Latest research in football - week 5 - 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 In Professional Male Soccer Players, Time-Loss Groin Injury Is More Associated With the Team Played for Than Training/Match Play Duration

Reference: J Orthop Sports Phys Ther. 2022 Feb 5;1-26. doi: 10.2519/jospt.2022.10845. Online ahead of print.

Authors: Andrea B Mosler, David L Carey, Kristian Thorborg, Adam Weir, Cristiano Eirale, Nicol van Dyk, Per Hӧlmich, Rod J Whiteley, Tim J Gabbett, Kay M Crossley

Summary: The aim was to investigate the relationship between training/match play duration and time-loss groin injury in professional male soccer players and determine if previously identified intrinsic risk factors influenced this relationship. A total of 590 professional male soccer players were prospectively followed from July 2013-June 2015. Time-loss groin injuries, and individual training and match play duration were recorded using standardized surveillance methods. Acute and chronic training/match play duration were considered as interacting variables. Nonlinear cox regression analysis (modelled using restricted cubic splines), clustered by player identification number, examined the relationship between training/match play duration and groin injury. Previously identified intrinsic risk factors of previous groin injury and eccentric adduction strength were included in the multivariable regression analysis. There was no clinically meaningful relationship between training/match play duration and groin injury risk. Team had the strongest influence on groin injury risk (relative HR= -2.27 to 0.97). Groin injury risk was highest when accumulated chronic and acute training duration was also highest, but large confidence intervals indicate considerable uncertainty around this finding. Previous groin injury and eccentric adduction strength were not associated with groin injury risk when training/match play duration and team were included in the model. In professional male soccer players, there was no clinically meaningful relationship between groin injury risk and training/match play duration. Team played for either protected or increased groin injury risk, indicating that team-related factors not measured in this study had greater effect on groin injury risk than training/match play duration



#2 Repeated Interval Loughborough Soccer Passing Tests: An Ecologically Valid Motor Task to Induce Mental Fatigue in Soccer

Reference: Front Physiol. 2022 Jan 20;12:803528. doi: 10.3389/fphys.2021.803528. eCollection 2021.

Authors: Chao Bian, Ajmol Ali, George P Nassis, Yongming Li

Download link:

Summary: Most studies investigating mental fatigue (MF) in soccer utilized a computerized Stroop task to induce MF. However, the traditional key-pressing task has been challenged for its lack of ecological validity. The limited relevance to real-life soccer made it difficult to bridge the gap between the research and the applied setting. Therefore, a novel soccer-specific inducing task is in urgent need. This study compared a novel MF-inducing task in soccer with the Stroop task and investigated the impact of induced MF on cognitive and soccer-specific skill performance. A randomized, counterbalanced crossover design was employed. Fifteen well-trained male soccer players randomly participated in three MF-inducing tasks. Two of them were motor tasks consisting of 10 repeated interval Loughborough Soccer Passing Test (10xLSPT or LSPT) in clockwise passing order (10xC-LSPT) with each block starting every 2 min. The two tasks share the same movement pattern, but C-LSPT is considered to have lower cognitive demands. The third was the 20-min Stroop task (Stroop-20). MF was assessed immediately before and after each task by visual analog scale (VAS), the cognitive performance in a 3-min Stroop task, and the skill performance in one LSPT. Subjective MF increased similarly after 10xLSPT and Stroop-20 (+ 25.4 ± 10.3 vs. + 23.4 ± 10.8 AU, p = 0.607). The induced MF by 10xLSPT and Stroop-20 had no impact on cognitive performance and movement time but similarly affected in a significantly negative manner on penalty time (+ 5.9 ± 4.9 vs. + 5.4 ± 4.2 s, p = 0.748) and passing accuracy (-1.4 ± 1.5 vs. -1.0 ± 1.3, p = 0.465). Two motor tasks shared similar intensity, but 10xC-LSPT was inefficient to induce MF. The results showed that the 20-min repeated interval LSPT could induce a similar MF as the Stroop task. The induced MF had detrimental effects on soccer skill performance. The novel motor task is recommended for MF studies in soccer as an inducement task. Practitioners should be cautious about the prolonged cognitive-demanding skill section of the pre-match warm-up to avoid the negative effect of MF on the upcoming match. This motor task pattern could be followed as a supplementary training protocol.



#3 Hip external rotation isometric torque for soccer, basketball, and volleyball athletes: normative data and asymmetry index

Reference: Braz J Phys Ther. 2022 Jan 31;26(1):100391. doi: 10.1016/j.bjpt.2022.100391. Online ahead of print.

Authors: Luciana De Michelis Mendonça, Natália Franco Netto Bittencourt, Roberta Lima Freire, Vinicius Castro Campos, Thiago Vinícius Ferreira, Paula Lanna Silva

Download link:

Summary: Deficits in strength of the hip external rotators (ER) affect trunk, hip, and knee movement patterns, potentially contributing to injury in athletes. The objective was to provide normative data on isometric torque for hip ER in athletes of three distinct sports and to determine if isometric torque for the hip ER and torque asymmetry between legs differ among sports and between sexes. Basketball, soccer, and volleyball athletes (n=451) were evaluated. Hip ER torque was quantified bilaterally with athletes in prone and 90° of knee flexion using a hand-held dynamometer. Data are expressed as mean and 95% confidence interval. Hip ER torque values in Nm/kg for the dominant and non-dominant limbs were, respectively, 0.46 (0.44, 0.48) and 0.42 (0.40, 0.44) for male soccer athletes; 0.35 (0.32, 0.37) and 0.27 (0.25, 0.29) for male basketball athletes; and 0.37 (0.34, 0.39) and 0.35 (0.32, 0.37) for male volleyball athletes. Hip ER torque in Nm/kg for the female volleyball athletes was 0.29 (0.26, 0.33) for the dominant and 0.29 (0.25, 0.32) for the non-dominant limb. The Limb Symmetry Index for male soccer, basketball, and volleyball players was, respectively, 94% (91, 97), 81% (75, 87), and 95% (91, 99). For female volleyball players the Limb Asymmetry Index was 102% (95, 108). Male volleyball athletes showed higher torque values than female volleyball athletes. This study reported normative values for hip ER isometric torque of youth athletes. Clinicians can use the reported data as reference to identify torque deficits in athletes of the three reported sports.



#4 Binocular Function Parameters in Elite Football Players

Reference: J Binocul Vis Ocul Motil. 2022 Feb 10;1-8. Online ahead of print.

Authors: Jorge Jorge, Alberto Diaz-Rey

Summary: The aim was to investigate the binocular function in elite football players, and to analyze the differences (i) between athletes who play in different positions and (ii) between players of different ethnicities. We screened 102 professional football players from four teams. The screening consisted of the measurement of refractive error. The binocular function parameters evaluated were: horizontal and vertical ocular alignment for distance (DF) and near fixation (NF), the values of break and recovery for negative and positive fusional vergences at DF and NF, vergence facility at NF, monocular accommodative facility at NF, near point of convergence (NPC) (break and recovery points), and NF stereopsis. All the athletes were men with a mean age of 24.6 ± 4.1 years. No statistically significant differences were found based on the athletes' ethnicity, except for ametropia prevalence, negative fusional vergences at DF, and NPC. We verified a statistically significant difference for the value of the break of negative fusional vergence at DF. The values found for Arab athletes are higher by more than 2 prism diopters than athletes of other ethnicities (p = .021). Arab athletes also show NPC values more distant than other athletes (p = .019, and p = .002 for break and recovery, respectively). Arab athletes have some binocular function parameters better than the remaining athletes, in particular when compared to Caucasian athletes. When compared to reference studies, athletes' binocular function seems to be better than those of the general population.



#5 The high frequency of alcohol advertising during televised English Premier League football games shown in Ethiopia

Reference: Harm Reduct J. 2022 Feb 5;19(1):11. doi: 10.1186/s12954-022-00591-y.

Authors: Mulugeta Tamire, Alex Barker, Sefonias Getachew, Rachael L Murray, Rihanna Amedala, John Britton, Wakgari Deressa, Andrew W Fogarty

Download link:

Summary: Excessive alcohol consumption is an important risk factor for increased morbidity, mortality and other social harms globally. Televised sport allows the promotion of alcoholic drinks to a large and often young audience, and thus can be used to develop new markets for alcohol in low- and middle-income countries. This study aimed to analyse the alcohol advertising displayed during televised English Premier League (EPL) games, which is widely viewed in Ethiopia, and are particularly popular among young people. Nineteen live televised EPL football matches broadcast in Ethiopia on the SuperSport channels over 4 weeks of the 2018/19 season were digitally recorded from the digital satellite television. Exposure to alcohol advertising was measured by calculating the total elapsed time duration with the alcohol content from the pre-match to the end of the post-game period of the broadcast. Data were available for a total of 2451 min broadcast time. Alcohol advertising accounted for 205.2 min (8.4%) with a mean duration of 10.8 min per match (range 5.5 to 22.6). The dominant format of alcohol advertisement was the display of logos associated with an alcoholic drink on the television (TV) screen, which accounted for approximately 43% of the total alcohol advertising time. This was followed by pitch side virtual display (17.7%) and a glass of alcohol drink on the TV screen (17.6%). Over three quarters of alcoholic drink advertising (77.7%) was during active football playing time. None of the advertisements on the televised football games showed cigarettes. There is a high frequency of exposure to alcohol advertising during televised EPL matches in Ethiopia. It is important to ensure that the newly introduced domestic ban on alcohol advertising is also applied to foreign satellite broadcasters. This is likely to have relevance to other sub-Saharan African countries in promoting public health strategies to reduce harm from alcohol consumption.



#6 Incidence of calcaneal apophysitis (Sever's disease) and return-to-play in adolescent athletes of a German youth soccer academy: a retrospective study of 10 years

Reference: J Orthop Surg Res. 2022 Feb 9;17(1):83. doi: 10.1186/s13018-022-02979-9.

Authors: Patrick Belikan, Lars-Christopher Färber, Frédéric Abel, Tobias E Nowak, Philipp Drees, Stefan G Mattyasovszky

Summary: Calcaneal apophysitis, or Sever's disease, is the most common cause of heel pain in childhood and adolescence. It is regarded as an overuse syndrome. Studies on the incidence of calcaneal apophysitis in young athletes and their associated return-to-play time are lacking in the current literature. The aim of our current study was to identify the incidence of calcaneal apophysitis in professional youth soccer, the associated time to return-to-play, predisposing factors and their impact on time to return-to-play. Retrospective evaluation of injury data gathered from a German youth soccer academy in the years 2009-2018. In total, 4326 injury cases in 612 players were included in the study. The diagnosis and the follow-up visits were carried out in a weekly consultation hour at the youth academy. During the observation period of 10 years, 22 cases of calcaneal apophysitis were detected. The incidence of calcaneal apophysitis per 100 athletes per year was found to be 0.36. The mean age of the affected athletes at the time of diagnosis was 11.8 ± 2.1 years (MW ± SD). The complaints were unilateral in 20 and bilateral in two cases. Three of the 22 detected cases of calcaneal apophysitis (13.6%) were recurrent injuries. The mean time to return-to-play of the affected athletes was 60.7 ± 64.9 days (MW ± SD). Athletes with recurrent complaints showed longer recovery time and time to return-to-play when compared to players with primary diagnosed disease. Our results could show that neither age nor body mass index at the time of diagnosis had an impact on time to return-to-play. This is the first study investigating the incidence of calcaneal apophysitis and the associated time to return-to-play in youth elite soccer. Calcaneal apophysitis results in substantial time loss for the athletes. Further prospective clinical studies are required to fully understand the etiology and risk factors for calcaneal apophysitis and therefore develop preventive strategies.



#7 Acute effects from the half-squat performed using a repetition versus differential approach in youth soccer players

Reference: BMC Sports Sci Med Rehabil. 2022 Feb 9;14(1):23. doi: 10.1186/s13102-022-00413-5.

Authors: Diogo Coutinho, Eduardo Abade, Bruno Gonçalves, Sara Santos, Wolfgang Schöllhorn, Jaime Sampaio

Summary: Over the last years there have been a wide body of research exploring the best strategies to promote acute enhancements in players' performance. Despite that, most studies have been focused on adult and elite players, and different results may be identified when considering players from lower levels of performance and belonging to youth categories. In addition, most studies conducted in this domain focused in repetitive movement patterns, and while adding variability has been considered as a useful approach to enhance players' performance at short and long-term perspectives, less is known regarding it applicability to acute enhance players physical performance. Therefore, this study aimed to compare the acute enhancement effects of performing the half-squat in a flywheel ergometer between a more-repetitive approach (low noise) and a more variable approach (differential learning, high noise) in youth soccer players. A total of sixteen players (age = 16.2 ± 0.6 years) was exposed to four conditions in a randomized order: (1) repetitive intervention for 30 s; (2) repetitive intervention for 10-min; (3) differential learning intervention for 30 s; (4) differential learning intervention for 10-min. Each condition consisted in 3 sets of 6 repetitions of eccentric half squats performed in a flywheel ergometer. Countermovement jump, 10 m and 30 m linear sprint, and change-of-direction ability were measured every session at baseline (pre-test) and after each protocol (post-test). No potentiation effect was observed overall with any of the interventions. In addition, no differences between protocols were found for sprinting. However, the repetitive intervention impaired jumping performance for both 30 s (small effects, p ≤ .05) and 10-min intervals (small effects, p ≤ .05), as well as in the change-of-direction task for 30 s (p ≤ .05). These results may be due to the players' low experience in eccentric flywheel training. Despite these findings, individual potentiation responses emerged from both protocols when considering the individual responses, reinforcing the need to establish more personalized approaches.



#8 Playing Position is Associated with Injury Incidence Rate in Male Academy Soccer Players

Reference: J Athl Train. 2022 Feb 10. doi: 10.4085/1062-6050-0346.21. Online ahead of print.

Authors: Elliott Cr Hall, Jon Larruskain, Susana M Gil, Josean A Lekue, Philipp Baumert, Edgardo Rienzi, Sacha Moreno, Marcio Tannure, Conall F Murtagh, Jack D Ade, Paul Squires, Patrick Orme, Liam Anderson, Craig M Whitworth-Turner, James P Morton, Barry Drust, Alun G William, Robert M Erskine

Summary: The aim was to determine if playing position is associated with injury in ASP. 369 ASP from Under 14 (U14) to U23 age groups, classified as 'post-peak height velocity' using maturity offset, and grouped as goalkeepers (GK), lateral defenders (LD), central defenders (CD), lateral midfielders (LM), central midfielders (CM) and forwards (FWD). Additional analysis compared central (CENT) with lateral/forward (LAT/FWD) positions. Injuries were recorded prospectively over one season. Injury prevalence proportion (IPP), days missed and injury incidence rate (IIR, injuries per 1000 training/match hours, n=116) were analysed according to playing position. No association with playing position was observed for any injury type/location regarding IPP (P≥0.089) or days missed (P≥0.235). The IIR was higher in CD than LD for general (9.30 vs. 4.18 injuries/1000h, P=0.009), soft-tissue (5.14 vs. 1.95 injuries/1000h, P=0.026) and ligament/tendon injuries (2.69 vs. 0.56 injuries/1000h, P=0.040). Regarding CENT vs. LAT/FWD, there were no associations with IPP (P≥0.051) or days missed (P≥0.083), but general IIR was greater in CENT than LAT/FWD (8.67 vs. 6.12 injuries/1000h, P=0.047). ASP playing position was not associated with IPP or days missed but the higher general, soft-tissue and ligament/tendon IIR in CD suggests this position warrants specific attention regarding injury prevention strategies. These novel findings highlight the importance of including training/match exposure when investigating the influence of playing position on injury in ASP.



#9 Neuromuscular Training Warm-up Prevents Acute Noncontact Lower Extremity Injuries in Children's Soccer: A Cluster Randomized Controlled Trial

Reference: Orthop J Sports Med. 2021 Apr 28;9(4):23259671211005769. doi: 10.1177/23259671211005769. eCollection 2021 Apr.

Authors: Matias Hilska, Mari Leppänen, Tommi Vasankari, Sari Aaltonen, Pekka Kannus, Jari Parkkari, Kathrin Steffen, Urho M Kujala, Niilo Konttinen, Anu M Räisänen, Kati Pasanen 

Summary: Prevention of sports injuries is essential in youth, as injuries are associated with less future physical activity and thus greater all-cause morbidity. The purpose was to investigate whether a neuromuscular training warm-up operated by team coaches is effective in preventing acute lower extremity (LE) injuries in competitive U11-U14 soccer players. Twenty top-level U11 to U14 soccer clubs in Finland were randomized into intervention and control groups and assessed for 20 weeks. Participants included 1403 players (280 female, 1123 male; age range, 9-14 years): 673 players (44 teams) in the intervention group and 730 players (48 teams) in the control group. The intervention group team coaches were introduced to a neuromuscular training warm-up to replace the standard warm-up 2 to 3 times per week. The control teams were asked to perform their standard warm-up. Injury data collection was done via weekly text messages. The primary outcome measure was a soccer-related acute LE injury, and the secondary outcome measure was an acute noncontact LE injury. A total of 656 acute LE injuries occurred: 310 in the intervention group and 346 in the control group. The overall acute LE injury incidence was 4.4 per 1000 hours of exposure in the intervention group and 5.5 per 1000 hours of exposure in the control group, with no significant difference between groups (incidence rate ratio [IRR], 0.82 [95% CI, 0.64-1.04]). There were 302 acute noncontact LE injuries: 129 in the intervention group (incidence, 1.8 per 1000 hours) and 173 in the control group (2.7 per 1000 hours). A significant reduction in acute noncontact LE injuries of 32% (IRR, 0.68 [95% CI, 0.51-0.93]) was observed in the intervention group compared with the control group. Furthermore, significant reductions in injury incidence in favor of the intervention group were seen in the subanalyses of acute noncontact LE injuries, leading to ≤7 days of time loss and fewer ankle and joint/ligament injuries. A neuromuscular training warm-up operated by team coaches was found to be effective in preventing acute noncontact LE injuries in children's soccer, but this was not seen in all acute LE injuries.



#10 Adductor Muscle Injuries in UEFA Soccer Athletes: A Matched-Cohort Analysis of Injury Rate, Return to Play, and Player Performance From 2000 to 2015

Reference: Orthop J Sports Med. 2021 Sep 23;9(9):23259671211023098. doi: 10.1177/23259671211023098. eCollection 2021 Sep.

Authors: Ophelie Lavoie-Gagne, Nabil Mehta, Sumit Patel, Matthew R Cohn, Enrico Forlenza, Benedict U Nwachukwu, Brian Forsythe

Summary: The effects of adductor muscle injury on performance in soccer athletes are unknown. The purpose was to (1) determine the rate and time to return to play (RTP) after adductor muscle injury, (2) investigate the rate of reinjury after RTP, and (3) investigate any long-term effects of injury on elite soccer player performance. Using publicly available records, athletes sustaining adductor muscle injury were identified across the 5 major European soccer leagues (English Premier League, Bundesliga, La Liga, Ligue 1, and Serie A) between 2000 and 2015. Injured athletes were matched to controls by demographic characteristics and performance metrics from 1 season before the index timepoint. Investigations included the rate of RTP, reinjuries, player characteristics associated with RTP within 2 seasons, player availability, field time, and performance metrics during the 4 seasons after injury. A total of 671 players with adductor muscle injury were included. Based on time to RTP, 86% of injuries were mild to moderate (4-28 days missed), and 4% required surgical intervention. Players with adductor muscle injury were absent for a median of 22 days (range, 1-700 days) and 4 games (range, 1-76 games). A total of 521 (78%) players returned at the same level, with no demographic or clinical characteristics associated with RTP on the multivariable regression. Of those returning to play, 143 (21%) experienced adductor reinjury. After RTP, defenders demonstrated decreased field time compared with controls (P < .05). As compared with controls, defenders and midfielders scored more points and goals per game during the season of the injury (P < .01), while attackers recorded more goals and assists per game the season after injury (P < .05). Only 3 in 4 players (78%) returned to participate in an official match, and the reinjury rate was high (21%). After RTP, defenders demonstrated decreased field time versus controls. On the other hand, defenders and midfielders recorded more points and goals per game, while attackers recorded more goals and assists per game versus controls. Although the multivariable analysis results did not identify player characteristics associated with RTP, there was a position-dependent association on player performance after RTP.



#11 Return to Play and Player Performance After Achilles Tendon Rupture in UEFA Professional Soccer Players: A Matched-Cohort Analysis of Players From 1999 to 2018

Reference: Orthop J Sports Med. 2021 Sep 27;9(9):23259671211024199. doi: 10.1177/23259671211024199. eCollection 2021 Sep.

Authors: Enrico M Forlenza, Ophelie Z Lavoie-Gagne, Yining Lu, Connor C Diaz, Jorge Chahla, Brian Forsythe

Summary: Achilles tendon rupture (ATR) is a potentially career-ending injury in professional athletes. Limited information exists regarding return to play (RTP) in professional soccer players after this injury. The aim was to determine the RTP rate and time in professional soccer players after ATR and to evaluate player performance relative to matched controls. We evaluated 132 professional soccer players who suffered an ATR between 1999 and 2018. These athletes were matched 2:1 to uninjured controls by position, age, season of injury, seasons played, and height. We collected information on the date of injury, the date of RTP, and player performance metrics (minutes played, games played, goals scored, assists made, and points per game) from official team websites, public injury reports, and press releases. Changes in performance metrics for the 4 years after the season of injury were compared with metrics 1 season before injury. Univariate comparisons were performed using independent-sample, 2-group t tests and Wilcoxon rank-sum tests when normality of distributions was violated. The mean age at ATR was 27.49 ± 4.06 years, and the mean time to RTP was 5.07 ± 2.61 months (18.19 ± 10.96 games). The RTP rate was 71% for the season after injury and 78% for return at any timepoint. Overall, 9% of the injured players experienced a rerupture during the study period. Compared with controls, the injured players played significantly less (-6.77 vs -1.81 games [P < .001] and -560.17 vs -171.17 minutes [P < .05]) and recorded fewer goals (-1.06 vs -0.29 [P < .05]) and assists (-0.76 vs -0.02 [P < .05]) during the season of their Achilles rupture. With the exception of midfielders, there were no significant differences in play time or performance metrics between injured and uninjured players at any postinjury timepoint. Soccer players who suffered an ATR had a 78% RTP rate, with a mean RTP time of 5 months. Injured players played less and demonstrated inferior performance during the season of injury. With the exception of midfielders, players displayed no significant differences in play time or performance during any of the 4 postinjury seasons.



#12 Predicting Dropout From Organized Football: A Prospective 4-Year Study Among Adolescent and Young Adult Football Players

Reference: Front Sports Act Living. 2022 Jan 17;3:752884. doi: 10.3389/fspor.2021.752884. eCollection 2021.

Authors: Nico W Van Yperen, Laura Jonker, Jan Verbeek

Download link:

Summary: Previous studies have shown that enjoyment is one of the key predictors of dropout from organized sport, including organized football. However, prospective studies, particularly studies focused on long-term dropout, are largely lacking. Drawing on the basic principles of interdependence theory, in the present prospective study among 1,762 adolescent and young adult football players (27.1% women, mean age 17.74 years, SD = 1.35), we tested the predictive value of sport enjoyment, perceived alternatives, and restraining forces on football players' short-term (6 months) and long-term (4 years) dropout from organized football. As anticipated, the results of the logistic regression and follow-up analyses indicate that players' enjoyment was the main predictor of (short-term and long-term) dropout. In addition, relative to remainers, dropouts perceived more alternatives in terms of other sports, had fewer family members involved in their football club, and were older at the time they started playing organized football. We conclude that particularly measures aimed at enhancing sport enjoyment may prevent players from dropping out from organized football in both the short and long term. In addition, dropout rates may be reduced by attracting and engaging youth at a very young age (from 6 years), and their siblings, parents, and other family members as well.



#13 Knee Dislocation With Vascular and Nerve Injury in a Professional Football Player: Return to Play

Reference: Cureus. 2022 Jan 25;14(1):e21607. doi: 10.7759/cureus.21607. eCollection 2022 Jan.

Authors: Bernardo Moreno, Pedro Vaz, Bruna Melo, Mafalda Cunha, Rui Vaz

Download link:

Summary: Traumatic knee dislocations are serious and complex injuries, defined as clinical and/or radiological loss of tibiofemoral congruence, which may represent real emergencies to the integrity of the affected limb. This lesion is responsible for multi-ligament tears but the most serious possible complications are related to vascular and peripheral nerve injuries. Recent studies show that surgical treatment has better functional results and higher return rates to sports practice compared to conservative treatment. However, there is still no consensus on the ideal surgical technique and the timing of surgery. After conservative management or surgical treatment, rehabilitation treatment plays a key role in the recovery process. There are few studies evaluating the return to competition after traumatic knee dislocation and those athletes who return have difficulty reaching the pre-injury level. Here, we report the case of a professional football player who suffered a traumatic knee dislocation, with multiple ligament tears associated with vascular and neurological damage. Three hours after the initial lesion a double interposition bypass was done with the great saphenous vein, returning flow distally. It was decided not to perform ligament surgery. Two years after a long and intense rehabilitation program the athlete successfully returned to competition.



#14 Effects of the COVID-19 lockdown on physical performance parameters in professional football

Reference: Zentralbl Arbeitsmed Arbeitsschutz Ergon. 2022 Jan 24;1-9. doi: 10.1007/s40664-022-00455-z. Online ahead of print.

Authors: D Friebe, M Fischer, F Giesche, E Füzéki, W Banzer

Download link:

Summary: Governmental measures in 2020 to contain the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) brought training and competition in professional soccer to a temporary halt in many countries. As a result of the lockdown, training possibilities were mostly limited to nonspecific home-based training methods. It is unclear whether the lack of sport-specific stimuli led to a reduction in the physical performance of soccer players. For the narrative review, the PubMed, Google Scholar and BISp-Surf databases were selectively searched for studies examining the effects of the lockdown on physical performance parameters in adult professional soccer players. In this review six prospective longitudinal studies were included. In all studies home-based training was performed during quarantine. Of the studies four compared the performance of the soccer players with data from previous seasons and two studies assessed the performance of players immediately before and after the lockdown period. While general strength and endurance performances can be maintained through home-based substitute training programs, the studies indicated that the lack of football-specific stimuli could have an impact on the rapid power and speed performances of soccer players. Progressive loading control especially for speed training should be considered when returning to regular training in order to reduce the risk of injuries.



#15 Quantifying volume and high-speed technical actions of professional soccer players using foot-mounted inertial measurement units

Reference: PLoS One. 2022 Feb 3;17(2):e0263518. doi: 10.1371/journal.pone.0263518. eCollection 2022.

Authors: Glyn Lewis, Christopher Towlson, Pietro Roversi, Chris Domogalla, Lee Herrington, Steve Barrett

Download link:

Summary: The aims of the study were two-fold: i) examine the validity and reliability of high-speed kicking actions using foot-mounted inertial measurement unit's (IMU), ii) quantify soccer players within-microcycle and inter-positional differences in both the frequency and speed of technical actions. During the in-season phase (25 weeks) of the UK domestic season, 21 professional soccer player ball releases, high-speed ball releases and ball release index were analysed. Pearson product-moment correlation coefficient and confidence intervals were used to determine the validity between the systems, whilst a general linear mixed model analysis approach was used to establish estimated marginal mean values for total ball releases, high-speed ball releases and ball release index. Good concurrent validity was observed for ball release velocity and high-speed kicks against a high-speed camera (r2- 0.96, CI 0.93-0.98). Ball releases, high-speed ball releases and ball release index all showed main effects for fixture proximity (p>0.001), playing positions (p>0.001) and across different training categories (p>0.001). The greatest high-speed ball releases were observed on a match-day (MD)+1 (17.6 ± 11.9; CI- 16.2 to 19) and MD-2 (16.8 ± 15; CI- 14.9 to 18.7), with MD+1 exhibiting the highest number of ball releases (161.1 ± 51.2; CI- 155.0 to 167.2) and ball release index (145.5 ± 45.2; CI- 140.1 to 150.9) across all fixture proximities. Possessions (0.3 ± 0.9; CI- 0.3 to 0.4) and small-sided games (1.4 ± 1.6; CI- 1.4 to 1.5), had the lowest values for high-speed ball releases with technical (6.1 ± 7.2; CI- 5.7 to 6.6) and tactical (10.0 ± 10.5; CI- 6.9 to 13.1) drills showing the largest high-speed ball releases. The present study provides novel information regarding the quantification of technical actions of professional soccer players. Insights into absolute and relative frequency and intensity of releases in different drill types, provide practitioners with valuable information on technical outputs that can be manipulated during the process of planning training programmes to produce desired outcomes. Both volume and speed of ball release actions should be measured, when monitoring the technical actions in training according to fixture proximity, drill type and player position to permit enhanced training prescription.



#16 The effect of long-term soccer training on changes in cardiac function during exercise in elite youth soccer players

Reference: Scand J Med Sci Sports. 2022 Feb 3. doi: 10.1111/sms.14140. Online ahead of print.

Authors: Viswanath Balagopalan Unnithan, Thomas Rowland, Keith George, Andisheh Bakhshi, Alexander Beaumont, Nicholas Sculthorpe, Rachel Nia Lord, David Lee Oxborough

Summary: It is unclear what the effect of long-term, high-volume soccer training has on left ventricular (LV) function during exercise in youth soccer players. This study evaluated changes in LV function during submaximal exercise in a group of highly-trained male soccer players (SP) as they transitioned over a three-year period from pre-adolescent to adolescent athletes. Data were compared to age-and sex-matched recreationally active controls (CON) over the same time period. Twenty-two SP from two professional English Premier League youth soccer academies (age: 12.0 ± 0.3 years at start of the study) and 15 CON (age: 11.7 ± 0.3 years) were recruited. Two-dimensional echocardiography was used to quantify LV function during exercise at the same submaximal metabolic load (approx. 45%VO2 peak) across the 3 years. After controlling for growth and maturation, there were training-induced changes and superiority (p<0.001) in cardiac index (QIndex) from year 1 in the SP compared to CON. SP (year 1: 6.13 ± 0.76; year 2: 6.94 ± 1.31 and year 3: 7.20 ± 1.81 L/min/m2 ) compared to CON (year 1: 5.15 ± 1.12; year 2: 4.67 ± 1.04 and year 3: 5.49 ± 1.06 L/min/m2 ). Similar training-induced increases were noted for mitral inflow velocity (E): SP (year 1: 129 ± 12; year 2: 143 ± 16 and year 3: 135 ± 18 cm/s) compared to CON (year 1: 113 ± 10; year 2: 111 ± 12 and year 3: 121 ± 9 cm/s).This study indicated that there was evidence of yearly, training-induced increases in left ventricular function during submaximal exercise independent from the influence of growth and maturation in elite youth SP.



#17 Effects of congested fixture and matches' participation on internal and external workload indices in professional soccer players

Reference: Sci Rep. 2022 Feb 3;12(1):1864. doi: 10.1038/s41598-022-05792-w.

Authors: Gabriel Rodrigues Garcia, Luiz Guilherme C Gonçalves, Filipe Manuel Clemente, Fábio Yuzo Nakamura, Hadi Nobari, Bruno Luiz Souza Bedo, Angelo Melim Azevedo, Mauro Antonio Guerra Jr, Rodrigo Aquino

Summary: This study aimed to verify the effects of congested fixture and matches' participation on internal and external workload indexes in professional Brazilian soccer players. Rate of perceived exertion-based training load (sRPE), distance- and accelerometry-based measures were daily monitored over 119 training sessions and 33 matches performed by 29 male outfield players. Weeks were classified as congested (n = 11, two or more matches within a 7-day period) and regular (n = 10, one match or less within a 7-day period). The players were divided based on the matches' participation: (1) players who played ≥ 60 min (G1); (2) players who played < 60 min (G2); (3) players who did not participate of the match (G3). The findings showed that independent of the levels of participation during the matches, regular weeks presented greater acute, monotony, and strain indices for internal and external workload measures than congested weeks. The G1 presented the highest values for most of the workload indices in both regular and congested weeks, except for monotony indices (internal and external load) that G2 showed greater values than G1 and G3. Coaches and practitioners should plan the training "doses" to reduce disparities of these different match's participation and congested schedule weeks.



#18 A Qualitative Exploration of Collective Collapse in a Norwegian Qualifying Premier League Soccer Match-The Successful Team's Perspective

Reference: Front Psychol. 2022 Jan 18;12:777597. doi: 10.3389/fpsyg.2021.777597. eCollection 2021.

Authors: Gaute S Schei, Tommy Haugen, Gareth Jones, Stig Arve Sæther, Rune Høigaard

Summary: The current case study focused on a crucial match in the qualification for the Norwegian Premier League (Eliteserien). In the match, the participants of the study experienced a radical change in performance toward the end of the second half, from being behind by several goals to scoring 3 goals in 6 min and winning the qualifying game. The purpose of this study was therefore to examine the perceptions and reflections of players and coaches (sporting director) on what occurred within their own team and within the opposing team. The momentum shift in the opposition team can be described as a collective collapse. In the study, the theoretical collective collapse process model was used as a guide for the design of the interview questions where five semi-structured interviews were conducted with participants involved in the match (players, coach, and sporting director). The participants watched excerpt clips from the match to recall the main events, which they subsequently reflected on. The results highlighted the importance of the "before-game" aspects (i.e., pressure, first game result), the "during-the-game" behavior (i.e., goals scored, playing with a low degree of risk) and the cognitive (i.e., feelings of pressure, despair) and emotional reactions (i.e., frustration, joy) to the match unfolding. In addition, social contagion processes were evident in both teams relating to emotion and behavior. Overall, the data from this study investigated the general structure of the process model of collective sport team collapse and found support for the notion of a temporal cascade of causes for a team collapse. Future research is encouraged to examine this model, to provide guidance to teams, coaches, and sport psychologists in order to make recommendations for dealing with collective collapse in sport teams.



#19 Calculating the Social Return on Investment of a Japanese Professional Soccer Team's Corporate Social Responsibility Activities

Reference: Front Sports Act Living. 2022 Jan 17;3:736595. doi: 10.3389/fspor.2021.736595. eCollection 2021.

Authors: Daichi Oshimi, Shiro Yamaguchi, Takayuki Fukuhara, Yoshifumi Tagami

Download link:

Summary: In response to the lack of evidence for visualizing the monetary value of professional sport teams' CSR-related social impact, this study aimed to calculate the social impact of a Japanese professional soccer team's corporate social responsibility (CSR) activity (i.e., community soccer/physical activity program) by using a social return on investment (SROI) framework. Specifically, Matsumoto Yamaga Football Club was used for the estimation. This professional soccer team was ranked in the top division of the league (J1) during the estimation period and engaged in CSR activities at 129 community soccer schools in a year (2019-2020). The SROI calculation involved five stages: (1) identifying key stakeholders, (2) mapping inputs, outputs, and outcomes, (3) measuring and valuing outcomes, (4) establishing impact, and (5) calculating SROI. For the first step, we specified seven major stakeholders (soccer team, nursery school children, parents, coaches, teachers, local governments, and local football associations) and conducted interview investigations with each stakeholder. Our result showed that the social value of the teams' targeted community soccer school was USD 54,160, and the total financial and non-financial inputs to the school were USD 10,134, meaning an SROI ratio of 5.3. This means that for every USD invested in a community soccer school, social benefit worth USD 5.3 was generated. This study contributes to advancing social impact research in sport by shedding light on the monetary value of the social impact of professional sport teams' CSR activities. In addition, it also has practical implications for team managers looking to utilize CSR activities as a management strategy, through cost-effective investment and optimization of resources.



#20 Youth-to-Senior Transition in Elite European Club Soccer

Reference: Int J Exerc Sci. 2021 Oct 1;14(6):1192-1203. eCollection 2021.

Authors: Thomas Carpels, Nairn Scobie, Niall G Macfarlane, Ole J Kemi

Download link:

Summary: The priority for soccer academies is to develop youth players that graduate and transfer directly to their senior squads. The aim of this study was to assess the effectiveness of this direct youth-to-senior pathway by examining the extent to which club-trained players (CTPs) are currently involved in elite male European soccer. Relevant demographic longitudinal studies between 2009 and 2020 conducted by the International Centre for Sports Studies Football Observatory were analysed. The main findings were that the proportion of CTPs in senior squads has decreased from 23% to 17% over this time period, while the proportion of expatriates (EXPs) has increased from 35% to 42%. Moreover, clubs resorted more frequently to making new signings (NS, i.e. association-trained players (ATPs) and/or EXPs), with squad proportion increasing from 37% to 44%, while only launching one debutant (DBT, i.e. CTP with no previous senior experience) on average per season. Similar trends are observed in the evolution of playing time: while the fielding of CTPs remained constant (15%), EXPs and NS are fielded increasingly more (49% and 36%, respectively), despite a positive relationship between CTP match fielding and league ranking, with a Spearman Rank correlation r = 0.712 (95% confidence interval [0.381-0.881]), p < 0.01. In conclusion, young talents are still provided opportunities; however, these are limited and increasingly less frequent at their parent clubs. This potentially suggests a dysfunctional direct youth-to-senior development pathway.



#21 The soccer goalkeeper profile: Bibliographics review

Reference: Phys Sportsmed. 2022 Feb 14. doi: 10.1080/00913847.2022.2040889. Online ahead of print.

Authors: Markel Perez Arroniz, Julio Calleja González, Jon Zabala-Lili, Asier Zubillaga

Summary: This article has reviewed the scientific literature related to the soccer goalkeeper, as long as they offered specific information about this position on the field, including a total of 56 scientific articles. Therefore, the knowledge already recollected by authors to be able to apply it on training, divided in the following chapters: anthropometric profile, conditional and performance profile (sprint, jump, agility, strength, aerobic capacity, mobility and specific game technique), external load profile and injury pathological profile. The most noteworthy conclusions obtained are: 1) the higher the level of the team, the higher and heavier the goalkeepers; 2) in early ages (9-13 years) the training of goalkeepers is not well posed, since compared to the players are worse both in physical capacities and technique; 3) the aerobic capacity at long distances does not influence the performance of the goalkeeper; 4) the sprint, the jump, the agility and the mobility are factors that determine the performance of the goalkeeper; 5) the goalkeepers are less likely to be injured than the field players, but there are certain typical injuries in the position that must be protected by a proper way of strengthening and technique.



#22 Treatment and Postinterventional Management of a Fusiform Intracranial Aneurysm in a Professional Soccer Player: A Case Report

Reference: Front Neurol. 2022 Jan 26;12:732640. doi: 10.3389/fneur.2021.732640. eCollection 2021.

Authors: Manina Maja Etter, Leo Bonati, Ioannis Tsogkas, Gregor Hutter, Kristine Blackham, Raphael Guzman, Marios-Nikos Psychogios

Download link:

Summary: While intracranial aneurysms are common lesions affecting between 1 and 5% of the general population, the prevalence in professional athletes remains unknown. The result is uncertainty and lack of guidelines on appropriate treatment of these patients. A 29-year-old professional soccer player presented in our hospital with an incidentally found intracranial aneurysm. After detailed depiction of the aneurysm and interdisciplinary discussion, endovascular treatment using a flow diverter was chosen to be the best treatment modality. Postinterventional medication consisted of dual antiplatelet therapy with aspirin and clopidogrel. The main challenge in managing the case of our patient was the combination of the dual antiplatelet treatment regime with his professional career in a contact sport. Due to lack of literature or similar reports regarding the management of professional athletes with intracranial aneurysms, the optimal treatment strategy remains unclear. Even though decisions should be made dynamically and case-adapted to each situation, developing a registry could help provide guidance and new ideas for similar cases in the future.


The Training Manager -