Latest research in football - week 8 - 2023

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 Impact of the COVID-19 Pandemic on Injury Incidence in Japanese Male Professional Soccer Players

Reference: Orthop J Sports Med. 2023 Feb 24;11(2):23259671221149373. doi: 10.1177/23259671221149373. eCollection 2023 Feb.

Authors: Ryo Matsunaga, Masashi Nagao, Ryuichiro Akagi, Atsushi Fukai, Takashi Sando, Hiroshi Ikeda, Shuji Taketomi

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Summary: The outbreak of the 2019 novel coronavirus disease (COVID-19) led to an enforced quarantine period and limited training and match activities for athletes. To report the influence of the COVID-19 pandemic on the occurrence of injury in Japanese male professional soccer players. In total, 21 clubs in the 2019 season and 28 clubs in the 2020 season from the Japan Professional Football League were prospectively followed, and 16 clubs in 2019 and 24 clubs in 2020 were analyzed in this study. Individual training, match exposure, and time-loss injuries were recorded using an electronic data capture system. The influence of COVID-19-related suspension during the 2020 season was retrospectively investigated via comparisons with the 2019 season. Total activity time included 114,001 hours in training and 16,339 hours in matches in 2019 and 170,798 hours in training and 25,411 hours in matches in 2020. The mean training interruption period caused by COVID-19 in 2020 was 39.9 days (range, 3-65 days), and the mean game-interruption period was 70.1 days (range, 58-79 days). The total number of injuries was 1495 in 2019 and 1701 in 2020. The overall injury incidence per 1000 hours of exposure was 5.7 in 2019 and 5.8 in 2020. The overall injury burden per 1000 hours of exposure was 155.5 days in 2019 and 130.2 days in 2020. The muscle injury incidence was highest in May 2020, immediately after the suspension period. The overall injury incidence did not differ between 2019 and 2020. However, muscle injury incidence notably increased in the 2 months after the COVID-19 pandemic suspension period.



#2 High-speed running and sprinting in professional adult soccer: Current thresholds definition, match demands and training strategies. A systematic review

Reference: Front Sports Act Living. 2023 Feb 13;5:1116293. doi: 10.3389/fspor.2023.1116293. eCollection 2023.

Authors: Antonio Gualtieri, Ermanno Rampinini, Antonio Dello Iacono, Marco Beato

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Summary: The aims of this systematic review were (1) to summarize the evidence on absolute velocity thresholds used to classify high-speed running and sprinting, (2) to examine the existing evidence about the individualized thresholds approach, (3) to describe high-speed and sprint running distance match demands, and (4) to provide training strategies for eliciting HSR and sprinting during training sessions in professional adult soccer. This systematic review was conducted following the PRISMA 2020 guidelines. After the authors' screening, 30 studies were included in this review. This review found that, to date, there is no consensus on the absolute thresholds defining high-speed and sprint running in adult soccer players. Until international standards are defined, it is reasonable to set absolute thresholds considering the range of values found in the literature collected in this review. Relative velocity thresholds could be considered for specific training sessions whose goal is to reach near maximal velocity exposure. During official matches, high-speed and sprint running distances ranged from 911 to 1,063 m and 223-307 m, respectively, in professional female soccer players, while ranges from 618 to 1,001 m and 153-295 m, respectively, in professional male soccer players. During training, game-based drills designed in formats using relative areas per player greater than 225 m2 and 300 m2 appear to be adequate for achieving high-speed running and sprinting exposure, respectively, for male players. The combination of game-based, running exercises and soccer circuit-based drills is advisable to ensure adequate high-speed and sprint running exposure both at a team and individual level.



#3 Football (Soccer) as a Probable Cause of Long-Term Neurological Impairment and Neurodegeneration: A Narrative Review of the Debate

Reference: Cureus. 2023 Jan 27;15(1):e34279. doi: 10.7759/cureus.34279. eCollection 2023 Jan.

Authors: Daniele Ramsay, Alice Miller, Bibire Baykeens, Hamaas Hassan, Steve Gentleman

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Summary: Football (soccer) is the most widely played sport across the globe. Due to some recent high-profile cases and epidemiological studies suggesting football can lead to neurodegeneration, scientific and public interest has been piqued. This has resulted in research into whether an association between football participation and neurodegeneration or neurological impairment is present. It has been theorised that a combination of repeated sub-concussive and concussive injuries, due to ball-heading and head collisions, may lead to neurodegeneration. However, evidence remains conflicting. Due to the popularity of the sport, and the serious conditions it has been linked to, it is important to determine whether repeated head impacts during football participation can play a causative role in neurodegenerative disease. To answer this question, a review of the current literature was carried out. Epidemiological evidence showed a higher incidence of amyotrophic lateral sclerosis amongst amateur and professional footballers and that footballers in positions that involve less contact and heading, e.g., goalkeepers lead significantly longer lives. Additionally, imaging studies reach a similar conclusion, reporting changes in brain structure, blood flow, and inflammatory markers in footballers when compared to controls. However, studies looking at an association between heading frequency and cognition show a lack of consensus on whether a higher heading exposure results in reduced cognition. Similarly, in neuropathological studies, signs of chronic traumatic encephalopathy (CTE) have been found in some former players, with contrasting studies suggesting low levels of CTE-type pathology are found in the general population, regardless of exposure to head trauma. The majority of studies suggest a link between football and neurodegenerative disease. However, the high prevalence of retrospective cohort and cross-sectional studies, often plagued by recall bias, undermine the conclusions drawn. Therefore, until larger prospective cohort studies are conducted, concrete conclusions cannot be made. However, caution can be exercised to limit head impacts.



#4 Dynamic valgus knee revealed with single leg jump tests in soccer players

Reference: J Sports Med Phys Fitness. 2023 Mar;63(3):461-470. doi: 10.23736/S0022-4707.22.14442-7.

Authors: Ádám Uhlár, Mira Ambrus, Zsombor Lacza

Summary: Dynamic valgus knee occurs in sports that involve jumps and landing such as soccer and pose an increased risk for anterior cruciate ligament injury. Visual estimation is biased by the athlete's body type, the experience of the evaluator and the movement phase at which the valgus is assessed - thus the result is highly variable. The aim of our study was to accurately assess dynamic knee positions during single and double leg tests through a video-based movement analysis system. Young soccer players (U15, N.=22) performed single leg squat, single leg jump, and double leg jump tests while the knee medio-lateral movement was monitored with a Kinect Azure camera. Jumping and landing phases of the movement were determined within the continuous recording of the knee medio-lateral position over the ankle and the hip vertical position. Kinect measurements were validated by Optojump (Microgate, Bolzano, Italy). Soccer players retained their predominantly varus knee positions in all phases of double-leg jumps, which was far less prominent in single leg tests. Interestingly, a marked dynamic valgus was observed in athletes who participated in traditional strengthening exercises, while this valgus shift was mostly prevented in those who participated in antivalgus training regimes. All these differences were only revealed during single leg tests, while the double leg jump tests masked all valgus tendencies. We propose to use single-leg tests and movement analysis systems for evaluating dynamic valgus knee in athletes. These methods can reveal valgus tendencies even in soccer players who have a characteristic varus knee while standing.



#5 Mortality of Spanish soccer referees and coaches: a retrospective cohort study

Reference: Sci Med Footb. 2023 Mar 2;1-7. doi: 10.1080/24733938.2023.2184485. Online ahead of print.

Authors: José Carlos Diz, Iván Rodríguez, Santiago Iglesias-Sueiro, Eva Diz Ferreira, Miguel A Sanchez-Lastra, Carlos Ayán

Summary: There is evidence that elite soccer players live longer than general population, but there is no information on soccer coaches and referees. We aimed to analyze the longevity of both professionals, comparing them with soccer players and with general population. In this retrospective cohort study, a total of 328 male Spanish soccer coaches, 287 referees, and 1230 soccer players, all born before 1950, were divided in two cohorts, matched 2:1 with coaches and referees. We compared the survival of the cohorts with the Kaplan-Meier estimator and significance with the log-rank test. We calculated hazard ratios of death for coaches and referees compared with male Spanish general population of the same period. Differences in survival among cohorts were found, but they did not reach statistical significance. The estimated median survival time was 80.1 years (95% CI 77.7-82.4) for referees, 78 years (95% CI 76.6-79.3) for coaches, 78.8 years (95% CI 77.6-80) for referees matched with players, and 76.6 years (95% CI 75.3-77.9) for coaches matched with players. Both coaches and referees had lower mortality than general population, but this advantage disappeared after 80 years of age. We found no differences in longevity among Spanish elite soccer referees, coaches and players born before 1950. Both coaches and referees had lower mortality than general population, but this advantage disappeared after 80 years of age.



#6 Speed-Related Abilities Are Similarly Improved After Sled Training Under Different Magnitudes of Velocity Loss in Highly Trained Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Jan 1;1-8. doi: 10.1123/ijspp.2022-0354. Online ahead of print.

Authors: Rafael Grazioli, Irineu Loturco, Filipe Veeck, Igor Setuain, Laura A Zandavalli, Martinho Inácio, Ronei S Pinto, Eduardo L Cadore

Summary: We examined the effects of two 8-week resisted-sprint training programs under different magnitudes of velocity loss (VL) on the speed-related performance of highly trained soccer players. Twenty-one soccer players (age: 25.9 [5.4] y) were randomly assigned to 1 of 2 groups: (1) the "moderate-load group," players who trained with sled loads that induced 15%VL relative to unloaded sprint velocity (n = 11); and (2) the "heavy-load group," players who trained with sled loads that induced 40% VL relative to unloaded sprint velocity (n = 10). Linear sprint (10 m), curve sprint, change-of-direction speed, resisted-sprint performance at 15% VL and 40% VL, and vertical jumping ability were tested pretraining and posttraining. A 2-way repeated-measures analysis of variance was used to test for differences between groups. In addition, percentage changes were calculated for speed-related abilities and compared with their respective coefficients of variation to determine whether individual changes in performance were greater than the test variance (ie, "true change"). A main effect of time was detected for 10-m sprint, curve sprint, change-of-direction speed, and 15% VL and 40% VL resisted-sprint times, with significant decreases in sprint times (P = .003, P = .004, P = .05, P = .036, and P = .019, respectively). Jump variables did not change significantly over time. There were no group-by-time interactions for any tested variable (P > .05), but the "true change" analysis revealed meaningful individual changes in both groups. Both moderate- and heavy-sled loading conditions may optimize the development of speed-related abilities in highly trained soccer players. Nevertheless, resisted-sprint training responses may differ meaningfully when assessed on an individual basis.



#7 Relationship between body size and skeletal age with muscle damage in young soccer players

Reference: Int J Sports Med. 2023 Mar 2. doi: 10.1055/a-2046-2747. Online ahead of print.

Authors: Luiz Fernando Ramos-Silva, Julio Cesar da Costa, Paulo Henrique Borges, Felipe A Moura, Rafael Deminice, Donizete Cícero Xavier de Oliveira, Raul Osiecki, Enio Ronque

Summary: This study verified the relationship between body size and skeletal age (SA) with the behavior of blood markers of muscle damage and delayed onset muscle soreness (DOMS) after a soccer match in the U-13 and U-15 categories. The sample consisted of 28 soccer players in the U-13 and 16 in the U-15 categories. Creatine kinase (CK), lactate dehydrogenase (LDH), and DOMS were evaluated up to 72h after the match. Muscle damage was elevated at 0h in U-13, and from 0h to 24h in U-15. DOMS increased from 0h to 72h in U-13 and from 0h to 48h in U-15. Significant associations of SA and fat-free mass (FFM) with muscle damage markers and DOMS were observed only in U-13, specifically at time 0h, when SA explained 56% of CK and 48% of DOMS and FFM explained 48% of DOMS. Concluded that in the U-13 category, higher SA is significantly associated with muscle damage markers, and increase in FFM is associated with muscle damage markers and DOMS. Furthermore, U-13 players need 24h to recover pre-match muscle damage markers and more than 72h to recover DOMS. In contrast, the U-15 category needs 48h to recover muscle damage markers and 72h to recover DOMS.



#8 Effects of short bout small-sided game training on acid-based balance markers in youth male soccer players

Reference: Sci Rep. 2023 Mar 2;13(1):3510. doi: 10.1038/s41598-023-30646-4.

Authors: Jakub Kryściak, Tomasz Podgórski, Paweł Chmura, Marek Konefał, Jan Chmura, Marius Brazaitis, Toni Modric, Marcin Andrzejewski

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Summary: This study aimed to compare the effects of 1 × 1 small-sided games (SSGs) with different bout durations on external (ETL) and internal training loads (ITL) in youth soccer players. Twenty U18 players were divided into two groups performing six 1 × 1 SSGs with 30 and 45 s bout durations on a playing field of 10 by 15 m. ITL indices, including the percentage of maximum heart rate (HR), blood lactate (BLa) level, pH, bicarbonate (HCO3-) level, and base excess (BE) level, were measured at rest, after each SSG bout, and 15 and 30 min after the entire exercise protocol. ETL (Global Positioning System metrics) was recorded during all six SSG bouts. The analysis showed that the 45 s SSGs had a greater volume (large effect) but a lower training intensity (small to large effect) than the 30 s SSGs. A significant time effect (p < 0.05) was observed in all ITL indices and a significant group effect (F1, 18 = 8.84, p = 0.0082, ƞ2 = 0.33) in the HCO3- level only. Finally, the changes in the HR and HCO3- level were smaller in the 45 s SSGs than in the 30 s SSGs. In conclusion, 30-s games, characterized by a higher intensity of training effort, are more physiologically demanding than 45-s games. Secondly during short-bout SSG training the HR and BLa level have limited diagnostic value for ITL. Extending ITL monitoring using other indicators, such as the HCO3- and BE levels, appears reasonable.



#9 Female athlete triad cross-sectional study of soccer players by level of competition

Reference: J Phys Ther Sci. 2023 Mar;35(3):170-174. doi: 10.1589/jpts.35.170. Epub 2023 Mar 1.

Authors: Chiaki Matsumoto, Masahiro Ishizaka, Akira Kubo, Masafumi Itokazu

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Summary: The aim was to determine the actual status of the Female Athlete Triad (low energy availability, menstrual dysfunction, and bone mineral density loss) in soccer players. The survey was conducted between February 1 and March 1, 2022. It included 115 females between the ages of 12 and 28 registered with the Japan Football Association, from teams at different levels. Players in the top league did not differ in height and weight but were older and had a better understanding of caloric intake. There were no differences in amenorrhea or history of bone fractures based on league. Of the female soccer players in the four different levels of competition, only the players in the top league had a better understanding of available energy and took preventive measures against the Female Athlete Triad.



#10 The Social Media Presence of Professional Sports Team Physicians Is High Among Major League Soccer, Major League Lacrosse, Major League Rugby, Winter Olympics, and Women's National Basketball Association, But Highest Among MLS Team Physicians

Reference: Arthrosc Sports Med Rehabil. 2022 Dec 20;5(1):e59-e65. doi: 10.1016/j.asmr.2022.10.008. eCollection 2023 Feb.

Authors: Sayyida S Hasan, Hashim Shaikh, Keshin Visahan, Sergio Navarro, Irvin Sulapas, Theodore Shybut

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Summary: The purpose was to quantify the social media utilization of professional sports team physicians on popular platforms and analyze differences between physician users and physician non-users for smaller major professional sports: Major League Soccer (MLS), Major League Lacrosse (MLL), Major League Rugby (MLR), Winter Olympics (WO) and Women's National Basketball Association (WNBA). Physicians for the MLS, MLL, MLR, WO, and WNBA were identified and characterized based on training background, practice setting, years of experience, and geographic location. Social media presence on Facebook, Twitter, LinkedIn, Instagram, and ResearchGate were determined. Differences between social media users and non-users were analyzed via chi-squared tests for nonparametric variables. Secondary analysis consisted of univariate logistic regression to identify associated factors. 86 team physicians were identified. 73.3% of physicians had at least one social media profile. 80.2% of physicians were orthopedic surgeons. Specifically, 22.1% had a professional Facebook page, 24.4% had a professional Twitter page, 58.1% had a LinkedIn profile, 25.6% a ResearchGate profile, and 9.3% an Instagram account. All physicians with a social media presence were fellowship-trained. Seventy-three percent of team physicians in the MLS, MLL, MLR, WO, or WNBA have social media presence, with over half using LinkedIn. Fellowship-trained physicians were significantly more likely to use social media, and 100% of physicians with social media presence were fellowship trained. MLS and WO team physicians were significantly more likely to use LinkedIn (P = .02). MLS team physicians were significantly more likely to use social media overall (P = .004). No other metric significantly impacted social media presence. The influence of social media is vast. It is important to explore the extent that sports team physicians utilize social media and how this use may influence patient care.



#11 Comparison of soccer instep kicking kinematics with and without elastic taping

Reference: Sports Biomech. 2023 Mar 3;1-12. doi: 10.1080/14763141.2023.2184419. Online ahead of print.

Authors: Nahoko Sato, Hiroyuki Nunome, Yuichi Mizukami

Summary: The present study aimed to determine the effect of elastic taping on soccer instep kicking kinematics. Fifteen male university soccer players performed maximal instep kicking with and without Y-shaped elastic taping on the skin surface of the rectus femoris muscle. Their kicking motions were captured at 500 Hz using a motion capture system. The thickness of the rectus femoris muscle was measured using an ultrasound scanner prior to the kicking session. The thickness of the rectus femoris muscle and kicking leg kinematics in both the conditions were compared. The thickness of the rectus femoris muscle increased significantly after elastic tape application. In conjunction with this change, kinematic variables of the kicking leg, such as peak hip flexion angular velocity and knee and foot linear velocities significantly increased. However, there was no change in the knee extension angular and hip linear velocities. The elastic tape application caused deformation of the rectus femoris muscle and improvement of the instep kicking performance. The study findings provide a new insight on the effect of elastic taping on dynamic sports performance, such as in soccer instep kicking.



#12 Changes in Estimated Body Composition and Physical Fitness of Adolescent Boys after One Year of Soccer Training

Reference: Children (Basel). 2023 Feb 16;10(2):391. doi: 10.3390/children10020391.

Authors: Cíntia França, Diogo V Martinho, Élvio Rúbio Gouveia, Francisco Martins, Adilson Marques, Tiago Ribeiro, Marcelo de Maio Nascimento, Helder Lopes, Ana Rodrigues, Andreas Ihle

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Summary: Sports participation is one of the most popular forms of physical activity among youngsters. This study aimed to examine the changes in the estimated body composition, strength, and flexibility of adolescent boys after 12 months of soccer training compared with those of age-matched controls with non-sports participation. We assessed 137 boys (62 soccer players and 75 controls) at baseline (TM1) and 12 months later (TM2). The differences in estimated body composition, strength, and flexibility were investigated using a repeated measure analysis of variance. The analysis revealed a significant main effect of soccer training on fat mass (F = 73.503, p ≤ 0.01, η2 = 0.59) and fat-free mass (F = 39.123, p ≤ 0.01, η2 = 0.48). Over time, the soccer group decreased their fat mass and increased their fat-free mass, while the opposite results were observed for the controls. Among physical fitness tests, a substantial effect of soccer training was evidenced for the sit-up performance (F = 16.224, p ≤ 0.01, η2 = 0.32). Regarding the time factor, significant effects were noted for height and handgrip strength. No significant differences were detected for flexibility. Overall, the benefits of soccer training were exhibited by the larger improvements in fat mass, fat-free mass, sit-ups, and handgrip strength performance, underlining the important role of soccer participation during adolescence.



#13 Validation of a New Soccer Shooting Test Based on Speed Radar Measurement and Shooting Accuracy

Reference: Children (Basel). 2023 Jan 20;10(2):199. doi: 10.3390/children10020199.

Authors: Felix Engler, Andreas Hohmann, Maximilian Siener

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Summary: Due to poor results, the German talent identification and development of the German soccer association DFB no longer performs a shooting test since a few years. The aim of this study was to create and validate a new soccer shooting test that allows valid conclusions to be drawn from the shooting quality of youth soccer players about their overall soccer skills. The shooting test was performed with a total of 57 male club players (age: 15.24 ± 0.864 years) from four different teams from the first, second, fifth, and the seventh division of the respective age group (under 15-year-olds until under 17-year-olds). Each subject took one shot at maximum shot speed and eight target shots, measuring accuracy and the shot speed. A multivariable linear regression analysis with forward selection revealed significant values for the variables average shot speed nondominant leg (p < 0.001) and total score (p = 0.004; accuracy × speed of every target shot). Based on these two variables, the soccer skills could be derived from the shooting skills of the adolescents in 57.4% of the cases. The study shows the importance of a good technique with the nondominant leg and of the ability to shoot accurately as well as fast simultaneously.



#14 Using A-Mode Ultrasound to Assess the Body Composition of Soccer Players: A Comparative Study of Prediction Formulas

Reference: Diagnostics (Basel). 2023 Feb 12;13(4):690.doi: 10.3390/diagnostics13040690.

Authors: Paul Muntean, Monica Neagu, Elena Amaricai, Horia G Haragus, Roxana Ramona Onofrei, Adrian Neagu

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Summary: For elite athletes, monitoring body composition is important for maximizing performance without health risks. Amplitude (A)-mode ultrasound (AUS) has attracted increasing attention as an alternative to skinfold thickness measurements commonly used for assessing the amount of body fat in athletes. AUS accuracy and precision, however, depend on the formula used to predict body fat percentage (%BF) from subcutaneous fat layer thicknesses. Therefore, this study evaluates the accuracy of the 1-point biceps (B1), 9-sites Parrillo, 3-sites Jackson and Pollock (JP3), and 7-sites Jackson and Pollock (JP7) formulas. Relying on the previous validation of the JP3 formula in college-aged male athletes, we took AUS measurements in 54 professional soccer players (aged 22.9 ± 3.83 y, mean ± SD) and compared the results given by different formulas. The Kruskal-Wallis test indicated significant differences (p < 10-6), and Conover's post hoc test revealed that the JP3 and JP7 data come from the same distribution, whereas the data given by B1 and P9 differ from all the others. Lin's concordance correlation coefficients for B1 vs. JP7, P9 vs. JP7, and JP3 vs. JP7 were 0.464, 0.341, and 0.909, respectively. The Bland-Altman analysis indicated mean differences of -0.5 %BF between JP3 and JP7, 4.7 %BF between P9 and JP7, and 3.1 %BF between B1 and JP7. This study suggests that JP7 and JP3 are equally valid, whereas P9 and B1 overestimate %BF in athletes.



#15 Sudden Cardiac Arrest in Basketball and Soccer Stadiums, the Role of Automated External Defibrillators: A Review. For the BELTRAN Study (BaskEtbaLl and soccer sTadiums: Registry on Automatic exterNal defibrillators)

Reference: Arrhythm Electrophysiol Rev. 2023 Jan;12:e03. doi: 10.15420/aer.2022.30.

Authors: Mario D Bassi, Juan M Farina, Jorge Bombau, Mario Fitz Maurice, Guillermo Bortman, Elaine Nuñez, Manlio Márquez, Norberto Bornancini, Adrian Baranchuk

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Summary: Sudden cardiac arrest (SCA) during sports events has a dramatic impact on stadium-goers and the public and is often associated with poor outcomes unless treated with an automated external defibrillator (AED). Despite this, stadiums vary in AED use. This review aims to identify the risks and incidences of SCA, and the use of AEDs in soccer and basketball stadiums. A narrative review of all relevant papers was conducted. Athletes across all sports face an SCA risk of 1:50,000 athlete-years, with the greatest risk of SCA in young male athletes (1:35,000 person-years) and black male athletes (1:18,000 person-years). Africa and South America have the poorest soccer SCA outcomes at 3% and 4% survival. AED use on-site improves survival greater than defibrillation by emergency services. Many stadiums do not have AEDs implemented into medical plans and the AEDs are often unrecognisable or are obstructed. Therefore, AEDs should be used on-site, use clear signalling, have certified trained personnel, and be incorporated into stadiums' medical plans.



#16 Age of first exposure to soccer heading: Associations with cognitive, clinical, and imaging outcomes in the Einstein Soccer Study

Reference: Front Neurol. 2023 Feb 9;14:1042707. doi: 10.3389/fneur.2023.1042707. eCollection 2023.

Authors: Molly F Charney, Kenny Q Ye, Roman Fleysher, Bluyé DeMessie, Walter F Stewart, Molly E Zimmerman, Mimi Kim, Richard B Lipton, Michael L Lipton

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Summary: The objective of this study is to assess the role of age at first exposure (AFE) to soccer heading as a predictor of known adverse associations of recent and longer-term heading with brain microstructure, cognitive, and behavioral features among adult amateur soccer players. The sample included 276 active amateur soccer players (196 male and 81 female) aged 18-53 years old. AFE to soccer heading was treated as a binary variable, dichotomized at ≤ 10 years vs. >10 years old, based on a recently promulgated US Soccer policy, which bans heading for athletes ages 10 and under. We found that soccer players who began heading at age 10 or younger performed better on tests of working memory (p = 0.03) and verbal learning (p = 0.02), while accounting for duration of heading exposure, education, sex, and verbal intelligence. No difference in brain microstructure or behavioral measures was observed between the two exposure groups. The findings indicate that, among adult amateur soccer players, AFE to heading before age 10 compared to later start of heading, is not associated with adverse outcomes, and may be associated with better cognitive performance in young adulthood. Cumulative heading exposure across the lifespan, rather than early life exposure, may drive risk for adverse effects and should be the focus of future longitudinal studies to inform approaches to enhance player safety.



#17 How do soccer players sprint from a tactical context? Observations of an English Premier League soccer team

Reference: J Sports Sci. 2023 Feb 27;1-12. doi: 10.1080/02640414.2023.2183605. Online ahead of print.

Authors: Paul Caldbeck, Thomas Dos'Santos

Summary: The aim of this study was to quantify and tactically contextualise (i.e., phase of play and tactical outcome [TO]) sprints (≥7.0 m/s) of an English Premier League (EPL) soccer team during match-play. Videos of 901 sprints (10 matches) were evaluated using the Football Sprint Tactical-Context Classification System. Sprints occurred within a variety of phases of play (attacking/defensive organisation and transitions) and TOs, both out- and in-possession, with position-specific differences. Most sprints were completed out-possession (58%), with "closing down" the most observed TO (28%). In-possession, "run the channel" (25%) was the most observed TO. Centre backs predominantly performed "ball down the side" sprints (31%), whereas central midfielders mostly performed "covering" sprints (31%). Central forwards and wide midfielders mostly performed "closing down" (23% and 21%) and "run the channel" (23% and 16%) sprints when out- and in-possession, respectively. Full backs most frequently performed "recovery" and "overlap" runs (14% each). This study provides insights into the specific physical-tactical characteristics of sprints performed from an EPL soccer team. This information can be used to assist in the development of position-specific physical preparation programmes, and more ecologically valid and contextualised gamespeed and agility sprint drill construction to better reflect the demands of soccer.



#18 Indirect Rectus Femoris Injury Mechanisms in Professional Soccer Players: Video Analysis and Magnetic Resonance Imaging Findings

Reference: Clin J Sport Med. 2023 Feb 28. doi: 10.1097/JSM.0000000000001131. Online ahead of print.

Authors: Aleksi Jokela, Sandra Mechó, Giulio Pasta, Pavel Pleshkov, Alvaro García-Romero-Pérez, Stefano Mazzoni, Jussi Kosola, Filippo Vittadini, Javier Yanguas, Ricard Pruna, Xavier Valle, Lasse Lempainen

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Summary: The aim was to describe injury mechanisms and magnetic resonance imaging (MRI) findings in acute rectus femoris (RF) injuries of soccer players using a systematic video analysis. Professional male soccer players aged between 18 and 40 years, referred for injury assessment within 7 days after a RF injury, with an available video footage of the injury and a positive finding on an MRI. Rectus femoris injury mechanisms (specific scoring based on standardized models) in relation to RF muscle injury MRI findings were used as independent variables while Rectus femoris injury mechanism (playing situation, player/opponent behavior, movement, and biomechanics), location of injury in MRI were used as main outcome measures. Twenty videos of RF injuries in 19 professional male soccer players were analyzed. Three different injury mechanisms were seen: kicking (80%), sprinting (10%), and change of direction (10%). Isolated single-tendon injuries were found in 60% of the injuries. Of the kicking injuries, 62.5% included complete tendon ruptures, whereas both running injuries and none of the change of direction injuries were complete ruptures. The direct tendon was involved in 33% of the isolated injuries, and the common tendon was affected in all combined injuries. Rectus femoris injuries typically occur during kicking among football players. Most of the RF injuries involve a complete rupture of at least one tendon. Kicking injuries can also affect the supporting leg, and sprinting can cause a complete tendon rupture, whereas change of direction seems not to lead to complete ruptures.



#19 Erratum: The Qatar 2022 World Cup warm-up: Football goal-scoring evolution in the last 14 FIFA World Cups (1966-2018)

Reference: Front Psychol. 2023 Feb 10;14:1156698. doi: 10.3389/fpsyg.2023.1156698. eCollection 2023.

Authors: Frontiers Production Office

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#20 The Design of GNSS/IMU Loosely-Coupled Integration Filter for Wearable EPTS of Football Players

Reference: Sensors (Basel). 2023 Feb 4;23(4):1749. doi: 10.3390/s23041749.

Authors: Mingu Kim, Chulwoo Park, Jinsung Yoon

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Summary: This study presents the filter design of GNSS/IMU integration for wearable EPTS (Electronic Performance and Tracking System) of football players. EPTS has been widely used in sports fields recently, and GNSS (Global Navigation Satellite System) and IMU (Inertial Measurement Unit) in wearable EPTS have been used to measure and provide players' athletic performance data. A sensor fusion technique can be used to provide high-quality analysis data of athletic performance. For this reason, the integration filter of GNSS data and IMU data is designed in this study. The loosely-coupled strategy is considered to integrate GNSS and IMU data considering the specification of the wearable EPTS product. Quaternion is used to estimate a player's attitude to avoid the gimbal lock singularity in this study. Experiment results validate the performance of the proposed GNSS/IMU loosely-coupled integration filter for wearable EPTS of football players.



#21 Definition of High-Risk Motion Patterns for Female ACL Injury Based on Football-Specific Field Data: A Wearable Sensors Plus Data Mining Approach

Reference: Sensors (Basel). 2023 Feb 15;23(4):2176. doi: 10.3390/s23042176.

Authors: Stefano Di Paolo, Eline M Nijmeijer, Laura Bragonzoni, Alli Gokeler, Anne Benjaminse

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Summary: The aim of the present study was to investigate if the presence of anterior cruciate ligament (ACL) injury risk factors depicted in the laboratory would reflect at-risk patterns in football-specific field data. Twenty-four female footballers (14.9 ± 0.9 year) performed unanticipated cutting maneuvers in a laboratory setting and on the football pitch during football-specific exercises (F-EX) and games (F-GAME). Knee joint moments were collected in the laboratory and grouped using hierarchical agglomerative clustering. The clusters were used to investigate the kinematics collected on field through wearable sensors. Three clusters emerged: Cluster 1 presented the lowest knee moments; Cluster 2 presented high knee extension but low knee abduction and rotation moments; Cluster 3 presented the highest knee abduction, extension, and external rotation moments. In F-EX, greater knee abduction angles were found in Cluster 2 and 3 compared to Cluster 1 (p = 0.007). Cluster 2 showed the lowest knee and hip flexion angles (p < 0.013). Cluster 3 showed the greatest hip external rotation angles (p = 0.006). In F-GAME, Cluster 3 presented the greatest knee external rotation and lowest knee flexion angles (p = 0.003). Clinically relevant differences towards ACL injury identified in the laboratory reflected at-risk patterns only in part when cutting on the field: in the field, low-risk players exhibited similar kinematic patterns as the high-risk players. Therefore, in-lab injury risk screening may lack ecological validity.


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