Latest research in football - week 1 - 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 Variability of External Intensity Comparisons between Official and Friendly Soccer Matches in Professional Male Players

Reference: Healthcare (Basel). 2021 Dec 8;9(12):1708. doi: 10.3390/healthcare9121708.

Authors: Hadi Nobari, João Paulo Brito, Jorge Pérez-Gómez, Rafael Oliveira

Download link:

Summary: The aims of this study were to compare the external intensity between official (OMs) and friendly matches (FMs), and between first and second halves in the Iranian Premier League. Twelve players participated in this study (age, 28.6 ± 2.7 years; height, 182.1 ± 8.6 cm; body mass, 75.3 ± 8.2 kg). External intensity was measured by total duration, total distance, average speed, high-speed running distance, sprint distance, maximal speed and body load. In general, there was higher intensity in OMs compared with FMs for all variables. The first half showed higher intensities than the second half, regardless of the type of the match. Specifically, OMs showed higher values for total sprint distance (p = 0.012, ES = 0.59) and maximal speed (p < 0.001, ES = 0.27) but lower value for body load (p = 0.038, ES = -0.42) compared to FMs. The first half of FMs only showed lower value for body load (p = 0.004, ES = -0.38) than FMs, while in the second half of OMs, only total distance showed a higher value than FMs (p = 0.013, ES = 0.96). OMs showed higher demands of high intensity, questioning the original assumption of FMs demands. Depending on the period of the season that FMs are applied, coaches may consider requesting higher demands from their teams.



#2 Effect of Cycle-Based High-Intensity Interval Training and Moderate to Moderate-Intensity Continuous Training in Adolescent Soccer Players

Reference: Healthcare (Basel). 2021 Nov 25;9(12):1628. doi: 10.3390/healthcare9121628.

Authors: Bin Fang, Yonghwan Kim, Moonyoung Choi

Download link:

Summary: Cardiorespiratory fitness, anaerobic power, and lower extremity strength are essential for soccer players at all levels. An effective program should be developed to improve physical strength for adolescent soccer players who need to combine academic and technical training. This study analyzed the impact of short-term high intensity interval training (HIIT) training and traditional moderate intensity continuous training (MICT) on adolescent soccer players. Participants included 56 adolescent soccer players who were divided into HIIT and MICT groups. The training program was conducted 3 times a week for 4 weeks using cycle ergometer. Each session included the same resistance training program, and the characteristics of HIIT and MICT were applied to improve cardiorespiratory fitness and anaerobic power. Body composition analysis, graded exercise test for peak oxygen uptake (VO2 peak), Wingate anaerobic power test, and isokinetic knee strength test were performed. VO2 peak was improved in HIIT and MICT, but anaerobic threshold and heart rate recovery significantly improved in the HIIT group. Wingate anaerobic peak power had increased significantly in sets 1, 2, and 3 in the HIIT group, but showed significant improvement only in set 1 in the MICT group. The isokinetic strength improved significantly in the HIIT group at 60°/s and in the MICT group at 240°/s. There was no significant change in body composition in either group. In conclusion, short-term HIIT administered to adolescent soccer players effectively improved cardiorespiratory fitness in HIIT and MICT groups. While HIIT increased anaerobic threshold and power, MICT effectively improved muscle endurance. Short-term intensive training can be considered a time-efficient training strategy.



#3 The "Hockey" Assist Makes the Difference-Validation of a Defensive Disruptiveness Model to Evaluate Passing Sequences in Elite Soccer

Reference: Entropy (Basel). 2021 Nov 30;23(12):1607. doi: 10.3390/e23121607.

Authors: Leander Forcher, Matthias Kempe, Stefan Altmann, Leon Forcher, Alexander Woll

Download link:

Summary: With the growing availability of position data in sports, spatiotemporal analysis in soccer is a topic of rising interest. The aim of this study is to validate a performance indicator, namely D-Def, measuring passing effectiveness. D-Def calculates the change of the teams' centroid, centroids of formation lines (e.g., defensive line), teams' surface area, and teams' spread in the following three seconds after a pass and therefore results in a measure of disruption of the opponents' defense following a pass. While this measure was introduced earlier, in this study we aim to prove the usefulness to evaluate attacking sequences. In this study, 258 games of Dutch Eredivisie season 2018/19 were included, resulting in 13,094 attacks. D-Def, pass length, pass velocity, and pass angle of the last four passes of each attack were calculated and compared between successful and unsuccessful attacks. D-Def showed higher values for passes of successful compared to unsuccessful attacks (0.001 < p ≤ 0.029, 0.06 ≤ d ≤ 0.23). This difference showed the highest effects sizes in the penultimate pass (d = 0.23) and the maximal D-Def value of an attack (d = 0.23). Passing length (0.001 < p ≤ 0.236, 0.08 ≤ d ≤ 0.17) and passing velocity (0.001 < p ≤ 0.690, -0.09 ≤ d ≤ 0.12) showed inconsistent results in discriminating between successful and unsuccessful attacks. The results indicate that D-Def is a useful indicator for the measurement of pass effectiveness in attacking sequences, highlighting that successful attacks are connected to disruptive passing. Within successful attacks, at least one high disruptive action (pass with D-Def > 28) needs to be present. In addition, the penultimate pass ("hockey assist") of an attack seems crucial in characterizing successful attacks.



#4 The New Generation of Professional Soccer Talent Is Born under the Bias of the RAE: Relative Age Effect in International Male Youth Soccer Championships

Reference: Children (Basel). 2021 Dec 2;8(12):1117. doi: 10.3390/children8121117.

Authors: Benito Pérez-González, Jairo León-Quismondo, José Bonal, Pablo Burillo, Álvaro Fernández-Luna

Download link:

Summary: In 2019, numerous championships of youth categories soccer national teams were held. In the present study, we analyzed the existence of the Relative Age Effect (RAE) in four major male championships that, due to their importance and participating teams, most likely brought together the great bulk of the players who will dominate professional soccer in the next decade. Participants were professional and amateur youth male soccer players who participated in the last international championships: UEFA European Under-21 Championship (2017-2019); UEFA European Under-19 Championship (2019); South American Youth Football Championship (also known as Conmebol U-20) (2019); and FIFA U-20 World Cup (2019), with 823 players (20.25 ± 0.84 years). In the four championships analyzed, the existence of RAE was found for all players (p < 0.001). Analyzing the players when considering their position on the pitch and their championship, RAE was found, statistically significant, in 10 of the 16 classifications. New generations of elite soccer players arrive with a clear bias in the selection of talent; an unfair bias, based on unequal opportunities in early categories, which should be reviewed by sports authorities.



#5 The Impact of COVID-19 on Physical Performance and Mental Health-A Retrospective Case Series of Belgian Male Professional Football Players

Reference: Front Sports Act Living. 2021 Dec 13;3:803130. doi: 10.3389/fspor.2021.803130. eCollection 2021.

Authors: Jente Wagemans, Peter Catteeuw, Jan Vandenhouten, Jordi Jansen, Xander de Corte, Ciesse Ceusters, Dirk Vissers

Download link:

Summary: As every season, physical performance of players of Royal Antwerp FC's first team was regularly tested and mental well-being and mood were assessed during football season 2020-2021. Just like in the general population, several professional athletes were infected by SARS-CoV-2 during that season. COVID-19 is a complex disorder affecting multiple body systems, potentially damaging lungs, affecting the cardiovascular system or causing muscle weakness. Therefore, the impact of COVID-19 on performance was a major concern for the affected football players and their entourage.  The aim was to retrospectively examine the influence of COVID-19 on physical performance and mental health in professional football athletes during the season 2020-2021. Thirty-three professional athletes (age: 25.37 ± 4.11 years; height: 182.75 ± 7.62 cm; weight: 78.90 ± 8.97 kg) of a Belgian first division football club were assessed weekly during the 2020-2021 season. Weekly assessments comprised strength values of the hamstrings, hip abductors and hip adductors, jump performance, a modified Hooper questionnaire to assess mental status and nose swab PCR tests for COVID-19. Data analysis was performed from 2 weeks prior to COVID-19 contamination up to 8 weeks after the first positive test. Post-hoc Bonferroni correction was applied when performing statistical analysis.  Eleven players tested positive for COVID-19. Duration of contamination was 13 ± 7 days. There was no statistically significant difference before and after COVID-19 infection for jump performance, and adductor and abductor muscle strength (p > 0.05). Functional hamstring strength improved significantly 2 weeks (MD: 41.48; 95%CI: -3.79 to 86.75; p = 0.009) and 4 weeks (MD: 34.76; 95%CI: -8.91 to 78.42; p = 0.019) after COVID-19, whereas mood (MD: -0.60; 95%CI: -1.46 to 0.26; p = 0.041), stress levels (MD: -0.83; 95%CI: -1.85 to 0.20; p = 0.020) and total wellness (MD: -2.41; 95%CI: -5.25 to 0.43; p = 0.015) showed a significant reduction 8 weeks after confirmed COVID-19.  Physical performance varied considerably across outcomes before and 8 weeks after COVID-19 contamination in a sample of first division football players. However, affected football players' overall well-being, stress levels and mood diminished after a positive COVID-19 test.



#6 Effect of Position Specific Physiotherapy Training on performance of Indian football players: A Randomized Control Trial

Reference: Res Sports Med. 2021 Dec 28;1-9. doi: 10.1080/15438627.2021.2020787. Online ahead of print.

Authors: Ujwal L Yeole, N Praneetha, Chinmoyee Panigrahy

Summary: This study evaluated the effect of Position-Specific Physiotherapy Training on Agility, Speed endurance, and Balance in Indian Football Players. Around 70 football players were approached of which 48 gave consent to participate, and further 30 players sufficing inclusion criteria were recruited. They were divided into three groups, Forwards (Group A, n = 10), Defenders (Group B, n = 10), and Control (Group C, n = 10), according to their On-field Position. These participants underwent Position Specific Physiotherapy Training for 4 weeks. Significant improvement was noted in the Agility of Group A (p ≤ 0.001) and Group B (p ≤ 0.001) as compared to Group C (p = 0.071). Speed Endurance improved for Group A (p ≤0.001) and Group B (p ≤ 0.001) as compared to Group C (p = 0.111). Fatigue Index of Group A (p ≤ 0.001) and Group B (p ≤ 0.001) improved significantly as compared to Group C (p = 0.383). The Balance of Group A (p = 0.0063) and Group B (p = 0.0019) improved significantly as compared to Group C (p = 0.0632). Position-Specific Physiotherapy Training was found to be effective in improving Agility, Speed endurance, and Balance ability of the Indian Football Players.



#7 Quantitative evaluation of ankle cartilage in asymptomatic adolescent football players after season by T2-mapping magnetic resonance imaging

Reference: Biomed Eng Online. 2021 Dec 28;20(1):130. doi: 10.1186/s12938-021-00970-9.

Authors: Sipin Luo, Yi Cao, Peng Hu, Nan Wang, Yeda Wan

Download link:

Summary: Ankle sprain affects the structure and function of ankle cartilage. However, it is not clear whether the daily training and competition affect the ankle cartilage without acute injury. Changes in ankle cartilage without injury may influence future strategies to protect ankle function in athletes. This study aimed to evaluate whether the composition of ankle cartilage significantly altered in asymptomatic adolescent football players after a whole season of training and competition using T2-mapping magnetic resonance imaging (MRI). 12 local club's U17 asymptomatic adolescent football players without abnormalities in routine MRI were included. Routine and T2-mapping MRI were performed to measure the cartilage thickness of tibiotalar joint (TT) and posterior subtalar joint (pST) and T2 values in pre- and post-seasons. All of them took the right side as dominant foot. In the pre- and post-seasons, cartilage T2 values in TT (talus side) and pST (calcaneus side) were higher than that of TT (tibial side) and pST (talus side) (all p < 0.05), which was caused by magic angle effect and gravity load. No statistically significant differences in thickness after season in the other cartilages of ankle were found compared with that before the season (all p > 0.05). However, T2 values of TT (tibial side and talus side) cartilage in the dominant foot were significantly reduced after season (p = 0.008; p = 0.034). These results indicate that the microstructure of articular cartilage changes in the joints with greater mobility, although no trauma occurred and the gross morphology of cartilage did not change. Changes in the T2 values of tibiotalar joint cartilage in the dominant foot of healthy young athletes before and after the season suggest that the microstructure of cartilage had changed during sports even without injury. This finding suggests that the dominant ankle joint should be protected during football to delay degeneration of the articular cartilage.



#8 Global evaluation of the chemical hazard of recycled tire crumb rubber employed on worldwide synthetic turf football pitches

Reference: Sci Total Environ. 2021 Dec 22;812:152542. doi: 10.1016/j.scitotenv.2021.152542. 

Authors: Daniel Armada, Maria Llompart, Maria Celeiro, Pablo Garcia-Castro, Nuno Ratola, Thierry Dagnac, Jacob de Boer

Download link:

Summary: Social and environmental concern about the use of crumb rubber from end-of-life car tires in the construction of different sport and recreational facilities is increasing due to the presence of hazardous compounds. The aim of this research was the assessment of 42 organic chemicals, including polycyclic aromatic hydrocarbons (PAHs), phthalates, adipates, antioxidants and vulcanisation agents in a large number of infill samples (91) from synthetic turf football pitches of diverse characteristics and geographical origin. Samples were taken worldwide, in 17 countries on 4 continents, to show the global dimension of this problem. Ultrasound assisted extraction was employed to extract the target compounds, followed by gas chromatography coupled to tandem-mass spectrometry (UAE-GC-MS/MS). Seventy-eight crumb rubber samples as well as thirteen samples of alternatives materials, such as cork granulates, thermoplastic elastomers and coconut fibre, were analyzed. The results highlight the presence of all target PAH in most rubber samples at concentrations up to μg g-1, including the eight ECHA (European Chemicals Agency) PAHs considered as carcinogenic, and anthracene (ANC), pyrene (PYR) and benzo[ghi]perylene (B[ghi]P), catalogued as substances of very high concern (SVHC). Endocrine disruptors such as some plasticizers (mainly phthalates), and other compounds like benzothiazole (BTZ) and 2-mercaptobenzothiazole (MBTZ) were found reaching the mg g-1 level. This confirms the presence of the hazardous substances in the recycled crumb rubber samples collected all around the world. Three crumb rubber samples exceeded the limit of 20 μg g-1 for the sum of the eight ECHA PAHs. Regarding the chemical composition of other infill alternatives, cork appears to be adequate, while the thermoplastic elastomers contained high levels of some plasticizers. In addition, the plastic infill as well as the crumb rubber both are microplastics. Microplastics are considered contaminants of emerging concern since they do not biodegrade and remain in the environment for a long time.



#9 Air Pollutants Reduce the Physical Activity of Professional Soccer Players

Reference: Int J Environ Res Public Health. 2021 Dec 8;18(24):12928. doi: 10.3390/ijerph182412928.

Authors: Michał Zacharko, Robert Cichowicz, Marcin Andrzejewski, Paweł Chmura, Edward Kowalczuk, Jan Chmura, Marek Konefał

Download link:

Summary: The aim of the study was to determine the impact of air quality-analyzed on the basis of the model of integrating three types of air pollutants (ozone, O3; particulate matter, PM; nitrogen dioxide, NO2)-on the physical activity of soccer players. Study material consisted of 8927 individual match observations of 461 players competing in the German Bundesliga during the 2017/2018 and 2018/2019 domestic seasons. The measured indices included players' physical activities: total distance (TD) and high-intensity effort (HIE). Statistical analysis showed that with increasing levels of air pollution, both TD (F = 13.900(3); p = 0.001) and HIE (F = 8.060(3); p = 0.001) decrease significantly. The worsening of just one parameter of air pollution results in a significant reduction in performance. This is important information as air pollution is currently a considerable problem for many countries. Improving air quality during training sessions and sports competitions will result in better well-being and sporting performance of athletes and will also help protect athletes from negative health effects caused by air pollution.



#10 Effects of Copenhagen Adduction Exercise on the Architectural Characteristics of Adductors in U-17 Male Soccer Players: A Randomized Controlled Trial

Reference: Int J Environ Res Public Health. 2021 Dec 8;18(24):12956.  doi: 10.3390/ijerph182412956.

Authors: Alejandra Alonso-Calvete, Miguel Lorenzo-Martínez, Alexis Padrón-Cabo, Ezequiel Rey

Download link:

Summary: Groin injuries are one of the most prevalent in male soccer players, especially due to the hip adductor muscles' weakness which is considered as a risk factor in these injuries. The Copenhagen adduction (CA) exercise has been demonstrated to increase the strength of adductor muscles, but its effects on the architectural characteristics of adductor muscles have not been studied yet. This study aimed to analyze the effects of the CA exercise on the muscle thickness of the adductors. Twelve male U-17 soccer players were randomized into two groups: the control group with no intervention and the experimental group with an intervention based on an eight-week training with CA exercise. The muscle thickness of adductors was measured before and after the intervention using ultrasound imaging. A significant increase in muscle thickness was found in both control (p = 0.002) and experimental group (p < 0.001), but the experimental group did not show additional effects in comparison with the control group. In conclusion, an 8-week CA exercise intervention does not increase the muscle thickness of adductors in U-17 soccer players more than their regular training.



#11 Adherence to an Injury Prevention Warm-Up Program in Children's Soccer-A Secondary Analysis of a Randomized Controlled Trial

Reference: Int J Environ Res Public Health. 2021 Dec 13;18(24):13134. doi: 10.3390/ijerph182413134.

Authors: Matias Hilska, Mari Leppänen, Tommi Vasankari, Sari Aaltonen, Jani Raitanen, Anu M Räisänen, Kathrin Steffen, Hannele Forsman, Niilo Konttinen, Urho M Kujala, Kati Pasanen

Download link:

Summary: This study examined the impact of high adherence to a neuromuscular training (NMT) warm-up on the risk of lower extremity (LE) injuries in children's soccer. Twenty U11-U14 youth clubs (n = 92 teams, 1409 players) were randomized into intervention (n = 44 teams) and control (n = 48 teams) groups. The intervention group was advised to perform an NMT warm-up 2 to 3 times a week for 20 weeks. Team adherence, injuries, and exposure were registered throughout the follow-up. Primary outcomes were the incidence of soccer-related acute LE injuries and the prevalence of overuse LE injuries. Intervention teams conducted mean 1.7 (SD 1.0) NMT warm-ups weekly through follow-up. The seasonal trend for adherence declined significantly by -1.9% (95% CI -0.8% to -3.1%) a week. There was no difference in the incidence of acute injuries nor the prevalence of overuse LE injuries in high team adherence group (n = 17 teams) compared to controls. However, the risk for acute noncontact LE injuries was 31% lower in the high team adherence group compared to controls (IRR 0.69, 95% CI 0.49 to 0.97). In an efficacy analysis (n = 7 teams), there was a significant reduction of 47% in the rate of noncontact LE injuries (IRR 0.53, 95% CI 0.29 to 0.97). In conclusion, teams conducted NMT warm-up sessions regularly, but with a declining trend. A greater protective effect was seen in teams with the highest adherence to the NMT warm-up.



#12 Exercise-Based Training Strategies to Reduce the Incidence or Mitigate the Risk Factors of Anterior Cruciate Ligament Injury in Adult Football (Soccer) Players: A Systematic Review

Reference: Int J Environ Res Public Health. 2021 Dec 18;18(24):13351. doi: 10.3390/ijerph182413351.

Authors: Jesús Olivares-Jabalera, Alberto Fílter-Ruger, Thomas Dos'Santos, Jose Afonso, Francesco Della Villa, Jaime Morente-Sánchez, Víctor Manuel Soto-Hermoso, Bernardo Requena

Download link:

Summary: Anterior cruciate ligament (ACL) is one of the most concerning injuries for football players. The aim of this review is to investigate the effects of exercise-based interventions targeting at reducing ACL injury rate or mitigating risk factors of ACL injury in adult football players. Following PRISMA guidelines, a systematic search was conducted in CINAHL, Cochrane Library, PubMed, Scopus, SPORTDiscus and Web of Science. Studies assessing the effect of exercise-based interventions in ACL injury incidence or modifiable risk factors in adult football players were included. 29 studies evaluating 4502 male and 1589 female players were included (15 RCT, 8 NRCT, 6 single-arm): 14 included warm-up, 7 resistance training, 4 mixed training, 3 balance, 1 core stability and 1 technique modification interventions. 6 out of 29 studies investigated the effect of interventions on ACL injury incidence, while the remaining 23 investigated their effect on risk factors. Only 21% and 13% studies evaluating risk of injury variables reported reliability measures and/or smallest worthwhile change data. Warm-up, core stability, balance and technique modification appear effective and feasible interventions to be included in football teams. However, the use of more ecologically valid tests and individually tailored interventions targeting specific ACL injury mechanisms are required.



#13 Contextual Variables Affect Running Performance in Professional Soccer Players: A Brief Report

Reference: Front Sports Act Living. 2021 Dec 13;3:778813. doi: 10.3389/fspor.2021.778813. eCollection 2021.

Authors: Diêgo Augusto, João Brito, Rodrigo Aquino, Pedro Figueiredo, Fabio Eiras, Márcio Tannure, Bruno Veiga, Fabrício Vasconcellos

Download link:

Summary: This study aimed to investigate the effects of contextual variables on running performance in Brazilian professional soccer players. Twenty male players from one club participating in the 1st Division of the Brazilian soccer championship were analyzed during 35 matches. Global Positioning System was used to determine total distance (TD) covered, distance covered and actions in high intensity and sprinting, and the number of accelerations, and decelerations. The independent variables used were match location, match outcome, opposition ranking, change of head coach, and distance traveled to play the matches. Total distance was higher in a way than home matches (9,712 vs. 9,533 m; p ≤ 0.05), and losses than draws and wins (9,846 vs. 9,400 vs. 9,551 m; p ≤ 0.05), whereas distance in sprinting was higher in draws than losses (203 vs. 175 m; p ≤ 0.01). Changing the head coach during the season resulted in overall lower distance covered in high intensity, sprinting, high-intensity actions (p ≤ 0.01), and decelerations (p ≤ 0.05). Higher values for distance covered in sprinting and high intensity were found in matches without travel compared to those with long-travel (p ≤ 0.05). Overall, running performance was affected by the location, match outcome, change of head coach, and distance traveled during the season.



#14 Skill assessments in youth soccer: A scoping review

Reference: J Sports Sci. 2021 Dec 30;1-29. doi: 10.1080/02640414.2021.2013617. Online ahead of print.

Authors: William McCalman, Zachary J Crowley-McHattan, Job Fransen, K J M Bennett

Summary: Talent identification in youth soccer is a complex decision-making process that requires selectors to judge an individual's future potential. While there has been considerable research into the performance characteristics of talented players, investigators have limited consensus on the best approach to assess soccer skills. Most of the research explains why we should measure skill instead of how we go about assessing skill. Therefore, the current scoping review aimed to synthesize and analyse skill assessments in youth soccer. Four electronic databases (EBSCO, ProQuest, PubMed, and Scopus) were searched for relevant studies. Information regarding the sample characteristics and methodological design of the skill assessments were extracted, synthesised, and presented in a qualitative analysis. Overall, 226 skill assessments were used across the 93 included studies. Male players from different ages (U/7-U/23) and playing levels comprised most (89%) of the collective sample. The majority of assessments were performed in settings not representative of football match-play (68%), focused on offensive skills (99%), and included skill outcome measures (95%). The variability of assessments highlights some confusion about the best way to assess soccer skill, potentially limiting selectors ability to identify skilful players. Ultimately, this will impact the number of quality players within the talent pool.



#15 Perceptions of professional soccer coaches, support staff and players toward virtual reality and the factors that modify their intention to use it

Reference: PLoS One. 2021 Dec 30;16(12):e0261378. doi: 10.1371/journal.pone.0261378. eCollection 2021.

Authors: Ben Greenhough, Steve Barrett, Chris Towlson, Grant Abt

Download link:

Summary: A small evidence base supports the use of virtual reality in professional soccer, yet there is a lack of information available on perceptions and desire to use the technology from those employed at professional soccer clubs. Therefore, the aim of the study was to compare and quantify the perceptions of virtual reality use in soccer, and to model behavioural intentions to use this technology. This study surveyed the perceptions of coaches, support staff, and players in relation to their knowledge, expectations, influences and barriers of using virtual reality via an internet-based questionnaire. To model behavioural intention, modified questions and constructs from the Unified Theory of Acceptance and Use of Technology were used, and the model was analysed through partial least squares structural equation modelling. Respondents represented coaches and support staff (n = 134) and players (n = 64). All respondents generally agreed that virtual reality should be used to improve tactical awareness and cognition, with its use primarily in performance analysis and rehabilitation settings. Generally, coaches and support staff agreed that monetary cost, coach buy-in and limited evidence base were barriers towards its use. In a sub-sample of coaches and support staff without access to virtual reality (n = 123), performance expectancy was the strongest construct in explaining behavioural intention to use virtual reality, followed by facilitating conditions (i.e., barriers) construct which had a negative association with behavioural intention. Virtual reality has the potential to be a valuable technology within professional soccer although several barriers exist that may prevent its widespread use.



#16 Angle specific analysis of hamstrings and quadriceps isokinetic torque identify residual deficits in soccer players following ACL reconstruction: a longitudinal investigation

Reference: J Sports Sci. 2022 Jan 5;1-7. doi: 10.1080/02640414.2021.2022275. Online ahead of print.

Authors: Paul J Read, Robin Trama, Sebastien Racinais, Sean McAuliffe, Jasenko Klauznicer, Marine Alhammoud

Summary: Analysing the isokinetic curve is important following ACL reconstruction as there may be deficits in torque production at specific points throughout the range of motion. We examined isokinetic (60°.s-1) torque-angle characteristics in 27 male soccer players (24.5 ± 3.9 years) at 3 time-points (17 ± 5; 25 ± 6; and 34 ± 7 weeks post-surgery). Extracted data included knee flexor and extensor peak torque, conventional hamstrings: quadriceps (H/Q) ratio, and angle-specific torque using Statistical Parametric Mapping (SPM). There were significant involved limb increases in extension peak torque at each assessment (p<0.001); however, asymmetry favouring the un-involved limb was observed (p<0.01). Flexion peak torque was greater on the un-involved limb at assessments 1 and 2 only (p<0.05). The angle of peak torque was not significantly different at individual time-points or within-limbs across the 3 assessments. SPM revealed involved limb angle-specific reductions in extension torque across the full range of motion at time-points 1 and 2 (p<0.001) but only in angles [51-80°] at assessment 3 (p<0.05). Between limb H/Q angle differences [33-45°] were shown at assessments 2 and 3. The ratio ranged from 1.60-0.74 depending on the angle tested. Angle-specific moment curves are useful for monitoring patterns of strength development during rehabilitation.



#17 Quadriceps and Hamstrings Strength Reference Values for Athletes With and Without Anterior Cruciate Ligament Reconstruction Who Play Popular Pivoting Sports, Including Soccer, Basketball, and Handball: A Scoping Review

Reference: J Orthop Sports Phys Ther. 2021 Dec 31;1-35. doi: 10.2519/jospt.2022.10693. Online ahead of print.

Authors: Nicky van Melick, Walter van der Weegen, Nick van der Horst

Summary: The aim was to synthesize and present reference values for quadriceps and hamstring strength tests in healthy athletes who play pivoting sports and athletes with anterior cruciate ligament reconstruction (ACLR) who play pivoting sports. PubMed, the Cochrane Library, MEDLINE, Embase and Web of Science was searched until January 26, 2021. We included reference values in two different categories: I) quadriceps and hamstring strength test outcomes from healthy pivoting sport athletes and II) quadriceps and hamstring strength test outcomes from pivoting sport athletes with ACLR at a specific time point during rehabilitation. We performed a qualitative synthesis for reference values from isokinetic (at 60, 180 and 300°/sec) and isometric quadriceps and hamstring strength tests. We summarized the data for type of sport, sex, sport participation level and age group. Of the 42 included studies, 26 reported reference values from healthy soccer players, 4 from healthy basketball players, 4 from healthy handball players and 11 from other healthy pivoting sport athletes. LSI dominant/non-dominant (LSI-D/ND) ranged from 98% to 114% for healthy athletes. Six studies reported reference values from pivoting sport athletes with ACLR at a specific time point during rehabilitation. After 7 months and beyond, strength values for athletes with ACLR are comparable to those of healthy pivoting sport athletes. This scoping review summarizes quadriceps and hamstrings strength reference values for athletes who play the most common pivoting sports, including soccer, basketball and handball. 



#18 Comparison of Head Impact Exposure Across Common Activities in Youth Soccer

Reference: Neurology. 2022 Jan 4;98(1 Supplement 1):S24. doi: 10.1212/01.wnl.0000801964.42946.75.

Authors: Stewart Pritchard, Tanner Filben, Sebastian Haja, Logan Miller, Mark Espeland, Joel Stitzel, Jillian Urban

Summary: The objective of this study was to compare head impact exposure across common training activities in soccer. Soccer is a popular youth sport in the United States, but repetitive head impacts during training may result in neurocognitive deficits. Current research has identified factors associated with increased head impact exposure in soccer, but research has yet to contextualize head impact exposure across soccer activities. Modifying practice structure may be an avenue for reducing head impact exposure and concussion risk in soccer. Eight U15 soccer players participated in this study for 2 soccer seasons. Players wore a custom instrumented mouthpiece sensor during all practices and games. On-field activities were recorded with a time-synchronized camera. Research personnel recorded the duration of all practice (e.g., technical training, team interaction) and game activities performed by each player, and film review was performed to identify all head contact events during each session. Head impact exposure was quantified in terms of peak kinematics and impacts per player per hour. The amount of time an athlete was exposed to an activity was also evaluated. Mixed effects models were used to compare peak kinematics and generalized linear models were used to compare impact rates across activity types. Activity types were associated with peak kinematics and impact rate. Technical training activities were associated with higher impact rates and lower mean kinematics compared to other activity types. Team interaction activities and game play were associated with the highest rotational kinematics, but the lowest impact rates. A similar number of player-to-player contact events occurred within technical training, team interaction, and game play activities. Interventions designed to reduce head impact frequency in soccer may benefit from targeting technical training activities; whereas, interventions designed to reduce head impact magnitude may benefit from targeting team interaction and game activities.



#19 Cam morphology is associated with MRI-defined cartilage defects and labral tears: a case-control study of 237 young adult football players with and without hip and groin pain

Reference: BMJ Open Sport Exerc Med. 2021 Dec 15;7(4):e001199. doi: 10.1136/bmjsem-2021-001199. eCollection 2021.

Authors: Joshua Heerey, Joanne Kemp, Rintje Agricola, Ramya Srinivasan, Anne Smith, Tania Pizzari, Matthew King, Peter Lawrenson, Mark Scholes, Thomas Link, Richard Souza, Sharmila Majumdar, Kay Crossley

Download link:

Summary: Football players are at risk of developing hip osteoarthritis (OA). Cam morphology (present in almost two of every three football players) may explain this heightened risk, but there is limited research on its role in hip OA development in younger athletes. Knowledge of this relationship will advance our understanding of the aetiology of hip OA in football players. We aimed to study the relationship between cam morphology size and MRI-defined cartilage defects and labral tears, and if this relationship differs by symptomatic state in young adult football players. For this case-control study, 182 (288 hips) symptomatic (hip and/or groin pain >6 months and positive flexion-adduction-internal-rotation (FADIR) test) and 55 (110 hips) pain-free football players (soccer or Australian football) underwent anteroposterior and Dunn 45° radiographs, and 3-Tesla MRI. Cam morphology size was defined using alpha angle, and cartilage defects and labral tears were scored semiquantitatively. Presence, location and score (severity) of cartilage defects and labral tears were determined. Each participant completed the International Hip Outcome Tool 33 and Copenhagen Hip and Groin Outcome Score. Greater alpha angle was associated with cartilage defects (OR 1.03, 95% CI 1.01 to 1.04) and labral tears (OR 1.02, 95% CI 1.01 to 1.04). Greater alpha angle was associated with superolateral cartilage defects (OR 1.03, 95% CI 1.02 to 1.05) and superior labral tears (OR 1.03, 95% CI 1.02 to 1.05). The association of alpha angle with MRI-defined cartilage defects and labral tears was no greater in football players with symptoms than in those without (p=0.189-0.937). Cam morphology size was associated with cartilage defects and labral tears in young adult football players with and without pain. This study provides evidence that cam morphology may contribute to the high prevalence of hip OA in football players. Prospective studies of football players are now needed to establish if cam morphology causes progression of cartilage defects and labral tears and development of hip OA.



#20 Are cam morphology size and location associated with self-reported burden in football players with FAI syndrome?

Reference: Scand J Med Sci Sports. 2022 Jan 3. doi: 10.1111/sms.14119. Online ahead of print.

Authors: Mark J Scholes, Joanne L Kemp, Benjamin F Mentiplay, Joshua J Heerey, Rintje Agricola, Matthew G King, Adam I Semciw, Peter R Lawrenson, Kay M Crossley

Download link:

Summary: Cam morphology size and location might affect the severity of reported burden in people with femoroacetabular impingement (FAI) syndrome. We investigated the relationship between cam morphology size (i.e., alpha angle) and self-reported hip/groin burden (i.e., scores for the International Hip Outcome Tool-33 (iHOT-33) and Copenhagen Hip and Groin Outcome Score (HAGOS)), examined separately for the anteroposterior pelvis (AP) and Dunn 45° radiographs in football players with FAI syndrome. In total, 118 (12 female) sub-elite football (soccer or Australian football) players with FAI syndrome with cam morphology (alpha angle ≥60°) participated. One blinded assessor quantified superior and anterosuperior cam morphology size by measuring alpha angles for the AP and Dunn 45° radiographs, respectively. Linear regression models investigated relationships between alpha angle (continuous independent variable, measured separately for the AP and Dunn 45° radiographs) and iHOT-33 and HAGOS scores (dependent variables). Larger anterosuperior cam morphology (seen on the Dunn 45° radiograph) was associated with lower (i.e., worse) scores for the iHOT-Total, iHOT-Symptoms, iHOT-Job, and iHOT-Social subscales (unadjusted estimate range -0.553 to -0.319 [95% confidence interval -0.900 to -0.037], P=0.002 to 0.027), but not the iHOT-Sport (P=0.459) nor any HAGOS scores (P=0.110 to 0.802). Superior cam morphology size (measured using the AP radiograph) was not associated with any iHOT-33 or HAGOS scores (P=0.085 to 0.975). Larger anterosuperior cam morphology may be more relevant to pain and symptoms in football players with FAI syndrome than superior cam morphology, warranting investigation of its effects on reported burden and hip disease over time.



#21 Is Football or Badminton Associated With More Positive Affect? The Links Between Affects and Sports Club Membership Among French Adolescents

Reference: Front Psychol. 2021 Dec 17;12:735189. doi: 10.3389/fpsyg.2021.735189. eCollection 2021.

Authors: Alexis Barbry, Annie Carton, Jérémy Coquart, Hervé Ovigneur, Camille Amoura, Williams Nuytens, Gabor Orosz

Download link:

Summary: Prior studies extensively examined the way sports club membership can lead to beneficial affective outcomes. Prior experiments also found that team sports, intensive sports, and sports that are frequently pursued can lead to even more affective benefits. However, no prior studies examined the differences between the affective benefits of specific sports. Based on prior results, we supposed that certain sports that meet all the previously set criteria-will provide the greatest affective benefits. The present large-scale investigation examined the data of adolescents (N = 12,849, female = 5,812, aged between 10 and 18, M age = 12.56 years, and SD age = 2.00) and aimed to fill this gap. Firstly, the results showed that-although differences in affect can be found between the lack of club membership and most of the sports club memberships-the differences between the specific sports are less striking. Secondly, the sports that are associated with the highest level of positive and the lowest level of negative affectivity are not necessarily the ones expected. Finally, adolescents who practice athletics, reported the lowest means of negative, and the highest means of positive affect. However, it did not differ significantly from the results regarding the most practiced sport in France: soccer. Our results suggest that soccer as the most practice sport among French adolescents was associated with more positive affects than the majority of the 10 most licensed members French sports practiced by teens between 2008 and 2019. All in all, being a member of a sports club is associated with affective benefits, and some specific sports clubs can have some extra benefits.


The Training Manager -