Latest research in football - week 39 - 2020

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 The Interplay Between Plasma Hormonal Concentrations, Physical Fitness, Workload and Mood State Changes to Periods of Congested Match Play in Professional Soccer Players
Reference: Front Physiol. 2020 Jul 21;11:835. doi: 10.3389/fphys.2020.00835. eCollection 2020.
Authors: Karim Saidi, Abderraouf Ben Abderrahman, Daniel Boullosa, Grégory Dupont, Anthony C Hackney, Benoit Bideau, Thomas Pavillon, Urs Granacher, Hassane Zouhal
Summary: The regular assessment of hormonal and mood state parameters in professional soccer are proposed as good indicators during periods of intense training and/or competition to avoid overtraining. The aim of this study was to analyze hormonal, psychological, workload and physical fitness parameters in elite soccer players in relation to changes in training and match exposure during a congested period of match play. Sixteen elite soccer players from a team playing in the first Tunisian soccer league were evaluated three times (T1, T2, and T3) over 12 weeks. The non-congested period of match play was from T1 to T2, when the players played 6 games over 6 weeks. The congested period was from T2 to T3, when the players played 10 games over 6 weeks. From T1 to T3, players performed the Yo-Yo intermittent recovery test level 1 (YYIR1), the repeated shuttle sprint ability test (RSSA), the countermovement jump test (CMJ), and the squat jump test (SJ). Plasma Cortisol (C), Testosterone (T), and the T/C ratio were analyzed at T1, T2, and T3. Players had their mood dimensions (tension, depression, anger, vigor, fatigue, confusion, and a Total Mood Disturbance) assessed through the Profile of Mood State questionnaire (POMS). Training session rating of perceived exertion (sRPE) was also recorded on a daily basis in order to quantify internal training load and elements of monotony and strain. Significant performance declines (T1 < T2 < T3) were found for SJ performance (p = 0.04, effect size [ES] ES1 - 2 = 0.15-0.06, ES2 - 3 = 0.24) from T1 to T3. YYIR1 performance improved significantly from T1 to T2 and declined significantly from T2 to T3 (p = 0.001, ES1 - 2 = 0.24, ES2 - 3 = -2.54). Mean RSSA performance was significantly higher (p = 0.019, ES1 - 2 = -0.47, ES2 - 3 = 1.15) in T3 compared with T2 and T1. Best RSSA performance was significantly higher in T3 when compared with T2 and T1 (p = 0.006, ES2 - 3 = 0.47, ES1 - 2 = -0.56), but significantly lower in T2 when compared with to T1. T and T/C were significantly lower in T3 when compared with T2 and T1 (T: p = 0.03, ES3 - 2 = -0.51, ES3 - 1 = -0.51, T/C: p = 0.017, ES3 - 2 = -1.1, ES3 - 1 = -1.07). Significant decreases were found for the vigor scores in T3 when compared to T2 and T1 (p = 0.002, ES1 - 2 = 0.31, ES3 - 2 = -1.25). A significant increase was found in fatigue scores in T3 as compared to T1 and T2 (p = 0.002, ES1 - 2 = 0.43, ES2 - 3 = 0.81). A significant increase was found from T1 < T2 < T3 intension score (p = 0.002, ES1 - 2 = 1.1, ES2 - 3 = 0.2) and anger score (p = 0.03, ES1 - 2 = 0.47, ES2 - 3 = 0.33) over the study period. Total mood disturbance increased significantly (p = 0.02, ES1 - 2 = 0.91, ES2 - 3 = 1.1) from T1 to T3. Between T1-T2, significant relationships were observed between workload and changes in T (r = 0.66, p = 0.003), and T/C ratio (r = 0.62, p = 0.01). There were significant relationships between performance in RSSAbest and training load parameters (workload: r = 0.52, p = 0.03; monotony: r = 0.62, p = 0.01; strain: r = 0.62, p = 0.009). Between T2-T3, there was a significant relationship between Δ% of total mood disturbance and Δ% of YYIR1 (r = -0.54; p = 0.04), RSSAbest (r = 0.58, p = 0.01), SJ (r = -0,55, p = 0.01), T (r = 0.53; p = 0.03), and T/C (r = 0.5; p = 0.04). An intensive period of congested match play significantly compromised elite soccer players' physical and mental fitness. These changes were related to psychological but not hormonal parameters; even though significant alterations were detected for selected measures. Mood monitoring could be a simple and useful tool to determine the degree of preparedness for match play during a congested period in professional soccer.

#2 Building social cohesion between Christians and Muslims through soccer in post-ISIS Iraq
Reference: Science. 2020 Aug 14;369(6505):866-870. doi: 10.1126/science.abb3153.
Authors: Salma Mousa
Summary: Can intergroup contact build social cohesion after war? I randomly assigned Iraqi Christians displaced by the Islamic State of Iraq and Syria (ISIS) to an all-Christian soccer team or to a team mixed with Muslims. The intervention improved behaviors toward Muslim peers: Christians with Muslim teammates were more likely to vote for a Muslim (not on their team) to receive a sportsmanship award, register for a mixed team next season, and train with Muslims 6 months after the intervention. The intervention did not substantially affect behaviors in other social contexts, such as patronizing a restaurant in Muslim-dominated Mosul or attending a mixed social event, nor did it yield consistent effects on intergroup attitudes. Although contact can build tolerant behaviors toward peers within an intervention, building broader social cohesion outside of it is more challenging.

#3 Family History of Hypertension Impairs the Autonomic Balance, but not the Endothelial Function, in Young Soccer Players
Reference: Arq Bras Cardiol. 2020 Jul;115(1):52-58. doi: 10.36660/abc.20180441. Epub 2020 Aug 7.
Authors: Walter Vargas , Katya Rigatto
Summary: Background The family history of hypertension (FHH) imposes consistent risk for diverse chronic diseases that are accompanied by hypertension. Furthermore, the heart rate variability (HRV) and flow-mediated dilation (FMD) are both related to maximal oxygen uptake (VO2max), and are usually impaired during hypertension Objective To compare the autonomic modulation, the endothelial function (EF) and maximum oxygen uptake (VO2max) of young athletes, separated according to their parents' blood pressure (BP) history, in order to study the influence of their genetic background on those parameters. Methods A total of 46 young male soccer players (18±2 years of age) were divided into four groups: 1-normotensive father and mother (FM-N); 2-only father was hypertensive (F-H); 3-only mother was hypertensive (M-H); 4-father and mother were hypertensive (FM-H). Measurements of BP, FMD, HRV and VO2maxwere performed. The significance level adopted in the statistical analysis was 5%. Results The standard deviation of normal RR intervals (SDNN; FM-N=314±185; FM-H=182.4± 57.8), the square root of the mean squared differences in successive RR intervals (RMSSD; FM-N=248±134; FM-H=87±51), the number of interval differences of successive NN intervals greater than 50ms (NN50; FM-N=367±83.4; FM-H=229±55), the ratio derived by dividing NN50 by the total number of NN intervals (pNN50; FM-N=32.4±6.2; FM-H=21.1±5.3) and the high (HF; FM-N=49±8.9; FM-H=35.3±12) and low-frequency (LF; FM-N=50.9±8.9; FM-H=64.6±12) components, in normalized units (%), were significantly lower in the FM-H group than in the FM-N group (p<0.05). On the other hand, the LF/HF ratio (ms2) was significantly higher (p<0.05). We found no significant difference between the groups in VO2maxand FMD (p<0.05). Conclusions In young male soccer players, the FHH plays a potentially role in autonomic balance impairment, especially when both parents are hypertensive, but present no changes in VO2maxand FMD. In this case, there is a decrease in the sympathetic-vagal control, which seems to precede the endothelial damage (Arq Bras Cardiol. 2020; 115(1):52-58).

#4 Anthropometric and Functional Profile of Selected vs. Non-Selected 13-to-17-Year-Old Soccer Players
Reference: Sports (Basel). 2020 Aug 9;8(8):E111. doi: 10.3390/sports8080111.
Authors: Erik Nughes, Vincenzo Rago, Rodrigo Aquino , Georgios Ermidis, Morten B Randers, Luca Paolo Ardigò
Summary: The purpose of this study was to compare anthropometric and functional profiles of 13-to-17-year-old soccer players according to their competitive level. Height, body mass, percentage of body fat, countermovement jump height, change of direction ability, 5- and 15-m sprint times, repeated sprint ability (RSA), intermittent recovery performance, and dribbling skills were collected in 115 young Italian soccer players. Players were divided into selected (i.e., competing at national level, n = 17 U15 and 47 U17) and non-selected (i.e., competing at regional level, n = 43 U15 and 8 U17) groups. U17 selected players were taller, quicker over 5 and 15 m, more agile, and had better RSA, prolonged intermittent recovery ability, and dribbling skills than their non-selected counterparts (d = 0.28-0.55, p < 0.05). In particular, selected players showed lower times on the first three and the last shuttle of the RSA test (d = 0.28-0.34, p < 0.05). No significant differences were observed in U15 players (p > 0.05). Discriminant analysis revealed that dribbling skills, 15-m sprint time, and height best discriminate U17 players by competitive level (p < 0.001). Anthropometric characteristics and functional abilities can discriminate across competitive standards between male U17 but not U15 soccer players. In particular, these findings suggest the importance of dribbling skills, 15-m sprint, and height in U17 players.

#5 The use of technology in tracking soccer players' health performance: a scoping review
Reference: BMC Med Inform Decis Mak. 2020 Aug 11;20(1):184. doi: 10.1186/s12911-020-01156-4.
Authors: Jassim Almulla, Abdulrahman Takiddin, Mowafa Househ
Summary: Quantifying soccer players' performance using different types of technologies helps coaches in making tactical decisions and maintaining players' health. Little is known about the relation between the performance measuring technologies and the metrics they measure. The aim of this study is to identify and group the different types of technologies that are used to track the health-related performance metrics of soccer players. We conducted a systematic search for articles using IEEE Xplore, PubMed, ACM DL, and papers from the Sports Medicine Journal. The papers were screened and extracted by two reviewers. The included papers had to fall under several criteria, including being about soccer, measuring health-related performance, and using technology to measure players' performance. A total of 1,113 papers were reviewed and 1,069 papers were excluded through the selection process. We reviewed 44 papers and grouped them based on the technology used and health-related metrics tracked. In terms of technology, we categorized the used technologies into wearable technologies (N=27/44) and in-field technologies (N=14/44). We categorized the tracked health-related metrics into physiological metrics (N=16/44) and physical metrics (N=44/44). We found out that wearable technologies are mainly used to track physical metrics (N=27/27) and are also used to track physiological metrics (N=14/27). In-field technologies are only used to track physical metrics (N=24/24). Understanding how technology is related to players' performance and how it is used leads to an improvement in the monitoring process and performance outcomes of the players.

#6 Soccer heading and concussion are not associated with reduced brain volume or cortical thickness
Reference: PLoS One. 2020 Aug 10;15(8):e0235609. doi: 10.1371/journal.pone.0235609. eCollection 2020.
Authors: Tiago Gil Oliveira, Chloe Ifrah, Roman Fleysher, Michael Stockman, Michael L Lipton
Summary: Soccer is the most popular sport in the world and, since it is a contact sport, players are at risk for head injury, including concussion. Here, we proposed to investigate the association of heading and concussion with macroscopic brain structure among adult amateur soccer players. For this study, 375 amateur soccer players (median age 23 years) completed HeadCount-12m to estimate heading over the 12 months prior to MRI and lifetime concussion. T1-weighted 3D magnetization prepared rapid acquisition gradient echo (MP-RAGE) MRI was performed at 3 Tesla. Parcellation was performed using Freesurfer to extract regional gray and white matter volumes as well as regional cortical thickness and total intracranial volume. Regional cortical brain volumes were normalized by total intracranial volume. We categorized heading into quartiles and concussion as 0, 1 or 2 or more. Generalized linear regressions were used to test the association of heading or concussion with each brain morphometry metric, including age and sex, as covariates. Neither heading nor concussion were associated with reduced brain volume or cortical thickness. We observed that greater heading was associated with greater gray matter volume in the left inferior parietal area, which may reflect effects related to training.

#7 Effects of Training with an Agility Ladder on Sprint, Agility, and Dribbling Performance in Youth Soccer Players
Reference: J Hum Kinet. 2020 Jul 21;73:219-228. doi: 10.2478/hukin-2019-0146. eCollection 2020 Jul.
Authors: Alexis Padrón-Cabo, Ezequiel Rey, Anton Kalén, Pablo B Costa
Summary: The aim of this study was to examine the effects of coordination training using an agility ladder compared with a control group on physical fitness and technical performance in youth soccer players. Eighteen male youth soccer players (age: 12.2 ± 0.4 years; body height: 158.3 ± 10.8 cm; body mass: 45.0 ± 8.0 kg) were randomly assigned to an agility ladder group (n = 10) or a control group (n = 8). The intervention program was carried out three times a week over six weeks. Before and after the training period, the 10 m sprint, 20 m sprint, dribbling speed test, agility test, and slalom dribbling test performances were assessed. Within-group analysis showed significant improvements (p < 0.005) in 10 m and 20 m sprint performance from the pre- to the post-test for the agility ladder group (-2.39% and -2.10%) and the control group (-2.54% and -1.44%). No significant differences (p > 0.005) were found from the pre- to the post-test in the dribbling speed test, agility test, slalom dribbling test, and skill index. In the between-group analysis, there were no differences between the agility ladder group and the control group in any variable. In conclusion, the findings of this study suggest coordination training with an agility ladder does not seem to be effective to improve physical fitness and dribbling. Therefore, this information could be beneficial to players and coaches for programming tasks during soccer training sessions.

#8 Evidence for the Relative Age Effect in the Spanish Professional Soccer League
Reference: J Hum Kinet. 2020 Jul 21;73:209-218. doi: 10.2478/hukin-2019-0145. eCollection 2020 Jul.
Authors: José María Yagüe, Olga Molinero, José Ángel Alba, Juan Carlos Redondo
Summary: The concept of the relative age effect refers to the consequences of the physical and psychological differences that may exist between those born earlier or later within the same calendar year. The objective of the present study was to examine this phenomenon in Spanish professional soccer, identifying the influences of the competitive level and the club of origin. The sample comprised 2,130 individuals from five competitive categories: under 12 (U12; n = 480), under 14 (U14; n = 338), under 16 (U16; n = 390), under 19 years old (U19; n = 489) and professional players (n = 433), with nine teams from the Spanish professional soccer league (PSL). Statistical analysis was based on a chi-squared test followed by calculation of the odds ratios and 95% confidence intervals. The main results show that at all levels of competition there was over-representation of individuals born in the first few months of the year. By clubs, the same over-representation was observed. It may be concluded that the relative age effect is consistent and exists throughout Spanish soccer, whether at youth or professional levels. An analysis by age categories showed a more pronounced effect in those competitions in which the youngest players participate, while in clubs the effect continued to be significantly present in all cases investigated in the study.

#9 A Comparison of Incremental Running Field and Treadmill Tests in Young Soccer Players
Reference: J Hum Kinet. 2020 Jul 21;73:193-201. doi: 10.2478/hukin-2019-0143. eCollection 2020 Jul.
Authors: Yusuf Köklü, Utku Alemdaroğlu, Ramazan Demirhan, Yunus Arslan
Summary: The purpose of this study was to compare the incremental running tests performed by young soccer players on a treadmill (Tr) and in the field (FTcod: 100 m change of direction and FTcir: 100 m circle). Nineteen players (average age 17.4 ± 1.1 years; body height 172.0 ± 5.7 cm; body mass 68.9 ± 6.7 kg) volunteered to perform incremental Tr , FTcod and FTcir running tests. In all three tests, players ran for 3 min at 8, 10, 12 and 14 km∙h-1 and were given a 1 min rest interval between subsequent stages. Blood lactate concentrations (La-) were measured at 1 min rest intervals and the heart rate (HR) responses of players were recorded during the tests. After a 5 min recovery period, the second part of the test started; players ran at 15 km∙h-1 with velocity increments of 1 km∙h-1 every 1 min until exhaustion. This part was performed to determine maximum HR, maximum La- and the players' final velocities. The results showed that players had significantly lower La- (F = 6.93, p = 0.07, η2 = 0.46, 95%CI(TR-FTcir) = -1.91/-0.34, 95%CI(TR-FTcod) = -1.59/-0.05) and HR (F = 9.08, p = 0.02, η2 = 0.53, 95%CI(TR-FTcir) = -6.98/-1.68, 95%CI(TR-FTcod) = -7.19/1.08) responses in the Tr test than in the FTcir and FTcod tests at 14 km∙h-1. It was also found that players completed the Tr test (F = 58.22, p = 0.00, η2 = 0.87) at higher final running velocities than the FTcir (95%CI(TR-FTcir) = 1.67/2.78) and FTcod (95%CI(TR-FTcod) = 1.69/2.85) tests. In conclusion, when coaches or sports scientists plan to train at higher running velocities or according to the final velocity in the test, it is advisable to carry out testing in the circumstances under which training will be carried out (in the field or on a treadmill).

#10 How do Elite Soccer Teams Perform to Ball Recovery? Effects of Tactical Modelling and Contextual Variables on the Defensive Patterns of Play
Reference: J Hum Kinet. 2020 Jul 21;73:165-179. doi: 10.2478/hukin-2019-0141. eCollection 2020 Jul.
Authors: Tiago Fernandes, Oleguer Camerino, Júlio Garganta, Raúl Hileno, Daniel Barreira
Summary: Researchers in soccer match analysis have been using limited procedures to express the dynamics of the game and mainly focus on the attack. Therefore, the aims of this paper were to detect the successful teams' ball recovery defensive patterns of play and study the influence of tactical modelling, halves, match status, opponent quality and stage competition on those patterns. The sample consisted of 1323 situations of defensive ball possession of the semi-finalist teams from the 2014 FIFA World Cup play-offs, which was collected by a valid and reliable observational instrument (Soccer-Defence). The Kruskal-Wallis H, Mann-Whitney U, Chi-square, Z-, multinomial logistic regression tests and sequential analysis (p < .05; z > 1.96) were used accordingly to test the differences and associations among and within teams of tactical modelling, tactical-technical behaviours and contextual variables to ball recovery. We found that among teams ball recovery differed in duration; H(3) = 14.958, p = .002. Germany were more likely to perform ball recovery by the goalkeeper than Argentina (p = .04; OR = 0.47) or the Netherlands (p < .05; OR = 0.50). Nevertheless, Brazil was the least likely to concede a shot off goal. Teams facing lower-ranked opponents were 0.63 times less likely to perform ball recovery by interception (p <.001). Additionally, sequential analysis illustrated that teams varied between central and lateral high-pressure zones before ball recovery in lower zones of the field. Finally, coaches could use such findings to design training exercises, create their own style of play, and set strategies.

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