Latest research in football - week 41 - 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 Small-Sided Games Are Not as Effective as Intermittent Running to Stimulate Aerobic Metabolism in Prepubertal Soccer Players
Reference: Int J Sports Physiol Perform. 2020 Aug 19;1-7. doi: 10.1123/ijspp.2019-0966. Online ahead of print.
Authors: Anasthase Massamba, Stéphane P Dufour, Fabrice Favret, Thomas J Hureau
Summary: The purpose of this study was to investigate the influence of the soccer pitch area during small-sided games (SSG) in prepubertal children on physiological and technical demands, and to compare them, for the physiological demands, to high-intensity interval training (HIIT). Ten young soccer players (13.0 [0.3] y) performed a HIIT and 3 SSG of various field sizes (30 × 20 m, 42 × 38 m, and 51 × 34 m). Each SSG was performed with 5 players per team, during 4 × 4-minutes interspaced with 1 minute of passive recovery in between. HIIT also followed a 4 × 4-minute protocol with running speed set on an individual basis. Heart rate (HR) was continuously monitored during training sessions. For each exercise modality, time spent above 90% of HRmax (T≥90%,HRmax) was calculated, and technical actions were quantified during SSG by video analysis. T≥90%,HRmax was similar between the 3 SSG (∼587 [276] s; P > .2) but 24% to 37% lower than during HIIT (826 [140] s, P < .05). Coefficients of variations in T≥90%,HRmax were 2.3 to 3.5 times larger in SSG compared with HIIT. For technical actions, greater number of possessions (21 [6] vs ∼14 [4]), and lower ball touches per possession (2.4 [0.6] vs ∼2.9 [0.6]) were found in the small SSG compared with larger SSG, respectively (P < .05). The 3 SSG led to lower acute stimulation of the aerobic metabolism, suggesting a lower potential for chronic aerobic adaptations, compared with HIIT. Moreover, interindividual variability in the physiological response was substantially greater in SSG compared with HIIT, indicating increased heterogeneity among players performing the same training protocol.

#2 Effects of Combined Strength and Power Training on Physical Performance and Interlimb Asymmetries in Adolescent Female Soccer Players
Reference: Int J Sports Physiol Perform. 2020 Aug 20;1-9. doi: 10.1123/ijspp.2019-0265. Online ahead of print.
Authors: Elena Pardos-Mainer, José Antonio Casajús, Chris Bishop, Oliver Gonzalo-Skok
Summary: The purpose was to examine the effects of an 8-week combined strength and power training intervention on physical performance and interlimb asymmetries in adolescent female soccer players. Thirty-seven adolescent female soccer players (age 16.1 [1.1] y) were randomly assigned to a control group (n = 18) or experimental group (n = 19). The experimental group performed combined strength and power training twice a week, which consisted of strength and power exercises that trained the major muscles of the lower body and trunk musculature. Preintervention and postintervention tests included unilateral and bilateral horizontal and countermovement jump tests, a 40-m sprint test (10- and 30-m split times), a 10-m sprint with a 180° change-of-direction (COD) test, and a multiple-COD test (V-cut test). Asymmetries were also analyzed in the unilateral tests. Significant group-by-time interaction of the improvement between pretest and posttest was observed for speed (effect size [ES]: -1.30 to -1.16) and COD tests (ES: -0.62 to -0.61) but not in jumping (ES: -0.09 to 0.28) and interlimb-asymmetry tests (ES: -0.13 to 0.57). The short-term in-season combined strength and power training program induced greater speed and COD performance improvements than soccer training alone in adolescent female soccer players.

#3 Epidemiology of soccer-related head injury in children 5-14 years in Victoria, Australia
Reference: J Paediatr Child Health. 2020 Aug 20. doi: 10.1111/jpc.15114. Online ahead of print.
Authors: Amy E Smith, Catherine Krejany, Moyez Jiwa
Summary: Our aim was to use epidemiological data to determine the incidence of soccer-related head injuries in children aged 5-14 years who presented at emergency departments (EDs) or were admitted in hospitals in Victoria, Australia. ED presentation and hospital admission de-identified aggregate data were from the Victorian Injury Surveillance Unit. Soccer participation data were compared with the soccer-related head injury data to determine the incidence of this injury among these children. The incidence of ED presentations was 0.17% of children participating in soccer during the study period (financial years 2011-2012 to 2015-2016). The 10-14-years age group presented with more head injuries than the 5-9-years age group. For the admissions data, soccer had a significantly lower (P = 0.0379) incidence of head injury when compared with 'sport as a whole'. The low incidence of soccer-related head injuries presenting to an ED or admission to hospital is consistent with international findings.

#4 External Validity of the T-SAFT90: A Soccer Simulation Including Technical and Jumping Activities
Reference: Int J Sports Physiol Perform. 2020 Aug 18;1-7. doi: 10.1123/ijspp.2019-0057. Online ahead of print.
Authors: Cristiano D da Silva, Ric Lovell
Summary: The purpose was to examine the physiological, muscle-damage, endocrine, and immune responses to a modified soccer-simulation protocol to include technical and jumping activities characteristic of match play (the Technical Soccer-Specific Aerobic Field Test; T-SAFT90). Eighteen university players (age 23 [2] y, stature 175 [5] cm, body mass 74 [11] kg) performed the 90-minute protocol, with acute physiological responses monitored via heart rate, ratings of perceived exertion (6-20 scale), and body mass changes. Creatine kinase, myoglobin, cortisol, and leukocyte subset concentrations were measured at baseline, immediately (0 h), and 24 hours post T-SAFT90. T-SAFT90 incurred an average heart rate equivalent to 87% (5%) of maximum, 16 (2) a.u. ratings of perceived exertion, and a 1.5% (1.0%) body mass deficit. Moderate to large proliferation of leukocyte subsets (P ≤ .01; leukocytes: 6.4-fold; neutrophils: 5.5-fold; lymphocytes: 2.0-fold) and increases in cortisol (2.3-fold) were observed at 0 hours (effect size = 1.13-3.52), each returning to baseline by 24 hours (P > .45; effect size = 0.05-0.50). Myoglobin peaked immediately post T-SAFT90 (4.8-fold), whereas creatine kinase (24 h: 6.0-fold) showed a delayed time course (both P ≤ .001; very large effects; effect size = 2.66 and 3.43, respectively).
Conclusions: The magnitude and time course of the physiological, immune, endocrine, and muscle-damage markers observed during and following T-SAFT90 are similar to values reported in match-play literature, demonstrating external validity of the simulation.

#5 Effects of Integrative Neuromuscular Training on Motor Performance in Prepubertal Soccer Players
Reference: J Strength Cond Res. 2020 Aug 12. doi: 10.1519/JSC.0000000000003666. Online ahead of print.
Authors: Glauber B Menezes , Diego R O Alexandre, Júlio C B L Pinto, Tereza V L Assis, Avery D Faigenbaum, Arnaldo L Mortatti
Summary: The present study examined the effects of integrative neuromuscular training (INT) on motor performance in prepubertal soccer players. Subjects were randomly assigned to the experimental group (INT; n = 20, age: 8.2 ± 1.2 years; body mass: 28.4 ± 6.4 kg; height: 1.3 ± 0.1 m) or the control group (CON; n = 18, age: 8.5 ± 1.3 years; body mass: 32.8 ± 8.9 kg; height: 1.3 ± 0.1 m). Integrative neuromuscular training program was performed twice per week during the 12-week training intervention. Balance, flexibility, countermovement vertical jump height (CVJH), sprint speed, and change of direction speed (CODS) were assessed in both groups at baseline, sixth week and 12th week. A mixed model repeated measures analysis of variance was used to examine the group changes in performance for each variable. There was a time effect for balance in the INT from pre to 12th weeks (p < 0.001, g = 0.72), and from 6th to 12th weeks (p = 0.005, g = 0.34). An interaction effect for balance was also observed between INT and CON after the 12th week. A time effect in flexibility was observed in INT from baseline to 6th and 12th weeks (p = 0.02; g = 0.45 and p < 0.001; g = 0.71) and from 6 to 12th weeks (p = 0.003; g = 0.24). There was a time effect in CVJH, from baseline to 12th week and from 6th to 12th weeks (p < 0.05; g = 0.34 and g = 0.53, respectively). There was no significant between-group speed performance change. A time effect was found in CODS in INT, but only from baseline to 12th week (p = 0.02; g = 0.31). There were significant improvements in the percent change (Δ%) from baseline to 12 weeks (p < 0.05) for balance, flexibility, and CVJH in INT. These findings indicate that the addition of an INT program to soccer practice can improve selected motor performance skills in prepubertal soccer players.

#6 Exercise intensity and cardiovascular health outcomes after 12 months of football fitness training in women treated for stage I-III breast cancer: Results from the football fitness After Breast Cancer (ABC) randomized controlled trial
Reference: Prog Cardiovasc Dis. 2020 Aug 12;S0033-0620(20)30154-7. doi: 10.1016/j.pcad.2020.08.002. Online ahead of print.
Authors: Jacob Uth, Bjørn Fristrup, Victor Sørensen, Eva Wulff Helge, Maja Kjærgaard Christensen, Julie Boye Kjærgaard, Trine Kjeldgaard Møller, Magni Mohr, Jørn Wulff Helge, Niklas Rye Jørgensen, Mikael Rørth, Eva Soelberg Vadstrup, Peter Krustrup
Summary: The aim was to examine the exercise intensity and impact of 12 months of twice-weekly recreational football training on cardiorespiratory fitness (CRF), blood pressure (BP), resting heart rate (HRrest), body fat mass, blood lipids, inflammation, and health-related quality of life in women treated for early-stage breast cancer (BC). Sixty-eight women who had received surgery for stage I-III BC and completed adjuvant chemo- and/or radiation therapy within 5 years were randomized in a 2:1 ratio to a Football Fitness group (FFG, n = 46) or a control group (CON, n = 22). Football Fitness sessions comprised a warm-up, drills and 3-4 × 7 min of small-sided games (SSG). Assessments were performed at baseline, 6 months and 12 months. Outcomes were peak oxygen uptake (VO2peak), blood pressure (BP), HRrest, total body fat mass, and circulating plasma lipids and hs-CRP, and the 36-Item Short Form Health Survey (SF36). Intention-to-treat (ITT) analyses were performed using linear mixed models. Data are means with SD or 95% confidence intervals. Adherence to training in participants completing the 12-months follow-up (n = 33) was 47.1% (22.7), and HR during SSG was ≥80% of HRmax for 69.8% (26.5) of total playing time. At baseline, VO2peak was 28.5 (6.4) and 25.6 (5.9) ml O2/kg/min in FFG and CON, respectively, and no significant changes were observed at 6- or 12 months follow-up. Systolic BP (SBP) was 117.1 (16.4) and 116.9 (14.8) mmHg, and diastolic BP (DBP) was 72.0 (11.2) and 72.4 (8.5) mmHg in FFG and CON, respectively, at baseline, and a 9.4 mmHg decrease in SBP in CON at 12 months resulted in a between-group difference at 12 months of 8.7 mmHg (p = .012). Blood lipids and hs-CRP were within the normal range at baseline, and there were no differences in changes between groups over the 12 months. Similarly, no differences between groups were observed in HRrest and body fat mass at 6- and12-months follow-up. A between-group difference in mean changes of 23.5 (0.95-46.11) points in the role-physical domain of the SF36 survey favored FFG at 6 months CONCLUSION: Football Fitness training is an intense exercise form for women treated for breast cancer, and self-perceived health-related limitations on daily activities were improved after 6 months. However, 1 year of Football Fitness training comprising 1 weekly training session on average did not improve CRF, BP, blood lipids, fat mass, or HRrest.

#7 How has COVID-19 modified training and mood in professional and non-professional football players?
Reference: Physiol Behav. 2020 Aug 25;227:113148. doi: 10.1016/j.physbeh.2020.113148. Online ahead of print.
Authors: Daniel Mon-López, Abraham García-Aliaga, Alberto Ginés Bartolomé, Diego Muriarte Solana
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Summary: Coronavirus disease 2019 (COVID-19) has restricted freedom of movement with several countries 'locked down' worldwide. During this isolation period or quarantine, habits have been modified. This might have had negative effects on physiological variables but also influenced numerous emotional aspects, especially in elite athletes, which can have a negative impact on training and sleep quality, affecting their performance. 175 Spanish professional and non-professional association football players answered an online survey about demographic and training habits, as well as two validated questionnaires to assess psychological variables (POMS and WLEIS-S). The results showed that the confinement period reduced the load of training (p < 0.01), and modified the sleeping behaviour (both, sleep time (p < 0.05) and quality (p < 0.001)) across soccer players. Higher emotional intelligence (EI) values were positively related to training variables and strongly correlated with the mood. Interestingly, athletes' mood was affected differently depending on gender. We found that confinement period affects both, training load and recovery process and that mood states and EI could predict the training variables and performance of top-level football players.

#8 The association of the ACTN3 R577X and ACE I/D polymorphisms with athlete status in football: a systematic review and meta-analysis
Reference: J Sports Sci. 2020 Aug 28;1-12. doi: 10.1080/02640414.2020.1812195. Online ahead of print.
Authors: Alexander B T McAuley, David C Hughes , Loukia G Tsaprouni, Ian Varley, Bruce Suraci, Thomas R Roos, Adam J Herbert, Adam L Kelly
Summary: The aim of this review was to assess the association of ACTN3 R577X and ACE I/D polymorphisms with athlete status in football and determine which allele and/or genotypes are most likely to influence this phenotype via a meta-analysis. A comprehensive search identified 17 ACTN3 and 19 ACE studies. Significant associations were shown between the presence of the ACTN3 R allele and professional footballer status (OR = 1.35, 95% CI: 1.18-1.53) and the ACE D allele and youth footballers (OR = 1.18, 95% CI: 1.01-1.38). More specifically, the ACTN3 RR genotype (OR = 1.48, 95% CI: 1.23-1.77) and ACE DD genotype (OR = 1.29, 95% CI: 1.02-1.63) exhibited the strongest associations, respectively. These findings may be explained by the association of the ACTN3 RR genotype and ACE DD genotype with power-orientated phenotypes and the relative contribution of power-orientated phenotypes to success in football. As such, the results of this review provide further evidence that individual genetic variation may contribute towards athlete status and can differentiate athletes of different competitive playing statuses in a homogenous team-sport cohort. Moreover, the ACTN3 R577X and ACE I/D polymorphisms are likely (albeit relatively minor) contributing factors that influence athlete status in football.

#9 Evaluation of Gross Motor Coordination and Physical Fitness in Children: Comparison between Soccer and Multisport Activities
Reference: Int J Environ Res Public Health. 2020 Aug 14;17(16):E5902. doi: 10.3390/ijerph17165902.
Authors: Boris Popović, Marko Gušić, Danilo Radanović, Slobodan Andrašić, Dejan M Madić, Draženka Mačak, Dušan Stupar, Goran Đukić, Dragan Grujičić, Nebojša Trajković
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Summary: The early detection and continuous monitoring of children's motor competence levels and physical fitness is very important. The purpose of this study was to determine the differences in motor coordination of children enrolled in soccer and multisport activities. The participants of this study included 147 boys and girls (mean age 7.60 ± 0.85 years). The total sample of subjects was composed of two subgroups: children who were enrolled in organized exercise programs-multisports (n = 77), and children who were engaged in soccer training (n = 70). Motor coordination was evaluated with the Kiphard-Schilling body coordination test (KTK). Physical fitness was assessed with a 20 m shuttle run test, 4 × 10 m shuttle run test, standing long jump, and handgrip strength. The ANCOVA showed significant differences (p < 0.05) with large effect size between groups for tests hopping for height (d = 0.93), total motor quotient (d = 1.31), jumping sideways (d = 1.32), and moving sideways (d = 1.59), after adjusting for age and gender. There were no significant differences between groups in the physical fitness tests. It can be concluded that children enrolled in multisport activities have higher levels of motor coordination than children who are enrolled only in soccer. Therefore, multiple sport training programs should be considered and encouraged by parents, educators, and other training professionals.

#10 A Fraction of Recommended Practices: Implementation of the FIFA 11+ in NCAA Soccer Programs
Reference: Medicina (Kaunas). 2020 Aug 19;56(9):E417.
doi: 10.3390/medicina56090417.
Authors: Lawrence W Judge, Jeffrey C Petersen, Donald L Hoover, Bruce W Craig, Nick Nordmann, Makenzie A Schoeff , Brian D Fox, D Clark Dickin, David M Bellar
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Summary: National Collegiate Athletic Association (NCAA) soccer coaches implement numerous warm-up and flexibility strategies to prepare athletes for training and competition. The Fédération Internationale de Football Association (FIFA) developed the 11+ injury prevention program to reduce non-contact injuries. This study aimed to analyze the level of familiarity with and implementation of the evidence-based FIFA 11+ amongst NCAA Division I (DI) and Division III (DIII) men's and women's soccer coaches. NCAA soccer coaches in the United States received an Institutional Review Board-approved survey hyperlink. A total of 240 coaches completed the survey. The respondents represented 47.5% men's and 52.5% women's teams distributed within DI and DIII programs. Descriptive statistics are reported as frequency counts and mean ± standard deviation where applicable. Pearson's chi-square tests were performed to assess potential differences with a significance level set at α < 0.05. The results indicated that approximately 62% of the respondents reported being familiar with the FIFA 11+ program. Of those coaches familiar with the program, 15.0% reported full implementation, 57.5% reported partial implementation, and 27.5% reported no implementation. Chi-square analyses revealed significant differences in FIFA 11+ implementation based upon division level (χ2 = 4.56, p = 0.033) and coaching certification levels (χ2 = 13.11, p = 0.011). This study indicates that there is a gap between FIFA 11+ knowledge and actual implementation. To reduce the risk of non-contact injury, there is a need to educate coaches and athletic trainers on the purpose of the FIFA 11+ program and how to perform the exercises correctly.

#11 Power, Muscle, and Take-Off Asymmetry in Young Soccer Players
Reference: Int J Environ Res Public Health. 2020 Aug 19;17(17):E6040. doi: 10.3390/ijerph17176040.
Authors: Petr Bahenský, David Marko, Václav Bunc, Pavel Tlustý
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Summary: The objective of the study was to check the relationship between laterality, amount of muscle mass (MM), and selected strength parameters on lower extremities and assessment of asymmetry like a result of training. The screened sample consisted of soccer players (n = 65, age = 16.0 ± 1.2 years). The legs were assessed for MM, height of reflection on a force plate, and power over 30 s Wingate anaerobic test (WAnT). The relationships between the individual parameters and age dependence were assessed using a correlation analysis. The differences between the dominant and non-dominant leg were assessed using the t-test. A relationship between the jump height and the mean 30 s power in WAnT (r = 0.375, p ˂ 0.01) and between the amount of MM and the absolute power of the individual legs in WAnT (r = 0.695-0.832, p ˂ 0.01) was proved. A relationship between the take-off force and the MM, or between the MM and the relative power during a velocity force load was not found. The amount of MM in young soccer players does not affect take-off force or strength power in WAnT. The more specific the movement is, the lower the effect on the achieved power output of the concerned MM. Differences in the performance between the dominant and non-dominant leg decrease with duration of the training.

#12 Reliability and Validity of a 6-Minute Yo-Yo Intermittent Endurance Test Level 2 in Subelite Part Time Male Soccer Players
Reference: J Strength Cond Res. 2020 Aug 18. doi: 10.1519/JSC.0000000000003641. Online ahead of print.
Authors: Neil Gibson, Chris Easton, Michael Williams, Robert McCunn , Neil V Gibson
Summary: The aim of this study was to assess the reliability and relationship to maximal intermittent running performance of the 6-minute Yo-Yo Intermittent Endurance Test Level 2 (YYIET2), among subelite part time soccer players. Twenty male soccer players (15-22 years) completed three 6-minute YYIET2 trials with heart rate (HR), PlayerLoad, and rating of perceived exertion assessed during the protocol and HR and blood lactate assessed during 5 minutes of recovery. Subjects also completed a maximal version of the YYIET2 and the maximal Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1) and 2 (YYIRT2). Heart rate at 4 and 6 minutes, PlayerLoad at 4 minutes, and HR recovery at 2, 3, 4, and 5 minutes during recovery from the 6-minute YYIET2 demonstrated little variance between tests. Correlations between variables measured during and after the 6-minute YYIET2 and distance covered in maximal tests ranged from r = 0.02 to -0.72. The 6-minute YYIET2 provides practitioners with a method of reliably assessing HR responses within subelite part time soccer players, although large correlations with maximal assessments suggest it can be used as a proxy measure for maximal intermittent running performance. Given its ease of administration and low time cost, the 6-minute YYIET2 offers practitioners a useful means of tracking training status and movement efficiency in players longitudinally.

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