Latest research in football - week 49 - 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 Football as a Health Promotion Strategy
Reference: Dtsch Arztebl Int. 2019 Oct 25;116(43):721-728. doi: 10.3238/arztebl.2019.0721.
Authors: Eberl M1, Tanaka LF, Klug SJ, Adamek HE.
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Summary: Football training can be a primary prevention strategy to reach people who otherwise would not be physically active. This systematic review summarizes the evidence on the health effects of controlled recreational football training as an intervention in children, adolescents, adults and the elderly. A systematic review (PROSPERO record CRD42018083665) of the literature was carried out in MEDLINE, Cochrane, Scopus, and SPORTDiscus databases to identify randomized and non-randomized intervention studies in which healthy individuals of any age participated in controlled football training and were investigated for health outcomes related to prevention of obesity, hypertension, diabetes mellitus, and cardiovascular disease. The studies included-14 randomized and three non-randomized intervention studies-have sample sizes too small for reliable statistical analysis and bear a considerable risk of systematic bias. The evidence of positive effects of playing football is limited to short-term loss of body fat and improvement in aerobic fitness. For all other health outcomes, no conclusive results were found. A considerable number of intervention studies reporting on football-based intervention programs have been published, and there is a widespread assumption that such programs have positive health effects. However, this systematic review shows that the empirical evidence is insufficient to permit such a conclusion.

#2 Methods to collect and interpret external training load using microtechnology incorporating GPS in professional football: a systematic review
Reference: Res Sports Med. 2019 Nov 22:1-22. doi: 10.1080/15438627.2019.1686703. [Epub ahead of print]
Authors: Rago V, Brito J, Figueiredo P, Costa J, Barreira D, Krustrup P, Rebelo A
Summary: The aim of this article was to systematically review the methods adopted to collect and interpret external training load (ETL) using microtechnology incorporating global positioning system (GPS). The main deficiencies identified concerned the non-collection of match ETL, and the non-consideration of potential confounders (e.g. playing position, fitness level, starting status or session content). Also, complementary training (individual/reconditioning) and pre-match warm-up were rarely quantified. To provide a full picture of the training demands, ETL was commonly complemented by internal training load monitoring with the rating of perceived exertion predominantly adopted instead of heart rate recordings. Continuous data collection and interpretation of ETL data in professional football vary widely between observational studies, possibly reflecting the actual procedures adopted in practical settings. Evidence about continuous ETL monitoring in female players, and female as well as male goalkeepers is lacking.

#3 Psychological factors and future performance of football players: A systematic review with meta-analysis
Reference: J Sci Med Sport. 2019 Nov 1. pii: S1440-2440(19)30559-6. doi: 10.1016/j.jsams.2019.10.021. [Epub ahead of print]
Authors: Ivarsson A, Kilhage-Persson A, Martindale R, Priestley D, Huijgen B, Ardern C, McCall A
Summary: This systematic review had 3 key objectives: (1) to investigate whether psychological factors were associated with future football performance (e.g., progression to professional football, better game statistics during the next season); (2) to critically review the methodological approaches used in the included studies and summarize the evidence for the current research question; (3) to provide guidelines for future studies. Electronic databases (SPORTDiscus, PubMed and PsycINFO) and previously published systematic and scoping reviews were searched. Only prospective studies were considered for inclusion. Eleven published studies that reported 39 effect sizes were included. Psychological factors; task orientation, task-oriented coping strategies and perceptual-cognitive functions had small effects on future performance in football (ds=0.20-0.29). Due to high risk of bias there were low certainty of evidence for psychological factors relationship with future football performance. Psychological factors investigated showed small effects on future football performance, however, there was overall uncertainty in this evidence due to various sources of bias in the included studies. Therefore psychological factors cannot be used as a sole deciding factor in player recruitment, retention, release strategies, however it would appear appropriate to include these in the overall decision-making process. Future, studies with more appropriate and robust research designs are urgently needed to provide more certainty around their actual role.

#4 Physical preparation and return to sport of the football player with a tibia-fibula fracture: applying the 'control-chaos continuum'
Reference: BMJ Open Sport Exerc Med. 2019 Oct 30;5(1):e000639. doi: 10.1136/bmjsem-2019-000639. eCollection 2019.
Authors: Taberner M, van Dyk N, Allen T, Richter C, Howarth C, Scott S, Cohen DD
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Summary: Contact in elite football can result in severe injury such as traumatic fracture. Limited information exists regarding the rehabilitation and return to sport (RTS) of these injuries especially in elite football. We outline the RTS of an elite English Premier League footballer following a tibia-fibula fracture including gym-based physical preparation and the use of 'control-chaos continuum' as a framework for on-pitch sport-specific conditioning, development of technical skills while returning the player to pre-injury chronic running loads considering the qualitative nature of movement in competition. Strength and power diagnostics were used to back up clinical reasoning and decision-making throughout rehabilitation and the RTS process. The player returned to full team training after 7.5 months, completed 90 min match-play after 9 months and remains injury-free 11 months post-RTS.

#5 The Attacking Process in Football: A Taxonomy for Classifying How Teams Create Goal Scoring Opportunities Using a Case Study of Crystal Palace FC
Reference: Front Psychol. 2019 Oct 16;10:2202. doi: 10.3389/fpsyg.2019.02202. eCollection 2019.
Authors: Kim J, James N, Parmar N, Ali B, Vučković G
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Summary: Whilst some studies have comprehensively described the different features associated with the attacking process in football they have not produced a methodology of practical use for performance enhancement. This study presents a framework of comprehensive and meaningful metrics to objectively describe the attacking process so that useful performance profiles can be produced. The attacking process was categorized into three independent situations, no advantage (stable), advantage, and unstable (potential goal scoring opportunity) situations. Operational definitions for each situation enhanced their reliability and validity. English Premier League football matches (n = 38) played by Crystal Palace Football Club in the 2017/2018 season were analyzed as an exemplar. Crystal Palace FC created a median of 53.5 advantage situations (IQR = 16.8) and 23 unstable situations (IQR = 8.8) per match. They frequently utilized wide areas (Median = 21.5, IQR = 9.8) to progress, but only 26.6% resulted in unstable situations (Median = 6.0, IQR = 3.8), the lowest rate compared to the other advantage situations. This classification framework, when used with contextual factors in a multi-factorial manner, including individual player contributions, will provide practically useful information for applied practice. This approach will help close the so called theory-practice gap and enable academic rigor to inform practical problems.

#6 Recovery Kinetics After Speed-Endurance Training in Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Nov 21:1-14. doi: 10.1123/ijspp.2018-0984. [Epub ahead of print]
Authors: Tzatzakis T, Papanikolaou K, Draganidis D, Tsimeas P, Kritikos S, Poulios A, Laschou VC, Deli CK, Chatzinikolaou A, Batrakoulis A, Basdekis G, Mohr M, Krustrup P, Jamurtas AZ, Fatouros IG.
Summary: The purpose was to determine the recovery kinetics of performance, muscle damage, and neuromuscular fatigue following 2 speed-endurance production training (SEPT) protocols in soccer. Ten well-trained, male soccer athletes randomly completed 3 trials: work-to-rest ratio (SEPT) 1:5, SEPT/1:8, and a control trial. Training load during SEPT was monitored using global positioning system and heart-rate monitors. Performance (isokinetic strength of knee extensors and flexors, speed, and countermovement jump) and muscle damage (delayed-onset muscle soreness [DOMS] and creatine kinase) were evaluated at baseline and at 0, 24, 48 and 72 h posttraining. Maximal voluntary contraction (fatigue index) of knee extensors and flexors was additionally assessed at 1, 2, and 3 h posttraining. Fatigue increased (P < .05) in SEPT/1:5 (∼4-30%) for 3 h and in SEPT/1:8 (∼8-17%) for 2 h. Strength performance declined (P < .05) in both SEPT trials (∼5-20%) for 48 h. Speed decreased (∼4-18%; P < .05) for 72 h in SEPT/1:5 and for 48 h in SEPT/1:8. Countermovement-jump performance decreased (∼7-12%; P < .05) in both SEPT trials for 24 h. DOMS increased (P < .05) in SEPT/1:5 (∼2-fold) for 72 and in SEPT/1:8 (∼1- to 2-fold) for 48 h. Creatine kinase increased (∼1- to 2-fold, P < .05) in both SEPT trials for 72 h. SEPT induces short-term neuromuscular fatigue; provokes a prolonged deterioration of strength (48 h), speed (72 h), and jump performance (24 h); and is associated with a prolonged (72-h) rise of DOMS and creatine kinase. Time for recovery is reduced when longer work-to-rest ratios are applied. Fitness status may affect quality of SEPT and recovery kinetics.

#7 Effect of opposition quality and match location on the positional demands of the 4-2-3-1 formation in elite soccer
Reference: J Exerc Sci Fit. 2020 Jan;18(1):40-45. doi: 10.1016/j.jesf.2019.11.001. Epub 2019 Nov 3.
Authors: Paraskevas G, Smilios I, Hadjicharalambous M
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Summary: The present study examined the influence of match location, quality of opposition team, and playing position on physical performance indicators of the 4-2-3-1 formation. Twenty-six (n = 26) games (with 184 player-observations; n = 17 players, played full 90 min games) were recorded with a video system and the physical demands of the players were analyzed according to their specific playing position (classified into central and wide defenders, central and wide midfielders and forwards). Match performance variables analyzed included total distance (TD), high-intensity running (HIR), very-high-intensity running (VHIR) and sprinting (SPR). There was a main effect of position for TD (F = 37.84, p < 0.001), HIR (F = 41.19, p < 0.001), VHIR (F = 27.89, p < 0.001) and SPR (F = 22.25, p < 0.001). Wide defenders covered the most SPR and -along with the central midfielders-the most VHIR. Central midfielders covered the most TD and HIR. Match location and opposition quality had interactive effects on TD (F = 12.96, p < 0.001), HIR (F = 8.33 p = 0.004) and VHIR (F = 8.17 p = 0.005). Competing against "weak" opponents, more TD, HIR and VHIR covered during home games compared to away games (p < 0.05). However, more TD was covered during away games against "strong" opponents compared to away games against "weak" opponents (p < 0.05). The current study supports more intense-based drills (i.e. repeated sprint training) for wide defenders and more volume-based drills (i.e. long interval training) for central midfielders, whilst total weekly training load can be adjusted based on match location and quality of oppositions on the anticipated game-load.

#8 Effects of Two Competitive Soccer Matches on Landing Biomechanics in Female Division I Soccer Players
Reference: Sports (Basel). 2019 Nov 14;7(11). pii: E237. doi: 10.3390/sports7110237.
Authors: Snyder BJ, Hutchison RE, Mills CJ, Parsons SJ
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Summary: Fatigue has been proposed to increase the risk of knee injury. This study tracked countermovement jump, knee isometric strength, and kinetics and kinematics in 8 female soccer players (experimental group) during an anticipated sidestep maneuver before and after two matches played over a 43-h period. Time points were: Before and after match 1 (T0 and T1), 12 h after the first match (T2), and immediately after the second match (T3). A control group participated only in practice sessions. Isometric knee extension strength decreased by 14.8% at T2 (p = 0.003), but knee flexion was not affected until T3, declining by 12.6% (p = 0.018). During the sidestep maneuver, knee joint degrees of flexion at initial contact was increased by 17.1% at T3, but maximum knee and hip angle at initial contact were unchanged. Peak resultant ground reaction force (GRF) increased by 12.6% (p = 0.047) at T3 (3.03 xBW) from 2.69 xBW at T0, while posterior GRF was significantly higher than T0 at all three subsequent time points (T1 = 0.82 ± 0.23 xBW, T2 = 0.87 ± 0.22 xBW, T3 = 0.89 ± 0.22 xBW). Anterior tibial shear force increased significantly (p = 0.020) at T3 (1.24 ± 0.12 xBW) compared to T1 (1.15 ± 0.13 xBW), an 8.8% increase. Lateral tibial shear force was significantly higher at both T1 (0.95 ± 0.20 xBW) and T3 (1.15 ± 0.38 xBW) compared to T0 (0.67 ± 0.25 xBW). These findings suggest that participation in a soccer match has significant effects on both physical performance parameters and kinetics/kinematics during a sidestep cut, but these can be more pronounced after a second match with short rest.

#9 Higher neck strength is associated with lower head acceleration during purposeful heading in soccer: A systematic review
Reference: J Sci Med Sport. 2019 Nov 12. pii: S1440-2440(19)30660-7. doi: 10.1016/j.jsams.2019.11.004. [Epub ahead of print]
Authors: Peek K, Elliott JM, Orr R
Summary: The purpose was to systematically review the literature to investigate the potential relationship between neck strength and head acceleration during purposeful heading in soccer. Comprehensive search of five electronic databases: EMBASE, MEDLINE, CINAHL, SportsDiscus and Web of Science. Studies were included if they reported data on the relationship between neck strength and head impact and/or acceleration during purposeful soccer heading, published in English (or translation available). From an initial search of 1174 potentially eligible papers, five cross-sectional studies met the eligibility criteria for inclusion in this review. Data from cross-sectional studies indicate that higher neck strength is associated with lower head acceleration during purposeful heading in soccer (p=<0.05; r<-0.5). This review provides evidence that higher neck strength may lower head acceleration during purposeful heading in soccer. Further research is required to determine the most effective method to strengthen the neck musculature in soccer players.

#10 Superior cardiac mechanics without structural adaptations in pre-adolescent soccer players
Reference: Eur J Prev Cardiol. 2019 Nov 28:2047487319890177. doi: 10.1177/2047487319890177. [Epub ahead of print]
Authors: Beaumont A, Oxborough D, George K, Rowland TW, Sculthorpe N, Lord R, Unnithan VB
Summary: This study aimed to evaluate left ventricular structure, function and mechanics, in highly-trained, pre-adolescent soccer players compared with age- and sex-matched controls. The study design was a prospective, cross-sectional comparison of left ventricular structure, function and mechanics. Twenty-two male soccer players from two professional youth soccer academies (age: 12.0 ± 0.3 years) and 22 recreationally active controls (age: 11.7 ± 0.3 years) were recruited. Two-dimensional conventional and speckle tracking echocardiography were used to quantify left ventricular structure, function and peak/temporal values for left ventricular strain and twist, respectively. End-diastolic volume index was larger in soccer players (51 ± 8 mm/(m2)1.5 vs. 45 ± 6 mm/(m2)1.5; p = 0.007) and concentricity was lower in soccer players (4.3 ± 0.7 g/(mL)0.667 vs. 4.9 ± 1.0 g/(mL)0.667; p = 0.017), without differences in mean wall thickness between groups (6.0 ± 0.4 mm vs. 6.1 ± 0.5 mm; p = 0.754). Peak circumferential strain at the base (-22.2% ± 2.5% vs. -20.5% ± 2.5%; p = 0.029) and papillary muscle levels (-20.1% ± 1.5% vs. -18.3% ± 2.5%; p = 0.007) were greater in soccer players. Peak left ventricular twist was larger in soccer players (16.92° ± 7.55° vs. 12.34° ± 4.99°; p = 0.035) and longitudinal early diastolic strain rate was greater in soccer players (2.22 ± 0.40 s-1 vs. 2.02 ± 0.46 s-1; p = 0.025). Highly-trained soccer players demonstrated augmented cardiac mechanics with greater circumferential strains, twist and faster diastolic lengthening in the absence of differences in wall thickness between soccer players and controls.

#11 The Role of Somatic Maturation on Bioimpedance Patterns and Body Composition in Male Elite Youth Soccer Players
Reference: Int J Environ Res Public Health. 2019 Nov 26;16(23). pii: E4711. doi: 10.3390/ijerph16234711.
Authors: Campa F, Silva AM, Iannuzzi V, Mascherini G, Benedetti L, Toselli S
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Summary: The purpose of this study was to examine the influence of chronological age (CA) and somatic maturation on body composition (BC) and bioimpedance parameters in male elite soccer players. BC and bioimpedance variables were measured in a sample of 249 players aged 9-18 years of age and registered in two professional Italian soccer teams. Results from segmental analysis showed transition time points where the influence of CA and somatic maturation on bioimpedance patterns and BC characteristics increased or subsided. The accelerated phases were assessed for fat free mass, total body water, and upper muscle area, with a starting time point at approximately -2.00 years from peak at velocity (YPHV), and for body cell mass, whose developmental tempo sped up around -1.00 YPHV. An increase in the rate of development was also observed close to -2.00 YPHV for phase angle (PA), although without accelerated phases. From a CA point of view, significant slope changes were found for all BC and bioimpendance variables, except for the calf muscle area. Although the starting points and the span of the accelerated phases were different, they subsided or disappeared at ~ 15 years, except for PA, whose growth waned at ~ 17 years.

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