Latest research in football - week 31 - 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 Monitoring Accumulated Training and Match Load in Football: A Systematic Review

Reference: Int J Environ Res Public Health.  2021 Apr 8;18(8):3906.  doi: 10.3390/ijerph18083906.

Authors: José E Teixeira, Pedro Forte, Ricardo Ferraz, Miguel Leal, Joana Ribeiro, António J Silva, Tiago M Barbosa, António M Monteiro

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Summary: Training load monitoring has become a relevant research-practice gap to control training and match demands in team sports. However, there are no systematic reviews about accumulated training and match load in football. Following the preferred reporting item for systematic reviews and meta-analyses (PRISMA), a systematic search of relevant English-language articles was performed from earliest record to March 2020. The search included descriptors relevant to football, training load, and periodization. The literature search returned 7972 articles (WoS = 1204; Pub-Med = 869, SCOPUS = 5083, and SportDiscus = 816). After screening, 36 full-text articles met the inclusion criteria and were reviewed. Eleven of the included articles analyzed weekly training load distribution; fourteen, the weekly training load and match load distribution; and eleven were about internal and external load relationships during training. The reviewed articles were based on short-telemetry systems (n = 12), global positioning tracking systems (n = 25), local position measurement systems (n = 3), and multiple-camera systems (n = 3). External load measures were quantified with distance and covered distance in different speed zones (n = 27), acceleration and deceleration (n = 13) thresholds, accelerometer metrics (n = 11), metabolic power output (n = 4), and ratios/scores (n = 6). Additionally, the internal load measures were reported with perceived exertion (n = 16); heart-rate-based measures were reported in twelve studies (n = 12). The weekly microcycle presented a high loading variation and a limited variation across a competitive season. The magnitude of loading variation seems to be influenced by the type of week, player's starting status, playing positions, age group, training mode and contextual variables. The literature has focused mainly on professional men; future research should be on the youth and female accumulated training/match load monitoring.



#2 Home-Advantage during COVID-19: An Analysis in Portuguese Football League

Reference:  Int J Environ Res Public Health. . 2021 Apr 4;18(7):3761.  doi: 10.3390/ijerph18073761.

Authors: Rui Matos, Diogo Monteiro, Raul Antunes, Diogo Mendes, João Botas, João Clemente, Nuno Amaro

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Summary: Covid-19 pandemic forced, at the final rounds of 2019-2020 season, in many different sport leagues worldwide, teams to play without an audience. Therefore, the present paper aims to compare the home advantage score in the last ten rounds in 2019-2020 season with the first 24 rounds in same season using Pollard's (1986) and Matos et al.'s (2020) methods. In addition, comparisons across different seasons (2016-2017; 2017-2018; 2018-2019 and 2019-2020) using the same methods were also analyzed. Results showed no differences (p > 0.05) between first 24 rounds and the last 10 in 2019-2020 season as well as in the 3 previous seasons. With Pollard's method, no differences (p > 0.05) were also found among those four seasons on global (all 34 rounds) home advantage. However, a significance difference between 2017-2018 and 2019-2020 (p < 0.05) was founded using Matos et al.'s (2020) method, which is an indicator of the importance of using complementary methods when analyzing the same realities. Overall, despite what might be expectable from recent findings, the lack of an audience in the last 10 rounds of Portuguese Football League 2019-2020 season, due to COVID-19 pandemic, did not affect home advantage. Therefore, future studies could try to analyze other different variables in Portuguese Football League, such as referees' behaviors, rules changing (e.g., the possibility of making five substitutions, instead of three), crowd dimension and density as well as include variables about odds as forecasts in football being played without crowds.



#3 A 2D video-analysis scoring system of 90° change of direction technique identifies football players with high knee abduction moment

Reference: Knee Surg Sports Traumatol Arthrosc. 2021 Apr 29.  doi: 10.1007/s00167-021-06571-2.

Authors: Francesco Della Villa, Stefano Di Paolo, Dario Santagati, Edoardo Della Croce, Nicola Francesco Lopomo, Alberto Grassi, Stefano Zaffagnini

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Summary: Abnormal joint biomechanics and poor neuromuscular control are modifiable risk factors for Anterior Cruciate Ligament (ACL) injury. Although 3D motion capture is the gold standard for the biomechanical evaluation of high-speed multidirectional movements, 2D video analysis is a growing-interest alternative because of its higher cost-effectiveness and interpretability. The aim of the present study was to explore the possible association between a 2D evaluation of a 90° change of direction (COD) and the KAM measured with gold standard 3D motion analysis. Thirty-four competitive football (soccer) players (age 22.8 ± 4.1, 18 male and 16 females) were enrolled. Each athlete performed a series of pre-planned 90° COD at the maximum speed possible in a laboratory equipped with artificial turf. 3D motion analysis was recorded using 10 stereophotogrammetric cameras, a force platform, and three high-speed cameras. The 2D evaluation was performed through a scoring system based on the video analysis of frontal and sagittal plane joint kinematics. Five scoring criteria were adopted: limb stability (LS), pelvis stability (PS), trunk stability (TS), shock absorption (SA), and movement strategy (MS). For each criterion, a sub-score of 0/2 (non-adequate), 1/2 (partially adequate), or 2/2 (adequate) was attributed to the movement, based on objective measurements. The intra-rater and inter-rater reliability were calculated for each criterion and the total score. The Knee Abduction Moment (KAM) was extracted from the 3D motion analysis and grouped according to the results of the 2D evaluation. Excellent intra-rater reliability (ICC > 0.88) and good-to-excellent inter-rater reliability (ICC 0.68-0.92) were found. Significantly higher KAM was found for athletes obtaining a 0/2 score compared to those obtaining a 2/2 score in all the sub-criteria and the total score (20-47% higher, p < 0.05). The total score and the LS score showed the best discriminative power between the three groups. The 2D video-analysis scoring system here described was a simple and effective tool to discriminate athletes with high and low KAM in the assessment of a 90° COD and could be a potential method to identify athletes at high risk of non-contact ACL injury.



#4 The effect of motor control training according to the Kinetic Control concept on the back pain of female football players

Reference: J Back Musculoskelet Rehabil. 2021 Apr 23.  doi: 10.3233/BMR-200226. Online ahead of print.

Authors: Kamil Zaworski, Krystyna Gawlik, Anna Krȩgiel-Rosiak, Joanna Baj-Korpak

Summary: Due to a significant burden associated with training sessions and matches, female football players often suffer from lumbar pain. Physical exercise is considered an effective form of therapy for this condition. The exercises in the Kinetic Control concept are one of the forms of motor control training. The aim of the study was to evaluate the effectiveness of motor control training according to the Kinetic Control concept on the level of lumbar spine pain, degree of disability, functional level and load distribution of lower limbs in football players. The study included 18 football players, randomly divided into two study groups: A - female players implementing their training plan with additional Kinetic Control training (n= 9) and B (control) - female players implementing their training plan only (n= 9). Pain intensity was measured using Visual Analogue Scale (VAS) and Laitinen's questionnaire. Functional disability was assessed using Oswestry Disability Index (ODI) and Back Pain Functional Scale (BPFS). The asymmetry index was assessed in a balance test with open and closed eyes and a countermovement jump (CMJ). There was a significant statistical difference between the groups (p< 0.05) in measurements using VAS, ODI and BPFS, in favor of group A. Asymmetry index values in tests on the dynamometer platform did not differ significantly between the groups (p> 0.05). A statistically significant correlation was found between the asymmetry index score in the closed-eye balance test (r= 0.567, p= 0.049) and the CMJ landing phase (r= 0.641, p= 0.033), and the level of pain measured using VAS. Motor control training in the Kinetic Control concept reduced the pain symptoms of the lumbar spine and the degree of disability and increased the functional level in football female players.



#5 Dose-Response Relationships between Training Load Measures and Physical Fitness in Professional Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 19;18(8):4321.  doi: 10.3390/ijerph18084321.

Authors: Saeid Younesi, Alireza Rabbani, Filipe Manuel Clemente, Rui Silva, Hugo Sarmento, António José Figueiredo

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Summary: The aim of this cohort study was two-fold: (i) to analyze within-group changes of final velocity in a 30-15 intermittent fitness test (VIFT), final velocity in a Vameval test (Vvameval), 20-m sprint and countermovement jump (CMJ); (ii) to explore the relationships between VIFT and Vvameval outcomes and their changes with internal and external loads. Twenty-two professional soccer players (mean ± SD; age 27.2 ± 3.4 years, height 174.2 ± 3.6 cm, body mass 69.1 ± 6.4 kg, and body fat 10.4 ± 4.1%, 3.1 ± 1.5 years in the club) participated in this study. External and internal loads were obtained using global positioning system, heart rate and rate of perceived effort (sRPE) after each training session. Players were assessed in CMJ, 20-m sprint, Vameval and 30-15 intermittent fitness test, before and after the observed period. Very large relationships were observed between VIFT and Vameval for pre- (r = 0.76), post (r = 0.80) and pooled-data (r = 0.81). Vvameval showed less sensitivity (-22.4%, [-45.0 to 9.4]), ES -0.45 [-1.05 to 0.16]) than VIFT. ∆VIFT had unclear associations with all sRPE, but had moderate correlations with objective internal and external measures, while, ∆Vvameval varied between large and very large relationships with all sRPE, but had unclear associations with all other selected training loads. Objective internal and external loads may be used to track aerobic power related changes from VIFT.



#6 Effects of Recreational Small-Sided Soccer Games on Bone Mineral Density in Untrained Adults: A Systematic Review and Meta-Analysis

Reference: Healthcare (Basel). 2021 Apr 13;9(4):457.  doi: 10.3390/healthcare9040457.

Authors: Filipe Manuel Clemente, Rodrigo Ramirez-Campillo, Hugo Sarmento, Daniel Castillo, Javier Raya-González, Thomas Rosemann, Beat Knechtle

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Summary: This systematic review with meta-analysis was conducted to assess the effects of small-sided games (SSG)-based training programs on bone mineral density (BMD) in untrained adults. The data sources utilized were Cochrane, Embase, Medline (PubMed), Scopus, SPORTDiscus, and Web of Science. The study eligibility criteria were: (i) untrained adults (>18 years old) of any sex, with or without a noncommunicable disease; (ii) SSG-based programs with a minimum duration of four weeks and no restrictions regarding frequency (number of sessions per week); (iii) passive or active control groups; (iv) pre-post values of BMD; (v) only randomized controlled trials; and (vi) only original and full-text studies written in English. The database search initially yielded 374 titles. From those, nine articles were eligible for the systematic review and meta-analysis. The age of included population varied from a minimum of 20 and a maximum of 71 years old. Non-significant differences between SSG and passive and active control groups on total BMD (ES = 0.14; p = 0.405 and ES = 0.28; p = 0.05, respectively). Meanwhile, significant differences in favor of SSGs vs. passive and control groups were detected, evidencing an improvement of BMD in lower limbs of the adult population for both sexes (ES = 0.26; p = 0.05 and ES = 0.28; p = 0.156, respectively). As conclusions, SSGs can be used as a non-pharmacological alternative to increase the BMD in the lower limbs despite having no significant impact on total body BMD. Careful generalization should be done of the level of heterogeneity.



#7 Examination of the Sprinting and Jumping Force-Velocity Profiles in Young Soccer Players at Different Maturational Stages

Reference: Int J Environ Res Public Health. 2021 Apr 27;18(9):4646.  doi: 10.3390/ijerph18094646.

Authors: Luis Miguel Fernández-Galván, Daniel Boullosa, Pedro Jiménez-Reyes, Víctor Cuadrado-Peñafiel, Arturo Casado

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Summary: The aim was to determine the relationships among components of the force-velocity (F-V) profiles in jumping and sprinting, with both biological and chronological ages in 89 young soccer players belonging to categories from U10 to U18. Participants performed countermovement jumps (CMJ) and 20-m sprint tests. F-V components assessed were associated with both maturity offset and chronological age, using correlation and multiple linear regression analyses. Horizontal (i.e., maximal theoretical force [F0] and velocity [V0], maximal power [Pmax] and F-V slope) and vertical (i.e., [F0] and [Pmax]) F-V components displayed very large correlations (i.e., 0.79 ≤ r ≤ 0.92) with both chronological age and maturity offset. The combination of sprinting Pmax and training experience and jumping F0 and training experience explained up to 94% of the variances in maturity offset and chronological age. Furthermore, similar correlations were found between sprinting and jumping performances, and components of the F-V profiles, and both maturity offset and chronological age. Identification of vertical jump and sprint mechanical determinants may assist in strengthening those components of the F-V profile which are weaker throughout the training process. Sprinting and jumping capabilities can be indistinctly monitored with respect to their chronological age or maturity offset in young soccer players.



#8 Dynamic Knee Alignment and Pelvic Balance: Comparison Regarding Gender in Young Soccer Athletes

Reference: Rev Bras Ortop (Sao Paulo). 2021 Apr;56(2):175-180.  doi: 10.1055/s-0040-1721361. Epub 2021 Apr 26.

Authors: Flaviano Moreira da Silva, Denis Bordoni Canêz, Andressa Rodeghiero Madeira, Gustavo Dias Ferreira

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Summary: The aim was to evaluate knee alignment in the frontal plane and pelvic balance during the step-down test in female and male soccer players.  Cross-sectional study carried out with male and female soccer players from under-15 and under-17 teams of a professional club in Southern Brazil. The step-down test was performed, filmed with a video camera, and evaluated according to the angular measurements obtained during movement using the Kinovea software (open source), version 0.8.24. The sample consisted of 38 individuals, 19 males and 19 females. Female athletes had a greater varus angle (9.42° ± 1.65°) compared to male athletes (3.91° ± 2.0°; p = 0.04). There was no difference regarding the unilateral pelvic drop between the groups. In addition, the association between the hip-related pelvic drop and the projection angle on the frontal plane of the knee was weak in both genders. Even though the pelvic drop was observed in both genders, young female athletes had greater varus knee angles on the step-down test, which require greater attention to minimize the risk of injury.



#9 High and highly bonded: Fused football fans who use cocaine are most likely to be aggressive toward rivals

Reference: Int J Drug Policy. 2021 May 3;103263.  doi: 10.1016/j.drugpo.2021.103263. Online ahead of print.

Authors: Martha Newson

Summary: Cocaine use among British football fans has yet to be quantified, despite its association with football-related aggression by the media. Identity fusion, a potent form of social bonding, is a well-established predictor of fan violence, which has never been investigated in relation to stimulant use. British football fans (n = 1486) completed a self-selected online survey about how bonded they were to their club and fellow fans, their cocaine use, and aggressive behavior toward rival fans over the prior 12-months. Fans reported more cocaine use than the national average (6.19%). Of fans who attended stadia matches, 1.08% had used cocaine in stadia, and 30.05% had witnessed other fans take cocaine at matches. Fans who used cocaine reported significantly more aggression toward rivals than fans who did not. Cocaine and identity fusion significantly interacted, such that highly 'fused' cocaine users were especially likely to have behaved aggressively toward their rivals. Men were more fused and more aggressive than women. Football mirrors wider society, be it in social issues or drug use. The widespread availability of cheap but high purity cocaine may be associated with fan aggression, especially among fans who are highly bonded to their clubs and fellow fans.



#10 Drilling under the COVID-19 pandemic: A diary study of professional football players' mental health and workout performance

Reference: Stress Health. 2021 May 4.  doi: 10.1002/smi.3059.

Authors: Shuhua Sun, Stephen X Zhang, Asghar Afshar Jahanshahi, Mehdi Jahanshahi

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Summary: There is little research examining how individuals' daily experience during a pandemic affects their daily mental health status and work performance. To address this knowledge gap, we invoke conservation of resources theory to propose a resource-based framework explaining how individuals' daily COVID-19 intrusive experience affects their daily mental health status (depression and anxiety) and work performance via its effect on daily psychosocial resource loss and gain; We further examine whether their supervisors' daily visionary leadership behaviour alleviates the adverse impacts of daily COVID-19 intrusive experience. Results, based on daily diary data from 139 football players (or soccer players) at 15 professional football clubs over 5 days during the COVID-19 pandemic, provided support for our predictions. Our study extends the literature by providing previously undocumented evidence on daily within-person variations in mental health status and work performance during a pandemic and by offering theory-driven insights into the mediating and moderating mechanisms involved in within-person variations.



#11 The effects of training on hormonal concentrations and physical performance of football referees

Reference: Physiol Rep. 2021 Apr;9(8):e14740.  doi: 10.14814/phy2.14740.

Authors: Antonella Muscella, Erika Stefàno, Santo Marsigliante

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Summary: As no study has explored the impact of physical stress on hypothalamic-pituitary-gonadal axis hormones over a long period, the purpose of this study was to determine the effects of the football season period on plasma cortisol and testosterone concentrations and referee's physical performances. Physical tests and plasma cortisol and testosterone concentrations were assayed before the beginning of the training period, just after the training period, at the middle of the season, and at the end of the season, in 29 male football referees and 30 healthy control subjects. Results showed significant differences in hormone concentrations at the four-time points evaluated. Plasma cortisol increased during the first training period from 15.8 ± 3.8 to 21.7 ± 5.1 µg/dl (p < 0.001), then decreased during the season and at the end of it was 18.7 ± 2.4 µg/dl. Before the beginning of the training period, plasma testosterone concentration was 386.1 ± 58.8 ng/dl; after the training period, it increased to 572.2 ± 88.1 ng/dl (p < 0.001) and then returned to baseline levels at the end of the season. Between the start of the training period and the end of the season, significant differences were observed in physical performances of referees. Plasma cortisol and testosterone levels significantly (p < 0.0001 for both) correlated with Yo-Yo intermittent recovery test level 1 (YYIRT1) and maximal oxygen consumption (VO2max ) at the end of the training period. In the middle season, plasma testosterone concentration only significantly (p < 0.0001) correlated with YYIRT1 and VO2max . These data underline the importance of set up training protocols that present the prospective to favor positive physiological adaptations.



#12 SARS-CoV-2 serological assay and viral testing: a report of professional football setting

Reference: Postgrad Med J. 2021 Apr 30;postgradmedj-2021-140176.  doi: 10.1136/postgradmedj-2021-140176. 

Authors: Bahar Hassanmirzaei, Zohreh Haratian, Ali Ahmadzadeh Amiri, Amir Ahmadzadeh Amiri, Navid Moghadam

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Summary: PCR is the current standard test for the diagnosis of SARS-CoV-2 infection. However, due to its limitations, serological testing is considered an alternative method for detecting SARS-CoV-2 exposure. In this study, we measured the level of SARS-CoV-2 IgM and IgG antibodies of male professional football players and compared the results with the standard PCR test to investigate the association between the two tests. Participants were male professional football players and team officials. Nasopharyngeal swabs and peripheral blood samples were collected for the PCR and serological tests, respectively. Also, previous records of COVID-19 testing and symptoms were gathered. Those with previous positive PCR tests who tested negative for the second time were considered to be recovered patients. Of the 1243 subjects, 222 (17.9%) were seropositive, while 29 (2.3%) tested positive for the SARS-CoV-2 PCR test. Sixty percent of symptomatic cases with a negative PCR were found to be seropositive. The mean level of IgM was significantly higher in PCR-positive and symptomatic subjects, whereas the recovered cases showed significantly higher levels of IgG. Our study revealed an inconsistency of results between the two tests; therefore, although application of serological assays alone seems insufficient in diagnosing COVID-19 disease, the findings are beneficial in the comprehension and the management of the disease.



#13 Physical Demands of Women's Soccer Matches: A Perspective Across the Developmental Spectrum

Reference: Front Sports Act Living. 2021 Apr 16;3:634696.  doi: 10.3389/fspor.2021.634696. eCollection 2021.

Authors: Jason D Vescovi, Elton Fernandes, Alexander Klas

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Summary: Female soccer players are exposed to specific physical demands during matches, which vary according to the standard of play. Existing studies have largely focused on quantifying the distances covered for professional and international level players. This approach is limited in scope regarding the broader aspects around physical demands and is detached from development pathway models. An understanding of the demands across all standards will provide valuable insights about appropriate player development and help ensure physical readiness for the demands of the sport. The aim of this perspective paper is to describe the physical demands experienced during women's soccer matches across the developmental spectrum. A combination of evidence from the literature and data from the author's research (JDV) is presented. Specifically highlighted are the trends for locomotor distances, acceleration and deceleration frequency, and metabolic power metrics for youth (≤U17), college (NCAA/U20), professional (domestic) and international standards of women's soccer. In addition, the changes in match demands between levels of play are used to help illustrate gaps that must be overcome in order to successfully achieve physical readiness to compete at higher levels. The evidence demonstrates the importance of training appropriate attributes to prepare female soccer players who are striving to play at progressively higher standards.


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