Latest research in football - week 14 - 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 Assessing the usefulness of submaximal exercise heart rates for monitoring cardiorespiratory fitness changes in elite youth soccer players

Reference: Sci Med Footb. 2022 Mar 29.  doi: 010.1080/24733938.2022.2060520. Online ahead of print.

Authors: Stefan Altmann, Ludwig Ruf, Rainer Neumann, Sascha Härtel, Alexander Woll, Martin Buchheit

Summary: This study aimed to assess the value of monitoring fitness in elite youth soccer players (U15 to U19 age groups) by analyzing the concomitant changes in heart rate at submaximal intensity (HR12km/h) and the velocity at a lactate concentration of 4 mmol/l (v4mmol/l). Players were tested by means of an incremental treadmill test on two occasions during the summer pre-season in two consecutive seasons. Based on data from a total of 170 test comparisons from the U15 (n = 48 test comparisons), U16 (n = 40 test comparisons), U17 (n = 46 test comparisons), and U19 (n = 36 test comparisons) age groups, the agreement between substantial changes in HR12km/h and v4mmol/l was analyzed using the threshold combination of HR12km/h = 4.5% and v4mmol/l = 6.0%. Results revealed 2% full mismatches, 36% partial agreements, and 62% full agreements for the whole sample in terms of fitness change interpretation between both variables. The respective values for the U15 to U19 age groups ranged between 0-5% full mismatches, 28-44% partial agreements, and 56-68% full agreements with no meaningful differences between age groups. In conclusion, our findings confirm the practical value of using HR12km/h to monitor fitness changes in elite youth soccer players when lactate sampling during incremental tests is not possible.



#2 Acute effects of beetroot juice and caffeine co-ingestion during a team-sport-specific intermittent exercise test in semi-professional soccer players: a randomized, double-blind, placebo-controlled study

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 29;14(1):52. doi: 10.1186/s13102-022-00441-1.

Authors: Erfan Berjisian, Kerry McGawley, Bryan Saunders, Raúl Domínguez, Majid S Koozehchian, Caio Victor Coutinho de Oliveira, Ramin Rafiei, Hossein Miraftabi, Amir Sarshin, Alireza Naderi

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Summary: Beetroot juice (BJ) and caffeine (CAF) are considered as ergogenic aids among athletes to enhance performance, however, the ergogenic effects of BJ and CAF co-ingestion are unclear during team-sport-specific performance. This study aimed to investigate the acute effects of BJ and CAF co-ingestion on team-sport-specific performance, compared with placebo (PL), BJ, and CAF alone. Sixteen semi-professional male soccer players (age: 19.8 ± 2.2 years, body mass: 69.2 ± 6.1 kg, height: 177.3 ± 6.0 cm) completed four experimental trials using a randomized, double-blind study design: BJ + CAF, CAF + PL, BJ + PL, and PL + PL. Countermovement jump with arm swing (CMJAS) performance and cognitive function by Stroop Word-Color test were evaluated before and after the Yo-Yo Intermittent Recovery Test level 1 (YYIR1). Also, rate of perceived exertion (RPE), heart rate, and gastrointestinal (GI) discomfort were measured during each session. No significant differences were shown between test conditions for total distance covered in YYIR1 (BJ + CAF: 1858 ± 455 m, CAF + PL: 1798 ± 422 m, BJ + PL: 1845 ± 408 m, PL + PL 1740 ± 362 m; p = 0.55). Moreover, CMJAS performance, cognitive function, and RPE during the YYIR1 were not significantly different among conditions (p > 0.05). However, the average heart rate during the YYIR1 was higher in CAF + PL compared to PL + PL (by 6 ± 9 beats/min; p < 0.05), and GI distress was greater in BJ + CAF compared to PL + PL (by 2.4 ± 3.6 a.u.; p < 0.05). These results suggest, neither acute co-ingestion of BJ + CAF nor BJ or CAF supplementation alone significantly affected team-sport-specific performance compared to the PL treatment.



#3 Epidemiology of soccer injuries in Korea women national team for 5 years

Reference: J Exerc Rehabil. 2022 Feb 24;18(1):68-73.  doi: 10.12965/jer.2142698.349. eCollection 2022 Feb.

Authors: Chang-Hwa Joo

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Summary: The purpose of this study was to analyze the characteristics of injuries in female national soccer players. The injuries data were recorded by Korea Football Association medical staff using the Daily Medical Report provided by the Asian Football Confederation during a total 21 training camps and friendly and official matches from January 2014 to December 2018. A total of 483 players in the national team training camps and matches participated in the study, of which 377 players experienced more than one injury. Sports injuries accounted for 89% of the total 1,019 injuries; general diseases accounted for the remaining 11%. The number of injuries per 1,000 exposure hours was higher in matches than in training sessions. Most injuries that occurred during training and matches involved the lower extremities (79%). The most common injury diagnosed during training and matches was muscle rigidity (45%), followed by contusions/hematomas/bruises (22%) and sprain (15%). The largest proportions of injuries in terms of absence from soccer play were minimal injury (67%), followed by mild (29%), moderate (3.5%), and severe (1%). As conclusion, the characteristics of injuries during training sessions and matches were different. Rehabilitation and injury prevention programs need to developed for female soccer players to improve the players' performance.



#4 Incidence of Injury for Professional Soccer Players in the United States: A 6-Year Prospective Study of Major League Soccer

Reference: Orthop J Sports Med. 2022 Mar 24;10(3):23259671211055136. doi: 10.1177/23259671211055136. eCollection 2022 Mar.

Authors: Brian Forsythe, Derrick M Knapik, Matthew D Crawford, Connor C Diaz, David Hardin, John Gallucci, Holly Jacinda Silvers-Granelli, Bert R Mandelbaum, Lawrence Lemak, Margot Putukian, Eric Giza

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Summary: Despite an abundance of injury research focusing on European professional soccer athletes, there are limited injury data on professional soccer players in the United States. The aim was to describe the epidemiology of injury across multiple years in Major League Soccer (MLS) players. A web-based health management platform was used to prospectively collect injury data from all MLS teams between 2014 and 2019. An injury was defined as an incident that required medical attention and was recorded into the health management platform anytime over the course of the 2014-2019 seasons. Injuries and exposure data were recorded in training and match settings to calculate injury incidence. A total of 9713 injuries were recorded between 2014 and 2019. A mean 1.1 injuries per year per player were identified, with midfielders sustaining the largest number of injuries. The most common injuries were hamstring strains (12.3%), ankle sprains (8.5%), and adductor strains (7.6%). The mean time missed per injury was 15.8 days, with 44.2% of injuries resulting in no days missed. Overall injury incidence was 8.7 per 1000 hours of exposure, declining over the course of the investigation, with a 4.1-times greater mean incidence during matches (14.0/1000 h) than training (3.4/1000 h). Between 2014 and 2019, the most commonly reported injuries in MLS players were hamstring strains, ankle sprains, and adductor strains. Injury incidence during matches was 4.1 times greater when compared with training, while overall injury incidence was found to decline during the course of the study period.



#5 Biomechanical Analysis and Training Method Research on Head Shot Strength of Football Players

Reference: J Healthc Eng. 2022 Mar 15;2022:7594124. doi: 10.1155/2022/7594124. eCollection 2022.

Authors: Yipeng Yao, Shanshan Xiang

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Summary: With the development of intelligent sports in China and the rapid improvement of the strength of colleges and universities, the reform of traditional football players' header shooting training methods is becoming more and more urgent in order to solve some problems in the development of sports and speed up the intelligent training of Chinese football players. Based on this, this paper studies the biomechanical analysis and training method based on the integration of header strength data of football players. A dynamic header tracking model of football players based on a local search algorithm is designed. The data collection is realized from the aspects of athletes' header shooting training, skill improvement, physical consumption, and trajectory. The biological data of header shooting power is comprehensively analyzed and evaluated by using a local search algorithm. The results show that the training system based on a local search algorithm has the advantages of high feasibility, high data accuracy, and fast response speed. It can effectively conduct accurate guidance and improve the shooting accuracy according to the biological characteristics of header shooting intensity. This paper studies the biological analysis and training method of header strength of football players based on a local search algorithm. This has certain reference significance for accelerating the construction of intelligent training of Chinese football players.



#6 Biomechanical Load Quantification Using a Lower Extremity Inertial Sensor Setup During Football Specific Activities

Reference: Sports Biomech. 2022 Mar 28;1-16. doi: 10.1080/14763141.2022.2051596. Online ahead of print.

Authors: Bram J C Bastiaansen, Riemer J K Vegter, E Wilmes, Cornelis J de Ruiter, Koen A P M Lemmink, Michel S Brink

Summary: Training load monitoring systems in football do not focus on lower extremities and therefore potentially neglect important information to optimise performance or reduce injury risk. The current study aims to present joint and segment angular accelerations as novel indicators to quantify lower extremity biomechanical load measured by a new inertial sensor setup. Relationships were explored with commonly used whole-body training load indicators using principal component analysis (PCA). Sixteen male amateur football players performed a linear sprint and an agility T-test. An inertial sensor setup, and local position measurement system were used to collect training load data. Hip Load, Knee Load, Thigh Load and Shank Load were introduced to quantify lower extremity biomechanical load. Three principal components were identified for both tests, explaining 91% and 86% of the variance. The indicators for the lower extremities contributed to the second principal component for both tests and provide distinct information compared to whole-body load indicators. The results show the potential to use an inertial sensor setup combined with common monitoring systems to evaluate training load, which may help optimise future performance and reduce injury risk. These relationships should be further examined during other football specific activities such as shooting or jumping.



#7 How spatial constraints afford successful and unsuccessful penetrative passes in elite association football

Reference: Sci Med Footb. 2022 Mar 30.  doi: 10.1080/24733938.2022.2060519. Online ahead of print.

Authors: Bruno Travassos, Ricardo Monteiro, Diogo Coutinho, Farzad Yousefian, Bruno Gonçalves

Summary: The aim of the present study was to examine the spatial relations between teams (macro-level) and groups of players (meso-level) that afford successful penetrative passes (off-ball advantage) in elite football. Three balanced home matches from a Premier League team with 91 ball possessions in which a pass was performed into the opposition defensive area and overpassed the first defensive line, promoting a perturbation of the defensive team equilibrium, were selected for analysis. The spatial relations between teams were measured through spatial variables that captured the areas occupied by the teams, while the spatial relations between players were measured through variables that captured the distances and angles between attacking and defending players near the ball. Results revealed, at the macro-level, higher values of width ratio between teams and the width of the attacking team for unsuccessful penetrative passes (UPP), when compared to successful penetrative passes (SPP). At the meso-level, a general decrease in distances and an increase in angles between attacking and defending players were observed between successful to unsuccessful penetrative passes. These findings highlight the importance of using positional data analysis to identify teams' tactical profiles and to potentiate coaches' interventions.



#8 Physical demands on professional Spanish football referees during matches

Reference: Sci Med Footb. 2022 Apr 7.  doi: 10.1080/24733938.2022.2064539. Online ahead of print.

Authors: Gemma Martínez-Torremocha, Maria Luisa Martin-Sanchez, Jorge Garcia-Unanue, Jose Luis Felipe, Víctor Moreno-Pérez, Víctor Paredes-Hernández, Leonor Gallardo, Javier Sanchez-Sanchez

Summary: Refereeing is a demanding and intermittent activity that combines high-speed and low-intensity action. The aim of this study is to analyse the external and internal load of professional Spanish football referees during matches, and to compare the physical demands between halves and between referees in different categories. The physical demands on 40 professional football referees from the first and second divisions were recorded using global positioning system (GPS) technology and heart rate bands. External load (distance covered, speed, acceleration and deceleration) and internal load (perceived exertion [RPE] and heart rate [HR]) were analysed. The referees in the first division reported lower mean HR and RPE results than those in the second division (p < 0.05). The total distance covered was similar between the categories (p > 0.05), but the distance covered at different speed ranges was different (p < 0.05). Finally, greater reductions in performance between the first and the second halves were found in the second division referees (p < 0.05). The results of this study show differences according to the category of referee. This emphasises the need for specific training for professional referees according to their level to ensure optimal performance during matches.



#9 Comparing Sleep in Shared and Individual Rooms during a Training Camp in Elite Youth Soccer Player's: A Short Report

Reference: J Athl Train. 2022 Apr 5.  doi: 10.4085/1062-6050-0042.22. Online ahead of print.

Authors: Júlio A Costa, Pedro Figueiredo, Michele Lastella, Fábio Y Nakamura, José Guilherme, João Brito

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Summary: The study aims were to analyse the impact of sleeping in shared (SR) vs. individual (IR) rooms on objective and subjective sleep, and on slow-wave sleep (SWS)-derived cardiac autonomic activity during an official training camp in elite youth soccer players. Training and match workloads were characterized between training camps. Players slept significantly longer during IR than SR (+ 1:28 [1:18-1:42] min, P < .001). Sleep efficiency was significantly higher during IR than SR (+ 12 [10-15] %; P < .001), while sleep latency was significantly shorter during IR than SR (-3 [-15 - -4] min; P < .001). Subjective sleep quality was significantly lower during IR than SR (-2 [-3- -2] arbitrary units; P < .001). No significant differences were found for SWS-derived cardiac autonomic activity, neither for training/match workloads between training camps. Sleep may be affected by sleeping in shared compared to individual rooms during soccer training camps.



#10 The influence of angle-specific torque of the knee flexors and extensors on the angle-specific dynamic control ratio in professional female soccer players

Reference: J Sports Sci. 2022 Apr 7;1-8. doi: 10.1080/02640414.2022.2061251. Online ahead of print.

Authors: Steven James Eustace, Rhys Morris, Jason Tallis, Richard Michael Page, Matt Greig

Summary: The purpose of this study was to assess whether dynamic torque ratios (DCR) from isokinetic strength assessments of eccentric knee flexors (eccKF) and concentric knee extensors (conKE) display differences when stratified into specific angle-specific DCR (DCRAST) groups. Fifty-two professional female soccer players (age 21.30 ± 4.44 years; height 166.56 ± 5.17 cm; mass 61.55 ± 5.73 kg) from the English Women's Super League completed strength assessments of both lower limbs on an isokinetic dynamometer at 60°∙s-1. Angle-specific torque (AST) were used to calculate DCRAST to create sub-groups using clustering algorithms. The results identified for the dominant side that the Medium DCRAST group elicited significantly higher conKE AST when compared to Low and High DCRAST groups at increased knee extension (P ≤ 0.05). For the non-dominant side, the High DCRAST group had significantly higher and lower eccKF and conKE AST compared to the Low DCRAST group at increased knee extension (P ≤ 0.05). This study highlights that the inclusion of AST data may subsequently help practitioners to prescribe exercise that promotes strength increases at targeted joint angles. In turn, these approaches can be used to help reduce injury risk, identify rehabilitation responses and help inform return to play.



#11 Relative Skeletal Maturity and Performance Test Outcomes in Elite Youth Middle Eastern Soccer Players

Reference: Med Sci Sports Exerc. 2022 Apr 1. doi: 10.1249/MSS.0000000000002912. Online ahead of print.

Authors: Lorenzo Lolli, Amanda Johnson, Mauricio Monaco, Valter Di Salvo, Warren Gregson

Summary: The aim was to explore the influence of differences in relative skeletal maturity on performance test outcomes in elite youth soccer players from the Middle East. We integrated skeletal age and performance assessments using mixed-longitudinal data available for 199 outfield players (chronological age range: 11.7 to 17.8 yr) enrolled as academy student-athletes (annual screening range: 1 to 5 visits). Skeletal age was determined as per the Tanner-Whitehouse II (TW-II) protocol. Relative maturity was calculated as the difference (∆) between TW-II skeletal age minus chronological age. Performance test outcomes of interest were 10-m sprinting, 40-m sprinting, countermovement jump (CMJ) height and maximal aerobic speed (MAS). Separate random-effects generalized additive models quantified differences in performance test outcomes by relative skeletal maturity. Estimated differences were deemed practically relevant based on the location of the confidence interval (95%CI) against minimal detectable change values for each performance test outcome. For 40-m sprinting, differences of +0.51 s (95%CI, +0.35 to +0.67 s) and + 0.62 s (95%CI, +0.45 to +0.78 s) were practically relevant for relative maturity status of ∆ = -1.5 yr versus ∆ = +0.5 and ∆ = +1 yr, respectively. For CMJ height, a difference of -8 cm (95%CI, -10 to -5 cm) was practically relevant for ∆ = -1.5 yr versus ∆ = +1 yr relative maturity status comparison. Effects for 10-m sprinting and MAS were unclear. Integration of skeletal age and performance assessments indicated conventional maturity status classification criteria were inconsistent to inform player development processes in our sample. Between-player differences in test performance may depend on a substantial delay in skeletal maturation (∆ ≤ -1.5 yr) and the performance outcome measure.



#12 Sex-related Anthropometrics in a Lower-Body Mobility Assessment Among Professional Soccer Athletes

Reference: Int J Sports Phys Ther. 2022 Apr 2;17(3):474-482. doi: 10.26603/001c.32595. eCollection 2022.

Authors: Corbin A Hedt, Jessica T Le, Tyler Heimdal, Justin Vickery, Erin Orozco, Patrick C McCulloch, Bradley S Lambert

Summary: The functional movement screen (FMS™) and Y-balance test (YBT) are commonly used to evaluate mobility in athletes. The primary aim of this investigation was to determine the relationship between demographic and anthropometric factors such as sex, body composition, and skeletal dimension and scoring on YBT and FMS™ in male and female professional soccer athletes. During pre-season assessments, athletes from two professional soccer clubs were recruited and underwent body composition and skeletal dimension analysis via dual-energy X-ray absorptiometry (DEXA) scans. Balance and mobility were assessed using the YBT and FMS™. A two-tailed t-test was used to compare YBT between sexes. Chi-square was used for sex comparisons of FMS™ scores. Correlation analysis was used to determine if body composition and/or skeletal dimensions correlated with YBT or FMS™ measures. Type-I error; α=0.05. 40 Participants were successfully recruited: (24 males: 27±5yr, 79±9kg; |16 females: 25±3yr, 63±4kg). YBT: Correlations were found between anterior reach and height (r=-0.36), total lean mass (LM)(r=-0.39), and trunk LM(r=-0.39) as well as between posterolateral reach and pelvic width (PW)(r=0.42), femur length (r=0.44), and tibia length (r=0.51)(all p<0.05). FMS™: The deep squat score was correlated with height(r=-0.40), PW(r=0.40), LM(r=-0.43), and trunk LM (r =-0.40)(p<0.05). Inline lunge scores were correlated with height(r=-0.63), PW(r=0.60), LM(r=-0.77), trunk LM(r=-0.73), and leg LM(r=0.70)(all p<0.05). Straight leg raise scores were correlated with PW (r=0.45, p<0.05). Females scored higher for the three lower body FMS™ measures where correlations were observed (p<0.05). Lower body FMS™ scores differ between male and female professional soccer athletes and are related to anthropometric factors that may influence screening and outcomes for the FMS™ and YBT, respectively. Thus, these anatomical factors likely need to be taken into account when assessing baseline performance and risk of injury to improve screening efficacy.



#13 C-Reactive Protein and Skin Temperature of the lower limbs of Brazilian elite soccer players like load markers following three consecutive games

Reference: J Therm Biol. 2022 Apr;105:103188.  doi: 10.1016/j.jtherbio.2022.103188. Epub 2022 Feb 3.

Authors: Warley Duarte, Jorge L Rodrigues Júnior, Leandro V Paula, Mauro H Chagas, André G P Andrade, Christiano E Veneroso, Suene F N Chaves, Tane K F Serpa, Eduardo M Pimenta

Summary: The aim of the study was to compare the levels and relative responses of C-Reactive Protein (CRP) and Skin Temperature (Tsk) of the lower limbs (LLs) of elite soccer players following three consecutive games with short intervals (< 4 days). Eleven male professional athletes (age, 29.26 ± 4.52 years) from an Brazil elite team were evaluated, with measurements obtained before (Baseline), and at Post-Games times (24, 48 and 72h). CRP and Tsk levels at 24 h and 48 h Post-Games times were higher than Baseline levels (CRP, p < 0.001, d > 0.9; Tsk, p < 0.04, d > 0.58), additionally, the levels of these variables (CRP vs. Tsk) showed positive correlations (p < 0.05, rs = 0.60-0.88). The relative responses these variables were evaluated (Δ%CRP; Δ%Tsk). The 48h responses of Game 3 are respectively higher than 48 h responses of games 1 and 2, in Δ%CRP (p < 0.03; G3 vs. G1, r = 0.66; G3 vs. G2, r = 0.88) and in Δ%Tsk (p < 0.003; G3 vs. G1, r = 0.88; G3 vs. G2, r = 0.88). The 48 h Post-Game time seems to represent valuable contributions to understanding the development regarding the magnitude and duration of inflammatory processes associated with recovery. Additionally, the positive correlations that were verified allow an increase in the robustness of the analysis of the load of consecutive games through CRP and Tsk of the LLs. Then, these results indicate a physiological stress and a probable cumulative effect of the game loads due to short intervals (< 4 days), which is reinforced by the verified outcome of the Total Distance covered (G3 < G2, p = 0.003; r = 0.88). These findings can contribute to better load control and greater robustness of injury prevention programs.



#14 Repeated Sprint Protocols With Standardized Versus Self-Selected Recovery Periods in Elite Youth Soccer Players: Can They Pace Themselves? A Replication Study

Reference: Pediatr Exerc Sci. 2022 Apr 7;1-9. doi: 10.1123/pes.2021-0082. Online ahead of print.

Authors: Florian A Engel, Stefan Altmann, Hamdi Chtourou, Alexander Woll, Rainer Neumann, Tomer Yona, Billy Sperlich

Summary: Replicating the studies of Gibson et al and Brownstein et al to assess performance, and physiological, and perceived variables during a repeated sprint protocol (RSP) with standardized versus self-selected recovery in youth soccer players. Nineteen male soccer players (age 13.1 [1.3] y) completed 2 separate RSPs. RSP1: 10 × 30-m sprints with 30-second recovery and RSP2: 10 × 30-m sprints interspersed with self-selected recovery periods. Mean time of both 10 × 30-m RSPs and self-selected recovery periods of RSP2 were assessed. Heart rate, blood lactate concentration, and rates of perceived exertion were measured following RSPs. RSP2 revealed longer recovery periods (RSP1: 30.0 [0.0] s; RSP2: 39.0 [7.7] s; P < .001; effect size d = 1.648) with shorter repeated sprint time (mean 30-m sprint time: RSP1: 4.965 [0.256] s; RSP2: 4.865 [0.227] s; P = .014; d = 0.414). Blood lactate concentration (P = .002-.005; d = 0.730-0.958), heart rate (P < .001; d = 1.353), and rates of perceived exertion (RSP1: 14.9 [1.9]; RSP2: 12.9 [2.1]; P = .016; d = 1.046) were higher following RSP1. In contrast to the original studies, the present replication study demonstrated that self-selected recovery periods during a RSP leads to better repeated sprint performance compared with standardized recovery periods in youth soccer players. The better repeated sprint performance with individual recovery durations in RSP2 was achieved with less physiological and perceived effort.



#15 Predicting Hamstring Strains in Soccer Players Based on ROM: An Analysis From a Gender Perspective

Reference: Res Q Exerc Sport. 2022 Apr 8;1-7. doi: 10.1080/02701367.2021.2011091. Online ahead of print.

Authors: Ángela Molina-Cárdenas, Tania Álvarez-Yates, Oscar García-García

Summary: The aim of this study was to explore if specific hip and knee range-of-movement (ROM) tests can predict a risk factor for hamstring strain (HS) injury in male and female soccer players. One hundred amateur soccer players (56 men and 44 women) performed six tests to determine hip and knee ROM: straight leg raise test (SLR), modified Thomas test (TT), hip internal and external rotation (ER), hip abduction and adduction, Nachlas test and Ridge test. A logistic regression analysis was carried out to create a predictive model for HS injuries. The percentage of HS injury was 20.45% and 30.35%, for female and male players. The logistic regression showed a significant model for both genders on the logit of suffering an HS injury with active-SLR and TT variables for females (R2CS = 0.491; R2N = 0.771) and active SLR and ER variables for males (R2CS = 0.623; R2N = 0.882). The predictive models correctly classify 95.5% and 94.6% of cases presenting good sensitivity (77.8% and 88.2%) and full (100%) and high (97.4%) specificity respectively. Furthermore, female players showed a greater ROM than males (p ≤ 0.01). Both female and male soccer players that suffered a HS injury had lower ROM in SLR, NT and RT and higher ROM in the TT that non-injured players. The tests that most likely predict HS injury are SLR and TT in females and SLR and ER in males. Thus, it is suggested to including specific exercises in amateur soccer players training programs to improve hip and knee ROM for injury prevention.



#16 Foot and ankle Osteoarthritis and Cognitive impairment in retired UK Soccer players (FOCUS): protocol for a cross-sectional comparative study with general population controls

Reference: BMJ Open. 2022 Apr 4;12(4):e054371. doi: 10.1136/bmjopen-2021-054371.

Authors: Shima Espahbodi, Gwen Fernandes, Eef Hogervorst, Ahmed Thanoon, Mark Batt, Colin W Fuller, Gordon Fuller, Eamonn Ferguson, Tobias Bast, Michael Doherty, Weiya Zhang

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Summary: Professional footballers commonly experience sports-related injury and repetitive microtrauma to the foot and ankle, placing them at risk of subsequent chronic pain and osteoarthritis (OA) of the foot and ankle. Similarly, repeated heading of the ball, head/neck injuries and concussion have been implicated in later development of neurodegenerative diseases such as dementia. A recent retrospective study found that death from neurodegenerative diseases was higher among former professional soccer players compared with age matched controls. However, well-designed lifetime studies are still needed to provide evidence regarding the prevalence of these conditions and their associated risk factors in retired professional football players compared with the general male population. The aim was to determine whether former professional male footballers have a higher prevalence than the general male population of: (1) foot/ankle pain and radiographic OA; and (2) cognitive and motor impairments associated with dementia and Parkinson's disease. Secondary objectives are to identify specific football-related risk factors such as head impact/concussion for neurodegenerative conditions and foot/ankle injuries for chronic foot/ankle pain and OA. This is a cross-sectional, comparative study involving a questionnaire survey with subsamples of responders being assessed for cognitive function by telephone assessment, and foot/ankle OA by radiographic examination. A sample of 900 adult, male, ex professional footballers will be recruited and compared with a control group of 1100 age-matched general population men between 40 and 100 years old. Prevalence will be estimated per group. Poisson regression will be performed to determine prevalence ratio between the populations and logistic regression will be used to examine risk factors associated with each condition in footballers. This study was approved by the East Midlands-Leicester Central Research Ethics Committee on 23 January 2020 (REC ref: 19/EM/0354). The study results will be disseminated at national and international meetings and submitted for peer-review publication.



#17 Body Pose Estimation Integrated With Notational Analysis: A New Approach to Analyze Penalty Kicks Strategy in Elite Football

Reference: Front Sports Act Living. 2022 Mar 10;4:818556. doi: 10.3389/fspor.2022.818556. eCollection 2022.

Authors: Guilherme de Sousa Pinheiro, Xing Jin, Varley Teoldo Da Costa, Martin Lames

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Summary: Body orientation of football players has proven to be an informative resource related to successful penalty kicks. OpenPose is one of the most popular open-source pose estimation technologies. This study aims: (i) to verify whether OpenPose can detect relevant body orientation angles from video data of penalty kicks in elite football and (ii) to investigate the relationship between these body angles and observable behaviors analyzed via an observational system for penalty kick analysis in football (OSPAF) with the penalty taker and goalkeeper strategy. A total of 34 penalty videos, with standardized viewing angle, from the main European leagues (2017-2020) were analyzed. Relevant body orientation variables were selected for penalty kicks analysis and were extracted from video data through OpenPose technique. The OSPAF, previously validated by experts, was used. The mean confidence score of OpenPose measures was 0.80 ± 0.14. OpenPose Retest reliability values was 0.976 ± 0.03. Logistic regressions were performed to investigate the relationship between OpenPose investigated variables (penalty taker: shoulder, hips, and nonkicking foot orientation; goalkeeper: right and left foot, anticipation), observable behaviors (OSPAF variables), and the strategy (penalty taker: goalkeeper dependent or independent; goalkeeper: shooter dependent or independent) in penalty kicks. The selected body orientation angle (goalkeeper anticipation) measured through OpenPose correlated significantly with the goalkeeper strategy. The prediction model of the goalkeeper's strategy had its accuracy increased to 97% when the variable goalkeeper anticipation was included [ χ2(35)χ(35)2 = 49.648, p < 0.001]. Lower degrees of goalkeeper anticipation, the goalkeeper tactical action (awaiting), and run up speed (slow) were associated with a kicker-dependent strategy. Regarding the penalty taker, the selected body angles measured through OpenPose did not associate significantly with the shooter strategy. Body orientation analysis by using OpenPose has shown sufficient reliability and provides practical applications for analyzing the strategies adopted by goalkeepers in penalty kicks in elite football.



#18 The exchange of health and performance information when transitioning from club to National football teams: A Delphi survey of National team practitioners

Reference: J Sci Med Sport. 2022 Mar 24;S1440-2440(22)00073-1. doi: 10.1016/j.jsams.2022.03.011. 

Authors: Alan McCall, Mike Davison, Andrew Massey, Chelsea Oester, Alexis Weber, Matthew Buckthorpe, Rob Duffield

Summary: To establish agreement in National team contexts when players transition from club to National team about (i) what medical and physical information to collect, (ii) how to use information (iii) identifying challenges to collection and (iv) collection methods. A series of sequential online questionnaires were sent to heads of medical and performance of the 32 National teams following the FIFA 2018 World Cup. Two separate Delphi's; 'Medical' and 'Physical' were administered. The 'Medical' respondent was the person responsible for player health. 'Physical' referred to the person responsible for physical performance. Content analyses were performed, with subsequent rounds designed according to responses of the previous. Agreement was considered at ≥70%. Twenty-three Medical (72%) and 14 (44%) Physical heads participated in Round 1 (3 rounds total). Seventeen Medical and 12 Physical respondents completed all rounds. Medical information agreed upon injury epidemiology, screening and injury treatment strategies. Physical information included training/match-loads, fatigue, wellness and current exercise programmes. Both Medical and Physical agreed information should be used to plan and individualise player programmes. Additionally medical information should guide coaches' national team selection. Communication, willingness to share and quality/completeness of information were agreed as main challenges. Medical and Physical respondents agreed a standardised reporting form and electronic shared database as best option to collect information. Our findings highlight the importance of health and performance information exchange between national and club teams. Further, this exchange should be cooperative, symbiotic and a two-way process to assist with improving player health.



#19 Comparing lab and field agility kinematics in young talented female football players: implications for ACL injury prevention

Reference: Eur J Sport Sci. 2022 Apr 11;1-25. doi: 10.1080/17461391.2022.2064771. Online ahead of print.

Authors: S Stefano Di Paolo, Eline Nijmeijer, Laura Bragonzoni, Evelien Dingshoff, Alli Gokeler, Anne Benjaminse

Summary: Modifiable (biomechanical and neuromuscular) anterior cruciate ligament (ACL) injury risk factors have been identified in laboratory settings. These risk factors were subsequently used in ACL injury prevention measures. Due to the lack of ecological validity, the use of on-field data in the ACL injury risk screening is increasingly advocated. Though, the kinematic differences between laboratory and on-field settings have never been investigated. The aim of the present study was to investigate the lower-limb kinematics of female footballers during agility movements performed both in laboratory and football field environments.Twenty-eight healthy young female talented football (soccer) players (14.9 ± 0.9 years) participated. Lower-limb joint kinematics was collected through wearable inertial sensors (Xsens Link) in three conditions: 1) laboratory setting during unanticipated sidestep cutting at 40-50°; on the football pitch 2) football-specific exercises (F-EX) and 3) football games (F-GAME). A hierarchical two-level random effect model in Statistical Parametric Mapping was used to compare joint kinematics among the conditions. Waveform consistency was investigated through Pearson's correlation coefficient and standardized z-score vector.In-lab kinematics differed from the on-field ones, while the latter were similar in overall shape and peaks. Lower sagittal plane range of motion, greater ankle eversion, and pelvic rotation were found for on-field kinematics (p<0.044). The largest differences were found during landing and weight acceptance.The biomechanical differences between lab and field settings suggest the application of context-related adaptations in female footballers and have implications in ACL injury prevention strategies.Highlights- Talented youth female football players showed kinematical differences between the lab condition and the on-field ones, thus adopting a context-related motor strategy.- Lower sagittal plane range of motion, greater ankle eversion, and pelvic rotation were found on the field. Such differences pertain to the ACL injury mechanism and prevention strategies.- Preventative training should support the adoption of non-linear motor learning to stimulate greater self-organization and adaptability- It is recommended to test football players in an ecological environment to improve subsequent primary ACL injury prevention programs.


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