Latest research in football - week 21 - 2022

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases. 


Following studies were retrieved for this week:

#1 The muscle contractile properties in female soccer players: inter-limb comparison using tensiomyography

Reference: J Musculoskelet Neuronal Interact. 2022 Mar 1;22(2):179-192.

Authors: Armin H Paravlic, Zoran Milanović, Ensar Abazović, Goran Vučković, Darjan Spudić, Ziva Majcen Rošker, Maja Pajek, Janez Vodičar

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Summary: The present study aimed to: i) determine the contractile properties of the major lower limb muscles in female soccer players using tensiomyography; ii) investigate inter-limb differences; and iii) compare inter-limb differences between different selections and playing positions. A total of 52 female soccer players (A team; U19 and U17) were recruited. The vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), gastrocnemius medialis (GM), lateralis (GL) and tibialis anterior (TA) of both lower limbs were evaluated. When the entire sample was assessed regardless of selection or playing position, there were significant inter-limb differences in all measured muscles except BF. Compared to the non-dominant limb, the dominant limb had higher delay time in VL (p=0.008), while showing lower values in VM (p=0.023), GL (p=0.043) and GM (p=0.006). Contraction time was lower in the RF of the dominant limb (p=0.005) and VM (p=0.047), while showing higher values in VL (p=0.036) and TA (p<0.001) as compared to the non-dominant limb. Given the differences found between the limbs in the whole sample studied, it is necessary to examine both limbs to gather a more in-depth understanding of underlying mechanisms related to neuromuscular functions in female soccer players.



#2 Age-Related Differences in the Anthropometric and Physical Fitness Characteristics of Young Soccer Players: A Cross-Sectional Study

Reference: Children (Basel). 2022 May 1;9(5):650. doi: 10.3390/children9050650.

Authors: Koulla Parpa, Marcos Michaelides

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Summary: Considering that most professional academies seek to optimize the early detection and physical development of their younger players, the purpose of this study was to examine the anthropometric and physical fitness characteristics in a large cross-sectional sample of youth soccer players in Eastern Europe, starting from a very young age during their in-season period. Three hundred and thirteen soccer players (n = 313), grouped into eight age categories, participated in the study. On the basis of chronological age, the group categories were: 7 (n = 26), 8 (n = 41), 9 (n = 46), 10 (n = 48), 11 (n = 42), 12 (n = 47), 13 (n = 43), and 14 years old (n = 20). The players underwent an anthropometric evaluation, flexibility, handgrip strength, vertical jump performance, speed, and agility assessments. A one-way multivariate analysis of variance (MANOVA) indicated significant differences in the anthropometric and physical fitness variables based on chronological age (F = 13.40, p &lt; 0.05, Wilk's Λ = 0.08, partial η2 = 0.30). Concurrently, there were significant growth and physical fitness differences even in players born in the same chronological year. It is believed that the results have important practical implications, especially for those involved in youth soccer. Based on our results, coaches should contemplate speed and agility development in training sessions starting from a much younger age, as sprinting while changing directions has been considered an essential prerequisite in soccer.



#3 Alterations in Cortical Activation among Soccer Athletes with Chronic Ankle Instability during Drop-Jump Landing: A Preliminary Study

Reference: Brain Sci. 2022 May 19;12(5):664. doi: 10.3390/brainsci12050664.

Authors: Xiaoya Zhang, Wanrongyu Su, Bin Ruan, Yu Zang

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Summary: Chronic ankle instability (CAI) is a common peripheral joint injury and there is still no consensus on the mechanisms. It is necessary to investigate electrocortical parameters to provide clinical insight into the functional alterations of brain activity after an ankle sprain, which would greatly affect the implementation of rehabilitation plans. The purpose of this study was to assess cortical activation characteristics during drop-jump landing among soccer athletes with CAI. A total of 24 participants performed the drop-jump landing task on a force platform while wearing a 64-channel EEG system. The differences of power spectral density (PSD) in theta and alpha (alpha-1 and alpha-2) bands were analyzed between two groups (CAI vs. CON) and between two limbs (injured vs. healthy). CAI participants demonstrated significantly higher theta power at the frontal electrode than that in healthy control individuals (F(1,22) = 7.726, p = 0.011, η2p = 0.260). No difference in parietal alpha-1 and alpha-2 power was found between groups (alpha-1: F(1,22) = 0.297, p = 0.591, η2p = 0.013; alpha-2: F(1,22) = 0.118, p = 0.734, η2p = 0.005). No limb differences were presented for any frequency band in selected cortical areas (alpha-1: F(1,22) = 0.149, p = 0.703, η2p = 0.007; alpha-2: F(1,22) = 0.166, p = 0.688, η2p = 0.007; theta: F(1,22) = 2.256, p = 0.147, η2p = 0.093). Theta power at the frontal cortex was higher in soccer athletes with CAI during drop-jump landing. Differences in cortical activation provided evidence for an altered neural mechanism of postural control among soccer athletes with CAI.



#4 Acute arm and leg muscle glycogen and metabolite responses to small-sided football games in healthy young men

Reference: Eur J Appl Physiol. 2022 Jun 1. doi: 10.1007/s00421-022-04970-y. Online ahead of print.

Authors: Jeppe Panduro, Jeppe F Vigh-Larsen, Georgios Ermidis, Susana Póvoas, Jakob Friis Schmidt, Karen Søgaard, Peter Krustrup, Magni Mohr, Morten Bredsgaard Randers

Summary: Studies have indicated upper body involvement during football, provoking long-term muscular adaptations. This study aimed at examining the acute metabolic response in upper and lower body skeletal muscle to football training organized as small-sided games (SSG). Ten healthy male recreational football players [age 24 ± 1 (± SD) yrs; height 183 ± 4 cm; body mass 83.1 ± 9.7 kg; body fat 15.5 ± 5.4%] completed 1-h 5v5 SSG (4 × 12 min interspersed with 4-min recovery periods). Muscle biopsies were obtained from m. vastus lateralis (VL) and m. deltoideus (DE) pre- and post-SSG for muscle glycogen and metabolite analyses. Blood lactate samples were obtained at rest, middle and end of the SSG. Muscle glycogen in VL decreased (P < 0.01) by 21% and tended (P = 0.08) to decrease in DE by 13%. Muscle lactate increased in VL (117%; P < 0.001) and DE (81%; P < 0.001) during the game, while blood lactate rose threefold. Muscle ATP and PCr were unaltered, but intermuscular differences were detected for ATP at both time points (P < 0.001) and for PCr at pre-SSG (P < 0.05) with VL demonstrating higher values than DE, while muscle creatine rose in VL (P < 0.001) by 41% and by 22% in DE (P = 0.02). Baseline citrate synthase maximal activity was higher (P < 0.05) in VL compared to DE, whereas baseline muscle lactate concentration was higher (P < 0.05) in DE than VL. The upper body may be extensively involved during football play, but besides a rise in muscle lactate in the deltoideus muscle similar to the leg muscles, the present study did not demonstrate acute metabolic changes of an order that may explain the previously reported training effect of football play in the upper extremities.



#5 The Navigation Ability Test (NAT 2.0): From Football Player Performance to Balance Rehabilitation in Chronic Unilateral Vestibular Loss

Reference: Audiol Res. 2022 May 10;12(3):249-259. doi: 10.3390/audiolres12030026.

Authors: Paolo Gamba, Riccardo Guidetti, Cristiano Balzanelli, Maurizio Bavazzano, Andrea Laborai

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Summary: In humans, spatial orientation consists of the ability to move around the environment through memorized and pre-programmed movements, according to the afferent sensory information of the body and environmental analysis of the Central Nervous System (CNS). The purpose of this study is to analyze the abilities of professional athletes, such as footballers, to use mental navigation systems, cognitive maps, and memorized motor patterns in order to obtain better physical performance and to obtain useful information for training both non-sports subjects and vestibular patients for rehabilitation purposes. All the motor performances of sportsmen, healthy non-sporting subjects, or vestibular patients are based on the acquisition of visual-spatial and training information. In this study, we analyzed the visual-spatial performance of 60 trained sportsmen (professional footballers), 60 healthy non-sports subjects, and 48 patients affected by chronic unilateral vestibular loss by means of the Navigation Ability Test 2.0. A score based on the number of targets correctly reached in the various tests quantifies the degree of performance of the subjects. NAT 2.0 scores progressively improve from vestibular subjects to healthy non-sporting subjects to footballers. NAT 2.0 scores improve in all three subject groups as the number of tasks performed in all patient groups increases, regardless of gender and age. The analysis of performance data through NAT 2.0 in athletes (footballers) opens new perspectives for rehabilitation purposes, regardless of age, sex, and training conditions, both in healthy non-sporting subjects to improve their sporting potential and in patients affected by chronic vestibular dysfunction, in order to optimize their motor skills and prevent falls.



#6 Off-ball behavior in association football: A data-driven model to measure changes in individual defensive pressure

Reference: J Sports Sci. 2022 May 31;1-14. doi: 10.1080/02640414.2022.2081405. Online ahead of print.

Authors: Mat Herold, A Hecksteden, D Radke, F Goes, S Nopp, T Meyer, M Kempe

Summary: This study describes an approach to evaluate the off-ball behaviour of attacking players in association football. The aim was to implement a defensive pressure model to examine an offensive player's ability to create separation from a defender using 1411 high-intensity off-ball actions including 988 Deep Runs (DRs) DRs and 423 Change of Directions (CODs). Twenty-two official matches (14 competitive matches and 8 friendlies) of the German National Team were included in the research. To validate the effectiveness of the pressure model, each pass (n = 25,418) was evaluated for defensive pressure on the receiver at the moment of the pass and for the pass completion rate (R = -.34, p < .001). Next, after assessing the inter-rater reliability (Fleiss Kappa of 80 for DRs and 78 for CODs), three expert raters annotated all DRs and CODs that met the pre-set criteria. A time-series analysis of each DR and COD was calculated to the nearest 0.1 second, finding a slight increase in pressure from the start to the end of the off-ball actions as defenders re-established proximity to the attacker after separation was created. A linear mixed model using run type (DR or COD) as a fixed effect with the local maximum as a fixed effect on a continuous scale resulted in p < 0.001, d = 4.81, CI = 0.63 to 0.67 for the greatest decrease in pressure, p < 0.001, d = 0.143, CI = 9.18 to 10.61 for length of the longest decrease in pressure, and p < 0.001, d = 1.13, CI = 0.90 to 1.11 for the fastest rate of decrease in pressure. As these values pertain to the local maximum, situations with greater starting pressure on the attacker often led to greater subsequent decreases. Furthermore, there was a significant (p < .0001) difference between offensive and defensive positions and the number of off-ball actions. Results suggest the model can be applied to quantify and visualise the pressure exerted on non-ball-possessing players. This approach can be combined with other methods of match analysis, providing practitioners with new opportunities to measure tactical performance in football.



#7 COVID-19 Infection among Elite Football Players: A Nationwide Prospective Cohort Study

Reference: Vaccines (Basel). 2022 Apr 19;10(5):634. doi: 10.3390/vaccines10050634.

Authors: Dimitrios Papagiannis, Theodoros Laios, Konstantinos Tryposkiadis, Konstantinos Kouriotis, Xenophon Roussis, Georgios Basdekis, Panagiotis Boudouris, Christos Cholevas, Stergios Karakitsios, Pindaros Kakavas, Theoharis Kiriakidis, Panagiotis Kouloumentas, Georgios Kouvidis, Grigoris Manoudis, Pantelis Nikolaou, Christos Theos, Andreas-Nikolaos Piskopakis, Ioannis Rallis, Stavros Ristanis, Alexandros Toliopoulos, Grigoris Zisis, Yiannis Theodorakis, Konstantinos I Gourgoulianis, Georgios Rachiotis

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Summary: Little is known about the risk of COVID-19 infection among footballers. We aimed to investigate the incidence and characteristics of COVID-19 infection among footballers. In total, 480 football players of Super League Greece and 420 staff members participated in a prospective cohort study, which took place from May 2020 to May 2021. Nasopharyngeal swabs were collected from footballers and staff members weekly. All samples (n = 43,975) collected were tested using the reverse transcriptase polymerase chain reaction (RT-PCR) test for the detection of "SARS-CoV-2". In total, 190 positive cases (130 among professional football players and 60 among staff) were recorded. Out of the 190 cases that turned positive, 64 (34%) cases were considered as symptomatic, and 126 (66%) cases were asymptomatic. The incidence rate of a positive test result for footballers was 0.57% (confidence interval (CI) 0.48-0.68%) and for staff members it was 0.27% (CI 0.20%, 0.34%), respectively. Footballers recorded a twofold increased risk of COVID-19 infection in comparison to staff members (relative risk = 2.16; 95% CI = 1.59-2.93; p-value &lt; 0.001). No significant transmission events were observed during the follow-up period. We found a low incidence of COVID-19 infection among professional footballers over a long follow-up period. Furthermore, the implementation of a weekly diagnostic testing (RT-PCR) was critical to break the transmission chain of COVID-19, especially among asymptomatic football players and staff members.



#8 Physical Demands during the Game and Compensatory Training Session (MD + 1) in Elite Football Players Using Global Positioning System Device

Reference: Sensors (Basel). 2022 May 19;22(10):3872. doi: 10.3390/s22103872.

Authors: Gabriel Calderón-Pellegrino, Leonor Gallardo, Jorge Garcia-Unanue, Jose Luis Felipe, Antonio Hernandez-Martin, Víctor Paredes-Hernández, Javier Sánchez-Sánchez

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Summary: The aims of this study were to analyze the differences of physical demands of non-starter players regarding the playing time during the competition and to evaluate the physical demands of the compensatory training (MD + 1C) for substitute players in elite football. The match statistics and MD + 1C of substitute players from a professional Spanish LaLiga football club were analyzed using a 10-Hz global positioning system (GPS) Apex GPS system device, which has been validated as a reliable and valid method to analyze performance in team sports, during all games of the 2016/2017, 2017/2018 and 2018/2019 seasons. The starting players showed both lower total distances covered and high-intensity actions compared to the substitutes. Regarding the minutes played by the substitutes, greater physical performance was found for the players with fewer minutes (5-15 min). Furthermore, no differences were found between first and second divisions regarding physical performance of substitutes (p &gt; 0.05). This study highlights the importance of individualizing the workload of training sessions for substitutes and starters. Furthermore, the complementary session should be individualized according to the minutes played by the substitutes. These players are potentially under-loaded compared to starters, especially in terms of high-intensity actions, therefore additional session-specific training for each substitute would be useful to reach the optimal training load according to the minutes played during the game.



#9 The Influence of Maximum Squatting Strength on Jump and Sprint Performance: A Cross-Sectional Analysis of 492 Youth Soccer Players

Reference: Int J Environ Res Public Health. 2022 May 11;19(10):5835. doi: 10.3390/ijerph19105835.

Authors: Michael Keiner, Torsten Brauner, Björn Kadlubowski, Andre Sander, Klaus Wirth

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Summary: This study aims to analyze the influence of relative strength performance, determined by parallel back squats (REL SQ), on 30 m sprinting (LS) and on jumping performance (squat [SJ], countermovement [CMJ]) in a large sample (n = 492) of elite youth soccer players. The soccer players were divided into subgroups based on their strength performance: strength level 1 (0.0-0.5 REL SQ), strength level 2 (&gt;0.5-1.0 REL SQ), strength level 3 (&gt;1.0 to 1.5 REL SQ), strength level 4 (&gt;1.5 to 2.0 REL SQ), and strength level 5 (&gt;2.0 REL SQ). The results of this study show that REL SQ explains 45-53% (r = |0.67-0.73|) of the variance of SJ, CMJ, and LS for the total sample. Strength levels 2-4 showed similar coefficients of correlation in jumping performance (r = |0.42-0.55|) and strength levels 2 and 3 in sprint performance (r = |0.41|). The respective extreme strength levels showed lower coefficients of correlation with the sprinting and jumping performance variables (r = |0.11-0.29|). No coefficients could be calculated for strength level 5 because no athlete achieved an appropriate strength level (&gt;2.0 REL SQ). The data from this study show a clear influence of REL SQ on sprint and jump performance, even in a large sample.



#10 Validation of Instrumented Football Shoes to Measure On-Field Ground Reaction Forces

Reference: Sensors (Basel). 2022 May 11;22(10):3673. doi: 10.3390/s22103673.

Authors: Alexandre Karamanoukian, Jean-Philippe Boucher, Romain Labbé, Nicolas Vignais

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Summary: Ground reaction forces (GRF) have been widely studied in football to prevent injury. However, ambulatory tools are missing, posing methodological limitations. The purpose of this study was to assess the validity of an innovative football shoe measuring normal GRF (nGRF) directly on the field through instrumented studs. A laboratory-based experiment was first conducted to compare nGRF obtained with the instrumented shoe (IS) to vertical GRF (vGRF) obtained with force platform (FP) data, the gold standard to measure vGRF. To this aim, three subjects performed 50 steps and 18 counter-movement jumps (CMJs). Secondly, eleven subjects completed running sprints at different velocities on a football field, as well as CMJs, while wearing the IS. Good to excellent agreement was found between the vGRF parameters measured with the FP and the nGRF measured by the IS (ICC &gt; 0.75 for 9 out of 11 parameters). Moreover, on-field nGRF patterns demonstrated a progressive and significant increase in relation with the running velocity (p &lt; 0.001). This study demonstrated that the IS is a highly valid tool to assess vGRF patterns on a football field. This innovative way to measure vGRF in situ could give new insights to quantify training load and detect neuromuscular fatigue.



#11 Nutritional Intake and Training Load of Professional Female Football Players during a Mid-Season Microcycle

Reference: Nutrients. 2022 May 21;14(10):2149. doi: 10.3390/nu14102149.

Authors: César Leão, António Pedro Mendes, Catarina Custódio, Mafalda Ng, Nuno Ribeiro, Nuno Loureiro, João Pedro Araújo, José Afonso, Sílvia Rocha-Rodrigues, Francisco Tavares

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Summary: Football (soccer) is a high-intensity intermittent sport with large energy demands. In a repeated-measures design, we analysed the nutritional intake and training load of fourteen female football players (22.50 ± 4.38 y; 57.23 ± 8.61 kg; 164 ± 6.00 cm; 18.33 ± 2.48% of fat mass and 23.71 ± 2.51 kg of muscle mass) competing in the highest female Football Portuguese League across a typical mid-season microcycle. The microcycle had one match day (MD), one recovery session (two days after the MD, MD+2), three training sessions (MD-3, MD-2, MD-1) and two rest days (MD+1). Energy intake and CHO ( intake were lower on the days before the competition (MD+2, MD-3, MD-2 and MD-1 vs. MD; p &lt; 0.05; ES: 0.60-1.30). Total distance, distance covered at high-speed running (HSRD) and the high metabolic distance load (HMLD) were lower on MD+2, MD-3 and MD-1 compared with MD (p &lt; 0.05; ES: &lt;0.2-5.70). The internal training load was lower in all training sessions before the competition (MD+2, MD-3, MD-2 and MD-1 vs. MD; p ≤ 0.01; ES: 1.28-5.47). Despite the small sample size and a single assessment in time, the results suggest that caloric and CHO intake were below the recommendations and were not structured based on the physical requirements for training sessions or match days.



#12 Cardiopulmonary Exercise Testing and Cardiac Biomarker Measurements in Young Football Players: A Pilot Study

Reference: J Clin Med. 2022 May 14;11(10):2772. doi: 10.3390/jcm11102772.

Authors: Alexandru-Dan Costache, Mihai Roca, Cezar Honceriu, Irina-Iuliana Costache, Maria-Magdalena Leon-Constantin, Ovidiu Mitu, Radu-Ștefan Miftode, Alexandra Maștaleru, Dan Iliescu-Halițchi, Codruța-Olimpiada Halițchi-Iliescu, Adriana Ion, Ștefania-Teodora Duca, Delia-Melania Popa, Beatrice Abălasei, Veronica Mocanu, Florin Mitu

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Summary: Constant and intense physical activity causes physiological adaptive changes in the human body, but it can also become a trigger for adverse events, such as sudden cardiac arrest or sudden cardiac death. Our main objective was to assess the use of combined cardiopulmonary exercise testing (CPET) and cardiac biomarker determinants in young professional athletes. We conducted a study which involved the full examination of 19 football players, all male, aged between 18 and 20 years old. They underwent standard clinical and paraclinical evaluation, a 12-lead electrocardiogram (ECG), and transthoracic echocardiography (TTE). Afterwards, a tailored CPET was performed and peripheral venous blood samples were taken before and 3 h after the test in order to determine five biomarker levels at rest and post-effort. The measured biomarkers were cardiac troponin I (cTnI), myoglobin (Myo), the MB isoenzyme of creatine-kinase (CK-MB), the N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and D-dimers. While cTnI and NT-proBNP levels were undetectable both at rest and post-effort in all subjects, the variations in Myo, CK-MB and D-dimers showed significant correlations with CPET parameters. This highlights the potential use of combined CPET and biomarker determinants to evaluate professional athletes, and encourages further research on larger study groups.



#13 Neuromuscular Fatigue in Cerebral Palsy Football Players after a Competitive Match According to Sport Classification and Playing Position

Reference: Int J Environ Res Public Health. 2022 May 17;19(10):6070. doi: 10.3390/ijerph19106070.

Authors: Matías Henríquez, Luis Felipe Castelli de Campos, Fernando Muñoz-Hinrichsen, María Isabel Cornejo, Javier Yanci, Raul Reina

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Summary: This study aimed to determine the rated perceived exertion (RPE) and match load (RPE-ML) to compare pre-post-match vertical jump (VJ) capacity according to cerebral palsy (CP) players' sport classes (i.e., FT1-FT3) and playing positions and to explore whether the neuromuscular performance variation is associated with the internal load of para-footballers with CP. Fifty-six male para-footballers performed two VJ tests before and immediately after a competitive CP football match, followed by measurements of the players' RPE and RPE-ML. There were no significant differences (p &gt; 0.05) in the pairwise comparisons for RPE and RPE-ML according to sport classes and playing position. A significant reduction in the VJ performance was found for each player sport class and playing position in squat jump (SJ) (p &lt; 0.01; 0.24 &lt; dg &lt; 0.58) and countermovement jump (CMJ) (p &lt; 0.05; 0.22 &lt; dg &lt; 0.45). Regarding the pairwise comparisons, players with the minimal impairment criteria (FT3) obtained higher deficit scores during SJ than those belonging to the FT1 and FT2 (p = 0.003; 1.00 &lt; dg &lt; 1.56). Defenders experienced the lowest performance compared to midfielders and attackers in SJ performance (p = 0.027; 0.94 &lt; dg &lt; 1.28). Significant correlations were obtained between ΔSJ or ΔCMJ and RPE or RPE-ML (r = -0.58 to -0.75; p &lt; 0.001). These findings provide novel information supporting the notion that fatigue induced after a competitive match causes notable impairments in VJ performance differentiated according to sport class and playing position in para-footballers with CP.



#14 Sex Differences in Pre-Season Anthropometric, Balance and Range-of-Motion Characteristics in Elite Youth Soccer Players

Reference: Healthcare (Basel). 2022 Apr 28;10(5):819. doi: 10.3390/healthcare10050819.

Authors: Luis Llurda-Almuzara, Albert Pérez-Bellmunt, Noé Labata-Lezaun, Carlos López-de-Celis, Jason Moran, Nicholas C Clark

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Summary: In soccer, injury epidemiology differs between males and females. It is clinically useful to know whether there are between-sex differences in selected characteristics relevant to primary injury risk and injury prevention practices. The purpose of this study was to explore between-sex differences in anthropometric, balance, and range-of-motion characteristics in Spanish elite male and female youth soccer players. This was a pre-season cross-sectional study. Sixty-nine males (age 16.8 ± 0.9 yr; height 175.9 ± 6.8 cm; mass 67.9 ± 6.3 kg) and thirty-seven females (age 17.2 ± 1.7 yr; height 164.0 ± 6.3 cm; mass 59.0 ± 5.8 kg) participated. Anthropometrics (standing/sitting height, bodymass, right/left leg length) and right/left anterior reach test (ART), hip internal/external active range of motion, active knee extension (AKE), and weightbearing lunge test (WBLT) were measured. Between-sex differences were assessed with Bonferroni-corrected Mann-Whitney U tests and Cliff's delta (d). Between-sex significant differences (p &lt; 0.003, d ≥ 0.50) were observed for anthropometric data and for hip internal rotation. No between-sex significant differences were observed for ART/AKE/WBLT measures. Between-sex significant differences with large effect sizes were identified for anthropometric data and right/left hip internal rotation. The present study adds new data to the literature for young Spanish male and female soccer players. The present findings will help inform clinical reasoning processes and future injury prevention research for elite male and female youth soccer players.



#15 Associations between Training Load and Well-Being in Elite Beach Soccer Players: A Case Report

Reference: Int J Environ Res Public Health. 2022 May 20;19(10):6209. doi: 10.3390/ijerph19106209.

Authors: Júlio A Costa, Pedro Figueiredo, Alberto Prata, Tiago Reis, Joana F Reis, Luís Nascimento, João Brito

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Summary: The current case study aimed to quantify within-subjects correlations between training load and well-being in elite male beach soccer players. Data were obtained over three consecutive days during the preparation camp for the FIFA Beach Soccer World Cup Russia 2021. The session rating of perceived exertion (s-RPE) and external training load metrics using global positioning system (GPS) were recorded. Eleven players reported perceived well-being (sleep quality, fatigue, muscle soreness and stress) using a Likert scale (Hooper Index) before breakfast. Within-subjects correlation coefficients between workload and well-being were calculated. Workload metrics and perceived well-being indices were significantly lower on day three than on days one and two. The Hooper Index presented a very large positive correlation with s-RPE (r = 0.86 [0.67, 0.94], 95% confidence interval, CI), exposure time (r = 0.88 [0.71, 0.95]), total distance (r = 0.83 [0.60, 0.93]), high-speed distance (r = 0.77 [0.50, 0.91]), and number of sprints (r = 0.75 [0.47, 0.90]). Sleep quality presented a moderate to large positive correlation with s-RPE (r = 0.51 [0.11, 0.77]), exposure time (r = 0.50 [0.10, 0.76]), high-speed distance (r = 0.53 [0.15, 0.78]), number of sprints (r = 0.62 [0.28, 0.83]) and total distance (r = 0.41 [0.18, 0.78]). Fatigue presented a large to very large positive correlation with s-RPE (r = 0.85 [0.66, 0.94]), exposure time (r = 0.90 [0.78, 0.96]), total distance (r = 0.86 [0.68, 0.94]), high-speed distance (r = 0.65 [0.31, 0.84]) and number of sprints (r = 0.56 [0.18, 0.79]). Muscle soreness presented a large to very large positive correlation with s-RPE (r = 0.79 [0.56, 0.91]), exposure time (r = 0.83 [0.62, 0.93]), total distance (r = 0.81 [0.59, 0.92]), high-speed distance (r = 0.75 [0.47, 0.89]) and number of sprints (r = 0.59 [0.22, 0.81]). Overall, workload presented a meaningful correlation with perceived well-being indices in elite male beach soccer players during a training camp. These findings suggest that workload metrics and perceived well-being indices can be implemented into the daily routine of an elite beach soccer team, which may assist coaches, sports scientists, and practitioners in better preparing players for beach soccer competitions.



#16 A low-volume Nordic hamstring curl programme improves change of direction ability, despite no architectural, strength or speed adaptations in elite youth soccer players

Reference: Res Sports Med. 2022 Jun 1;1-12. doi: 10.1080/15438627.2022.2079984. Online ahead of print.

Authors: James Siddle, Kristian Weaver, Matt Greig, Damian Harper, Christopher Michael Brogden

Summary: Nordic hamstring curls (NHC) are a commonly used injury intervention method in amateur team sports. Seventeen elite male academy soccer players performed an 8-week low volume NHC programme. Pre-post intervention measures of isokinetic eccentric knee flexor (KF) strength, linear speed, COD performance, hamstring muscle thickness, pennation angle and fascicle length were recorded. No significant main effects were observed for measures of isokinetic KF strength (P ≥ 0.19), linear sprint speed (P ≥ 0.47) or hamstring muscle architecture (P ≥ 0.30). However, significance was noted for improved COD performance (P < 0.01; mean difference, -0.06, p = 0.001, 95% CI = 0.03 to 0.09; d = 0.80), exceeding the minimal detectable difference (MDD = 0.05 s). A low-volume NHC intervention may contribute to significant improvements in COD ability, independent of no significant changes in eccentric KF strength, linear sprint speed or muscle architectural properties in elite youth soccer players.



#17 Semantic Concept Mining Based on Hierarchical Event Detection for Soccer Video Indexing

Reference: J Multimed. 2009 Oct;4(5):298-312. doi: 10.4304/jmm.4.5.298-312.

Authors: Maheshkumar H Kolekar, Kannappan Palaniappan, Somnath Sengupta, Gunasekaran Seetharaman

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Summary: In this paper, we present a novel automated indexing and semantic labeling for broadcast soccer video sequences. The proposed method automatically extracts silent events from the video and classifies each event sequence into a concept by sequential association mining. The paper makes three new contributions in multimodal sports video indexing and summarization. First, we propose a novel hierarchical framework for soccer (football) video event sequence detection and classification. Unlike most existing video classification approaches, which focus on shot detection followed by shot-clustering for classification, the proposed scheme perform a top-down video scene classification which avoids shot clustering. This improves the classification accuracy and also maintains the temporal order of shots. Second, we compute the association for the events of each excitement clip using a priori mining algorithm. We pro- pose a novel sequential association distance to classify the association of the excitement clip into semantic concepts. For soccer video, we have considered goal scored by team-A, goal scored by team-B, goal saved by team-A, goal saved by team-B as semantic concepts. Third, the extracted excitement clips with semantic concept label helps us to summarize many hours of video to collection of soccer highlights such as goals, saves, corner kicks, etc. We show promising results, with correctly indexed soccer scenes, enabling structural and temporal analysis, such as video retrieval, highlight extraction, and video skimming.



#18 Modelling the potential spread of virus during soccer matches

Reference: BMJ Open Sport Exerc Med. 2022 May 12;8(2):e001268. doi: 10.1136/bmjsem-2021-001268. eCollection 2022.

Authors: Nikolas Sten Knudsen, Manuel Mounir Demetry Thomasen, Thomas Bull Andersen

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Summary: In the present study, we model the potential spread of virus during soccer matches. Tracking data from 14 elite soccer matches was used. One player in each match was designated as a virus carrier (called 'infected player') for the purpose of the study. The exposure score (measured in seconds) was calculated as time spent closer than 1.5 m from the infected player or time spent in an exponentially declining zone, where the infected player was positioned earlier. The results revealed that, on average, each player was exposed for 87.8 s per match. Potential spread of virus during soccer matches was modelled and it revealed that the exposure to a virus during soccer matches is limited.



#19 Sponsorship by food and beverage companies in soccer: an analysis of the 2019 Copa América

Reference: Rev Saude Publica. 2022 May 27;56:41. doi: 10.11606/s1518-8787.2022056003491. eCollection 2022.

Authors: Larissa Cardoso de Miranda Araujo, Juliana de Paula Matos, Paula Martins Horta

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Summary: The aim was to identify the sponsorship by food and beverage companies of the teams participating in the 2019 Copa América Soccer Cup and associate this sponsorship with characteristics of the teams and their respective countries. The sponsors of the 10 teams participating in the 46th edition of the Copa América were identified. These entities were classified into (i) food companies, (ii) alcoholic beverage companies, and (iii) other segments. The food companies were classified according to their products, according to the NOVA classification. In addition, data on the number of titles previously won by the teams in the Copa America and the World Cup were obtained, as well as data on the countries' Human Development Index, annual per capita sales of ultra-processed foods, and annual per capita consumption of alcoholic beverages. A total of 89 sponsorships were identified for the 10 teams studied, some of these supporting two or more teams. Eighteen percent of the sponsors were food companies, with 12.4% being ultra-processed foods. The alcoholic beverage category represented 7.9% of the sponsors. Ultra-processed beverage and alcoholic beverage companies sponsored seven of the 10 teams studied. We noted higher participation of ultra-processed foods company sponsors in teams from countries with higher Human Development Index, sales of ultra-processed foods, and number of Copa América and World Cup titles. The sponsorship by alcoholic beverage companies was higher for teams from countries with lower Human Development Index, alcohol consumption, and number of Copa América and World Cup titles. A significant presence of ultra-processed food and alcoholic beverage companies as sponsors of South American soccer teams was noted, along with the fact that sport performance characteristics of the teams and socioeconomic and market issues of the countries are associated with the occurrence of sponsorship.



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