Latest research in footbal - week 8 - 2019

#1 Finding Roles of Players in Football Using Automatic Particle Swarm Optimization-Clustering Algorithm
Reference: Big Data. 2019 Feb 15. doi: 10.1089/big.2018.0069. [Epub ahead of print]
Authors: Behravan I, Zahiri SH, Razavi SM, Trasarti R
Summary: Recently, professional team sport organizations have invested their resources to analyze their own and opponents' performance. So, developing methods and algorithms for analyzing team sports has become one of the most popular topics among data scientists. Analyzing football is hard because of its complexity, number of events in each match, and constant flow of circulation of the ball. Finding roles of players with the purpose of analyzing the performance of a team or making a meaningful comparison between players is crucial. In this article, an automatic big data clustering method, based on a swarm intelligence algorithm, is proposed to automatically cluster the data set of players' performance centers in different matches and extract different kinds of roles in football. The proposed method created using particle swarm optimization algorithm has two phases. In the first phase, the algorithm searches the solution space to find the number of clusters and, in the second phase, it finds the positions of the centroids. To show the effectiveness of the algorithm, it is tested on six synthetic data sets and its performance is compared with two other conventional clustering methods. After that, the algorithm is used to find clusters of a data set containing 93,000 objects, which are the centers of players' performance in about 4900 matches in different European leagues.


#2 Shared Knowledge and Verbal Communication in Football: Changes in Team Cognition Through Collective Training
Reference: Front Psychol. 2019 Jan 31;10:77. doi: 10.3389/fpsyg.2019.00077. eCollection 2019.
Authors: Blaser MA, Seiler R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6365450/pdf/fpsyg-10-00077.pdf
Summary: One of the psychological mechanisms that contribute to effective and efficient team actions is team cognition, defined either as shared knowledge states about game situations, teammates' skills, and action probabilities or direct communication processes in the team action itself. Particularly in interactive team sports (e.g., football), characterized by highly complex, dynamic, and uncertain situations, sharing a common understanding concerning potential future actions and how to coordinate these actions may be an advantage. Otherwise, team members must communicate their thoughts and ideas on the fly, which might be impossible due to time pressure, cognitive costs or noisy environments. This study examined if shared knowledge and verbal communication change through collective training. Forty-six under-18 and under-21 youth football players performed a football task in teams of two. The task consisted of passing and running elements common in football. After a training phase, and before two testing phases, players evaluated their actions and the actions of their assigned teammate regarding action type, location, and timing. Out of these evaluations, two indices of common understanding were computed. Furthermore, verbal communication during the task was video-and audio-recorded. Data analysis showed that shared knowledge considerably increased over time and with practice. Simultaneously, overall verbal communication and verbal communication consisting of orienting information was significantly reduced. Additionally, there was a tendency for a correlation that when shared knowledge increased, orienting verbal communication decreased. Overall, the players used orienting communications the most (77%). The study revealed that shared knowledge states and verbal communication change through collective training and that there might be a relation between the level of shared knowledge and the use of orienting verbal communication. Further studies in and off the field are needed to disentangle the complex interplay of team cognitions.


#3 Echocardiographic diagnosis of congenital coronary artery abnormalities in a continuous series of adolescent football players
Reference:  Eur J Prev Cardiol. 2019 Feb 12:2047487319825520. doi: 10.1177/2047487319825520. [Epub ahead of print]
Authors: Gerling S, Loose O, Zant R, Michel H, Melter M, Gündisch C, Krutsch V, Krutsch W
Summary: Sudden cardiac death (SCD) in children and adolescents is rare. Several studies have reported a higher risk of SCD during athletic competition. High risk congenital coronary artery abnormalities are the second leading cause of SCD in young athletes in the USA. Echocardiographic assessment of coronary arteries has not been routinely used in screening programmes for junior athletes so far. All athletes underwent a standardized cardiovascular screening protocol with a medical history, a physical examination, 12-lead resting electrocardiogram and a complete transthoracic 2D-echocardiography. Two athletes (0.19%) showed a high-risk coronary artery abnormality (CAA) with a right coronary artery originating abnormal from the aorta and coursing inter-arterial. Low-risk CAAs were found in 16 athletes (1.53%). There was an ectasia of the left coronary artery (+3.9z and +4.3z) and a fistula from the left coronary artery in two cases (0.19%), respectively. In 1.05% ( n = 11) we found a high take-off (2.3-6.8 mm) and in one case (0.096%) there was a tangential take-off of the right main coronary artery. Variants of coronary arterial anatomy were identified in 335 of 1045 athletes (32.06%). Basic pre-participation screening tests including 12-lead or exercise electrocardiogram do not safely identify high-risk CAAs. In adolescent athletes an expert cardiologist is able to describe the origin and the proximal course of the coronary arteries and identify major abnormalities in most of the cases by transthoracic 2D-echocardiography.


#4 Complete Rupture of the Triceps Tendon and Ulnar Collateral Ligament of the Elbow in a 13-Year-Old Football Player: A Case Report
Reference: J Orthop Case Rep. 2018 Sep-Oct;8(5):15-18. doi: 10.13107/jocr.2250-0685.1188.
Authors: Khalil LS, Alkhelaifi K, Meta F, Lizzio VA, Shehab R, Makhni EC
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6367299/pdf/JOCR-8-15.pdf
Summary: With the increasing number of children and adolescents participating in sports, pathologies once reserved for high-level athletes are now emerging in this younger population. Distal triceps tendon tears represent an injury infrequently seen even among older, skeletally mature athletes. We report a case of distal triceps tendon tear with concomitant ulnar collateral ligament (UCL) injury in a skeletally-immature football player. This is a rare case of traumatic triceps tendon tear with UCL injury in a 13-year-old male football player during a fall and hyperextension of his elbow. Management included surgical treatment of the triceps tear with suture anchors in double row technique. The concomitant UCL injury was treated conservatively. This case suggests that this type of injury can occur in young athletes, but good prognosis can be expected with prompt management. Surgical repair of a functionally deficient triceps tendon tear and conservative management of associated UCL injury can result in returntoplay within 6 months.


#5 A Meta-Comparison of the Effects of High-Intensity Interval Training to Those of Small-Sided Games and Other Training Protocols on Parameters Related to the Physiology and Performance of Youth Soccer Players
Reference: Sports Med Open. 2019 Feb 21;5(1):7. doi: 10.1186/s40798-019-0180-5.
Authors: Kunz P, Engel FA, Holmberg HC, Sperlich B
Summary: High-intensity interval training (HIIT) is frequently employed to improve the endurance of various types of athletes. To determine whether youth soccer players may benefit from the intermittent load and time efficiency of HIIT, we performed a meta-analysis of the relevant scientific literature. Our primary objective was to compare changes in various physiological parameters related to the performance of youth soccer players in response to running-based HIIT to the effects of other common training protocols (i.e., small-sided games, technical training and soccer-specific training, or high-volume endurance training). A secondary objective was to compare specifically running-based HIIT to a soccer-specific form of HIIT known as small-sided games (SSG) in this same respect, since this latter type of training is being discussed extensively by coaches. A systematic search of the PubMed, SPORTDiscus, and Web of Science databases was performed in August of 2017 and updated during the review process in December of 2018. The criteria for inclusion of articles for analysis were as follows: (1) comparison of HIIT to SSG or some other training protocol employing a pre-post design, (2) involvement of healthy young athletes (≤ 18 years old), and (3) assessment of variables related to endurance or soccer performance. Hedges' g effect size (dppc2) and associated 95% confidence intervals for the comparison of the responses to HIIT and other interventions were calculated. Nine studies, involving 232 young soccer players (mean age 16.2 ± 1.6 years), were examined. Endurance training in the form of HIIT or SSG produced similar positive effects on most parameters assessed, including peak oxygen uptake and maximal running performance during incremental running (expressed as Vmax or maximal aerobic speed (MAS)), shuttle runs (expressed as the distance covered or time to exhaustion), and time-trials, as well as submaximal variables such as running economy and running velocity at the lactate threshold. HIIT induced a moderate improvement in soccer-related tests involving technical exercises with the soccer ball and other game-specific parameters (i.e., total distance covered, number of sprints, and number of involvements with the ball). Neuromuscular parameters were largely unaffected by HIIT or SSG. The present meta-analysis indicates that HIIT and SSG have equally beneficial impacts on variables related to the endurance and soccer-specific performance of youth soccer players, but little influence on neuromuscular performance.


#6 Caffeine Supplementation and Physical Performance, Muscle Damage and Perception of Fatigue in Soccer Players: A Systematic Review
Reference: Nutrients. 2019 Feb 20;11(2). pii: E440. doi: 10.3390/nu11020440.
Authors: Mielgo-Ayuso J, Calleja-Gonzalez J, Del Coso J, Urdampilleta A, León-Guereño P, Fernández-Lázaro D
Summary: Soccer is a complex team sport and success in this discipline depends on different factors such as physical fitness, player technique and team tactics, among others. In the last few years, several studies have described the impact of caffeine intake on soccer physical performance, but the results of these investigations have not been properly reviewed and summarized. The main objective of this review was to evaluate critically the effectiveness of a moderate dose of caffeine on soccer physical performance. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines in the Medline/PubMed and Web of Science databases from January 2007 to November 2018. The search included studies with a cross-over and randomized experimental design in which the intake of caffeine (either from caffeinated drinks or pills) was compared to an identical placebo situation. There were no filters applied to the soccer players' level, gender or age. This review included 17 articles that investigated the effects of caffeine on soccer-specific abilities (n = 12) or on muscle damage (n = 5). The review concluded that 5 investigations (100% of the number of investigations on this topic) had found ergogenic effects of caffeine on jump performance, 4 (100%) on repeated sprint ability and 2 (100%) on running distance during a simulated soccer game. However, only 1 investigation (25%) found as an effect of caffeine to increase serum markers of muscle damage, while no investigation reported an effect of caffeine to reduce perceived fatigue after soccer practice. In conclusion, a single and moderate dose of caffeine, ingested 5⁻60 min before a soccer practice, might produce valuable improvements in certain abilities related to enhanced soccer physical performance. However, caffeine does not seem to cause increased markers of muscle damage or changes in perceived exertion during soccer practice.


#7 Defining the Early, Mid, and Late Subsections of Sprint Acceleration in Division I Men's Soccer Players
Reference: J Strength Cond Res. 2019 Feb 14. doi: 10.1519/JSC.0000000000003088. [Epub ahead of print]
Authors: Bellon CR, DeWeese BH, Sato K, Clark KP, Stone MH
Summary: The purpose of this study was to investigate whether the acceleration phase of sprinting could be split into subphases specific to the competitive demands of a soccer match by comparing sprint metrics at various sprint distances in Division I men's soccer players. Twenty-three Division I men's soccer athletes completed 2 maximal-effort 20-m sprints from a standing start position through an optical measurement system. Sprint metrics measured included sprint velocity (SV), step length (SL), step frequency (SF), and ground contact time (GCT). Each metric was recorded at approximately 2.5, 6, and 12 m. Sprint metrics at each distance were compared using a 2-tailed, 1-way repeated-measures analysis of variance. The results indicated that SV, SL, and SF were statistically greater at 12 m in comparison with 6 m (p < 0.001) and 2.5 m (p < 0.001), whereas GCT was statistically shorter at 12 m compared with 6 m (p < 0.001) and 2.5 m (p < 0.001). In addition, sprint metrics at 6 m also displayed the same relationships when compared to 2.5 m, with SV, SL, and SF being statistically greater (p < 0.001) at this distance, and GCT being statistically shorter (p < 0.001) as well. These results suggest that the acceleration phase may effectively be differentiated into early, mid, and late subphases based on differences in key sprint metrics at distances of 2.5, 6, and 12 m, respectively, in Division I men's soccer athletes.


#8 Compression Stockings Used During Two Soccer Matches Improve Perceived Muscle Soreness and High-Intensity Performance
Reference: J Strength Cond Res. 2019 Feb 14. doi: 10.1519/JSC.0000000000003048. [Epub ahead of print]
Authors: Gimenes SV, Marocolo M, Pavin LN, Spigolon LMP, Barbosa Neto O, da Silva BVC, Duffield R, da Mota GR
Summary: Evidence on the use of compression stockings (CS) during soccer matches is limited. Thus, we evaluated the acute effects of CS on match-based physical performance indicators and perceptual responses during 2 consecutive soccer matches with 72-hour recovery. Twenty outfield players were randomly allocated to the CS group (20-30 mm Hg) or control group (non-CS) and performed 2 matches (5 players using CS or regular socks per team/match). Match loads {rating of perceived exertion × minutes; CS ∼830 vs. control 843 (arbitrary units [AU])} and heart rate (HR) responses (both CS and control ∼86% HRpeak) did not differ (p > 0.05) between CS and control groups. Although total distance covered did not differ (p > 0.05) between groups, CS increased distances (effect size [ES] = 0.9-1.32) in higher-speed zones (>19 km·h CS ∼550 m vs. control ∼373 m) alongside an increased number of accelerations (-50.0 to -3.0 m·s) than control (CS: 33.7 ± 11.2 vs. control: 23.8 ± 7.9; p = 0.003; ES = 1.04). Perceived recovery did not differ (p > 0.05) between groups for either match but was worse in the second match for both groups. Perceived muscle soreness increased in control after match 2 (from 3.1 ± 1.9 to 6.3 ± 1.6 AU; p < 0.0010) but did not in CS (from 2.8 ± 1.4 to 4.1 ± 1.9 AU; p = 0.6275; ES = 1.24 CS vs. control after match). Accordingly, CS use during 2 soccer matches with 72-hour recovery reduces perceived muscle soreness in the second match and increases higher-speed match running performance.


#9 Are Linear Speed and Jumping Ability Determinants of Change of Direction Movements in Young Male Soccer Players?
Reference: J Sports Sci Med. 2019 Feb 11;18(1):109-117. eCollection 2019 Mar.
Authors: Popowczak M, Rokita A, Świerzko K, Szczepan S, Michalski R, Maćkała K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370957/pdf/jssm-18-109.pdf
Summary: The study was undertaken to investigate the relationships between linear speed, change of direction, and explosive power in the lower limbs of young soccer players. We aimed to determine the variables associated with effective change-of-direction speeds (time) based on the 30-m ZigZag (cutting maneuver) under 60° (CODS1), and 30 m sprint divided into forward-backward-forward movement (CODS2). Sixty young soccer players (age: 17.4 ± 0.7 years, height: 1.76 ± 0.06 m, weight: 68.1 ± 8.9 kg) from soccer sport clubs were included. The participants performed 30-m change-of-direction sprints and 30-m backward and forward sprints. For the maximum speed evaluation, a straight-line 30-m sprint test was performed. Counter-movement jumps and standing broad jumps were used to assess jumping ability. Pearson's linear correlation and a multiple stepwise linear regression model were used to adjust for variations related to the influence of functional speed and explosive power variables, which were analyzed based on the CODS1 and CODS2 data. Our results showed that 30-m CODS2 and standing broad jumps were associated with CODS1. The variation for the 30-m change-of-direction maneuvers under 60° could be explained by the results of 30-m forward-backward-forward change-of-direction. The standing broad jump explained 10% variation for the performances in change-of-direction sprint decrements and 9% variation for the 5-m change-of-direction with the best times, whereas straight-line sprinting was related to forward-backward-forward change-of-direction. The 10-m sprint explained 50% variation of the performances in the first 10-m forward running in the CODS2 and 12% variation for 10-m backward-forward change-of-direction. The 30-m sprint explained 36% variation for 30-m forward-backward-forward change-of-direction. The 30-m sprint and overall body mass also explained 58% variation for 10-m forward-backward change-of-direction. For coaching purposes, we report that forward-backward-forward and cutting maneuver change-of-direction movements are independent and highly useful skills. This information can help to provide better training prescriptions.


#10 The Use of GPS Analysis to Quantify the Internal and External Match Demands of Semi-Elite Level Female Soccer Players during a Tournament
Reference: J Sports Sci Med. 2019 Feb 11;18(1):73-81. eCollection 2019 Mar.
Authors: Strauss A, Sparks M, Pienaar C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370966/pdf/jssm-18-73.pdf
Summary: The purpose of this study was to make use of global positioning system technology to quantify the internal and external match demands of sub-elite female soccer players. Secondly, the study aims to describe the magnitude of change of these variables within and between matches over the course of a tournament to determine the effect of player fatigue. Thirty sub-elite female soccer players were assessed throughout a local tournament. Differences in match demands within and between matches were assessed using percent difference, effect size and 90% confidence intervals. One-way ANOVA was used to compare differences in the match demands and running intensities among playing positions and Bonferroni corrections were used to determine differences where significant effects of position were observed. A paired sample t-test in conjunction with the Cohen effect size was used to compare changes in match performance. Total distance covered averaged 5917 m. Midfielders covered the greatest absolute and relative total distances, and achieved the highest low-intensity activity and player load per minute of play. Defenders covered significantly (p ≤ 0.05) less relative distance and low-intensity activity per minute of play compared to midfielders. Forwards covered the greatest distance at high-intensity, while the greatest percentage of time at high-intensity heart rate was measured among the defenders. Within match comparisons revealed that player load decreased significantly (p ≤ 0.05) in the second half (ES: 0.4). Relative distance, low-intensity activity and high-intensity activity also decreased in the second half with possibly trivial to likely small changes. Small to large differences in variables were observed throughout the tournament. The biggest magnitude of change was seen with a large decrease (ES: -1.2) in relative distance covered between match 2 and 5. Despite generally small reductions in performance measures, there is evidence that accumulated fatigue throughout a multi-day tournament would affect performance negatively.


#11 Preseason Dynamic Balance Performance in Healthy Elite Male Soccer Players
Reference: Am J Mens Health. 2019 Jan-Feb;13(1):1557988319831920. doi: 10.1177/1557988319831920.
Authors: Onofrei RR, Amaricai E, Petroman R, Surducan D, Suciu O
Download link: https://journals.sagepub.com/doi/pdf/10.1177/1557988319831920
Summary: Lower limb musculoskeletal injuries in sports are linked with balance abnormalities and altered postural control. Dynamic balance screening should be performed in order to identify athletes at risk. The purpose of the study was to evaluate the preseason dynamic balance performance and side-to-side asymmetry of healthy elite male soccer players, using modified Star Excursion Balance Test (mSEBT). Seventy-three elite soccer players (23.8 ± 5.4 years) were evaluated using the mSEBT. Normalized reach distances, side-to-side asymmetries, and composite scores were determined. The composite scores were 93.33% ± 8.99% for dominant leg and 93.36% ± 9.23% for nondominant leg. No significant differences were found between dominant and nondominant limb in any direction. The mSEBT is an easy-to-use tool to measure the dynamic balance performance in elite athletes. It can be applied successfully during preseason physical examinations. Future studies are needed to establish predictive cutoff points in order to increase mSEBT use in screening soccer players for dynamic balance abnormalities and identify those at risk for noncontact lower limb injuries.