Latest research in football - week 15 - 2023

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


Following studies were retrieved for this week:

#1 Quantifying the Magnitude and Longevity of the Effect of Repetitive Head Impacts in Adolescent Soccer Players: Deleterious Effect of Long Headers Extend Beyond a Month

Reference: Neurotrauma Rep. 2023 Apr 21;4(1):267-275. doi: 10.1089/neur.2022.0085. eCollection 2023.

Authors: Farzin Shamloo, Maria Kon, Elizabeth Ritter, Anne B Sereno

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Summary: There is growing interest in the effects of sports-related repetitive head impacts (RHIs) on athletes' cognitive capabilities. This study examines the effect of RHIs in data collected from adolescent athletes to estimate the magnitude and longevity of RHIs on sensorimotor and cognitive performance. A non-linear regression model estimated the longevity of RHI effects by adding a half-life parameter embedded in an exponential decay function. A model estimate of this parameter allows the possibility of RHI effects to attenuate over time and introduces a mechanism to study the cumulative effect of RHIs. The posterior distribution of the half-life parameter associated with short-distance headers (<30 m) is centered around 6 days, whereas the posterior distribution of the half-life parameter associated with long-distance headers extends beyond a month. Additionally, the magnitude of the effect of each short header is around 3 times smaller than that of a long header. The results indicate that, on both tasks, response time (RT) changes after long headers are bigger in magnitude and last longer compared to the effects of short headers. Most important, we demonstrate that deleterious effects of long headers extend beyond 1 month. Although estimates are based on data from a relatively short-duration study with a relatively small sample size, the proposed model provides a mechanism to estimate long-term behavioral slowing from RHIs, which may be helpful to reduce the risk of additional injury. Finally, differences in the longevity of the effects of short and long RHIs may help to explain the large variance found between biomechanical input and clinical outcome in studies of concussion tolerance.



#2 Relationship between respiratory muscles ultrasound parameters and running tests performance in adolescent football players. A pilot study

Reference: PeerJ. 2023 Apr 17;11:e15214. doi: 10.7717/peerj.15214. eCollection 2023.

Authors: Małgorzata Pałac, Damian Sikora, Tomasz Wolny, Paweł Linek

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Summary: Assessing the relationship between ultrasound imaging of respiratory muscles during tidal breathing and running tests (endurance and speed) in adolescent football players. Ultrasound parameters of the diaphragm and intercostal muscles (shear modulus, thickness, excursion, and velocity), speed (30-m distance), and endurance parameters (multi-stage 20-m shuttle run test) were measured in 22 male adolescent football players. The relation between ultrasound and running tests were analysed by Spearman's correlation. Diaphragm shear modulus at the end of tidal inspiration was moderately negatively (R = - 0.49; p = 0.2) correlated with the speed score at 10 m. The diaphragm and intercostal muscle shear modulus ratio was moderately to strongly negatively correlated with the speed score at 10 m and 30 m (about R = - 0.48; p = 0.03). Diaphragm excursion was positively correlated with the speed score at 5 m (R = 0.46; p = 0.04) and 10 m (R = 0.52; p = 0.02). Diaphragm velocity was moderately positively correlated with the speed score at 5 m (R = 0.42; p = 0.06) and 30 m (R = 0.42; p = 0.07). Ultrasound parameters were not significantly related to all endurance parameters (R ≤ 0.36; p ≥ 0.11). Ultrasound parameters of the respiratory muscles are related to speed score in adolescent football players. The current state of knowledge does not allow us to clearly define how important the respiratory muscles' ultrasound parameters can be in predicting some performance parameters in adolescent athletes.



#3 Piloting the use of football club community Trust's to create social Hubs for older adults

Reference: Public Health Pract (Oxf). 2023 Apr 2;5:100381. doi: 10.1016/j.puhip.2023.100381. eCollection 2023 Jun.

Authors: Steve Bullough, Lee Edmondson, Robbie Millar

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Summary: The research summarises the findings from a three-year pilot delivered through the EFL Trust and eleven Club Community Organisations. The aim was to create local social Hubs for older adults, to bring together local people to increase social connections, which may lead to additional physical activity, rather than a targeted physical activity intervention. The study was a three-year evaluation of the pilot, to track changes in attitudes and behaviours of participants, and gather feedback on the delivery mechanism and the service providers. The study included participant tracking surveys alongside interviews and focus groups with participants and service providers over the three-year pilot. The greatest impact was on participants' mental wellbeing as opposed to their physical activity levels or attitude/motivation for physical activity. Covid-19 restrictions were felt particularly hard by the most vulnerable in society and the tracking of participants quantified the negative impact of lockdown on life satisfaction and happiness, which the presence of the Hubs helped to redress. The Hubs model can offer a relatively low cost community based solution which adds to the menu of options in local health systems. The Hubs can help to tackle loneliness, enhance social interactions using the power of the football club to generate demand. The learning showed how to recruit, retain, and sustain networks of older adults using Hubs. The pilot showed the value CCOs can have in local service delivery for older adults, providing semi-structured Hubs which act as a conduit to wider engagement.



#4 The prevalence of relative age effects and the influence of the talent pool size on Australian male and female youth football

Reference: J Sports Sci. 2023 Apr 27;1-9. doi: 10.1080/02640414.2023.2204582. Online ahead of print.

Authors: Kyle J M Bennett, Andrew R Novak, Job Fransen, Rob Duffield

Summary: The current study explored the association between talent pool size and relative age effects in Football Australia's talent pathway. It also compared relative age effects between male and female players. Participants were 54,207 youth football players (females: n = 12,527, age-range = 14.0-15.9; males: n = 41,680, age-range = 13.0-14.9) eligible for the National Youth Championships. We developed linear regression models to examine the association between the member federation size and the probability of a player being born earlier in the year. We also analysed selection probabilities based on birth quartile and year half across three layers. Overall, talent pool size was associated with a higher probability of selecting a player born in the first half of the year over the second. More specifically, an increase of 760 players led to a 1% higher selection probability for those born in the first six months of a chronological age group. In addition, there were more occurrences of relative age effects in the male than the female sample. Future studies should focus on the impact of the talent pool size on relative age effects at each major talent identification/selection stage of a talent pathway.



#5 Tactical Knowledge by Decision Making and Motor Efficiency of Young Football Players in Different Playing Positions during a Three-a-Side Small-Sided Game

Reference: Behav Sci (Basel). 2023 Apr 5;13(4):310. doi: 10.3390/bs13040310.

Authors: Rui Matos, Carlos Moreira, Emília Alves, José Eduardo Teixeira, Filipe Rodrigues, Diogo Monteiro, Raul Antunes, Pedro Forte

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Summary: The aim of this study was to compare the tactical knowledge of young football players in different playing positions during a three-a-side small-sided game (SSG). Observational data was collected from 71 players (M = 12.16; SD = 1.55 years): 11 goalkeepers, 22 defenders, 15 midfielders, and 23 forwards. In total, 4 min of three-a-side SSGs (GR + 3 vs. 3 + GR) were recorded to assess tactical performance using a digital camera (GoPro Hero 6® version 02.01). The SSGs were performed on a field with a constant area (36 × 27 m). Video analyses were performed using LongoMatch® version 1.5.9 to record football performance; we then assessed tactical performance by using the Football Tactical Assessment System (Fut-Sat). This instrument evaluates the average of well-defined action indexes for each game in decision making principle and motor skills, specifically: (i) Decision Making Index (DMI); (ii) Motor Effectiveness Index (MEI); (iii) Effectiveness Index (I). The indexes were calculated by the ratio between the correct actions and the total. The Kruskal-Wallis test was used to evaluate differences between playing positions. The results showed that tactical performance by principles seems to be significantly different according to playing position. Differences were found between defenders and forwards (H = -11.92; p = 0.03) and defenders and midfielders (H = -16.13; p = 0.01) in contention principle. In conclusion, tactical knowledge of training based on the principles of the game can help coaches and players better understand and predict each player's actions during the game.



#6 Thermoregulatory, Cardiovascular and Perceptual Responses of Spectators of a Simulated Football Match in Hot and Humid Environmental Conditions

Reference: Sports (Basel). 2023 Mar 31;11(4):78. doi: 10.3390/sports11040078.

Authors: Johannus Q de Korte, Thijs M H Eijsvogels, Maria T E Hopman, Coen C W G Bongers

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Summary: Major sporting events are often scheduled in thermally challenging environments. The heat stress may impact athletes but also spectators. We examined the thermal, cardiovascular, and perceptual responses of spectators watching a football match in a simulated hot and humid environment. A total of 48 participants (43 ± 9 years; n = 27 participants <50 years and n = 21 participants ≥50 years, n = 21) watched a 90 min football match in addition to a 15 min baseline and 15 min halftime break, seated in an environmental chamber (Tair = 31.9 ± 0.4 °C; RH = 76 ± 4%). Gastrointestinal temperature (Tgi), skin temperature (Tskin), and heart rate (HR) were measured continuously throughout the match. Mean arterial pressure (MAP) and perceptual parameters (i.e., thermal sensation and thermal comfort) were scored every 15 min. Tri (37.3 ± 0.4 °C to 37.4 ± 0.3 °C, p = 0.11), HR (76 ± 15 bpm to 77 ± 14 bpm, p = 0.96) and MAP (97 ± 10 mm Hg to 97 ± 10 mm Hg, p = 0.67) did not change throughout the match. In contrast, an increase in Tskin (32.9 ± 0.8 °C to 35.4 ± 0.3 °C, p < 0.001) was found. Further, 81% of participants reported thermal discomfort and 87% a (slightly) warm thermal sensation at the end of the match. Moreover, the thermal or cardiovascular responses were not affected by age (all p-values > 0.05). Heat stress induced by watching a football match in simulated hot and humid conditions does not result in substantial thermal or cardiovascular strain, whereas a significant perceptual strain was observed.



#7 Relationship between Football-Specific Training Characteristics and Tibial Bone Adaptation in Male Academy Football Players

Reference: Sports (Basel). 2023 Apr 19;11(4):86. doi: 10.3390/sports11040086.

Authors: Ian Varley, Craig Sale, Julie P Greeves, John G Morris, Caroline Sunderland, Chris Saward

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Summary: We examined the relationship between football-specific training and changes in bone structural properties across a 12-week period in 15 male football players aged 16 years (Mean ± 1 SD = 16.6 ± 0.3 years) that belonged to a professional football academy. Tibial scans were performed at 4%, 14% and 38% sites using peripheral quantitative computed tomography immediately before and 12 weeks after increased football-specific training. Training was analysed using GPS to quantify peak speed, average speed, total distance and high-speed distance. Analyses were conducted with bias-corrected and accelerated bootstrapped 95% confidence intervals (BCa 95% CI). There were increases in bone mass at the 4% (mean ∆ = 0.15 g, BCa 95% CI = 0.07, 0.26 g, g = 0.72), 14% (mean ∆ = 0.04 g, BCa 95% CI = 0.02, 0.06 g, g = 1.20), and 38% sites (mean ∆ = 0.03 g, BCa 95% CI = 0.01, 0.05 g, g = 0.61). There were increases in trabecular density (4%), (mean ∆ = 3.57 mg·cm-3, BCa 95% CI = 0.38, 7.05 mg·cm-3, g = 0.53), cortical dentsity (14%) (mean ∆ = 5.08 mg·cm-3, BCa 95% CI = 0.19, 9.92 mg·cm-3, g = 0.49), and cortical density (38%) (mean ∆ = 6.32 mg·cm-3, BCa 95% CI = 4.31, 8.90 mg·cm-3, g = 1.22). Polar stress strain index (mean ∆ = 50.56 mm3, BCa 95% CI = 10.52, 109.95 mm3, g = 0.41), cortical area (mean ∆ = 2.12 mm2, BCa 95% CI = 0.09, 4.37 mm2, g = 0.48) and thickness (mean ∆ = 0.06 mm, BCa 95% CI = 0.01, 0.13 mm, g = 0.45) increased at the 38% site. Correlations revealed positive relationships between total distance and increased cortical density (38%) (r = 0.39, BCa 95% CI = 0.02, 0.66), and between peak speed and increased trabecular density (4%) (r = 0.43, BCa 95% CI = 0.03, 0.73). There were negative correlations between total (r = -0.21, BCa 95% CI = -0.65, -0.12) and high-speed distance (r = -0.29, BCa 95% CI = -0.57, -0.24) with increased polar stress strain index (38%). Results suggest that despite football training relating to increases in bone characteristics in male academy footballers, the specific training variables promoting adaptation over a 12-week period may vary. Further studies conducted over a longer period are required to fully elucidate the time-course of how certain football-specific training characteristics influence bone structural properties.



#8 Relationships between contract status and player performance in the Australian Football League

Reference: J Sports Sci. 2023 Apr 27;1-11. doi: 10.1080/02640414.2023.2190564. Online ahead of print.

Authors: Sam McIntosh, Sam Robertson

Summary: This study analysed the extent to which player performance differs within the Australian Football League (AFL) with respect to the status of a player's contract. AFL Player Ratings (AFLPR) and contract data were obtained during the 2013-2020 AFL seasons for all 827 players listed by an AFL club at the beginning of the 2020 season. A model of "expected performance" was created allowing for an exploration into the differential with actual performance as a function of contract status. Paired t-tests indicated that there was a difference in performance pre- and post-signing their contract for players who signed mid-season (mean change and 95% confidence interval of -1.48 ± 0.93 and -0.49 ± 0.48 AFLPR, at ten match intervals for those in- and out-of-contract at the conclusion of that year's season, respectively). Further differences existed between the groups of players who signed mid-season, as compared to those who signed during the off-season. Correlation analyses indicated that more consistent performers are somewhat less likely to see a reduction in performance post signing as compared to less consistent performers. The applications of these findings have the potential to support organisational decisions relating to the timing and nature of player contracting.



#9 What Are the Load and Wellness of Young Second-Team Football Players When Transitioning to the First Team? A Comparison of 2 Consecutive Preseasons

Reference: Int J Sports Physiol Perform. 2023 Apr 27;1-8. doi: 10.1123/ijspp.2022-0324. Online ahead of print.

Authors: Imanol Martin-Garetxana, Jon Ciaurri, Susana M Gil, Xabier Monasterio, Aitor Ugarte, Jose A Lekue, Jon Larruskain

Summary: The aim was to compare the load and wellness of second-team academy football players during a first-team preseason with those of first-team players and those of their previous second-team preseason. Athletic Club's first- (n = 10) and second-team (n = 9) players were prospectively followed during the 2019-20 first- and second-team and 2020-21 first-team preseasons. Weekly external and internal loads and average wellness z-scores (fatigue, sleep quality, muscle soreness, stress, and mood) were compared between preseasons and teams. While training together during the 2020-21 preseason, second-team players performed more decelerations <-3 m/s2 per week than first-team players (moderate effect size). For first-team players, there were only small differences between preseasons in external load, but session rating of perceived exertion was higher (moderate) and stress (moderate) and mood (large) z-scores were worse in 2020-21. For second-team players, more total distance (large), accelerations >3 m/s2 (large), and decelerations <-3 m/s2 (very large) were performed; total loading (moderate) and session rating of perceived exertion (moderate) were higher; and fatigue (very large) and stress (moderate) z-scores were worse during the 2020-21 first-team preseason compared to their previous second-team preseason. Players transitioning from the second team faced higher external and internal loads, fatigue, and stress during the first-team preseason compared to the previous second-team preseason. Player development and monitoring plans appear necessary to manage the transition from the academy to the first team.



#10 Characterization of Head Acceleration Exposure During Youth Football Practice Drills

Reference: J Appl Biomech. 2023 Apr 27;1-12. doi: 10.1123/jab.2022-0196. Online ahead of print.

Authors: Ty D Holcomb, Madison E Marks, N Stewart Pritchard, Logan Miller, Mark A Espeland, Christopher M Miles, Justin B Moore, Kristie L Foley, Joel D Stitzel, Jillian E Urban

Summary: Many head acceleration events (HAEs) observed in youth football emanate from a practice environment. This study aimed to evaluate HAEs in youth football practice drills using a mouthpiece-based sensor, differentiating between inertial and direct HAEs. Head acceleration data were collected from athletes participating on 2 youth football teams (ages 11-13 y) using an instrumented mouthpiece-based sensor during all practice sessions in a single season. Video was recorded and analyzed to verify and assign HAEs to specific practice drill characteristics, including drill intensity, drill classification, and drill type. HAEs were quantified in terms of HAEs per athlete per minute and peak linear and rotational acceleration and rotational velocity. Mixed-effects models were used to evaluate the differences in kinematics, and generalized linear models were used to assess differences in HAE frequency between drill categories. A total of 3237 HAEs were verified and evaluated from 29 football athletes enrolled in this study. Head kinematics varied significantly between drill categorizations. HAEs collected at higher intensities resulted in significantly greater kinematics than lower-intensity drills. The results of this study add to the growing body of evidence informing evidence-based strategies to reduce head impact exposure and concussion risk in youth football practices.



#11 Programming High-Speed and Sprint Running Exposure in Football: Beliefs and Practices of More Than 100 Practitioners Worldwide

Reference: Int J Sports Physiol Perform. 2023 Apr 28;1-16. doi: 10.1123/ijspp.2023-0013. Online ahead of print.

Authors: Antonio Dello Iacono, Marco Beato, Viswanath B Unnithan, Tzlil Shushan

Summary: The aim was to gain knowledge on the beliefs and practices of football practitioners applying high-speed and sprint running exposure programming strategies. One hundred two football practitioners from 22 different countries participated in a study consisting of a survey including 5 domains: demographic and professional characteristics (Who); importance of high-speed and sprint running exposure for physical-capability development, preparation for competition, and injury-prevention strategies (Why); exposure timing (When); methodological procedures for exposure monitoring and training scheduling (What); and effectiveness of common training practices (How). Data were analyzed using a combination of descriptive statistics, generalized mixed effects, and multinomial logistic regression models. Data revealed 5 main findings: (1) overall agreement on the importance of exposure for physical-capability development, preparation for competition, and injury-prevention strategies; (2) different exposure timing and selective training scheduling for starting and nonstarting players across typical and congested weeks; (3) lack of consensus on the conceptual constructs defining high-speed and sprint running metrics and the methodological procedures used for monitoring; (4) a probable association between match-related outcomes and exposure strategies used in training; and (5) a broad range of training methods considered effective to elicit exposure. This study provides actionable insights into the planning, implementing, and monitoring strategies for high-speed and sprint running exposure in football. While some conform with the evidence on high-speed and sprint running training in football, further research and professional debate are warranted to develop empirical knowledge and provide pragmatic recommendations to help practitioners in adopting evidence-informed decisions.



#12 Air pollution and elite adolescent soccer players' performance and well-being; an observational study

Reference: Environ Int. 2023 Apr 27;175:107943. doi: 10.1016/j.envint.2023.107943. Online ahead of print.

Authors: Adam Beavan, Sascha Härtel, Jan Spielmann, Michael Koehle

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Summary: Exercising outdoors may inadvertently lead to individuals inhaling levels of air pollution that may be detrimental to their health and activity-related performance. Endurance athletes are a particularly susceptible subgroup due to their high ventilation rates sustained over prolonged periods of time coupled with high training loads that often occur outdoors. In this study, we estimate the effects of air pollution on a series of athletic performance parameters in an elite adolescent soccer team. External, internal, and subjective loads and wellness questionnaires were recorded for the 26 matches and 197 training sessions carried out during the 2018-19 season for a U19 team competing in Germany. Each session was combined with hourly information on the concentration of PM10, O3 and NO2 in spatial proximity to each playing field for the duration of training or playing. Increases in PM10 and O3 had significant (p <.001) associations with decreasing total distance (m) ran per session. Furthermore, increases in O3 and NO2 concentrations were related to an increase in average heart rate (p <.05). Moreover, increases in PM10 concentration was associated with increased rating of perceived exertion (p <.001). Last, the total inhaled dose of O3 and NO2 over one session was linked to significant (p <.05) decreases in athletes' wellness scores on the following morning. We find supporting evidence of the negative effects of air pollution in elite adolescent soccer players in both matches and training. The negative impacts observed on several aspects of performance are present within an elite team that regularly trained in pollution levels well within the normal ranges of what the World Health Organisation (WHO) reports to be suitable air quality. Therefore, mitigation strategies such as monitoring the air quality at the training pitch are recommended to reduce athlete exposure to air pollution even when exercising in moderate air quality.



#13 Most modifiable risk factors for hamstring muscle injury in women's elite football are extrinsic and associated with the club, the team, and the coaching staff and not the players themselves: the UEFA Women's Elite Club Injury Study

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 May 1. doi: 10.1007/s00167-023-07429-5.

Authors: Jan Ekstrand, Anna Hallén, Vittoria Marin, Håkan Gauffin

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Summary: The aim was to describe the perceived importance of suggested hamstring injury risk factors according to chief medical officers (CMOs) of European women's professional football clubs. A secondary objective was to compare if these perceptions differed between teams with a lower-than-average and higher-than-average hamstring injury burden. The CMOs of eleven European professional women's football clubs were initially asked to suggest modifiable risk factors for hamstring injury. These risk factors were rated in according with their perceived importance on a 5-graded Likert scale. Participating teams were divided in two groups depending on their hamstring injury burden during the 2020/21 season. The LOW group consisted of six teams that had a lower-than-average hamstring injury burden. The HIGH group consisted of five teams that had a higher-than-average hamstring injury burden. Twenty-one risk factors were suggested, most of which were extrinsic in nature, hence associated with the coaching staff, the team or the club organization rather than with the players themselves. The risk factors with the highest average importance were: "lack of communication between medical staff and coaching staff" and "load on players" (each with a weighted average of 3.9), followed by "lack of regular exposure to high-speed football actions during training" and "playing matches 2-3 times a week" (weighted average of 3.8 and 3.7). Differently from the LOW group, the HIGH group perceived the coaching factors (style of coach leadership, training/exercise surveillance by coaching staff) as more important. In accordance to the eleven CMOs recruited in this study, most risk factors for hamstring injuries are extrinsic in nature and associated with the club, the team, and the coaching staff, and not the players themselves.



#14 Incidence of football injuries sustained on artificial turf compared to grass and other playing surfaces: a systematic review and meta-analysis

Reference: EClinicalMedicine. 2023 Apr 13;59:101956. doi: 10.1016/j.eclinm.2023.101956. eCollection 2023 May.

Authors: Ilari Kuitunen, Ville Immonen, Oskari Pakarinen, Ville M Mattila, Ville T Ponkilainen

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Summary: Prior reviews have not conducted statistical synthesis of injury incidence on artificial turf in football. To analyse and compare the incidence of injuries sustained playing football (soccer) on artificial turf compared to grass and other playing surfaces. This was a systematic review and meta-analysis. We searched PubMed, Scopus, SPORTDiscus, and Web of Science databases in October 2022 without filters. All observational studies (prospective or retrospective) that analysed injuries sustained playing football on artificial turf and which included a control group that played on grass or other surface were included. Studies were included if they reported the number of injuries and the exposure time for the playing surfaces. Risk of bias was assessed by Newcastle-Ottawa Scale. A random effects model was used to calculate the pooled incidence rate ratios (IRR) with 95% confidence intervals. Protocol was registered with PROSPERO on October 30th, 2022. Registration number: CRD42022371414. We screened 1447 studies, and evaluated 67 full reports, and finally included 22 studies. Risk of bias was a notable issue, as only 5 of the 22 studies adjusted their analysis for potential confounders. Men (11 studies: IRR 0.82, CI 0.72-0.94) and women (5 studies: IRR 0.83, CI 0.76-0.91) had lower injury incidence on artificial turf. Professional players had a lower incidence of injury (8 studies: IRR 0.79, CI 0.70-0.90) on artificial turf, whereas there was no evidence of differences in the incidence of injury in amateur players (8 studies: IRR 0.91, CI 0.77-1.09). The incidence of pelvis/thigh (10 studies: IRR 0.72, CI 0.57-0.90), and knee injuries (14 studies: IRR 0.77, CI 0.64-0.92) were lower on artificial turf. The overall incidence of football injuries is lower on artificial turf than on grass. Based on these findings, the risk of injury can't be used as an argument against artificial turf when considering the optimal playing surface for football.



#15 Impact of (long) COVID on athletes' performance: a prospective study in elite football players

Reference: Ann Med. 2023 Dec;55(1):2198776. doi: 10.1080/07853890.2023.2198776.

Authors: E Wezenbeek, S Denolf, J G Bourgois, R M Philippaerts, B De Winne, T M Willems, E Witvrouw, S Verstockt, J Schuermans

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Summary: The aim was to investigate possible persistent performance deficits after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in elite athletes. A prospective cohort study in three Belgian professional male football teams was performed during the 2020 - 2021 season. Participants were submitted to strength, jump, and sprint tests and an aerobic performance test (the Yo-Yo Intermittent Recovery test (YYIR)). These tests were repeated at fixed time intervals throughout the season. Assessment of SARS-CoV-2 infection was performed by a polymerase chain reaction (PCR) test before each official game. Of the 84 included participants, 22 were infected with SARS-CoV-2 during follow-up. At the first testing after infection (52.0 ± 11.2 days after positive PCR testing) significantly higher percentages of maximal heart rate (%HRmax) were seen - within the isolated group of infected players- during (p = .006) and after the YYIR (2 min after, p = .013), compared to pre-infection data. This increase in %HRmax was resolved at the second YYIR testing after infection (127.6 ± 33.1 days after positive PCR testing). Additionally, when comparing the first test after infection in formerly infected to non-infected athletes, significantly higher %HRmax were found during (p < .001) and after the YYIR test (p < .001),No significant deficits were found for the jump, muscular strength or sprint tests. Aerobic performance seems compromised even weeks after infection. Simultaneously, anaerobic performance seemed to be spared. Because of the potential detrimental effects on the immune system, caution might be advised with high-intensity exposure until aerobic performance is restored.KEY MESSAGESElite football players' aerobic performance seems to be affected for weeks after they return to sports after a SARS-CoV-2 infection.Similarly, anaerobic performance tests showed no discernible changes between both before and after SARS-CoV-2 infections.Regular YYIR testing is recommended to monitor aerobic performance after SARS-CoV-2 infection.



#16 Electrocardiogram of Brazilian Elite Football Players: Filling a Gap

Reference: Arq Bras Cardiol. 2023 May 1;120(4):e20230090.  doi: 10.36660/abc.20230090. [Article in English, Portuguese]

Authors: Ricardo Stein, Filipe Ferrari, Anderson Donelli da Silveira

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#17 Youth-to-senior transition in women's and girls' football: Towards a better understanding of relative age effects and gender-specific considerations

Reference: PLoS One. 2023 May 4;18(5):e0283781. doi: 10.1371/journal.pone.0283781. eCollection 2023.

Authors: Paolo Riccardo Brustio, Roberto Modena, Gennaro Boccia, Matteo Vogliazzo, Adam Leigh Kelly

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Summary: This study aimed to evaluate youth-to-senior transition and the relative age effect in Italian female football national teams. Birthdate data of 774 female players selected for Under 17 (N = 416), 19 (N = 265) and National Senior team (N = 93) were analysed. The youth-to-senior transition rate was determined by the number of youth players competing in the Senior National team (and vice versa), whilst birth quarter (Q) distributions with a chi-square goodness-of-fit test. Only 17.4% of youth players were able to be selected for the Senior National team, whereas 31.2% of the players reached the high-senior level without being selected for youth age groups. Data revealed a skewed birth date distribution in Under 17 and 19 teams (on average, Q1 = 35.6% vs Q4 = 18.5%) but not in the Senior National team. Youth players born in Q1 were two times more likely to be selected than in Q4. In Under 17, goalkeepers, defenders, and midfielders of Q1 players were overrepresented. However, Q4 players recorded higher conversion rates than Q1 (Q1 = 16.4% vs. Q4 = 25.0%). National youth experience may not be a prerequisite for being selected at the senior level. Moreover, this confers a higher probability of playing in the National Senior team than players not selected in youth rosters.



#18 Performance in field-tests and dynamic knee valgus in soccer players psychologically ready and not ready to return to sports after ACL reconstruction

Reference: Knee. 2023 Apr 27;42:297-303. doi: 10.1016/j.knee.2023.04.011. Online ahead of print.

Authors: Ricardo V Correa, Evert Verhagen, Renan A Resende, Juliana M Ocarino

Summary: The objective was to compare the performance in field tests, dynamic knee valgus, knee function, and kinesiophobia of soccer players who were psychologically ready and not ready to return to unrestricted training or competitions after ACL reconstruction. Thirty-five male soccer players who had undergone primary ACL reconstruction at least 6 months were divided based on the Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) questionnaire score into ready (≥60) and not-ready (<60) groups. The modified Illinois change of direction test (MICODT) and reactive agility test (RAT) were used to impose the demand for directional change and reactive decision-making. We assessed the frontal plane knee projection angle (FPKPA) during a single-leg squat and distance in crossover hop test (CHD). In addition, we assessed kinesiophobia through the shortened version of the Tampa Scale of Kinesiophobia (TSK-11) and knee function using the International Knee Documentation Committee Subjective Knee Form (IKDC). Independent t-tests were used to compare the groups. The not-ready group had lower performance on the MICODT (effect size (ES) = -1.2; p < 0.001) and RAT (ES = -1.1; p = 0.004) tests and higher FPKPA (ES = 1.5; p < 0.001). In addition, they presented lower IKDC (ES = 3.1; p < 0.001) and higher TSK-11 (ES = -3.3; p < 0.001) scores. Physical and psychological deficits may persist in some individuals after rehabilitation. On-field tests and dynamic knee alignment evaluation should be included in the athlete evaluation before the decision-making about clearance to sports participation, especially in athletes who perceive themselves as psychologically not ready.



#19 Better decision-making skills support tactical behaviour and reduce physical wear under physical fatigue in soccer

Reference: Front Physiol. 2023 Apr 12;14:1116924. doi: 10.3389/fphys.2023.1116924. eCollection 2023.

Authors: Felipe Dambroz, Israel Teoldo

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Summary: The purpose of this study was to verify whether decision-making skills influence the tactical behavior and physical performance of soccer players under acute physical fatigue, assessed in an actual game-play. The sample was comprised of 24 trained soccer players (18.25 ± 1.48 years old) from two Brazilian clubs grouped into two categories with 12 players each (with high and low decision-making skills). The assessment of decision making, tactical behavior, and physical performance were carried out using TacticUP®, FUT-SAT, and GPSports®, respectively. Acute physical fatigue was induced through the T-SAFT90 test. Results showed that under acute physical fatigue players with high decision-making skills maintained tactical behavior efficiency and had their paces reduced, in addition to displaying reduced total distance covered (p < 0.001), number of accelerations (p < 0.001), and decelerations (p < 0.001), and average movement speed (p < 0.001). On the other hand, players with low decision-making skills displayed reduced tactical behavior efficiency (p = 0.002) and maintained their movement pace under physical fatigue. It is concluded that decision-making skills contribute to players' tactical behavior efficiency under acute physical fatigue, besides promoting reduced physical strain in movement actions throughout the field.


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