maximal voluntary contraction (0, 24, 48, and 72 h), and 20 m sprint (0 and 48 h) decreased significantly on both occasions. Decreases were higher at End-R than BR. Creatine kinase levels increased significantly at 24 and 48 h at BR and End-R (p < 0.05). Uric acid increased at 0 and 24 h only on BR. Muscle soreness increased throughout the recovery period at both occasions, with a higher level at End-R. Stress rating increased only at 0 h on End-R, while fatigue rating increased at 24 h at BR and at 0, 24, and 48 h at End-R. Perturbations in physical performance and subjective ratings parameters were higher at the end of Ramadan. However, the results of this study showed that Ramadan fasting did not adversely affect the recovery following soccer match simulation in professional soccer players.

#7 Return to Play in Amateur Soccer Players Undergoing Hip Arthroscopy: Short- to Mid-Term Follow-Up
Reference: Arthroscopy. 2019 Dec 19. pii: S0749-8063(19)30727-3. doi: 10.1016/j.arthro.2019.08.027. [Epub ahead of print]
Authors: Ortiz-Declet V, Yuen LC, Schwarzman GR, Chen AW, Perets I, Domb BG
Summary: The purpose was to describe patient-reported outcomes (PROs) and return to play at any level in amateur soccer players undergoing hip arthroscopy for femoroacetabular impingement syndrome at short- to mid-term follow-up. Data were prospectively collected and retrospectively reviewed for patients who underwent hip arthroscopy between March 2009 and June 2014. Patients who participated in amateur soccer within 1 year prior to surgery and intended to return to their sport after hip arthroscopy for femoroacetabular impingement syndrome were considered for inclusion in our study. Patients were excluded if they had a preoperative Tönnis osteoarthritis grade of 2 or greater, previous ipsilateral hip conditions or hip surgical procedures, or Workers' Compensation status. The patients from the initial group who had preoperative and minimum 2-year postoperative measures for the modified Harris Hip Score, Non-Arthritic Hip Score, Hip Outcome Score-Sports Specific Subscale, and visual analog scale for pain were included in our final group. In addition to PROs, data regarding the patients' return to soccer, surgical complications, and secondary surgical procedures were collected. A total of 41 patients were eligible for inclusion in our study, of whom 34 (82.9%) had a mean follow-up period of 47.4 months. Five patients were not eligible because they did not intend to return to soccer. There were 15 male hips (44.1%) and 19 female hips (55.9%). The mean age at surgery was 20.8 ± 7.4 years. All PROs and the visual analog scale score improved significantly from preoperatively to latest follow-up. Of the 34 patients, 27 (79.4%) returned to soccer. Of the patients who returned to soccer, 19 (70.4%) were competing at the same level or a higher level compared with their highest level within 1 year of surgery. Regardless of competitive level, 21 patients (77.8%) reported that their athletic ability was the same as or higher than it was within 1 year of surgery. Hip arthroscopy was associated with significant improvements in PROs for amateur soccer players. There was a high level of return to soccer and a high proportion of patients whose competitive level was similar or improved. As such, hip arthroscopy is a good option for soccer players, in the absence of underlying osteoarthritis, presenting with hip pathology.

#8 Editorial Commentary: Anterior Cruciate Ligament Injury and Reconstruction in Soccer Players: The Major Challenge Is Always Going for Our Goals!
Reference: Arthroscopy. 2020 Jan;36(1):196-198. doi: 10.1016/j.arthro.2019.10.005.
Authors: Stein SM, Mandelbaum BR
Summary: Anterior cruciate ligament (ACL) injury affects a large number of athletes worldwide, and long-term rate of return to soccer is approximately 50% or less. ACL injury, which is noncontact in approximately 90% of cases, has a complex multifactorial etiology. Younger and higher-level players do better, and 10-year outcomes are superior to baseline. The role of genomics, hormonal status, neuromuscular deficiencies, anatomy, and the environment are all potential contributory risk factors that vary with respect to the individual, especially the female athlete. Furthermore, ACL injury results in a local and regional catabolic cascade and cytokine release, creating an intra-articular environment that is a homeostatic perfect storm and spectrum of scalable articular cartilage and meniscal injury. Once these complexities in the knee organ are defined and understood, the surgeon's early objectives are stabilization, repair, and restoration with full harmonization of biomechanics, neuromuscular control, and homeostasis. The goal is optimizing long-term outcomes, decreasing the rate of subsequent ACL injury, and preventing osteoarthritis.

#9 Positional Differences in Peak- and Accumulated- Training Load Relative to Match Load in Elite Football
Reference: Sports (Basel). 2019 Dec 23;8(1). pii: E1. doi: 10.3390/sports8010001.
Authors: Baptista I, Johansen D, Figueiredo P, Rebelo A, Pettersen SA
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Summary: Quantification of training and match load is an important method to personalize the training stimulus' prescription to players according to their match demands. The present study used time-motion analysis and triaxial-accelerometer to quantify and compare: a) The most demanding passages of play in training sessions and matches (5-min peaks); b) and the accumulated load of typical microcycles and official matches, by playing position. Players performance data in 15 official home matches and 11 in-season microcycles were collected for analysis. Players were divided into four different playing positions: Centre-backs, wing-backs, centre midfielders, and centre forwards. The results show that match demands were overperformed for acceleration counts (acccounts) (131%-166%) and deceleration counts (deccounts) (108%-134%), by all positions. However, relative to match values, training values for sprint distance (sprintdist) and high-intensity run distance (HIRdist) were considerably lower (36%-61% and 57%-71%) than for accelerations and decelerations. The most pronounced difference on the 5-min peaks was observed in sprints (sprintpeak), with wing-backs achieving during the microcycle only 64% of the sprintpeak in matches, while centre backs, centre midfielders, and centre forwards levelled and overperformed the match values (107%, 100%, and 107%, respectively). Differences observed across playing positions in matches and microcycles underline the lack of position specificity of common training drills/sessions adopted by coaches in elite football.

#10 Why do football clubs fail financially? A financial distress prediction model for European professional football industry
Reference: PLoS One. 2019 Dec 26;14(12):e0225989. doi: 10.1371/journal.pone.0225989. eCollection 2019.
Authors: Alaminos D, Fernández MÁ
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Summary: The study of financial distress has been the focus of financial research in recent decades and has led to the development of models for predicting financial distress that help assess the financial situation and the risks faced by companies. These models have focused exclusively on industrial and financial companies. However, a specific model that reflects the special characteristics of the football industry has not yet been created. Since recently the governing bodies of the football industry have increased the financial control of the clubs, as in the case of UEFA with the approval of the Financial Fair Play Regulation and demand a pronouncement on going concern in the annual financial statements of clubs as well as presenting a break-even deficit caused by losses, it seems necessary to have a model adapted to the characteristics of this industry. The present study provides a new model of prediction of financial distress for the football industry with an accuracy that exceeds 90%. It also offers a vision of the challenges facing the football industry in financial matters, helping the different interest groups to assess the financial solvency expectations of the clubs.

#11 A multilevel hypernetworks approach to capture meso-level synchronisation processes in football
Reference: J Sports Sci. 2019 Dec 26:1-9. doi: 10.1080/02640414.2019.1707399. [Epub ahead of print]
Authors: Ribeiro J, Lopes R, Silva P, Araújo D, Barreira D, Davids K, Ramos J, Maia J, Garganta J
Summary: Understanding team behaviours in sports performance requires understanding the interdependencies established between their levels of complexity (micro-meso-macro). Previously, most studies examined interactions emerging at micro- and macro-levels, thus neglecting those emerging at a meso-level (reveals connections between player and team levels, depicted by the emergence of coordination in specific sub-groups of players-simplices during performance). We addressed this issue using the multilevel hypernetworks approach, adopting a cluster-phase method, to record player-simplice synchronies in two performance conditions where the number, size and location of goals were manipulated (first-condition: 6 × 6 + 4 mini-goals; second-condition: Gk + 6 × 6 + Gk). We investigated meso-level coordination tendencies, as a function of ball-possession (attacking/defending), field-direction (longitudinal/lateral) and teams (Team A/Team B). Generally, large synergistic relations and more stable patterns were observed in the longitudinal direction of the field than the lateral direction for both teams, and for both game phases in the first condition. The second condition displayed higher synchronies and more stable patterns in the lateral direction than the longitudinal plane for both teams, and for both game phases. Results suggest: (i) usefulness of hypernetworks in assessing synchronisation of teams at a meso-level; (ii) coaches may consider manipulating these task constraints to develop levels of local synchronies within teams.

#12 Differences in Technical Performance of Players From 'The Big Five' European Football Leagues in the UEFA Champions League
Reference: Front Psychol. 2019 Dec 6;10:2738. doi: 10.3389/fpsyg.2019.02738. eCollection 2019.
Authors: Yi Q, Groom R, Dai C, Liu H, Gómez Ruano MÁ
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Summary: The current study aimed to identify the differences in technical performance between players from clubs of Bundesliga (Germany), La Liga (Spain), Ligue 1 (France), Premier League (England) and Serie A (Italy) when competing in the matches of the UEFA Champions League. Technical performance-related match data of 1,291 players from 1,125 matches (9,799 observations) of the UEFA Champions League (seasons 2009/2010-2017/2018) were collected and analysed. The generalised mixed linear modelling was employed taking the names of the league as the independent variable to predict the count number of 20 technical performance-related match actions and events performed by players belonging to different leagues. The non-clinical magnitude-based inference was used to evaluate the uncertainty in the true effects of the predictor. Results showed that differences in the technical performances between players from La Liga, Premier League and Ligue 1 were all trivial. Bundesliga players made higher numbers of shots than players from La Liga, Premier League and Serie A and achieved more long balls than players from Ligue 1. Serie A players achieved lower numbers of ball touches, passes and lower pass accuracy per match than players from any of the other four leagues. In addition, players from Serie A performed a higher number of long balls per match than Ligue 1 players and lower number of dribbles per match than Premier League players. Non-significant differences in other variables related to passing and organising and all variables related to defending were identified in players between the five leagues. The identified differences in technical performance among leagues could provide a more thorough understanding for practitioners working within the fields of talent identification, player development, player recruitment, coaching and match preparation.

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