Latest research in football - week 3 - 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 Effect of Respiratory Muscle Training on the Pulmonary Function, Lung Ventilation, and Endurance Performance of Young Soccer Players
Reference: Int J Environ Res Public Health. 2019 Dec 28;17(1). pii: E234. doi: 10.3390/ijerph17010234.
Authors: Mackała K, Kurzaj M, Okrzymowska P, Stodółka J, Coh M, Rożek-Piechura K
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Summary: This study investigated whether the addition of eight weeks of inspiratory muscle training (IMT) to a regular preseason soccer training program, including incremental endurance training (IET), would change pulmonary function, lung ventilation, and aerobic performance in young soccer players. Sixteen club-level competitive junior soccer players (mean age 17.63 ± 0.48 years, height 182 ± 0.05 cm, body mass 68.88 ± 4.48 kg) participated in the study. Participants were randomly assigned into two groups: experimental (n = 8) and control (n = 8). Both groups performed regular preseason soccer training, including endurance workouts as IET. In addition to this training, the experimental group performed additional IMT for eigght weeks with a commercially available respiratory muscle trainer (Threshold IMT), with a total of 80 inhalations (twice per day, five days per week). Pre- and post-intervention tests of pulmonary function, maximal inspiratory pressure, and the Cooper test were implemented. Eight weeks of IMT had a positive impact on expiratory muscle strength (p = 0.001); however, there was no significant effect on respiratory function parameters. The results also indicate increased efficiency of the inspiratory muscles, contributing to an improvement in aerobic endurance, measured by VO₂max estimated from running distance in the cardiorespiratory Cooper test (p < 0.005).

#2 Effects of Nordic Hamstring Exercise on Hamstring Injuries in High School Soccer Players: A Randomized Controlled Trial
Reference: Int J Sports Med. 2020 Jan 5. doi: 10.1055/a-1034-7854. [Epub ahead of print]
Authors: Hasebe Y, Akasaka K, Otsudo T, Tachibana Y, Hall T, Yamamoto M
Summary: We evaluated a range of physical characteristics related to hamstring injuries, as well as the Nordic Hamstring Exercise compliance rate, and whether this influenced the rate hamstring injury. Subjects comprised 259 male soccer players from seven high schools randomly clustered into two groups, a Nordic Hamstring Exercise group and a control group. Training and match time were logged, as well as details of hamstring injury, and subsequent time lost to hamstring injury recorded over a period of 27 weeks. The Nordic Hamstring Exercise compliance rate, injury rate per 10000 playing hours and time-lost-to-sport-injury rate were calculated. The relative risk and hamstring injury severity were also calculated. The hamstring injury rate was 1.04/10 000 h in the control group and 0.88/10 000 h in the intervention group. The relative risk for hamstring injury was 1.14. The time-lost to injury rate was 1116.3/10 000 h in the control group and 113.7/10 000 h in the intervention group; with relative risk 9.81. The Nordic Hamstring Exercise in high school soccer players significantly reduced hamstring injury severity compared to a control intervention. Our results indicate that the time-lost to injury rate should be taken into account when analyzing the severity of hamstring injury.

#3 Taking the First Steps Toward Integrating Testing and Training Cognitive Abilities Within High-Performance Athletes; Insights From a Professional German Football Club
Reference: Front Psychol. 2019 Dec 13;10:2773. doi: 10.3389/fpsyg.2019.02773. eCollection 2019.
Authors: Beavan A, Spielmann J, Mayer J
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#4 Corrigendum: Observational Studies in Male Elite Football: A Systematic Mixed Study Review
Reference: Front Psychol. 2019 Dec 16;10:2682. doi: 10.3389/fpsyg.2019.02682. eCollection 2019.
Authors: Preciado M, Anguera MT, Olarte M, Lapresa D
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#5 Rapid hamstrings to quadriceps ratio at long muscle lengths in professional football players with previous hamstring strain injury
Reference: Eur J Sport Sci. 2020 Jan 9:1-16. doi: 10.1080/17461391.2020.1714741. [Epub ahead of print]
Authors: Correia P, Santos P, Mil-Homens P, Gomes M, Dias A, Valamatos MJ
Summary: Hamstring strain injuries (HSI) are the most common injury in male professional football and are potentially a primary risk factor to re-injury. Although the isokinetic strength ratios have often been used to identify strength imbalances that can augment the risk of injury in football players, the rate of torque development hamstring to quadriceps ratio (RTD H/Q) has rarely been considered in previous reports. Furthermore, little consideration has been given to selective hamstring lengths (30° of knee flexion) and its influence on torque production. The aim of this study was to investigate the RTD H/Q at long hamstring lengths, conventional (concentric/concentric) and functional (eccentric/concentric) H/Q ratios in football players with and without previous HSI. Twenty-four professional male football players (12 with and 12 without previous HSI) performed maximal voluntary isometric contractions at long hamstring lengths (knee and hip flexed at 30° and 85°, respectively) and isokinetic concentric and eccentric contractions at 180°.s-1 and 60°.s-1. Conventional and functional H/Q ratios based on peak torque throughout the entire isokinetic range of motion and at long hamstring lengths were calculated. The RTD H/Q was extracted at long hamstring lengths in incrementing time periods of 50 milliseconds (ms) from the onset of contraction (50-250ms). No significant differences were found between groups in any H/Q ratios studied. However, small effects (d=0.4) were found in previously injured hamstrings to lower RTD H/Q at 50ms and flexor eccentric torque. Previous HSI group showed small to moderate (0.4>d<0.6) higher RTD H/Q in late time intervals (>100ms).

#6 Hill on a mountaintop: A longitudinal and cross-sectional analysis of the relative age effect in competitive youth football
Reference: J Sports Sci. 2020 Jan 9:1-7. doi: 10.1080/02640414.2019.1706830. [Epub ahead of print]
Authors: Jackson RC, Comber G
Summary: The aim of this study was to examine the origin and persistence of the relative age effect (RAE) in competitive youth football. To examine its origin, birthdates of 121 category one Premier League academy players recruited over 6 years were compared with 691 Under 8 (U8) players in one of the regional grassroots leagues from which academy players are selected. To examine the persistence of the RAE we conducted a longitudinal comparison of retention rates in early-birth and late-birth academy players from U9 to U15, and made a cross-sectional comparison of birthdate distributions from U7 to U18 in 10,857 regional league players. The results revealed birthdate asymmetry in both the academy and grassroots players but a much larger RAE in the academy. Longitudinal analysis revealed that the cumulative probability of retention at the academy was higher for early-birth than late-birth players. A small to medium RAE persisted across grassroots football age groups though it declined somewhat from U15 to U18. The implication of these results for academy player recruitment is discussed.

#7 Agility Testing in Youth Football (Soccer)Players; Evaluating Reliability, Validity, and Correlates of Newly Developed Testing Protocols
Reference: Int J Environ Res Public Health. 2020 Jan 1;17(1). pii: E294. doi: 10.3390/ijerph17010294.
Authors: Krolo A, Gilic B, Foretic N, Pojskic H, Hammami R, Spasic M, Uljevic O, Versic S, Sekulic D
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Summary: Reactive agility (RAG) and change of direction speed (CODS) are important determinants of success in football (soccer), but there is an evident lack of information on reliable and valid football-specific testing procedures which will be applicable in defining sport-specific RAG and CODS in youth players. This study evaluated reliability and construct validity of newly developed tests of football-specific RAG (FS_RAG) and CODS (FS_CODS), which involved the ball kicking football technique. Additionally, factors associated with FS_RAG and FS_CODS were evaluated. The participants were youth football players (n = 59; age: 13.40 ± 1.25 years) divided according to their age into U13 (11-12 years of age; n = 29), and U15 (13-14 years of age; n = 30) categories. Additionally, performance levels (starters [first-team] vs. non-starters [substitutes]) were observed in each age category. The dependent variables were newly developed FS_RAG and FS_CODS tests. The independent variables were sprinting capacities over 10 and 20 meters (S10M, S20M), countermovement jump (CMJ), the reactive strength index (RSI), and a generic CODS test of 20 yards (20Y). The newly developed FS_CODS and FS_RAG were observed as dependent variables. Results showed appropriate intra-testing and inter-testing reliability of the FS_RAG and FS_CODS, with somewhat better reliability of the FS_CODS (ICC=0.82 and 0.79, respectively). Additionally, better reliability was evidenced in U15 than in U13 (ICC: 0.82-0.85, and 0.78-0.80 for U15 and U13, respectively). Independent samples t-test indicated significant differences between U13 and U15 in S10 (t-test: 3.57, p < 0.001), S20M (t-test: 3.13, p < 0.001), 20Y (t-test: 4.89, p < 0.001), FS_RAG (t-test: 3.96, p < 0.001), and FS_CODS (t-test: 6.42, p < 0.001), with better performance in U15. Starters outperformed non-starters in most capacities among U13, but only in FS_RAG among U15 (t-test: 1.56, p < 0.05). Multiple regression calculations indicated nonsignificant association between independent and dependent variables in U13 (FS_CODS: 19%, FS_RAG: 21% of the explained variance, both p > 0.05), but independent variables explained significant proportion of both dependent variables in U15 (FS_CODS: 35%, FS_RAG: 33% explained variance, both p < 0.05). The study confirmed the applicability of newly developed tests in distinguishing studied age categories of players. Results indicate that superiority in all studied fitness capacities is translated into performance level in U13. Meanwhile, FS_RAG seems to be important determinant of quality in U15.

#8 BDNF Val66Met Positive Players Demonstrate Diffusion Tensor Imaging Consistent With Impaired Myelination Associated With High Levels of Soccer Heading: Indication of a Potential Gene-Environment Interaction Mechanism
Reference: Front Neurol. 2019 Dec 11;10:1297. doi: 10.3389/fneur.2019.01297. eCollection 2019.
Authors: Hunter LE, Freudenberg-Hua Y, Davies P, Kim M, Fleysher R, Stewart WF, Lipton RB, Lipton ML
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Summary: The purpose of this study was to examine the potential effect modifying role of the BDNF Val66Met polymorphism on the association of soccer heading with white matter microstructure. We studied 312 players enrolled in the ongoing Einstein Soccer Study, a longitudinal study of amateur soccer player in New York City and surrounding areas. At enrollment and 2 years later, total heading in the prior 12 months (12-mo.) was estimated using an established self-report instrument and diffusion tensor imaging (DTI) was performed. Generalized Estimating Equations (GEE) logistic regression models were employed to test effect modification by the BDNF Val66Met polymorphism on the association between 12-mo. heading exposure and DTI. We identified a significant interaction of 12-mo heading*BDNF Val66Met genotype on the presence of low Radial Diffusivity, a DTI marker associated with myelination. Only Met (+) players demonstrated significantly reduced odds of low RD [OR (95 % CI): -2.36 (-3.53, -1.19)] associated with the highest vs. lowest quartile of 12-mo heading exposure. BDNF Val66Met (+) soccer players with long-term exposure to high levels of heading exhibit less low Radial Diffusivity, suggesting impaired re-myelination may be a substrate of the previously reported association between heading and poor functional outcomes in soccer players.

#9 Effect of deep transverse friction massage vs stretching on football players' performance
Reference: World J Orthop. 2020 Jan 18;11(1):47-56. doi: 10.5312/wjo.v11.i1.47. eCollection 2020 Jan 18.
Fakhro MA1, Chahine H2, Srour H2, Hijazi K2.
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Summary: Flexibility, agility and muscle strength are key factors to either win or lose a game. Recently the effect of a new technique, deep transverse friction massage (DTFM) on muscle extensibility as compared to traditional stretching techniques has been examined. The aim was to compare the effect of DTFM vs static and dynamic stretching techniques on the hamstring's extensibility, agility, and strength amongst Lebanese and Syrian football players. Recording the incidence of non-contact hamstring muscle injury was a secondary objective. This study is a single-blinded prospective longitudinal randomized controlled trial. The experiment took place over a period of four weeks. Football players were randomized into three intervention groups (static stretching; dynamic stretching; DTFM). Participants of each group were followed-up carefully by assessors during their intervention sessions three times per week, for a total of 12 sessions and during the data collection. Extensibility, agility, and strength were compared between intervention groups at (baseline; acute; and chronic) phases. Straight leg raise and 1 repetition maximum tests were used to measure the dominant leg hamstring muscle extensibility and maximal strength respectively. T-drill test was used to assess the lower extremities agility. Of 103 Lebanese and Syrian male football players aged between 18 and 35 were sampled from Damascus-Syria and South of Lebanon to participate in this study. Between-groups measures of acute strength (P = 0.011) and chronic extensibility (P = 0.000) solely showed a significant difference, and the static group showed to be superior as compared to the other groups. No loss to follow-up or protocol violation was recorded. Static stretching is showing to be superior to the other techniques used, regarding gaining long-term extensibility and short-term maximal muscle strength. In addition, DTFM showed improvements but did not outweigh the effects on footballers' performance when comparing it to static and dynamic techniques. Finally, no difference between the interventions is recorded regarding the rate of muscle injuries incidence.

#10 Evaluation of the Technical Performance of Football Players in the UEFA Champions League
Reference: Int J Environ Res Public Health. 2020 Jan 17;17(2). pii: E604. doi: 10.3390/ijerph17020604.
Authors: Yi Q, Gómez-Ruano MÁ, Liu H, Zhang S, Gao B, Wunderlich F, Memmert D
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Summary: This study aimed to assess the technical match performance of top-class football players in a long-term perspective. Technical performance profiles of players according to five playing positions (central defender, full back, wide midfielder, central midfielder, forward) and five situational variables (competition stage, match location, quality of team, quality of opponent, match outcome) were established. Technical match data of players in the UEFA Champions League from season 2009-2010 to 2016-2017 were analyzed. The true effects of positional and situational variables on players' technical performance were evaluated by the non-clinical magnitude-based inference. Results showed that the effect of competition stage on player's performance was negligible. Quality of team, quality of opponent and match outcome revealed the strongest effects on player's performance (ES: -0.42 ± 0.10-0.59 ± 0.10) while the effect of match location was relatively lower (ES: -0.32 ± 0.10-0.23 ± 0.07). The number of variables that showed statistical differences under five competing contexts for wide midfielders and forwards were higher than those of central defenders, full backs, and central midfielders. Differences of players' match performance could mainly be identified in variables related to goal scoring, passing, and organizing, these findings may provide important insights for coaches and analysts during the match preparation and training session.

#11 Scale-Up and Scale-Out of a Gender-Sensitized Weight Management and Healthy Living Program Delivered to Overweight Men via Professional Sports Clubs: The Wider Implementation of Football Fans in Training (FFIT)
Reference: Int J Environ Res Public Health. 2020 Jan 16;17(2). pii: E584. doi: 10.3390/ijerph17020584.
Authors: Hunt K, Wyke S, Bunn C, Donnachie C, Reid N, Gray CM
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Summary: Increasing prevalence of obesity poses challenges for public health. Men have been under-served by weight management programs, highlighting a need for gender-sensitized programs that can be embedded into routine practice or adapted for new settings/populations, to accelerate the process of implementing programs that are successful and cost-effective under research conditions. To address gaps in examples of how to bridge the research to practice gap, we describe the scale-up and scale-out of Football Fans in Training (FFIT), a weight management and healthy living program in relation to two implementation frameworks. The paper presents: the development, evaluation and scale-up of FFIT, mapped onto the PRACTIS guide; outcomes in scale-up deliveries; and the scale-out of FFIT through programs delivered in other contexts (other countries, professional sports, target groups, public health focus). FFIT has been scaled-up through a single-license franchise model in over 40 UK professional football clubs to 2019 (and 30 more from 2020) and scaled-out into football and other sporting contexts in Australia, Canada, New Zealand, England and other European countries. The successful scale-up and scale-out of FFIT demonstrates that, with attention to cultural constructions of masculinity, public health interventions can appeal to men and support them in sustainable lifestyle change.

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