Latest research in football - week 43 - 2018

#1 Bone mineral density in lifelong trained male football players compared with young and elderly untrained men
Reference: J Sport Health Sci. 2018 Apr;7(2):159-168. doi: 10.1016/j.jshs.2017.09.009. Epub 2017 Sep 20.
Authors: Hagman M, Helge EW, Hornstrup T, Fristrup B, Nielsen JJ, Jørgensen NR, Andersen JL, Helge JW, Krustrup P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180542/pdf/main.pdf
Summary: The purpose of the present controlled cross-sectional study was to investigate proximal femur and whole-body bone mineral density (BMD), as well as bone turnover profile, in lifelong trained elderly male football players and young elite football players compared with untrained age-matched men. One hundred and forty healthy, non-smoking men participated in the study, including lifelong trained football players (FTE, n = 35) aged 65-80 years, elite football players (FTY, n = 35) aged 18-30 years, as well as untrained age-matched elderly (UE, n = 35) and young (UY, n = 35) men. All participants underwent a regional dual-energy X-ray Absorptiometry (DXA) scan of the proximal femur and a whole-body DXA scan to determine BMD. From a resting blood sample, the bone turnover markers (BTMs) osteocalcin, carboxy-terminal type-1 collagen crosslinks (CTX-1), procollagen type-1 amino-terminal propeptide (P1NP), and sclerostin were measured. FTE had 7.3%-12.9% higher (p < 0.05) BMD of the femoral neck, wards, shaft, and total proximal femur in both legs compared to UE, and 9.3%-9.7% higher (p < 0.05) BMD in femoral trochanter in both legs compared to UY. FTY had 24.3%-37.4% higher (p < 0.001) BMD in all femoral regions and total proximal femur in both legs compared to UY. The whole-body DXA scan confirmed these results, with FTE showing similar whole-body BMD and 7.9% higher (p < 0.05) leg BMD compared to UY, and with FTY having 9.6% higher (p < 0.001) whole-body BMD and 18.2% higher (p < 0.001) leg BMD compared to UY. The plasma concentration of osteocalcin, CTX-1, and P1NP were 29%, 53%, and 52% higher (p < 0.01), respectively, in FTY compared to UY. BMD of the proximal femur and whole-body BMD are markedly higher in lifelong trained male football players aged 65-80 years and young elite football players aged 18-30 years compared to age-matched untrained men. Elderly football players even show higher BMD in femoral trochanter and leg BMD than untrained young despite an age difference of 47 years.

#2 A rare case of non-contact salter harris type 2 fracture of distal femur during a football match
Reference: Med J Malaysia. 2018 Oct;73(5):342-343.
Authors: Razzi M, Nordin A
Download link: http://www.e-mjm.org/2018/v73n5/distal-femoral-physeal-fractures.pdf
Summary: Distal femoral physeal fractures in adolescents are often due to high velocity injuries. We present an unusual case of a non-contact distal femoral physeal fracture that occurred during a football match. A torsional force had been directed at the fracture site occurring at the growth plate causing a transverse fracture rather than a spiral fracture. It is important to be aware that such fractures can occur despite little or no evidence of contact. These type of injuries should also be treated as an emergency to reduce the risk of further complications.


#3 Using Network Science to Analyse Football Passing Networks: Dynamics, Space, Time, and the Multilayer Nature of the Game
Reference: Front Psychol. 2018 Oct 8;9:1900. doi: 10.3389/fpsyg.2018.01900. eCollection 2018.
Authors: Buldú JM, Busquets J, Martínez JH, Herrera-Diestra JL, Echegoyen I, Galeano J, Luque J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6186964/pdf/fpsyg-09-01900.pdf


#4 Multilevel modelling of longitudinal changes in isokinetic knee extensor and flexor strength in adolescent soccer players
Reference: Ann Hum Biol. 2018 Oct 31:1-4. doi: 10.1080/03014460.2018.1521470. [Epub ahead of print]
Authors: Duarte JP, Valente-Dos-Santos J, Costa D, Coelho-E-Silva MJ, Deprez D, Philippaerts R, Lenoir M, Vaeyens R, Malina RM
Summary: The purpose of the study was to model the longitudinal development of knee extension (KE) and flexion (KF) strength in adolescent soccer players. A mixed-longitudinal sample composed of 67 soccer players aged 11.0-13.9 years at baseline was followed on three-to-five occasions over 5 years. Stature, body mass and several skinfold thicknesses were measured. Fat mass was estimated from skinfolds and fat-free mass (FFM) derived. Skeletal age was estimated with the TW2-RUS protocol. An isokinetic dynamometer was used to obtain peak torque of KE and KF from concentric assessments at an angular velocity of 180°/s. Multilevel random effects regression analyses were performed. Among youth soccer players aged 11-16 years, isokinetic strength of the knee muscle groups was reasonably predicted from chronological age (CA), stature and FFM: KE = -66.170 + 5.353 × (CA) + 0.594 × (CA2) + 0.552 × (stature) + 1.414 × (FFM), and KF = -9.356 + 2.708 × (CA) + 1.552 × (FFM). In conclusion, CA per se accounted for annual increments of 5.4 Nm in KE and 2.7 Nm in KF.


#5 Artificial neural networks and player recruitment in professional soccer
Reference: PLoS One. 2018 Oct 31;13(10):e0205818. doi: 10.1371/journal.pone.0205818. eCollection 2018.
Authors: Barron D, Ball G, Robins M, Sunderland C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205818&type=printable
Summary: The aim was to objectively identify key performance indicators in professional soccer that influence outfield players' league status using an artificial neural network. Mean technical performance data were collected from 966 outfield players' (mean SD; age: 25 ± 4 yr, 1.81 ±) 90-minute performances in the English Football League. ProZone's MatchViewer system and online databases were used to collect data on 347 indicators assessing the total number, accuracy and consistency of passes, tackles, possessions regained, clearances and shots. Players were assigned to one of three categories based on where they went on to complete most of their match time in the following season: group 0 (n = 209 players) went on to play in a lower soccer league, group 1 (n = 637 players) remained in the Football League Championship, and group 2 (n = 120 players) consisted of players who moved up to the English Premier League. The models created correctly predicted between 61.5% and 78.8% of the players' league status. The model with the highest average test performance was for group 0 v 2 (U21 international caps, international caps, median tackles, percentage of first time passes unsuccessful upper quartile, maximum dribbles and possessions gained minimum) which correctly predicted 78.8% of the players' league status with a test error of 8.3%. To date, there has not been a published example of an objective method of predicting career trajectory in soccer. This is a significant development as it highlights the potential for machine learning to be used in the scouting and recruitment process in a professional soccer environment.


#6 Oculomotor dynamics in skilled soccer players: The effects of sport expertise and strenuous physical effort
Reference: Eur J Sport Sci. 2018 Oct 31:1-9. doi: 10.1080/17461391.2018.1538391. [Epub ahead of print]
Authors: Zwierko T, Jedziniak W, Florkiewicz B, Stępiński M, Buryta R, Kostrzewa-Nowak D, Nowak R, Popowczak M, Woźniak J
Summary: The ability to quickly locate objects within the visual field has a significant influence on athletic performance. Saccades are conjugate eye movements responsible for the rapid shift that brings a new part of the visual field into foveal vision. The aim of this study was to investigate the effects of sport expertise and intense physical effort on saccade dynamics during a free-viewing visual search task in skilled soccer players. Two groups of male subjects participated in this study: 18 soccer players and 18 non-athletes as the control group. Two sessions of visual search tasks without a sport-specific design were employed. Eye movements during the visual search tasks were recorded binocularly. Between pre- and post-test sessions, athletes performed a maximal incremental treadmill test. Cardiorespiratory parameters were measured continuously. Capillary lactate samples were collected. Pre-test findings indicated that athletes, in comparison to non-athletes, achieve higher values of the following characteristics of saccades (1) average acceleration, (2) acceleration peak, (3) deceleration peak, and (4) average velocity. An increase in post-test saccade duration and a decrease in post-test saccade velocity was observed in athletes due to the strenuous physical effort in relation to the pre-test state. Athletes may transfer high saccadic function efficiency to non-specific visual stimuli. The findings partially confirm that physical exertion can reduce oculomotor efficiency in athletes.


#7 Accumulation of high magnitude acceleration events predicts cerebrovascular reactivity changes in female high school soccer athletes
Reference: Brain Imaging Behav. 2018 Oct 30. doi: 10.1007/s11682-018-9983-0. [Epub ahead of print]
Authors: Svaldi DO, Joshi C, McCuen EC, Music JP, Hannemann R, Leverenz LJ, Nauman EA, Talavage TM
Summary: Mitigating the effects of repetitive exposure to head trauma has become a major concern for the general population, given the growing body of evidence that even asymptomatic exposure to head accelerations is linked with increased risk for negative life outcomes and that risk increases as exposure is prolonged over many years. Among women's sports, soccer currently exhibits the highest growth in participation and reports the largest number of mild traumatic brain injuries annually, making female soccer athletes a relevant population in assessing the effects of repetitive exposure to head trauma. Cerebrovascular biomarkers may be useful in assessing the effects of repetitive head trauma, as these are thought to contribute directly to neurocognitive symptoms associated with mild traumatic brain injury. Here we use fMRI paired with a hypercapnic breath hold task along with monitoring of head acceleration events, to assess the relationship between cerebrovascular brain changes and exposure to repetitive head trauma over a season of play in female high school soccer athletes. We identified longitudinal changes in cerebrovascular reactivity that were significantly associated with prolonged accumulation to high magnitude (> 75th percentile) head acceleration events. Findings argue for active monitoring of athletes during periods of exposure to head acceleration events, illustrate the importance of collecting baseline (i.e., pre-exposure) measurements, and suggest modeling as a means of guiding policy to mitigate the effects of repetitive head trauma.


#8 Are oral health and fixed orthodontic appliances associated with sports injuries and postural stability in elite junior male soccer players?
Reference: BMC Sports Sci Med Rehabil. 2018 Oct 20;10:16. doi: 10.1186/s13102-018-0105-5. eCollection 2018.
Authors: Solleveld H, Flutter J, Goedhart A, VandenBossche L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6196014/pdf/13102_2018_Article_105.pdf
Summary: Dental caries and periodontitis are associated with elevated levels of pro-inflammatory cytokines which may trigger muscle fatigue during exercise, a strong risk factor for sports injuries. Fixed orthodontic appliances (FOA) may cause poor oral health and may disturb proprioceptive inputs of the stomatognathic system. This study aims to explore associations of poor oral health and of use of a FOA with injury frequency and postural stability. One hundred eighty seven Belgian elite junior male soccer players, aged 12-17 years, completed a self-report questionnaire asking about injuries in the past year, oral health problems, use of a FOA, demographics and sports data, and stood in unipedal stance with eyes closed on a force plate to assess postural stability. Ordinal logistic regression with number of injuries in the past year as ordinal dependent variable and dental caries and/or gum problems, age and player position as covariates, showed that participants who reported dental caries and/or gum problems and never had had a FOA reported significant more injuries in the past year compared to the reference group of participants who reported no oral health problems and never had had a FOA (adjusted OR = 2.45; 95% CI, 1.19-5.05; p = 0.015). A 2 (temporomandibular joint problems) × 2 (FOA) × 2 (age) ANOVA with postural stabilities as dependent variables, showed a significant FOA x age interaction for the non-dominant (standing) leg. Post-hoc t-tests showed a significant better postural stability for the non-dominant leg (and a trend for the dominant leg) for the older compared with the younger participants in the non-FOA group (p = .002, ES = 0.61), while no age differences were found in the FOA-group. These results indicate that poor oral health may be an injury risk factor and that a FOA may hinder the development of body postural stability.


#9 Physical and technical differences between domestic and foreign soccer players according to playing positions in the China Super League
Reference: Res Sports Med. 2018 Oct 30:1-12. doi: 10.1080/15438627.2018.1540005. [Epub ahead of print]
Authors: Gai Y, Leicht AS, Lago C, Gómez MÁ
Summary: Physical demands and technical skills of different playing positions within soccer match-play have been rarely studied in competitions from Asia that have unique restrictions that limit the number of foreign players per team. Therefore, the aims of this study were to identify the technical and physical differences between domestic and foreign soccer players according to playing-positions in the China Super League (CSL); and to classify domestic and foreign players (best/worst) based on their match performance characteristics. Data were provided by Amisco Sports Analysis Services (n = 3468 observations). Discriminant and ANOVA analyses showed important differences between domestic and foreign players in the CSL in terms of physical and technical performance indicators for various playing positions. The unique match performance profiles of domestic and foreign players within the CSL highlighted important features for coaches and managers to improve the recruitment process within a league that implements a restrictive foreign player policy.


#10 The First Decade of Web-Based Sports Injury Surveillance: Descriptive Epidemiology of Injuries in US High School Boys' Soccer (2005-2006 Through 2013-2014) and National Collegiate Athletic Association Men's Soccer (2004-2005 Through 2013-2014)
Reference: J Athl Train. 2018 Sep;53(9):893-905. doi: 10.4085/1062-6050-166-17.
Authors: Kerr ZY, Putukian M, Chang CJ, DiStefano LJ, Currie DW, Pierpoint LA, Knowles SB, Wasserman EB, Dompier TP, Comstock RD, Marshall SW
Summary: The advent of Web-based sports injury surveillance via programs such as the High School Reporting Information Online system and the National Collegiate Athletic Association Injury Surveillance Program has aided the acquisition of boys' and men's soccer injury data. The purpose was to describe the epidemiology of injuries sustained in high school boys' soccer in the 2005-2006 through 2013-2014 academic years and collegiate men's soccer in the 2004-2005 through 2013-2014 academic years using Web-based sports injury surveillance. Online injury surveillance from soccer teams of high school boys (annual average = 100) and collegiate men (annual average = 41) were utilized. Boys' or men's soccer players who participated in practices and competitions during the 2005-2006 through 2013-2014 academic years in high school and the 2004-2005 through 2013-2014 academic years in college, respectively. Athletic trainers collected time-loss (≥24 hours) injury and exposure data. Injury rates per 1000 athlete-exposures (AEs), injury rate ratios (IRRs) with 95% confidence intervals (CIs), and injury proportions by body site and diagnosis were calculated as main outcome measures. High School Reporting Information Online documented 2912 time-loss injuries during 1 592 238 AEs; the National Collegiate Athletic Association Injury Surveillance Program documented 4765 time-loss injuries during 686 918 AEs. The injury rate was higher in college than in high school (6.94 versus 1.83/1000 AEs; IRR = 3.79; 95% CI = 3.62, 3.97). Injury rates increased with smaller school size for high schools and were higher in Division I than in Divisions II and III. The injury rate was higher during competitions than during practices in both high school (IRR = 3.55; 95% CI = 3.30, 3.83) and college (IRR = 3.45; 95% CI = 3.26, 3.65). Most injuries were to the lower extremity. However, concussion was a common injury, particularly in collegiate goalkeepers and at all positions for high school players. Concussions accounted for more than one-fifth of injuries in high school games. Injury-prevention interventions should be tailored to reflect variations in the incidence and type of injury by level of competition, event type, and position.