Latest research in football - week 22 - 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 Determining the Reliability and Usability of Change of Direction Speed Tests in Adolescent Female Soccer Players: A Systematic Review
Reference: J Sports Med Phys Fitness. 2020 May;60(5):720-732. doi: 10.23736/S0022-4707.20.10178-6.
Authors: Elena Pardos-Mainer , José A Casajús , Cristina Julián , Chris Bishop, Oliver Gonzalo-Skok 
Summary: This review aimed 1) to describe the most common tests used for assessing change of direction (COD) performance; 2) to detail the reliability of current COD tests; 3) to provide an overview of current intervention strategies used to improve COD performance in adolescent female soccer players. A computerized search was conducted in the PubMed, Cochrane Plus and Web of Science (from 1995 to January 2020) for English and Spanish language and peer-reviewed investigations. A total of 221 studies were identified, with only 16 meeting the specific search criteria. The main findings were that eleven different tests have been used to assess COD performance with intraclass correlation coefficient and coefficient of variation values between 0.72-0.99 and 1-10.6%, respectively. The number of CODs performed during each test ranged from 1 to 9 within a range of 45º to 180º and with a duration <5 s, 5-9 s and >10 s. Findings indicate that the reliability of the COD tests seems to depend on: the equipment used, the surface tested on and the technical level of the soccer player. These results should be interpreted with caution as they may be influenced by the period of growth and maturation, the playing position of the player and the period of the soccer season. Finally, strength and power drills could be considered as appropriate to improve COD performance.

#2 Game-based vs Mulitaleral Approach: Effects of a 12-week Program on Motor Skill Acquisition and Physical Fitness Development in Soccer School Children
Reference: J Sports Med Phys Fitness. 2020 May 20.  doi: 10.23736/S0022-4707.20.10726-6. Online ahead of print.
Authors: Federico Abate Daga, Luca Baseggio, Massimiliano Gollin, Luca Beratto
Summary: The purpose of this study was to investigate the effects of a 12-week- game-based training versus a traditional multilateral approach on motor skills acquisition and physical fitness, in a group of U9 children playing soccer. 40 Children 9 years old or younger (U9) recruited from a local soccer school were assigned in a 1:1 ratio to a game-based training program (GB) or a multilateral training (MA) approach. The training programs lasted 12 weeks, and players were tested at baseline and at the end of the program (12-week follow-up). The outcomes were: standing long jump test, shuttle dribble test, 10x5 shuttle run test and Mini-Cooper test. Within-group comparisons showed statistically-significant improvements in both of the groups: standing long lump (p < 0.0001), shuttle dribble test (p < 0.0001), shuttle run test (p < 0.0001) and Mini-Cooper test (p < 0.0001). Furthermore, the MA group showed better performance in the shuttle run test after 12 weeks of training compared to the GB group (p= 0.0002; +8%).  A multilateral approach promotes physical development in U9 soccer players without affecting learning of soccer skills. Therefore, a multilateral approach should be included in soccer training programs to ensure an optimal development in young soccer players.

#3 Effects of in Season Multi-Directional Plyometric Training on Vertical Jump Performance, Change of Direction Speed and Dynamic Postural Control in U-21 Soccer Players
Reference: Front Physiol. 2020 Apr 30;11:374.  doi: 10.3389/fphys.2020.00374. eCollection 2020.
Authors: Mohamed Chedly Jlid, Jérémy Coquart, Nicola Maffulli, Thierry Paillard, Gian Nicola Bisciotti, Karim Chamari
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Summary: The aim of the study was to assess the effects of multi-directional plyometric training (MPT) on vertical jump height, change of direction speed (CODS), and dynamic postural control (DPC) of soccer players under 21 year (U-21). Twenty-seven male soccer players were randomly allocated to either an experimental group (EG; n = 14; age: 19.0 ± 0.9 years) or a control group (CG; n = 13; age: 19.0 ± 0.7 years). The EG introduced 6 weeks MPT, 2 days per week into their in-season training, while CG continued training without change. Measurements of vertical jump height, CODS and DPC were completed at the beginning and end of the 6 week MPT. ANOVA demonstrated a significant group × time interaction for SJ (F = 6.03, p = 0.021), CMJ (F = 9.10, p = 0.006), and T-Test (F = 10.46, p = 0.002). The Bonferroni Post Hoc test demonstrated significant increase for the three tests in both group (EG and CG). For SJ (EG: p < 0.001; CG: p < 0.001), CMJ (EG: p < 0.001; CG: p = 0.005) and T-Test (EG: p < 0.001; CG: p = 0.02). For DPC on the dominant leg, there was a significant group × time interaction for four axes [anterior (F = 5.48, p = 0.028), antero-lateral (F = 4.82, p = 0.038), postero-lateral (F = 4.82, p = 0.038), and medial (F = 6.77, p = 0.015)]. The Bonferroni Post Hoc test demonstrated significant increase in EG (p < 0.001), but no significant change in CG in four axes (anterior, antero-lateral, postero-lateral and medial). Furthermore DPC on the non-dominant leg, there was a significant group × time interaction for three axes [lateral (F = 8.09, p = 0.009), postero-lateral (F = 11.92, p = 0.002), and medial (F = 5.84, p = 0.023)]. The Bonferroni Post Hoc test demonstrated significant increase in EG (p < 0.001), but no significant change in CG in three axes (lateral, postero-lateral, and medial). In conclusion, incorporating MPT into the in-season regimen of under 21 soccer players improved performance of various indices related to soccer activity (i.e., CMJ, CODS, and DPC). MPT has the potential to be appealing to coaches, as it requires little time while yielding valuable results in the physical preparation of soccer players.

#4 A Possible Antioxidant Role for Vitamin D in Soccer Players: A Retrospective Analysis of Psychophysical Stress Markers in a Professional Team
Reference: Int J Environ Res Public Health. 2020 May 16;17(10):E3484. doi: 10.3390/ijerph17103484.
Authors: Davide Ferrari, Giovanni Lombardi, Marta Strollo, Marina Pontillo, Andrea Motta, Massimo Locatelli
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Summary: The health benefits of physical activity are recognized, however, high levels of exercise may lead to metabolic pathway imbalances that could evolve into pathological conditions like the increased risk of neurological disease observed in professional athletes. We analyzed the plasma/serum levels of 29 athletes from a professional soccer team playing in the Italian first league and tested the levels of psychophysical stress markers (vitamin D, creatine kinase, reactive oxygen species (ROS) and testosterone/cortisol ratio) during a period of 13 months. The testosterone/cortisol ratio was consistent with an appropriate training program. However, most of the athletes showed high levels of creatine kinase and ROS. Despite the large outdoor activity, vitamin D values were often below the sufficiency level and, during the "vitamin D winter", comparable with those of the general population. Interestingly, high vitamin D values seemed to be associated to low levels of ROS. Based on the results of our study we proposed a vitamin D supplementation as a general practice for people who perform high levels of physical exercise. Beside the known effect on calcium and phosphate homeostasis, vitamin D supplementation should mitigate the high reactivity of ROS which might be correlated to higher risk of neurodegenerative diseases observed in professional athletes.

#5 Latarjet Procedures on anterior shoulder instability in professional soccer players
Reference: Acta Ortop Bras. Mar-Apr 2020;28(2):84-87.
doi: 10.1590/1413-785220202802225433.
Authors: Guilherme Augusto Stirma, Ewerton Borges DE Souza Lima, Deginaldo Holanda Chaves, Paulo Santoro Belangero, Carlos Vicente Andreoli, Benno Ejnisman
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Summary: Anterior glenohumeral instability is a frequent cause of professional soccer players' removal, reduced performance, and prolonged recovery. Players are subjected to intense physical contact and high performance, thus demanding lower rates of recurrence after surgical correction so they can return to sport quickly. The purpose was to assess professional soccer players treated by the Lartajet technique considering the rate and time of return to sports activities, complications or failures. Analysis held between 2010 and 2018 of professional soccer players diagnosed with anterior shoulder instability operated by the open procedure of Lartajet in our service. The mean return to professional sports was 93.5 days. The mean time of surgery in relation to the first dislocation was 12.4 months. Each athlete had 4.3 shoulder dislocations until the procedure was performed. The rate of recurrence was zero and subluxation was not observed. The Latarjet procedure allowed all professional athletes to return to competitive activities quickly, without dislocations and subluxation, negative seizure and without complications during follow-up.

#6 Heart Rate-Index Estimates Aerobic Metabolism in Professional Soccer Players
Reference: J Sci Med Sport. 2020 Apr 27;S1440-2440(19)31624-X.  doi: 10.1016/j.jsams.2020.04.015. Online ahead of print.
Authors: Alessandro L Colosio, Maarten Lievens, Silvia Pogliaghi, Jan G Bourgois, Jan Boone
Summary: This study aimed at proposing a new heart rate (HR) method to track aerobic metabolism in soccer by: (i) validating a recently developed HR index (HRindex) in professional soccer players, (ii) comparing HRindex vs the most common HR parameters and (iii) testing the agreement between measured and estimated VO2 values using HRindex. 184 professional soccer players performed a step incremental running test on a treadmill while VO2 and HR were recorded. HRindex was calculated (actual HR/resting HR) and its relationship with VO2 was compared with the relationships with the metabolism of actual HR, net HR, and % of HR reserve. Finally, HRindex was used to predict VO2=((HRindex·6)-5)·3.5) and measured and estimated VO2 were compared by 2W RM-ANOVA and Bland-Altman analysis. HRindex/VO2 relationship explained 85% of the variability in data, showing a higher performance than actual HR (77%) and similar values to the other parameters. Measured and estimated VO2 were not significantly different ≤14kmh-1, whereas at speeds ≥14kmh-1 measured VO2 was higher than estimated VO2. Finally, measured and estimated VO2 were highly correlated (R2=0.85, p=0.000), and showed no significant bias (bias=-1.03, z=-0.69, precision=3.75mlkgmin-1). We validated the HRindex/VO2 relationship in professional soccer players. HRindex showed better agreement with metabolism than actual HR and similar agreement to the other HR parameters. HRindex allowed to estimate VO2, but at very high-intensity HRindex underestimated VO2. Future studies should test this in real game conditions. HRindex could offer a time-efficient and easy-to-use "field" method to monitor aerobic metabolism in soccer.

#7 Risk Factors in Elite, Adolescent Male Soccer Players: Prospective Study
Reference: Clin Pediatr (Phila). 2020 Jun;59(6):596-605. doi: 10.1177/0009922820916895.
Authors: Dai Sugimoto, Adam J Loiacono, Alexandra Blenis, Jennifer M Morse, Dennis R Borg, William P Meehan 3rd
Summary: The aim was to find risk factors for soccer-related musculoskeletal injuries among elite, adolescent male soccer players. Prior to the season, various physical, clinical, and functional measurements were taken. One season was used as an injury surveillance period. Then, after the season, measures of potential risk factors were compared between (1) those players who sustained musculoskeletal injuries and (2) those who remained injury free. Among 61 players, 37.7% (23/61) sustained soccer-related musculoskeletal injuries. After adjusting for covariates in a logistic regression model, presence of previous hip and low back injury (adjusted odds ratio [aOR] = 8.93, P = .046) and Functional Movement Screen (FMS) scores (aOR = 1.92, P = .022) were independently associated with musculoskeletal injures. Elite, adolescent male soccer players with a history of hip and back injury are at greater risk of sustaining a soccer-related musculoskeletal injury. In addition, our study indicated greater risk of sustaining a future soccer-related injury as FMS scores increase.

#8 Estimating Postmatch Fatigue in Soccer: The Effect of Individualization of Speed Thresholds on Perceived Recovery
Reference: Int J Sports Physiol Perform. 2020 May 18;1-7.  doi: 10.1123/ijspp.2019-0399. Online ahead of print.
Authors: Gustavo Tomazoli, Joao B Marques, Abdulaziz Farooq, Joao R Silva
Summary: The aim was to investigate the effectiveness of different individualization methods of speed zones during match play to estimate postmatch perceptual recovery in soccer. Twelve players under the age of 19 y undertook field-based assessments to determine their maximal aerobic speed (MAS) and maximal sprint speed (MSS). External load (extracted from 10-Hz GPS over 10 official matches) was measured and classified into 4 categories as follows: low-speed running, moderate-speed running, high-speed running, and sprinting. Match running distribution into different speed zones was categorized using either MAS, MSS, MAS and MSS as measures of locomotor capacities, and absolute values. Players perceived recovery status was recorded immediately postmatch (Post) and 24 (G+24H) and 48 hours (G+48H) after each game. Different individualization methods resulted in distinct match outputs in each locomotor category. Perceived recovery status was lower (P < .001) at Post (3.8 [1.32], 95% confidence interval [CI], 3.6 to 4.2), G+24H (5.2 [1.48], 95% CI, 4.9 to 5.6), and G+48H (6.0 [1.22], 95% CI, 5.7 to 6.3) compared with prematch values (7.1 [1.05], 95% CI, 6.8 to 7.3). The absolute perceived recovery-status score was better associated with high-speed running using the locomotor-capacities method at Post (β = -1.7, 95% CI, -3.2 to -0.22, P = .027), G+24H (β = -2.08, 95% CI, -3.22 to -0.95, P = .001), and G+48H (β = -1.32, 95% CI, -2.2 to -0.4, P = .004) compared with other individualization methods. The authors' results suggest that locomotor capacities may better characterize the match intensity distribution (particularly for the high-speed running and sprinting categories) and should be preferred over MAS and MSS to estimate perceived recovery.

#9 Youth Soccer Parents' Perceptions of Long-Term Effects of Concussion
Reference: Dev Neuropsychol. Apr-Jun 2020;45(3):110-117.  doi: 10.1080/87565641.2020.1766464. Epub 2020 May 18.
Authors: Philip Schatz, Mary Corcoran, Anthony P Kontos, R J Elbin
Summary: Increased focus on sports-related concussion (SRC) in football in the media, and mandatory concussion education for parents of youth sport athletes, may result in parental concern that youth athletes will experience long-term effects from concussion. We sought to identify beliefs about long-term effects of concussion in parents of youth soccer athletes. Four hundred and eleven parents from soccer leagues in three states completed a survey assessing parents' perceptions and knowledge of long-term effects of SRC. Nearly all youth soccer parents surveyed (96.5%) believe there are long-term effects from SRCs, 76% reported concern their child would sustain a concussion, and 71% had talked with their child about concussion symptoms/reporting. Parents ranked tackle football as having the highest risk for concussion, followed by soccer, ice hockey, cheerleading, and lacrosse. Parents of children that had previously sustained a concussion were 8.3x more likely to be concerned their child would sustain a concussion, and parents with a personal history of concussion were 2x more likely to consider not allowing their child to participate in youth sports. There are wide-spread beliefs among youth soccer parents regarding long-term effects of SRCs, and concerns their children will sustain concussions while participating in youth sports.

#10 An Injury Audit in High-Level Male Youth Soccer Players From English, Spanish, Uruguayan and Brazilian Academies
Reference: Phys Ther Sport. 2020 May 4;44:53-60. doi: 10.1016/j.ptsp.2020.04.033. Online ahead of print.
Authors: Elliott C R Hall, Jon Larruskain, Susana M Gil, Jose A Lekue, Philipp Baumert, Edgardo Rienzi, Sacha Moreno, Marcio Tannure, Conall F Murtagh, Jack D Ade, Paul Squires, Patrick Orme, Liam Anderson, Craig M Whitworth-Turner, James P Morton, Barry Drust, Alun G Williams, Robert M Erskine
Summary: The purpose was to identify the most common injury types/locations in high-level male youth soccer players (YSP). Six hundred and twenty-four high-level male YSP [Under 9 (U9) to U23 year-old age groups] from academies in England, Spain, Uruguay and Brazil. Injury type, location and severity were recorded during one season. Injury severity was compared between age groups, while injury type and location were compared between nations. Four hundred and forty-three training or match injuries were recorded, giving an injury rate of 0.71 per player. Non-contact injuries were most common (58.5%), with most (44.2%) resolved between 8 and 28 days. Most injuries (75.4%) occurred in the lower limbs, with muscle (29.6%) the most commonly injured tissue. U14 and U16 suffered a greater number of severe injuries relative to U12 and U19/U20/U23/Reserves. Tendon injury rate was higher in Brazil vs. Spain (p < 0.05), with low back/sacrum/pelvis injury rate highest in Spain (p < 0.05). The proportion of severe injuries in U14 and U16 suggests YSP injury risk is maturation-dependent. Minimal differences in type and location between high-level YSP from four different countries suggest injury rates in this population are geographically similar.

#11 Vaccination Practices and Influenza in Professional Football Players in Greece
Reference: Occup Med (Lond). 2020 May 20;kqaa004.  doi: 10.1093/occmed/kqaa004. Online ahead of print.
Authors: D Papagiannis, G Rachiotis, A Xanthopoulos, A Simou, C Zilidis, F Triposkiadis
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Summary: There is limited data on vaccination practices for professional footballers globally. The aim was to record vaccination practices employed by medical staff of individual football teams of the Super League Greece, and absenteeism of footballers related to influenza illness. A brief questionnaire was distributed to chief medical officers (CMOs) of the sixteen teams of the Super League Greece. Participants were asked to report vaccines they recommended for footballers. In addition, the questionnaire included questions on new cases of influenza and absenteeism due to influenza. Descriptive statistics (absolute and relative frequencies) were used for the presentation of the results. Overall, 87% of the CMOs recommended seasonal influenza vaccine, 62% hepatitis B vaccine and 50% pneumococcal vaccine. Fourteen CMOs (87%) reported that the occurrence of seasonal influenza in the 2016-17 northern hemisphere season ranged from one to five cases, while two medical officers (12%) reported zero workdays lost due to influenza. Our survey shows considerable variation in vaccination practices of CMOs of the Super League Greece. The results of this survey should stimulate further evaluation of vaccination policy and influenza-related absenteeism in footballers.

#12 Pre-season Football Preparation in the Era of COVID-19: Croatian Football Association Model
Reference: J Glob Health. 2020 Jun;10(1):010352. doi: 10.7189/jogh.10.010352.
Authors: Dragan Primorac, Vid Matišić, Vilim Molnar, Zoran Bahtijarević, Ozren Polašek
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