Latest research in football - week 50 - 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 Reactive Task Performance Under Varying Loads in Division I Collegiate Soccer Athletes

Reference: Front Sports Act Living. 2021 Oct 13;3:707910. doi: 10.3389/fspor.2021.707910. eCollection 2021.

Authors: Lauren E Rentz, Cheryl L Brandmeir, Bobby G Rawls, Scott M Galster

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Summary: This study was conducted to identify whether team-wide or positional differences exist in simple or choice reactivity of collegiate soccer athletes when completed under various loads. Much research exists surrounding the assessment of reaction time in the general population, but given variations in training, little insight exists surrounding how unique and elite populations may differ based upon performance demands and task translatability to training. Reactive performance was assessed using the Dynavision D2 in 24 female soccer players (19.73 ± 1.05 years old) from a team within a power five conference of the National Collegiate Athletic Association. Evaluated loads included two conditions of simple reactivity (no additional load and with a concurrent lower body motor task) and three conditions of choice reactivity (no additional load, with a concurrent lower body motor task, and prolonged durations). Paired t-tests and ANOVAs were used to identify differences in task performance based upon load and positional group. No significant load-based or positional differences existed in measured simple reaction times. Performances in choice reaction tasks across the team were found to be slower when completed across extended durations (p < 0.0001) and faster when completed concurrent with an added balance task (p = 0.0108), as compared to performance under normal conditions. By assessment of positional differences, goalkeepers tended to be slower than other positions in reactivity during choice tasks, despite no differences existing in simple task performance. Given the unique population utilized herein, measured reactivity in different tasks suggests a strong relation to the training demands of soccer, as well as those of goalkeepers as compared to field positions. Findings suggest that sport and positional demands may be substantial contributors to population- and individual-based reactivity performance.



#2 National vs. Non-national Soccer Referee: Physiological, Physical and Psychological Characteristics

Reference: Res Q Exerc Sport. 2021 Nov 2;1-9. doi: 10.1080/02701367.2021.1923626. Online ahead of print.

Authors: Alfonso Castillo-Rodríguez, Cristóbal Muñoz-Arjona, Wanesa Onetti-Onetti

Summary: The objectives of the present study were to analyze the relationship between psychological variables (self-esteem, anxiety and self-confidence) assessed before the competition and physical and physiological responses demonstrated during the competition in soccer referees and to compare these psychophysical and physiological responses by category (CAT; national and non-national). A total of 153 soccer referees participated (age Mage = 23.2; SD = 4.8 years; experience Mage = 6.0; SD = 4.5 years) in the study. The CSAI-2 and Rosenberg questionnaires were conducted before the match, and match performance data were collected using GPS devices. The results showed significant differences in self-esteem and self-confidence across CATs (p < .001; d > .84). The national referees had higher psychological and physical-physiological responses (mean and maximum heart rate) Some correlations were observed among the psychophysical and physiological responses, CAT and age, demonstrating that the age could explain up to 48.4% of the variance the referee CAT (p < .001) and this CAT could explain self-esteem, anxiety and self-confidence by up to 20% of the variance. national referees presented better psychological responses prior to the competition, and also obtained greater physical and physiological records, which could be translated into a better position on the pitch in conflicting plays in order to make a right and just decision.



#3 Increased Lower Extremity Injury Risk Associated With Player Load and Distance in Collegiate Women's Soccer

Reference: Orthop J Sports Med. 2021 Oct 26;9(10):23259671211048248. doi: 10.1177/23259671211048248. eCollection 2021 Oct.

Authors: Michelle Xiao, Jessica N Nguyen, Calvin E Hwang, Geoffrey D Abrams

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Summary: There is limited research regarding the impact of workload on injury risk specific to women's soccer. Wearable global positioning system (GPS) units can track workload metrics such as total distance traveled and player load during games and training sessions. These metrics can be useful in predicting injury risk. The purpose was to examine the relationship between injury risk and player workload as collected from wearable GPS units in National Collegiate Athletic Association (NCAA) Division I women's soccer players. Lower extremity injury incidence and GPS workload data (player load, total distance, and high-speed distance) for 65 NCAA Division I women's soccer players were collected over 3 seasons. Accumulated 1-, 2-, 3-, and 4-week loads and acute-to-chronic workload ratios (ACWR) were classified into discrete ranges by z-scores. ACWR was calculated using rolling averages and exponentially weighted moving averages (EWMA) models. Binary logistic regression models were used to compare the 7:28 rolling average and EWMA ACWRs between injured and noninjured players for all GPS/accelerometer variables. The prior 1-, 2-, 3-, and 4-week accumulated loads for all GPS/accelerometer variables were compared between the injured and uninjured cohorts using 2-sample t tests. There were a total of 53 lower extremity injuries that resulted in lost time recorded (5.76/1000 hours "on-legs" exposure time; 34 noncontact and 19 contact injuries). The prior 2-week (7242 vs 6613 m/s2; P = .02), 3-week (10,533 vs 9718 m/s2; P = .02), and 4-week (13,819 vs 12,892 m/s2; P = .04) accumulated player loads and 2-week (62.40 vs 57.25 km; P = .04), 3-week (90.97 vs 84.10 km; P = .03), and 4-week (119.31 vs 111.38 km; P = .05) accumulated total distances were significantly higher for injured players compared with noninjured players during the same time frames. There were no significant differences in player load, total distance, or high-speed distance ACWR between injured and noninjured players for both the rolling averages and EWMA calculations. Higher accumulated player load and total distance, but not ACWR, were associated with injury in women's soccer players.



#4 Hymovis MO.RE. in the treatment of knee and ankle chondropathy in elite athletes: preliminary results of the CHAMPS (Cohort study about HYADD4-G Administration for Pain relief on Soccer players) prospective clinical study

Reference: Eur Rev Med Pharmacol Sci. 2021 Oct;25(20):6356-6364. doi: 10.26355/eurrev_202110_27009.

Authors: L Perticarini, A Baldari, M Bruzzone, F Combi, R Cugat, F De Vita, M Freschi, R Giagnorio, J G Iglesias, B Moretti, A Passelli, M Scorcu, J M Villalon, F Benazzo

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Summary: This study evaluated single intra-articular injections of Hymovis MO.RE., a hyaluronic acid hexadecyl derivative (HYADD4-G), to manage post-traumatic or degenerative knee or ankle chondropathy in professional soccer players. Twenty-five players affected by knee (n = 12) or ankle (n = 13) chondropathy were prospectively enrolled and treated by two single Hymovis MO.RE. (32 mg/4 ml) injections at the beginning of the football season (V0, baseline) and at mid-season (V1, 19-20 weeks thereafter), and were followed-up until the end of the season (V2, after further 19-20 weeks). Knee cases were evaluated using the 2000 IKDC knee subjective examination form and the modified Lysholm scoring system. Ankle cases were evaluated using the American Orthopaedic Foot Ankle Society (AOFAS) ankle-hindfoot score. Patients were also evaluated using a VAS Likert scale and a four-category scale recording both the patient's and the doctor's assessment on joint mobility in degrees and overall treatment efficacy. Adverse events, patient withdrawals and local reaction to injections were also assessed. In knee patients, the 2000 IKDC subjective score improved from 46.8 ± 11.4 at V0 to 83.1 ± 12.5 at V2. Their modified Lysholm score improved from 58.8 ± 8.9 at V0 to 90.6 ± 8.3 at V2. In the ankle patients, the AOFAS score improved from 52.2 ± 5.6 at V0 to 96.4 ± 4.5 at V2. VAS Likert values and subjective evaluations improved at V1 and were maintained at V2. No side effects were recorded. A single Hymovis MO.RE. (32 mg/4 ml) intra-articular injection, repeated after 19-20 weeks, may be a viable option to improve symptoms and function in professional soccer players suffering from knee and ankle chondropathy.



#5 Identification of Neuromuscular Performance Parameters as Risk Factors of Non-contact Injuries in Male Elite Youth Soccer Players: A Preliminary Study on 62 Players With 25 Non-contact Injuries

Reference: Front Sports Act Living. 2021 Oct 18;3:615330. doi: 10.3389/fspor.2021.615330. eCollection 2021.

Authors: Mathias Kolodziej, Kevin Nolte, Marcus Schmidt, Tobias Alt, Thomas Jaitner

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Summary: Elite youth soccer players suffer increasing numbers of injuries owing to constantly increasing physical demands. Deficits in neuromuscular performance may increase the risk of injury. Injury risk factors need to be identified and practical cut-off scores defined. Therefore, the purpose of the study was to assess neuromuscular performance parameters within a laboratory-based injury risk screening, to investigate their association with the risk of non-contact lower extremity injuries in elite youth soccer players, and to provide practice-relevant cut-off scores. Sixty-two elite youth soccer players (age: 17.2 ± 1.1 years) performed unilateral postural control exercises in different conditions, isokinetic tests of concentric and eccentric knee extension and knee flexion (60°/s), isometric tests of hip adduction and abduction, and isometric tests of trunk flexion, extension, lateral flexion and transversal rotation during the preseason period. Non-contact lower extremities injuries were documented throughout 10 months. Risk profiling was assessed using a multivariate approach utilizing a Decision Tree model [Classification and Regression Tree (CART) method]. Twenty-five non-contact injuries were registered. The Decision Tree model selected the COP sway, the peak torque for knee flexion concentric, the functional knee ratio and the path of the platform in that hierarchical order as important neuromuscular performance parameters to discriminate between injured and non-injured players. The classification showed a sensitivity of 0.73 and a specificity of 0.91. The relative risk was calculated at 4.2, meaning that the risk of suffering an injury is four times greater for a player, who has been classified as injured by the Decision Tree model. Measuring static postural control, postural control under unstable condition and the strength of the thigh seem to enable a good indication of injury risk in elite youth soccer players. However, this finding has to be taken with caution due to a small number of injury cases. Nonetheless, these preliminary results may have practical implications for future directions in injury risk screening and in planning and developing customized training programs to counteract intrinsic injury risk factors in elite youth soccer players.



#6 Body size, fatness and skeletal age in female youth soccer players

Reference: Int J Sports Med. 2021 Nov 3. doi: 10.1055/a-1686-4563. Online ahead of print.

Authors: Diogo V Martinho, Manuel J Coelho-E-Silva, João Gonçalves Santos, Tomas G Oliveira, Cláudia S Minderico, Andre Seabra, Joao Valente-Dos-Santos, Lauren B Sherar, Robert M Malina

Summary: Growth and maturation are central concerns in the organization of training and competitions in youth sports. This study examined maturity-associated variation in body size and adiposity among adolescent girls participating in competitive age group youth soccer. The sample included 441 players 10.08-16.73 years of age. Stature and body mass were measured and body composition was predicted. The Fels method was used to estimate skeletal age. Skeletally maturity status (late, average or early maturing) was based on the difference between chronological and skeletal age for each player. Mean stature approximated the 50th percentiles of the general population in all competitive age groups, while mean weight fluctuated between 50th and 75th percentiles. Age- and maturity-specific means for estimated fat mass ranged between 18.0% and 28.2%. The number of players classified as skeletally mature increased with competitive age groups (under-13: 0%; under-15: 8%; under-17: 49%). In general, early maturing girls tended to be heavier than their age group peers and especially when compared to late maturing players.



#7 Medial Meniscus Repair in Major League Soccer Players Results in Decreased Performance Metrics for One Year and Shortened Career Longevity

Reference: Open Access J Sports Med. 2021 Oct 28;12:147-157. doi: 10.2147/OAJSM.S337251. eCollection 2021.

Authors: David Heath, David Momtaz, Abdullah Ghali, Luis Salazar, Jonathan Bethiel, Boris Christopher, Caitlyn Mooney, Katherine C Bartush

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Summary: The rate of medial meniscus tear (MMT) in professional soccer players is high. There are no studies on objective performance metrics following medial meniscus repair in these athletes. The aim was to examine the impact of MMT treated with surgical repair on performance metrics and career longevity in Major League Soccer (MLS) players. MLS players who sustained an MMT between 1993 and 2019 were identified via publicly available databases. These players were each matched to 2 uninjured controls by debut date, experience, position, race, ethnicity, height, weight, and body mass index (BMI). Demographic data and performance metrics were then collected for both groups. Matches, minutes, goals, assists, shots, shots on target, duels, and duel percentage won are collectively referred to as performance metrics. Statistical analysis compared demographic distributions and performance metrics between the MMT and control groups. Thirty-three MLS players who had undergone medial meniscus repair were identified and matched to 66 controls. All performance metrics decreased in the MMT group when compared to their controls in the first year after injury. This difference remained significant even when the performance metrics were normalized with respect to time, indicating that the injured players both played less and were not as productive. At 2 years after injury, performance metrics returned to pre-injury levels and were equivalent to those of the healthy controls. Career length was found to be significantly different between the two groups at 8.81 ± 3.9 years for the MMT group and 12.63 ± 3.51 years for the control group (P < 0.001). MLS players undergoing medial meniscus repair had decreased performance metrics in the first year after injury but returned to baseline levels of play at the second year after injury. Their careers were also shorter than those of their uninjured controls.



#8 The rating of perceived exertion is able to differentiate the post-matches metabolomic profile of elite U-20 soccer players

Reference: Eur J Appl Physiol. 2021 Nov 5. doi: 10.1007/s00421-021-04838-7. Online ahead of print.

Authors: Alisson Henrique Marinho, Filipe Antonio de Barros Sousa, Rubens de Alcântara Moura Pimentel Vilela, Pedro Balikian Jr, Edson de Souza Bento, Thiago de Mendonça Aquino, Alessandre Crispim, Thays Ataide-Silva, Gustavo Gomes de Araujo

Summary: The study aimed to assess the metabolic impact of elite Brazilian U-20 players using the rating of perceived exertion scale (RPE) to discriminate metabolomics sensitivity post-two soccer games separated by a short recovery interval. Urine was collected immediately and then 20 h after two soccer matches of elite Brazilian U-20 players. RPE was collected after games. The spectra were pre-processed using TopSpin®3.2 software. Chenomx®software was used to identify metabolites in the urine through the available database. The results showed that the metabolic pathways related to energy production, cellular damage, and organic stresses were changed immediately after the game. 20 h after the games, antioxidant and anti-inflammatory pathways related to cell recovery were identified (e.g., gallic acid, ascorbate, and betaine). The matrix of positive correlations between metabolites was more predominant and stronger after game 2 than game 1. T-distribution registered metabolites discriminated below and above 7 on the RPE scale. Athletes with higher RPE values showed a high metabolite profile related to muscle damage (e.g., creatine, creatinine, and glycine) and energy production (e.g., creatine, formate, pyruvate, 1,3 dihydroxyacetone) 20 h post-soccer match. There was a different metabolic profile between athletes with higher and lower RPE values. Metabolomics analysis made it possible to observe the metabolic impacts of energy production and muscular damage. RPE identified internal load changes within the group as a result of match intensity in soccer. The correlation matrix indicated a greater predominance of positive and strong correlations between metabolites in the second game compared to the first game.



#9 Incidence of COVID-19 in Children and Young People Who Play Federated Football

Reference: Sports Health. 2021 Nov 9;19417381211055682. doi: 10.1177/19417381211055682. 

Authors: Rocío Seijo Bestilleiro, Jorge Suanzes Hernández, Diego Batalla Bautista, María José Pereira Rodríguez, Cristina González Martín, Mara Teresa Garcia Rodriguez, Sonia Pértega Díaz

Summary: The aim was to determine the incidence of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection in children and young people who play federated football. Prospective study, from October 2020 to January 2021, in players aged 4 to 19 years from federated football clubs in Galicia, Spain (N = 23,845). Outbreaks and cases of SARS-CoV-2 infection were recorded. The cumulative incidence was compared with the incidence registered in Galicia in the same age range. The cumulative incidence was 29.8 cases per 10,000 licenses in 4 months, lower than the incidence registered in the general population for all ages and both sexes (283.7 per 10,000 inhabitants; rate ratio = 9.5). It was higher in January (40.7 per 10,000), coinciding with the population peak. More cases were registered in futsal (42.9 vs 27.5 per 10,000) and competitions with periodic screenings (127.4 vs 9.1 per 10,000). There were 2 outbreaks in 2389 teams (0.08%). The results support the safety of football practice in children and young people with prevention protocols.



#10 The Effects of Ramadan Intermittent Fasting on Football Players and Implications for Domestic Football Leagues Over the Next Decade: A Systematic Review

Reference: Sports Med. 2021 Nov 10. doi: 10.1007/s40279-021-01586-8. Online ahead of print.

Authors: Matthew D DeLang, Paul A Salamh, Hamdi Chtourou, Helmi Ben Saad, Karim Chamari

Summary: The month of Ramadan will intersect with many football leagues' schedules over the next decade. Understanding the effects of Ramadan intermittent fasting (RIF) on physical performance is necessary to guide considerations for football players. The aim of this systematic review was to investigate the effects of RIF on physical factors in football players, and secondarily to consider the impact this may have on domestic club football leagues. We conducted a systematic review using PRISMA guidelines. The online literature search utilized CINAHL (EBSCO), Cochrane Library,, PubMed, and Scopus databases, and grey literature (all from database inception to May 2020). Inclusion criteria consisted of studies of football (soccer) players, data collected during and/or around Ramadan, with injury and/or performance data provided. The search yielded 11,226 studies. Twenty-two studies were included following a review of titles, abstracts, and full texts. Studies included some iteration of before-Ramadan, during-Ramadan, and after-Ramadan data. Common measures observed included ratings of perceived exertion (n = 8), sprinting (n = 7), sleep (n = 7), peak heart rate (n = 6), jumping (n = 5), Yo-Yo intermittent recovery tests (n = 4), Wingate anaerobic test (n = 3), field-specific tests (n = 3), and injury rates (n = 2). Decreased physical performance was commonly observed during late afternoon/evening testing (before breaking the fast) and with high-intensity exercise. There appears to be a performance deficit related to RIF in Muslim football players. Studies should explore the effects of RIF on actual match demands. Due to the month of Ramadan emerging into league calendars, considerations should be made to accommodate Muslim football players who are intermittently fasting.



#11 Running biomechanics in football players with and without hip and groin pain. A cross-sectional analysis of 116 sub-elite players

Reference: Phys Ther Sport. 2021 Oct 25;52:312-321. doi: 10.1016/j.ptsp.2021.10.011. Online ahead of print.

Authors: Mark J Scholes, Kay M Crossley, Matthew G King, Anthony G Schache, Joanne L Kemp, Adam I Semciw, Prasanna Sritharan, Joshua J Heerey, Benjamin F Mentiplay

Summary: The purpose was to examine whether football players with hip and/or groin (hip/groin) pain have impaired running biomechanics when compared to pain-free players, analysing men and women independently.Seventy-eight (62 men, 16 women) football players with >6months of hip/groin pain and a positive flexion-adduction-internal rotation test and 38 (25 men, 13 women) asymptomatic players participated in this study. Pelvis angles and hip, knee, and ankle joint angles and moments were analysed during the stance phase of overground running at 3-3.5 m⋅s-1. Continuous joint angle and moment data were compared between symptomatic and asymptomatic football players of the same sex using statistical parametric mapping. Joint moment impulses (area under the curve) were compared between groups using linear regression models. Symptomatic football players did not display significant differences in pelvis angles or lower-limb joint angles, moments, or moment impulses during the stance phase of running, when compared to asymptomatic players of the same sex. Our large sample of football players with hip/groin pain who were still participating in competitive sport displayed similar running biomechanics to asymptomatic players. Impaired running biomechanics might exist in people with worse hip/groin pain, warranting future investigation.



#12 Effects of plyometric jump training versus power training using free weights on measures of physical fitness in youth male soccer players

Reference: J Sports Sci. 2021 Nov 8;1-8. doi: 10.1080/02640414.2021.1976570. Online ahead of print.

Authors: Senda Sammoud, Raja Bouguezzi, Rodrigo Ramirez-Campillo, Yassine Negra, Olaf Prieske, Jason Moran, Helmi Chaabene

Summary: This study aimed to contrast the effects of power training (PT) and plyometric-jump-training (PJT) programmes on measures of physical fitness in prepubertal male soccer players. Thirty-three participants were randomly allocated to PT group (n = 11), PJT group (n = 11), and an active control group (CG; n = 11). Before and after 12 weeks of training, tests were performed for the assessment of sprint-speed , change-of-direction (CoD) speed, muscular strength , and aerobic-endurance (AE). Findings indicated significant group×time interaction effects for all sprint-speed intervals, CoD speed, AE, and strength (d = 0.20-0.32). Post-hoc analyses revealed significant, moderate-to-large improvements in all sprint-speed intervals, CoD speed, AE, and muscle strength following PT (ES = 0.71 to 1.38). The PJT induced significant, moderate-to-large enhancements in 10 m, 20 m, and 30 m sprint, CoD speed, and AE (ES = 0.51 to 0.96) with no significant changes for 5 m sprint-speed and muscle strength (ES = 0.71 and 0.16, respectively). No significant pre-post changes were observed for the CG . Overall, PT and PJT are effective means to improve various measures of physical fitness in prepubertal male soccer players. Notably, to additionally improve acceleration and muscle strength, PT has an advantage over PJT.



#13 Bilateral Post Traumatic Myositis Ossificans of Adductor Longus in a Young Soccer Player: A Case Report and Literature Review

Reference: Curr Sports Med Rep. 2021 Nov 1;20(11):584-587. doi: 10.1249/JSR.0000000000000904.

Authors: Raffaele Iorio, Carlo Massafra, Edoardo Viglietta, Daniele Mazza, Andrea Ferretti

Summary: Myositis ossificans traumatica (MOT) is a self-limiting and self-resolving pathology. In most cases, conservative treatment is chosen as the first step. Surgical treatment is reserved for cases of failure of conservative treatment with persistence of pain and mass. The case presented concerns an 18-year-old soccer player suffering from bilateral adductor longus (AL) MOT results following two different sports injuries. The patient reports the appearance of swelling and palpable mass at the proximal and medial region of the thigh, about 2 cm from the pubic symphysis, along the course of the adductor magnus. The radiological investigation showed the presence of a calcification along the course of the right and left AL muscles. Surgical treatment was considered for the right thigh injury, being symptomatic 1 year after the onset and refractory to other treatments. At 3 months of follow-up, the patient was asymptomatic and completed the rehabilitation program for the recovery of muscle strength and range of motion (ROM). In cases where MOT manifests with resistant pain, ROM restriction and daily activity reduction, surgical excision is the preferred option.



#14 Symptomatic ossicle lesion at the anterior tip of the medial malleolus in soccer players

Reference: J Orthop Sci. 2021 Nov;26(6):1069-1073. doi: 10.1016/j.jos.2020.09.008. Epub 2020 Oct 24.

Authors: Atsushi Teramoto, Kousuke Iba, Kota Watanabe, Tomoaki Kamiya, Yohei Okada, Toshihiko Yamashita

Summary: Unfused accessory ossification centers in the medial ankle are sometimes misdiagnosed and should be distinguished from other bone lesions such as fracture, stress fracture, os subtibiale, or pseudoarthrosis of the medial malleolus. The purpose of this study was to report our experience in treating soccer players with bony elements in the subtibial region. We surgically treated seven soccer players who experienced medial ankle pain with bony fragments at the tip of the medial malleolus. Their ages were between 13 and 27 years. The mean duration from symptom onset to hospital visit was 4.7 years (range: 2 months to 14 years). The bony lesion located at the anterior tip of the medial malleolus in all patients and we diagnosed the lesion as an unfused accessory ossification center. Three types of surgical treatments were performed in patients according to age, ossicle size, status of the epiphyseal plate, and degenerative changes around the lesion. Bony fusion was achieved in patients who underwent open reduction and fusion with bone graft. Patients who underwent focal drilling or removal of the bony fragment experienced improvement in symptoms, and all patients were allowed to resume their sports or full preinjury activities. We believe that surgery is the first-line treatment for the patients with unfused accessory ossification centers with their prolonged symptom and favorable outcomes can be expected. Bony fusion should be attempted in the patients with the large ossicle especially in their growth period.



#15 Guardiola, Klopp, and Pochettino: The Purveyors of What? The Use of Passing Network Analysis to Identify and Compare Coaching Styles in Professional Football

Reference: Front Sports Act Living. 2021 Oct 22;3:725554.doi: 10.3389/fspor.2021.725554. eCollection 2021.

Authors: Sebastian Immler, Philipp Rappelsberger, Arnold Baca, Juliana Exel

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Summary: We applied social networks analysis to objectively discriminate and describe interpersonal interaction dynamics of players across different top-coaching styles. The aim was to compare metrics in the passing networks of Jürgen Klopp, Pep Guardiola, and Mauricio Pochettino across the UEFA Champions League seasons from 2017 to 2020. Data on completed passes from 92 games were gathered and average passing networks metrics were computed. We were not only able to find the foundations on which these elite coaches build the passing dynamics in their respective teams, but also to determine important differences that represent their particular coaching signatures. The local cluster coefficient was the only metric not significantly different between coaches. Still, we found higher average shortest-path length for Guardiola's network (mean ± std = 3.00 ± 0.45 a.u.) compared to Klopp's (2.80 ± 0.52 a.u., p = 0.04) and Pochettino's (2.70 ± 0.39 a.u., p = 0.01). Density was higher for Guardiola's (64.16 ± 20.27 a.u.) than for Pochettino's team (51.42 ± 17.28 a.u., p = 0.008). The largest eigenvalue for Guardiola's team (65.95 ± 16.79 a.u.) was higher than for Klopp's (47.06 ± 17.25 a.u., p < 0.001) and Pochettino's (42,62 ± 12.01 a.u., p < 0.001). Centrality dispersion was also higher for Guardiola (0.14 ± 0.02 a.u.) when compared to Klopp (0.12 ± 0.03 a.u., p = 0.008). The local cluster coefficient seems to build the foundation for passing work, however, cohesion characteristics among players in the three teams of the top coaches seems to characterize their own footprint regarding passing dynamics. Guardiola stands out by the high number of passes and the enhanced connection of the most important players in the network. Klopp and Pochettino showed important similarities, which are associated to preferences toward more flexibility of interpersonal linkages synergies.



#16 Can small-sided games assess the training-induced aerobic adaptations in elite football players?

Reference: J Sports Med Phys Fitness. 2021 Nov 10. doi: 10.23736/S0022-4707.21.13144-5. Online ahead of print.

Authors: Andrea Riboli, Alexandre Dellal, Fabio Esposito, Giuseppe Coratella

Summary: The purose was to investigate whether or not SSGs could be used to evaluate the aerobic fitness status and the longitudinal training-induced adaptations in football players. Additionally, the capacity of SSGs to recreate the official match demands was investigated. Twenty-five elite football players were monitored. Total distance (TD), high-speed running, very high-speed running, sprint and accelerations plus decelerations distance were measured during 20 SSGs formats and 25 official-matches; in SSGs, average heart rate was also collected. During submaximal Yo-Yo test, heart rate at peak exercise, heart rate post-60s recovery and rate of perceived exertion were collected. Coefficient of variation, interclass correlation-coefficient and correlation-coefficient analysis were used to calculate validity, reliability, construct validity and, internal and external responsiveness of SSGs demands. In SSGs, a small variability (~6.0%) with moderate reliability (~0.542 to ~0.663) was found in TD and heart rate, while a high variability (~20.8% to ~60.3%) with poor to moderate reliability (~0.358 to ~0.605) was observed in the other metrics; in submaximal Yo-Yo, heart rate showed small variability (~3.7%) with good reliability (~0.933 to ~0.916). The SSGs demands showed poor internal and external responsiveness (p>0.05) to the training-induced aerobic adaptations as assessed by submaximal Yo-Yo. The construct validity of SSGs showed overall large to very large correlations (r=0.53 to 0.90, p<0.05) between SSGs and official match demands across the season. SSGs should not replace standardized field tests to detect the training-induced aerobic adaptations. However, SSGs could be confidently used to recreate specific contextual factors in elite football players.



#17 The influence of fixture congestion on physical performance response to U23 soccer match-play

Reference: Res Sports Med. 2021 Nov 7;1-15. doi: 10.1080/15438627.2021.2001649. Online ahead of print.

Authors: Greg Doncaster, Paul White, Robert Svenson, Richard Michael Page

Summary: This study sought to examine differences in measures of intense periods of physical performance during competitive match-play, between one-match (1 match weeks) and two-match microcycles (2 match week). 1, 3 and 5 min "peak" and mean averages for total distance (TD), high-speed running (HSR) and metabolic power (MP) were analysed for each 15 min period of match-play. Linear mixed models were employed to examine the differences in dependent variables for each method of measurement between the 1 and 2 game microcycles. No differences were reported for "peak" values for all epoch lengths, however, results revealed significantly reduced "average" values, during periods of fixture congestion, for 1, 3 and 5 min epochs for average TD, and 3 min epochs for average HSR towards the end of the match (75-90 min split). There was, however, a trend for the opposite response to occur in the 60-75-min period. The current data suggests that players potentially display altered pacing strategies during periods of fixture congestion, with these observed responses being dependent on sampling method and epoch length.



#18 A framework for the fine-grained evaluation of the instantaneous expected value of soccer possessions

Reference: Mach Learn. 2021;110(6):1389-1427. doi: 10.1007/s10994-021-05989-6. Epub 2021 May 24.

Authors: Javier Fernández, Luke Bornn, Daniel Cervone

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Summary: The expected possession value (EPV) of a soccer possession represents the likelihood of a team scoring or conceding the next goal at any time instance. In this work, we develop a comprehensive analysis framework for the EPV, providing soccer practitioners with the ability to evaluate the impact of observed and potential actions, both visually and analytically. The EPV expression is decomposed into a series of subcomponents that model the influence of passes, ball drives and shot actions on the expected outcome of a possession. We show we can learn from spatiotemporal tracking data and obtain calibrated models for all the components of the EPV. For the components related with passes, we produce visually-interpretable probability surfaces from a series of deep neural network architectures built on top of flexible representations of game states. Additionally, we present a series of novel practical applications providing coaches with an enriched interpretation of specific game situations. This is, to our knowledge, the first EPV approach in soccer that uses this decomposition and incorporates the dynamics of the 22 players and the ball through tracking data.



#19 Midseason Screening for Groin Pain, Severity, and Disability in 101 Elite American Youth Soccer Players: A Cross-Sectional Study

Reference: Clin J Sport Med. 2021 Nov 10. doi: 10.1097/JSM.0000000000000987. Online ahead of print.

Authors: Matthew D DeLang, J Craig Garrison, Joseph P Hannon, Ryan P McGovern, Philip J Sheedy, John J Christoforetti, Kristian Thorborg

Summary: The purpose was to (1) systematically screen for groin pain and type in young elite soccer players and (2) assess whether hip and groin-related severity and disability differed between players with different levels of groin pain and tenderness. One hundred one academy soccer players (mean age 14.3 ± 1.8 years participated in this study. All players underwent clinical examinations to classify groin pain by the Doha agreement taxonomy.Tests for groin-related severity and disability included the Copenhagen 5-second squeeze test, Copenhagen Hip and Groin Outcome Score (HAGOS), and Hip Outcome Score (HOS). Players were stratified into 3 groups: those with groin pain, those with tenderness, and those with no groin pain or tenderness. Twenty-two players (22%) reported groin pain. Adductor-related groin pain was the most common (n = 14), followed by iliopsoas-related (n = 3), and pubic-related (n = 2). Multiple locations were present in 3 players. Thirty-nine players (39%) did not have groin pain but were tender to palpation in 1 or more structures related to the Doha agreement taxonomy. Copenhagen 5-second squeeze test differentiated between players with and without groin pain (groin pain vs tenderness group: P = 0.011; groin pain vs no groin pain group P < 0.001). Four HAGOS subscales (pain, symptoms, sport/recreation, and quality of life) differentiated between players with and without groin pain (P < 0.05). One in five academy soccer players experiences groin pain with adductor-related most common during a midseason screening. Both Copenhagen 5-second squeeze test and HAGOS subscales can differentiate between players with and without groin pain.



#20 Personality and Team Identification Predict Violent Intentions Among Soccer Supporters

Reference: Front Sports Act Living. 2021 Oct 25;3:741277. doi: 10.3389/fspor.2021.741277. eCollection 2021.

Author: Joanna Lindström

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Summary: Soccer supporter violence remains a persistent global problem. The majority of research examining the psychological underpinnings of soccer supporter violence have focused primarily on the role of team identification. Relatively little research has examined the role of basic personality traits and willingness to engage in violence amongst soccer supporters. In a study amongst Swedish soccer supporters (N = 247), we examined whether honesty-humility and team identification predict violent behavioral intentions; examining if collective narcissism mediates these associations. Honesty-humility negatively predicted violent intentions, and team identification predicted violent intentions. Collective narcissism partially mediated these associations. When both Honesty-humility and team identification are accounted for though, collective narcissism did not predict violent intentions. Such findings have implications for the design of violence prevention interventions amongst soccer supporters.



#21 Examining the Dynamic Nature of Anterior Cruciate Ligament Injury Risk Factors in Women's Collegiate Soccer

Reference: J Sport Rehabil. 2021 Nov 12;1-8. doi: 10.1123/jsr.2021-0110. Online ahead of print.

Authors: Elena M D'Argenio, Timothy G Eckard, Barnett S Frank, William E Prentice, Darin A Padua

Summary: Anterior cruciate ligament (ACL) injuries are a common and devastating injury in women's soccer. Several risk factors for ACL injury have been identified, but have not yet been examined as potentially dynamic risk factors, which may change throughout a collegiate soccer season. Nine common clinical screening assessments for ACL injury risk, consisting of range of motion, movement quality, and power, were assessed in 29 Division I collegiate women's soccer players. Preseason and midseason values were compared for significant differences. Change scores for each risk factor were also correlated with cumulative training loads during the first 10 weeks of a competitive soccer season. Hip external rotation range of motion and power had statistically significant and meaningful differences at midseason compared with preseason, indicating they are dynamic risk factors. There were no significant associations between the observed risk factor changes and cumulative training load. Hip external rotation range of motion and power are dynamic risk factors for ACL injury in women's collegiate soccer athletes. Serial screening of these risk factors may elucidate stronger associations with injury risk and improve prognostic accuracy of screening tools.



#22 Running Performance during the Holy Month of Ramadan in Elite Professional Adult Soccer Players in Russia

Reference: Int J Environ Res Public Health. 2021 Nov 8;18(21):11731. doi: 10.3390/ijerph182111731.

Authors: Eduard Bezuglov, Oleg Talibov, Vladimir Khaitin, Bekzhan Pirmakhanov, Zbigniew Waśkiewicz, Mikhail Butovskiy, Ryland Morgans

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Summary: Religious fasting in the Holy Month of Ramadan is an important element of the Muslim culture during which no eating or drinking is permitted from dawn till dusk. A considerable number of Muslim soccer players abide by these restrictions, which may cause a negative impact on key running performance parameters during competitive matches. Alterations to diet and water intake during the Holy Month of Ramadan may affect various running performance parameters in elite Muslim professional adult soccer players. This study was conducted with two groups of soccer players from the Russian Premier League (RPL): The Exposure Group (EG) consisted of 13 Muslims age 24.0 ± 2.8 years abiding by religious fasting and the Control Group (CG) included 13 non-Muslim age 26.0 ± 4.4 years. Using the Instat system, the running performance of each player was controlled in both groups during matches from the RPL before and in the third week of Ramadan (a total of two matches for every player). None of the measured parameters demonstrated significant changes in any match. In conclusion, restrictions in diet and liquid intake during the Holy Month of Ramadan had no negative influence on the running performance of elite Muslim professional adult soccer players during daytime matches.



#23 Exploring the provision and motives behind the adoption of health-promotion programmes in professional football clubs across four European countries

Reference: PLoS One. 2021 Nov 19;16(11):e0259458. doi: 10.1371/journal.pone.0259458. eCollection 2021.

Authors: Øystein B Røynesdal, Femke van Nassau, Nai Rui Chng, Hugo Pereira, Eivind Andersen, Christopher Bunn, Judith G M Jelsma, Maria W G Nijhuis-van der Sanden, Glyn C Roberts, Marit Sørensen, Irene van de Glind, Theo van Actherberg, Cindy M Gray

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Summary: This study mapped existing health-promotion provisions targeting adults in professional football clubs across England, the Netherlands, Norway, and Portugal, and explored motives behind the clubs' adoption of the European Fans in Training (EuroFIT) programme. We surveyed top-tier football clubs in the four countries and interviewed representatives from football clubs and the clubs' charitable foundation who delivered EuroFIT. The findings showed large between-country differences, with football clubs in England reporting far greater healthy lifestyle provision than other countries. Relatively few health-promotion programmes targeted adults, particularly in the Netherlands, Portugal, and Norway. Club representatives reported that the motives for adopting the EuroFIT programme often involved adhering to both the social objectives of the football club or club's foundation and business-related objectives. They viewed the scientific evidence and evaluation underpinning EuroFIT as helpful in demonstrating the value and potential future impact of both the programme and the clubs' wider corporate social responsibility provision.



#24 Performance of Professional Soccer Players before and after COVID-19 Infection; Observational Study with an Emphasis on Graduated Return to Play

Reference: Int J Environ Res Public Health. 2021 Nov 7;18(21):11688. doi: 10.3390/ijerph182111688.

Authors: Anamarija Jurcev Savicevic, Jasna Nincevic, Sime Versic, Sarah Cuschieri, Ante Bandalovic, Ante Turic, Boris Becir, Toni Modric, Damir Sekulic

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Summary: The impact of the COVID-19 pandemic in sport has been the subject of numerous studies over the past two years. However, knowledge about the direct impact of COVID-19 infection on the performance of athletes is limited, and the importance of studies on this topic is crucial during the current pandemic era. This study aimed to evaluate the changes in the match running performance (MRP) of professional soccer players that occurred as a result of COVID-19 infection after fulfilling all of the prerequisites for a safe return to play (RTP). The participants were 47 professional soccer players from a team which competed in first Croatian division (21.6 years old on average) during the 2020/21 season. The total sample was divided into two subgroups based on the results of a PCR test for COVID-19, where 31 players tested positive (infected) and 16 tested negative. We observed the PCR test results (positive vs. negative PCR), the number of days needed to return to the team, number of days needed to RTP after quarantine and isolation, and MRP (10 variables measured by a global positioning system). The number of days where the infected players were not included in the team ranged from 7 to 51 (Median: 12). Significant pre- to post-COVID differences in MRP for infected players were only found for high-intensity accelerations and high-intensity decelerations (t-test = 2.11 and 2.13, respectively; p < 0.05, moderate effect size differences), with poorer performance in the post-COVID period. Since a decrease of the MRP as a result of COVID-19 infection was only noted in two variables, we can highlight appropriateness of the applied RTP. However, further adaptations and improvements of the RTP are needed with regard to high-intensity activities.



#25 Validity and Reliability of an Inertial Sensor Device for Specific Running Patterns in Soccer

Reference: Sensors (Basel). 2021 Oct 31;21(21):7255. doi: 10.3390/s21217255.

Authors: Guglielmo Pillitteri, Ewan Thomas, Giuseppe Battaglia, Giovanni Angelo Navarra, Antonino Scardina, Viviana Gammino, Dario Ricchiari, Marianna Bellafiore

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Summary: Electronic performance tracking devices are largely employed in team sports to monitor performance and improve training. To date, global positioning system (GPS) based devices are those mainly used in soccer training. The aim of this study was to analyse the validity and reliability of the inertial sensor device (ISD) in monitoring distance and speed in a soccer-specific circuit and how their performance compare to a GPS system. 44 young male soccer players (age: 14.9 ± 1.1, range 9-16, years, height: 1.65 ± 0.10 m, body mass: 56.3 ± 8.9 kg) playing in a non-professional soccer team in Italy, participated in the study. We assessed the players trough a soccer running sport-specific circuit. An ISD and a GPS were used to assess distance and speed. Data was compared to a video reference system, and the difference were quantified by means of the root mean square error (RMSE). Significant differences were found for both GPS and ISD devices for distance and speed. However, lower error for distance (dRMSE 2.23 ± 1.01 m and 5.75 ± 1.50 m, respectively) and speed (sRMSE 0.588 ± 0.152 m·s-1 and 1.30 ± 0.422 m·s-1, respectively) were attained by the ISD compared to the GPS. Overall, our results revealed a statistically significant difference between systems in data monitoring for either distance and speed. However, results of this study showed that a smaller error was obtained with the ISD than the GPS device. Despite caution is warranted within the interpretation of these results, we observed a better practical applicability of the ISD due to its small size, lower cost and the possibility to use the device indoor.



#26 It's not all about power: a systematic review and meta-analysis comparing sex-based differences in kicking biomechanics in soccer

Reference: Sports Biomech. 2021 Nov 16;1-44. doi: 10.1080/14763141.2021.1981426. Online ahead of print.

Authors: Molly Boyne, Ciaran Simms, Nicol van Dyk, Garreth Farrell, Emmet Farrell, Clíodhna McHugh, Julia Wall, David Mockler, Fiona Wilson

Summary: Kicking is fundamental in many field-based sports. Most studies investigating kicking performance have been conducted with male athletes, resulting in a dearth of specific data to inform coaching of this skill in female players. This systematic review aimed to compare kicking biomechanics in male and female athletes in field-based sports. As per PRISMA guidelines, articles were retrieved from searches across five online databases. Studies investigating kicking biomechanics in field-based athletes of both sexes were eligible for inclusion. Articles were screened using Covidence and data extracted based on STROBE recommendations. The review included 23 studies, featuring 455 soccer players. Male athletes produced significantly greater ball velocities and linear velocities of the ankle, foot, and toe than females. Males had greater ankle plantarflexion angles than females at ball strike, while females used larger trunk flexion ranges than males. Hip and knee torques and ball-to-foot velocity ratios were greater in men than women. Skilled players generated power using tension arcs; a technique not seen in novices. Skill level within sex may have a greater influence on kicking performance than differences between the sexes. This review highlights the need for further research investigating kicking performance in both sexes across the spectrum of sports.



#27 Three Main Mechanisms Characterize Medial Collateral Ligament Injuries in Professional Male Soccer-Blow to the Knee, Contact to the Leg or Foot, and Sliding: Video Analysis of 37 Consecutive Injuries

Reference: J Orthop Sports Phys Ther. 2021 Nov 16;1-33. doi: 10.2519/jospt.2021.10529. Online ahead of print.

Authors: Matthew Buckthorpe, Davide Pisoni, Filippo Tosarelli, Furio Danelon, Alberto Grassi, Francesco Della Villa

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Summary: The objective was to describe the mechanisms, situational patterns and biomechanics (kinematics) of medial collateral ligament (MCL) injuries in professional male soccer. 57 consecutive MCL injuries across two seasons of professional soccer matches were identified. We obtained and reviewed 37 (65% of 57 injuries) videos to establish the injury mechanism, and situational pattern and knee flexion angle. We used detailed biomechanical analysis to assess the indirect/non-contact injuries. Injury lay-off times, timing of injuries during the match and location of the injury on the pitch were also reported. 23 (62%) injuries were direct contact, 9 (24%) were indirect contact and 5 (14%) were non-contact. Three main sprain mechanisms were noted: (1) direct contact/blow to the knee (n=16), (2) contact to the leg or foot (lever-like) (n=7), and (3) sliding (n=9). 73% of MCL injuries occurred during two main situations: (1) pressing/tackling (n=14, 38%), and (2) being tackled (n=13, 35%). For indirect/non-contact injuries, knee valgus loading (100% of cases), hip abduction (73% of cases) and external foot rotation (92% of cases) were prominent injury kinematics, often with lateral trunk tilt (median, 10º, 64% of cases) and rotation (65% of cases). Knee flexion angles were higher for indirect/non-contact injuries (median, 100º) than direct contact injuries (median, 22º)(P<0.01). Nearly two-thirds of MCL injuries occurred after direct contact; one in every 4 MCL injuries occurred after indirect contact. Three sprain mechanisms characterized MCL injuries: (1) blow to knee, (2) contact to the leg or foot (lever-like), and (3) sliding.



#28 Comparison of Video-Identified Head Contacts and Sensor-Recorded Events in High School Soccer

Reference: J Appl Biomech. 2021 Nov 15;1-5. doi: 10.1123/jab.2021-0191. Online ahead of print.

Authors: Declan A Patton, Colin M Huber, Susan S Margulies, Christina L Master, Kristy B Arbogast

Summary: Field studies have evaluated the accuracy of sensors to measure head impact exposure using video analysis, but few have studied false negatives. Therefore, the aim of the current study was to investigate the proportion of potential false negatives in high school soccer head impact data. High school athletes (23 females and 31 males) wore headband-mounted Smart Impact Monitor-G impact sensors during competitive soccer games. Video footage from 41 varsity games was analyzed by 2 independent reviewers to identify head contact events, which were defined as visually observed contact to the head. Of the 1991 video-identified head contact events for which sensors were functioning and worn by the players, 1094 (55%) were recorded by the sensors. For female players, 45% of video-identified head contact events were recorded by the sensor compared with 59% for male players. For both females and males, sensitivity varied by impact mechanism. By quantifying the proportion of potential false negatives, the sensitivity of a sensor can be characterized, which can inform the interpretation of previous studies and the design of future studies using head impact sensors. Owing to the difficulty in obtaining ground truth labels of head impacts, video review should be considered a complementary tool to head impact sensors.


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