Latest research in football - week 30 - 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 Phase Angle Is Related to 10 m and 30 m Sprint Time and Repeated-Sprint Ability in Young Male Soccer Players

Reference: Int J Environ Res Public Health.  2021 Apr 21;18(9):4405.  doi: 10.3390/ijerph18094405.

Authors: Priscila Custódio Martins, Anderson Santiago Teixeira, Luiz Guilherme Antonacci Guglielmo, Juliana Sabino Francisco, Diego Augusto Santos Silva, Fábio Yuzo Nakamura, Luiz Rodrigo Augustemak de Lima

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Summary: The aim was to examine the association between phase angle (PhA) and bioelectrical impedance vector analysis (BIVA) and components of physical performance in male youth soccer players. Sixty-two players from two professional soccer academies were recruited. Electrical bioimpedance was used to obtain the PhA and BIVA. Body fat (BF) and lean soft tissue mass (LSTM) were measured by dual-energy X-ray absorptiometry. All players completed physical tests including the standing long jump (SLJ), Carminatti's test (peak speed at the end of the test, PST-CAR), 10 m and 30 m straight-line sprints, and repeated-sprint ability (RSA) test (RSAbest and RSAmean times). Adjusting for chronological age, BF, and LSTM, multiple regression analysis outputs showed that PhA remained inversely related to RSAmean (β = -0.362; p < 0.001), RSAbest (β = -0.239; p = 0.020), 10 m (β = -0.379; p = 0.012), and 30 m (β = -0.438; p < 0.001) sprint times, while the association with PST-CAR and SLJ performance were statistically non-significant. In addition, BIVA showed that differences in confidence ellipses were found between athletes in the reference population and the study sample (p < 0.05). The tolerance ellipses indicated that the athletes in the present study had more total body water (TCW) and lower proportions of intracellular water (ICW) to extracellular water (ECW). The reference population had more TCW and ICW/ECW. Our results suggest that young soccer players with higher PhA values, indicating better cell integrity and functionality, have better performance in typical anaerobic running activities, such as sprinting speed and RSA performance, adjusted to age and body composition characteristics.



#2 Match Analysis of Soccer Refereeing Using Spatiotemporal Data: A Case Study

Reference: Sensors (Basel). 2021 Apr 5;21(7):2541.  doi: 10.3390/s21072541.

Authors: Bruno Gonçalves, Diogo Coutinho, Bruno Travassos, João Brito, Pedro Figueiredo

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Summary: This case study explored how spatiotemporal data can develop key metrics to evaluate and understand elite soccer referees' performance during one elite soccer match. The dynamic position of players from both teams, the ball and three elite referees allowed to capture the following performance metrics: (i) assistant referees: alignment with the second last defender; (ii) referee: referee diagonal movement-a position density was computed and a principal component analysis was carried to identify the directions of greatest variability; and (iii) referee: assessing the distance from the referee to the ball. All computations were processed when the ball was in-play and separated by 1st and 2nd halves. The first metric showed an alignment lower than 1 m between the assistant referee and the second last defender. The second metric showed that in the 1st half, the referee position ellipsis area was 548 m2, which increased during the 2nd half (671 m2). The third metric showed an increase in the distance from the referee to the ball and >80% of the distance between 5-30 m during the 2nd half. The findings may be used as a starting point to elaborate normative behavior models from the referee's movement performance in soccer.



#3 Comparative Analysis of Soccer Performance Intensity of the Pre-Post-Lockdown COVID-19 in LaLiga™

Reference: Int J Environ Res Public Health. 2021 Apr 1;18(7):3685.  doi: 10.3390/ijerph18073685.

Authors: Abraham García-Aliaga, Moisés Marquina, Antonio Cordón-Carmona, Manuel Sillero-Quintana, Alfonso de la Rubia, Ignacio Refoyo Román 

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Summary: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) forced a stoppage in the 2019/2020 season of LaLiga™, possibly influencing performance indicators in the return to competition. Therefore, here, we evaluated whether the stoppage due to the coronavirus 2019 disease (COVID-19) lockdown influenced physical performance compared to the start of LaLigaTM in terms of high-intensity efforts. Using a semi-automatic, multiple-camera system, running activities during 22 matches were analyzed. We compared the first 11 matches of the season (pre-lockdown) with the 11 matches just after the restart of LaLiga™ (post-lockdown). The results showed higher (p < 0.05) performance in the pre-lockdown period compared with the post-lockdown period, including in medium-speed running (14.1-21 km/h), high-speed running (21.1-24 km/h), and sprinting speed running distances (>24 km/h). However, the number of accelerations/min and decelerations/min were significantly higher during the post-lockdown period. Therefore, we conclude that the stoppage due to the COVID-19 lockdown generated lower physical performance in the post-lockdown period compared with the pre-lockdown period, most likely due to the accumulation of matches (congested schedules).



#4 Effectiveness of the FIFA 11+ Referees Injury Prevention Program in reducing injury rates in male amateur soccer referees

Reference: Scand J Med Sci Sports. 2021 Apr 29.  doi: 10.1111/sms.13983. Online ahead of print.

Authors: Wesam Saleh A Al Attar, Mario Bizzini, Fahad Alkabkabi, Nasser Alshamrani, Saud Alarifi, Hosam Alzahrani, Hussain Ghulam, Eman Aljedaani, Ross H Sanders

Summary: The Fédération International de Football Association (FIFA) 11+ Referees Injury Prevention Program (FIFA 11+ Referees Program) is a structured warm-up program specially designed to prevent injuries in soccer referees. However, its effectiveness has yet to be fully documented in the literature. Therefore, the purpose of this study was to investigate the effectiveness of the FIFA 11+ Referees Program in reducing injury rates among soccer referees. A cluster randomized controlled trial was conducted. Two hundred male amateur soccer referees (mean±SD age, 31.6±4.1 years) participated in this study. Participants were randomly allocated to the experimental and control groups. The experimental group performed the FIFA 11+ Referees Program as a warm-up during training sessions at least twice a week, and the control group performed their usual warm-ups. The participants were followed up for one season. The outcome measures were the incidence of overall injury, initial injury, recurrent injury, injury mechanism, and injury severity (primary), and the rate of adherence to the intervention program (secondary). A total of 24 injuries were reported among 100 referees in the control group in 16606 hours of exposure (1.45 injuries/1000 exposure hours), and a total of nine injuries were reported across 100 referees within the experimental group in 17834 exposure hours (0.50 injuries/1000 exposure hours). The Injury Risk Ratio (IRR) was 0.35 (95% CI 0.26 to 0.45). The results indicated that the FIFA 11+ Referees Program effectively reduced injuries in the experimental group by 65% compared to the control group.



#5 The Influence of Playing Formation on Physical Demands and Technical-Tactical Actions According to Playing Positions in an Elite Soccer Team

Reference: Int J Environ Res Public Health. 2021 Apr 14;18(8):4148.  doi: 10.3390/ijerph18084148.

Authors: José Luis Arjol-Serrano, Miguel Lampre, Adrián Díez, Daniel Castillo, Fernando Sanz-López, Demetrio Lozano

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Summary: The aim of this study was to examine the differences in the physical demands and technical-tactical actions encountered by soccer players between two playing formations (1-4-2-3-1 and 1-4-4-2) for each playing position. Twenty-three professional male soccer players who played 31 official matches participated in this study. Players were classified according to their playing position: central defenders (CD), wide defenders (WD), central midfielders (CM), wide midfielders (WM), offensive midfielders (OM) and forwards (FW). The physical demands were collected as total distance (TD), distance covered in different speed thresholds, and number of accelerations and decelerations. Also, the technical-tactical variables were recorded. The results showed that the 1-4-2-3-1 playing formation demanded decelerations between 2-4 m·s2 (p = 0.027; ES = 0.26) in comparison with 1-4-4-2 for all players. Likewise, forwards (FW) and central midfielders (CM) registered higher physical demands playing with the 1-4-2-3-1 compared to the 1-4-4-2 formation. Regarding the technical-tactical actions, they showed differences between the playing positions of the two playing formations. The findings suggest coaches prescribe specific training programs based on the influence of the playing formation and playing position on the physical demands and technical-tactical actions encountered by players during official match-play.



#6 Muscle Damage and Performance after Single and Multiple Simulated Matches in University Elite Female Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 14;18(8):4134.  doi: 10.3390/ijerph18084134.

Authors: Tai-Ying Chou, Kazunori Nosaka, Trevor C Chen

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Summary: The present study aimed to compare changes in muscle damage and performance parameters after playing single versus multiple soccer matches to examine fixture congestion effects on performance. Twelve elite female university soccer players performed single, three and six consecutive 90-min bouts of the Loughborough Intermittent Shuttle Test (LIST) with ≥12-weeks between conditions in a pseudo-randomized order. Heart rate, blood lactate, rating of perceived exertion and covering distance in each LIST were examined. Changes in several types of muscle damage (e.g., maximal voluntary isometric torque of the knee extensors: MVC-KE) and performance measures (e.g., Yo-Yo Intermittent Recovery Test level 1: YYIR1) were taken before each LIST, 1 h, and 1-5 d after the last LIST. The total distance covered during the LIST was shorter (p < 0.05) in the 2nd-3rd, or 2nd-6th LISTs when compared with the 1st LIST. Changes (p < 0.05) in all measures were observed after the LIST, and the greatest changes were observed after the six than after the three LISTs followed by one LIST (e.g., largest changes in MVC-KE: -26 > -20 > -14%; YYIR1: -31 > -26 > -11%). Many of the variables did not recover to the baseline for 5 d after six LISTs. These suggest that fixture congestion induces greater muscle damage and performance decline than a single match.



#7 Comparison Between Soccer and Basketball of Bone Bruise and Meniscal Injury Patterns in Anterior Cruciate Ligament Injuries

Reference: Orthop J Sports Med. 2021 Apr 14;9(4):2325967121995844.  doi: 10.1177/2325967121995844. eCollection 2021 Apr.

Authors: Huijuan Shi, Li Ding, Yanfang Jiang, Haocheng Zhang, Shuang Ren, Xiaoqing Hu, Zhenlong Liu, Hongshi Huang, Yingfang Ao

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Summary: The varying effectiveness of anterior cruciate ligament (ACL) injury prevention programs between soccer and basketball may be due to differences in sport-specific injury mechanisms. Bone bruise patterns may provide information regarding injury mechanisms. The aim was to compare bone bruise and meniscal injury patterns for ACL injuries sustained in soccer versus basketball. Clinical notes, operative reports, and magnetic resonance imaging scans were reviewed for patients who sustained a noncontact ACL rupture while playing soccer or basketball between August 2016 and August 2018. The presence, location, and signal intensity of bone bruises on the tibia and femur were documented, and patterns were classified according to the location of the bone bruise in the lateral-medial direction. The meniscal and bone bruise injury patterns and the specific bone bruise locations were compared between the soccer and basketball groups. Overall, 138 patients were included (56 with soccer-related and 82 with basketball-related ACL injury). No significant difference between the groups was observed in bone bruise patterns (P = .743) or meniscal injury patterns (P = .952). Bone bruise on the lateral side only of both the femur and the tibia was the most common pattern in both soccer (41.9%) and basketball (47.0%) groups; the most common meniscal injury type was an isolated lateral meniscal injury in both soccer (50.0%) and basketball (45.0%) groups. For patients with bone bruises on both the lateral and the medial sides of both the femur and the tibia (BF+BT), the bone bruise signal intensity on the lateral side of the femur (P < .001) and tibia (P = .009) was significantly higher than that on the medial side for both groups. The bone bruises on the lateral side of the femur (P < .001) and tibia (P = .002) were significantly more anterior than those on the medial side for patients with the BF+BT pattern. No significant differences in bone bruise location or meniscal injury type were detected when comparing ACL injuries sustained during soccer versus basketball. The study results suggest a similar biomechanical loading pattern for ACL injuries in these sports.



#8 Distribution of Plantar Pressure in Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 15;18(8):4173. doi: 10.3390/ijerph18084173.

Authors: Arletta Hawrylak, Anna Brzeźna, Krystyna Chromik

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Summary: The aim of this study was to evaluate differences in the static and dynamic distribution of foot pressure on the ground and to investigate the relationships between body mass index (BMI) and mean variables of plantar pressure between soccer players and their non-athlete peers. The study involved 18 first-division Polish soccer players and 30 non-athlete physiotherapy students. The research experiment was conducted using the FreeMed platform. Basic descriptive statistics were calculated to summarize the variables. Additionally, in the static and dynamic tests, Spearman's rank correlations between body mass index (BMI) and plantar load were calculated. Statistically significant differences between groups were observed in the loading of the dominant limb. A statistically significant correlation between BMI and loading of both limbs was found in the static test and between BMI and loading of the dominant limb in the dynamic test. The baropodometric mat used in our study helped determine the plantar pressure distribution of soccer players and their non-athlete peers. Correlation analysis revealed that BMI was only associated with the mean plantar pressure of the dominant limb in the control group. Further research on a larger group of athletes is needed to determine how much sporting activity may affect the development to modifications within feet in soccer players.



#9 Motor Performance in Male Youth Soccer Players: A Systematic Review of Longitudinal Studies

Reference: Sports (Basel). 2021 Apr 19;9(4):53.  doi: 10.3390/sports9040053.

Authors: Maryam Abarghoueinejad, Adam D G Baxter-Jones, Thayse Natacha Gomes, Daniel Barreira, José Maia

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Summary: The aim of this systematic review was to identify and synthesize the available information regarding longitudinal data addressing young soccer players' motor performance changes. Following the Preferred Reporting Items for Systematic and Meta-analyses (PRISMA) statement, literature searches were performed in three databases: PubMed, ISI Web of Science and SCOPUS. The following descriptors were used: football, soccer, youth, young, player, athlete, physical performance, motor performance, longitudinal. The inclusion criteria were original articles in English with longitudinal data of young males (aged 10-18 years), with the aim to investigate motor performance serial changes. The initial search returned 211 records, and the final sample comprised 32 papers. These papers covered the European continent, and used mixed and pure longitudinal design with variation in sample size and age range. The reviewed studies tended to use different tests to assess the motor performance and aimed to identify changes in motor performance in several ways. In general, they indicated motor performance improvements with age, with a marked influence of biological maturity, body composition, and training stimuli. This review highlights the need for coaches and stakeholders to consider players' motor performance over time whilst considering biological maturation, biological characteristics, and training stimuli.



#10 Can Rules in Technical-Tactical Decisions Influence on Physical and Mental Load during Soccer Training? A Pilot Study

Reference: Int J Environ Res Public Health. 2021 Apr 19;18(8):4313. doi: 10.3390/ijerph18084313.

Authors: Tomás García-Calvo, Juan José Pulido, José Carlos Ponce-Bordón, Miguel Ángel López-Gajardo, Israel Teoldo Costa, Jesús Díaz-García

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Summary: This study aimed to analyze the effects of rules limitations in pass decisions during soccer tasks on physical and mental load reported by players. Participants were 40 semiprofessional Spanish soccer players (Mage = 22.40, SD = 2.25) from two male teams. Two training sessions with four tasks (same tasks with different score system: two maintaining ball possession games with goalkeepers, and two maintaining ball possession games) in counterbalanced order between teams were completed. To achieve a goal during limitation tasks, a minimum number of players had to participate in the passes before the goal. Internal (perceived effort and heart rate) and external physical load (distances), mental load (validated adaptation of the NASA-TXL) and fatigue (VASfatigue) were quantified. Paired t-test and magnitude-based inference were conducted. The results showed significantly higher mean speeds (p < 0.01), effort perception (p < 0.001), and mental fatigue (very likely positive) during possession games with restrictions. Additionally, performance satisfaction obtained significantly higher values with goalkeepers and pass restrictions (very likely positive). External physical load showed no significant differences between situations. The influence of mental fatigue on internal load and the complexity of the tasks could explain these results. Coaches can use this information to manipulate the training load in ecological conditions.



#11 Association between Training Load and Well-Being Measures in Young Soccer Players during a Season

Reference: Int J Environ Res Public Health. 2021 Apr 22;18(9):4451. doi: 10.3390/ijerph18094451.

Authors: Hadi Nobari, Ana Ruivo Alves, Hamed Haghighi, Filipe Manuel Clemente, Jorge Carlos-Vivas, Jorge Pérez-Gómez, Luca Paolo Ardigò

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Summary: This study aimed to analyze the correlations among weekly (w) acute workload (wAW), chronic workload (wCW), acute/chronic workload ratio (wACWR), training monotony (wTM), training strain (wTS), sleep quality (wSleep), delayed onset muscle soreness (wDOMS), fatigue (wFatigue), stress (wStress), and Hooper index (wHI) in pre-, early, mid-, and end-of-season. Twenty-one elite soccer players (age: 16.1 ± 0.2 years) were monitored weekly on training load and well-being for 36 weeks. Higher variability in wAW (39.2%), wFatigue (84.4%), wStress (174.3%), and wHI (76.3%) at the end-of-season were reported. At mid-season, higher variations in wSleep (59.8%), TM (57.6%), and TS (111.1%) were observed. Moderate to very large correlations wAW with wDOMS (r = 0.617, p = 0.007), wFatigue, wStress, and wHI were presented. Similarly, wCW reported a meaningful large association with wDOMS (r = 0.526, p < 0.001); moderate to very large associations with wFatigue (r = 0.649, p = 0.005), wStress, and wHI. Moreover, wTM presented a large correlation with wSleep (r = 0.515, p < 0.001); and a negatively small association with wStress (r = -0.426, p = 0.003). wTS showed a small to large correlation with wSleep (r = 0.400, p = 0.005) and wHI; also, a large correlation with wDOMS (r = 0.556, p = 0.028) and a moderate correlation with wFatigue (r = 0.343, p = 0.017). Wellness status may be considered a useful tool to provide determinant elite players' information to coaches and to identify important variations in training responses.



#12 External Loads in Under-12 Players during Soccer-7, Soccer-8, and Soccer-11 Official Matches

Reference: Int J Environ Res Public Health. 2021 Apr 26;18(9):4581.  doi: 10.3390/ijerph18094581.

Authors: Mario Sanchez, Rodrigo Ramirez-Campillo, Daniel Hernandez, Manuel Carretero, Jesus Maria Luis-Pereira, Javier Sanchez-Sanchez

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Summary: The aim of this study was to compare the external loads (i.e., displacement distances and velocities) of 10-11 years-old soccer players during Soccer-7 (i.e., seven-a-side), Soccer-8 (i.e., eight-a-side), and Soccer-11 (i.e., eleven-a-side) official matches. Male athletes (n = 133; age, 10.9 ± 0.8 years) were measured during official matches for total distance (TD), relative distance (Drel), maximal velocity (Vmax), acceleration (ACC), deceleration (DEC), and absolute and relative distance covered at different velocities. Data during matches were collected using a Global Positioning System unit. Greater TD was recorded during Soccer-11 compared to Soccer-7 and Soccer-8 (p < 0.01), and greater Drel during Soccer-11 compared to Soccer-8 (p < 0.05). Absolute ACC was greater during Soccer-11 compared to Soccer-7 (p < 0.01), although relative values for %ACC and %DEC were greater during Soccer-7 and Soccer-8 compared to Soccer-11 (p < 0.01). Globally, results show that Soccer-11 matches induce greater external loads compared to Soccer-7 and Soccer-8 matches. Current results may help coaches and soccer-related organizers to plan more suited soccer competitions for young players, with lower external loads.



#13 Exploring the Determinants of Repeated-Sprint Ability in Adult Women Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 26;18(9):4595. doi: 10.3390/ijerph18094595.

Authors: Lillian Gonçalves, Filipe Manuel Clemente, Joel Ignacio Barrera, Hugo Sarmento, Francisco Tomás González-Fernández, Markel Rico-González, José María Cancela Carral

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Summary: This study aimed to explore the main determinants of repeated-sprint ability (RSA) in women soccer players considering aerobic capacity, sprinting performance, change-of-direction, vertical height jump, and hip adductor/abductor isometric strength. Twenty-two women soccer players from the same team participating in the first Portuguese league were observed. Fitness assessments were performed three times during a 22-week cohort period. The following assessments were made: (i) hip abductor and adductor strength, (ii) squat and countermovement jump (height), (iii) change-of-direction test, (iv) linear sprinting at 10- and 30-m, (v) RSA test, and (vi) Yo-Yo intermittent recovery test level 1. Positive moderate correlations were found between peak minimum RSA and adductor and abductor strength (r = 0.51, p < 0.02 and r = 0.54, p < 0.01, respectively). Positive moderate correlations were also found between peak maximum RSA and adductor and abductor strength (r = 0.55, p < 0.02 and r = 0.46, p < 0.01, respectively). Lastly, a moderate negative correlation was found between fatigue index in RSA and YYIR1 test performance (r = -0.62, p < 0.004). In conclusion, abductor and adductor isometric strength-based coadjutant training programs, together with a high degree of aerobic endurance, may be suitable for inducing RSA in female soccer players.



#14 High Specialization among Female Youth Soccer Players Is Associated with an Increased Likelihood of Serious Injury

Reference: Med Sci Sports Exerc. 2021 Apr 28. doi: 10.1249/MSS.0000000000002693. Online ahead of print.

Authors: Michelle Xiao, Jacie L Lemos, Calvin E Hwang, Seth L Sherman, Marc R Safran, Geoffrey D Abrams

Summary: The purpose was to assess the associations between serious injury (> 3-month time loss) and level of specialization among high-level female soccer players and to compare the specialization and college commitment ages of female youth soccer players to Division I college and professional soccer athletes. Youth, college, and professional female soccer players in the United States playing in the top league at each level were recruited to complete an anonymous online survey. The survey collected information about player demographics, soccer specialization and training patterns, history of serious injuries from soccer, and perceptions surrounding soccer specialization. Comparisons between groups were performed using 2-sample t-tests, chi-squared analyses, and multiple logistic regression models controlling for differences in age. A p-value of less than 0.05 was set as significant. A total of 1,018 (767 youth, 251 college/professional) athletes completed the survey. Serious injuries affected 23.6% of youth and 51.4% of college/professional athletes. Anterior cruciate ligament (ACL) tears were more prevalent in college/professional players compared to youth athletes (18.3% vs 4.0%; p < 0.001). Highly specialized youth athletes (66.5%) were more likely to have sustained a serious injury from soccer compared to athletes with low specialization (Odds Ratio (OR) = 2.28 [1.38-3.92]; p=0.008) but not moderate specialization (OR = 1.37 [0.83-2.27]; p=0.43). A higher proportion of youth athletes specialized at a young age (< 10 years) compared to college/professional players (44.2% vs 25.9%; p < 0.001). High specialization in female youth soccer players is associated with an increased likelihood of sustaining a serious injury. Current youth soccer players are specializing earlier and committing to play college soccer at a younger age compared to when current college and professional players did.


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