Latest research in football - week 46 - 2019

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 A public data set of spatio-temporal match events in soccer competitions
Reference: Sci Data. 2019 Oct 28;6(1):236. doi: 10.1038/s41597-019-0247-7.
Authors: Pappalardo L, Cintia P, Rossi A, Massucco E, Ferragina P, Pedreschi D, Giannotti F
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Summary: Soccer analytics is attracting increasing interest in academia and industry, thanks to the availability of sensing technologies that provide high-fidelity data streams for every match. Unfortunately, these detailed data are owned by specialized companies and hence are rarely publicly available for scientific research. To fill this gap, this paper describes the largest open collection of soccer-logs ever released, containing all the spatio-temporal events (passes, shots, fouls, etc.) that occured during each match for an entire season of seven prominent soccer competitions. Each match event contains information about its position, time, outcome, player and characteristics. The nature of team sports like soccer, halfway between the abstraction of a game and the reality of complex social systems, combined with the unique size and composition of this dataset, provide an ideal ground for tackling a wide range of data science problems, including the measurement and evaluation of performance, both at individual and at collective level, and the determinants of success and failure.

#2 Soccer Injuries in Children and Adolescents
Reference: Pediatrics. 2019 Nov;144(5). pii: e20192759. doi: 10.1542/peds.2019-2759.
Authors: Watson A, Mjaanes JM
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Summary: Participation in youth soccer in the United States continues to increase steadily, with a greater percentage of preadolescent participants than perhaps any other youth sport. Despite the wide-ranging health benefits of participation in organized sports, injuries occur and represent a threat to the health and performance of young athletes. Youth soccer has a greater reported injury rate than many other contact sports, and recent studies suggest that injury rates are increasing. Large increases in the incidence of concussions in youth soccer have been reported, and anterior cruciate ligament injuries remain a significant problem in this sport, particularly among female athletes. Considerable new research has identified a number of modifiable risk factors for lower-extremity injuries and concussion, and several prevention programs have been identified to reduce the risk of injury. Rule enforcement and fair play also serve an important role in reducing the risk of injury among youth soccer participants. This report provides an updated review of the relevant literature as well as recommendations to promote the safe participation of children and adolescents in soccer.

#3 Arachnoid cyst in young soccer players complicated by chronic subdural hematoma: personal experience and review of the literature
Reference: Acta Neurol Belg. 2019 Oct 25. doi: 10.1007/s13760-019-01224-1. [Epub ahead of print]
Authors: Gregori F, Colistra D, Mancarella C, Chiarella V, Marotta N, Domenicucci M
Summary: Arachnoid cysts (ACs) are congenital intracranial benign cavities originating from the meninges during embryological development. Several studies have shown the existence of a relationship between AC and a higher risk to develop ipsilateral chronic subdural hematoma (CSH) especially in a young population. In the presence of an AC, the practice of sport activities may expose young patients to minor head trauma and to an increased risk of developing CSH. We describe three cases of young soccer players with AC associated with CSH. Then, we performed a literature review of all the reported cases in the literature of patients younger than 18 years with AC-associated CSH related to sport practice. A total of 33 cases, including the three cases reported by us, are analyzed. Soccer is the most represented sport activity in this association (39% of cases). The treatment of choice is surgical in all patients, with burr hole or craniotomy in similar proportions. In one-third of patients, the AC has been fenestrated. Outcome is good in all the reported cases. We reviewed the main pathogenic theories, the main surgical strategies described in literature, as well as recurrence rate of CSH, the association of AC and cranial deformities, and the clinical outcome. AC might be associated with skull deformities, but their real incidence remains unclear. The clinical detection of such anomalies should suggest performing further radiological investigations. If the presence of AC is confirmed, the practice of sport activities should not be avoided, as the real incidence of AC-associated CSH is not clear yet and the reported outcomes in literature are good. Surgical treatment of AC-associated CSH should be hematoma removal through burr hole, reserving AC fenestration only for cases with intracystic bleeding or recurrences. The surgeon should adequately advise and inform the young patients and their families that they could have an increased risk of developing CSH given by the presence of the AC, and that they should be referred to a neurosurgical center if they become symptomatic.

#4 Prevalence of Relative Age Effect in Russian Soccer: The Role of Chronological Age and Performance
Reference: Int J Environ Res Public Health. 2019 Oct 23;16(21). pii: E4055. doi: 10.3390/ijerph16214055.
Authors: Bezuglov EN, Nikolaidis PT, Khaitin V, Usmanova E, Luibushkina A, Repetiuk A, Waśkiewicz Z, Gerasimuk D, Rosemann T, Knechtle B
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Summary: The relative age effect (RAE) has been well studied in adolescent and adult soccer players; however, less information has been available about children engaged in regular soccer training and the role of performance. Thus, the aim of the present study was to examine the prevalence of RAE in children and adolescent soccer players, as well as the role of age and performance. Russian soccer players (n = 10,446) of various ages, playing positions and performance levels were examined for their date of birth. It was observed that RAE was widespread in Russian soccer teams of all age groups. RAE was most pronounced in children teams of the top tier Russian soccer academies and junior Russia national teams, where the proportions of soccer players born in the first quarter were 43.9% and 39.8%, respectively, whereas those born in the fourth quarter of the year were 7.7% and 6.3%, respectively. In top tier soccer academies, RAE did not vary by age group. In the middle tier soccer academies, RAE was less pronounced. It was still prevalent in the junior teams of the top tier clubs of the Russian Premier League, where 14.3% of the soccer players were born in the fourth quarter of the year compared to 42.9% born in the first quarter of the year. RAE can be observed in the top tier Russian adult teams as well, although it is less pronounced there. In summary, RAE is highly prevalent in Russian children and junior soccer and is associated with the level of competitiveness. At the same time, the proportion of players born in the fourth quarter of the year is higher in adult teams than in junior and youth teams, which is most likely due to the wider selection of players, not limited by their age and place of residence. In junior teams, RAE results in a bias towards selection of players who are more physically mature, whereas children who may be more talented but are less developed due to their younger chronological age tend to be overlooked.

#5 Women Are at Higher Risk for Concussions Due to Ball or Equipment Contact in Soccer and Lacrosse
Reference: Clin Orthop Relat Res. 2019 Oct 17. doi: 10.1097/CORR.0000000000000995. [Epub ahead of print]
Authors: Ling DI, Cheng J, Santiago K, Ammerman B, Jivanelli B, Hannafin J, Casey E
Summary: There is ample evidence to suggest sex- and gender-based differences in the incidence of sports-related concussions. The mechanisms of concussion may vary between male and female athletes and contribute to this observed difference. Understanding the underlying etiology by pooling data from primary studies across different settings and sport types will inform interventions that can reduce concussion rates. Specifically, we asked: (1) In which sports are female athletes less likely to experience concussions from player contact? (2) In which sports are female athletes more likely to experience concussions because of ball or equipment contact? PubMed, EMBASE, and Cochrane Library databases were searched to identify articles published from January 2000 to December 2018. Ten studies met the inclusion criteria, which were studies that reported concussion incidence by mechanism for both male and female athletes. Exclusion criteria included non-English studies, conference abstracts, and studies on non-sports related concussions. The sports represented by the 10 studies included ice hockey (n = 4), soccer (n = 5), basketball (n = 4), baseball/softball (n = 4), and lacrosse (n = 5). The rate ratio was calculated as the incidence rate in female athletes/male athletes for each concussion mechanism or activity. Data were pooled using the DerSimonian-Laird random-effects model. Study quality was assessed with the Newcastle-Ottawa Scale. Female athletes were at lower risk of player-contact-induced concussions in lacrosse (pooled rate ratio 0.33 [95% CI 0.25 to 0.43]; p < 0.001), basketball (pooled rate ratio 0.86 [95% CI 0.76 to 0.97]; p = 0.01), ice hockey (pooled rate ratio 0.64 [95% CI 0.56 to 0.73]; p < 0.001), soccer (pooled rate ratio 0.70 [95% CI 0.66 to 0.75]; p < 0.001), and soccer heading (pooled rate ratio 0.80 [95% CI 0.72 to 0.90]; p < 0.001); in these sports, men were at higher risk of concussions from player contact. Female athletes were more likely to experience concussions because of ball or equipment contact in lacrosse (pooled rate ratio 3.24 [95% CI 2.10 to 4.99]; p < 0.001), soccer (pooled rate ratio 2.04 [95% CI 1.67 to 2.49]; p < 0.001), and soccer heading (pooled rate ratio 2.63 [95% CI 1.84 to 3.77]; p < 0.001). The mechanism or activity underlying concussions differs between male and female athletes across different sports. This finding remains the same regardless of whether there are rule differences between the men's and women's games. The implementation of other interventions are required to further ensure player safety, including protective head equipment, concussion prevention training, or rules limiting player contact in the men's game.

#6 Jump performance in male and female football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Oct 30. doi: 10.1007/s00167-019-05747-1. [Epub ahead of print]
Authors: Arundale AJH, Kvist J, Hägglund M, Fältström A
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Summary: The purpose was to examine differences between men and women football players in clinically feasible jumping measures. Female football players (N = 46, ages 16-25) were matched based on age, training frequency, and playing position with 46 male players. All players performed the tuck jump and drop vertical jump (DVJ). DVJ was assessed quantitatively for valgus knee motion and probability of a high peak knee abduction moment (pKAM), as well as sagittal plane hip, knee, and ankle angles, and qualitatively with visual assessment of the player's knees upon landing; graded as good, reduced, or poor control. Women had higher total tuck jump scores (5 ± 2) (more technique flaws), than men (3 ± 2, P < 0.01). The quantitative analysis of the DVJ found that men had greater asymmetries between limbs, but women landed bilaterally in more knee valgus (interaction P = 0.04, main effect of sex P = 0.02). There was no difference in pKAM (interaction n.s.). Women also landed in less hip flexion (P = 0.01) and ankle dorsiflexion (P = 0.01) than men. The qualitative DVJ analysis found that more women (48%) had poor knee control compared to men (11%, P < 0.01). The results indicate that women perform worse on the tuck jump assessment than men. The results support previous findings that women land in more knee valgus than men, but also found that men may have larger asymmetries in knee valgus. These results from clinically feasible measures provide some suggestions for clinicians to consider during ACL reconstruction rehabilitation to enhance performance.

#7 Game-specific abilities in elite youth football players: validity and sensitivity to change in subjective coach ratings compared to objectively assessed data
Reference: J Sports Med Phys Fitness. 2019 Oct 25. doi: 10.23736/S0022-4707.19.10084-9. [Epub ahead of print]
Authors: Niederer D, Damm M, Grigereit A, Banzer W, Vogt L
Summary: Little is known on the accuracy of coaches' ratings of game-specific physical abilities in elite youth football players. The present study on elite youth football players aims to assess whether 1) the coaches' subjective assessment of the level of performance of each athlete within the team is in accordance with objectively collected data and 2) the coaches rate changes in the athletes'' performance level accurately or not. Data on jumping ability, sprinting speed, change of direction and strength were collected in seven age groups at a football youth academy (n = 150). The diagnostic battery was repeated after seven months (n = 138). Before the second session, the head coaches completed Likert-scaled closed questions on 1) the importance of running speed and reactive strength components and their relevance to the individual game performance of each of their athletes, 2) level of performance of their athletes, and 3) the change between the first and second performance testing results. Validity and sensitivity of change of their ratings in comparison to the performance data were calculated using analyses of interrelationship. The data of the head coaches showed a low to medium effect size in the agreement with the performance data (Cohen's W = .33 - .71). The evaluation of the change in level of performance was poorer (Cohen's W =.04 - .2; n.s.). Our results underline that functional/physical testing twice during a season may be crucial for displaying performance levels of elite youth football players. Simple self-reported ratings by the coach may be valid in recent performance level assessment but not for performance changes.

#8 Internal training load monitoring in professional football: a systematic review of methods using rating of perceived exertion
Reference: J Sports Med Phys Fitness. 2019 Oct 24. doi: 10.23736/S0022-4707.19.10000-X. [Epub ahead of print]
Authors: Rago V, Brito J, Figueiredo P, Costa J, Krustrup P, Rebelo A
Summary: The rate of perceived exertion (RPE) is widely adopted to quantify internal training load (ITL) in professional football. The aim of this study was to systematically review the use RPE-based methods in professional football. Observational studies conducted during training routines of professional football players over a minimum of one- week were selected based on the preferred reporting items for systematic reviews and meta-analyses statement. Thirty-eight articles met the inclusion criteria (average qualitative score was 6.3 out of 10 [3 to 9]). The main deficiencies identified concerned the poor description of study design (~52% of the studies), and the non-quantification of match load (~44%). Ten studies complemented RPE-based ITL information with time-motion analysis (~26%) and seven studies added HR recordings (~18%). Nine studies collected RPE data after complementary training, separately to field sessions (~3%). Operational questions (e.g. How was your workout? ~71%) were preferred to instructions (e.g. Please rate the intensity of today's session; ~8%). Session-RPE (s-RPE; RPE multiplied by training duration) was more commonly adopted as measure of exercise intensity than isolated RPE (~76 vs. ~8%). RPE-derived variables calculated on weekly values included absolute week-to-week change, acute: chronic workload ratio, monotony and strain and were not frequently used (7 to 15%). Four studies (~11%) divided RPE in two components: respiratory and muscular. There is a lack of consensus for the use of RPE in professional football and "good practices" are warranted. This review might help practitioners regarding procedures to adopt in RPE data collection and interpretation.

#9 No association between perceived exertion and session duration with hamstring injury occurrence in professional football
Reference: Scand J Med Sci Sports. 2019 Oct 30. doi: 10.1111/sms.13591. [Epub ahead of print]
Authors: Lolli L, Bahr R, Weston M, Whiteley R, Tabben M, Bonanno D, Gregson W, Chamari K, Di Salvo V, van Dyk N
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Summary: Training and competition loads have emerged as modifiable composite risk factors of non-contact injury. Hamstring strains are the most common injuries in football with substantial burden on the individual player and club. Nevertheless, robust evidence of a consistent load-hamstring injury relationship in professional football is lacking. Using available data from the Qatar Stars League over three competitive seasons, this study investigated the separate and combined effects of perceived exertion and session duration on hamstring injury occurrence in a sample of 30 outfield football players. Load variables were calculated into 7-day, 14-day, 21-day, 28-day periods of data, and week-to-week changes for average ratings of perceived exertion (RPE; au) score and session-RPE (s-RPE; session-duration X score), plus the cumulative training and match minutes and s-RPE, respectively. Conditional logistic regression models estimated load-injury relationships per 2-within-subject standard deviation increments in each candidate variable. Associations were declared practically important based on the location of the confidence interval in relation to thresholds of 0.90 and 1.11 defining small beneficial and harmful effects, respectively. The uncertainty for the corrected odds ratios show that typically high within-subject increments in each candidate variable were not practically important for training- and match-related hamstring injury (95% confidence intervals range: 0.85 to 1.16). We found limited exploratory evidence regarding the value of perceived exertion and session duration as aetiological factors of hamstring injury in Middle-East professional football. Monitoring remains valuable to inform player load management strategies, but our exploratory findings suggest its role for type-specific injury risk determination appears empirically unsupported.

#10 Risk of acute and overuse injuries in youth elite soccer players: Body size and growth matter
Reference: J Sci Med Sport. 2019 Oct 10. pii: S1440-2440(19)30355-X. doi: 10.1016/j.jsams.2019.10.001. [Epub ahead of print]
Authors: Rommers N, Rössler R, Goossens L, Vaeyens R, Lenoir M, Witvrouw E, D'Hondt E
Summary: This study investigated anthropometric measures and growth as risk factors for overuse and acute injuries in younger (U10-U12) and older (U13-U15) elite level soccer players. Height, weight, and sitting height were measured at the start and the end of the 2016-2017 competitive season and growth velocities were calculated. Throughout the season, injuries were registered continuously by the (para-)medical staff of the included clubs. We analyzed the injury risk using multilevel Poisson regression models, accounting for club and team clustering. Of the included 314 players (11.7±1.7 years of age), 160 players sustained 133 overuse and 163 acute injuries (i.e. 106 injuries in 69 players of the younger group, 190 in 91 players of the older group). In the younger group, risk of overuse injuries was associated with an increase in leg length over the season (incidence rate ratio (IRR) 1.620 [95% CI 1.230-2.117]) and risk of acute injuries with relatively younger age (IRR 1.003 [95% CI 1.000-1.006]). In the older group, a higher leg length was associated with an increased risk of overuse injuries (IRR 1.055 [95% CI 1.011-1.108]), and a higher weight and a lower growth rate with an increased risk of acute injuries (IRR 1.043 [95% CI 1.021-1.067] and 0.903 [95% CI 0.831-0.981], respectively). Injury risk factors differ by age group and type of injury. The age-specific anthropometric and growth-related risk factors should be monitored and these risk profiles should be considered to manage injury risk effectively.

#11 Effects of Ramadan fasting on physical performances in soccer players: a systematic review
Reference: Tunis Med. 2019 Oct;97(10):1114-1131.
Authors: Chtourou H, Trabelsi K, Boukhris O, Ammar A, Shephard RJ, Bragazzi NL.
Summary: The purpose was to evaluate the effects of Ramadan fasting on physical performance measures in soccer players through a systematic appraisal of the literature. Systematic review Data sources: The entire content of two databases, PubMed/MEDLINE and Web of Science. Eligibility criteria for selecting studies: Both singlegroup, pre-post and crossover design studies published in any language before March 15, 2019 were included. Assessments of physical performance were accepted for analysis. study appraisal: The methodological quality of the included studies was assessed using 'QualSyst'. Of 18 selected articles, 16 were generally of strong quality and the remaining studies (n=2) were rated as moderate, although most lacked significant details about the Ramadan fasting. Most studies showed that Ramadan fasting did not impair short-term maximal performances in soccer players (i.e., vertical jump, sprint performance, maximal voluntary contraction, hand grip, agility performance). During the 30-s Wingate test, the repeated sprint exercise (RSE) tasks, and the long-duration incremental and non-incremental exercises, most studies reported some negative effects of Ramadan fasting even when the training load was maintained. For the soccer specific skills and test with ball, most studies reported that there was no significant negative effects of the fasting month on performance when the training load was maintained or slightly reduced during the Ramadan. The continuance of training during Ramadan fasting, with maintained training load, has no negative effects on short-term maximal performances and soccer specific skills and test with ball. However, performances of the 30-s Wingate test, the RSE tasks, and the long-duration incremental and non-incremental exercises were significantly impaired during Ramadan fasting even when the training load was maintained.

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