Latest research in football - week 38 - 2022

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 Effects of osteopathic manipulative treatment of the pivots on lower limb function in young professional football players

Reference: J Bodyw Mov Ther. 2022 Oct;32:1-6. doi: 10.1016/j.jbmt.2022.05.017. Epub 2022 May 19.

Authors: Ewan Thomas, Marco Petrucci, Massimo Barretti, Giuseppe Messina, Antonio Rosario Cavallaro, Antonino Bianco

Summary: The most frequent injuries in professional soccer players are those pertinent to the lower limbs. In particular, strains of the hamstrings and ligamentous injuries of the knee. Therefore, preventive measures are aimed to reduce such events. We aimed to investigate if an osteopathic manipulative treatment (OMT) of the pivots could improve lower limb function in young professional football players. Thirty-eight young male professional football players were recruited (mean age 17.8 ± 0.44 years). These were randomly assigned to an OMT or control group (n = 20 and 18, respectively). Both groups underwent osteopathic evaluation. A sit-and-reach test, a vertical jump test, a hand-grip strength test, a cervical ROM test and a balance evaluation were also performed. A significant improvement (p < 0.01) was observed between pre and post measures in the OMT for dysfunctional assessment of the pivots. However, only L3 and C2 also differed from the control group post evaluation (p < 0.0001). No differences were present for any functional measure in the control group. Only the sit-&-reach of the OMT increased significantly (p < 0.001). Static balance with open eyes in the OMT, but not in the control group, improved during post evaluation (p < 0.01). The OMT of the pivots was able to increase the sit-and-reach measure, improve postural control with open eyes and improve dysfunctional patterns of the lumbosacral and upper cervical spine in young professional football players.



#2 Prevalence of Dehydration and The Relationship with Fluid Intake and Self-Assessment of Hydration Status in Czech First League Soccer Players

Reference: J Hum Kinet. 2022 Apr 26;82:101-110.doi: 10.2478/hukin-2022-0035. eCollection 2022 Apr.

Authors: Iva Klimesova, Jakub Krejci, Michal Botek, Andrew J McKune, Ales Jakubec, Filip Neuls, Barbora Sladeckova, Michal Valenta

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Summary: The objective of this cross-sectional study was to evaluate the hydration status of Czech First League soccer players, and to compare the reported fluid intake, perceived fluid intake and thirst sensation of euhydrated (EU) and dehydrated (DE) players. The study involved 124 Czech male professional soccer players (age 25.2±5.0 years) participating in annual winter, pre-season laboratory testing. Hydration status was assessed based on urine specific gravity (USG), euhydration was set at USG≤1.020. Fluid intake and thirst perception were evaluated by a questionnaire. The sample mean for USG was 1.021±0.008, 56% of players were dehydrated. Reported daily fluid intake was significantly (p<0.001, d=0.95, large effect) higher in EU compared to DE players. Daily fluid intake negatively correlated with USG (rS=-0.46, p<0.001, medium effect). The fluid intake perception score was significantly (p=0.005, d=0.54, medium effect) better in EU compared to DE players. Reported intake perception scores negatively correlated with USG (rS=-0.32, p<0.001, medium effect). However, there was no correlation (rS=-0.09, p=0.34, trivial effect) between thirst perception scores and USG. Thirst perception scores were not significantly different between EU and DE players (p=0.35, d=0.18, trivial effect). Our results indicated that self-assessment of both daily fluid intake and perceived fluid intake matched with objective hydration status, while self-assessment of thirst perception was not an appropriate indicator of hydration status in elite soccer players.



#3 Influence of crowd size on home advantage in the Japanese football league

Reference: Front Sports Act Living. 2022 Sep 9;4:927774. doi: 10.3389/fspor.2022.927774. eCollection 2022.

Authors: Ryota Nomura

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Summary: This study aimed to investigate the influence of crowd size on home advantage (HA). Data of the 2019 and 2020 seasons of the J1 League (Japan Professional Football's First Division League) were analyzed. Matches during the 2019 season were played under regular conditions, while there was low stadium occupancy during the 2020 season to prevent the spread of COVID-19. Regarding average points won, HA disappeared. By using multiple group structural equation modeling, it was examined the routes of influence via which a reduction in crowd size influenced HA. The results indicated that the influence from the crowd size to the referee's decisions disappeared during the 2020 season. However, the factors including the referee's decisions have lower effects on the outcome factor. Hence, no dominant route was detected in the present study.



#4 Repeat Anterior Cruciate Ligament Injury and Return to Sport in Australian Soccer Players After Anterior Cruciate Ligament Reconstruction With Hamstring Tendon Autograft

Reference: Am J Sports Med. 2022 Oct 3;3635465221125467. doi: 10.1177/03635465221125467.

Authors: Jonathan R Manara, Lucy J Salmon, Faisal M Kilani, Gerardo Zelaya de Camino, Claire Monk, Keran Sundaraj, Leo A Pinczewski, Justin P Roe

Summary: Soccer is the most commonly played team sport in the world and a high-risk sport for anterior cruciate ligament (ACL) injury and subsequent ACL reconstruction (ACLR). The aim was to assess the rate of further ACL injury in patients who have undergone ACLR with hamstring tendon autograft after soccer injuries in Australia and to determine factors associated with repeat ACL injury and return to soccer. From a prospectively collected database, a series of 1000 consecutive ACLRs using hamstring autografts performed in soccer players were identified. Patients were surveyed at a minimum 5 years after reconstruction, including details of further ACL injuries to either knee, return to soccer or other sports, and psychological readiness per the Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) scale. Of the 862 participants reviewed, ACL graft rupture occurred in 85 (10%) and contralateral ACL rupture in 68 (8%) within 5 years after the reconstruction. The 5-year ACL graft survivorship was 94% for females and 88% for males. The survivorship of the contralateral ACL was 92% for males and 90% for females. When compared with those aged >25 years, the odds of ACL graft rupture was increased by 4 to 5 times in those aged 19 to 25 years and 3 to 7 times in those ≤18 years. Further ACL injury to the graft or contralateral knee occurred in 44% of males aged ≤18 years. Risk factors for further ACL injury were younger age at time of surgery, male sex, and return to soccer. Graft diameter did not influence ACL graft rupture rates, and 70% of patients returned to soccer after ACLR. The mean ACL-RSI score was 59, and patients who reported more fear of reinjury on this scale were less likely to have returned to soccer. The prevalence of ACL graft rupture (10%) and contralateral ACL rupture (8%) was near equivalent over 5 years in this large cohort of mostly recreational Australian soccer players. ACLR with hamstring autograft is a reliable procedure, allowing 70% of patients to return to soccer in this high-risk population. Risk factors for further ACL injury are progressively younger age at time of surgery, male sex, and return to soccer. Graft diameter was not a factor in ACL graft rupture, indicating that other factors, particularly age, are of primary importance.



#5 Contextual variables affect peak running performance in elite soccer players: A brief report

Reference: Front Sports Act Living. 2022 Sep 16;4:966146. doi: 10.3389/fspor.2022.966146. eCollection 2022.

Authors: Diêgo Augusto, João Brito, Rodrigo Aquino, Dailson Paulucio, Pedro Figueiredo, Bruno Luiz Souza Bedo, Deborah Touguinhó, Fabrício Vasconcellos

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Summary: The current brief research report aimed to investigate the influence of contextual variables on peak running performance in male elite soccer players. We analyzed 29 matches of an elite soccer team during the Brazilian Serie A 2019. Twenty players were tracked using GPS units. Peak physical performance was determined using moving average running values with different time windows (1, 3, and 5-min periods). The variables analyzed were total distance covered, total distance covered in high-intensity running (≥19.8 km·h-1), and the distance in accelerations (≥2 m·s-2) and decelerations ( ≤-2 m·s-2). Four contextual variables were considered: 1) positional status; 2) match location; 3) match outcome; and 4) match status. Central defenders showed a lower 1-min peak total distance in relation to all other positions (p = 0.001-0.03). Peak physical performance was higher in away matches for high-intensity running, acceleration, and deceleration (p = 0.01-0.03). In matches that ended in losses, peak values for high-intensity running and acceleration were higher compared to draws and wins (p = 0.01-0.04). Regarding the match status, higher values were observed in draws than wins and losses (p = 0.01). Peak running performance vary according to contextual variables of the match in male elite soccer players. Positional differences were found for peak periods, and physical performance was higher in away matches.



#6 Daily and weekly external loads in the microcycle: Characterization and comparison between playing positions on amateur soccer

Reference: Front Sports Act Living. 2022 Sep 15;4:943367. doi: 10.3389/fspor.2022.943367. eCollection 2022.

Authors: Mauro Miguel, Alberto Cortez, Felix Romero, Nuno Loureiro, Javier García-Rubio, Sergio José Ibáñez

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Summary: Ensuring adequate levels of training and recovery to maximize player performance is critical; however, there are methodological challenges in designing a periodized training program for soccer teams. This study aims to describe and characterize the daily and weekly external load in an amateur soccer team and based on the weighting factors determined by the match reference, compare the external loads between playing positions. Twenty-four amateur soccer players (22.3 ± 1.7 years) were monitored using a global positioning system. Data collected comprises 19 competitive microcycles with a standard structure composed of 3 training sessions (matchday-5, matchday-3, and matchday-2) and one match. Match-reference values were calculated as the mean of the five best values recorded during official matches. The results show, on matchday-5 session, the existence of significant differences between playing positions to relative total distance covered (p = 0.050), relative sprint distance (p = 0.001), relative moderate-intensity accelerations (p < 0.001), relative high-intensity accelerations (p = 0.003), relative moderate-intensity decelerations (p < 0.001), and relative high-intensity decelerations (p = 0.017). On matchday-3 session, there are significant differences to relative very high-speed running distance (p = 0.017) and relative moderate-intensity decelerations (p = 0.014). On matchday-2 session, there are significant differences to relative high-speed running distance (p = 0.025), relative very high-speed running distance (p = 0.008), and relative moderate-intensity decelerations (p < 0.001). Weekly significant differences are observed between the playing positions to relative moderate-intensity accelerations (p = 0.002), relative high-intensity accelerations (p < 0.001), and relative moderate-intensity decelerations (p < 0.001). The weekly load is characterized by a greater weighting on accelerations and decelerations, compared to distances at very-high speed and sprint. The training loads must respect a standard training model that contemplates the individualization of the physical demands of the match, for each playing position, as for each individual.



#7 Obturator Internus Bursitis Mimicking Groin Pain in a Football Player: A Case Report

Reference: J Orthop Case Rep. 2022 Feb;12(2):106-111. doi: 10.13107/jocr.2022.v12.i02.2688.

Authors: Omkar Sadigale, Anjali Tiwari, Madhankumar Ramanathan, Himanshu Choudhury, Farokh Wadia, Vaibhav Bagaria

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Summary: Traumatic groin pain (GP) is frequently the result of acute trauma, often an indirect muscle injury. The most affected muscles in traumatic GP are the rectus abdominis, adductors, and iliopsoas. The obturator internus bursitis as a cause of GP is very rare. The present case describes a rare indirect injury of obturator internus bursitis in a 22-year-old male football player who reported GP that used to worsen with sprinting and change in directions. The pain was relieved with rest and sprinting at 80% capacity. The patient had been diagnosed clinically and on magnetic resonance imaging (MRI) as a case of obturator internus insertional tendinopathy with bursitis. His symptoms resolved after ultrasound-guided injection in the inflamed tendon sheath at its insertion point. After 2 years, the patient was followed up with a triumphant return to professional football with no recurrence and a good prognosis in a relatively short recovery time. Clinical diagnosis of obturator injuries is often tricky. GP not responding to conservative management presents a unique challenge to the physician and the rehabilitation team. MRI must follow the radiological investigations and ultrasound if the reports were inconclusive of the diagnosis. In the present case study, the usual causes of such pain (osteitis pubis, and adductor muscle strains/tendinosis) were ruled out, and a specific unique condition was diagnosed with the help of the MRI.



#8 Assessing the Sprint Force-Velocity Profile in International Football Players with Cerebral Palsy: Validity, Reliability and Sport Class' Profiles

Reference: J Hum Kinet. 2022 Apr 26;82:253-262. doi: 10.2478/hukin-2022-0065. eCollection 2022 Apr.

Authors: Iván Peña-González, Alejandro Javaloyes, José Manuel Sarabia, Manuel Moya-Ramón

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Summary: This study assessed and described the Sprint Force-velocity (SFv) profile, and its validity and reliability in international cerebral palsy (CP) football players. Twenty international male CP football players (age: 26.9±7.4) performed a 30-m sprint, a vertical jump (CMJ), a change of direction (MAT), a dribbling and an intermittent endurance (Yo-YoIR1) test. The SFv profile and physical performance variables were shown according to the players' sport class with the estimation of the effect sizes between classes. The SFv showed high reliability (ICC=0.77 to 0.99; SEM=0.89 to 8.66%). Validity for the SFv was provided by its positive correlation with the players' sport class (r=0.53 to 0.75; p=.02 to <.01) and the rest of the physical performance tests (r=0.45 to 0.99; p=.04 to <.01). The RFmax was the main SFv profile variable that explained players' performance in the rest of the tests (β=0.77 to 1.0; p<.05; R2=0.59 to 0.99). The SFv profile seems to be an efficient test to assess international CP football players' physical performance. This provides information about the players' individual sprint mechanical characteristics and their sprint strengths and weaknesses, allowing coaches and conditioning trainers to individualize their training interventions to optimize sprint performance.



#9 Service quality in football tourism: an evaluation model based on online reviews and data envelopment analysis with linguistic distribution assessments

Reference: Ann Oper Res. 2022 Sep 22;1-34. doi: 10.1007/s10479-022-04992-x. Online ahead of print.

Authors: Adjei Peter Darko, Decui Liang, Yinrunjie Zhang, Agbodah Kobina

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Summary: The emergence of sports tourism has compelled sports managers to rethink the management and improvement of sports facilities. Through service quality analysis, sports managers can identify the strengths and weaknesses of their activities for possible advancement. Hence, this study aims to develop a decision support model based on integrating online reviews and data envelopment analysis to measure the degree of tourist satisfaction and provide benchmarking goals for service improvement. The proposed model employs text mining techniques to discover service quality attributes from text reviews. According to the discovered service quality attributes, we conduct sentiment analysis to reveal the sentiment polarities of the text reviews. Then, we refine the polarities and ratings of online reviews into linguistic distribution assessments. Furthermore, we develop a linguistic distribution output-oriented non-discretionary bestpoint slack-based measure (BP-SBM) to compute the degree of tourist satisfaction and benchmarking goals. The linguistic distribution output-oriented non-discretionary BP-SBM can handle both positive and negative data values, thus overcoming the flaws of the traditional model. Meanwhile, the proposed decision support model investigates how the service-quality attributes interact to provide improvement pathways for an underperforming stadium based on association rule mining. We test the applicability of the proposed decision support model on some Elite stadia in Europe.



#10 Evidence-Based Recovery in Soccer - Low-Effort Approaches for Practitioners

Reference: J Hum Kinet. 2022 Apr 26;82:75-99. doi: 10.2478/hukin-2022-0082. eCollection 2022 Apr.

Authors: Nils Haller, Erik Hübler, Thomas Stöggl, Perikles Simon

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Summary: Strategies to improve recovery are widely used among soccer players at both amateur and professional levels. Sometimes, however, recovery strategies are ineffective, improperly timed or even harmful to players. This highlights the need to educate practitioners and athletes about the scientific evidence of recovery strategies as well as to provide practical approaches to address this issue. Therefore, recent surveys among soccer athletes and practitioners were reviewed to identify the recovery modalities currently in use. Each strategy was then outlined with its rationale, its physiological mechanisms and the scientific evidence followed by practical approaches to implement the modality. For each intervention, practical and particularly low-effort strategies are provided to ensure that practitioners at all levels are able to implement them. We identified numerous interventions regularly used in soccer, i.e., sleep, rehydration, nutrition, psychological recovery, active recovery, foam-rolling/massage, stretching, cold-water immersion, and compression garments. Nutrition and rehydration were classified with the best evidence, while cold-water immersion, compression garments, foam-rolling/massage and sleep were rated with moderate evidence to enhance recovery. The remaining strategies (active recovery, psychological recovery, stretching) should be applied on an individual basis due to weak evidence observed. Finally, a guide is provided, helping practitioners to decide which intervention to implement. Here, practitioners should rely on the evidence, but also on their own experience and preference of the players.



#11 Influence of Tactical Behaviour on Running Performance in The Three Most Successful Soccer Teams During the Competitive Season of The Spanish First Division

Reference: J Hum Kinet. 2022 Apr 26;82:135-144. doi: 10.2478/hukin-2022-0040. eCollection 2022 Apr.

Authors: Jose Asian-Clemente, Luis Suarez-Arrones, Bernardo Requena, Alfredo Santalla

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Summary: The purpose of this study was to analyze the influence of tactical behavior on physical performance of the three best Spanish soccer teams. Team 1 employed a 1-4-4-2 formation with compact defence and direct attacks, Team 2 employed an indirect style of play with a 1-4-3-3 formation and Team 3 used a 1-4-3-3 formation with elaborate attacks and strong counter-attacks. 816 individual situations of 54 professional soccer players categorized as fullbacks (FB), central defenders (CD), central midfielders (MF), wide midfielders (WM), and strikers (S) were included in the analysis. Their performance was examined with a player-tracking system. The analyzed variables included total distance covered, distance covered above 14, 21 and 24 km·h-1, as well as distance covered in possession of the ball and without possession of the ball. Team 2 covered a substantially lower distance >14 km·h-1 than Team 1 and substantially lower distances >14, >21, and >25km·h-1 than Team 3. No differences in running activity were found between Teams 1 and 3. However, there were substantial differences between the specific positions of the three teams. CD in Team 1 covered the lowest distance by a substantial margin in almost all variables analysed, whereas MF travelled substantially greater distances than did other positions. WM in Team 1 covered the greatest distance >18 and >21km·h- 1, while S in Team 2 had the lowest distance covered in almost all the variables, and FB in Team 3 showed the lowest total distance covered and distance covered >14km·h-1. WM in Team 2 had the greatest distance covered in possession, while S in Team 3 had the greatest distance covered out of possession. The results indicate that different team formations and associated tactical demands have a significant influence on running performance.



#12 Hip adduction and abduction strength in youth male soccer and basketball players with and without groin pain in the past year

Reference: PLoS One. 2022 Oct 5;17(10):e0275650. doi: 10.1371/journal.pone.0275650. eCollection 2022.

Authors: Jan Marušič, Nejc Šarabon

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Summary: The objectives of this study were to 1) assess the differences between youth soccer and basketball players with and without past year groin pain (GP) in hip adduction and abduction strength and several training characteristics (age at the start of regular training, weekly training frequency, warm-up and training duration, use of stretching and/or stabilisation exercises during warm-up, use of resistance training); 2) present strength reference values for youth soccer and basketball players. 227 players participated (age 16.9 ± 1.4 years; height 184.2 ± 8.5 cm; mass 75.5 ± 11.9 kg). Hip adduction and abduction strength was measured in supine position (hip, knee and ankle in neutral position) using a MuscleBoard dynamometer. Interlimb asymmetries and hip adduction:abduction ratios were calculated. Past year GP and training characteristics were assessed with a retrospective questionnaire. 11.9% of players reported past year GP (16.9% in soccer and 6.4% in basketball). The only significant difference between the past year GP and the control groups was found in the age of the players at the start of regular training (7.2 ± 1.8 years for the GP group vs. 8.5 ± 2.6 years for the control group). Additionally, soccer players without past year GP have significantly higher hip adduction strength (1.1 ± 0.2 Nm/kg vs. 1.0 ± 0.2 Nm/kg) and adduction:abduction strength ratio (1.10 ± 0.18 vs. 1.03 ± 0.16) compared to basketball players. Our results show that hip adduction and abduction strength, interlimb asymmetry and hip adduction:abduction ratio do not differentiate between players with and without past year GP (p = 0.29-0.90), which means that their adduction or abduction strength can be analysed regardless of the GP presence in the past year. Additionally, players with past year GP started regularly training at significantly lower age, which could indicate the problematic nature of early/premature sports specialisation.



#13 Soccer-related injuries pre- and post-COVID-19 lockdown in Saudi Arabia: an epidemiological study

Reference: J Sports Med Phys Fitness. 2022 Oct 7.  doi: 10.23736/S0022-4707.22.14073-9. Online ahead of print.

Authors: Wesam S Al Attar, Alaa A Khushhal

Summary: Soccer predisposes players to injuries because it involves running, jumping, and interactions between players; players must maintain fitness through training and matches. Coronavirus disease (COVID-19) caused a global lockdown, and the ministry of sports suspended all sports activities, forcing players to train indoors. This study aimed to determine the number and nature of soccer injuries per thousand hours of exposure pre and post the COVID-19 lockdown in Saudi Arabia. In total, 45 soccer teams (630 players) competing in the amateur leagues were followed for two seasons (pre- and post-COVID-19 lockdown). The medical staff of the participating teams was requested to report all new injuries during matches and training. Exposure during all matches and training and number of overall, initial, recurrent, severity, and types of injuries reported pre- and post-COVID lockdown were recorded. A total of 43 injuries were reported pre-COVID-19 lockdown in 50130 h of exposure (0.86 injuries/1000 exposure hours). A total of 91 injuries were reported post-COVID-19 lockdown in 47622 hours of exposure (1.91 injuries/1000 exposure hours). The injury risk ratio was 0.45 (0.31 to 0. 65; P = 0.0001), suggesting that the injuries increased by 55% post-COVID-19 lockdown. The study results indicated that the COVID-19 lockdown influenced soccer-related injuries, as the overall number of soccer injuries increased because of the COVID-19 lockdown.



#14 Comparison of external load indicators between official matches and sport-specific training in semi-professional soccer players: focus on intensity and strength

Reference: J Sports Med Phys Fitness. 2022 Oct 7. doi: 10.23736/S0022-4707.22.14189-7. Online ahead of print.

Authors: Guglielmo Pillitteri, Valerio Giustino, Giuseppe Messina, Marco Petrucci, Alessio Rossi, Marianna Bellafiore, Angelo Iovane, Ewan Thomas, Antonino Bianco, Antonio Palma, Giuseppe Battaglia

Summary: The aim of this study was to investigate any differences in External Load indicators (ELi) between Official Matches (OM) and sport-specific tasks in semi-professional soccer players. 1932 observations among 28 semi-professional soccer players (FC Palermo, Italy, age: 25±6 years, height: 183±6 cm, weight: 75.2±7 kg) were collected through GPS devices (Qstarz BT-Q1000EX, 10 Hz) and the related software (LaGalaColli V: during the season 2019-2020. Participants were monitored during OM, Friendly Matches (FM), Small Sided Games (SSG), and Match-Based Exercises (MBE), considering the percentage of intense accelerations (%int acc), percentage of intense decelerations (%int dec), and Passive Recovery time /min (PrT/m) as Eli. We detected the highest mean value for PrT/m in OM and the lowest in MBE and SSG (18.36±4.38 and 13.4±5.26 and 13.4±4.29 (s/min), respectively). The lowest mean values of %int acc and %int dec were found in OM and the highest in SSG (8.64±1.52 vs 13.02±3.14 and 9.25±1.56 vs 15.68±3.14, for %int acc and %int dec, respectively). Significant differences between the four tasks for all the ELi considered (p<0.001). The posthoc pairwise comparisons revealed significant differences for all the ELi between all tasks (p<0.001) except for the %int acc between MBE vs FM (p=0.003). No significant difference was found in PrT/m between MBE vs FM and SSG vs FM. ELi are in accordance with the performance model by achieving better values in training than OM, suggesting the fundamental role of GPS for monitoring external load in soccer.



#15 The Dose-Response Relationship Between Training-Load Measures and Changes in Force-Time Components During a Countermovement Jump in Male Academy Soccer Players

Reference: Int J Sports Physiol Perform. 2022 Oct 11;1-8. doi: 10.1123/ijspp.2022-0107. Online ahead of print.

Authors: Matthew Ellis, Tony Myers, Richard Taylor, Rhys Morris, Ibrahim Akubat

Summary: The aim was to manage physical performance in soccer, practitioners monitor the training load (TL) and the resulting fatigue. A method frequently used to assess performance is the countermovement jump (CMJ). However, the efficacy of CMJ to detect fatigue from soccer matches and training remains uncertain, as does the relationship between TL and change in CMJ performance. The aims of the present study were 2-fold. One was to observe the changes of CMJ force-time components and jump height (JH). The second was to examine dose-response relationships between TL measures and CMJ over a 6-week preseason. Twelve male academy soccer players (17 [1] y, 71.2 [5.6] kg, and 178 [5.8] cm) were recruited. Daily changes in CMJ were assessed against baseline scores established before preseason training, along with internal and external TL measures. A series of Bayesian random intercept models were fitted to determine probability of change above/below zero and greater than the coefficient of variation established at baseline. Jumps were categorized into match day minus (MD-) categories where the higher number indicated more time from a competitive match. JH was lowest on MD - 3 (28 cm) and highest on MD - 4 (34.6 cm), with the probability of change from baseline coefficient of variation highly uncertain (41% and 61%, respectively). Changes to force-time components were more likely on MD - 3 (21%-99%), which provided less uncertainty than JH. Bayes R2 ranged from .22 to .57 between TL measures and all CMJ parameters.



#16 The evaluation of playing styles integrating with contextual variables in professional soccer

Reference: Front Psychol. 2022 Sep 23;13:1002566. doi: 10.3389/fpsyg.2022.1002566. eCollection 2022.

Authors: Lingfeng Kong, Tianbo Zhang, Changjing Zhou, Miguel-Angel Gomez, Yue Hu, Shaoliang Zhang

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Summary: Playing styles play a key role in winning soccer matches, but the technical and physical styles of play between home and away match considering team quality in the Chinese Soccer Super League (CSL) remain unclear. The aim of this study was to explore the technical and physical styles of play between home and away matches integrating with team quality in the CSL. The study sample consists of 480 performance records from 240 matches during the 2019 competitive season in the CSL. These match events were collected using a semi-automatic computerized video tracking system, Amisco Pro®. A k-means cluster analysis was used to evaluate team quality and then using principal component analysis (PCA) to identify the playing styles between home and away matches according to team quality. Differences between home and away matches in terms of playing styles were analyzed using a linear mixed model. Our study found that PC1 presented a positive correlation with physical-related variables such as HIRD, HIRE, HSRD, and HSRE while PC2 was positively associated with the passing-related variables such as Pass, FPass, PassAcc, and FPAcc. Therefore, PC1 typically represents intense-play styles while PC2 represents possession-play styles at home and away matches, respectively. In addition, strong teams preferred to utilize intensity play whereas medium and weak teams utilized possession play whenever playing at home or away matches. Furthermore, the first five teams in the final overall ranking in the CSL presented a compensated technical-physical playing style whereas the last five teams showed inferior performance in terms of intensity and possession play. Intensity or possession play was associated with the final overall ranking in the CSL, and playing styles that combine these two factors could be more liable to win the competition. Our study provides a detailed explanation for the impact of playing styles on match performances whereby coaches can adjust and combine different playing styles for ultimate success.



#17 Repetitive soccer heading adversely impacts short-term learning among adult women

Reference: J Sci Med Sport. 2022 Aug 26;S1440-2440(22)00222-5. doi: 10.1016/j.jsams.2022.08.011.

Authors: Kenny Ye, Roman Fleysher, Richard B Lipton, Molly E Zimmerman, Walter F Stewart, Martin J Sliwinski, Mimi Kim, Michael L Lipton

Summary: The purpose was to determine the impact of 12-month heading exposure on short-term learning. A total of 105 active amateur soccer players, 45 women and 60 men, were administered an EMA-based test of working memory, a version of the two-back, once daily for 14 days. Heading exposure of the participants was assessed using "HeadCount", a validated structured questionnaire at the baseline visits. The short-term rate of learning of each individual is quantified by first fitting a quadratic model to the daily performance on the two-back test over a two-week period, then taking the instantaneous rate of the quadratic function at the 7th test. A linear regression model was used to test the association of heading exposure with rates of learning, including age, sex, years of education and history of concussion as covariates, as well as variables describing soccer play and heading within the two-week period. Sensitivity analyses were performed using different methods for quantifying the learning effects and different transformations on 12-month heading exposure. Greater 12-month heading was associated with lower rates of learning among women (p = 0.008) but not among men (p = 0.74). We have identified evidence for an adverse, albeit subclinical, effect of soccer heading on brain function among young adult players, which selectively affects women in our sample.



#18 The soccer season: performance variations and evolutionary trends

Reference: PeerJ. 2022 Oct 5;10:e14082. doi: 10.7717/peerj.14082. eCollection 2022.

Author: Joao Renato Silva

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Summary: The physiological demands of soccer challenge the entire spectrum of the response capacity of the biological systems and fitness requirements of the players. In this review we examined variations and evolutionary trends in body composition, neuromuscular and endurance-related parameters, as well as in game-related physical parameters of professional players. Further, we explore aspects relevant for training monitoring and we reference how different training stimulus and situational variables (e.g., competition exposure) affect the physiological and performance parameters of players. Generally, improvements of small magnitude in non- (non-CMJ) and countermovement-based jumps (CMJBased) and in the sprint acceleration (ACCPhase) and maximal velocity phase (MVPhase) are observed from start of preparation phase (PPS) to beginning of competition phase (BCP). A greater magnitude of increases is observed in physiological and endurance performance measures within this period; moderate magnitude in sub-maximal intensity exercise (velocity at fixed blood lactate concentrations; V2-4mmol/l) and large magnitude in VO2max, maximal aerobic speed (MAS) and intense intermittent exercise performance (IE). In the middle of competition phase (MCP), small (CMJBased and ACCPhase), moderate (non-CMJ; MVPhase; VO2max; sub-maximal exercise) and large (MAS and IE) improvements were observed compared to PPS. In the end of competition period (ECP), CMJBased and MVPhase improve to a small extent with non-CMJ, and ACCPhase, VO2max, MAS, sub-maximal intensity exercise and IE revealing moderate increments compared to PPS. Although less investigated, there are generally observed alterations of trivial magnitude in neuromuscular and endurance-related parameters between in-season assessments; only substantial alterations are examined for IE and sub-maximal exercise performance (decrease and increase of small magnitude, respectively) from BCP to MCP and in VO2max and IE (decrements of small magnitude) from MCP to ECP. Match performance may vary during the season. Although, the variability between studies is clear for TD, VHSR and sprint, all the studies observed substantial increments in HSR between MCP and ECP. Finally, studies examining evolutionary trends by means of exercise and competition performance measures suggests of a heightened importance of neuromuscular factors. In conclusion, during the preseason players "recover" body composition profile and neuromuscular and endurance competitive capacity. Within in-season, and more robustly towards ECP, alterations in neuromuscular performance seem to be force-velocity dependent, and in some cases, physiological determinants and endurance performance may be compromised when considering other in-season moments. Importantly, there is a substantial variability in team responses that can be observed during in-season. Consequently, this informs on the need to both provide a regular training stimulus and adequate monitorization throughout the season.


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