Latest research in football - week 29 - 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 A Case Study Comparison of Objective and Subjective Evaluation Methods of Physical Qualities in Youth Soccer Players
Reference: J Sports Sci. 2020 Jun 13;1-9. doi: 10.1080/02640414.2020.1766177. Online ahead of print.
Authors: James H Dugdale, Dajo Sanders, Tony Myers, A Mark Williams, Angus M Hunter
Summary: Subjective and objective assessments may be used congruently when making decisions regarding player recruitment in soccer, yet there have been few attempts to examine the level of agreement between these methods. Therefore, we compare levels of agreement between subjective and objective assessments of physical qualities associated with youth soccer performance. In total, 80 male youth soccer players (13.2 ± 1.9 years), and 12 professional coaches volunteered to participate. Players were objectively assessed using five fitness measures: Yo-Yo Intermittent Recovery Test Level 1; Countermovement vertical jump; Functional Movement Screen™; 5/20 m sprint; alongside anthropometric measures. Additionally, coaches subjectively rated each player on the same five physical qualities using 5-point Likert scales. Inter-rater agreement between ratings from lead and assistant coaches was established for each age group. Moreover, Bayesian regression models were fitted to determine how well coach ratings were able to predict fitness test performance. Although inter-rater agreement between lead and assistant coaches was moderate-to-substantial (ω = 0.48-0.68), relationships between coaches subjective rating's and corresponding fitness test performance were only highly related for the highest and lowest performing players. We suggest that while ratings derived from objective and subjective assessment methods may be related when attempting to differentiate between distinct populations, concerns exist when evaluating homogeneous samples using these methods. Our data highlight the benefits of using both types of measures in the talent identification process.

#2 Recommendations for Initial Examination, Differential Diagnosis and Management of Concussion and Other Head Injuries in High-Level Football
Reference: Scand J Med Sci Sports. 2020 Jun 17. doi: 10.1111/sms.13750. Online ahead of print.
Authors: Nina Feddermann-Demont, Georges Chiampas, Charlotte M Cowie, Tim Meyer, Anna Nordström, Margot Putukian, Dominik Straumann, Efraim Kramer
Summary: Head injuries can result in substantially different outcomes, ranging from no detectable effect to transient functional impairments to life-threatening structural lesions. In high-level international football (soccer) tournaments, on average, one head injury occurs in every third match. Making the diagnosis and determining the severity of a head injury immediately on-pitch or off-field is a major challenge for team physicians, especially because clinical signs of a brain injury can develop over several minutes, hours or even days after the injury. A standardised approach is useful to support team physicians in their decision whether the player should be allowed to continue to play or should be removed from play after head injury. A systematic, football-specific procedure for examination and management during the first 72 hours after head injuries and a graduated Return-to-Football programme for high-level players has been developed by an international group of experts based on current national and international guidelines for the management of acute head injuries. The procedure includes seven stages from the initial on-pitch examination to the graduated Return-to-Football programme. Details of the assessments and the consequences of different outcomes are described for each stage. Criteria for emergency management (red flags), removal from play (orange flags), and referral to specialists for further diagnosis and treatment (persistent orange flags) are provided. The guidelines for Return-to-Sport after concussion-type head injury are specified for football. Thus, the present paper presents a comprehensive procedure for team physicians after a head injury in high-level football.

#3 Position Statement of the Royal Spanish Football Federation for the Resumption of Football Activities After the COVID-19 Pandemic (June 2020)
Reference: Br J Sports Med 2020 Jun 16;bjsports-2020-102640. doi: 10.1136/bjsports-2020-102640. Online ahead of print.
Authors: Helena Herrero-Gonzalez, Rafael Martín-Acero, Juan Del Coso, Carlos Lalín-Novoa, Rafel Pol, Pilar Martín-Escudero, Ana Isabel De la Torre, Christopher Hughes, Magni Mohr, Francisco Biosca, Rafael Ramos
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#4 The Effects of High-Intensity Interval Training (HIIT) in Improving VO2 Max
Reference: Enferm Clin. 2020 Jun;30 Suppl 4:507-511. doi: 10.1016/j.enfcli.2019.10.130.
Authors: Dilli Dwi Kuswoyo, Jori Lahinda, Syamsudin
Summary: This study aims to determine the effect of High-Intensity Interval Training (HIIT) in improving VO2 Max in Football Students Activity Unit, University of Musamus. This research is an experimental study with one group pretest and posttest design research. The population in this study was Football Students Activity Unit, the University of Musamus, which numbered 22 students who were the subjects of the study. Data retrieval technique is by tests and measurements. The instrument used is a multi-stage fitness test (bleep test). The students were given HIIT; it carried out twice a week for four weeks. Analysis of the data used is using t-test at 0.05% as the significance level. Based on the results, the number of pretests showed on 39.6773. While at the posttest after there was an improvement, the number showed on 48.5863. Based on the results of data analysis on the hypothesis in the study, it was found that there was a significant effect of HIIT in improving VO2 Max football student activity unit, University of Musamus, it was indicated by the score of t-count that higher than t-table (13.015>2.080). There was a significant effect of the HIIT in improving football students' VO2 of Max at University of Musamus.

#5 Prior Workload Has Moderate Effects on High-Intensity Match Performance in Elite-Level Professional Football Players When Controlling for Situational and Contextual Variables
Reference: J Sports Sci. 2020 Jun 16;1-12. doi: 10.1080/02640414.2020.1778355. Online ahead of print.
Authors: Matthew Springham, Sean Williams, Mark Waldron, Anthony J Strudwick, Chris Mclellan, Robert U Newton
Summary: This investigation examined the effect of prior workload on high-intensity football match performance. Player load variables were recorded using a global positioning system and converted into composite variables: rolling season accumulated load (AL), exponentially weighted moving average acute, chronic and acute:chronic workload ratio (A:C). Match-play high-intensity performance-per-minute: accelerations (ACC), sprints, high-speed running (HSR) and high metabolic load (HMLd) distances; and situational and contextual variables were recorded for all games. Partial least squares modelling, and backward stepwise selection determined the most parsimonious model for each performance variable. Quadratic relationships of small to moderate effect sizes were identified for sprint AL and sprint performance, HSR AL and HSR performance, acute HMLd and HMLd performance, acute sprint load and ACC performance and A:C sprint load and ACC performance. Match performance was typically greatest between the mean and +1SD. High chronic HMLd, and combined acceleration and deceleration (ACC+DEC) load exerted small beneficial effects on HMLd and HSR performance, whereas high acute load exerted trivial to moderate negative effects. High sprint A:C exerted a small beneficial effect on sprint performance and playing position exerted small effects on HSR and HMLd performance. Prior workload has trivial to moderate effects on high-intensity match performance in professional players.

#6 Adapted Recreational Football Small Sided Games Improves Cardiac Capacity, Body Composition and Muscular Fitness in Patients With Type 2 Diabetes: Results From a Pilot Study
Reference: J Sports Med Phys Fitness. 2020 Jun 12. doi: 10.23736/S0022-4707.20.10498-5. Online ahead of print.
Authors: Annamaria Mancini, Anna A Turco, Carlo G Tocchetti, Georgios Ermidis, Francesca Cozzolino, Giacomo Campi, Paolo Parrella, Valentina Mercurio, Ciro G Mainolfi, Teresa Mannarino, Adriana D'antonio, Maurizio Marra, Rita Polito, Luca Russomando, Domenico Martone, Stefania Orrù, Aurora Daniele, Brunella Capaldo, Francesco Salvatore, Pasqualina Buono
Summary: The usefulness of adapted small-side games (SSGs) in improving cardiac function in subjects with T2DM is still debated. Here we evaluated the effects of 18weeks Indoor Muscular Activation training (6 wks; IMA) followed by adapted SSGs football training (12wks) on cardiac function, muscular fitness, Body Composition and adiponectin expression in sedentary T2DM volunteers. 6 T2DM patients underwent IMA protocol of 6 wks, 2/wk followed by 12 wks SSGs (5vs5; once a wk) training. Glucose, lipid profile and serum homocysteine concentration, Body Composition (BC), bone mineral density (DEXA), were determined at baseline and after 18wks (IMA+SSGs). VO2max and muscular fitness were recorded at baseline and after IMA (6wks) and SSGs (12 wks), respectively. No significant differences were found for VO2max and muscular fitness after 6wks of IMA. After 18wks (6 wks IMA+ 12 wks SSGs) of training, significant improvements were found in the following parameters: work capacity, VO2peack, Ventilation (VEpeack), breathing reserve consumption and oxygen uptake efficiency (OUES) (p<0.05); leg fitness (p<0.05), BC (p<0.05), vertebral column T-score (p<0.01) and adiponectin (total and High Molecular Weight, HMW; p<0.05). Compared to baseline, a reduction in serum homocystein (Hcy) occurred after 18 wks of training (p<0.05). We evidenced that weekly adapted SSGs friendly football matches for 12 weeks improve cardiorespiratory capacity and the expression of independent markers associated with cardiovascular risk in T2DM patients, suggesting an overall reduced CVD-risk in these patients. These preliminary data encourage us to test the efficacy of this type of exercise in a larger population.

#7 Physical Fitness and Activity Changes After a 24-week Soccer-Based Adaptation of the U.S Diabetes Prevention Program Intervention in Hispanic Men
Reference: Prog Cardiovasc Dis. 2020 Jun 27;S0033-0620(20)30135-3. doi: 10.1016/j.pcad.2020.06.012. Online ahead of print.
Authors: Jennifer K Frediani, Alan F Bienvenida, Jianheng Li, Melinda K Higgins, Felipe Lobelo
Summary: One third of the U.S. adult population is estimated to have prediabetes. Hispanics have a 50% higher type 2 diabetes (T2DM) death rate compared to non-Hispanic whites, yet low participation in lifestyle change programs, making this subgroup an important target for prevention efforts. The purpose of this study was to determine the effects of an exercise intervention implementing the Center for Disease Control and Prevention National Diabetes Prevention Program (NDPP) plus recreational soccer (RS) in Hispanic men. Overweight and obese Hispanic men, aged 30-57 years with prediabetes at screening were recruited from the community. Trained soccer coaches led 30-min facilitated discussion of the NDPP modules after each RS session, with two weekly sessions delivered over 12 wks, then once a wk until 24 wks. The 1-h RS sessions followed the Football Fitness curriculum structure. Standardized study assessments included objectively measured physical activity via fitness tracker, physical fitness via validated field tests, global positional system soccer specific metrics and behavior change questionnaires. Mixed models assessed the outcomes as a function of time and cohort and incorporated an unstructured covariance structure to examine the difference between baseline, 12 and 24 wks. All analyses were conducted as intent-to-treat and generated using SAS v 9.4. Hispanic males (n = 41; mean age 41.9 [6.2 SD] years) were obese at baseline (mean BMI 32.7, standard error [0.7]). After 24 wks of the NDPP+RS intervention, there were significant beneficial changes in vertical jump (2.8 [1.3] cm; p = 0.048), agility and lower extremity muscular power (figure 8-run) at 12 wks (-4.7% change; p = 0.001) and 24 wks (-7.2% change; p < 0.0001), predicted VO2 max (12 wks: 1.9%; p = 0.007; 24 wks 1.0%; p = 0.036), modified push-ups increased 22% (p < 0.0001) at 12 wks and 31% (p < 0.0001) at 24 wks, dynamic sit-ups increased 10% (p = 0.005) at 12 wks and 15% (p < 0.0001) at 24 wks. Among middle-aged Latino men, broad-ranging significant improvements in physical fitness were observed after 24 wks participating in lifestyle education plus RS in a single arm feasibility trial.

#8 Analysis of Physical and Technical Performance of Substitute Players in Professional Soccer
Reference: Res Q Exerc Sport. 2020 Jun 30;1-8. doi: 10.1080/02701367.2020.1755414. Online ahead of print.
Authors: Miguel Lorenzo-Martínez, Alexis Padrón-Cabo, Ezequiel Rey, Daniel Memmert
Summary: Current soccer scientific literature is scarce with regard to examining the technical performance of substitute players. This study aimed to analyze the physical and technical performance of substitute players versus those who completed the entire match or were replaced and also examine the performance of substitutes across different playing positions. The sample was composed of 6,631 match observations from 431 professional soccer players competing in the German Bundesliga during the season 2018-2019. These observations were divided into three groups: entire match (n = 3,807), replaced (n = 1,412), and substitutes (n = 1,412). Linear mixed models were adjusted to compare the performance of the three groups independently of playing position and separately for each position (central defenders, fullbacks, central midfielders, wide midfielders, and attackers). Substitute players showed higher total distance covered (effect sizes [ES]: 0.99-1.06), number of sprints (ES: 0.60-0.64), and number of fast runs (ES: 0.83-0.91) relative to playing time than replaced and entire match players. The differences in technical performance between groups varied according to playing position. Substitute central defenders showed less possession (ES: 0.39-0.41), touches (ES: 0.47-0.57), and passes (ES: 0.54-0.59) but higher defensive performance (ES: 0.51-0.54) than replaced and entire match players. Substitutes in midfield and attack positions displayed more possession (ES: 0.22-0.47), touches (ES: 0.27-0.37), and shots (ES: 0.22-0.28) than replaced and entire match players. This study has shown that substitutes are able to improve the performance of the players who completed the entire match or were replaced in both physical and some technical variables depending on playing position.

#9 Changes in Perceptions of Mental Fatigue During a Season in Professional under-23 English Premier League Soccer Players
Reference: Res Sports Med. 2020 Jun 30;1-11. doi: 10.1080/15438627.2020.1784176. Online ahead of print.
Authors: William Abbott, Thomas E Brownlee, Robert J Naughton, Tom Clifford, Richard Page, Liam D Harper
Summary: The present study assessed changes in academy soccer players' perception of mental fatigue (MF) across a competitive season, investigating the relationship between MF and other subjective measures of wellness. Ten players completed a modified Brief Assessment of Mood (BAM+) questionnaire that included the question: "How mentally fatigued do you feel"? on match-day (MD) and one (MD+1), two (MD+2) and three (MD+3) days post-match (35 matches). Players reported their MF, along with other subjective measures (sleep, muscle soreness, fatigue and motivation). Results found MF was elevated on MD+1 (43±1 mm) compared to all other days (all P≤0.001). Players reported lower MF on MD+1 in the late-season phase (34±2 mm) compared to both early- (50±2 mm, P≤0.001) and mid-season (46±2 mm, P≤0.001). This coincided with an 80%-win rate in the late-season phase versus the early- (33%) and mid-season (50%). There were very strong repeated-measures correlations between changes in MF and sleep (r=-0.77), muscle soreness (r=0.94), fatigue (r=0.92) and motivation (r=-0.89; all P ≤ 0.0005). In conclusion, MF was closely aligned to match success and other wellness variables. This data suggests a potential lack of sensitivity for identifying MF using a subjective questionnaire. Therefore, researchers and practitioners could work together to identify other ways of practically assessing MF.

#10 Evolution of Soccer as a Research Topic
Reference: Prog Cardiovasc Dis . 2020 Jun 26;S0033-0620(20)30134-1. doi: 10.1016/j.pcad.2020.06.011. Online ahead of print.
Authors: Donald T Kirkendall, James R Urbaniak
Summary: Soccer has not only the largest number of worldwide participants, it is also the most studied sport, with nearly 14,000 citations listed on Pubmed and nearly 60% more articles than the next most studied sport. Research about soccer was limited until the late 1970s when exponential growth began; approximately 98% of all soccer-related research publications have occurred since 1980. This vast repository of soccer research shows trends in various major (e.g., 'sex' or 'age group' or 'performance' or 'injury') and specialty (e.g., agility, deceleration, elbow-head impact injuries, behavior) topics. Examining trends of the various topics provides insights into which subjects have come in and out of favor as well as what topics or demographics have been neglected and worthy of inquiry. A further examination can be used by students to learn the most productive researchers, which programs have a strong history of inquiry, and what journals have demonstrated a commitment to publishing research on soccer.

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