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Latest research in football - week 47 - 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 Are We Jumping to the Wrong Conclusions? Longer Jumps and More Hops in Female Football Players Who Went on to Sustain a Primary or Secondary ACL Injury Compared to Those Who Did Not

Reference: Sports Med Open. 2023 Nov 10;9(1):105. doi: 10.1186/s40798-023-00656-7.

Authors: Anne Fältström, Joanna Kvist, Martin Hägglund

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Summary: Different functional performance tests are used to assess patients in the clinic and before return to sport (RTS), where the rehabilitation goal is to reach good strength and jumping ability. A limb symmetry index of ≥ 90% is a common target in rehabilitation before RTS. The aim of this short communication is to use data from our 2-year prospective cohort study on female football players, either with or without an anterior cruciate ligament (ACL) reconstruction, to discuss whether hop performance in 3 commonly used hop tests can inform safe football participation, that is, with a low risk for ACL injury or reinjury. At baseline, 117 active female football players (mean age ± standard deviation, 20 ± 2 years) were included 19 ± 9 months after ACL reconstruction as well as 119 matched female knee-healthy players (age 19 ± 3 years). All players performed a single hop for distance test, 5-jump test and side hop test at baseline and were then prospectively followed for 2 years. Twenty-eight (24%) players sustained a second ACL injury and 8 (7%) sustained a primary ACL injury. Longer jumps in the 5-jump test (922 cm vs. 865 cm, Cohen's d = - 0.60) and more hops in the side hop test for both limbs (41-42 hops vs. 33-36 hops, d = - 0.43 to - 0.60) were seen in players who sustained a second ACL injury compared with those who did not. Longer jumps in the single hop for distance test (both limbs) (139-140 cm vs. 124-125 cm, d = - 0.38 to - 0.44), in the 5-jump test (975 cm vs. 903 cm, d = -0.42) and more hops in the side hop test (both limbs) (48-49 hops vs. 37-38 hops, d = - 0.38 to - 0.47) were seen in players who sustained a primary ACL injury compared with those who did not. The average hop performance, i.e. longer jumps or more hops, was greater in players who went on to sustain a primary or secondary ACL injury compared to those who did not over a two-year follow-up period. Even though hop tests are not used in isolation to evaluate readiness to RTS, their interpretation needs consideration in the decision-making process of returning to pivoting sports.




#2 'More than likely the men come first. That's just very frustrating'. A qualitative exploration of contextual factors affecting the implementation of injury prevention initiatives and the provision of effective injury management in elite-level women's club football in Ireland

Reference: Br J Sports Med. 2023 Nov 9:bjsports-2022-106548. doi: 10.1136/bjsports-2022-106548.

Authors: Dan Horan, Eamonn Delahunt, Mark Roe, Martin Hägglund, Catherine Blake, Seamus Kelly

Summary: The aim of our study was to explore the contextual factors that affect the implementation of football injury prevention initiatives and the provision of effective injury management in the Irish Women's National League (WNL). We used a criterion-based purposive sampling approach to recruit coaches (n=7), players (n=17) and medical personnel (n=8) representing eight of the nine clubs in the WNL to participate in one-to-one semistructured interviews. Our study was located within an interpretivist, constructivist research paradigm. The interview data were analysed using reflexive thematic analysis. The participants identified academic and work pressures, financial challenges, conflict with college football, inadequate facilities and gender inequity as being barriers to the implementation of injury prevention initiatives and the provision of effective injury management. Financial constraints within clubs were perceived to limit the provision of medical care and strength and conditioning (S&C) support and this was deemed to be associated with a heightened risk of injuries. Specific contextual factors were identified which curtail the implementation of injury prevention initiatives and the provision of effective injury management in elite-level women's club football in Ireland. Gender inequity was identified as one of the factors impacting the availability of high-quality medical care, S&C support, as well as access to training and match facilities. Our results provide new insights that could be used to inform the design and implementation of injury prevention and management initiatives for women football players in Ireland.



#3 Generations, events, and social movement legacies: Unpacking social change in English football (1980-2023)

Reference: Br J Sociol. 2023 Nov 10.  doi: 10.1111/1468-4446.13065. Online ahead of print.

Authors: Mark Turner, Jan Andre Lee Ludvigsen

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Summary: This article critically employs the case of association football in England, from 1980 to 2023, as a social movement timescape, to examine the political consciousness and long-term mobilisations of a generation of football supporter activists, and their capacity to influence politics, and respond to new, emerging, critical junctures, through networks of trust and shared memories of historical events. This is of crucial importance to sociology because it reveals the tensions between what are considered legitimate and illegitimate social practices which characterise contemporary society's moral economy. Focusing on temporal contestations over regulation, policing, governance and cultural rituals, the article deconstructs the role of generations in social movements, and critically synthesises relational-temporal sociology and classic and contemporary work on the sociology of generations, to show how legacy operates as a multifaceted maturing concept of power and time. In English football's neoliberal timescape, the supporters' movement has reached a critical juncture; the future will require a new generation of activists, to negotiate, resist and contest the new hegemonic politics of social control and supporter engagement.



#4 Relationships Between Task Constraints, Visual Constraints, Joint Coordination and Football-Specific Performance in Talented Youth Athletes: An Ecological Dynamics Approach

Reference: Percept Mot Skills. 2023 Nov 10:315125231213124. doi: 10.1177/00315125231213124.

Authors: Pieter Heuvelmans, Stefano Di Paolo, Anne Benjaminse, Laura Bragonzoni, Alli Gokeler

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Summary: Individual performance in team sports is a multifactorial reflection of how well a player can cope and accomplish tasks in varied playing situations. Thus, performance analysis should not only focus on outcomes, but also on underlying mechanisms of those outcomes. We adopted principles of the ecological dynamics approach (EDA) to investigate the effect of introducing constraints on players' joint coordination responses for a football-specific performance drill outcome. Seventeen talented youth football (soccer) players performed a football-specific drill under different conditions: basic constraints, additional defender dummies, stroboscopic glasses, and a combination of the latter two constraints. We recorded these players' execution time, passing accuracy, and lower extremity joint kinematics. We calculated joint coordination for hip-knee, knee-ankle, and trunk-hip couplings. The added constraints negatively affected execution time and passing accuracy, and caused changes in joint coordination. Furthermore, we identified a relationship between execution time and joint coordination. This study serves as an example how the EDA can be adopted to investigate mechanisms that underlie individual performance in team sports.



#5 Prediction of ACL-tear by lower limbs muscle strength and flexibility: a prospective cohort study in 95 female soccer players

Reference: Res Sports Med. 2023 Nov 15:1-23. doi: 10.1080/15438627.2023.2280554. Online ahead of print.

Authors: Antonio Cejudo, José Manuel Armada-Zarco, Francisco Ayala, Pilar Sainz de Baranda

Summary: The aims of the study were to build models using logistic regression analysis of flexibility and strength tests to prospectively predict risk factors for anterior cruciate ligament tear (ACL-tear) in female soccer (FS) players, and to determine training cut-off for risk factors of the predictive model built. A prospective cohort study of 95 female players (aged 14-33 years) was conducted. Age, anthropometric data, soccer history, lower limb range of motion (ROM) and hip maximal isometric strength (MIS) were measured. At the prospective follow-up after 12 months, 7.4% of the players had developed an ACL-tear. The model showed a significant relationship (χ2(93) = 30.531, p < 0.001) between the ACL-tear and the predictor variables (leg length, HAD-NH [hip adduction] MIS, asymmetric ROM [ankle dorsiflexion with knee extended (AD-KE) and with knee flexed (AD-KF), and HE (hip extension)], hip ROM [HIR (internal rotation) and HAB (abduction)]). The Akaike Information Criteria (AIC) and Bayesian Information Criteria (BIC) for model fit were 30.24 and 51.79, respectively. The value R2 showed good model fit, 76.5% for Nagelkerke´s R2, 71.4% for McFadden´s R2 and 67.5% for Tjur´s R2. For the screening test, cut-off for leg length of ≥0.40 m, for HIR ROM of ≤44º and for asymmetry of HE ROM of ≥5° were set, which have an acceptable (AUC ≥ 0.755) discriminatory ability for the development of ACL-tear.



#6 Determinants of Performance in Professional Soccer Players at 2 and 5 Years After ACL Reconstruction

Reference: Am J Sports Med. 2023 Nov 13:3635465231207832. doi: 10.1177/03635465231207832.

Authors: Vítor Hugo Pinheiro, Kyle A Borque, Mitzi S Laughlin, Mary Jones, Ganesh Balendra, Madison R Kent, Ryan Ajgaonkar, Andy Williams

Summary: A number of studies have investigated return to play after anterior cruciate ligament reconstruction (ACLR) in professional soccer players, but it is unclear which factors are associated with a return to the preinjury performance and ability to play over time. The purpose was to identify factors that contribute to a professional soccer player's return to preinjury performance after ACLR, as well as to report their playing performance at 2 and 5 years after ACLR compared with their preinjury performance. A consecutive cohort of professional soccer players undergoing primary ACLR were analyzed between 2005 and 2019. A minimum 2-year follow-up was required. The effect of patient, surgical, and postoperative factors on performance rates, defined as a combination of league level and playing time, was evaluated with univariate and multivariate logistic regression models. A total of 200 male professional soccer players were included. When combining league level and playing time, 30% of athletes returned to their preinjury performance at 2 years and 22% at 5 years. However, 53% of athletes returned to their preinjury performance for at least 1 season by year 5. At 2 years, a chondral lesion of grade 3 or 4 decreased the odds of return to preinjury performance (odds ratio [OR], 0.37; P = .010). Athletes receiving an ACLR with the addition of a lateral extra-articular tenodesis procedure were 2.42 times more likely to return to preinjury performance at 2 years than athletes with ACLR alone (P = .004). By 5 years after ACLR, athletes aged ≥25 years at the time of reconstruction were 3 times less likely to be performing at their preinjury performance (OR, 0.32; P < .001), and those with a grade ≥3 chondral lesion were >2 times less likely to be performing at their preinjury performance (OR, 0.43; P = .033). The presence of >50% thickness chondral pathology, ACLR without lateral extra-articular tenodesis, and age >25 years at the time of surgery were all significant risk factors of worse performance rates after ACLR. Significant decreases in performance rates were noted at 2 and 5 years postoperatively.



#7 Adaptation of YOLOv7 and YOLOv7_tiny for Soccer-Ball Multi-Detection with DeepSORT for Tracking by Semi-Supervised System

Reference: Sensors (Basel). 2023 Oct 25;23(21):8693. doi: 10.3390/s23218693.

Authors: Jorge Armando Vicente-Martínez, Moisés Márquez-Olivera, Abraham García-Aliaga, Viridiana Hernández-Herrera

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Summary: Object recognition and tracking have long been a challenge, drawing considerable attention from analysts and researchers, particularly in the realm of sports, where it plays a pivotal role in refining trajectory analysis. This study introduces a different approach, advancing the detection and tracking of soccer balls through the implementation of a semi-supervised network. Leveraging the YOLOv7 convolutional neural network, and incorporating the focal loss function, the proposed framework achieves a remarkable 95% accuracy in ball detection. This strategy outperforms previous methodologies researched in the bibliography. The integration of focal loss brings a distinctive edge to the model, improving the detection challenge for soccer balls on different fields. This pivotal modification, in tandem with the utilization of the YOLOv7 architecture, results in a marked improvement in accuracy. Following the attainment of this result, the implementation of DeepSORT enriches the study by enabling precise trajectory tracking. In the comparative analysis between versions, the efficacy of this approach is underscored, demonstrating its superiority over conventional methods with default loss function. In the Materials and Methods section, a meticulously curated dataset of soccer balls is assembled. Combining images sourced from freely available digital media with additional images from training sessions and amateur matches taken by ourselves, the dataset contains a total of 6331 images. This diverse dataset enables comprehensive testing, providing a solid foundation for evaluating the model's performance under varying conditions, which is divided by 5731 images for supervised system and the last 600 images for semi-supervised. The results are striking, with an accuracy increase to 95% with the focal loss function. The visual representations of real-world scenarios underscore the model's proficiency in both detection and classification tasks, further affirming its effectiveness, the impact, and the innovative approach. In the discussion, the hardware specifications employed are also touched on, any encountered errors are highlighted, and promising avenues for future research are outlined.



#8 Under-Fuelling for the Work Required? Assessment of Dietary Practices and Physical Loading of Adolescent Female Soccer Players during an Intensive International Training and Game Schedule

Reference: Nutrients. 2023 Oct 24;15(21):4508. doi: 10.3390/nu15214508.

Authors: Samuel J McHaffie, Carl Langan-Evans, Juliette A Strauss, José L Areta, Christopher Rosimus, Martin Evans, Ruth Waghorn, James P Morton

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Summary: Previous studies demonstrate that "under-fuelling" (i.e., reduced carbohydrate (CHO) and energy intake (EI) in relation to recommended guidelines) is prevalent within adult female soccer players, the consequence of which may have acute performance and chronic health implications. However, the dietary practices of adolescent female soccer players, a population who may be particularly at risk for the negative aspects of low energy availability (LEA), are not well documented. Accordingly, we aimed to quantify EI and CHO intake, physical loading and estimated energy availability (EA) in elite national team adolescent female soccer players (n = twenty-three; age, 17.9 ± 0.5 years) during a 10-day training and game schedule comprising two match days on day six (MDa) and nine (MDb). The players self-reported their EI via the remote food photography method, whilst the physical loading and associated exercise energy expenditure were assessed via GPS technology. The relative CHO intake was significantly greater (all p < 0.05) on the day before the first match (MD-1a) (4.1 ± 0.8 g·kg-1), on the day before the second match (MD-1b) (4.3 ± 1.1 g·kg-1), MDa (4.8 ± 1.2 g·kg-1) and MDb (4.8 ± 1.4 g·kg-1) in comparison to most other days (<4 g·kg-1). The mean daily measured EA over the 10-day period was 34 ± 12 kcal·kg FFM-1·day-1 (with six players, i.e., 34%, presenting LEA), though, when adjusting the energy intake for potential under-reporting, these values changed substantially (44 ± 14 kcal·kg FFM-1·day-1, only one player was classed as presenting LEA). Such data suggest that the prevalence of LEA amongst female team sport athletes may be over-estimated. Nonetheless, players are still likely under-fuelling for the work required in relation to the daily CHO recommendations (i.e., >6 g·kg-1) for intensive training and game schedules. These data provide further evidence for the requirement to create and deliver targeted player and stakeholder education and behaviour change interventions (especially for younger athletes) that aim to promote increased daily CHO intake in female soccer players.



#9 Rehabilitation of Soccer Players' Knee Injuries: Cartilage Reconstruction, Anterior Cruciate Ligament Surgery, and Intensive Recovery-A Pilot Study

Reference: J Clin Med. 2023 Nov 1;12(21):6893. doi: 10.3390/jcm12216893.

Authors: Bartłomiej Kacprzak, Karolina Rosińska

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Summary: Knee injuries, particularly anterior cruciate ligament (ACL) damage and cartilage defects, are highly prevalent among athletes and affect their sports performance and long-term joint function. The purpose of this research was to evaluate the effectiveness of a comprehensive combination therapy approach for individuals with ACL and cartilage injuries. Twelve professional soccer players aged 18 to 30 years underwent bone-tendon-bone ACL reconstruction, microfracture cartilage repair surgery, and hyaluronic acid scaffold treatment. Early postoperative rehabilitation included immediate supervised physiotherapy and complete weight bearing. Follow-up assessments involved clinical evaluations, functional joint assessments, and magnetic resonance imaging (MRI) scans to measure cartilage defect repair and symptom alleviation. The results showed that patients resumed pain-free activities within 3-4 weeks and returned to their pre-injury level within 4.5 months. MRI demonstrated the absence of inflammatory reactions, repair of marrow edema, and the emergence of new cartilage. Six months and one year after surgery, the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Short Form (36) Health Survey (SF-36) questionnaire results demonstrated considerable improvement in patients' health condition and quality of life. Overall, the study suggests that the combination of Hyalofast membranes, microfracture surgery, tissue adhesive, and intensive postoperative physical therapy may be a potential alternative to commonly used treatments for patients with ACL rupture, allowing them to recover efficiently and return to sports activities.



#10 Normative data on horizontal power, acceleration, and change-of-direction ability in amateur youth female soccer players

Reference: J Sports Med Phys Fitness. 2023 Nov 13. doi: 10.23736/S0022-4707.23.15426-0. Online ahead of print.

Authors: William H Suits, Meg A Darmofal, Ryan A Bean

Summary: Physical performance measures such as horizontal power, acceleration, and change-of-direction ability are related to performance in soccer, and may aid in talent selection, coaching decisions and the prescription of training programs. The purpose of this study was to describe the normative values of three performance tests in amateur female youth soccer players. A cross-sectional descriptive study design was employed with 151 amateur female youth soccer players (age 14.20±1.13 years). Physical performance measures included the standing broad jump, 10-meter sprint, and Pro-Agility Test. Time since peak height velocity (PHV) was calculated to represent physical maturity status. Descriptive statistics were sought, and Pearson's correlation coefficients were used to identify correlations between variables. One-Way Analysis of Variance with a Tukey post-hoc test was used to calculate the relationship between categorical groups of chronological ages and years since PHV. Significance was set at P<0.05. Normative data for each physical performance measure are presented based on chronological age and physical maturity status for amateur female youth soccer players. Chronological age was significantly associated with improved performance in standing broad jump (R=0.558; 95% CI: 0.436, 0.658; P<0.01), 10-meter sprint time (R=-0.375; 95% CI: -0.495, -0.217; P<0.01), and Pro-Agility Test time (R=-0.424; 95% CI: -0.546, -0.284; P<0.01). Physical maturity status was also significantly associated with improved performance in standing broad jump (R=0.650; 95% CI: 0.426, 0.711; P<0.01), 10-meter sprint time (R=-0.430; 95% CI: -0.507, -0.232; P<0.01), and Pro-Agility Test time (R=-0.453; 95% CI: -0.554, -0.293; P<0.01). The normative data from this study demonstrates differences in physical performances across chronological ages and physical maturity status. Physical maturity status had a slightly stronger association for all performance measures than chronological age. The variance and range tended to increase across performance measures with increasing age.



#11 Reliability and validity of a reactive agility test with soccer goalkeeper-specific movements for adolescents

Reference: J Sports Med Phys Fitness. 2023 Nov 13. doi: 10.23736/S0022-4707.23.15048-1. Online ahead of print.

Authors: Yosuke Abe, Masao Nakayama, Noriteru Morita

Summary: There is a lack of objective measures and assessments of goalkeeping proficiency and performance in the literature. Furthermore, no reports have focused on adolescent goalkeepers (under the age of 15). The aim of this study was to determine the reliability and validity of the Goalkeeper Reactive Agility Test for Adolescents (GRATA). Content validity was assessed by seven experts and the Item-Content Validity Index (I-CVI) was calculated. We used similar settings to an agility test for college-aged goalkeepers, although the number of repetitions and running direction of the latter parts of the test were modified (number of repetitions: from 3 to 2; running direction: from forward to backward). Eighty-five adolescent male goalkeepers (age: 13.4 years) performed the test three times. The intraclass correlation coefficient (ICC) was used for relative reliability and the standard error of measurement (SEM) and the smallest worthwhile change (SWC) for absolute reliability. The I-CVI was 0.86, above the acceptable level of 0.78. The mean running time of the GRATA was 11.98 s. The ICC value was 0.91 (P<0.01; 95% confidence interval [95% CI]: 0.87-0.94), the SEM 0.26 s and the SWC 0.17 s.



#12 Comparable Outcomes between Bone-Patellar Tendon-Bone Autograft and Quadriceps Tendon Autograft for ACL Reconstruction in an All-Female Soccer Player Cohort with Mean 4.8-Year Follow Up

Reference: J ISAKOS. 2023 Nov 10:S2059-7754(23)00592-8. doi: 10.1016/j.jisako.2023.11.002.

Authors: Zachary J Herman, Neilen Benvegnu, Sahil Dadoo, Audrey Chang, Robert Scherer, Ehab M Nazzal, Emre Anil Özbek, Janina Kaarre, Jonathan D Hughes, Bryson P Lesniak, Dharmesh Vyas 

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Summary: The purpose is to compare functional outcomes, return to soccer rates, and revision rates in an all-female soccer player cohort undergoing quadriceps tendon (QT) autograft ACLR versus bone-patellar tendon-bone (BPTB) autograft ACLR. Female soccer players who sustained an ACL rupture and underwent primary anatomic, single-bundle ACLR with BPTB autograft or QT autograft were included. Demographic and surgical characteristics were collected. Outcomes of interest included Tegner score, International Knee Documentation Committee (IKDC) score, Marx score, return to soccer rates, and failure rates. Data on 23 patients undergoing BPTB autograft ACLR and 14 undergoing QT autograft ACLR was available. Average age was 18.7 years, and average follow up was 4.8 years. Overall, 76% (28/37) returned to soccer and 5.4% (2/37) underwent revision ACLR. No major significant differences were found in demographic or surgical characteristics. No differences were found in postoperative IKDC scores, preoperative, postoperative, or change from pre-to postoperative Marx activity scores, or pre-and postoperative Tegner scores between the groups. QT autograft ACLR patients had significantly less change in Tegner scores pre-to postoperatively compared to the BTPB autograft ACLR group (0.6 + 1.2 versus 2.1 + 1.8; p = 0.02). Both groups had similar rates of return to soccer [78% (18/23) BPTB autograft ACLR versus 71% (10/14) QT autograft ACLR; p = 0.64]. BPTB autograft ACLR and QT autograft ACLR produced comparable, successful functional and return to soccer outcomes in this all-female soccer player cohort study. Larger, prospective studies are needed to improve the strength of conclusions and provide more information on the optimal graft choice for female soccer players.



#13 The impact of crowd effects on home advantage of football matches during the COVID-19 pandemic-A systematic review

Reference: PLoS One. 2023 Nov 16;18(11):e0289899. doi:10.1371/journal.pone.0289899. eCollection 2023.

Authors: Sihang Wang, Yang Qin

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Summary: This review aimed to (1) analyze whether the home advantage was diminished; (2) investigate the impact of the crowds' support on the match outcome and team performance; (3) explore the bias of the referee without crowds. Based on the PRISMA 2020 (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines, this systematic review searched of literature was conducted in December 2022. The keywords related to soccer, COVID-19 and home advantage were used. The search returned 135 articles. After screening the records against set criteria, 28 articles were analyzed. Results showed that the absence of crowds would reduce the home advantage of teams, but the findings varied by country. Most leagues have evidence that without the support of the spectators, their technical, tactical and physical performances would be worse. The referee seems likely to be fairer when the spectators are absent. Therefore, crowd supports is an important factor affecting home advantage, the clubs can at least try to strengthen the home advantage and increase the winning possibility by encouraging spectators to enter the stadium or reducing the ticket price.



#14 Mental, physiological and medical considerations for elite football players in the Saudi Pro League: a call for action

Reference: BMJ Open Sport Exerc Med. 2023 Nov 7;9(4):e001789. doi: 10.1136/bmjsem-2023-001789. eCollection 2023.

Authors: Ismail Dergaa, Helmi Ben Saad, Abdelfatteh El Omri, Juan David Peña Duque, Mokthar Chaabane, Karim Chamari

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#15 Effects of tactical dimension and situational variables in throw-ins on the offensive performance in football

Reference: PLoS One. 2023 Nov 15;18(11):e0294317. doi: 10.1371/journal.pone.0294317. eCollection 2023.

Authors: Claudio A Casal, Vasilis Armatas, José Luis Losada, Michalis Mitrotasios

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Summary: The aim of the study was to describe the usual practices in the execution of throw-ins by La Liga teams during the 2021-2022 season, identify tactical indicators related to the outcome of plays that start with a throw-in, calculate their predictive power, and finally analyse the influence of situational variables on the effectiveness of these plays. A total of 2,658 throw-ins, during 80 matches were analysed. Two UEFA PRO coaches designed an ad hoc observation instrument "Thrinfoot" and two observers coded the data after a training process. Inter and intra-observer reliability was calculated using Cohen´s Kappa coefficient, revealing almost perfect agreement. Multinomial logistic regression was applied to predict the throw-ins outcome (p<0.05). Results showed how fast throw-ins (OR = 0.7, p<0.05), without pressing (OR = 0.4, p<0.001), short and backwards (OR = 0.3, p<0.01) in the central zone (OR = 0.6, p<0.01) and made in the 16´-30´ (OR = 0.6, p<0.01), 61´-75´ (OR = 0.7, p< 0.05) periods, presented higher probabilities of continuing with possession. Match status losing>2 (OR = 4.1, p< 0.05) showed higher probabilities of success. On the other hand, throw-ins from the defensive zone presented higher probabilities of unsuccess (OR = 8.6, p<0.01) and losing possession (OR = 1.8, p<0.01). Finally, the bottom teams showed the highest probability of losing the ball. In conclusion, tactical indicators such as duration, press, distance, direction and zone were identified as key performance indicators and the situational variables team quality, match status and time influence the outcome of throw-ins. These findings provide valuable insights to coaches regarding the factors that influence the outcome of throw-ins. This allows them to design optimal strategies for both executing and defending these plays based on the game situation and their immediate aims.



#16 #ReadyToPlay: health problems in women's football-a two-season prospective cohort study in the Norwegian premier league

Reference: Br J Sports Med. 2023 Nov 15:bjsports-2023-107141. doi: 10.1136/bjsports-2023-107141.

Authors: Roar Amundsen, Solveig Thorarinsdottir, Benjamin Clarsen, Thor Einar Andersen, Merete Møller, Roald Bahr

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Summary: The aim was to describe the prevalence, incidence and burden of all health problems in the Norwegian women's premier league. During the 2020 and 2021 seasons, players in the Norwegian women's premier league reported all health problems (sudden-onset injuries, gradual-onset injuries and illnesses) weekly, using the Oslo Sports Trauma Research Centre Questionnaire on Health Problems. Team medical staff diagnosed reported problems using the Sport Medicine Diagnostic Coding System. We calculated average weekly prevalence, incidence and burden of all health problems reported. We included 294 players (age: 22±4 years) from 11 teams. Response rate to the weekly questionnaire was 79%. On average, 32% (95% CI: 31% to 33%) of the players reported at least one health problem at any time and 22% (95% CI: 21% to 23%) reported a substantial health problem negatively affecting their training volume or performance. The overall incidence was 10.7 health problems per 1000 hours of football exposure. Sudden-onset injuries were most severe (68% of the total time loss), followed by gradual-onset injuries (25%) and illnesses (8%). Thigh was the most common injury location (26%), while knee injuries were most severe, causing 42% of the total injury time loss. Anterior cruciate ligament (ACL) injuries alone caused 30% of the total injury time loss. One in five players had a health problem negatively affecting their training volume or performance at any time. Sudden-onset injuries represented the most burdensome health problem. Thigh injuries were most frequent, while knee injuries, ACL injuries especially, were most severe.






Exposures to near-to-maximal speed running bouts during different turnarounds in elite football: association with match injuries

The present study aimed to describe the occurrence of near-to-maximal sprinting speed (near-to-MSS) running bouts during training and hamstring injuries during the consecutive match.





Sand and grass surfaces are equally effective in promoting positive adaptations in the sprint performance of elite soccer players

This study compared the effects of two sprint-jump training programmes, performed on either sand or grass surfaces, on the sprint and jump performance of elite young soccer players over an 8-week training period.





Effective playing time affects physical match performance in soccer: An analysis according to playing position

This study aimed to analyse the influence of effective playing time on physical match performance according to playing position in professional soccer.





Best distributors: Top100 worldwide

In many cases the midfield of a team plays a vital role in football competition and the quality of players might have a decisive role.


Below are the passing statistics of the top 20 out or the top 100 midfield distributors who played at least 450 domestic leagues minutes during the current season.


An index was created taking into account the number of successful passes per match, the percentage of successful passes, the ratio of passes compared to teammates, as well as the average level of matches played. 


The top three are Rodri Hernandez (Manchester City), Frankie de Jong (Barcelona) and Toni Kroos (Real Madrid). 


Bayer Leverkusen presents two members inside the top10 players, Exequiel Palacios and Granit Xhaka. 


The top-ranked players outside the European big-5 are Aschraf El Mahdioui (Al-Taawoun, 6th), Álvaro Fidalgo (CF América, 8th) and Yahya Jabrane (Wydad AC, 10th).


Three players who have not yet celebrated their 21st birthday rank in the top 100: João Neves of Benfica (34nd) and Eduardo Camavinga of Real Madrid (71th). 


Despite the index, ranking in accordance to percentage of successful passes only shows a slightly different picture.



However, three players from CF America are sitting inside the top 20, i.e. Jonathan dos Santos, Alvaro Fidalgo and Richard Sanchez are still present.







Quantification of training load across two competitive seasons in elite senior and youth footballers

This study aimed to compare the daily training load (TL) in first-team and U-18 soccer players from an English Premiership club.





Does player age influence match physical performance? A longitudinal four-season analysis in Spanish Soccer LaLiga

This study aims to analyse the evolution of match running performance in relation to the age distribution of professional soccer players using a large-scale analysis.





Latest research in football - week 46 - 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 Hamstring muscle fibre typology is not associated with hamstring strain injury history or performance in amateur male soccer players: a retrospective magnetic resonance spectroscopy study

Reference: Biol Sport. 2023 Oct;40(4):1177-1186. doi: 10.5114/biolsport.2023.126663. Epub 2023 May 31.

Authors: Joke Schuermans, Erik Witvrouw, Evi Wezenbeek, Eline Lievens

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Summary: Hamstring strain injuries (HSI) are still the most common injuries in soccer. Recent research has been focusing on the role of hamstring muscle morphology and architecture. The hamstring's fibre type composition might play a role as well, but this has never been investigated in the light of HSI risk in an athletic population. The purpose of this study was to investigate the association between hamstring muscle fibre type, hamstring strain injury history (HSIH), performance and isokinetic strength in a population of amateur male soccer players. In this cross-sectional observational study, 44 male soccer players (22 with and 22 without HSIH) participated. The research consisted of a non-invasive fibre composition evaluation using proton magnetic resonance spectroscopy (1H-MRS), functional performance (evaluated by means of maximal jumping height, maximal sprinting speed and hamstring muscle strength endurance (single leg hamstring bridge testing)), and isokinetic strength testing. The results revealed that hamstring carnosine concentration demonstrated a high inter-individual variability within this soccer population and was not significantly associated with either HSIH or with any of the functional performance parameters. The only secondary outcome measure presenting a significant association with the intramuscular carnosine content was the hamstrings' explosive strength production capacity, objectified by means of the time to peak torque (TPT), measured concentrically at an angular velocity of 240 degrees/second (°/s) during isokinetic strength testing. This TPT was significantly shorter in players presenting higher carnosine concentrations (p = 0.044). The findings indicate that in male amateur soccer players (1) the hamstrings have no distinct fibre type dominance and (2) fibre typology in this population does not relate to HSIH or performance.



#2 Match running performance characterizing the most elite soccer match-play

Reference: Biol Sport. 2023 Oct;40(4):949-958. doi: 10.5114/biolsport.2023.124847. Epub 2023 Feb 3.

Authors: Toni Modric, Sime Versic, Ryland Morgans, Damir Sekulic

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Summary: In order to identify match running performance (MRP) characterizing the most elite soccer match-play, this study aimed to examine position-specific differences in the MRP of players competing in "big five" (BFLTs) and "non-big five" league teams (N-BFLTs). The data were obtained from 24 teams (BFLTs; n = 14, N-BFLTs; n = 10) during the UEFA Champions League (UCL) matches (n = 20) in the 2020/21 season using a semiautomatic video system. The differences in MRP between BFLTs and N-BFLTs, while controlling for contextual factors, were examined using linear mixed model. No differences in overall MRP between fullbacks, central midfielders, wide midfielders and forwards from BFLTs and their peers from N-BFLTs were found, while only central defenders from BFLTs covered more high-intensity running than central defenders from BFLTs (moderate effects size). For players on all playing positions from BFLTs, total- and low-intensity distance covered were lower in offensive phase of game and greater in defensive phase of game compared to their peers from N-BFLTs (all large effect sizes). This study demonstrated that the most elite match-play in soccer is characterized by increased efforts in defensive phase of game, and decreased efforts in offensive phase of game. Soccer training programmes should be adapted accordingly.



#3 Physical qualities and body composition predictors of running performance in national level women's official soccer matches

Reference: Biol Sport. 2023 Oct;40(4):1187-1195. doi: 10.5114/biolsport.2023.118026. Epub 2022 Sep 15.

Authors: Eero H J Savolainen, Tomi Vänttinen, Johanna K Ihalainen, Simon Walker

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Summary: The purpose of the study was to (1) determine match running performance, anthropometry and various physical qualities of national level women soccer players and (2) identify key physical qualities and anthropometric predictors of match running profile during a competitive season. Twenty-five national level Finnish soccer players participated in the study. Players performed countermovement jump, loaded squat jumps, 30-meter sprint, maximum isokinetic knee flexor and extensor contractions, an incremental treadmill test and underwent body composition assessment in the lab. Match running performance was analyzed from 115 match observations during competitive league matches over 11 weeks after the laboratory tests. Pearson's correlation was used to determine bivariate relationships between match running variables and physical qualities and anthropometric variables. Identified significant bivariate relationships were then entered into multiple regression analyses to identify the best predictors of match running performance. Physical qualities and anthropometric variables predicted 65% of very high-intensity (VHIR) (> 19 km/h) and 63% of high-intensity (HIR) (13-19 km/h) running distances covered during matches, but only 22% of low-intensity (LIR) and 43% of total distances. Body fat percentage and high-speed knee flexor concentric strength were the most important predictors to VHIR and HIR while aerobic capacity-related variables were most important predictors to LIR and total distance. Physical qualities and anthropometry can predict a large portion of players' VHIR and HIR performance during matches in women's national level soccer. To increase player's VHIR and HIR distance, coaches could aim to develop players' high-speed (especially knee flexor concentric) strength and optimize player's body composition.



#4 Effective playing time affects physical match performance in soccer: An analysis according to playing position

Reference: Biol Sport. 2023 Oct;40(4):967-973. doi: 10.5114/biolsport.2023.123320. Epub 2023 Feb 3.

Authors: Stefan Altmann, Leon Forcher, Alexander Woll, Sascha Härtel

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Summary: This study aimed to analyse the influence of effective playing time on physical match performance according to playing position in professional soccer. Official match data from 267 matches (3,731 single observations) during the 2018/2019 season of the German Bundesliga were used and the effective playing time (duration of play after subtracting the time taken up by stoppages, substitutions, injuries, and goals) was captured for each match. The physical match performance parameters total distance, high-intensity distance, sprinting distance, maximum velocity, and accelerations were analysed. Players were categorized as central defender, wide defender, central defensive midfielder, central offensive midfielder, wide midfielder, and forward. Effective playing time influenced physical match performance, with total distance and accelerations (r = 0.48-0.61) being the most and high-intensity distance, sprinting distance, and maximum velocity (r = -0.17-0.03) the least affected parameters. Players covered on average 10% more total distance and performed 13% more accelerations, while sprinting 7-10% less in matches with long (> 65 min) compared to short (< 50 min) effective playing times. The influence of effective playing time was rather similar between playing positions. Still, physical performance of wide midfielders and forwards partly deviated from the pattern observed in the other positions. Coaches and practitioners should be aware that effective playing time influences physical match performance in the German Bundesliga, while special attention should be given to wide midfielders and forwards. Effective playing time and its general and position-specific effects should be taken into account when interpreting physical match performance, thereby facilitating load management practices and training design.



#5 Effects of free play or artificial rules on young soccer players' individual tactical behaviour: a one-by-one analysis

Reference: Biol Sport. 2023 Oct;40(4):1069-1078. doi: 10.5114/biolsport.2023.124845. Epub 2023 Mar 6.

Authors: Asier Gonzalez-Artetxe, Hugo Folgado, José Pino-Ortega, Markel Rico-González, Asier Los Arcos

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Summary: This study assessed the effects of playing freely and introducing artificial rules on individual tactical behaviour during the team-possession game phase in two youth soccer categories. Thirty-two developmental players from U-14 and U-16 teams participated in the study, which consisted of four identical training sessions and two test sessions performed before and after the intervention. Each team was divided into two balanced groups, free-play and conditioned, that faced each other during three eight-a-side games (Gk + 7 vs 7 + Gk) in all training sessions. The free-play groups played freely, while the conditioned ones did so constrained by artificial rules. Individual tactical behaviour was assessed during a non-constrained eight-a-side match by the distance to centroid, spatial exploration index, their entropy measures, and the regularity of each player's displacement on the length and width of the pitch using a local positioning system. In addition to the average outcomes of all the players all together, the one-by-one analysis considered the mean values of each player to appraise individual responses. While the average outcomes of all the players in both groups and categories barely changed (Cohen's d ≤ small), with a very high inter-player variability, the one-by-one analysis revealed that the training intervention affected each player's tactical behaviour differently. Introducing artificial rules decreased and raised considerably (Cohen's d ≥ moderate) in-width and exploratory regularities of most U-14 and U-16 players, respectively. Therefore, assessing the training effects of game-based interventions from the individual to the whole team may provide unique and meaningful insight regarding the tactical competence of each player.



#6 Relationships between external loads, sRPE-load, and self-reported soreness across a men's collegiate soccer season

Reference: Biol Sport. 2023 Oct;40(4):1141-1150. doi: 10.5114/biolsport.2023.125587. Epub 2023 Apr 6.

Authors: Nicholas M Kuhlman, Margaret T Jones, Andrew R Jagim, Mary Kate Feit, Richard Aziz, Thomas Crabill, Jennifer B Fields

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Summary: The purpose was to examine relationships between external loads (ELs), perceived exertion, and soreness. Collegiate men soccer players (n = 19) were monitored for 72 sessions (training: n = 53; matches: n = 19). Likert scale assessments (0-6) of lower body soreness were collected prior to each session, and ELs were collected using positional monitoring technology. Session rate of perceived exertion (sRPE-load) was calculated by multiplying perceived exertion values (Borg CR-10 Scale) by respective session duration to determine internal load. Multiple analyses of variance were used to determine differences in ELs across seasons (pre-season, in-season, post-season) and sessions (training, match). Bivariate Pearson correlation coefficients and linear regression analyses were used to evaluate relationships among soreness, ELs, and sRPE-load. Greatest ELs were observed during pre-season and post-season phases (p < 0.001). Sessions with high perceived exertion and low soreness were associated with higher ELs (p < 0.05). Duration (t = 16.13), total distance (t = 9.17), sprint distance (t = 7.54), player load (t = 4.22), top speed (t = 4.69), and acceleration (t = 2.02) positively predicted sRPE-load (F = 412.9, p < 0.001, R2 = 0.75). Soreness was weakly and trivially correlated with ELs (p < 0.05). The very strong relationship between ELs and sRPE-load highlights the utility of sRPE-load as a practical means to estimate workload; however, more research into the relationship between soreness and workload is warranted.



#7 Validity and reproducibility of match-derived ratios of selected external and internal load parameters in soccer players: A simple way to monitor physical fitness?

Reference: Biol Sport. 2023 Oct;40(4):1039-1046. doi: 10.5114/biolsport.2023.124850. Epub 2023 Mar 6.

Authors: Jan Schimpchen, Paulo Freitas Correia, Tim Meyer

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Summary: The study aim was to assess whether match-derived external-to-internal load ratios are a valid and reliable tool to measure physical fitness. Sixteen elite youth soccer players (17 ± 1 years) performed two maximal fitness tests. Subsequently, players participated in three intra-squad soccer matches in three consecutive weeks. Three GPS-based parameters of external load (total distance, PlayerLoad, high-intensity distance) were divided by three heart rate-based parameters of internal load (iTRIMP, Banister TRIMP, average percentage heart rate reserve) for the ratio calculations. Validity was established by comparing the ratios with results of the fitness tests, while between-athlete and within-athlete reliability were quantified. Most integrated load ratios were moderately-to-largely correlated with the various fitness parameters. Overall, a ratio consisting of PlayerLoad and average percentage heart rate reserve demonstrated the most consistent correlations with maximum treadmill speed (r = 0.69, P = 0.003) and the speeds associated with 4 mmol/L of blood lactate (r = 0.56, P = 0.024) and 80% of heart rate reserve (r = 0.54, P = 0.031). Most of the ratios displayed acceptable levels of reproducibility (intraclass correlation coefficient > 0.8 and coefficient of variation < 10%), with the minimal detectable change of all ratios ranging between 7.1 and 37.8%. Given their associations with physical fitness and non-invasive nature, certain external-to-internal load ratios may be used to monitor physical fitness in soccer players. However, the ratios may not be sensitive enough to detect small yet practically relevant alterations in player fitness.



#8 Quantification of training load across two competitive seasons in elite senior and youth male soccer players from an English Premiership club

Reference: Biol Sport. 2023 Oct;40(4):1197-1205. doi: 10.5114/biolsport.2023.126667. Epub 2023 Jun 12.

Authors: Ryland Morgans, Dave Rhodes, Jose Teixeira, Toni Modric, Sime Versic, Rafael Oliveira

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Summary: This study aimed to compare the daily training load (TL) in first-team and U-18 soccer players from an English Premiership club. 36 first-team (age 23.2 ± 5.9 years, weight 75.2 ± 8.1 kg, height 1.83 ± 0.06 m), and 22 U-18 players (age 17.5 ± 1.1 years, weight 71.1 ± 8.2 kg, height 1.78 ± 0.08 m) participated. GPS metrics were measured during all pitch training sessions throughout the 2020-21 and 2021-22 seasons. Linear mixed-effect model analyses revealed that, irrespective of training day, U-18 players covered greater total and explosive distance than first-team players, and performed a higher number of accelerations and decelerations, whereas first-team players covered greater sprint distance. Irrespective of the team, all examined variables were greater at match-day (MD)-3, while the number of accelerations and decelerations were higher at MD-4. Significant team-by-training day interactions revealed that U-18 players covered greater total and high-intensity distances than first-team players at MD-4, MD-2, and MD-1, whereas first-team players covered greater total and high-intensity distances at MD-3. Sprint distance was greater for first-team players at MD-3 and MD-4, while explosive distance was greater for U-18 players at MD-2. Also, U-18 players performed a higher number of accelerations than first-team players at MD-3 and MD-2, and a higher number of decelerations at MD-4. The present results provide novel information on TL patterns in English Premiership soccer and contribute to understanding how training methods to physically develop players are implemented in different countries and leagues.



#9 Different pitch configurations constrain the external and internal loads of young professional soccer players during transition games

Reference: Biol Sport. 2023 Oct;40(4):1047-1055. doi: 10.5114/biolsport.2023.124848. Epub 2023 Apr 7.

Authors: Jose A Asian-Clemente, Alberto Rabano-Muñoz, Luis Suarez-Arrones, Bernardo Requena

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Summary: The aims of this study were to compare the influence of transition game (TG) size on the external and internal loads of young professional soccer players and to describe the high-speed profile of these drills in response to pitch dimensions. Eighteen young professional soccer players (age: 16.1 ± 0.3 years; height: 178.3 ± 5.4 cm; weight: 70.1 ± 6.2 kg) performed a 3vs2 TG on pitches measuring 40 × 30 m (TG30), 40 × 50 m (TG50) and 40 × 70 m (TG70) m. Distance covered (DC); accelerations-decelerations above 1.0 m · s-2 and 2.5 m · s-2; rate of perceived exertion (RPE); maximal heart rate and time above 90%; DC at 18.0 to 21.0 km · h-1 (DC 18-20.9 km · h-1); DC at 21.0 to 23.9 km · h-1 (DC 21-23.9 km · h-1); DC above 24.0 km · h-1 (DC > 24 km · h-1); and peak speed and sprint profile (duration, distance and maximal speed) were measured. TG30 achieved lower DC, DC above 18 km · h-1, peak speed, sprint distance and RPE than TG50 and TG70 (p < 0.01 and p < 0.05) and lower sprint duration and maximal speed sprint than TG70 (p < 0.01). TG30 and TG50 achieved higher Acc > 1.0 and > 2.5 m · s-2 respectively than TG70 (p < 0.05). TG70 showed greater DC above 21 km · h-1, peak speed, sprint distance and maximal speed sprint than TG50 (p < 0.01). Soccer coaches should use larger TGs to overload variables related to high speed and sprint demands during training and smaller TG formats to stimulate the accelerations of the soccer players.



#10 Does player age influence match physical performance? A longitudinal four-season analysis in Spanish Soccer LaLiga

Reference: Biol Sport. 2023 Oct;40(4):1097-1106. doi: 10.5114/biolsport.2023.124844. Epub 2023 Mar 21.

Authors: Tomás García-Calvo, Florentino Huertas, José Carlos Ponce-Bordón, Roberto López Del Campo, Ricardo Resta, Rafael Ballester

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Summary: This study aims to analyse the evolution of match running performance in relation to the age distribution of professional soccer players using a large-scale analysis. An explorational-longitudinal and retrospective study was designed and a total of 36,883 individual match observations were collected on outfield players competing across four consecutive Spanish LaLiga seasons (from 2015/16 to 2018/19), using an optical tracking system (ChyronHego). Soccer players were divided into 3 age groups: young (18-24 years old), middle-aged (25-30 years old), and seniors (31-41 years old). Relative total distance (TD/min), distance covered at 21-24 km · h-1 (HIRD/min), and > 24 km · h-1 per minute (VHIRD/min) were analysed; also, the number of efforts at 21-24 km · h-1 (Sp21) and > 24 km · h-1 (Sp24) were taken into consideration. Seasons were divided into four phases (P): P1 (matches 1-10), P2 (11-19), P3 (20-29), and P4 (30-38). The results showed that young players covered significantly greater TD, HIRD and VHIRD than the rest of the players (p < .05) in all season phases. In addition, TD significantly decreased along season phases in all player age group (p < .01). Crucially, young players performed significantly greater numbers of Sp21 and Sp24 than the rest of the players (p < .05) in all season phases. In addition, Sp21 and SP24 significantly decreased in middle-aged (p < .01) and senior players (p < .05) across the seasons. This study demonstrated that players' match running performance decreases with increasing years, especially in high-intensity running distances.



#11 Sand and grass surfaces are equally effective in promoting positive adaptations in the sprint performance of elite young soccer players

Reference: Biol Sport. 2023 Oct;40(4):993-1001. doi: 10.5114/biolsport.2023.123324. Epub 2023 Feb 3.

Authors: Lucas A Pereira, Renan F H Nunes, Tomás T Freitas, Carlos A Paes, Juan H S Conde, Luiz F Novack, Thiago Kosloski, Rodrigo L P Silva, Paulo H S M Azevedo, Irineu Loturco

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Summary: This study compared the effects of two sprint-jump training programmes, performed on either sand or grass surfaces, on the sprint and jump performance of elite young soccer players over an 8-week training period. Fifteen under-20 soccer players were randomly allocated to the sand (n = 7) or grass (n = 8) group. Athletes performed 12 training sessions, comprising vertical and horizontal jump exercises, and linear and change-of-direction (COD) sprint drills. Pre- and post-measurements were completed in the following order: vertical jump, sprint speed at 10 m and 17 m, curve sprint (CS), and modified Zigzag COD tests. Between-group differences were determined using a two-way ANOVA with repeated measures and effect sizes (ES). No improvements in jump performance were found in either group. Significant increases were observed in the sand group for acceleration in 0-10 m and for 10- and 17-m linear sprint velocity (ES = 1.15, 1.16, and 1.81, respectively; P < 0.05). In contrast, no significant differences were detected for acceleration and linear sprint velocity in the grass group, comparing pre- and post-tests (ES ranging from 0.01 to 0.47; P > 0.05). Both sand and grass groups revealed similar increases in the CS and COD velocities after the training period (ES ranging from 0.98 to 1.93; P < 0.05). In conclusion, sprint-jump training programmes performed on both grass and sand surfaces elicited significant improvements in CS and COD performances, whereas acceleration and linear sprint velocity increased only in the sand group, after a short-term training period. The sand training surface was proven to be a practical strategy to improve sprint performance in all its forms in soccer players, which is of great interest and importance for coaches and sport scientists working in elite soccer.



#12 The Effects of Melatonin Supplementation on Professional Football Player Performance: A Systematic Review

Reference: Nutrients. 2023 Oct 21;15(20):4467. doi: 10.3390/nu15204467.

Authors: Antonio Almendros-Ruiz, Alejandro Lopez-Moro, Javier Conde-Pipò, Alfredo Santalla, Bernardo Requena, Miguel Mariscal-Arcas

Summary: Melatonin is a hormone that has shown anti-inflammatory actions, reduced oxidative stress, and has effects on physical performance, so the aim of this study was to review the effects of melatonin supplementation on the performance of professional soccer players. Critical and systematic review. Data were obtained by performing searches in the following bibliographic databases: Web of Science, MEDLINE (via PubMed), Embase, Cochrane Library, and Scopus. The terms used were "Soccer Athlete", "Melatonin", and "Soccer Performance", using "Humans" as a filter. The search update was in May 2023. Having applied the inclusion and exclusion criteria, eight articles were selected out of 59 retrieved references. The dose of melatonin administered in the studies ranged between 5 and 8 mg. The outcomes showed a decrease in oxidative stress, muscle damage, and inflammatory markers in the melatonin-treated group. Exogenously administered melatonin seems to attenuate some of the effects derived from physical exercise, such as oxidative stress, inflammation, and muscle damage, in professional football players, and since it has no potential adverse effects, it could be interesting to apply it in this population. However, the direct effects of melatonin supplementation on physical performance have not been demonstrated, so more research is needed on the intervention period and effective dose and with larger participant populations.



#13 Bone Health, Body Composition and Physiological Demands in 70-85-Year-Old Lifelong Male Football Players

Reference: Sports (Basel). 2023 Oct 18;11(10):205. doi: 10.3390/sports11100205.

Authors: Domenico Martone, Daniela Vitucci, Annamaria Mancini, Georgios Ermidis, Jeppe Panduro, Loretta Francesca Cosco, Morten Bredsgaard Randers, Malte Nejst Larsen, Magni Mohr, Pasqualina Buono, Peter Krustrup

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Summary: The effects of lifelong football training on bone health, body composition and physiological demands were evaluated. A total of 20 veteran football players (VPG; 73.4 ± 3.7 years) and 18 untrained age-matched men (CG; 75.6 ± 4.2 years) were enrolled. Whole-body and regional dual-energy X-ray absorptiometry scans of arms, legs, proximal femur and lower spine (L1-L4) were recorded in all participants. We observerd higher bone mineral density (BMD) in the whole-body, arms and femoral regions and higher bone mineral content (BMC) in the legs and lower spine compared to the CG (p < 0.05), also higher total lean body mass (p < 0.05) and lower total body fat percentage (p < 0.05), were found. No differences in food habits were evidenced between the VPG and the CG, as evaluated using 3-day food records. Resting heart rate (RHR), blood pressure (BP) and activity profile during a football match were recorded using a global positioning system only in the VPG. The mean heart rate (HR)of theoretical maximal HR (ThHRmax), and peak of ThHRmax were 83.9 ± 8.6% and 98.6 ± 10.2%, respectively; the mean of total distance covered was 3666 ± 721 m, and the means of accelerations and decelerations were 419 ± 61 and 428 ± 65, respectively. Lifelong participation in football training improves regional BMD and BMC in legs, femur and lumbar spine compared to the CG. A high number of intense actions in term of HR and accelerations and decelerations suggests an elevated energy expenditure that in turn correlates to the healthier body composition observed in the VPG compared to the CG.



#14 Retracted: Evaluation of Football Teaching Quality Based on Big Data

Reference: Comput Math Methods Med. 2023 Oct 18:2023:9782167. doi: 10.1155/2023/9782167. eCollection 2023.

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#15 The effects of simulated vision impairment on performance in football

Reference: J Sports Sci. 2023 Oct 25:1-13. doi: 10.1080/02640414.2023.2273093. Online ahead of print.

Authors: Oliver R Runswick, Alexander Rawlinson, Peter M Allen, Benjamin T Sharpe, Chris Pocock, Naomi Datson, Phil Birch, Richard Bruce, David L Mann

Summary: Footballers with vision impairment (VI) are eligible to compete in the Para sport if they meet a minimum impairment criteria (MIC) based on measures of their visual acuity (VA) and/or visual field. Despite the requirements of the International Paralympic Committee Athlete Classification Code that each sport uses an evidence-based classification system, VI football continues to use a medical-based system that lacks evidence to demonstrate the relationship between impairment and performance in the sport. The aim of this study was to systematically simulate vision loss to establish the minimum level of impairment that would affect performance in futsal. Nineteen skilled sighted players completed tests of individual technical skill and anticipation performance under six levels of simulated blur that decreased both VA and contrast sensitivity (CS). VA needed to be reduced to a level of acuity that represents worse vision than that currently used for inclusion in VI football before meaningful decreases in performance were observed. CS did not have a clear effect on football performance. These findings produce the first evidence for the minimum impairment criteria in VI football and suggest a more severe degree of impairment may be required for the MIC.



#16 Internal workload in elite female football players during the whole in-season: starters vs non-starters

Reference: Biol Sport. 2023 Oct;40(4):1107-1115. doi: 10.5114/biolsport.2023.124849. Epub 2023 Mar 7.

Authors: Blanca Romero-Moraleda, Jaime González-García, Esther Morencos, Verónica Giráldez-Costas, José María Moya, Rodrigo Ramirez-Campillo

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Summary: The aim of this study was to quantify weekly internal workload across the in-season and compare the workload variables between starter and non-starter Spanish female first league (Liga Iberdrola) football players. Twenty-six participants belonging to the same team (age, height, and mass: 25.4 ± 6.1 years, 167.4 ± 4.8 cm and 57.96 ± 6.28 kg, respectively) participated in this study. Training loads (TL) and match loads (ML) were assessed through breath-cardiovascular (RPEbreath), leg-musculature (RPEleg) and cognitive (RPEcog) rating of perceived exertion (RPE0-10) for each training session and match during the in-season phase (35 weeks). Session-RPE (sRPE) was calculated by multiplying each RPE value by session duration (minutes). From these, total weekly TL (weekly TL+ML), weekly TL, weekly ML, chronic workload, acute:chronic workload ratio, training monotony, and training strain were calculated. Linear mixed models were used to assess differences for each dependent variable, with playing time (starter vs non-starter players) used as a fixed factor, and athlete, week, and team as random factors. The results showed that total weekly TL (d = 1.23-2.04), weekly ML (d = 4.65-5.31), training monotony (d = 0.48-1.66) and training strain (d = 0.24-1.82) for RPEbreath, RPEleg and RPEcog were higher for starters in comparison with non-starters (p = 0.01). Coaches involved in elite female football should consider implementing differential sRPE monitoring strategies to optimize the weekly load distribution for starters and non-starters and to introduce compensatory strategies to equalise players' total weekly load.



#17 Exposures to near-to-maximal speed running bouts during different turnarounds in elite football: association with match hamstring injuries

Reference: Biol Sport. 2023 Oct;40(4):1057-1067. doi: 10.5114/biolsport.2023.125595. Epub 2023 Mar 6.

Authors: Martin Buchheit, Maxime Settembre, Karim Hader, Derek McHugh

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Summary: The aim was to describe the occurrence of near-to-maximal sprinting speed (near-to-MSS) running bouts during training and hamstring injuries during the consecutive match of the same turnaround in elite football (soccer). Retrospective data from 36 team-seasons (16 elite teams performing in top European leagues) were analyzed (627 players, 96 non-contact time loss match hamstring injuries). We described 1) the occurrence of > 85%, > 90% or > 95% MSS exposures during training within each turnaround and match hamstring injuries and 2) whether the above-mentioned injury occurrences differed depending on the day(s) of the turnarounds (i.e., the period separating two consecutive matches, which is generally from 3 to 8 days) when these speed exposures occurred. The longer the length of the turnarounds and the lower the speed thresholds, the greater the number (and proportion) of near-to-MSS exposures (e.g., 18%, 45% and 72% of turnarounds with > 85% runs for 3, 5 and 7-turnarounds, respectively). For half of the turnarounds examined, there were no match hamstring injuries when players were exposed to running bouts > 95% MSS during training (e.g., injury rates: 0; CI: 0-15). Injuries still occurred during 85% of the turnarounds when there were no or lower relative speed exposures (i.e., > 85 or > 90%, injury rates: 2-5, CI: 0-6). Finally, irrespective of the turnaround length, there were no match hamstring injuries when > 95% MSS exposures occurred at D-2, while in contrast, injuries still happened when players were not exposed at all, or when these exposures occurred at D-3 and/or earlier within the turnaround. While the present observational study design precludes the examination of causal relationships, the programming of > 95% MSS exposures at D-2 may help mitigate match hamstring injury occurrences in elite football.







Different pitch configurations constrain the external and internal loads of young professional soccer players during transition games

The aims of this study were to compare the influence of transition game (TG) size on the external and internal loads of young professional soccer players and to describe the high-speed profile of these drills.





Validity and reproducibility of match-derived ratios of selected load parameters: A simple way to monitor physical fitness?

The study aim was to assess whether match-derived external-to-internal load ratios are a valid and reliable tool to measure physical fitness.





Latest research in football - week 43 - 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 Training Volume and High-Speed Loads Vary Within Microcycle in Elite North American Soccer Players

Reference: J Strength Cond Res. 2023 Nov 1;37(11):2229-2234. doi: 10.1519/JSC.0000000000004522.

Authors: Ai Ishida, Garrison Draper, Matthew Wright, Jonathan Emerson, Michael H Stone

Summary: The purposes of this study were to reduce dimensionality of external training load variables and examine how the selected variables varied within microcycle in elite North American soccer players. Data were collected from 18 players during 2018-2020 in-seasons. Microcycle was categorized as 1, 2, 3, 4, 5 days before match day (MD-1, MD-2, MD-3, MD-4, and MD-5, respectively). Training load variables included total distance, average speed, maximum velocity, high-speed running distance (HSR), average HSR, HSR efforts, average HSR efforts, sprint distance, average sprint distance, sprint efforts, average sprint efforts, total PlayerLoad, and average PlayerLoad. The first principal component (PC) can explain 66.0% of the variances and be represented by "high-speed load" (e.g., HSR and sprint-related variables) with the second PC relating to "volume" (e.g., total distance and PlayerLoad) accounting for 17.9% of the variance. Average sprint distance and total distance were selected for further analysis. Average sprint distance was significantly higher at MD-3 than at MD-2 (p = 0.01, mean difference = 0.36 m•minute-1, 95% confidence intervals [CIs] = 0.07-0.65 m•minute-1) and MD-4 (p = 0.012, mean difference = 0.26 m•minute-1, 95% CIs = 0.10-0.41 m•minute-1). Total distance was significantly higher at MD-3 than at MD-1 (p < 0.001, mean difference = 1,465 m, 95% CIs = 1,003-1926 m), and MD-2 (p < 0.001, mean difference = 941 m, 95% CIs = 523-1,360 m). Principal component analysis may simplify reporting process of external training loads. Practitioners may need to choose "volume" and "high-speed load" variables. Elite North American Soccer players may accumulate higher average sprint distance at MD-3 than at other training days.



#2 Short-Term Effects of Lower-Extremity Heavy Resistance versus High-Impact Plyometric Training on Neuromuscular Functional Performance of Professional Soccer Players

Reference: Sports (Basel). 2023 Oct 4;11(10):193. doi: 10.3390/sports11100193.

Authors: Michał Boraczyński, José Magalhães, Jacek J Nowakowski, James J Laskin

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Summary: The purpose was to compare the effects of short-term 8 week heavy-resistance or plyometric training protocols (HRT or PLY) incorporated into regular soccer practice on measures of neuromuscular functional performance in professional soccer players, a single-blind randomized controlled trial was conducted. Forty-seven participants aged 22.3 ± 3.52 years were assigned to three groups: HRT (n = 15), PLY (n = 15), and control (CON; n = 17). The HRT group performed 3 sets and 10 repetitions twice a week using 80% of their baseline 1-RM (weeks 1-3), followed by 8 repetitions at 85% 1-RM (weeks 4-6), and 6 repetitions at 90% 1-RM (weeks 7-8) of 6 lower-body strength exercises with a 1 min rest period between sets. The PLY protocol involved a preparatory phase (weeks 1-2), followed by two 3-week progressive periods (weeks 3-5 and weeks 6-8). The plyometric sessions consisted of four jump exercises/drills with progressively increasing number of sets and total number of foot contacts. The rest intervals between repetitions and sets were 15 and 90 s, respectively. Outcome measures included tests assessing 10 and 30 m speed (t10m and t30m), one-repetition maximum half-back squat (1-RM squat), isokinetic peak torques for the quadriceps and hamstring muscles (Qcon and Hcon), countermovement jump (CMJ), and squat jump (SJ). Two-way ANOVA detected main effects of time and group×time interactions for all examined variables, except t30m, 1-RM, and relative 1-RM. Post hoc analyses revealed significant increases in the HRT group (t10m: 6.3%, t30m: 7.1%; absolute 1-RM: 29.6%; relative 1-RM: 30.3%, Qcon: 24.5%; Hcon: 14.4%; CMJ: 5.9%; SJ: 7.2%, all p < 0.001) and the PLY group (t10m: 3.1%; t30m: 4.1%; absolute 1-RM:19.1%; relative 1-RM: 20.3%; Qcon: 12.6%; Hcon: 8.7%; CMJ: 3.3%; SJ: 3.5%, all p < 0.001). HRT was superior compared to PLY in relative 1-RM, Qcon and Hcon (all p < 0.001). In addition, we found knee muscular strength imbalance in 70.5% of participants from the total sample (H/Q ratio < 60%). The HRT and PLY protocols resulted in improved neuromuscular functional performance compared to the regular soccer regime. This study showed that during the pre-competitive season, additional HRT and PLY drills/exercises as a substitute for standard soccer training as part of a regular 90 min practice twice a week for 8 weeks, can produce acute physical performance-enhancing effects in professional soccer players.



#3 Comparisons and associations among anthropometric indices of first and second division and assistant soccer referees

Reference: Front Psychol. 2023 Oct 10:14:1149779. doi: 10.3389/fpsyg.2023.1149779. eCollection 2023.

Authors: Meysam Rostamzadeh Samarein, Mohammad Hossein Samanipour, Foad Asjodi, Pooya Shokati, Zanyar Fallahi, Thomas E Brownlee, João Paulo Brito, Nicola Luigi Bragazzi, Rafael Oliveira

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Summary: Body composition is an important predictor of performance and a key component of health and physical fitness. Therefore, the purposes of this study were to compare soccer referees of the first and second divisions and field assistant referees from Iran and to analyze associations of a body shape index (ABSI), body adiposity index (BAI), abdominal volume index (AVI), body roundness index (BRI), conicity index (ConI), and body mass index (BMI) with body fat percentage (%BF). A total of 270 male soccer referees from the first (n = 124) and second (n = 72) divisions and assistant referees (n = 74) participated in this study. Skinfold thickness (measured at the chest, biceps, triceps, subscapular, abdominal, iliac crest, and front thigh), height, weight, hip circumference, and waist circumference were assessed to evaluate waist-to-height ratio (WHtR), %BF, and also ABSI, BRI, BAI, ConI, and AVI according to the ISAK protocol. The main results indicated differences in WHR, WHtR, ABSI, BRI, AVI, ConI, and BF% with the assistant referees presenting higher values (p < 0.05). When considering the backward selection model, there were some associations with %BF in each group, specifically BMI, BAI, and ABSI in the first division; BMI, WHR, and ABSI in the second division; and BMI in the assistant referee group (all p < 0.05). The present study did not confirm the hypothesis that the first-division referees presented better body composition-related variables than the second division or assistant referees. Instead, it showed that the assistant referees that participated in both divisions showed a tendency to higher values which suggests that the level of division is not a major factor when analyzing body composition.



#4 Average demands and most demanding passages of national-level female soccer matches: do small- and large-sided games replicate match demands?

Reference: Front Sports Act Living. 2023 Oct 11:5:1236112. doi: 10.3389/fspor.2023.1236112. eCollection 2023.

Authors: E H J Savolainen, T Vänttinen, J Peltonen, J K Ihalainen, S Walker

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Summary: This study aims to (1) determine the average and most demanding passage (MDP) load of national-level female soccer matches and (2) evaluate the relationship between average and MDP load during small-sided games (SSGs), large-sided games (LSGs), and matches. A total of 37 national-level female soccer players from a single club senior team and the U18 team participated. The average and 1-, 3-, and 5-min MDP external (total, high-speed, and very-high-speed running distances, acceleration and deceleration distances, average metabolic power, and high-metabolic load distance) and internal loads (average heart rate, rate of perceived exertion) of the 29 league matches, ten 4 vs. 4 + goalkeepers SSGs, and six 8 vs. 8 + goalkeepers LSGs were analyzed by the Polar Team Pro player tracking system. In matches, the external load variables during 1-, 3-, and 5-min MDPs were 167%-1,165%, 135%-504%, and 126%-359%, of match average values, respectively. In LSGs, all external load variables reached higher average values compared with those during matches, except for the very-high-speed running distance; however, no variable reached higher values of 1-min MDP compared with those during the matches. In SSGs, the average acceleration and deceleration distances were higher compared with those during the matches. The findings from the present study suggest that LSGs and SSGs can be used to overload the average values of the selected external load variables compared with those during the matches; however, other training options must be explored to overload 1-min match MDPs.



#5 Normative reference and cut-offs values of maximal aerobic speed-20 m shuttle run test and maximal oxygen uptake for Tunisian adolescent (elite) soccer players

Reference: Heliyon. 2023 Oct 10;9(10):e20842. doi: 10.1016/j.heliyon.2023.e20842. eCollection 2023 Oct.

Authors: Hatem Ghouili, Amel Dridi, Nejmeddine Ouerghi, Mohamed Ben Aissa, Anissa Bouassida, Noomen Guelmami, Andrew Sortwell, Luís Branquinho, Pedro Forte, Ismail Dergaa

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Summary: This study aimed to develop reference curves of aerobic parameters of 20 m shuttle run test for Tunisian soccer players. The study was conducted in the 2022/2023 pre-season. The reference curves of the maximal aerobic speed (MAS) and the maximal oxygen uptake (VO2max) were developed according to the Lambda, Mu and Sigma (LMS) method, using data from 742 Tunisian premier league soccer players aged 11-18 years. Measured variables included: weight, height, body mass index and maximal heart rate (HRmax). HRmax was measured when the participants completed the maximal aerobic speed. VO2max was estimated using the 20 m shuttle run test protocol (speed increment every minute). Our results presented the smoothed percentiles (3rd, 10th, 25th, 50th, 75th, 90th and 97th) of MAS (km/h) and VO2max (ml/kg•min⁻1) according to age. In addition, raw data showed that VO2 max was positively correlated with age (r = 0.333; P < 0.001), height (cm) (r = 0.279; P < 0.001), weight (kg) (r = 0.266; P < 0.001), practice period (years) (r = 0.324; P < 0.001) and BMI (kg/m2) (r = 0.10; P < 0.05). However, it was negatively correlated to HRmax (bpm) (r = -0.247; P < 0.001). Only the measurements within the age group [12-12.99] are significantly higher (p < 0.001; ES = 0.63) compared with the previous age group [11-11.99]. Finally, regarding prevalence, our findings showed that 15.5 % of the players in our sample had VO2max values above the 87.7th percentile cut-off, while only 0.3 % exceeded the 99.18th percentile. The development of normative curves could help coaches and physical trainers to more accurately detect weaknesses in the aerobic performance of their players in order to sustain high-intensity repetitive actions during a soccer match.



#6 Data Analysis of Psychological Approaches to Soccer Research: Using LDA Topic Modeling

Reference: Behav Sci (Basel). 2023 Sep 22;13(10):787. doi: 10.3390/bs13100787.

Authors: Jea Woog Lee, Doug Hyun Han

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Summary: This study identifies the topical areas of research that have attempted a psychological approach to soccer research over the last 33 years (1990-2022) and explored the growth and stagnation of the topic as well as research contributions to soccer development. Data were obtained from 1863 papers from the Web of Science database. The data were collected through keyword text mining and data preprocessing to determine the keywords needed for analysis. Based on the keywords, latent Dirichlet allocation-based topic modeling analysis was performed to analyze the topic distribution of papers and explore research trends by topic area. The topic modeling process included four topic area and fifty topics. The "Coaching Essentials in Football" topic area had the highest frequency, but it was not statistically identified as a trend. However, coaching, including training, is expected to continue to be an important research topic, as it is a key requirement for success in the highly competitive elite football world. Interest in the research field of "Psychological Skills for Performance Development" has waned in recent years. This may be due to the predominance of other subject areas rather than a lack of interest. Various high-tech interventions and problem-solving attempts are being made in this field, providing opportunities for qualitative and quantitative expansion. "Motivation, cognition, and emotion" is a largely underrated subject area in soccer psychology. This could be because survey-based psychological evaluation attempts have decreased as the importance of rapid field application has been emphasized in recent soccer-related studies. However, measuring psychological factors contributes to the study of football psychology through a new methodology and theoretical background. Recognizing the important role of psychological factors in player performance and mental management, as well as presenting new research directions and approaches that can be directly applied to the field, will advance soccer psychology research.



#7 Artificial Turf Increases the Physical Demand of Soccer by Heightening Match Running Performance Compared with Natural Grass

Reference: J Strength Cond Res. 2023 Nov 1;37(11):2222-2228. doi: 10.1519/JSC.0000000000004539.

Authors: Toni Modric, Michael Esco, Sandro Perkovic, Zlatko Basic, Sime Versic, Ryland Morgans, Damir Sekulic

Summary: This study aimed to determine differences in match running performance (MRP) of elite soccer players (n = 31) during matches played on artificial turf (AT) and natural grass (NG). The players' MRP (AT; 131 observations, NG; 135 observations) were collected during official matches (n = 32) using global positioning system and classified according to their playing positions as central defenders, central midfielders, fullbacks, forwards, and wingers. The MRP variables included total distance covered (TD), low-intensity running (LIR), moderate-intensity running (MIR), high-intensity running (HIR), total (Tacc) and high-intensity accelerations (Hacc), and total (Tdec) and high-intensity decelerations (Hdec). The influence of match outcome, location, and opponent quality was controlled for as contextual factors. Playing matches on AT resulted in (a) increased TD (Cohen's d (d) = 0.55, 0.61, and 0.28, respectively), MIR (d = 0.91, 0.79, and 0.49, respectively), and HIR (d = 0.67, 0.44, and 0.38, respectively) for central defenders, central midfielders, fullbacks; (b) increased Tacc (d = 0.38, 0.37, and 0.4, respectively) and Tdec (d = 0.31, 0.34, and 0.31, respectively) for central defenders, central midfielders, and wingers; and (c) decreased Hdec (d = -1.5) for forwards. These results show that playing on AT is more physically demanding for defensive and midfield players than playing on NG. Soccer coaches should consider implementing preparatory strategies that mitigate the increased demands of playing on AT for these players, especially before a competitive period when transitions between pitch surfaces routinely occur.



#8 Application of a Custom Device to Measure Isometric Knee Strength: Possible Injury Correlation in Professional Soccer (Football) Players

Reference: J Funct Morphol Kinesiol. 2023 Oct 5;8(4):141. doi: 10.3390/jfmk8040141.

Authors: Paolo Cigni, Tommaso Minuti, Andrea Mannini, Alessandro Cucini, Michele Costagli, Stefano Rapetti, Luca Alimonta, Erika Cione, Roberto Cannataro, Leonardo Ricotti

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Summary: Injury in sports is an occurrence that prevents athletes from participating in training and competitions and has an incidence of 8.1 injuries/1000 h of practice. This translates into a cost and also into danger, especially if the event is repeated, for the health of the athlete; the injury certainly has a multifactorial causality. On the other hand, having instruments that can represent an alarm could be helpful for those involved in sports science. We used a specifically designed instrument, presented in a previous work, which shows excellent reliability and repeatability in measuring the strength of the knee flexors and extensors to test 107 players belonging to three different teams playing in the Italian Serie A. We took three measurements, beginning of the season, mid-season, and close to the end of the season. This retrospective study on 107 professional soccer players demonstrates that isometric force-related parameters of the knee extensors and flexors are associated with the risk of injury to lower limbs. Logistic regression evidenced a significant correlation between the parameter indicating the imbalance of the force between the flexors of the two limbs (p≤0.05, OR = 1.089) and the occurrence of injuries. Survival analyses (p≤0.001) evidenced a correlation between the population survival time and the injury incidence. We demonstrated that the analysis of the strength imbalance is correlated with injury occurrence, but it is well known that sports injuries are a multifactorial event; so, they cannot be predicted by only one parameter. However, the method proposed in this paper could represent a useful tool for sport scientists.



#9 The Reliability of Linear Speed with and without Ball Possession of Pubertal Soccer Players

Reference: J Funct Morphol Kinesiol. 2023 Oct 16;8(4):147. doi: 10.3390/jfmk8040147.

Authors: Nikolaos Manouras, Christos Batatolis, Panagiotis Ioakimidis, Konstantina Karatrantou, Vassilis Gerodimos

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Summary: Reliable fitness tests with low day-to-day and trial-to-trial variation are a prerequisite for tracking a player's performance or for identifying meaningful changes in training interventions. The present study examined the inter- and intra-session reliability of 30 m linear speed with and without ball possession as well as the reliability of a specific performance index of pubertal soccer players. A total of 40 pubertal (14.87 ± 1.23 years old) male soccer players performed two testing sessions (test-retest) separated by 72 h. Both testing sessions included a protocol consisting of two maximal trials of 30 m linear speed with and without ball possession. A performance index, indicating the difference between the two speed tests, was also calculated using two different equations (delta value and percentage value). The relative and absolute inter-session reliabilities were good/high for all testing variables (ICC = 0.957-0.995; SEM% = 0.62-8.83). There were also good/high relative and absolute intra-session reliabilities observed for all testing variables (ICC = 0.974-0.987; SEM% = 1.26-6.70%). According to the Bland-Altman plots, the differences between test-retest and trials for all observations were within the defined 95% limits of agreement. The reliable testing protocols and performance index for the evaluation of linear speed with and without ball possession, observed in this study, may be used in speed monitoring and training planning of pubertal soccer players.



#10 Action-Evaluator: A Visualization Approach for Player Action Evaluation in Soccer

Reference: IEEE Trans Vis Comput Graph. 2023 Oct 25:PP. doi: 10.1109/TVCG.2023.3326524.

Authors: Anqi Cao, Xiao Xie, Mingxu Zhou, Hui Zhang, Mingliang Xu, Yingcai Wu

Summary: In soccer, player action evaluation provides a fine-grained method to analyze player performance and plays an important role in improving winning chances in future matches. However, previous studies on action evaluation only provide a score for each action, and hardly support inspecting and comparing player actions integrated with complex match context information such as team tactics and player locations. In this work, we collaborate with soccer analysts and coaches to characterize the domain problems of evaluating player performance based on action scores. We design a tailored visualization of soccer player actions that places the action choice together with the tactic it belongs to as well as the player locations in the same view. Based on the design, we introduce a visual analytics system, Action-Evaluator, to facilitate a comprehensive player action evaluation through player navigation, action investigation, and action explanation. With the system, analysts can find players to be analyzed efficiently, learn how they performed under various match situations, and obtain valuable insights to improve their action choices. The usefulness and effectiveness of this work are demonstrated by two case studies on a real-world dataset and an expert interview.



#11 Contemporary reflection on the educational levels of high-performance soccer players in Brazil

Reference: Einstein (Sao Paulo). 2023 Oct 23:21:eAO0269. doi: 10.31744/einstein_journal/2023AO0269. eCollection 2023.

Authors: Paulo Roberto Santos-Silva, Júlia Maria D Andrea Greve, Renato Luis da Silva, Marcelo Mesquita Spinola

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Summary:  Santos-Silva et al. demonstrated that, for Brazilian soccer players, pursuing higher education is still a distant reality. This is because, in relative numbers, only 2.5% of the athletes have completed elementary school, whereas 67% and 5.5% completed high school and higher education, respectively. The mean initial professionalization age is 17.5 years, indicating that soccer players take on a crucial responsibility in a very early stage of life. However, they are still immature in terms of dealing with money,contractual relations with the club, and decision-making. Only 5.5% of Brazilian soccer players surveyed completed higher education. Of these 179 athletes, 67% completed high school. The most educated were goalkeepers and defenders at 37% (66/179). Physical education for sports is different from educating the mind in terms of brain plasticity. As the soccer culture in Brazil is more popular than schooling, this study reflected on the formal education levels of soccer (football) players through descriptive and quantitative analyses. We evaluated 179 national soccer players playing various positions on different teams across six seasons (2012, 2013, 2014, 2015, 2016, and 2022). Data were collected using a questionnaire comprising the following variables: age, position in the pitch, age of professionalization, and education (years of study). The data were distributed according to the pitch position. The mean age, length of professional career, and professionalization age were 23±6 years, 7±5 years, and 17±2 years, respectively. In terms of education, 121 athletes (67%) completed high school, equivalent to 11 years of study. Only 5.5% completed higher education, with defensive players (goalkeepers and defenders) being the most educated at 37% (66/179). According to 2017 figures from the Pesquisa Nacional por Amostra de Domicílios Contínua of the Federal Government of Brazil, the schooling rate is 31.7%, wherein 46.1% of Brazilians aged 25 years or over have completed education. In this study of 179 athletes, 67% had completed high school. Thus, players outrank the Brazilian population in terms of achieving a high school education. There were marked disparities in the relative proportions of goalkeepers (85%), defensive players (68%), midfielders (63%), and forward players (64%) in terms of their education. Our survey revealed that attending higher education remains a distant reality in Brazil.



#12 Sports, health, and banking: soccer in the lives of bank workers in São Paulo, 1929-1932

Reference: Hist Cienc Saude Manguinhos. 2023 Oct 23:30:e2023054. doi: 10.1590/S0104-59702023000100054. eCollection 2023. [Article in Portuguese]

Authors: Gabriela Marta Marques de Oliveira, Edivaldo Góis Junior

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Summary: This study investigates how soccer was part of the lives of bank workers in the city of São Paulo between 1929 and 1932, looking at who these workers were and the meaning they attributed to sports in the Banking Athletic Sports League (Liga Bancária de Esportes Atléticos). Sources included reports, documents, and publications of the São Paulo State Bank Employees' Association. Reflections on "class" and "class culture," the concept of "experience," and the notion of "middle class" were all utilized in analyzing the sources, and revealed variations in representations of sports and soccer among these employees.



#13 Soccer's Transition

Reference: Sports Health. 2023 Nov-Dec;15(6):779-780. doi: 10.1177/19417381231204483.

Authors: Edward M Wojtys

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#14 Association between sports expertise and visual attention in male and female soccer players

Reference: PeerJ. 2023 Oct 19:11:e16286. doi: 10.7717/peerj.16286. eCollection 2023.

Authors: Peng Jin, Zheqi Ji, Tianyi Wang, Xiaomin Zhu

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Summary: Visual attention plays a crucial role in daily living and in sports, affecting an athlete's performance and thus, potentially, the outcome of a match. However, studies assessing the association between the level of sports expertise and visual attention have yielded mixed results. This study was conducted to examine whether visual attention could be developed with increased sports expertise, and whether visual attention differed between male athletes and female athletes. A total of 128 participants were included in this study: 64 first-level national soccer athletes recruited from college soccer teams (considered elite athletes; 32 men and 32 women with similar soccer performance requirements and training experience), and 64 physical education college students with limited soccer experience (considered novice athletes; 32 men and 32 women with matched soccer experience). To assess visual attention, we used a multiple object tracking (MOT) task with four targets among a total of 10 objects moving at a fixed speed of 10°/s in random directions across a computer monitor screen. Tracking accuracy on the MOT task was calculated for each participant as the proportion of correctly selected targets. A univariate analysis of variance was performed, with group (expert, novice) and sex (male, female) as independent variables, and tracking accuracy on the MOT task as the dependent variable to assess whether sports expertise or sex influenced visual attention. Simple effects tests followed by comparisons with Bonferroni corrections were used, and effect size calculations were performed using Cohen's f statistic. Tracking accuracy on the MOT task was significantly affected by sports expertise (F(1,124) = 91.732, p < 0.001, ηP2 = 0.425), with accuracy among expert soccer athletes superior to that among novice soccer athletes. Moreover, a statistically significant interaction between sports expertise and sex was detected (F(1,124) = 7.046, p = 0.009, η P2= 0.054). Better tracking performance was observed for male soccer players (mean [SD], 0.39 [0.12]) than for female soccer players (mean [SD], 0.27 [0.08]); p < 0.01; d=1.17; r = 0.51) but only in the novice group. No significant sex difference was detected in tracking performance between elite male soccer athletes (mean [SD], 0.51 [0.09]) and elite female soccer athletes (mean [SD], 0.49 [0.11]). These findings confirm previous results indicating that long-term extensive sports training develops visual attention as assessed by MOT performance and extend previous findings to include soccer athletes. The findings of a sex difference in visual attention among novice soccer players but not among elite soccer athletes who had similar performance requirements and training experience suggest that long-term extensive training may minimize the sex difference in visual attention.







Short-Term Effects of Heavy Resistance versus High-Impact Plyometric Training on Neuromuscular Performance of Professional Soccer Players

The aims of this study was To compare the effects of short-term 8 week heavy-resistance or plyometric training protocols (HRT or PLY) incorporated into regular soccer practice on measures of neuromuscular functional performance in professional soccer players, a single-blind randomized controlled trial was conducted.





Hamstring muscle fibre typology is not associated with hamstring strain injury history or performance in male soccer players

The purpose of this study was to investigate the association between hamstring muscle fibre type, hamstring strain injury history (HSIH), performance and isokinetic strength in a population of amateur male soccer players.





Latest research in football - week 42 - 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 Return-to-performance in elite soccer players after Achilles tendon ruptures: a study using a weighted plus/minus metric and matched-control analysis

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Oct 18.  doi: 10.1007/s00167-023-07607-5.

Authors: Pedro Diniz, Diogo Lacerda, Bruno Mendes, Hélder Pereira, Frederico Castelo Ferreira, Gino M M J Kerkhoffs

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Reference: Studies have shown decreased match participation and shortened careers in athletes suffering Achilles tendon ruptures (ATRs), but assessment using a true performance metric is lacking. Plus/minus (PM) metrics provide a practical and objective approach to player performance assessment and are commonly used in other sports. This study aimed to quantify and compare individual player performance variations in elite football league players who sustained ATRs and returned to play within 1 year compared to those without ATRs, using a PM metric. Player and team data were sourced from Male players sustaining ATRs between 2007 and 2018 were identified through injury reports. A control group (CTRL) was matched by position, age, height, and league, with a 6:1 ratio of controls to ATR subjects. The day of injury was considered "time zero". Year -1 corresponds to the 360 days preceding injury, and Year 1 to the interval between 360 and 720 days after. Performance in the player's main team was evaluated using a previously validated weighted PM metric. Only data from Year -1 and Year 1 were used for ATR versus CTRL group comparisons. Statistical significance was set at p < 0.05. The ATR group included 125 athletes. Data from more than 76,000 matches were analyzed. No statistically significant differences in net weighted PM metric between Year -1 and Year 1 were found. No differences were found between athletes suffering from ATRs and controls regarding the weighted PM metric.



#2 Relative match load in young professional soccer players during Soccer-7 and Soccer-11

Reference: Int J Sports Med. 2023 Oct 16. doi: 10.1055/a-2192-8704. Online ahead of print.

Authors: Alberto Rabano-Munoz, Luis Suarez-Arrones, Bernardo Requena, Jose Asian-Clemente

Summary: The aim of this study was to analyze the differences in internal and external load during Soccer-7 and Soccer-11, comparing positional requirements and neuromuscular fatigue in both modalities. Twenty-four young soccer players were monitored in Soccer-7 and Soccer-11 matches using global positioning systems. Total distance covered (TD), distance covered at high speed (HSR), distance covered at very high speed (VHSR), peak speed, accelerations and decelerations (Acc and Dec) and rate of perceived exertion (RPE) were recorded differentiating between central backs (CB), midfielders (MF), external players (EX) and forwards (FW). Neuromuscular fatigue were assessed using a jump test. During Soccer-11, players showed significantly higher TD, HSR and VHSR, with low Acc and greater RPE compared with Soccer-7. During Soccer-11, all positions recorded significantly greater TD, distance at HSR and at VHSR than Soccer-7. In terms of playing position, CB, MF and FW achieved significantly higher Peak Speed during Soccer-1, but there was no difference for EX. During Soccer-7 all positions performed significantly higher numbers of Acc. Although the Soccer-7 modality is considered an optimal format for the development of young soccer players, there is a significant difference in match running activity for all playing positions with respect to the Soccer-11 format.



#3 Surveying the youth-to-senior transition landscape in Major league Soccer: a new frontier

Reference: Sci Med Footb. 2023 Oct 20. doi: 10.1080/24733938.2023.2272605. Online ahead of print.

Authors: Patrick Mannix, Simon J Roberts, Kevin Enright, Martin Littlewood

Summary: The aim of this study was to survey Major League Soccer stakeholders' attitudes and perspectives on the youth-to-senior transition with a particular interest in the league's evolving club structures, specifically the reserve team and youth academy entities. The survey assessed various stakeholders' views on clubs' organisational aims and structure, the capabilities of club entities to prepare players for the first team, and the transition process to the first team within MLS. A total of 80 participants working in various 'player operation' roles for MLS clubs in the United States and Canada voluntarily completed the online survey. The predominant aim for both reserve teams and academies in MLS are to develop players for the first team. The organisational structure and governance of reserve teams are varied across the league, but an overarching feature is their function as a development team. When players are transitioning, communication between staff may or may not be clear and effective. Finally, for players within an MLS club's talent pathway, a variety of support strategies are made available during the transition into the first team, but psychological support in particular may be limited or unavailable. Similar to European soccer, the aim of MLS reserve teams and youth academies is to develop first team players for the club. Though, while players are transitioning into the first team, communication may or may not be clear and effective, and psychological support may be absent, which may impair player development initiatives.



#4 Temporal changes in intensity and volume of external training loads during a 1 × 1 short-bout, small-sided games in elite youth soccer players

Reference: Sci Rep. 2023 Oct 19;13(1):17892. doi: 10.1038/s41598-023-45277-y.

Authors: Jakub Kryściak, Maciej Tomczak, Tomasz Podgórski, Paweł Chmura, Marek Konefał, Jan Chmura, Tomas Maly, Toni Modric, Marcin Andrzejewski

Summary: This study compared external training load (ETL) and its temporal changes across repetitions during a speed endurance production (SEP) training comprised of 1 × 1 short-bout, small-sided games (SSGs) in elite youth soccer players. Twenty U18 players were divided into two groups (SEP1 and SEP2) performing six 30 s and 45 s bouts of SSG (work-to-rest ratio 1:4) on a 10 by 15 m field. ETL was characterized by the total distance covered, Player Load, the total number of accelerations/decelerations, and their relative values (per minute). Significant overall decreases in the ETL parameter values across six repetitions in both SSG groups were observed relative to the measurement in the first set beginning in 3rd (SEP1) or 4th (SEP2) repetitions. Significant greater decreases in Player Load (F(5.90) = 2.99, p < 0.05, η P2 = 0.14), Player Load per minute (F(5,90) = 11.32, p < 0.001, η P2 = 0.39), total distance per minute (F(3.43,61.73) = 7.72, p < 0.001, η P2 = 0.30) and accelerations per minute (F(5,90) = 2.59, p < 0.05, η P2 = 0.13) were observed in the 30-s games than in the 45-s games. In conclusion, the use of SSGs in SEP training is associated with a decrease in the effectiveness of physical work performed across repetitions. In practice, due to the decrease in the measured ETL indicators already in the 3rd or 4th repetition (especially in the SEP1 group), the work-to-rest ratio could be increased from the applied 1:4 to 1:6.



#5 Testing the peak running speed in analytical and contextual-based scenarios: Applied research in young adult soccer players

Reference: J Sports Sci. 2023 Oct 19:1-11. doi: 10.1080/02640414.2023.2273085. Online ahead of print.

Authors: Filipe Manuel Clemente, Zeki Akyildiz, Joel Garrett, Marco Beato, Mehmet Yildiz, Sabri Birlik, Jason Moran

Summary: The primary aim was to compare the peak running speed (PRS) attained in the 40-m linear sprint test, in an analytical-based soccer drill, in the 5-0-5 test, and a training match scenario. The secondary aim of the study was to evaluate the differences between the three assessment sessions and identify how the tests can vary from session to session. Additionally, we aimed to investigate the within-test variability to understand how consistent the performance is within each test format across the different sessions. Forty male under-19 players competing at the national level participated in this study. A training session was observed for each of the three study weeks in which the following tests/scenarios were monitored using a GPS. The 40-m linear sprint test and the analytical-based soccer drill presented the smallest within-subject coefficients of variation between the sessions. A large correlation (r = 0.742) was found between the PRS during the 40-m linear sprint test and the analytical-based soccer drill. The 40-m linear sprint test was the best method of those examined for measuring PRS. The analytical drill provides a reliable method for measuring PRS, although it differs from the 40-metre linear sprint test.



#6 Match-Play External Load and Internal Load in NCAA Division II Women's Soccer

Reference: J Strength Cond Res. 2023 Oct 16. doi: 10.1519/JSC.0000000000004578. Online ahead of print.

Authors: Erin E Choice, James J Tufano, Kristen L Jagger, Kristen C Cochrane-Snyman

Summary: The purpose of this study was to describe average match-play demands for NCAA DII women's soccer, including positional and time-specific differences, and relationships between variables. External load was assessed using total distance, relative distance, sprint distance, number of power plays, peak speed, and Player Load. Internal load was assessed using session rating of perceived exertion (sRPE). Mixed factor analysis of variance was used to assess time by position (midfielder, forward, or defender) for dependent measures. Correlations were assessed between separate pair groups. Average match-play demands included 9,463 ± 2,591 m total distance, 172 ± 48 m·min-1 relative distance, 531 ± 301 m sprint distance, peak speeds of 26 ± 1.6 kph, 46.71 ± 21.75 power plays, and 457.84 ± 121.78 AU Player Load. Significant (p < 0.05) positional differences were found for total distance, Player Load, match load, and peak speed. Significant, moderate correlations were found between relative distance and match load, and sRPE and total distance, Player Load, and power plays (all p < 0.001). Results indicate there are positional differences within a women's DII soccer team, with midfielders accumulating the longest distances (10,509 ± 2,913 m) and greatest Player Load (527.79 ± 130.5 AU) and match load (576 ± 343 AU), forwards running the fastest peak speeds (26.8 ± 1.5 kph), and defenders maintaining most consistent performance. Match-play external and internal load data should be monitored by player position and half for DII women's soccer.



#7 Diet diversity and food quality score in male football players and healthy non-athlete controls in relation to oxidative stress biomarkers: a descriptive-analytical study

Reference: BMC Sports Sci Med Rehabil. 2023 Oct 20;15(1):136. doi: 10.1186/s13102-023-00748-7.

Authors: Mahsa Zare, Maede Makhtoomi, Fatemeh Mansouri, Mehran Nouri, Parvin Sarbakhsh, Mohammad Hasan Eftekhari, Bahram Pourghassem Gargari, Zainab Shateri

Summary: Dietary patterns that include high-quality and varied food groups have the potential to modulate oxidative status. This research was conducted to determine dietary diversity score (DDS) and food quality score (FQS) in football players and their matched non-athletes, also their associations with oxidative indicators assessed by the urinary levels of F2alpha-isoprostane (F2a-IP) and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Participants consisted of 45 male football players and 45 male non-athletes in two age-and body mass index (BMI)-matched groups from Shiraz City, Iran. Anthropometric measurements were performed, and urine samples were analyzed to determine oxidative biomarkers. Dietary data derived from a reliable food frequency questionnaire with 168 items was completed to determine DDS and FQS. For data analysis, an appropriate generalized estimating equation model was set up. Our results demonstrated that FQS (β = 5.46; P < 0.001) and DDS (β = 1.30; P < 0.001) scores were significantly higher in the footballers in comparison to the non-athletes. Moreover, FQS was negatively associated with 8-OHdG (β=-0.35; P = 0.008) and F2a-IP (β=-4.30; P = 0.01) levels in all participants. In addition, DDS was inversely related to 8-OHdG (β=-1.25; P = 0.01) and F2a-IP (β=-11.67; P = 0.04) levels in all participants. Food quality scores and dietary diversity of footballers' diets were found to be higher in comparison to the non-athletes. Furthermore, a higher FQS and DDS were associated with lower levels of oxidative biomarkers in all participants.



#8 Differences in playing style and technical performance according to the team ranking in the Spanish football LaLiga. A thirteen seasons study

Reference: PLoS One. 2023 Oct 20;18(10):e0293095. doi: 10.1371/journal.pone.0293095. eCollection 2023.

Authors: Joaquín González-Rodenas, Jordi Ferrandis, Víctor Moreno-Pérez, Roberto López-Del Campo, Ricardo Resta, Juan Del Coso

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Summary: This study aimed to explore the differences in playing style and technical performance according to the ranking level in Spanish football teams. The sample comprised 38 professional teams that competed in LaLiga from 2008/09 to 2020/21, with a total of 4940 matches. The teams were grouped by their final ranking position: Champion (1st); Champions League (2nd-4th); Europa League (5th-6th); middle teams (7th-17th); and relegated teams (18th-20th). Linear mixed models were used to examine the effects of the team ranking on variables related to playing style and technical performance. The F2 statistic was calculated as effect size (ES). Regarding the style of play, the Champion teams initiated offensive sequences from a more advanced field position than the remaining ranking groups with a descending effect as the ranking position decreased (p < 0.001; ES = medium). The sequence duration and passes per sequence showed a decreasing effect across ranking groups (both p < 0.001; ES = small). In contrast, the direct speed showed an increasing effect as the ranking position decreased (p < 0.001; ES = small). A decreasing effect was observed in the number of sequences ending in the final third as the ranking position decreased (p < 0.001; ES = large) while no effect was found for the sequences ending in a shot. There was a reduction effect in ball possession, passing accuracy, through balls and crosses as the teams' ranking decreased (all p < 0.001; ES = small-to-large). In summary, higher-ranked teams had an advanced starting position, longer offensive sequences, slower progression speed, more ball possession, higher passing accuracy, and more crosses and through balls than lower-ranked teams. Football coaches should consider that adopting a playing style focused on regaining the ball possession in advanced field zones and using long passing sequences can be an effective tactical strategy to improve the teams' ranking during the season.



#9 Complete Distal Rupture of the Rectus Femoris in an Elite Football Player: A Non-operative Treatment

Reference: Cureus. 2023 Sep 18;15(9):e45494. doi: 10.7759/cureus.45494. eCollection 2023 Sep.

Authors: Alexandre Fernandes, Julio Pinto, Pedro Cunha, Carlos Duarte, Alexandre Estaca, Tiago Pereira, Mónica Bettencourt, Isabel Candelária, Miguel Reis E Silva

Summary: Although muscle injuries represent the most frequent injury in professional football, isolated complete distal ruptures of the rectus femoris (RF) muscle are rare, and there is no consensus on their treatment and return to play (RTP). In this article, we report a clinical case of successful non-surgical management of an RF grade 4c muscle injury in a professional football player, in which the athlete was able to RTP 21 weeks after the injury, had no re-injury >1 year after RTP, and is playing at an elite level in the Portuguese Football First League.



#10 Depression and anxiety-related disorders and suicide among Swedish male elite football players: a nationwide cohort study

Reference: Br J Sports Med. 2023 Oct 19:bjsports-2023-107286. doi: 10.1136/bjsports-2023-107286.

Authors: Manzur Kader, Björn Pasternak, Carl-Emil Lim, Martin Neovius, Magnus Forssblad, Henrik Svanström, Jonas F Ludvigsson, Peter Ueda

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Summary: The aim was to assess whether male elite football players, during and after their active career, were at increased risk of depression and anxiety-related disorders and suicide, as compared with the general male population. We included male football players active in the Swedish top division 1924-2019 and general male population (matched to football players based on age and region of residence) aged <65 years in 1997. Using nationwide registers, we followed the football players from their first season in the top division (or the date of their first registered residency in Sweden) or 1 January 1997, and compared the risk of depression and anxiety-related disorders (captured through diagnoses from hospital admissions and outpatient visits, and use of prescription drugs) among football players versus controls. In a secondary analysis using data from death certificates, we compared the risk of suicide between football players and general population males who were alive in 1969 (when cause of death became available) . During follow-up through 31 December 2020, 504 (13.6%) of 3719 football players and 7455 (22.3%) of 33 425 general population males had a depression or anxiety-related disorder. In analyses accounting for age, region of residence and calendar time, the risk of anxiety and depression-related disorders was lower among football players versus general population males (HR 0.61, 95% CI 0.55 to 0.66). The protective association was attenuated with increasing age, and from around age 70 years the risk was similar in the two groups. The risk of suicide was lower among football players versus general population males (HR 0.48, 95% CI 0.32 to 0.72). In this nationwide cohort study in Sweden, elite male football players had a lower risk of depression and anxiety-related disorders and suicide as compared with the general population.



#11 Survey of the current practices of German football academies towards biological maturation assessment

Reference: Sci Med Footb. 2023 Oct 15. doi: 10.1080/24733938.2023.2270563. Online ahead of print.

Authors: Lukas Arenas, Monika Frenger, Sabrina Skorski, Tim Meyer

Summary: This study aimed to examine the importance assigned to assessing and considering biological maturation in thematic areas of player development and provide an overview of current practices in German football academies regarding its consideration in training and competition. An online survey was sent to 56 elite German football academies. A total of 46 responded to the questionnaire (82% response rate). Six participants provided incomplete information resulting in a total of 40 completed surveys in the period from March to May 2022. Only 20 of participants regularly carried out maturation assessments, despite 95% recognizing its importance for load management, 90% for player development, and 85% for injury prevention. There was no consistent approach to modifying training and competition formats based on maturity status, with a primary focus on gym-based sessions for load management. The survey results highlight limited implementation of maturation assessment and training modification based on maturity status in German elite youth football academies. Despite recognizing the importance of load monitoring, reporting to parents, and long-term player development in considering biological maturation, practices are not widespread. The predominant use of the maturity offset method suggests an opportunity to improve accuracy by exploring alternative measurement methods and increasing assessment frequency. Moreover, a lack of established procedures for incorporating maturity status into training and competition exists, hindering comprehensive consideration of biological maturation and injury risk prevention. Further research is needed to understand the reasons for inconsistent approaches in maturation assessment and load modification during training and competition.



#12 Room for Improvement in Sports Nutrition Knowledge amongst Parents and Caregivers of Male Academy Soccer Players in the UK: A Cross-Sectional Study

Reference: Nutrients. 2023 Oct 11;15(20):4331. doi: 10.3390/nu15204331.

Authors: Luke Callis, Mark Russell, Howard Hurst, Jack Hardwicke, Charlie Jon Roberts

Summary: In professional soccer clubs in the UK, nutrition support is often polarised towards senior players or those in the senior academy age groups seeking first team selection/involvement. Accordingly, there is an increased reliance on parents and caregivers to provide support regarding nutritional intake. Therefore, the aim of this study was to evaluate the quality of nutrition knowledge of parents and caregivers of male youth soccer players within developmental academies in the UK. Across a single competitive season, 360 registered parents and caregivers of male soccer players from English Premier League under 9-11 (Foundation Phase) and under 12-16 (Youth Development Phase) age group academies completed an online version of the 88-item validated Nutrition for Sport Knowledge Questionnaire. Nutrition knowledge scores were classified as "poor" (43 ± 23%). Nutrition knowledge scores were significantly greater in respondents with dependents representing Category 1 (45 ± 13%) vs. Category 2 (39 ± 15%) academies and in Foundation Phase (44 ± 13%) vs. Youth Development Phase (41 ± 15%). These results demonstrate that there is room for improvement in the nutrition knowledge levels of parents and caregivers of male soccer academy players. We recommend that club academies provide appropriate resources towards nutritional education for parents and caregivers.



#13 Dietary Habits of Elite Soccer Players: Variations According to Competitive Level, Playing Position and Sex

Reference: Nutrients. 2023 Oct 10;15(20):4323. doi: 10.3390/nu15204323.

Authors: Jaime Sebastiá-Rico, Jose M Soriano, Jesús Sanchis-Chordà, Miguel Alonso-Calvar, Pedro López-Mateu, David Romero-García, José Miguel Martínez-Sanz

Summary: Soccer is a sport practiced worldwide by both men and women, where nutrition plays a fundamental role in the performance of soccer players, providing them with the nutrients necessary for energy, muscle recovery and injury prevention. The aim of this study is to describe the dietary habits in elite soccer players and their association with their competitive level, playing position and sex. A descriptive and non-experimental comparative study was conducted during the 2021-2022 competitive season. A total of 105 players belonging to a Spanish elite soccer team completed a food frequency questionnaire (FCFQ). It was observed that male players presented a higher consumption of carbohydrate-rich foods (p < 0.05), fermented foods (p = 0.014), frozen foods (p = 0.049) and red meat (p = 0.012) compared to female players, with the exception of lean meats, which were higher in females (p = 0.012). Furthermore, the U16-15 categories stand out for consuming carbohydrate-rich foods such as pasta (p = 0.000), bread (p = 0.004) and sweets (p = 0.046), as well as frozen foods (p = 0.002). Finally, alcohol consumption is higher in the senior categories (42.9%), where men are more likely to drink mixed drinks (6.2%), and beer and wine by women (10.7%). Practically no differences were found between the playing positions. In conclusion, differences were found in FCFQ according to competitive level and sex.



#14 Relation of Jump and Change of Direction Inter-Limb Asymmetries with Fitness in Youth Male Soccer Players

Reference: Medicina (Kaunas). 2023 Sep 29;59(10):1749. doi: 10.3390/medicina59101749.

Author: Yiannis Michailidis

Summary: Asymmetries between the lower limbs were evaluated by both researchers and practitioners as they seem to be related to the occurrence of injuries and the effect on performance. The purposes of this study were to (a) detect asymmetries of the lower limbs using a unilateral jump (single-leg countermovement jump (SLCMJ)) and 505 agility test, and (b) examine asymmetry effects on fitness (acceleration, speed, squat jump, Illinois agility test), in U16 youth male soccer players. Twenty U16 soccer players performed an SLCMJ and a 505 test to calculate the asymmetry index. They also performed the above fitness tests. The difference between the lower limbs was tested using the paired samples t-test (dominant vs. non-dominant). The correlations between the asymmetries of the lower extremities with the performance indicators were tested using the Pearson's correlation test. The level of significance was set at p < 0.05. The lower limbs differed significantly in the SLCMJ and 505 tests (p < 0.05). The only correlation was between the asymmetry in SLCMJ and performance in SJ (r = -0.641, p = 0.002). Asymmetries did not affect performance on most fitness tests. The two asymmetry tests identified asymmetries in different limbs. This indicates the variability in asymmetries and the need for specialized tests depending on the kinematic chain. The asymmetries observed should be eliminated using individualized training programs so that athletes are protected from injuries and from the possible negative impact on performance. Also, the detection of asymmetries in developmental age offers a greater time period for their elimination before the athlete enters professional sports.







Match running performance characterizing the most elite soccer match-play

In order to identify match running performance (MRP) characterizing the most elite soccer matchplay, this study aimed to examine position-specific differences in the MRP of players competing in “big five” (BFLTs) and “non-big five” league teams (N-BFLTs).





Relationships between external loads, sRPE-load, and self-reported soreness across a men’s collegiate soccer season

The purpose was to examine relationships between external loads (ELs), perceived exertion, and soreness.





Latest research in football - week 41 - 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 Discrete Hamstring: Quadriceps Strength Ratios Do Not Represent Angle-Specific Ratios in Premier League Soccer Players

Reference: J Strength Cond Res. 2023 Oct 6. doi: 10.1519/JSC.0000000000004574. Online ahead of print.

Authors: David E Lunn, Gareth Nicholson, Mark Cooke, Rubén Crespo, Tom Robinson, Rob J Price, Josh Walker

Summary: This study compared angle-specific hamstring:quadriceps (H:Q) ratios with their discrete counterparts during strength testing in professional male soccer players. Twenty-seven professional English Premier League soccer players were recruited for this study (age: 22 ± 4 years; stature: 1.81 ± 0.08 m; body mass: 74.7 ± 6.5 kg). Isokinetic testing of the knee flexors and extensors was conducted concentrically at two angular velocities (60° and 240°·s-1) and eccentrically (for the knee flexors only) at 30°·s-1. Conventional H:Q ratio was calculated as the ratio between peak joint moment in the flexors and extensors at 60°·s-1. Functional H:Q ratio was calculated as the peak joint moment in the flexors during the eccentric condition and the extensors at 240°·s-1. Discrete conventional and functional H:Q ratios were 0.56 ± 0.06 and 1.28 ± 0.22, respectively. The residual differences between discrete values and angle-specific residual values were 13.60 ± 6.56% when normalized to the magnitude of the discrete value. For the functional ratios, the normalized residual was 21.72 ± 5.61%. Therefore, neither discrete ratio was representative of angle-specific ratios, although the conventional ratio had lower error overall. Therefore, practitioners should consider H:Q ratio throughout the full isokinetic range of motion, not just the discrete ratio calculated from peak joint moments, when designing and implementing training programs or monitoring injury risk, recovery from injury, and readiness to return to play.



#2 Daily energy requirements of male academy soccer players are greater than age-matched non-academy soccer players: A doubly labelled water investigation

Reference: J Sports Sci. 2023 Oct 9:1-13. doi: 10.1080/02640414.2023.2263707. Online ahead of print.

Authors: Reuben G Stables, Marcus P Hannon, Adam D Jacob, Oliver Topping, Nessan B Costello, Lynne M Boddy, Catherine Hambly, John R Speakman, Jazz S Sodhi, Graeme L Close, James P Morton

Summary: This study aimed to test the hypothesis that the total daily energy expenditure (TDEE) of male academy soccer players is greater than players not enrolled on a formalised academy programme. English Premier League academy (ACAD: n = 8, 13 years, 50 ± 6 kg, 88 ± 3% predicted adult stature, PAS) and non-academy players (NON-ACAD: n = 6, 13 years, 53 ± 12 kg, 89 ± 3% PAS) were assessed for TDEE (via doubly labelled water) during a 14-day in-season period. External loading was evaluated during training (ACAD: 8 sessions, NON-ACAD: 2 sessions) and games (2 games for both ACAD and NON-ACAD) via GPS, and daily physical activity was evaluated using triaxial accelerometry. Accumulative duration of soccer activity (ACAD: 975 ± 23 min, NON-ACAD: 397 ± 2 min; p < 0.01), distance covered (ACAD: 54.2 ± 8.3 km, NON-ACAD: 21.6 ± 4.7 km; p < 0.05) and time engaged in daily moderate-to-vigorous (ACAD: 124 ± 17 min, NON-ACAD: 79 ± 18 min; p < 0.01) activity was greater in academy players. Academy players displayed greater absolute (ACAD: 3380 ± 517 kcal · d-1, NON-ACAD: 2641 ± 308 kcal · d-1; p < 0.05) and relative TDEE (ACAD: 66 ± 6 kcal · kg · d-1, NON-ACAD: 52 ± 10 kcal · kg · d-1; p < 0.05) versus non-academy players. Given the injury risk associated with high training volumes during growth and maturation, data demonstrate the requirement for academy players to consume sufficient energy (and carbohydrate) intake to support the enhanced energy cost of academy programmes.



#3 Comparison of the effects of pea protein and whey protein on the metabolic profile of soccer athletes: a randomized, double-blind, crossover trial

Reference: Front Nutr. 2023 Sep 22:10:1210215. doi: 10.3389/fnut.2023.1210215. eCollection 2023.

Authors: Luiz Lannes Loureiro, Tathiany Jéssica Ferreira, Fábio Luiz Candido Cahuê, Victor Zaban Bittencourt, Ana Paula Valente, Anna Paola Trindade Rocha Pierucci

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Summary: Pea protein (PP) concentrate is a plant-based alternative to animal protein sources, such as whey protein (WP). In addition to its valuable amino acid composition, PP has a low environmental impact, making it a sustainable, nutritious, and viable alternative for enhanced sports performance, such as in soccer. PP Therefore, this study aimed to evaluate the effects of PP and WP supplementation on biochemical and metabolic parameters in soccer players. Twelve male under-20 soccer players were included in this double-blind, randomized crossover intervention study. For 10 consecutive days, each participant received either 0.5 g/kg of the PP or WP supplementation after training, starting 7 days before the test game, and continuing until 2 days after. After a 4-day washout period, the athletes switched groups and the intervention was restarted. Blood samples were collected before and after the game, as well as 24 h, 48 h, and 72 h intervals thereafter. Creatine kinase (CK), aspartate transaminase, alanine transaminase (ALT), lactate (LA), urea, creatinine, and uric acid were analyzed using commercial kits. Exploratory metabolic profiling of the serum samples was performed using nuclear magnetic resonance spectroscopy. A comparison of biochemical markers showed that the PP group had lower CK in the post-game moment, 24 h, and 48 h. Lower LA in the post-game moment, and lower ALT in the post-game moment and at 24 h. Of the 48 metabolites analyzed, 22 showed significant differences between the time points, such as amino acids, ketone bodies, and glucose metabolism. Glutamate and lactate levels significantly increased between the pre- and post-game moments in the WP group. After the game, the WP group exhibited reduced levels of metabolites such as arginine and taurine, whereas no such change was observed in the PP group. There was no difference in metabolites 72 h after the game. Despite the slight advantage of the PP group in specific biochemical markers, these differences are not sufficient to justify the choice of a particular type of protein. However, the results highlight the viability of plant protein as a potential alternative to animal protein without compromising athletic performance or recovery.



#4 Does Restricted Ankle Joint Mobility Influence Hamstring Muscle Strength, Work and Power in Football Players after ACL Reconstruction and Non-Injured Players?

Reference: J Clin Med. 2023 Oct 1;12(19):6330. doi: 10.3390/jcm12196330.

Authors: Łukasz Oleksy, Anna Mika, Maciej Kuchciak, Grzegorz Bril, Renata Kielnar, Olga Adamska, Paweł Wolański, Michał Deszczyński

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Summary: This study was aimed at observing how the limitation of ankle dorsiflexion ROM affects hamstring muscle Peak Torque/BW (%), Average Power (W), and Total Work (J), and whether this effect is similar in football players after ACL rupture and reconstruction and in those without injuries. The study included 47 professional football players who were divided into two groups: Group 1 (n = 24) after ACL reconstruction and Group 2 (n = 23) without injuries in the past 3 years. Based on the Weight-Bearing Lunge Test (WBLT), the following subgroups in Groups 1 and 2 were distinguished: N (normal ankle joint dorsiflexion) and R (restricted ankle joint dorsiflexion). The concentric isokinetic test (10 knee flexions and extensions at 60°/s) was performed on both limbs. Significantly lower values of Peak Torque/BW and Average Power were observed in Group 1 compared to Group 2, as well as in subjects with normal and restricted ankle dorsiflexion. However, no significant differences were noted for either group in any of the strength variables comparing subjects with normal and restricted ankle dorsiflexion. A poor and non-significant correlation was exhibited between the ankle joint range of dorsiflexion and all the strength variables. The area under the ROC curve (AUC) for all the evaluated variables in both groups was below 0.5, or very close to this value, indicating that ankle dorsiflexion ROM has no diagnostic accuracy for hamstring muscle strength. Based on the obtained results, it can be assumed that ankle dorsiflexion limitation, which is common in football players, is not a factor in weakening hamstring muscle strength, either in football players after ACL reconstruction or among those without injuries. However, some authors have reported that limited mobility of the ankle joint can have a destructive effect on the work of the lower limbs and may also be a factor in increasing the risk of football injuries in this area. Therefore, we have suggested that hamstring muscle weakness and increased risk of injury may occur due to factors other than limited ankle mobility. These observations may be of great importance in the selection of prevention methods by including a broad spectrum of physical techniques, not just exercises that focus on the improvement of mobility or stability of the lower limbs.



#5 Epidemiology of Injuries in Professional and Amateur Football Men (Part II)

Reference: J Clin Med. 2023 Sep 29;12(19):6293. doi: 10.3390/jcm12196293.

Authors: Tudor Vladimir Gurau, Gabriela Gurau, Carmina Liana Musat, Doina Carina Voinescu, Lucretia Anghel, Gelu Onose, Constantin Munteanu, Ilie Onu, Daniel Andrei Iordan

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Summary: Men's football is a physically demanding contact sport that involves intermittent bouts of sprinting, jogging, walking, jumping and changes of direction. The physical demands of the game vary by level of play (amateur club, sub-elite and open club or international), but injury rates at all levels of the men's football game remain the highest of all sports. The aim of this study is to conduct a systematic review of data from the epidemiological literature regarding the profile, severity and mechanisms of injuries and the frequency of recurrent injuries in professional and amateur football players. A systematic review, according to PRISMA guidelines, was performed up to June 2023 in the databases of PubMed, Web of Science, Google academic, Google scholar and the Diva portal. Twenty-seven studies that reported data on the type, severity, recurrence and mechanisms of injury in professional and amateur men's football were selected and analyzed. Two reviewers independently audited data and assessed the study quality using the additional and adapted version of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement and the Newcastle Ottawa Scale (NOS) to assess risk of bias for the quality of external validity. In professional male football players, the mean prevalence of muscle/tendon injuries was 39.78%, followed by joint and ligament injuries-21.13%, contusions-17.86%, and fractures-3.27%, and for amateur football players, the prevalence's were 44.56% (muscle/tendon injuries), 27.62% (joint and ligament injuries), 15.0% (contusions) and 3.05% (fracture), respectively. The frequency of traumatic injuries was higher in amateur football players (76.88%) compared to professional football players (64.16%), the situation being reversed in the case of overuse injuries: 27.62% in professional football players and 21.13% in amateur football players. Most contact injuries were found in professional footballers (50.70%), with non-contact injuries predominating in amateur footballers (54.04%). The analysis of the severity of injuries showed that moderate injuries dominated in the two categories of footballers; the severe injuries in amateur footballers exceeded the severe injuries recorded in professional footballers by 9.60%. Recurrence proportions showed an inverse relationship with the level of play, being higher in amateur footballers (16.66%) compared to professional footballers (15.25%). Football-related injuries have a significant impact on professional and amateur football players and their short- and long-term health status. Knowing the frequency of severe diagnoses, such as strains, tears and cramps of the thigh muscles, ankle ligament sprains and hip/groin muscle strain requires the establishment of adequate programs to prevent them, especially in amateur football players, who are more prone to serious injuries.



#6 Injury Patterns and Incidence in an Elite Youth Football Academy-A Prospective Cohort Study of 138 Male Athletes

Authors: Johannes Weishorn, Ayham Jaber, Severin Zietzschmann, Jan Spielmann, Tobias Renkawitz, Yannic Bangert

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Summary: There is a lack of evidence regarding injury incidence in German elite youth football academies, and the risk of re-injury is unknown. Therefore, the objectives of this study were (1) to determine injury patterns and incidence in an elite youth football academy in Germany, (2) to monitor overuse-/trauma-related injuries over the course of the season, and (3) determine the risk of re-injury. A prospective cohort study was conducted in the 2012/2013 season among 138 male players from an elite youth football academy in Germany. Injuries were recorded according to the consensus statement on injury definitions and data collection in studies of football injuries. Injury incidence was reported as the number of injuries per 1000 h of exposure and the number of injuries per squad season. A total of 109 injuries were reported, resulting in a cumulative time-loss of 2536 days. A squad of 25 players sustained 19.7 injuries per season, with an average of 23.3 days (15.7-30.9; 95% CI lower-upper) of absence per injury. Ligament sprains (28%), muscle strains (19%) and physeal injuries (12%) were the most common causes of time-loss. Physeal injuries were the most common severe type of injury (29%), with a mean time-loss of 29.7 days (18.2-41.2; 95% CI lower-upper). Re-injuries accounted for 3% of all injuries and resulted in significantly more time-loss than non-re-injuries (60 vs. 23 days; p = 0.01). In the youth academies studied, a team of 25 players sustained an average of 19.7 injuries per season, resulting in a cumulative time-loss of 459 days. Physeal injuries are a major contributor to severe injuries and therefore require special attention.



#7 Injury incidence in male elite youth football players is associated with preceding levels and changes in training load

Reference: BMJ Open Sport Exerc Med. 2023 Oct 6;9(4):e001638. doi: 10.1136/bmjsem-2023-001638. eCollection 2023.

Authors: Tania Nilsson, Mats Börjesson, Matilda Lundblad, Andreas Ivarsson, Dan Fransson

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Summary: Elite youth football players miss out on a large part of seasonal training due to injury. Limited research suggests an association between external and internal training load (TL) and injury incidence in elite youth football. This study analysed external and internal TL variables and their association with injury incidence in a group of male elite youth football players over four seasons. Measures of external and internal TL and injury incidence of 56 male elite youth football players (age 17-19 years) were collected throughout four seasons. Heart rate, session rating of perceived exertion andGlobal Positioning System (GPS) variables were analysed. Individual players' TL during the 30 days leading up to injury was compared with 30-day injury-free control periods. Change in TL through the periods was also analysed. Eighty-five injuries were included for analysis, showing that for most TL variables, the average levels were significantly lower during the period leading up to injury. Significant increases for the majority of TL variables were also found during the periods leading up to injury, while the control periods did not show any significant change. A lower and/or increasing average TL volume over 30 days might increase the risk of injury in male elite youth football players. Avoiding long-term drops in TL and balance increases in TL might be beneficial to reduce injury risk.



#8 Influence of a football match on landing biomechanics and jump performance in female football players

Reference: Scand J Med Sci Sports. 2023 Oct 12. doi: 10.1111/sms.14518. Online ahead of print.

Authors: Aaron Miralles-Iborra, Jose L L Elvira, Juan Del Coso, Sergio Hernandez-Sanchez, Jose Pino-Ortega, Victor Moreno-Pérez

Summary: This study aimed to assess the acute effect of a competitive football match on jump performance and kinematic parameters during jump landing in semiprofessional female football players. Twenty-two semiprofessional players (20 ± 3 years) underwent a drop jump task for a posterior video analysis of the landing phase. These measurements were obtained at (1) baseline, (2) after, and (3) 48 h after a competitive football match. A one-way ANOVA with repeated measures was employed to detect differences over the time. There was a main effect of time for maximal knee flexion angle during drop landing (p = 0.001). In comparison with baseline, maximal knee flexion angle was reduced immediately post-match and was still reduced 48 h after the match (63.4 ± 8.6 vs 57.0 ± 11.7 vs 48.9 ± 19.1, p ≤ 0.038). There was also a main effect of time for drop jump height (p < 0.001). Drop jump height was reduced immediately post-match and remained low 48 h after the match in comparison with baseline (27.3 ± 3.6 vs 24.5 ± 2.8 ~ 25.5 ± 3.0 cm, p ≤ 0.002). There was a main effect of time on hip flexion angle during landing (p = 0.001), but the pairwise comparison revealed that this variable was not affected immediately post-match but was lower 48 h after the match than at baseline (50.1 ± 10.1 ~ 50.8 ± 13.2 vs 38.1 ± 17.8 °, p ≤ 0.005). A competitive football match worsened jump performance and several landing biomechanical parameters in female football players, which were still decreased in comparison with baseline even 48 h after the match.



#9 Relationship between perceived social support and mental health among Chinese college football athletes: a moderated mediation model

Reference: BMC Psychol. 2023 Oct 11;11(1):329. doi: 10.1186/s40359-023-01357-2.

Authors: Zongyu Liu, Xiuhan Zhao, Liangyu Zhao, Liguo Zhang

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Summary: Previous researches have confirmed that perceived social support has a profound effect on individuals' mental health. However, the effects and potential mechanisms of perceived social support on mental health of college athletes are still largely unknown, especially during and after the COVID-19 pandemic. Thus, the aim of this study was to explore the relationship between perceived social support and mental health in college football athletes, and to evaluate whether hopelessness and psychological pressure affected this relationship. A sample of 672 Chinese college football athletes (37.9% girls; Mage = 20.43 years; SDage = 1.68) were investigated with the Perceived Social Support Scale (PSSS), the Kessler Psychological Distress Scale (K10), the Beck Hopelessness Scale (BHS) and the Perceived Stress Scale (PSS). Surveys were voluntary and anonymous. The findings revealed that, after adjusting for demographic factors, hopelessness mediated the relationship between Chinese college football athletes' perceived social support and their mental health. Furthermore, psychological pressure moderated the negative association between perceived social support and hopelessness, and the association was stronger for them with high-level psychological pressure. These results underline the need for focused strategies in the prevention and treatment of mental health issues among Chinese college football athletes.



#10 Distinct profiles of multisensory processing between professional goalkeepers and outfield football players

Reference: Curr Biol. 2023 Oct 9;33(19):R994-R995. doi: 10.1016/j.cub.2023.08.050.

Authors: Michael Quinn, Rebecca J Hirst, David P McGovern

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Summary: In association football (soccer), the position of goalkeeper is the most specialised position in the sport and has the primary objective of stopping the opposing team from scoring. While previous studies have highlighted differences in physiological and match performance profiles between goalkeepers and outfield players1, surprisingly little research has focused on whether goalkeepers differ in terms of their perceptual-cognitive abilities. Given that goalkeepers use multiple sensory cues and are often required to make rapid decisions based on incomplete multisensory information to fulfil their role2, we hypothesised that professional goalkeepers would display enhanced multisensory temporal processing relative to their outfield counterparts. To test this hypothesis, we measured the temporal binding windows - the time window within which signals from the different senses are integrated into a single percept - of professional goalkeepers, professional outfield players, and a control group with no professional football experience using the sound-induced flash illusion3. Our results indicated a marked difference in multisensory processing between the three groups. Specifically, we found that the goalkeepers displayed a narrower temporal binding window relative to both outfielders and control participants, indicating more precise audiovisual timing estimation. However, this enhanced multisensory temporal processing was accompanied by a general reduction in crossmodal interactions relative to the other two groups that could be attributed to an a priori tendency to segregate sensory signals. We propose that these differences stem from the idiosyncratic nature of the goalkeeping position that puts a premium on the ability of goalkeepers to make quick decisions, often based on partial or incomplete sensory information.



#11 Dark Chocolate Intake Positively Modulates Gut Permeability in Elite Football Athletes: A Randomized Controlled Study

Reference: Nutrients. 2023 Sep 28;15(19):4203. doi: 10.3390/nu15194203.

Authors: Cristina Nocella, Elena Cavarretta, Chiara Fossati, Fabio Pigozzi, Federico Quaranta, Mariangela Peruzzi, Fabrizio De Grandis, Vincenzo Costa, Carwyn Sharp, Massimo Manara, Antonia Nigro, Vittoria Cammisotto, Valentina Castellani, Vittorio Picchio, Sebastiano Sciarretta, Giacomo Frati, Simona Bartimoccia, Alessandra D'Amico, Roberto Carnevale

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Summary: Gut barrier disruption can lead to enhanced intestinal permeability, which allows endotoxins, pathogens, and other proinflammatory substances to move through the intestinal barrier into circulation. Intense exercise over a prolonged period increases intestinal permeability, which can be further worsened by the increased production of reactive oxygen species (ROS) and pro-inflammatory cytokines. The aim of this study was to assess the degree of intestinal permeability in elite football players and to exploit the effect of cocoa polyphenols on intestinal permeability induced by intensive physical exercise. Biomarkers of intestinal permeability, such as circulating levels of zonulin, a modulator of tight junctions, occludin, a tight junction protein, and LPS translocation, were evaluated in 24 elite football players and 23 amateur athletes. Moreover, 24 elite football players were randomly assigned to either a dark chocolate (>85% cocoa) intake (n = 12) or a control group (n = 12) for 30 days in a randomized controlled trial. Biochemical analyses were performed at baseline and after 30 days of chocolate intake. Compared to amateur athletes, elite football players showed increased intestinal permeability as indicated by higher levels of zonulin, occludin, and LPS. After 30 days of dark chocolate intake, decreased intestinal permeability was found in elite athletes consuming dark chocolate. In the control group, no changes were observed. In vitro, polyphenol extracts significantly improved intestinal damage in the human intestinal mucosa cell line Caco-2. These results indicate that chronic supplementation with dark chocolate as a rich source of polyphenols positively modulates exercise-induced intestinal damage in elite football athletes.



#12 Influence of physical fitness on decision-making of soccer referees throughout the match

Reference: Heliyon. 2023 Sep 6;9(9):e19702. doi: 10.1016/j.heliyon.2023.e19702. eCollection 2023 Sep.

Authors: Alfonso Castillo-Rodríguez, Emilio José Alejo-Moya, Antonio Figueiredo, Wanesa Onetti-Onetti, Francisco Tomás González-Fernández

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Summary: The purpose of this study was to analyze the relationships between physical fitness and physical performance in competition and the decision-making (successes and errors). A sample of 22 male national-level soccer referees (weight: 72.7 kg; height: 178.0 cm; age: 23.4 years) participated in this study. Physical fitness was assessed through 6 series of 40 m (velocity) and Yo-yo (aerobic) test in annual exam by Soccer Committee, physical performance was performed through the total distance covered in competition (Experiment 1), and decision-making was registered through a simulated Video Assistant Referee system (VAR) with the consensus of 2 national referees evaluating only warnings (yellow cards), expulsions (red cards), established penalties and obvious goal actions (called and no called) (Experiments 2 and 3). Results showed that physical fitness test was related with total distance (rho = 0.63, p < .01) and success rate percentage (rho = 0.74, p < .05) registered during competition. The success rate percentage, in the first half, was observed 44% successes, and in the second half, 59% successes. The number of events called was related with the physical fitness test score (R2 = 0.71, p = .035; R2 = 0.64, p = .056, respectively). As conclusion, the main finding of this study has provided insight into decision-making behavior in real competitive matches and the physical fitness was the predictor of the successful decision-making being able to determine the permanency, promotion or decrease of category.



#13 The impact of verbal encouragement during the repeated agility speed training on internal intensity, mood state, and physical enjoyment in youth soccer players

Reference: Front Psychol. 2023 Sep 21:14:1180985. doi: 10.3389/fpsyg.2023.1180985. eCollection 2023.

Authors: Okba Selmi, Hilmi Jelleli, Souheir Bouali, Bilel Aydi, Omar Hindawi, Antonella Muscella, Anissa Bouassida, Katja Weiss, Beat Knechtle

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Summary: Verbal encouragement (VE) can be used by coaches to boost morale and commitment during training exercises. This investigation aimed to study the impacts of VE given by coaches on the physiological aspects, players' internal intensity, mood, and perceived enjoyment of youth soccer players during repeated agility speed training (RAS). A total of 17 male youth soccer players (mean ± SD; age: 13.8 ± 0.4 years; body mass: 59.1 ± 6.7 kg; height: 170.0 ± 6.2 cm; training experience: 5.1 ± 0.7 years) participated, in a randomized order, in two experimental training sessions that consisted of a RAS (i.e., the Illinois course) either with VE (RAS-E) or without VE (RAS-NE), with a 7-day interval between the testing sessions. Heart rate (HR) was registered throughout the exercise. The rating of perceived exertion, blood lactate concentration [La], and perceived enjoyment were measured after each training session. The mood state was recorded before and after each protocol. HR mean (Cohen's coefficient d = 0.45, small), %HRmax (d = 0.37, small), HR peak (d = 0.66, moderate), [La] (d = 0.56, small), and the PACES score (d = 2.8, very large) were higher in RAS-E compared to RAS-NE (all, P < 0.001). Compared to the RAS-E trial, the RAS-NE trial showed higher fatigue (P < 0.01), tension (P < 0.05), anger (0.05), total mood score (P < 0.001), and lower vigor (P < 0.001). Coaches may use VE during RAS to improve psychophysiological responses, mood state, and perceived enjoyment in youth soccer players.



#14 Performance Management in Elite Football: A Teamwork Modeling Approach

Reference: International Journal of Sports Physiology and Performance

Authors: Marques J, Chamari K

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Summary: Winning matches and getting 3 competition points is commonly established as a key performance indicator (KPI) for elite football (soccer) teams to achieve their objectives during the season. While winning is the responsibility of the football players, sport-science and -medicine practitioners’ responsibility is to support them by increasing their availability for matches (a key contributing factor to winning the games and ensuring team success). Unfortunately, it is not uncommon to observe sport-science (eg, strength and conditioning coach, physiologist) and -medicine (e.g., physician, physiotherapist) practitioners working in silos in a football setting. As such, we are proposing a teamwork modeling approach for practitioners with elite football teams. Our model comprises specific KPIs to enhance players’ performance while reducing injury risk. This model has the potential to attract the attention of practitioners and researchers aiming to prevent injuries and improving players’ recovery for enhanced football performance.






Differences in playing style and technical performance according to the team ranking in LaLiga - A thirteen seasons study

This study aimed to explore the differences in playing style and technical performance according to the ranking level in Spanish football teams.





Influence of Tactical Behaviour on Running in the 3 Most Successful Soccer Teams During the Season of the Spanish First Division

The purpose of this study was to analyze the influence of tactical behavior on physical performance of the three best Spanish soccer teams.






Latest research in football - week 40 - 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 Predicting Risk Factors of Lower Extremity Injuries in Elite Women's Football: Systematic Review and Meta-Analysis

Reference: Sports (Basel). 2023 Sep 20;11(9):187. doi: 10.3390/sports11090187.

Authors: Feim Gashi, Tine Kovacic, Arbnore Ibrahimaj Gashi, Arben Boshnjaku, Ismet Shalaj

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Summary: This study identified and analyzed the risk factors of lower extremity injuries (LEI) in elite women football players to improve career and health outcomes. To address this aim, a systematic review and meta-analysis methodology was used. In total, four relevant research articles were identified through database searching and screening using the PRISMA flow diagram. From these articles, eight predictors were identified that influence the risk of LEI among elite women football players: higher body mass index (OR 1.51, 95% CI); previous knee injury (OR 3.57, 95% CI); low normalized knee separation (≤10th percentile) (RR 1.92, 95% CI); all previous injury (previous ACL tear: OR 5.24, 95% CI; ankle sprain: 1.39, 95% CI; knee sprain: 1.50, 95% CI); and previous injury in the lower body (OR 2.97, 95% CI). Meanwhile, lower knee valgus angle in a drop-jump landing (OR 0.64, 95% CI) was found to decrease the risk of LEI among elite women football players.



#2 Determinants of international football performance: Empirical evidence from the 1994-2022 FIFA World Cup

Reference: Heliyon. 2023 Sep 17;9(10):e20252. doi: 10.1016/j.heliyon.2023.e20252. eCollection 2023 Oct.

Authors: Mu Fan, Fei Liu, Dong Huang, Hui Zhang

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Summary: In the past 30 years, the global influence of the FIFA World Cup has continued to grow. According to statistics, the final match of the 2022 World Cup in Qatar attracted an audience of over 3 billion. Nowadays, nations (and regions) emphasize the correlation between overall social progress, football tradition, and national sporting prowess. This study aims to comprehend the dynamics of international football development and secure a competitive edge in the global arena. The study collected panel data from 68 countries (regions) participating in the final stage of the World Cup from 1994 to 2022. It modelled them using a generalized linear mixed model (GLMM) to reveal the macro determinants of success and winning patterns in international football performance. The findings show that (1) football tradition's "characteristic values" (e.g. World Cup host, the experience of hosting the World Cup and the number of all-time World Cup winners) and national comprehensive sporting strength (as represented by the Olympic Games results) have significantly contributed to the national team's World Cup performance; (2) the country's Human Development Index (HDI) has a significant negative impact on World Cup performance; (3) the history of football participation (e.g. the number of years of membership in the Intercontinental Football Association (IFA), history of professional leagues) will have little impact on World Cup performance; (4) two interactive variables: population scale × national comprehensive sporting strength (GPOP × CSOGMedals) and economic level × football tradition (lnGDP × PLHistory), have a negative and positive combined effect on World Cup performance, respectively.



#3 Contemporary practices of physical trainers in professional soccer: A qualitative study

Reference: Front Psychol. 2023 Sep 19:14:1101958. doi: 10.3389/fpsyg.2023.1101958. eCollection 2023.

Authors: Joel Barrera-Díaz, António J Figueiredo, Adam Field, Bruno Ferreira, Sérgio M Querido, João Renato Silva, João Ribeiro, Ismael Pinto, Patricio Cornejo, Hernan Torres, Alvaro Saffa, Hugo Sarmento

Summary: Physical trainers (PTs) are integral for managing load, reducing injury and optimizing performance in professional soccer. However, little is known about how this practitioners operate in the applied setting and how some of the nuances experienced influence practice. This study explored the contemporary practices of PTs in professional soccer. Semi-structured interviews were undertaken with eight PTs from different professional teams in European and South American leagues. Interview questions were designed to extract information on the evaluation of physical abilities, monitoring and control of training and injury prevention. Subsequently, the interviews were video-recorded, transcribed, translated and analyzed using a content analysis approach. The results suggest that the evaluation of physical capacities is carried out by PTs at the beginning of the preseason. It also appears that it is attempted that this process of regular testing is applied during the competitive period, with most participants conducting partial physiological and physical evaluations at different stages throughout the competitive season. In relation to the monitoring and control of training, subjective feedback scales are used to estimate the internal load, and the use of GPS devices is common to quantify external loads. Injury prevention programmes were implemented by all participants and were generally in a multi-component format focused on preventing or optimizing physical capabilities. These insights can be used as a scientific reference point to inform applied practice in professional soccer, especially for practitioners that are inexperienced and aspiring to enhance how they operate in the field. Future investigations should explore the practices of PTs in detail and across a wider network in order to gain deeper and comprehensive insights into the applied soccer environment.



#4 An Unlikely Cause of Groin Pain: Obturator Externus Tear in a Professional Soccer Player

Reference: Cureus. 2023 Sep 3;15(9):e44612. doi: 10.7759/cureus.44612. eCollection 2023 Sep.

Authors: Rui Silva, Adriana Pereira, Sérgio Rodrigues-Gomes, Tiago Lopes

Summary: Groin pain is a common and complex problem in athletes, especially soccer players, associated with a wide variety of possible injuries in numerous anatomical structures. One of the causes of groin pain is damage to the deep muscles of the hip region, with isolated traumatic injury of the obturator externus muscle rarely described and probably underdiagnosed. This report describes a clinical case of a soccer player who presented with acute hip pain and buttock pain resulting from a rapid change of position in load, associated with pain with active hip external rotation and passive internal rotation. MRI demonstrated the presence of subaponeurotic/myo-aponeurotic obturator externus muscle tear. A conservative treatment was decided, targeting pain reduction and progressing range of motion gain and muscle strengthening of the stabilizing muscles of the pelvis and hip, and subsequently, it led to re-athletisation, with soccer-specific exercises. Return to play was 23 days after injury. This case shows that a high level of suspicion is necessary for the correct diagnosis; treatment is generally conservative and the isolated rupture of the external obturator can be considered relatively benign. However, it has the potential to be associated with a long period of absence from training and games.



#4 Physical demands in a small-sided soccer game: a comparison between arbitrary and individualized speed and metabolic power thresholds

Reference: J Sports Med Phys Fitness. 2023 Oct 4. doi: 10.23736/S0022-4707.23.15112-7. Online ahead of print.

Authors: Victor Staibano, Alexandre Moreira, Valéria L Panissa, Marcelo Marques, Emerson Franchini

Summary: This study compared the arbitrary and individualized speed and metabolic power (P<inf>met</inf>) intensity thresholds in a small-sided game (SSG) regarding: 1) distance covered; 2) variations of the physical parameters during the SSG; and 3) associations with physical fitness. Twenty-four amateur soccer players (age: 20.0±1.7 years; height: 176.4±4.2 cm; body mass: 67.6±3.2 kg), after being tested for maximal aerobic speed (MAS) and maximal sprinting speed (MSS), participated in a SSG in a separate session and were monitored with global positioning systems (GPS). The distance covered was classified into three intensity zones for each variable (speed and P<inf>met</inf>) using arbitrary and individualized zones based on MAS. There were differences in the distance covered between methods in zones 1 and 2 for both speed and P<inf>met</inf> (P<0.001), and in zone 3 only for P<inf>met</inf> (P<0.001). There were no variations in any variable analyzed during the SSG. MAS was positively correlated with the distance covered in zone 3 in the arbitrary speed (r=0.67; P<0.001) and P<inf>met</inf> (r=0.60; P<0.01). MSS was negatively correlated with the distance covered in zone 3 in the individualized speed (r=-0.49; P<0.05) and P<inf>met</inf> (r=-0.48; P<0.05). This study showed that arbitrary and individualized provide different information. While the individualized method could be used to monitor physical demands, the arbitrary could be used to assess running physical performance.



#5 Combined influence of psychological and biomechanical factors in muscular loads in soccer : A new approach for the prevention of muscle injuries

Reference: Orthopadie (Heidelb). 2023 Oct 2. doi: 10.1007/s00132-023-04437-8. Online ahead of print. [Article in German]

Authors: Simon Auer, Simone Kubowitsch, Sebastian Dendorfer

Summary: When mental stress and musculoskeletal loading interact, the risk for injury increases due to altered body kinematics and increased muscle tension. These changes can be detected with musculoskeletal models, and mental loading and stress must be analyzed at emotional, cognitive, and behavioral levels. To investigate these kinematic and loading changes under stress, competitive athletes were subjected to mental stress during highly dynamic movements, and musculoskeletal models were used to analyze the biomechanical loading. It was shown that under mental stress, independent of the subjective perception, a strong change in muscle forces can occur. Accordingly, competitive athletes should undergo screenings to assess individual movement patterns and promote general stress resilience.



#6 Hyper-acute effects of sub-concussive soccer headers on brain function and hemodynamics

Reference: Front Hum Neurosci. 2023 Sep 14:17:1191284. doi: 10.3389/fnhum.2023.1191284. eCollection 2023.

Authors: Carissa Grijalva, Dallin Hale, Lyndia Wu, Nima Toosizadeh, Kaveh Laksari

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Summary: Sub-concussive head impacts in soccer are drawing increasing research attention regarding their acute and long-term effects as players may experience thousands of headers in a single season. During these impacts, the head experiences rapid acceleration similar to what occurs during a concussion, but without the clinical implications. The physical mechanism and response to repetitive impacts are not completely understood. The objective of this work was to examine the immediate functional outcomes of sub-concussive level impacts from soccer heading in a natural, non-laboratory environment. Twenty university level soccer athletes were instrumented with sensor-mounted bite bars to record impacts from 10 consecutive soccer headers. Pre- and post-header measurements were collected to determine hyper-acute changes, i.e., within minutes after exposure. This included measuring blood flow velocity using transcranial Doppler (TCD) ultrasound, oxyhemoglobin concentration using functional near infrared spectroscopy imaging (fNIRS), and upper extremity dual-task (UEF) neurocognitive testing. On average, the athletes experienced 30.7 ± 8.9 g peak linear acceleration and 7.2 ± 3.1 rad/s peak angular velocity, respectively. Results from fNIRS measurements showed an increase in the brain oxygenation for the left prefrontal cortex (PC) (p = 0.002), and the left motor cortex (MC) (p = 0.007) following the soccer headers. Additional analysis of the fNIRS time series demonstrates increased sample entropy of the signal after the headers in the right PC (p = 0.02), right MC (p = 0.004), and left MC (p = 0.04). These combined results reveal some variations in brain oxygenation immediately detected after repetitive headers. Significant changes in balance and neurocognitive function were not observed in this study, indicating a mild level of head impacts. This is the first study to observe hemodynamic changes immediately after sub-concussive impacts using non-invasive portable imaging technology. In combination with head kinematic measurements, this information can give new insights and a framework for immediate monitoring of sub-concussive impacts on the head.



#7 In professional football the decline in high-intensity running activities from first to second half is more pronounced in players with a fast muscle typology

Reference: Scand J Med Sci Sports. 2023 Oct 4. doi: 10.1111/sms.14508. Online ahead of print.

Authors: Freek Van de Casteele, Dieter Deprez, Jan Van Haaren, Wim Derave, Eline Lievens

Summary: Muscle typology is heterogeneous among national level football (soccer) players, but positional differences remain unclear. Furthermore, fast typology (FT) individuals fatigue more than slow typology (ST) individuals in lab conditions. Therefore, we investigated if muscle typology is different between playing positions and if the decay in high-intensity activities from the first to the second half is larger in FT football players than in ST players. We estimated muscle typology in 147 male professional football players by measuring soleus and gastrocnemius muscle carnosine via proton magnetic resonance spectroscopy. Players were classified as ST, intermediate typology (IT) or FT and categorized as goalkeeper, center back, full back, midfielder, winger or forward. Across four seasons in-game distances covered in multiple running speed, acceleration and deceleration zones were collected during the first and second half. We found no differences in muscle typology between positions (p = 0.412). FT players covered 10.9% more high acceleration distance (>3 m.s-2 ) in the first half than ST players (p = 0.021) and high acceleration distance decay was larger for FT players (-12.4%) than ST (-7.7%; p = 0.006) and IT players (-7.3%; p = 0.010). Moreover, the decline in distance covered in several high-intensity zones tended to be larger in FT players (-11.2% high-intensity >15 km.h-1 ; -12.7% high deceleration <-3 m.s-2 ; -11.5% medium acceleration 2-3 m.s-2 ) than in ST players (-7.1% high-intensity; -8.1% high deceleration; -8.1% medium acceleration; 0.05 < p < 0.1). In conclusion, possessing a particular muscle typology is not required to play any football position at the national level. However, there are indications that FT players might fatigue more toward the end of the game compared to ST players.



#8 Decision making influences movement variability and performance of high-level female football players in an elastic resistance task

Reference: Front Psychol. 2023 Sep 15:14:1175248. doi: 10.3389/fpsyg.2023.1175248. eCollection 2023.

Authors: Sílvia Tuyà Viñas, Bruno Fernández-Valdés Villa, Carla Pérez-Chirinos Buxadé, Jacob González, Gerard Moras Feliu

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Summary: The inclusion of sport-specific constraints in resistance training promotes the development of player abilities in an integrated way, which maximises the effectiveness of player adaptations induced by training. Considering that perceptual-cognitive abilities play a fundamental role in football, decision making could be introduced to enhance the cognitive similarity of resistance tasks to sport actions. However, it is unknown how decision making as a constraint could affect the player during an elastic resistance task. Therefore, the aim of this study was to investigate the effects of decision making of high-level female football players on movement variability and performance during an elastic band resistance task. Twenty-three high-level female football players performed the elastic resistance task with a ball, both as attackers and as defenders without decision making (NDM) and with decision making (DM). The movement variability was quantified using the sample entropy derived from the acceleration recorded with an accelerometer placed at the lower back of each player. The passing accuracy of the attacker was quantified using a scoring scale. Results revealed that adding decision making to an elastic resistance task increased the movement variability of the defender but did not affect the movement variability of the attacker. In contrast, the passing accuracy of the attacker was reduced. Overall, the attacker had a higher movement variability compared to the defender. These findings suggest that decision making, as a football-specific constraint, can enhance the potential of an elastic resistance task in training. This is due to the fact that it reduces control and regularity of movement for the defensive role player and increases technical difficulty for the attacking role player. Furthermore, these effects are beneficial, as they can promote the adaptive processes necessary to optimise the performance of the players.



#9 Impact of COVID-19 lockdown on injury risk in Qatar's professional football

Reference: J Sci Med Sport. 2023 Sep 19:S1440-2440(23)00410-3. doi: 10.1016/j.jsams.2023.09.008.

Authors: Karim Chamari, Yorck Olaf Schumacher, Mokhtar Chaabane, Raouf Nader Rekik, Souhail Chebbi, Ramadan Daoud, Lena Kristin Bache-Mathiesen, Khalid Alkhelaifi, Roald Bahr, Montassar Tabben

Summary: The aim was to compare injury incidence, burden and characteristics between the pre- and post-COVID-19 lockdown periods in Qatari professional football. Injury and exposure data for two post-COVID-19 lockdown periods [early post-lockdown period: short-term ~2 months (54 matches) and late post-lockdown period: long-term 8-months (183 matches)] were compared to the benchmark of the same periods from the three previous seasons (2017/18-2019/20). We observed no difference in overall, training or match incidence between early post-lockdown period and the benchmark reference. However, this short-term period resulted in lower burden for overall- (RR 0.80, P < 0.0001), training- (RR 0.73, P < 0.0001) and match-injuries (RR 0.40, P < 0.0001) compared to the benchmark. During late post-lockdown period match injury incidence (RR 0.72, P = 0.0010) and match injury burden (RR 0.69, P < 0.001) were lower than the benchmark. In contrast, both overall- (RR 1.30, P < 0.001) and training-injury burden (RR 1.65, P < 0.001) were higher. A significant increase in adductor strains in both post-lockdown periods was observed. Immediately after the COVID-19 lockdown (short-term effect), there was no difference in injury incidence but a lower injury burden compared to benchmark. Moreover, the rapid return to competition for the successive season (long-term effect) was associated with a higher overall- and training-injury burden, but a lower match-injury burden compared to the benchmark.



#10 Validity and Reliability of the Acceleration-Speed Profile for Assessing Running Kinematics' Variables Derived From the Force-Velocity Profile in Professional Soccer Players

Reference: J Strength Cond Res. 2023 Oct 16. doi: 10.1519/JSC.0000000000004637. Online ahead of print.

Authors: Antonio Alonso-Callejo, Jorge García-Unanue, Marc Guitart-Trench, Carlos Majano, Leonor Gallardo, Jose Luis Felipe

Summary: This research aim to assess the validity and reliability of the acceleration-speed profile (ASP) for measuring the mechanical variables of running kinematics when compared with the force-velocity profile (FVP) obtained by reference systems. The ASP and FVP of 14 male players of an elite football club were assessed during a competitive microcycle. Three ASPs were tested according to the number and type of sessions included in its plotting (ASP1: 5 training sessions and competitive match; ASP2: 5 training sessions; ASP3: competitive match). Force-velocity profile was tested 4 days before match (MD-4) with a 30-m linear sprint using 3 previously validated devices (encoder, mobile App, and global positioning system). Level of significance was p < 0.05. Acceptable reliability (intraclass correlation coefficient > 0.5) was found between the ASP1 and the encoder for all variables (F 0 -A 0 , V 0 -S 0 , and V max ). The more reliable ASP method was the ASP1 showing a lower bias than the ASP2 and ASP3 methods for almost all variables and reference systems. For ASP1, lower mean absolute error (MAE: 0.3-0.5) and higher correlation (P-M corr: 0.57-0.92) were found on variables related to the velocity in comparison with variables related to the early acceleration phase (F 0 -A 0 ; MAE: 0.49-0.63; P-M corr: 0.13-0.41). Acceleration-speed profile, when computed with data from a complete competitive week, is a reliable method for analyzing variables derived from velocity and acceleration kinematics. From these results, practitioners could implement ASP and the applications of the FVP previously studied, such as resistance training prescription, performance assessment, and return-to-play management.



#11 Injuries in professional women's elite soccer players in Kosovo: epidemiological injury study

Reference: BMC Sports Sci Med Rehabil. 2023 Oct 12;15(1):131. doi: 10.1186/s13102-023-00746-9.

Authors: Feim Gashi, Tine Kovačič, Ismet Shalaj, Bekim Haxhiu, Arben Boshnjaku

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Summary: An emphasis has been given lately towards women's engagement together with their potential in soccer. As this sport develops with athletes becoming more physically fit and skilled, it is unclear what the consequences in terms of injuries are. Having this in mind, this study aimed to investigate the major injuries that occur in women's soccer players. This descriptive epidemiological study invited all 286 women's soccer players from the 12 participating women clubs in the Kosovo 1st Soccer League (elite football level) during the 2021/2022 season, out of which 142 from 12 clubs participated. Exposure time for 1000 h of playing and training were recorded in addition to the anthropometric data, playing position, and prior injury history during the end of the season, practice, and match. The exact type of injury, severity, and post-injury recovery time, as well as the circumstances surrounding the injuries, were recorded. In total 84 injuries were registered with an overall injury ratio (IR) being 3.21 (CI: 2.56, 3.98) injuries/1000 exposure hours. During the competitive season, each player sustained 1.4 injuries on average. IRs were significantly higher during competition (n = 50; IR = 1.57; CI: 1.52, 1.62) compared to training (n = 34; IR = 0.26, CI: 0.25, 0.27). Out of a total of 142 women players, 84 (59.2%) injuries occurred, and no record of injuries was made in 58 (40.8%) players. The overall IR was observed to be 3.21 (CI: 1.24, 3.27), with moderate and severe injuries accounting for 38.1% of total injuries (each), followed by mild (16.7%) and minimal (7.1%) injuries. The women IR in Kosovo women's soccer players is low while being circa 11% below the international average. Almost 2 out of every 4 injuries were categorized as traumatic, with the IRs being more than 5-fold larger during games than during training. Additionally, these findings emphasize the higher rate of injuries amongst younger athletes, suggesting caution to be taken by the coaches when planning for the match. The collected data may help coaches and trainers create more targeted women's soccer injury prevention programs.



#12 The Homeless World Cup through storytelling: The narratives of Street Soccer players from Scotland and the USA

Reference: Psychol Sport Exerc. 2023 Oct 9:102549. doi: 10.1016/j.psychsport.2023.102549. Online ahead of print.

Authors: Jordan A Donnelly, Meredith A Whitley, Daryl T Cowan, Sara McLaughlin, Rosie Arthur

Summary: The purpose of this paper was to explore: (a) What stories do the Street Soccer players draw upon to construct meaning around their experiences of trauma, social exclusion, and homelessness? and (b) What stories are linked to the subjective sport programming experience and resulting future orientations? A longitudinal narrative approach was adopted with semi-structured interviews conducted with players from Scotland and the United States (n = 16, 7 female, 9 male, M age = 27.5) across three time points. Interviews were also conducted with significant others (n = 13) at time point three. All data were analyzed using thematic narrative analysis and represented in creative non-fiction approaches through three composite narratives. These narratives depicted visceral accounts of complex and developmental trauma, along with consequential experiences that unfolded before, during, and after the Homeless World Cup. While both preparing for and attending the event, players recalled concurrent feelings of anxiety and pride which manifested in various resilient and maladaptive coping behaviors. As the stories progressed, players battled a post event crash by engaging in support seeking and/or self-destructive behaviors before positive implications of the Homeless World Cup materialized. Through creative narrative approaches, this study presents novel and engaging accounts of players' experiences before, during, and after the event. We also identify potential safeguarding concerns that can be addressed through trauma-informed practices.



#13 Are non-starters accumulating enough load compared with starters? Examining load, wellness, and training/match ratios of a European professional soccer team

Reference: BMC Sports Sci Med Rehabil. 2023 Oct 10;15(1):129. doi: 10.1186/s13102-023-00743-y.

Authors: Rafael Oliveira, Rui Canário-Lemos, Ryland Morgans, Tiago Rafael-Moreira, José Vilaça-Alves, João Paulo Brito

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Summary: The aims of the study were to: (i) compare accumulated load and wellness between starters and non-starters of a European professional soccer team; (ii) analyze the relationships between wellness and load measures and; (iii) compare training/match ratio (TMr) of external and internal load between starters and non-starters. Ten players were considered starters while seven were classified as non-starters over a 16-week period in which six training sessions and match day (MD) were considered in each weekly micro-cycle. The following measures were used: wellness (fatigue, quality of sleep, muscle soreness, stress, and mood); load (rated of perceived exertion (RPE), session-RPE (s-RPE), high-speed running (HSR), sprinting, accelerations (ACC) and decelerations (DEC)). Accumulated wellness/load were calculated by summing all training and match sessions, while TMr was calculated by dividing accumulated training load by match data for all load measures and each player. Mann-Whitney U test was used for wellness variables, while independent T-test was used for the remaining variables to compare groups. Moreover, relationships among variables were explored using the Spearman's Rho correlation coefficient. The main results showed that non-starters presented higher significant values for fatigue (p < 0.019; g = 0.24) and lower significant values for duration (p < 0.006; ES = 1.81) and s-RPE (p < 0.001; ES = 2.69) when compared to starters. Moreover, positive and very large correlation was found between quality of sleep and RPE, while negative and very large correlation were found between stress and deceleration, and mood and deceleration (all, p < 0.05). Finally, non-starters presented higher values in all TMr than starters, namely, RPE (p = 0.001; g = 1.96), s-RPE (p = 0.002; g = 1.77), HSR (p = 0.001; g = 2.02), sprinting (p = 0.002; g = 4.23), accelerations (p = 0.001; g = 2.72), decelerations (p < 0.001; g = 3.44), and duration (p = 0.003; g = 2.27). In conclusion, this study showed that non-starters produced higher TMr in all examined variables despite the lower match and training durations when compared with starters, suggesting that physical load was adjusted appropriately. Additionally, higher RPE was associated with improved sleep while higher number of decelerations were associated with decreased wellness, namely, stress and mood for non-starters.



#14 Using Microtechnology and the Fourier Transform for the Analysis of Effective Activity Time in Professional Soccer

Reference: J Strength Cond Res. 2023 Oct 6. doi: 10.1519/JSC.0000000000004615. Online ahead of print.

Authors: José M Oliva-Lozano, Paweł Chmura, Paulino Granero-Gil, José M Muyor

Summary: This study aimed to investigate the use of the fast Fourier transform (FFT) for the analysis of effective activity time in professional soccer by (a) exploring the relationship between this variable and standard external load parameters and (b) analyzing the effective activity time during official professional soccer matches. Twenty-six male players participated in the study. Each player was categorized as midfielder, central defender, full-back, wide-midfielder, or forward. Tracking systems based on inertial sensors (4 3D accelerometers, 3 3D gyroscopes, and 1 magnetometer), and global positioning systems technology were used to collect external load measures for 35 matches. Each match was analyzed considering 15-minute periods to explore the evolution of effective activity time during the matches. The extra time from each match was also included. Fast Fourier transform duration may be a representative variable of effective activity time, given the strong positive correlation with the external load variables (p < 0.001). The linear regression analysis showed that the variables that significantly contributed to the model (R2 = 0.97) were the total of steps and the distance covered. The mean effective activity time in soccer match play was ∼48.69 minutes. This time significantly changed depending on factors such as the period of the match (F = 239.05; p < 0.001; ηp2 = 0.60) or playing position (F = 16.99; p < 0.001; ηp2 = 0.06). The greatest effective activity time was observed for all playing positions in the 0'-15' period. However, the 60'-75' period showed the lowest effective activity times compared with the rest of the 15-minute periods for all positions except for forwards (75'-90'). From a practical standpoint, sports performance practitioners may consider these results to improve the individualization of training and match demands. Also, a more accurate indicator of exercise intensity may be obtained (e.g., multiplying the rating of perceived exertion by the effective activity time).



#15 Effects of Upper-Body and Lower-Body Conditioning Activities on Postactivation Performance Enhancement During Sprinting and Jumping Tasks in Female Soccer Players

Reference: J Strength Cond Res. 2023 Oct 6. doi: 10.1519/JSC.0000000000004562. Online ahead of print.

Authors: Vinicius Santos da Silva, Fábio Yuzo Nakamura, Petrus Gantois, João Nuno Nogueira Gouveia, Javier Peña, Marco Beato, Eduardo Abade

Summary: This study aimed to investigate the postactivation performance enhancement (PAPE) effects of "specific" (half-back squat) and "nonspecific" (bench press) conditioning activities on sprinting and jumping performances in female soccer players. Fourteen players (mean ± SD: age = 22.3 ± 4.0 years; body mass = 60.2 ± 7.8 kg; height = 164.1 ± 4.2 cm) competing at national level (first League) participated in this within-subject crossover study. The players performed a warm-up protocol including 3 sets of 3 repetitions of half-back-squat or bench press exercises at 90% 1RM or a warm-up protocol without lifting weights (i.e., control condition). Forty-meter shuttle sprints (20 + 20 m with change of direction [COD-180°]), countermovement jump (CMJ), and horizontal jump (HJ) performances were recorded 6 minutes after the conditioning activities protocols or the control condition. Nonsignificant large positive effects were found for the HJ after the half-back-squat (ES = 1.68; p > 0.05) and bench press (ES = 1.68; p > 0.05) protocols. Although nonsignificant, HJ changes (Δ = 0.07 m) were greater than the smallest worthwhile change (0.02 m) and standard error of measurement (0.03 m) after both conditioning activities. Moreover, no significant changes were found for sprint and CMJ performance after neither half-back-squat nor bench press protocols (p > 0.05). In conclusion, both specific and nonspecific conditioning activities using heavy loads (i.e., 90% 1RM) may be suitable to enhance individual HJ. Finally, both conditioning activities are potentially ineffective for increasing sprint and CMJ performance in the context of this study.







The impact of verbal encouragement during the RSA speed training on internal intensity, mood state, and enjoyment in youth soccer players

This investigation aimed to study the impacts of Verbal encouragement (VE) given by coaches on the physiological aspects, players’ internal intensity, mood, and perceived enjoyment of youth soccer players during repeated agility speed training (RAS).





Are non‑starters accumulating enough load compared with starters? Examining load, wellness, training/match ratios of a professional team

The aims of the study were to: (i) compare accumulated load and wellness between starters and nonstarters of a European professional soccer team; (ii) analyze the relationships between wellness and load measures and; (iii) compare training/match ratio (TMr) of external and internal load between starters and non-starters.





Latest research in football - week 39 - 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 Are Late-Born Young Soccer Players Less Mature Than Their Early-Born Peers, Although No Differences in Physical and Technical Performance Are Evident?

Reference: Sports (Basel). 2023 Sep 8;11(9):179. doi: 10.3390/sports11090179.

Authors: Eduard Bezuglov, Georgiy Malyakin, Anton Emanov, Grigory Malyshev, Maria Shoshorina, Evgeny Savin, Artemii Lazarev, Ryland Morgans

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Summary: The aim of the study was to compare the status of somatic maturity, anthropometry, strength, speed, and soccer-specific technical skills of players from leading youth soccer academies born in different quarters of the same calendar year. A total of 678 young male soccer players from eight leading Russian soccer academies took part in the study. The following anthropometric measures and physical characteristics were measured: height, weight, body mass index, countermovement jumps (CMJ), 5, 10, and 20 m sprints, speed dribbling, foot and body ball juggling, and short and long pass accuracy. The determination of somatic maturity as a percentage of projected adult height was collected. All subject dates of birth were divided into four quartiles according to the month of birth. The analysis of all data obtained was conducted both within the total sample and by quartiles of birth, according to the age group categories of 12-13 years, 14-15 years, and 16-17 years and the degree of somatic maturity. There was a widespread relative age effect, with 43.5% of early-born players and only 9.6% of late-born players representing the sample. Early-born players were more mature than late-born players (p < 0.001 and p < 0.001) but had no statistically significant differences in strength, speed, or soccer-specific skills.



#2 Acute Effect of Four Stretching Protocols on Change of Direction in U-17 Male Soccer Players

Reference: Sports (Basel). 2023 Sep 1;11(9):165.  doi: 10.3390/sports11090165.

Authors: Mohamed Amine Ltifi, Mohamed Chedly Jlid, Jérémy Coquart, Nicola Maffulli, Roland van den Tillaar, Ridha Aouadi

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Summary: The ability to rapidly change direction while sprinting is a desirable athletic skill in soccer. Enhancing change of direction (COD) performance depends almost exclusively on specific training, with stretching traditionally considered one such intervention. However, the comparative impact of diverse stretching methods on COD in soccer players remains an area of interest. Therefore, this study aimed to compare the effects of different stretching methods on COD ability in soccer players. Twelve male soccer players playing in the national championship football division II (age: 16.3 ± 0.3 years, height: 1.81 ± 0.10 m, body mass: 67.7 ± 7.2 kg) were tested for COD performance (i.e., Illinois agility test) after (1) control condition (20 min general warm-up without stretching), (2) static stretching, (3) dynamic stretching, (4) combined static-dynamic stretching, and (5) combined dynamic-static stretching. The duration of stretching intervention was approximately 6 min for static and dynamic stretching and 12 min for both the combined stretching conditions. The experimental sessions were separated by 72 h. COD improved after dynamic stretching when compared to any other condition (p: 0.03-0.002; ηp2: 0.56-0.73), except for the control condition (p = 0.146; ηp2 = 0.18). In contrast, static stretching induced a detrimental effect on COD when compared only to the dynamic stretching condition (p < 0.01; ES = 1.35). Dynamic stretching exercises used by male soccer players in the warm-up improved COD. Other forms of stretching exercises, particularly static stretching, negatively impacted the COD performance. Therefore, coaches can consider integrating dynamic stretching protocols tailored to the athletes' specific needs. Moreover, extending the investigation to encompass a wider range of athletes, including different age groups and genders, would enhance the applicability and generalization of the findings.



#3 The Effects of Different Re-Warm-Up Strategies on Power, Changing of Direction and Ball Shooting Velocity in Well-Trained Soccer Players

Reference: Sports (Basel). 2023 Sep 5;11(9):169. doi: 10.3390/sports11090169.

Authors: Demetris Matsentides, Marios Christou, Nikolaos Zaras

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Summary: The purpose of the study was to investigate whether a re-warm-up training session either with tuck jumps and linear sprints or with changing of directions may enhance power, agility or ball shooting velocity in well-trained soccer players. Ten soccer players (age: 18.2 ± 1.7 years; body mass: 64.4 ± 8.0 kg; body height: 1.71 ± 0.04 m) participated in the study. Players performed three different re-warm-up interventions including no re-warm-up (C), change of direction (COD) and jump-sprint condition (JS). Before each re-warm-up intervention, players performed the same warm-up condition followed by 8 min of passive rest. Following the re-warm-up interventions, countermovement jump (CMJ), T-Test agility time-trial and ball shooting velocity were measured. Performance in CMJ height, power and power per body mass remained unchanged following all three conditions (p > 0.05). However, the agility time-trial was significantly reduced following COD re-warm-up compared to C (-1.7 ± 1.6%, p = 0.03). Ball shooting velocity was increased following COD compared to C (4.7 ± 3.8%, p = 0.014), while a statistical trend was found between JS and C interventions (4.8 ± 5.4%, p = 0.060). These results suggest that a re-warm-up intervention including changing of directions may significantly enhance T-Test agility time-trial and ball shooting velocity in well-trained soccer players.



#4 Soccer and Disability, Is It Possible? Analysis of the Learning and Coaching Context in Spain

Reference: Sports (Basel). 2023 Aug 28;11(9):161. doi: 10.3390/sports11090161.

Author: Antonio Burgos-García

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Summary: Coaching a youth soccer player is important, and the coach's role is key. Actually, there is no profile or coaching program for grassroots-soccer coaches that favor the practice of soccer and disability, according to different research and experts. The main purpose of this study is to identify and analyze the professional profile of the grassroots-soccer coach who has soccer players with disabilities (learning and coaching context). This research applies a quantitative method, specifically, non-experimental, cross-sectional, descriptive, and inferential methodology. The sample of analysis is the staff members of the professional soccer clubs of LaLigaSantander Genuine (Spain). An important result is that half of the grassroots-soccer coaches have not received specific education to coach youth soccer players with disabilities. Finally, one important conclusion of this research is that by generating a climate of trust and empathy, grassroots-soccer coaches improve the performance of their soccer players with disabilities by recognizing and understanding their emotional states.



#5 Assessing the Association Between On-Field heading technique and head impact kinematics in a cohort of female youth soccer players

Reference: Sci Med Footb. 2023 Sep 27. doi: 10.1080/24733938.2023.2264272. Online ahead of print.

Authors: Tanner M Filben, Brian T Tomblin, N Stewart Pritchard, Garrett S Bullock, Jordan M Hemmen, Kristina E Neri, Victoria Krug, Christopher M Miles, Joel D Stitzel, Jillian E Urban

Summary: There is concern that exposure to soccer headers may be associated with neurological sequelae. Training proper heading technique represents a coachable intervention that may reduce head acceleration exposure. The objective was to assess relationships between heading technique and head kinematics in female youth soccer players. Fourteen players (mean age = 14.4 years) wore instrumented mouthpieces during practices and games. Headers were reviewed by three raters to assign a technique score. Mixed models and LASSO regression evaluated associations of technique with peak linear acceleration (PLA), rotational acceleration (PRA), rotational velocity (PRV), and head impact power ratio (HIP Ratio) while adjusting for session type and ball delivery. Two hundred eighty-nine headers (n = 212 standing, n = 77 jumping) were analyzed. Technique score (p = 0.043) and the technique score - session type interaction (p = 0.004) were associated with PRA of standing headers, whereby each ten-unit increase in technique score was associated with an 8.6% decrease in PRA during games but a 5.1% increase in PRA during practices. Technique was not significantly associated with any other kinematic metrics; however, peak kinematics tended to decrease as technique score increased. LASSO regression identified back extension and shoulder/hip alignment as important predictors of peak kinematics. Additional research on heading technique and head acceleration is recommended.



#6 Health problems occurring in national-level female soccer players are different between leagues and throughout the season: a 6-month prospective cohort study

Reference: BMJ Open Sport Exerc Med. 2023 Sep 20;9(3):e001595. doi: 10.1136/bmjsem-2023-001595. eCollection 2023.

Authors: Anna Dettwiler, Nora Wieloch, Stefan Fröhlich, Florian Imhoff, Johannes Scherr, Jörg Spörri

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Summary: This study investigated the prevalence and severity of health problems in national-level female soccer players with respect to league and seasonality. In a prospective cohort study, 46 female soccer players aged 22.8±3.9 years playing in the three highest leagues in Switzerland were surveyed biweekly using the Oslo Sports Trauma Research Centre health problem (OSTRC-H) questionnaire. All definitions and measures followed the OSTRC-H-specific recommendations. The 6-month observation period included parts of the off-season and one half of the match season. The average 2-weekly health problem prevalence was 37.3% (illnesses: 8.8%; sudden onset injuries-both acute and repetitive mechanisms: 19.7%; repetitive gradual onset injuries: 12.4%) and 25.1% for substantial problems as defined in the OSTRC-H context (7.3%; 12.0% and 7.3%, respectively). The absolute injury rates amounted to 148 injuries per 100 players per half season, of which 96 injuries per 100 players per half season were substantial. Female players in the 2nd and 3rd highest national leagues showed more gradual onset injuries (p<0.001) and fewer illnesses than those in the top league (p<0.05). At the same time, there were no league-specific differences in sudden onset injuries. Such injuries had a higher cumulative severity score than gradual onset injuries. Among sudden onset injuries, the ankle was the most affected body part, while the thigh was affected by for gradual onset injuries. The average 2-weekly health problem prevalence values steadily increased during the match season. Among national-level female soccer players, the risk of health problems is relatively high and differs between leagues and across seasons.



#7 The effects of high-intensity interval training at the anaerobic and psychomotor fatigue thresholds on physiological parameters in young soccer players: a prospective study

Reference: Front Physiol. 2023 Sep 7:14:1221121. doi: 10.3389/fphys.2023.1221121. eCollection 2023.

Authors: Paweł Chmura, Jan Chmura, Wiktor Chodor, Adrian Drożdżowski, Andrzej Rokita, Marek Konefał

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Summary: This study aimed to investigate the effects of a 4-week specific high-intensity interval training (HIIT) program performed between the anaerobic threshold (ANT) and the psychomotor fatigue threshold (PFT) on physiological parameters in 14 professional soccer players at the under-17 level. The first and second stages of the research protocol included a treadmill running exercise with increasing load and six 3-min four-versus-four games of soccer with a 3-min break between games. Players then participated in a training microcycle involving three specific HIIT exercises twice per week for 4 weeks, after which they repeated stages one and two, followed by an assessment of changes. The measurement of lactate (LA) determined ANT, whereas the choice reaction time (CRT) indicated PFT among other selected physiological parameters. The repeated-measure analysis of variance (ANOVA) compared mean values for the examined variables using Bonferroni post hoc test. It demonstrated significantly increased maximal oxygen consumption (VO2 max) from 45.9 ± 3.0 to 48.7 ± 2.6 at the ANT and from 49.1 ± 3.4 to 52.0 ± 3.6 on the PFT after 4 weeks of training. A significant increase in the running speed (RS) at both thresholds and heart rate (HR) at the ANT (p ≤ 0.05) was also recorded. Moreover, the players exceeded their intensity of effort during ANT while playing four-versus-four soccer matches, but they did not reach intensity during PFT. In conclusion, the findings of the study demonstrated that both thresholds shifted toward higher loads and the proposed specific HIIT effectively increased the exercise capacity of soccer players.



#8 Trends in Soccer-Related Craniomaxillofacial Injuries, United States 2003-2022

Reference: J Oral Maxillofac Surg. 2023 Sep 9:S0278-2391(23)01092-3. doi: 10.1016/j.joms.2023.09.001. Online ahead of print.

Authors: Lang Liang, Sung-Kiang Chuang

Summary: Soccer is one of the most popular sports worldwide. However, it has risks of injury to craniomaxillofacial regions such as the head, neck, and mouth. The purpose of this study is to determine which demographic and injury characteristics among soccer players with craniomaxillofacial injuries are associated with increased hospitalizations. This is a retrospective cohort study utilizing the National Electronic Injury Surveillance System. Subjects included in this study experienced an injury to a craniomaxillofacial area from soccer between January 1, 2003, and December 31, 2022. The predictor variables included demographics (age, sex, race) and injury characteristics (craniomaxillofacial region, diagnosis). The primary outcome variable was injury severity defined as hospitalization outcome after injury (yes/no). The secondary outcome variable was the trends in the incidence of soccer craniomaxillofacial injuries over time (2003-2022). The covariates were the heterogenous set of predictor variables in this study. Descriptive statistics and univariate analyses were computed. Survey-weighted univariate and multivariate logistic regression were used to measure the association of demographic and injury variables with hospitalization outcome. Statistical significance was defined as P < .05. The study sample included 26,642 subjects (national estimate, 799,393). The national incidence of craniomaxillofacial soccer injuries generally increased between 2003 and 2012 and decreased between 2016 and 2020. Subjects in the ≥30 age group had increased odds of hospitalization compared to those in the 10-19 age group (odds ratio [OR], 2.12; P < .001). Compared to females, males had significantly higher odds of hospitalization (OR, 1.53; P < .001). Head (OR, 8.42; P < .001) and neck (OR, 15.8; P < .001) injuries had increased odds of hospitalization compared to facial injuries. Relative to contusions/abrasions, subjects with fractures (OR, 94.7; P < .001), dental injuries (OR, 41.3; P < .001), and concussions (OR, 5.33; P = .017) were at significantly higher odds of hospitalization. Age, sex, craniomaxillofacial region, and diagnosis were significant predictors of hospitalization outcome after craniomaxillofacial soccer injury. Safer playing styles, use of mouthguards, and proper medical management may reduce future risks of craniomaxillofacial injury from soccer.



#9 Synchronization of passes in event and spatiotemporal soccer data

Reference: Sci Rep. 2023 Sep 23;13(1):15878. doi: 10.1038/s41598-023-39616-2.

Authors: Henrik Biermann, Rumena Komitova, Dominik Raabe, Eric Müller-Budack, Ralph Ewerth, Daniel Memmert

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Summary: The majority of soccer analysis studies investigates specific scenarios through the implementation of computational techniques, which involve the examination of either spatiotemporal position data (movement of players and the ball on the pitch) or event data (relating to significant situations during a match). Yet, only a few applications perform a joint analysis of both data sources despite the various involved advantages emerging from such an approach. One possible reason for this is a non-systematic error in the event data, causing a temporal misalignment of the two data sources. To address this problem, we propose a solution that combines the SwiftEvent online algorithm (Gensler and Sick in Pattern Anal Appl 21:543-562, 2018) with a subsequent refinement step that corrects pass timestamps by exploiting the statistical properties of passes in the position data. We evaluate our proposed algorithm on ground-truth pass labels of four top-flight soccer matches from the 2014/15 season. Results show that the percentage of passes within half a second to ground truth increases from 14 to 70%, while our algorithm also detects localization errors (noise) in the position data. A comparison with other models shows that our algorithm is superior to baseline models and comparable to a deep learning pass detection method (while requiring significantly less data). Hence, our proposed lightweight framework offers a viable solution that enables groups facing limited access to (recent) data sources to effectively synchronize passes in the event and position data.



#10 Minimal Number of Events Required for Acceleration-Speed Profiling in Elite Women's Soccer

Reference: Int J Sports Physiol Perform. 2023 Sep 23:1-4. doi: 10.1123/ijspp.2023-0223. Online ahead of print.

Authors: Patrick Cormier, Ming-Chang Tsai, Cesar Meylan, Victor H T Soares, David C Clarke, Marc Klimstra

Summary: The aim was to determine the minimum number of events (training or matches) for producing valid acceleration-speed (AS) profiles from global navigation satellite system (GNSS) data. Nine elite female soccer players participated in a 4-week training camp consisting of 19 events. AS profile metrics calculated from different combinations of athlete events were compared to force-velocity (FV) profile metrics from 2 × 40-m stand-alone sprint effort trials, using the same GNSS 10-Hz technology. Force-velocity profiles were calculated, from which AS profiles were obtained. AS profiles from training and matches were generated by plotting acceleration and speed points and performing a regression through the maximal points to obtain the AS metrics (theoretical maximal speed, x-intercept [in meters per second], theoretical maximal acceleration, y-intercept [in meters per second squared], and the slope per second). A linear mixed model was performed with the AS metrics as the outcome variables, the number of events as a fixed effect, and the participant identifier as a mixed effect. Dunnett post hoc multiple comparisons were used to compare the means of each number of event grouping (1-19 events) to those estimated from the dedicated sprint test. Theoretical maximal speed and theoretical maximal acceleration means were no longer significantly different from the isolated sprint reference with 9 to 19 (small to trivial differences = -0.31 to -0.04 m·s-1, P = .12-.99) and 6 to 19 (small differences = -0.4 to -0.28 m·s-2, P = .06-.79) events, and the slopes were no longer different with 1 to 19 events (trivial differences = 0.06-0.03 s-1, P = .35-.99). AS profiles can be estimated from a minimum of 9 days of tracking data. Future research should investigate methodology resulting in AS profiles estimated from fewer events.



#11 Growth-related sports injuries among young male professional football players in the Netherlands: a prospective cohort study concerning injury incidence, severity and burden

Reference: Sci Med Footb. 2023 Sep 23:1-12. doi: 10.1080/24733938.2023.2261399. Online ahead of print.

Authors: Else E A E Juch, Vincent C van de Koppel, Donna Blokland, Renko A Wouters, Frank J G Backx, Edwin A Goedhart, Nick van der Horst

Summary: The aim was to investigate the incidence, type and location of growth-related sports injuries (GRSI) in youth professional football in the Netherlands. Secondary, to gain more knowledge on the injury severity and burden of GRSI. In this prospective, longitudinal cohort study, 813 players aged 10-18 are included. Data collection is performed by instructing the medical staff of six professional football club academies to register GRSI by means of standardized forms. Training and match exposure are registered individually on a weekly basis. Injury incidence was calculated as number of GRSI per 1000 hours, injury severity as the median number of days lost in categories and injury burden as the number of days lost per 1000 hours. A total of 62 GRSI were documented in the football season 2021-2022. The total incidence of GRSI was 0.62/1000 hours football exposure. Morbus Osgood Schlatter and Morbus Sever were most common types of GRSI, both with incidence rates of 0.22/1000 hours exposure. About 58.3% of the documented GRSI were classified as major (>28 days lost). Within this group, the mean severity was 55 days time-loss to football. GRSI are relatively common in youth professional football. The most common types are Morbus Sever and Morbus Osgood Schlatter. Morbus Osgood Schlatter has the highest injury severity and burden compared to other types of GRSI.



#12 The Role of Football Players as a Model for Promoting Community Health

Reference: Iran J Public Health. 2023 Aug;52(8):1779-1780. doi: 10.18502/ijph.v52i8.13419.

Authors: Tohid Seif Barghi, Mohammad Mahdi Tavana

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#13 Motivation among Teenage Football Players: A Longitudinal Investigation throughout a Competitive Season

Reference: Eur J Investig Health Psychol Educ. 2023 Sep 4;13(9):1717-1727. doi: 10.3390/ejihpe13090124.

Authors: Filipe Rodrigues, Diogo Monteiro, Rui Matos, Miguel Jacinto, Raúl Antunes, Nuno Amaro

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Summary: The present study aimed to investigate the dynamic changes in behavioral regulations among teenage football players throughout a competitive season, with three measurement points (T1, T2, and T3). The total sample size for the study comprised 108 participants (78 male; 30 female). The participants' mean age was 14.31 (SD = 1.48). A MANOVA repeated measures analysis was performed within the group for all six behavioral regulations based on self-determination theory. The results of the study revealed noteworthy patterns in the behavioral regulations and intrinsic motivation scores over the competitive season. Identified regulation demonstrated a significant increase from T1 to T3 (p < 0.01, η2p = 0.13). Intrinsic motivation displayed a significant decrease over the same period from T1 to T3 (p < 0.01, η2p = 0.12). On the other hand, amotivation, external regulation, introjected regulation, and integrated regulation did not show significant changes between the three time points. The findings have practical implications for coaches and sports practitioners, as they highlight the need to create a supportive and autonomy-promoting environment to sustain athletes' intrinsic motivation throughout a competitive season. Also, recognizing the increase in identified regulation can inform strategies that align team goals and training sessions with players' individual values, thereby enhancing their commitment and dedication to the team's success.



#14 Anthropometric Profiling and Changes in Segmental Body Composition of Professional Football Players in Relation to Age over the Training Macrocycle

Reference: Sports (Basel). 2023 Sep 5;11(9):172. doi: 10.3390/sports11090172.

Authors: Wiktoria Staśkiewicz-Bartecka, Elżbieta Grochowska-Niedworok, Grzegorz Zydek, Mateusz Grajek, Agata Kiciak, Agnieszka Białek-Dratwa, Ewa Niewiadomska, Oskar Kowalski, Marek Kardas

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Summary: Body composition is an important indicator of the overall health and fitness of team sports athletes, including in football, and therefore, anthropometric profiling of elite football players is useful as part of determining their skills, strengths, and weaknesses to develop effective strength and conditioning programs. One of the tools available to coaches to track correlates of performance and health is routine body composition assessment. The purpose of this study is to describe and compare the body composition and anthropometric profiles of players using the Direct Segmental Multi-Frequency Bio-Electrical Impedance Analysis method, and to manage body composition throughout the round in the 2020-2021 season. The investigation was carried out during the Polish football league, PKO BP Ekstraklasa, spring round of the football season 2020-2021, in which male football players participated. Athletes between the ages of 18 and 25 (n = 16) made up the younger age group, while those between the ages of 26 and 31 (n = 22) made up the older age group. This manuscript is a continuation of the presentation of the results of the study, which was conducted between 7 January and 23 July 2021. At different stages of the macrocycle, participants underwent six different body composition analyses. The younger and older groups of athletes were compared, as well as measurements of time points 1-6. The dominant extremities, assisting extremities, and trunk had larger fat-free mass contents in the older age group. In the study groups, there was a difference in the fat-free mass content between measures 1-6 that was statistically significant. In the younger group, there was a statistically significant difference in the amount of fat mass content between measurements 1-6. In the older age group, no statistically significant changes were found. The study showed changes in fat-free mass and fat mass in body segments; differences were observed between age groups and between different moments of measurement. Age is an important factor in determining body composition and is also related to an athlete's experience and seniority. Anthropometric profiling and comprehensive body composition analysis are important tools used in preparing athletes for competition.



#15 Cryo plus Ultrasound Therapy, a Novel Rehabilitative Approach for Football Players with Acute Lateral Ankle Injury Sprain: A Pilot Randomized Controlled Trial

Reference: Sports (Basel). 2023 Sep 9;11(9):180. doi: 10.3390/sports11090180.

Authors: Antonio Ammendolia, Alessandro de Sire, Lorenzo Lippi, Valerio Ammendolia, Riccardo Spanò, Andrea Reggiani, Marco Invernizzi, Nicola Marotta

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Summary: Acute lateral ankle sprains are common injuries among athletes, but the optimal treatment strategies in elite athletes are still debated. This proof-of-concept study aimed to assess the impact of cryo-ultrasound therapy on the short-term recovery of football players with acute lateral ankle sprains. Semi-professional football players with grade I or II lateral ankle sprains were randomly assigned to the experimental group (receiving cryo-ultrasound therapy combined with conventional physical therapy) or control group (sham cryo-ultrasound therapy combined with conventional physical therapy). Pain intensity and physical functioning were assessed by the Numeric Rating Scale (NRS) and Foot and Ankle Disability Index (FADI) at baseline (T0) at the end of treatment (T1), after one month (T2), and two months after treatment (T3). After the study intervention, significant between groups differences were reported in terms of pain relief (NRS: 4.08 ± 1.29 vs. 5.87 ± 1.19; p = 0.003) and physical function (FADI: 50.9 ± 10.3 vs. 38.3 ± 11.5; p = 0.021). However, no significant between group differences were reported at T2 and T3. No adverse effects were reported. Cryo-ultrasound therapy combined with conventional physical therapy can accelerate recovery and early return to sport in elite football players with acute lateral ankle sprains. While this study contributes valuable insights into the potential benefits of cryo-ultrasound therapy, further investigations with a longer follow-up are needed to validate and optimize the application of physical agent modalities in the management of ankle injuries.






Injury incidence in male elite youth football players is associated with preceding levels and changes in training load

This study analysed external and internal TL variables and their association with injury incidence in a group of male elite youth football players over four seasons.





Relative Individual Sprint in Most Demanding Passages of Play in Spanish Professional Soccer Matches

The objective of this research was to analyse the most demanding passages (MDP) considering the sprint variable relative to the maximum level of sprint ability of each player as a function of player position, final outcome and part of the match during the competitive phase of a professional soccer season.





Net transfer: Winners and losers

With the recent exodus of players into Saudi Arabia it seemed reasonable to have a look on net transfers over certain time frames. 


The following graphs display the 30 most active clubs starting with the ones having the greatest volume of financial transaction over the last 10 years.  The figures published include fixed transfer fees, any add-ons regardless of whether they have actually been paid, as well as sums invested in the context of paying loans. Amounts negotiated for loans with an obligation to buy are included in the breakdown for the year of the transfer. Within the limits of available information, the data on beneficiaries considers sell-on fees negotiated by previous clubs.

During the last 10 years, Manchester United has the most negative balance (-€1.396 billion), followed by Chelsea and Paris St-Germain.



The former clubs are also inside the top 5 in the post-covid area.



The usual Spanish, German, French and Italian suspects are listed as well. Milan AC as the first Italian site followed by Bayern, Real and Barcelona. Galatasaray and Al-Hilal are the two clubs that have the highest negative net transfer balance outside big-5 league clubs with the lalter sitting in 2nd place in the 2023 period (2nd graph below).


Generally, there are 17 out of 30 clubs from the English Premier league showing intense financial activity.  Consequently, the sum of the net transfer of the English clubs far exceeds other nations. 




Having looked at the negative balances it seems interesting to check the positive ones as well. 


Benfica accumulated close to 780 mio€ over the last decade sitting comfortably at the top of the table, followed by Ajax and RB Salzburg. 



Additional two Portuguese sites (Sporting and FC Porto) inside the top 6 clubs display the ability to create positive net income selling players. Generally, the landscape seems more diverse with regards to positive income. That is Netherlands, Austria, Belgium and other leagues are able to create financial surplus from transfers.



The top three clubs over the last decade are dominating in the post-covid area as well. 



The last figure presents the most recent analysis, net transfer plus in 2023. Villareal as the “new” top site followed by Benfica and Stade Rennais.








The Effect of High-Intensity Accelerations and Decelerations on Match Outcome of an Elite English League Two Football Team

The influence of high-intensity actions on match performance outcomes has not been established. The aim of the present study was to identify the influence of high-intensity accelerations (ACC) and decelerations (DEC) on match performance outcomes (i.e., win, draw, lost).





Are Late-Born Soccer Players Less Mature Than Their Early-Born Peers - No Differences in Physical and Technical Performance Are Evident?

The aim of the study was to compare the status of somatic maturity, anthropometry, strength, speed, and soccer-specific technical skills of players from leading youth soccer academies born in different quarters of the same calendar year.





Latest research in football - week 38 -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 Significant Changes in Resting Metabolic Rate Over a Competitive Match Week Are Accompanied by an Absence of Nutritional Periodization in Male Professional Soccer Players

Reference: Int J Sport Nutr Exerc Metab. 2023 Sep 21;1-11.  doi: 10.1123/ijsnem.2023-0069. Online ahead of print.

Authors: Jennie L Carter, David J Lee, Craig G Perrin, Mayur K Ranchordas, Matthew Cole

Summary: Resting metabolic rate (RMR) is an important component of total daily energy expenditure; however, it is currently not understood how it varies across a typical competitive match week in professional soccer players. For the first time, we aimed to assess RMR throughout an in-season competitive week in professional soccer players. Additionally, we aimed to assess energy and carbohydrate intake across the same week. Twenty-four professional soccer players from an English Premier League club (age: 18 ± 1.6 years) completed the study. RMR was assessed each morning of a typical competitive match week (match day [MD] -3, -2, -1, +1, +2, and + 3), and dietary intake (including MD) was assessed daily via the remote food photography method and 24-hr recall. Daily training load was quantified using Global Positioning System, daily muscle soreness ratings were recorded, and body composition was assessed via dual-energy X-ray absorptiometry. There was a significant (p = .0004) increase in mean RMR of ∼261 kcal/day on MD + 1, compared with MD - 1. Additionally, volume of oxygen consumed significantly increased at MD + 1 (p = .0002) versus MD - 1. There were no significant differences in daily energy or carbohydrate intake across the competitive week (p > .05), with inadequate carbohydrate intakes on MD - 1 (∼3.9 g/kg body mass), MD (∼4.2 g/kg body mass), and MD + 1 (∼3.6 g/kg body mass) in relation to current recommendations. We report, for the first time, that RMR is significantly increased following a competitive match in professional soccer players. In addition, we confirm previous findings to reinforce that players exhibit inadequate nutrition periodization practices, which may impair physical performance and recovery.



#2 Elite North American soccer performance in thermally challenging environments: An explorative approach to tracking outcomes

Reference: J Sports Sci. 2023 Sep 21;1-8. doi: 10.1080/02640414.2023.2259262. Online ahead of print.

Authors: Garrison Draper, Greg Atkinson, Paul Chesterton, Matthew Portas, Matthew Wright

Summary: The physiologic challenges related to performances in hot conditions calls for dedicated consideration when planning athlete training, although complete amelioration of the effects of heat may not be possible. We aimed to quantify within-subject correlations between different measures of environmental temperature and performance changes over multiple elite soccer competitions. Thirty-seven elite male soccer players (age: 26 ± 3.4 years, height: 171 ± 2 cm, body mass: 78 ± 7.1 kg) competed in North America over four seasons (range: 3 to 98 matches). Players wore global positioning system devices during games and reported differential-RPE immediately post game. Temperatures at kick-off, week average temperature, the difference between game-day and week average (DiffTemp), and heat index at kick-off were obtained. Within-player correlations were calculated using general linear models to quantify associations between fluctuations in temperature measures and physical and perceived outputs. Correlations between total distance and the various temperature measures were trivial to small (range: -0.08 to 0.13, p=<0.001-0.02). Small negative correlations were found between all temperature measures except DiffTemp and high-speed running (HSR) (range: -0.17 to -0.14, p=<0.001). Most correlations between differential-RPE and temperature measures were trivial to small and not significant (r = 0.06 to 0.18 p = 0.03-0.92) although breathlessness-RPE and heat index showed a small significant association (P = 0.018). Decrements in HSR appear to be associated with increased environmental temperature, however, these associations are small in magnitude.



#3 Improved physical performance of elite soccer players based on GPS results after 4 days of carbohydrate loading followed by 3 days of low carbohydrate diet

Reference: J Int Soc Sports Nutr. 2023 Dec;20(1):2258837. doi: 10.1080/15502783.2023.2258837. Epub 2023 Sep 20.

Authors: Abdolreza Kazemi, Ghazi Racil, Amir Hossein Ahmadi Hekmatikar, Mohadeseh Behnam Moghadam, Parisa Karami, Menno Henselmans

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Summary: Carbohydrate loading is an established sports nutrition strategy for endur- 16 ance exercise performance. We tested if carbohydrate loading could improve the performance of 17 elite soccer players under ecologically valid circumstances using Global Positioning System (GPS) data. Twenty-two adult Iran Premier league soccer players were divided into a carbohydrate-loading group (CLG) and Control group (CG). The carbohydrate loading group restricted carbohydrate intake for three days to 1.5 g/kg/d while increasing exercise intensity. From days four to seven, exercise intensity was decreased and carbohydrate intake was considerably increased up to 7.5 g/kg/d on the day of the match, during which performance was analyzed using GPS data. The control group performed the same exercise training but maintained their habitual carbohydrate intake of 5-6 g/kg/d. The data were analyzed using a univariate ANCOVA with baseline data from a pre-intervention match as the control variable. The carbohydrate loading team scored significantly higher on running distance, maximum speed and the number of top and repeated sprints; the carbohydrate loading group scored significantly lower on player load, metabolic power and running imbalance compared to the control team during their match. Our findings suggest carbohydrate loading enabled elite soccer players to achieve greater running outputs with greater metabolic efficiency and lower fatigue compared to their habitual diets.



#4 Imaging-detected sports injuries and imaging-guided interventions in athletes during the 2022 FIFA football (soccer) World Cup

Reference: Skeletal Radiol. 2023 Sep 16. doi: 10.1007/s00256-023-04451-z. Online ahead of print.

Authors: Marcelo Bordalo, Andreas Serner, Eduardo Yamashiro, Emad Al-Musa, Mohamed Abdelatif Djadoun, Khalid Al-Khelaifi, Yorck Olaf Schumacher, Abdulaziz Jaham Al-Kuwari, Andrew Massey, Pieter D'Hooghe, Marco Cardinale

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Summary: The aim was to describe imaging-detected musculoskeletal injuries and image-guided interventional procedures during the 2022 FIFA football (soccer) World Cup. Retrospective analysis of all radiologic examinations performed in a central medical facility for athletes was performed by two board certified musculoskeletal radiologists. Data on muscle, tendon, ligament, cartilage, and bone injuries were collected according to imaging modality and body part. A total of 143 radiology examinations in 94 athletes were evaluated at the central medical facility. Magnetic resonance imaging (MRI) was the most utilized modality (67%), followed by radiography (12%), ultrasonography (9%), and computed tomography (4%). Image-guided interventions corresponded to 8% of all radiological examinations. There were 112 injuries described, affecting muscles and tendons (42%), ligaments (25%), cartilage (21%), and bone (12%). Most injured body parts were thigh (27%), foot and ankle (23%), knee (23%), and hip/groin (8%). Most injured players were within the age range of 24-35 years old (71%). Imaging was utilized in 11% of players who participated in the 2022 FIFA World Cup in Qatar. MRI was the most utilized modality, and acute muscle tears were the most diagnosed type of injury. Diagnostic imaging played an important role in diagnosing sports-related injuries during the 2022 FIFA World Cup.




#5 FIFA football nurse - A task sharing approach in sports and exercise medicine practice in grassroots women's football in low- and middle- income settings. A study protocol for a cluster randomised controlled trial

Reference: PLoS One. 2023 Sep 21;18(9):e0278428. doi: 10.1371/journal.pone.0278428. eCollection 2023.

Authors: Nonhlanhla Sharon Mkumbuzi, Andrew Massey, Samuel Kiwanuka Lubega, Ben Sorowen, Enock Madalitso Chisati

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Summary: Football (soccer) is a very popular team sport among African women and girls, with player numbers continuing to rise at all levels of the sport. Whereas the participation in football and associated injuries are on the rise, there are not enough sports and exercise medicine (SEM) personnel to attend to these women football players. While Africa may not currently have enough SEM trained medical doctors and/or physiotherapists, it has relatively higher numbers of other healthcare workers; for example, nurses, who lead healthcare services provision from community to tertiary levels. The primary objective of this study will be to compare sports medicine practices; injury prevention behaviours; injury risk parameters; incidence and prevalence of injuries and illnesses in teams with and without a Football Nurse during one competitive season in Malawi's Women's football league. This study will be a cluster randomised control trial will recruit 24 teams from the Women's Football League in Malawi, which will be randomised to either the intervention group or the control group. A cohort of 12 nurses will receive training in basic football medicine; after which they will be attached to a total of 12 women's football teams (intervention group) during one competitive season. The Football Nurses will be directly report to a physiotherapist or doctor in their district to whom they will refer serious injuries for investigations, or further management. The teams with Football Nurses will be compared to other teams that will not have Football Nurses. We expect to develop a low cost, sustainable and context relevant solution to manage the treatment gap of football injuries/illnesses in underserved communities such as women's football. Trial registration number: Pan African Clinical Trial Registry (PACTR202205481965514).



#6 The assessment of the match performance of association football referees: Identification of key variables

Reference: PLoS One. 2023 Sep 21;18(9):e0291917. doi: 10.1371/journal.pone.0291917. eCollection 2023.

Authors: Vítor Carvalho, Pedro T Esteves, Célia Nunes, Werner F Helsen, Bruno Travassos

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Summary: The purpose of this study was to understand the contribution of each performance indicator to evaluate match performance of football referees. Thirty-four elite Referee Match Observers (RMOs) from the Portuguese FA participated voluntarily in the study. From the official assessment sheet of each game, the referee's game score was categorized in two groups according to referee's game score: i) Referees with a Low Score (LFS) and ii) Referees with High Score (HFS). A multivariable binary logistic regression model was used to assess the relationship between the Performance Indicators (PIs) of the dimensions i) game difficulty and game intervention and ii) disciplinary actions and game management in relation to the referee's match assessment score. The model proposed revealed that only the PIs negative application of the laws of the game and referee teamwork, from the dimension disciplinary actions and game management, significantly defined the final game referee's assessment score. This study suggests that the PIs scored by the RMOs contributed in a different way to the referee's game score. The model explains 60.4% of the referee's game score based on the variables referee teamwork and negative application of the laws of the game.



#7 Bonitation assessment of intensively used football turf depending on the date and area of observation

Reference: Sci Rep. 2023 Sep 20;13(1):15580. doi: 10.1038/s41598-023-42562-8.

Authors: Karol Wolski, Łukasz Sobol, Henryk Bujak

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Summary: This article aimed to evaluate the visual and functional characteristics of intensively used football turf over 10 years, depending on the different areas of the game. The research was conducted on the football turf of the AZS Environmental Club in Wrocław (N: 51° 7' 31'' E:17° 4' 14''). High variability of the evaluated parameters was observed regarding seasonality, year of observation, and the area of play. It has been shown that the goal area and penalty box areas have the lowest functional value, which are vital areas of the game from the point of view of gaining an advantage in the game. Also, these places are more susceptible to creating sites without plants (requiring additional overseeding) due to the potential of hollowing and goalkeeper interventions ending with the body landing on the ground. The middle area was characterized by the highest overall aspect, color, and turf density values. In the vast majority of cases, there was a downward trend in the turfs' functional value with the turf's age, which is an essential finding in the context of the use of intensively used, athletic natural grass surfaces.



#8 Can the Copenhagen Adduction Exercise Prevent Groin Injuries in Soccer Players? A Critically Appraised Topic

Reference: J Sport Rehabil. 2023 Sep 21;1-4. doi: 10.1123/jsr.2023-0088. Online ahead of print.

Authors: Marcos Quintana-Cepedal, Omar de la Calle, Hugo Olmedillas

Summary: Injuries that affect the groin region are among the most common in football players. To prevent this condition, studies have focused on strengthening the adductors, hip flexors, or abdominal muscles. Recent investigations have used an eccentric-biased exercise (Copenhagen Adduction Exercise [CAE]) that promotes functional and architectural adaptations in the muscle tissue, though its effect on injury risk reduction is unknown. Can the Copenhagen Adduction Exercise prevent groin injuries in soccer players, was the research question. The literature was searched for studies investigating the potential groin injury risk reduction effect of the CAE. (1) Three studies met the inclusion criteria and were used for this appraisal; (2) one study observed a significantly lower injury rate ratio favoring the group that used the CAE program; and (3) 2 studies found similar or higher injury rates in the intervention groups, not supporting the inclusion of the CAE as a preventative tool. There is conflicting evidence that usage of the CAE is superior to not performing adductor strengthening exercises in mitigating the risk of sustaining groin injuries. Given the evidence supporting these findings, it is advisable to exercise caution when contemplating the incorporation of the CAE into training regimens aimed at preventing groin injuries.



#9 Dental injuries in Swiss soccer supporters: A comparative study of regular fans, ultras, and hooligans for public health strategies

Reference: Clin Exp Dent Res. 2023 Sep 21. doi: 10.1002/cre2.783. Online ahead of print.

Authors: Clarissa Schneider, Michelle Simonek, Florin Eggmann, Andreas Filippi

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Summary: Violence among soccer supporters continues to pose a significant public health concern in many parts of the world. In Switzerland, hooliganism is largely uninvestigated. This study aimed to examine incidents of violence and associated dental injuries among different groups of soccer supporters, as well as assess the impact of intoxicants on their behavior, using survey data from regular fans, ultras, and hooligans in the Swiss Football League. A cross-sectional survey using a standardized questionnaire was conducted among distinct factions of soccer supporters in the Swiss Football League in 2022. A total of 165 participants self-identified as belonging to one of three subgroups: "regular fan," "ultra," or "hooligan." Data were gathered on physical altercations, dental injuries, possession of mouthguards, intoxicant use, and medical assistance. Descriptive statistics, logistic regression models, and significance tests were used for data analysis (α = .05). Hooligans had a higher frequency of dental injuries resulting from fights than ultras and regular fans. Hooligans with 11-20 fights per soccer season had a 9.6 times higher probability of dental trauma than those with 0-5 fights (p = .048). Possession of a mouthguard was associated with a lower risk of dental injuries for hooligans but an increased risk for ultras. Additionally, hooligans were found to differ significantly from other groups in their consumption of amphetamines and cocaine (p < .001). The study found a strong link between physical altercations and dental injuries among soccer supporters. To promote better prevention, there is a necessity for enhanced educational initiatives facilitated by dentists to amplify the dissemination of mouthguards. Furthermore, it is crucial to raise awareness regarding their proper fitting to minimize the occurrence of combat-related dental injuries. Health authorities and other stakeholders should take a comprehensive approach to addressing some of the root causes of violent behavior, which include alcohol abuse and illicit substance consumption.



#10 Daytime sleepiness in Chinese professional, semi professional and students soccer players in the Shanghai lockdown

Reference: BMC Sports Sci Med Rehabil. 2023 Sep 22;15(1):119. doi: 10.1186/s13102-023-00730-3.

Authors: Songhui You, Antonio Cicchella

Summary: April-May 2021 Shanghai city was under strict lockdown. Soccer players suffered from the restrictions, being unable to train and have a social life. The aim of this study was to compare differences in daytime sleepiness between genders and qualification levels in a cohort university Chinese soccer player under 0 Covid policy restrictions in the urban area of Shanghai. 491 questionnaires of Epworth Sleepiness Scales (ESS) were compiled online by male and female Soccer Students (SS), Semi-Professional players (SP) and Professional Players (PP) during the ongoing restriction measures post Shanghai lockdown. ANOVA was performed for players levels and gender. Significant differences were found between the 3 levels and between males and females. PP showed a very low score in the ESS (5,97) well below the threshold of 8 for daytime sleepiness, while SS and SP showed an ESS score above the threshold. Female showed higher scores in comparison to males. Differences between males and females reflect the confinement conditions in the ESS items, showing more difference in the item of ESS which are related with indoor situations. This study shows the first data on sleepiness in Chinese soccer players of different level of qualification immediately post lockdown condition. Professional male's players sleepiness was lower, than females, SS and SP after the exceptional lockdown measures. The reasons can reside in the more ordered lifestyle of PP in comparison to SS and SP, which mitigated the effects of the lockdown. Our results suggest that measures to improve sleep in females' soccer player should be adopted if these exceptional conditions will happen again.



#11 The relationship of player load and anaerobic performance in different football playing strategies

Reference: Physical Education of Students, 2023;27(4):190–200.

Authors: Erol M, Kapelman AE, Kızılet A. 

Summary: The purpose of the present study is to determine the effect of player load on the anaerobic performance of soccer players. Eighty Turkish Super League U21 players (age:19.56±1.3 years, height: 180.3±2.1cm, weight: 75.9±3.7kg) were involved in this study. The players completed eight different 11v11 training games. While one team practiced the ball possession and “defense as a team” strategy, the other team implemented the counterattacking strategy. The formation was kept as “4-4-2”. The games were played as 2x20-min training matches. Maximum heart rate, player load, ratings of perceived exertion, high running speed, and sprint performances were analyzed. Pearson’s correlation analysis was used in determining the level of correlation between quantitative variables. Linear regression analyses were carried out to examine the effect of player load on anaerobic performance components in different strategies and positions. Compared to tactical strategy, player load values were found to be different from all positions. It was observed that maximum hearth rate, ratings of perceived exertion, high running speed, and sprint data were correlated with player load data (p<0.05). Given the results achieved from the regression analysis, it was determined that an increase in player load data caused an increment in these data. In conclusion, it was observed that player load data affect position-specific anaerobic performance in football. It is thought that the use of the data related to player load, acceleration, and deceleration in the training planning in accordance with the positions of players and the team strategies will increase the performance of the athlete.



#12 Individual Locating of Soccer Players from a Single Moving View

Reference: Sensors (Basel). 2023 Sep 16;23(18):7938. doi: 10.3390/s23187938.

Authors: Adrien Maglo, Astrid Orcesi, Julien Denize, Quoc Cuong Pham

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Summary: Positional data in team sports is key in evaluating the players' individual and collective performances. When the sole source of data is a broadcast-like video of the game, an efficient video tracking method is required to generate this data. This article describes a framework that extracts individual soccer player positions on the field. It is based on two main components. As in broadcast-like videos of team sport games, the camera view moves to follow the action and a sport field registration method estimates the homography between the pitch and the frame space. Our method estimates the positions of key points sampled on the pitch thanks to an encoder-decoder architecture. The attention mechanisms of the encoder, based on a vision transformer, captures characteristic pitch features globally in the frames. A multiple person tracker generates tracklets in the frame space by associating, with bipartite matching, the player detections between the current and the previous frames thanks to Intersection-Over-Union and distance criteria. Tracklets are then iteratively merged with appearance criteria thanks to a re-identification model. This model is fine-tuned in a self-supervised way on the player thumbnails of the video sample to specifically recognize the fine identification details of each player. The player positions in the frames projected by the homographies allow the obtaining of the real position of the players on the pitch at every moment of the video. We experimentally evaluate our sport field registration method and our 2D player tracker on public datasets. We demonstrate that they both outperform previous works for most metrics. Our 2D player tracker was also awarded first place at the SoccerNet tracking challenge in 2022 and 2023.



#13 Preliminary Baseline Vestibular Ocular Motor Screening Scores in Pediatric Soccer Athletes

Reference: J Sport Rehabil. 2023 Sep 27:1-7. doi: 10.1123/jsr.2022-0327. Online ahead of print.

Authors: Morgan Anderson, Christopher P Tomczyk, Aaron J Zynda, Alyssa Pollard-McGrandy, Megan C Loftin, Tracey Covassin

Summary: The utility of baseline vestibular and ocular motor screening (VOMS) in high school and collegiate athletes is demonstrated throughout the literature; however, baseline VOMS data at the youth level are limited. In addition, with the recent adoption of the change scoring method, there is a need to document baseline VOMS total and change scores in a pediatric population. To document baseline VOMS total and change scores and to document the internal consistency of the VOMS in pediatric soccer athletes. We hypothesized that the VOMS would demonstrate strong internal consistency in pediatric soccer athletes. Pediatric soccer athletes (N = 110; range = 5-12 y) completed the VOMS at baseline. Descriptive statistics summarized demographic information, VOMS total scores, and VOMS change scores. Cronbach α assessed internal consistency for VOMS total scores and change scores. Twenty-one (19.1%) participants had at least one total score above clinical cutoffs (≥2 on any VOMS component and ≥5 cm on average near point convergence). Forty (36.4%) participants had at least one change score above clinical cutoffs (≥1 on any VOMS component and ≥3 cm on average near point convergence). The internal consistency was strong for total scores with all VOMS components included (Cronbach α = .80) and change scores (Cronbach α = .89). Although results suggest VOMS items measure distinct components of the vestibular and ocular motor systems, caution should be taken when interpreting VOMS total and change scores in pediatric athletes, as overreporting symptoms is common, thereby impacting the false-positive rate.



#14 Street soccer and homelessness: Exploring social identities, health, and well-being

Reference: Psychol Sport Exerc. 2023 Sep 3:70:102529. doi: 10.1016/j.psychsport.2023.102529. Online ahead of print.

Authors: Joseph J O'Rourke, Andrea Bundon, Guy Faulkner, Tegan Cruwys, Mark R Beauchamp

Summary: Membership in social and physical activity groups has the potential to help people with a range of physical and mental health challenges. The purpose of this study was to examine the experiences of members of a unique physical activity group: people who were formerly or currently homeless participating in a street soccer program in Western Canada. Ten participants in the Vancouver Street Soccer League (VSSL) were interviewed about the extent to which this program fostered a sense of community, social connectivity, and quality of life among people with experience of homelessness. Interviews were augmented with a Social Identity Mapping activity and observations from the first author who took part in weekly practice with the VSSL for over a year. The data were analysed using thematic analysis, in which four themes were developed to reflect the findings. These included (1) Coming together through soccer, (2) Dynamics motivating continued involvement in the league, (3) Leaders and leadership: Social influence in the league, and (4) The league and health outcomes. The findings provide insight into how a street soccer program which fostered shared social identity, psychological safety, friendly competition, and social support contributed to the well-being of people impacted by homelessness, various traumas, and marginalisation.







Acute Effect of Four Stretching Protocols on Change of Direction in Young Male Soccer Players

Therefore, this study aimed to compare the effects of different stretching methods on COD ability in soccer players.





Effects of a Short-Term Detraining Period on the Strength Deficit and Functional Performance of Highly Trained Soccer Players

The purpose of the study was to investigate whether a re-warm-up training session either with tuck jumps and linear sprints or with changing of directions (COD) may enhance power, agility or ball shooting velocity.





Latest research in football - week 37 - 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 Prevalence of lower limb pain and disability in football, hockey, and floorball players

Reference: J Back Musculoskelet Rehabil. 2023 Aug 19. doi: 10.3233/BMR-230048. Online ahead of print.

Authors: Magdaléna Hagovská, Alena Buková, Peter Takáč

Summary: Currently there are not enough studies that compared frequent types of collective sports with regard to the prevalence of pain and disability of the lower limb. The aim was to determine the prevalence of lower limb pain and disability in team sports players. 388 athletes with average age 27.26 ± 4.69, from sports clubs at the national level were included in the study. The Oxford Hip Score was used to determine the prevalence of hip pain. The International Knee Documentation Committee was used to determine the prevalence of knee pain. The Foot and Ankle Disability Index was used to determine the prevalence of ankle pain. Hockey players had a prevalence of hip pain of 97.2% and a 14.3 times higher risk of developing hip pain compared with football and floorball players. Floorball players had a 81.9% prevalence of knee pain, with a 3.8 times higher the risk of knee pain compared with football and hockey. Floorball players had a 62.3% prevalence of ankle pain and a 1.8 times higher the risk of developing ankle pain compared with football and hockey players. The highest percentage of knee 81.9% and ankle 62.3% pain, as well as the greatest risk of pain, was found among floorball players. Hockey players had the highest prevalence (97.2%) and risk of developing hip pain.



#2 The effect of COVID-19 on home advantage in high- and low-stake situations: Evidence from the European national football competitions

Reference: Psychol Sport Exerc. 2023 Nov;69:102492. doi: 10.1016/j.psychsport.2023.102492. Epub 2023 Jul 19.

Authors: Merim Bilalić, Mario Graf, Nemanja Vaci

Summary: The Covid-19 pandemic has significantly altered the way sporting events are observed. With the absence or limited presence of spectators in stadiums, the traditional advantage enjoyed by home teams has diminished considerably. This underscores the notion that the support of home fans can often be considered a key factor of the home advantage (HA) phenomenon, wherein teams perform better in front of their own supporters. However, the impact of reduced attendance on games with higher stakes, as opposed to low-stakes friendly matches, remains uncertain. In this study, we investigate the recently concluded European football championship (EURO 20), wherein several teams had the advantage of playing at home in high-stakes games with only one-third of the stadium capacity filled. Firstly, we demonstrate that the Covid-19 restrictions, leading to reduced fan attendance, resulted in a nearly 50% decrease in HA compared to the HA exhibited by the same teams during the qualification stage preceding EURO 20, even after accounting for team strength. Secondly, we show that while low-stakes friendly matches generally exhibit a smaller overall HA compared to high-stakes games, the absence of fans led to a similar reduction in HA during the low-stakes matches. Utilizing the recently developed Home Advantage Mediated (HAM) model (Bilalić, Gula, & Vaci, 2021, Scientific Reports, 21558), we were able to attribute the reduction in both high- and low-stakes games to poorer team performance, with no significant contribution from referee bias.



#3 The obligation to succeed when it matters the most-The influence of skill and pressure on the success in football penalty kicks

Reference: Psychol Sport Exerc. 2023 Mar;65:102369. doi: 10.1016/j.psychsport.2022.102369. Epub 2022 Dec 20.

Authors: Michel Brinkschulte, Fabian Wunderlich, Philip Furley, Daniel Memmert

Summary: In order to gain a more comprehensive understanding of the influence of skill and pressure on the success in football penalty kicks, we analyzed 1711 penalties taken over a 15-year period in major international tournaments. We conducted a multiple correspondence analysis in order to reduce six variables that are associated with skill and pressure to two dimensions that reflect our target concepts. Then, we used these two factors as independent variables in a logistic regression and fit different models using three binary dependent variables. The results show that high situational pressure significantly increases the probability of missing the goal entirely by about 6%, independent of the player's skill level. The probability that the goalkeeper saves a penalty significantly decreases by roughly 4% when a highly skilled player takes the shot. In general, high situational pressure decreases the probability of scoring a penalty kick. Furthermore, the probability to score a penalty increases if a highly skilled player takes the kick which indicates that a high skill level can act as a kind of buffer against debilitating effects caused by performance pressure.



#4 The causal impacts of empty stadiums on women's sports activities: Evidence from European football leagues

Reference: Psychol Sport Exerc. 2023 May;66:102385. doi: 10.1016/j.psychsport.2023.102385. Epub 2023 Jan 11.

Authors: Dávid Zoltán Szabó, Péter Kerényi

Summary: This paper examines the effect of spectators on women's football games. COVID-19 and related restrictions provide a unique opportunity with an adequate sample size to test the effect of lockdown on sports activities. Studies have recently exploited this opportunity for men's football to better understand the potential causes of home advantage and, more specifically, assess the psychological consequences when matches are played without supporters. Despite the increased scientific interest, there was only one paper that focused on women's football. Therefore, we aim to contribute to this research field by considering matches from four major European women's football leagues. The findings suggest that for three of these leagues, lockdown has a statistically significant effect on the sanctioned yellow cards by either reducing the number of yellow cards sanctioned to the away teams or increasing the number of yellow cards sanctioned to the home teams. Nonetheless, lockdown does not affect any final match outcomes; therefore, it does not significantly affect the magnitude of home advantage for women's games.



#5 Using video docuseries to explore male professional football head coaches' well-being experiences throughout a season

Reference: Psychol Sport Exerc. 2023 Nov;69:102488. doi: 10.1016/j.psychsport.2023.102488. Epub 2023 Jul 8.

Authors: Andrew J Higham, James L Rumbold, James A Newman, Joseph A Stone

Summary: Football coaches have disclosed how their work environment is unpredictable and demanding, comprising a multitude of stressors which can impede well-being. Additionally, the masculine culture within football often promotes suppression of voice, causing internalisation of thoughts and isolation. Due to professional football head coaches being a seldom-heard group, little is known about how they experience well-being within their given context (i.e., ecological niche). The present study utilised football docuseries and a bioecological framework to explore how four male professional head coaches experienced well-being whilst working in one of the top European football leagues (Premier League, La Liga). Four docuseries were sampled and resulted in the analysis of 31 episodes (Mduration = 46.6 min, SD = 4.5 min). The study implemented an adapted interpretative phenomenological analysis approach to illuminate convergences and divergences in contextual accounts. These accounts resulted in five group experiential themes: 'I belong to the game'; 'he belongs to the game'; 'you need the right people around you'; 'it's difficult to describe the manager without describing the person'; and 'people are trying to stab you'. The findings indicate that football coaches may experience identity conflicts and become deeply absorbed in their work. This impacts not only their well-being but also their family's, who they often turn to for social support. Consequently, by unveiling nuanced challenges to coaches' well-being, organisations may be better informed to offer more aligned and bespoke well-being support systems.



#6 Association between back-leg-chest muscle strength and kicking speed in soccer players: an observational study

Reference: J Sports Med Phys Fitness. 2023 Sep 15. doi: 10.23736/S0022-4707.23.15183-8. Online ahead of print.

Authors: Arijit Debnath, Vandana Esht, Aksh Chahal, Faizan Z Kashoo, Mohammed M Alshehri, Mohammad A Shaphe, Ghufran Jaleel, Masood Khan, Ahmad H Alghadir

Summary: Several studies have been performed on soccer kicks and stressed the significance of strength/power and coordination between the agonist and antagonist muscles of the lower limb. Along with accuracy, speed is also an important factor in a successful kick. It is reported that trunk musculature, hip and knee extensors of the non-kicking extremity, and hip adductors of the kicking side have a role in increasing the foot velocity while kicking. Since muscles do not work in isolation while kicking and several muscle groups of the leg and trunk have been reported to have a role in high-speed kicks, therefore measuring the combined strength of the leg, trunk, and arm muscles will be an appropriate method to examine their association with the kicking speed. The aim of this study was to examine the association of the combined strength of the lower extremities, back, chest, and arm muscles with the kicking speed of soccer players. Forty male soccer players (mean age 15.7 years) participated in the study. The back-leg-chest (BLC) dynamometer (Baseline, New York, NY, USA) and the mobile camera measured isometric muscle strength and kicking speed, respectively. The BLC dynamometer measured the isometric strength of the knee, hip, back extensors, and arm muscles. The kicking speed was measured by asking participants to kick a football in three directions - right, middle, and left - from 11 meters. Significant (P<0.001) negative correlations of isometric strength of the back, leg, chest, and arm muscles and kicking speeds were found in all three directions. In all three correlations, Pearson's correlation coefficient was -0.989. Simple linear regression results showed that 97.8% (adjusted R2) of the variance observed in kicking speed (KS; RT), KS (MD), and KS (LT), was explained by the movement in BLC muscle strength values. Kicking speeds in the right, middle, and left directions were negatively associated with the isometric strengths of the back, leg, chest, and arms muscles, measured using the BLC dynamometer, in participating soccer players.



#7 Predicting Injury and Illness with Machine Learning in Elite Youth Soccer: A Comprehensive Monitoring Approach over 3 Months

Reference: J Sports Sci Med. 2023 Sep 1;22(3):476-487. doi: 10.52082/jssm.2023.476. eCollection 2023 Sep.

Authors: Nils Haller, Stefan Kranzinger, Christina Kranzinger, Julia C Blumkaitis, Tilmann Strepp, Perikles Simon, Aleksandar Tomaskovic, James O'Brien, Manfred Düring, Thomas Stöggl

Summary: The search for monitoring tools that provide early indication of injury and illness could contribute to better player protection. The aim of the present study was to i) determine the feasibility of and adherence to our monitoring approach, and ii) identify variables associated with up-coming illness and injury. We incorporated a comprehensive set of monitoring tools consisting of external load and physical fitness data, questionnaires, blood, neuromuscular-, hamstring, hip abductor and hip adductor performance tests performed over a three-month period in elite under-18 academy soccer players. Twenty-five players (age: 16.6 ± 0.9 years, height: 178 ± 7 cm, weight: 74 ± 7 kg, VO2max: 59 ± 4 ml/min/kg) took part in the study. In addition to evaluating adherence to the monitoring approach, data were analyzed using a linear support vector machine (SVM) to predict illness and injuries. The approach was feasible, with no injuries or dropouts due to the monitoring process. Questionnaire adherence was high at the beginning and decreased steadily towards the end of the study. An SVM resulted in the best classification results for three classification tasks, i.e., illness prediction, illness determination and injury prediction. For injury prediction, one of four injuries present in the test data set was detected, with 96.3% of all data points (i.e., injuries and non-injuries) correctly detected. For both illness prediction and determination, there was only one illness in the test data set that was detected by the linear SVM. However, the model showed low precision for injury and illness prediction with a considerable number of false-positives. The results demonstrate the feasibility of a holistic monitoring approach with the possibility of predicting illness and injury. Additional data points are needed to improve the prediction models. In practical application, this may lead to overcautious recommendations on when players should be protected from injury and illness.



#8 Quantitative Analysis of Ball-Head Impact Exposure in Youth Soccer Players

Reference: J Sports Sci Med. 2023 Sep 1;22(3):591-596. doi: 10.52082/jssm.2023.591. eCollection 2023 Sep.

Authors: Victoria E Wahlquist, Thomas A Buckley, Jaclyn B Caccese, Joseph J Glutting, Todd D Royer, Thomas W Kaminski

Summary: Since the implementation of the US Soccer heading guidelines released in 2015, little to no research on ball-head impact exposure in the United States youth soccer population has been conducted. The purpose was to compare ball-head impact exposure across sex and age in youth soccer players over a weekend tournament. Ten male and female games for each age group (Under-12 [U12], U13, and U14) were video recorded at a weekend tournament for a total of 60 games. Ball-head impact exposure for each game was then coded following a review of each recording. Male players were 2.8 times more likely to have ball-head impacts than female players, (p < 0.001) particularly in the U14 age group when compared to the U12 age group (p = 0.012). Overall 92.4% of players experienced 0-1 ball-head impacts per game with the remaining players experiencing 2+ ball-head impacts per game. Ball-head impact exposure levels are low in the youth players. Most youth soccer players do not head the soccer ball during match play and those that did, only headed the ball on average once per game. Overall, the difference in ball-head impact exposure per player was less than 1 between all the groups, which may have no clinical meaning.



#9 Strategic analysis of body composition indices and resting platelet ATP levels in professional soccer players for better platelet-rich plasma therapy

Reference: Front Bioeng Biotechnol. 2023 Aug 30;11:1255860. doi: 10.3389/fbioe.2023.1255860. eCollection 2023.

Authors: Takashi Ushiki, Tomoharu Mochizuki, Katsuya Suzuki, Masami Kamimura, Hajime Ishiguro, Tatsuya Suwabe, Satoshi Watanabe, Go Omori, Noriaki Yamamoto, Tomoyuki Kawase

Summary: Autologous platelet-rich plasma (PRP) therapy is ambiguously thought to be more effective in elite athletes than in sedentary patients, although the possible importance of recipient responsiveness remains poorly understood. To address this issue, along with the well-known PRP quality, in this initial study, we evaluated two candidate biomarkers: body composition indices (BCIs), which reflect systemic physical conditions, and resting platelet ATP levels, which reflect platelet energy expenditure and the mass of energy generation units. In this cross-sectional cohort study, blood samples were collected from male professional soccer players (PSPs) on a local professional team during the off-season and platelet ATP levels were quantified using an ATP luminescence assay kit. BCIs were measured using the body mass impedance method. Age-matched male sedentary participants were used as the controls. Among the BCIs, the body mass index, basal metabolic rate (BMR), and skeletal muscle weight levels were higher in the PSPs than in the controls. The platelet ATP levels in the PSPs group were significantly lower than those in the control group. The correlation between BMR and platelet ATP levels was moderately negative in the control group, but weakly positive in the PSPs group. Owing to regular physical exercise, PSPs had higher BMR levels and lower platelet ATP levels without a significant mutual correlation compared to sedentary controls. This study did not indicate the influence of these biomarkers on the success of PRP therapy but provided evidence for a better understanding of PRP therapy, particularly for elite athletes.



#10 Relationship between Relative age Measured Through Decimal age, physical variables and anthropometry in elite youth soccer players

Reference: Phys Sportsmed. 2023 Sep 12. doi: 10.1080/00913847.2023.2258768. Online ahead of print.

Authors: Iván Asín-Izquierdo, Marcos Chena 1, Vicente de Dios-Álvarez 3, Carlos Galiano 2

Summary: Age differences between athletes born in the same year, as well as an over-representation of older players, are known as the Relative Age Effect (RAE). Players born at the beginning of the selection year have a physical and anthropometric advantage over their younger peers. Experts keep looking for new prediction variables for talent identification. The aim of the study is to correlate anthropometric, strength and power variables with the relative age (RA) and the level of the teams in which players played in each age category. All players (N = 366) from an elite soccer academy of a Spanish club volunteered to participate in the study (U23-U10). There was a significant correlation between the RA of the players and the level of the team in which they played in each age category but no correlation between trimester of birth and level of the team. We found significant correlations between the players' physical capacities, anthropometry, RA and the level of the team in which they played for the same age category, mainly from U16 to U10. U23 did not show any correlation between RA and physical or anthropometric variables. Coaches should be cautious of choosing players based only on anthropometric or physical attributes.



#11 Chronic Beetroot Juice Supplementation Attenuates Neuromuscular Fatigue Etiology During Simulated Soccer Match Play

Reference: Appl Physiol Nutr Metab. 2023 Sep 11. doi: 10.1139/apnm-2023-0179. Online ahead of print.

Authors: Wael Daab, Firs Zghal, George P Nassis, Haitham Rebai, Wassim Moalla, Mohamed Amine Bouzid

Summary: The aim of the present study was to assess the effect of beetroot juice supplementation (BEET) on neuromuscular fatigue etiology during simulated soccer match play. In a randomized, double-blind, crossover design, 13 soccer players completed the Loughborough Intermittent Shuttle Test (LIST). Players received either BEET (2*150ml; ~ 8mmol/l nitrate) or PLA for 7 days (6 days prior to the experimental session and on the day trial, 2h before LIST). Neuromuscular assessments were performed at baseline, 45min (half time: HT) and at 90min (final time: FT) following LIST. Maximal voluntary contraction (MVC) and twitch responses, delivered through electrical femoral nerve stimulation, were used to asses peripheral (quadriceps resting twitch force, Qtw,pot) and central fatigue (voluntary activation, VA). Compared to baseline, MVC Qtw,pot and VA values decreased in PLA and BEET conditions at HT and FT (p<0.05). Compared to PLA, the decrease in MVC and Qtw,potat were significantly attenuated with BEET at HT and FT(p <0.001). Likewise, BEET attenuated the decrease in VA at HT (p <0.001, d = 1.3) and FT (p <0.001, d = 1.5) compared to PLA condition. Chronic beetroot juice supplementation attenuates neuromuscular fatigue development during simulated soccer match and this is due to both central and peripheral factors. Consequently, chronic beetroot may optimize physical performance.



#12 Football and respiratory medicine-Time to start kicking goals

Reference: Respirology. 2023 Sep 10. doi: 10.1111/resp.14600. Online ahead of print.

Authors: Natasha Smallwood

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#13 Menthol mouth rinsing and performance in elite football referees in the heat: A study protocol for a randomized crossover trial

Reference: Contemp Clin Trials Commun. 2023 Aug 22;35:101202. doi: 10.1016/j.conctc.2023.101202. eCollection 2023 Oct.

Authors: Maria Roriz, João Brito, Filipe J Teixeira, Konstantinos Spyrou, Vitor Hugo Teixeira

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Summary: Within professional European competitions, matches can be played in extreme environmental temperatures, ranging from -5 °C to +30 °C in different countries. Furthermore, the World Cups are usually played in the summer months, when temperatures can exceed 35 °C, increasing physiological stress. Practical and cost-effective cooling strategies may be implemented to help players and referees to cope with exercising in the heat. No study has evaluated the effect of non-thermal internal cooling techniques regarding performance responses on elite football referees, so far. This study aims to analyse the effects of a menthol mouth rinse regarding physical, physiological, and perceptual performance in elite male football referees, during a 90-min football protocol in the heat. At least thirteen male football referees will be recruited to perform two intermittent football protocols, separated by no less than 7 days. After passing the eligibility criteria, the participants will be randomly assigned to 1 of 2 beverages: (1) intervention - menthol solution 0.01% and (2) placebo - noncaloric berry-flavored solution, both at room temperature. The beverages will be given before warm-up (pre-cooling) and at the half-time (per-cooling). The trials will follow a randomized counterbalanced crossover design, single blinded, and will take place in indoor facilities, with Wet Bulb Globe Temperature (WBGT) > 30 °C, at the same time of the day to control for circadian variations. The results of this study are expected to determine whether mouth rinsing a menthol solution before and during a football exercise protocol performed in the heat will alter perceptual measures and help ease physiological strain and attenuate performance decrements in elite male football referees, comparing to a non-cooling strategy. Thus, we can be closer to defining nutritional strategies of internal cooling that may be an advantage for the performance of the football referees in the heat.



#14 Motivation and goal-pursuit for injury prevention training in amateur football coaches: a cross-sectional study using the Health Action Process Approach

Reference: Inj Prev. 2023 Sep 11;ip-2023-044978. doi: 10.1136/ip-2023-044978. Online ahead of print.

Authors: Hanna Lindblom, Martin Hägglund

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Summary: Adoption of injury prevention exercise programmes (IPEPs) in team sports is contingent on behaviour change among coaches. The aim was to study motivation and goal-pursuit in IPEP use among coaches of amateur football players. A cross-sectional study using web-based questionnaires was administered to coaches in one Swedish regional football district. The study was carried out one season after dissemination of the IPEP Knee Control+. The questionnaire was based on the Health Action Process Approach and covered perceptions and beliefs about using Knee Control+. Questions were rated on 1-7 Likert scales. 440 coaches participated (response rate 32%). Coaches were neutral about injury risks (median 4-5) and knowledge about preventing injuries (median 5) but had positive outcome expectancies of preventive training (median 6). Coaches who had used an IPEP perceived they had more knowledge about preventing injuries than non-users (median 5 vs 4, small effect size d=0.43). Coaches who used Knee Control+ were positive about their practical ability to use it (median 6) and had high intention to prioritise continuous use (median 7). Highly adherent coaches to higher extent believed that specific training may prevent injuries and had plans for how to instruct the players and how to work around barriers compared with low adherent coaches. Coaches need more knowledge and support on IPEP usage and how to structure training. Coaches who had adopted Knee Control+ had high belief in their abilities but may need constructive plans on how to use the programme and to overcome barriers.



#15 Characteristics of brain activation in high-level football players at different stages of decision-making tasks off the ball: an fMRI study

Reference: Front Hum Neurosci. 2023 Aug 28;17:1189841. doi: 10.3389/fnhum.2023.1189841. eCollection 2023.

Authors: Ming-Hao Huang, Jian Lang, Ju Li, Zhe Qin, Ya-Ping Cao

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Summary: This study aimed to examine the neural mechanisms underlying the decision-making process of off-ball movements among high-level football players and ordinary college students, as well as the effect of long-term skill training on these neural mechanisms using functional magnetic resonance imaging (fMRI). The study recruited 20 professional college football players as the expert group (EG) and 20 novice football players with no background in sports-related disciplines as the novice group (NG). The participants performed the motor video observation and button-decision-making tasks, and fMRI data were acquired, pre-processed, and analyzed. During the decision-making process regarding running without the ball, whole-brain fMRI scans were conducted on both the EG and NG. The analysis of these scans revealed noteworthy disparities in brain activity between the two groups. These disparities were observed during tasks involving motor video observation and button-based decision-making. According to the behavioral data, the EG made more correct decisions than the NG (p < 0.05); however, there was no significant difference in their reaction speed (p > 0.05). During video observation, both the EG and NG exhibited simultaneous activation in the frontoparietal cognitive area, primary somatosensory cortex, visual cortex, and insula. However, there were no significant differences between the two groups in terms of activated brain regions [false discovery rate (FDR) corrected to p < 0.05]. Regarding button-press decisions, the areas of the brain that were commonly activated in both the NG and EG were primarily located in the frontoparietal cognitive area, temporal cortex, and cuneus cortex. Notably, the left superior temporal gyrus, left inferior temporal gyrus, and left middle occipital gyrus exhibited greater activation in the NG compared to those in the EG (FDR corrected to p < 0.05). This study demonstrated that during motor video observation, the EG's sports experience and professional knowledge can help them achieve better visual information processing strategies in specific areas of sports. During button decision-making, the EG was more economical, whereas the NG required more brain function activity to process visual information, confirming the "neural efficiency" hypothesis.



#16 Plasma myoglobin indicates muscle damage associated with acceleration/deceleration during football

Reference: J Sports Med Phys Fitness. 2023 Sep 15. doi: 10.23736/S0022-4707.23.15203-0. Online ahead of print.

Authors: Yoshitomo Saita, Kazuhiko Hattori, Atsushi Hokari, Tomoko Ohyama, Junya Inoue, Tomoaki Nishimura, Shota Nemoto, Seiji Aoyagi

Summary: Monitoring muscle damage in athletes assists not only coaches to adjust the training workload but also medical staff to prevent injury. Measuring blood myoglobin concentration can help evaluate muscle damage. The novel portable device utilized in this study allows for easy on-site measurement of myoglobin, providing real-time data on the player's muscle damage. This study investigated the relationship between external load (global positioning system parameters) and internal loads (myoglobin concentration and creatine kinase activity) in 15 male professional football players before and after a match. Whole blood samples from participants' fingertips were collected before the match (baseline) and at 2, 16, and 40 h after the match. Myoglobin concentrations were measured using the IA-100 compact immunoassay system. Creatine kinase concentrations were measured in a clinical laboratory, and match loads were monitored using a global positioning system device. The mean myoglobin concentration was significantly higher at 2 h than at the other time points (P<0.05), and decreased to baseline levels within 16 h post-match. The mean creatine kinase concentration increased after the match but did not reach a significant level. Muscle damage monitored by myoglobin after football match-play was strongly associated with acceleration/deceleration metrics rather than the sprint/high-speed running distance. Our findings indicate that myoglobin is a more sensitive marker of muscle damage than creatine kinase after football match-play. Monitoring myoglobin in athletes can aid in determining their recovery status from the previous training load and help practitioners manage the training load.



#17 Health and performance effects of 12 weeks of small-sided street football training compared to grass football training in habitually active young men

Reference: Eur J Appl Physiol. 2023 Sep 15. doi: 10.1007/s00421-023-05308-y. Online ahead of print.

Authors: Morten B Randers, Marie Hagman, Jesper F Christensen, Susana Póvoas, Jens Jung Nielsen, Peter Krustrup

Summary: The purpose of the present study was to investigate the health and exercise performance effects of street football training on very small pitches surrounded by boards in young habitually active men in comparison to small-sided football training on grass. Thirty-nine habitually active men (30.7 ± 6.7 years, 90.9 ± 16.6 kg, 183.8 ± 4.5 cm, 39.6 ± 6.0 mL/min/kg) were randomly assigned to a street football training group (ST) or grass football group (GR) playing small-sided games for 70 min, 1.5 and 1.7 times per week for 12 weeks, respectively, or an inactive control group (CO). Intensity during training was measured using heart rate (HR) and GPS units. Pre- and post-intervention, a test battery was completed. Mean HR (87.1 ± 5.0 vs. 84.0 ± 5.3%HRmax; P > 0.05) and percentage of training time above 90%HRmax (44 ± 28 vs. 34 ± 24%; P > 0.05) were not different between ST and GR. VO2max increased (P < 0.001) by 3.6[95% CI 1.8;5.4]mL/min/kg in GR with no significant change in ST or CO. HR during running at 8 km/h decreased (P < 0.001) by 14[10;17]bpm in ST and by 12[6;19]bpm in GR, with no change in CO. No changes were observed in blood pressure, resting HR, total body mass, lean body mass, whole-body bone mineral density, fasting blood glucose, HbA1c, plasma insulin, total cholesterol(C), LDL-C or HDL-C. Moreover, no changes were observed in Yo-Yo IE2 performance, 30-m sprint time, jump length or postural balance. Small-sided street football training for 12 weeks with 1-2 weekly sessions led to improvements in submaximal exercise capacity only, whereas recreational grass football training confirmed previous positive effects on submaximal exercise capacity as well as cardiorespiratory fitness.







In‑season monotony, strain and workload of perceived exertion, GPS running based variables between positions of an elite football team

The interpretation of the load variations across a period seems important to control the weekly progression or variation of the load, or to identify within- micro and mesocycle variations. The aim of this study was to describe the in-season variations of training monotony, training strain, and acute:chronic workload ratio (ACWR) through session rating of perceived exertion (s-RPE), total distance (TD) and high-speed running (HSR) according to playing positions in an elite soccer team.






Exploring Factors Related to Goal Scoring Opportunities in Professional Football

Outscoring opponents is the primary goal in football. To optimise goal scoring opportunities (GSOs), it is important to understand the preceding physical and tactical performance. This observational study explored whether running behaviour prior to GSOs related to the subsequent outcome or contextual factors.





Match duration: over 100’ on average

With the recent development in playing time I thought it would be interesting to see the average duration of matches during the current or last completed season. 52,4% of matches are over 100 minutes. 

However, the match duration varies greatly between leagues: from 100% in the top division of the United Arab Emirates to just 6.7% in the Swiss second division being over 100’. In the European big-5, the values stretches from 84.6% in Spain to 61.1% in France.


The overall average is 100’15’’, with a maximum of over 106’ in the top two Saudi competition levels. Interestingly, the top 4 leagues are from the middle east, followed by the 1. Division (CYP) and the La Liga.



The Spanish La Liga is the competition where referees add the most injury time among the European big-5 (on average 13’03’’). The second big 5 league is the English Premier League with 11'46'' in 12th place, the Italian Serie A 11’04’’ in 18th place. 






What are the significant turning demands of match play of an English Premier League soccer team?

This study aimed to compare the significant turning demands of English Premier League soccer match play relative to playing position using LiDAR technology.





Effects of the Timing of Carbohydrate Intake on Metabolism and Performance in Soccer Players

This study aims to provide information to improve the performance of athletes comparing the effects of carbohydrate–electrolyte intake before and during exercise on metabolism and performance in soccer players.





Latest research in football - week 36 - 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 Corrigendum: The relationship between locus of control and pre-competitive anxiety in highly trained soccer players

Reference: Front Psychol. 2023 Aug 21;14:1272127. doi: 10.3389/fpsyg.2023.1272127. eCollection 2023.

Authors: Imen Ben Amar, Chiraz Gomni, Oussama Gaied Chortane, Aymen Khemiri, Rania Ghouaiel, Julien S Baker

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#2 Adherence to the Mediterranean diet in young male soccer players

Reference: BMC Nutr. 2023 Sep 4;9(1):101. doi: 10.1186/s40795-023-00761-6.

Authors: César Leão, Sílvia Rocha-Rodrigues, Inês Machado, João Lemos, Sandra Leal, Hadi Nobari

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Summary: Nutrition is vital in health and sports performance by improving anthropometric-related parameters and dietary habits, especially in the youngest ages. The Mediterranean diet (MD) has been highly recognized for its positive health effects and low adverse environmental impact. We aimed to characterize adherence to the MD and analyze its association with anthropometric parameters in young soccer players. In the present study, 132 male young soccer players from under 9 to under 15 categories (aged 7 to 15 years) from a Portuguese football club participated. The Mediterranean Diet Quality Index for Children and Adolescents (KIDMED) questionnaire was applied to assess adherence to the MD. Anthropometric-related parameters, including body mass, height, triceps skinfold thickness (TSKF), suprailiac skinfold thickness (SISKF), body mass index (BMI) and body fat percentage (%BF), were determined. The differences between groups were performed accordingly to normal and non-normal distribution. Spearman's correlations were performed to analyze the hypothetical correlation between KIDMED and BMI. Players reached an average KIDMED score of 8.36 ± 1.92, showing that 68.2% (n = 90) reached high adherence to the MD, 31.1% (n = 41) had moderate adherence to the MD, and 0.78% (n = 1) had poor adherence to the MD. When the analysis was made for age group and BMI classification, no significant differences were observed in adherence to the MD. Considering the main characteristics of the MD, 50.8% consumed fruit (vs. 49,2%), 52.3% consumed vegetables (vs. 47,7%), and only 20% consumed oleaginous dried fruits (vs. 80%). Dairy consumption throughout the day was 49,2% (vs. no: 50,8%). Data from the present study showed that many soccer players adhered to the MD, and no differences were observed for age group or BMI classification.



#3 Financial burden of anterior cruciate ligament reconstructions in football (soccer) players: an Australian cost of injury study

Reference: Inj Prev. 2023 Sep 3;ip-2023-044885. doi: 10.1136/ip-2023-044885. Online ahead of print.

Authors: Andrew George Ross, Blaise Agresta, Marnee McKay, Evangelos Pappas, Tegan Cheng, Kerry Peek

Summary: The aim was to estimate the financial burden of anterior cruciate ligament (ACL) reconstructions in amateur football (soccer) players in Australia over a single year, including both direct and indirect cost. Available national direct and indirect cost data were applied to the annual incidence of ACL reconstructions in Australia. Age-adjusted and sex-adjusted total and mean costs (ACL and osteoarthritis (OA)) were calculated for amateur football (soccer) players in Australia using an incidence-based approach. The estimated cost of ACL reconstructions for amateur football players is $A69 623 211 with a mean total cost of $A34 079. The mean indirect costs are 19.8% higher than the mean direct costs. The mean indirect costs are lower in female (11.5%, $A28 628) and junior (15.3%, $A29 077) football players. The mean ACL costs are 3-4-fold greater than the mean OA costs ($A27 099 vs $A6450, respectively), remaining consistent when stratified by sex and age group. Our model suggests that for every 10% increase in adherence to injury prevention programmes, which equates to approximately 102 less ACL injuries per year, $A9 460 224 in ACL costs could be saved. While the number of ACL reconstructions per year among football players in Australia is relatively small, the annual financial burden is high. Our study suggests that if injury prevention exercises programmes are prioritised by stakeholders in football, significant cost-savings are possible.



#4 The relationship between deliberate practice, play, and futsal in childhood and adolescence and the development of different decision-making skills in professional female soccer players

Reference: Psychol Sport Exerc. 2023 Sep;68:102470. doi: 10.1016/j.psychsport.2023.102470. Epub 2023 Jun 12.

Authors: Guilherme Machado, Sixto González-Víllora, Israel Teoldo

Summary: Soccer players' ability to make efficient and quick decisions has gained more importance due to the increase in game speed in the last few years. Therefore, this study aimed to examine the relationship between the engagement in previous developmental activities in soccer and futsal with the quality and speed of decision-making skills in different phases of sport development of elite female soccer players. The sample comprised 77 elite Brazilian professional female soccer players. Players' decision-making skills were assessed based on an objective video-based test - TacticUP®. We used a retrospective questionnaire to collect information about previous participation in different developmental activities. The results showed that engagement in deliberate practice in soccer and futsal, especially during childhood and early adolescence, is related to a better quality of offensive decision-making skills, although showing small to medium effect sizes. We highlight that deliberate practice in futsal is associated only with offensive decision-making skills with the ball and near the ball. In turn, engaging in deliberate play in soccer, mainly in childhood and early adolescence, is related to quicker offensive and defensive decision-making skills, showing mostly medium effect sizes. To the best of our knowledge, it was the first study to measure the relationship of decision-making speed with developmental activities in soccer. It is concluded that deliberate practice in soccer and deliberate play in soccer are associated with different dimensions of decision-making skills.



#5 A random forest approach to explore how situational variables affect perceived exertion of elite youth soccer players

Reference: Psychol Sport Exerc. 2023 Jul;67:102429. doi: 10.1016/j.psychsport.2023.102429. Epub 2023 Mar 21.

Authors: Diego Marqués-Jiménez, Jaime Sampaio, Julio Calleja-González, Ibon Echeazarra

Summary: The aim of this study was to explore how situational variables affect youth soccer players' perceived exertion (RPE) after official matches. Thirty-five elite youth male players (14.33 ± 0.86 years; 173.49 ± 6.16 cm; 63.44 ± 5.98 kg) who belonged to two different teams of a professional club participated in this study. Data collection was conducted during two seasons (2016-2017, 2017-2018) and included 60 official matches (30 official matches per team). Ten minutes after each match players rated their RPE and using a modified Borg CR-10 scale. A Random Forest Regression was used to quantify the importance of match-related situational variables in RPE. Afterwards, a linear mixed model analysis was applied to identify the variability in RPE among the situational variables. The game-playing time, the player status (starter or substitute) and the player identity were the strongest predictors of RPE. Moreover, the match outcome and the final scoreline showed significant effects on both starter and substitute players but the main effect of the quality of the opponent was only identified in starter players (p < 0.05). These results allow practitioners to know how situational variables interact and modulate RPE after official matches and help them to prescribe and adapt the players' training content and load before and after matches.



#6 A developmental perspective on decision making in young soccer players: The role of executive functions

Reference: Psychol Sport Exerc. 2023 Mar;65:102362. doi: 10.1016/j.psychsport.2022.102362. Epub 2022 Dec 6.

Authors: Sinikka M Heisler, Babett H Lobinger, Lisa Musculus

Summary: Lately, interest in both domain-specific and domain-general cognitive processes has increased as a means to explain soccer player expertise. While the two types of processes have mostly been studied separately, we sought to connect these lines of research by investigating the role of executive functions in soccer players' decision making from a developmental perspective. As these cognitive processes as well as their relation might differ between age groups, we took a developmental perspective to better understand this link in a sample of N = 128 soccer players (Mage = 10.69 years, SD = 1.44). Two age groups (younger vs. older players) performed a video-based option-generation and decision-making task that used temporal occlusion. Additionally, executive functions were assessed with standardized computer-based tests. Results show a link between executive functions and sport-specific decision making, most prominent for working memory. Further, older players generated better options and showed better inhibition and cognitive flexibility than younger players. We suggest there is a crucial turning point in cognitive development around the age of 11 years.



#7 Gritting One's way to success - Grit explains skill in elite youth soccer players beyond (deliberate) practice

Reference: Psychol Sport Exerc. 2023 Jan;64:102328. doi: 10.1016/j.psychsport.2022.102328. Epub 2022 Oct 31.

Authors: Paul Larkin, Dijana Cocić, David T Hendry, A Mark Williams, Donna O'Connor, Merim Bilalić

Summary: Practice is one of the most important predictors of skill. To become an expert, performers must engage in practice for a prolonged time to develop the psychological characteristics necessary for outstanding performance. Deliberate practice (DP), that is focused repetitive activities with corrective feedback, is particularly beneficial for skill development. The amount of accumulated DP differentiates experts and novices. However, the predictive strength of DP weakens considerably when it comes to differentiating between differently skilled experts, leaving a way clear for other non-practice related factors to exercise their influence. In this paper, we demonstrate using a large sample (388) of elite youth soccer players that one such factor, the personality trait of grit, predicts expertise level both directly and indirectly. Grittier players accumulated more time in coach-led team practice, the activity, which is arguably closest to DP in team sports, which in turn predicted the skill level. Other practice activities, such as self-led training or playing with peers, were not predictive of skill level, neither were they influenced by grit. Grit, however, continued to exert a direct positive influence on the skill level of players even after accounting for the hours of DP accumulated. Overall, a standard deviation of change in the grit score resulted in at least a third of standard deviation improvement in skill. Our findings highlight the need for the inclusion of additional factors in theoretical frameworks in situations where the predictive power of traditional expertise factors, such as practice, is limited.



#8 The profiles of single leg countermovement jump kinetics and sprinting in female soccer athletes

Reference: Heliyon. 2023 Aug 19;9(8):e19159. doi: 10.1016/j.heliyon.2023.e19159. eCollection 2023 Aug.

Authors: Honghao Fu, Zhiyuan Li, Xiao Zhou, Jiaoqin Wang, Zhuo Chen, Guanrong Sun, Jingbo Sun, Hongtao Zeng, Laihong Wan, Yueying Hu, Feng Wang, Junyi Zheng

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Summary: The purposes were to evaluate kinetics in lower limbs using single leg countermovement jump (SLCMJ) and to identify the differences in SLCMJ kinetics between sprinting fast players and sprinting slow players in elite university female soccer players. Seventeen participants at the national tournament level completed the survey. SLCMJ and 30 m sprinting tests were performed. A force-plate was used to collect the data of the SLCMJ test. Significant differences of concentric maximum rate of force development (RFD), concentric RFD, concentric RFD/body weight (BW), peak net takeoff force/BW, peak power, and peak power/BW existed between both legs during the SLCMJ among all the participants. For further analysis, the participants were divided into fast group and slow group based on sprinting performance. Significant differences existed between the two groups in concentric peak velocity (nondominant, p = 0.028) and vertical velocity at takeoff (nondominant, p = 0.021). Concentric maximum RFD (p = 0.036) was significantly different between both legs in the slow group. Among elite university female soccer players, the players who presented more increased asymmetry of kinetic characteristics of jumping, also showed weak sprinting performance. Moreover, the players presented the best performance in velocity of the jumping variables and also had the best sprinting performance. Coaches and players should focus on keeping inter-limb balance and developing jumping velocity to improve sports performance. In future, the cause-and-effect relationship between jumping and sprinting should be identified.



#9 The Effects of Nitrate Supplementation on Performance as a Function of Habitual Dietary Intake of Nitrates: A Randomized Controlled Trial of Elite Football Players

Reference: Nutrients. 2023 Aug 25;15(17):3721. doi: 10.3390/nu15173721.

Authors: Matjaž Macuh, Nenad Kojić, Bojan Knap

Summary: Nitrates are an effective ergogenic supplement; however, the effects of nitrate supplements based on habitual dietary nitrate intake through diet alone are not well understood. We aimed to assess this in a group of 15 highly trained football players from Slovenian football's First Division. Participants underwent two separate Cooper performance tests either with nitrate supplementation (400 mg nitrates) or placebo while having their nutrition assessed for nitrate intake, as well as energy and macronutrient intake. Nitrate supplementation had a statistically significant positive effect on performance if baseline dietary nitrate intake was below 300 mg (p = 0.0104) in both the placebo and intervention groups. No effects of nitrate supplementation when baseline dietary nitrate intake was higher than 300 mg in the placebo group could be concluded due to the small sample size. Nitrate supplementation did not have a significant effect on perceived exertion. The daily nitrate intake of the participants was measured at 165 mg, with the majority of nitrates coming from nitrate-rich vegetables.



#10 Epidemiology of Injuries in Men's Professional and Amateur Football (Part I)

Reference: J Clin Med. 2023 Aug 26;12(17):5569. doi: 10.3390/jcm12175569.

Authors: Tudor Vladimir Gurau, Gabriela Gurau, Doina Carina Voinescu, Lucretia Anghel, Gelu Onose, Daniel Andrei Iordan, Constantin Munteanu, Ilie Onu, Carmina Liana Musat

Summary: Football is the most popular sport among men, associated with a certain risk of injury, which leads to short- and long-term health consequences. While the injury profile of professional footballers is known, little is known about the injury profile of amateur footballers; amateur football is a major and diverse area, the development of which should be a priority for football associations around the world and UEFA. The aim of this study was to perform a systematic review of epidemiological literature data on injuries in professional and amateur football players belonging to certain leagues. A systematic review according to the PRISMA guidelines was performed until June 2023 in the databases PubMed, Web of Science, Google Academic, Google Scholar, and Diva portal. Forty-six studies reporting injury incidence in professional and amateur men's football were selected and analyzed. Two reviewers independently extracted data and assessed study quality using an adapted version of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement and the Newcastle Ottawa Scale (NOS) to assess risk of bias for the quality of external validity. The overall incidence of injuries in professional male football players was 7.75 ± 2.28, 95% confidence interval, injuries/1000 h of exposure and that of amateur football players was 7.98 ± 2.95, 95% confidence interval, injuries/1000 h of exposure. The incidence of match injuries (30.64 ± 10.28, 95% confidence interval, injuries/1000 exposure hours) was 7.71 times higher than the training injury incidence rate (3.97 ± 1.35, 95% confidence interval, injuries/1000 h) in professional football players and 5.45 times higher in amateurs (17.56 ± 6.15 vs. 3.22 ± 1.4, 95% confidence interval, injuries/1000 h). Aggregate lower extremity injuries had the highest prevalence in both categories of footballers, being 83.32 ± 4.85% in professional footballers and 80.4 ± 7.04% in amateur footballers: thigh, ankle, and knee injuries predominated. Professional and amateur football players are at substantial risk of injury, especially during matches that require the highest level of performance. Injury rates have implications for players, coaches, and sports medicine practitioners. Therefore, information on football injuries can help develop personalized injury risk mitigation strategies that could make football safer for both categories of football players. The current findings have implications for the management, monitoring, and design of training, competition, injury prevention, especially severe injury, and education programs for amateur football players.



#11 Football players with hip dysplasia: The relationship between muscle strength, functional performance, self-reported sport and recreation, cartilage defects and sex. A cross-sectional study

Reference: J Orthop Sports Phys Ther. 2023 Sep 8;1-24. doi: 10.2519/jospt.2023.12026. Online ahead of print.

Authors: Michael J M O'Brien, Joanne L Kemp, Adam Ivan Semciw, Inger Mechlenburg, Julie S Jacobsen, Matthew G King, Mark J Scholes, Peter R Lawrenson, Kay Crossley, Rintje Agricola, Richard B Souza, Joshua Heerey

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Summary: In symptomatic football players with hip dysplasia, we aimed to explore the relationships between self-reported sport and recreation ability and (i) hip muscle strength, (ii) functional performance, and investigate if these relationships were modified by sex or cartilage defects. In this cross-sectional study, (n=50) football players with longstanding (>6 months) hip and/or groin pain, a positive flexion/adduction/internal rotation (FADIR) test and a lateral-centre-edge angle <250 were included. Hip muscle strength and functional performance were assessed. Self-reported sport and recreation ability was quantified using the sports and recreational subscales from the International Hip Outcome Tool-33 (iHOT-Sport) and the Copenhagen Hip and Groin Outcome Score (HAGOS-Sport). Relationships were evaluated using regression models with sex and cartilage defects as potential effect modifiers. There was a positive linear relationship between the one-leg-rise test and the iHOT-Sport subscale (β 0.61; 95% CI: 0.09 to 1.14). A polynomial (concave) relationship was found between peak eccentric adduction strength and the HAGOS-Sport subscale (β -30.88; 95% CI: -57.78 to -3.99). Cartilage defects modifed the relationship between peak isometric adduction strength and HAGOS-Sport, with those with cartilage.



#12 An intelligent data analysis-based medical management method for lower limb health of football athletes

Reference: Math Biosci Eng. 2023 Jun 21;20(8):14005-14022. doi: 10.3934/mbe.2023624.

Authors: Xiang Wang, Yongcheng Wang, Limin He

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Summary: With increasingly mature commercial operations, football has become the most popular sport in the world. As the main body of football, athletes are prone to injury due to an increasing degree of competition intensity. Their health determines the length of these athletes careers, especially regarding the lower limbs that are mainly used. Therefore, the smart visualization approaches that can realize such function are in urgent demand in the area of sports healthcare. Benefitted by the strong ability of perception and analysis, a convolutional neural network (CNN) is utilized to construct an intelligent data analysis-based medical management method for the lower limb health of football athletes. First, the CNN is formulated as the main backbone, and its parameters are optimized for multiple rounds during the training stage. Then, a statistical analysis software named SPSS is introduced to assess the effect mechanism of different postures on lower limbs. Some experiments are carried out on simulative data to evaluate the proposed method, and results show a good performance of the proposed method.



#13 The effects of high-velocity hamstring muscle training on injury prevention in football players

Reference: Front Physiol. 2023 Aug 21;14:1219087. doi: 10.3389/fphys.2023.1219087. eCollection 2023.

Authors: Sigitas Kamandulis, Joan Aureli Cadefau, Audrius Snieckus, Mantas Mickevicius, Inga Lukonaitiene, Pornpimol Muanjai, Danguole Satkunskiene, Victor Molina, Xavier de Blas Foix, Daniele Conte

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Summary: Explosive and fast body movements, sprints, jumps and quick changes of direction, which are characteristic of the football training, place considerable strain on the hamstring muscles. Due to the high occurrence of hamstring injuries, new preventive strategies are required that focus on high-velocity training. The purpose was to assess the effectiveness of high-velocity elastic-band training in reducing the occurrence of hamstring injuries in football players. Male football players from 15 teams (n = 319) playing in national competitions participated in this study. The players were involved in a 5-week exercise period in either the intervention group (INT) or the control group (CON), with a follow-up period of ∼4 months where hamstring injuries and exposure time were recorded. The INT group had two to three sessions per week of elastic-band training with low-load, high-velocity leg curls while lying prone; the CON group performed self-paced football-specific drills. The incidence rate of hamstring injuries was 6.5% in the INT group (8 out of 123 players) and 9.2% in the CON group (18 out of 196 players). Although the INT group showed almost 1/3 reduction in hamstring injury incidence compared to the CON group, the difference was not statistically significant (p > 0.05). Moreover, no differences (p > 0.05, odds ratio [OR] = trivial-to-small) in distribution between the groups were found in hamstring injury characteristics (leg dominance and mechanism) except for the distribution of injuries that occurred during matches or training (p = 0.036; OR = 6.14, moderate). The program of high-velocity elastic-band training did not prove to be effective in preventing hamstring muscle injuries in football players despite displaying some positive indications that could be considering when creating injury prevention programs.



#14 Comparative Risk Analysis of Low Back Pain among Professional Football, Ice Hockey, and Floorball Athletes

Reference: Med Sci Monit. 2023 Sep 6;29:e941386. doi: 10.12659/MSM.941386.

Authors: Magdaléna Hagovská, Alena Buková, Peter Takáč, Viliam Knap, Perla Ondová, Katarína Oravcová, Anna Kubincová

Summary: Low back pain (LBP) is a common concern among professional athletes, potentially hindering performance and career longevity. However, comparative assessments of LBP prevalence and severity across various sports remain scarce. This study aimed to evaluate the factors associated with LBP in 388 professional athletes, including football, ice hockey, and floorball players. Conducted from June 2021 to September 2022, this cross-sectional study incorporated 388 athletes from national elite clubs, including football (n=148), ice hockey (n=179), and floorball (n=61). The Oswestry Disability Index (ODI), comprising sections like pain intensity, self-care, lifting, walking, sitting, standing, sleeping, sexual life, social life, and traveling, was employed to evaluate spinal pain and disability. The study found no significant disparities in the LBP assessment among the groups. The relative risk (OR) of LBP and disability varied among the sports: football players displayed a lower risk (OR=0.49; 95% CI 0.32-0.74, P≤0.001), while ice hockey players had a higher risk (OR=2.18; 95% CI 1.45-3.29, P≤0.001) compared to the others. In contrast, the risk for floorball players (OR=0.82; 95% CI 0.47-1.41) did not significantly deviate from that of the other two sports. LBP prevalence stood at 42.6% for football players, 60.1% for ice hockey players, and 49.2% for floorball players. Among these, ice hockey players exhibited a 2.18-fold increased risk of developing LBP and associated disability when compared to their football and floorball counterparts.



#15 Radiographic assessment of the pubic symphysis in elite male adolescent football players: Development and reliability of the Maturing Adolescent Pubic Symphysis (MAPS) classification

Reference: Eur J Radiol. 2023 Aug 28;167:111068. doi: 10.1016/j.ejrad.2023.111068. Online ahead of print.

Authors: Astrid van Ovost, David Frederikus Hanff, Andreas Serner, Pim van Klij, Rintje Agricola, Adam Weir

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Summary: The pubic symphysis is susceptible to growth related injuries long after the adolescent growth spurt. Our study describes the radiographic maturation of the pubic symphysis on pelvic radiographs in adolescent football players and introduces the Maturing Adolescent Pubic Symphysis classification (MAPS classification). Anteroposterior pelvic radiographs of 105 healthy adolescent male football players between 12 and 24 years old were used to develop the classification system. The radiological scoring of the symphyseal joint was developed over five rounds. The final MAPS classification items were scored in random order by two experienced readers, blinded to the age of the participant and to each other's scoring. The inter- and intra-rater reliability were examined using weighted kappa (κ). We developed a classification system with descriptive definitions and an accompanying pictorial atlas. The symphyseal joint was divided into three regions: the superior corners, and the upper and lower regions of the joint line. Inter-rater reliability was substantial to almost perfect: superior region: κ = 0.70 (95% CI 0.60---0.79), upper region of the joint line: κ = 0.89 (95% CI 0.86---0.92), lower region of the joint line: κ = 0.65 (95% CI 0.55---0.75). The intra-observer reliability showed similar results. The Maturing Adolescent Pubic Symphysis classification (MAPS classification) is a reliable descriptive classification of the radiographic maturation of the pubic symphysis joint in athletic males. The stages can provide a basis for understanding in clinical practice and will allow future research in this field.



#16 Examining the effect of task constraints on the emergence of creative action in young elite football players by using a method combining expert judgement and frequency count

Reference: Psychol Sport Exerc. 2023 Nov;69:102502. doi: 10.1016/j.psychsport.2023.102502. Epub 2023 Aug 3.

Authors: Tom de Joode, John van der Kamp, Geert J P Savelsbergh

Summary: In adult football, small-sided games are associated with increased action variability and suggested to promote more creative actions compared to regular 11v11 formats. This aligns with predictions from an ecological approach to perception and action that creative actions emerge in environments that grant variability in action, instead of being an expression of the individual player's ability to generate ideas. To further evidence for this prediction, the current study aimed to expand this observation to elite youth football players. To this end, the number of different and creative actions in 4v4 small-sided game and a 11v11 regular-sided game among 10- to 12-year-old elite football players were examined. We analyzed a total of 7922 actions, which were categorized for type and creativity. Based on a subset of these actions, a panel of elite football coaches judged action types occurring below 0.5% as significantly more creative than more frequent action types. Hence, we used an occurrence of 0.5% as threshold to distinguish creative actions from non-creative actions. The results showed that the total number of actions, the number of different action types, the number creative actions and the number of different creative action types was significantly higher for the small-sided game format than the regular-sided game. In conclusion, this study confirms that in elite youth football, small-sided games induce a more variable and creative action repertoire. This shows that practitioners can design learning environments that promote the emergence of creative actions.







Changes in Physical Performance Throughout Professional Soccer Match-Play

The aim of this study was to explore the changes in physical performance by playing position throughout professional soccer match-play.





Association between physical demands, skin temperature and wellbeing status in elite football players

The This study aimed to evaluate the relationship between physical demands, skin temperature, and well‐being status in 30 Spanish professional football players over a 12‐week competitive period. 





Latest research in football - week 35 - 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 Long-term Intensive Soccer Training Induced Dynamic Reconfiguration of Brain Network

Reference: Neuroscience. 2023 Aug 26;S0306-4522(23)00372-X. doi: 10.1016/j.neuroscience.2023.08.020. Online ahead of print.

Authors: Ju Li, Minghao Huang, Yaping Cao, Zhe Qin, Jian Lang

Summary: Long-term motor skill learning has been shown to impact the functional plasticity of the brain. Athletes, as a unique population, exhibit remarkable adaptive changes in the static properties of their brain networks. However, studying the differences between expert and novice athletes using a dynamic brain network framework can provide a fresh perspective on how motor skill learning affects the functional organization of the brain. In this study, we investigated the dynamic properties of brain networks in expert and novice soccer players at the whole-brain, network, and region-based levels. Our findings revealed that expert soccer players displayed reduced integration and increased segregation at the whole-brain level. As for network level, experts exhibited increased segregation and reduced flexibility in the visual network, enhanced integration between the visual and ventral attention networks, and decreased integration in the subcortical-sensorimotor and subcortical-cerebellar networks. Additionally, specific brain regions within the visual network exhibited greater recruitment in expert soccer players compared to novices at the nodal level. Furthermore, classification analyses demonstrated the critical role played by the visual network in the classification process. In conclusion, our study provides new insights into the dynamic properties of brain networks in expert and novice soccer players, and suggests that reduced integration and increased segregation in the visual network may be neuroimaging marker that distinguish expert soccer players from novices. Our findings may have implications for the training and development of athletes and advance our understanding of how motor skill learning affects brain functional organization.



#2 MAS and MANS Predicts Repeated Sprint Ability in Youth Soccer Players

Reference: Int J Exerc Sci. 2023 Jul 1;16(6):846-854. eCollection 2023.

Authors: Jørgen D Olsen, Henrik R Rognhaug, Daniel Kvamme, Øyvind Støren, Eva Maria Støa

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Summary: The study investigated the impact of maximal aerobic speed (MAS) and maximal anaerobic sprint (MANS) on repeated sprint ability (RSA) in soccer. 17 amateur-to semi-professional soccer players, age 19 (± 4) years, were tested for maximal oxygen consumption (VO2max), oxygen cost of running (Cr), RSA consisting of 15·20m sprint each divided by a 100 seconds dribble track, and 40-meter sprint performance. MAS was calculated as VO2max · Cr-1, and MANS was defined as the highest velocity in the 40-meter sprint. There was a strong correlation between MAS and average 20-meter RSA velocity (r = 0.760; p < 0.01), and between MAS and performance decrement (r = -0.648; p < 0.01). The product of 0.5MAS + 0.5MANS exhibited the strongest correlation with RSA (r = 0.813; p < 0.01). The combination of MAS and MANS strongly predicted RSA. High-intensity aerobic interval training (HIIT) and maximal strength training (MST) are recommended to improve MAS and MANS, and could thus lead to better RSA on the soccer field.



#3 Perspectives and practices of nutritionists on dietary supplements for elite soccer teams: a cross-sectional survey study

Reference: Front Sports Act Living. 2023 Aug 11;5:1230969. doi: 10.3389/fspor.2023.1230969. eCollection 2023.

Authors: Rodrigo Abreu, Catarina B Oliveira, João Brito, Vitor H Teixeira

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Summary: Dietary supplements are part of the nutritional strategies frequently applied in sports performance support. With growing research on this subject and high demand from athletes, nutritionists need to keep up to date with the latest evidence and utility of dietary supplements, particularly in real-world contexts. As information about the use of dietary supplements among elite soccer players is still scarce, this work aimed to know how nutritionists working with elite soccer teams perceive and use these substances in their daily practice. A questionnaire previously used to describe nutritionists' beliefs and attitudes regarding the use of dietary supplements in a clinical context was adapted for this study. The online questionnaire was addressed to nutritionists working with elite soccer teams from six European Leagues and Brazil, between November 2022 and February 2023. Overall, the participants considered themselves well-trained (76.9%), knowledgeable (95.4%), and interested in dietary supplements (95.4%). The majority (70.8%) of the participants agreed or strongly agreed to recommend dietary supplements to soccer players. Personal usage of dietary supplements was associated with recommending supplements (p < 0.001), but no relationships were found with years of experience and academic level. Nutritionists working with elite soccer players consider the use of dietary supplements for performance-enhancement purposes and not only to compensate for nutritional deficits, which might contribute to their higher interest, training and perceived knowledge about this topic. Participants recognize players' interest in dietary supplements, and are mindful of the safety and efficacy of these products. The present study suggests that nutritionists working with elite soccer teams are among the highest prescribers of dietary supplements, although personal usage is lower than that of nutritionists working in a clinical context.



#4 Brain Spectroscopy Analysis in Retired Soccer Players With Chronic Exposure to Mild Traumatic Brain Injuries

Reference: Neurotrauma Rep. 2023 Aug 18;4(1):551-559. doi: 10.1089/neur.2023.0020. eCollection 2023.

Authors: Lucas Lopes Resende, Claudia da Costa Leite, Bruno Fraccini Pastorello, Davi Jorge Fontoura Solla, Pedro Nascimento Martins, Bernardo Fernandes Pelinca da, Mateus Rozalem Aranha, Suely Fazio Ferraciolli, Maria Concepción García Otaduy

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Summary: Soccer players are at risk of suffering cranial injuries in the short and long term. There is growing concern that this may lead to traumatic brain injury in soccer players. Magnetic resonance spectroscopy (MRS) is an analytical method that enables the measurement of changes in brain metabolites that usually occur before significant structural changes. This study aimed to use MRS to compare variations in brain metabolite levels between retired soccer players and a control group. Twenty retired professional soccer players and 22 controls underwent magnetic resonance imaging, including MRS sequences and Mini-Mental State Examination (MMSE). Metabolite analysis was conducted based on absolute concentration and relative ratios. N-acetyl-aspartate, choline, glutamate, glutamine, and myoinositol were the metabolites of interest for the statistical analysis. Retired soccer players had an average age of 57.8 years, whereas the control group had an average age of 63.2 years. Median cognitive evaluation score, assessed using the MMSE, was 28 [26-29] for athletes and 29 [28-30] for controls (p = 0.01). Uni- and multi-variate analyses of the absolute concentration of metabolites (mM) between former athletes and controls did not yield any statistically significant results. Comparison of metabolites to creatine ratio concentrations did not yield any statistically significant results. There were no changes in concentrations of brain metabolites that indicated brain metabolic changes in retired soccer players compared with controls.



#5 Normative data in resting and maximum heart rates and a prediction equation for young Tunisian soccer players: a cross-sectional study

Reference: EXCLI J. 2023 Jul 17;22:670-680. doi: 10.17179/excli2023-6215. eCollection 2023.

Authors: Hatem Ghouili, Zouhaier Farhani, Sofiane Amara, Soukaina Hattabi, Amel Dridi, Noomen Guelmami, Anissa Bouassida, Nicola Bragazzi, Ismail Dergaa

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Summary: Heart rate (HR) is an important indicator of work intensity during physical activity. Maximum heart rate (MHR) is a physiological measure that is frequently used as a benchmark for maximal exercise intensity. The aim of this study was to establish reference curves for maximum heart rate (MHR) and resting heart rate (RHR) and to develop an estimated equation for Tunisian adolescent footballers. The study involved 801 adolescent players, aged 11 to 18, who belonged to five Tunisian first-division soccer teams. The LMS method was used for smoothing the curves and the multivariate linear regression to develop a prediction equation of MHR. Our results showed that MHR and RHR reference curves decrease with age. The values of the median curves of MHR and RHR ranged from 208.64 bpm (11 years) to 196.93 (18 years) and 73.86 (11 years) to 63.64 (18 years), respectively. The prediction equation obtained from the model was MHR= 225.08 - 1.55 X Age (years) (R2 = 0.317; P < 0.001; standard error of the estimate (SEE) = 5.22). The comparisons between the estimated values and the measured values have found that our model (- 0.004 ±5.22 bpm) was to be more accurate than two other widely known models. BOX's equation underestimates the measured MHR values by -3.17 ± 5.37 bpm and TANAKA's equation overestimates by + 4.33 ±5.5 bpm. The reference curves can be used by coaches and physical trainers to classify the resting heart rate (RHR) and maximum heart rate (MHR) of each adolescent player, track their evolution over time, and design tailored training programs with specific intensities for Tunisian soccer players.



#6 External Workloads Vary by Position and Game Result in US-based Professional Soccer Players

Reference: Int J Exerc Sci. 2023 Jun 1;16(6):688-699. eCollection 2023.

Authors: Gary M Long, Sam M Joyce, Robert T Herrington, Kyle B Fox, Jack E Mumaugh

Summary: Professional soccer is a physically demanding sport that requires players to be highly trained. Advances using GPS allow the tracking of external workloads for individual players in practice and competition, however, there is a lack of evidence on how these measures impact match results. Therefore, we analyzed external workloads by player position and determined if they vary depending on the result of competitive matches. External workloads were analyzed in professional soccer players (n = 25) across 28 competitive games. One-way ANOVA determined if workloads varied by position (striker - ST, wide midfielder - WM, central midfielder - CM, wide defender - WD, central defender - CD) or across games won (n = 8), lost (n = 13) or tied (n = 7). Repeated-measures ANOVA assessed differences in workloads specific to each position in each of the result categories. Statistical significance was set at p < 0.05. Across all games, more high-speed and very-high speed running was done by ST and WD compared to CD (p < 0.001) and CM (p < 0.001 - 0.02). Whole-team data showed no differences in any external workload variable with respect to match result (p > 0.05), however, in games won ST did more very high-speed running than in losing games (p = 0.03) and defending players did more high and very high-speed running in games tied vs. those won or lost (p < 0.05). Whole-team external workloads do not vary depending on the match result; however, high speed running may be a differentiating factor at the positional level. Coaches should consider position-specific analysis when examining player workloads.



#7 Concomitant Injuries Associated With ACL Rupture in Elite Professional Alpine Ski Racers and Soccer Players: A Comparative Study With Propensity Score Matching Analysis

Reference: Orthop J Sports Med. 2023 Aug 17;11(8):23259671231192127. doi: 10.1177/23259671231192127. eCollection 2023 Aug.

Authors: Luca Farinelli, Robert Csapo, Amit Meena, Elisabeth Abermann, Christian Hoser, Christian Fink

Summary: For elite professional soccer players and alpine skiers, injuries associated with anterior cruciate ligament (ACL) rupture, such as meniscal, cartilage, or collateral ligament lesions, could result in a delayed return to sport compared with isolated ACL injury. The purpose of the study was to provide a detailed description of associated injuries at the time of primary ACL reconstruction in elite soccer players and alpine skiers. It was hypothesized that soccer players and skiers would present different typical injury patterns due to different injury mechanisms. Surgical reports and arthroscopic images of elite professional soccer players and alpine skiers who underwent primary ACL reconstruction at a single institution between January 2010 and June 2022 were analyzed retrospectively. The presence and location of multiligamentous injury, meniscal tears, and chondral lesions were compared between the athlete groups. A propensity score matching analysis with 1:1 ratio was performed between skiers and soccer players to limit the effect of selection bias. Included were ACL reconstruction data representative of 37 soccer players and 44 alpine skiers. Meniscal pathology was found in 32 (86%) soccer players and 30 (68%) skiers. Chondral injuries were reported in 11 (30%) soccer players and 15 (34%) skiers. Results of the propensity score matching analysis in 15 pairs of soccer players and skiers indicated that soccer players had a significantly higher rate of medial meniscal injuries (73% vs 27%; P = .03) and lateral posterior root tears (33% vs 0%; P = .04) compared with skiers. A higher prevalence of combined chondral and meniscal injuries versus isolated ACL injuries was observed in both groups of athletes. Professional soccer players were characterized by higher prevalence of medial meniscal tears and lateral posterior root lesions compared with professional alpine skiers.



#8 Advancing and critical appraisal of an integrative load monitoring approach in microcycles in professional soccer

Reference: PLoS One. 2023 Sep 1;18(9):e0286372. doi: 10.1371/journal.pone.0286372. eCollection 2023.

Authors: Linda Ammann, Ludwig Ruf, Adam Beavan, Paweł Chmura, Stefan Altmann

Summary: Despite load monitoring being considered an integral part of targeted performance management, including injury and illness prevention, there is currently no consensus of an effective monitoring system in professional soccer. Thus, the aims were to apply an integrative load monitoring approach, previously established in rink-hockey, in professional soccer; extend this approach with further data (Short Recovery and Stress Scale); assess this (extended) approach, thereby further evaluating the relationship between the used external load (EL) measures (total distance, distance above 55% and 70% of individual maximal speed, number of accelerations and decelerations > 4 m/s2, total loading) and the internal load (IL) measure session rate of perceived exertion training load (sRPE-TL) as well as between the used EL measures and sRPE. This retrospective observational cohort study analyzed data from a Swiss team collected over a 14 week-period during the 2021/22 season. Based on our findings, the integrative approach tested proved to be an applicable load monitoring tool in professional soccer, placing players on a fitness-fatigue continuum throughout the different microcycle sessions without using tests, thus providing relevant information to individually tailor training programs. sRPE-TL (ρ [95% CI] = .55 [.51 to .59] to .87 [.85 to .88]; all p < .001) better reflected the EL experienced by players than sRPE (ρ [95% CI] = .45 [.40 to .50] to .71 [.69 to .75]; all p < .001) supporting the definition of sRPE-TL as a measure of IL. However, for even stronger relevance of the tested tool, further research is warranted, especially to ascertain its sensitivity and determine an optimal selection of EL and IL measures. In sum, the present data clearly demonstrate the importance of load management taking place at an individual level, even within team structures, thereby analyzing a set of both EL and IL measures.



#9 Prolonged cognitive effort impairs inhibitory control and causes significant mental fatigue after an endurance session with an auditive distractor in professional soccer players

Reference: Psychol Sport Exerc. 2023 Sep 5;102533. doi: 10.1016/j.psychsport.2023.102533.

Authors: Maria E C Ferreira, Dalton Lima-Junior, Heloiana Faro, Bart Roelands, Leonardo S Fortes

Summary: Throughout official soccer matches, the presence of cheer by the crowd could be considered a critical auditive distraction that could further impair the cognitive interference control system, multiple object tracking (MOT) skill, heart rate variability (HRV), and increase mental fatigue. As the resource is not immediately replenished, the impairment of the cognitive interference control system may be delayed following a soccer game. Then, evaluating the recovery time course of the cognitive interference control system, MOT skill, HRV, and mental fatigue after prolonged tasks combining physical, endurance, and cognitive effort are essential. We aimed to analyze the acute effect of cognitive effort and auditive distractor with 24-h follow-up throughout a prolonged endurance session on inhibitory control, subjective mental fatigue, MOT skill, and HRV in professional soccer players. Twenty professional male soccer players were recruited (23.56 ± 3.8 years, 78.1 ± 6.9 kg, 1.77 ± 0.06 m, and 12.5 ± 5.3% body fat). The sessions were performed in a randomized and counterbalanced crossover design, divided into four experimental conditions: endurance, endurance + MOT, endurance + MOT + AD, and endurance + AD. The soccer players completed the incongruent Stroop task utilizing an eye-tracker to assess cognitive effort. MOT task, subjective mental fatigue, and HRV were evaluated before the endurance training (60%Δ of maximal aerobic velocity during 40-min) and after 30-min and 24-h of recovery. These sessions were designed to investigate the acute effect of prolonged cognitive effort (repeated MOT throughout the endurance task) and AD (constant crowd noise and coach's voice each 15-40 s, totalizing = 80 voices) on inhibitory control, MOT skills, HRV, and subjective mental fatigue after a fixed endurance training session. There was no condition × time interaction for accuracy of inhibitory control (p > 0.05, ηp2 = 0.001). There was a significant condition × time interaction for inhibitory control response time (p < 0.05, ηp2 = 0.16). A higher response time of inhibitory control was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was a significant condition × time interaction for subjective mental fatigue (p < 0.05, ηp2 = 0.46). A higher subjective mental fatigue was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was no condition × time interaction for HRV (p > 0.05, ηp2 = 0.02). We concluded that cognitive effort throughout a prolonged endurance session impaired inhibitory control and increased mental fatigue without promoting greater MOT skill and HRV changes in professional soccer players.



#10 Erratum. Inconsistent Effect of Psychometric-Scale Familiarization on the Relationship Between Ratings of Perceived Exertion and External Load Measures in Elite Youth Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Sep 7;1. doi: 10.1123/ijspp.2023-0345. Online ahead of print.

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#11 Total Score of Athleticism: Profiling Strength and Power Characteristics in Professional Soccer Players After Anterior Cruciate Ligament Reconstruction to Assess Readiness to Return to Sport

Reference: Am J Sports Med. 2023 Sep 8;3635465231194778. doi: 10.1177/03635465231194778.

Authors: Luca Maestroni, Anthony Turner, Konstantinos Papadopoulos, Vasileios Sideris, Paul Read

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Summary: There is no consensus on the optimal testing procedure to determine return-to-sport (RTS) readiness after anterior cruciate ligament (ACL) reconstruction. Current approaches use limb symmetry across a range of tests, but this does not consider a patient's level of athleticism or benchmarks relative to his or her noninjured counterparts. The aim was tro examine the utility of the Total Score of Athleticism (TSA), a composite scale including strength, power, and reactive strength assessments, to aid RTS decision-making. A total of 95 professional soccer players (60 who underwent ACL reconstruction [mean age, 25.1 ± 12.6 years] and 35 who were uninjured [mean age, 23.8 ± 2.8 years]) completed a battery of tests including isokinetic knee extension and flexion torque, bilateral and unilateral countermovement jump height, relative peak power, and reactive strength index-modified. The TSA score (derived from Z scores) was calculated, and we (1) examined differences between the ACL-reconstructed and uninjured groups at the time of RTS, (2) assessed the predictive ability of the TSA to identify the player's status (ACL reconstruction vs uninjured control), and (3) included a case series to discuss the characteristics of players who sustained a subsequent injury within 4 months after RTS. A large difference between the ACL-reconstructed and uninjured groups in the TSA score (d = 0.84; P < .0001) was evident. For every additional increase of 1 unit in the TSA score, the odds of belonging to the ACL-reconstructed group decreased by 74% (95% CI, 0.19-0.56). By visual inspection, the frequency of reinjured players was higher in the low (4/7) TSA tertile compared with the medium (2/7) and high (1/7) TSA tertiles. Preliminary evidence indicates that the TSA may be a useful RTS readiness tool, as the composite score derived from strength and power measures was different in soccer players at the time of RTS after ACL reconstruction compared with healthy matched controls. There was also a higher frequency of low TSA scores in players who sustained a second injury after RTS. Therefore, it is recommended to routinely administer RTS tests encompassing strength, power, and reactive strength qualities each season across the largest possible number of players (ideally teammates).



#12 Methods to predict the timing and status of biological maturation in male adolescent soccer players: A narrative systematic review

Reference: PLoS One. 2023 Sep 8;18(9):e0286768. doi: 10.1371/journal.pone.0286768. eCollection 2023.

Authors: Joseph Sullivan, Simon J Roberts, John Mckeown, Martin Littlewood, Christopher McLaren-Towlson, Matthew Andrew, Kevin Enright

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Summary: The aim of this review was to summarise the methods used to predict and assess maturity status and timing in adolescent, male, academy soccer players. A systematic search was conducted on PubMed, Scopus, Web of Science, CINAHL, Medline and SPORTDiscus. Only experimental studies including male, academy players aged U9-U18 years registered with a professional soccer club were included. The methodological quality of the included studies was assessed using guidelines from the Framework of Potential Biases. Fifteen studies fulfilled our inclusion criteria. Studies were mainly conducted in European countries (n = 12). In total, 4,707 players were recruited across all 15 studies, with an age range of 8-18 years. Five studies were longitudinal, two studies were mixed-method designs and eight studies were cross-sectional. Due to high heterogeneity within the studies, a meta-analysis was not performed. Our findings provided no equivalent estimations of adult height, skeletal age, or age at PHV. Discrepancies were evident between actual and predicted adult height and age at PHV. The Bayley-Pinneau [1952], Tanner-Whitehouse 2 [1983] and Khamis-Roche [1994] methods produced estimates of adult height within 1cm of actual adult height. For age at PHV, both Moore [2015] equations produced the closest estimates to actual age at PHV, and the Fransen [2018] equation correlated highly with actual age at PHV (>90%), even when the period between chronological age and age at PHV was large. Medical imaging techniques (e.g., Magnetic Resonance Imaging, X-Ray, Dual energy X-ray Absorptiometry) demonstrated high intra/inter-rater reliability (ICC = 0.83-0.98) for skeletal maturity assessments. The poor concordance between invasive and non-invasive methods, is a warning to practitioners to not use these methods interchangeably for assessing maturational status and timing in academy soccer players. Further research with improved study designs is required to validate these results and improve our understanding of these methods when applied in this target population.



#13 Motivational climate dimensions predict youth soccer players' psychosocial well-being over time

Reference: Psychol Sport Exerc. 2023 Aug 24;70:102518. doi: 10.1016/j.psychsport.2023.102518.

Authors: Lindsay E Kipp, Nicole D Bolter

Summary: This study tested a longitudinal model of relationships, based on self-determination theory, to determine whether motivational climate dimensions predicted young athletes' psychological need satisfaction and, in turn, personal and social responsibility. Youth soccer players (N = 161; M = 10.8 years-old, SD = 1.0 year) completed a survey at two time points, spaced 4 months apart, on average. Several significant direct effects emerged. First, greater perceptions that coaches punished for mistakes predicted decreases in relatedness with coaches and teammates. Second, greater perceptions of relatedness with coaches and teammates predicted increases in personal and social responsibility. Indirect effects also emerged: (a) punishment for mistakes predicted decreases in personal responsibility and social responsibility, and (b) cooperative learning predicted increases in social responsibility, through effects on coach and teammate relatedness. Results suggest that coaches who provide opportunities for collaborative learning and minimize mistake-contingent punishment will foster athletes' sense of connection and enhance their psychosocial well-being.



#14 Effectiveness of a Preventative Program for Groin Pain Syndrome in Elite Youth Soccer Players: A Prospective, Randomized, Controlled, Single-Blind Study

Reference: Healthcare (Basel). 2023 Aug 22;11(17):2367. doi: 10.3390/healthcare11172367.

Authors: Filippo Cotellessa, Luca Puce, Matteo Formica, Maria Cesarina May, Carlo Trompetto, Marco Perrone, Andrea Bertulessi, Vittorio Anfossi, Roberto Modenesi, Lucio Marinelli, Nicola Luigi Bragazzi, Laura Mori

Summary: Groin pain syndrome (GPS) is a prevalent issue in soccer. This study assessed the effectiveness of a new preventive protocol on GPS for youth soccer players. The protocol included targeted stretching and strengthening exercises for the adductor and core muscles from preseason to midseason. A questionnaire and two pain provocation tests were used for the evaluation. Mild GPS required positive results in at least two evaluations, while severe GPS was associated with pain incompatible with engagement in any activity confirmed by diagnostic ultrasound. Forty-two elite male athletes (aged 16.9 ± 0.7 years) participated in the study, with half of them assigned to the usual training (control group) and the remaining athletes undergoing the preventive protocol (treatment group) for 24 weeks. GPS rates were 14.3% (three diagnoses: two mild, one severe) in the treatment group and 28.6% (six diagnoses: three mild, three severe) in the control group. Toward the end of the season, three players, one from the treatment group and two from the control group had to stop playing due to severe GPS problems. In addition, one player in the control group stopped midseason. Even though the reduction in the risk of developing GPS was not significant (relative risk of 0.50 ([95%CI 0.14 to 1.74], p = 0.2759), the halved incidence of severe GPS and the increased muscle strength related to the treatment (p = 0.0277) are encouraging data for future studies.



#15 Endurance performance adaptations between SSG and HIIT in soccer players: A meta-analysis

Reference: Int J Sports Med. 2023 Sep 7. doi: 10.1055/a-2171-3255. Online ahead of print.

Authors: Filipe Manuel Clemente, Jason Moran, Rodrigo Ramirez-Campillo, Marco Beato, José Afonso

Summary: The objective of this systematic review with meta-analysis was to compare the endurance performance chronic adaptations induced by running-based high-intensity interval training (HIIT), small-sided games (SSGs), and combined HIIT+SSGs in male and female youth and adult soccer players. The studies included in this review followed the PICOS criteria: (i) healthy soccer players; (ii) interventions based on SSGs; (iii) comparators exposed to only HIIT or combined SSGs+HIIT; (iv) endurance performance variables. Studies were searched for in the following databases: (i) PubMed; (ii) Scopus; (iii) SPORTDiscus; (iv) Web of Science. After conducting an initial database search that retrieved a total of 5,389 records, a thorough screening process resulted in the inclusion of 20 articles that met the eligibility criteria. Sixteen studies reported outcomes related to endurance performance measured through field-based tests, while 5 studies provided results from direct measurements of maximal oxygen uptake (VO2max). Results showed a non-significant small-magnitude favoring effect for the HIIT groups compared to the SSGs groups (ES=0.37, p=0.074) for endurance, while a non-significant small-magnitude favoring SSGs was observed (ES=-0.20, p=0.303) for VO2max. Despite the very low certainty of evidence, the findings suggest similar effects induced by both SSG and HIIT on improving endurance performance and VO2max.






Effective playing time affects technical-tactical and physical parameters in football

Effective playing time has been debated as a topic of major concern in football. Thus, the current experimental study aimed to investigate the effects of effective playing time on technical-tactical and physical match parameters in football.





In-season autoregulation of one weekly strength training session maintains physical and external load match performance

The aim of this study was to compare the effects of autoregulating strength training volume based on an objective (external load match performance) vs. a subjective (self-selected) method in professional footballers.





Latest research in football - week 34 - 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 Effects of the Timing of Carbohydrate Intake on Metabolism and Performance in Soccer Players

Reference: Nutrients. 2023 Aug 17;15(16):3610. doi: 10.3390/nu15163610.

Authors: Ki-Woong Noh, Jung-Hwan Oh, Sok Park

Summary: This study aims to provide information to improve the performance of athletes comparing the effects of carbohydrate-electrolyte intake before and during exercise on metabolism and performance in soccer players. The study had a single-blind cross-over design. Drust's protocol is a soccer-specific intermittent exercise test. The carbohydrate-electrolyte intake experiments were divided into three timings: first, pre-exercise; second, half-time; and third, mixed. Eight participants were included in the data analysis (age: 21.32 ± 1.19 years; BMI: 22.69 ± 1.91 kg/m2; height: 176.5 ± 7.52 cm; weight: 69.5 ± 9.18 kg; Vmax: 16.75 0.71 km/h). The results of the mixed test showed a significantly lower respiratory exchange ratio than those of the placebo and half-time tests (p < 0.05). The mixed test showed significantly more fat oxidation than the half-time test (p < 0.05). The running times are placebo (422.13 ± 133.44 s) and mixed (677.38 ± 217.75 s), and the distances are placebo (1577.25 ± 517.02 m) and mixed (2530.00 ± 832.71 m) (p < 0.05). The mixed test showed a significantly lower rating of perceived exertion than the placebo test (p < 0.05). Carbohydrate oxidation and heart rate showed no significant differences between the experiments (p > 0.05). The exercise protocol in this study showed the metabolic response of soccer players to intermittent high-intensity exercise and subsequent endurance exercise. In conclusion, it can be seen that the intake of carbohydrate-electrolytes improves the performance of soccer players, and the effect varies depending on the timing of carbohydrate-electrolyte intake.



#2 Walking football for Health - physiological response to playing and characteristics of the players

Reference: Sci Med Footb. 2023 Aug 26;1-8. doi: 10.1080/24733938.2023.2249426. Online ahead of print.

Authors: Helena Andersson, Andreas Caspers, Manne Godhe, Torbjörn Helge, Julia Eriksen, Dan Fransson, Mats Börjesson, Elin Ekblom-Bak

Summary: Walking Football (WF) is one type of recreational football increasing in popularity, targeting older adults. Further knowledge on the intensity and physical workload of WF, characteristics of the players, the social context, and reasons for playing WF is needed. Thus, the aim of the study was to characterize the individuals that regularly play WF and their experience of WF, and the physiological characteristics of the sport. Sixty-three players from three clubs taking part in organised WF in Sweden were included. The players participated in up to four WF-games and underwent performance tests and answered a questionnaire. The participants mean age was 70.9 years, ranging from 63 to 85 years with 71% (n = 27) of the men and 68% (n = 13) of the women having a BMI > 25. Fifty-one percent (n = 27) of the players had hypertension, and 73% (n = 39) regularly used prescription drugs due to illness. During WF, the players covered on average 2,409 m (2,509 m for men and 2,205 m for women, p = .001). Expressed in percentage of their age-estimated maximal heart rate, mean heart rate represented 80 ± 9 and 80 ± 8% of max for men, and 78 ± 9 and 79 ± 9% of max for women in the first and second halves, respectively, hence WF can be considered a moderate intensity activity for older adults. The main reason for WF participation was to socialize. WF includes a considerable number of accelerations and decelerations, making it more energetically and mechanically demanding than walking.



#3 Effect of High Intensity Interval Training Under Mask on Forced Vital Capacity in Football Players

Reference: Int J Exerc Sci. 2023 May 1;16(6):576-586. eCollection 2023.

Authors: Bumrung Neranoch, Manimmanakorn Apiwan, Traiperm Natthapon

Summary: The purpose of the study was to investigate the effect of high interval training (HIIT) under mask on forced vital capacity in football players. Fourteen male football players (age 20 ± 2 years) were randomized into the without mask group (CON) or with the 2 difference mask groups [Surgical mask (SM), FFP2 mask (FM)]. HIIT program were implemented six movements in each session three times per week. Body composition, forced vital capacity and percutaneous oxygen saturation test were taken before and after 4 weeks intervention. The results show that forced vital capacity was statistically significant increased with both types of masks (SM: 5.68 ± 1.07 L; FM: 5.26 ± 0.86 L; CON: 4.66 ± 0.48 L, p < 0.01). Additionally, not significant difference in percutaneous oxygen saturation (SpO2) was found, and fat free mass (SM: 54.45 ± 4.01 kg; FM: 57.08 ± 4.38kg; CON: 58.34 ± 1.81 kg, p<0.01) were statistically significant changed with SM and CON but not FM. In conclusion, wearing surgical masks and FFP2 face mask during high-intensity interval exercise showed certain positive impacts on cardiopulmonary function. This short-term high-intensity interval training can be used to improve forced vital capacity performance among football players. This finding can be applied to develop the strength of breathing muscles in the future.



#4 The effect of bio-electro-magnetic-energy-regulation therapy on sleep duration and sleep quality among elite players in Norwegian women's football

Reference: Front Psychol. 2023 Aug 8;14:1230281. doi: 10.3389/fpsyg.2023.1230281. eCollection 2023.

Authors: Frode Moen, Svein Arne Pettersen, Kine Gjertsås, Marte Vatn, Martijn Ravenhorst, Atle Kvålsvoll, Kristian Hovde Liland, Ellen F Mosleth

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Summary: The current study investigated if physical loads peak on game days and if Bio-Electro-Magnetic-Energy-Regulation (BEMER) therapy is affecting sleep duration and sleep quality on nights related to game nights among elite players in Norwegian women's elite football. The sample included 21 female football players from an elite top series club with a mean age of ~24 years (± 2.8). Sleep was measured every day over a period of 273 consecutive days with a Somnofy sleep monitor based on ultra-wideband (IR-UWB) pulse radar and Doppler technology. The current study was conducted as a quasi-experiment, where each player was their own control based on a control period that lasted for 3 months, and an experimental period that lasted for 5 months. Accordantly, the time each player spent with BEMER therapy was used as a control variable. Multivariate analyses of variance using FFMANOVA and univariate ANOVA with False Discovery Rate adjusted p-values show that physical performance (total distance, distance per minute, sprint meters >22.5 kmh, accelerations and decelerations) significantly peak on game day compared with ordinary training days and days related to game days. The results also show that sleep quantity and quality are significantly reduced on game night, which indicate disturbed sleep caused by the peak in physical load. Most sleep variables significantly increased in the experiment period, where BEMER therapy was used, compared to the control period before the introduction of BEMER therapy. Further, the analyses show that players who spent BEMER therapy >440 h had the most positive effects on their sleep, and that these effects were significantly compared to the players who used BEMER therapy <440 h. The findings are discussed based on the function of sleep and the different sleep stages have on recovery.



#5 Effective playing time affects technical-tactical and physical parameters in football

Reference: Front Sports Act Living. 2023 Aug 8;5:1229595. doi: 10.3389/fspor.2023.1229595. eCollection 2023.

Authors: Óscar Tojo, Konstantinos Spyrou, João Teixeira, Paulo Pereira, João Brito

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Summary: Effective playing time has been debated as a topic of major concern in football. Thus, the current experimental study aimed to investigate the effects of effective playing time on technical-tactical and physical match parameters in football. One hundred and seventy-nine male highly trained football players (aged 27.9 ± 5.1 years) from twelve teams performed two different match-play conditions: 45 min of match-play without stopping the chronometer (T45), and 30 min of match-play by stopping the chronometer every time the ball was out-of-play (T30). T30 presented a significantly higher total time (49:30 vs. 45:00 min; p = <.001; ES = 0.76), effective playing time (28:70 vs. 26:80 min; p = <.001; ES = 0.62), and stopped time (20:60 vs. 18:20 min; p = 0.003; ES = 0.38) compared to T45. Total ball possession (54.4% vs. 45.6%; p = 0.002) and 1/3 ball possession (55.3% vs. 44.7%; p = 0.018) was higher in T30 condition when compared to T45. Regarding match external load, total distance covered (4,899 vs. 4,481 m; p = <.001; ES = 0.71), moderate-speed running (607 vs. 557 m; p = 0.002; ES = 0.26) and high-speed running (202 vs. 170 m; p = <.001; ES = 0.33), high-speed activities (284 vs. 245 m; p = 0.003; ES = 0.24), accelerations (27 vs. 24; p = <.001; ES = 0.32), and decelerations (31 vs. 28; p = 0.005; ES = 0.26) were higher in T30 compared to T45. In conclusion, these findings suggest that higher effective playing time may affect technical-tactical and physical parameters during football games.



#6 Association between physical demands, skin temperature and wellbeing status in elite football players

Reference: Sci Rep. 2023 Aug 23;13(1):13780. doi: 10.1038/s41598-023-40396-y.

Authors: Carlos Majano, Jorge Garcia-Unanue, Ismael Fernández-Cuevas, Víctor Escamilla-Galindo, Antonio Alonso-Callejo, Javier Sanchez-Sanchez, Leonor Gallardo, Jose Luis Felipe

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Summary: The demanding nature of elite football requires players to be closely monitored to ensure optimal performance and minimize injury risk. This study aimed to evaluate the relationship between physical demands, skin temperature, and well-being status in 30 elite football players over a 12-week competitive period. Thermography assessments, weekly Well-being questionnaires, and daily training and match load recordings were used to gather data. Results indicated that along the microcycles there was a decrease in high-intensity accelerations and decelerations distance completed, while maintaining other high-intensity actions. Furthermore, it was found that high-intensity movements contribute to the generation of thermal asymmetries in the thighs; the adductor thermal asymmetry showed a positive relationship with stress and muscle soreness, the knee thermal asymmetry had a positive relationship with fatigue and a negative relationship with rest and quality of rest, and finally the hamstrings muscles exhibited significant differences between the thermal asymmetry groups, with the high asymmetry completing less high intensity actions than the low asymmetry group. In conclusion, this study highlights the interconnections between physical demands, skin temperature, and well-being in elite football players and provides valuable insights for coaches and trainers in their efforts to optimize performance and health.



#7 Skinfold thickness in elite male professional football players: changes across 3 seasons including a COVID-19 lockdown period

Reference: Sci Med Footb. 2023 Aug 22;1-8. doi: 10.1080/24733938.2023.2248062. Online ahead of print.

Authors: Craig Flannigan, Mark Robinson, Nidia Rodriguez-Sanchez, Barry Drust, Ruairidh McGregor, Stuart Galloway

Summary: This study investigates variations in skinfold thickness in a European professional football team within and across multiple seasons, including before and after COVID-19 restrictions. Skinfold thickness was measured in 49 male players on 32 occasions across three seasons (2018/19, 2019/20 and 2020/21). Intra- and inter-seasonal trends were examined by comparing values for the sum of eight skinfolds (sum8) at key time points using linear mixed models. In each season, the largest differences in sum8 occurred after the preseason period. These differences ranged from a mean difference (Mdiff) of -11.0 mm (p < 0.001) in 2018/19 to -4.8 mm (p < 0.001) in 2020/21. Increases in sum8 occurred after each off-season; however, the increase after the off-season before the 2020/21 season (which included the COVID-19 lockdown period) was the lowest in magnitude and was not statistically significant (Mdiff = 2.9 mm, p = 0.06). Changes occurring in sum8 between the start and end of the competitive season did not follow a consistent pattern and were generally smaller in magnitude than the changes between other seasonal time points. Despite the notable heterogeneity in sum8 between players, changes within players generally followed a similar pattern between the different seasonal timepoints. In summary, changes in skinfold thickness were predominantly related to off-season and 'preparation for competition' periods. Increases in skinfold thickness can be mitigated during extended remote training periods with appropriate training and nutritional strategies.



#8 Competitive season effects on polyunsaturated fatty acid content in erythrocyte membranes of female football players

Reference: J Int Soc Sports Nutr. 2023 Dec;20(1):2245386. doi: 10.1080/15502783.2023.2245386.

Authors: Nere Peña, Javier Amézaga, Gerard Marrugat, Alba Landaluce, Toscana Viar, Julen Arce, Jon Larruskain, Josean Lekue, Carla Ferreri, José María Ordovás, Itziar Tueros

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Summary: An optimal and correctly balanced metabolic status is essential to improve sports performance in athletes. Recent advances in omic tools, such as the lipid profile of the mature erythrocyte membranes (LPMEM), allow to have a comprehensive vision of the nutritional and metabolic status of these individuals to provide personalized recommendations for nutrients, specifically, the essential omega-3 and omega-6 fatty acids, individuating deficiencies/unbalances that can arise from both habitual diet and sportive activity. This work aimed to study the LPMEM in professional female football players during the football season for the first time and compare it with those defined as optimal values for the general population and a control group. An observational study was carried out on female football players from the Athletic Club (Bilbao) playing in the first division of the Spanish league. Blood samples were collected at three points: at the beginning, mid-season, and end of the season for three consecutive seasons (2019-2020, 2020-2021, and 2021-2022), providing a total of 160 samples from 40 women. The LPMEM analysis was obtained by GC-FID by published method and correlated to other individual data, such as blood biochemical parameters, body composition, and age. We observed a significant increase in docosahexaenoic acid (DHA) (p 0.048) and total polyunsaturated fatty acid (PUFA) (p 0.021) in the first season. In the second season, we observed a buildup in the membrane arachidonic acid (AA) (p < .001) and PUFA (p < .001) contents when high training accumulated. In comparison with the benchmark of average population values, 69% of the football players showed lower levels of omega-6 dihomo-γ-linolenic acid (DGLA), whereas 88%, 44%, and 81% of the participants showed increased values of AA, eicosapentaenoic acid (EPA), and the ratio of saturated and monounsaturated fatty acids (SFA/MUFA), respectively. Regarding relationships between blood biochemical parameters, body composition, and age with LPMEM, we observed some mild negative correlations, such as AA and SFA/MUFA ratio with vitamin D levels (coefficient = -0.34 p = .0019 and coefficient = -.25 p = .042); DGLA with urea and cortisol (coefficient = -0.27 p < .006 and coefficient = .28 p < .0028) and AA with age (coefficient = -0.33 p < .001). In conclusion, relevant variations in several fatty acids of the membrane fatty acid profile of elite female football players were observed during the competitive season and, in comparison with the general population, increased PUFA contents were confirmed, as reported in other sportive activities, together with the new aspect of DGLA diminution, an omega-6 involved in immune and anti-inflammatory responses. Our results highlight membrane lipidomics as a tool to ascertain the molecular profile of elite female football players with a potential application for future personalized nutritional strategies (diet and supplementation) to address unbalances created during the competitive season.



#9 Age-Related Reference Intervals for Physical Performance Test Outcomes Relevant to Male Youth Middle Eastern Football Players

Reference: Int J Sports Physiol Perform. 2023 Aug 21;1-13. doi: 10.1123/ijspp.2023-0145. Online ahead of print.

Authors: Lorenzo Lolli, Warren Gregson, Daniele Bonanno, Sami Kuitunen, Valter Di Salvo

Summary: The purpose was to develop age-specific reference intervals for physical performance test outcomes relevant to male youth Middle Eastern football players. We analyzed mixed-longitudinal data (observations range: 1751-1943 assessments) from a sample of 441 male youth outfield football players (chronological age range: 11.7-18.4 y) as part of the Qatar Football Association and Aspire Academy development program over 14 competitive seasons. Semiparametric generalized additive models for location, scale, and shape estimated age-specific reference centiles for 10-m sprinting, 40-m sprinting, countermovement jump height, and maximal aerobic speed variables. The estimated reference intervals indicated that the distribution of the physical performance test scores increased monotonically and nonlinearly with advancing chronological age for sprinting and countermovement jump outcome measures, reaching a plateau after 16 years common to each of these performance variables. The maximal aerobic speed median score increased substantially until ∼14.5 years, with the nonlinear trend flattening off toward relatively older chronological ages. We developed age-related reference intervals for physical performance test outcomes relevant to youth Qatari football players. Country-wide age-specific reference intervals can assist in the longitudinal tracking of the individual players' progress over time against benchmark values derived from the reference population.



#10 Stakeholder governance and sustainability in football: A bibliometric analysis

Reference: Heliyon. 2023 Aug 4;9(8):e18942. doi: 10.1016/j.heliyon.2023.e18942. eCollection 2023 Aug.

Authors: Juan Alejandro Hernández-Hernández, Abraham Londoño-Pineda, Jose Alejandro Cano, Rodrigo Gómez-Montoya

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Summary: This study presents a bibliometric analysis of stakeholder governance and sustainability in football. The PRISMA statement and the main techniques from the existing bibliometric analysis toolbox are applied to guide the research. The analysis includes 127 documents from Scopus and WoS, covering the period from 2007 to mid-2023, to examine the performance analysis and science mapping of the subject over time. The study's key findings highlight publication-related metrics, citation-and-publication-related metrics, co-authorship analysis, and co-word analysis. The analysis also identifies research gaps, including the need to explore barriers to stakeholder governance in football, the application of stakeholder pressure frameworks in football clubs, the examination of mimetic and normative pressures in the context of sustainability and governance in football, and the involvement of stakeholders and football institutions in collaborative efforts to enhance the effectiveness and impact of sustainability initiatives.



#11 Association between Dietary Consumption of Meals Combining the Five Food Groups and Stage of Change in the Fifth and Sixth Elementary and Junior High School-Aged Children in Sports Clubs: A Cross-Sectional Research at Soccer Clubs

Reference: J Nutr Sci Vitaminol (Tokyo). 2023;69(4):243-250. doi: 10.3177/jnsv.69.243.

Authors: Satoko Ozawa, Shuko Tanakadate, Chinatsu Watanabe, Naomi Omi

Summary: This study examined the relationship between dietary intake and stage of change for "combining the five food groups" (grains, fish and meat, vegetables, milk, and fruits) and examined characteristics of dietary intake by stage of change among fifth and sixth graders in elementary and junior high school in sports clubs. The 395 children who completed the self-reported dietary consumption form and questionnaire on stage of change for combining the five food groups were analyzed. Logistic regression analysis was conducted to analyze the relationship between intake of the combined five food groups and stage of change, with frequency of the five meals as dependent variable and stage of change as independent variable. Compared to the precontemplation stage, action (A) and maintenance stages (M) were associated with a higher frequency of the number of meals combining the five food groups (A, stage adjusted odds ratio [AOR]: 5.11, 95% confidence interval (CI): 1.50-17.36, p=0.009; M, AOR: 3.84, 95%CI: 1.58-9.33, p=0.003). In breakfast, the number of and each of combining the five food groups meal, and in dinner, the number of combining the five food groups meal, vegetable dishes and fruits were significantly higher in the A and M than in the pre-action stages. These findings suggest that the number of times meals combining the five food groups are consumed was associated with stage of change while breakfast and dinner showed differences in meal consumption between stages in the fifth and sixth grades elementary and junior high school students belonging to sports clubs.



#12 Inconsistent Effect of Psychometric-Scale Familiarization on the Relationship Between Ratings of Perceived Exertion and External Load Measures in Elite Youth Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Aug 30;1-9. doi: 10.1123/ijspp.2022-0428. Online ahead of print.

Authors: Efthymios Kyprianou, Lorenzo Lolli, Matthew Weston, Warren Gregson

Summary: The aim was to examine the moderating effect of familiarization on the relationship between external load and ratings of perceived exertion (RPEs) in elite youth soccer players. Thirty-five elite male youth soccer players were monitored over a 31-week period. Players had no previous experience using the centiMax scale (arbitrary units [AU]). The final sample included familiarized (blackness test; n = 20) and nonfamiliarized players (n = 15) with the Borg centiMax scale. Players recorded a global RPE and differential RPEs (dRPE) for breathlessness (RPE-B) and leg-muscle exertion (RPE-L) 15 to 30 minutes following training sessions and competitive matches. Separate multivariable-adjusted random-effects generalized additive models with restricted maximum likelihood quantified familiarization versus no-familiarization differences in actual perceived exertion score (in AU) by number of accelerations, decelerations, and high-speed running distance (in meters) as predictor variables, respectively. Players improved their blackness test score from 39% to 78%. For explorations by number of accelerations, familiarization effects were not practically relevant for the RPE and RPE-B variables. The width and sign of the effects for the RPE-L variable at 30 efforts of 10 AU (95% CI, 4-16 AU) suggested that scores were lower for players who underwent familiarization versus players who did not. Familiarization effects were not practically relevant for any RPE variable irrespective of the number of deceleration efforts and high-speed running distance covered. Improved performance on the blackness test did not have a moderating effect on the relationship between proxy measures of external load and RPEs.



#13 Preece-Baines 1 model validation for cross-sectional data in male soccer players according to maturity status

Reference: Am J Hum Biol. 2023 Aug 29;e23980. doi: 10.1002/ajhb.23980. Online ahead of print.

Authors: Luis Alberto Flores Olivares, Maria Isabel Caldas Januário Fragoso

Summary: The aim of the present study was to compare the Preece-Baines 1 (PB1) model fit between longitudinal and cross-sectional data in male soccer players and to adjust the height growth curve by maturity status. A final sample of 57 male Portuguese soccer players from professional soccer academies was included. Longitudinal height records were measured between 8 and 17 times in each subject from 2-8 years to 14-17 years. Additionally, longitudinal height records were used as cross-sectional data along with 1087 cross-sectional height records taken from 602 Portuguese soccer players. Skeletal age was estimated by Tanner-Whitehouse III method from a left hand-wrist radiograph. Age at peak height velocity (PHV) was estimated by PB1 model for longitudinal and cross-sectional data and by maturity status. No significant differences were found between all the longitudinal estimates of 57 players and the random cross-sectional samples for, S1 parameter and for growth velocity at PHV, at TO, and for age at PHV. The age at PHV in early, on-time, and late maturers were 12.26, 12.9, and 13.58 years, respectively. PB1 adjusted the height growth of Portuguese male soccer players from cross-sectional data, obtaining an estimate PHV very similar to that found from longitudinal data. A maturity time difference of ≈0.6 years was found between the age at PHV of on-time, early, and on-time and late maturity state.







Effects of eccentric-emphasized leg curl intervention on muscle strength imbalance markers in professional soccer players

The effects of strength training on muscle strength imbalance are unclear in professional soccer players. As a result, this study examined the effects of an 8-week strength training program comprising eccentric emphasized prone leg curl adjusted according to the individual strength imbalance status.





Effects of different training schedules based on distance and accelerometry measures: A full‑season in professional soccer players

This study aimed to evaluate external load based on distance and accelerometry measures in six different microcycle schedules with congested (CW2, CW3, and CW4) and regular weeks (RW4, RW5, and RW6) in professional soccer players.





Latest research in football - week 33 - 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 Comparison of external load measures per minute based on match seasonal periods and playing positions of a soccer Turkish super league team

Reference: BMC Musculoskelet Disord. 2023 Aug 17;24(1):656. doi: 10.1186/s12891-023-06787-y.

Authors: Zeki Akyildiz, Yılmaz Yüksel, Yaşar Birgonül, Halil İbrahim Ceylan, Rafael Oliveira, Erhan Çene, Coskun Parim, Filipe Manuel Clemente, Hadi Nobari

Summary: Turkish Super League teams need more information about the external load. Considering the specific country and the coaches' philosophies, the purpose of this study was to compare the external match load of a Turkish Super League team considering the different playing positions and in-season periods. A longitudinal study design was employed by observing 29 official matches of the same team. A total of fifteen players, consisting of five defenders, five midfielders, and five forwards, were analyzed using the Sentio Sports Optical Tracking System. The following outcomes were extracted in each match: total distance (TD), walking [from 0 to 7.2 km/h], jogging [from 7.2 to 14.4 km/h], running [from 14.4 to 20 km/h], high speed running (HSR) [> 20 km/h], metabolic power (MP), maximum deceleration (Decmax) [Dec < -3 m/s2], total deceleration distance (Dectotal), maximum acceleration (Accmax) [Acc > 3 m/s2], and total acceleration distance (Acctotal). Statistical analysis consisted of ANOVA and Bonferroni correction post hoc tests. The main results showed that all variables were similar between periods of the season (p > 0.05) except for walking (p = 0.021 witha large effect size), which revealed lower values in the mid-season period. When analyzing periods of the season considering playing positions, there were several significant results for TD, walking, jogging, running, HSR, Dectotal and Acctotal (p < 0.05, with small to large effects). A tendency for higher values was noted in the mid and end-season. Considering the playing positions comparisons, midfielders showed higher values than defenders for TD, MP, Dectotal and Acctotal (p < 0.05 with large effect for all). Midfielders also showed higher values than forwards for TD, jogging, Dectotal and Acctotal (p < 0.05 with a large effect for all). The present study emphasizes the significance of analyzing data based on minute, playing position, and season period. Findings reveal that defenders consistently displayed the lowest values in all external load measures during matches compared to other positions throughout the season. Furthermore, midfielders demonstrated a higher activity profile during the initial and middle stages of the season compared to other positions, with a slight tendency to decrease load towards the end of the season.



#2 The bone mineral density and isokinetic knee strength in amputee soccer players

Reference: Rev Assoc Med Bras (1992). 2023 Aug 14;69(8):e20230100. doi: 10.1590/1806-9282.20230100. eCollection 2023.

Authors: Izzet Islamoglu, Mehmet Çebi, Fevziye Canbaz Tosun

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Summary: The aim of this study was to examine the isokinetic knee strength, H/Q ratio (%), and bone mineral density values between amputees (n=14; amputee soccer players) and healthy football players (n=14; non-amputee soccer players). A total of 28 amputee soccer players and non-amputee soccer players participated in the study. An isokinetic dynamometer was used to determine the knee flexion/extension forces of the dominant legs of the athletes at 60, 180, and 240°/s. Bone mineral density scans were performed using dual-energy X-ray absorptiometry. H/Q ratio and 60º/s flexion and 180 and 240º/s flexion/extension strength (p<0.05) were found to be high (180º/s, p=0.03; 240º/s, p=0.048) in the non-amputee soccer player group. Accordingly, the bone mineral density values of the lumbar vertebra, femoral neck, proximal metaphysis of the femur (p<0.01), tibia/fibula proximal metaphysis, and tibia/fibula distal metaphysis (p<0.05) were found to be high. A correlation was observed between the 60º/s knee extension strength and tibia/fibula diaphyseal bone mineral density (p=0.025; r=0.594) and tibia/fibula distal metaphysis bone mineral density (p=0.017; r=0.623) values in the amputee soccer players group. The Z-scores of the amputee soccer players and non-amputee soccer players were in the expected range according to age (>-2). The bone mineral density, H/Q ratio, and all measured angular velocities of isokinetic strength were high in non-amputee soccer players. This finding made us think that lower extremity amputation may also be associated with losing strength. However, it was observed that the relationship between strength and bone mineral density in amputee athletes might vary according to different angular velocities. It is recommended that isokinetic strength measurement can be evaluated together with bone mineral density in athletes.



#3 Effect of curcumin supplementation on inflammatory status and muscle damage in competitive female soccer players: a placebo-controlled, singleblind, nonrandomized, crossover pilot study

Reference: Phys Act Nutr. 2023 Jun;27(2):34-38. doi: 10.20463/pan.2023.0016. Epub 2023 Jun 30.

Authors: Youngju Choi, Song-Gyu Ra, Takahiko Nishijima, Seiji Maeda

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Summary: Curcumin, a major component of turmeric, has anti-inflammatory and antioxidative properties, which are associated with protective effects against muscle damage. This study examined the effects of dietary curcumin on inflammation and muscle damage in female competitive soccer players. A single-blinded, placebo-controlled, nonrandomized, crossover pilot study was conducted. Six competitive female soccer players (20.0 ± 2.0 yearsold) who participated in a 2-week preseason training program were assigned to two conditions: placebo and curcumin. The participants ingested a placebo or curcumin dosage (270 mg/day) during 2 weeks of preseason training, with 1 week of washout. Fasting blood samples were collected under resting conditions before (day 0) and after (day 15) the training period to examine changes in the concentration of interleukin 6 (IL-6), an inflammatory marker, and indices reflective of muscle damage. Curcumin decreased the concentration of IL-6 released (mean decrease, -30.2 ± 28.1%), whereas no decrease was observed in the placebo condition (13.4 ± 17.4%). Changes in plasma IL-6 concentrations were significantly greater in the curcumin condition than in the placebo condition (p &lt; 0.05). However, curcumin supplementation had no significant effects on muscle damage indices. The present study shows that curcumin supplementation could attenuate inflammation, as indicated by IL-6 concentrations, in competitive female soccer players during the training period.



#4 Republication of "High-Speed Video Analysis of Syndesmosis Injuries in Soccer-Can It Predict Injury Mechanism and Return to Play? A Pilot Study"

Reference: Foot Ankle Orthop. 2023 Aug 11;8(3):24730114231195048. doi: 10.1177/24730114231195048. eCollection 2023 Jul.

Authors: Neil Jain, David Murray, Steve Kemp, James Calder

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Summary: Ankle syndesmosis injuries in professional soccer may lead to an unpredictable and prolonged recovery. This injury has been investigated in anatomical and radiologic studies but the precise mechanism leading to syndesmosis injury is not well understood and remains debated. The 2 goals of this study were to (1) evaluate the relationship between the mechanism of syndesmosis injury as determined by high-speed video analysis and the injured structures identified by clinical and radiologic examination and to (2) investigate the relationship between mechanism of injury and time of return to play. This pilot study prospectively reviewed high-speed video analysis of 12 professional soccer players who sustained syndesmosis injuries. The mechanism of injury was compared with the clinical and MRI evaluation and the time taken to return to play. Higher-grade syndesmosis injuries occurred during ankle external rotation with dorsiflexion. Supination-inversion injuries with a standard lateral ankle sprain (rupture of the anterior talofibular ligament) may extend proximally, causing a lower-grade syndesmosis injury. These may present with signs of a high ankle sprain but have a quicker return to sport than those following a dorsiflexion-external rotation injury (mean 26 days vs 91 days). Video analysis confirmed that at least 2 mechanisms may result in injury to the ankle syndesmosis. Those "simple" ankle sprains with signs of syndesmosis injury had a quicker return to play. This new finding may be used by club medical teams during their initial assessment and help predict the expected time away from soccer in players with suspected high ankle sprains.



#5 A Schatzker Type III Tibial Plateau Fracture in a Soccer Player: A Case Report

Reference: Cureus. 2023 Jul 17;15(7):e42015. doi: 10.7759/cureus.42015. eCollection 2023 Jul.

Authors: Kevin Do, Alan A Zakaria, Tais G O Bertasi, Raphael A O Bertasi, Rock P Vomer, Jeffrey Nadwodny, George G A Pujalte

Summary: The tibial plateau is an important load-bearing surface in the knee, and when fractured, there is subsequent loss of motion and stability. These fractures typically result from axial loading and twisting. Our case outlines a tibial plateau fracture in a 15-year-old soccer player. The physical examination was positive for a decreased range of motion, pain with valgus stress, and positive ballottement. Radiography of the knee revealed joint effusion but no definite fracture. MRI revealed a Schatzker Type III fracture and a partial medial collateral ligament (MCL) tear. Our patient was referred for open repair and internal fixation. The Schatzker classification system is divided by type and location of fracture. Types I through III are located laterally, Type IV is medial, Type V identifies bicondylar fractures, and Type VI identifies tibial diaphysis separation from the metaphysis. These fractures are managed both nonoperatively and operatively. Nonoperative management is recommended for minimally displaced fractures that will heal without notable deformity. Operative management is indicated for displaced and unstable fractures, which include all fracture Types IV through VI, and certain Type I through III fractures that have valgus alignment or large articular surface involvement. Recovery time is lengthy and largely dependent on the fracture type. The first six weeks usually involve non-weightbearing, the second six weeks include weightbearing as tolerated, with knee range of motion exercises and muscle strengthening. Although open repair and internal fixation usually provide good results, some athletes cannot return to their previous levels of activity.



#6 The relationship between locus of control and pre-competitive anxiety in highly trained soccer players

Reference: Front Psychol. 2023 Aug 3;14:1227571. doi: 10.3389/fpsyg.2023.1227571. eCollection 2023.

Authors: Imen Ben Amar, Chiraz Gomni, Oussema Gaied, Aymen Khmiri, Rania Ghouaiel, Julien S Baker

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Summary: Previous studies have not considered the potential association between locus of control and precompetitive anxiety in elite soccer players. Accordingly, this cross-sectional study examined The prediction of locus of control on precompetitive anxiety in highly trained cadet soccer players. Based on a literature review, our research question was: can the locus of control be considered as an explanatory element of precompetitive anxiety? Thirty-five Tunisian highly trained soccer players licensed from two regional soccer clubs aged between 15 and 16 years participated in the resent study. All participants were evaluated using the Competitive State Anxiety Inventory-2 (CSAI-2) and the Internal-External Locus of Control Scale. The relationship between measures of anxiety, self-confidence and the locus of control scores were analyzed using Pearson's product-moment correlation coefficient. Further, multiple linear stepwise multiple regression models were calculated to determine the most robust predictors of the locus of control. Based on our findings, the regression analysis explains up to 21.3% of the total variation of our independent variable (locus of control) and explains only 21.3% of the variability of our dependent variable somatic anxiety. Furthermore, locus of control explains 61.9% of the variability in self-confidence. The locus of control can be used for the detection and selection of young athletic talent to identify individuals with the best psychological aptitude to cope with psychological problems related to sports performance. Preparing highly trained soccer players on how to deal with their anxiety could prevent them from becoming overwhelmed when they feel powerless to change their situation during competition.



#7 The effects of a smartphone game training intervention on executive functions in youth soccer players: a randomized controlled study

Reference: Front Sports Act Living. 2023 Aug 3;5:1170738. doi: 10.3389/fspor.2023.1170738. eCollection 2023.

Authors: Florian Heilmann, Damiano Formenti, Athos Trecroci, Franziska Lautenbach

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Summary: Cognitive training primarily aims to improve executive functions (EFs). It has become a popular research topic, as previous studies have provided preliminary evidence that EFs relate to sports performance. However, whether a domain-generic cognitive training intervention can improve EFs in high-performance athletes is still unclear. The present randomized controlled study aimed to examine the effects of an eight-week (5 min/day, 5 days/week) smartphone-based domain-generic cognitive training intervention (i.e., the smartphone game "Fruit Ninja") on EFs in youth soccer athletes (N = 33; intervention: n = 15, passive control: n = 18; German youth soccer academy). We assessed working memory (3-back task), inhibition (Flanker & Go/NoGo task), and cognitive flexibility (number-letter task) in a pre-post design with computerized tasks. The results showed no significant time x group differences attributable to the cognitive training between the intervention group and the control group, except for a response time variable of the Go/NoGo task. These preliminary results do not suggest an application of CT as a smartphone-based game to improve EFs performance in soccer players. However, more research is needed to establish the efficacy of domain-specific interventions in high-level team sport athletes.



#8 Posterior hip fracture dislocation from a non-contact injury while playing soccer. "A Case Report"

Reference: Trauma Case Rep. 2023 Aug 7;47:100885. doi: 10.1016/j.tcr.2023.100885. eCollection 2023 Oct.

Authors: Jared A Nowell, Stefan Coombs, Abhishek Tippabhatla, Basilia O Nwankwo

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Summary: 35-Year old male presented with acute right hip pain after a pivoting motion while playing soccer. This was a non-contact injury. Imaging revealed a posterior hip dislocation with an associated posterior wall acetabular fracture. He was treated with closed reduction of the hip followed by subsequent open reduction internal fixation of the acetabular fracture. Posterior hip fracture dislocations can occur in adults following low energy non-contact injuries. Successful outcomes can be achieved if they are treated in a timely fashion, but unrecognized injuries can lead to devastating consequences.



#9 Identifying Soccer Players' Playing Styles: A Systematic Review

Reference: J Funct Morphol Kinesiol. 2023 Jul 26;8(3):104. doi: 10.3390/jfmk8030104.

Authors: Spyridon Plakias, Serafeim Moustakidis, Christos Kokkotis, Marina Papalexi, Themistoklis Tsatalas, Giannis Giakas, Dimitrios Tsaopoulos

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Summary: Identifying playing styles in football is highly valuable for achieving effective performance analysis. While there is extensive research on team styles, studies on individual player styles are still in their early stages. Thus, the aim of this systematic review was to provide a comprehensive overview of the existing literature on player styles and identify research areas required for further development, offering new directions for future research. Following the PRISMA guidelines for systematic reviews, we conducted a search using a specific strategy across four databases (PubMed, Scopus, Web of Science, and SPORTDiscus). Inclusion and exclusion criteria were applied to the initial search results, ultimately identifying twelve studies suitable for inclusion in this review. Through thematic analysis and qualitative evaluation of these studies, several key findings emerged: (a) a lack of a structured theoretical framework for player styles based on their positions within the team formation, (b) absence of studies investigating the influence of contextual variables on player styles, (c) methodological deficiencies observed in the reviewed studies, and (d) disparity in the objectives of sports science and data science studies. By identifying these gaps in the literature and presenting a structured framework for player styles (based on the compilation of all reported styles from the reviewed studies), this review aims to assist team stakeholders and provide guidance for future research endeavors.



#10 Female Soccer Periodization on Anaerobic Power/Capacity

Reference: J Strength Cond Res. 2023 Aug 22. doi: 10.1519/JSC.0000000000004555. Online ahead of print.

Authors: Troy M Purdom, Kyle S Levers, Gregory A Ryan, Lindsey Brown, Jacob Giles, Chase McPherson

Summary: The purpose of this study was to observe changes in anaerobic power and capacity (resistance to fatigue) over an annual training cycle (ATC) in 14 Division I female soccer athletes (19.4 ± 1.0 years, 60.8 ± 5.4 kg, 164.9 ± 6.2 cm, 19.5 ± 3.2% body fat, and 48.9 ± 3.9 kg fat free mass). All subjects were evaluated across the ATC at 5 testing blocks (B1-B5) representing seasonal transitions: postcompetition I (B1), prespring (B2), postspring training (B3), precompetition (B4), and postcompetition II (B5) using 3 tests: countermovement vertical jump to measure peak vertical power (PVP), 40-yard sprint to measure peak horizontal power (PHP), and 35-m running anaerobic sprint test to measure anaerobic capacity via fatigue index (FI). Repeated measures analysis of variance was used with the Bonferroni post hoc test when relevant along with Cohen's d to evaluate effect size. Data are represented as mean ± SD; significance set to p < 0.05. Significant performance increases were observed from postseason I to spring season training (B1-B3) in PVP (6.61 ± 3.18 and 7.71 ± 3.20; p < 0.01, d = 1.12) while changes occurred from prespring season to postspring season (B2-B3) in PVP (6.84 ± 3.15 and 7.71 ± 3.20; p = 0.03, d = 0.93) and PHP (6.65 ± 0.97 and 7.55 ± 1.26; p < 0.01, d = 1.06) with no change in body composition. No other significant changes were observed across the ATC (p > 0.05). Increases in PHP and PVP occurred with directed training after B3 and then declined remaining so across the competitive season. Peak horizontal power and PVP may be more sensitive to coaching style and seasonal transition compared with FI and body composition changes.



#11 Leadership cycles, styles, and antecedent factors: the perspective of coaches and young soccer athletes from national Slovak leagues

Reference: Front Psychol. 2023 Aug 7;14:1218290. doi: 10.3389/fpsyg.2023.1218290. eCollection 2023.

Authors: Elena Lisá, Jacinta Sousa, Catarina Morais, António Rui Gomes

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Summary: Building positive relationships and interactions between coaches and athletes is critical to an athlete's success. The current study aimed to overview how coaches and their young athletes perceive three elements of the Leadership Efficacy Model (philosophy, practice, and criteria). The aim was examined with four goals of analysis: the perceptions of coaches and athletes about coaches' leadership philosophy, practice, and criteria (1); the differences between athletes' and coaches' perceptions of leadership cycles (2); the differences between athletes' and coaches' perceptions of leadership styles (3); and the differences between athletes' and coaches' perceptions of leadership antecedent factors (4). The study involved 304 athletes and 20 coaches competing in the youth national leagues U15, U16, U17, and U19. Two-source data collection was applied: coaches completed the questionnaires from their point of view, and so did athletes. The coaches were paired then with their athletes to compare the answers. Coaches fulfilled Leadership Cycles Questionnaire (LEQ), Multidimensional Scale of Leadership in Sport (MSLS), and Leadership Antecedent Factors Questionnaire (LAFQ). Athletes completed the same questionnaires as the coaches did and also fulfilled the Sport Performance Perception Questionnaire (SPPQ). Athletes' age and SPPQ served as control variables. Both athletes (37.5%) and coaches (40%) perceived that the philosophy of the leadership efficacy model should be increased. Coaches evaluated their philosophy (F = 4.43; p = 0.036; η2 = 0.014), support in MSLS (F = 5.05; p = 0.025; η2 = 0.016) and active management in MSLS (F = 4.08; p = 0.044; η2 = 0.013) higher than their athletes. The athletes assessed the maturity of the team members (LAFQ dimension) (F = 13.98; p <0.001; η2 = 0.044), negative feedback in MSLS (F = 6.02; p = 0.015; η2 = 0.020), and passive management in MSLS (F = 4.95; p = 0.027; η2 = 0.016) higher than their coaches. The tendency of coaches to have a more positive perception of their leadership behavior compared to their athletes represents the coach-athlete perception gap of leadership. Future research can examine the efficacy of congruent perceptions of leadership between athletes and coaches during the sports season and the impact produced by objective performance indicators.



#12 Changes in Physical Performance Throughout Professional Soccer Match-Play

Reference: J Strength Cond Res. 2023 Aug 23. doi: 10.1519/JSC.0000000000004579. Online ahead of print.

Authors: José M Oliva-Lozano, Paulino Granero-Gil, Marco Panascì

Summary: The aim of this study was to explore the changes in physical performance by playing position throughout professional soccer match-play. Global Positioning Systems were used for the collection of external load measures during 35 matches. Each match was divided into 15-minute periods. Physical performance varied according to the period in distance covered (F = 25.69; p < 0.001; partial eta-squared [ηp2] = 0.11), sprinting distance (SPD, F = 4.35; p < 0.001; ηp2 = 0.02), sprinting actions (SPAs, F = 5.19; p < 0.001), high-intensity accelerations (Acc+3, F = 2.18; p = 0.05; ηp2 = 0.01), high-intensity decelerations (Dec+3, F = 4.51; p < 0.001; ηp2 = 0.02), and high-metabolic load distance (HMLD, F = 5.59; p < 0.001; ηp2 = 0.03). The period with the greatest mean physical performance was usually from the first half of the matches: 0-15 minutes (distance, Acc+3, and Dec+3) and 30-45 minutes (HMLD, SPA, and SPD). However, the lowest mean physical performance compared with the rest of 15-minute periods was observed in the 60-75-minute period (distance, HMLD, Acc+3, and Dec+3), except for SPA and SPD (15-30 minutes and 75-90 minutes). Overall, no significant differences (p > 0.05) were observed in the physical performance between the extratime periods. In addition, the playing position had a significant effect on all performance variables (F = 39.99-133.29; p < 0.001; ηp2 = 0.14-0.34). Central defenders showed the lowest physical performance throughout the periods of match-play, whereas wide midfielders showed the greatest physical performance in all variables, except for distance covered, in which midfielders had the greatest performance. In conclusion, there were changes in physical performance during the matches depending on the period of match-play and playing position.



#13 Toward a New Conceptual Approach to "Intensity" in Soccer Player's Monitoring: A Narrative Review

Reference: J Strength Cond Res. 2023 Sep 1;37(9):1896-1911. doi: 10.1519/JSC.0000000000004503.

Authors: Guglielmo Pillitteri, Filipe M Clemente, Marco Petrucci, Alessio Rossi, Marianna Bellafiore, Antonino Bianco, Antonio Palma, Giuseppe Battaglia

Summary: In the last decade, monitoring physiological and match-related demands in soccer has become an increasingly common practice in sports sciences. One of the great challenges during monitoring process is the identification of key indicators that permit to generalize evidence and sustain decision-making process during training prescription. Actually, one of the major debates in the scientific community and among practitioners is the identification of the "intensity" concept. Defining a given training session or exercise based on "intensity" is difficult due to the fact that a huge amount of indicators are available (related both to the performed activities and to the athletes' psychophysiological responses). These indicators can lead to specific outcomes with different interpretations. The current narrative review aims to discuss the different measures approaches used in soccer to describe the intensity for both internal and external demands. In addition, a second purpose of this review is to propose general recommendations for combining intensity indicators with the aim of defining an overall intensity score of a training session or drill.



#14 SARS-CoV-2 Infection Increases the Risk of Muscle Injury in Professional Male Soccer Players-A Retrospective Analysis of the Italian and Spanish Major Leagues

Reference: Infect Dis Rep. 2023 Jul 26;15(4):425-435. doi: 10.3390/idr15040043.

Authors: Sandra Miccinilli, Marco Bravi, Giorgio Conti, Federica Bressi, Silvia Sterzi, Fabio Santacaterina, Massimo Ciccozzi

Summary: A retrospective cohort study on professional soccer players from the Serie A and LaLiga was conducted to investigate the correlation between SARS-CoV-2 infection and muscle injuries. Players were divided into two groups based on whether they contracted the SARS-CoV-2 infection (C+) or not (C-) during the 2020/2021 season. In the 2019-2020 season, both championships showed a similar number of muscular injuries (MI) between C+ and C- (Serie A: p = 0.194; 95% CI: -0.044 to 0.215, LaLiga p = 0.915; 95% CI: -0.123 to 0.137). In the 2020-2021 season, C+ had a significantly higher number of MI compared to C- in both championships (Serie A: p < 0.05; 95% CI 0.731 to 1.038; LaLiga: p < 0.05; 95% CI: 0.773 to 1.054). Multiple linear regression analysis confirmed that belonging to C+ in the season 2020/2021 was the variable that most strongly influenced the probability of having a muscle injury. Survival analysis revealed a hazard ratio of 3.73 (95% CI 3.018 to 4.628) and of 5.14 (95% CI 3.200 to 8.254) for Serie A and LaLiga respectively. We found an association between SARS-CoV-2 infection and increased risk of muscle injury, emphasizing the importance of carefully considering the infection in the decision-making process for returning to sport. Therefore, SARS-CoV-2 infection should be judged as a real injury requiring specific assessment and training programs.



#15 Is there a relationship between executive functions and resilience in youth elite soccer players?

Reference: Brain Behav. 2023 Aug 25;e3122. doi: 10.1002/brb3.3122. Online ahead of print.

Authors: Jennifer Lehmann

Summary: While the relationship between cognitive performance and sport performance in youth elite soccer players has proponents as well as opponents, many aspects of this relationship remain unclear. Therefore, this quasi-experimental study wants to contribute to this relationship including the psychological aspect of resilience when investigating youth elite soccer players during an assessment selection for a representative team. Questionnaires as well as computer-based tests were conducted. Results of this study showed no relationship between resilience and executive function in youth elite soccer players. Furthermore, no differences in executive functions or in resilience were found between those players who are selected for a representative team and those who were not selected. The results indicate that further research needs to be conducted to clarify possible relationships in more detail.



#16 Soccer, Sleep, Repeat: Effects of Training Characteristics on Sleep Quantity and Sleep Architecture

Reference: Life (Basel). 2023 Aug 2;13(8):1679. doi: 10.3390/life13081679.

Authors: Patricia Frytz, Dominik P J Heib, Kerstin Hoedlmoser

Summary: Due to the high demands of competitive sports, the sleep architecture of adolescent athletes may be influenced by their regular training. To date, there is no clear evidence on how training characteristics (intensity, time of day, number of sessions) influence sleep quality and quantity. 53 male soccer players (M = 14.36 years, SD = 0.55) of Austrian U15 (n = 45) and U16 elite teams (n = 8) were tested on at least three consecutive days following their habitual training schedules. Participants completed daily sleep protocols (7 a.m., 8 p.m.) and questionnaires assessing sleep quality (PSQI), chronotype (D-MEQ), competition anxiety (WAI-T), and stress/recovery (RESTQ). Electrocardiography (ECG) and actigraphy devices measured sleep. Using sleep protocols and an ECG-based multi-resolution convolutional neural network (MCNN), we found that higher training intensity leads to more wake time, that later training causes longer sleep duration, and that one training session per day was most advantageous for sleep quality. In addition, somatic complaints assessed by the WAI-T negatively affected adolescent athletes' sleep. Individual training loads and longer recovery times after late training sessions during the day should be considered in training schedules, especially for adolescent athletes. MCNN modeling based on ECG data seems promising for efficient sleep analysis in athletes.






Soccer-drill specificity in top-class male players with reference to peak match locomotor demands

The purpose was to compare the locomotor demands of several ball/running drills with the official match peak, demands determined across different time-windows of the same duration in top-class male soccer players.





Effects of a Short-Term Detraining Period on the Strength Deficit and Functional Performance of Highly Trained Soccer Players

The aim of this study was to examine the effects of a 4-week detraining period on the neuromuscular performance of highly trained soccer players.





Latest research in football - week 32 - 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 Exposure assessment for repeated sub-concussive head impacts in soccer: The HEalth and Ageing Data IN the Game of football (HEADING) study

Reference: Int J Hyg Environ Health. 2023 Aug 6;253:114235. doi: 10.1016/j.ijheh.2023.114235.

Authors: Ioannis Basinas, Damien M McElvenny, Finley Brooker, Steven Robertson, Yvonne van Hoecke, Simon Kemp, Neil Pearce, Valentina Gallo, John W Cherrie

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Summary: The purpose of this paper was to develop exposure estimates for repetitive sub-concussive head impacts (RSHI) for use in epidemiological analyses. We used a questionnaire to collect lifetime history of heading and other head contacts associated with training and playing football from 159 former footballers all members of the English professional football association. We used linear mixed effect regression with player as the random effect, to model the number of headers, blows to the head and head-to-head impacts as a function of potential exposure affecting factors, which were treated as the fixed effects. Exposure affecting factors included playing position, league, context of play (game vs training) and decade of play. Age at time of response to the questionnaire was also included in the models. In model results, playing position was important, with RSHIs being highest among defenders and lowest among goalkeepers. Players headed the ball more during games than in training, and when playing in amateur or youth leagues compared with semi-professional or professional leagues. The average number of reported head impacts declined linearly throughout the observation period (1949-2015). The derived final model for headers explained 43%, 9% and 36% of the between player, within player and total variance in exposure, respectively with good precision and predictive performance. These findings are generally in agreement with previously published results pointing towards the models forming a valid method for estimating exposure to RSHI among former footballers although some further external validation is still warranted.



#2 Repeated stroboscopic vision training improves anticipation skill without changing perceptual-cognitive skills in soccer players

Reference: Appl Neuropsychol Adult. 2023 Aug 8;1-15. doi: 10.1080/23279095.2023.2243358.

Authors: Leonardo S Fortes, Heloiana Faro, Jocelyn Faubert, Carlos G Freitas-Júnior, Dalton de Lima-Junior, Sebastião S Almeida

Summary: In this study we aimed to analyze the repeated effect of stroboscopic vision training on perceptual-cognitive skills in soccer players. A total of 28 male soccer players participated in this experimental and randomized study with parallel groups. The soccer players were pair-matched according to perceptual-cognitive skills and randomized into two groups: Stroboscopic vision training and Control. Multiple object tracking, anticipation, and decision-making skills were measured before and after the 8-week intervention. An increase in multiple object tracking (p < 0.05) and decision-making skills (p < 0.05) from baseline to post-experiment was found in both groups without main group effect (p > 0.05). The findings showed an increase in anticipation skill from baseline to post-experiment in both groups (p < 0.05), with higher anticipation skill for the stroboscopic group than in the control group post-experiment (p < 0.05). Thus, we conclude that repeated stroboscopic vision training could improve anticipation skill in soccer athletes.



#3 Position Comparison of sport-related Concussions in female youth soccer players

Reference: Phys Sportsmed. 2023 Aug 11. doi: 10.1080/00913847.2023.2246869. Online ahead of print.

Authors: Hannah Worrall, Caroline Podvin, Claire Althoff, Jane Chung, Dai Sugimoto, Mathew Stokes, Luke C Radel, Munro Cullum, Shane Miller, Jacob Jones

Summary: Youth soccer participation, particularly among females, continues to grow worldwide. With the high incidence of sport-related concussion (SRC) in soccer, it is important to investigate if SRC occurs disproportionally by positions. Our hypothesis was to see no positional differences of SRCs, SRC-related characteristics, and outcomes among in female youth soccer athletes. Data were prospectively collected from participants at a single sports medicine institution between August 2015-April 2021. Female participants aged 8-18 diagnosed with SRC sustained during an organized soccer practice, scrimmage, or game were separated into 4 groups based on position: Forward, Midfielder, Defender, and Goalkeeper. Demographics, medical history, injury-related details, and outcomes were reviewed. A chi square test or Fisher's exact test were used for categorical variables. Continuous variables were compared with Mann-Whitney or Kruskal-Wallis test. Two hundred fourteen participants were included: 52 Forwards, 65 Midfielders, 63 Defenders, and 34 Goalkeepers. No significant differences between the groups in age, race, ethnicity, or previous concussion history. Differences in mechanism existed with Goalkeepers most commonly reporting Head to Body Part. Goalkeepers, which make up 1/11 of the total positions on the field, had a significantly higher proportion of SRCs compared to Field Positions. (9.1% vs 15.9%)At 3-month post-enrollment, there were no significant differences in reported symptoms or return-to-play between the different positions. In youth female soccer players, goalkeepers sustained a higher proportion of sport-related concussions compared to field players based upon the composition of a soccer team. The mechanism of injury also differed among the different soccer positions. However, no differences in concussion characteristics, outcomes, or RTP were seen across the different soccer positions.



#4 The effect of three different pre-match warm-up structures on male professional soccer players' physical fitness

Reference: PeerJ. 2023 Aug 3;11:e15803. doi: 10.7717/peerj.15803. eCollection 2023.

Authors: Mehdi Ben Brahim, Alejandro Sal-de-Rellán, Adrián García-Valverde, Hussain Yasin, Javier Raya-González

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Summary: Optimizing the soccer players' match preparation is one of the most relevant concerns of coaches for strength and conditioning training. Thus, the aim of this study was to analyze the effects of three pre-match warm-up structures on the physical condition of male professional soccer players. Seventeen male professional soccer players (age: 20.9 ± 2.4 years) of one Tunisian Professional Soccer League team participated in this study. Players performed three times a typical pre-match warm-up (WU) [aerobic phase (AE); neuromuscular phase (NM); velocity phase (VL); and ball-specific phase (BS) variating the order of the included phases/exercises: WU1 (AE + BS + NM + VL); WU2 (AE + NM + VL + BS); and WU3 (AE + VL + BS + NM). After each warm-up phase, players completed the following physical fitness tests: linear sprint test, countermovement jump test, 15-m ball dribbling agility test and ball shooting test. Additionally, the rate of perceived exertion (RPE) was registered after each warm-up. The results indicated significant differences between WU1 and WU3, with better results in the ball shooting test and RPE in WU3. In addition, there were no significant differences in the other variables and between other warm-up structures. These findings could be of great interest for coaches to the strength and conditioning coaches for professional soccer teams in order to improve the players physical performance and perceived exertion.



#5 Using Bar Velocity to Assess Post-match Neuromuscular Fatigue in Young Soccer Players

Reference: Int J Sports Med. 2023 Aug 7. doi: 10.1055/a-2150-0960. Online ahead of print.

Authors: João Barreira, Petrus Gantois, Jorge Castro, Xavier Mesquita, Rafael Peixoto, Miguel Ferreira Cid, Irineu Loturco, Ana Sousa, Fábio Yuzo Nakamura

Summary: This study aimed to investigate the recovery of neuromuscular performance using mechanical parameters collected during jump (vertical and horizontal) and strength-power exercises in youth soccer players after official soccer matches. Twenty-one outfield highly trained youth male soccer athletes (age: 18.23 ± 0.73 years; weight: 72.12 ± 6.99 kg; height: 1.78 ± 0.08 m) from two teams competing in the 1st division of U-19 Portuguese National Championship participated in this study. Players completed a battery of physical tests at -2h, +30 min, +24h, and +48h in relation to the match. Countermovement jump height, horizontal jump distance, and bar velocity during the half-squat, bench press, and hip-thrust exercises, at fixed loads, were recorded. Countermovement jump was impaired until 24h post-match (-1.7% from pre to 24h post, p=0.050; ES=-0.82). Half-squat bar velocity was reduced immediately following the match (-6.8 % from pre- p=0.004; ES=-0.64) but recovered at +24h (+2.9%, p=1.00; ES=0.02). Hip-thrust bar velocity was reduced for up to 48h post-match (-7.4% from pre to 48h post, p<0.001; ES=-0.80). No impairments were found in the horizontal jump and bench press at any moment. Our findings show prolonged decrements in strength of the posterior chain following a soccer match, measured in the hip-thrust exercise, while the other exercises displayed faster recovery dynamics.



#6 Two-Dimensional and Three-Dimensional Biomechanical Factors During 90° Change of Direction are Associated to Non-Contact ACL injury in Female Soccer Players

Reference: Int J Sports Phys Ther. 2023 Aug 1;18(4):887-897.  doi: 10.26603/001c.84308. eCollection 2023.

Authors: Stefano Di Paolo, Alberto Grassi, Filippo Tosarelli, Matteo Crepaldi, Laura Bragonzoni, Stefano Zaffagnini, Francesco Della Villa

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Summary: The two-dimensional (2D) video-analysis of the change of direction (COD) technique has never been used to attempt to predict the risk of ACL injury in female football players. The purpose of the present pilot study was to prospectively investigate the biomechanical predictors of ACL injury during a COD task in female football players using both gold standard 3D motion capture and a qualitative scoring system based on 2D video-analysis. Sixteen competitive female football (soccer) players (age 21.4 ± 4.3) performed a series of pre-planned 90° COD tasks. 3D motion data was recorded through 10 stereophotogrammetric cameras and a force platform. 2D frontal and transverse plane joint kinematics were computed through video-analysis from three high-speed cameras. A scoring system based on five criteria was adopted: limb stability, pelvis stability, trunk stability, shock absorption, and movement strategy. The players were prospectively followed for the next two consecutive football seasons and the occurrence of severe knee injuries was registered. Four players (25%) experienced an ACL injury. In 3D analysis, ACL-injured players showed greater knee valgus, knee internal rotation, and lower knee flexion (p= 0.017 - 0.029). Lower hip flexion coupled with greater external rotation (p= 0.003 - 0.042), ankle eversion, and contralateral pelvic drop (p<0.001) were also noted. In 2D analysis, ACL-injured players showed greater internal foot rotation, contralateral pelvic drop, lower knee flexion, and contralateral trunk tilt (moderate-to-large effect size). Pelvis stability and trunk stability showed the highest predictive value towards ACL injury. Total score was significantly lower in ACL-injured players with a moderate effect size (d=0.45). Both 3D and 2D methodologies depicted biomechanical risk factors and offered predictive insights towards the ACL injury risk. Awareness should rise in women's football regarding the high risk of ACL injury and the strategies to assess and mitigate it.



#7 Clinical, Biomechanical, and Self-reported Health Status After ACL Reconstruction With Meniscal Repair in Soccer Players: Results at Minimum 1-Year Follow-up

Reference: Orthop J Sports Med. 2023 Aug 2;11(8):23259671231177309. doi: 10.1177/23259671231177309. eCollection 2023 Aug.

Authors: Lorenzo Moretti, Ilaria Bortone, Michelangelo Delmedico, Danilo Giuseppe Cassano, Nuccio Caringella, Davide Bizzoca, Biagio Moretti

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Summary: Performing meniscal repair with anterior cruciate ligament reconstruction (ACLR) has been shown to contribute to the long-term preservation of knee health and gait biomechanics. The purpose was to evaluate the role of meniscal repair in the performance of semiprofessional soccer players who returned to sport after ACLR. This study included 51 male soccer players (mean ± SD age, 28.82 ± 5.33 years) who underwent ACLR at a single institution between July 2018 and July 2019. The players were divided into 3 groups according to surgery type: ACLR only (n = 30), ACLR with lateral meniscal repair (n = 9), and ACLR with medial meniscal repair (n = 12). Outcomes were evaluated through clinical examination, self-reported health questionnaires (Cincinnati Knee Rating System, Tegner activity score, Tegner Lysholm Knee Scoring Scale, Tampa Scale of Kinesiophobia, and ACL-Return to Sport After Injury), and biomechanical performance evaluations (balance, strength, coordination, and symmetry tests). Parametric and nonparametric tests were carried out for multiple comparisons. The mean ± SD follow-up time was 20.75 ± 9.38 months. Although no significant differences emerged in clinical and self-reported health status, almost all the physical parameters tested resulted in lower performance in players treated with ACLR and meniscal repair. Moreover, patients with ACLR with lateral meniscal repair reported higher pain and fear of reinjury, with lower outcomes in terms of strength, symmetry, and coordination as compared with the other 2 groups. Balance abilities were significantly affected in players who underwent meniscal repair as compared with those who underwent ACLR only. The findings showed that biomechanical performance measures and fear of reinjury were significantly worse in soccer players with associated meniscal repair at a minimum 1-year follow-up, especially in those with a lateral meniscal tear.



#8 Resultant equations for training load monitoring during a standard microcycle in sub-elite youth football: a principal components approach

Reference: PeerJ. 2023 Aug 4;11:e15806. doi: 10.7717/peerj.15806. eCollection 2023.

Authors: José Eduardo Teixeira, Pedro Forte, Ricardo Ferraz, Luís Branquinho, Ryland Morgans, António José Silva, António Miguel Monteiro, Tiago M Barbosa

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Summary: Applying data-reduction techniques to extract meaningful information from electronic performance and tracking systems (EPTS) has become a hot topic in football training load (TL) monitoring. The aim of this study was to reduce the dimensionality of the internal and external load measures, by a principal component approach, to describe and explain the resultant equations for TL monitoring during a standard in-season microcycle in sub-elite youth football. Additionally, it is intended to identify the most representative measure for each principal component. A principal component analysis (PCA) was conducted with a Monte Carlo parallel analysis and VariMax rotation to extract baseline characteristics, external TL, heart rate (HR)-based measures and perceived exertion. Training data were collected from sixty sub-elite young football players during a 6-week training period using 18 Hz global positioning system (GPS) with inertial sensors, 1 Hz short-range telemetry system, total quality recovery (TQR) and rating of perceived exertion (RPE). Five principal components accounted for 68.7% of the total variance explained in the training data. Resultant equations from PCA was subdivided into: (1) explosiveness, accelerations and impacts (27.4%); (2) high-speed running (16.2%); (3) HR-based measures (10.0%); (4) baseline characteristics (8.3%); and (5) average running velocity (6.7%). Considering the highest factor in each principal component, decelerations (PCA 1), sprint distance (PCA 2), average HR (PCA 3), chronological age (PCA 4) and maximal speed (PCA 5) are the conditional dimension to be considered in TL monitoring during a standard microcycle in sub-elite youth football players. Current research provides the first composite equations to extract the most representative components during a standard in-season microcycle in sub-elite youth football players. Futures research should expand the resultant equations within training days, by considering other well-being measures, technical-tactical skills and match-related contextual factors.



#9 Evaluation of electrocardiographic parameters in amputee football players

Reference: Front Psychol. 2023 Jul 24;14:1189712. doi: 10.3389/fpsyg.2023.1189712. eCollection 2023.

Authors: Ahmet Kurtoğlu, Ertuğrul Kurtoğlu, Alkame Akgümüş, Bekir Çar, Özgür Eken, Ioan Sârbu, Carmen Iulia Ciongradi, Dan Iulian Alexe, Iuliana Laura Candussi

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Summary: The present study aimed to compare electrocardiographic (ECG) parameters of amputee football players (AF) with football players without disability (FP) and sedentary individuals without disability (SI). A total of 32 participants (AF = 9, FP = 11, SI = 12) were included in the study. ECG parameters including P-wave amplitude, P-wave duration, PR interval, QRS duration, RR interval, QT interval, corrected-QT interval (QTc), ST segment duration, Tp-e duration, Tp-e/QT and Tp-e/QTc ratios were assessed in all the study participants by using a 12-lead ECG device. OneWay ANOVA Test was used for statistical analysis. Of all ECG parameters, P-wave amplitude and QTc were significantly higher in the AF group in comparison to FP and SI groups. QRS duration was found to be lower in the AF group when compared to FP and SI groups. Myocardial repolarization parameters including Tp-e duration, Tp-e/QT and Tp-e/QTc ratios were similar between groups, as were other parameters such as P-wave duration, PR interval, RR interval, QRS duration and QT interval. It was found that some ECG parameters of amputee football players differ from those with non-disabled players and non-disabled sedentary individuals. These different parameters were within normal limits.



#10 Health status of university football athletes through multidimensional screening

Reference: Phys Sportsmed. 2023 Aug 10;1-8. doi: 10.1080/00913847.2023.2246178. Online ahead of print.

Authors: Naruto Yoshida, Shogo Miyazaki, Hideaki Waki, Yoichi Minakawa, Masaaki Koido, Sonoko Mashimo

Summary: Adequate conditioning results from various physical, environmental, and psychological factors in sports activities. In this study, we aimed to clarify the concurrence and relevance of injuries, psychological problems, and sleep disturbance in university football (soccer) players. Biomechanical characteristics and risk factors for those injuries were also investigated. Overall, 1,084 university football players participated in this cross-sectional study using a web-based health history questionnaire. Assessments were made via the presence of injuries for physical problems, the Athlete Psychological Strain Questionnaire (APSQ) for psychologicalproblems, and the Athlete Sleep Screening Questionnaire (ASSQ) for sleep difficulties. There were 200 (19%) athletes with injuries; 413 (38%) of these were APSQ-positive, 246 (23%) were ASSQ-positive, and 468 (43%) athletes had no physical, psychological, or sleep problems. APSQ-positive respondents were significantly more likely to have a current injury than those who were APSQ-negative. No significant difference was observed between the number of ASSQ-positive and -negative respondents and current injuries. Those with sleep problems were significantly more likely to have psychological problems. More than 60% of university football players had one or more physical, psychological, or sleep problems. Players may have co-occurring problems, and it is important to address them for these athletes to reach peak performance.



#11 Creatine kinase concentration on the second post-match day is not associated with risk of subsequent muscle injury in professional football players: a four-season cohort study

Reference: Phys Sportsmed. 2023 Aug 10;1-6. doi: 10.1080/00913847.2023.2246175. Online ahead of print.

Authors: Augusto Camillo Tamujo, Hebert Nunes Flores, Tiago Cetolin, João Breno Ribeiro-Alvares, Alessandro Haupenthal, Bruno Manfredini Baroni

Summary: The objective of this study was to examine the relationship between creatine kinase (CK) concentration following official matches and the risk of subsequent muscle injury in professional male football (soccer) players. Blood samples were collected on the second post-match day for CK analysis over four consecutive seasons in a professional football club. Players were then followed for five days to observe any occurrence of indirect muscle injury (structural or functional in nature). Players exposed to at least 45 minutes in two consecutive matches within seven days were considered valid cases for analysis. Eighty players participated in the study, generating 1,656 cases eligible for analysis, of which 229 resulted in muscle injuries. The hamstrings were the most frequently injured muscle group (54%), followed by the adductor (21%), triceps surae (19%), quadriceps (5%), and psoas (1%). While CK concentration was higher in muscle injury cases [783 ± 507 U/L (95%CI, 717 to 849; min-max, 105-2,800)] compared with uninjured cases [688 ± 446 U/L (95%CI, 665 to 711; min-max, 100-2,950)], it was not an accurate predictor of subsequent muscle injury risk in professional football players (sensitivity = 56%; specificity = 55%; odds ratio = 1.00; area under curve = 0.557). CK concentration on the second post-match day cannot be used to effectively screen subsequent muscle injury risk in professional male football players.



#12 Do non-contact injuries occur during high-speed running in elite football? Preliminary results from a novel GPS and video-based method

Reference: J Sci Med Sport. 2023 Jul 22;S1440-2440(23)00180-9. doi: 10.1016/j.jsams.2023.07.007.

Authors: Francesco Aiello, Christian Di Claudio, Maurizio Fanchini, Franco M Impellizzeri, Alan McCall, Carwyn Sharp, Susan J Brown

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Summary: Understanding how injuries occur (inciting circumstances) is useful for developing etiological hypotheses and prevention strategies. The aims of this study were 1) to evaluate the feasibility of a method combining video and Global Positioning System data to estimate the speed and acceleration of activities leading to injuries and 2) to use this method to analyse the inciting circumstances leading to non-contact injuries. Injury inciting circumstances from 46 elite players over three seasons were analysed from video recordings and from external load measures collected through Catapult Vector S7 Global Positioning System. In total 34 non-contact injuries were analysed. Sixteen out of the seventeen hamstring injuries occurred when players were running for (median and interquartile range) 16.75 m (8.42-26.65 m) and achieved a peak speed of 29.28 km·h-1 (26.61-31.13 km·h-1) which corresponded to 87.55 % of players' maximal speed (78.5 %-89.75 %). Of the three adductor injuries, one occurred whilst the player was decelerating without the ball, one occurred whilst the player was accelerating and controlling the ball at knee level, and one occurred whilst the player was performing an instep kick. Two quadriceps injuries occurred whilst the players were kicking either whilst walking or running. From the preliminary results reported in this study most hamstring injuries occurred when players ran >25 km·h-1 and above 80 % of their maximal speed. This study suggests that this novel approach can allow a detailed and standardised analysis of injury inciting circumstances.



#13 Higher age and present injury at the start of the season are risk factors for in-season injury in amateur male and female football players-a prospective cohort study

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Aug 5. doi: 10.1007/s00167-023-07517-6.

Authors: Sofi Sonesson, Hanna Lindblom, Martin Hägglund

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Summary: The aim was to describe the injury prevalence, injury pattern, and potential baseline risk factors for injuries in male and female adolescent and adult amateur football players. This prospective study followed adolescent and adult amateur football players over one season March-October 2020. The study was completed by 462 players (130 men, age 20.0 ± 5.7, 14-46 years) who answered a baseline survey and a weekly web survey during the season. A total of 1456 weekly surveys were registered from males and 5041 from females. Injuries were recorded with the Oslo Sports Trauma Research Center Overuse Injury Questionnaire (OSTRC-O2). Potential baseline risk factors (age, performance of strength/conditioning training, participation in other sports, perceived importance of sporting success, self-rated training and match load, perceived balance between training/match load and recovery, previous/present injury at start of season, and injury beliefs) and their association with injury were analysed with Poisson regressions within each sex. Males reported 95 injuries (262 injury weeks, weekly prevalence 18.0% (95% CI 16.1-20.1)) and females 350 injuries (1206 injury weeks, weekly prevalence 23.9% (95% CI 22.8-25.1)). Gradual-onset injuries accounted for 57% of the injuries in males and 66% in females. For males, substantial injuries were most common in the hip/groin (weekly prevalence 3.8%), ankle (2.1%), posterior thigh (2.0%), and knee (2.0%); and for females, in the knee (4.3%), ankle (2.5%), and lower leg/Achilles tendon (2.0%). Significant risk factors for injury were higher age (rate ratio males 1.05 per year increase (95% CI 1.02-1.08), females 1.03 (95% CI 1.01-1.05)), and present injury at baseline (males 1.92 (95% CI 1.27-2.89), females 1.58 (95% CI 1.19-2.09)). At any given week, almost one in five male and one in four female amateur football players reported new or ongoing injuries. Hip/groin injuries were more frequent in males, while female players had a higher prevalence of knee injuries. Older players and those with an existing injury at the start of the season were more prone to new injury during the season. Rehabilitation of pre-season injury and complaints are key to reduce the injury burden in amateur football.



#14 Case Report: Indirect Traumatic Optic Neuropathy from Sub-Concussive Soccer Headers in a 62-year-old Athlete

Reference: Optom Vis Sci. 2023 Aug 14. doi: 10.1097/OPX.0000000000002051. Online ahead of print.

Authors: Radha P Pandya, Shruti Pandya, Kelly H Thomann

Summary: Traumatic optic neuropathy (TON) is an uncommon but devastating cause of vision loss following injury to the head. Soccer players may have a heightened risk due to the game's emphasis on heading the ball, a technique in which a player hits the soccer ball with their head. This paper reviews the case of an avid soccer player with traumatic optic neuropathy that occurred after numerous soccer ball headings during a game. This paper also (1) provides a summary of the pathophysiology and epidemiology of traumatic optic neuropathy, (2) reviews the current literature on head and eye injuries in soccer, and (3) discusses biomechanical differences in orbital structure throughout aging, which may predispose older patients to traumatic optic neuropathy. We present the case of a 62-year-old male patient who reported to the clinic, following repeated sub-concussive soccer ball headers the previous day, with symptoms of blurred vision and "seeing stars" in the right eye and a right inferior visual field impairment. Physical examination, subsequent lab work, and neurologic consults implicated TON as the primary diagnosis, and halting soccer playing resulted in symptom improvement. Though not commonly encountered in soccer players, the potential for TON exists. Older athletes may be predisposed due to morphological changes of the orbit. Future direction may look to further investigate hazards promoting traumatic optic neuropathy in older athletes and determine possible protections against injury.



#15 Measuring the popularity of football players with Google Trends

Reference: PLoS One. 2023 Aug 16;18(8):e0289213. doi: 10.1371/journal.pone.0289213. eCollection 2023.

Authors: Pilar Malagón-Selma, Ana Debón, Josep Domenech

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Summary: Google Trends is a valuable tool for measuring popularity since it collects a large amount of information related to Google searches. However, Google Trends has been underused by sports analysts. This research proposes a novel method to calculate several popularity indicators for predicting players' market value. Google Trends was used to calculate six popularity indicators by requesting information about two football players simultaneously and creating popularity layers to compare players of unequal popularity. In addition, as the main idea is to obtain the popularity indicators of all players on the same scale, a cumulative conversion factor was used to rescale these indicators. The results show that the proposed popularity indicators are essential to predicting a player's market value. In addition, using the proposed popularity indicators decreases the transfer fee prediction error for three different models that are fitted to the data using the multiple linear regression, random forest, and gradient boosting machine methods. The popularity indicator Min, which is a robust reflection of the popularity that represents a player's popularity during the periods when they are less popular, is the most important popularity indicator, with a significant effect on the market value. This research provides practical guidance for developing and incorporating the proposed indicators, which could be applied in sports analytics and in any study in which popularity is relevant.



#16 Acute Effects of Different Conditioning Activities on Amateur Soccer Players

Reference: Int J Sports Med. 2023 Aug 18. doi: 10.1055/a-2126-5972. Online ahead of print.

Authors: Manoel E Silva-Neto, Saulo F M Oliveira, José Igor V Oliveira, Willemax S Gomes, Hugo A A S Lira, Leonardo S Fortes

Summary: Several warm-up activities are used to prepare soccer players for training and games. However, few studies have focused on comparing different activities (strength vs. stretching) in young and amateur athletes, especially for performance improvement in explosive actions. Thus, in order to compare the effect of four conditioning activities on jump and sprint performances, 12 soccer athletes (age: 19±0.8; weight (kg): 72.8±8.0; height (cm): 180±6.7) performed four warm-up activities: strength exercise (cluster system), combined exercise, plyometric exercise, and static stretching (control). The countermovement jump (CMJ) and 30-meter run (30-m Sprint) were performed 10 min after each experimental condition. A ONE-WAY ANOVA test of repeated measures was conducted with a Tukey's post-hoc test to compare the conditions. The strength conditioning activity protocol (33.68±2.87) showed a significant difference for the CMJ from static stretching (30.96±3.16) (p>0.05). There were significant differences regarding the 30-m Sprint test between strength conditioning (4.72±0.19) and combined activities (4.71±0.21) compared to static stretching (4.84±0.21) (p>0.05). In conclusion, the combined conditioning activity and strength protocols can be chosen in warm-up activities instead of static stretching (control condition) for improved immediate sprint and jump abilities in amateur soccer players.






Effects of sprint versus strength training on risk factors for hamstring injury in football players

This study aimed to compare the effects of in-season sprint training vs. Nordic hamstring exercise (NHE) training on risk factors for hamstring strain injuries (HSI).





Analysis of the Competitive Weekly Microcycle in Elite Soccer: Comparison of Workload Behavior in Absolute and Relative Terms

This study aimed to analyze the locomotion activity of elite-level soccer players throughout the weekly microcycle by playing position, and compare the training-load (TL) behavior in relation tomatch-play in absolute and relative (meters or events per minute) terms.





Latest research in football - week 31 - 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 Low-load strength resistance training with blood flow restriction compared with high-load strength resistance training on performance of professional soccer players: a randomized controlled trial

Reference: J Sports Med Phys Fitness.2023 Aug 3.  doi: 10.23736/S0022-4707.23.14974-7. Online ahead of print.

Authors: Christian Castilla-López, Natalia Romero-Franco

Summary: The aim of this study is to evaluate the effectiveness of low-load blood flow restriction strength resistance training (LL-BFR) compared to high load strength resistance training (HL) on performance of professional soccer players. Eighteen male players from National Soccer Professional League were randomly allocated into two groups: LL-BFR, who performed a 6-weeks strength training program with low load (20-35% of one-repetition maximum-[1RM]), or HL, who performed a 6-week resistance training program with high load (70-85% 1RM). Before and after, thigh girth, vertical jump, lower limb strength, vertical force-velocity profile (F-v), and 30-m sprint were evaluated. After the training program, both LL-BFR and HL induced significant increases compared to baseline in thigh girth (+3.3% for LL-BFR and +3.1% for HL) and maximal velocity during sprinting (+6.0 and +6.2%, respectively), without between-group differences. In reference to FV, only HL players improved imbalance (-54.4%), maximal theoretical force production (+10.4%) and decreased extension velocity (-20.5%) compared to baseline, without between-group differences. Only LL-BFR induced increases in maximum voluntary contraction of left hamstring compared to baseline (+13.8%), without between-group differences. No differences were shown for the rest of variables (P>0.05). Although LL-BFR may increase muscle circumference and sprint ability, these results are similar to those induced with HL in male professional soccer. In terms of F-v, only HL induced improvements, but these changes were not greater than those observed after LL-BFR.



#2 Blink-related EEG oscillations are neurophysiological indicators of subconcussive head impacts in female soccer players: a preliminary study

Reference: Front Hum Neurosci. 2023 Jul 19;17:1208498. doi: 10.3389/fnhum.2023.1208498. eCollection 2023.

Authors: Sahar Sattari, Rebecca Kenny, Careesa Chang Liu, Sujoy Ghosh Hajra, Guy A Dumont, Naznin Virji-Babul

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Summary: Repetitive subconcussive head impacts can lead to subtle neural changes and functional consequences on brain health. However, the objective assessment of these changes remains limited. Resting state blink-related oscillations (BROs), recently discovered neurological responses following spontaneous blinking, are explored in this study to evaluate changes in BRO responses in subconcussive head impacts. We collected 5-min resting-state electroencephalography (EEG) data from two cohorts of collegiate athletes who were engaged in contact sports (SC) or non-contact sports (HC). Video recordings of all on-field activities were conducted to determine the number of head impacts during games and practices in the SC group. In both groups, we were able to detect a BRO response. Following one season of games and practice, we found a strong association between the number of head impacts sustained by the SC group and increases in delta and beta spectral power post-blink. There was also a significant difference between the two groups in the morphology of BRO responses, including decreased peak-to-peak amplitude of response over left parietal channels and differences in spectral power in delta and alpha frequency range post-blink. Our preliminary results suggest that the BRO response may be a useful biomarker for detecting subtle neural changes resulting from repetitive head impacts. The clinical utility of this biomarker will need to be validated through further research with larger sample sizes, involving both male and female participants, using a longitudinal design.



#3 Fifth metatarsal strain distribution during cutting motions in soccer

Reference: Sports Biomech. 2023 Aug 2;1-17. doi: 10.1080/14763141.2023.2241839. Online ahead of print.

Authors: Yusuke Miyazaki, Rui Sugizaki, Miku Kawasaki, Takumi Nakagawa, Yasuaki Saho, Tomohiko Tateishi

Summary: The objective of this study was to determine the fifth metatarsal strain generation mechanism during cutting motions performed while playing soccer using a finite element foot model. Five collegiate soccer players performed the side-step cutting and the cross-step cutting motions to measure the three-dimensional foot kinematics, ground reaction force, and plantar pressure distribution. In addition, a finite-element model of a foot consisting of bony structures, ligaments, and skin was constructed from computed tomography images. Simulations were conducted to perform the cutting motions, using the measured foot motion and distributed load on the plantar surface as boundary conditions for the model. During the side-step cutting, the maximum principal strain on the fifth metatarsal was correlated to forefoot adduction angle during stepping out. For cross-step cutting, the maximum principal strain was correlated with plantar pressure at the distal end of the fifth metatarsal. Therefore, to prevent a fracture, it is necessary to take measures to reduce the lateral bending deformation of the forefoot while stepping out during side-step cutting and to reduce the plantar pressure on the distal end of the fifth metatarsal during cross-step cutting.



#4 SoccerNet: A Gated Recurrent Unit-based model to predict soccer match winners

Reference: PLoS One. 2023 Aug 1;18(8):e0288933. doi: 10.1371/journal.pone.0288933. eCollection 2023.

Authors: Jassim AlMulla, Mohammad Tariqul Islam, Hamada R H Al-Absi, Tanvir Alam

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Summary: Winning football matches is the major goal of all football clubs in the world. Football being the most popular game in the world, many studies have been conducted to analyze and predict match winners based on players' physical and technical performance. In this study, we analyzed the matches from the professional football league of Qatar Stars League (QSL) covering the matches held in the last ten seasons. We incorporated the highest number of professional matches from the last ten seasons covering from 2011 up to 2022 and proposed SoccerNet, a Gated Recurrent Unit (GRU)-based deep learning-based model to predict match winners with over 80% accuracy. We considered match- and player-related information captured by STATS platform in a time slot of 15 minutes. Then we analyzed players' performance at different positions on the field at different stages of the match. Our results indicated that in QSL, the defenders' role in matches is more dominant than midfielders and forwarders. Moreover, our analysis suggests that the last 15-30 minutes of match segments of the matches from QSL have a more significant impact on the match result than other match segments. To the best of our knowledge, the proposed model is the first DL-based model in predicting match winners from any professional football leagues in the Middle East and North Africa (MENA) region. We believe the results will support the coaching staff and team management for QSL in designing game strategies and improve the overall quality of performance of the players.



#5 Residual Deficits in Reactive Strength After Anterior Cruciate Ligament Reconstruction in Soccer Players

Reference: J Athl Train. 2023 May 1;58(5):423-429. doi: 10.4085/0169-20.

Authors: Paul J Read, William T Davies, Chris Bishop, Sean McAuliffe, Mathew G Wilson, Anthony N Turner

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Summary: Deficits in plyometric abilities are common after anterior cruciate ligament reconstruction (ACLR). Vertical rebound tasks may provide a targeted evaluation of knee function. The aim was to examine the utility of a vertical hop test for assessing function after ACLR and establishing factors associated with performance. Soccer players with a history of ACLR (n = 73) and matched control individuals (n = 195) participated in this study. The 10-second vertical hop test provided measures of jump height, the Reactive Strength Index (RSI), and asymmetry. We also examined possible predictors of hop performance, including single-legged vertical drop jump, isokinetic knee-extension strength, and the International Knee Documentation Committee questionnaire score. Between-limbs differences were identified only for the ACLR group, and asymmetry scores increased in those with a history of ACLR (P < .001) compared with the control group. The single-legged vertical drop jump, RSI, and knee-extension torque were significant predictors of 10-second hop height (R2 = 20.1%) and RSI (R2 = 47.1%). Vertical hop deficits were present after ACLR, even after participants completed a comprehensive rehabilitation program. This may have been due to reduced knee-extension and reactive strength. Vertical hop tests warrant inclusion as part of the return-to-sport test battery.



#6 The relationship between wellness and training and match load in professional male soccer players

Reference: PLoS One. 2023 Jul 31;18(7):e0289374. doi: 10.1371/journal.pone.0289374. eCollection 2023.

Authors: Rafael Franco Soares Oliveira, Rui Canário-Lemos, Rafael Peixoto, José Vilaça-Alves, Ryland Morgans, João Paulo Brito

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Summary: The aims of this study were to: (i) analyse the within-microcycle variations in professional soccer players; (ii) analyse the relationships between wellness and training and match load demands; (iii) analyse the relationships between match-day (MD) demands and wellness during the following day (MD+1); and (iv) analyse the relationships between MD and wellness during the day before match-play (MD-1). Thirteen professional soccer players (age: 24.85±3.13 years) were monitored daily over 16-weeks for wellness and training and match-play intensity. The daily wellness measures included fatigue, quality of sleep, muscle soreness, mood and stress using a 1-5 scale. Internal intensity was subjectively measured daily using the rating of perceived exertion (RPE) and the multiplication of RPE by session duration (s-RPE). While external intensity was quantified utilising high-speed running, sprinting, and acceleration and deceleration metrics. Data was analysed from each training session before (i.e., MD-5) or after the match (i.e., MD+1). Repeated measures ANOVA or Friedman ANOVA was used to analyse the aims (i) where Spearman correlation was applied to analyse the relationships between the aims (ii) and (iii) between sleep quality and training intensity. The main results for aim (i) showed that MD+1 presented the lowest values for wellness variables (p < 0.05). While MD-1 presented the lowest internal and external load values (for all variables), with MD presenting the highest values (p < 0.05). Regarding aim (ii), the main result showed significant large negative correlations between fatigue and s-RPE (r = -0.593; p = 0.033). Considering aim (iii), significant small to very large negative correlations were found for sleep quality, fatigue and muscle soreness with all internal and external variables (p < 0.05). Lastly, the main results for aim (iv) showed large negative correlations for fatigue and session duration; fatigue and s-RPE; muscle soreness and session duration; muscle soreness and s-RPE; and muscle soreness and decelerations (p < 0.05, for all). The main conclusions were that MD had an influence on wellness and internal and external training intensity, notably MD-1 and MD+1 were most affected. In this regard, a tendency of higher internal and external intensity on MD was associated with lower wellness measures of sleep quality, muscle soreness and fatigue on MD+1.



#7 Reliability and sensitivity to change of post-match physical performance measures in elite youth soccer players

Reference: Front Sports Act Living. 2023 Jul 13;5:1173621. doi: 10.3389/fspor.2023.1173621. eCollection 2023.

Authors: Alberto Franceschi, Mark A Robinson, Daniel Owens, Thomas Brownlee, Duccio Ferrari Bravo, Kevin Enright

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Summary: To effectively monitor post-match changes in physical performance, valid, reliable and practical measures which are sensitive to change are required. This study aimed to quantify test-retest reliability and sensitivity to change of a range of physical performance measures recorded during an isometric posterior chain (IPC) lower-limb muscle test and a countermovement jump (CMJ) test. Eighteen Italian Serie A academy soccer players performed three IPC repetitions per limb and five CMJ trials in 4 testing sessions. Test-retest reliability was evaluated between two testing sessions seven days apart using typical error of measurement, coefficient of variation and intraclass correlation coefficient. Sensitivity to change was assessed on two additional testing sessions performed before and immediately after a soccer match through Hedges' g effect size (g) and comparisons to typical error. Absolute reliability (coefficient of variations) ranged from 1.5 to 8.8%. IPC and CMJ measures demonstrated moderate to excellent relative reliability (intraclass correlation coefficients ranged from 0.70 to 0.98). A wide range of physical performance measures showed significant alterations post-match (p < 0.05; g: small to moderate). IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric forces (mean breaking force, mean deceleration force, peak force, force at zero velocity) and CMJ mean power measures had post-match changes greater than their typical variation, demonstrating acceptable sensitivity in detecting performance changes at post-match. IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric phase forces and CMJ mean power were found to be both reliable and sensitive to change, and thus may be appropriate for monitoring post-match neuromuscular performance in youth soccer population.



#8 What happens in the prefrontal cortex? Cognitive processing of novel and familiar stimuli in soccer: An exploratory fNIRS study

Reference: Eur J Sport Sci. 2023 Aug 3;1-11. doi: 10.1080/17461391.2023.2238699. Online ahead of print.

Authors: Lena F Schmaderer, Mathilda Meyer, Rüdiger Reer, Nils Schumacher

Summary: The importance of both general and sport-specific perceptual-cognitive abilities in soccer players has been investigated in several studies. Although these perceptual-cognitive skills could contribute significantly to soccer players' expertise, the underlying cortical mechanisms have not been clarified yet. Examining activity changes in the prefrontal cortex under different cognitive demands may help to better understand the underlying mechanisms of sports expertise. The aim of this study was to analyse the prefrontal activity of soccer experts during general and sport-specific cognitive tasks. For this purpose, 39 semi-professional soccer players performed four perceptual-cognitive tests, two of which assessed general cognition, the other two assessed sport-specific cognition. Since soccer is a movement-intensive sport, two tests were performed in motion. While performing cognitive tests, prefrontal activity was recorded using functional near-infrared spectroscopy (fNIRS) (NIRSport, NIRx Medical Technologies, USA). Differences of prefrontal activity in general and sport-specific cognitive tasks were analysed using paired t-tests. The results showed significant increases in prefrontal activity during general cognitive tests (novel stimuli) compared to sport-specific tests (familiar stimuli). The comparatively lower prefrontal activity change during sport-specific cognition might be due to learned automatisms of experts in this field. These results seem in line with previous findings on novel and automated cognition, "repetition suppression theory" and "neural efficiency theory". Furthermore, the different cortical processes could be caused by altered prefrontal structures of experts and might represent a decisive factor for expertise in team sports. However, further research is needed to clarify the prefrontal involvement on expertise in general and sport-specific cognition.



#9 The association between hip/groin pain and hip strength in football players: An exploratory analysis of the FORCe cohort

Reference: J Sci Med Sport. 2023 Jul 20;S1440-2440(23)00179-2. doi: 10.1016/j.jsams.2023.07.008.

Authors: C Bonello, M G King, K M Crossley, J J Heerey, M J Scholes, P Lawrenson, M A Girdwood, J L Kemp, A B Mosler, B F Mentiplay, A I Semciw

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Summary: The aim was to explore associations between peak hip strength in football players with hip/groin pain and healthy controls. Male and female sub-elite football players (soccer and Australian football) with hip/groin pain >6-month duration and players without hip/groin pain were recruited across Melbourne and Brisbane, Australia. Demographic information and two questionnaires; the Copenhagen Hip and Groin Outcome Score and the International Hip Outcome Tool 33 were collected. Hand-held dynamometry was used to measure isometric hip strength for flexion, extension, abduction, adduction, internal rotation, and external rotation. Linear mixed effects models were used to compare strength measures between groups. 190 football players with hip/groin pain (mean ± standard deviation age, 27.8 ± 6.3 years) and 64 controls (age, 27.3 ± 5.6 years) were included in this study. Of these, 291 symptomatic limbs and 128 control limbs were used for analyses. Symptomatic players had lower peak hip adduction (adjusted mean difference = -0.18: 95 % confidence interval -0.27 to -0.08, P : 0.001), external rotation (-0.06: 95 % confidence interval -0.09 to -0.02, P : 0.003), and internal rotation strength (-0.06: 95 % confidence interval -0.10 to -0.03, P : 0.001) compared to controls. A sport-specific interaction was observed for hip abduction strength. When separated by football code, abduction strength was lower in symptomatic Australian football players compared to their same sport peers (-0.20: 95 % confidence interval -0.33 to -0.06, P : 0.004), but not in symptomatic soccer players (-0.05: 95 % confidence interval -0.15 to 0.06, P : 0.382). Hip adduction, internal rotation, and external rotation strength appears lower in football players with hip/groin pain independent of sex and football code. Hip abduction strength was lower in symptomatic Australian football players but not in soccer players.



#10 Media Framing of Women's Football During the COVID-19 Pandemic

Reference: Commun Sport. 2023 Jun;11(3):592-615. doi: 10.1177/21674795211041024. Epub 2021 Dec 8.

Authors: Keith D Parry, Beth G Clarkson, Ali Bowes, Laura Grubb, David Rowe

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Summary: This article examines British media coverage of women's association football during the coronavirus (COVID-19) pandemic, to identify how the media framed the women's game and how these frames could shape the public perceptions of it. Through a database search of British-based news coverage of women's football, 100 news articles were identified in the first 6 months after the start of the pandemic. A thematic analysis was conducted, and five dominant frames were detected in the context of COVID-19: 1) financial precariousness of women's football; 2) the commercial prioritisation of men's football; 3) practical consideration of the sport (e.g., alterations to national and international competitions); 4) debating the future of women's football and 5) concern for players (e.g., welfare, uncertain working conditions). These frames depart from the past trivialisation and sexualisation of women's sport, demonstrate the increased visibility of women's football, and shift the narrative towards the elite stratum of the game. Most of this reporting was by women journalists, while men were shown to write less than women about women's football. This research advocates continued diversification of the sports journalism workforce to dissolve the hegemonic masculine culture that still largely dominates the industry.



#11 Return to Play After the Diagnosis of Reactive Arthritis in a Professional Football Player

Reference: Cureus. 2023 Jun 29;15(6):e41139. doi: 10.7759/cureus.41139. eCollection 2023 Jun.

Authors: Alexandre Fernandes, Pedro Cunha, Julio Pinto, Carlos Duarte, Alexandre Estaca, Tiago Pereira, Mónica Bettencourt, Miguel Reis E Silva, Susana Fernandes

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Summary: In professional football, most of the injuries are traumatic; however, these athletes may suffer from rheumatologic diseases, that may present as sports-related injuries. Reactive arthritis (ReA) is classified as a sub-group of the spondyloarthritis family and is relatively rare. In this article, we highlight the successful return to play (RTP) process after the ReA diagnosis in an elite football player in the Portuguese first league. The athlete was able to RTP four months and one week after the diagnosis, had no ReA recurrence nor re-injury >8 months after RTP, and is playing at an elite level.



#12 Players', Head Coaches', And Medical Personnels' Knowledge, Understandings and Perceptions of Injuries and Injury Prevention in Elite-Level Women's Football in Ireland

Reference: Sports Med Open. 2023 Jul 29;9(1):64. doi: 10.1186/s40798-023-00603-6.

Authors: Dan Horan, Seamus Kelly, Martin Hägglund, Catherine Blake, Mark Roe, Eamonn Delahunt

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Summary: To manage injuries effectively, players, head coaches, and medical personnel need to have excellent knowledge, attitudes, and behaviours in relation to the identification of risk factors for injuries, the implementation of injury prevention initiatives, as well as the implementation of effective injury management strategies. Understanding the injury context, whereby specific personal, environmental, and societal factors can influence the implementation of injury prevention initiatives and injury management strategies is critical to player welfare. To date, no qualitative research investigating the context of injuries, has been undertaken in elite-level women's football. The aim of our study was to explore the knowledge, attitudes, and behaviours of players, head coaches, and medical personnel in the Irish Women's National League (WNL) to injury prevention and injury management. We used qualitative research methods to explore the knowledge, attitudes, and behaviours of players, head coaches, and medical personnel in the Irish WNL to injury prevention and injury management. Semi-structured interviews were undertaken with 17 players, 8 medical personnel, and 7 head coaches in the Irish WNL. The data were analysed using thematic analysis. Our study is located within an interpretivist, constructivist research paradigm. The participants had incomplete knowledge of common injuries in elite-level football, and many held beliefs about risk factors for injuries, such as menstrual cycle stage, which lacked evidence to support them. Jumping and landing exercises were commonly used to reduce the risk of injuries but evidence-based injury prevention exercises and programmes such as the Nordic hamstring curl, Copenhagen adduction exercise, and the FIFA 11+ were rarely mentioned. Overall, there was dissatisfaction amongst players with their medical care and strength and conditioning (S & C) support, with resultant inadequate communication between players, head coaches, and medical personnel. Poor quality and availability of medical care and S & C support were considered to be a major obstacle in the effective implementation of injury risk reduction strategies and successful return-to-sport practices. More original research is required in elite-level women's football to explore injury risk factors, injury prevention initiatives, and contextual return-to-sport strategies, so that players, head coaches, and medical personnel can use evidence that is both up-to-date and specific to their environment.



#13 A Systematic Review of the Physical, Physiological, Nutritional and Anthropometric Profiles of Soccer Referees

Reference: Sports Med Open. 2023 Aug 10;9(1):72. doi: 10.1186/s40798-023-00610-7.

Authors: Diogo V Martinho, Adam Field, André Rebelo, Élvio R Gouveia, Hugo Sarmento

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Summary: The importance of soccer referees is widely accepted by international soccer organizations and governing bodies, although there is little research summarizing and appraising the literature on soccer referees. The aim of this study was to systematically review the information related to physical demands, nutrition and physiological profiling of soccer referees. Conforming with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searches of three electronic databases (Web of Sciences, PubMed and Scopus) were conducted on 24 April 2022. The following search terms were used: (Soccer OR football AND refer*) AND (physical OR physiolo* OR load* OR "body composition" OR "fat mass" OR "fat free mass" OR "body size" OR "nutrition*" OR "nutritional assessment" OR "nutritional intake" OR "macronutrient*" OR "micronutrient*"). The inclusion criteria of the manuscripts written in English were that articles with male and/or female soccer referees and included relevant data concerning performance, physical testing, nutrition, body composition, body size and/or physiology of soccer referees. The tools developed by the National Institute of Health were used to assess risk of bias according to the study design. In total, 110 manuscripts were included in the present review. Match activities of soccer referees and assistant referees are not comparable. Variation in performance is influenced by competitive level and competitive schedules. Additionally, match performance is often used to validate field protocols. The associations between match indicators and field protocols were not constant across the included studies, particularly in short-maximal tests. An age decline in physical performance was not conclusive. Body size did not discriminate between referees and assistant referees, as well as referees of different competitive levels. Few studies focused on nutritional guidelines among referees, particularly exercise energy expenditure. Energy intake was comparable across studies, but referees did not follow the daily dietary recommendations. Aerobic output was frequently assessed, and it was not comparable to the values for soccer players. Although there are decreases in the running profiles of older referees, they maintain the same distances from the ball, and thus, age per se should not be used to define participation at the international level. The assessment of physical fitness warrants future consideration given the levels of fatigue that are apparent at the end of matches. In order to attain ideal levels of body composition, future studies need to provide guidelines for daily energy expenditure and nutritional intake.



#14 Evolution of Tactics in Professional Soccer: An Analysis of Team Formations from 2012 to 2021 in the Spanish LaLiga

Reference: J Hum Kinet. 2023 Jul 15;87:207-216. doi: 10.5114/jhk/167468. eCollection 2023 Jul.

Authors: Joaquín González-Rodenas, Víctor Moreno-Pérez, Roberto López-Del Campo, Ricardo Resta, Juan Del Coso

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Summary: The aim of this investigation was to explore the evolution of team formations (TFs) in a top national professional soccer league. A comparative analysis of a total of 3420 matches was performed in 32 professional soccer teams that competed from the 2012/13 to the 2020/21 season in the Spanish LaLiga. The frequency distribution of TFs across seasons presented a statistically significant change (p < 0.001). A 4.2-3.1 TF was most common from 2012/13 to 2016/17, while a 4.4.2 TF was most used from 2017/18 to 2020/2021. TFs such as 4.3.3 and 4.5.1 showed a relatively stable trend over the seasons. Overall, there was a reduction of TFs with 5 midfielders and an increase in the frequency of 2-forward formations (p < 0.001). When the ranking of teams was considered, a 4.3.3 TF was implemented with higher frequency by the Champion and teams that qualified for the Champions League (p < 0.05). However, a 4.2-3.1 TF was most frequent for teams qualified for the UEFA Europa League or teams that got relegated to an inferior category (p < 0.05). These findings highlight that teams competing in LaLiga evolved from the implementation of very few TFs led by the 4.2-3.1 TF, towards a more diverse scenario with a greater variety of tactical positional structures.



#15 The decision-making in dribbling: a video analysis study of U10 soccer players' skills and coaches' quality evaluation

Reference: Front Psychol. 2023 Jul 24;14:1200208. doi: 10.3389/fpsyg.2023.1200208. eCollection 2023.

Authors: Enzo Iuliano, Valerio Bonavolontà, Dafne Ferrari, Nicola Bragazzi, Benito Capasso, Goran Kuvačić, Andrea De Giorgio

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Summary: Dribbling is an important soccer skill that, when effective, allows players to overcome opponents. It can provide a strong tactical advantage; for this reason, all of its components (sprint, speed, and ball control) are fundamental to the development of young players. Dribbling can also be considered a decision-making process, and due to its characteristics, it is not always easy to study ecologically. Using a video analysis study, this research aimed to determine whether dribbling skills, specifically dribbling choice (i.e., decision-making), were related to U10 soccer players' quality. Several outcomes measures, divided into three categories, were taken during video analyses: (i) measures related to the efficacy of dribbling skill; (ii) measures related to the ability of players without the ball to support the player in possession; and (iii) measures related to ball circulation. These data were retrospectively assessed to whether the coaches had formed the teams in training through an implicit knowledge of the players' dribbling skills. The percentage of accurate dribbling (that is, the ability to perform correct passes after a successful dribble) was found to be the variable that coaches may have implicitly used in creating the three groups differentiated by technical skills (p < 0.05). In fact, this percentage was 12.9%, 24.0%, and 48.1% for the groups with lower, average, and higher technical skills, respectively. Overall, the results demonstrate that dribbling accuracy has an important weight in the coach's evaluation of the technical skills level of young soccer players.






The Three-Level Model of Factors Contributing to High-Intensity Intermittent Performance in Male Soccer Players

This study aims to propose a three-level model of factors contributing to YYIR2 performance, based on the investigation of relationships with aerobic endurance, repeated sprint ability (RSA), and the linear and change-of-direction (COD) variables.





Planning the Microcycle in Elite Football: To Rest or Not to Rest?

The purpose was to examine the association between the programming of days off (ie, no pitch training, days off feet) within turnarounds of varying length and injury rate in elite soccer.





Latest research in football - week 30 - 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 Is ball-possession style more physically demanding than counter-attacking? The influence of playing style on match performance in professional soccer

Reference: Front Psychol. 2023 Jul 7;14:1197039. doi: 10.3389/fpsyg.2023.1197039. eCollection 2023.

Authors: Leon Forcher, Leander Forcher, Hagen Wäsche, Darko Jekauc, Alexander Woll, Timo Gross, Stefan Altmann

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Summary: In soccer, the offensive style of play describes characteristic behavioral features of the players at team level during the offensive phase of matches. This study aimed to investigate the effect of offensive playing style (i.e., while in ball possession) on physical and technical match performance during offensive play as well as success-related factors. The sample consisted of official tracking and event data of 153 matches of the 2020/21 German Bundesliga season. For every team in every match an offensive playing style coefficient was calculated to locate teams on a continuum between ball possession and counter-attacking style. This calculation contains 11 technical and physical performance parameters and has already been validated. In addition, dependent physical (e.g., sprinting distance), technical (e.g., passes), and success-related (e.g., goals) variables were examined. A separate linear mixed model was calculated for each dependent variable. While teams with lower playing style coefficient values (= counter-attacking style) covered more high-intensity (p ≤ 0.01; R2 = 0.13) and sprinting distances per second in possession (p ≤ 0.01; R2 = 0.14), teams with higher playing style coefficient values (= ball possession style) were physically more demanded over a whole match (e.g., more accelerations (p ≤ 0.01; R2 = 0.69), decelerations (p ≤ 0.01; R2 = 0.69), high-intensity (p ≤ 0.01; R2 = 0.36), sprint distance (p = 0.03; R2 = 0.08)). Furthermore, teams with higher playing style coefficient values played more horizontal passes (p ≤ 0.01; R2 = 0.73) and revealed better passing success rates (p ≤ 0.01; R2 = 0.17). In contrast, teams with lower playing style coefficient values played more long passes (p < 0.01; R2 = 0.58). The influence of the playing style coefficient on success-related variables was smaller (p ≤ 0.36; R2 = 0.10-0.13). Concluding, offensive playing style affects physical and technical match performance, but has limited influence on success. Hence, coaches can use the findings to optimize training contents to prepare players for the physical demands of a match.



#2 Building Bridges Instead of Putting Up Walls: Connecting the "Teams" to Improve Soccer Players' Support

Reference: Sports Med. 2023 Jul 22. doi: 10.1007/s40279-023-01887-0. Online ahead of print.

Authors: João Renato Silva, Martin Buchheit, Karim Hader, Hugo Sarmento, José Afonso

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Summary: The increase in the economic value of soccer occurred in parallel with an increase in competing demands. Therefore, clubs and federations evolved to greater specialization (e.g., state-of-the-art facilities and high-profile expertise staff) to support players' performance and health. Currently, player preparation is far from exclusively club or national team centered, and the lack of control in each player's environment can be more prevalent than expected. For example, an elite group of professional players faces disruptions in the season club-oriented planification due to involvement in national teams. Moreover, as elite players' financial resources grow, it is common for them to employ specialized personal staff (e.g., strength and conditioning, nutritionist, and sports psychologist) to assist in their preparation, resulting in complex three-fold relationships (i.e., club, player's staff, national team). Although efforts have been made to improve communication with and transition from the club to the national team supervision, this new reality (club-players' staff) may generate serious compound role-related problems and difficulties in monitoring load and training adaptation and having a unified message. Therefore, efforts must be implemented to ensure a more informed management of the players' performance environment, where the existence and impact of these various personal staff are considered to avoid a long-term non-zero sum for all intervening parties. If left unchecked, current professional thinking may collide or overlap, potentially triggering conflict escalation and impairing athletic performance or health, especially if effective communication routes are not adequately established. Moreover, diluted personal responsibility regarding performance may ensue, resulting in decreased productivity from all involved, which may cause more harm than benefits for the player's overall health and performance. This emerging reality calls for developing a joint working framework (i.e., between the player's personalized support team and the clubs' team) and better managing of a player-centered process.



#3 A 3-min weighted vests re-warmups induce sprint performance enhancements at the start of the second half of a soccer match-play

Reference: Front Physiol. 2023 Jul 6;14:1173991. doi: 10.3389/fphys.2023.1173991. eCollection 2023.

Authors: Mohamed Amine Ltifi, Olfa Turki, Ghazi Racil, Alin Larion, Mohamed Souhaiel Chelly, Helmi Ben Saad, Riadh Khalifa, Karim Chamari, Johnny Padulo

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Summary: This study aimed to investigate the effect of re-warm-up (RWUP) activities consisting of three sets of 15-m sprints with weighted vests on 20-m sprint performance after the break. Using a randomized, and counterbalanced cross-over design, twenty U15 elite soccer players performed four RWUP trials which consisted of 15-min of passive rest (control: CONT), 3 × 15-m sprint (RW0%), sprinting with a vest-loaded at 5% of body-mass (BM) (RW5%), sprinting with a 10% BM vest (RW10%). The 3-min RWUP protocols started 10-min after the commencement of the 15-min between-halves break and concluded 2-min before its end. During each testing session, the participant's RPE scores, and 20-m sprint performance were registered before the first half, and at the end of the break of the simulated match-play. Significant time effects [F (1.72) = 54.37, d = 1.88, p < 0.001; F (1.72) = 9.07, d = 0.77, p = 0.003], and condition effects [F (3.72) = 11.81, d = 1.53, p < 0.001; F (3.72) = 7.36, d = 1.21, p = 0.003] were observed for RPE scores and 20-m sprint performance, respectively. Significant condition-by-time interactions were found for RPE scores (p < 0.003, d = 0.54), and 20-m sprint performance (p < 0.002, d = 0.70). Contrast analysis showed significantly higher RPE scores (p < 0.001, d = 1.55), and improved 20-m sprint performance (p = 0.0004, d = 1.19) in the RW10% condition compared to all other conditions. Sprinting for 3-min with a 10% body-mass vest resulted in the highest RPE scores and the most substantial enhancements in 20-m sprint performance. Young elite soccer players should incorporate 10% body-mass weighted vests in their re-warm-ups to boost post-break sprint performance.



#4 Adductor longus and brevis lesion in an amateur soccer player: platelet rich plasma and multifractioned hyaluronic acid injections to enhance clinical recovery

Reference: J Sports Med Phys Fitness. 2023 Jul 24. doi: 10.23736/S0022-4707.23.14938-3. Online ahead of print.

Authors: Silvana Giannini, Sebastiano Vasta, Arrigo Giombini, Chiara Fossati, Ugo Riba, Giuseppe Massazza, Rocco Papalia, Fabio Pigozzi

Summary: Groin pain is a common issue in athletes, with a particularly high incidence in male soccer players. Adductor muscles are the most involved site of the groin, accounting for up to one-fourth of muscle injuries of that region. Physical therapy and rehabilitation programs for adductor-related groin pain using active exercises are effective in getting athletes back to sport. However, the return-to-play time varies according to the injury severity. Minor lesions can recover in 1-2 weeks, while severer injuries require 8-12 weeks. To enhance tendon healing and shorten the return to play time, intrandentinous injections of Platelet Rich Plasma (PRP) have been proposed. An increasing body of evidence in literature have shown efficacy of platelet rich plasma in aiding the healing process in tendinopathies. Similarly, more recent evidences have proven hyaluronic (HA) acid to have anti-inflammatory, proliferative, repairing, and analgesic effects. This case report presents the clinical application of combined PRP and a multifractioned (a mixture of different molecular weights) HA in a 24-year-old athlete suffering from a hip adductor rupture.



#5 Effects of Resistance Training of Upper Limb and Trunk Muscles on Soccer Instep Kick Kinematics

Reference: J Appl Biomech. 2023 Jul 24;1-10. doi: 10.1123/jab.2022-0323. Online ahead of print.

Authors: Miguel Arcanjo de Assis, Thiago Ribeiro Teles Santos, Sergio Teixeira Fonseca, André Gustavo Pereira de Andrade, Priscila Albuquerque Araújo, Thales Rezende de Souza, Renan Alves Resende, Juliana Melo Ocarino

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Summary: The upper body and trunk muscles are crucial to perform soccer kicks. Resistance training targeting these muscles may modify the pattern adopted during kicking. This study aimed to investigate the effect of resistance training of the arm and anterior trunk muscles on instep kicking kinematics. Twenty-six male participants were randomly allocated into a training group or control group. The training group underwent resistance training of arm and trunk muscles and practiced the instep kick for 8 weeks. The control group only practiced kicking during the same period. The trunk, hip, and knee kinematics were assessed during the instep kick before and after the intervention. Kinematics were analyzed according to their data distribution with statistical parametric or nonparametric mapping. The effect of the training on the 1-repetition maximum test was analyzed using a repeated-measures multivariate analysis of variance. The training group showed greater hip extension after the training during the backswing phase (Hedge g effect size of 0.316-0.321) and increased 1-repetition maximum for all exercises. There were no other differences. The present study documented the nonlocal effect of strengthening training in which arm and trunk muscle training resulted in changes in hip kinematics during the backswing phase of the instep kick.



#6 Morphological Characteristics of Elite International Soccer Referees: Somatotype and Bioelectrical Impedance Vector Analysis

Reference: J Funct Morphol Kinesiol. 2023 Jul 24;8(3):100. doi: 10.3390/jfmk8030100.

Authors: Pascal Izzicupo, Cristian Petri, Sofia Serafini, Giorgio Galanti, Gabriele Mascherini

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Summary: This study aimed to assess the physical characteristics of elite international soccer referees, compare them with other referee populations in the literature, and establish reference tolerance ellipses for the bioelectrical impedance vector analysis (BIVA) point graph. Forty-one elite international soccer referees (age 38.8 ± 3.6 years) participated in the study. The participants underwent body composition assessments, including dual-energy X-ray absorptiometry, BIVA, and somatotype. The Somatotype Attitudinal Distance (SAD), the two-sample Hotelling's T2 test and the Mahalanobis test were used to determine somatotype and bioelectrical vector differences with the literature. The average somatotype of the referees was a balanced mesomorph (2.8, 6.5, 2.8). Elite international referees significantly differed from other samples in the literature (SAD = 2.1, 2.6, 2.9 with respect to Zimbabwean, Brazilian, and South African referees, respectively). The bioelectrical vector was significantly different from the general population (T2 ≤ 76.6; F = 38.8; D = 1.44; p < 0.001) and athletes (T2 ≤ 25.3; F = 12.6; D = 0.8; p < 0.001). Somatotype values and tolerance ellipses from this study may be useful as a reference for developing training programs and improving the selection process of referees in soccer.



#7 Mental toughness among national soccer officials: A comparative analysis

Reference: J Public Health Afr. 2022 Dec 7;13(Suppl 2):2423. doi: 10.4081/jphia.2022.2423.

Authors: Mahabir Nath, Vikas Singh, Anshuman Mishra

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Summary: Few studies have looked at the psychological mechanisms that govern soccer officials' performance to this point. The main goal of the study is to identify age-related changes in mental toughness among officials. Sixty active national officials were chosen at random from the All-India Football Federation's national officials' roster (AIFF). Group A is 25-30 years old, with a mean and SD of 27.4±3.39 (lower age group); Group B is 31-35 years old, with a mean and SD of 31.8±1.28 (middle age group); and Group C is 36-40 years old, with a mean and SD of 37.6±1.98 (higher age group). The Psychological Performance Inventory (PPI), developed by James E. Loehr in 1982, was chosen as the research's test item. This instrument evaluates seven aspects of mental toughness, including selfconfidence, negative energy control, attention control, visualisation and imagery control, motivation, positive energy control, and attitude control. One-way analysis of variance (ANOVA), with a significance threshold of 0.05, was used as the statistical approach to assess the study's hypothesis. The finding of the research paper shows no significant difference among various groups.



#8 Pilot Study: The Relationship between Foot Posture and Movement Quality in Non-Professional Male Football Players

Reference: Life (Basel). 2023 Jul 17;13(7):1574. doi: 10.3390/life13071574.

Authors: José Algaba-Del-Castillo, Aurora Castro-Méndez, Ana Juana Pérez-Belloso, José Gabriel Garrido-Barragán, Alberto Aguilar Sánchez, Manuel Coheña-Jiménez

Summary: This study focusses on establishing the relationship between quality of movement (based on the functional movement screen, or FMS) and foot posture (based on the foot posture index, or FPI-6). We hypothesised that a poor FMS test score may be derived from the foot position in the space measured by FPI-6. A quasi-experimental and cross-sectional study was designed to analyse foot posture in 30 healthy football players, using the foot posture index and the functional movement screen. No significant relationships were found between movement quality and foot posture. Poor movement quality is present in more than half of all foot positions, supination, pronation, and neutral. Good quality seems to be more associated with a neutral foot position (23.3%) and supinated (16.6%) than a pronated foot position (6.6%). This study found no relationship between the two tests; therefore, we cannot demonstrate that foot posture is relevant in the quality of the movement of the football players studied.



#9 Maturity-Associated Polygenic Profiles of under 12-16-Compared to under 17-23-Year-Old Male English Academy Football Players

Reference: Genes (Basel). 2023 Jul 12;14(7):1431. doi: 10.3390/genes14071431.

Authors: Alexander B T McAuley, Ian Varley, Adam J Herbert, Bruce Suraci, Joseph Baker, Kathryn Johnston, Adam L Kelly

Summary: The purpose of this study was to examine polygenic profiles previously associated with maturity timing in male academy football players across different age phases. Thus, 159 male football players from four English academies (U12-16, n = 86, aged 13.58 ± 1.58 years; U17-23, n = 73, aged 18.07 ± 1.69 years) and 240 male European controls were examined. Polygenic profiles comprised 39 single nucleotide polymorphisms and were analysed using unweighted and weighted total genotype scores (TGSs; TWGSs). There were significant differences in polygenic profiles between groups, whereby U17-23 players had more genetic variants associated with later maturity compared to U12-16 players (TGS, p = 0.010; TWGS, p = 0.024) and controls (TGS, p = 0.038; TWGS, p = 0.020). More specifically, U17-23 players had over two-times the odds of possessing >36 later-maturing alleles than <30 compared to U12-16 players (odds ratio (OR) = 2.84) and controls (OR = 2.08). These results suggest there was a greater proportion of relatively later-maturing players as maturation plateaus towards adulthood, which may be explained by the 'underdog hypothesis'. This study provides the first known molecular evidence that supports the notion that a maturity selection bias exists within male academy football.



#10 Dropping Out or Continuing Playing-A Case Study of Adolescent's Motives for Participation in Football

Reference: Sports (Basel). 2023 Jul 3;11(7):128. doi: 10.3390/sports11070128.

Authors: Jostein Bergin, Pål Lagestad

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Summary: The purpose of this study was to investigate dropout and continuation motives among boys in youth football. Semi-structured interviews were conducted with all players from a former football team, consisting of 13 young people who were 17 years old when the in-depth interviews were conducted. Short interviews with the same players five years earlier (at the age of 12) were also included as part of the data. This strategy was used to gain a longitudinal perspective and a better insight into the participants' experience of organized football. Including in-depth data from all players at a football team-both players that dropped out and continued playing football, and also including some short interviews data from a longitudinal perspective, this study bring new findings into the discussion about sport participation. When the in-depth interviews were conducted, six of the participants had dropped out of football, while seven were still active. The results show that social factors, ambition, other interests and differences in skill and physical development, were all reasons for dropout from this team. Among those who continued playing football, the social aspect of football, their love for the sport, competitive instinct and the training benefits the sport provided, were reasons they continued playing. Furthermore, the findings showed that those who reported the lowest ambitions at the age of twelve, had dropped out of football, while the one with the highest ambitions had continued playing football. Our findings indicate that ambition can be a crucial factor in relation to participation in football, and also that the social aspect of football is an important motivational factor that coaches and parents should be aware of.



#11 Retracted: Research on Video Target Detection and Tracking in Football Matches

Reference: Comput Intell Neurosci. 2023 Jul 19;2023:9801425. doi: 10.1155/2023/9801425. eCollection 2023.

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#12 Commotio Cordis Returns…When We Least Expected It: Cardiac Arrest in A Professional Football Player

Reference: Am J Cardiol. 2023 Jul 24;S0002-9149(23)00396-X. doi: 10.1016/j.amjcard.2023.06.027.

Authors: Barry J Maron, N A Mark Estes

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Summary: For the first time in 52 years, an American professional football player (Damar Hamlin) collapsed in cardiac arrest during a game, viewed in real-time on national television. The cause of this profound event was commotio cordis, that is, blunt non-penetrating chest blow-initiated ventricular fibrillation triggered by physical contact not considered unusual for football. The athlete survived because of timely cardiopulmonary resuscitation and defibrillation provided by first responders organized by the National Football League. Commotio cordis, albeit rare, was most prominently identified initially in competitive and also recreational sports participants. More recently it became apparent that similar events could occur in almost any circumstance involving a chest blow, such as during everyday activities around the home and with innocent play. The determinant of a commotio cordis event is a blow over the heart in a narrow vulnerable electrical window during dispersion of repolarization. Survival from these events has increased substantially to >60% due to enhanced recognition and prompt resuscitation/defibrillation. In conclusion, in this commentary, we take a timely opportunity to describe in detail the relevant demographics, mechanism/pathophysiology, and clinical course of commotio cordis.



#13 Protective guidelines and mitigation strategies for hot conditions in professional football: starting 11 Hot Tips for consideration

Reference: BMJ Open Sport Exerc Med. 2023 Jul 21;9(3):e001608. doi: 10.1136/bmjsem-2023-001608. eCollection 2023.

Authors: Vincent Gouttebarge, Rob Duffield, Steve den Hollander, Ron Maughan

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Summary: Elevated heat, humidity and solar load combined with low air movement independently and additively impair performance, increase the perception of effort and the risk of heat-related illnesses. For the specific context of professional football, the Fédération Internationale de Football Association (FIFA) heat guidelines are often used as the default policy. Still, these seem less protective than guidelines in other sports or from countries traditionally exposed to extreme hot conditions. Following several high-profile international and continental competitions played in hot conditions (eg, 2014 FIFA World Cup Brazil), a series of cross-sectional studies showed that national team players and their managers unanimously mentioned that the hot and humid conditions during these matches made it difficult as a team to perform. Such a concern is likely to be relevant for the upcoming 2026 FIFA World Cup that will be held in the traditional June-July window across 16 host cities in Canada, Mexico and USA. Therefore, to better protect players' health and performance during training and match play in hot conditions, we present our starting 11 Hot Tips that should be considered and facilitated by governing bodies, competition organisers, clubs, staff members and players.



#14 Disagreement between talent scouts: Implications for improved talent assessment in youth football

Reference: J Sports Sci. 2023 Jul 25;1-8. doi: 10.1080/02640414.2023.2239614. Online ahead of print.

Authors: Dennis Lüdin, Lars Donath, Michael Romann

Summary: Reliable talent identification and selection (TID) processes are prerequisites to accurately select young athletes with the most potential for talent development programmes. Knowledge about the agreement between scouts who play a key role in the initial TID in football is lacking. Therefore, the aim of the present study was to evaluate the agreement within four groups of a total of n = 83 talent scouts during rank assessment of under-11 male youth football players (n = 24, age = 11.0 ± 0.3 years) and to describe scouts' underlying approach to assess talent. Krippendorff's α estimates indicated disagreement of scouts' rankings within all groups of scouts (αA = 0.09, αB = 0.03, αC = 0.05, αD = 0.02). Scouts reported relying mainly on their overall impression when forming their final prediction about a player. Reportings of a consistent, structured approach were less prevalent. Taken together, results indicated that different approaches to TID may be associated with disagreement on selection decisions. In order to overcome disagreement in TID, football organisations are encouraged to establish a more structured process. Future research on the elaboration and benefit of ranking guidelines incorporating decomposed and independently evaluated sub-predictors is recommended to improve the reliability of TID.



#15 Leadership in Finnish elite football: associations between players' self-assessed leadership roles and player-assessed head coach leadership behavior by player gender and age

Reference: Sci Med Footb. 2023 Jul 25;1-7. doi: 10.1080/24733938.2023.2237483. Online ahead of print.

Authors: Sakari Holopainen, Mihály Szeróvay, Niilo Konttinen, Marja Kokkonen

Summary: We investigated the associations between Finnish top tier footballers' self-assessed leadership roles (task, motivational, social, external) and player-assessed head coach leadership behavior (supportiveness/emotional composure, negative activation) and leadership role in both practices and games. We also explored the player age- and gender-related differences. Online survey data were anonymously collected from 53 male and 91 female footballers. One player did not identify as male or female, and one chose not to answer the question. Spearman rank-order correlations revealed that players' self-assessed leadership roles correlated positively with their evaluation of their head coach's supportiveness/emotional composure and negatively with negative activation during practices and games. Independent samples T-tests showed that male footballers rated their head coaches lower on negative activation during games and practices and themselves higher on external leadership than female players. The youngest age group, aged 17-20, rated themselves also lower on external leadership than the three older groups.



#16 Analysis of microbiota profile and nutritional status in male professional football players

Reference: J Sports Med Phys Fitness. 2023 Jul 24. doi: 10.23736/S0022-4707.23.15103-6. Online ahead of print.

Authors: Emre B Kenger, Fatih Eren, Tugce Ozlu, Fatma E Gunes

Summary: The interest in the effect of gut microbiota on athlete health has increased in recent years. Available data indicate a relationship between gut microbiota composition and physical activity, suggesting that changes in the microbiota may contribute to the host's physical performance. Studies show that leaky gut syndrome is highly correlated with upper respiratory infections and gastrointestinal disorders in endurance sports. This study aims to reveal the relationship between microbiota profiles, and the nutritional status of football players who perform endurance exercises. Twenty male professional football players playing in one of the Turkish Football Federation Second League clubs participated in the study. Fecal samples were collected and stored at -86 °C, and the fecal microbiota was analyzed through 16s rRNA gene sequencing. The body composition of the football players was measured using a bioelectrical impedance analyzer. In addition, the 3-day food intake of the participants was recorded with the help of a dietitian. In the microbiota of football players, four phyla, 10 genera, and four species with densities above 1% were found. Body fat percentage was observed to be negatively correlated with the species of Faecalibacterium prausnitzii and Bacteroides vulgatus and the genus of Faecalibacterium (P<0.05). Considering the nutritional status, the fat intake was found to be positively correlated with Actinobacteria and Blautia coccoides; energy and fiber intake with Prevotella and Prevotella copri (P<0.05). In addition, there was a negative correlation between carbohydrate intake and Faecalibacterium (P<0.05). Our study is the first to reveal the microbiota profile of professional Turkish football players. It was found that football players' nutritional status and anthropometric measurements of are significantly related to phylum, genus and species ranks in the microbiota. These results support the bidirectional interaction between microbiota and sports. The relationship between microbiota and sports health/performance is thought to be further clarified with future studies.



#17 How the 12th Man Influences Football Matches: The Role of Fans and Referees in Home Advantage Phenomenon

Reference: Percept Mot Skills. 2023 Jul 24;315125231191683. doi: 10.1177/00315125231191683.

Authors: Ali Işın, Miguel Ángel Gómez Ruano

Summary: Home advantage and referee bias are two sport factors that have been widely studied in the football (i.e., soccer) context. However, the mediating effect of spectators on these factors is not well understood, especially in the Turkish Super League. We examined (a) how variables of home advantage, referee bias, and spectator presence interacted to affect the outcome of past football matches; (b) how these variables have changed over time in the Turkish Super League; (c) and whether home advantage and referee bias differ in matches with spectators and ghost matches (without spectators). We analyzed regular season matches played in the Turkish Super League between the 2014-2015 and 2021-2022 seasons. We found that home teams had a significant advantage over away teams in matches with spectators (p < .001) and in ghost matches (p < .05 and p < .001), with small to medium effect sizes (d = .09 and .34, respectively). Regarding referee bias, away teams received more yellow cards and fewer penalties than home teams in matches with spectators (p < .001; d = -.10), and away teams received fewer yellow cards than home teams in ghost matches (p > .05; d = .05). There was no statistically significant difference between home and away teams on number of red cards in either type of match (p > .05). Thus, our data reveal that home teams have an edge over away teams with and without spectators, but this advantage is reduced during ghost matches (without spectators). We also revealed weak evidence of referee bias in favor of home teams, but only for some variables and only when spectators were present.



#18 Clustering U-14 Portuguese regional team football players by lower limb strength, power, dynamic balance, speed and change of direction: understanding the field position factor

Reference: PeerJ. 2023 Jul 19;11:e15609. doi: 10.7717/peerj.15609. eCollection 2023.

Authors: Tatiana Sampaio, Daniel Marinho, José Eduardo Teixeira, João Oliveira, Jorge Morais

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Summary: The aim of this study was to cluster U-14 Portuguese regional team football players based on variables related to lower limb strength and power, dynamic balance, linear sprint, and change of direction. The sample consisted of 22 young male soccer players (13.83 ± 0.44 years). A set of variables related to lower limb strength and power, dynamic balance, linear sprint, and change of direction was measured. Overall, a non-significant field position was observed. The countermovement jump (p < 0.001, η2 = 0.73), squat jump (p < 0.001), and 30 m linear sprint (p = 0.001) were the main variables responsible for establishing the clusters. Cluster 1 was characterized by a high slalom, i.e., it took longer to complete the test (speed and change of direction) and a low composite score in the dynamic balance. Cluster 2 was characterized by high squat jump, countermovement jump, and reactive strength ratio (lower limb strength and power). Cluster 3 was characterized by low squat jump and countermovement jump (lower limb strength and power), and a high 30 m sprint, i.e., it took longer to complete the test (speed and change of direction). Based on the results of the territorial map, the clusters consisted of: (i) cluster 1: two forwards, one midfielder, and five defenders; (ii) cluster 2: three forwards, two midfielders, and two defenders, and; (iii) cluster 3: four midfielders and three defenders. Players from different field positions composed the three clusters. There was no cluster composed exclusively of players of the same field position. The development of individualized and specific enrichment training programs should consider a cluster analysis, as the positional effect can be overlooked.






Congested Period in Professional Soccer Players Showed a Different High Decelerations Profile and a Specific Positional Behaviour

This study aimed to compare the running demands of professional youth soccer players in congested periods according to their specific playing positions.





Relative age effects and the youth-to-senior transition in Italian soccer: the underdog hypothesis versus knock-on effects of relative age

Relative Age Effects (RAEs) appear largely throughout youth soccer. However, little is known about how RAEs at youth levels can impact transition at senior levels.





Latest research in football - week 29 - 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 Junior to senior transition pathway in Italian Football: The rocky road to the top is not determined by youth national team's selections

Reference: PLoS One. 2023 Jul 18;18(7):e0288594. doi: 10.1371/journal.pone.0288594. eCollection 2023.

Authors: Gennaro Boccia, Paolo Riccardo Brustio, Rocco Rinaldi, Ruggero Romagnoli, Marco Cardinale, Maria Francesca Piacentini

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Summary: Football is a popular sport, but little is known about the youth-to-senior transition rates in elite players, particularly in large and successful countries. This study aims to investigate the youth-to-senior transition rate in the Italian national football team, both prospectively and retrospectively, and to explore if Relative Age Effects (RAEs) affect this transition. Data from 885 players selected in youth and senior Italian national teams between 2000 and 2021 were included in the study. For each player, the birthdate and the number of selection in Under 16, 17, 19, 21 and senior team was considered. The transition rate was determined by the number of youth players competing in the Senior National team (and vice versa), whilst birth quarter (Q) distributions with a chi-square goodness-of-fit test. Prospectively, the transition rate increased as age increased (i.e., from ~20% in U16 to ~50% in U19). Retrospectively, less than 10-20% of youth players were subsequently selected for the senior team. Data revealed a skewed birth date distribution in all age groups, and the RAEs magnitude decreased when age increased (i.e., ORs for Q1 vs Q4 was ~ 9 in U16 and ~ 1.7 in senior teams). Nevertheless, the RAE magnitude was smaller for successfully transitioned players. In conclusion, most players in the senior team were not previously selected for youth teams suggesting that junior international experience may not be a prerequisite for later success. Moreover, while the birthdate strongly influences the selection of youth national teams, its impact is less evident in the youth-to-senior transition.



#2 Are hip biomechanics during running associated with symptom severity or cam morphology size in male football players with FAI syndrome?

Reference: Gait Posture. 2023 Jun 29;105:17-26. doi: 10.1016/j.gaitpost.2023.06.021. Online ahead of print.

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

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Summary: Femoroacetabular impingement (FAI) syndrome is considered a motion-related condition. Little is known about the influence of symptom severity and cam morphology on hip biomechanics for individuals with FAI syndrome. Our research question was: Are hip biomechanics during running associated with symptom severity or cam morphology size in male football players with FAI syndrome? Forty-nine male, sub-elite football (soccer or Australian football) players (mean age= 26 years) with FAI syndrome completed the International Hip Outcome Tool-33 (iHOT-33) and Copenhagen Hip and Groin Outcome Score (HAGOS) and underwent radiographic evaluation. Biomechanical data were collected during overground running (3-3.5 m∙s-1) using three-dimensional motion capture technology and an embedded force plate. Various discrete hip angles and impulses of joint moments were analysed during the stance phase. Linear regression models investigated associations between running biomechanics data (dependent variables) and iHOT-33 and HAGOS scores and cam morphology size (independent variables). Hip joint angles during running were not associated with symptom severity in football players with FAI syndrome. A positive association was found between the impulse of the hip external rotation moment and HAGOS-Sport scores, such that a smaller impulse magnitude occurred with a lower HAGOS-Sport score (0.026 *10-2 [95%CI <0.001 *10-2 to 0.051 *10-2], P = 0.048). Larger cam morphology was associated with a greater peak hip adduction angle at midstance (0.073 [95%CI 0.002-0.145], P = 0.045). Hip biomechanics during running did not display strong associations with symptom severity or cam morphology size in male football players with FAI syndrome who were still participating in training and match play. Future studies might consider investigating associations during tasks that utilise end range hip joint motion or require greater muscle forces.



#3 Adherence to Injury Prevention Exercise Programmes in Amateur Adolescent and Adult Football: A Detailed Description of Programme Use from a Randomised Study

Reference: Sports Med Open. 2023 Jul 15;9(1):57. doi: 10.1186/s40798-023-00608-1.

Authors: Hanna Lindblom, Markus Waldén, Martin Hägglund

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Summary: Injury prevention exercise programmes (IPEPs) efficaciously reduce injuries. However, it is challenging to achieve sufficient adherence across a season. The main aim was to describe adherence to IPEPs in three groups of coaches and players partaking in a cluster randomised trial. Secondary aims were to describe perceptions of IPEPs, use of programme material, and overall preventive strategies. This is a sub-study analysing data from a three-armed randomised trial with teams randomised to use either a comprehensive IPEP (extended Knee Control) or an adductor strength programme, and non-randomised teams that already used a self-chosen IPEP regularly at study start (comparison group). Teams were instructed to use their respective intervention across the 2020 football season. Male and female, adolescent (≥ 14 years of age), and adult amateur players took part. Coaches and players responded to weekly and end-of-season questionnaires. Data were presented descriptively. Weekly player data were reported by 502 players (weekly response rate 65%), 289 (58%) responded to end-of-season questionnaires. Teams in the extended Knee Control and comparison group used their respective IPEP in 483/529 (91%) and 585/641 (91%) of training sessions, and teams in the adductor group in in 199/315 (63%) sessions. Regarding utilisation fidelity, 42-52% of players in each group used 1-10 repetitions per exercise. Seven out of 17 teams in the adductor group had progressed as recommended in terms of number of repetitions. Two teams (10%) in the extended Knee Control group, and 7/24 of comparison teams used the same exercises across the season. Coaches accessed the IPEPs by different means (printed material, films, workshops, etc.), but half did not use the provided digital material. The players appreciated that the IPEPs could reduce injury risk and that they improved their exercise performance, but disliked that they had less time for football and that the exercises were boring. Forty-nine players had experienced pain during IPEP performance. Adherence with the IPEPs was generally high. To meet different coach needs, programme material should be available via different digital and printed resources. The number of players reporting pain during IPEP performance is a noteworthy finding.



#4 Effects of Acute Caffeine Ingestion on Cognitive Performance before and after Repeated Small-Sided Games in Professional Soccer Players: A Placebo-Controlled, Randomized Crossover Trial

Reference: Nutrients. 2023 Jul 10;15(14):3094. doi: 10.3390/nu15143094.

Authors: Rodrigo Freire de Almeida, Mateus de Oliveira, Isadora Clivatti Furigo, Rodrigo Aquino, Neil David Clarke, Jason Tallis, Lucas Guimaraes-Ferreira 

Summary: Soccer is a team sport that requires players to process a significant amount of information quickly and respond with both speed and accuracy to the ever-changing demands of the game. As such, success in soccer depends not only on physical attributes but also on cognitive abilities such as perception and decision-making. The aim of the current study was to investigate the acute effects of caffeine ingestion on Stroop test performance before and after repeated small-sided games (SSG) in professional soccer players. Twelve professional male soccer players (29 ± 4.1 years; 78.1 ± 7.7 kg body mass) participated in this study. A randomized crossover double-blind placebo-controlled trial was used. Caffeine (5 or a placebo was ingested 45 min before a protocol consisting of five 5 min SSG with 1 min rest intervals. A computerized version of the colour Stroop test was completed immediately before and after the exercise protocol. During the Stroop test, words appeared on the computer screen in three different ways: (i) neutral words (neutral condition); (ii) correspondent colour (i.e., "red" painted in red; congruent condition), or; (iii) different colour (i.e., "red" painted in green; incongruent condition). The incongruent condition aimed to cause the interference effect, as the colour and the word did not match. Ratings of perceived exertion (RPE) were assessed after each SSG. RPE increased during the five sets of the SSG protocol (p < 0.001), without differences between the caffeine and placebo trials. The soccer-specific exercise protocol promoted a faster response during the Stroop test (two-way ANOVA main effect for SSG protocol: p < 0.05), with no differences in accuracy (p > 0.05). Caffeine ingestion resulted in slower reaction time during the Stroop test during the congruent and neutral trials but not during the incongruent trial (two-way ANOVA main effect for supplementation: p = 0.009, p = 0.045, and p = 0.071, respectively). Accuracy was lower in the caffeine trial in congruent and incongruent trials (p < 0.05 caffeine vs. placebo both on the pre- and post-SSG protocol). In conclusion, a soccer-specific exercise protocol improved the Stroop test performance in professional soccer players, but acute caffeine ingestion (5 was detrimental.



#5 The Effect of Environmental Disasters on Endocrine Status, Hematology Parameters, Body Composition, and Physical Performance in Young Soccer Players: A Case Study of the Aral Sea Region

Reference: Life (Basel). 2023 Jul 3;13(7):1503. doi: 10.3390/life13071503.

Authors: Valerii O Erkudov, Kenjabek U Rozumbetov, Francisco Tomás González-Fernández, Andrey P Pugovkin, Ilal I Nazhimov, Azat T Matchanov, Halil İbrahim Ceylan

Summary: The Aral Sea region (Uzbekistan) is infamous because of the ecological disaster characterized by the disappearance of the Aral Sea due to excessive uncontrolled water intake for agriculture needs. A new desert occurrence, soil and climate aridization led to pesticide and toxic metals environment pollution. The impact of environmental conditions in some areas of Uzbekistan on the health of soccer players is not as noticeable as, for example, the effectiveness of training, so it is not widely discussed in scientific papers. The aim of the present study was to study the features of endocrine status, hematology parameters (e.g., red blood cells (RBC) and hemoglobin (Hb)), and their influence on body composition and physical fitness performance in local young soccer players of the Aral Sea region as the territory of ecological disaster. The study involved 60 male soccer players aged from 18 to 22 years. Participants were divided into two groups: the experimental group (EG), which consisted of 30 soccer players living on the territory of the Aral ecological disaster region, and the control group (CG), which included 30 soccer players, natives of the ecologically favorable region of Uzbekistan. All volunteers had anthropometric measurements, concentrations of insulin-like growth factor-1 (IGF-1), total testosterone (TT), estradiol (E2), cortisol (C), RBC, and Hb count. Moreover, Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1) and professional skills tests such as dribbling shuttle test (DSt) and goal accuracy test (GAt) were assessed. When comparing the CG group to the EG group, it was observed that the EG group exhibited statistically significantly reduced levels of TT and E2 (p < 0.05). No significant statistical difference was observed between the two groups in terms of IGF-1 and C (p > 0.05). Regarding hematological parameters, Hb, Ht, and mean corpuscular volume (MCV) were found to be significantly lower in the EG compared with the CG (p < 0.05). Moreover, the distance covered in the YYIR1 test was found to be significantly lower in soccer players within the EG compared with the CG (p < 0.05). Additionally, it was determined that there was no significant difference between the groups in terms of DSt and GAt values (p > 0.05). Lastly, significant differences were observed between the EG and CG in terms of anthropometric characteristics (diameters, skinfold, and somatotype profile) (p < 0.05). The present study showed that the changes in evaluated characteristics might result from the complex influence of endocrine-disrupting chemicals, the content of which is high in the environment of the Aral Sea region. The results obtained may help monitor the health of athletes living in an environmentally unfriendly environment.



#6 Match Running Performance Profile and Heart Rate Response in Amputee Soccer Players

Reference: Int J Environ Res Public Health. 2023 Jul 13;20(14):6357. doi: 10.3390/ijerph20146357.

Authors: Foteini-Vasiliki Panagiotopoulou, Yiannis Michailidis, Athanasios Mandroukas, Aris Mavropoulos, Vasilios Tsimaras, Pantelis T Nikolaidis, Kosmas Christoulas, Thomas Metaxas

Summary: The purpose of this study was (a) to create a profile of the running performances of male amputee soccer players in different speed zones, (b) to investigate the relationship between heart rate (HR) and running distance in two soccer matches, and (c) to study the effect of the level of amputation on the running distance covered during a match. The participants were male amputee soccer players (n = 10, Greek, n = 5; Belgian, n = 5) who played two international, friendly matches. Distances were measured using a global positioning system, and HRs were recorded using a Polar Team Pro. No differences in the distances covered were observed between participants with different levels of amputation (p > 0.05). Nevertheless, there was a trend that participants with a below-the-knee amputation tended to cover longer distances in total (difference +262.3 m, Cohen's d = 0.40) and in zones 2 (+324.4 m, d = 0.79), 3 (+ 7.1 m, d = 0.65), 4 (+22.7 m, d = 0.43), and 5 (+0.4 m, d = 0.20) and less distance in zone 1 (-207.2 m, d = 0.88). They also tended to perform more accelerations (+3.9, d = 0.89) and decelerations (+4.2, d = 0.87) and had a higher mean HR (+8.4%, d = 2.04) than those with an above-the-knee amputation. Moreover, the mean HR corresponded to 83.3% of the HRmax and did not correlate with distance in any speed zone. It was concluded that the level of amputation might influence running performance and acute physiological response during a soccer match.



#7 Replicative Study in Performance-Related Genes of Brazilian Elite Soccer Players Highlights Genetic Differences from African Ancestry and Similarities between Professional and U20 Youth Athletes

Reference: Genes (Basel). 2023 Jul 14;14(7):1446. doi: 10.3390/genes14071446.

Authors: Tane Kanope, Caleb G M Santos, Feliciana Marinho, Gustavo Monnerat, Mario Campos-Junior, Ana Carolina P da Fonseca, Verônica M Zembrzuski, Miller de Assis, Michael W Pfaffl, Eduardo Pimenta

Summary: Classically, genetic association studies have attempted to assess genetic polymorphisms related to human physiology and physical performance. However, the heterogeneity of some findings drives the research to replicate, validate, and confirmation as essential aspects for ensuring their applicability in sports sciences. Genetic distance matrix and molecular variance analyses may offer an alternative approach to comparing athletes' genomes with those from public databases. Thus, we performed a complete sequencing of 44 genomes from male Brazilian first-division soccer players under 20 years of age (U20_BFDSC). The performance-related SNP genotypes were obtained from players and from the "1000 Genomes" database (European, African, American, East Asian, and South Asian). Surprisingly, U20_BFDSC performance-related genotypes had significantly larger FST levels (p < 0.00001) than African populations, although studies using ancestry markers have shown an important similarity between Brazilian and African populations (12-24%). U20_BFDSC were genetically similar to professional athletes, showing the intense genetic selection pressure likely to occur before this maturation stage. Our study highlighted that performance-related genes might undergo selective pressure due to physical performance and environmental, cognitive, and sociocultural factors. This replicative study suggests that molecular variance and Wright's statistics can yield novel conclusions in exercise science.



#8 Another Way to Confuse Motor Control: Manual Technique Supposed to Shorten Muscle Spindles Reduces the Muscular Holding Stability in the Sense of Adaptive Force in Male Soccer Players

Reference: Brain Sci. 2023 Jul 21;13(7):1105. doi: 10.3390/brainsci13071105.

Authors: Frank N Bittmann, Silas Dech, Laura V Schaefer

Summary: Sensorimotor control can be impaired by slacked muscle spindles. This was shown for reflex responses and, recently, also for muscular stability in the sense of Adaptive Force (AF). The slack in muscle spindles was generated by contracting the lengthened muscle followed by passive shortening. AF was suggested to specifically reflect sensorimotor control since it requires tension-length control in adaptation to an increasing load. This study investigated AF parameters in reaction to another, manually performed slack procedure in a preselected sample (n = 13). The AF of 11 elbow and 12 hip flexors was assessed by an objectified manual muscle test (MMT) using a handheld device. Maximal isometric AF was significantly reduced after manual spindle technique vs. regular MMT. Muscle lengthening started at 64.93 ± 12.46% of maximal voluntary isometric contraction (MVIC). During regular MMT, muscle length could be maintained stable until 92.53 ± 10.12% of MVIC. Hence, muscular stability measured by AF was impaired after spindle manipulation. Force oscillations arose at a significantly lower level for regular vs. spindle. This supports the assumption that they are a prerequisite for stable adaptation. Reduced muscular stability in reaction to slack procedures is considered physiological since sensory information is misled. It is proposed to use slack procedures to test the functionality of the neuromuscular system, which is relevant for clinical practice.



#9 The Effects of FIFA 11+ Kids Prevention Program on Kinematic Risk Factors for ACL Injury in Preadolescent Female Soccer Players: A Randomized Controlled Trial

Reference: Children (Basel). 2023 Jul 12;10(7):1206. doi: 10.3390/children10071206.

Authors: Maedeh Taghizadeh Kerman, Claudia Brunetti, Ali Yalfani, Ahmad Ebrahimi Atri, Chiarella Sforza

Summary: This study aimed to investigate the effects of the 8-week FIFA 11+ Kids program on kinematic risk factors for ACL injury in preadolescent female soccer players during single-leg drop landing. For this, 36 preadolescent female soccer players (10-12 years old) were randomly allocated to the FIFA 11+ Kids program and control groups (18 players per group). The intervention group performed the FIFA 11+ Kids warm-up program twice per week for 8 weeks, while the control group continued with regular warm-up. Trunk, hip, and knee peak angles (from initial ground contact to peak knee flexion) were collected during the single-leg drop landing using a 3D motion capture system. A repeated measure ANOVA was used to analyze groups over time. Significant group × time interactions were found for the peak knee flexion, with a medium effect size (p = 0.05; effect size = 0.11), and peak hip internal rotation angles, with a large effect size (p < 0.01; effect size = 0.28). We found that the FIFA 11+ Kids program was effective in improving knee flexion and hip internal rotation, likely resulting in reducing ACL stress during single-leg drop landing in young soccer players.



#10 Oxidative Stress and Performance after Training in Professional Soccer (European Football) Players

Reference: Antioxidants (Basel). 2023 Jul 22;12(7):1470. doi: 10.3390/antiox12071470.

Authors: Michele Abate, Raffaello Pellegrino, Angelo Di Iorio, Vincenzo Salini

Summary: Vitamins, hormones, free radicals, and antioxidant substances significantly influence athletic performance. The aim of this study was to evaluate whether these biological mediators changed during the season and if this was associated with the rate of improvement in performance after training, assessed by means of a standardized test. Professional male soccer players took part in the study. Two evaluations were performed: the first in the pre-season period and the second at the mid-point of the official season, after about 6 months of intensive training and weekly matches. Blood levels of vitamins D, B12, and folic acid, testosterone and cortisol, free radicals, and antioxidant substances were measured. Two hours after breakfast, a Yo-Yo test was performed. The relationships between the biological mediators and the rate of improvement after training (i.e., the increase in meters run in the Yo-Yo test between the pre-season and mid-season periods) were evaluated by means of a linear mixed models analysis. Results: Eighty-two paired tests were performed. The athletes showed better performance after training, with an increase in the meters run of about 20%. No significant relationships between the vitamin and hormone values and the gain in the performance test were observed. Plasmatic levels of free radicals increased significantly, as did the blood antioxidant potential. An indirect relationship between oxidative stress and the improvement in performance was observed (free radicals β ± SE: = -0.33 ± 0.10; p-value = 0.001), with lower levels of oxidative stress being associated with higher levels of performance in the Yo-Yo test. Monitoring the measures of oxidative stress could be a useful additional tool for coaches in training and/or recovery programs tailored to each player.



#11 The Effect on Flexibility and a Variety of Performance Tests of the Addition of 4 Weeks of Soleus Stretching to a Regular Dynamic Stretching Routine in Amateur Female Soccer Players

Reference: Sports (Basel). 2023 Jul 19;11(7):138. doi: 10.3390/sports11070138.

Authors: Mohammad Alimoradi, Mansour Sahebozamani, Elham Hosseini, Andreas Konrad, Sajad Noorian

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Summary: The purpose of this study was to investigate the effects of 4 weeks of soleus stretching on ankle flexibility and dynamic balance, as well as selected monitoring and performance tests in soccer. Forty-five healthy female soccer players were randomly divided into a regular stretching group, a regular stretching group with soleus stretching, and a control group. Dynamic stretching protocols were performed for 4 weeks during three sessions per week as part of routine exercises. The regular group stretched three muscle groups (i.e., gastrocnemius, quadriceps, and hamstrings), while the regular + soleus group also stretched the soleus muscle. Before and after the stretching intervention, the ankle range of motion test, Y-balance test, drop jump test, dynamic knee valgus test, and Illinois Agility Running Test were performed. Ankle ROM, Y-balance, and DJ significantly improved in both intervention groups compared to controls. Only the regular + soleus group showed improvement in the Illinois Agility Running Test. Additionally, athletes performing the additional soleus stretching had greater improvements in ankle ROM and DJ but not in DKV or Y-balance. The results showed that adding soleus stretching into regular protocols can provide benefits for female soccer players in terms of performance parameters.



#12 The effect of beetroot juice (Beta Vulgaris L.) supplementation on ṼO2max of youth soccer athletes

Reference: J Public Health Afr. 2022 Dec 7;13(Suppl 2):2406. doi: 10.4081/jphia.2022.2406.

Authors: Fajar Rachman Adji, Zaenal M Sofro, Mirza Hapsari

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Summary: Soccer athletes' performance is influenced by perfect ṼO2max. However, athletes often receive rigorous exercise without being supported by proper nutrition which can lead to oxidative stress. It is necessary to maintain performance by supplementing beetroot juice which contains betalains and inorganic nitrates so that oxidative stress can be controlled. This research is aimed to determine the effect of beetroot juice on the ṼO2max of soccer athletes. By using true experimental with randomized pre-test post-test control group design, 16 healthy males aged 16-19 years old were divided into two groups, treatment, and control. Data were analyzed by independent sample t-test and paired t-test. There is a significant difference in weight and body mass index (p<0.05). There is no significant difference in age, height, pre-body fat, post-body fat, Δbody fat, nutrition intake, school hours, sleep hours, and physical exercise as well as ṼO2max before and after intervention (p>0.05). There is a significant difference in ṼO2max change in both groups (p<0.05). Thus, both beetroot juice and placebo significantly affected the increase of ṼO2max levels in soccer athletes.



#13 Effects of Aerobic and Speed Training Versus Active Control on Repeated Sprint Ability and Measures of Self-confidence and Anxiety in Highly Trained Male Soccer Players

Reference: Sports Med Open. 2023 Jul 27;9(1):63. doi: 10.1186/s40798-023-00619-y.

Authors: Walid Selmi, Raouf Hammami, Sofien Kasmi, Sonia Sehli, Haithem Rebai, Michael Duncan, Mokhtar Chtara, Urs Granacher

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Summary: While there is ample evidence on the effects of single-mode aerobic and speed training on physical fitness in soccer players, less is known on the combined effects of these exercise regimens on physical and psychological factors. This study aimed to compare the effects of aerobic and speed training with soccer-specific training versus soccer-specific training only on aerobic performance during the YOYO intermittent fitness test level 1 (final velocity, total distance [TD], maximal oxygen consumption [VO2max]), repeated sprint ability (best, total sprint time [RSABT, RSATT], sprint decrement [RSA dec]) performance and somatic anxiety (SA), cognitive anxiety (CA), and self-confidence (SC) adaptations in soccer players. Thirty-eight highly trained male athletes aged 18.9 ± 0.5 years were randomly assigned to an aerobic and speed training group (COMB-G; n = 20) or an active control group (CON-G; n = 18). Aerobic training comprised intermittent exercises at 110-120% of the final velocity achieved at the end of the YOYO IL1 test. Speed training involved maximal sprints over 15-20-m with 5-6 sets per session. Aerobic or speed training lasted 20 min per session and replaced parts of the soccer-specific training. CON-G performed the soccer-specific training including technical, tactical drills and small-sided games. Training volume was similar between groups. Pre, post intervention, all participants performed a repeated-sprint ability (RSA) test, the YO-YO IL1 test and the players completed a Competitive Scale Anxiety Inventory (CSAI-2). A two (group: COMB-G, CON-G) by two (time: pre, post) mixed ANOVA (group-by-time) was computed. Significant group-by-time interactions were found for RSATT (F = 117.3; p < 0.001; Pη2 = 1.78), RSABT (F = 82.4; p < 0.001; Pη2 = 1.53), final velocity (F = 85.8; p < 0.001; Pη2 = 1.53), TD (F = 87.1; p < 0.001; Pη2 = 1.56), and VO2max (F = 18.0; p < 0.001; Pη2 = 0.72). In addition, significant group-by-time interactions were observed for SC (F = 90.2; p < 0.001; d = 1.60), SA (F = 60.5; p < 0.001; Pη2 = 1.70), and CA (F = 20.7; p < 0.001; Pη2 = 0.75). Post-hoc analyses indicated significant improvements for all dependent variables from pre- to post-training in favor of COMB-G. Aerobic and speed training in combination with soccer-specific training is a safe and effective training method as it exerts positive effects not only for physical fitness but also for self-confidence and the coping of anxiety in male soccer players.



#14 Effects of Flywheel vs. Free-Weight Squats and Split Squats on Jumping Performance and Change of Direction Speed in Soccer Players

Reference: Sports (Basel). 2023 Jun 23;11(7):124. doi: 10.3390/sports11070124.

Authors: Jakub Jarosz, Paulina Królikowska, Patryk Matykiewicz, Piotr Aschenbrenner, Paulina Ewertowska, Michał Krzysztofik

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Summary: The objective of this study was to compare (i) The effects of a flywheel and free-weight resistance training program; and (ii) The effects of performing lateral and frontal split squats as part of a flywheel-resistance training program on jumping performance, the 5-0-5 change of direction test time, and the one-repetition maximum (1RM) back squat in soccer players. Twenty-four male amateur soccer players participated in this study and were randomly and equally assigned to one of three different test groups: forward split-squat group (FSQ); lateral split-squat group (LSQ); and free-weight training group (TRAD). Athletes in the FSQ group performed a squat and a forward split squat on a flywheel device, while those in the LSQ group performed a squat and a lateral split squat (instead of a forward split squat) on a flywheel device. Each training lasted 4 weeks. The main finding was that all training groups, such as TRAD, FSQ, and LSQ, significantly improved broad jump length (p = 0.001; effect size [ES] = 0.36), 5-0-5 COD time with a turn on the dominant limb (p = 0.038; ES = 0.49), and 1RM back squat (p = 0.001; ES = 0.4). In turn, both flywheel-resistance training groups (FSQ and LSQ) significantly improved their counter-movement jump height (p = 0.001; ES = 0.8 and p = 0.002; ES = 0.58; respectively) with no effect in the TRAD (p = 0.676; ES = 0.07) training group. Both free-weight and flywheel-resistance training lasting 4 weeks performed in-season contributed to significant improvement in 1RM back squat, broad jump performance, and 5-0-5 change of direction testing time, while flywheel-resistance training might be superior in counter-movement jump height enhancement in soccer players. Moreover, the manner in which split squats were performed was not a factor influencing the obtained results.



#15 Star Excursion Balance Test as a Predictor of Musculoskeletal Injury and Lower Back Pain in Non-Professional Soccer Players

Reference: Sports (Basel). 2023 Jul 6;11(7):129. doi: 10.3390/sports11070129.

Authors: Iva Sklempe Kokic, Katarina Petric, Danijela Kuna, Stjepan Jelica, Tomislav Kokic

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Summary: Soccer is a sport with worldwide popularity but has a substantial risk of injury. Clinical screening tools are an important factor in strategies of injury prevention. The purpose of the study was to examine the relationship between the Star Excursion Balance Test (SEBT) and injury and lower back pain (LBP) in amateur soccer players. The research was performed as a longitudinal cohort study on 42 amateur male soccer players with 15.8 ± 6.6 years of soccer playing (age: 25.5 ± 6 years). Participants were surveyed with regard to their soccer playing, injuries, and LBP, and the SEBT was performed. They were followed for 3.5 months. At the follow-up, an additional set of data regarding injuries and LBP was gathered. Significant differences were found in all directions and in the composite score of the SEBT between uninjured and injured players. Shorter distance in all directions and a lower composite score were associated with injury in general. Shorter distances in all but the anterior direction and a lower composite score were associated with lower extremity injury, and shorter anterior distance was associated with LBP. Amateur soccer players with lower SEBT scores are more prone to injuries in general, as well as injuries of the lower extremities. SEBT presents as a useful clinical screening tool in identifying amateur soccer players at risk of injury.






Effects of High-Intensity Position-Specific Drills on Physical and Technical Skill Performance in Elite Youth Soccer Players

The purpose of this study was to investigate the feasibility and short-term effects of a novel position-specific conditioning training (PSCT) paradigm on physical and technical abilities of young soccer players.





Effects of substitute allowance on match activity characteristics in Japanese professional football across 2019, 2020, and 2021 seasons

This study aimed to examine the effects of substitute player allowance per match on running performance in Japanese professional football over three consecutive seasons with different numbers of maximum substitutes.





Latest research in football - week 28 - 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 Prediction of defensive success in elite soccer using machine learning - Tactical analysis of defensive play using tracking data and explainable AI

Reference: Sci Med Footb. 2023 Jul 21. doi: 10.1080/24733938.2023.2239766. Online ahead of print.

Authors: Leander Forcher, Tobias Beckmann, Oliver Wohak, Christian Romeike, Ferdinand Graf, Stefan Altmann

Summary: The interest in sports performance analysis is rising and tracking data holds high potential for game analysis in team sports due to its accuracy and informative content. Together with machine learning approaches one can obtain deeper and more objective insights into the performance structure. In soccer, the analysis of the defense was neglected in comparison to the offense. Therefore, the aim of this study is to predict ball gains in defense using tracking data to identify tactical variables that drive defensive success. We evaluated tracking data of 153 games of German Bundesliga season 2020/21. With it, we derived player (defensive pressure, distance to the ball, & velocity) and team metrics (inter-line distances, numerical superiority, surface area, & spread) each containing a tactical idea. Afterwards, we trained supervised machine learning classifiers (logistic regression, XGBoost, & Random Forest Classifier) to predict successful (ball gain) vs. unsuccessful defensive plays (no ball gain). The expert-reduction-model (Random Forest Classifier with 16 features) showed the best and satisfying prediction performance (F1-Score (test) = 0.57). Analyzing the most important input features of this model, we are able to identify tactical principles of defensive play that appear to be related to gaining the ball: press the ball leading player, create numerical superiority in areas close to the ball (press short pass options), compact organization of defending team. Those principles are highly interesting for practitioners to gain valuable insights in the tactical behavior of soccer players that may be related to the success of defensive play.



#2 Finite element brain deformation in adolescent soccer heading

Reference: Comput Methods Biomech Biomed Engin. 2023 Jul 21;1-11. doi: 10.1080/10255842.2023.2236746. Online ahead of print.

Authors: Colin M Huber, Declan A Patton, Jalaj Maheshwari, Zhou Zhou, Svein Kleiven, Kristy B Arbogast

Summary: Finite element (FE) modeling provides a means to examine how global kinematics of repetitive head loading in sports influences tissue level injury metrics. FE simulations of controlled soccer headers in two directions were completed using a human head FE model to estimate biomechanical loading on the brain by direction. Overall, headers were associated with 95th percentile peak maximum principal strains up to 0.07 and von Mises stresses up to 1450 Pa, and oblique headers trended toward higher values than frontal headers but below typical injury levels. These quantitative data provide insight into repetitive loading effects on the brain.



#3 Determining the effect of one decade on fitness of elite Austrian youth soccer players using propensity score matching

Reference: Front Sports Act Living. 2023 Jul 5;5:1186199. doi: 10.3389/fspor.2023.1186199. eCollection 2023.

Authors: Christoph Gonaus, Erich Müller, Thomas Stöggl, Jürgen Birklbauer

Summary: Current trends in attacking strategies and increases in external workload have led to a need for fast and well-conditioned athletes in modern soccer. More recently, progressions in speed, coordination, power and endurance were found over a decade in elite Austrian youth players. However, possible confounders such as relative age, maturation, learning effects, and academy philosophy may have influenced these changes. The present study aimed to determine the decade effect on fitness under statistical control of players' exact age, height, body mass, test location as well as total number of pretests and time interval between test and pretest. Players annually completed a battery of anthropometric, general and soccer-specific fitness tests. MANCOVA was calculated to identify the overall impacts of the covariates on fitness. To balance the covariates of initially 2,530 "former" (2002 to 2005) and 2,611 "recent" (2012 to 2015) players, 1:1 nearest neighbor propensity score (PS) matching was used, resulting in 587 U13, 573 U14, 475 U15, 325 U16, 262 U17, and 129 U18 matched pairs. The decade effect on fitness was assessed by independent t-tests and Cohen's d separately at each age group. Superior performances of recent players were found for linear sprint across all age categories (d = 0.154-0.476) as well as for agility (d = 0.125-0.340) and change-of-direction speed (d = 0.172-0.466) in U15 to U18. Reaction speed increased in U13 (d = 0.288) and U15 (d = 0.310). Flexibility reduced over the decade in all age categories (d = -0.151 to -0.589) and upper-limb power decreased (d = -0.278 to -0.347) in U13 and U14. Balancing the covariate distribution via PS matching generally confirmed previous findings, with fitness decade effects reflecting the athletic needs for modern soccer. Since fitness performance changed over time, reference values should be periodically updated. Coaches favor both physical and cognitive fast players nowadays. Thus, training should target all aspects of speed, without disregarding flexibility, upper-limb power and other preventive strategies that keep the players on the pitch.



#4 The Effect of COVID-19 on Home Advantage in Women's Soccer: Evidence From Swedish Damallsvenskan

Reference: Am Behav Sci. 2023 Sep;67(10):1168-1178. doi: 10.1177/00027642221118259. Epub 2022 Aug 23.

Authors: Alex Krumer, Vetle A O Smith

Summary: Most studies of the effect of COVID-19 restrictions on home advantage have been conducted on men's soccer, with the women's game lacking scientific attention. The present study fills this gap by investigating games in Swedish Damallsvenskan women's soccer league. Comparing games in the 2019 and 2020 seasons, we find a slight, but not statistically significant reduction in home advantage in games without crowds in terms of goals scored and points achieved. However, unlike in most studies on men's soccer, we find that away teams received significantly more yellow cards in games without crowds compared to games with crowds. We discuss our results in the context of the findings in men's soccer.



#5 Pre-sleep feeding, sleep quality, and markers of recovery in division I NCAA female soccer players

Reference: J Int Soc Sports Nutr. 2023 Dec;20(1):2236055. doi: 10.1080/15502783.2023.2236055.

Authors: Casey E Greenwalt, Elisa Angeles, Matthew D Vukovich, Abbie E Smith-Ryan, Chris W Bach, Stacy T Sims, Tucker Zeleny, Kristen E Holmes, David M Presby, Katie J Schiltz, Marine Dupuit, Liliana I Renteria, Michael J Ormsbee

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Summary: Pre-sleep nutrition habits in elite female athletes have yet to be evaluated. A retrospective analysis was performed with 14 NCAA Division I female soccer players who wore a WHOOP, Inc. band - a wearable device that quantifies recovery by measuring sleep, activity, and heart rate metrics through actigraphy and photoplethysmography, respectively - 24 h a day for an entire competitive season to measure sleep and recovery. Pre-sleep food consumption data were collected via surveys every 3 days. Average pre-sleep nutritional intake (mean ± sd: kcals 330 ± 284; cho 46.2 ± 40.5 g; pro 7.6 ± 7.3 g; fat 12 ± 10.5 g) was recorded. Macronutrients and kcals were grouped into high and low categories based upon the 50th percentile of the mean to compare the impact of a high versus low pre-sleep intake on sleep and recovery variables. Sleep duration (p = 0.10, 0.69, 0.16, 0.17) and sleep disturbances (p = 0.42, 0.65, 0.81, 0.81) were not affected by high versus low kcal, PRO, fat, CHO intake, respectively. Recovery (p = 0.81, 0.06, 0.81, 0.92), RHR (p = 0.84, 0.64, 0.26, 0.66), or HRV (p = 0.84, 0.70, 0.76, 0.93) were also not affected by high versus low kcal, PRO, fat, or CHO consumption, respectively. Consuming a small meal before bed may have no impact on sleep or recovery.



#6 Factors Associated with Children's Physical Activity During Youth Soccer Practices

Reference: Res Q Exerc Sport. 2023 Jul 19;1-7. doi: 10.1080/02701367.2023.2225563. Online ahead of print.

Authors: Emily R Shull, Kerry McIver, Alexander C McLain, Eva Monsma, Russell R Pate

Summary: The aim was to identify practice and social contextual factors that associate with physical activity (PA) levels of children during their participation in a youth soccer program. Twenty-seven youth soccer teams serving children ages 6-11 years participated. Research staff directly observed and recorded PA intensity and practice and social contextual factors using momentary time-sampling procedures. Each team was observed for 1 practice, during which approximately 6 children were each observed for twenty 30-s observation blocks (10-s observation, 20-s recording). In total, children were observed for 3,102 intervals. Multilevel logistic regression analyses were conducted to describe associations between PA intensity and practice and social contexts. Interaction terms were introduced into the models to determine if the associations differed across girls-only, boys-only, and coed teams. A total of 158 children were observed across the 27 teams. Children were more likely to engage in moderate or vigorous PA while performing fitness (Odds Ratio [OR], 9.9, 95% CI = 5.34-18.04), game (OR, 4.0, 95% CI = 2.88-5.66), warm-up (OR, 2.8, 95% CI = 1.85-4.11), and drill (OR, 1.9, 95% CI = 1.41-2.67) activities compared to tactic/instructional activities. The associations between PA intensity levels and practice and social contexts did not differ across girls-only, boys-only, and coed teams. Fitness activities and full-team game play were associated with higher PA intensity levels during children's participation in youth soccer practices. Youth sport practice protocols can be modified to increase children's physical activity.



#7 Effects of peripheral electromagnetic stimulation after an eccentric exercise-induced delayed-onset muscle soreness protocol in professional soccer players: a randomized controlled trial

Reference: Front Physiol. 2023 Jul 3;14:1206293. doi: 10.3389/fphys.2023.1206293. eCollection 2023.

Authors: Hugo Keriven, Alberto Sánchez-Sierra, Diego Miñambres-Martín, Ángel González de la Flor, Guillermo García-Pérez-de-Sevilla, Diego Domínguez-Balmaseda

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Summary: The aim was to examine the effects of peripheral electromagnetic stimulation in male professional soccer players on markers of Delayed Onset Muscular Soreness (DOMS), induced by a protocol of exercise (60 min of eccentric and plyometric). A randomized controlled trial with fourty-five professional soccer players aged 22.33 ± 4.82 years participated in the study. Twenty-three participants were assigned to the experimental group with peripheral electromagnetic stimulation (5 stimulations of 5 s at 100 HZ with 55 s of rest for a total of 5 min of treatment) and the remaining 22 participants were assigned to the control group. Pain pressure threshold (PPT) of the vastus medialis, the Visual Analogue Scale-Fatigue (VAS-F), half squat (HS) test and the maximum voluntary contraction of the quadriceps were assessed. All evaluations were performed before and after 1 h of the eccentric exercise induced DOMS, as well as at post 24-48, and 72 h. Group-by-time interaction was observed in PPT of the vastus medialis (p = 0.040) with a medium effect size (η2 p = 0.069). From 48 to 72 h the experimental group showed an increase of PPT compared to control group (p = 0.015). There was no group-by-time interaction for HS, quadriceps strength and VAS-F (p > 0.05). Peripheral electromagnetic stimulation in male professional soccer players did not produce significant improvements in the power and strength of the lower limbs but decreased the peripheral sensitization of the vastus medialis after eccentric exercise protocol.



#8 Effects of dietary supplements on athletic performance in elite soccer players: a systematic review

Reference: J Int Soc Sports Nutr. 2023 Dec;20(1):2236060. doi: 10.1080/15502783.2023.2236060.

Authors: Rodrigo Abreu, Catarina B Oliveira, Júlio A Costa, João Brito, Vitor H Teixeira

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Summary: Dietary supplements are widely used among athletes, and soccer players are no exception. Nevertheless, evidence supporting the use of dietary supplements aiming to enhance performance in soccer is somewhat contradictory, scarce, or even nonexistent. Thus, the present study aimed to systematically review and synthesize the effects of dietary supplements on athletic performance (e.g. distance covered, sprinting, jump performance) in elite soccer players. Studies enrolling highly trained, elite, and world-class soccer players using dietary supplements were searched in MEDLINE/PubMed, Web of Science, Scopus, and EBSCO databases in June 2022. In total, 1043 studies were identified, and 18 met the eligibility criteria. The studies evaluated the impacts on athletic performance of several dietary supplements, including caffeine, creatine, protein, beverages with carbohydrates and electrolytes, tart cherry juice, nitrate-rich beetroot juice, sodium bicarbonate with minerals, yohimbine, and a proprietary nutraceutical blend. Caffeine supplementation in doses between 3 and 6 mg/kg of body mass may improve jump height and sprint ability, particularly in female players, but individual response to caffeine must be considered. Creatine may improve sprint, agility, and in female players, jump performance. Protein supplementation can improve sprint and jump performance between matches, especially if protein ingested from food is not up to recommendations. Beverages containing carbohydrates and electrolytes can be used as part of the strategies to achieve carbohydrate intake during training and match-days but used alone do not benefit athletic performance. Tart cherry juice might be useful for maintaining athletic performance after matches that produce higher force loss and exercise-induced muscle damage, although polyphenols from the diet might attenuate the effects of tart cherry supplementation. Nitrate-rich beetroot concentrate can attenuate performance decrease in the days following matches. Further investigation with sodium bicarbonate alone is necessary, as supplementation protocols with elite players included other substances. Finally, the available data does not support yohimbine supplementation or the use of Resurgex Plus® to improve athletic performance in elite soccer players. Still, more well-designed research with elite soccer players is needed to improve support and advice regarding the use of dietary supplements for athletic performance enhancement.



#9 Quality of Life of Following Mild Traumatic Brain Injury in Youth Soccer Players Title Page

Reference: J Athl Train. 2023 Jul 18. doi: 10.4085/1062-6050-0011.23. Online ahead of print.

Authors: Scott L Rosenthal, Tess S Simpson, Michael W Kirkwood, Robin L Peterson

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Summary: Pediatric mild traumatic brain injuries (mTBI) represent an evolving field of interest in youth athletics. While most players recover within 4 weeks, some have symptoms that last longer. Little is known about youth health-related quality of life (HRQoL) following mTBI. The aim was to characterize youth HRQoL following soccer-related mTBI and to identify predictors of individual differences in HRQoL recovery. Soccer players, ages 8-17 years, who sustained mTBI (n=23), orthopedic injuries (OI, n=24), or remained uninjured (n=23) during a single season participated in this study. HRQoL was assessed via the Pediatric Quality of Life Version 4.0 and post-concussive symptomatology via the Health and Behavior Index. Serial assessments occurred at 24-48 hours, 7 days, 30 days and 90 days post-injury via telephone interview. Seven days post-injury, the mTBI and OI groups had poorer Total HRQoL (F[2,67] =11.35, p<0.001) than uninjured controls. At 7 days, the mTBI group had the poorest Psychosocial HRQoL, while OI had the poorest Physical HRQoL. Differences between the mTBI group and uninjured controls resolved by 30 days. Within the mTBI group, players with significant post-concussive symptoms at 7 days had poorer Total (F[1,21]=23.071, p<=0.001; F[1,21]=5.798, p=0.028), Psychosocial (F[1,21]=16.488, p=<0.001; F[1,21]=5.050, p=0.039), and Physical HRQoL (F[1,21]=21.671, p=<0.001; F[1,21]=5.119, p=0.038) at 7 and 30 days than players with minimal symptoms, and these differences resolved by 90 days. As a groups, youth soccer players who sustained mTBI had transient impairments in HRQoL that resolved by 30 days. A subset of players with significant post-concussive symptoms at 7 days post-injury have poorer HRQoL for at least 30 days post-injury than those whose post-concussive symptoms had resolved within a week of injury. This suggests ongoing recovery in this subset at 30 days and potential utility of HRQoL as a measure of recovery.



#10 Cognitive Function and Heading Frequency Among Retired Professional Soccer Players-Heading for Clarity?

Reference: JAMA Netw Open. 2023 Jul 3;6(7):e2324368. doi: 10.1001/jamanetworkopen.2023.24368.

Authors: Peter Ueda

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#11 Heading Frequency and Risk of Cognitive Impairment in Retired Male Professional Soccer Players

Reference: JAMA Netw Open. 2023 Jul 3;6(7):e2323822. doi: 10.1001/jamanetworkopen.2023.23822.

Authors: Shima Espahbodi, Eef Hogervorst, Tara-Mei Povall Macnab, Ahmed Thanoon, Gwen Sacha Fernandes, Bonnie Millar, Ashley Duncan, Maria Goodwin, Mark Batt, Colin W Fuller, Gordon Fuller, Eamonn Ferguson, Tobias Bast, Michael Doherty, Weiya Zhang

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Summary: Although professional soccer players appear to be at higher risk of neurodegenerative disease, the reason remains unknown. The aim was to examine whether heading frequency is associated with risk of cognitive impairment in retired professional soccer players. A UK nationwide cross-sectional study was conducted between August 15, 2020, and December 31, 2021, in 459 retired male professional soccer players older than 45 years and registered with the Professional Footballers' Association or a League Club Players' Association. Data on heading frequency in 3 bands-0 to 5, 6 to 15, and more than 15 times per match or training session and other soccer-specific risk factors, such as player position and concussion-were collected through a self-reported questionnaire. Cognitive impairment was defined using the Telephone Interview for Cognitive Status-modified as scores of less than or equal to 21. Hopkins Verbal Learning Test, verbal fluency, and independent activities of daily living were also assessed. Test Your Memory and physician-diagnosed dementia/Alzheimer disease were self-reported via the questionnaire. Adjusted odds ratios (AORs) with 95% CIs were calculated. Of 468 retired male professional soccer players who completed questionnaires (mean [SD] age, 63.68 [10.48]; body mass index, 27.22 [2.89]), 459 reported heading frequency: 114 headed 0 to 5 times, 185 headed 6 to 15 times, 160 headed more than 15 times per match, and 125 headed 0 to 5 times, 174 headed 6 to 15 times, and 160 headed more than 15 times per training session during their careers. The prevalence of cognitive impairment was 9.78% (0-5 times), 14.78% (6-15 times), and 15.20% (>15 times) per match (P = .51). Compared with players reporting 0 to 5 headers per match, the AORs were 2.71 (95% CI, 0.89-8.25) for players reporting 6 to 15 headers per match and 3.53 (95% CI, 1.13-11.04) for players reporting more than 15 headers per match (P = .03 for trend). Corresponding AORs for heading frequency per training session were 2.38 (95% CI, 0.82-6.95) for those reporting 6 to 15, and 3.40 (95% CI, 1.13-10.23) for those reporting more than 15 in comparison with those who reported 0 to 5 (P = .03 for trend). Concussion involving memory loss was also associated with a greater risk of cognitive impairment (AOR, 3.16; 95% CI, 1.08-9.22). Similar results were observed with other cognitive tests and self-reported physician-diagnosed dementia/Alzheimer disease. The findings of this study suggest that repetitive heading during a professional soccer career is associated with an increased risk of cognitive impairment in later life. Further study is needed to establish the upper threshold for heading frequency to mitigate this risk.



#12 Streaming the beautiful game: exploring big tech's growing presence in the soccer industry

Reference: Front Sports Act Living. 2023 Jun 29;5:1156601. doi: 10.3389/fspor.2023.1156601. eCollection 2023.

Authors: Alexis Fakataulavelua, Markus Lang, Jérémy Moulard

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Summary: This study investigates the evolving role of major technology corporations-namely, Amazon, Apple, Microsoft, Facebook, Netflix, and Google-in the sports industry, with a specific focus on soccer. By employing a qualitative content analysis of media reports, scientific literature, and annual reports from 2000 to 2021, the research scrutinizes the varying approaches and investments of these tech giants in the domain of sports. The findings classify these companies into three distinct categories: (1) those actively securing broadcast rights for major competitions and leagues (Google, Facebook, Amazon); (2) those primarily producing and disseminating soccer documentaries (Netflix); and (3) those not directly engaging in media rights but advancing the technological aspects of clubs and leagues (Apple and Microsoft). This study underscores the escalating significance of Big Tech in reshaping the sports media landscape and calls for further research to comprehend the broader implications of their presence in sports broadcasting and fan engagement.



#13 Effects of combined plyometric, strength and running technique training program on change-of-direction and countermovement jump: A two-armed parallel study design on young soccer players

Reference: Gait Posture. 2023 Jul 1;105:27-34. doi: 10.1016/j.gaitpost.2023.06.025. Online ahead of print.

Authors: Ricardo Martín-Moya, Ana Filipa Silva, Filipe Manuel Clemente, Francisco Tomás González-Fernández

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Summary: Players must be capable to have a good change-of-direction (COD) skill aiming to be the fastest as possible to react immediately to the opponent or even to help players to be more agile since COD is a physical determinant of agility. Thus, the aim of this study was to test the effects of a six-week combined training intervention in the COD and countermovement jump (CMJ) of young soccer players, while comparing with a control group only performing the regular field-based training sessions. A sample of 80 non-professional players (40 experimental group and 40 control group) between the ages of ten and twelve was taken [(Age: 10.70 ± 1.02)]. The tests that were carried out from the beginning to the end of the intervention were: CMJ test, 505COD Test and Illinois Test. Paired sample t-test was used for determining differences as a repeated measures analysis (pre- post). An ANCOVA test was performed using the pretest as a covariate and the times pre and post as factors. Repeated measures ANCOVA revealed significant influence of baseline level on the 5-0-5 COD (p = 0.001; ηp2=0.170), the Illinois (p = 0.018; ηp2=0.070) and the CMJ (p = 0.047; ηp2=0.050). Significant interactions group*time (p < 0.001; ηp2=0.137), 5-0-5 COD (p < 0.001; ηp2=0.274), and CMJ (p < 0.001; ηp2=0.392) were found, while no significant interactions were found in Illinois (p = 0.293; ηp2=0.014). The current research revealed that a combined training intervention consisting of strength training, plyometrics, and running techniques can be significantly beneficial for improving COD performance and CMJ.



#14 Lightweight Football Motion Recognition and Intensity Analysis Using Low-Cost Wearable Sensors

Reference: Appl Bionics Biomech. 2023 Jul 12;2023:2354728. doi: 10.1155/2023/2354728. eCollection 2023.

Authors: Qian Xie, Ning Jin, Shanshan Lu

Summary: In recent years, machine learning has been utilized in health informatics and sports science. There is a great demand and development potential for combining the Internet of Things (IoT) and artificial intelligence (AI) to be applied to football sports. The conventional teaching and training methods of football sports have limited collection and mining of real raw data using wearable devices, and lack human motion capture and gesture recognition based on sports science theories. In this study, a low-cost AI + IoT system framework is designed to recognize football motion and analyze motion intensity. To reduce the communication delay and the computational resource consumption caused by data operations, a multitask learning model is designed to achieve motion recognition and intensity estimation. The model can perform classification and regression tasks in parallel and output the results simultaneously. A feature extraction scheme is designed in the initial data processing, and feature data augmentation is performed to solve the small sample data problem. To evaluate the performance of the designed football motion recognition algorithm, this paper proposes a data extraction experimental scheme to complete the data collection of different motions. Model validation is performed using three publicly available datasets, and the features learning strategies are analyzed. Finally, experiments are conducted on the collected football motion datasets and the experimental results show that the designed multitask model can perform two tasks simultaneously and can achieve high computational efficiency. The multitasking single-layer long short-term memory (LSTM) network with 32 neural units can achieve the accuracy of 0.8372, F1 score of 0.8172, mean average precision (mAP) of 0.7627, and mean absolute error (MAE) of 0.6117, while the multitasking single-layer LSTM network with 64 neural units can achieve the accuracy of 0.8407, F1 score of 0.8132, mAP of 0.7728, and MAE of 0.5966.



#15 Isolated adductor longus avulsion in a young semi-professional football player: Imaging contribution and therapeutic considerations

Reference: J Clin Ultrasound. 2023 Jul 19. doi: 10.1002/jcu.23525. Online ahead of print.

Authors: Michele Abate, Luigi Sammarchi, Roberto Calà, Giacomo Milesi, Carmine Stefano Poerio, Riccardo Del Vescovo, Antonio Corvino, Andrea Delli Pizzi, Giulio Cocco, Vincenzo Salini

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Summary: Adductor longus injuries are usually observed at the proximal musculo-tendinous junction, but isolated tendinous ruptures (i.e., avulsion) at the origin on the pubic bone are uncommon. In this article, we report a new case of isolated adductor longus avulsion that occurred in a young athlete and was treated with conservative therapy. An 18 years old semi-professional football player, in the attempt to reach the ball with his right leg, reported acute pain and functional limitation in his left adductor area. Clinical examination showed tenderness on palpation associated with mild swelling. Manual strength testing of adductor muscles showed weakness and elicited moderate pain in the proximal groin region near the pubic bone. The diagnostic evaluations (ultrasound [3-14 MHz linear probe] and magnetic resonance imaging [1.5 Tesla magnetic field]), performed a few days after the event, showed a complete isolated avulsion of the proximal adductor longus tendon associated with a fluid collection, with a gap of about 9.5 mm from its insertion on the pubic bone. Degenerative alterations (sub-chondral sclerosis, bone edema, erosions, cortical irregularities, calcifications) were found. These findings were crucial in the treatment choice because conservative management is suggested when the gap is below 1 cm and when no important displacement of proximal torn tendon's end at dynamic ultrasound is appreciated. A structured rehabilitation protocol was implemented, allowing the player to come back to his full athletic activity after 146 days. Return to play was allowed when several subjective and objective parameters were fully satisfied (full hip range of motion, pain-free football-specific activities, less than a 5%-10% difference in hip adduction strength between the injured and uninjured legs, advanced anatomical healing of the adductor longus tendon seen on diagnostic exams, and Hip And Groin Outcome Score [HAGOS] scores similar to baseline data). This case report emphasizes the importance of diagnostic imaging and clinical assessments in the management of an adductor longus avulsion with short retraction (about 1 cm). Both imaging techniques are non-invasive and without risks, allow contra-lateral examination and may guide in the treatment choice; moreover, they significantly influence the post-care approach by enabling to fine-tune a safe return to full athletic activity with minor re-injury rate. While US can be used as primary imaging modality, MRI offers a higher level of accuracy.






Better decision-making skills support tactical behaviour and reduce physical wear under physical fatigue in soccer

We examined the influence of accumulated match-play exposure on the occurrence of hamstring strain injury in professional football from 2 teams (Spanish 1st Division, LaLiga) over 3 seasons, and determined specific cut-off points as indicators of injury risk. 





Is ball-possession style more physically demanding than counter-attacking? The influence of playing style on match performance

This study aimed to investigate the effect of offensive playing style (i.e., while in ball possession) on physical and technical match performance during offensive play as well as success-related factors.





Latest research in football - week 27 - 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 Coping with COVID-19: Can a Sense of Coherence and Social Support Play a Protective Role in the Perception of COVID-19 by Polish Women Football Players? A Cross-Sectional Study

Reference: Int J Environ Res Public Health. 2023 Jul 6;20(13):6308. doi: 10.3390/ijerph20136308.

Authors: Anna Ussorowska-Krokosz, Jan Blecharz, Malgorzata Siekanska, Monika Grygorowicz

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Summary: Athletes have demonstrated a significant increase in anxiety and stress connected to the COVID-19 pandemic. Drawing on the theory of salutogenesis, this study examined the relationship between the sense of coherence and social support and competitive elite-level athletes' perception of the COVID-19 pandemic situation. The perceived secondary gains associated with the pandemic were analysed with a quasi-qualitative research methodology. The sample consisted of 204 competitive elite-level female football players aged 14-36 (M = 17.61, SD = 4.42) who completed the Sense of Coherence Questionnaire (SOC-29), the Berlin Social Support Scales (BSSS), and the researchers' own questionnaire to assess the perception of the COVID-19 situation. The results confirmed a relationship between a sense of coherence and coping better with the difficult situation caused by the coronavirus pandemic. No protective role of social support in the adaptive perception of the pandemic situation was identified. The data from the quasi-qualitative study testify to the use of the adversity of the pandemic to grow in many areas of female football players' lives. The sense of coherence was a protective factor in mitigating the negative consequences of the COVID-19 pandemic situation.



#2 Carbohydrate Nutrition and Skill Performance in Soccer

Reference: Sports Med. 2023 Jul 8. doi: 10.1007/s40279-023-01876-3. Online ahead of print.

Authors: Ian Rollo, Clyde Williams

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Summary: In soccer, players must perform a variety of sport-specific skills usually during or immediately after running, often at sprint speed. The quality of the skill performed is likely influenced by the volume of work done in attacking and defending over the duration of the match. Even the most highly skilful players succumb to the impact of fatigue both physical and mental, which may result in underperforming skills at key moments in a match. Fitness is the platform on which skill is performed during team sport. With the onset of fatigue, tired players find it ever more difficult to successfully perform basic skills. Therefore, it is not surprising that teams spend a large proportion of their training time on fitness. While acknowledging the central role of fitness in team sport, the importance of team tactics, underpinned by spatial awareness, must not be neglected. It is well established that a high-carbohydrate diet before a match and, as a supplement during match play, helps delay the onset of fatigue. There is some evidence that players ingesting carbohydrate can maintain sport-relevant skills for the duration of exercise more successfully compared with when ingesting placebo or water. However, most of the assessments of sport-specific skills have been performed in a controlled, non-contested environment. Although these methods may be judged as not ecologically valid, they do rule out the confounding influences of competition on skill performance. The aim of this brief review is to explore whether carbohydrate ingestion, while delaying fatigue during match play, may also help retain sport soccer-specific skill performance.



#3 Head movement direction in football - a field study on visual scanning activity during the UEFA-U17 and -U21 European Championship 2019

Reference: J Sports Sci. 2023 Jul 13;1-11. doi: 10.1080/02640414.2023.2235160. Online ahead of print.

Authors: Marius Pokolm, Marie Kirchhain, Daniel Müller, Geir Jordet, Daniel Memmert

Summary: Visual exploration (scanning) of one's environment is a key aspect in team sports. Based on Gibson's (1979) ecological approach of visual perception, this study aims to advance the understanding of scanning by focusing on the direction of head movements in football and its implications for subsequent on-ball actions. The video-based data analysis consisted of nine selected matches and 162 players of the Union of European Football Associations (UEFA) U17 and U21 European Championship 2019. The results indicate that the direction of the last scan prior to receiving the ball is related to the foot used for the first ball contact. This relationship was further analysed in view of the game context (direction of play and opponent pressure) and with information about the player's dominant foot. The findings reveal a relationship between the direction of the last scan before receiving the ball and the direction the game is proceeded in. Further, when a player performs the last scan to the side of their dominant foot, the probability increases that their dominant foot is used for the subsequent first ball contact. Depending on the direction of the last scan, opponent pressure had various effects on the foot used for the first contact.



#4 Assessing the agreement between a global navigation satellite system and an optical-tracking system for measuring total, high-speed running, and sprint distances in official soccer matches

Reference: Sci Prog. 2023 Jul-Sep;106(3):368504231187501. doi: 10.1177/00368504231187501.

Authors: Piotr Makar, Ana Filipa Silva, Rafael Oliveira, Marcin Janusiak, Przemysław Parus, Małgorzata Smoter, Filipe Manuel Clemente

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Summary: This study aimed to compare the agreement of total distance (TD), high-speed running (HSR) distance, and sprint distance during 16 official soccer matches between a global navigation satellite system (GNSS) and an optical-tracking system. A total of 24 male soccer players, who are actively participating in the Polish Ekstraklasa professional league, were included in the analysis conducted during official competitions. The players were systematically monitored using Catapult GNSS (10-Hz, S7) and Tracab optical-tracking system (25-Hz, ChyronHego). TD, HSR distance, sprint distance, HSR count (HSRC), and sprint count (SC) were collected. The data were extracted in 5-min epochs. A statistical approach was employed to visually examine the relationship between the systems based on the same measure. Additionally, R2 was utilized as a metric to quantify the proportion of variance accounted for by a variable. To assess agreement, Bland-Altman plots were visually inspected. The data from both systems were compared using the estimates derived from the intraclass correlation (ICC) test and Pearson product-moment correlation. Finally, a paired t-test was employed to compare the measurements obtained from both systems. The interaction between Catapult and Tracab systems revealed an R2 of 0.717 for TD, 0.512 for HSR distance, 0.647 for sprint distance, 0.349 for HSRC, and 0.261 for SC. The ICC values for absolute agreement between the systems were excellent for TD (ICC = 0.974) and good for HSR distance (ICC = 0.766), sprint distance (ICC = 0.822). The ICC values were not good for HSRCs (ICC = 0.659) and SCs (ICC = 0.640). t-test revealed significant differences between Catapult and Tracab for TD (p < 0.001; d = -0.084), HSR distance (p < 0.001; d = -0.481), sprint distance (p < 0.001; d = -0.513), HSRC (p < 0.001; d = -0.558), and SC (p < 0.001; d = -0.334). Although both systems present acceptable agreement in TD, they may not be perfectly interchangeable, which sports scientists and coaches must consider when using them.



#5 Horizontal jump asymmetries are associated with reduced range of motion and vertical jump performance in female soccer players

Reference: BMC Sports Sci Med Rehabil. 2023 Jul 8;15(1):80. doi: 10.1186/s13102-023-00697-1.

Authors: Alberto Roso-Moliner, Demetrio Lozano, Hadi Nobari, Chris Bishop, Antonio Carton-Llorente, Elena Mainer-Pardos

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Summary: Performance in jumping and change of direction tests are good proxies to reflect the skill level during soccer-specific actions. Greater inter-leg asymmetries have been identified as a risk factor for developing acute and overuse injuries and jeopardizing soccer performance. The aim of this study was to assess the association between asymmetry in the unilateral vertical and horizontal jump tests, ankle range of motion, linear velocity, and change of direction in a sample of highly trained adult female soccer players. Thirty-eight highly trained female soccer players underwent a testing protocol including ankle dorsiflexion, single leg jumps for height (CMJ), distance (HJ), 40 m sprint and 180° change of direction tests. Within-session reliability was acceptable (CV ≤ 7.9%), and relative reliability showed good to excellent (ICC: 0.83 to 0.99). The one-way ANOVA reported higher inter-limb differences for change of direction deficit (10.9 ± 8.04%) and single leg CMJ (5.70 ± 5.22%). Pearson correlations highlighted significant relationships between horizontal jump asymmetries and ankle dorsiflexion (r = -0.41), CMJ (r = -0.36 to -0.49) and HJ (r = -0.28 to -0.56). Assessing inter-limb asymmetries through different methods can help scientists understand the specificity of their detrimental effects on soccer performance. Practitioners should be aware of these specificities as well as the magnitude and direction of the asymmetries when aiming to improve specific on-field skills.



#6 Evaluating the Suitability of the Low Energy Availability in Females Questionnaire (LEAF-Q) for Female Football Players

Reference: Sports Med Open. 2023 Jul 13;9(1):54. doi: 10.1186/s40798-023-00605-4.

Authors: Marcus S Dasa, Oddgeir Friborg, Morten Kristoffersen, Gunn Pettersen, Jørn V Sagen, Jorunn Sundgot-Borgen, Jan H Rosenvinge

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Summary: The Low Energy Availability in Females Questionnaire (LEAF-Q) is a screening tool developed to detect endurance athletes and dancers at risk for development of persistent low energy availability (LEA) and the female athlete triad (Triad). This study investigated the applicability of the LEAF-Q in a cohort of sixty professional female football players. The participants were classified as at risk (≥ 8) or not at risk (< 8) for persistent LEA and the Triad according to their LEAF-Q score, before being compared. Receiver operating curves were then conducted to examine the ability of the overall LEAF-Q and subcategories to correctly determine the presence of clinically defined markers of the Triad. Additionally, Youden's index was calculated to determine the best fitting cut-off values. Thirty-two percent of participants were classified as at risk by the LEAF-Q. We found no statistically significant differences between the two groups for any markers associated with persistent LEA. Except for acceptable accuracy in determining menstrual status, all other LEAF-Q components exhibited poor accuracy and predictive values. Youden's index scores imply that increasing the overall and injury cut-off values to ≥ 10 and ≥ 5 respectively, would yield increased performance. Our findings do not support the use of the LEAF-Q for the purpose of detecting LEA and Triad conditions among female football players.



#7 Qatar 2022: challenges and implications related to the medical follow-up of a national football team

Reference: Rev Med Suisse. 2023 Jul 12;19(835):1374-1377. doi: 10.53738/REVMED.2023.19.835.1374. [Article in French]

Authors: Pierre-Étienne Fournier, Markus Tschopp, Philippe M Tscholl

Summary: The preparation and medical follow-up of a national team during a major tournament, in particular climatic conditions and at an unusual date posed several problems, acclimatization, recovery in connection with a busy championship game, seasonal risk of infection, which had to be resolved. Close collaboration between the various people involved, team manager, coaches, physiologist, fitness coach and doctors is essential in order to prepare to face the challenges to be met to accompany an ambitious team.



#8 The impact of COVID-19 lockdown on the quality of life of Chinese football referees: the chain mediating role of occupational stress and job burnout

Reference: BMC Public Health. 2023 Jul 10;23(1):1314. doi: 10.1186/s12889-023-16248-9.

Authors: Xianliang Wang, Kehao Zong, Yubo Gao, Bochen Li, Shuzhen Wang, Liguo Zhang

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Summary: COVID-19 lockdown measures have had a great negative impact on the development of sports competition in China, as well as on the quality of life of football referees. This study aims to explore the impact of lockdown measures implemented in response to the COVID-19 pandemic on the quality of life of football referees in China and its mechanism of action. The Impact of Event Scale-Revised (IES-R), the Effort-Reward Imbalance Scale (ERI), the Maslach Burnout Inventory General Survey (MBI-GS), and the World Health Organization Quality of Life Brief Version (WHOQOL-BREF). The scale was used from August to September 2022. Using an online questionnaire, 350 questionnaires were sent out and 338 were returned, for a return rate of 96.57%. Invalid questionnaires were excluded, and 307 football referees with referee grades in 29 provinces registered with the CFA were surveyed. SPSS 24.0 and Mplus 8.0 were used for data analysis and structural equation model testing in this study. The results showed that the COVID-19 lockdown had no significant impact on the quality of life of Chinese football referees. However, the COVID-19 lockdown can affect the quality of life of Chinese football referees through occupational stress or job burnout. Occupational stress and job burnout also play a chain intermediary role between the COVID-19 lockdown and the quality of life of Chinese football referees. In addition, this study further explores the quality of life by dividing it into four dimensions (physical, social, psychological, and environmental). The results show that all four dimensions satisfy the chain mediation model. Therefore, the quality of life of Chinese football referees can be improved by reducing their occupational stress and job burnout during the COVID-19 lockdown.



#9 Isokinetic Assessment of Knee Flexor and Extensor Strength and Lower Extremity Flexibility Assessment of an NCAA Division III Men's Soccer Team

Reference: Int J Sports Phys Ther. 2023 Jun 1;V18(3):626-635. doi: 10.26603/001c.74971. eCollection 2023.

Authors: Savanna Perkins, Paul Canavan

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Summary: Strength imbalances and flexibility deficits of the hamstrings and hip flexors have been identified as potential risk factors for hamstring injuries, but research on athletes at the Division III level are limited, potentially due to a lack of resources and technology. The purpose of this study was to conduct isokinetic and flexibility assessments to screen male soccer athletes at risk of sustaining a hamstring injury. Standardized isokinetic testing of concentric muscle performance, measured by peak torque of the quadriceps and hamstrings and hamstring-to-quadriceps ratios, was conducted using a Biodex isokinetic dynamometer at speeds of 60 and 180°/sec. Additionally, the Active Knee Extension (AKE) test and the Thomas test were performed bilaterally to objectively measure flexibility. Paired sample t-tests were used to compare left and right lower extremities for all outcomes, with the level of significance set at p<0.05. Participants were ranked for risk and given a set of exercises sourced from the FIFA 11 Injury Prevention Program. At 60°/sec, the mean PT/BW bilateral deficit was 14.1% for extension and 12.9% for flexion. At 180°/sec, the mean deficit was 9.9% for extension and 11.4% for flexion. The team's average for left and right H:Q ratios for each speed were 54.4 and 51.4 at 60°/sec and 61.6 and 63.1 at 180°/sec, respectively. The team's average AKE range of motion was 158° for the left leg and 160° for the right leg. The mean Thomas test measurements were 3.6° away from the neutral position on the right and 1.6° on the left, with nine positive tests. There were no statistically significant differences between left and right knee extension or flexion PT/BW or H:Q ratios at either speed. There was no significant difference between left and right AKE measurements (p=0.182). The results of this screening suggest that isokinetic testing and flexibility testing may be useful to identify non-optimal strength ratios and flexibility deficits in male collegiate soccer players. The benefits of this research have direct implications, as participants received both their screening data and a set of exercises aimed to help decrease their injury risk, in addition to the offering data that is useful for determining what normative values for flexibility and strength profiles might look like for Division III male soccer players.



#10 Incidence, characteristics and cost of head, neck and dental injuries in non-professional football (soccer) using 3 years of sports injury insurance data

Reference: Dent Traumatol. 2023 Jul 10. doi: 10.1111/edt.12869.

Authors: Mille Greve Hansen, Andrew George Ross, Tim Meyer, Christian Knold, Ian Meyers, Kerry Peek

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Summary: This descriptive epidemiological study aimed to quantify the incidence, characteristics and costs of head, neck and dental injuries in non-professional football players. Injury data were coded (using Orchard Sports Injury and Illness Classification System) from a de-identified insurance database containing three seasons (2018-2020) of data. Cost data included direct and indirect costs presented by type of injury, age group and sex using means ± SD, range of costs ($AU) and total costs ± SE. Chi-squared tests were used to analyse the data (significance level p < .05) with injury incidence rates (IR) calculated per 1000 match hours and per 1000 injury insurance claims. A total of 388 injuries affecting 240 players were sustained. Of these, 43% (n = 102) of players also sustained one or more secondary injuries, mainly to the head or neck area. Dental injuries (n = 143, 39%, IR = 0.008) accounted for the highest number of primary and secondary injuries and the highest mean direct cost per injury ($AU1152), while head and facial injuries accounted for the highest proportion of total costs ($AU434,101). Players who sustained one or more secondary injuries had the highest direct and indirect mean cost per injury. Given the frequency and cost of dental injuries in non-professional football players, injury prevention initiatives warrant further investigation.



#11 The relationship between ambient temperature and match running performance of elite soccer players

Reference: PLoS One. 2023 Jul 11;18(7):e0288494. doi: 10.1371/journal.pone.0288494. eCollection 2023.

Authors: Ryland Morgans, Eduard Bezuglov, Dave Rhodes, Jose Teixeira, Toni Modric, Sime Versic, Rocco Di Michele, Rafael Oliveira

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Summary: The influence of environmental factors on key physical parameters of soccer players during competitive match-play have been widely investigated in the literature, although little is known on the effects of sub-zero ambient temperatures on the performance of adult elite soccer players during competitive matches. The aim of this study was to assess how the teams' match running performance indicators are related to low ambient temperature during competitive matches in the Russian Premier League. A total of 1142 matches played during the 2016/2017 to 2020/2021 seasons were examined. Linear mixed models were used to assess the relationships between changes in ambient temperature at the start of the match and changes in selected team physical performance variables, including total, running (4.0 to 5.5 m/s), high-speed running (5.5 to 7.0 m/s) and sprint (> 7.0 m/s) distances covered. The total, running and high-speed running distances showed no significant differences across temperatures up to 10°C, while these showed small to large decreases at 11 to 20°C and especially in the >20°C ranges. On the contrary, sprint distance was significantly lower at temperature of -5°C or less compared to higher temperature ranges. At sub-zero temperatures, every 1°C lower reduced team sprint distance by 19.2 m (about 1.6%). The present findings show that a low ambient temperature is negatively related to physical match performance behavior of elite soccer players, notably associated with a reduced total sprint distance.



#12 Description of the menstrual cycle status, energy availability, eating behavior and physical performance in a youth female soccer team

Reference: Sci Rep. 2023 Jul 11;13(1):11194. doi: 10.1038/s41598-023-37967-4.

Authors: Ana Carolina Paludo, Marta Gimunová, Marcos Michaelides, Magdalena Kobus, Koulla Parpa

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Summary: The aim of the study was to describe the menstrual status and perception, risk of low energy availability (LEA) and the presence of orthorexia nervosa (ON) in youth female from a soccer team. Also, verify the possible effect of LEA and ON on physical performance. Data from 19 female players (14.6 ± 1.42 yr) belonging to a soccer team from Cyprus was taken during pre-season. The menstrual cycle status was evaluated by specific questions, LEA by the Low Energy Availability in Females Questionnaire (LEAF-Q), ON by the ORTO-R questionnaire and physical performance by jump, handgrip and cardiorespiratory exercise tests. Players were separated into the risk of LEA and ON. Comparison and correlation tests were performed with a significance set at p < 0.05. As the main results, 66.7% of players perceived that the menstrual period affects their performance in the game, 83.3% did not communicate with coaches about their menstrual cycle; the prevalence of risk of LEA was 26.3%; players with risk of LEA also presented higher scores ON; neither LEA nor ON presented a significant association with players performance. The findings highlighted that youth players perceived an impact of the menstrual period on performance, but did not communicate with the coach about it. Players with the risk of LEA and high values of ON seem not to be associated with a decrease in physical performance during the pre-season evaluation. Attention is required as the players were assessed once. Monitoring these parameters throughout the sports season is recommended to obtain better clarification about the topic.



#13 Landing Posture in Elite Female Athletes During a Drop Vertical Jump Before and After a High-Intensity Ergometer Fatigue Protocol: A Study of 20 Japanese Women's Soccer League Players

Reference: Orthop J Sports Med. 2023 Jun 2;11(6):23259671231171859. doi: 10.1177/23259671231171859. eCollection 2023 Jun.

Authors: Aguri Kamitani, Kunio Hara, Yuta Fujii, Shohei Yoshida

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Summary: Even elite athletes, who usually show stable postural control, sometimes cannot control their posture after high-load training. This instability may contribute to anterior cruciate ligament injury. The purpose of this study was to evaluate the landing posture of elite female soccer players before and after a novel high-intensity fatigue-inducing exercise protocol. We hypothesized that the landing posture will change before versus after the fatigue protocol. The study participants were 20 female elite soccer players. All athletes performed 3 drop vertical jumps (DVJs), pedaled an ergometer 8 times with full force for 10 seconds each (fatigue protocol), and then repeated the 3 DVJs. We measured and compared the athletes' blood lactate levels before and after the fatigue protocol, as well as the hip flexion, knee flexion, and ankle dorsiflexion angles and final landing posture during the DJVs. Blood lactate levels increased significantly pre- to postprotocol (from 2.7 ± 1.9 to 15.0 ± 3.6 mmol/L; P < .001), while there were decreases in hip flexion angle (from 35.0° ± 11.2° to 22.4° ± 8.8°; P < .001) and ankle dorsiflexion angle (from 26.4° ± 3.9° to 20.0° ± 3.7°; P < .001). The number of athletes who could not maintain a stable DVJ final landing posture increased from 10% before the fatigue protocol to 70% after. The elite female athletes in our study showed significant decreases in hip flexion and ankle dorsiflexion angles in the DVJ landing after a fatigue-inducing protocol. Most elite athletes were unable to maintain a stable posture on the DVJ landing after the fatigue protocol. 



#14 Asymmetries of foot strike patterns during running in high-level female and male soccer players

Reference: BMC Sports Sci Med Rehabil. 2023 Jul 14;15(1):86. doi: 10.1186/s13102-023-00696-2.

Authors: Stanislav Dimitri Siegel, Joel Mason, Daniel Hamacher, Anna Lina Rahlf, Astrid Zech

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Summary: Foot strike pattern (FSP) is defined by the way the foot makes initial ground contact and is influenced by intrinsic and extrinsic factors. This study investigated the effect of running speed on asymmetries of FSP. Seventeen female and nineteen male soccer players performed an incremental running test on an instrumented treadmill starting at 2.0 m/s until complete exhaustion. Force plate data were used to categorize foot strikes into rearfoot (RFS) and non-rearfoot strikes. Additionally, peak vertical ground reaction force (peakGRF) and stride time were calculated. The symmetry index (SI) was used to quantify lateral asymmetries between legs. The SI indicated asymmetries of the rate of RFS (%RFS) of approximately 30% at slow running speed which decreased to 4.4% during faster running speed (p = 0.001). There were minor asymmetries in peakGRF and stride time at each running stage. Running speed influenced %RFS (p < 0.001), peakGRF (p < 0.001) and stride time (p < 0.001). Significant interaction effects between running speed and sex were shown for %RFS (p = 0.033), peakGRF (p < 0.001) and stride time (p = 0.041). FSP of soccer players are asymmetric at slower running speed, but symmetry increases with increasing speed. Future studies should consider that FSP are non-stationary and influenced by running speed but also differ between legs.







The relationship between ambient temperature and match running performance of elite soccer players

The aim of this study was to assess how the teams’ match running performance indicators are related to low ambient temperature during competitive matches in the Russian Premier League.





Technical and locomotor demands in elite soccer: manipulating area per player during SSG to replicate official match demands

The present study aimed to investigate the area per player (ApP) to replicate the technical and locomotor match demands using small-sided games (SSGs) in male footballers competing in European and UEFA competitions.





Latest research in football - week 26 - 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 Backheel Pass During Forward Running as a Mechanism of Severe Acute Hamstring Injury in Football: A Case Report

Reference: Clin J Sport Med. 2023 Jun 23. doi: 10.1097/JSM.0000000000001168. Online ahead of print.

Authors: Goran Markovic, Ivan Karuc

Summary: Proximal hamstring tendon avulsions represent the most severe hamstring injury in sports and are typically sustained during stretch-related movements in closed kinetic chain: forced hip hyperflexion combined with knee extension. Here, we present the case study of the right-foot dominant professional football player with a severe proximal hamstring tendon avulsion injury and concomitant lower-grade injuries of hamstring muscle-tendon complex caused by a potentially new football-specific injury mechanism: right-foot backheel pass during forward running (ie, a kick directly backward). This mechanism involves a specific stretch-shortening cycle action of hamstring muscles in open-kinetic chain movement that has not yet been described in the scientific literature. Although further studies related to this football-specific hamstring injury mechanism are needed, clinicians and coaches working in football should be aware of it and potentially introduce additional injury mechanism-specific exercises and strategies for prevention of severe hamstring injuries which often require surgical intervention.



#2 The correlation of centre of mass evaluation utilising accelerometry-based measurement and the clinical dynamic balance test in professional football athletes with chronic ankle instability

Reference: Heliyon. 2023 Jun 15;9(6):e17318. doi: 10.1016/j.heliyon.2023.e17318. eCollection 2023 Jun.

Authors: Chairat Phuaklikhit, Thanwarat Junsri, Usa Maikaew

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Summary: Similar to a modified star excursion balance test, the Y-balance test is recommended for use in clinical settings to evaluate dynamic balance, particularly in athletes with chronic ankle instability. However, due to the testing errors, there are certain restrictions. As a result, the modification of the centre of mass tracking system was developed in order to aid in the detection of the ability to control the dynamic balance. Therefore, the purpose of this study was to correlate the usage of an accelerometer for the shifting of the centre of mass during a dynamic balance test with a Y-balance test reach distance score. Forty professional football athletes with CAI participated in this study by performing the Y-balance test three times while wearing an accelerometer. The jerk, RMS sway amplitude, mean velocity from the time domain, and the normalised reach distance scores of the Y-balance test in the anterior, posteromedial, and posterolateral directions were all collected. There was a strong positive correlation of jerk and RMS sway amplitude with the normalised reach distance scores in the posteromedial direction (r = 0.706 and 0.777, respectively), a moderate positive correlation of jerk and RMS sway amplitude with the normalised reach distance scores in the posterolateral direction (r = 0.609 and 0.606, respectively), a moderate positive correlation of jerk and RMS sway amplitude with the composite reach distance scores (r = 0.531 and 0.573, respectively) and significant differences in the posteromedial, posterolateral and overall directions (p-value < 0.001). These findings indicate that the area of the centre of mass shifting as represented by the accelerometer can disclose the body's ability to control the centre of mass over the base of support when the body is moving. Furthermore, in this study, the RMS sway variable in the posteromedial direction appears to be the most prominent.



#3 An injury burden heat map of all men's and women's teams of a professional football club over a decade

Reference: Res Sports Med. 2023 Jun 26;1-11. doi: 10.1080/15438627.2023.2228959. Online ahead of print.

Authors: Jon Larruskain, Jose A Lekue, Paco Angulo, Juan M Santisteban, Gontzal Diaz-Beitia, Imanol Martin-Garetxana, Susana M Gil, Iraia Bidaurrazaga-Letona, Xabier Monasterio

Summary: The aim was to present a descriptive 10-season summary of injury data from all teams of a professional football club using a heat map approach. Injuries and exposure time were registered according to the FIFA consensus in all men's and women's teams from Athletic Club over 10 seasons. A team-by-injury table was created, showing the incidence, median severity, and burden in each cell. Cells were coloured based on the injury burden value using a green - yellow-red gradient (lowest to highest). The highest overall injury burden was found in the women's 2nd and 1st teams and the men's U(under)17 team (>200 days lost/1000 h). Muscle injury burden demonstrated an increasing pattern with age. Knee joint/ligament injuries, particularly anterior cruciate ligament ruptures, had the highest impact on women's teams, followed by the men's 2nd team. In comparison, ankle joint/ligament injuries had a relatively low injury burden in most teams. Growth-related injuries were the most impactful injuries in the men's U15 and younger teams, and the women's U14 team. In conclusion, epidemiological data on injuries can inform and guide injury management processes. New and improved visualization methods might be important assets when presenting injury data to key decision-makers.



#4 The type and extent of travel for professional footballers undertaking national team duties for a national football federation

Reference: Biol Sport. 2023 Jul;40(3):707-713. doi: 10.5114/biolsport.2023.119288. Epub 2022 Oct 6.

Authors: Ewan Clements, Fabian Ehrmann, Andrew Clark, Mark Jones, Donna Lu, Rob Duffield

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Summary: Elite football (soccer) involves club, continental and international fixtures, requiring players to undertake extensive travel [1]. For a national football federation, this includes the transport of players between club and camp/tournament commitments, which is often a point of contention between respective organisations [2]. Partly this contention results from the effects of travel, whereby jet lag and travel fatigue can negatively affect physical performance [3-5] and athlete wellbeing [6, 7]. Given the scarcity of data on elite players following travel, an initial step for any national football federation is to understand the volume and nature of travel undertaken by national team players. Such insight may better identify the schedule, timelines and needs of athletes' post travel. Better awareness of these travel needs can help maximise availability for training and minimise the impact of travel related stresses on performance or wellbeing. However, the regularity and volume of travel to national football team commitments has not previously been described. Further, travel demands are likely to vary significantly based on the location of the athlete and the national team camp. For countries outside of Europe, such as Australia, the travel demands and ensuing effects on player preparation can be substantial for both arrival into national team and on return to clubs [7]. Hence, detailed information regarding the type, frequency, and extent of travel for national team duties is important to aid in planning optimal travel schedules and interventions to assist players for international or club duty.



#5 Position specific physical demands in different phases of competitive matches in national level women's football

Reference: Biol Sport. 2023 Jul;40(3):629-637. doi: 10.5114/biolsport.2023.118337. Epub 2022 Sep 15.

Authors: Juho K Mäkiniemi, Eero Hj Savolainen, Taija Finni, Johanna K Ihalainen

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Summary: The purpose of the present study was twofold: to investigate position-specific physical match demands of national level women's football; and to examine if demands change during a match (comparison between first and second half and in 15-minute intervals). Seven teams from the Finnish National League participated in the study. Eighty-five players met the inclusion criteria, and a total of 340 individual match observations from 68 individual matches were included for analysis. The Polar Team Pro -player tracking system (with 10 Hz GPS units, including 200 Hz tri-axial accelerometer, gyroscope, magnetometer and HR monitor) was used to assess positional data and HR response of the players. This study demonstrated that women's national level football matches place a range of physical demands on players, which in general were highest for wide midfielders, and lowest for central defenders. Wide midfielders and forwards performed significantly more 'very high-speed' running, sprinting, accelerations, and decelerations than other outfield positions (p < 0.05). HRmean varied from 84-87% of HRmax and was significantly lower for central defenders than central midfielders (p < 0.001). External load variables varied during a match and generally decreased especially after 60 minutes of play compared to first 15-min period of the match. Present study showed that national level women football players' positional differences in match demands are similar to those reported with elite players in previous studies. On national level, players' physical performance tended to decrease towards the end of the match, especially in terms of total distance (~10%), high-speed running (~20%), and decelerations (~20%).



#6 Development of an algorithm-based approach using neuromuscular test results to indicate an increased risk for non-contact lower limb injuries in elite football players

Reference: BMJ Open Sport Exerc Med. 2023 Jun 21;9(2):e001614. doi: 10.1136/bmjsem-2023-001614. eCollection 2023.

Authors: Jente Wagemans, Arie-Willem De Leeuw, Peter Catteeuw, Dirk Vissers

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Summary: This retrospective cohort study explored an algorithm-based approach using neuromuscular test results to indicate an increased risk for non-contact lower limb injuries in elite football players. Neuromuscular data (eccentric hamstring strength, isometric adduction and abduction strength and countermovement jump) of 77 professional male football players were assessed at the start of the season (baseline) and, respectively, at 4, 3, 2 and 1 weeks before the injury. We included 278 cases (92 injuries; 186 healthy) and applied a subgroup discovery algorithm. More injuries occurred when between-limb abduction imbalance 3 weeks before injury neared or exceeded baseline values (threshold≥0.97), or adduction muscle strength of the right leg 1 week before injury remained the same or decreased compared with baseline values (threshold≤1.01). Moreover, in 50% of the cases, an injury occurred if abduction strength imbalance before the injury is over 97% of the baseline values and peak landing force in the left leg 4 weeks before the injury is lower than 124% compared with baseline. This exploratory analysis provides a proof of concept demonstrating that a subgroup discovery algorithm using neuromuscular tests has potential use for injury prevention in football.



#7 Football and dementia: looking at other factors - Authors' reply

Reference: Lancet Public Health. 2023 Jul;8(7):e483. doi: 10.1016/S2468-2667(23)00104-4.

Authors: Peter Ueda, Björn Pasternak, Carl-Emil Lim, Martin Neovius, Jonas F Ludvigsson, Henrik Svanström

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#8 Multiple regression analysis for competitive performance assessment of professional soccer players

Reference: Technol Health Care. 2023 Jun 29. doi: 10.3233/THC-230275. Online ahead of print.

Authors: Radakovic Radivoje, Dasic Lazar, Dopsaj Milivoj, Filipovic Nenad

Summary: Being in peak physical condition and having specific motor abilities are necessity for every top-level soccer player in order to achieve success in competition. In order to correctly assess soccer players' performance, this research uses laboratory and field measurements, as well as results of competitive performance obtained by direct software measurements of players' movement during the actual soccer game. The main goal of this research is to give insight into the key abilities that soccer players need to have in order to perform in competitive tournaments. Besides training adjustments, this research also gives insight into what variables need to be tracked in order to accurately assess the efficiency and functionality of the players. The collected data need to be analyzed using descriptive statistics. Collected data is also used as input for multiple regression models that can predict certain key measurements: total distance covered, percent of effective movements and high index of effective performance movements. Most of the calculated regression models have high predictability level with statistically significant variables. Based on the results of regression analysis it can be deduced that motor abilities are important factor in measuring soccer player's competitive performance and team's success in the match.



#9 Effect of body composition on the athletic performance of soccer referees

Reference: J Nutr Sci. 2023 Jun 27;12:e66. doi: 10.1017/jns.2023.47. eCollection 2023.

Authors: Azad Ilhan, Surhat Muniroglu, Neslişah Rakıcıoğlu

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Summary: Nutrition plays an important role in improving sports performance. The present study aimed at nutritional assessment and examined the relationship between athletic performance and body composition in soccer referees at different levels. The study participants were 120 male soccer referees. 5, 10 and 30 metres (m) sprint tests to measure speed and cooper test for physical fitness were applied in the referees. Participants were divided into two groups as city and class soccer referee. The anthropometric measurements, excluding fat mass (FM) (%), were higher in class referees. Fat mass (%) differences (14⋅1 ± 4⋅28 v. 12⋅3 ± 4⋅41) were statistically significant (P < 0⋅05). Daily energy and nutrient intakes were similar. The inadequacy percentages of energy, vitamin A and calcium were the highest (29⋅2, 30⋅0 and 34⋅2 %, respectively). It was found that a negative significant correlation between FM% and cooper test score (P < 0⋅01; r = -0⋅35), a positive significant correlation between FM% and 5, 10 and 30 m sprint test scores (P < 0⋅01, r = 0⋅38; P < 0⋅01, r = 0⋅38 and P < 0⋅01, r = 0⋅48, respectively). Similarly, there was a negative significant correlation between waist circumference (WC) and cooper test score (P < 0⋅01; r = -0⋅31), a positive significant correlation between WC and 5, 10 and 30 m sprint test scores (P < 0⋅01, r = 0⋅33; P < 0⋅01, r = 0⋅40; P < 0⋅01, r = 0⋅33, respectively). Nutritional recommendations for soccer referees should be made specific to the individual, considering body composition, training intensity and match frequency by a dietician.



#10 Technical and locomotor demands in elite soccer: manipulating area per player during small-sided games to replicate official match demands

Reference: Biol Sport. 2023 Jul;40(3):639-647. doi: 10.5114/biolsport.2023.118338. Epub 2022 Sep 15.

Authors: Andrea Riboli, Fabio Esposito, Giuseppe Coratella

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Summary: The present study aimed to investigate the area per player (ApP) to replicate the technical and locomotor match demands using small-sided games (SSGs) in male soccer players (n = 20) competing in major European and UEFA competitions. The relative number of each individual technical activity per minute (number · min-1; technical demands) was counted and the relative (m · min-1) total (TD), high-speed running (HSRD), very high-speed running (VHSRD), sprint and acceleration+deceleration (Acc+Dec) distances were collected during different SSG formats (n = 24; 4 vs 4 to 10 vs 10 with an ApP from 60 to 341 m2 · player-1) and official matches (n = 28). Data were collected during two full seasons. A linear mixed model analysis was used to calculate the individual relationship between technical/locomotor demands and the ApP during SSGs; the correlation coefficient was also calculated. With the exception of an inverse moderate (r = -0.457) correlation for Acc+Dec, each locomotor metric (TD, HSRD, VHSRD and sprint) showed a positive large to very large (r = 0.560 to 0.710) correlation with ApP (P < 0.001). The technical demands showed an inverse moderate correlation (r = -0.529) with ApP. Additionally, inverse moderate to large correlations (r = -0.397 to -0.600; P < 0.05) between the technical demands and the locomotor demands (TD, HSR, VHSR and sprint) were found. Lastly, an ApP of ~243 m2 · player was found to replicate the official match technical demand and it was quite similar to the ApP required to replicate HSRD, VHSRD and sprint. These findings may help practitioners to replicate, overload and underload both technical and locomotor demands using a specific ApP during SSGs in elite soccer.



#11 Association between internal training load and muscle injuries in Brazilian professional soccer players

Reference: Biol Sport. 2023 Jul;40(3):675-679. doi: 10.5114/biolsport.2023.119285. Epub 2022 Sep 15.

Authors: Pedro A Mohr, Thiago S Matias, Ricardo D de Lucas

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Summary: The training load is associated with injury risk in a variety of sports. This study aimed to evaluate the association between the internal training load and injury risk in Brazilian professional soccer players. The data were collected from 32 soccer players across two full seasons (2017 and 2018). The rating of perceived exertion (RPE) for every training/match session was used as an internal load variable. The cumulative training load from 3 and 4 weeks (C3 and C4) and the acute:chronic workload ratio (ACWR) were calculated. A generalized estimating equation analysis was applied to examine associations of non-contact muscle injuries with C3, C4 and ACWR. A total of 33 injuries were recorded across the two full seasons. A significant association was found between cumulative training load for three (C3, p = 0.003) and four weeks (C4, p = 0.023) and the occurrence of injuries. Players in the "high load" group presented greater injury risk in relation to the "moderate load" group (C4: OR = 4.5; IC 95% 1.5-13.3; C3: OR = 3.7; IC 95% 1.7-8.1). There was no association between ACWR and injury occurrence. The athletes exposed to a high cumulative load in a period of 3 to 4 weeks presented higher injury risk in comparison to those who had moderate cumulative training loads. Besides that, there was no association between ACWR and injury occurrence.



#12 The selection advantages associated with advanced biological maturation vary according to playing position in national-level youth soccer

Reference: Biol Sport. 2023 Jul;40(3):715-722. doi: 10.5114/biolsport.2023.119983. Epub 2022 Oct 6.

Authors: Liam Sweeney, Sean P Cumming, Áine MacNamara, Dan Horan

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Summary: This study investigated the extent to which biological maturation selection biases existed according to playing position in national-level youth soccer. A total of 159 players from the U13 to U16 age groups in the Football Association of Ireland's national talent pathway and international representative squads had their relative biological maturity status assessed using the Khamis-Roche method for the percentage of predicted adult height at the time of observation. Players were categorised as goalkeeper (GK), central defender (CD), full-back (FB), centre defensive midfielder (CDM), centre midfielder (CM), centre attacking midfielder (CAM), wide midfielder (WM) or centre forward (CF). A series of one-sampled means t-tests were used to examine the degree to which biological maturation selection biases existed across playing positions. A non-parametric Kruskal-Wallis test was used to evaluate inter-positional differences. A small to very large selection bias in favour of early maturing players existed for GK (D = 0.7), CD (D = 1.65), FB (D = 0.49), CM (D = 0.62), WM (D = 0.78), and CF (D = 0.76) (p < 0.05). Maturational selection biases did not exist for CDM or CAM. Moreover, CD were significantly more advanced in maturation compared to FB, CDM and CAM (p < 0.05). This study supports the contention that maturation selection biases exist in youth soccer, but the magnitude of this bias is highly dependent upon playing position. The very strong maturity selection biases at the national level evidenced in this investigation highlight the need for Football Associations to explore strategies, such as futures programmes, to help to retain talented, yet late maturing athletes.



#13 The effect of two sessions of combined jump and sprint training per week on fitness parameters in soccer players. A randomized controlled trial

Reference: Biol Sport. 2023 Jul;40(3):699-706. doi: 10.5114/biolsport.2023.119287. Epub 2022 Sep 22.

Authors: Mattia Bianchi, Liam Anderson, Thomas E Brownlee, Lorenzo Bossi, Marco Beato

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Summary: This study aimed to investigate the effect of a combined jump and sprint training program, two sessions a week for 6 weeks, on sprinting, change of directions (COD) and jumping performance in semi-professional soccer players. Twenty soccer players were enrolled in this randomized controlled trial (age 20 ± 2 years, body mass 74.3 ± 5.9 kg). Players were randomized into two groups such as training group (TG, n = 10 players) or control group (CG, n = 10 players). Physical tests were performed before and after 6 weeks of training such as sprint 10 m, sprint 30 m, 505-COD test and standing long jump (LJ). The two groups performed the same training except for the combined jump and sprint training performed twice a week by TG. After 6 weeks of training, between-group analysis reported statistical difference in favor of the TG in sprint 10 m (p = 0.015, η2 = 0.295, large), sprint 30 m (p < 0.001, η2 = 0.599, large), in 505-COD (p = 0.026, η2 = 0.154, large), and LJ (p = 0.025, η2 = 0.027, small). These data indicate that combined sprint and jump training, when performed twice a week, for the duration of 6 weeks, in addition to the regular team training, can improve specific physical performance in male soccer players. This study has shown that a volume increment of 10% after 3 weeks of training can be a suitable training dose progression and that a combination of 64-70 jumps and 675-738 m of sprinting training per session can yield benefits in sprint, COD and jump performance.



#14 Typical weekly physical periodization in French academy soccer teams: a survey

Reference: Biol Sport. 2023 Jul;40(3):731-740. doi: 10.5114/biolsport.2023.119988. Epub 2022 Oct 14.

Authors: Tom Douchet, Christos Paizis, Christopher Carling, Carole Cometti, Nicolas Babault

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Summary: In elite-level youth soccer players, weekly training periodization is of paramount importance to plan for short- and long-term physical development. The present study investigated current practices for physical periodization strategies in elite male French academies. An online survey was completed by elite French academies strength and conditioning coaches to determine the typical weekly periodization with particular reference to daily training in relation to match day (MD) in youth soccer players. The survey attempted to characterize the importance of physical development compared to match result, and practices used (expected difficulty and content) for each training session according to duration, exercises, and objective. The frequency rates of the responses were compared using two-tailed Chi-square tests with the significance level set at p < 0.05. Fortyfive questionnaires were analyzed. Respondents indicated that their training sessions focused mainly on physical development (95.6%) rather than match result. Active recovery (34.2%) and aerobic conditioning exercises (40.8%) were primarily conducted on MD+1 and MD+2 using passing circuits and aerobic technical drills. Physical development was mostly pursued during sessions on MD-4 (38.8%) and MD-3 (37.3%). The number of large-sided games was highest on MD-3 (58.1%). On MD-2 and MD-1, a decrease in the training load was highlighted, with speed (40.4%) and tapering sessions (52.4%) mostly implemented. Intensive use of small-sided games (92.3%) and reactivity exercises was observed at MD-1 (100.0%). Our results revealed discrepancies between the physical objectives set for each day and the content implemented, which could potentially be more physically demanding than expected.



#15 Chronic Traumatic Encephalopathy in Soccer Players: Review of 14 Cases

Reference: Clin J Sport Med. 2023 Jul 4. doi: 10.1097/JSM.0000000000001174. Online ahead of print.

Authors: Gerard Hageman, Ivar Hageman, Jik Nihom

Summary: Exposure to repetitive sports-related concussions or (sub)concussive head trauma may lead to chronic traumatic encephalopathy (CTE). Which impact (heading or concussion) poses the greatest risk of CTE development in soccer players? A literature search (PubMed) was conducted for neuropathologic studies in the period 2005-December 2022, investigating soccer players with dementia and a CTE diagnosis, limited to English language publications. 210 papers were selected for final inclusion, of which 7 papers described 14 soccer players. Magnetic resonance imaging studies in soccer players show that lifetime estimates of heading numbers are inversely correlated with cortical thickness, grey matter volume, and density of the anterior temporal cortex. Using diffusion tensor imaging-magnetic resonance imaging, higher frequency of headings-particularly with rotational accelerations-are associated with impaired white matter integrity. Serum neurofilament light protein is elevated after heading. Chronic traumatic encephalopathy pathology, history of concussion, heading frequency was used as outcome measures. In 10 of 14 soccer players, CTE was the primary diagnosis. In 4 cases, other dementia types formed the primary diagnosis and CTE pathology was a concomitant finding. Remarkably, 6 of the 14 cases had no history of concussion, suggesting that frequent heading may be a risk for CTE in patients without symptomatic concussion. Rule changes in heading duels, management of concussion during the game, and limiting the number of high force headers during training are discussed. Data suggest that heading frequency and concussions are associated with higher risk of developing CTE in (retired) soccer players. However based on this review of only 14 players, questions persist as to whether or not heading is a risk factor for CTE or long-term cognitive decline.



#16 Prediction of ball direction in soccer penalty through kinematic analysis of the kicker

Reference: J Sports Sci. 2023 Jul 6;1-9. doi: 10.1080/02640414.2023.2232679. Online ahead of print.

Authors: Bruno Secco Faquin, Luis Augusto Teixeira, Cristiane Regina Coelho Candido, Daniel Boari Coelho, Juliana Bayeux Dascal, Victor Hugo Alves Okazaki

Summary: The penalty kick is a crucial opportunity to score and determine the outcome of a soccer match or championship. Anticipating the direction of the ball is key for goalkeepers to enhance their defensive capabilities, considering the ball's swift travel time. However, it remains unclear which kinematic cues from the kicker can predict the ball's direction. This study aimed to identify the variables that predict the ball's direction during a soccer penalty kick. Twenty U19 soccer players executed penalty kicks towards four targets positioned in the goal, while kinematic analysis was conducted using a 3D motion analysis system. Logistic regression analysis revealed that trunk rotation in the transverse plane (towards the goal - left; or slightly to the right - right) served as the primary predictor of the ball's horizontal direction at 250 and 150 ms before the kicking foot made contact. Additionally, the height of the kicking foot in the sagittal plane solely predicted the vertical direction at the moment of contact. This information, encompassing trunk rotation and kicking foot height, can be employed in perceptual training to enhance decision-making and the implementation of feints during penalty kicks.







Association between internal training load and muscle injuries in Brazilian professional soccer players

The training load is associated with injury risk in a variety of sports. This study aimed to evaluate the association between the internal training load and injury risk in Brazilian professional soccer players.





The selection advantages associated with advanced biological maturation vary according to position in national-level youth soccer

This study investigated the extent to which biological maturation selection biases existed according to playing position in national-level youth soccer.