Latest research in football - week 48 - 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 Observational Studies in Male Elite Football: A Systematic Mixed Study Review
Reference: Front Psychol. 2019 Oct 18;10:2077. doi: 10.3389/fpsyg.2019.02077. eCollection 2019.
Authors: Preciado M, Anguera MT, Olarte M, Lapresa D
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Summary: This systematic mixed study review, focuses on the use of observation methodology in elite men's football matches, which constitutes an innovative approach, that opens up a new panorama of useful and productive research. The methods used in this study follow the recommendations for systematic reviews and meta-analysis guidelines (PRISMA). The search was carried out in five databases. Ninety-four articles out of 3,195 were selected and analyzed. In order to achieve a quality assessment, the guide was used to inform evaluations based on observation methodology (GREOM) (Portell et al., 2015), recognized by the EQUATOR network. From the methodological review analysis, information obtained indicates that 97% of the researches used direct observation and 3% indirect observation. On the other hand, 56.5% of the articles explain the instrument used and 77% justify the applied observational design. A quantitative comparison of the proportions was made in several methodological aspects, which resulted in only 15.21% reviewing the quality of the data, and that 67.3% of the articles contributed to the mixed methods approach. The methodological review allowed us to establish procedural profiles. The results indicate that 67% of the articles have been published in English, and of these, 77% were published in journals that have an impact factor. The majority of the researchers, 53.26%, belong to Spanish entities. The most studied substantive aspects were goal (34%), possession of the ball (28%), and corner (27%). The most observed events were Leagues, World Cups, individual players and other events. The results obtained refer to both substantive and methodological aspects and allow us to configure a systematic review of mixed studies, in which we emphasize the aspects of a "systematic review" and a "mixed study," within an integrated perspective.

#2 Hamstring injury prevention in Belgian and English elite football teams
Reference: Acta Orthop Belg. 2019 Sep;85(3):373-380.
Authors: Van Crombrugge G, Duvivier BM, Van Crombrugge K, Bellemans J, Peers K.
Summary: Hamstring injury is the most common injury in European professional football. The purpose of this study was to provide insight into the content of hamstring injury prevention programmes in English and Belgian elite football teams. Fifteen premier league teams (10 from Belgium and 5 from England) completed a questionnaire on hamstring injury prevention. Most football teams (93%) screened for hamstring injury risk factors. Less than 60% screened for risk factors including gluteus muscle strength, neural tension and body posture during running. While 80% of the teams had a hamstring injury prevention programme during preseason and official season ; only 47% had a prevention programme during mid-season break. Hamstring muscle strength exercises were mainly performed before (77%) instead of after warming-up. In conclusion, while most investigated football teams perform hamstring injury prevention, the content and implementation of the prevention programmes is suboptimal in many Belgian and English elite football teams.

#3 The Functional Movement Screen total score and physical performance in elite male collegiate soccer players
Reference: J Exerc Rehabil. 2019 Oct 28;15(5):657-662. doi: 10.12965/jer.1938422.211. eCollection 2019 Oct.
Authors: Lee S, Kim H, Kim J
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Summary: The objectives of this study were to compare the differences in physical performance of elite male collegiate soccer players according to the Functional Movement Screen (FMS) total scores and to investigate the association between the FMS total score and physical performance. A total of 20 elite male collegiate soccer players (mean age, 19.6±0.7 years; height, 173.4±4.4 cm; body weight, 66.9±7.3 kg; and body mass index, 22.0±2.0 kg/m2) participated in the present study. The subjects were divided into two groups: the high FMS (FMS total score ≥14 points, n=10) and low FMS (FMS total score <14 points, n=10). All participants completed 10-m and 30-m sprint tests, the arrowhead agility test (right and left), and a coordination test. The statistical methods used to verify the study results were the independent sample t-test and Kendall's Tau b correlation test. There were significant differences between the high and low FMS groups in the 10-m (P=0.014) and 30-m sprint (P=0.002) and arrowhead agility tests (right, P=0.039). Conversely, there were no significant differences in the arrowhead agility (left) and coordination tests between the two groups (P>0.05). Moreover, the FMS total score was found to have significant negative correlations with the 10-m sprint (r=-0.444, P=0.017), 30-m sprint (r=-0.425, P=0.016), and arrowhead agility tests (right, r=-0.389, P=0.023). These results suggest that higher FMS total scores could have a positive effect on the physical performance of the players.

#4 Comparison of three types of warm-up upon sprint ability in experienced soccer players
Reference: J Sport Health Sci. 2019 Nov;8(6):574-578. doi: 10.1016/j.jshs.2016.05.006. Epub 2016 May 24.
Authors: van den Tillaar R, Lerberg E, von Heimburg E
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Summary: The study aimed to compare the effects of a long general warm-up, a long specific warm-up, and a short specific warm-up upon sprint ability in soccer players. Twelve male soccer players (age: 18.3 ± 0.8 years, mean ± SD; body mass: 76.4 ± 7.2 kg; body height: 1.79 ± 0.05 m) conducted 3 types of warm-ups with 1 week in between: a long general warm-up, a long specific warm-up, and a short specific warm-up followed by 3 sprints of 40 m each. The best, average, and total sprinting times together with heart rate and ratings of perceived exertion were measured. The sprint times (best, average, and total time) were significantly better when performing a long specific or short specific warm-up compared with the long general warm-up (all p < 0.05). The received perception exertion was significantly lower during the specific short warm-up (4.92 ± 0.90) compared with the longer ones (6.00 ± 0.74 and 6.25 ± 0.87, respectively). Specificity is more important in a warm-up routine before sprint performance than the duration of the warm-up.

#5 The effect of fatigue and duration knowledge of exercise on kicking performance in soccer players
Reference: J Sport Health Sci. 2019 Nov;8(6):567-573. doi: 10.1016/j.jshs.2016.02.001. Epub 2016 Feb 2.
Authors: Ferraz RMP, van den Tillaar R, Pereira A, Marques MC
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Summary: The purpose of this study was to investigate the influence of fatigue upon kicking maximal ball velocity and the target-hitting accuracy of soccer players; and also to examine the effect of the knowledge of the exercise duration upon these 2 parameters. Twenty-four semi-professional soccer players participated in this study and performed maximal instep kicks before and after the implementation of an exercise protocol, either with or without knowledge of the duration of this protocol. A mixed model of analysis of variance showed that kicking maximal ball velocity was significantly affected (F(5, 85) = 11.6, p < 0.001, η 2 = 0.39) but only after just 1 circuit of the fatigue protocol and then remained similar. Accuracy did not change during the protocol (F(5, 75) = 0.23, p = 0.76, η 2 = 0.03) and knowing the duration of exercitation did not affect accuracy and velocity development (F(1, 23) ≤ 1.04, p ≥ 0.32, η 2 ≤ 0.06). These findings demonstrated the potential negative effects of fatigue on kicking ball velocity in soccer but not in the kicking accuracy and that the effect of fatigue may not be progressive over time. Knowing or not knowing the duration of exercitation did not affect the results.

#6 Effect of contextual factors in body composition of professional soccer players. A retrospective study
Reference: Nutr Hosp. 2019 Nov 13. doi: 10.20960/nh.02783. [Epub ahead of print] [Article in Spanish]
Authors: López Cáceres PA, Chena M, Asín Izquierdo I, Moreno-Ortega A, Moreno Rojas R
Summary: The requirements of physical demands in soccer have evolved in recent years, determining the need to investigate those aspects that condition athletic performance. The objective of this study was to describe the incidence of individualized training, company at meals, race, and demarcation on the anthropometric variables of professional soccer players since these four factors affect body composition, which is considered a predictor of performance and an indicator of lifestyle in these individuals. For this purpose, a retrospective study was developed in 51 professional players of the Spanish Football League Second Division B during the 2015/2016, 2016/2017, and 2017/2018 seasons. The anthropometric assessment was carried out under the technical standards of measurement recommended by the International Working Group of Kinanthropometry, adopted by the International Society for the Advancement of Kinanthropometry (ISAK). The results revealed that individualized training and company during meals were the factors that most influence exerted on the anthropometric variables that were collected. The values of fat mass and muscle mass, and the sum of fold measurements are sensitive to the effect of the intervention with these factors. The highest levels of interaction occurred between company during the meals and individualized training, and between demarcation and company during the meals. Considering body composition as an aspect to be taken into account in the development of performance, it should be considered that the application of certain training contents according to the individual characteristics and lifestyle of players are factors that may have a significant influence on professional soccer players.

#7 A case study of the use of verbal reports for talent identification purposes in soccer: A Messi affair!
Reference: PLoS One. 2019 Nov 12;14(11):e0225033. doi: 10.1371/journal.pone.0225033. eCollection 2019.
Authors: Reeves MJ, McRobert AP, Lewis CJ, Roberts SJ
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Summary: Using a two-study approach, the main purpose of this case study was to explore the use of a verbal reporting methodology to better understand the thought processes of soccer talent scouts during an in-situ talent identification environment. Study 1 developed a standardized coding-scheme to examine verbal cognitions during a single soccer game. Study 2 then utilized this methodology to examine two full-time recruitment staff trained in the use of concurrent verbal reporting before undertaking a live, in-game task. Participants also participated in a debrief interview following the game. The findings of the two studies suggest that developing a verbal reporting protocol is viable, however when applied in a live-game environment it is problematic. Future research should therefore consider a modified version of this task to further explore the cognitions of scouts whilst observing and identifying potential talent.

#8 Late Activation of the Vastus Medialis in Determining the Risk of Anterior Cruciate Ligament Injury in Soccer Players
Reference: J Sport Rehabil. 2019 Nov 7:1-4. doi: 10.1123/jsr.2019-0026. [Epub ahead of print]
Authors: Marotta N, Demeco A, de Scorpio G, Indino A, Iona T, Ammendolia A.
Summary: Activation time of the quadriceps is important in determining injury risk in professional soccer players. The objective was to compare the activation time of the quadriceps and hamstrings muscles during a movement that puts stress on anterior cruciate ligament (ACL) to assess the risk of ACL injury. Twenty (10 males and 10 females) professional soccer players participated in this study. An inertial sensor and 4 electrodes positioned on the quadriceps and hamstrings muscles were used for the surface electromyography. The athlete resting on 1 leg dropped, from a 32-cm-high platform, on the suspended foot (testing leg), without jumping or lowering his center of gravity and maintaining single-leg landing for 5 seconds. Using a software, it is possible to calculate the activation time of the rectus femoris, vastus medialis (VM), biceps femoris, and semimembranosus muscles before ground contact. The main outcome was to evaluate the activation times of the rectus femoris, VM, biceps femoris, and semitendinosus muscles before ground contact in comparison with the range of normality calculated by the manufacturer. All male soccer players demonstrated a low risk related to the correct activation of all the examined muscles, while female soccer players demonstrated delayed activation of the VM. Delayed activation of the VM registered in females determines an increase in anterior shear force, which is an important risk factor for incurring an ACL injury. This testing protocol becomes adequate for the screening of high-risk athletes and for targeting interventions to specific imbalances that may increase injury risk.

#9 Poor Sleep Quality's Association With Soccer Injuries: Preliminary Data
Reference: Int J Sports Physiol Perform. 2019 Nov 10:1-6. doi: 10.1123/ijspp.2019-0185. [Epub ahead of print]
Authors: Silva A, Narciso FV, Soalheiro I, Viegas F, Freitas LSN, Lima A, Leite BA, Aleixo HC, Duffield R, de Mello MT.
Summary: The purpose was to investigate the relationship between sleep quality and quantity and injuries in elite soccer players and to compare sleep-wake variables and injury characteristics. The current investigation was a prospective cohort study of 23 elite male soccer players competing for 2 teams over 6 mo in the highest-level Brazilian competition. The players' sleep behavior was monitored for 10 d in the preseason using self-reporting sleep diaries and wrist activity monitors to determine sleep duration and quality. Furthermore, injuries were recorded by the respective club's medical teams into a specific database. Details of injuries recorded included the type, location, and severity of each injury. The results were expressed as descriptive statistics, and the significance level was set at 5%. The Mann-Whitney U test was performed to compare the sleep variables between groups. Spearman correlation coefficient and linear-regression analysis were used. The results indicated a moderate negative correlation between sleep efficiency and particular injury characteristics, including absence time, injury severity, and amount of injuries. The linear-regression analysis indicated that 44% of the total variance in the number of injuries can be explained by sleep efficiency, 24% of the total variance in the absence time after injury (days) can be explained by sleep efficiency, and 47% of the total variance in the injury severity can be explained by sleep efficiency. Soccer players who exhibit lower sleep quality or nonrestorative sleep show associations with increased number and severity of musculoskeletal injuries.

#10 Was Zika introduced to Brazil by participants at the 2013 Beach Soccer World Cup held in Tahiti: A phylogeographical analysis
Reference: Travel Med Infect Dis. 2019 Nov 5:101512. doi: 10.1016/j.tmaid.2019.101512. [Epub ahead of print]
Authors: Le Hingrat Q, Perrier M, Charpentier C, Jacquot A, Houhou-Fidouh N, Descamps D, Visseaux B
Summary: Zika virus (ZIKV) was initially responsible for a limited number of punctual epidemics throughout Africa and Asia. Recently, large epidemics occurred in French Polynesia, Brazil and Pan-America. These outbreaks were associated with severe outcomes such as Guillain-Barré Syndrome and microcephaly of in-utero infected newborns. Previous studies demonstrated that ZIKV was introduced in Brazil from French Polynesia but failed to identify a founding event. All publicly available ZIKV full-genome sequences (n = 182) were phylogenetically analyzed, using Bayesian method, to estimate the introduction date of ZIKV into Brazil. Introduction date into Brazil was estimated between 8th of July 2013 and 4th of November 2013, encompassing the Beach Soccer World Cup held in French Polynesia, in September 2013, which gathered Brazilian athletes and supporters. We also observed that ZIKV sequences from travelers infected in South-East Asia or in Pacific islands were closely related to viruses identified prior to the French Polynesian epidemic, underlining an endemic circulation of ZIKV in those countries since 2007, at least. This work provides a narrower estimation of ZIKV introduction into Brazil and illustrates the need for a better exploration of ZIKV circulation and endemicity in South-East Asia, while epidemiological and prevention efforts have been mainly focused on the Pan-American epidemic.

#11 Constructing Spaces and Times for Tactical Analysis in Football
Reference: IEEE Trans Vis Comput Graph. 2019 Nov 8. doi: 10.1109/TVCG.2019.2952129. [Epub ahead of print]
Authors: Andrienko G, Andrienko N, Anzer G, Bauer P, Budziak G, Fuchs G, Hecker D, Weber H, Wrobel S.
Summary: A possible objective in analyzing trajectories of multiple simultaneously moving objects, such as football players during a game, is to extract and understand the general patterns of coordinated movement in different classes of situations as they develop. For achieving this objective, we propose an approach that includes a combination of query techniques for flexible selection of episodes of situation development, a method for dynamic aggregation of data from selected groups of episodes, and a data structure for representing the aggregates that enables their exploration and use in further analysis. The aggregation, which is meant to abstract general movement patterns, involves construction of new time-homomorphic reference systems owing to iterative application of aggregation operators to a sequence of data selections. As similar patterns may occur at different spatial locations, we also propose constructing new spatial reference systems for aligning and matching movements irrespective of their absolute locations. The approach was tested in application to tracking data from two Bundesliga games of the 2018/2019 season. It enabled detection of interesting and meaningful general patterns of team behaviors in three classes of situations defined by football experts. The experts found the approach and the underlying concepts worth implementing in tools for football analysts.

#12 The real penalty: number of OMFS patients presenting to the emergency department at Sunderland Royal Hospital after England fixtures before and during the 2018 FIFA Football World Cup
Reference: Br J Oral Maxillofac Surg. 2019 Nov 9. pii: S0266-4356(19)30709-0. doi: 10.1016/j.bjoms.2019.10.313. [Epub ahead of print]
Authors: Miller N, Kearns A, Bartram A, Banks R
Summary: The aim of this study was to establish a link between a large televised sporting event and the incidence of patients presenting to the emergency department with oral and maxillofacial injuries. When compared with daily attendances throughout the year, the mean (SD) number rose from 2.53 (1.69) to 4.00 (1.53) (p=0.005) between 1 November 2017 and 31 July 2018 on the day after an England fixture, an increase of 58%. These data show the need for workforce planning during large-scale national sporting events because of the rise in the number of patients presenting. They show that the increase in workload is caused by a higher number of both traumatic and non-traumatic injuries.

#13 Yo-Yo intermittent tests are a valid tool for aerobic fitness assessment in recreational football
Reference: Eur J Appl Physiol. 2019 Nov 9. doi: 10.1007/s00421-019-04258-8. [Epub ahead of print]
Authors: Castagna C, Krustrup P, Póvoas S
Summary: The purpose was to examine the suitability of three versions and two levels of the Yo-Yo intermittent tests for assessing and tracking aerobic fitness status development in male recreational football players. Sixty-six untrained participants (age 39 ± 6 years, VO2max 41.2 ± 6.2 ml kg-1 min-1, body mass 81.9 ± 10.8 kg, height 173.2 ± 6.4 cm) partook in a 12-week recreational football training program. They were evaluated during the Yo-Yo intermittent endurance level 1 (YYIE1) and 2 (YYIE2) tests and the Yo-Yo intermittent recovery level 1 test (YYIR1), and during a treadmill test for VO2max assessment, at baseline. Thirty-two out of these 66 participants replicated all these tests at post-intervention. An additional group of 30 male age-matched recreational football players that afterwards started the 12-week recreational football program (age 39 ± 6 years, VO2max 45.3 ± 5.8 ml kg-1 min-1, body mass 82.5 ± 7.8 kg, height 172.8 ± 5.4 cm) was evaluated at baseline to test cross-validation. The Yo-Yo tests showed very large associations with VO2max at baseline (r = 0.75-0.77; P < 0.0001) and at post-intervention (r = 0.76-0.82; P < 0.0005). Post-training, very large associations were found between YYIE2 performance and VO2max (r = 0.65, P < 0.0001). Cross-validation revealed small to large differences between the observed and estimated VO2max values (1.5-2.96 ml kg-1 min-1) with moderate typical error of estimation (7.9-8.7%) across the tests. Performance in the YYIE1, YYIE2 and YYIR1 tests of ≥ 1760, 480 and 600 m, respectively, indicated good to excellent VO2max values. The Yo-Yo tests considered here showed robust and consistent criterion validity. The YYIE2 could be a more accurate option to track aerobic fitness development in recreational football players.

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