Latest research in football - week 16 - 2021

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 Epidemiology of Achilles Tendon Rupture in Italian First Division Football (Soccer) Players and Their Performance After Return to Play 

Reference: Clin J Sport Med. 2021 Feb 1. doi: 10.1097/JSM.0000000000000879. Online ahead of print. 

Authors: Alberto Grassi, Silvio Caravelli, Mario Fuiano, Pieter D'Hooghe, Matteo Filippini, Francesco Della Villa, Massimiliano Mosca, Stefano Zaffagnini 

Summary: The aim was to evaluate the epidemiology, incidence rate, incidence proportion, and prevalence of Achilles tendon ruptures (ATRs) in professional footballers and their performance after the injury. Professional male footballers participating in Serie A in 11 consecutive seasons (2008/2009-2018/2019) were screened to identify ATRs through the online football archive Exposure in matches and training was calculated. The number of matches played in the 5 seasons before and after ATRs was obtained, when possible, together with transfers to a different team or participation in lower Divisions. Eleven ATRs were found in 11 footballers with a mean age of 29.8 ± 4.4 years; 72% of ATR involved the nondominant leg; 58% occurred during matches and 42% during training, with no peculiar distribution along the playing season. The overall incidence proportion was 0.17% (0.11% during matches and 0.06% during training). The overall incidence rate was 0.007 injuries per 1000 hours of play (0.051 during matches and 0.003during training; P < 0.0001). All players returned to play soccer after a mean of 170 ± 35 days after ATRs and participated in an official match after a mean of 274 ± 98 days. However, 2 seasons after ATRs, 3 footballers were playing in a lower Division; 1 played less than 10 matches (compared with >25 matches in the 5 seasons before an ATR) and 1 had retired. An overall ATR rate of 0.007 per 1000 hours of soccer play and an incidence proportion of 0.17% were reported. All footballers return to play; however, up to 40% players decreased the level of play by reducing the number of games or participating in a lower Division 2 seasons after an ATR. 



#2 Morphological Changes of the Hip Commonly Associated With Femoroacetabular Impingement Are Not Correlated With Rotational Range of Hip Motion in Elite Soccer Athletes

Reference: Sports Health. 2021 Feb 4;1941738120973662. doi: 10.1177/1941738120973662.  

Authors: André Orlandi Bento, Guilherme Falótico, Keelan Enseki, Ronaldo Alves Cunha, Benno Ejnisman, Gustavo Arliani, Moisés Cohen

Summary: Morphological changes characteristic of femoroacetabular impingement (FAI) are common in soccer players. However, the clinical relevance of such anatomical variations is still not well-defined. We hypothesized that high alpha angle values and/or acetabular retroversion index (ARI) are correlated with rotational range of motion (ROM) of the hip and that there are clinical-radiological diferences between the dominant lower limb (DLL) and nondominant lower limb (NDLL) in professional soccer players. A total of 59 male professional soccer players (average age 25.5 years, range 18-38 years) were evaluated in the preseason. As main outcome measures, we evaluated the alpha angle and the ARI and hip IR and ER ROM with radiographic analysis. The measurements taken on DLL and NDLL were compared and a significant difference was found between the sides in the ER (P = 0.027), where the DLL measures were 1.54° (95% CI, 0.18-2.89) greater than the NDLL. There were no significant differences between the sides in the measures of IR (P > 0.99), total ROM (P = 0.07), alpha angle (P = 0.250), and ARI (P = 0.079). The correlations between the rotation measurements and the alpha angle in each limb were evaluated and the coefficient values showed no correlation; so also between the ARI and rotation measures. Morphological changes of the femur or acetabulum are not correlated with hip IR and ER ROM in male professional soccer players. ER on the dominant side was greater than on the nondominant side. There was no significant difference in the other measurements between sides. In clinical practice, it is common to attribute loss of hip rotational movement to the presence of FAI. This study shows that anatomical FAI may not have a very strong influence on available hip rotational movement in professional soccer athletes. 



#3 Accelerometry-Workload Indices Concerning Different Levels of Participation during Congested Fixture Periods in Professional Soccer: A Pilot Study Conducted over a Full Season

Reference: Int J Environ Res Public Health. 2021 Jan 28;18(3):1137. doi: 10.3390/ijerph18031137. 

Authors: Filipe Manuel Clemente, Rui Silva, Yung-Sheng Chen, Rodrigo Aquino, Gibson Moreira Praça, Julen Castellano, Hadi Nobari, Bruno Mendes, Thomas Rosemann, Beat Knechtle 

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Summary: The aim of this study was to analyze the variations of acute load (AL), acute: chronic workload ratio (ACWR), training monotony (TM), and training strain (TS) of accelerometry-based GPS measures in players who started in three matches (S3M), two matches (S2M), and one match (S1M) during congested weeks. Nineteen elite professional male players from a Portuguese team (age: 26.5 ± 4.3 years) were monitored daily using global positioning systems (GPSs) over a full season (45 weeks). Accelerometry-derived measures of high metabolic load distance (HMLD), high accelerations (HA), and high decelerations (HD) were collected during each training session and match. Seven congested weeks were classified throughout the season, and the participation of each player in matches played during these weeks was codified. The workload indices of AL (classified as ACWR, TM, and TS) were calculated weekly for each player. The AL of HMLD was significantly greater for S2M than S1M (difference = 42%; p = 0.002; d = 0.977) and for S3M than S1M (difference = 44%; p = 0.001; d = 1.231). Similarly, the AL of HA was significantly greater for S2M than S1M (difference = 25%; p = 0.023; d = 0.735). The TM of HD was significantly greater for S2M than S3M (difference = 25%; p = 0.002; d = 0.774). Accelerometry-based measures were dependent on congested fixtures. S2M had the greatest TS values, while S3M had the greatest TM. 



#4 Mortality of Spanish Former Elite Soccer Players and Coaches 

Reference: Int J Sports Med. 2021 Feb 1. doi: 10.1055/a-1308-3116. Online ahead of print. 

Authors: José Carlos Diz, Santiago Iglesias Sueiro, Eva Diz Ferreira, Miguel Adriano Sanchez-Lastra, Carlos Ayán

Summary: We analyzed whether male Spanish elite soccer players live longer than the general population. Secondly, we compared their mortality with a cohort of soccer players who continued working as soccer elite coaches after retirement. Using age and calendar-date adjusted life tables, we analyzed the mortality hazard ratio of 1333 Spanish male players born before 1950, and who played in elite leagues from 1939, compared with the Spanish population. Using Cox proportional hazards model we compared their mortality with a cohort of 413 players who continued as coaches. Players showed significantly lower mortality than the general population, but this advantage decreased with advanced age, disappearing after 80 years. Coaches showed a similar pattern. Comparing players versus coaches, date of birth and years as professional were associated with survival, but debut age and player position were not. Unadjusted median survival time was 79.81 years (IQR 72.37-85.19) for players and 81.8 years (IQR 74.55-86.73) for coaches. Kaplan-Meier estimator adjusted for covariables showed no difference between cohorts (p=0.254). In conclusion, former Spanish male players showed lower mortality than the general population, but this effect disappeared after 80 years of age. Continuing their career as coaches after retirement from playing did not confer major benefits. 



#5 Unilateral vs. bilateral hamstring strength assessments: comparing reliability and inter-limb asymmetries in female soccer players 

Reference: J Sports Sci. 2021 Jan 31;1-8. doi: 10.1080/02640414.2021.1880180. Online ahead of print. 

Authors: Matthew Cuthbert, Paul Comfort, Nicholas Ripley, John J McMahon, Martin Evans, Chris Bishop

Summary: The aims in the present study were to assess reliability for two unilateral and two bilateral field-based hamstring assessments and compare magnitude, direction and agreement of inter-limb asymmetry between tests and sessions. Twenty-nine female soccer players (age: 21.1 ± 4.5 years; height: 169.7 ± 5.8 cm; body mass: 66.2 ± 6.4 kg) performed three repetitions per leg of unilateral isometric 30° and 90° knee flexion (KF) tasks, and three repetitions total for a bilateral 90° isometric KF and Nordic hamstring exercise. Absolute reliability of most methods were acceptable (<10%). Relative reliability within-session was fair to excellent (ICC≥0.784; lower bound 95%CI ≥0.623). Greater variability in between-session relative reliability was observed during the unilateral tests, demonstrating poor to good (ICC = 0.698-0.798; lower bound 95%CI = 0.274-0.638). Bilateral assessments demonstrated similar ranges of poor to excellent (ICC = 0.679-0.963; lower bound 95%CI = 0.231-0.790). Agreement between-session for inter-limb asymmetry identification was slight and fair in the unilateral tests, with moderate to substantial agreement demonstrated in the bilateral. Being the most reliable within- and between-sessions, demonstrating substantial agreement in asymmetry between-sessions, the NHE would be most appropriate to identify inter-limb asymmetry and assess chronic changes in hamstring strength. 



#6 Game Insight Skills as a Predictor of Talent for Youth Soccer Players 

Reference: Front Sports Act Living. 2021 Jan 15;2:609112. doi: 10.3389/fspor.2020.609112. eCollection 2020. 

Authors: Tom de Joode, Drewes J J Tebbes, Geert J P Savelsbergh

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Summary: Perceptual-cognitive skills are found to be important factors for soccer players. The aim of this study was, therefore, to find within-group differences for game insight in an elite group of youth soccer players by means of a Game Insight inDicator (GID). In addition, the prospective value of perceptual-cognitive skills was examined by following the trajectory of the participants. The GID consisted of film clips that show game situations. The task of the players was to predict the trajectory and destination of the ball and move toward the correct position to receive the pass of a teammate. The film clips stopped 80 ms before, at, and 80 ms after the football contact of a teammate. We also sought to validate the GID against game performance. Participants were talented soccer players 11-13 years old and playing at the elite level for their age. Based on eight independent elite-coach judgments, two groups were created: highly talented players (HT) and less talented players (LT). The coach ratings were supported by a significant difference between the two groups based on the objective notational analysis of their game performance in 4 vs. 4 and 11 vs. 11 matches. With respect to the GID, a significant interaction effect for the groups (HT vs. LT) by occlusion time (-80, 0, and +80 ms) was found, showing that the HT performs better than the LT in 0 and +80 ms condition. In addition, GID scores were compared with soccer levels at the mean age of 19 years. Longitudinal data did not show significant differences between elite and sub-elite. Overall, the GID was found to be a valid and useful indicator for players anticipating the ball's trajectory and destination at age 11-13 years but failed to predict the players' level at age 19 years. The latter indicates how difficult it is to predict talent development. 



#7 Change in Soccer Substitutions Rule Due to COVID-19: Why Only Five Substitutions? 

Reference: Front Sports Act Living. 2021 Jan 15;2:588369. doi: 10.3389/fspor.2020.588369. eCollection 2020. 

Authors: Gustavo R Mota, Izabela Aparecida Santos, Moacir Marocolo

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#8 How Does Cognitive Effort Influence the Tactical Behavior of Soccer Players? 

Reference: Percept Mot Skills. 2021 Jan 31;31512521991405. doi: 10.1177/0031512521991405.

Authors: Felippe da S L Cardoso, Tomás García-Calvo, Tomas Patrick, José Afonso, Israel Teoldo

Summary: In the present study, we aimed to investigate the association between soccer players' cognitive effort and their tactical behavior. We assessed 52 young male soccer players from a first division Brazilian club, using FUT-SAT to evaluate tactical behavior efficiency and Mobile Eye Tracking-XG software and a video test protocol to measure pupillary behavior and cognitive effort. Following data collection, statistical analyses were performed using the Kolmogorov-Smirnov normality test, and linear regression. We found a high inverse association between cognitive effort and tactical behavior efficiency; players with less cognitive effort during the task displayed higher values of tactical behavior efficiency on the field. We concluded that sustaining less cognitive effort in game situations helped players realize better tactical behavior and enabled better performance. 



#9 Goalkeeping in the soccer penalty kick: The dive is coordinated to the kicker's non-kicking leg placement, irrespective of time constraints

Reference: Hum Mov Sci. 2021 Jan 29;76:102763. doi: 10.1016/j.humov.2021.102763. Online ahead of print. 

Authors: Ran Zheng, Caroline de Reus, John van der Kamp

Summary: Traditionally, goalkeeping in the soccer penalty kick has been studied using video-based technology, in which goalkeepers watched video footage of penalty kicks and indicated perceived ball direction. By omitting the requirement to actually dive or jump to the ball, these studies overlooked how action capabilities constrain goalkeepers' actions. By contrast, we examined whether goalkeeping in the penalty kick is consistent with affordance-based control, that is, whether goalkeepers guide their dive by taking into account their action capabilities (i.e., the time they need to intercept the ball). To this end, high- and moderate-skilled goalkeepers faced in-situ penalty kicks. Time constraints were manipulated by varying the kicking distance and the kicker's run-up speed. The results showed that goalkeepers of both skills level scaled the lateral dive onset to their action capabilities, but high-skilled goalkeepers acted closer to their maximum action boundary. In doing so, goalkeepers did not take the varying time constraints into account. Instead, high-skilled goalkeepers acted consistent with a strategy in which they coordinated the onset of the dive with the landing of kicker's non-kicking leg next to the ball. Consequently, we only find partial support for affordance-based control. We propose that this is explained by reliable information becoming available (too) late within the spatiotemporal constraints of the penalty kick. 



#10 Assessment of External Load During Matches in Two Consecutive Seasons Using the Mediacoach ® Video Analysis System in a Spanish Professional Soccer Team: Implications for Injury Prevention

Reference: Int J Environ Res Public Health. 2021 Jan 27;18(3):1128. doi: 10.3390/ijerph18031128. 

Authors: Manuel Alcantarilla-Pedrosa, David Álvarez-Santana, Sergio Hernández-Sánchez, Angel Yañez-Álvarez, Manuel Albornoz-Cabello

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Summary: Knowledge of competition loads is a relevant aspect of injury prevention. We aimed to describe the training and match injury incidence and physical demand variables observed during a competition using a multi-camera video analysis system (Mediacoach®) (LaLigaTM, Madrid, Spain) in a professional Spanish soccer team during two consecutive seasons. 30 players (age: 26.07 ± 3.78 years) participated in the study. Physical variables of 74 matches were collected retrospectively. Injury characteristics of both seasons were also collected. Differences in these variables between the two seasons and by player position and correlations between variables were explored. There were statistically significant differences between the two seasons in the total distance traveled and the distance traveled at a high-intensity sprint (p < 0.05). During the two seasons, there was an average of 4.7 ± 2.2 injuries. The total distance traveled was different according to the playing position, and statistically significant correlations were found in the total distance and sprint at a high intensity for certain positions with different injury severity The match performance data recorded by the Mediacoach® system may provide relevant information by player position to technical and medical staff for injury prevention. 



#11 Fluid Balance, Sweat Na + Losses, and Carbohydrate Intake of Elite Male Soccer Players in Response to Low and High Training Intensities in Cool and Hot Environments

Reference: Nutrients. 2021 Jan 27;13(2):401. doi: 10.3390/nu13020401. 

Authors: Ian Rollo, Rebecca K Randell, Lindsay Baker, Javier Yanguas Leyes, Daniel Medina Leal, Antonia Lizarraga, Jordi Mesalles, Asker E Jeukendrup, Lewis J James, James M Carter

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Summary: Hypohydration increases physiological strain and reduces physical and technical soccer performance, but there are limited data on how fluid balance responses change between different types of sessions in professional players. This study investigated sweat and fluid/carbohydrate intake responses in elite male professional soccer players training at low and high intensities in cool and hot environments. Fluid/sodium (Na+) losses and ad-libitum carbohydrate/fluid intake of fourteen elite male soccer players were measured on four occasions: cool (wet bulb globe temperature (WBGT): 15 ± 7 °C, 66 ± 6% relative humidity (RH)) low intensity (rating of perceived exertion (RPE) 2-4, m·min-1 40-46) (CL); cool high intensity (RPE 6-8, m·min-1 82-86) (CH); hot (29 ± 1 °C, 52 ± 7% RH) low intensity (HL); hot high intensity (HH). Exercise involved 65 ± 5 min of soccer-specific training. Before and after exercise, players were weighed in minimal clothing. During training, players had ad libitum access to carbohydrate beverages and water. Sweat [Na+] (mmol·L-1), which was measured by absorbent patches positioned on the thigh, was no different between conditions, CL: 35 ± 9, CH: 38 ± 8, HL: 34 ± 70.17, HH: 38 ± 8 (p = 0.475). Exercise intensity and environmental condition significantly influenced sweat rates (L·h-1), CL: 0.55 ± 0.20, CH: 0.98 ± 0.21, HL: 0.81 ± 0.17, HH: 1.43 ± 0.23 (p =0.001), and percentage dehydration (p < 0.001). Fluid intake was significantly associated with sweat rate (p = 0.019), with no players experiencing hypohydration > 2% of pre-exercise body mass. Carbohydrate intake varied between players (range 0-38 g·h-1), with no difference between conditions. These descriptive data gathered on elite professional players highlight the variation in the hydration status, sweat rate, sweat Na+ losses, and carbohydrate intake in response to training in cool and hot environments and at low and high exercise intensities. 



#12 Injury rates decreased in men's professional football: an 18-year prospective cohort study of almost 12 000 injuries sustained during 1.8 million hours of play 

Reference: Br J Sports Med. 2021 Feb 5;bjsports-2020-103159. doi: 10.1136/bjsports-2020-103159.

Authors: Jan Ekstrand, Armin Spreco, Håkan Bengtsson, Roald Bahr

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Summary: The UEFA Elite Club Injury Study is the largest and longest running injury surveillance programme in football. The aim was to analyse the 18-season time trends in injury rates among male professional football players. 3302 players comprising 49 teams (19 countries) were followed from 2000-2001 through 2018-2019. Team medical staff recorded individual player exposure and time-loss injuries. A total of 11 820 time-loss injuries were recorded during 1 784 281 hours of exposure. Injury incidence fell gradually during the 18-year study period, 3% per season for both training injuries (95% CI 1% to 4% decrease, p=0.002) and match injuries (95% CI 2% to 3% decrease, p<0.001). Ligament injury incidence decreased 5% per season during training (95% CI 3% to 7% decrease, p<0.001) and 4% per season during match play (95% CI 3% to 6% decrease, p<0.001), while the rate of muscle injuries remained constant. The incidence of reinjuries decreased by 5% per season during both training (95% CI 2% to 8% decrease, p=0.001) and matches (95% CI 3% to 7% decrease, p<0.001). Squad availability increased by 0.7% per season for training sessions (95% CI 0.5% to 0.8% increase, p<0.001) and 0.2% per season for matches (95% CI 0.1% to 0.3% increase, p=0.001). Over 18 years: (1) injury incidence decreased in training and matches, (2) reinjury rates decreased, and (3) player availability for training and match play increased. 



#13 Confirmatory Factor Analysis and Validity of the Sexual Harassment Scale in Football Refereeing

Reference: Int J Environ Res Public Health. 2021 Feb 3;18(4):1374. doi: 10.3390/ijerph18041374. 

Authors: Josefa Sánchez, Sara Serrat, Estefanía Castillo, Alberto Nuviala

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Summary: Inequalities between men and women in the workplace are reflected in professional sports, specifically football refereeing. This phenomenon sometimes becomes sexual harassment since it is a stereotypically considered male profession in which women are a minority. To measure that behavior, it is necessary to count on valid and reliable tools. Therefore, the goal of this study was to determine the factorial structure and the discriminant and convergent validity of the 'sexual experiences questionnaire', version of the Department of Defence (SEQ-DoD). Eighty-nine male football referees and ninety-four female football referees, with a mean age of 23.30 ± 4.85 years, participated in this studio conducted questionnaire in Andalusia, Spain. A confirmatory factor analysis was performed using the robust maximum-likelihood estimation method. The goodness of fit was assessed, and the factorial invariance was calculated to determine the stability of the model. Subsequently, the validity was confirmed. The results corroborated the validity and reliability of the questionnaire adapted to the population studied. Therefore, it can be used as a research instrument. 



#14 Characteristics of Cognitive Abilities among Youths Practicing Football 

Reference: Int J Environ Res Public Health. 2021 Feb 3;18(4):1371. doi: 10.3390/ijerph18041371. 

Authors: Wojciech Paśko, Maciej Śliż, Mariusz Paszkowski, Janusz Zieliński, Klementyna Polak, Maciej Huzarski, Krzysztof Przednowek

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Summary: The aim of the study was to assess selected cognitive abilities depending on age, anthropometric parametres, physical fitness and technical skills in the group of young players training football. The study covered a group of 258 young players practicing football (age: 12.1± 2.03), who were divided into 5 age categories (8-9 years old, 10-11 years old, 12-13 years old, 14-15 years old, 16-17 years old). Selected cognitive abilities include: simple reaction time (SIRT), complex reaction time (CHORT), hand-eye coordination (HECOR) and spatial orientation (SPANT). Studies were performed using Test2Drive computer tests. In addition, the level of physical fitness was measured using: The standing long jump, 30 m sprint, 20 m shuttle run test (without and with the ball) and slalom (without and with the ball). The analysis showed a statistically significant relationship between age and cognitive abilities. There was also a statistically significant correlation between fitness tests and reaction time in individual cognitive tests. There were no statistically significant relationships between technical skills and cognitive abilities. The study confirms that age and physical fitness affect the level of cognitive abilities. 



#15 Knowledge and attitude towards hazardous effects of laser pointers among attendees of football matches in Riyadh, Saudi Arabia 

Reference: Saudi J Ophthalmol. 2020 Nov 22;34(1):25-29. doi: 10.4103/1319-4534.301293. eCollection Jan-Mar 2020. 

Authors: Rahaf Altwijri, Suliman A Alsuliman, Latifa Alanazi, Shaikha H Aldossari, Abeer Ahmad, Hassan Al Dhibi, Sulaiman M Alsulaiman

Summary: There has been a recent increase in accidental retinal injuries due to the careless use of handheld laser devices. The scenarios under which these incidents occur suggest a lack of awareness of the sight-threatening hazards of some handheld lasers. This study aimed to assess knowledge of the population to plan awareness programs and establish protective health policies. This observational cross-sectional study used a newly-developed, validated, and pilot-tested questionnaire to survey attendees of football matches in Saudi Arabia between September to October 2018. Five-hundred and sixty-nine attendees were surveyed, and 76% of respondents knew laser pointers were harmful and could damage the eye. However, 73% of respondents did not think that the blue laser was dangerous, indicating poor awareness regarding this particular laser. Only 38% knew which ocular structure is most commonly damaged, and 15.6% did not realize that brief exposure can cause vision loss. Females had better knowledge compared to males. Respondents between 25 and 40 years old, females, and married individuals had the highest levels of a positive attitude. There was no statistically significant difference in the mean knowledge score between those in the medical field and other fields (P = 0.5). There is an inadequate knowledge of protective measures against handheld lasers. However, there's an overall positive attitude towards spreading awareness about this issue. Yet, targeted awareness campaigns are still needed in addition to more strict government laws to prevent importing or using high-powered handheld laser pointers. 


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