Blog archive

Fri

21

Jan

2022

Sprint Variables Are Associated with the Odds Ratios of Non-Contact Injuries in Professional Soccer Players

Evidence has emerged that a high volume of sprinting during training is associated with an increased risk of non-contact injuries in professional footballers. Training load has been reported as a modifiable risk factor for successive injury in football.

Thu

20

Jan

2022

Influence of 2D:4D ratio on fitness parameters and accumulated training load in elite youth footballer

The purpose of the study was : (1) to analyze the influence of anthropometric and 2D:4D ratio on variations of accumulated training load (ATL) and fitness parameters: maximal oxygen uptake (V̇O2max), countermovement jump (CMJ), isometric muscular strength of quadriceps (ISQ) and hamstring (ISH); along three stages of evaluation of footballers based on playing positions; (2) to analyze the correlations between 2D:4D ratio and mentioned parameters; and (3) to investigate if variance in fitness levels and ATL can explain the 2D:4D ratio.

Wed

19

Jan

2022

Latest research in football - week 46 - 2021

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 Multiscale fractal dimension applied to tactical analysis in football: A novel approach to evaluate the shapes of team organization on the pitch

Reference: PLoS One. 2021 Sep 1;16(9):e0256771. doi: 10.1371/journal.pone.0256771. eCollection 2021.

Authors: Murilo José de Oliveira Bueno, Maisa Silva, Sergio Augusto Cunha, Ricardo da Silva Torres, Felipe Arruda Moura

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8409646/pdf/pone.0256771.pdf

Summary: The aim of this study was to evaluate different shape descriptors applied to images of polygons that represent the organization of football teams on the pitch. The effectiveness of different shape descriptors (area/perimeter, fractal area, circularity, maximum fractal, rectangularity, multiscale fractal curve-MFC), and the concatenation of all shape descriptors (except MFC), denominated Alldescriptors (AllD)) was evaluated and applied to polygons corresponding to the shapes represented by the convex hull obtained from players' 2D coordinates. A content-based image retrieval system (CBIR) was applied for 25 users (mean age of 31.9 ± 8.4 years) to evaluate the relevant images. Measures of effectiveness were used to evaluate the shape descriptors (P@n and R@n). The MFD (P@5, 0.46±0.37 and P@10, 0.40±0.31, p < 0.001; R@5, 0.14±0.13 and R@10, 0.24±0.19, p < 0.001) and AllD (P@5 = 0.43±0.36 and P@10 = 0.39±0.32, p < 0.001; R@5 = 0.13±0.11 and R@10 = 0.24±0.20, p < 0.001) descriptors presented higher values of effectiveness. As a practical demonstration, the best evaluated shape descriptor (MFC) was applied for tactical analysis of an official match. K-means clustering technique was applied, and different shapes of organization could be identified throughout the match. The MFC was the most effective shape descriptor in relation to all others, making it possible to apply this descriptor in the analysis of professional football matches.

 

 

#2 Psychological factors and performance in women's football: A systematic review

Reference: Scand J Med Sci Sports. 2021 Sep 5. doi: 10.1111/sms.14043. Online ahead of print.

Authors: Susann Dahl Pettersen, Frode Adolfsen, Monica Martinussen

Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.14043

Summary: The amount of research conducted on female football players, compared to male players, is sparce. Even though research on female football players has increased the past decade, there is still a lack of studies of how psychological factors affect their performance. The objective of the current systematic review was therefore to summarize existing quantitative research into the relationship between psychological factors and performance in women's football. Literature was sourced from MEDLINE/PubMed, Embase, and PsychInfo. Two independent reviewers applied the selection criteria and assessed the quality of the studies. A total of 14 studies met the inclusion criteria. The total number of participants was 1449, and 15 psychological factors were examined in relation to football performance. The results revealed a tendency for higher leveled players to score higher on psychological factors like mental toughness, conscientiousness, and executive functions. They also had lower levels of anxiety. Enjoyment and a perceived mastery climate were related to increased levels of performance and perceived competence. Mood was unrelated to performance. Limitations and implications for future research are discussed.

 

 

#3 Football and Ice Hockey Fans' Experience of a 12-Week Training and Weight-Loss Pilot Intervention (ViSiT) in Sweden-A Focus Group Study

Reference: Front Sports Act Living. 2021 Aug 18;3:616427. doi: 10.3389/fspor.2021.616427. eCollection 2021.

Authors: Janna Skagerström, Magdalena Hjertstedt, Petra Dannapfel, Ulrika Müssener, Matti Leijon

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8416276/pdf/fspor-03-616427.pdf

Summary: Excess weight is associated with an increased risk of poor health and premature mortality. This is more problematic for men than for women because men have a lower life expectancy and a higher prevalence of several lifestyle-related diseases. A concept whereby overweight male supporters of professional football clubs are recruited and offered a weight-loss intervention has been developed in Scotland. In the present study, we explore participants' experiences of a similar pilot intervention, called ViSiT, conducted with supporters in one ice hockey club and one football club in Sweden to assess the feasibility of using the intervention in a Swedish context. In this user centered evaluation, focus groups were conducted with 12 men who had completed the 12-week ViSiT intervention. Participants discussed reasons for participating in and completing the intervention, effects of the intervention, advantages, and areas of improvement of the intervention, and thoughts on the club's involvement. The material was analyzed using thematic analysis according to Braun and Clarke. The analyses revealed four themes: reasons to participate, motivation and reinforcement, change of habit, and areas for improvement. The intervention was seen as an opportunity to change daily lifestyle behaviors. The group format, as well as the involvement of a prestigious sports club, was important for signing up to the intervention and for motivating continued involvement. The intervention had also resulted in increased knowledge on health and changed mindsets about being more attentive to regulating day-to-day behavior. Although the overall feedback on the intervention was positive, the participants suggested that possibilities to have more individual coaching should be added. The ViSiT weight loss and lifestyle intervention may be feasible in a Swedish context to reach overweight men at risk of poor health. The ice hockey and football club supporters expressed similar experiences from participating in the intervention. ViSiT seem to have a potential to be adopted by many sports clubs for a widespread reach to a group normally considered reluctant to participate in lifestyle change programs.

 

 

#4 Influence of the MCT1-T1470A polymorphism (rs1049434) on repeated sprint ability and blood lactate accumulation in elite football players: a pilot study

Reference: Eur J Appl Physiol.2021 Sep 4.doi: 10.1007/s00421-021-04797-z. Online ahead of print.

Authors: M Massidda, L Flore, N Kikuchi, M Scorcu, F Piras, P Cugia, P Cięszczyk, F Tocco, C M Calò

Summary: The aim of this study is to investigate the influence of the MCT1 T1470A polymorphism (rs1049434) on repeated sprint ability (RSA) and lactate accumulation after RSA testing. Twenty-six elite Italian male football players (age: 17.7 ± 0.78 years; height: 179.2 ± 7.40 cm; weight: 72.1 ± 5.38 kg) performed RSA testing (6 × 30-m sprints with an active recovery between sprints), and lactate measurements were obtained at 1, 3, 5, 7, and 10 min post-exercise. Genotyping for the MCT1 T1470A polymorphism was performed using PCR. Genotype distributions were in Hardy-Weinberg equilibrium, being 42% wildtype (A/A), 46% heterozygotes (T/A), and 12% mutated homozygotes (T/T). Significant differences between genotypic groups were found in the two final sprint times of the RSA test. Under a dominant model, carriers of the major A-allele (Glu-490) in the dominant model showed a significantly lower sprint time compared to footballers with the T/T (Asp/Asp) genotype (5th Sprint time: A/A + T/A = 4.60 s vs TT = 4.97 s, 95% CI 0.07-0.67, p = 0.022; 6th Sprint: A/A + T/A = 4.56 s vs T/T = 4.87 s, 95% CI 0.05-0.57, p = 0.033). The T1470A (Glu490Asp) polymorphism of MCT1 was associated with RSA. Our findings suggest that the presence of the major A-allele (Glu-490) is favourable for RSA in football players.

 

 

#5 A 2D qualitative movement assessment of a deceleration task detects football players with high knee joint loading

Reference: Knee Surg Sports Traumatol Arthrosc.2021 Sep 4. doi: 10.1007/s00167-021-06709-2.

Authors: Stefano Di Paolo, Stefano Zaffagnini, Filippo Tosarelli, Fabrizio Aggio, Laura Bragonzoni, Alberto Grassi, Francesco Della Villa

Download link: https://link.springer.com/content/pdf/10.1007/s00167-021-06709-2.pdf

Summary: The deceleration (pressing) is a common situational pattern leading to anterior cruciate ligament (ACL) injury in football. Although mainly assessed for performance purposes, a stronger focus on movement quality might support the screening of at-risk athletes. The aim of the present study was to describe a 2D scoring system for the assessment of the deceleration task and to associate it with the knee joint loading (knee abduction moment) evaluated through the gold standard 3D motion capture. The hypothesis was that lower 2D scores would be associated with higher knee joint loading. Thirty-four competitive football (soccer) players (age 22.8 ± 4.1, 16 females) performed a series of deceleration tasks. 3D motion analysis was recorded using ten stereophotogrammetric cameras, a force platform, and three high-speed cameras. The 2D qualitative assessment was performed via a scoring system based on the video analysis of frontal and lateral planes joint kinematics for five scoring criteria. The intra- and inter-rater reliabilities were calculated for each 2D scoring criteria. The peak knee abduction moment was extracted and grouped according to the results of the 2D evaluation. An ICC > 0.94 was found for all the 2D scoring criteria, both for intra-rater and inter-rater reliability. The players with low 2D frontal plane scores and low total scores (0-4) showed significantly higher peak knee abduction moment values (p < 0.001). A significant negative rank correlation was found between the total score and the peak knee abduction moment (ρ = - 0.25, p < 0.001). The qualitative 2D scoring system described successfully discerned between athletes with high and low knee joint loading during a deceleration task. The application of this qualitative movement assessment based on a detailed and accurate scoring system is suitable to identify players and patients with high knee joint loading (high knee abduction moments) and target additional training in the scenario of the primary and secondary ACL injury risk reduction.

 

 

#6 3-Week passive acclimation to extreme environmental heat (100± 3 °C) in dry sauna increases physical and physiological performance among young semi-professional football players

Reference: J Therm Biol. 2021 Aug;100:103048. doi: 10.1016/j.jtherbio.2021.103048. Epub 2021 Jul 1.

Authors: I Bartolomé, J Siquier-Coll, M Pérez-Quintero, M C Robles-Gil, F J Grijota, D Muñoz, M Maynar-Mariño

Summary: This manuscript aims to evaluate the influence of a novel passive heat acclimation program among human participants in the physical performance, as well as in several physiological parameters. 36 male football players were acclimated using a dry sauna bath to extreme hot (100 ± 3 °C), performing a total of nine sauna sessions with a weekly frequency of three sessions. The players were randomly into the sauna group (SG; n = 18; age: 20.69 ± 2.09 years) and the control group (CG; n = 18; age: 20.23 ± 1.98 years). All participants performed maximal effort test until exhaustion as well as hamstring flexibility test before and after the acclimation program. Anthropometric, respiratory, circulatory, hematological and physiological variables were evaluated at the beginning and at the end of the survey. Statistical analysis consisted of a Mann-Whitney U test to determine differences between groups at the beginning and at the end of the survey and a Wilcoxon test for paired samples to compare the differences for each group separately. Additionally, size effects of the pre-post acclimation changes were calculated. After the acclimation program SG participants experienced a diminution in body weight (p < 0.01), body mass index (p < 0.01), body fat (p < 0.05) and fat percentage (p < 0.05) decreased. Hamstring flexibility (p < 0.05) and work capacity (p < 0.05) increased. External basal temperature decreased (p < 0.05) as well as post-exercise systolic and diastolic blood pressures (p < 0.05). Finally, maximal oxygen uptake (ml Kg-1 min-1) (p < 0.05), maximal minute ventilation (p < 0.05) and maximal breath frequency (p < 0.05) increased at the end of the intervention. There were no significant changes in the CG in any variable. Favorable adaptations have been observed in this survey, suggesting a beneficial effect of extreme heat acclimation on physical performance. Several of the observed responses seem interesting for sport performance and health promotion as well. However, this is a novel, extreme protocol which requires further research.

 

 

#7 The Training of Medium- to Long-Distance Sprint Performance in Football Code Athletes: A Systematic Review and Meta-analysis

Reference: Sports Med. 2021 Sep 9. doi: 10.1007/s40279-021-01552-4. Online ahead of print.

Authors: Ben Nicholson, Alex Dinsdale, Ben Jones, Kevin Till

Download link: https://link.springer.com/content/pdf/10.1007/s40279-021-01552-4.pdf

Summary: Within the football codes, medium-distance (i.e., > 20 m and ≤ 40 m) and long-distance (i.e., > 40 m) sprint performance and maximum velocity sprinting are important capacities for success. Despite this, no research has identified the most effective training methods for enhancing medium- to long-distance sprint outcomes. This systematic review with meta-analysis aimed to (1) analyse the ability of different methods to enhance medium- to long-distance sprint performance outcomes (0-30 m, 0 to > 30 m, and the maximum sprinting velocity phase [Vmax]) within football code athletes and (2) identify how moderator variables (i.e., football code, sex, age, playing standard, phase of season) affected the training response. We conducted a systematic search of electronic databases and performed a random-effects meta-analysis (within-group changes and pairwise between-group differences) to establish standardised mean differences (SMDs) with 95% confidence intervals and 95% prediction intervals. This identified the magnitude and direction of the individual training effects of intervention subgroups (sport only; primary, secondary, tertiary, and combined training methods) on medium- to long-distance sprint performance while considering moderator variables. In total, 60 studies met the inclusion criteria (26 with a sport-only control group), totalling 111 intervention groups and 1500 athletes. The within-group changes design reported significant performance improvements (small-moderate) between pre- and post-training for the combined, secondary (0-30 and 0 to > 30 m), and tertiary training methods (0-30 m). A significant moderate improvement was found in the Vmax phase performance only for tertiary training methods, with no significant effect found for sport only or primary training methods. The pairwise between-group differences design (experimental vs. control) reported favourable performance improvements (large SMD) for the combined (0 to > 30 m), primary (Vmax phase), secondary (0-30 m), and tertiary methods (all outcomes) when compared with the sport-only control groups. Subgroup analysis showed that the significant differences between the meta-analysis designs consistently demonstrated a larger effect in the pairwise between-group differences than the within-group change. No individual training mode was found to be the most effective. Subgroup analysis identified that football code, age, and phase of season moderated the overall magnitude of training effects. This review provides the first systematic review and meta-analysis of all sprint performance development methods exclusively in football code athletes. Secondary, tertiary, and combined training methods appeared to improve medium-long sprint performance of football code athletes. Tertiary training methods should be implemented to enhance Vmax phase performance. Nether sport-only nor primary training methods appeared to enhance medium to long sprint performance. Performance changes may be attributed to either adaptations specific to the acceleration or Vmax phases, or both, but not exclusively Vmax. Regardless of the population characteristics, sprint performance can be enhanced by increasing either the magnitude or the orientation of force an athlete can generate in the sprinting action, or both.

 

 

#8 Cardiac magnetic resonance and follow up of professional soccer players recovering from COVID-19

Reference: Medicina (B Aires). 2021;81(4):491-495. [Article in Spanish]

Authors: Roberto Peidro, Rubén Argemi, Jorge Batista, Lucas Logioco, Diego Perez De Arenaza, Guillermo Bortman

Download link: http://www.medicinabuenosaires.com/PMID/34453790.pdf

Summary: The incidence of post-COVID-19 cardiac compromise is not well known. The eventual cardiac repercussions on a return to high-performance sport are unclear. A prospective observational study with evaluation by physical examination, electrocardiogram, Doppler echocardiogram and cardiac magnetic resonance imaging (CMR) was carried out in international level professional soccer players recovering from COVID-19 who had the disease asymptomatic or with mild symptoms. Four-month follow-up with participation in national and international competitions. Twenty-four soccer players were included, age 27.13 years (between 20 and 36). Nine (37.5%) had asymptomatic disease and 15 (62.5%) had mild symptoms. No athletes required hospitalization. Physical, electrocardiographic, and echocardiographic examinations did not reveal heart disease. CMRs showed ventricular thicknesses and volumes consistent with high-performance athletes. In T1, T2 and fat saturation signals, no fat infiltration or signs of edema were observed. No late enhancement after gadolinium injection. They began their training between 12 and 14 days after diagnosis. Eleven (45.8%) participated between 4 and 6 international matches of Libertadores de América International Cup. The remaining 13 completed high intensity training sessions and participated in local league competitions. At 4 months after diagnosis, none of the soccer players developed cardiac events and training and competitions were well tolerated. These findings suggest low cardiovascular impact of COVID 19 and excellent tolerance to early post-COVID high intensity exercise of young athletes recovering from the disease with no or mild symptoms.

 

 

#9 Estimation of final standings in football competitions with a premature ending: the case of COVID-19

Reference: Adv Stat Anal. 2021 Sep 2;1-18. doi: 10.1007/s10182-021-00415-7. Online ahead of print.

Authors: P Gorgi, S J Koopman, R Lit

Free PMC article

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8412877/pdf/10182_2021_Article_415.pdf

Summary: We study an alternative approach to determine the final league table in football competitions with a premature ending. For several countries, a premature ending of the 2019/2020 football season has occurred due to the COVID-19 pandemic. We propose a model-based method as a possible alternative to the use of the incomplete standings to determine the final table. This method measures the performance of the teams in the matches of the season that have been played and predicts the remaining non-played matches through a paired-comparison model. The main advantage of the method compared to the incomplete standings is that it takes account of the bias in the performance measure due to the schedule of the matches in a season. Therefore, the resulting ranking of the teams based on our proposed method can be regarded as more fair in this respect. A forecasting study based on historical data of seven of the main European competitions is used to validate the method. The empirical results suggest that the model-based approach produces more accurate predictions of the true final standings than those based on the incomplete standings.

 

 

#10 Expert and Novice Goalkeepers' Perceptions of Changes During Open Play Soccer

Reference: Percept Mot Skills. 2021 Aug 29;315125211040750. doi: 10.1177/00315125211040750.

Authors: Jie Li, Jing Yang, Yue Qin, Yu Zhang

Summary: In the present study we investigated expert and novice football (i.e., soccer) goalkeepers' three stages of perceiving changes in open play situations-detection, localization, and identification-with and without time constraints. We adopted the continual cycling flicker paradigm to investigate goalkeepers' perceptions when provided with sufficient time (Experiment 1), and we utilized the limited display one-shot change detection paradigm to study their perceptions under time constraints (Experiment 2). Images of goalkeepers' first-person views of open play soccer scenes were used as stimuli. Semantic or non-semantic changes in these scenes were produced by modifying one element in each image. Separate groups of expert and novice goalkeepers were required to detect, localize, and identify the scene changes. We found that expert goalkeepers detected scene changes more quickly than novices under both time allowances. Furthermore, compared to novices, experts localized the changes more accurately under time constraints and identified the changes more quickly when given sufficient time. Additionally, semantic changes were detected more quickly and localized and identified more accurately than non-semantic changes when there was sufficient time. Under time constraints expert goalkeepers' greater efficiency was likely due to pre-attentive processing; with sufficient time, they were able to focus attention to extracting detailed information for identification.

 

 

#11 COVID-19 Outbreak Among a University's Men's and Women's Soccer Teams - Chicago, Illinois, July-August 2020

Reference: MMWR Morb Mortal Wkly Rep. 2020 Oct 30;69(43):1591-1594.  doi: 10.15585/mmwr.mm6943e5.

Authors: Richard A Teran, Isaac Ghinai, Stephanie Gretsch, Tracy Cable, Stephanie R Black, Stefan J Green, Omar Perez, George E Chlipala, Mark Maienschein-Cline, Kevin J Kunstman, Susan C Bleasdale, Marielle J Fricchione

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7659918/pdf/mm6943e5.pdf

Summary: Data on transmission of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), among college athletes are limited. In August 2020, the Chicago Department of Public Health (CDPH) was notified of a cluster of COVID-19 cases among a university's men's and women's soccer teams. CDPH initiated an investigation, interviewed members of both teams, and collated laboratory data to understand transmission of SARS-CoV-2 within the teams. Numerous social gatherings with limited mask use or social distancing preceded the outbreak. Transmission resulted in 17 laboratory-confirmed COVID-19 cases across both teams (n = 45), likely from a single source introduction of SARS-CoV-2 (based on whole genome sequencing) and subsequent transmission during multiple gatherings. Colleges and universities are at risk for COVID-19 outbreaks because of shared housing and social gatherings where recommended prevention guidance is not followed. Improved strategies to promote mask use and social distancing among college-aged adults need to be implemented, as well as periodic repeat testing to identify asymptomatic infections and prevent outbreaks among groups at increased risk for infection because of frequent exposure to close contacts in congregate settings on and off campus.

 

 

#12 Contemporary practices of strength and conditioning coaches in professional soccer

Reference: Biol Sport. 2021 Sep;38(3):377-390. doi: 10.5114/biolsport.2021.99328. Epub 2020 Oct 24.

Authors: Anthony Weldon, Michael J Duncan, Anthony Turner, Jaime Sampaio, Mark Noon, Del P Wong, Vivian W Lai

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8329977/pdf/JBS-38-99328.pdf

Summary: This study describes the contemporary practices of strength and conditioning coaches in professional soccer. Fifty-two strength and conditioning coaches from professional leagues across 18 countries completed an online survey, consisting of 45 questions, with eight sections: (a) background information, (b) muscular strength and power development, (c) speed development, (d) plyometrics, (e) flexibility development, (f) physical testing, (g) technology use, and (h) programing. A frequency analysis was used to assess and report responses to fixed response questions, and thematic-analysis used for open-ended questions to create clear, identifiable and distinct themes. All strength and conditioning coaches were educated to degree level or higher, 65% held strength and conditioning certifications and 54% held soccer coaching certifications. Concentric (100%) and eccentric (98%) modes of resistance were the most commonly prescribed, whereas the squat (including variations) (52%) was deemed the most important exercise for soccer players. Hang clean (33%) and multiple hops/lunges (89%) were the most programed Olympic weightlifting and plyometric exercises. Global Positioning Systems (94%) were the most utilized technology-based equipment. Time, scheduling and fixtures were the biggest issues faced, which made it difficult to periodize training programs and apply appropriate training loads. Furthermore, strength and conditioning coaches would like to further integrate technology to comprehensively monitor and test players, while also believing that technology will continue to be developed and integrated in the future. Strength and conditioning coaches from professional soccer can use the information from this study to review current practices and also provide ideas for diversifying or modifying future practices.

 

 

#13 Effects of 30 days of ketogenic diet on body composition, muscle strength, muscle area, metabolism, and performance in semi-professional soccer players

Reference: Randomized Controlled TrialJ Int Soc Sports Nutr. 2021 Sep 16;18(1):62.  doi: 10.1186/s12970-021-00459-9.

Authors: A Antonio Paoli, Laura Mancin, Massimiliano Caprio, Elena Monti, Marco V Narici, Lorenzo Cenci, Fabio Piccini, Matteo Pincella, Davide Grigoletto, Giuseppe Marcolin

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8447662/pdf/12970_2021_Article_459.pdf

Summary: A ketogenic diet (KD) is a nutritional approach, usually adopted for weight loss, that restricts daily carbohydrates under 30 g/day. KD showed contradictory results on sport performance, whilst no data are available on team sports. We sought to investigate the influence of a KD on different parameters in semi-professional soccer players. Subjects were randomly assigned to a iso-protein (1.8 g/Kg body weight/day) ketogenic diet (KD) or western diet (WD) for 30 days. Body weight and body composition, resting energy expenditure (REE), respiratory exchange ratio (RER), cross sectional area (CSA) and isometric muscle strength of quadriceps, counter movement jump (CMJ) and yoyo intermittent recovery test time were measured. There was a significantly higher decrease of body fat (p = 0.0359), visceral adipose tissue (VAT) (p = 0.0018), waist circumference (p = 0.0185) and extra-cellular water (p = 0.0060) in KD compared to WD group. Lean soft tissue, quadriceps muscle area, maximal strength and REE showed no changes in both groups. RER decreased significantly in KD (p = 0.0008). Yo-yo intermittent test improved significantly (p < 0.0001) in both groups without significant differences between groups. CMJ significantly improved (p = 0.0021) only in KD. This is the first study investigating the effects of a KD on semi-professional soccer players. In our study KD athletes lost fat mass without any detrimental effects on strength, power and muscle mass. When the goal is a rapid weight reduction in such athletes, the use of a KD should be taken into account.

 

 

#14 Association Between Endocrine Markers, Accumulated Workload, and Fitness Parameters During a Season in Elite Young Soccer Players

Reference: Front Psychol. 2021 Aug 31;12:702454. doi: 10.3389/fpsyg.2021.702454. eCollection 2021.

Authors: Hadi Nobari, Elena Mainer-Pardos, José Carmelo Adsuar, Juan Manuel Franco-García, Jorge Rojo-Ramos, Marco Antonio Cossio-Bolaños, Luis Urzua Alul, Jorge Pérez-Gómez2

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8438147/pdf/fpsyg-12-702454.pdf

Summary: The purpose of this study was to analyze differences between endocrine markers in soccer players, based on playing positions, and correlations between endocrine markers (testosterone, cortisol, growth hormone, and insulin-like growth factor-1), with accumulated workload training and fitness parameters [maximal oxygen uptake (VO2max), countermovement jump (CMJ), and isometric maximal strength (1-RM) of the knee for hamstring (ISH) and quadriceps (ISQ) muscles] during early-, mid-, and end-seasons. Twenty-four elite soccer players under 17 participated in this study. The results showed that there was no difference between levels of the endocrine markers among the different positions of the players. Significant correlations were observed between endocrines parameters and fitness performance (ISQ, ISH, VO2max, and CMJ). Regression analysis showed that 1-RM and VO2max were the best predictors of endocrine markers. These findings demonstrated that the activity profiles of youth soccer players were not influenced by endocrine markers. Also, it may be assumed that endocrines levels can be used to better explain the physical capacities of this population. Finally, endocrines markers may help to predict changes in 1-RM and VO2max.

 

 

#15 The influence of playing surface on external demands and physiological responses during a soccer match simulation

Reference: J Sports Sci. 2021 Sep 17;1-9. doi: 10.1080/02640414.2021.1976472. Online ahead of print.

Authors: Daniel Wt Wundersitz, Craig A Staunton, Brett A Gordon, Michael Ic Kingsley

Summary: We investigated the effects of playing surfaces with different impact absorption characteristics on external demand and physiological responses. Fifteen participants completed a soccer match simulation on natural grass, synthetic turf and concrete surfaces. Accelerometry-derived PlayerLoadTM per minute (PL·min-1) and average net force (AvFNet) were used to quantify external demands at the centre of mass (CoM), upper-back, mid-back and hip. Heart rate, oxygen uptake, energy expenditure and RPE quantified physiological responses. The concrete surface exhibited the least impact absorption, with peak decelerations ~3.5x synthetic turf and ~10x natural grass (p < 0.001). Despite this, there was no differences in external demand between surfaces (surface: p ≥ 0.194; η2p≤0.092). Both AvFNet and PL·min-1 (location: p < 0.001; η2p≥0.859) were higher at the hip (613(91)N; 12.5(1.2)arb.u), reduced at the mid-back (521(67)N; 8.8(0.7)arb.u) and upper-back (502(60)N; 8.8(0.7)arb.u) when compared to CoM (576(78)N; 10.7(1.0)arb.u). Although playing surface did not influence the external demands, heart rate or oxygen uptake (p > 0.05), energy expenditure was highest on natural grass compared to synthetic turf (P = 0.034) and RPE was highest on synthetic turf compared to concrete (p = 0.026). Different playing surfaces can alter physiological responses to soccer-specific activity even when the external demands are similar.

 

 

#16 Muscle Fibre Typology as a Novel Risk Factor for Hamstring Strain Injuries in Professional Football (Soccer): A Prospective Cohort Study

Reference: Sports Med. 2021 Sep 13. doi: 10.1007/s40279-021-01538-2. Online ahead of print.

Authors: E Lievens, K Van Vossel, F Van de Casteele, E Wezenbeek, D Deprez, S Matthys, B De Winne, S McNally, W De Graaf, J B Murdoch, J G Bourgois, E Witvrouw, Wim Derave

Summary: Hamstring strain injuries (HSI) are prevalent in team sports and occur frequently in the later phase of matches. In the search for interindividual factors that determine muscle fatigue and possibly injury risk, muscle fibre typology is a likely candidate. The aim of the study was to determine whether muscle fibre typology is a risk factor for HSI. A prospective cohort study was conducted over three seasons in professional football players competing in the Belgian Jupiler Pro League (n = 118) and in the English Premier League (n = 47). A total of 27 HSI were sustained during this period. Muscle fibre typology was non-invasively estimated using proton magnetic resonance spectroscopy and was characterized as a fast, slow, or intermediate typology based on the carnosine concentration in the soleus. A multivariate Cox model was used to identify risk factors for HSI. Football players exhibited a wide variety of muscle typologies (slow 44.9%, intermediate 39.8%, fast 15.3%). In the combined cohort, players with a fast typology displayed a 5.3-fold (95% confidence interval [CI] 1.92-14.8; P = 0.001) higher risk of sustaining an index HSI than slow typology players. This was also independently observed in both leagues separately as, respectively, a 6.7-fold (95% CI 1.3-34.1; P = 0.023) and a 5.1-fold (95% CI 1.2-20.4; P = 0.023) higher chance was found in fast typology players than in slow typology players of the Jupiler Pro League and the Premier League cohort.

 

 

#17 Mind your step: predicting maximum ankle inversion during cutting movements in soccer

Reference: Sports Biomech. 2021 Sep 13;1-15. doi: 10.1080/14763141.2021.1974533. Online ahead of print.

Authors: Paul Miller, Daniel J Brinkmann, Christina Ramsenthaler, Albert Gollhofer, Dominic Gehring

Summary: The objective of this investigation was to identify parameters at initial contact that would predict the subsequent maximum ankle inversion angle during cutting movements. We conducted a secondary data analysis and calculated kinematics of 1,400 cuttings performed by 46 male soccer athletes. The movement task consisted of an approach run, followed by a pre-planned cutting movement. A linear mixed regression model was applied to predict the maximum ankle inversion angle during the first 100 ms of ground contact. The prediction was made based on six predictors that describe change-of-direction intensity and foot placement as found to be relevant in the literature. The model explained 62% of the variance of maximum ankle inversion angles. A change of the main predictors (foot rotation, cutting angle and initial ankle inversion) by 1 SD caused a reduction of the subsequent maximum ankle inversion angle by 2.6-4.4°. Regarding the intensity of a change-of-direction movement, cutting angle seems to have a higher influence on maximum ankle inversion angle than approach velocity. With respect to the individual foot positioning, the maximum ankle inversion angle can be reduced by increasing exorotation and eversion of the foot while shifting towards forefoot landing.

 

 

#18 Variations in Elite Female Soccer Players' Sleep, and Associations With Perceived Fatigue and Soccer Games

Reference: Front Sports Act Living. 2021 Aug 25;3:694537. doi: 10.3389/fspor.2021.694537. eCollection 2021.

Authors: Frode Moen, Maja Olsen, Gunvor Halmøy, Maria Hrozanova

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8424084/pdf/fspor-03-694537.pdf

Summary: The current study investigated the associations between female perceived fatigue of elite soccer players and their sleep, and the associations between the sleep of players and soccer games. The sample included 29 female elite soccer players from the Norwegian national soccer team with a mean age of ~26 years. Perceived fatigue and sleep were monitored over a period of 124 consecutive days. In this period, 12.8 ± 3.9 soccer games per player took place. Sleep was monitored with an unobtrusive impulse radio ultra-wideband Doppler radar (Somnofy). Perceived fatigue was based on a self-report mobile phone application that detected daily experienced fatigue. Multilevel analyses of day-to-day associations showed that, first, increased perceived fatigue was associated with increased time in bed (3.6 ± 1.8 min, p = 0.037) and deep sleep (1.2 ± 0.6 min, p = 0.007). Increased rapid eye movement (REM) sleep was associated with subsequently decreased perceived fatigue (-0.21 ± 0.08 arbitrary units [AU], p = 0.008), and increased respiration rate in non-REM sleep was associated with subsequently increased fatigue (0.27 ± 0.09 AU, p = 0.002). Second, game night was associated with reduced time in bed (-1.0 h ± 8.4 min, p = <0.001), total sleep time (-55.2 ± 6.6 min, p = <0.001), time in sleep stages (light: -27.0 ± 5.4 min, p = <0.001; deep: -3.6 ± 1.2 min, p = 0.001; REM: -21.0 ± 3.0 min, p = <0.001), longer sleep-onset latency (3.0 ± 1.2 min, p = 0.013), and increased respiration rate in non-REM sleep (0.32 ± 0.08 respirations per min, p = <0.001), compared to the night before the game. The present findings show that deep and REM sleep and respiration rate in non-REM sleep are the key indicators of perceived fatigue in female elite soccer players. Moreover, sleep is disrupted during game night, likely due to the high physical and mental loads experienced during soccer games. Sleep normalizes during the first and second night after soccer games, likely preventing further negative performance-related consequences.

 

 

#19 Vestibular performance in high-level soccer and ice hockey players: Sport-specific norm values and implications

Reference: J Sci Med Sport. 2021 Aug 13;S1440-2440(21)00198-5. doi: 10.1016/j.jsams.2021.08.003. Online ahead of print.

Authors: Alexander Andrea Tarnutzer, Konrad Peter Weber, Christopher J Bockisch, Dominik Straumann, Nina Feddermann-Demont

Download link: https://www.jsams.org/action/showPdf?pii=S1440-2440%2821%2900198-5

Summary: Quantitative vestibular testing in athletes after sports-related concussion (SRC) has become more popular due to accompanying injuries of the peripheral-vestibular organs that require targeted treatment. Sports-specific normative values are currently not available. Taking into account potential adaptational mechanisms, we obtained sports-specific, age- and peak-head-velocity-corrected normative values of peripheral-vestibular function and postural-stability in football (soccer, FB) and ice-hockey (IH) players. Pre-seasonal angular vestibulo-ocular reflex (aVOR) gains and cumulative-saccadic-amplitudes were obtained using the video-head-impulse test and performance in the balance-error-scoring-system (BESS) was recorded and compared in high-level FB-players (n = 510, 197 females) and IH-players (n = 210, males only) (age-range = 13-39y) and in healthy normals (n = 49, 22 females). Statistical analysis was performed using a generalized linear model. aVOR-gain values were significantly higher for FB-players than for IH-players (1.07 ± 0.21 vs. 0.98 ± 0.13, p < 0.001) and controls (1.07 ± 0.21 vs. 0.97 ± 0.17, p < 0.001). Significant age-related changes in aVOR-gains were only observed for the anterior and posterior canals in the IH-players. Cumulative-saccadic-amplitudes were clearly below established cut-off values (0.73°/trial). BESS scores were significantly higher in IH-players than in FB-players (15.4 ± 5.1 vs. 11.2 ± 4.9, p < 0.001). The significantly better performance of the FB players in the vertical aVOR-gains and the BESS compared to the IH-players could be related to sports-specific differences influencing visuo-vestibular and balance performance. Therefore, we recommend using the established normative aVOR-gain values for high-level FB-players, whereas in IH obtaining individual pre-seasonal (baseline) aVOR-gain values is proposed. Further studies should add sports-specific normative aVOR-gain values for IH and other sports.

 

 

#20 Traumatic Leg Fractures in UEFA Football Athletes: A Matched-Cohort Analysis of Return to Play, Reinjury, Player Retention, and Performance Outcomes

Reference: Orthop J Sports Med. 2021 Sep 8;9(9):23259671211024218. doi: 10.1177/23259671211024218. eCollection 2021 Sep.

Authors: Ophelie Lavoie-Gagne, Matthew F Gong, Sumit Patel, Matthew R Cohn, Avinaash Korrapati, Enrico M Forlenza, Moses Barmonyallah, Kevin C Parvaresh, Theodore S Wolfson, Brian Forsythe

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8436324/pdf/10.1177_23259671211024218.pdf

Summary: The average professional soccer team experiences 1 to 2 traumatic leg fractures per season, with unknown effects on player performance. The purpose was to (1) determine the rate and time to return to play (RTP) following leg fracture, (2) investigate the rate of reinjury following RTP, and (3) investigate long-term effects that lower extremity (LE) fracture may have on elite soccer player performance. Using publicly available records, we identified athletes sustaining a traumatic leg fracture across the 5 major European soccer leagues (English Premier League, Bundesliga, La Liga, Ligue 1, and Serie A) between 2000 and 2016. Athletes with leg fracture (femur, tibia, and/or fibula) were matched 1:2 to controls by demographic characteristics and performance metrics 1 season before the index timepoint. Investigations included the RTP rate, reinjury rate, player characteristics associated with RTP within 2 seasons, long-term player retention, performance metrics during the 4 following seasons, and subgroup analysis by player position. A total of 112 players with LE fracture and 224 controls were identified. Players with LE fractures were absent for a mean of 157 days (range, 24-601 days) and 21 games (range, 2-68 games). The rate of RTP within 1 season was 80%, with 4% experiencing subsequent refracture. Injured players remained active in the league at a higher rate than their uninjured counterparts. As compared with controls, injured athletes played 309 fewer total minutes (P < .05), scored 0.09 more assists per game (P < .01) 1 season after injury, and scored 0.12 more points per game 4 seasons after injury (P < .01). Defenders were most affected by an LE fracture, playing 5.24 fewer games (P < .05), 603 fewer total minutes (P < .01), and recording 0.19 more assists per 90 minutes of play as compared with controls 1 season after injury (P < .001). Attackers and midfielders demonstrated no significant difference in metrics after RTP when compared with controls. Most players sustaining an LE fracture returned to elite soccer at the same level after a significant loss of playing time, with a 4% rate of refracture. Player retention was higher for those sustaining an LE fracture versus uninjured controls. Overall, injured players did not experience a decline in performance after recovery from an LE fracture.

 

 

#21 Portuguese Football Federation consensus statement 2020: nutrition and performance in football

Reference: BMJ Open Sport Exerc Med. 2021 Aug 26;7(3):e001082.  doi: 10.1136/bmjsem-2021-001082. eCollection 2021.

Authors: Rodrigo Abreu, Pedro Figueiredo, Paulo Beckert, José P Marques, Samuel Amorim, Carlos Caetano, Pedro Carvalho, Carla Sá , Ricardo Cotovio, Joana Cruz , Tiago Dias , Gonçalo Fernandes, Elton Gonçalves , César Leão , Alexandre Leitão, João Lopes, Eduardo Machado, Mónica Neves , André Oliveira , Ana I Pereira , Bruno Pereira , Fernando Ribeiro , Luis M Silva, Filipe Sousa , Tânia Tinoco, Vitor H Teixeira, Monica Sousa, João Brito

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8395276/pdf/bmjsem-2021-001082.pdf

Summary: Nutrition is an undeniable part of promoting health and performance among football (soccer) players. Nevertheless, nutritional strategies adopted in elite football can vary significantly depending on culture, habit and practical constraints and might not always be supported by scientific evidence. Therefore, a group of 28 Portuguese experts on sports nutrition, sports science and sports medicine sought to discuss current practices in the elite football landscape and review the existing evidence on nutritional strategies to be applied when supporting football players. Starting from understanding football's physical and physiological demands, five different moments were identified: preparing to play, match-day, recovery after matches, between matches and during injury or rehabilitation periods. When applicable, specificities of nutritional support to young athletes and female players were also addressed. The result is a set of practical recommendations that gathered consensus among involved experts, highlighting carbohydrates periodisation, hydration and conscious use of dietary supplements.

 

 

#22 Higher risk of ACL rupture in amateur football compared to professional football: 5-year results of the 'Anterior cruciate ligament-registry in German football'

Reference: Knee Surg Sports Traumatol Arthrosc. 2021 Sep 15. doi: 10.1007/s00167-021-06737-y.

Authors: Dominik Szymski, Leonard Achenbach, Johannes Zellner, Johannes Weber, Matthias Koch, Florian Zeman, Gunnar Huppertz, Christian Pfeifer, Volker Alt, Werner Krutsch

Download link: https://link.springer.com/content/pdf/10.1007/s00167-021-06737-y.pdf

Summary: Anterior cruciate ligament (ACL) injuries are a common severe type of football injury at all levels of play. A football-specific ACL registry providing both prospective ACL injury data according to the skill level and risk factors for ACL injury is lacking in the literature. This study is based on the prospective 'ACL registry in German Football' implemented in the 2014-15 season. Professional (1st-3rd league), semi-professional (4th-6th league) and amateur leagues (7th league) were analysed regarding the incidence and risk factors for ACL injuries. Injuries were registered according to the direct reports of the injured players to the study office and double-checked via media analysis. After injury registration, the players received a standardised questionnaire. Data were analysed from the 2014-15 to the 2018-19 football season. Overall, 958 ACL injuries were registered during the 5-year study period. The incidence of ACL injuries was highest in amateur football (0.074/1000 h football exposure) compared to professional (0.058/1000 h; p < 0.0001) and semi-professional football (0.043/1000 h; p < 0.0001). At all skill levels, match incidence (professional: 0.343; semi-professional: 0.249; amateur: 0.319) was significantly higher than training incidence (professional: 0.015; semi-professional: 0.004; amateur: 0.005). Major risk factors were previous ACL injury (mean: 23.3%), other knee injuries (mean: 19.3%) and move to a higher league (mean: 24.2%). This sports-specific ACL registry provides detailed information on the incidence and risk factors for ACL injuries in football over five years. Risk factors are skill level, match exposure, move to a higher league and previous knee injury. These factors offer potential starting points for screening at-risk players and applying targeted prevention.

 

 

#23 Football player dominant region determined by a novel model based on instantaneous kinematics variables

Reference: Sci Rep. 2021 Sep 14;11(1):18209. doi: 10.1038/s41598-021-97537-4.

Authors: Fabio Giuliano Caetano, Sylvio Barbon Junior, Ricardo da Silva Torres, Sergio Augusto Cunha, Paulo Régis Caron Ruffino, Luiz Eduardo Barreto Martins, Felipe Arruda Moura

Free PMC article

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8440569/pdf/41598_2021_Article_97537.pdf

Summary: Dominant regions are defined as regions of the pitch where a player can reach before any other and are commonly determined without considering the free-spaces in the pitch. We presented an approach to football players' dominant regions analysis, based on movement models created from players' positions, displacement, velocity, and acceleration vectors. 109 Brazilian male professional football players were analysed during official matches, computing over 15 million positional data obtained by video-based tracking system. Movement models were created based on players' instantaneous vectorial kinematics variables, then probabilities models and dominant regions were determined. Accuracy in determining dominant regions by the proposed model was tested for different time-lag windows. We calculated the areas of dominant, free-spaces, and Voronoi regions. Mean correct predictions of dominant region were 96.56%, 88.64%, and 72.31% for one, two, and three seconds, respectively. Dominant regions areas were lower than the ones computed by Voronoi, with median values of 73 and 171 m2, respectively. A median value of 5537 m2 was presented for free-space regions, representing a large part of the pitch. The proposed movement model proved to be more realistic, representing the match dynamics and can be a useful method to evaluate the players' tactical behaviours during matches.

 

 

#24 Load Monitoring Practice in Elite Women Association Football

Reference: Front Sports Act Living. 2021 Aug 27;3:715122. doi: 10.3389/fspor.2021.715122. eCollection 2021.

Authors: Live S Luteberget, Kobe C Houtmeyers, Jos Vanrenterghem, Arne Jaspers, Michel S Brink, Werner F Helsen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8430212/pdf/fspor-03-715122.pdf

Summary: The description of current load monitoring practices may serve to highlight developmental needs for both the training ground, academia and related industries. While previous studies described these practices in elite men's football, no study has provided an overview of load monitoring practices in elite women's football. Given the clear organizational differences (i.e., professionalization and infrastructure) between men's and women's clubs, making inferences based on men's data is not appropriate. Therefore, this study aims to provide a first overview of the current load monitoring practices in elite women's football. Twenty-two elite European women's football clubs participated in a closed online survey (40% response rate). The survey consisted of 33 questions using multiple choice or Likert scales. The questions covered three topics; type of data collected and collection purpose, analysis methods, and staff member involvement. All 22 clubs collected data related to different load monitoring purposes, with 18 (82%), 21 (95%), and 22 (100%) clubs collecting external load, internal load, and training outcome data, respectively. Most respondents indicated that their club use training models and take into account multiple indicators to analyse and interpret the data. While sports-science staff members were most involved in the monitoring process, coaching, and sports-medicine staff members also contributed to the discussion of the data. Overall, the results of this study show that most elite women's clubs apply load monitoring practices extensively. Despite the organizational challenges compared to men's football, these observations indicate that women's clubs have a vested interest in load monitoring. We hope these findings encourage future developments within women's football.

 

 

#25 Home advantage during the COVID-19 pandemic: Analyses of European football leagues

Reference: Psychol Sport Exerc. 2021 Sep;56:102013. doi: 10.1016/j.psychsport.2021.102013. Epub 2021 Jul 6.

Authors: Dane McCarrick, Merim Bilalic, Nick Neave, Sandy Wolfson

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8422080/pdf/main.pdf

Summary: The home advantage (HA) is a robust phenomenon in football whereby the home team wins more games and scores more goals than the away team. One explanation is that the home crowd spurs on home team performance and causes the referee to unconsciously favour the home team. The Covid-19 (COVID) pandemic provided a unique opportunity to assess this explanation for HA, as European football leagues played part of the 2019/2020 season with crowds present and concluded with crowds absent. Using multi-level modelling we compared team performance and referee decisions pre-COVID (crowd present) and during-COVID (crowd absent) across 4844 games from 15 leagues in 11 countries. HA (goals scored and points gained) was significantly reduced during-COVID, which reflected the inferior performance of the home team. In games without fans, home teams created significantly fewer attacking opportunities and referee-bias was diluted when controlling for the attacking dominance of teams; such that the number of fouls and yellow cards ruled against away sides, while still significant, was reduced and no effects were observed for red cards. Implications for sporting practice and directions for future research are discussed.

 

 

#26 Muscle Fibre Typology as a Novel Risk Factor for Hamstring Strain Injuries in Professional Football (Soccer): A Prospective Cohort Study

Reference: Sports Med. 2021 Sep 13. doi: 10.1007/s40279-021-01538-2. Online ahead of print.

Authors: E Lievens, K Van Vossel, F Van de Casteele, E Wezenbeek, D Deprez, S Matthys, B De Winne, S McNally, W De Graaf, J B Murdoch, J G Bourgois, E Witvrouw, Wim Derave

Summary: Hamstring strain injuries (HSI) are prevalent in team sports and occur frequently in the later phase of matches. In the search for interindividual factors that determine muscle fatigue and possibly injury risk, muscle fibre typology is a likely candidate. The aim of the study was to determine whether muscle fibre typology is a risk factor for HSI. A prospective cohort study was conducted over three seasons in professional football players competing in the Belgian Jupiler Pro League (n = 118) and in the English Premier League (n = 47). A total of 27 HSI were sustained during this period. Muscle fibre typology was non-invasively estimated using proton magnetic resonance spectroscopy and was characterized as a fast, slow, or intermediate typology based on the carnosine concentration in the soleus. A multivariate Cox model was used to identify risk factors for HSI. Football players exhibited a wide variety of muscle typologies (slow 44.9%, intermediate 39.8%, fast 15.3%). In the combined cohort, players with a fast typology displayed a 5.3-fold (95% confidence interval [CI] 1.92-14.8; P = 0.001) higher risk of sustaining an index HSI than slow typology players. This was also independently observed in both leagues separately as, respectively, a 6.7-fold (95% CI 1.3-34.1; P = 0.023) and a 5.1-fold (95% CI 1.2-20.4; P = 0.023) higher chance was found in fast typology players than in slow typology players of the Jupiler Pro League and the Premier League cohort. We identified muscle fibre typology as a novel and potent risk factor for HSI in team sports.

 

 

#27 Monitoring post-match fatigue during a competitive season in elite youth soccer players

Reference: J Athl Train. 2021 Sep 20. doi: 10.4085/1062-6050-0245.21. Online ahead of print.

Authors: Daniel A Evans, Daniel T Jackson, Adam L Kelly, Craig A Williams, Alexander B T McAuley, Harry Knapman, Paul T Morgan

Download link: https://watermark.silverchair.com/10.4085_1062-6050-0245.21.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAv0wggL5BgkqhkiG9w0BBwagggLqMIIC5gIBADCCAt8GCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMQbYnyIg_bbSlYwW6AgEQgIICsBJeCF-Uc4RKVjDbWV-tgock3K6CgNLOg_mA0XOvT30_uF7WCpXc8yMRaGIeushPliLELVPmvDp55PMsE9oPvL1G9Udbe6n74Hugonr767y02T-7YeqcWTz5o0LZGkyi-7xjUyUPMmdseubXYz3DBADLUZ1sy_bzr7y6D7lcqTr5U82Wt8Lp5UT7mKoVFMoZJG_xTQM2RkBYlfbzLhhD--WqRQts9GtfCCfD4ZZtblKBQ6GGXSLli5k3yxZiaYQkddDrb-ipgte9LhczxP3pRugJ_rp_BHOCmBpdncIMp1z8F5uBtX2j3IDOlJ-CnpOwcxKn8l46kzio23ZSmLbRiaHXQ0iXYtOwAcGDu7MJw2nZkzIdBzZpEitP9uxvbxSFOCb4SlsSBR6AVbAuACCf1KLDH_DZINXXcnixWAPp_ojOR8deicG484GBAhg9YsjED_Yja0ER6IruseZyPGlfkrNmQrSYhmVsJyA7-wCCK4a_oSXeYKGdVanO2QBurDcUHSCgZQwTSEQdGTchTndu3dAZ923qWkZJIIifjI9z5YzMqxU7iAtQF0xDRKT0VZOVVbrVBHIMBlcjWS5QuQSRCnG8L_nvYe-bDuB2Ax8kgR110rxcw4e6ZQy0ZwdTiyMvOkRvtvlqCs52OqqgTWKJesdXyE_7iOm0LmihsuhMGrgJ_c6cmMb-vB7-DHcz6zkB9b9D_ZPPptc7NO9jXCx3DMxf9swco-7qGjoBHn0cedW2Fy1ePV3g3fVG26a1zB8b0NGiLIb4JMbcUjSHahQPg2S63oDo7uFx7cqfy6zwF6LMWTD7X9Lp9TzwbP3YdcZ0PZK10omNFHY7s-XYXGr2qKZisR3P4ENMpgse6cNcYXUcIT8WwFEPZfHfDXXnuqgsiG3oXKTdUchIC0UIMTm5RBI

Summary: Countermovement jump (CMJ) and perceived wellness measures are useful for monitoring fatigue. Fatigue indicators should simultaneously show sensitivity to previous load and demonstrate influence on subsequent physical output; however, this has not been examined. This study examined the efficacy of CMJ and wellness measures to both detect post-match fatigue and predict subsequent physical match output in elite youth soccer. Sixteen soccer players (18 ± 1 years) participated in 36 English Football League Youth Alliance League fixtures. Physical match outputs (total distance, high-speed running, very high-speed running, and accelerations and decelerations) were recorded using a 10 Hz global positioning system and 200 Hz accelerometer device during competitive match play. CMJ height and perceived wellness were assessed weekly and daily, respectively, as indirect indicators of fatigue. Four sub-units of wellness (perceived soreness, energy, general stress, and sleep) were measured using customised psychometric questionnaires. Simple linear regression showed that match accelerations and decelerations (AD) were predictive of energy (R2 = 0.08, P = 0.001), stress (R2 = 0.09, P < 0.001), and total wellness (R2 = 0.06, P = 0.002) 2 days post-match. CMJ (R2 = 0.05, P = 0.002), stress (R2 = 0.08, P < 0.001), sleep (R2 = 0.03, P = 0.034), and total wellness (R2 = 0.05, P = 0.006) 5 days pre-match (MD-5) were predictive of AD during the subsequent match. CMJ and wellness may be useful in detecting post-match fatigue. Wellness scores, but not CMJ, on MD-5 influence subsequent match output and therefore may be used to plan and periodise training for the upcoming microcycle.

 

Tue

18

Jan

2022

Associations between Physical Status and Training Load in Women Soccer Players

This study aimed to analyze the variations of fitness status, as well as test the relationships between accumulated training load and fitness changes in women soccer players.

Mon

17

Jan

2022

Effects of a Specific Core Stability Program on the Sprint and Change-of-Direction Performance in Footballers

The objective of this study was to analyze the effects of the level of specificity of a CORE stability program on specific football actions.

Fri

14

Jan

2022

Latest research in football - week 45 - 2021

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 Distance Between Players During a Soccer Match: The Influence of Player Position

Reference: Front Psychol. 2021 Aug 19;12:723414. doi: 10.3389/fpsyg.2021.723414. eCollection 2021.

Authors: David Garrido, Daniel R Antequera, Roberto López Del Campo, Ricardo Resta, Javier M Buldú

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8417069/pdf/fpsyg-12-723414.pdf

Summary: In this study, we analyse the proximity between professional players during a soccer match. Specifically, we are concerned about the time a player remains at a distance to a rival that is closer than 2 m, which has a series of consequences, from the risk of contagion during a soccer match to the understanding of the tactical performance of players during the attacking/defensive phases. Departing from a dataset containing the Euclidean positions of all players during 60 matches of the Spanish national league (30 from LaLiga Santander and 30 from LaLiga Smartbank, respectively, the first and second divisions), we analysed 1,670 participations of elite soccer players. Our results show a high heterogeneity of both the player-player interaction time (from 0 to 14 min) and the aggregated time with all opponents (from <1 to 44 min). Furthermore, when the player position is taken into account, we observe that goalkeepers are the players with the lowest exposure (lower than 1 min), while forwards are the players with the highest values of the accumulated time (~21 min). In this regard, defender-forward interactions are the most frequent. To the best of our knowledge, this is the largest dataset describing the proximity between soccer players. Therefore, we believe these results may be crucial to the development of epidemiological models aiming the predict the risk of contagion between players and, furthermore, to understand better the statistics of all actions that involve proximity between players.

 

 

#2 Weekly Variations of Short-Duration Maximal Jumping Performance in Soccer Players: Exploring Relationships With Accumulated Training Load and Match Demands

Reference: Front Physiol. 2021 Aug 19;12:690353.  doi: 10.3389/fphys.2021.690353. eCollection 2021.

Authors: Rui Silva, Filipe Manuel Clemente, Francisco Tomás González-Fernández, André Bernardo, Luca Paolo Ardigò

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8417052/pdf/fphys-12-690353.pdf

Summary: The aim of this study was 2-fold: (1) to analyze variations of short-duration maximal jumping performance in players exposed to a match and those who were not and (2) to analyze the relationships between changes in the short-duration maximal jumping performance and different accumulated training load and match demands measures.  Twenty-four professional soccer players (age: 20.3 ± 1.7 years) were monitored daily for their training load and match demands over 6 weeks. In addition, they performed a weekly short-duration maximal jumping performance test (72 h after the last match). Negative moderate correlations were found between percentage of change of countermovement jump (CMJ) height and Acummulated training load (ATL) of total distance (TD), high metabolic load (HML), accelerations (ACC), and decelerations (DEC) (r = -0.38, p = 0.004; r = -0.33, p = 0.013; r = -0.39, p = 0.003; and r = -0.30, p = 0.026). No correlations were found for match load (ML). TD, HML, ACC, and DCC (r = 0.27, r = 0.25, r = 0.31, and r = 0.22, respectively) were used to predict the percentage of change of CMJ height.  Match participation has negative effects on CMJ performance. The ATL of HML, ACC, DCC, and TD have a significant influence on both CMJ measures changes. Also, the ATL values of those metrics are the best predictors of the percentage changes of CMJ performance.

 

 

#3 Scoping review of tests to assess tactical knowledge and tactical performance of young soccer players

Reference: J Sports Sci. 2021 Sep 6;1-17. doi: 10.1080/02640414.2021.1916262. Online ahead of print.

Authors: Leandro Rechenchosky, Vanessa Menezes Menegassi, Matheus de Oliveira Jaime, Paulo Henrique Borges, Hugo Sarmento, David Mancha-Triguero, Jaime Serra-Olivares, Wilson Rinaldi

Summary: This scoping review aimed to systematically map studies/tests for assessing the tactical domain of young soccer players. The study followed the PRISMA-ScR and Joanna Briggs Institute guidelines. The databases searched were Scopus, SPORTDiscus, SciELO, LILACS, and BDTD. The eligibility criteria were defined based on the elements of population, context, and concept, without restrictions on the period, language, and type of publication. Twenty-four papers were included, from 1997 to 2020, totalling 29 tests/instruments for the assessment of the tactical domain, with the majority of studies having an European sample. Twelve terms were used to nominate the tactical component, regardless of the assessment method and approach. Six tests met eight or nine criteria in the critical appraisal: TCTOF, TACSIS Spanish version, Semi-Structured Interview, TCTP-OE, GPET, and FUTSAT. Thus, it is concluded that studies and tests for the assessment of the tactical domain of young soccer players are recent and mainly European; there is no consensus about the adopted terminology; and few tests met the majority of the quality criteria. Therefore, we suggest: a) the construction/adaptation of tests with samples from other continents; b) the use of the proposed criteria; and c) that the terms tactical knowledge and tactical performance are adopted.

 

 

#4 Oxidative Stress and Abnormal Tendon Sonographic Features in Elite Soccer Players (A Pilot Study)

Reference: Rev Bras Ortop (Sao Paulo). 2021 Aug;56(4):432-437.  doi: 10.1055/s-0040-1721364. Epub 2021 Feb 10.

Authors: Michele Abate, Luigi Di Carlo, Giulio Cocco, Antonino Cocco, Ernesto Sabatini, Vincenzo Salini

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8405266/pdf/10-1055-s-0040-1721364.pdf

Summary: Sound experimental data suggest that oxidative stress plays an important role in the pathogenesis of tendinopathies. However, this hypothesis in humans remains speculative given that clinical data are lacking to confirm it. Recently, a new methodology has allowed to quantify the oxidative stress in vivo by measuring the concentration of hydroperoxides of organic compounds, which have been utilized as an oxidative stress-related marker in several pathologic and physiologic conditions. Given the reliability of this test and the lack of information in subjects with tendinopathies, the aim of the present study was to assess the oxidative stress status in elite professional soccer players with and without ultrasonographic features of tendon damage.  In 73 elite players, blood metabolic parameters were evaluated and oxidative stress was measured by means of a specific test (expressed as U-Carr units). Therefore, an ultrasonographic evaluation of the Achilles and patellar tendons was performed.  No significant relationships were observed between metabolic parameters and oxidative stress biomarkers. The Achilles and patellar tendons showed a normal echographic pattern in 58 athletes, and sonographic abnormalities in 15. The athletes with ultrasonographic alterations, compared to those with normal US picture, showed significantly higher U-Carr levels ( p = 0.000), body mass index (BMI) values ( p = 0.03) and were older ( p = 0.005). The difference in U-Carr values among the subjects remained significant also after adjustment for age and BMI.  The results of the present study support the hypothesis that oxidative substances, also increased at systemic and not only at local level, may favor tendon damage. 

 

 

#5 Physical activity on mental wellbeing in senior English Premier League soccer players during the COVID-19 pandemic and the lockdown

Reference: Eur J Sport Sci. 2021 Sep 3;1-25. doi: 10.1080/17461391.2021.1976841. Online ahead of print.

Authors: Sophie Grimson, Gary Brickley, Nicholas J Smeeton, Will Abbott, Adam Brett 

Summary: The COVID-19 pandemic and the subsequent lockdown created new stressors that could potentially attenuate mental wellbeing (MW) in athletes, who are already susceptible to poor MW. This study aims to describe fluctuations to MW during 'lockdown' and subsequent 'return to sport' protocols, in comparison to the normal 'in-season' in professional soccer.Twenty-five English Premier League (EPL) soccer players completed the Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS) every two weeks, during the 2019/2020 season, and every week during 'lockdown' and 'return to training' for 28 weeks. The duration of each physical activity (PA) session completed was recorded. No significant differences were found for MW between time points (In-season, lockdown, return to training, and the restart) (51.5±5.6 vs. 50.7±4.8 vs. 50.8±5.7 vs. 50.7±5.6 (p >0.05)) respectively. Individually, differences were identified; in-season weekly session duration (243±38 min) was higher than during lockdown (180±62 min) (p <0.05). During lockdown, weekly MW scores were related to the previous 7-day number of sessions (r = 0.151) and active min (r = 0.142) (p <0.05). Furthermore, participants that exercised >250 min in lockdown, had higher MW scores (52.46 ± 4.65) than <250 min (50.35±6.55) (p <0.05). MW responses to lockdown were best understood on an individual basis. Additionally, PA only had a measurable effect on MW when >250 min. Further, stressors imposed upon players during an EPL season, are potentially greater than those inflicted by the lockdown. Implications for monitoring MW in EPL soccer players and the potential inclusion of an in-season break are discussed.

 

 

#6 The dominant leg is more likely to get injured in soccer players: systematic review and meta-analysis

Reference: Biol Sport. 2021 Sep;38(3):397-435.  doi: 10.5114/biolsport.2021.100265. Epub 2020 Oct 28.

Authors: Matthew D DeLang, Paul A Salamh, Abdulaziz Farooq, Montassar Tabben, Rodney Whiteley, Nicol van Dyk, Karim Chamari

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8329968/pdf/JBS-38-100265.pdf

Summary: In soccer (football), dominant limb kicking produces higher ball velocity and is used with greater frequency than the non-dominant limb. It is unclear whether limb dominance has an effect on injury incidence. The purpose of this systematic review with meta-analysis is to examine the relationship between limb dominance and soccer injuries. Studies were identified from four online databases according to PRISMA guidelines to identify studies of soccer players that reported lower extremity injuries by limb dominance. Relevant studies were assessed for inclusion and retained. Data from retained studies underwent meta-analyses to determine relative risk of dominant versus non-dominant limb injuries using random-effects models. Seventy-four studies were included, with 36 of them eligible for meta-analysis. For prospective lower extremity injury studies, soccer players demonstrated a 1.6 times greater risk of injury to the dominant limb (95% CI [1.3-1.8]). Grouped by injury location, hamstring (RR 1.3 [95% CI 1.1-1.4]) and hip/groin (RR 1.9 [95% CI 1.3-2.7]) injuries were more likely to occur to the dominant limb. Greater risk of injury was present in the dominant limb across playing levels (amateurs RR 2.6 [95% CI 2.1-3.2]; youths RR 1.5 [95% CI 1.26-1.67]; professionals RR 1.3 [95% CI 1.14-1.46]). Both males (RR 1.5 [95% CI 1.33-1.68)] and females (RR 1.5 [95% CI 1.14-1.89]) were more likely to sustain injuries to the dominant limb. Future studies investigating soccer injury should adjust for this confounding factor by using consistent methods for assigning limb dominance and tracking use of the dominant versus non-dominant limb.

 

 

#7 Differences in worst-case scenarios calculated by fixed length and rolling average methods in professional soccer match-play

Reference: Biol Sport. 2021 Sep;38(3):325-331. doi: 10.5114/biolsport.2021.99706. Epub 2020 Oct 24.

Authors: José M Oliva-Lozano, Isabel Martín-Fuentes, Víctor Fortes, José M Muyor 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8329979/pdf/JBS-38-99706.pdf

Summary: The aims of this study were to describe the worst-case scenarios (WCS) in professional soccer players calculated by fixed length and rolling average methods with regards to each playing position. This was done, firstly, by comparing total distance (TD covered in the WCS; secondly, by comparing high-speed running distance (HSRD); and thirdly, by comparing sprint distance (SPD). The study was conducted over a three-mesocycle competitive period. The WCS of three distance-related variables (TD, HSRD, SPD) in four time windows (1, 3, 5, 10 minutes) were calculated according to playing position (central defender; full-back; midfielder, wide midfielder, and forward) using fixed length and rolling average methods. A significant effect of the type of method used to calculate the WCS in TD (F(1, 142) = 151.49, p < 0.001, ηp2 = 0.52), HSRD (F(1, 138) = 336.95, p < 0.001, ηp2 = 0.71) and SPD (F(1, 138) = 76.74, p < 0.001, ηp2 = 0.36) was observed. In addition, there was a significant interaction between type of method and WCS duration in TD (F(1.36, 193.53) = 41.95, p < 0.001, ηp2 = 0.23), HSRD (F(2.28, 315.11) = 21.77, p < 0.001, ηp2 = 0.14) and SPD (F(2.59, 358.41) = 6.93, p < 0.001, ηp2 = 0.05). In conclusion, the use of fixed length methods of different durations significantly underestimated the WCS of TD, HSRD and SPD across the most common playing positions in professional soccer players. Therefore, the application of rolling averages is recommended for an appropriate WCS analysis in professional soccer match-play.

 

 

#8 Acute Effects of Foam Rolling on Blood Flow Measured by Ultrasonography in Soccer Players

Reference: J Strength Cond Res. 2021 Sep 1. doi: 10.1519/JSC.0000000000004125. Online ahead of print.

Authors: Alejandra Alonso-Calvete, Alexis Padrón-Cabo, Miguel Lorenzo-Martínez, Ezequiel Rey

Summary: In recent years, foam rolling (FR) has become a popular device for recovery to increase range of motion and decrease pain after sport practice and competition. However, there is little evidence about the underlying physiological effects of FR, specifically in blood flow parameters. Thus, the aim of this study was to analyze acute effects of FR on blood flow parameters (maximal velocity and maximal volume) measured by Doppler ultrasonography in soccer players. Twelve soccer players were assessed in 3 different situations: pre-FR intervention, immediately after FR intervention, and 30 minutes after FR intervention. The femoral artery was measured in the dominant leg with subjects in horizontal lying position. Before the intervention, subjects completed one familiarization session with FR. The FR intervention consisted of 2 sets, each with 45 seconds of FR and 15 seconds of rest between sets with a high-density foam roller in quadriceps, hamstrings, and iliotibial band. Results showed a significant increase in both maximal velocity (p < 0.001; effect size [ES] = 0.81) and maximal volume (p = 0.001; ES = 1.73) after intervention in comparison with pretest, but after 30 minutes, there were no significant differences. Therefore, this increase of the blood flow could promote important advantages for postexercise recovery, suggesting an acute effect that may contribute to the understanding of local physiological mechanism of FR.

 

 

#9 The Influence of Environmental Constraints in 360° Videos on Decision Making in Soccer

Reference: J Sport Exerc Psychol. 2021 Sep 1;1-10. doi: 10.1123/jsep.2020-0166. Online ahead of print.

Authors: Lisa Musculus, Jurek Bäder, Lukas Sander, Tobias Vogt 

Summary: Decision making is an important prerequisite of soccer expertise. Beyond expertise, considering the effects of environmental constraints on decision-making processes could help specify existing theories. To address this gap, expert and nonexpert soccer players were enrolled to test how environmental constraints affect decision-making processes. Environmental constraints were experimentally manipulated: Opponent pressure was implemented by presenting a close opponent player in soccer scenes, time constraint was implemented by providing short time intervals for making the decision, and first-person perspective was implemented by using 360° videos. The experts outperformed the nonexperts, and the results showed significant main effects of time constraint and opponent pressure, but not perspective. The players' option and decision quality improved under the time constraint but were negatively affected by opponent pressure. The negative effects of opponent pressure were especially true under limited time and in third-person perspective. The results, alternative manipulations, and implications of environmental effects are discussed for decision-making research.

 

 

#10 Moving Beyond One-Size-Fits-All Approaches to Injury Prevention: Evaluating How Tailored Injury Prevention Programs Are Developed and Implemented in Academy Soccer

Reference: J Orthop Sports Phys Ther. 2021 Sep;51(9):432-439. doi: 10.2519/jospt.2021.10513.

Authors: James O'Brien, Emanuel Santner, Josef Kröll

Summary: The aim was to evaluate the real-world development and implementation of tailored injury prevention exercise programs (IPEPs) in academy soccer players. The participants were 38 players and staff members (eg, coaches, physical therapists) from 4 male teams in 1 European soccer academy. The content and nature of the 4 teams' IPEPs and the degree of implementation across 1 playing season were evaluated. Additionally, participants took part in semi-structured interviews and focus groups, focusing on the development of tailored IPEPs and implementation barriers and facilitators. Teams employed multiple IPEPs, developed by the team physical therapists and strength and conditioning coaches. A range of sources, including scientific literature, guidelines, individual player screening data, and previous experience, influenced IPEP development. Across all teams, 76% of IPEP sessions were completed as originally planned and a further 11% were completed in modified form. The key barriers to implementation during the season were related to scheduling changes and managing player workload. Thematic coding of interviews and focus groups identified 25 IPEP implementation barriers (eg, time and scheduling, player workload) and 41 facilitators (eg, program adaptability, facilities and equipment). In a male soccer academy setting, physical therapists and strength and conditioning coaches played the key role in IPEP development. Teams employed a range of different, internally developed programs. The key implementation factors were related to time and scheduling and managing player workload. 

 

 

#11 Association between offensive and defensive playing style variables and ranking position in a national football league

Reference: J Sports Sci. 2021 Sep 9;1-9. doi: 10.1080/02640414.2021.1976488. Online ahead of print.

Authors: Alejandro Lopez-Valenciano, Jose Alberto Garcia-Gómez, Roberto López-Del Campo, Ricardo Resta, Victor Moreno-Perez, Hugo Blanco-Pita, Ángel Valés-Vázquez, Juan Del Coso

Summary: The aim of this study was to determine the association of playing style and efficacy variables with football success in a professional football league. Match statistics were obtained from 23 football teams competing in the 2017-2018 and 2018-2019 seasons of the Spanish national league(LaLiga). Offensive and defensive playing style and efficacy variables were calculated. Pearson's correlation coefficient tests and principal component analysis (PCA) were applied to establish the influence of these variables on the number of points obtained at the end of the season and on the ranking position. In isolation, the efficacy of completion showed the highest association with ranking points and position. A two-dimension PCA explained 77.8% of the variance in the ranking position. In dimension-1 (58.5%), game initiative and attack building, and in dimension-2 (19.3%), efficacy of defensive containment and a lower rate of long passes were within the variables that explained more variance in the ranking position. Success in football, measured by ranking position at the end of the Spanish national league, was associated with several playing style and efficacy variables. Overall, a dominant game style with high efficacy to finish attacking plays, and an offensive game initiative, are most associated with successful football.

 

 

#12 Acceleration profile of high-impact movements during young football games: a cross-sectional study involving healthy children

Reference: Sports Biomech. 2021 Sep 7;1-15. doi: 10.1080/14763141.2021.1970796. Online ahead of print.

Authors: Shogo Sasaki, Yasuharu Nagano, Yusaku Suganuma, Takeshi Koyama, Hiroshi Ichikawa

Summary: Repetitive high-impact movements cause growth-related injuries in children. This study aimed to identify which movements during junior football games require >6 G and >8 G acceleration and the frequency at which they occur. Additionally, we compared the components of acceleration among movements with >8 G resultant acceleration. Eleven young male footballers (10.7 ± 0.4 years) played 8-a-side games while wearing a tri-axial accelerometer on their upper back. The number and frequency of the movements that generated >6 G and >8 G were calculated, and each directive acceleration of the top five items was compared using two-way ANOVA to examine the effect of movements. The frequency of movements that generated >6 G and >8 G acceleration during junior football games was 8.70 case/min and 2.62 case/min, respectively. The top five >8 G movements were braking and pre-braking in shuffle, slowdown, stop, and run/jog items. The vertical acceleration was significantly greater during braking in shuffle than during slowdown, stop, and run/jog and also greater during stop and pre-braking in shuffle than during run/jog movement. This pilot study suggests that decelerated movements mainly provoked high-impact situations and may be key actions for preventing overuse injury in young footballers.

 

 

#13 No Fans-No Pressure: Referees in Professional Football During the COVID-19 Pandemic

Reference: Front Sports Act Living. 2021 Aug 19;3:720488. doi: 10.3389/fspor.2021.720488. eCollection 2021.

Authors: Michael Christian Leitner, Fabio Richlan 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8416626/pdf/fspor-03-720488.pdf

Summary: Due to the COVID-19 pandemic, European elite football (a.k.a. soccer) leagues played the remaining season 2019/20 without or strongly limited attendance of supporters (i.e., "ghost games"). From a sport psychological perspective this situation poses a unique opportunity to investigate the crowd's influence on referee decisions and the associated effect of "home advantage." A total of 1286 matches-played in the top leagues of Spain, England, Germany, Italy, Russia, Turkey, Austria and the Czech Republic-were analyzed for results, fouls, bookings and reasons for bookings and contrasted between respective matchdays of season 2018/19 (regular attendance) and season 2019/20 (ghost games). Following recent methodological developments in the research on the home advantage effect, four different statistical analyses-including Pollard's traditional method-were used for the assessment of the home advantage effect. There are two main findings. First, home teams were booked significantly more often with yellow cards for committing fouls in ghost games. Most importantly, this effect was independent of the course of the games. In contrast, bookings for other reasons (criticism and unfair sportsmanship) changed similarly for both home and away teams in ghost games. Second, the overall home performance and home advantage effect in the respective elite leagues-identified in the respective matches of the regular 2018/19 season-vanished in the ghost games of the 2019/20 season. We conclude that the lack of supporters in top European football during the COVID-19 pandemic led to decreased social pressure from the ranks on referees, which also had a potential impact on the home advantage. Referees assessed the play of home teams more objectively, leading to increased yellow cards awarded for fouls committed by the home teams. Since there were no significant changes in referee decisions against the away teams, we argue that our observations reflect a reduction of unconscious favoritism of referees for the home teams.

 

 

#14 Perceived load, fatigue and recovery responses during congested and non-congested micro-cycles in international football tournaments

Reference: J Sci Med Sport. 2021 Jul 9;S1440-2440(21)00177-8.  doi: 10.1016/j.jsams.2021.07.001. 

Authors: Denny Noor, Alan McCall, Mark Jones, Craig Duncan, Fabian Ehrmann, Tim Meyer, Rob Duffield

Summary: The aim was to describe the perceived load, fatigue and recovery profiles during congested and non-congested schedules in international football tournaments. Internal load (session-rating of perceived exertion [s-RPE]) and perceived ratings of fatigue, muscle soreness, psychological status, sleep quality, and sleep duration were recorded daily from 37 national team footballers during the competition phase of 3 international tournaments. ANOVA and Effect Size (ES) analyses compared individualised internal load and perceived response profiles between congested and non-congested acute 2-match schedules. Conditions included Acute Congestion (≤4 days between two matches), Non-Congestion (>4 days between two matches), Single-Match, and No-Match. Significantly higher s-RPE match loads (p < 0.001) within the single- and multi-match conditions resulted in significantly worsened (p < 0.05) subjective ratings of perceived fatigue, muscle soreness and sleep duration in the 24-48 h post-match. Internal load profiles were not different between the Acute-Congestion or Non-congestion conditions (p > 0.05); though Acute-Congestion had significantly worsened pre-match subjective ratings compared to Non-Congestion on both MD1 (p = 0.040; ES = 0.94) and MD2 (p = 0.033; ES = 0.94). However, between-match differences in Acute-Congestion showed no further impairments in perceived response between the first and second matches (p > 0.05). During international tournaments, internal load and perceived fatigue/recovery profiles are largely determined by their exposure (or lack thereof) to match-play. Periods of acute match congestion impaired players pre-match perceived status when compared to non-congested microcycles. However, acute match congestion does not appear to exacerbate players post-match fatigue/recovery response within the context of international football tournaments.

 

 

#15 The effect of the adapted soccer programme on motor learning and psychosocial behaviour in adolescents with Down syndrome

Reference: J Intellect Disabil Res. 2021 Sep 9. doi: 10.1111/jir.12881. Online ahead of print.

Authors: D B Perić, B Milićević-Marinković, D Djurović

Summary: Numerous studies have proven the significant positive impact of the regular physical activity on general health conditions and quality of life of people with intellectual disability. In practice, various adapted sports activities are used. The current study deals with the effects of the soccer programme. The purpose of the study is to evaluate the effects of adapted soccer on the motor learning and some psychosocial characteristics in adolescents with Down syndrome. Twenty-five participants were recruited and randomised into two groups (exercise and control). Adolescents placed in the exercise group carried out a special soccer programme twice a week during 16 weeks, while adolescents placed in the control group continued with their usual daily regime. Specific motor coordination, level of aggression, attention disorders, level of anxiety and depression, and social problems were measured before and after the training period. Mixed ANOVA were used to evaluate the effects of the experimental treatment. The exercise group had significant improvements (P < 0.05) in one of three motor variables (only in the easiest task) and in all psychosocial variables. There are no one significant change in the control group. The adapted soccer programme influenced more seriously on psychosocial characteristics than on motor learning of adolescent with DS. The results suggest that adapted soccer training can decrease aggression, anxiety and depression levels, and improve attention, social behaviour and simple motor skills in adolescents with Down syndrome.

 

 

#16  Ankle Injuries in Soccer Players: A Narrative Review

Reference: Cureus. 2021 Aug 16;13(8):e17228. doi: 10.7759/cureus.17228. eCollection 2021 Aug.

Authors: Spyridon Kolokotsios, Gianna Drousia, Ioannis Koukoulithras, Minas Plexousakis

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8445148/pdf/cureus-0013-00000017228.pdf

Summary: Soccer is one of the most popular sport, with many describing it as the "king of sports." In recent years, increased global participation in soccer has led to an inevitable increase in injury rates, especially in the lower extremities. Consequently, there is an increase in the epidemiology of soccer injuries, both in professionals and amateur athletes. The cause of an injury is multifactorial and depends on psychosocial, predisposing, intrinsic, and extrinsic factors. Also, contact with another player and non-contact injuries seem to be the most widespread mechanisms of injuries. The most common injuries recorded in soccer are ankle sprains and hamstrings injuries. More specifically, many studies have shown a correlation between the previous injury in lower extremities, weakness of abductors muscle, and psychosocial factors with the ankle sprain. Additionally, according to study results, injuries in adult men, adolescent men, and women during a match are higher than injuries during training. This narrative review aims to record the epidemiology of ankle injuries, risk factors, and the relationship between circadian rhythm, sleep, and injuries.

 

 

#17 Ball heading and subclinical concussion in soccer as a risk factor for anterior cruciate ligament injury

Reference: J Orthop Surg Res. 2021 Sep 19;16(1):566.: 10.1186/s13018-021-02711-z.

Authors: George Kakavas, Nikolaos Malliaropoulos, Wieslaw Blach, Georgios Bikos, Filippo Migliorini, Nicola Maffulli 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8451147/pdf/13018_2021_Article_2711.pdf

Summary: Soccer players have a high risk of anterior cruciate ligament (ACL) injury, a potentially career-ending event. ACL rupture has been linked with abnormal neuromuscular control in the lower limb. Additionally, heading the ball with the unprotected head during game play is increasingly recognized as a major source of exposure to concussive and sub-concussive repetitive head impacts. This article provides a hypothesis of potential connection of ACL injury with ball heading in soccer players. The study reviews literature sources regarding the impact of neurocognitive alterations after ball headings in ACL injuries. Poor baseline neurocognitive performance or impairments in neurocognitive performance via sleep deprivation, psychological stress, or concussion can increase the risk for subsequent musculoskeletal injury.

 

 

#18 The LEAF questionnaire is a good screening tool for the identification of the Female Athlete Triad/Relative Energy Deficiency in Sport among young football players

Reference: PeerJ. 2021 Sep 3;9:e12118.  doi: 10.7717/peerj.12118. eCollection 2021.

Authors: Edyta Łuszczki, Pawel Jagielski, Anna Bartosiewicz, Maciej Kuchciak, Katarzyna Dereń, Artur Stolarczyk, Paweł Pakosz, Lukasz Oleksy

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8420870/pdf/peerj-09-12118.pdf

Summary: It has been noticed that Female Athlete Triad (Fat) and Relative Energy Deficiency (Red-S) in Sport are characterized by the symptoms of impaired endocrine-metabolic function and bone health in female athletes. In addition, it may be evaluated with a qualitative tool, such as Low Energy Availability in Females questionnaire (LEAF-Q) and quantitative measurements: bone mineral density (BMD), resting energy expenditure (REE), body composition, 24-hour dietary recall. The aim of this study was to assess the prevalence of Triad and Red-S using the LEAF-Q in youth female football players. Additionally, the difference in the BMD, body composition, REE and energy intake (EI) were assessed between the Triad/Red-S risk and not at-risk groups. Almost two thirds (64.7%) of participants are classified as being at-risk for the triad according to their LEAF-Q scores. There were no statistically significant differences (p > 0.05) between most of the values among children from the analyzed groups. There was a statistically significant difference (p < 0.001) between the EI values among girls from the two analyzed groups: at-risk (1,773.18 kcal ± 232.57) and not at-risk (2,054.00 kcal ± 191.39). Girls who did not meet the energy intake recommendations were 10.00 as likely to be in the Triad/Red-S risk group. Early identification of Fat/Red-S symptoms by screening tools such as the LEAF questionnaire is important in protecting young athletes from long-term damage due to the progression of the risk factors associated with the Fat/Red-S.

 

 

#19 Perceptions of Football Analysts Goal-Scoring Opportunity Predictions: A Qualitative Case Study

Reference: Front Psychol. 2021 Sep 6;12:735167. doi: 10.3389/fpsyg.2021.735167. eCollection 2021.

Authors: Rubén D Aguado-Méndez, José Antonio González-Jurado, Álvaro Reina-Gómez, Fernando Manuel Otero-Saborido

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8450592/pdf/fpsyg-12-735167.pdf

Summary: This study aimed to understand the way tactical football analysts perceive the general match analysis issues and to analyze their tactical interpretation of the predictive models of conceded goal-scoring opportunities. Nine tactical analysts responded to the semi-structured interviews that included a general section on the match analysis and a specific one on the results of a study on goal-scoring opportunities conceded by a Spanish La Liga team. Following their transcription, the interviews were codified into categories by the two researchers using Atlas Ti® software. Subsequently, frequency count and co-occurrence analysis were performed based on the encodings. The content analysis reflected that analysts play a crucial role in the analysis of their own team and that of the opponent, the essential skills to exercise as a tactical analyst being "understanding of the game" and "clear observation methodology." Based on the case study of the conceded goal-scoring opportunities, the major causes and/or solutions attributed by analysts in some of the predictive models were the adaptability of the "style of play" itself according to the "opponent" and "pressure after losing."

 

 

#20 Shedding Light on Incidence and Burden of Physeal Injuries in Youth Elite Football Academy: A 4-Season Prospective Study

Reference: Scand J Med Sci Sports. 2021 Sep 22.  doi: 10.1111/sms.14059. Online ahead of print.

Authors: Olivier Materne, Karim Chamari, Abdulaziz Farooq, Montassar Tabben, Adam Weir, Per Holmich, Roald Bahr, Matt Greig, Lars R McNaughton

Summary: Physeal injuries have been overlooked in epidemiological research in youth sports. Our prospective study investigated the incidence, severity, and burden of physeal injuries in a youth elite football academy. 551 youth male football players from Under-9 to Under-19 were included and observed over four consecutive seasons. Injuries involving the physis were diagnosed and recorded according to type, location, and diagnosis. Injury incidence (II), severity (days lost), and injury burden (IB) were calculated per squad per season (25 players/squad). There were 307 physeal injuries: 262 apophyseal- (85%), 26 physeal- (9%), 2 epiphyseal- (1%) and 17 other physeal-injuries (5%) with 80% (n=245) causing time-loss. The overall mean incidence of time-loss physeal injuries was 6 injuries/squad-season leading to a total of 157 days lost/squad-season. The U-16s had the highest burden with 444 days lost per squad-season [Median: 20 (95%CI:12-30) days; II: 10 (95%CI:7.3.1-13.4)]. Apophyseal injuries of the hip-pelvis resulted in the greatest burden [Median: 13 (95%CI: 10-17); II: 2.5 (95%CI: 2.1-3.0)]. Peak apophyseal injury incidence per body parts occurred in U-11 for foot-ankle (II: 2.4; 95% CI: 1.0-4.9), U-14 for knee (II: 4.5; 95% CI: 2.7-7.1), and in U-17 for hip-pelvis (II: 6.4; 95% CI: 4.2-9.3). Physeal injuries accounted for a quarter of all-time loss with the largest injury burden in U-16. Most physeal injuries involved the lower limb and affected the apophysis. Physeal and apophyseal injuries incidence, burden and pattern vary substantially depending on age. Hip-pelvic apophyseal injuries accounted for the largest injury burden.

 

 

#21 Integrating video tracking and GPS to quantify accelerations and decelerations in elite soccer

Reference: Sci Rep. 2021 Sep 17;11(1):18531. doi: 10.1038/s41598-021-97903-2.

Authors: Eduard Pons, Tomás García-Calvo, Francesc Cos, Ricardo Resta, Hugo Blanco, Roberto López Del Campo, Jesús Díaz-García, Juan José Pulido-González

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8448836/pdf/41598_2021_Article_97903.pdf

Summary: The aim of this study was to analyze the degree of agreement comparing number and distance covered in different acceleration and deceleration sections registered by a video tracking system (MEDIACOACH) and a GPS device (WIMU PRO) during official competition. Data from a Spanish professional club were registered over the course of a season. First, the descriptive statistics presented more bursts of accelerations and decelerations in WIMU PRO than in MEDIACOACH, whereas the distances covered recorded by both systems were similar. Second, negative relationships were found (i.e., negative bias) comparing WIMU PRO to MEDIACOACH in the number of accelerations and decelerations between 0/1 m/s2 and ½ m/s2 (p < 0.05), and in the distances covered in accelerations and decelerations (p < 0.05) between 0/1 m/s2 and in accelerations and decelerations registered between 2/3 m/s2 and more than 3 m/s2. Moreover, the differences in means (i.e., standardized mean bias) across the two devices were trivial (> 0.19) and small (0.2-0.59) for most variables. The standardized typical errors in the estimate (TEE) were moderate (0.3-0.59) and small to moderate (0.1-0.29 to 0.3-0.59), respectively. Also, the Intra class Correlation Coefficients (ICCs) for agreement and consistency between systems showed good and excellent values (> 0.90). The magnitude of change in means (%) between systems, defined as the percentage change between the numbers or values, was below 14% and 7% for number and distances covered, respectively. All scores in the smallest worthwhile change were lower than 9% and in the coefficients of variation were lower than 95% and 15%, respectively. Thus, both systems demonstrated an acceptable degree of agreement and could be useful in analyzing players' acceleration demands in professional soccer. However, caution is required when interpreting the results and a comparison with a gold standard is required in order to validate both systems.

 

 

#22 Effect of bio-banding on physiological and technical-tactical key performance indicators in youth elite soccer

Reference: Eur J Sport Sci. 2021 Sep 19;1-9. doi: 10.1080/17461391.2021.1974100. Online ahead of print.

Authors: Dennis Lüdin, Lars Donath, Stephen Cobley, Michael Romann

Summary: Bio-banding has been introduced to reduce the impact of inter-individual differences due to biological maturation among youth athletes. Existing studies in youth soccer have generally examined the pilot-testing application of bio-banding. This is the first study that investigated whether bio-banded (BB) versus chronological age (CA) competition affects reliable physiological and technical-tactical in-game key performance indicators (KPIs) using a randomized cross-over repeated measures design. Sixty-five youth elite soccer players from the under-13 (U13) and under-14 (U14) age category and with maturity offsets (MO) between -2.5 and 0.5 years, competed in both a BB and CA game. For statistical analysis, players were divided into four sub-groups according to CA and MO: U13MOlow (CA ≤ 12.7, MO ≤ -1.4), U13MOhigh (CA ≤ 12.7, MO > -1.4), U14MOlow (CA > 12.7, MO ≤ -1.4), U14MOhigh (CA > 12.7, MO > -1.4). The two-factor mixed ANOVA revealed significant (p < .05) interactions between competition format and sub-group for the KPIs high accelerations (η2pηp2 = .176), conquered balls (η2pηp2 = .227) and attack balls (η2pηp2 = .146). Especially, U13MOhigh (i.e. early maturing players) faced a higher physiological challenge by having more high accelerations (|d| = 0.6) in BB games. Notably, U14MOlow (i.e. late maturing players) had more opportunities to show their technical-tactical abilities during BB games with more conquered balls (|d| = 1.1) and attack balls (|d| = 1.6). Affected KPIs indicate new challenges and learning opportunities during BB competition depending on a player's individual maturity status. Bio-banding can beneficially be applied to enhance the talent development of youth elite soccer players.

 

 

#23 Comparison of Immediate Effects of Foam Rolling and Dynamic Stretching to Only Dynamic Stretching on Flexibility, Balance, and Agility in Male Soccer Players

Reference: J Sport Rehabil. 2021 Sep 20;1-7. doi: 10.1123/jsr.2021-0017. Online ahead of print.

Authors: Erhan Seçer, Derya Özer Kaya

Summary: Dynamic stretching (DS) is typically suggested during warm-up protocols. Also, foam rolling (FR), which is applied with a foam cylinder, has increased popularity in recent years. However, the combined effects of DS and FR in improving flexibility, dynamic balance, and agility performance are unclear in current literature. Therefore, this study aim to evaluate and compare the acute effects of DS as well as DS followed by FR (DS + FR) on flexibility, dynamic balance, and agility in male soccer players. Thirty volunteer male soccer players (mean age 18.80 [0.66] y) were included in the study. Each participant performed the 2 sessions (DS and DS + FR) on separate occasions in a randomized order, with an interval of 72 hours. All sessions were performed in the indoor gym at the sports club. Flexibility was assessed by sit-and-reach test, dynamic balance was assessed by Y balance test, and agility was assessed by t test. Compared with the pretest results, significant improvement in flexibility was observed in both groups (change = 0.55, percentage change = 2.05, effect size [ES] = 0.15, P = .041; change = 0.64, percentage change = 2.36, ES = 0.20, P = .025; respectively). Balance scores did not significantly improve in either group (change = 0.40, percentage change = 0.45, ES = 0.09, P = .342; change = 0.93, percentage change = 1.02, ES = 0.23, P = .103; respectively). Agility performance significantly improved in both groups (change = -0.12, percentage change = -1.18, ES = 0.19, P = .021; change = -0.21, percentage change = -2.18, ES = 0.38, P = .005; respectively). Both DS and DS + FR improved flexibility and agility and did not affect balance. DS + FR was not superior to DS at improving flexibility and agility as compared only with DS. Both methods are effective warm-up protocols to augment factors related to injury risk and performance. It seems that further studies that investigate the combined effects of FR and DS are needed.

 

 

#24 Impact of COVID-19 lockdown on the epidemiology of soccer muscle injuries in Italian Serie A professional football players

Reference: J Sports Med Phys Fitness. 2021 Sep 21. doi: 10.23736/S0022-4707.21.12903-2. Online ahead of print.

Authors: Nicola Marotta, Alessandro DE Sire, Alessandra Gimigliano, Andrea Demeco, Lucrezia Moggio, Andrea Vescio, Teresa Iona, Antonio Ammendolia

Summary: The aim was to evaluate the influence that COVID-19 lockdown had on the epidemiology of soccer musculoskeletal injuries during 2019/2020 Italian First Football League Serie A in professional football players. In this retrospective study we analyzed records from media-based platform (Trasfermarkt, https://www.transfermarkt.com), describing the epidemiology of muscle injuries before and after the first COVID-19 lockdown phases in Italian professional football players. We also classified the severity of the injury as the number of missing days from participation. We assessed a lower prevalence of post-lockdown injuries, albeit showing a similar injury rate at 1000 game-hours (pre-lockdown: 16.9 [13.0-20.7], post-lockdown: 15.5 [9.9-21.1]; RR: 0.92 [0.46-1.8]). All risk ratios for injury rate were not significantly different (p> .05) between pre- and post-lockdown. The incidence of muscle injuries has not significantly changed after the first COVID-19 lockdown in Italian professional soccer players. Recognizing injury rates might be crucial for physician to evaluate adequate preventive measures.

 

 

#25 Association of phase angle and appendicular upper and lower body lean soft tissue with physical performance in young elite soccer players: a pilot study

Reference: J Sports Med Phys Fitness. 2021 Sep 21. doi: 10.23736/S0022-4707.21.12911-1. Online ahead of print.

Authors: Tindaro Bongiovanni, Alessio Rossi, F Marcello Iaia, Giampietro Alberti, Giulio Pasta, Athos Trecroci

Summary: In soccer, a better understanding of the bioimpedance parameters with physical performance may be useful to efficiently monitor and interpret players' performance variation throughout a certain period of the season. Therefore, this study aimed to examine the association between phase angle (PhA) and arms and legs lean soft tissue (ALST and LLST) with physical performance in young elite soccer players. Fifteen young male elite soccer players (age = 14.2±1.2 years, BMI = 20.51±1.38 kg/m2) participated in this investigation. Raw bioimpedance parameters (reactance, resistance, and phase angle) were obtained by a bioelectrical impedance analysis (BIA) device. Then, ALST and LLST were estimated. All players underwent a physical testing battery including countermovement jump (CMJ), 10-m and 20-m sprint, and Yo-Yo Intermittent Recovery Test level 1 (YoYo IRTL1) in the domains of anaerobic and aerobic performance, respectively. The results showed that LST (total, arms and legs) positively correlated with CMJ (0.64 < r < 0.69; p < 0.001) and negatively correlated with 10-m (-0.59 < r < -0.63; p < 0.05) and 20-m sprint (-0.67 < r < -0.73; p < 0.001), while PhA positively correlated with CMJ (r = 0.57; p < 0.05) and negatively correlated (r = -0.54; p < 0.05) only with 20-m sprint. No significant association was found between the BIA-related parameters (PhA and LST) and Yo- Yo IRT level 1. The present findings highlight the existing association of PhA and LST with jumping and sprinting performance in young elite soccer players. This result supports the use of BIA-related measures as a simple and practical approach to monitoring anaerobic performance changes, rather than aerobic, over time throughout the season.

 

 

#26 Predicting Cardiorespiratory Fitness in Female Soccer Players: The Basque Female Football Cohort Study

Reference: Int J Sports Physiol Perform. 2021 Sep 21;1-8. doi: 10.1123/ijspp.2020-0848. Online ahead of print.

Authors: Ibai Garcia-Tabar, Aitor Iturricastillo, Julen Castellano, Eduardo L Cadore, Mikel Izquierdo, Igor Setuain

Summary: The purpose was to develop gender-specific operational equations for prediction of cardiorespiratory fitness in female footballers. Forty-eight semiprofessional female footballers performed an intermittent progressive maximal running test for determination of fixed blood lactate concentration (FBLC) thresholds. Relationships between FBLC thresholds and the physiological responses to submaximal running were examined. Developed equations (n = 48) were compared with equations previously obtained in another investigation performed in males (n = 100). Submaximal velocity associated with 90% maximal heart rate was related to FBLC thresholds (r = .76 to .79; P < .001). Predictive power (R2 = .82 to .94) of a single blood lactate concentration (BLC) sample measured at 10 or 11.5 km·h-1 was very high. A single BLC sample taken after a 5-minute running bout at 8.5 km·h-1 was related to FBLC thresholds (r = -.71; P < .001). No difference (P = .15) in the regression lines predicting FBLC thresholds from velocity associated with 90% maximal heart rate was observed between the female and male cohorts. However, regressions estimating FBLC thresholds by a single BLC sample were different (P = .002). Velocity associated with 90% maximal heart rate was robustly related to FBLC thresholds and might serve for mass field testing independently of sex. BLC equations accurately predicted FBLC thresholds. However, these equations are gender-specific. This is the first study reporting operational equations to estimate the FBLC thresholds in female footballers. The use of these equations reduces the burden associated with cardiorespiratory testing. Further cross-validation studies are warranted to validate the proposed equations and establish them for mass field testing.

 

 

#26 Endoscopic Flexor Hallucis Longus Transfer for the Management of Acute Achilles Tendon Ruptures in Professional Soccer Players Foot

Reference: Ankle Int. 2021 Sep 24;10711007211036439.  doi: 10.1177/10711007211036439. Online ahead of print.

Authors: Nasef Mohamed N Abdelatif, Jorge Pablo Batista 

Summary: Acute Achilles tendon ruptures (AATRs) that occur in athletes can be a career-ending injury. The aim of this study was to describe return to play and clinical outcomes of isolated endoscopic flexor hallucis longus (FHL) transfer in active soccer players with AATR. Twenty-seven active male soccer players who underwent endoscopically assisted FHL tendon transfer for acute Achilles tendon ruptures were included in this study. Follow up was 46.2 (±10.9) months after surgery. Return to play criteria and clinical outcome measures were evaluated. All players returned to playing professional competitive soccer games. Return to active team training was at a mean of 5.8 (±1.1) months postoperatively. However, return to active competitive match play occurred at a mean of 8.3 (±1.4) months. Twenty-two players (82%) were able to return to their preinjury levels and performances and resumed their professional careers at the same soccer club as their preinjury state. One player (3.7%) shifted his career to professional indoor soccer. At 26 months postoperatively, the mean Tegner activity scale score was 9.7 (±0.4), the mean Achilles tendon total rupture score was 99 (±2), and the mean American Orthopaedic Foot & Ankle Society ankle-hindfoot score was 99 (±3). No patients reported any great toe complaints or symptomatic deficits of flexion strength. The current study demonstrated satisfactory and comparable return to play criteria and clinical results with minimal complications when using an advanced endoscopically assisted technique involving FHL tendon transfer to treat acute Achilles tendon ruptures in this specific subset of patient cohort.

 

 

#27 Strength training in professional soccer: effects on short-sprint and jump performance

Reference: Int J Sports Med. 2021 Sep 24. doi: 10.1055/a-1653-7350. Online ahead of print.

Authors: Javier Nuñez, Luis Suarez-Arrones, Moisés de Hoyo, Irineu Loturco

Summary: Several studies have confirmed the efficacy of strength training to maximize soccer player performance during competition. The aim of this meta-analysis was to determine the effects of different strength training protocols on short-sprint and vertical jump performance of professional soccer players from the first division of their countries. The following inclusion criteria were employed for the analysis: (a) randomized studies; (b) high validity and reliability instruments; (c) studies published in a high-quality peer-reviewed journal; (d) studies involving professional soccer players from the first division; (e) studies with descriptions of strength training programs; and (f) studies where countermovement jump and 10-m sprint time were measured pre and post training. Overall, the different strength-oriented training schemes produced similar performance improvements, which seem not to depend on the training strategy. Strength training appears to have a lower effect when applied during in-season than when applied in pre-season periods in first division soccer players. In this meta-analysis it is not possible to confirm that strength training in isolation is capable of improving the short-sprint and jump performance of elite soccer players. The congested fixture schedule and, thus, the limited time to perform complementary (non-specific) training sessions, may contribute to these reduced effects.

 

 

Thu

13

Jan

2022

Influence of the Area per Player in Non-Professional Footballers: A Pilot Study Focused on Positional Roles

This study analyses the influence of different area per player on the average metabolic power (MP) and other soccer-related performance variables in relation to the positional roles.

Wed

12

Jan

2022

Running Performance of Footballers Induces Muscle Damage and Fatigue Up to 24 h Postgame

This study aimed to determine the impact of a soccer game on the creatine kinase (Ck) response and recovery and the specific Global Positioning System (GPS)-accelerometry-derived performance analysis during matches and comparing playing positions.

Sat

08

Jan

2022

Latest research in football - week 44 - 2021

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 High-Intensity Intermittent Exercise Performed on the Sand Induces Higher Internal Load Demands in Soccer Players

Reference: Front Psychol. 2021 Jul 30;12:713106. doi: 10.3389/fpsyg.2021.713106. eCollection 2021.

Authors: Tiago Cetolin, Anderson Santiago Teixeira, Juliano Fernandes da Silva, Alessandro Haupenthal, Fábio Yuzo Nakamura, Carlo Castagna, Luiz Guilherme Antonacci Guglielmo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8360849/pdf/fpsyg-12-713106.pdf

Summary: This study aimed to examine the acute physiological effect of shuttle-run-based high-intensity intermittent exercise (HIIE) performed at the same relative speed (i. e., 100% PST-CAR) on sand (SAND) and grass (GRASS) in male junior soccer players. Seven Under-23 Brazilian national league ("Série A") soccer players completed four testing sessions in either SAND or GRASS surface condition. The first two testing sessions consisted of performing a maximal progressive shuttle-run field protocol until volitional exhaustion (Carminatti's test, T-CAR), whereas the third and fourth sessions comprised a HIIE session on each ground surface. The HIIE session consisted of three 5-min bouts [12 s shuttle-run (with a direction change every 6 s)/12 s of passive rest] performed at 100% of T-CAR peak speed (PST-CAR) with 3 min of passive recovery between sets. Measurements of oxygen uptake (VO2), heart rate (HR), blood lactate concentration ([La]), and rating of perceived exertion (RPE) were performed during all conditions. The SAND condition elicited significantly higher %VO2peak (94.58 ± 2.73 vs. 87.45 ± 3.31%, p < 0.001, d = 2.35), %HRpeak (93.89 ± 2.63 vs. 90.31 ± 2.87%, p < 0.001, d = 1.30), RPE (8.00 ± 0.91 vs. 4.95 ± 1.23 a.u., p < 0.001, d = 2.82), and [La] (10.76 ± 2.37 vs. 5.48 ± 1.13 mmol/L, p < 0.010, d = 2.84). This study showed that higher internal workloads are experienced by the players during a single HIIE session performed on a softer surface as SAND, even when the exercise intensity was individualized based on 100%PST-CAR.

 

 

#2 Assessing Inter-Limb Asymmetries in Soccer Players: Magnitude, Direction and Association with Performance

Reference: J Hum Kinet. 2021 Jul 28;79:41-53. doi: 10.2478/hukin-2021-0081. eCollection 2021 Jul.

Authors: Marc Madruga-Parera, Thomas Dos'Santos, Chris Bishop, Anthony Turner, David Blanco, Vicente Beltran-Garrido, Victor Moreno-Pérez, Daniel Romero-Rodríguez

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336558/pdf/hukin-79-041.pdf

Summary: In this study, we aimed to analyze the magnitude and direction of inter-limb asymmetries in ankle dorsiflexion range of motion (ROM), power (using iso-inertial devices), and a neuromuscular skill (change of direction). Secondarily, we aimed to determine the relationship between inter-limb asymmetry scores for each test and also between these scores and the scores for the different performance tests. Sixteen semiprofessional male soccer players (age: 25.38 ± 6.08 years; body height: 1.78 ± 0.64 m; body mass: 79.5 ± 14.9 kg) participated in this study. We calculated inter-limb asymmetries using five tests: ankle dorsiflexion ROM, change of direction (COD 180º), and iso-inertial resistance tasks in the open (leg extension strength (LE), leg curl strength (LC)) and closed (crossover step (CRO)) kinetic chain. Our results showed that asymmetry magnitudes differed between all tests with highest inter-limb asymmetries displayed during iso-inertial overloading. In addition, we observed that the direction of asymmetries varied depending on the test-specificity, and that the CRO asymmetries had a negative association with LE and CRO performance. These findings highlight the independent nature of asymmetries and that CRO could be an appropriate test to detect asymmetries related with the performance of soccer-specific actions (such as changes of direction). Practitioners are encouraged to use multiple tests to detect existing inter-limb differences according to the specific characteristics of each sport.

 

 

#3 The Relationship Between Performance and Asymmetries in Different Multidirectional Sprint Tests in Soccer Players

Reference: J Hum Kinet. 2021 Jul 28;79:155-164. doi: 10.2478/hukin-2021-0069. eCollection 2021 Jul.

Authors: Alberto Fílter, Vicente Beltrán-Garrido, Thomas Dos'Santos, Daniel Romero-Rodríguez, Bernardo Requena, Irineu Loturco, Marc Madruga-Parera

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336547/pdf/hukin-79-155.pdf

Summary: Practitioners usually include change of direction (COD) and linear speed measurements in the testing batteries of soccer players; however, despite being a commonly occurring action, curve sprint (CS) ability is rarely assessed in soccer. The aims of this study were to analyze the association between linear sprint, CS, and COD speed performances, and compare the association and direction of asymmetries between these skills. Thirty-three male soccer players performed linear sprint (17 m), CS (17 m), and COD-90⍛ speed tests (COD [8.5 + 8.5 m]). Our main findings were (a) a large relationship between linear and multidirectional tasks (COD-90⍛ and CS tests) (r = from 0.6 to 0.64, p < 0.05), (b) a moderate relationship between CS and COD-90⍛ tests (r = from 0.33 to 0.41, p < 0.05), with a certain opposite tendency (higher relationships between opposing directions [CurveLEFT - CODRIGHT; r = 0.41] than between equal directions [CurveLEFT - CODLEFT; r = 0.33]), and (c) no relationship (p > 0.05) between COD and CS asymmetries, with opposing directional dominance in ~70% of players (e.g., curve left and COD right dominance). These results indicate that performance in linear sprints is strongly related to performance in multidirectional trajectories, whereas CS and COD-90⍛ seem to be more independent actions. Additionally, the direction of asymmetry or dominance is generally opposite between the non-linear tasks measured.

 

 

#4 The effect of core stability-based corrective exercises on gait parameters in elite soccer players diagnosed with Middle Crossed Syndrome

Reference: J Bodyw Mov Ther. 2021 Jul;27:620-627. doi: 10.1016/j.jbmt.2021.04.016. Epub 2021 Apr 24.

Authors: Nima Nakisa, Mahboobeh Ghasemzadeh Rahbardar, Yahya Sokhangouei, Zohreh Afsharmand

Summary: The aim of this study was to investigate the effect of eight weeks of core stability-based corrective exercises, on gait parameters in elite soccer players diagnosed with middle crossed syndrome. 15 male elite soccer players (aged 18-28) were enrolled in a same-subject intervention trial to assess if the middle crossed syndrome could be influenced through core stability exercise. Core stability-based corrective exercises were completed 3 times per week for 8 weeks and changes in gait parameters (pre- and post- intervention) were measured. The results showed that most gait parameters including stride length (p = 0.025), gait speed (p = 0.023), number of strides (p = 0.007), length of shots (p = 0.003), and also soccer players' height (p = 0.011) improved significantly in post-intervention in comparison to pre-intervention. Stride width in post-intervention did not show changes in comparison with pre-intervention (p = 0.083). The results indicate the significant effectiveness of core stability-based corrective exercises on gait parameters in those with middle crossed syndrome. By doing corrective exercises based on core stability during the study period, gait parameters in the post-intervention surpass the results in the pre-intervention in most parameters. Therefore, it is proposed that corrective exercises based on core stability is a safe and useful method for improving function in those with middle crossed syndrome and it could be used as a therapy to help players identified with this finding. In this regard, it is suggested to researchers and coaches to correct imbalances in order to achieve better results in training programs.

 

 

#5 Kinesiotape on quadriceps and gluteus in counter movement jump and sprint in soccer players

Reference: J Bodyw Mov Ther. 2021 Jul;27:42-47.  doi: 10.1016/j.jbmt.2021.02.021. Epub 2021 Mar 4.

Authors: J Reina Abellán, Juan L Yuste, O Mora Cabrera, C Gómez-Tomás

Summary: Kinesiotape (KT) is a technique commonly used in sports practice. It may be beneficial in enhancing muscle function by additional cutaneous afferent stimulation. The objective of this study was to analyse the effect of KT on countermovement jump (CMJ) and 20-m sprints (sp) immediately and 24 h after its application on the quadriceps and gluteus maximus. 37 male soccer players (19.7 ± 0.9 years old) were randomly assigned to one of 3 groups: experimental group: KT activation (KTact), placebo group: sham tape (KTst), and control group (CG). Participants performed a 30-min preliminary warm-up, after which they conducted CMJ and 20-m sp tests. These tests were repeated later (with KT application or not) and after 24 h. Intergroup results found no significant differences either post-test (CMJ, p = 0.115; sp, p = 0.307) or after 24 h (p = 0.053). Intragroup results showed no significant results for CMJ, although 20-m sp seemed to display significant differences in the (KTst) (p = 0.002, post-hoc: 0.015 in pre_sp vs post_sp) and the (KTact) (0.021, in post-hoc: 0.007 in pre_sp vs post_sp), with a moderate effect in pre_sp vs post_sp (0.66) in the (KTact) after KT was applied. KT application on the gluteus maximus and quadriceps in young soccer players increases the sprint execution time immediately and 24 h after application, even that the sprint execution time had not been grater that one tenth of the second (0.08 s). It also has no effect on CMJ.

 

 

#6 Fascial therapy, strength exercises and taping in soccer players with recurrent ankle sprains: A randomized controlled trial

Reference: J Bodyw Mov Ther. 2021 Jul;27:256-264. doi: 10.1016/j.jbmt.2021.03.022. Epub 2021 Apr 2.

Authors: Ruben Allois, Adriano Niglia, Alessandro Pernice, Rubén Cuesta-Barriuso

Summary: Recurrent ankle sprains are common in soccer players, characterized by restricted range of motion, pain, and decreased proprioception, strength, and postural control. The objective was to evaluate the effectiveness of a fascial therapy and strength training program, combined with kinesiotaping, in improving ankle range of motion, pain, strength and stability in footballers with recurrent sprains. A simple blind randomized clinical trial was conducted on soccer players. Thirty-six federated footballers were recruited and randomized to the two study groups. The experimental group received an intervention using myofascial techniques applied to the subastragaline joint, eccentric training with an isoinertial device and neuromuscular taping. The control group was administered an intervention using myofascial techniques on the subastragaline joint and eccentric training with an isoinertial device. The results were recorded for all players at baseline, after 4 weeks of intervention, and at the end of the 4-week follow-up period. Subsequent to intervention and follow-up, we found statistically significant improvements in the experimental group in ankle mobility, strength and stability. The control group exhibited improvements in all study variables. No differences in the improvement of variables were found based on the allocation of athletes to one group or another. The combination of fascial therapy and eccentric strength training with an isoinertial device improves ankle mobility, strength and stability in footballers with recurrent ankle sprains. The use of taping techniques failed to provide a greater improvement of the study variables when combined with manual therapy and strength techniques.

 

 

#7 Scanning activity of elite football players in 11 vs. 11 match play: An eye-tracking analysis on the duration and visual information of scanning

Reference: PLoS One. 2021 Aug 20;16(8):e0244118.  doi: 10.1371/journal.pone.0244118. eCollection 2021.

Authors: Karl Marius Aksum, Lars Brotangen, Christian Thue Bjørndal, Lukas Magnaguagno, Geir Jordet

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8378692/pdf/pone.0244118.pdf

Summary: Visual perception in football ("soccer" in the U.S.) is increasingly becoming a key area of interest for researchers and practitioners. This exploratory case study investigated a sub-set of visual perception, namely visual exploratory scanning. The aim of this study was to examine the scanning of four elite football midfield players in an 11 vs. 11 real-game environment using mobile eye-tracking technology. More specifically, we measured the duration and information (number of teammates and opponents) of the players' scanning behavior. The results showed that the players' scanning duration was influenced by the ball context and the action undertaken with the ball at the moment of scan initiation. Furthermore, fixations were found in only 2.3% of the scans. Additionally, the results revealed that the stop point is the most information-rich part of a scan and that the players had more opponents than teammates inside their video frame during scans. Practical applications and further research recommendations are presented.

 

 

#8 Associations of Vitamin D Levels with Physical Fitness and Motor Performance; A Cross-Sectional Study in Youth Soccer Players from Southern Croatia

Reference: Biology (Basel). 2021 Aug 5;10(8):751. doi: 10.3390/biology10080751.

Authors: Barbara Gilic, Jelena Kosor, David Jimenez-Pavon, Josko Markic, Zeljka Karin, Daniela Supe Domic, Damir Sekulic

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8389772/pdf/biology-10-00751.pdf

Summary: Vitamin D level is known to be a factor potentially influencing physical fitness, but few studies have examined this phenomenon among youth athletes. We aimed to evaluate the associations of vitamin D levels (as measured by 25-hydroxyvitamin D concentrations-25(OH)D) with various physical fitness and motor performance tests in youth football (soccer) players. This cross-sectional study included a total of 52 youth soccer players (15.98 ± 2.26 years old) from Southern Croatia. The participants were evaluated at the end of the winter period and data were collected of anthropometric measures (body mass and body height), vitamin D status (25(OH)D levels), physical fitness tests (sprints of 10 and 20 m, 20 yards test, the countermovement jump, the reactive strength index (RSI)) and motor performance tests (the soccer-specific CODS, the soccer-specific agility, and static balance). Among the studied players, 54% had 25(OH)D insufficiency/deficiency, showing a lack of 25(OH)D is widespread even in youth athletes living at a southern latitude. The 25(OH)D level was correlated with sprint 20 m, 20 yards tests, and RSI, showing a greater role of 25(OH)D in physical fitness tests where energetic capacity is essential than in sport-related motor performance tests where skills are crucial. Our results support the idea that vitamin D can play a determinant role in physical fitness tests with a clear physiological component, but is not crucial in motor performance tests related to specific sports where skills are a key component. Future studies should investigate the effects of vitamin D supplementation on the performance in physical fitness and motor performance tests among youth athletes.

 

 

#9 Quantifying Accelerations and Decelerations in Elite Women Soccer Players during Regular In-Season Training as an Index of Training Load

Reference: Sports (Basel). 2021 Jul 31;9(8):109. doi: 10.3390/sports9080109.

Authors: Tom Douchet, Allex Humbertclaude, Carole Cometti, Christos Paizis, Nicolas Babault

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8402484/pdf/sports-09-00109.pdf

Summary: Accelerations (ACC) and decelerations (DEC) are important and frequent actions in soccer. We aimed to investigate whether ACC and DEC were good indicators of the variation of training loads in elite women soccer players. Changes in the training load were monitored during two different selected weeks (considered a "low week" and a "heavy week") during the in-season. Twelve elite soccer women playing in the French first division wore a 10-Hz Global Positioning System unit recording total distance, distance within speed ranges, sprint number, ACC, DEC, and a heart rate monitor during six soccer training sessions and rated their perceived exertion (RPE). They answered the Hooper questionnaire (sleep, stress, fatigue, DOMS) to get an insight of their subjective fitness level at the start (Hooper S) and at the end of each week (Hooper E). A countermovement jump (CMJ) was also performed once a week. During the heavy week, the training load was significantly greater than the low week when considering number of ACC >2 m·s-2 (28.2 ± 11.9 vs. 56.1 ± 10.1, p < 0.001) and number of DEC < -2 m·s-2 (31.5 ± 13.4 vs. 60.9 ± 14.4, p < 0.001). The mean heart rate percentage (HR%) (p < 0.05), RPE (p < 0.001), and Hooper E (p < 0.001) were significantly greater during the heavy week. ACC and DEC showed significant correlations with most outcomes: HR%, total distance, distance per min, sprint number, Hooper index of Hooper E, DOMS E, Fatigue E, RPE, and session RPE. We concluded that, for elite women soccer players, quantifying ACC and DEC alongside other indicators seemed to be essential for a more complete training load monitoring. Indeed, it could lead to a better understanding of the reasons why athletes get fatigued and give insight into neuromuscular, rather than only energetic, fatigue.

 

 

#10 External and Internal Load Measures During Preseason Training in Men Collegiate Soccer Athletes

Reference: J Strength Cond Res. 2021 Sep 1;35(9):2572-2578. doi: 10.1519/JSC.0000000000004092.

Authors: Jennifer B Fields, Justin M Merigan, Sina Gallo, Jason B White, Margaret T Jones

Summary: Collegiate athletes are exposed to high volume loads during preseason training. Monitoring training load can inform training and recovery periods. Therefore, the purpose was to examine changes in and bidirectional relationship between external and internal load metrics in men collegiate soccer athletes (n = 20; age, 20 ± 1 year). Internal load measures of heart rate variability (HRV), salivary testosterone (T) and cortisol (C), and self-assessment wellness and ratings of perceived exertion scales were collected daily. External load measures of total distance, player load, high-speed distance, high inertial movement analysis, and repeated high-intensity efforts were collected in each training session using global positioning system/global navigation satellite system technology. A 1-way analysis of variance determined weekly changes in external load, physiological, hormonal, and subjective self-assessment measures of internal load. Bidirectional prediction of external load markers and self-assessment measures on physiological and hormonal markers of internal load were assessed by hierarchical linear regression models (p < 0.05). External load measures, C, energy, sleep, and rate of perceived exertion (RPE) decreased (p < 0.01), whereas T, T:C ratio, anger, depression, and vigor increased (p < 0.01) from week 1 to week 2. Morning C positively predicted afternoon external load and post-training RPE (p < 0.05); T:C ratio negatively predicted afternoon external load and post-training RPE (p < 0.05); and morning HRV negatively predicted post-training RPE (p = 0.031). Despite reduced hormonal stress and external load across weeks, negative perceptions of fatigue increased, suggesting fatigue patterns may have a delayed response. Load may have a more belated, chronic effect on perceptions of fatigue, whereas hormonal changes may be more immediate and sensitive to change. Practitioners may wish to use a variety of external and internal load measures to understand athletes' stress responses to training.

 

 

#11 Soccer Scores, Short-Term Mood and Fertility

Reference: Eur J Popul1. 2021 Apr 14;37(3):625-641. doi: 10.1007/s10680-021-09576-2. eCollection 2021 Jul.

Authors: Fabrizio Bernardi, Marco Cozzani

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8333242/pdf/10680_2021_Article_9576.pdf

Summary: Previous research has shown that seemingly irrelevant events such as unexpected outcomes in sporting events can affect mood and have relevant consequences for episodes of crime and violence, investing behavior and political preferences. In this article, we test whether mood shocks associated with unexpected results in soccer matches in Spain affect fertility. We use data on betting odds and actual scores to define mood shocks and link them to births by month and province in Spain, between 2001 and 2015. We find that unexpected losses of local teams lead to a small decrease in the number of births nine months thereafter. The effect is larger for more unexpected losses, in those provinces with the largest amount of support for the local team and robust to a number of placebo tests. We argue that these results are consistent with the gain-loss asymmetry predicted by prospect theory.

 

 

#12 Correlation between strength and skin temperature asymmetries in the lower limbs of Brazilian elite soccer players before and after a competitive season

Reference: J Therm Biol. 2021 Jul;99:102919. doi: 10.1016/j.jtherbio.2021.102919. Epub 2021 Apr 24.

Authors: Jorge L Rodrigues Júnior, Warley Duarte, Hugo Falqueto, André G P Andrade, Rodrigo F Morandi, Maicon R Albuquerque, Miller G de Assis, Tane K F Serpa, Eduardo M Pimenta

Summary: This study aimed to investigate the correlation between strength and skin temperature (Tsk) asymmetries in the lower limbs of elite soccer players before and after a competitive season. The sample (n = 20) was composed of elite male soccer players. Strength asymmetry and Tsk asymmetry was measured through the countermovement jump (CMJ) test and infrared thermography, respectively. Asymmetries were quantified using the symmetry angle (SA) equation. A strong correlation was found between the SA of rate of force development (RFD) and the SA of Tsk before (baseline) (r = 0.7; r2 = 0.43; p = 0.03) and after (r = 0.6; r2 = 0.42; p = 0.04) the competitive season. Moreover, after the competitive season there were significant decreases in Peak force (p < 0.018), Impulse (p < 0.04), RFD (p = 0.0001) and CMJ height (p = 0.05), and significant increases in Tsk (p < 0.03), C-reactive protein (p = 0.03), Creatine kinase (p = 0.0001) and Cortisol (p = 0.04), even after a 3-day rest interval (no training). These results suggest that the CMJ test can be combined with infrared thermography for monitoring strength asymmetry and contribute to the prevention of muscle injuries.

 

 

#13 Age-related differences in linear sprint in adolescent female soccer players

Reference: BMC Sports Sci Med Rehabil. 2021 Aug 22;13(1):97. doi: 10.1186/s13102-021-00327-8.

Authors: Elena Mainer-Pardos, Oliver Gonzalo-Skok, Hadi Nobari, Demetrio Lozano, Jorge Pérez-Gómez

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8381494/pdf/13102_2021_Article_327.pdf

Summary: Several studies have observed the contribution of chronological age, biological maturation, and anthropometric characteristics to sprinting performance in young soccer players. Nevertheless, there are no studies that have analysed the contribution of these characteristics to running speed qualities in adolescent female soccer players. This study investigated age-related differences in sprint performance in adolescent female soccer players. Also, it examined the possible influence of anthropometry [body mass and body mass index (BMI)] and biological maturation [age at peak height velocity (APHV)] in sprint performance. Eighty adolescent female soccer players [under (U) 14, n = 20; U16, n = 37; U18, n = 23] participated in this study. Players were tested for 40 m sprint (each 10 m split times). Posthoc analysis revealed better performance in all split sprint times of older soccer players (U18 and U16) compared with younger category (F: 3.380 to 6.169; p < 0.05; ES: 0.64 to 1.33). On the contrary in all split sprint times, there were no significant changes between U16 and U18 (p < 0.05; ES: 0.03 to 0.17). ANCOVA revealed differences in all parameters between groups, controlled for APHV (p < 0.05). In contrast, all between-group differences disappeared after body mass and BMI adjustment (p > 0.05). Finally, the results indicate that BMI and body mass were significantly correlated with 40 m sprint (p < 0.05; r: -0.31) and 20 m flying (p < 0.01; r: 0.38), respectively. In the present players' sample, body mass and BMI had a significant impact on running speed qualities.

 

 

#14 Why are female soccer players experiencing a concussion more often than their male counterparts? A scoping review

Reference: Phys Ther Sport. 2021 Aug 8;52:54-68. doi: 10.1016/j.ptsp.2021.08.001. Online ahead of print.

Authors: Rebecca Jane Blyth, Mark Alcock, Dr Steve Tumilty

Summary: The risk of concussion is particularly high in female soccer players. There is no consensus as to why female soccer players are at an elevated risk. The aim was to synthesise current evidence investigating reasons for the increased concussion rate in female soccer players. Searching of six databases (MEDLINE, Scopus, CINAHL, SportDiscus, Web of Science and the Cochrane Library) and grey literature was performed between 13/07/2020-31/07/2020. Keywords were concussion-related terms, terms relating to female football/soccer and terms relating to the mechanism/cause. No constraints were placed on publication date and quantitative or exploratory studies meeting inclusion criteria were eligible. Exclusion criteria were studies not published in English and qualitative studies. Several hypotheses were identified to explain increased concussion rates in female soccer players, these include, reduced neck strength/anthropometrics, increased head acceleration, increased ball-to-head concussions, differences in hormones and brain structure/function, and reduced visual awareness. Promising ideas/reasons have been identified for increased concussion rates in female soccer players. Despite hypothesis generation there is scarce high-level evidence which is required to guide injury prevention and/or rule changes to protect female soccer players. The level of evidence for included studies is level 2-3 with most being observational cross-sectional or cohort studies.

 

 

#15 Relationship between Physical Fitness and Match Performance Parameters of Chile Women's National Football Team

Reference: Int J Environ Res Public Health. 2021 Aug 9;18(16):8412.  doi: 10.3390/ijerph18168412.

Authors: Rodrigo Villaseca-Vicuña, Fernando Manuel Otero-Saborido, Jorge Perez-Contreras, Jose Antonio Gonzalez-Jurado

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8391224/pdf/ijerph-18-08412.pdf

Summary: The aim of this study was to analyze the relationships between the level of physical fitness and the physical performance parameters recorded by GPS in official FIFA matches of the Chilean women's senior national football team in the period 2018-2020. Twenty-six female field players (age (mean ± SD) 26.8 ± 3.3 years, height 157.8 ± 21.5 cm, weight 58.9 ± 4.9 kg) participated in the study. Physical fitness variables were assessed: muscular strength, countermovement jump (CMJ), speed, agility and aerobic fitness. Physical performance variables were recorded by GPS in 26 official FIFA matches. The most notable associations with significant statistical significance (p < 0.001) were those observed between neuromuscular variables such as time to run 10 m (T10; r = -0.629) and jump (CMJ; r = 0.502) and the number of accelerations; aerobic fitness showed a highly significant relationship with meters run per minute (M/M; r = 0.589). The findings of this study provide evidence of how the level of physical fitness (neuromuscular and aerobic) relates to physical performance parameters recorded in official competitions.

 

 

#16 A comparison of the internal and external load demands imposed on professional soccer referees in FIFA's current model of physical test in relation to games

Reference: J Sports Med Phys Fitness. 2021 Sep 9. doi: 10.23736/S0022-4707.21.12104-8. Online ahead of print.

Authors: Artur A Preissler, Pedro Schons, Rochelle R Costa, Thaís Reichert, Henrique B Oliveira, Guilherme D DE Vargas, Felipe L Ribeiro, Giovanni R Brito, Jonas C Zanella, Lucas M Klein, Benedito S Denadai, Luiz F Kruel

Summary: Based on the need to investigate the demands imposed on referees in the current model of physical evaluation and during professional games, this study's objective was to compare these demands in the physical test versus the games. Thus, it evaluated the heart rate, distance covered, time, and speed of all 14 referees in the physical test and during Brazil's first division state championship games using a Global Positioning System enabled heart rate monitor. The maximum heart rate (HRmax) and maximum speed were higher in the physical test (183.86 ± 12.79 bpm) and (26.80 ± 0.96 km/h), respectively, than in the games (170.25 ± 17.71 bpm) (p = 0.008) and (24.27 ± 1.68 km/h) (p = 0.001), respectively. In the HRmax zone ≥90 and ≤100%, the time and percentage distance were greater in the physical test (47.87 ± 16.60% and 58.57 ± 22.78%), respectively, than in the games (17.82% ± 18.29% and 18.84% ± 18.92%, respectively; p < 0.001). However, in the speed zone <13 km/h, the time and the percentage distance were longer in the game (93.73 ± 1.26% and 86.13 ± 2.31%), respectively, than in the physical test (68.73 ± 12,31% and 39.65 ± 9.74%, respectively; p < 0.001). Thus, it is concluded that the professional referees perform at greater intensities during the physical test than in the games. In contrast, the demands for intensities corresponding to aerobic metabolism are greater in games or equal to those in physical testing, depending on the intensity reference.

 

 

#17 Soccer participation is associated with benefits in tibial bone cross-sectional geometry and strength in young women

Reference: J Sports Med Phys Fitness. 2021 Sep 9. doi: 10.23736/S0022-4707.21.12519-8. Online ahead of print.

Authors: Julie M Hughes, D Clark Dickin, He Wang

Summary: Soccer has been hypothesized to be an ideal sport to stimulate favorable changes in bone properties due the high-intensity, multidirectional movements performed during play. The purpose of this study was to determine if participation in soccer is associated with enhanced bone properties such as volumetric bone mineral density (vBMD), cross-sectional geometry, and estimated strength in the tibias of young, healthy women. Twenty female soccer players (20±1 yr) and twenty mass- and height-matched healthy women (21±1 yr) participated in this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Stratec Medizintechnik, Pforzheim, Germany) was used to assess bone characteristics, including vBMD, cross-sectional moments of inertia (CSMI), and strength/strain index (SSI) at 14%, 38%, and 66% of the tibial length proximal to the distal end plate. One-way multivariate analysis of variances was run to determine the influence of soccer training history on tibial properties. Compared to healthy controls, soccer players had approximately 1.5% - 3% lower cortical vBMD but 18.5% - 30% greater CSMI and 16.5% -19% greater SSI at the three cross-sectional sites along the tibial diaphysis (all p < 0.05). These results suggest that soccer participation is associated with favorable bone cross-sectional geometry and estimates of bone strength. However, randomized controlled intervention trials are needed to confirm whether soccer participation results in favorable bone adaptations in young, healthy adults.

 

 

#18 Low back pain prevalence and risk factors in Italian adolescent male soccer players: results from an online survey

Reference: J Sports Med Phys Fitness. 2021 Sep 9. doi: 10.23736/S0022-4707.21.12696-9. Online ahead of print.

Authors: Lucia Cugusi, Andrea Manca, Ernest Fishback, Claudio Secci, Marco Bergamin, Stefano Gobbo, Andrea DI Blasio, Andrea Montella, Pasquale Bandiera, Franca Deriu

Summary: The purpose of this retrospective survey was to analyse the prevalence of low back pain (LBP) among Italian adolescent soccer players, and to identify potential risk factors. Participants were requested to answer an online survey based on the standardized Nordic questionnaires for musculoskeletal symptoms. Data were obtained from 204 male soccer players aged 14-17 years competing at the national and regional level. More than half of the players had experienced LBP in their lives. One-way ANOVA revealed that the players with LBP were taller, heavier and with a higher BMI (all p values<0.00001). When considering the playing position, ANOVA revealed that 14-15 years-old strikers displayed higher LBP scores than all other roles (all p values<0.05). Accordingly, strikers were exposed to a higher risk of LBP than midfielders (RR=1.48; 95%CI:1.10-2.01; p=0.01) and goalkeepers (RR=1.48; 95%CI:1.02-2.971; p=0.04), but not defenders (RR=1.23; 95%CI:0.93-1.63; p=0.15). Within the 14-15 age-class, strikers were, again, those most exposed to LBP risk (all p values<0.05). Anthropometric and soccer-related features should be monitored to ensure early identification of potential risk factors for LBP. This information should be considered along with the specific playing position as strikers emerged as the roles most exposed to LBP risk.

 

 

#19 Predictive Strength of Contextual and Personal Variables in Soccer Players' Goal Orientations

Reference: Int J Environ Res Public Health. 2021 Sep 6;18(17):9401. doi: 10.3390/ijerph18179401.

Authors: Enrique Iglesias-Martínez, Jorge Roces-García, David Méndez-Alonso

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8431439/pdf/ijerph-18-09401.pdf

Summary: Psychological variables, such as perceived motivational climate, goal orientation, self-determined motivation, and personality, have an influence on sports success performance. This study aimed to examine the relationships among a set of psychological variables (perceived motivational climate, goal orientation, self-determined motivation, and personality) in male and female footballers. Participants were 167 footballers (106 male, 61 female), aged 12 to 26, competing with clubs in the Spanish Football League. They all took four questionnaires aimed at evaluating motivational climate, goal orientations, self-determined motivation, and personality. The analyses of correlation and regression showed statistically significant relations among the variables. Neuroticism and psychoticism negatively relate to mastery motivational climate, the best predictor of self-determined motivation. It was concluded that contextual variables carry more weight in predicting goal orientations and self-determined motivation among participant footballers.

 

 

#20 Impact of the Result of Soccer Matches on the Heart Rate Variability of Women Soccer Players

Reference: Int J Environ Res Public Health. 2021 Sep 6;18(17):9414. doi: 10.3390/ijerph18179414.

Authors: Rosa Mª Ayuso-Moreno, Juan Pedro Fuentes-García, Hadi Nobari, Santos Villafaina

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8430763/pdf/ijerph-18-09414.pdf

Summary: The present study aimed to evaluate the effects of a match lost and a match won on post-competitive heart rate variability (HRV) in semi-professional female soccer athletes. A total of 13 players, with a mean age of 23.75 (5.32), from the Cáceres Women Football Club of the Spanish Second National Division participated in our study. They were evaluated in two microcycles which correspond to a match lost and a match won. For each microcycle, baseline and post-competitive measures were collected. Results indicate that HRV was significantly reduced before a match lost and won. Significant differences in HRV variables were observed when compared the lost match, and the match won. Results highlight the importance and usefulness of analyzing the HRV as an indicator of post-competitive fatigue in semiprofessional soccer players. Therefore, a competition's results could be considered a relevant variable to consider when programming training load.

 

 

#21 Win, Draw, or Lose? Global Positioning System-Based Variables' Effect on the Match Outcome: A Full-Season Study on an Iranian Professional Soccer Team

Reference: Sensors (Basel). 2021 Aug 24;21(17):5695. doi: 10.3390/s21175695.

Authors: Hadi Nobari, Norbert Keshish Banoocy, Rafael Oliveira, Jorge Pérez-Gómez 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8434520/pdf/sensors-21-05695.pdf

Summary: The aim of the study was to determine the between-match and between-halves match variability of various Global Positioning System (GPS) variables and metabolic power average (MPA) in competitions, based on the match results obtained by professional soccer players over a full season. Observations on individual match performance measures were undertaken on thirteen outfield players competing in the Iranian Premier League. The measures selected for analysis included total duration, accelerations in zones (AccZ1, 2, and 3), decelerations in zones (DecZ1, 2, and 3), and MPA collected by the Wearable Inertial Measurement Unit (WIMU). The GPS manufacturer set the thresholds for the variables analyzed as follows: AccZ1 (<2 m·s-2); AccZ2 (2 to 4 m·s-2); AccZ3 (>4 m·s-2); DecZ1 (<-2 m·s-2); DecZ2 (-2 to -4 m·s-2); DecZ3 (>-4 m·s-2). The results revealed significant differences between wins and draws for the duration of the match and draws compared to wins for the first- half duration (p ≤ 0.05; ES = 0.36 [-0.43, 1.12]), (p ≤ 0.05; ES = -7.0 [-8.78, -4.78], respectively. There were significant differences on AccZ1 during the first-half between draws and defeats (p ≤ 0.05; ES = -0.43 [-1.32, 0.46]), for AccZ3 in the second-half between draws and defeats (p ≤ 0.05; ES = 1.37 [0.48, 2.25]). In addition, there were significant differences between wins and draws (p ≤ 0.05; ES = 0.22 [-0.62, 1.10]), and wins and defeats for MPA in the first- half (p ≤ 0.05; ES = 0.34 [-0.65, 1.22]). MPA showed further differences between draws and defeats in the second- half (p ≤ 0.05; ES = 0.57 [-0.22, 1.35]). Descriptive analysis revealed differences between the first and second half for wins in AccZ2 (p = 0.005), DecZ2 (p = 0.029), and MPA (p = 0.048). In addition, draws showed significant differences between the first and second half in duration, AccZ1, AccZ2, and DecZ2 (p = 0.008), (p = 0.017), (p = 0.040), and (p = 0.037) respectively. Defeats showed differences between the first and second half in AccZ1, AccZ3, and MPA (p = 0.001), (p = 0.018), and (p = 0.003) respectively. In summary, the study reveals large variations between the match duration, accelerometer variables, and MPA both within and between matches. Regardless of the match outcome, the first half seems to produce greater outputs. The results should be considered when performing a half-time re-warm-up, as this may be an additional factor influencing the drop in the intensity markers in the second half in conjunction with factors such as fatigue, pacing strategies, and other contextual variables that may influence the results.

 

 

#22 REPIMPACT - a prospective longitudinal multisite study on the effects of repetitive head impacts in youth soccer

Reference: Brain Imaging Behav. 2021 Sep 10. doi: 10.1007/s11682-021-00484-x. Online ahead of print.

Authors: Inga K Koerte, Roald Bahr, Peter Filipcik, Jolien Gooijers, Alexander Leemans , Alexander P Lin, Yorghos Tripodis, Martha E Shenton, Nir Sochen, Stephan P Swinnen, Ofer Pasternak, REPIMPACT Consortium Investigators

Download link: https://link.springer.com/content/pdf/10.1007/s11682-021-00484-x.pdf

Summary: Repetitive head impacts (RHI) are common in youth athletes participating in contact sports. RHI differ from concussions; they are considered hits to the head that usually do not result in acute symptoms and are therefore also referred to as "subconcussive" head impacts. RHI occur e.g., when heading the ball or during contact with another player. Evidence suggests that exposure to RHI may have cumulative effects on brain structure and function. However, little is known about brain alterations associated with RHI, or about the risk factors that may lead to clinical or behavioral sequelae. REPIMPACT is a prospective longitudinal study of competitive youth soccer players and non-contact sport controls aged 14 to 16 years. The study aims to characterize consequences of exposure to RHI with regard to behavior (i.e., cognition, and motor function), clinical sequelae (i.e., psychiatric and neurological symptoms), brain structure, function, diffusion and biochemistry, as well as blood- and saliva-derived measures of molecular processes associated with exposure to RHI (e.g., circulating microRNAs, neuroproteins and cytokines). Here we present the structure of the REPIMPACT Consortium which consists of six teams of clinicians and scientists in six countries. We further provide detailed information on the specific aims and the design of the REPIMPACT study. The manuscript also describes the progress made in the study thus far. Finally, we discuss important challenges and approaches taken to overcome these challenges.

 

 

#23 Match-related physical performance in professional soccer: Position or player specific?

Reference: PLoS One. 2021 Sep 10;16(9):e0256695. doi: 10.1371/journal.pone.0256695. eCollection 2021.

Authors: Stefan Altmann, Leon Forcher, Ludwig Ruf, Adam Beavan, Timo Groß, Philipp Lussi, Alexander Woll, Sascha Härtel

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8432651/pdf/pone.0256695.pdf

Summary: The purpose of this study was to examine to what extent the physical match performance of professional soccer players is both position and player specific. First, official match data from the 2019/20 German Bundesliga season was used to search for players that met the inclusion criteria of playing a minimum of four entire matches in at least two different playing positions. Overall, 25 players met the criteria prior to the COVID-19 induced break, playing a minimum of eight matches. Second, the physical match performance of these players was analyzed separately for each position they played. The following four parameters were captured: total distance, high-intensity distance, sprinting distance, and accelerations. Third, the 25 players' physical match performance data was then compared to normative data for each position they played to understand whether players adapted their physical performance (position dependent), or maintained their performance regardless of which position they were assigned to (position independent). When switching the position, the change in physical match performance of the respective players could be explained by 44-58% through the normative positional data. Moreover, there existed large individual differences in the way players adapted or maintained their performance when acting in different positions. Coaches and practitioners should be aware that some professional soccer players will likely incur differences in the composition of physical match performance when switching positions and therefore should pay special consideration for such differences in the training and recovery process of these players.

 

Sat

08

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2022

The Effect of High-Intensity Accelerations and Decelerations on Match Outcome of an Elite English League Two Football Team

The aim of the present study was to identify the influence of high-intensity accelerations (ACC) and decelerations (DEC) on match performance outcomes (i.e., win, draw, lost).

Fri

07

Jan

2022

Intra- and Inter-Limb Strength Asymmetry in Soccer: A Comparison of Professional and Under-18 Players

The present study examined the isokinetic peak torque exerted by both knee extensors and flexors, anterior–posterior imbalance and the magnitude and direction of inter-limb asymmetry in professional and academy soccer players.

Thu

06

Jan

2022

Latest research in football - week 43 - 2021

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 Assessment of Body Composition, Lower Limbs Power, and Anaerobic Power of Senior Soccer Players in Portugal: Differences According to the Competitive Level

Reference: Int J Environ Res Public Health. 2021 Jul 30;18(15):8069.10.3390/ijerph18158069.

Authors: Diogo Tereso, Rui Paulo, João Petrica, Pedro Duarte-Mendes, José M Gamonales, Sergio J Ibáñez

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345566/pdf/ijerph-18-08069.pdf

Summary: During a soccer game, the most diversified stimuli occur all the time, the physical condition level plays a determinant role, and there may be variations according to the competitive level. In this sense, the present study aimed to verify differences in body composition, lower limbs power, and anaerobic power, comparing senior soccer players of different competitive levels. Participants were 81 players belonging to six soccer teams, aged between 18 and 35 years, with a mean age of 23.14 ± 4.23 years, who were divided into three distinct competitive levels: Elite, Sub-Elite and Non-Elite. The players performed bioimpedance evaluations on a tetrapolarInbody270 scale (body composition), the Countermovement Jump (CMJ) through the ChronoJump (lower limbs power), and Running Anaerobic Sprint Test (RAST) (anaerobic power). Based on the competitive level analysis, we verified that the players present body composition values similar to each other regardless of the competitive level in which they play. Concerning the performance evaluations, we verified that the elite players present higher values of highest jump (p = 0.012; d = 0.76, moderate; and p = 0.022; d = 0.71, moderate) and maximum force produced (p = 0.05; d = 0.64, moderate; and p = 0.002; d = 1.00, moderate), together with higher values of anaerobic power (p < 0.001; d = 2.43, very large; and p < 0.001; d = 2.22, very large), compared to the others. We can thus conclude that there is a homogeneity regarding the body composition of soccer players, regardless of their competitive level; in turn, elite players show better performance indicators in all variables.

 

 

#2 Wearable Inertial Measurement Unit to Accelerometer-Based Training Monotony and Strain during a Soccer Season: A within-Group Study for Starters and Non-Starters

Reference: Int J Environ Res Public Health. 2021 Jul 28;18(15):8007.

 doi: 10.3390/ijerph18158007.

Authors: Hadi Nobari, Mustafa Sögüt, Rafael Oliveira, Jorge Pérez-Gómez, Katsuhiko Suzuki, Hassane Zouhal

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345473/pdf/ijerph-18-08007.pdf

Summary: The purpose of this study was to analyze the intragroup differences in weekly training monotony (TM) and training strain (TS) between starter and non-starter male professional soccer players at accelerometry based variables throughout the periods of a season. TM and TS of different accelerations and decelerations zones for twenty-one players were followed for forty-eight weeks. Regardless of group, players obtained the highest mean TM (starters = 3.3 ± 0.6, non-starters = 2.2 ± 1.1, in arbitrary unit, AU) and TS (starters = 1288.9 ± 265.2, non-starters = 765.4 ± 547.5, AU) scores in the pre-season for accelerations at Zone 1 (<2 m/s2). The results also indicated that both groups exhibited similar TM and TS scores in accelerations at Zones 2 (2 to 4 m/s2) and 3 (>4 m/s2) across the entire season. While the starters showed the highest TM and TS scores at deceleration Zone 1 (<-2 m/s2) in the end-season, the non-starters exhibited the highest scores at the deceleration Zone 1 in pre-season. It seems that in pre-season, coaches applied higher levels of training with greater emphasis on deceleration for non-starters. This tendency was reduced over time for non-starters, while starters presented higher values of deceleration Zone 1. These results highlight the variations in TM and TS across the different periods of a full season according to match starting status among professional soccer players, and the results suggest that non-starter players should receive higher levels of load to compensate for non-participation in matches throughout a soccer season.

 

 

#3 Training Load in Different Age Category Soccer Players and Relationship to Different Pitch Size Small-Sided Games

Reference: Sensors (Basel). 2021 Jul 31;21(15):5220.  doi: 10.3390/s21155220.

Authors: Fernando J Santos, Teresa P Figueiredo, Dalton M Pessôa Filho, Carlos E L Verardi, Anderson G Macedo, Cátia C Ferreira, Mário C Espada

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8348483/pdf/sensors-21-05220.pdf

Summary: This study sought to evaluate the training load in different age category soccer players associated with distinct pitch size small-sided games (SSGs). Twenty-four soccer players (eight in each age category: U-12, U-15, and U-23) performed three consecutive 4 vs. 4 ball possession SSGs (SSG1: 16 × 24 m; SSG2: 20 × 30 m; and SSG3: 24 × 36 m) all with 3 min duration and 3 min rest. Subjects carried ultra-wideband-based position-tracking system devices (WIMU PRO, RealTrack System). Total distance covered increased from SSG1 to SSG3 in all age categories and predominantly in running speeds below 12 km·h-1. Moreover, distance covered in 12-18 km·h-1 running speed was different in all performed SSGs and age categories. Residual or null values were observed at 18-21 km·h-1 or above running speed, namely in U-12, the only age category where metabolic power and high metabolic load distance differences occurred throughout the performed SSGs. Edwards' TRIMP differences between age categories was only observed in SSG2 (U-12 < U-15). The design of SSGs must consider that the training load of the players differs according to their age category and metabolic assessment should be considered in parallel to external load evaluation in SSGs. Wearable technology represents a fundamental support in soccer.

 

 

#4 Muscle Damage Biomarkers in Congestion Weeks in English Premier League Soccer Players: A Prospective Study for Two Consecutive Seasons

Reference: Int J Environ Res Public Health. 2021 Jul 28;18(15):7960.  doi: 10.3390/ijerph18157960.

Authors: Álvaro García-Romero-Pérez, Francisco Javier Ordonez, Fernando Reyes-Gil, Elena Sonsoles Rodríguez-López, Ángel Oliva-Pascual-Vaca

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345565/pdf/ijerph-18-07960.pdf

Summary: The current study was conducted to compare muscle damage biomarkers in single- vs. multi-match weeks in elite soccer players for two consecutive seasons. A secondary objective was to analyze the influence of playing position and exposure time on muscle damage in single- vs. multi-match weeks. This is a prospective cohort study performed in a professional elite soccer club in the English Premier League during the 2018-2019 and 2019-2020 seasons up until the lockdown due to the COVID-19 pandemic. Data were collected in the Medical Department Room of an English Premier League Club before and after the soccer game from a total of 29 elite soccer players (mean ± S.D.; age = 27.59 ± 3.83 years; height = 1.83 ± 0.05 m; body mass = 80.16 ± 7.45 kg) who were enrolled in the club during both seasons. The main outcome measurements were creatine kinase (CK), weight, lean mass, % fat DEXA, high speed running, total distance, density of total distance and high-speed running and wellbeing questionnaires. Significance was set at p < 0.05. Players who completed more than 60 min in the previous game had significantly increased pregame CK levels and fatigue in multi-match weeks. Midfielders had both significantly increased pregame CK and muscle soreness in multi-match weeks. Midfielders and players with an exposure time of at least 60 min showed higher pregame CK values that should play a key role for deciding substitutions.

 

 

#5 Low Horizontal Force Production Capacity during Sprinting as a Potential Risk Factor of Hamstring Injury in Football

Reference: Int J Environ Res Public Health. 2021 Jul 23;18(15):7827.  doi: 10.3390/ijerph18157827.

Authors: Pascal Edouard, Johan Lahti, Ryu Nagahara, Pierre Samozino, Laurent Navarro, Kenny Guex, Jérémy Rossi, Matt Brughelli, Jurdan Mendiguchia, Jean-Benoît Morin

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345704/pdf/ijerph-18-07827.pdf

Summary: Clear decreases in horizontal force production capacity during sprint acceleration have been reported after hamstring injuries (HI) in football players. We hypothesized that lower FH0 is associated with a higher HI occurrence in football players. We aimed to analyze the association between sprint running horizontal force production capacities at low (FH0) and high (V0) velocities, and HI occurrence in football. This prospective cohort study included 284 football players over one season. All players performed 30 m field sprints at the beginning and different times during the season. Sprint velocity data were used to compute sprint mechanical properties. Players' injury data were prospectively collected during the entire season. Cox regression analyses were performed using new HI as the outcome, and horizontal force production capacity (FH0 and V0) was used at the start of the season (model 1) and at each measurement time point within the season (model 2) as explanatory variables, adjusted for individual players' (model 2) age, geographical group of players, height, body mass, and previous HI, with cumulative hours of football practice as the time scale. A total of 47 new HI (20% of all injuries) were observed in 38 out of 284 players (13%). There were no associations between FH0 and/or V0 values at the start of the season and new HI occurrence during the season (model 1). During the season, a total of 801 measurements were performed, from one to six per player. Lower measured FH0 values were significantly associated with a higher risk of sustaining HI within the weeks following sprint measurement (HR = 2.67 (95% CI: 1.51 to 4.73), p < 0.001) (model 2). In conclusion, low horizontal force production capacities at low velocity during early sprint acceleration (FH0) may be considered as a potential additional factor associated with HI risk in a comprehensive, multifactorial, and individualized approach.

 

 

#6 Virtual reality promotes greater improvements than video-stimulation screen on perceptual-cognitive skills in young soccer athletes

Reference: Hum Mov Sci. 2021 Aug 11;79:102856. doi: 10.1016/j.humov.2021.102856. Online ahead of print.

Authors: Leonardo S Fortes, Sebastião S Almeida, Gibson M Praça, José R A Nascimento-Júnior, Dalton Lima-Junior, Bruno Teixeira Barbosa, Maria E C Ferreira

Summary: The literature has shown the positive effect of virtual reality (VR) in percepto-cognitive skills. However, the literature lacks findings about at what extent VR would be better than video. Purpose This study aimed to analyze the chronic effect of VR and video-stimulation screen training on passing decision-making, visual search behavior, and inhibitory control performance in young soccer athletes. Method A total of 26 young soccer players underwent an 8-week training protocol after being randomly assigned to the VR (n = 13) or video-screen (VID, n = 13) group. Passing decision-making, visual search behavior, and inhibitory control performance were measured before and after both interventions. Results A group x time interaction was found for decision-making performance (p < 0.01) and visual search behavior (p < 0.01). Both groups improved both decision-making performance (p < 0.01) and visual search behavior (p < 0.01); however, greater improvements were verified in VR (p < 0.01). Both VR and VID improved inhibitory control (p < 0.01), but no group interaction effect was observed (p > 0.05). Conclusion Our results suggest that VR leads to greater improvements in decision-making and visual search behavior in young soccer athletes than VID.

 

 

#7 Analysis of Selected Lymphocyte (CD45+) Subset Distribution in Capillary Blood of Young Soccer Players

Reference: J Strength Cond Res. 2021 Aug 1;35(8):2279-2286. doi: 10.1519/JSC.0000000000003105.

Authors: Robert Nowak, Dorota Kostrzewa-Nowak, Rafał Buryta

Summary: Mechanisms responsible for increasing athletes' physical capacity and induction of exercise-induced immunosuppression processes are not fully understood. The aim of the study was to monitor changes in percentages of lymphocyte subsets: T, Th, Tc, B, and NK cells in capillary blood of junior soccer players. Ten subjects median aged 18 years (range 17-19 years) were recruited form young soccer players. Capillary blood was collected 24 hours after each soccer match during the 8 weeks of the final phase of Central Junior League competition, and white blood cell (WBC) phenotyping was performed to determine the percentages of B lymphocytes, NK cells, and T-lymphocyte subsets. Cumulative match-time (a sum of time spend playing the game by each athlete during the observation period) was also calculated. Significant changes in the percentage of total lymphocytes (p = 0.00005) and T cells (p = 0.00006) were observed. The slight increases in lymphocytes' and Th cells' median percentages correlated with increasing cumulative match-time of studied subjects, although the correlation was not strong (R = 0.24; p = 0.0205 and R = 0.30; p = 0.0035, for lymphocytes and Th cells, respectively). It seems that the exercise bouts are among considerable factors influencing the changes in WBC subsets, especially in CD3+ cells, among young soccer players. Regarding the number of games played and training loads, they are more susceptible to immunosuppression and subsequent infections and thus should be monitored regarding WBC phenotype assessment.

 

 

#8 Effects of a Neuromuscular Warm-Up Program in Youth Female Soccer Players

Reference: J Hum Kinet. 2021 Jul 28;79:29-40. doi: 10.2478/hukin-2021-0080. eCollection 2021 Jul.

Authors: Elena Isla, Blanca Romero-Moraleda, José María Moya, Francisco Esparza-Ros, Javier Mallo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336551/pdf/hukin-79-029.pdf

Summary: The protective effects of different warm-up injury prevention routines in youth female soccer players have been demonstrated in the literature, however, there is a paucity of information regarding the effects that these kinds of programs have on soccer-specific physical performance variables. The purpose of this study was to assess the effectiveness of a 12-week neuromuscular warm-up program on physical performance in youth female soccer players. Players (age: 13.94 ± 0.82 years) were divided into two groups. One group performed a neuromuscular activation program (n = 21) twice per week whereas the other group (control, n = 17) continued with their habitual warm-up routine for the same duration. Both groups of players performed strength, jumping and balance tests before and after the intervention period. Substantially greater improvements were detected in the mean velocity for the squat (p < 0.001; Effect Size = 0.95) and the hip thrust (p < 0.001; Effect Size = 0.51) in the experimental group in comparison to the control group. In addition, after the intervention period players in the experimental group showed an increase in the jumping height in the unloaded double-leg and single-leg counter-movement jumps (p = 0.003-0.012; Effect Size = 0.42-0.46). The results of this study provide evidence that a 12-week neuromuscular warm-up program can be effective to improve different physical performance variables in youth female soccer players.

 

 

#9 The Fifth Metatarsal Bone Fracture in Athletes - Modalities of Treatment Related to Agility in Soccer Players

Reference: J Hum Kinet. 2021 Jul 28;79:101-110. doi: 10.2478/hukin-2020-0059. eCollection 2021 Jul.

Authors: Krzysztof Ficek, Natalia Kędra, Radosław Skowronek, Kamila Kluczniok, Magdalena Strózik, Paweł Gwiazdoń, Grzegorz Hajduk

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336555/pdf/hukin-79-101.pdf

Summary: The 5th metatarsal fracture is a common foot fracture which could exclude a player from competition for several months and significantly affect his or her career. This manuscript presents the treatment and rehabilitation of professional soccer players who had acute fractures of the 5th metatarsal bone and a cannulated screw fixation. The main purpose of the analysis was to determine the minimum time necessary for a permanent return to the sport after a 5th metatarsal fracture among professional soccer players. We followed the surgical and rehabilitation path of 21 professional soccer players from the Polish League (Ist and IInd divisions) who suffered from the 5th metatarsal bone fracture. All players underwent standard percutaneous internal fixation with the use of cannulated screws. The total inability to play lasted for 9.2 (± 1.86) weeks among players treated only surgically (n = 10), 17.5 (± 2.5) weeks in the conservative and later surgery group, excluding players with nonunion (n = 6), and 24.5 (± 10.5) weeks for nonunion and switch treatment (n = 4) players. Prompt fracture stabilization surgery is recommended for athletes, enabling the implementation of an aggressive rehabilitation protocol as soon as possible. Early limb loading after surgery (from week 2) does not delay fracture healing or hinder the bone union, thus rehabilitation plays a crucial role in shortening the time of RTP (return to play) and is obligatory for each athlete who undergoes surgical treatment.

 

 

#10 Long-Term Trend Analysis of Playing Styles in the Chinese Soccer Super League

Reference: J Hum Kinet. 2021 Jul 28;79:237-247. doi: 10.2478/hukin-2021-0077. eCollection 2021 Jul.

Authors: Changjing Zhou, Carlos Lago-Peñas, Alberto Lorenzo, Miguel-Ángel Gómez

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336544/pdf/hukin-79-237.pdf

Summary: The aim of this study was to identify playing styles adopted by teams in the Chinese Soccer Super League (CSL) and to investigate their evolution across a 6-season period. Data were collected from 1,429 CSL matches from 2012 to 2017 seasons using the Amisco system. Seventeen technical performance-related indicators and eleven physical performance-related indicators were included in the factor analysis (PCA: principal components analysis) in order to group them into performance factors (styles of play). Seven factors were obtained (eigenvalues greater than 1) and explained 74.44% of the total variance. Multivariate analyses of covariance (MANCOVA) were used to check differences among seven styles of play (team's ranking was used as a covariate) during the six seasons under study. The main findings showed that Factor 1 (high intensity play) and factor 3 (offensive actions) of CSL soccer increased substantially along the seasons. Coaches and sports scientists should take into consideration these performance trends when preparing training and controlling for matches.

 

 

#11 Coach Encouragement During Soccer Practices Can Influence Players' Mental and Physical Loads

Reference: J Hum Kinet. 2021 Jul 28;79:277-288. doi: 10.2478/hukin-2021-0079. eCollection 2021 Jul.

Authors: Jesús Díaz-García, Juan José Pulido, José Carlos Ponce-Bordón, Carlos Cano-Prado, Miguel Ángel López-Gajardo, Tomás García-Calvo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336561/pdf/hukin-79-277.pdf

Summary: This study analyzed the influence of the coaches' encouragement on the mental and physical load in soccer practices. The participants were 36 semiprofessional Spanish soccer players (Mage = 22.40; SD = 2.25) belonging to two male teams and one female team. Following the same practices' design and order, two training sessions of each team were completed. In one session, coaches maintained a passive verbal attitude, whereas in the other session, coaches intervened with an active attitude through continuous general encouragement. The mental load and fatigue were measured using self-reported questionnaires (Likert scales), and internal and external physical loads were quantified using the rating of perceived exertion and the Global Position System. A t-test for related samples and magnitude based on an inference spreadsheet was performed. The results demonstrated that mental and internal physical loads increased when coaches participated with active verbal encouragement. Especially, increases in performance satisfaction, mental effort, and RPE values, and decreases in unsafety values were detected due to encouragement interventions. Nevertheless, the external physical load did not show a clear trend. Based on these findings, coaches can use this information to manipulate their verbal encouragement during practices according to their physical and mental objectives with specific soccer strategies.

 

 

#12 The Coaches' Efficacy Expectations of Youth Soccer Players with Different Maturity Status and Physical Performance

Reference: J Hum Kinet. 2021 Jul 28;79:289-299. doi: 10.2478/hukin-2021-0083. eCollection 2021 Jul.

Authors: Iván Peña-González, Tomas García-Calvo, Eduardo M Cervelló, Manuel Moya-Ramón

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336556/pdf/hukin-79-289.pdf

Summary: This study aimed to report possible anthropometrical and physical performance differences between youth soccer players with different maturity status and to report the coaches' expectations, hypothesizing that coaches would expect more from players with advanced maturity. One hundred twenty-two (122) players completed a physical performance battery. Their maturity status was estimated and the coaches' efficacy expectations (CEEs) were assessed. Players with advanced maturation had better physical performance (F = 26.5-73.4; p < 0.01) and their CEEs for strength-related tasks were different according to the maturity status (F = 8.3-10.9; p < 0.01), but not for speed-related tests, nor for their general ability to play soccer. Normalized data showed significant differences between physical performance tests and their respective CEEs within each maturity group, especially in the Post-PHV group. This study confirms the physical advantages of players with advanced maturity while it shows controversial results of how maturation affects the coaches' perceptions and, indirectly, the coaches' identification and selection of talented players.

 

 

#13 Neuromuscular Performance and Training Workload Over an In-Season Mesocycle in Elite Young Soccer Players

Reference: Int J Sports Physiol Perform. 2021 Aug 17;1-7. doi: 10.1123/ijspp.2020-0834. Online ahead of print.

Authors: Colin Clancy, Nigel Gleeson, Tom Mercer

Summary: The purpose of this study was to assess neuromuscular performance capabilities over an in-season mesocycle in early-career professional soccer players and examine the relationship with training workload. Neuromuscular performance capabilities (isometric knee extensor: peak force, rate of force development, and peak twitch force) of 12 professional soccer players were assessed weekly over a 6-week period. Training and match workload were also recorded over the same period for each player (high-intensity running distance). Changes in neuromuscular performance and workload variables were analyzed. There was evidence of fluctuations in neuromuscular performance capability over the mesocycle that reached statistical (P < .05) and practical (13.3% [peak-to-peak]) significance alongside interweek heterogeneity in training and match workload (∼17.5% [coefficient of variation], P < .05). Congruence among fluctuating patterns of intramesocycle training load and concomitant neuromuscular performance responses was noted over time for acute training load and acute:chronic workload ratio with peak force and rate of force development. Neuromuscular performance capabilities fluctuate over an in-season mesocycle and are influenced by high-intensity running workload, emphasizing the need for acute monitoring in elite soccer players.

 

 

#14 The Influence of Menstrual Cycle on Bioimpedance Vector Patterns, Performance, and Flexibility in Elite Soccer Players

Reference: Int J Sports Physiol Perform. 2021 Aug 17;1-9. doi: 10.1123/ijspp.2021-0135. Online ahead of print.

Authors: Francesco Campa, Matteo Levi Micheli, Matilde Pompignoli, Roberto Cannataro, Massimo Gulisano, Stefania Toselli, Gianpiero Greco, Giuseppe Coratella

Summary: The aim was to examine whether menstrual cycle affects body composition and bioimpedance vector analysis (BIVA) patterns, jumping and sprinting ability, and flexibility in elite soccer players. A total of 20 elite female soccer players (age: 23.8 [3.4] y, height: 1.63 [0.04] m, body mass: 61.4 [5.9] kg, and body mass index: 22.5 [2.4] kg/m2) were monitored during the early follicular and ovulatory phase across 2 consecutive menstrual cycles. Bioimpedance analysis was performed using foot-to-hand technology, and total body water and fat mass were determined by specific equations developed for athletes. Bioelectrical resistance and reactance were adjusted according to the BIVA procedures and plotted as a vector within the resistance-reactance graph. In addition, countermovement jump, 20-m sprint, and sit and reach were assessed. A time effect (P < .05) was found for body mass, total body water, bioelectrical resistance and reactance, and flexibility. Specifically, body mass increased (P = .021) along with a gain in total body water (P = .001) from the ovulatory to the early follicular phase, while it decreased from the early follicular to the ovulatory phase during the second menstrual cycle. The BIVA vector shortened during the early follicular phases (P < .001). No change in jumping and sprinting capacity was observed (P > .05). Flexibility was impaired during the early follicular phases (P < .05). Specific bioelectrical impedance analysis and BIVA procedures are able to detect menstrual cycle-induced changes in body composition in elite soccer players. The early follicular phase resulted in fluid accumulations and BIVA vector shortening. In addition, while menstrual cycle did not affect performance, a fluctuation in flexibility was observed.

 

 

#15 Screening Youth Soccer Players by Means of Cognitive Function and Agility Testing

Reference: Percept Mot Skills. 2021 Aug 17;315125211040283. doi: 10.1177/00315125211040283. 

Authors: Nicola Lovecchio, Gianluca Manes, Luca Filipas, Matteo Giuriato, Antonio La Torre, F Marcello Iaia, Roberto Codella

Summary: Talent identification in sports is a heavily debated topic. Previous studies have separately explored either executive functions or gross motor skills to predict the success of top-level soccer players or, more generally, to characterize elite performance in soccer. However, at mid-childhood, the possibility to scope sport-specific requirements remains elusive. We aimed in this study to investigate a valid and simple method of testing for a unique combination of cognitive and speed abilities for identifying promising soccer players at mid-childhood. We measured cognitive functions by means of a Stroop smartphone application and agility with a T-Drill Ball-success test, in two groups of (a) elite- (n = 31) and (b) low-division (n = 37) Italian 7-year-old male soccer players. We administered the tests in a randomized order to both groups. We found better inhibitory control, cognitive flexibility and soccer-specific agility in high-division versus low-division players (p < .001). Inhibitory response and agility were positively associated with the augmented quality of the performance from low-division players to high-division players (r = .55; p = .0001). These results suggest that, even at an early age, cognitive control together with soccer-specific skills is associated with better performance.

 

 

#16 Hamstring Strain Injury (HSI) Prevention in Professional and Semi-Professional Football Teams: A Systematic Review and Meta-Analysis

Reference: Int J Environ Res Public Health. 2021 Aug 4;18(16):8272. doi: 10.3390/ijerph18168272.

Authors: Carlo Biz, Pietro Nicoletti, Giovanni Baldin, Nicola Luigi Bragazzi, Alberto Crimì, Pietro Ruggieri

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8394329/pdf/ijerph-18-08272.pdf

Summary: Hamstring Strain Injuries (HSIs) are the most common type of lesion in professional footballers and the leading cause of absence days from sports. However, recent studies have shown that high-level football teams apparently do not apply any HSI prevention protocol. The aim of the study was to determine the effect of preventive strategies and protocols in reducing the incidence of hamstring muscle injuries in professional and semi-professional football teams. A literature search of PubMed/MEDLINE, ISI/Web of Science and Scopus databases was conducted with the keywords "hamstring* and (injury* or strain) and prevent* and (soccer or football)". Quality and bias assessment was completed through the Kennelly modified scale. The Injury Incidence Rate (IIR) and the Incidence Rate Ratio (IRR) were assessed in the statistical analysis. In the meta-analysis, data were extracted, pooled and analysed with "Comprehensive Meta-Analysis Version 3.3.070" software. In total, 8 of the 1017 original search studies met the inclusion criteria of this review. The total exposure of the studies was 170,221.8 h, while the number of HSIs recorded was 165 in the intervention groups and 224 in the control groups. The average score of the quality assessment was 23.6/34. The meta-analysis of six of the eight included studies provided strong evidence that interventions are effective in reducing hamstring injuries. The IRR of the effect size was 0.443, with p-value = 0.001. The studies analysed applied different preventive strategies: the Nordic hamstring exercise, the FIFA 11+ programme and exercises for core stability or balance training. All these interventions proved to have a successful effect on prevention of hamstring injuries.

 

 

#17 Effects of Match Location, Quality of Opposition and Match Outcome on Match Running Performance in a Portuguese Professional Football Team

Reference: Entropy (Basel). 2021 Jul 29;23(8):973. doi: 10.3390/e23080973.

Authors: José E Teixeira, Miguel Leal, Ricardo Ferraz, Joana Ribeiro, José M Cachada, Tiago M Barbosa, António M Monteiro, Pedro Forte 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8391710/pdf/entropy-23-00973.pdf

Summary: The aim of this study was to analyze the effects of match location, quality of opposition and match outcome on match running performance according to playing position in a Portuguese professional football team. Twenty-three male professional football players were monitored from eighteen Portuguese Football League matches during the 2019-2020 season. Global positioning system technology (GPS) was used to collect time-motion data. The match running performance was obtained from five playing positions: central defenders (CD), fullbacks (FB), central midfielders (CM), wide midfielders (WM) and forwards (FW). Match running performance was analyzed within specific position and contextual factors using one-way analysis of variance (ANOVA) for repeated measures, standardized (Cohen) differences and smallest worthwhile change. CM and WM players covered significantly greater total distance (F = 15.45, p = 0.000, η2 = 0.334) and average speed (F = 12.79, p < 0.001, η2 = 0.294). WM and FB players covered higher distances at high-speed running (F = 16.93, p = 0.000, η2 = 0.355) and sprinting (F = 13.49; p < 0.001, η2 = 0.305). WM players covered the highest number of accelerations (F = 4.69, p < 0.001, η2 = 0.132) and decelerations (F = 12.21, p < 0.001, η2 = 0.284). The match running performance was influenced by match location (d = 0.06-2.04; CI: -0.42-2.31; SWC = 0.01-1.10), quality of opposition (d = 0.13-2.14; CI: -0.02-2.60; SWC = 0.01-1.55) and match outcome (d = 0.01-2.49; CI: -0.01-2.31; SWC = 0.01-0.35). Contextual factors influenced the match running performance with differential effects between playing positions. This study provides the first report about the contextual influence on match running performance in a Portuguese professional football team. Future research should also integrate tactical and technical key indicators when analyzing the match-related contextual influence on match running performance.

 

 

#18 Skeletal muscle phenotype and game performance in elite women football players

Reference: Scand J Med Sci Sports. 2021 Aug 24. doi: 10.1111/sms.14022. 

Authors: Magni Mohr, Ioannis G Fatouros, Athanasios Z Jamurtas, Dimitrios Draganidis, Martin Thomassen, Christina Ørntoft, Georgios Ermidis, Georgios Loules, Dimitrios Batsilas, Athanasios Poulios, Konstantinos Papanikolaou, Morten B Randers, Peter Krustrup, Lars Nybo

Summary: We combined game activity analyses with skeletal muscle phenotypes and comprehensive physiological testing to elucidate factors of importance for physical performance in elite women's football. GPS-data from an experimental game, sprint and endurance testing, and muscle tissue analysis of metabolic enzyme activity, protein expression and fiber type composition were completed for international top-level women players (n = 20; age; 23 ± 4 yrs, height; 166 ± 10 cm, weight; 60 ± 8 kg; VO2max ; 51 ± 6 ml/min/kg). Muscle monocarboxylate transporter 4 (MCT4) protein expression explained 46% of the variance in total game distance, while the ability to maintain high-intensity running (HIR) during the final 15 min of the game correlated to myosin heavy chain 1 (MHCI) and Na+ -K+ ATPase β1, FXYD1 (phospholemman) and superoxide dismutase 2 (SOD2) protein expression (range: r = 0.51-0.71; all p < 0.05). Total HIR distance correlated with (MHCIIa) protein expression (r = 0.51; p < 0.05), while muscle Na+ /H+ exchanger 1 (NHE1) protein explained 36% of the variance in game sprint distance (p < 0.05). Total game accelerations (actions >4 m/s2 ) correlated with platelet endothelial cell adhesion molecule (PECAM-1) protein expression (r = 0.51; p < 0.05), while concentric knee flexor strength explained 42-62% of the variance in intense decelerations (>4 m/s2 ). In conclusion, for elite women players' game endurance performance and resistance to end-game fatigue were affected by monocarboxylate transporter expression and myosin heavy chain profile. HIR was also correlated to ion transporter expression and muscle antioxidative capacity. Finally, the importance of functional strength and measures of muscle vascularization in relation to total game decelerations and accelerations, respectively, illustrates the complex physiological demands in elite women's football.

 

 

#19 Evaluation of the effect of high-intensity interval training on macular microcirculation via swept-source optical coherence tomography angiography in young football players

Reference: Indian J Ophthalmol. 2021 Sep;69(9):2334-2339. doi: 10.4103/ijo.IJO_3079_20.

Authors: Yalçın Karaküçük, Nilsel Okudan, Banu Bozkurt, Muaz Belviranlı, Fatih Tobakçal

Summary: This study was conducted to evaluate the effect of high intensity interval training (HIIT) on macular microcirculation, measured by swept source optical coherence tomography angiography (ss OCTA) in young football players. Football players between 18-20 years old were included. After a detailed ophthalmological examination, physiological parameters, including height, body weight, body fat, systemic blood pressure, hematocrit values, oxygen saturation, and heart rate, were recorded. Intraocular pressure and ss OCTA parameters were measured one day before and the day after the high intensity interval training program using DRI OCT Triton (Topcon, Tokyo, Japan) between 11:00 am and 1:00 pm. Fifteen participants completed the study. All were males with a mean age of 18.1 ± 0.4 years. Systolic and diastolic blood pressure and oxygen saturation did not change significantly (P > 0.05), while hematocrit levels increased remarkably (P = 0.049) after the HIIT program. Heart rates and intraocular pressure decreased (P = 0.003, P = 0.017, respectively). There was a significant increase in the central vessel density in deep capillary plexus (before: 18.7 ± 3.8%, after: 21.1 ± 4.5%) and central vessel density in choriocapillaris (before: 54.5 ± 2.8%, after 56.9 ± 2.2%) (P = 0.02, P = 0.02, respectively), although no changes were observed in other ss OCTA or in the central macular thickness and subfoveal choroidal thickness. A 6 week, high intensity interval training program with three exercise sessions per week seems not to alter mean superficial vascular densities, deep foveal avascular zone, and superficial foveal avascular zones, central macular thickness, or subfoveal choroidal thickness, while the central deep vascular density and central choriocapillaris vascular density increased remarkably among ss OCTA parameters.

 

 

#20 Incidence of injury in adult elite women's football: a systematic review and meta-analysis

Reference: BMJ Open Sport Exerc Med. 2021 Jul 13;7(3):e001094. doi: 10.1136/bmjsem-2021-001094. eCollection 2021.

Authors: Lawrence Mayhew, Mark I Johnson, Peter Francis, Christoph Lutter, Ali Alali, Gareth Jones

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8323459/pdf/bmjsem-2021-001094.pdf

Summary: The aim was to estimate the incidence of injury in adult elite women's football and to characterise the nature and anatomical location of injuries. Combinations of the key terms were entered into the following electronic databases (PubMed, SPORTDiscus, Science Direct and Discover) from inception to May 2021. (1) Used a prospective cohort design; (2) captured data on elite adult women players; (3) reported injury incidence by anatomical site; (4) captured data of at least one season or national team tournament; (5) included a definition of injury; and (6) written in English. The search identified 1378 records. Twelve studies published between 1991 and 2018 were included in our review and sampled 129 teams. In domestic club football, injury incidence rate was estimated to be 5.7/1000 hours (total), 19.5/1000 hours (match) and 3.1/1000 hours (training). In tournament, football match incidence was estimated to be 55.7/1000 hours. The knee (22.8%; 368/1822) was the most common site of injury in domestic club football. The ankle (23.7%, 105/443) was the most common site of injury in tournament football. Ligament sprains were the most common type of injury (27.8%), followed by muscle strains (19.1%). Severn studies (58%) had a high risk of bias associated with exposure definition and measurement and considerable heterogeneity exists between the included studies (I2=49.7%-95%). Ligament sprains occur more frequently in adult elite women football players. We advise caution in interpretating point estimates of the incidence of injury due to high statistical heterogeneity. Standardising injury reporting and the accurate recording of match and training exposure will overcome such limitations.

 

 

#21 Physical preparation and return to performance of an elite female football player following ACL reconstruction: a journey to the FIFA Women's World Cup

Reference: BMJ Open Sport Exerc Med. 2020 Dec 1;6(1):e000843. doi: 10.1136/bmjsem-2020-000843. eCollection 2020.

Authors: Matt Taberner, Nicol van Dyk, Tom Allen, Neil Jain, Chris Richter, Barry Drust, Esteban Betancur, Daniel D Cohen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8323467/pdf/bmjsem-2020-000843.pdf

Summary: ACL injuries are among the most severe knee injuries in elite sport, with a high injury burden and re-injury risk. Despite extensive literature on the injury and the higher incidence of injury and re-injury in female athletes, there is limited evidence on the return to sport (RTS) of elite female football players following ACL reconstruction (ACLR). RTS is best viewed on a continuum aligning the recovery and rehabilitation process with the ultimate aim - a return to performance (RTPerf). We outline the RTS and RTPerf of an elite female football player following ACLR and her journey to the FIFA Women's World Cup, including the gym-based physical preparation and the on-pitch/sports-specific reconditioning. We used the 'control-chaos continuum' as a framework for RTS, guiding a return above pre-injury training load demands while considering the qualitative nature of movement in competition. We then implemented the 'RTPerf pathway' to facilitate a return to team training, competitive match play and a RTPerf. Objective information, clinical reasoning and shared decision-making contributed to this process and helped the player to reach her goal of representing her country at the FIFA Women's World Cup.

 

 

#22 Effects of Postoperative Rehabilitation on Gait Parameters and Electromyography Variables in Acute and Chronic Anterior Cruciate Ligament Reconstruction Surgery in Football Players

Reference: Evid Based Complement Alternat Med. 2021 Aug 13;2021:9912795. doi: 10.1155/2021/9912795. eCollection 2021.

Authors: Gopal Nambi, Walid Kamal Abdelbasset, Anju Verma, Shereen H Elsayed, Osama R Aldhafian, Naif Bin Nwihadh, Mohamed A Omar, Tohamy G T Hassan, Ayman K Saleh

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8378949/pdf/ECAM2021-9912795.pdf

Summary: The results of the a-ACLR, c-ACLR, and control groups were compared. At 8 weeks following postoperative rehabilitation, the a-ACLR group shows more significant changes than the c-ACLR group (p < 0.001). At 6 and 12 months, there are normal values of kinematic and kinetic values in a-ACLR compared with the results of the control group (p < 0.001). The study showed that postoperative rehabilitation provides significant effects in the kinematic, kinetic, and EMG gait parameters in acute ACLR than chronic ACLR subjects. Early surgical intervention and postrehabilitation are mandatory to get the significant effects in the clinical parameters in acute and chronic ACL injury.

 

 

#23 Methodological Characteristics, Physiological and Physical Effects, and Future Directions for Combined Training in Soccer: A Systematic Review

Reference: Healthcare (Basel). 2021 Aug 20;9(8):1075. doi: 10.3390/healthcare9081075.

Authors: Jorge Ribeiro, José Afonso, Miguel Camões, Hugo Sarmento, Mário Sá, Ricardo Lima, Rafael Oliveira, Filipe Manuel Clemente

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8393610/pdf/healthcare-09-01075.pdf

Summary: Combined training (CT) may combine strength and endurance training within a given time period, but it can also encompass additional protocols consisting of velocity, balance, or mobility as part of the same intervention. These combined approaches have become more common in soccer. This systematic review was conducted to (1) characterize the training protocols used in CT studies in soccer, (2) summarize the main physiological and physical effects of CT on soccer players, and (3) provide future directions for research. Methods: A systematic review of Cochrane Library, PubMed, Scopus, SPORTDiscus, and Web of Science databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PICOS were defined as follows: P (soccer players of any age or sex); I (CT combining strength and endurance or sprinting or balance or mobility training); C (the control group (whenever applicable), with or without comparative interventions in addition to usual soccer training); O (acute and/or chronic responses: biochemical, physiological and physical); S (must have at least two groups, either randomized or non-randomized). The database search initially identified 79 titles. From those, eight articles were deemed eligible for the systematic review. Three studies analyzed acute responses to concurrent training, while the remaining five analyzed adaptations to CT. In those tested for acute responses, physiological (hormonal) and physical (strength and power external load, internal load) parameters were observed. Adaptations were mainly focused on physical parameters (strength and power, sprints, jumps, repeated sprint ability, aerobic, change-of-direction), with relatively little focus on physiological parameters (muscle architecture). Short-term responses to CT can affect hormonal responses of testosterone after resistance training with internal and external load. In turn, these responses' effects on strength and power have produced mixed results, as have adaptations. Specifically, strength and hypertrophy are affected to a lesser extent than speed/power movements. Nevertheless, it is preferable to perform CT before endurance exercises since it is a limiting factor for interference. Volume, intensity, rest between sessions, and athletes' fitness levels and nutrition dictate the degree of interference.

 

Wed

05

Jan

2022

Reduced Injury Prevalence in Footballers Following GPS Guided Acclimatization

This article reports the utility of GPS technology to help develop and monitor incremental increases in training load while transitioning from off-season to in season to reduce musculoskeletal injury.

Tue

04

Jan

2022

The Effects of Exercise Difficulty and Time-of-Day on the Perception of the Task and Soccer Performance in Child Soccer Players

Players who are able to kick more accurately under various difficulties, i.e. time pressure, shooting distance, have advantages. The aim of the present study was to investigate the effect of exercise difficulty and time-of-day on perceived task difficulty and kicking performance.

Sun

02

Jan

2022

Latest research in football - week 42 - 2021

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 Automated Classification of Changes of Direction in Soccer Using Inertial Measurement Units

Reference: Sensors (Basel). 2021 Jul 6;21(14):4625. doi: 10.3390/s21144625.

Authors: Brian Reilly, Oliver Morgan, Gabriela Czanner, Mark A Robinson

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8309627/pdf/sensors-21-04625.pdf

Summary: Changes of direction (COD) are an important aspect of soccer match play. Understanding the physiological and biomechanical demands on players in games allows sports scientists to effectively train and rehabilitate soccer players. COD are conventionally recorded using manually annotated time-motion video analysis which is highly time consuming, so more time-efficient approaches are required. The aim was to develop an automated classification model based on multi-sensor player tracking device data to detect COD > 45°. Video analysis data and individual multi-sensor player tracking data (GPS, accelerometer, gyroscopic) for 23 academy-level soccer players were used. A novel 'GPS-COD Angle' variable was developed and used in model training; along with 24 GPS-derived, gyroscope and accelerometer variables. Video annotation was the ground truth indicator of occurrence of COD > 45°. The random forest classifier using the full set of features demonstrated the highest accuracy (AUROC = 0.957, 95% CI = 0.956-0.958, Sensitivity = 0.941, Specificity = 0.772. To balance sensitivity and specificity, model parameters were optimised resulting in a value of 0.889 for both metrics. Similarly high levels of accuracy were observed for random forest models trained using a reduced set of features, accelerometer-derived variables only, and gyroscope-derived variables only. These results point to the potential effectiveness of the novel methodology implemented in automatically identifying COD in soccer players.

 

 

#2 Co-Attendance Communities: A Multilevel Egocentric Network Analysis of American Soccer Supporters' Groups

Reference: Int J Environ Res Public Health. 2021 Jul 9;18(14):7351.  doi: 10.3390/ijerph18147351.

Authors: Adam R Cocco, Matthew Katz, Marion E Hambrick

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8305332/pdf/ijerph-18-07351.pdf

Summary: The growth of professional soccer in the United States is evident through the rapid expansion of franchises and increased game attendance within Major League Soccer (MLS) and the United Soccer League (USL). Coinciding with this growth is the emergence of European-style supporters' groups filling sections of MLS and USL stadiums. In this study, the authors utilized an egocentric network analysis to explore relationships among supporters' group members for two professional soccer clubs based in the United States. Egocentric network research focuses on the immediate social environment of individuals and is often viewed as an alternative approach to sociocentric (i.e., whole network) analyses. This study employed hierarchical linear modeling as an example of multilevel modeling with egocentric data, using ego- and alter-level variables to explain the strength of co-attendance ties. The results indicate the perceived commitment of fellow fans to the team, shared membership in a supporters' group, age, and interactions with other fans in team settings related to higher levels of co-attendance. The outcomes of this study are both theoretical, as they advance an understanding of sport consumer behavior within soccer supporters' groups, and methodological, as they illustrate the unique value of employing egocentric network analysis in sport fan research.

 

 

#3 Chronic effects of flywheel training on physical capacities in soccer players: a systematic review

Reference: Res Sports Med. 2021 Jul 27;1-21.  doi: 10.1080/15438627.2021.1958813. Online ahead of print.

Authors: William J C Allen, Kevin L De Keijzer, Javier Raya-González, Daniel Castillo, Giuseppe Coratella, Marco Beato 

Summary: The aims of the current systematic review were to evaluate the current literature surrounding the chronic effect of flywheel training on the physical capacities of soccer players, and to identify areas for future research to establish guidelines for its use.Studies were identified following a search of electronic databases (PubMed and SPORTDiscus) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA).Eleven studies met the inclusion criteria and were included. The methodological quality of the included studies ranged between 10 and 18 with an average score of 15 points using the PEDro scale. The training duration ranged from 6 weeks to 27 weeks, with volume ranging from 1 to 6 sets and 6 to 10 repetitions, and frequency from 1 to 2 times a week. This systematic review reported that a diverse range of flywheel training interventions can effectively improve strength, power, jump, and changes of direction in male soccer players of varying levels.Flywheel training interventions improve the physical capacities of soccer players of varying levels. Nonetheless, the current literature suggests contrasting evidence regarding flywheel training induced changes in sprint speed and acceleration capacity of soccer players.

 

 

#4 Test-retest reliability of a functional electromechanical dynamometer on swing eccentric hamstring exercise measures in soccer players

Reference: PeerJ. 2021 Jul 14;9:e11743. doi: 10.7717/peerj.11743. eCollection 2021.

Authors: Antonio Jesús Sánchez-Sánchez, Luis Javier Chirosa-Ríos, Ignacio Jesús Chirosa-Ríos, Agustín José García-Vega, Daniel Jerez-Mayorga 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8286058/pdf/peerj-09-11743.pdf

Summary: The use of a functional electromechanical dynamometer (FEMD) has been proposed as a valid and effective tool to evaluate specific movement patterns. The aim of this study was to determine the reliability of FEMD on swing eccentric hamstring exercise (SEHE) measures in soccer players. Nineteen federated male soccer players (20.74 ± 4.04 years) performed the SEHE at three different isokinetic velocities (20-40-60 cm/s). These evaluations were conducted in four sessions, two for familiarization and two for registration. The average and maximum load (N) of the three isokinetic velocities was calculated from the values obtained from the FEMD (Dynasystem®, Bangalore). The main results of this research showed that the reliability was high for the average load in the condition of 40 cm/s, presenting the highest ICC value (0.94). For maximum load, reliability was high in the condition of 20 cm/s. The manifestation of the most reliable load was the maximum load (ICC = 0.91-0.87). FEMD (Dynasystem®, Bangalore) is a reliable device to evaluate the eccentric strength of the hamstring muscles in soccer players.

 

 

#5 Comparison of women's collegiate soccer header kinematics by play state, intent, and outcome

Reference: J Biomech. 2021 Jul 9;126:110619.  doi: 10.1016/j.jbiomech.2021.110619. Online ahead of print.

Authors: Tanner M Filben, N Stewart Pritchard, Kathryn E Hanes-Romano, Logan E Miller, Christopher M Miles, Jillian E Urban, Joel D Stitzel

Summary: Although most head impacts in soccer are headers, limited knowledge exists about how header magnitude varies by on-field scenario. This study aimed to compare head kinematics during on-field headers by play state (i.e., corner kick, goal kick, free kick, throw-in, drill, or live ball), intent (i.e., pass, shot, or clearance), and outcome (i.e., successful or unsuccessful). Fifteen female collegiate soccer players were instrumented with mouthpiece-based head impact sensors during 72 practices and 24 games. A total of 336 headers were verified and contextualized via film review. Play state was associated with peak linear acceleration, rotational acceleration, and rotational velocity (all p < .001) while outcome was associated with peak linear acceleration (p < .010). Header intent was not significantly associated with any kinematic metric. Headers during corner kicks (22.9 g, 2189.3 rad/s2, 9.87 rad/s), goal kicks (24.3 g, 2658.9 rad/s2, 10.1 rad/s), free kicks (18.0 g, 1843.3 rad/s2, 8.43 rad/s), and live balls (18.8 g, 1769.7 rad/s2, 8.09 rad/s) each had significantly greater mean peak linear acceleration (all p < .050), rotational acceleration (all p < .001), and rotational velocity (all p < .001) than headers during drills (13.0 g, 982.4 rad/s2, 5.28 rad/s). Headers during goal kicks also had a significantly greater mean rotational acceleration compared to headers during live ball scenarios (p < .050). Successful headers (18.3 g) had a greater mean peak linear acceleration compared to unsuccessful headers (13.8 g; p < .010). Results may help inform efforts to reduce head impact exposure in soccer.

 

 

#6 Association between Clinical Vision Measures and Visual Perception and Soccer Referees' On-field Performance

Reference: Optom Vis Sci. 2021 Jul 1;98(7):789-801.  doi: 10.1097/OPX.0000000000001722.

Authors: Antonio M G Baptista, Pedro M Serra, Muhammad Faisal, Brendan T Barrett 

Summary: The decisions taken by soccer officials are critically important to game management. Understanding the underlying processes that mediate expert performance in soccer refereeing may lead to a better standard of officiating. Vision is the dominant source of incoming information upon which officials rely to make their on-field decisions. We tested the hypothesis that performance on generic tests of vision and visual perception predicts domain-specific performance in elite-level soccer referees (R) and assistant referees (AR). We assessed the vision of R and AR who officiate at the highest level in Portugal. To be eligible for inclusion, R and AR had to have officiated for at least two consecutive seasons across the 2014/2015, 2015/2016, and 2016/2017 seasons. A single, rank-order list of the performance of eligible officials was created based on the rank-order list for each season that was made by the Portuguese Soccer Federation. Clinical vision measures included visual acuity and stereoacuity, and visual perception measures were gathered using the Test of Visual Perceptual Skills, Third Edition. A total of 59 officials participated (21 R, 38 AR), 17 of whom officiated at the international level. The R and AR groups did not differ in vision or visual perception measures. We found that better stereoacuity (P < .001) and visual memory (P = .001) are associated with a higher rank order of on-field performance after adjusting for the age, experience, the national/international status, and the regional affiliation of the officials. Together, these two measures explain 22% of the variance in rank-order performance. This is the first study to show a link between the vision of officials and their on-field performance. The origin and significance of these findings remain to be established, and further work is required to establish whether they are component skills in the domain of soccer refereeing.

 

 

#7 An Accessible, 16-Week Neck Strength Training Program Improves Head Kinematics Following Chest Perturbation in Young Soccer Athletes

Reference: J Sport Rehabil. 2021 Jul 30;1-8.  doi: 10.1123/jsr.2020-0537. Online ahead of print.

Authors: Enora Le Flao, Andrew W Pichardo, Sherwin Ganpatt, Dustin J Oranchuk

Summary: Neck size and strength may be associated with head kinematics and concussion risks. However, there is a paucity of research examining neck strengthening and head kinematics in youths. In addition, neck training is likely lacking in youth sport due to a perceived inadequacy of equipment or time. Examine neck training effects with minimal equipment on neck strength and head kinematics following chest perturbations in youth athletes. Twenty-five (14 men and 11 women) youth soccer athletes (9.8 [1.5] y). Sixteen weeks of twice-weekly neck-focused resistance training utilizing bands, body weight, and manual resistance. Head kinematics (angular range of motion, peak anterior-posterior linear acceleration, and peak resultant linear acceleration) were measured by an inertial motion unit fixed to the apex of the head during torso perturbations. Neck-flexion and extension strength were assessed using weights placed on the forehead and a plate-loaded neck harness, respectively. Neck length and circumference were measured via measuring tape. Neck extension (increase in median values for all: +4.5 kg, +100%, P < .001; females: +4.5 kg, +100%, P = .002; males: +2.2 kg, +36%, P = .003) and flexion (all: +3.6 kg, +114%, P < .001; females: +3.6 kg, +114%, P = .004; males: +3.6 kg, +114%, P = .001) strength increased following the intervention. Men and women both experienced reduced perturbation-induced head pitch (all: -84%, P < .001). However, peak resultant linear acceleration decreased in the female (-53%, P = .004), but not male (-31%, P = 1.0) subgroup. Preintervention peak resultant linear acceleration and extension strength (R2 = .21, P = .033) were the closest-to-significance associations between head kinematics and strength. Young athletes can improve neck strength and reduce perturbation-induced head kinematics following a 16-week neck strengthening program. However, further research is needed to determine the effect of improved strength and head stabilization on concussion injury rates.

 

 

#8 Whole-body energy transfer strategies during football instep kicking: implications for training practices

Reference: Sports Biomech. 2021 Jul 27;1-16.  doi: 10.1080/14763141.2021.1951827. Online ahead of print.

Authors: Simon Augustus, Penny E Hudson, Nick Harvey, Neal Smith

Summary: Knowledge of whole-body energy transfer strategies during football instep kicking can help inform empirically grounded training practices. The aim of this study was thus to investigate energy transfer strategies of 15 semi-professional players performing kicks for speed and accuracy. Three-dimensional kinematics and GRFs (both 1000 Hz) were incorporated into segment power analyses to derive energy transfers between the support leg, torso, pelvis and kick leg throughout the kick. Energy transferred from support leg (r = 0.62, P = 0.013) and torso (r = 0.54, P = 0.016) into the pelvis during tension arc formation and leg cocking was redistributed to the kick leg during the downswing (r = 0.76, P < 0.001) and were associated with faster foot velocities at ball contact. This highlights whole-body function during instep kicking. Of particular importance were: (a) regulating support leg energy absorption, (b) eccentric formation and concentric release of a 'tension arc' between the torso and kicking hip, and (c) coordinated proximal to distal sequencing of the kick leg. Resistance exercises that replicate the demands of these interactions may help develop more powerful kicking motions and varying task and/or environmental constraints might facilitate development of adaptable energy transfer strategies.

 

 

#9 Motion Analysis of Match Play in U14 Male Soccer Players and the Influence of Position, Competitive Level and Contextual Variables

Reference: Int J Environ Res Public Health. 2021 Jul 7;18(14):7287.  doi: 10.3390/ijerph18147287.

Authors: Erling Algroy, Halvard Grendstad, Amund Riiser, Tone Nybakken, Atle Hole Saeterbakken, Vidar Andersen, Hilde Stokvold Gundersen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8307654/pdf/ijerph-18-07287.pdf

Summary: This study aimed to investigate match running performance in U14 male soccer players in Norway, and the influence of position, competitive level and contextual factors on running performance. Locomotion was monitored in 64 different U14 players during 23 official matches. Matches were played at two different competitive levels: U14 elite level (n = 7) and U14 sub-elite level (n = 16). The inclusion criterion was completed match halves played in the same playing position. The variables' influence on match running performance was assessed using mixed-effect models, pairwise comparisons with Bonferroni correction, and effect size. The results showed that the U14 players, on average, moved 7645 ± 840 m during a match, of which 1730 ± 681 m (22.6%) included high-intensity running (HIR, 13.5-18.5 km·h-1) and sprinting (>18.5 km·h-1). Wide midfielders (WM) and fullbacks (FB) covered the greatest sprint distance (569 ± 40 m) and, in addition to the centre midfield position (CM), also covered the greatest total distance (TD) (8014 ± 140 m) and HIR distance (1446 ± 64 m). Centre forwards (CF) performed significantly more accelerations (49.5 ± 3.8) compared other positions. TD (7952 ± 120 m vs. 7590 ± 94 m) and HIR (1432 ± 57 m vs. 1236 ± 43 m) were greater in U14 elite-level matches compared with sub-elite matches. Greater TD and sprint distances were performed in home matches, but, on the other hand, more accelerations and decelerations were performed in matches played away or in neutral locations. Significantly higher TD, HIR and sprinting distances were also found in lost or drawn matches. In conclusion, physical performance during matches is highly related to playing position, and wide positions seem to be the most physically demanding. Further, competitive level and contextual match variables are associated with players' running performance.

 

 

#10 Postural balance impairment in Tunisian second division soccer players with groin pain: A case-control study

Reference: Phys Ther Sport. 2021 Jul 15;51:85-91.  doi: 10.1016/j.ptsp.2021.07.003. Online ahead of print.

Authors: Fatma Chaari, Haithem Rebai, Sébastien Boyas, Abderrahmane Rahmani, Thouraya Fendri, Mohammed A Harrabi, Sonia Sahli

Summary: The aim was to compare postural balance outcomes between soccer players with and without groin pain (GP). Fifty-four soccer players, 27 with GP (GP group: GPG) and 27 healthy ones (control group: CG) participated in this study. Static and dynamic postural balance were assessed with a force platform and Y-balance test (Y-BT), respectively. Hip abduction, internal rotation (IR), external rotation (ER) and total rotation (TR) of both limbs were evaluated. The GPG exhibited significant higher centre of pressure values in the bipedal posture only on the foam surface in eyes opened and closed compared to controls. Besides, they had lower anterior, posteromedial and posterolateral reach distances and composite Y-BT score on the injured limb (IL) compared to non-injured limb (NIL) and dominant-limb (DL) of the CG. Moreover, they showed lower abduction, IR, ER, and TR on the IL compared to NIL and DL. Dynamic unipedal postural balance disorder could be one of the limiting factors of performance in soccer players with non-time loss GP. Hence, postural balance data in these players could enable sport coaches and physical therapists to better understand the mechanisms contributing for performance decrease.

 

 

#11 Observed and predicted ages at peak height velocity in soccer players

Reference: PLoS One. 2021 Jul 26;16(7):e0254659.  doi: 10.1371/journal.pone.0254659. eCollection 2021.

Authors: Robert M Malina, Manuel J Coelho-E-Silva, Diogo V Martinho, Paulo Sousa-E-Siva, Antonio J Figueiredo, Sean P Cumming, Miroslav Králík, Sławomir M Kozieł

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8312932/pdf/pone.0254659.pdf

Summary: The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status.

 

 

#12 Effects of Age on Match-related Acceleration and Deceleration Efforts in Elite Soccer Players

Reference: Int J Sports Med. 2021 Jul 26.  doi: 10.1055/a-1337-2961. 

Authors: Miguel Lorenzo-Martínez, Francisco J Corredoira, Carlos Lago-Peñas, Roberto López-Del Campo, Fabio Nevado-Garrosa, Ezequiel Rey

Summary: The aim of this study was to examine the effects of chronological age on acceleration and deceleration match performance in professional soccer players. A total of 5317 individual match observations were collected on 420 professional players competing in the Spanish LaLiga during the 2018-2019 season, using a multiple-camera computerised tracking system (TRACAB; ChyronHego, Melville, NY, USA). Players were classified using a k-means cluster analysis into four different age groups: 17-23 years, 24-27 years, 28-30 years, and 31-38 years. Linear mixed models were adjusted to compare the players' match performance according to their age group and playing position (central defenders, external defenders, central midfielders, external midfielders, and forwards). The results showed that players aged between 31-38 years performed a significantly less total number of accelerations (ES=0.30-0.48) and decelerations (ES=0.29-0.49) in comparison with younger players. These age-related physical performance declines were more pronounced among central defenders, central midfielders, and forwards. However, no significant effects were obtained for players' maximum acceleration and deceleration capacities. The current findings provide useful information for coaches and strength and conditioning specialists to better understand the effects of age on players' physical performance and to develop age-tailored training programs.

 

 

#13 Professional Soccer and Dementia Risk-The Ugly Side of the Beautiful Game

Reference: JAMA Neurol. 2021 Aug 2.  doi:0.1001/jamaneurol.2021.2246. Online ahead of print.

Authors: Breton M Asken, Gil D Rabinovici

Summary: While an increased risk for late-life neurodegenerative disease and dementia has consistently been observed in professional athletes with very high exposure to repetitive head impacts, such as former professional boxers and US football players, much less is known about neurologic outcomes in sports with lower head trauma exposure. Soccer, known to most of the world as football, is by far the most popular sport globally, with an estimated 270 million active players worldwide.1 The Brazilian superstar Pelé famously referred to soccer as “the beautiful game,” inspired by the fancy footwork and orchestral movement displayed by footballers at the highest level. However, heading the ball (known as headers) is also an integral part of the game, and additional incidental head impacts occur via collisions with other players or the ground. A 2017 summit on head injury in soccer concluded that the frequency of headers increases from the youth level to the professional level.2 Both overall header exposure and the force of impact generated by headers were deemed relatively low but with considerable individual variability. Linear forces generated by heading the ball can range from as low as 5g to as high as 60g. Studies have inconsistently detected acute and chronic sequelae of soccer headers,3 with some studies reporting associations between more frequent headers, worse cognitive test performance, and compromised white matter integrity on magnetic resonance imaging.4

 

 

#14 Association of Field Position and Career Length With Risk of Neurodegenerative Disease in Male Former Professional Soccer Players

Reference: JAMA Neurol. 2021 Aug 2;e212403.  doi: 10.1001/jamaneurol.2021.2403. Online ahead of print.

Authors: Emma R Russell, Daniel F Mackay, Katy Stewart, John A MacLean, Jill P Pell, William Stewart

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8329793/

Summary: Neurodegenerative disease mortality is higher among former professional soccer players than general population controls. However, the factors contributing to increased neurodegenerative disease mortality in this population remain uncertain. The aim was to investigate the association of field position, professional career length, and playing era with risk of neurodegenerative disease among male former professional soccer players. This cohort study used population-based health record linkage in Scotland to evaluate risk among 7676 male former professional soccer players born between January 1, 1900, and January 1, 1977, and 23 028 general population control individuals matched by year of birth, sex, and area socioeconomic status providing 1 812 722 person-years of follow-up. Scottish Morbidity Record and death certification data were available from January 1, 1981, to December 31, 2016, and prescribing data were available from January 1, 2009, to December 31, 2016. Database interrogation was performed on December 10, 2018, and data were analyzed between April 2020 and May 2021. Outcomes were obtained by individual-level record linkage to national electronic records of mental health and general hospital inpatient and day-case admissions as well as prescribing information and death certification. Risk of neurodegenerative disease was evaluated between former professional soccer players and matched general population control individuals. In this cohort study of 30 704 male individuals, 386 of 7676 former soccer players (5.0%) and 366 of 23 028 matched population control individuals (1.6%) were identified with a neurodegenerative disease diagnosis (hazard ratio [HR], 3.66; 95% CI, 2.88-4.65; P < .001). Compared with the risk among general population control individuals, risk of neurodegenerative disease was highest for defenders (HR, 4.98; 95% CI, 3.18-7.79; P < .001) and lowest for goalkeepers (HR, 1.83; 95% CI, 0.93-3.60; P = .08). Regarding career length, risk was highest among former soccer players with professional career lengths longer than 15 years (HR, 5.20; 95% CI, 3.17-8.51; P < .001). Regarding playing era, risk remained similar for all players born between 1910 and 1969. The differences in risk of neurodegenerative disease observed in this cohort study imply increased risk with exposure to factors more often associated with nongoalkeeper positions, with no evidence this association has changed over the era studied. While investigations to confirm specific factors contributing to increased risk of neurodegenerative disease among professional soccer players are required, strategies directed toward reducing head impact exposure may be advisable in the meantime.

 

 

#15 Confirmation of early non-bulbar onset of amyotrophic lateral sclerosis in Spanish league soccer players

Reference: J Neurol Sci. 2021 Jul 24;428:117586.  doi: 10.1016/j.jns.2021.117586. Online ahead of print.

Authors: Josep Gamez, Francesc Carmona

Summary: Sports-related activity has been proposed as a risk factor for ALS, particularly among professionals playing American football and soccer, with a reported prevalence between two and forty times higher than the general population. Early onset (by two decades) was described among Italian soccer players as early as 2005. This study aims to characterise the phenotype of seven Spanish retired professional and semi-professional soccer players. The cases were identified using the following sources: (i) personal archives from a leading ALS Unit, (ii) PubMed and specialised websites, and (iii) self-reports of patients in the media. Age and site of onset, survival time, history of trauma, playing position and time between retirement and first symptoms were investigated for soccer players in the Spanish league diagnosed between 2000 and 2020. Seven ALS cases were identified. The mean age at onset was 41.5 years (SD 9.2, median 45.5, range 31.5-51.2). Onset was bulbar in one individual, while six experienced spinal onset. Three patients had the flail arm syndrome variant. Two cases were goalkeepers, two defenders and three midfielders. Four had a history of trauma (two serious). Survival time for the two deceased patients was 71.8 months. Mean time between retirement and first symptoms was 9.4 years (SD 8.0, median 15.2, range 0.1-17.5). Our study has the largest sample size of non-Italian league soccer professionals and semi-professionals, and our results corroborate early onset (by 23.7 years). Unlike the Italian cohorts, bulbar onset is rare, and upper limb onset is most common.

 

 

#16 Expertise Classification of Soccer Goalkeepers in Highly Dynamic Decision Tasks: A Deep Learning Approach for Temporal and Spatial Feature Recognition of Fixation Image Patch Sequences

Reference: Front Sports Act Living. 2021 Jul 26;3:692526. doi: 10.3389/fspor.2021.692526. eCollection 2021.

Authors: Benedikt Hosp, Florian Schultz, Enkelejda Kasneci, Oliver Höner

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8350442/pdf/fspor-03-692526.pdf

Summary: The focus of expertise research moves constantly forward and includes cognitive factors, such as visual information perception and processing. In highly dynamic tasks, such as decision making in sports, these factors become more important to build a foundation for diagnostic systems and adaptive learning environments. Although most recent research focuses on behavioral features, the underlying cognitive mechanisms have been poorly understood, mainly due to a lack of adequate methods for the analysis of complex eye tracking data that goes beyond aggregated fixations and saccades. There are no consistent statements about specific perceptual features that explain expertise. However, these mechanisms are an important part of expertise, especially in decision making in sports games, as highly trained perceptual cognitive abilities can provide athletes with some advantage. We developed a deep learning approach that independently finds latent perceptual features in fixation image patches. It then derives expertise based solely on these fixation patches, which encompass the gaze behavior of athletes in an elaborately implemented virtual reality setup. We present a CNN-BiLSTM based model for expertise assessment in goalkeeper-specific decision tasks on initiating passes in build-up situations. The empirical validation demonstrated that our model has the ability to find valuable latent features that detect the expertise level of 33 athletes (novice, advanced, and expert) with 73.11% accuracy. This model is a first step in the direction of generalizable expertise recognition based on eye movements.

 

 

#17 The Impact of Environmental Conditions on Player Loads During Preseason Training Sessions in Women's Soccer Athletes

Reference: J Strength Cond Res. 2021 Aug 11.  doi: 10.1519/JSC.0000000000004112. Online ahead of print.

Authors: Alexis B Austin, Sean M Collins, Robert A Huggins, Brittany A Smith, Thomas G Bowman

Summary: Our objective was to determine the impact of environmental conditions on player loads during preseason training sessions in women's soccer athletes. Eleven women's NCAA Division III soccer players (age = 20 ± 1 year, height = 167.28 ± 8.65 cm, body mass = 60.18 ± 5.42 kg, V[Combining Dot Above]O2max = 43.70 ± 3.95 ml·kg-1·min-1) volunteered to wear Global Positioning System (GPS) devices (Sports Performance Tracking, Melbourne, Australia) that provided measures of training session external intensity throughout all preseason practices (n = 15). We recorded wet-bulb globe temperature (WBGT), session Rating of Perceived Exertion-Training Load (sRPE-TL), and ΔBM during each preseason training session and set α ≤ 0.05. The combination of WBGT, sRPE-TL, and ΔBM explained 34% of the variance in GPS-based intensity score (proprietary measure) (F3,153 = 26.25, p < 0.001). Wet-bulb globe temperature (t156 = -2.58, p = 0.01), sRPE (t156 = 8.24, p < 0.001), and ΔBM (t156 = 2.39, p = 0.02) were significantly associated with intensity. The ΔBM from prepractice (60.00 ± 5.21 kg) to postpractice (59.61 ± 5.10 kg) was statistically significant (p < 0.001); however, ΔBM from the beginning of preseason (59.87 ± 5.31 kg) to the end of preseason (59.91 ± 5.58 kg) was not significant (p = 0.89). Despite relatively low to moderate environmental conditions, increases in WBGT were associated with reductions in GPS intensity and elevated internal load via sRPE-TL. Our findings support the association between exercise intensity and WBGT, internal load, and hydration status; thus, coaches and exercise scientists should take these factors into account when monitoring or interpreting intensity metrics. Furthermore, these findings support the continued use of environmental monitoring and hydration best-practice policies to limit exercise intensity in the heat so as to mitigate excessive heat stress.

 

 

#18 Injury Profile among Elite Youth Male Football Players in a German Academy

Reference: Int J Sports Med. 2021 Aug 9. doi: 10.1055/a-1516-4139. 

Authors: Ayham Jaber, Johannes Weishorn, Gregor Berrsche, Henning Ott, Yannic Bangert

Summary: Studies that report injuries in elite youth football players are scarce. So far, no such studies have been reported in Germany. The aim of this study is to descriptively and statistically report the incidence of injuries that resulted in time-loss ≥ 4 days in the TSG Hoffenheim football academy by 138 male players aged between 12 and 19 years during one season. A total of 109 injuries were sustained by 76 players: 6.9 injuries occurred per 1000 hours of matches (95% CI, 5.0-9.6) and 0.7 injuries per 1000 hours of training (95% CI, 0.5-0.9) with a ratio of 9.8. Some 66% of all injuries occurred during matches. Injuries involved the lower limb (81%), upper limb (9%), head & neck (5%) and trunk injuries (5%). 21 (19%) of all injuries were regarded as severe and resulted in time-loss > 28 days. U16-U19 teams sustained more injuries (74, 68%) than U12-U15 (35, 32%) (P= 0.032). The most frequent diagnosis was thigh strain (22%). Time-loss ranged from 4-339 days (SD: 40, Average: 23). Many injuries were a result of strain. Available injury prevention programs should be adhered to more strictly. Dedicated epidemiological studies are needed to optimize focused injury prevention programs.

 

 

#19 Preseason weight-bearing ankle dorsiflexion in male professional football players with and without a history of severe ankle injury: A novel analysis in an English Premier League club

Reference: Phys Ther Sport. 2021 Jul 28;52:21-29.  doi: 10.1016/j.ptsp.2021.07.006. Online ahead of print.

Authors: Nicholas C Clark, Stuart D Campbell

Summary: Ankle injuries are common in professional football and have profound player/team/club consequences. The weight-bearing lunge-test (WBLT) assesses ankle dorsiflexion range-of-motion in football primary/secondary injury prevention and performance contexts. Data for uninjured and previously ankle-injured players in the English Premier League (EPL) is not available. This study analysed WBLT measurements (cm) within and between uninjured and previously severe ankle-injured players (injured-stiff group, injured-lax group) in one EPL club. Forty-nine players (age 22.9 ± 4.6 yr; height 181.6 ± 5.2 cm; mass 77.7 ± 7.6 kg) participated in this study. Prevalence (%) of previous unilateral severe ankle injury (USAI). Side-to-side (right/left, dominant/nondominant, injured/uninjured) WBLT comparisons at group-level (t-test [within-group]; Welch's ANOVA [between-group]; effect sizes [within-/between-group]) and individual-level (limb symmetry index [%]; absolute-asymmetry [%]) were used as outcome measures. Prevalence of USAI was 38.7%. There were no statistically-significant side-to-side differences for within-/between-group comparisons. Effect sizes: just-below-large (injured-stiff) and extremely-large (injured-lax) for within-group injured-side/uninjured-side comparisons; just-below-medium (injured-lax) to just-above-medium (injured-stiff) for injured-side comparisons to uninjured players. Absolute-asymmetries: uninjured players, 15.4±13.2%; injured-stiff, 21.8±33.6%; injured-lax 20.4±13.6%. Over one-third of players had previous USAI. Effect sizes indicate substantial within-group side-to-side differences and less substantial between-group differences. Across groups, some players had absolute-asymmetries that may elicit concern in ankle primary/secondary injury prevention and performance contexts.

 

 

#20 Optimizing the Explosive Force of the Elite Level Football-Tennis Players through Plyometric and Specific Exercises

Reference: Int J Environ Res Public Health. 2021 Aug 3;18(15):8228. doi: 10.3390/ijerph18158228.

Authors: Anamaria Gherghel, Dana Badau, Adela Badau, Liviu Moraru, Gabriel Marian Manolache, Bogdan Marian Oancea, Corina Tifrea, Virgil Tudor, Raluca Maria Costache

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345974/pdf/ijerph-18-08228.pdf

Summary: The aim of the research was to implement an athletic program to improve the explosive force in order to optimize physical fitness at the level of elite football-tennis players and evaluate the progress made through specific tests using the Opto Jump. The research included 10 elite European and world-class players, on whom an experimental program was applied in order to improve the explosive force of the limbs in conditions of speed, endurance, and dynamic balance. Study tests: five vertical jumps on the spot, on the left/right leg; five back and forth jumps on the left/right leg; five left/right side jumps on the left/right leg; vertical jumps on both legs 60 s; BFS vertical jumps. For each test, the following parameters specific to the explosive force were statistically analyzed: contact time (s); flight time (s); jump height (cm), jump power (w/kg); RSI-Reactive Strength Index, defined as Height (m/s). In the study, the average value of the parameters specific to the jumps performed in each test was taken into account. During the study, the tests were performed and processed on the Opto Jump device and software. In all tests of the experiment monitored through Opto Jump, significant progress was made in the final test compared to the initial one, which demonstrates the efficiency of the physical training program implemented for the development of explosive force, with an impact on the sports performance of elite players. The most relevant results obtained for the left leg regarding the improvement of the explosive force of the lower limbs materialized in the jump height parameter was in the test of five vertical jumps on one leg on the spot, and for the right leg in the tests of: five back and forth jumps and five left/right side jumps. The most significant advances in the study were in the tests, in descending order of their weight: 60 s vertical jumps on both legs; five back-and-forth jumps and five left/right side jumps, five vertical jumps on one leg standing, and BFS vertical jumps.

 

 

#21 Should I Stay or Should I Go? The Impact of Social Networks on the Choice to Play for a National Team in Football

Reference: Int J Environ Res Public Health. 2021 Jul 21;18(15):7719.  doi: 10.3390/ijerph18157719.

Authors: Klaus Seiberth, Ansgar Thiel

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345438/pdf/ijerph-18-07719.pdf

Summary: In the course of their careers, elite athletes are faced with crucial decisions. This applies particularly to adolescent athletes who additionally have to cope with a variety of age-related developmental tasks. For young top football players with a migrant background, this can be even more challenging as they often attract the interest of national associations. From a network-theoretical perspective, it can be considered likely that the decision to join a top national association is not taken independently of the players' networks. This article addresses the role of network actors within the players' decision-making process. Our analysis is guided by constructivist network theory and based on a qualitative research approach that used guided expert interviews as its core research tool. Ten interviews with German-born youth internationals with a migrant background were conducted. The present analysis reveals several network actors such as family, coaches and players' agents involved in the 'national team question'. Evidently, most relevant networks of players with a migrant background are sports-related. These networks turned out to be highly functionalized and leave only limited room for manoeuvring. At the same time, the interviews reveal 'structural holes' within the players' networks and indicate a considerable need for the optimization of talent counselling.

 

 

Fri

31

Dec

2021

Association Between Endocrine Markers, Accumulated Workload, and Fitness Parameters During a Season in Elite Young Soccer Players

The purpose of this study was to analyze differences between endocrine markers with accumulated training workload training and fitness parameters during early-, mid- and end-seasons.

Wed

29

Dec

2021

Effects of ketogenic diet on body composition, strength, muscle area, metabolism and performance in semi-professional soccer players

Effects of ketogenic diet on body composition, strength, muscle area, metabolism and performance in semi-professional soccer players.

Tue

28

Dec

2021

Latest research in football - week 41 - 2021

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 Automated Classification of Changes of Direction in Soccer Using Inertial Measurement Units

Reference: Sensors (Basel). 2021 Jul 6;21(14):4625. doi: 10.3390/s21144625.

Authors: Brian Reilly, Oliver Morgan, Gabriela Czanner, Mark A Robinson

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8309627/pdf/sensors-21-04625.pdf

Summary: Changes of direction (COD) are an important aspect of soccer match play. Understanding the physiological and biomechanical demands on players in games allows sports scientists to effectively train and rehabilitate soccer players. COD are conventionally recorded using manually annotated time-motion video analysis which is highly time consuming, so more time-efficient approaches are required. The aim was to develop an automated classification model based on multi-sensor player tracking device data to detect COD > 45°. Video analysis data and individual multi-sensor player tracking data (GPS, accelerometer, gyroscopic) for 23 academy-level soccer players were used. A novel 'GPS-COD Angle' variable was developed and used in model training; along with 24 GPS-derived, gyroscope and accelerometer variables. Video annotation was the ground truth indicator of occurrence of COD > 45°. The random forest classifier using the full set of features demonstrated the highest accuracy (AUROC = 0.957, 95% CI = 0.956-0.958, Sensitivity = 0.941, Specificity = 0.772. To balance sensitivity and specificity, model parameters were optimised resulting in a value of 0.889 for both metrics. Similarly high levels of accuracy were observed for random forest models trained using a reduced set of features, accelerometer-derived variables only, and gyroscope-derived variables only. These results point to the potential effectiveness of the novel methodology implemented in automatically identifying COD in soccer players.

 

 

#2 Co-Attendance Communities: A Multilevel Egocentric Network Analysis of American Soccer Supporters' Groups

Reference: Int J Environ Res Public Health. 2021 Jul 9;18(14):7351.  doi: 10.3390/ijerph18147351.

Authors: Adam R Cocco, Matthew Katz, Marion E Hambrick

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8305332/pdf/ijerph-18-07351.pdf

Summary: The growth of professional soccer in the United States is evident through the rapid expansion of franchises and increased game attendance within Major League Soccer (MLS) and the United Soccer League (USL). Coinciding with this growth is the emergence of European-style supporters' groups filling sections of MLS and USL stadiums. In this study, the authors utilized an egocentric network analysis to explore relationships among supporters' group members for two professional soccer clubs based in the United States. Egocentric network research focuses on the immediate social environment of individuals and is often viewed as an alternative approach to sociocentric (i.e., whole network) analyses. This study employed hierarchical linear modeling as an example of multilevel modeling with egocentric data, using ego- and alter-level variables to explain the strength of co-attendance ties. The results indicate the perceived commitment of fellow fans to the team, shared membership in a supporters' group, age, and interactions with other fans in team settings related to higher levels of co-attendance. The outcomes of this study are both theoretical, as they advance an understanding of sport consumer behavior within soccer supporters' groups, and methodological, as they illustrate the unique value of employing egocentric network analysis in sport fan research.

 

 

#3 Chronic effects of flywheel training on physical capacities in soccer players: a systematic review

Reference: Res Sports Med. 2021 Jul 27;1-21.  doi: 10.1080/15438627.2021.1958813. Online ahead of print.

Authors: William J C Allen, Kevin L De Keijzer, Javier Raya-González, Daniel Castillo, Giuseppe Coratella, Marco Beato 

Summary: The aims of the current systematic review were to evaluate the current literature surrounding the chronic effect of flywheel training on the physical capacities of soccer players, and to identify areas for future research to establish guidelines for its use.Studies were identified following a search of electronic databases (PubMed and SPORTDiscus) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA).Eleven studies met the inclusion criteria and were included. The methodological quality of the included studies ranged between 10 and 18 with an average score of 15 points using the PEDro scale. The training duration ranged from 6 weeks to 27 weeks, with volume ranging from 1 to 6 sets and 6 to 10 repetitions, and frequency from 1 to 2 times a week. This systematic review reported that a diverse range of flywheel training interventions can effectively improve strength, power, jump, and changes of direction in male soccer players of varying levels.Flywheel training interventions improve the physical capacities of soccer players of varying levels. Nonetheless, the current literature suggests contrasting evidence regarding flywheel training induced changes in sprint speed and acceleration capacity of soccer players.

 

 

#4 Test-retest reliability of a functional electromechanical dynamometer on swing eccentric hamstring exercise measures in soccer players

Reference: PeerJ. 2021 Jul 14;9:e11743. doi: 10.7717/peerj.11743. eCollection 2021.

Authors: Antonio Jesús Sánchez-Sánchez, Luis Javier Chirosa-Ríos, Ignacio Jesús Chirosa-Ríos, Agustín José García-Vega, Daniel Jerez-Mayorga 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8286058/pdf/peerj-09-11743.pdf

Summary: The use of a functional electromechanical dynamometer (FEMD) has been proposed as a valid and effective tool to evaluate specific movement patterns. The aim of this study was to determine the reliability of FEMD on swing eccentric hamstring exercise (SEHE) measures in soccer players. Nineteen federated male soccer players (20.74 ± 4.04 years) performed the SEHE at three different isokinetic velocities (20-40-60 cm/s). These evaluations were conducted in four sessions, two for familiarization and two for registration. The average and maximum load (N) of the three isokinetic velocities was calculated from the values obtained from the FEMD (Dynasystem®, Bangalore). The main results of this research showed that the reliability was high for the average load in the condition of 40 cm/s, presenting the highest ICC value (0.94). For maximum load, reliability was high in the condition of 20 cm/s. The manifestation of the most reliable load was the maximum load (ICC = 0.91-0.87). FEMD (Dynasystem®, Bangalore) is a reliable device to evaluate the eccentric strength of the hamstring muscles in soccer players.

 

 

#5 Comparison of women's collegiate soccer header kinematics by play state, intent, and outcome

Reference: J Biomech. 2021 Jul 9;126:110619.  doi: 10.1016/j.jbiomech.2021.110619. Online ahead of print.

Authors: Tanner M Filben, N Stewart Pritchard, Kathryn E Hanes-Romano, Logan E Miller, Christopher M Miles, Jillian E Urban, Joel D Stitzel

Summary: Although most head impacts in soccer are headers, limited knowledge exists about how header magnitude varies by on-field scenario. This study aimed to compare head kinematics during on-field headers by play state (i.e., corner kick, goal kick, free kick, throw-in, drill, or live ball), intent (i.e., pass, shot, or clearance), and outcome (i.e., successful or unsuccessful). Fifteen female collegiate soccer players were instrumented with mouthpiece-based head impact sensors during 72 practices and 24 games. A total of 336 headers were verified and contextualized via film review. Play state was associated with peak linear acceleration, rotational acceleration, and rotational velocity (all p < .001) while outcome was associated with peak linear acceleration (p < .010). Header intent was not significantly associated with any kinematic metric. Headers during corner kicks (22.9 g, 2189.3 rad/s2, 9.87 rad/s), goal kicks (24.3 g, 2658.9 rad/s2, 10.1 rad/s), free kicks (18.0 g, 1843.3 rad/s2, 8.43 rad/s), and live balls (18.8 g, 1769.7 rad/s2, 8.09 rad/s) each had significantly greater mean peak linear acceleration (all p < .050), rotational acceleration (all p < .001), and rotational velocity (all p < .001) than headers during drills (13.0 g, 982.4 rad/s2, 5.28 rad/s). Headers during goal kicks also had a significantly greater mean rotational acceleration compared to headers during live ball scenarios (p < .050). Successful headers (18.3 g) had a greater mean peak linear acceleration compared to unsuccessful headers (13.8 g; p < .010). Results may help inform efforts to reduce head impact exposure in soccer.

 

 

#6 Association between Clinical Vision Measures and Visual Perception and Soccer Referees' On-field Performance

Reference: Optom Vis Sci. 2021 Jul 1;98(7):789-801.  doi: 10.1097/OPX.0000000000001722.

Authors: Antonio M G Baptista, Pedro M Serra, Muhammad Faisal, Brendan T Barrett 

Summary: The decisions taken by soccer officials are critically important to game management. Understanding the underlying processes that mediate expert performance in soccer refereeing may lead to a better standard of officiating. Vision is the dominant source of incoming information upon which officials rely to make their on-field decisions. We tested the hypothesis that performance on generic tests of vision and visual perception predicts domain-specific performance in elite-level soccer referees (R) and assistant referees (AR). We assessed the vision of R and AR who officiate at the highest level in Portugal. To be eligible for inclusion, R and AR had to have officiated for at least two consecutive seasons across the 2014/2015, 2015/2016, and 2016/2017 seasons. A single, rank-order list of the performance of eligible officials was created based on the rank-order list for each season that was made by the Portuguese Soccer Federation. Clinical vision measures included visual acuity and stereoacuity, and visual perception measures were gathered using the Test of Visual Perceptual Skills, Third Edition. A total of 59 officials participated (21 R, 38 AR), 17 of whom officiated at the international level. The R and AR groups did not differ in vision or visual perception measures. We found that better stereoacuity (P < .001) and visual memory (P = .001) are associated with a higher rank order of on-field performance after adjusting for the age, experience, the national/international status, and the regional affiliation of the officials. Together, these two measures explain 22% of the variance in rank-order performance. This is the first study to show a link between the vision of officials and their on-field performance. The origin and significance of these findings remain to be established, and further work is required to establish whether they are component skills in the domain of soccer refereeing.

 

 

#7 An Accessible, 16-Week Neck Strength Training Program Improves Head Kinematics Following Chest Perturbation in Young Soccer Athletes

Reference: J Sport Rehabil. 2021 Jul 30;1-8.  doi: 10.1123/jsr.2020-0537. Online ahead of print.

Authors: Enora Le Flao, Andrew W Pichardo, Sherwin Ganpatt, Dustin J Oranchuk

Summary: Neck size and strength may be associated with head kinematics and concussion risks. However, there is a paucity of research examining neck strengthening and head kinematics in youths. In addition, neck training is likely lacking in youth sport due to a perceived inadequacy of equipment or time. Examine neck training effects with minimal equipment on neck strength and head kinematics following chest perturbations in youth athletes. Twenty-five (14 men and 11 women) youth soccer athletes (9.8 [1.5] y). Sixteen weeks of twice-weekly neck-focused resistance training utilizing bands, body weight, and manual resistance. Head kinematics (angular range of motion, peak anterior-posterior linear acceleration, and peak resultant linear acceleration) were measured by an inertial motion unit fixed to the apex of the head during torso perturbations. Neck-flexion and extension strength were assessed using weights placed on the forehead and a plate-loaded neck harness, respectively. Neck length and circumference were measured via measuring tape. Neck extension (increase in median values for all: +4.5 kg, +100%, P < .001; females: +4.5 kg, +100%, P = .002; males: +2.2 kg, +36%, P = .003) and flexion (all: +3.6 kg, +114%, P < .001; females: +3.6 kg, +114%, P = .004; males: +3.6 kg, +114%, P = .001) strength increased following the intervention. Men and women both experienced reduced perturbation-induced head pitch (all: -84%, P < .001). However, peak resultant linear acceleration decreased in the female (-53%, P = .004), but not male (-31%, P = 1.0) subgroup. Preintervention peak resultant linear acceleration and extension strength (R2 = .21, P = .033) were the closest-to-significance associations between head kinematics and strength. Young athletes can improve neck strength and reduce perturbation-induced head kinematics following a 16-week neck strengthening program. However, further research is needed to determine the effect of improved strength and head stabilization on concussion injury rates.

 

 

#8 Whole-body energy transfer strategies during football instep kicking: implications for training practices

Reference: Sports Biomech. 2021 Jul 27;1-16.  doi: 10.1080/14763141.2021.1951827. Online ahead of print.

Authors: Simon Augustus, Penny E Hudson, Nick Harvey, Neal Smith

Summary: Knowledge of whole-body energy transfer strategies during football instep kicking can help inform empirically grounded training practices. The aim of this study was thus to investigate energy transfer strategies of 15 semi-professional players performing kicks for speed and accuracy. Three-dimensional kinematics and GRFs (both 1000 Hz) were incorporated into segment power analyses to derive energy transfers between the support leg, torso, pelvis and kick leg throughout the kick. Energy transferred from support leg (r = 0.62, P = 0.013) and torso (r = 0.54, P = 0.016) into the pelvis during tension arc formation and leg cocking was redistributed to the kick leg during the downswing (r = 0.76, P < 0.001) and were associated with faster foot velocities at ball contact. This highlights whole-body function during instep kicking. Of particular importance were: (a) regulating support leg energy absorption, (b) eccentric formation and concentric release of a 'tension arc' between the torso and kicking hip, and (c) coordinated proximal to distal sequencing of the kick leg. Resistance exercises that replicate the demands of these interactions may help develop more powerful kicking motions and varying task and/or environmental constraints might facilitate development of adaptable energy transfer strategies.

 

 

#9 Motion Analysis of Match Play in U14 Male Soccer Players and the Influence of Position, Competitive Level and Contextual Variables

Reference: Int J Environ Res Public Health. 2021 Jul 7;18(14):7287.  doi: 10.3390/ijerph18147287.

Authors: Erling Algroy, Halvard Grendstad, Amund Riiser, Tone Nybakken, Atle Hole Saeterbakken, Vidar Andersen, Hilde Stokvold Gundersen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8307654/pdf/ijerph-18-07287.pdf

Summary: This study aimed to investigate match running performance in U14 male soccer players in Norway, and the influence of position, competitive level and contextual factors on running performance. Locomotion was monitored in 64 different U14 players during 23 official matches. Matches were played at two different competitive levels: U14 elite level (n = 7) and U14 sub-elite level (n = 16). The inclusion criterion was completed match halves played in the same playing position. The variables' influence on match running performance was assessed using mixed-effect models, pairwise comparisons with Bonferroni correction, and effect size. The results showed that the U14 players, on average, moved 7645 ± 840 m during a match, of which 1730 ± 681 m (22.6%) included high-intensity running (HIR, 13.5-18.5 km·h-1) and sprinting (>18.5 km·h-1). Wide midfielders (WM) and fullbacks (FB) covered the greatest sprint distance (569 ± 40 m) and, in addition to the centre midfield position (CM), also covered the greatest total distance (TD) (8014 ± 140 m) and HIR distance (1446 ± 64 m). Centre forwards (CF) performed significantly more accelerations (49.5 ± 3.8) compared other positions. TD (7952 ± 120 m vs. 7590 ± 94 m) and HIR (1432 ± 57 m vs. 1236 ± 43 m) were greater in U14 elite-level matches compared with sub-elite matches. Greater TD and sprint distances were performed in home matches, but, on the other hand, more accelerations and decelerations were performed in matches played away or in neutral locations. Significantly higher TD, HIR and sprinting distances were also found in lost or drawn matches. In conclusion, physical performance during matches is highly related to playing position, and wide positions seem to be the most physically demanding. Further, competitive level and contextual match variables are associated with players' running performance.

 

 

#10 Postural balance impairment in Tunisian second division soccer players with groin pain: A case-control study

Reference: Phys Ther Sport. 2021 Jul 15;51:85-91.  doi: 10.1016/j.ptsp.2021.07.003. Online ahead of print.

Authors: Fatma Chaari, Haithem Rebai, Sébastien Boyas, Abderrahmane Rahmani, Thouraya Fendri, Mohammed A Harrabi, Sonia Sahli

Summary: The aim was to compare postural balance outcomes between soccer players with and without groin pain (GP). Fifty-four soccer players, 27 with GP (GP group: GPG) and 27 healthy ones (control group: CG) participated in this study. Static and dynamic postural balance were assessed with a force platform and Y-balance test (Y-BT), respectively. Hip abduction, internal rotation (IR), external rotation (ER) and total rotation (TR) of both limbs were evaluated. The GPG exhibited significant higher centre of pressure values in the bipedal posture only on the foam surface in eyes opened and closed compared to controls. Besides, they had lower anterior, posteromedial and posterolateral reach distances and composite Y-BT score on the injured limb (IL) compared to non-injured limb (NIL) and dominant-limb (DL) of the CG. Moreover, they showed lower abduction, IR, ER, and TR on the IL compared to NIL and DL. Dynamic unipedal postural balance disorder could be one of the limiting factors of performance in soccer players with non-time loss GP. Hence, postural balance data in these players could enable sport coaches and physical therapists to better understand the mechanisms contributing for performance decrease.

 

 

#11 Observed and predicted ages at peak height velocity in soccer players

Reference: PLoS One. 2021 Jul 26;16(7):e0254659.  doi: 10.1371/journal.pone.0254659. eCollection 2021.

Authors: Robert M Malina, Manuel J Coelho-E-Silva, Diogo V Martinho, Paulo Sousa-E-Siva, Antonio J Figueiredo, Sean P Cumming, Miroslav Králík, Sławomir M Kozieł

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8312932/pdf/pone.0254659.pdf

Summary: The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status.

 

 

#12 Effects of Age on Match-related Acceleration and Deceleration Efforts in Elite Soccer Players

Reference: Int J Sports Med. 2021 Jul 26.  doi: 10.1055/a-1337-2961. 

Authors: Miguel Lorenzo-Martínez, Francisco J Corredoira, Carlos Lago-Peñas, Roberto López-Del Campo, Fabio Nevado-Garrosa, Ezequiel Rey

Summary: The aim of this study was to examine the effects of chronological age on acceleration and deceleration match performance in professional soccer players. A total of 5317 individual match observations were collected on 420 professional players competing in the Spanish LaLiga during the 2018-2019 season, using a multiple-camera computerised tracking system (TRACAB; ChyronHego, Melville, NY, USA). Players were classified using a k-means cluster analysis into four different age groups: 17-23 years, 24-27 years, 28-30 years, and 31-38 years. Linear mixed models were adjusted to compare the players' match performance according to their age group and playing position (central defenders, external defenders, central midfielders, external midfielders, and forwards). The results showed that players aged between 31-38 years performed a significantly less total number of accelerations (ES=0.30-0.48) and decelerations (ES=0.29-0.49) in comparison with younger players. These age-related physical performance declines were more pronounced among central defenders, central midfielders, and forwards. However, no significant effects were obtained for players' maximum acceleration and deceleration capacities. The current findings provide useful information for coaches and strength and conditioning specialists to better understand the effects of age on players' physical performance and to develop age-tailored training programs.

 

 

#13 Professional Soccer and Dementia Risk-The Ugly Side of the Beautiful Game

Reference: JAMA Neurol. 2021 Aug 2.  doi:0.1001/jamaneurol.2021.2246. Online ahead of print.

Authors: Breton M Asken, Gil D Rabinovici

Summary: While an increased risk for late-life neurodegenerative disease and dementia has consistently been observed in professional athletes with very high exposure to repetitive head impacts, such as former professional boxers and US football players, much less is known about neurologic outcomes in sports with lower head trauma exposure. Soccer, known to most of the world as football, is by far the most popular sport globally, with an estimated 270 million active players worldwide.1 The Brazilian superstar Pelé famously referred to soccer as “the beautiful game,” inspired by the fancy footwork and orchestral movement displayed by footballers at the highest level. However, heading the ball (known as headers) is also an integral part of the game, and additional incidental head impacts occur via collisions with other players or the ground. A 2017 summit on head injury in soccer concluded that the frequency of headers increases from the youth level to the professional level.2 Both overall header exposure and the force of impact generated by headers were deemed relatively low but with considerable individual variability. Linear forces generated by heading the ball can range from as low as 5g to as high as 60g. Studies have inconsistently detected acute and chronic sequelae of soccer headers,3 with some studies reporting associations between more frequent headers, worse cognitive test performance, and compromised white matter integrity on magnetic resonance imaging.4

 

 

#14 Association of Field Position and Career Length With Risk of Neurodegenerative Disease in Male Former Professional Soccer Players

Reference: JAMA Neurol. 2021 Aug 2;e212403.  doi: 10.1001/jamaneurol.2021.2403. Online ahead of print.

Authors: Emma R Russell, Daniel F Mackay, Katy Stewart, John A MacLean, Jill P Pell, William Stewart

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8329793/

Summary: Neurodegenerative disease mortality is higher among former professional soccer players than general population controls. However, the factors contributing to increased neurodegenerative disease mortality in this population remain uncertain. The aim was to investigate the association of field position, professional career length, and playing era with risk of neurodegenerative disease among male former professional soccer players. This cohort study used population-based health record linkage in Scotland to evaluate risk among 7676 male former professional soccer players born between January 1, 1900, and January 1, 1977, and 23 028 general population control individuals matched by year of birth, sex, and area socioeconomic status providing 1 812 722 person-years of follow-up. Scottish Morbidity Record and death certification data were available from January 1, 1981, to December 31, 2016, and prescribing data were available from January 1, 2009, to December 31, 2016. Database interrogation was performed on December 10, 2018, and data were analyzed between April 2020 and May 2021. Outcomes were obtained by individual-level record linkage to national electronic records of mental health and general hospital inpatient and day-case admissions as well as prescribing information and death certification. Risk of neurodegenerative disease was evaluated between former professional soccer players and matched general population control individuals. In this cohort study of 30 704 male individuals, 386 of 7676 former soccer players (5.0%) and 366 of 23 028 matched population control individuals (1.6%) were identified with a neurodegenerative disease diagnosis (hazard ratio [HR], 3.66; 95% CI, 2.88-4.65; P < .001). Compared with the risk among general population control individuals, risk of neurodegenerative disease was highest for defenders (HR, 4.98; 95% CI, 3.18-7.79; P < .001) and lowest for goalkeepers (HR, 1.83; 95% CI, 0.93-3.60; P = .08). Regarding career length, risk was highest among former soccer players with professional career lengths longer than 15 years (HR, 5.20; 95% CI, 3.17-8.51; P < .001). Regarding playing era, risk remained similar for all players born between 1910 and 1969. The differences in risk of neurodegenerative disease observed in this cohort study imply increased risk with exposure to factors more often associated with nongoalkeeper positions, with no evidence this association has changed over the era studied. While investigations to confirm specific factors contributing to increased risk of neurodegenerative disease among professional soccer players are required, strategies directed toward reducing head impact exposure may be advisable in the meantime.

 

 

#15 Confirmation of early non-bulbar onset of amyotrophic lateral sclerosis in Spanish league soccer players

Reference: J Neurol Sci. 2021 Jul 24;428:117586.  doi: 10.1016/j.jns.2021.117586. Online ahead of print.

Authors: Josep Gamez, Francesc Carmona

Summary: Sports-related activity has been proposed as a risk factor for ALS, particularly among professionals playing American football and soccer, with a reported prevalence between two and forty times higher than the general population. Early onset (by two decades) was described among Italian soccer players as early as 2005. This study aims to characterise the phenotype of seven Spanish retired professional and semi-professional soccer players. The cases were identified using the following sources: (i) personal archives from a leading ALS Unit, (ii) PubMed and specialised websites, and (iii) self-reports of patients in the media. Age and site of onset, survival time, history of trauma, playing position and time between retirement and first symptoms were investigated for soccer players in the Spanish league diagnosed between 2000 and 2020. Seven ALS cases were identified. The mean age at onset was 41.5 years (SD 9.2, median 45.5, range 31.5-51.2). Onset was bulbar in one individual, while six experienced spinal onset. Three patients had the flail arm syndrome variant. Two cases were goalkeepers, two defenders and three midfielders. Four had a history of trauma (two serious). Survival time for the two deceased patients was 71.8 months. Mean time between retirement and first symptoms was 9.4 years (SD 8.0, median 15.2, range 0.1-17.5). Our study has the largest sample size of non-Italian league soccer professionals and semi-professionals, and our results corroborate early onset (by 23.7 years). Unlike the Italian cohorts, bulbar onset is rare, and upper limb onset is most common.

 

 

#16 Expertise Classification of Soccer Goalkeepers in Highly Dynamic Decision Tasks: A Deep Learning Approach for Temporal and Spatial Feature Recognition of Fixation Image Patch Sequences

Reference: Front Sports Act Living. 2021 Jul 26;3:692526. doi: 10.3389/fspor.2021.692526. eCollection 2021.

Authors: Benedikt Hosp, Florian Schultz, Enkelejda Kasneci, Oliver Höner

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8350442/pdf/fspor-03-692526.pdf

Summary: The focus of expertise research moves constantly forward and includes cognitive factors, such as visual information perception and processing. In highly dynamic tasks, such as decision making in sports, these factors become more important to build a foundation for diagnostic systems and adaptive learning environments. Although most recent research focuses on behavioral features, the underlying cognitive mechanisms have been poorly understood, mainly due to a lack of adequate methods for the analysis of complex eye tracking data that goes beyond aggregated fixations and saccades. There are no consistent statements about specific perceptual features that explain expertise. However, these mechanisms are an important part of expertise, especially in decision making in sports games, as highly trained perceptual cognitive abilities can provide athletes with some advantage. We developed a deep learning approach that independently finds latent perceptual features in fixation image patches. It then derives expertise based solely on these fixation patches, which encompass the gaze behavior of athletes in an elaborately implemented virtual reality setup. We present a CNN-BiLSTM based model for expertise assessment in goalkeeper-specific decision tasks on initiating passes in build-up situations. The empirical validation demonstrated that our model has the ability to find valuable latent features that detect the expertise level of 33 athletes (novice, advanced, and expert) with 73.11% accuracy. This model is a first step in the direction of generalizable expertise recognition based on eye movements.

 

 

#17 The Impact of Environmental Conditions on Player Loads During Preseason Training Sessions in Women's Soccer Athletes

Reference: J Strength Cond Res. 2021 Aug 11.  doi: 10.1519/JSC.0000000000004112. Online ahead of print.

Authors: Alexis B Austin, Sean M Collins, Robert A Huggins, Brittany A Smith, Thomas G Bowman

Summary: Our objective was to determine the impact of environmental conditions on player loads during preseason training sessions in women's soccer athletes. Eleven women's NCAA Division III soccer players (age = 20 ± 1 year, height = 167.28 ± 8.65 cm, body mass = 60.18 ± 5.42 kg, V[Combining Dot Above]O2max = 43.70 ± 3.95 ml·kg-1·min-1) volunteered to wear Global Positioning System (GPS) devices (Sports Performance Tracking, Melbourne, Australia) that provided measures of training session external intensity throughout all preseason practices (n = 15). We recorded wet-bulb globe temperature (WBGT), session Rating of Perceived Exertion-Training Load (sRPE-TL), and ΔBM during each preseason training session and set α ≤ 0.05. The combination of WBGT, sRPE-TL, and ΔBM explained 34% of the variance in GPS-based intensity score (proprietary measure) (F3,153 = 26.25, p < 0.001). Wet-bulb globe temperature (t156 = -2.58, p = 0.01), sRPE (t156 = 8.24, p < 0.001), and ΔBM (t156 = 2.39, p = 0.02) were significantly associated with intensity. The ΔBM from prepractice (60.00 ± 5.21 kg) to postpractice (59.61 ± 5.10 kg) was statistically significant (p < 0.001); however, ΔBM from the beginning of preseason (59.87 ± 5.31 kg) to the end of preseason (59.91 ± 5.58 kg) was not significant (p = 0.89). Despite relatively low to moderate environmental conditions, increases in WBGT were associated with reductions in GPS intensity and elevated internal load via sRPE-TL. Our findings support the association between exercise intensity and WBGT, internal load, and hydration status; thus, coaches and exercise scientists should take these factors into account when monitoring or interpreting intensity metrics. Furthermore, these findings support the continued use of environmental monitoring and hydration best-practice policies to limit exercise intensity in the heat so as to mitigate excessive heat stress.

 

 

#18 Injury Profile among Elite Youth Male Football Players in a German Academy

Reference: Int J Sports Med. 2021 Aug 9. doi: 10.1055/a-1516-4139. 

Authors: Ayham Jaber, Johannes Weishorn, Gregor Berrsche, Henning Ott, Yannic Bangert

Summary: Studies that report injuries in elite youth football players are scarce. So far, no such studies have been reported in Germany. The aim of this study is to descriptively and statistically report the incidence of injuries that resulted in time-loss ≥ 4 days in the TSG Hoffenheim football academy by 138 male players aged between 12 and 19 years during one season. A total of 109 injuries were sustained by 76 players: 6.9 injuries occurred per 1000 hours of matches (95% CI, 5.0-9.6) and 0.7 injuries per 1000 hours of training (95% CI, 0.5-0.9) with a ratio of 9.8. Some 66% of all injuries occurred during matches. Injuries involved the lower limb (81%), upper limb (9%), head & neck (5%) and trunk injuries (5%). 21 (19%) of all injuries were regarded as severe and resulted in time-loss > 28 days. U16-U19 teams sustained more injuries (74, 68%) than U12-U15 (35, 32%) (P= 0.032). The most frequent diagnosis was thigh strain (22%). Time-loss ranged from 4-339 days (SD: 40, Average: 23). Many injuries were a result of strain. Available injury prevention programs should be adhered to more strictly. Dedicated epidemiological studies are needed to optimize focused injury prevention programs.

 

 

#19 Preseason weight-bearing ankle dorsiflexion in male professional football players with and without a history of severe ankle injury: A novel analysis in an English Premier League club

Reference: Phys Ther Sport. 2021 Jul 28;52:21-29.  doi: 10.1016/j.ptsp.2021.07.006. Online ahead of print.

Authors: Nicholas C Clark, Stuart D Campbell

Summary: Ankle injuries are common in professional football and have profound player/team/club consequences. The weight-bearing lunge-test (WBLT) assesses ankle dorsiflexion range-of-motion in football primary/secondary injury prevention and performance contexts. Data for uninjured and previously ankle-injured players in the English Premier League (EPL) is not available. This study analysed WBLT measurements (cm) within and between uninjured and previously severe ankle-injured players (injured-stiff group, injured-lax group) in one EPL club. Forty-nine players (age 22.9 ± 4.6 yr; height 181.6 ± 5.2 cm; mass 77.7 ± 7.6 kg) participated in this study. Prevalence (%) of previous unilateral severe ankle injury (USAI). Side-to-side (right/left, dominant/nondominant, injured/uninjured) WBLT comparisons at group-level (t-test [within-group]; Welch's ANOVA [between-group]; effect sizes [within-/between-group]) and individual-level (limb symmetry index [%]; absolute-asymmetry [%]) were used as outcome measures. Prevalence of USAI was 38.7%. There were no statistically-significant side-to-side differences for within-/between-group comparisons. Effect sizes: just-below-large (injured-stiff) and extremely-large (injured-lax) for within-group injured-side/uninjured-side comparisons; just-below-medium (injured-lax) to just-above-medium (injured-stiff) for injured-side comparisons to uninjured players. Absolute-asymmetries: uninjured players, 15.4±13.2%; injured-stiff, 21.8±33.6%; injured-lax 20.4±13.6%. Over one-third of players had previous USAI. Effect sizes indicate substantial within-group side-to-side differences and less substantial between-group differences. Across groups, some players had absolute-asymmetries that may elicit concern in ankle primary/secondary injury prevention and performance contexts.

 

 

#20 Optimizing the Explosive Force of the Elite Level Football-Tennis Players through Plyometric and Specific Exercises

Reference: Int J Environ Res Public Health. 2021 Aug 3;18(15):8228. doi: 10.3390/ijerph18158228.

Authors: Anamaria Gherghel, Dana Badau, Adela Badau, Liviu Moraru, Gabriel Marian Manolache, Bogdan Marian Oancea, Corina Tifrea, Virgil Tudor, Raluca Maria Costache

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345974/pdf/ijerph-18-08228.pdf

Summary: The aim of the research was to implement an athletic program to improve the explosive force in order to optimize physical fitness at the level of elite football-tennis players and evaluate the progress made through specific tests using the Opto Jump. The research included 10 elite European and world-class players, on whom an experimental program was applied in order to improve the explosive force of the limbs in conditions of speed, endurance, and dynamic balance. Study tests: five vertical jumps on the spot, on the left/right leg; five back and forth jumps on the left/right leg; five left/right side jumps on the left/right leg; vertical jumps on both legs 60 s; BFS vertical jumps. For each test, the following parameters specific to the explosive force were statistically analyzed: contact time (s); flight time (s); jump height (cm), jump power (w/kg); RSI-Reactive Strength Index, defined as Height (m/s). In the study, the average value of the parameters specific to the jumps performed in each test was taken into account. During the study, the tests were performed and processed on the Opto Jump device and software. In all tests of the experiment monitored through Opto Jump, significant progress was made in the final test compared to the initial one, which demonstrates the efficiency of the physical training program implemented for the development of explosive force, with an impact on the sports performance of elite players. The most relevant results obtained for the left leg regarding the improvement of the explosive force of the lower limbs materialized in the jump height parameter was in the test of five vertical jumps on one leg on the spot, and for the right leg in the tests of: five back and forth jumps and five left/right side jumps. The most significant advances in the study were in the tests, in descending order of their weight: 60 s vertical jumps on both legs; five back-and-forth jumps and five left/right side jumps, five vertical jumps on one leg standing, and BFS vertical jumps.

 

 

#21 Should I Stay or Should I Go? The Impact of Social Networks on the Choice to Play for a National Team in Football

Reference: Int J Environ Res Public Health. 2021 Jul 21;18(15):7719.  doi: 10.3390/ijerph18157719.

Authors: Klaus Seiberth, Ansgar Thiel

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8345438/pdf/ijerph-18-07719.pdf

Summary: In the course of their careers, elite athletes are faced with crucial decisions. This applies particularly to adolescent athletes who additionally have to cope with a variety of age-related developmental tasks. For young top football players with a migrant background, this can be even more challenging as they often attract the interest of national associations. From a network-theoretical perspective, it can be considered likely that the decision to join a top national association is not taken independently of the players' networks. This article addresses the role of network actors within the players' decision-making process. Our analysis is guided by constructivist network theory and based on a qualitative research approach that used guided expert interviews as its core research tool. Ten interviews with German-born youth internationals with a migrant background were conducted. The present analysis reveals several network actors such as family, coaches and players' agents involved in the 'national team question'. Evidently, most relevant networks of players with a migrant background are sports-related. These networks turned out to be highly functionalized and leave only limited room for manoeuvring. At the same time, the interviews reveal 'structural holes' within the players' networks and indicate a considerable need for the optimization of talent counselling.

 

 

Fri

24

Dec

2021

Latest research in football - week 40 - 2021

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 Key load indicators and load variability in professional soccer players: a full season study

Reference: Res Sports Med. 2021 Jul 14;1-13.  doi: 10.1080/15438627.2021.1954517. Online ahead of print.

Authors: José M Oliva-Lozano, Xavier Barbier, Víctor Fortes, José M Muyor 

Summary: The aims of this study were to 1) determine the key load indicators in professional soccer through principal component analysis (PCA); and 2) analyse the load variability of each training and match day within the microcycle considering the principal components. Data from 111 load variables were collected using tracking systems in both training and match days (MD). The results showed that 7 variables, which belonged to the first two components of the PCA, explained 80.3% of total variance. Specifically, these variables were Metabolic power, total of steps, Fourier transform (FFT) duration, deceleration distance covered (2-3 m/s2), total of running actions (12-18 km/h; 21-24 km/h), and distance covered (6-12 km/h). Regarding the analysis of the load variability of each training and match day within the microcycle, the lowest load variability was observed in -1MD. Also, a great load variability in +1MD with significant differences compared to -5MD (p<0.001; d=0.49) and -4MD (p=0.01; d=0.26) was found. This study suggests the use of the PCA in the context of team sports to reduce the large number of variables, which are daily managed by strength and conditioning coaches, in addition to the analysis of load variability of each training and match day within the microcycle.

 

 

#2 Perceptual and Biochemical Responses in Relation to Different Match-Day +2 Training Interventions in Soccer Players

Reference: Front Physiol. 2021 Jun 24;12:685804.  doi:10.3389/fphys.2021.685804. eCollection 2021.

Authors: Athos Trecroci, Enrico Perri, Giovanni Lombardi, Giuseppe Banfi, Riccardo Del Vescovo, Ermes M Rosa, Giampietro Alberti, F Marcello Iaia 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8264547/pdf/fphys-12-685804.pdf

Summary: The aim of this study was to examine the impact of two different post-match training interventions on the subsequent recovery of perceptual and biochemical parameters after the game. In a crossover design, eight sub-elite players underwent a soccer-specific training (SST) and an active recovery (AR) regimen on the second day after a match (+48 h). Muscle soreness as well as muscle damage (creatine kinase, CK), inflammatory (C-reactive protein and interleukin 6), immunological (e.g., lymphocytes, neutrophils, and monocytes), and endocrine (cortisol) markers were obtained at baseline (-72 h), immediately after (0 h), and 72 h post-match (+72 h). AR promoted a higher restoration of muscle soreness values (P = 0.004, η2 p = 0.49) together with a better restoration of CK within 72 h post-match compared with SST (P = 0.04, η2 p = 0.36). Conversely, no significant (P > 0.05, η2 p < 0.91) differences were observed in the recovery timeframe of inflammatory, immunological, and endocrine responses between SST and AR. Overall, AR elicited a quicker muscle soreness and CK restoration compared to SST intervention at 72 h post-match. Such information provides novel evidence-based findings on the appropriateness of different recovery strategies and may aid to improve the practitioners' decision-making process when two consecutive games are played within 3 days.

 

 

#3 Effects of respiratory muscle training in soccer players: a systematic review with a meta-analysis

Reference: Sportverletz Sportschaden. 2021 Jul 14.  doi: 10.1055/a-1524-0021. Online ahead of print.

Authors: Felipe León-Morillas, Martha Cecilia León-Garzón, María Del Mar Martínez-García, Javier Reina-Abellán, María Victoria Palop-Montoro, Silvana Loana de Oliveira-Sousa

Summary: Respiratory muscle training can improve strength and reduce respiratory muscle fatigue during high-intensity exercise. Little is known about the existing evidence in soccer players. A systematic review with a meta-analysis was performed to analyse the existing evidence on the effects of respiratory muscle training in soccer players. Two independent researchers reviewed 17 databases until July 2019. Inclusion criteria were controlled clinical trials (randomised or not), soccer players (professional or recreational), females and/or males, and respiratory muscle training compared with simulated or regular training groups. The methodological quality and quality of evidence were evaluated with the Cochrane Collaboration Tool and GRADE score, respectively. Statistical analysis was performed using the integral meta-analysis 3.3.070. Nine studies met the eligibility criteria. The meta-analysis was performed for eight variables related to respiratory muscle function, lung function and sports performance. Respiratory muscle training provided a significant improvement compared with simulated or regular training in maximal inspiratory buccal pressure (6 studies, SDM = 0.89; 95 % CI = 0.42, 1.35) and maximum consumption of oxygen (3 studies, SDM = 0.92; 95 % CI = 0.24; 1.61). No significant improvements were observed for other variables. The quality of the evidence was rated as low or very low.

 

 

#4 Evaluation of Lower Limb Arteriovenous Diameters in Indoor Soccer Athletes: Arterial Doppler Ultrasound Study

Reference: Front Physiol. 2021 Jun 28;12:687613.  doi: 10.3389/fphys.2021.687613. eCollection 2021.

Authors: Sónia Mateus, Rui Paulo, Patrícia Coelho, Francisco Rodrigues, Vasco Marques, Henrique P Neiva, Pedro Duarte-Mendes

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8273383/pdf/fphys-12-687613.pdf

Summary: The purpose of this study was to analyze the arterial and venous diameters of lower limbs in indoor soccer athletes and non-athletes using Doppler ultrasound to identify the differences in the variation of arterial and venous diameters between groups. Additionally, we intended to verify the differences of arterial and venous diameters between the skilled member (right member) and the not skilled member in each group. 74 male volunteers, aged between 19 and 30 years old, were divided in a group of athletes (n = 37, 24 ± 2.7 years, soccer players from national championship), and a group of non-athletes (n = 37, 26 ± 2.83 years). Vascular lower limb was assessed using Doppler ultrasound (Philips HD7 echograph with linear transducer 7-12 MHz). The athletes showed higher diameters of right common femoral artery (p = 0.009; moderate), left common femoral artery (p = 0.005; moderate), right deep femoral artery (p = 0.013; moderate), right popliteal artery (p = 0.003; moderate), and left popliteal artery (p = 0.017; small) than non-athletes. Veins' diameters were also higher in athletes, specifically the right deep femoral vein (p ≤ 0.001; large), left deep femoral vein (p ≤ 0.001; large), right popliteal vein (p ≤ 0.001; large), and left popliteal vein (p ≤ 0.001; large). Differences were found between the skilled and non-skilled leg in athletes in the popliteal vein (7.68 ± 1.44 mm vs. 7.22 ± 1.09 mm, respectively, p < 0.003). It seems that futsal athletes have superior mean diameters of lower limbs arteries and veins of the deep venous system to non-athletes. Moreover, the veins presented greater dilation, namely of the leg of the skilled lower limb.

 

 

#5 Feasibility and Effectiveness of a Novel Smartphone Music Application on Anxiety and Sleep in Elite Soccer Coaches

Reference: J Sports Sci Med. 2021 Jul 1;20(3):546-547. doi: 10.52082/jssm.2021.546. eCollection 2021 Sep.

Authors: Christopher Carling, Chloé Leprince, Thomas Pavillon, Stéphane Guétin, Franck Thivilier

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8256527/pdf/jssm-20-546.pdf

 

 

#6 Isolated papillary muscle hypertrophy in a professional soccer player: the end of an athlete's career?

Reference: Kardiol Pol. 2021 Jul 16. doi: 10.33963/KP.a2021.0063. Online ahead of print.

Authors: Cyntia Zulema Machain Leyva, Cuitláhuac Arroyo-Rodríguez, José Roberto Victoria-Nandayapa, Sergio Ramón Figueroa-Sauceda

Download link: https://journals.viamedica.pl/kardiologia_polska/article/view/KP.a2021.0063/63491

 

 

#7 Relationships between Vitamin D and Selected Cytokines and Hemogram Parameters in Professional Football Players-Pilot Study

Reference: Int J Environ Res Public Health. 2021 Jul 2;18(13):7124. doi: 10.3390/ijerph18137124.

Authors: Anna Książek, Aleksandra Zagrodna, Anna Bohdanowicz-Pawlak, Felicja Lwow, Małgorzata Słowińska-Lisowska

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8297090/pdf/ijerph-18-07124.pdf

Summary: Vitamin D affects both innate and adaptive immunity. Most of the effects of vitamin D on innate immunity are anti-inflammatory. In monocytes/macrophages, vitamin D suppresses the production of the inflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-8. Therefore, the aim of our study was to investigate the relationship between 25(OH)D concentration and selected cytokines-IL-6, TNF-α, and IL-1β, which are hemogram parameters for professional football players. We enrolled 41 Polish premier league soccer players. The mean age, career duration, and VO2max were, respectively: 22.7 ± 5.3 years, 14.7 ± 4.5 years, and 55.8 ± 4.0 mL/kg/min. Serum levels of 25(OH)D were measured by electrochemiluminescence (ECLIA) using the Elecsys system (Roche, Switzerland). Serum levels of IL-6, IL-1β, and TNF-α were measured by ELISA (R&D Systems, Minneapolis). Blood count with smear was measured on a Sysmex XT-4000i analyzer (Sysmex Corporation, Japan). Our study showed decreased serum 25(OH)D levels in 78% of the professional players. We found a significant negative correlation between 25(OH)D levels and TNF-α and LYMPH (%). The results also demonstrated a statistically significant positive correlation between vitamin D levels and NEUTH (%), NEUTH (tys/µL), and EOS (tys/µL). Based on the results of our study, we concluded that football players from Poland are not protected against vitamin D insufficiency in winter months. Moreover, vitamin D deficiency may be associated with an increased pro-inflammatory risk in well-trained athletes.

 

 

#8 Football sports safety and the health risk assessment system

Reference: Work. 2021 Jul 14. doi: 10.3233/WOR-205348. Online ahead of print.

Authors: Ning Jin, Xiao Zhang, Zhitao Hou

Summary: Football has various educational functions that can strengthen the physique and cultivate students' patriotism and collectivist spirit. However, the characteristics of antagonism and competitiveness of football make it have certain risks. The study aims to effectively help students clarify the safety of football sports, solve the risks caused by confrontation and competition in football projects, and guide students to exercise healthily and safely. The risks of campus football are identified, evaluated, responded to, and monitored. Specific empirical data and Pareto analysis compile the risk investigation and risk assessment table of campus football, and the prevention measures are put forward. The older the person is, the higher the possibility of risk occurrence is. The sports risk of boys is significantly higher than that of girls. The human factors and sports environment have the most significant impact on the health risk of football sports. Human factors mainly involve students' lack of discipline, poor safety awareness, low professional level of teachers, and students' lack of enthusiasm. The study requires changing the concept, improving the students' sports risk awareness, strengthening the construction of system and policy, and changing the passive into the active. The study can provide research ideas for the safety and risk management of football sports and promote the popularity of football on the campus.

 

 

#9 Relationship between the hip range of motion and functional motor system movement patterns in football players

Reference: J Sports Med Phys Fitness. 2021 Jul 19. doi: 10.23736/S0022-4707.21.12679-9. Online ahead of print.

Authors: Gabriela Siwecka, Ewa Wodka-Natkaniec, Łukasz Niedźwiedzki, Anna Świtoń, Tadeusz Niedźwiedzki

Summary: The aim of this study was to determine the hip range of motion and the movement patterns of football players assessed with an aid of a Functional Motor Systems test, and to find an association between these parameters and the risk for hip joint injury. The study included 50 men aged between 16 and 20 years: 25 footballers and 25 age- and body mass index-matched controls. The hip ranges of motion (flexion, extension, internal and external rotation, adduction and abduction) were determined, and the movement patterns were evaluated with the tests from the Functional Motor Systems battery. Football players presented with significantly higher ranges of the hip flexion, extension, internal and external rotation than the controls. Moreover, footballers and controls differed significantly in terms of their mean overall Functional Motor Systems scores (15.77 points ± 2.44 vs. 13.79 ± 3.02 points, P = 0.019). Football players scored best on the shoulder mobility test for the right side and worst on the rotary stability test for the left side. The scores on the trunk stability test and rotary stability test for the left side were significantly higher in footballers than in the controls. Nevertheless, the overall Functional Motor Systems scores of 14 points or less were recorded in the case of as many as 10/25 footballers. Altogether, these findings suggest that some football players present with a strain which may predispose them to future injuries. Future research should center around the etiology of reduced hip ROM observed in footballers. Furthermore, football training seems to result in a considerable motor asymmetry of the trunk which also predisposes to injury.

 

 

#10 Epidemiology of Injuries in National Collegiate Athletic Association Women's Soccer: 2014-2015 Through 2018-2019

Reference: J Athl Train. 2021 Jul 1;56(7):651-658. doi: 10.4085/1062-6050-372-20.

Authors: Avinash Chandran, Sarah N Morris, Adrian J Boltz, Hannah J Robison, Christy L Collins

Download link: https://watermark.silverchair.com/i1062-6050-56-7-651.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAtkwggLVBgkqhkiG9w0BBwagggLGMIICwgIBADCCArsGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMd8_qsa3kkF6ViOkKAgEQgIICjDBNQQJfPpEd9_2qHeFynBX94vUcm_EDnHdp4wGHhqfIU1zb1O8r6F9i7cg0ur1CLpNCba9sOyb2Mxw4UgIzfJvMyVMKv4l4w7VGpwMypwMfhe09xN-QPxQTm4zVXw69ZgU9jekmD-26KhCtEbFV5-vpsFotzUu01lofcRrP0cd1LJelyfQJ1ldMQO_BWOSN9gqdB-ciiahnd2AMG7oc4JMUIYXdlOpY17VlAX6Nclu-aa2QfYABeJj4rHjmfpPR0ixeoneJiExkxm7jwLSg-o-eutWWxvZAK4wFxLTInDPIXlV_dZor3xW2HPjOCupJDQUd1_LbSaRGE1UhjnASmriV7oZQUKHBGpB8GvVrSwUpB6MT_Qv02JYJQguj83H1fGtjsP8EwJpsmVGhPz_RGTt3WpeMQMdWmU28oQBx_rrPnmIKZxO4B2Kgt0JsR2ZhuUUcijwX18Z9_Q5MJCat1kTEZcNo9pwGaN51Tdn6NqR0mHg3uLWn9yO9B9nvdZ6woG8OEYKw9juix5FIAjodHx6xXwFU_BWFxGuR1SMN_sPFQ9w0gn7fNFzK24bAzCorkWKAYKwsadAnPaG30yyF1sl9qNAknCEeVhh-PxloCQyHX-DbT0X4cFdLwyohsTZj6pqLD9ZIWq2qtNRpE14s5i55twdmCiEeEbzwhIJCAqkgUVMSj5qukM4ieC32HCf9oNiQ1OvLUQ9rYMaxpM022QMgTwou48I51FqDzz5K9at03BHF16zhP7uQFO9BupzY4nq54SzfoAeQpBl6qgZSLADSVEXZqWGvqvUmMBtMd2lOB5RpR8iy0WE7-Ynkej7-B2jGA7iGrMDA5jLZUygmUrJTvAdcU0oS6ZvJRBE

Summary: The National Collegiate Athletic Association held the first women's soccer championship in 1982; sponsorship and participation have greatly increased since. Routine examinations of athlete injuries are important for identifying emerging temporal patterns. Exposure and injury data collected in the National Collegiate Athletic Association Injury Surveillance Program during the 2014-2015 through 2018-2019 seasons were analyzed. Injury counts, rates, and proportions were used to describe injury characteristics, and injury rate ratios were used to examine differential injury rates. The overall injury rate was 8.33 per 1000 athlete-exposures. Lateral ligament complex tears (ankle sprains) (8.6%), concussions (8.3%), and quadriceps tears (5.0%) were the most commonly reported injuries. Rates of lateral ligament complex tears followed an increasing trajectory during the study period, whereas quadriceps tear rates fluctuated during the early years, and concussion rates decreased then increased. The findings of this study were mostly consistent with existing evidence; notable temporal patterns were observed with regard to lateral ligament complex tears and concussions.

 

 

#11 Epidemiology of Injuries in National Collegiate Athletic Association Men's Soccer: 2014-2015 Through 2018-2019

Reference: J Athl Train. 2021 Jul 1;56(7):659-665. doi: 10.4085/1062-6050-370-20.

Authors: Avinash Chandran, Sarah N Morris, Adrian J Boltz, Hannah J Robison, Christy L Collins

Download link: https://watermark.silverchair.com/i1062-6050-56-7-659.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAtkwggLVBgkqhkiG9w0BBwagggLGMIICwgIBADCCArsGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQM9gEaR4Ntv_3eNwlvAgEQgIICjI-8WIa_z9LDASiGZo57xGI-xvOew_MeYN_tRmpfoowRTTQuQiqfN6ilR1_gZhIJgnfzTMEzlIMfYsgDzQiIq1YFDHFvFf9KKFOknHB3oNyaibzSOY_E_KakV90I4_KPnU2yFjT3EH6TbgFID_0A91rXenmAM7BP0CURoYr5mSkXhtUmtL96A5oiap_NiMgo6d6rUoQClo_zPiI7FMtPTlsIXPsCpd81_fo2XHa7utSPMk2GrjdHEY1YonDSD8j9IrwHG3UmHmZkZhlsoQBFxjair34geubbK0EWECin-Zha8Hcjoo8APfTnzt5xwBMlR5KEC5pZGOGlG3NBC_KlPM05xjQxocXDpxD-QmuL5hBc3UHuqBtYfeadZQ9J0vYbrkN0IlSQJQLJ0QAtbZj4AIRZQImYB0m6tLFPWAVmgez4Y7TCuD4V6WzQNWdfPPyR034Ut0yKWX08-3nOoiRX47BT8ViaK6C4q2Ab7nTm-G5eGyihBg1lRGrz8cIILdGRN6qc3BNoKgReIcBzA1iIlx7NclYqR2Qb5CuAx2HqXg-SeqJKwsGKaD4AiCt2tzH9ajMsB8q7D7Z_45Wd554S7KxJuiQGsp9D3zn_e5O70fLQACp0K1OGCRN32tIrmXjRJzMcEfMJjTEUA8Vlovk1vFltIDTBClphMC64Ul7tRBIhnqVABpB20ZRqzpXC06vqMtoejpuSrlXYVPnfQ2h20egPqyJwJNa7qo0FQoLarOXY6P534tA6WF7RPnXSABjShFTJT9L_pmsPbKA5OelCMIQE373C6fPlXsFw_-g69ATNcD5lKyCJ0Mf7mcROgmnrHW87MspPpiNYePodCJ67qp_bkSrBNKyDrveylKY

Summary: The National Collegiate Athletic Association has sponsored men's soccer programs since 1959, and the popularity of the sport has grown over time. Routine examinations of athlete injuries are important for identifying emerging temporal patterns. Exposure and injury data collected in the National Collegiate Athletic Association Injury Surveillance Program from 2014-2015 through 2018-2019 were analyzed. Injury counts, rates, and proportions were used to describe injury characteristics, and injury rate ratios were used to examine differential injury rates. The overall injury rate was 8.51 per 1000 athlete exposures. Lateral ligament complex tears (ankle sprains) (9.2%), hamstring tears (7.0%), and concussions (5.2%) were the most commonly reported injuries. Rates of lateral ligament complex tears remained stable from 2014-2015 through 2018-2019, whereas hamstring tear rates decreased and concussion rates increased. The findings of this study were in line with the existing epidemiological evidence, although notable temporal patterns were observed. Incidence trajectories of commonly observed injuries warrant particular attention in the future.

 

 

#12 Correlation between Official and Common Field-Based Fitness Tests in Elite Soccer Referees

Reference: J Funct Morphol Kinesiol. 2021 Jul 1;6(3):59. doi: 10.3390/jfmk6030059.

Authors: Veronica Romano, Manuel Tuzi, Ada Di Gregorio, Anna Maria Sacco, Immacolata Belviso, Felice Sirico, Stefano Palermi, Daria Nurzynska, Franca Di Meglio, Clotilde Castaldo, Angelo Pizzi, Stefania Montagnani

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8293311/pdf/jfmk-06-00059.pdf

Summary: Official tests are used to assess the fitness status of soccer referees, and their results correlate with match performance. However, FIFA-approved tests expose the referees to high physical demands and are difficult to implement during the sportive year. The aim of our study was to evaluate the correlation between the 6 × 40-m sprint and Yo-Yo Intermittent Recovery Level 1 (IR1) official tests and other field-based tests that require no or little equipment, are not time-consuming, and impose low physical demands. All tests were performed by male referees from the Regional Section of the Italian Referee Association (n = 30). We observed a strong correlation between 6 × 40-m sprint and Illinois agility tests (r = 0.63, p = 0.001) and a moderate correlation between Yo-Yo IR1 and hand-grip strength in the dominant (r = 0.45, p = 0.014) and non-dominant hand (r = 0.41, p = 0.031). Interestingly, only a moderate correlation (r = -0.42, p = 0.025) was observed between the FIFA official tests, 6 × 40-m sprint and Yo-Yo IR1. These results suggest that Illinois agility and hand-grip tests could represent simple and low-physical-impact tools for repeated assessment and monitoring of referee fitness throughout the sportive season.

 

 

#13 Fatigue Induced by Repeated Changes of Direction in Élite Female Football (Soccer) Players: Impact on Lower Limb Biomechanics and Implications for ACL Injury Prevention

Reference: Front Bioeng Biotechnol. 2021 Jul 5;9:666841. doi: 10.3389/fbioe.2021.666841. eCollection 2021.

Authors: Matteo Zago, Sina David, Filippo Bertozzi, Claudia Brunetti, Alice Gatti, Francesca Salaorni, Marco Tarabini, Christel Galvani, Chiarella Sforza, Manuela Galli

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8287513/pdf/fbioe-09-666841.pdf

Summary: The etiology of Anterior Cruciate Ligament (ACL) injury in women football results from the interaction of several extrinsic and intrinsic risk factors. Extrinsic factors change dynamically, also due to fatigue. However, existing biomechanical findings concerning the impact of fatigue on the risk of ACL injuries remains inconsistent. We hypothesized that fatigue induced by acute workload in short and intense game periods, might in either of two ways: by pushing lower limbs mechanics toward a pattern close to injury mechanism, or alternatively by inducing opposed protective compensatory adjustments. In this study, we aimed at assessing the extent to which fatigue impact on joints kinematics and kinetics while performing repeated changes of direction (CoDs) in the light of the ACL risk factors. This was an observational, cross-sectional associative study. Twenty female players (age: 20-31 years, 1st-2nd Italian division) performed a continuous shuttle run test (5-m) involving repeated 180°-CoDs until exhaustion. During the whole test, 3D kinematics and ground reaction forces were used to compute lower limb joints angles and internal moments. Measures of exercise internal load were: peak post-exercise blood lactate concentration, heart rate (HR) and perceived exertion. Continuous linear correlations between kinematics/kinetics waveforms (during the ground contact phase of the pivoting limb) and the number of consecutive CoD were computed during the exercise using a Statistical Parametric Mapping (SPM) approach. The test lasted 153 ± 72 s, with a rate of 14 ± 2 CoDs/min. Participants reached 95% of maximum HR and a peak lactate concentration of 11.2 ± 2.8 mmol/L. Exercise duration was inversely related to lactate concentration (r = -0.517, p < 0.01), while neither%HR max nor [La-] b nor RPE were correlated with test duration before exhaustion (p > 0.05). Alterations in lower limb kinematics were found in 100%, and in lower limb kinetics in 85% of the players. The most common kinematic pattern was a concurrent progressive reduction in hip and knee flexion angle at initial contact (10 players); 5 of them also showed a significantly more adducted hip. Knee extension moment decreased in 8, knee valgus moment increased in 5 players. A subset of participants showed a drift of pivoting limb kinematics that matches the known ACL injury mechanism; other players displayed less definite or even opposed behaviors. Players exhibited different strategies to cope with repeated CoDs, ranging from protective to potentially dangerous behaviors. While the latter was not a univocal effect, it reinforces the importance of individual biomechanical assessment when coping with fatigue.

 

 

#14 Quantifying and Comparing the Match Demands of U18, U23, and 1ST Team English Professional Soccer Players

Reference: Front Physiol. 2021 Jul 2;12:706451. doi: 10.3389/fphys.2021.706451. eCollection 2021.

Authors: James Reynolds, Mark Connor, Mikael Jamil, Marco Beato

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8283180/pdf/fphys-12-706451.pdf

Summary: The aim of this study was to quantify and compare the match load demands of U18, U23, and 1ST team players during the official season. A total of 65 matches and 495 (U18 = 146, U23 = 146, and 1ST team = 203) individual player game observations were included in this analysis. A 10-Hz global navigation satellite systems (GNSS) and 100-Hz triaxial accelerometer (STATSports, Apex, Northern Ireland) were used to monitor the following metrics during official matches: total distance, high-speed running distance (HSR), sprint distance, high metabolic distance, explosive distance, high-intensity bursts distance, speed intensity, and dynamic stress load (DSL) were analyzed. A multivariate analysis of variance test reported significant (p < 0.001) differences among the groups. HSR during matches was lower (d = small) for U18 players than the U23 and 1ST team players. Sprint distance and high-intensity bursts distance were lower (small) in U18 compared with the U23 and 1ST team. DSL was greater in 1ST compared with U18 (small) and U23 (small). This study reported that the differences between groups were greater for HSR, sprint distance, high-intensity bursts distance, and DSL, while total distance, high metabolic load distance, explosive distance, and speed intensity did not differ between the groups. These findings could be used to design training programs in the academy players (i.e., U18) to achieve the required long-term physical adaptations that are needed to progress into the U23 and 1ST teams.

 

 

#15 How to improve technical and tactical actions of dominant and non-dominant players in children's football?

Reference: PLoS One. 2021 Jul 22;16(7):e0254900. doi: 10.1371/journal.pone.0254900. eCollection 2021.

Authors: Mirjam Hintermann, Dennis-Peter Born, Jörg Fuchslocher, Raphael Kern, Michael Romann

Download link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0254900

Summary: As young football players develop important technical and tactical skills during competitive matches, this study investigated quantity and quality of technical and tactical actions in real game conditions in a 4v4 compared to the traditional 7v7 match format. In total, three matches of each format were played by 103 young football players (10.3±0.6 years) and video monitored for subsequent manual tagging of technical and tactical events. Based on the number of technical and tactical actions in the 7v7 matches, players were classified as dominant or non-dominant and changes in these subgroups were assessed during the 4v4 match format. The 4v4 match format significantly (P<0.001) increased total number of actions per player per minute compared to the 7v7 matches (5.59±1.44 and 2.78±0.73, respectively) and the number of successful (2.88±0.92 and 1.15±0.49, respectively) and unsuccessful (1.05±0.42 and 0.67±0.23, respectively) actions. Both dominant and non-dominant players increased their number of actions during the 4v4 compared to 7v7 match format. Despite a missing significant interaction effect, there was a larger percentage increase in number of actions for the non-dominant players (143%) compared to dominant players (72%) in 4v4. The 4v4 match format shows twice as many technical and tactical actions in real game conditions and, therefore, may improve players' skill development.

 

 

#16 How the COVID-19 Pandemic has Changed the Game of Soccer

Reference: Int J Sports Med. 2021 Aug 3. doi: 10.1055/a-1518-7778. Online ahead of print.

Authors: Daniel Link, Gabriel Anzer

Download link: https://www.thieme-connect.com/products/ejournals/pdf/10.1055/a-1518-7778.pdf

Summary: This study explores the influence of corona-specific training and playing conditions - especially empty stadiums - on match performance, contact behavior, and home advantage in the Bundesliga (BL) and Bundesliga 2 (BL2). We analyzed the 2017/18, 2018/19, and 2019/20 seasons and compared matches in rounds 26-34 before shutdown with "ghost" matches after restart. Results show increased running activity for high intensity distance: (+ 6.1%) and total distance covered (+ 4.3%). In BL2 in particular there were also changes in tactical aspects of the game (time in last third: -6.3%, pressure on pass receiver: -8.6%, success of attacking duels: -7.9%, share of long passes completed: + 15.6%, outplayed opponents per pass: -14.7%). Contact time to other players (< 2 m distance) was 15:35 mins per match. After restart, contact was reduced, especially when the ball was not in the last third (-11.2%). Away wins increased by +44.2% in BL and the home-away difference in yellow cards changed in favor of the away team (+31.2%) in BL2. We conclude that empty stadiums have reduced home advantage and decreased referee bias when awarding yellow cards. Player behavior might have been affected by tactical demands and/or conscious or unconscious self-protection.

 

 

#17 Towards soccer pass feasibility maps: the role of players' orientation

Reference: J Sports Sci. 2021 Aug 6;1-14.  doi: 10.1080/02640414.2021.1959176. Online ahead of print.

Authors: Adrià Arbués-Sangüesa, Adrián Martín, Javier Fernández, Gloria Haro, Coloma Ballester

Summary: Once player tracking has been established as one of the main data sources in soccer, many challenges have emerged for data scientists, who attempt to recognize patterns from 2D trajectories in order to build tools that might help coaches to improve the performance of their teams. For instance, pass models predict where the ball should go next during pass events. However, existing models are mainly fed with players' location and prior data, hence omitting critical pieces of information such as players' body orientation. This paper presents a computational model to obtain pass feasibility maps, where player orientation is exploited and analysed. As a matter of fact, orientation proves to be crucial when modelling field-of-view and correct positioning of players, since it limits the potential receiving area of all candidates. Different proposals are given to evaluate the proposed pass feasibility map, reaching 0.46 and 0.79 in Top1 and Top3 accuracy, respectively, with a + 0.2 boost obtained after merging positional data with orientation.

 

 

#18 Explaining the difference between men's and women's football

Reference: PLoS One. 2021 Aug 4;16(8):e0255407.  doi: 10.1371/journal.pone.0255407. eCollection 2021.

Authors: Luca Pappalardo, Alessio Rossi, Michela Natilli, Paolo Cintia

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336886/pdf/pone.0255407.pdf

Summary: Women's football is gaining supporters and practitioners worldwide, raising questions about what the differences are with men's football. While the two sports are often compared based on the players' physical attributes, we analyze the spatio-temporal events during matches in the last World Cups to compare male and female teams based on their technical performance. We train an artificial intelligence model to recognize if a team is male or female based on variables that describe a match's playing intensity, accuracy, and performance quality. Our model accurately distinguishes between men's and women's football, revealing crucial technical differences, which we investigate through the extraction of explanations from the classifier's decisions. The differences between men's and women's football are rooted in play accuracy, the recovery time of ball possession, and the players' performance quality. Our methodology may help journalists and fans understand what makes women's football a distinct sport and coaches design tactics tailored to female teams.

 

Thu

23

Dec

2021

Latest research in football - week 39 Part 2 - 2021

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 Effects of Warm-up on Hamstring Stiffness, Stress-Relaxation, Flexibility and Knee Proprioception in Young Soccer Players

Reference: J Athl Train. 2021 Jun 29.  doi: 10.4085/1062-6050-0416.20. Online ahead of print.

Authors: Danguole Satkunskiene, Mani Mirab Zadeh Ardekani, Ra'ad M Khair, Goda Kutraite, Kristina Venckuniene, Audrius Snieckus, Sigitas Kamandulis

Download link: https://watermark.silverchair.com/10.4085_1062-6050-0416.20.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAvowggL2BgkqhkiG9w0BBwagggLnMIIC4wIBADCCAtwGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMBCDmWfkBhMC8OffjAgEQgIICrXoWMxdZH92VW5htEBqgY4oOAgrBOq_6XyMbUbcYAvGmrBcLppjQ1TgOs-Y15bHir1hD3gA6aVfMd7Yok2ZH53Hg-geL5SnadPwvurkTL7Qx-NzMa2Hug-6Pko0_2krBbxKgGms1LwpLNRtTZmAaJmELRrh8Ww8vLUk_g8FJp9W77YENfFaLrJHyBzVlPNc9itiy99YxGZKd6YRPA0OPLMLc6_D3ehhxYaFY--eOtI3A97znn8V1tEoZoxgLMKN8RFHfHWTTWFZ6iHRTgjxgqbvZO61iCX3S5Kc2X5D98sebV-2OozqXdajj3Quhm90PJO4b1lFbPvxVB9PD7JWb8lF4Z6G4sVuaUDyWtRyVzVaND_bPgrnsONjR0Ub1KukRTQYQgwZ4bHuzfVxL7X7SwllurD_DN1xW40P24yxObqc2itAP1NPzXaXqvxRB54WLncuAPDLgTOlAdFmtXxxiUdHK2L2JrisnxZopL4CLZT29TGeIi5m7FpweQI0-767mpX-F8iSvi1kC6pn208G0-BMpUwFIKTXH3U8nnnU1DJSgIqvmk4wQywEy99VuZ36D7Noa83D4ovj7ghOU3V5iFM2VWtebx2IReCz0_8VMcb5YER0nP2YTdNqHdaVxvjuURK34ZwD_4CZS4aHQeywXIxQfw7BtRky_1Wj3XhGApGG4TGZ2CJnPQn4wx9Cq5A0klCdDF1XfZ6yo6x9JfGB-wXY0a7213Y0OiGnOFa9aunMxGu2qV61R0UFjwui16QMCtVzG-R-0FS-Y5-f1cpHhf_8U0KTQDzvx5lJMitzxTsqYGrvu4L9Z5nW_45z1t0hZzSjS5gQBf-qTdPWfeIEB0ktkQjpX4gJuyhYI6B16JYHqWQ0sAHB29EplW8lpKfHFphYaQwuLZxbJXHg6gD4

Summary: Nerves or fascia may limit motion in young soccer players, thereby contributing to frequent hamstring injuries. Nerve gliding exercises and self-myofascial release techniques may enhance the range of motion. The aim of this study was to compare the acute effect of foam rolling (FR) and neurodynamic nerve gliding (NDNG) on hamstring flexibility, passive stiffness, viscoelasticity and proprioception during the warm-up of soccer players. Fifteen male soccer players on the same team (age 18.0 ± 1.4 years, body mass 76.9 ± 7.8 kg, height 183 ± 6 cm). FR and NDNG included six sets of 45 s with 15 s rest between each set. Over a two-week period subjects performed NDNG and FR on two separate occasions. Hip flexion angle (SLR), knee extension range of motion (ROM), knee joint position sense (AKJPS), hamstring passive resistance torque (PRT), stiffness (STFmax and STF80%) and viscoelasticity (stress-relaxation test (SRT)). A significant interaction between time and intervention was found for knee ROM (p = 0.017), PRT (p = 0.044), and STFmax (p = 0.042). NDNG induced an increase in ROM (p = 0.011), PRT (p = 0.008), and STFmax (p = 0.030). Both NDNG and FR induced an increase in SLR (p < 0.001). No interaction or main effects was found for SRT and AKJPS. The inclusion of NDNG in the warm-up routine increased the ROM more in comparison with FR and may be of benefit to soccer players.

 

 

#2 Prior Injury, Health-Related Quality of Life, Disablement, and Physical Activity in Former Women's Soccer Players

Reference: J Athl Train. 2021 Jun 29.  doi: 10.4085/1062-6050-0731.20. Online ahead of print.

Authors: Shannon J Cross, Diane L Gill, Pam Kocher Brown, Erin J Reifsteck 

Download link: https://watermark.silverchair.com/10.4085_1062-6050-0731.20.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAvowggL2BgkqhkiG9w0BBwagggLnMIIC4wIBADCCAtwGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMbX3lkMt1cL6k0t8DAgEQgIICre6k9k3-GYZoRK93NrvdP0xJMcbyfPxYqx8Bp8T2NoD99h0iFidQpJmSkjC0CvniG0cJSA1PAYn8sRPKb9eWolXHfQKrYvR1uW281HyXwF4rAbP3QBKsV0zWYpCih5_GjhJziNYyleGfNMHDkXiQSuhC9kLs5jgmoHiV6FoWPmyKOQfFQOfmJl9TbkD26y234aoAbrlKUjo7CJXWXPzLv1zdxJT5PlPsp1895RL0qZTkXds7_c3cs0cpiNrdkSV66dvv26DcT9pjtELYUmFvdMowQQmAZeEJsLmED5eKX_E8sxX8C2hKFZIZDrtGOv1o2EIVgiGljMf97BvDZPqDcce6cL9EAONj0ShnIACV9VLXwTQO-CzcmKBWyTgNXcpPpXgobSuFraeQp2XX1Yi2RO6OGtc0gf9ehcpNARWnibkQD1ou3Qfe-1BctvnI_jo9c_LgcFYhP3s1qjkC8EMJDIO_6RSsBiDLpRcphMnGkVYaFpWafa29_4dzkVAaFtS1J9Ad5wMXjrVfeXoNqwA-QY_wv1AF-7ygc7Mh_2t3QZfQw_IpDjnYBadrKfNNbutXOo4262m3BfidAQ4FqB0KhX3XqTTPbhBuDm2HoeXM5-6Ir2qL3CrW-wgf3nkYMAs3OZlHF71TIufVP-eOHnPArxgtG66oaoZgWfJ9eiwyRGL3SUw9pAm-wpQVm_IpfykqMDz4UbmScfw74pWGcz4uRSktubyvWfNuq1-2ROxTVtUup4eak-ctWXH2U2-PWq182bpgjkHl9g2wR8ye8Va91hL7Q08CvN8Zdvp6Y1CDTHTx5c-7m1R4wEc_nL9A-RzAUjxK6CdvebB423ojSCxGqJwrxB_JH8bjpA3KEWTCwN0bD6o2Vu3A4XCyjmivbdkGEzDgzqjfsBMeyukLo4M

Summary: Former collegiate athletes may be at risk for negative health outcomes like lower health-related quality of life (HRQoL), higher disablement, and lower lifetime physical activity (PA) participation. A history of severe sports injury may play a role in these outcomes. The aim was to assess the role prior sports injury plays in self-reported HRQoL, levels of disablement, and PA behaviors of former Division I women's soccer players. Former NCAA Division I women's soccer players (n = 382, Mage = 36.41 ± 7.76) completed demographics, injury history, the Patient-Reported Outcomes Measurement Information System (PROMIS; HRQoL), the Disablement for the Physically Active Scale (DPA; disablement), and the Godin Leisure Time Physical Activity Questionnaire (PA). The dependent variables were physical and mental component summary scores for HRQoL and disablement, and frequency of moderate-to-vigorous PA. Means, standard deviations, and correlations among the main outcome variables were examined for those who reported a severe injury (n = 261) and those who did not (n = 121). To address the primary aim of the study, multiple regression analyses were used to predict PA, disablement, and HRQoL based on history of severe injury, accounting for age. Having a severe injury was significantly predictive of having worse physical disablement and worse physical HRQoL, with severe injury predicting a greater than 5-point increase and 2-point decrease on the respective scales. Injury status was not predictive of mental disablement, mental HRQoL, or PA. The majority of participants reported suffering a prior severe soccer-related injury, which may have a negative long-term impact on health outcomes for former women's soccer players. Athletic trainers should be aware of risk for decreased HRQoL and increased disablement with injury and encourage continued monitoring of relevant patient-reported outcomes (PROs).

 

 

#3 Post-match recovery profile of leukocyte cell subsets among professional soccer players

Reference: Sci Rep. 2021 Jun 25;11(1):13352. doi: 10.1038/s41598-021-92956-9.

Authors: Dorota Kostrzewa-Nowak, Paweł Wityk, Andrzej Ciechanowicz, Robert Nowak

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8233342/pdf/41598_2021_Article_92956.pdf

Summary: This study assessed the impact of cumulative match time on the distribution of CD45+ cell subtests in the capillary blood of professional soccer players. Twenty-two males (aged 18-30 years) took part in the 36-week study. Participants playing up to 540 in cumulative match time and less than 30 min in each single match during the observation period formed the control group. White blood cell (WBC) phenotyping and creatine kinase (CK) plasma activity analyses were performed. Also, counts for WBC subsets were determined. No significant differences in the hematological parameters or lymphocyte and NK cell percentages were observed between the control and study groups. Changes in the T cell percentage were significant during weeks 11 and 30 and in Th and Tc cell percentages during weeks 2 and 26. Significant correlations were found between the cumulative match time and Th, NK, and B cell percentages; monocyte counts; and CK activity in the control group. However, for the study group, correlations were found between cumulative match time and Th, Tc, and B cell percentages; CK activity; and the CK ratio. Our study suggests that the distribution of CD45+ cells might be a useful tool for monitoring the immune status of professional soccer players.

 

 

#4 Overseas Air Medical Repatriation of National Soccer Players Infected With Coronavirus Disease 2019 and Contacted Staff From Austria to South Korea

Reference: Case Reports Air Med J. Jul-Aug 2021;40(4):282-286.  doi: 10.1016/j.amj.2021.03.014. Epub 2021 Apr 2.

Authors: Hyo-Jeong Choi 1, Ho-Jung Kim 2, Gon Seo 3

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8017493/pdf/main.pdf

Summary: Korea rarely has a system to transport patients from abroad. However, single-patient transfers are steadily being performed, and there was an experience of transferring a large number of personnel regardless of whether they were confirmed or not due to coronavirus disease 2019. Recently, a national soccer game was held abroad, and a total of 8 players and staff were infected. A total of 15 people were transported through a charter fully equipped with quarantine equipment by a medical response team with experience in air transport.

 

 

#5 The Communication and Passing Contributions of Playing Positions in a Professional Soccer Team

Reference: J Hum Kinet. 2021 Jan 30;77:223-234.  doi: 10.2478/hukin-2020-0052. eCollection 2021 Jan.

Authors: Scott McLean, Paul M Salmon, Adam D Gorman, Karl Dodd, Colin Solomon

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008296/pdf/hukin-77-223.pdf

Summary: Determining the connectivity of team members in sport provides important information on team functioning. In soccer, teams that are highly connected via passing have been shown to be more successful compared to teams less connected via passing. In addition to passing connectivity, players are connected with each other via intra-team communication (ITC) through verbal instruction, and nonverbal cues. Despite ITC being a known component of effective teamwork to enhance strategy, efficiency, motivation and concentration, ITC of individual playing positions has not previously been measured during soccer games, nor has it been associated with passing connections in a performance context. In this study, the received ITC that was perceived to be beneficial to performance during 22 competitive professional soccer matches was measured, in conjunction with the passing connections between team members. In total, 526 ITC ratings were collected and analysed, and a total of 7,693 passes were analysed. From the ITC and passing measures, a player connectivity index (PCI) representing the coupling of ITC and passing, was developed to determine the overall connectivity of the individual playing positions. Social network analysis (SNA) centrality metrics were used to determine the connectivity of the playing positions. There were significant (p < .05) main effects between playing positions for beneficial ITC, passing, and the PCI for centrality metrics, indicating that different playing positions interact with other team members differently. Pairwise comparisons indicated significant differences between individual playing positions for ITC, passing and the PCI. The two central defenders and the two central defensive midfielders had the highest mean values for ITC, passing, and the PCI compared to the other playing positions. The current findings suggest that central defenders and central defensive midfielders are positioned tactically to be highly involved in the build-up of passing moves, and to deliver beneficial task related information to team members. These findings have implications for performance analysis, coaches, and for talent identification.

 

 

#6 The Relative Age Effect on Anthropometry, Body Composition, Biological Maturation and Motor Performance in Young Brazilian Soccer Players

Reference: J Hum Kinet. 2021 Jan 30;77:147-157.  doi: 10.2478/HUKIN-2021-0017. eCollection 2021 Jan.

Authors: Juliana Melo Altimari, Leandro Ricardo Altimari, Henrique Bortolotti, Adalberto Ferreira Junior, Juliano Moro Gabardo, Cosme Franklim Buzzachera, Ariobaldo Frisselli, Antonio Carlos de Moraes

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008302/pdf/hukin-77-147.pdf

Summary: The present study aimed to investigate the influence of months of birth on anthropometry, body composition, biological maturation, and motor performance in young Brazilian soccer players. Young Brazilian soccer players from the Under-13 (n = 50; 13.6 ± 0.3 years), Under-15 (n = 50; 15.5 ± 0.4 years), and Under-17 categories (n = 46; 17.7 ± 0.3 years) took part in this study. Athletes were divided according to chronological age, 1st tertile (January to April); 2nd tertile (May to August); and 3rd tertile (September to December). Anthropometry, body composition, biological maturation, and motor performance variables were evaluated for all participants. There were no differences between the U-13, U-15, and U-17 categories regarding birth tertiles (p > 0.05). Differences between the ages and birth tertiles were observed for the stature, body mass, and lean body mass (p < 0.05). Moreover, differences were found in maturational status between the ages and birth tertiles (p < 0.05). In general, U-13 players showed lower values compared to U-15 and U-17 players in tests of motor performance. In addition, there was a difference in motor performance between the birth tertiles only for RSA variables. The months of birth influenced the stature, body mass, lean body mass, and repeated sprint ability in the U-13 and U-15 categories. Thus, care should be taken during the process of talent selection, as many young players could be underestimated due to their date of birth.

 

 

#7 Acute Effects on Physical Performance Measures after 45 Min of Official Competition in Youth Soccer Players

Reference: J Funct Morphol Kinesiol. 2021 Jun 4;6(2):49. doi: 10.3390/jfmk6020049.

Authors: Federico Gazzo, Julián Giráldez, Rodrigo Villaseca-Vicuña, José Antonio González-Jurado, Santiago Zabaloy

Download link: https://www.mdpi.com/2411-5142/6/2/49/htm

Summary: An improved understanding of soccer players' match-related physical performance and recovery may help conditioning programs and re-warm up strategies to increase team performance during official competitions. Therefore, the aim of this study was to analyze the acute effects of 45 min of official competition (first half in matches) on physical performance variables in U-16 youth soccer players. (2) 20 male soccer players (age: 14.4 ± 0.5 years; height: 1.70 ± 0.05 cm; body mass: 65.1 ± 11.6 kg) were recruited to participate in this study. Data was collected from five official matches. Participants performed the assessments in two stages of each match: after the pre-match warm-up and after the first half. Tests included rate of perceived exertion (RPE), 30-m sprint and countermovement (CMJ). (3) Statistically significant differences were found (p < 0.001) when the measurements prior to the game were compared with those recorded after half time across all variables. Effect sizes (ES) were very large for RPE (ES = 1.82), moderate for 30-m sprint times (ES = 0.64) and small for CMJ (ES = -0.25). (4). After 45 min of official competition, our results suggest that U-16 soccer players demonstrated a reduction in sprint and jump performance, in addition to a higher RPE. Hence, this information could be useful when designing re-warming strategies that can be performed before the second half.

 

 

#8 Comparison of Official and Friendly Matches through Acceleration, Deceleration and Metabolic Power Measures: A Full-Season Study in Professional Soccer Players

Reference: Int J Environ Res Public Health. 2021 Jun 2;18(11):5980.  doi: 10.3390/ijerph18115980.

Authors: Hadi Nobari, Sara Mahmoudzadeh Khalili, Rafael Oliveira, Alfonso Castillo-Rodríguez, Jorge Pérez-Gómez, Luca Paolo Ardigò

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199659/pdf/ijerph-18-05980.pdf

Summary: Soccer is a popular team sport and highly demanding activity that requires high effort and long-term training plans. The goals of this study were to compare the accelerations, decelerations and metabolic power between official and friendly full matches, between the first and second halves of the matches, and between both halves of official and friendly matches. Twelve professional soccer players (age, 28.6 ± 2.7 years; height, 182.1 ± 8.6 cm; body mass, 75.3 ± 8.2 kg; BMI, 22.6 ± 0.7 kg/m2) participated in this study. A total of 33 official and 10 friendly matches were analyzed from the Iranian Premier League. All matches were monitored using GPSPORTS systems Pty Ltd. The following variables were selected: total duration of the matches, metabolic power, accelerations Zone1 (<2 m·s-2) (AccZ1), accelerations Zone2 (2 to 4 m·s-2) (AccZ2), accelerations Zone3 (>4 m·s-2) (AccZ3), decelerations Zone1 (<-2 m·s-2) (DecZ1), decelerations Zone2 (-2 to -4 m·s-2) (DecZ2) and decelerations Zone3 (>-4 m·s-2) (DecZ3). The major finding was shown in metabolic power, where higher values occurred in friendly matches (p < 0.05 with small effect size). Furthermore, total duration, AccZ3, DecZ1, DecZ2, and DecZ3 were revealed to be higher in official matches, while AccZ1 and AccZ2 were higher in friendly matches. The second half of the official matches revealed higher values for total duration compared to friendly matches (p < 0.05, moderate effect size). In conclusion, this study observed higher values of metabolic power in friendly matches compared to official matches. AccZ3, DecZ1, DecZ2, and DecZ3 were higher in official matches, while AccZ1 and AccZ2 were higher in friendly matches.

 

 

#9 The Role of Motor Imagery in Predicting Motor Skills in Young Male Soccer Players

Reference: Int J Environ Res Public Health. 2021 Jun 10;18(12):6316.  doi: 10.3390/ijerph18126316.

Authors: Dariusz Zapała, Emilia Zabielska-Mendyk, Andrzej Cudo, Marta Jaśkiewicz, Marcin Kwiatkowski, Agnieszka Kwiatkowska

Download link: https://www.mdpi.com/1660-4601/18/12/6316/htm

Summary: The study aimed to find out whether the imagery ability within the two subcomponents of motor imagery (visual and kinesthetic) allows predicting the results in simple response time task and eye-hand coordination task in a group of young male soccer players (9-15 years old). Non-specific simple response time and eye-hand coordination play a key role in predicting specific sports performance level. Participants performed Reaction Time Task, Eye-Hand Coordination Task, and completed Motor Imagery Questionnaire-Revised. Data were submitted to the structural equations analysis based on the maximum likelihood method in order to estimate a structural model of relationship between variables. Results indicate visual rather than kinesthetic motor imagery is associated with non-specific motor skills. Higher scores on the visual motor imagery scale were observed to correlate with faster reaction times and better coordination in the study group. This supports the idea that during learning a new perceptual-motor-task the visual control is required. Results provide the evidence for the specific role of the third-person perspective imagery in young athletes playing soccer.

 

 

#10 Effect of Online Training during the COVID-19 Quarantine on the Aerobic Capacity of Youth Soccer Players

Reference: Int J Environ Res Public Health . 2021 Jun 8;18(12):6195.  doi: 10.3390/ijerph18126195.

Authors: Paweł Kalinowski, Jakub Myszkowski, Jakub Marynowicz

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8229218/pdf/ijerph-18-06195.pdf

Summary: Motor abilities, such as endurance and the optimal level of physical activity, play a fundamental role in football as they are necessary to maintain the high effectiveness of the training process. The aim of this study was the observation of the trend of changes in the level of cardiorespiratory endurance of young football players in a one-year cycle overlapping with the COVID-19 lockdown and an assessment of the impact of the training intervention during home confinement. The participants of the study were 24 young football players. We analysed the results of the study in a one-year training cycle (lockdown from 11 March 2020 to 6 May 2020). The cardiorespiratory endurance was measured using the Multistage 20 m Shuttle Run test-Beep Test. A repeated measures analysis of variance was used in the study. Detailed comparisons were made using Tukey's HSD test. Statistically significant differences were noted in endurance in a one year cycle: F(5.115) = 22.65; p < 0.001; partial Eta-squared = 0.50. An increase in the level of endurance by mean = 179.17 m, SD ± 189.87 m was noted between T1 and T6. After the break caused by the COVID-19 restrictions, a decrease in the level of cardiorespiratory endurance was noted. Only after two training mesocycles was a significant increase in the mean value noted compared to the period before the pandemic (p < 0.05). With the negative impact of restrictions in mind, coaches and physiotherapists should exercise caution when planning training, taking into consideration the level of physical activity during the pandemic.

 

 

#11 Relationships between Fitness Status and Match Running Performance in Adult Women Soccer Players: A Cohort Study

Reference: Medicina (Kaunas). 2021 Jun 13;57(6):617.  doi: 10.3390/medicina57060617.

Authors: Lillian Gonçalves, Filipe Manuel Clemente, Joel Ignacio Barrera, Hugo Sarmento, Francisco Tomás González-Fernández, Luiz H Palucci Vieira, António José Figueiredo, Cain C T Clark, J M Cancela Carral

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8231904/pdf/medicina-57-00617.pdf

Summary: The aim of this study was twofold: (i) to analyze the relationships between fitness status (repeated-sprint ability (RSA), aerobic performance, vertical height jump, and hip adductor and abductor strength) and match running performance in adult women soccer players and (ii) to explain variations in standardized total distance, HSR, and sprinting distances based on players' fitness status.  The study followed a cohort design. Twenty-two Portuguese women soccer players competing at the first-league level were monitored for 22 weeks. These players were tested three times during the cohort period. The measured parameters included isometric strength (hip adductor and abductor), vertical jump (squat and countermovement jump), linear sprint (10 and 30 m), change-of-direction (COD), repeated sprints (6 × 35 m), and intermittent endurance (Yo-Yo intermittent recovery test level 1). Data were also collected for several match running performance indicators (total distance covered and distance at different speed zones, accelerations/decelerations, maximum sprinting speed, and number of sprints) in 10 matches during the cohort.  Maximal linear sprint bouts presented large to very large correlations with explosive match-play actions (accelerations, decelerations, and sprint occurrences; r = -0.80 to -0.61). In addition, jump modalities and COD ability significantly predicted, respectively, in-game high-intensity accelerations (r = 0.69 to 0.75; R2 = 25%) and decelerations (r = -0.78 to -0.50; R2 = 23-24%). Furthermore, COD had significant explanatory power related to match running performance variance regardless of whether the testing and match performance outcomes were computed a few or several days apart.  The present investigation can help conditioning professionals working with senior women soccer players to prescribe effective fitness tests to improve their forecasts of locomotor performance.

 

 

#12 Hamstring Injuries Prevention in Soccer: A Narrative Review of Current Literature

Reference: Review Joints. 2020 May 25;7(3):115-126.  doi: 10.1055/s-0040-1712113. eCollection 2019 Sep.

Authors: Gian Nicola Bisciotti, Karim Chamari, Emanuele Cena, Giulia Carimati, Alessandro Bisciotti, Andrea Bisciotti, Alessandro Quaglia, Piero Volpi

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8236328/pdf/10-1055-s-0040-1712113.pdf

Summary: Hamstring injuries and reinjuries are one of the most important sport lesions in several sport activities including soccer, Australian football, track and field, rugby, and in general in all sport activities requiring sprinting and acceleration. However, it is important to distinguish between the lesions of the biceps femoris and semitendinosus and semimembranosus. Indeed, three muscles representing the hamstring complex have a very different injury etiology and consequently require different prevention strategies. This fact may explain, at least in part, the high incidence of reinjuries. In soccer, hamstring injuries cause an important rate of time loss (i.e., in average 15-21 matches missed per club per season). The hamstring injury risk factors may be subdivided in three categories: "primary injury risk factors" (i.e., the risk factors mainly causing a first lesion), "recurrent injury risk factors" (i.e., the risk that can cause a reinjury), and bivalent injury risk factors" (i.e., the risk factors that can cause both primary injuries and reinjuries). The high incidence of hamstring lesions caused consequently an important increase in hamstring injury research. However, although the prevention has increased paradoxically, epidemiological data do not show a loss in injuries and/or reinjuries but, on the contrary, they show an increase in hamstring injuries. This apparent paradox highlights the importance both of the improvement in the prevention programs quality and the criteria for return to play after hamstring injury.

 

 

#13 Uniform Manifold Approximation and Projection Analysis of Soccer Players

Reference: Entropy (Basel). 2021 Jun 23;23(7):793.  doi: 10.3390/e23070793.

Authors: António M Lopes, José A Tenreiro Machado

Download link: https://www.mdpi.com/1099-4300/23/7/793/htm

Summary: In professional soccer, the choices made in forming a team lineup are crucial for achieving good results. Players are characterized by different skills and their relevance depends on the position that they occupy on the pitch. Experts can recognize similarities between players and their styles, but the procedures adopted are often subjective and prone to misclassification. The automatic recognition of players' styles based on their diversity of skills can help coaches and technical directors to prepare a team for a competition, to substitute injured players during a season, or to hire players to fill gaps created by teammates that leave. The paper adopts dimensionality reduction, clustering and computer visualization tools to compare soccer players based on a set of attributes. The players are characterized by numerical vectors embedding their particular skills and these objects are then compared by means of suitable distances. The intermediate data is processed to generate meaningful representations of the original dataset according to the (dis)similarities between the objects. The results show that the adoption of dimensionality reduction, clustering and visualization tools for processing complex datasets is a key modeling option with current computational resources.

 

 

#14 Poor Motor Coordination Elicits Altered Lower Limb Biomechanics in Young Football (Soccer) Players: Implications for Injury Prevention through Wearable Sensors

Reference: Sensors (Basel). 2021 Jun 25;21(13):4371.  doi: 10.3390/s21134371.

Authors: Stefano Di Paolo, Stefano Zaffagnini, Nicola Pizza, Alberto Grassi, Laura Bragonzoni

Download link: https://www.mdpi.com/1424-8220/21/13/4371/htm

Summary: Motor coordination and lower limb biomechanics are crucial aspects of anterior cruciate ligament (ACL) injury prevention strategies in football. These two aspects have never been assessed together in real scenarios in the young population. The present study aimed to investigate the influence of motor coordination on lower limb biomechanics in young footballers during an on-the-pitch training. Eighteen juvenile football players (10 y ± 2 m) were enrolled. Each player performed a training drill with sport-specific movements (vertical jump, agility ladders, change of direction) and the Harre circuit test (HCT) to evaluate players' motor coordination. Wearable inertial sensors (MTw Awinda, Xsens) were used to assess lower limb joint angles and accelerations. Based on the results of the HCT, players were divided into poorly coordinated (PC) and well-coordinated (WC) on the basis of the literature benchmark. The PC group showed a stiffer hip biomechanics strategy (up to 40% lower flexion angle, ES = 2.0) and higher internal-external hip rotation and knee valgus (p < 0.05). Significant biomechanical limb asymmetries were found only in the PC group for the knee joint (31-39% difference between dominant and non-dominant limb, ES 1.6-2.3). Poor motor coordination elicited altered hip and knee biomechanics during sport-specific dynamic movements. The monitoring of motor coordination and on-field biomechanics might enhance the targeted trainings for ACL injury prevention.

 

 

#15 An Exploratory Data Analysis on the Influence of Role Rotation in a Small-Sided Game on Young Soccer Players

Reference: Int J Environ Res Public Health. 2021 Jun 24;18(13):6773.  doi: 10.3390/ijerph18136773.

Authors: Moisés Falces-Prieto, Francisco Tomás González-Fernández, Jaime Matas-Bustos, Pedro Jesús Ruiz-Montero, Jesús Rodicio-Palma, Manuel Torres-Pacheco, Filipe Manuel Clemente

Download link: https://www.mdpi.com/1660-4601/18/13/6773/htm

Summary: The aim of the present study was to analyze the behavior of players in a standard small-sided game (SSG) according to the role played (offensive (OF), defensive (DF), and wildcard (W)) and its relationship with physical demands (PHYD), technical performance (TP), and internal load (RPE). A total of 24 young highly trained male soccer players (under 16: n = 12; under 19: n = 12) participated. During the SSG, the players alternated the three roles (OF, DF, and W). The duration of each repetition was 4 min with a passive rest of 3 min between them. Furthermore, it emphasized the high demand in all defensive parameters. In addition, DF roles showed higher values in PHYD and RPE, followed by the OF roles, and finally by the W roles. A complementary, positive moderate correlation was found between PHYD and RPE in the U16 dataset (r = 0.45, p < 0.006). Very large positive correlations were also found between PHYD and RPE in the U19 and merged dataset (r = 0.78, p < 0.001 and r = 0.46, p < 0.63, respectively). This information could be useful for coaches in order to structure the roles in SSGs and control training load.

 

 

#16 Effects of Combined Creatine and Sodium Bicarbonate Supplementation on Soccer-Specific Performance in Elite Soccer Players: A Randomized Controlled Trial

Reference: Int J Environ Res Public Health. 2021 Jun 28;18(13):6919.  doi: 10.3390/ijerph18136919.

Authors: Jooyoung Kim

Download link: https://www.mdpi.com/1660-4601/18/13/6919/htm

Summary: Creatine and sodium bicarbonate are both ergogenic aids for athletic performance. However, research on the combined creatine and sodium bicarbonate (CSB) supplementation in soccer is limited. This study investigated the changes in soccer-specific performance in elite soccer players after supplementing with CSB. Twenty well-trained elite soccer players participated in the study (age: 20.70 ± 1.08 years; height: 173.95 ± 2.81 cm; body weight: 70.09 ± 3.96 kg; soccer experience: 8 years; average training hours per week: 20 h). The participants were randomly allocated into CSB groups (CSB, n = 10) and placebo groups (PLA, n = 10). The CSB group took creatine (20 g/day) and sodium bicarbonate (0.3 g/kg/day); these two supplements were taken four times a day (morning, afternoon, evening, and before sleep) for seven days. Soccer-specific performance was assessed via 10- and 30-m sprint, coordination, arrowhead agility, and Yo-Yo intermittent recovery level 1 tests. Compared to the PLA group, the CSB group performed better in the 30-m sprint (CSB: -3.6% vs. PLA: -0.6%, p = 0.007, effect size (ES): 2.3) and both right and left arrowhead agility (right: CSB: -7.3% vs. PLA: -0.7%, p < 0.001, ES: 2.8; left: CSB: -5.5% vs. PLA: -1.2%, p = 0.001, ES: 2.1) tests. However, there were no differences in 10 m sprints, coordination, and Yo-Yo intermittent recovery level 1 tests between the two groups (p > 0.05). In conclusion, CSB supplementation improved sprint and agility in elite soccer players. However, it is still unclear whether such effect is synergistic effect of two supplements or the result of either one of them. Therefore, caution should be taken when interpreting the results, and the limitations should be examined further in future studies.

 

 

#17 Analysis of Head Impact Biomechanics in Youth Female Soccer Players Following the Get aHEAD Safely in Soccer™ Heading Intervention

Reference: Sensors (Basel). 2021 Jun 3;21(11):3859.  doi: 10.3390/s21113859.

Authors: Victoria E Wahlquist, Thomas W Kaminski

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199772/pdf/sensors-21-03859.pdf

Summary: The effects of repetitive head impacts associated with soccer heading, especially in the youth population, are unknown. The purpose of this study was to examine balance, neurocognitive function, and head impact biomechanics after an acute bout of heading before and after the Get aHEAD Safely in Soccer™ program intervention. Twelve youth female soccer players wore a Triax SIM-G head impact sensor during two bouts of heading, using a lightweight soccer ball, one before and one after completion of the Get aHEAD Safely in Soccer™ program intervention. Participants completed balance (BESS and SWAY) and neurocognitive function (ImPACT) tests at baseline and after each bout of heading. There were no significant changes in head impact biomechanics, BESS, or ImPACT scores pre- to post-season. Deficits in three of the five SWAY positions were observed from baseline to post-season. Although we expected to see beneficial changes in head impact biomechanics following the intervention, the coaches and researchers observed an improvement in heading technique/form. Lightweight soccer balls would be a beneficial addition to header drills during training as they are safe and help build confidence in youth soccer players.

 

 

#18 Relationships between Sleep, Athletic and Match Performance, Training Load, and Injuries: A Systematic Review of Soccer Players

Reference: Review Healthcare (Basel). 2021 Jun 26;9(7):808.  doi: 10.3390/healthcare9070808.

Authors: Filipe Manuel Clemente, José Afonso, Júlio Costa, Rafael Oliveira, José Pino-Ortega, Markel Rico-González 

Download link: https://www.mdpi.com/2227-9032/9/7/808/htm

Summary: The purpose of this systematic review was to summarize available evidence regarding the relationships between sleep and (i) athletic and match performance, (ii) training load, and (iii) injuries in soccer players. A systematic review of EBSCOhost (SPORTDiscus), PubMed, Cochrane Library, FECYT (Web of Sciences, CCC, DIIDW, KJD, MEDLINE, RSCI, and SCIELO) databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 297 titles were identified, of which 32 met the eligibility criteria. Results revealed that soccer players are no exception for sleep inadequacy. Although there was inconsistency in the findings, some studies suggested that sleep restrictions in soccer negatively affected athletic and match performance while also increasing the number and severity of musculoskeletal injuries. On the other hand, inconsistent results were found between sleep and athletic and match performance, and training load in soccer players. Physiological responses (and their intensity) during drill-based games were not influenced by changes in sleep. The available evidence is inconsistent; however, it appears to suggest that poor sleep affects soccer players' performance and increases the risk of injury. However, it remains important to study this complex relationship further.

 

 

#19 Actual and perceived motor competence mediate the relationship between physical fitness and technical skill performance in young soccer players

Reference: Eur J Sport Sci. 2021 Jun 30;1-20.  doi: 10.1080/17461391.2021.1948616. Online ahead of print.

Authors: Michael J Duncan, Emma L J Eyre, Mark R Noon, Rhys Morris, C Doug Thake, Neil D Clarke, Anna J Cunningham

Summary: This study examined the role of fundamental movement skills (FMS) and perceived competence in the relationship between physical fitness and technical soccer skills in children. Seventy boys aged 7-12 years of age (Mean ± SD = 9 ± 2 years) who were regularly engaged in grassroots soccer participated in the present study. The Test of Gross Motor Development-2 (Ulrich, 2001) was used to assess FMS and the Perceived Physical Ability Scale for Children (Colella, et al., 2008) was used to assess perceived competence. Technical skill was determined from three tests reflecting dribbling, passing and shooting. Z-scores of each measure were summed, creating a composite measure of technical skill. Three measures of physical fitness were employed; 15m sprint time, standing long jump, and seated medicine ball (1kg) throw. Z-scores for each measure were summed creating a composite measure of physical fitness. The relationship between technical skill and FMS, fitness, perceived competence and age was examined via path analysis. Results indicated two significant mediated pathways: from physical fitness to technical skills via FMS, and from physical fitness to technical skills via perceived competence. Once these mediators had been accounted for, there was no direct link from physical fitness to technical skills. Coaches should therefore seek to avoid one-sided delivery of practice by not solely focusing on football type drills, and focusing on a range of activities which enhance a broad foundation of FMS and promote strategies to positively influence a child's perception of their own competence.

 

 

#20 In-Season Internal and External Workload Variations between Starters and Non-Starters-A Case Study of a Top Elite European Soccer Team

Reference: Medicina (Kaunas). 2021 Jun 23;57(7):645.  doi: 10.3390/medicina57070645.

Authors: Rafael Oliveira, Luiz H Palucci Vieira, Alexandre Martins, João Paulo Brito, Matilde Nalha, Bruno Mendes, Filipe Manuel Clemente

Download link: https://www.mdpi.com/1648-9144/57/7/645/htm

Summary: Interpretation of the load variations across a period seems important to control the weekly progression or variation of the load, or to identify in-micro- and mesocycle variations. Thus, the aims of this study were twofold: (a) to describe the in-season variations of training monotony, training strain and acute:chronic workload ratio (ACWR) through session ratings of perceived exertion (s-RPE), total distance and high-speed running (HSR); and (b) to compare those variations between starters and non-starters.  Seventeen professional players from a European First League team participated in this study. They were divided in two groups: starters (n = 9) and non-starters (n = 8). The players were monitored daily over a 41-week period of competition where 52 matches occurred during the 2015-2016 in-season. Through the collection of s-RPE, total distance and HSR, training monotony, training strain and ACWR were calculated for each measure, respectively. Data were analyzed across ten mesocycles (M: 1 to 10). Repeated measures ANOVA was used with the Bonferroni post hoc test to compare M and player status.  The results revealed no differences between starters vs. non-starters (p > 0.05). M6 had a greater number of matches and displayed higher values for monotony (s-RPE, total distance and HSR), strain (only for total distance) and ACWR (s-RPE, TD and HSR). However, the variation patterns for all indexes displayed some differences.  The values of both starters and non-starters showed small differences, thus suggesting that the adjustments of training workloads that had been applied over the season helped to reduce differences according to the player status. Even so, there were some variations over the season (microcycles and mesocycles) for the whole team. This study could be used as a reference for future coaches, staff and scientists.

 

 

Wed

22

Dec

2021

Latest research in football - week 39 - 2021

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 Lower-Limb Muscle Strength, Anterior-Posterior and Inter-Limb Asymmetry in Professional, Elite Academy and Amateur Soccer Players

Reference: J Hum Kinet. 2021 Jan 30;77:135-146.  doi: 10.2478/hukin-2020-0058. eCollection 2021 Jan.

Authors: Marco Beato 1, Damien Young 2, Adam Stiff 1, Giuseppe Coratella 3

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008310/pdf/hukin-77-135.pdf

Summary: Given the importance of the lower-limb strength and strength balance in soccer players and its relationship with injury prevention and performance, the present study compared quadriceps and hamstrings strength, the conventional (Hconc:Qconc), functional (Hecc:Qconc) hamstrings-to-quadriceps ratio and inter-limb strength asymmetry in professional, elite academy and amateur male soccer players. In this cross-sectional study, two hundred-six soccer players (professional = 75, elite academy = 68, amateurs = 63) volunteered to participate. Quadriceps and hamstrings isokinetic peak torque was investigated at 60° .s-1 in both the concentric and eccentric modality and at 300°.s-1 in the concentric modality. The conventional Hconc:Qconc, functional Hecc:Qconc ratio and quadriceps and hamstrings inter-limb strength asymmetry were then calculated. Professional players presented greater quadriceps and hamstrings strength than elite academy (effect size from small to moderate) and amateur players (moderate to very large). Both the conventional Hconc:Qconc and functional Hecc:Qconc ratio were greater in professional than elite academy and amateur players (small to moderate). Overall, quadriceps and hamstrings inter-limb strength asymmetry was greater in amateurs than professional (small to very large) and elite academy (trivial to large) players. The present findings provide coaches and medical staffs with normative lower-limb muscle strength data on professional, academy and amateur soccer players. Overall lower-limb muscle strength and inter-limb strength asymmetry could be used to evaluate possible inference on injury prevention and performance. The hamstrings-to-quadriceps ratio poorly differentiates between the soccer players background and offers limited prediction for injury prevention and performance.

 

 

#2 Heading in Soccer: Does Kinematics of the Head-Neck-Torso Alignment Influence Head Acceleration?

Reference: J Hum Kinet. 2021 Jan 30;77:71-80. doi: 10.2478/hukin-2021-0012. eCollection 2021 Jan.

Authors: Stephan Becker, Joshua Berger, Oliver Ludwig, Daniel Günther, Jens Kelm, Michael Fröhlich

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008297/pdf/hukin-77-071.pdf

Summary: There is little scientific evidence regarding the cumulative effect of purposeful heading. The head-neck-torso alignment is considered to be of great importance when it comes to minimizing potential risks when heading. Therefore, this study determined the relationship between head-neck-torso alignment (cervical spine, head, thoracic spine) and the acceleration of the head, the relationship between head acceleration and maximum ball speed after head impact and differences between head accelerations throughout different heading approaches (standing, jumping, running). A total of 60 male soccer players (18.9 ± 4.0 years, 177.6 ± 14.9 cm, 73.1 ± 8.6 kg) participated in the study. Head accelerations were measured by a telemetric Noraxon DTS 3D Sensor, whereas angles for the head-neck-torso alignment and ball speed were analyzed with a Qualisys Track Manager program. No relationship at all was found for the standing, jumping and running approaches. Concerning the relationship between head acceleration and maximum ball speed after head impact only for the standing header a significant result was calculated (p = 0.024, R2 = .085). A significant difference in head acceleration (p < .001) was identified between standing, jumping and running headers. To sum up, the relationship between head acceleration and head-neck-torso alignment is more complex than initially assumed and could not be proven in this study. Furthermore first data were generated to check whether the acceleration of the head is a predictor for the resulting maximum ball speed after head impact, but further investigations have to follow. Lastly, we confirmed the results that the head acceleration differs with the approach.

 

 

#3 A New Foot-Mounted Inertial Measurement System in Soccer: Reliability and Comparison to Global Positioning Systems for Velocity Measurements During Team Sport Actions

Reference: J Hum Kinet. 2021 Jan 30;77:37-50. doi: 10.2478/hukin-2021-0010. eCollection 2021 Jan.

Authors: Mark Waldron, Jamie Harding, Steve Barrett, Adrian Gray

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008313/pdf/hukin-77-037.pdf

Summary: The aims of this study were to i) compare a foot-mounted inertial system (PlayerMaker™) to three commercially available Global Positioning Systems (GPS) for measurement of velocity-based metrics during team sport movements and ii) evaluate the inter-unit reliability of the PlayerMaker™. Twelve soccer players completed a soccer simulation, whilst wearing a PlayerMaker™ and three GPS (GPS#1, #2 and #3). A sub-sample (n = 7) also wore two PlayerMaker™ systems concurrently. The PlayerMaker™ measured higher (p < 0.05) total distance (518 ± 15 m) compared to GPS#1 (488 ± 15 m), GPS#2 (486 ± 15 m), and GPS#3 (501 ± 14 m). This was explained by greater (p < 0.05) distances in the 1.5-3.5 m/s zone (356 ± 24 m vs. 326 ± 26 m vs. 324 ± 18 m vs. 335 ± 24 m) and the 3.51-5.5 m/s zone (64 ± 18 m vs. 35 ± 5 vs. 43 ± 8 m vs. 41 ± 8 m) between the PlayerMaker™, GPS#1, GPS#2 and GPS#3, respectively. The PlayerMaker™ recorded higher (p < 0.05) distances while changing speed. There were no systematic differences (p > 0.05) between the two PlayerMaker™ systems. The PlayerMaker™ is reliable and records higher velocity and distances compared to GPS.

 

 

#4 Regular football training down-regulates miR-1303 muscle expression in veterans

Reference: Eur J Appl Physiol. 2021 Jul 1. doi: 10.1007/s00421-021-04733-1. Online ahead of print.

Authors: A Mancini, D Vitucci, F M Orlandella, A Terracciano, R M Mariniello, E Imperlini, E Grazioli, S Orrù, P Krustrup, G Salvatore, P Buono

Download link: https://link.springer.com/content/pdf/10.1007/s00421-021-04733-1.pdf

Summary: Regular exercise affects the expression of several genes, proteins and microRNAs (miRNAs) in time- and intensity-dependent manner promoting longevity. We previously identified from GeneChip Array analysis several differentially expressed genes and miRNAs in muscle from veteran football players (VPG) compared to active untrained elderly subjects (CG); here we focussed on miRNA-1303 (miR-1303). The aims of the present research were: to analyse the effects of football training on the expression of miR-1303 and to identify its putative target involved in the longevity pathways in skeletal muscle from VPG compared to CG. RNA samples from 12 VPG and 12 CG muscle biopsies were used to validate miR-1303 expression. Crossing four different bioinformatic algorithms, we identified 16 putative targets of miR-1303; from these, BAG-2, KLHL7 and KBTBD6 were chosen for further validation by Western blot analysis in LHCN-M2 human myoblasts transiently transfected with miR-1303. Football training down-regulates miR-1303 expression in muscle from VPG compared to CG and the expression of BAG-2, a chaperon protein involved in the autophagy pathway, inversely correlated to overexpression of miR-1303 in a time-dependent manner, indicating that it is a miR-1303 potential target. This is the first report, to our knowledge, describing miR-1303 regulation in skeletal muscle by football training and the identification of a target protein, BAG-2, involved in the autophagy pathway. This result contributes to the enlargement of knowledge on the molecular mechanisms linking football training, autophagy and longevity.

 

 

#5 Effect of Resisted Sprint and Plyometric Training on Lower Limb Functional Performance in Collegiate Male Football Players: A Randomised Control Trial

Reference: Int J Environ Res Public Health. 2021 Jun 22;18(13):6702. doi: 10.3390/ijerph18136702.

Authors: Shahnaz Hasan, Gokulakannan Kandasamy, Danah Alyahya, Asma Alonazi, Azfar Jamal, Radhakrishnan Unnikrishnan, Hariraja Muthusamy, Amir Iqbal

Download link: https://www.mdpi.com/1660-4601/18/13/6702/htm

Summary: The main objectives of this study were to evaluate the short-term effects of resisted sprint and plyometric training on sprint performance together with lower limb physiological and functional performance in collegiate football players. Ninety collegiate football players participated in this three-arm, parallel group randomized controlled trial study. Participants were randomly divided into a control group and two experimental groups: resisted sprint training (RST) (n = 30), plyometric training (PT) (n = 30), and a control group (n = 30). Participants received their respective training program for six weeks on alternate days. The primary outcome measures were a knee extensor strength test (measured by an ISOMOVE dynamometer), a sprint test and a single leg triple hop test. Measurements were taken at baseline and after 6 weeks post-training. Participants, caregivers, and those assigning the outcomes were blinded to the group assignment. A mixed design analysis of variance was used to compare between groups, within-group and the interaction between time and group. A within-group analysis revealed a significant difference (p < 0.05) when compared to the baseline with the 6 weeks post-intervention scores for all the outcomes including STN (RST: d = 1.63; PT: d = 2.38; Control: d = 2.26), ST (RST: d = 1.21; PT: d = 1.36; Control: d = 0.38), and SLTHT (RST: d = 0.76; PT: d = 0.61; Control: d = 0.18). A sub-group analysis demonstrated an increase in strength in the plyometric training group (95% CI 14.73 to 15.09, p = 0.00), an increase in the single leg triple hop test in the resisted sprint training group (95% CI 516.41 to 538.4, p = 0.05), and the sprint test was also improved in both experimental groups (95% CI 8.54 to 8.82, p = 0.00). Our findings suggest that, during a short-term training period, RST or PT training are equally capable of enhancing the neuromechanical capacities of collegiate football players. No adverse events were reported by the participants.

 

 

#6 Relationship between Posture and Non-Contact Lower Limb Injury in Young Male Amateur Football Players: A Prospective Cohort Study

Reference: Int J Environ Res Public Health. 2021 Jun 14;18(12):6424. doi: 10.3390/ijerph18126424.

Authors: Suzanne J Snodgrass, Kathleen E Ryan, Andrew Miller, Daphne James, Robin Callister

Download link: https://www.mdpi.com/1660-4601/18/12/6424/htm

Summary: Posture, a potentially modifiable injury risk factor, is considered important in injury screening/prevention in athletes, yet few studies investigate relationships between posture and injury. This prospective cohort study investigated whether static posture is associated with lower limb injury risk in male football players (n = 263). Nine aspects of static standing posture (left and right rearfoot, knee interspace, lateral knee, lumbar lordosis, thoracic kyphosis, scoliosis S and C, forward head) were assessed from photographs during the pre-season using the modified Watson and Mac Donncha scale, which was dichotomised for analysis (deviated or normal). Player characteristics (age, height, mass, body mass index, competition level), match/training exposure, and previous and in-season non-contact lower limb injuries were recorded. Binary logistic regression investigated relationships between posture and injury (previous and in-season). Eighty previous and 24 in-season lower limb injuries were recorded. Previous injury was not associated with any postural variable. In-season injury was associated with previous injury (OR = 3.04, 95% CI 1.20-7.68, p = 0.02) and having a normal thoracic curve compared to kyphosis (OR = 0.38, 95% CI 0.15-1.00, p = 0.05) but no other postural variables. Static postural deviations observed in male football players in the pre-season are not typically associated with non-contact lower limb injury risk; thus, they are unlikely to add value to pre-season screening programs.

 

 

#7 Sustainability in the football industry: An approach to the gap between theoretical formulation and practical application, through the results of the social fair play project

Reference: Heliyon. 2021 Jun 16;7(6):e07318. doi: 10.1016/j.heliyon.2021.e07318. eCollection 2021 Jun.

Authors: Roberto Fernández-Villarino

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8237602/pdf/main.pdf

Summary: This paper discusses the first experiences and results of a project titled Social Fair Play (SFP), whose objective is to install the principles of sustainability and social responsibility (SR) at the core of Spanish professional football. The project was implemented in clubs and foundations belonging to some of the categories of the Spanish National Professional Football League (LaLiga). Generally speaking, the football industry, despite its strong economic and social impact, has entered the debate on strategic management in SR late. This study's interest lies in determining whether these first results and evidences can contribute to the debate, reflected in the specialised literature, around the gap between the theoretical formulation and the practical application of SR and sustainability principles. A second source of interest is the question of whether, on the basis of this experience, a system of social performance measures can be developed for the whole industry which would enable us to compare results and ease their communication, along the lines of other economic sectors, taking as a model internationally recognised standards such as the GRI.

 

 

#8 Danger zone assessment in small-sided recreational football: providing data for consideration in relation to COVID-19 transmission

Reference: BMJ Open Sport Exerc Med. 2021 Jan 11;7(1):e000911. doi: 10.1136/bmjsem-2020-000911. eCollection 2021.

Authors: Morten B Randers, Nikolas Sten Knudsen, Manuel Mounir Demetry Thomasen, Jeppe Panduro, Malte Nejst Larsen, Magni Mohr, Zoran Milanovic, Peter Krustrup, Thomas Bull Andersen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7802394/pdf/bmjsem-2020-000911.pdf

Summary: During the COVID-19 pandemic, physical inactivity has increased, and a wide range of sporting activities locked down, with possible long-term implications for public health. Football is the most popular sport worldwide, and recreational football training leads to broad-spectrum health effects. Football is, however, deemed a contact sport with frequent close contact important to consider during COVID-19 pandemic. This study investigated time spent with close contact (danger zone (DZ) within 1.5 m), number of contacts and time per contact, and compared game formats in recreational small-sided football games for young and adult male football players. Movement analyses were performed on 10 Hz Global Positioning System (GPS) data collected during various small-sided football games prior to the COVID-19 outbreak. Time spent in the DZ was 4.3-7.9 s/h per per cent infected players, corresponding to 34.3-114.8 s/h if one player was infected. Number of contacts with one infected player was 23.5-87.7 per hour, with an average contact time of 1.1-1.4 s, and a total number of contacts of 311-691 per hour with all players. 53%-65% of all contacts were shorter than 1 s and 77%-85% shorter than 2 s. Trivial to small effects were found for number of participants and area per player, whereas standard of play and playing with/without boards had no effect. This study demonstrated that during small-sided football limited time is spent within DZ and that player contacts are brief. Recreational football may therefore more appropriately be deemed as sporting activity with brief, sporadic contact.

 

 

#9 Physical workload and fatigue pattern characterization in a top-class women's football national team. A case study of the 2019 fifa women's world cup

Reference: J Sports Med Phys Fitness. 2021 Jun 29. doi: 10.23736/S0022-4707.21.12811-7. Online ahead of print.

Authors: Farzad Yousefian, Hannah Hüttemann, Mats Borjesson, Pontus Ekblom, Magni Mohr, Dan Fransson

Summary: With the growing scientific interest in women's football it is critical to understand the match demands and fatigue patterns during a top-class women's competition. Physical characteristics and performance of top-class women football matches during the 2019 FIFA Women's World Cup was investigated from data collected using global positioning system for 21 outfield players during the tournament. Relative total distance (TD; mˑmin-1) was moderately lower (p≤0.05, ES:0.6) in the final match (96.1 ± 5.0 mˑmin-1) compared to the first (104.1±5.9 mˑmin-1) match. Performance in relative total high-speed running (THSR; mˑmin-1) declined -27.5% (p≥0.05) throughout the tournament following peak performance in M3 (5.3±1.7 mˑmin-1). Match performance between halves was reduced -25.4±0.13% (p≤0.05, ES:1.2-2.3) across all measures in M3. Relative high-intensity running (HIR; 25.9±3.5 mˑmin-1) and THSR (9.8±1.5 mˑmin-1) were greater (p≤0.05, ES:0.2-0.7) for forwards, while midfielders performed greater (p≤0.05, ES:0.6) relative total distance (102.0 ± 5.5 mˑmin-1), compared to central defenders (HIR: 16.1±3.7 mˑmin-1; THSR: 3.1±1.6 mˑmin-1; TD: 92.5±5.7 mˑmin-1). Reductions in relative HIR between halves (-10.9%), within the first half (-31.0%), and the start and end of the match (-36.9%) were most pronounced for midfielders (p≤0.05, ES:0.6-2.3). Across all matches, relative THSR performance was reduced, with moderate to large differences (p≤0.001, ES: 0.7-0.8) observed between halves, within the first half, and throughout the match. In conclusion, specific fatigue patterns observed within and between matches throughout the women's World Cup, may be influenced by playing positions, the rank of the opposition, as well as the stage of the tournament.

 

 

#10 Summated Training and Match Load Predictors of Salivary Immunoglobulin-A, Alpha-Amylase, Testosterone, Cortisol and T:C Profile Changes in Elite-Level Professional Football Players: A Longitudinal Analysis

Reference: Eur J Sport Sci. 2021 Jun 28;1-30.  doi: 10.1080/17461391.2021.1949638. Online ahead of print.

Authors: Matthew Springham, Sean Williams, Mark Waldron, Chris Mclellan, Robert U Newton

Summary: We examined how summated training and match load measures relate to salivary immunological and hormonal profile changes in professional football players. Data were collected from 18 elite-level professional male football players from one English Championship team across a complete 40 wk competitive season. Daily training (micro-technology) and match (computerised tracking) measures of total, high-speed and high-metabolic load running distance and sprint, acceleration, deceleration and sRPE load were converted into exponentially weighted moving average 'acute' (7d), 'chronic' (28d) and acute:chronic composite load measures. Bi-weekly morning saliva samples were analysed for immunoglobulin-A, alpha-amylase, testosterone, cortisol and testosterone:cortisol. A two-stage data reduction technique using partial least squares modelling and a backward stepwise selection procedure determined the most parsimonious model for each salivary variable. Testosterone had non-linear relationships with chronic total (P=0.015; Cohen's D: large), high-metabolic load (P=0.001;small) and high-speed (P=0.001;trivial) running distance and linear relationships with chronic sRPE (P=0.002;moderatei) and acute:chronic high-speed running distance (P=0.001; trivialh). Cortisol had a non-linear relationship with chronic high-speed running distance (P=0.001;trivial). Testosterone:cortisol had non-linear relationships with chronic decelerations (P=0.039;small) and chronic summated acceleration and deceleration load (P=0.039;small). Non-linear relationships typically indicated optimal hormonal responses at squad mean loads. No load variables clearly related to salivary immunoglobulin-A or alpha-amylase changes. We conclude that chronic total and high-intensity load measures relate to hormonal changes and might be useful indicators of player readiness. Acute load variables were not related to immunological or hormonal changes and consequently, should not be used as surrogate measures of player readiness in isolation.

 

 

#11 Time to Be Negative About Acceleration: A Spotlight on Female Football Players

Reference: J Strength Cond Res. 2021 Jun 28. doi: 10.1519/JSC.0000000000004061. Online ahead of print.

Authors: Jesse Griffin, Sean Horan, Justin Keogh, Melissa Andreatta, Clare Minahan

Summary: Women's football requires players to perform frequent changes in velocity (i.e., speed and direction) for successful performance. Although increases in velocity ("acceleration") are important, decreases in velocity ("deceleration") should also be considered equally important to performance and load monitoring. Currently, there is a disproportionate focus on acceleration and creating faster players. The aim of this review is to provide an understanding of deceleration for female football players. Given the limited research in this area, data from studies involving male football players and from other team-sport athletes were used to supplement the review where necessary. Most research focused on eccentric strength and its relationship with deceleration ability, highlighting the importance of slow eccentric strength of the quadriceps and hamstrings to deceleration. Technical and kinematic characteristics of deceleration were also investigated. Importantly, with deceleration being a unilateral motor skill, development requires similar amounts of training for both legs. Imbalances between legs in skill and strength characteristics may compromise performance or increase the risk of injury. Given the dependent nature of deceleration, several contextual factors were identified as important when considering deceleration as a part of training programs and performance. Deceleration is affected by the following factors: an athlete's momentum, the approach speed, change of direction angle, time or distance, anticipated or unanticipated task, fatigue, and the positional requirements of female football players. Further research is needed into deceleration and the physical characteristics associated with deceleration performance, particularly for female football players.

 

 

#12 Muscle metabolism and impaired sprint performance in an elite women's football game

Reference: Scand J Med Sci Sports. 2021 Jun 25. doi: 10.1111/sms.13970. Online ahead of print.

Authors: Peter Krustrup, Magni Mohr, Lars Nybo, Dimitrios Draganidis, Morten B Randers, Georgios Ermidis, Christina Ørntoft, Line Røddik, Dimitrios Batsilas, Athanasios Poulios, Niels Ørtenblad, Georgios Loules, Charikleia K Deli, Alexios Batrakoulis, Jakob L Nielsen, Athanasios Z Jamurtas, Ioannis G Fatouros

Summary: The present study examined skeletal muscle metabolism and changes in repeated sprint performance during match play for n = 20 competitive elite women outfield players. We obtained musculus vastus lateralis biopsies and blood samples before, after, and following intense periods in each half of a friendly match, along with 5 × 30-meter sprint tests and movement pattern analyses (10-Hz S5 Global Positioning System [GPS]). Muscle glycogen decreased by 39% and 42% after an intense period of the second half and after the match, respectively, compared to baseline (p < 0.05). Post-match, 80% type I fibers and 69% type II fibers were almost empty or completely empty of glycogen. Muscle lactate was higher (p < 0.05) after the intense period of the first half and post-match compared to baseline (14.3 ± 4.6 (±SEM) and 12.9 ± 5.7 vs. 6.4 ± 3.7 mmol/kg d.w.). Muscle phosphocreatine was reduced (p < 0.05) by 16% and 12%, respectively, after an intense period in the first and second half compared to baseline. Blood lactate and glucose increased during the match and peaked at 8.4 ± 2.0 and 7.9 ± 1.2 mmol/L, respectively. Mean 5 × 30 m sprint time declined by 3.2 ± 1.7 and 7.0 ± 2.1% after the first and second half, respectively, and 4.7 ± 1.6% (p < 0.05) after an intense period in the first half compared to baseline. In conclusion, match play in elite female football players resulted in marked glycogen depletion in both fiber types, which may explain fatigue at the end of a match. Repeated sprint ability was impaired after intense periods in the first half and after both halves, which may be associated with the observed muscle metabolite perturbations.

 

 

#13 Relationship between age, category and experience with the soccer referee's self-efficacy

Reference: PeerJ. 2021 Jun 10;9:e11472. doi: 10.7717/peerj.11472. eCollection 2021.

Authors: José López Aguilar, Alfonso Castillo-Rodriguez, José L Chinchilla-Minguet, Wanesa Onetti-Onetti

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199919/pdf/peerj-09-11472.pdf

Summary: Soccer referees (SRs) encounter stressful situations during competitions and sometimes even outside them, which may affect their decision making. Therefore, it is important that they possess or acquire optimal levels of self-efficacy, since it is related to less stress during competition, also guaranteeing sports performance and prevent sports abandonment. The objectives of this study were to characterize the profile, in terms of self-efficacy, of SRs depending on their category, age, and experience and to determine the relationship of these factors on SR self-efficacy. Two-hundred fifty-six Spanish referees participated in this study and Referee Self-Efficacy Scale was administered and completed. The results indicated that the SRs older than 25 years, of national category, and with experience greater than or equal to 8 years, have higher levels of self-efficacy than those with the least (p < .01). Likewise, moderate positive correlations were also observed between global self-efficacy and the category, age, and experience of the SRs. In conclusion, age, category and experience factors relate the self-efficacy of the SR, which can explain up to 17% of the variance, affecting decision-making and other decisive behaviors in the competition. These findings are of interest to delegations and referee committees seeking to implement psychological intervention programs to prevent burnout and abandonment of sports practice due to the consequences of low self-efficacy.

 

 

#14 Association Between Mental Imagery and Change of Direction Performance in Young Elite Soccer Players of Different Maturity Status

Reference: Front Psychol. 2021 Jun 10;12:665508. doi: 10.3389/fpsyg.2021.665508. eCollection 2021.

Authors: Dorsaf Sariati, Hassane Zouhal, Raouf Hammami, Cain C T Clark, Ammar Nebigh, Mokhtar Chtara, Anthony C Hackney, Nizar Souissi, Urs Granacher, Omar Ben Ounis

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8222513/pdf/fpsyg-12-665508.pdf

Summary: Previous studies have not considered the potential influence of maturity status on the relationship between mental imagery and change of direction (CoD) speed in youth soccer. Accordingly, this cross-sectional study examined the association between mental imagery and CoD performance in young elite soccer players of different maturity status. Forty young male soccer players, aged 10-17 years, were assigned into two groups according to their predicted age at peak height velocity (PHV) (Pre-PHV; n = 20 and Post-PHV; n = 20). Participants were evaluated on soccer-specific tests of CoD with (CoDBall-15m) and without (CoD-15m) the ball. Participants completed the movement imagery questionnaire (MIQ) with the three- dimensional structure, internal visual imagery (IVI), external visual imagery (EVI), as well as kinesthetic imagery (KI). The Post-PHV players achieved significantly better results than Pre-PHV in EVI (ES = 1.58, large; p < 0.001), CoD-15m (ES = 2.09, very large; p < 0.001) and CoDBall-15m (ES = 1.60, large; p < 0.001). Correlations were significantly different between maturity groups, where, for the pre-PHV group, a negative very large correlation was observed between CoDBall-15m and KI (r = -0.73, p = 0.001). For the post-PHV group, large negative correlations were observed between CoD-15m and IVI (r = -0.55, p = 0.011), EVI (r = -062, p = 0.003), and KI (r = -0.52, p = 0.020). A large negative correlation of CoDBall-15m with EVI (r = -0.55, p = 0.012) and very large correlation with KI (r = -0.79, p = 0.001) were also observed. This study provides evidence of the theoretical and practical use for the CoD tasks stimulus with imagery. We recommend that sport psychology specialists, coaches, and athletes integrated imagery for CoD tasks in pre-pubertal soccer players to further improve CoD related performance.

 

 

#15 Monitoring Elite Soccer Players Physical Performance Using Real-Time Data Generated by Electronic Performance and Tracking Systems

Reference: J Strength Cond Res. 2021 Jun 28. doi: 10.1519/JSC.0000000000004082. Online ahead of print.

Authors: José M Oliva-Lozano, Isabel Martín-Fuentes, Paulino Granero-Gil, José M Muyor

Summary: The aims of this technical report were to analyze the validity of real-time data collected by electronic performance and tracking systems (EPTS) and investigate the effect of varying real-time receiver's position on the real-time data collected. Physical performance data were collected from professional soccer players using EPTS. In addition, 3 real-time receivers, which were placed in different positions (i.e., central area of the stadium stands and right and left technical areas), were used to collect real-time data. The real-time data collected by each receiver were visualized on SVivo and compared with the data downloaded directly from the device on SPro. The results showed no statistically significant differences between the data collected by the real-time receivers compared with postsession data in any variable (p > 0.05), except for total distance and high-speed running distance covered, which showed significant differences but trivial effect size (p < 0.05; d = 0.01). The coefficient of determination (R2) and intraclass correlation coefficient were greater than 0.97 and 0.99, respectively. Regarding the analysis of varying the receiver's position on the real-time data collected, the results showed that there was no significant effect of the receiver's position on any variable (p > 0.05). Therefore, valid physical performance data may be obtained by real-time tracking systems such as SVivo, regardless of the position of the real-time receivers and distance to the players. Specifically, high-intensity running actions, distances covered at low and high speed, and accelerometer-derived variables such as player load may be accurately tracked by this real-time tracking software.

 

 

#16 Collective efficacy in soccer teams: a systematic review

Reference: Psicol Reflex Crit. 2021 Jun 26;34(1):18. doi: 10.1186/s41155-021-00183-y.

Authors: Mylena Aparecida Rodrigues Alves, Marcus Vinicius de Souza Lencina, Mayara Juliana Paes, Joice Mara Facco Stefanello

Summary: Collective efficacy, defined as a group's shared belief about its conjoint capability to organize and execute courses of action, plays a pivotal role in understanding the dynamics of sports teams, since it influences what individuals choose to do as team members, how much they invest in motivational terms to perform actions, how much they work collectively, and for how long they persist despite failure. Through a systematic review, it was investigated how collective efficacy has been assessed in the context of soccer and which indicators, attributes, and psychometric properties have been contemplated in the instruments used. Following the PRISMA guidelines, 22 articles were retrieved through electronic databases (APA PsycINFO; SPORTDiscus; Science Direct; BVS; Web of Science; Scopus; PubMed; and Scielo), using as descriptors, in English, Spanish, and Portuguese, collective efficacy and soccer, combined by the Boolean operators AND and OR. The study did not delimit the initial year of publication for the searches carried out, including all articles found until January 14, 2021 (date of the last update). The following eligibility criteria were adopted: scientific articles published in journals; original studies, which specified the instrument used to assess collective efficacy and carried out with soccer athletes. Five instruments (FCEQ, CEQS, CEI, CEC, and CEQsoccer) that evaluated technical-tactical and psychological attributes associated with collective efficacy in soccer players were identified. In most studies, psychometric properties were restricted to content validity and reliability (internal consistency), and there were no suitable validation processes for the instruments used to measure collective efficacy, which can be considered a limiting factor for understanding this psychological construct in soccer modality.

 

 

#17 Step techniques for backward and sideward sprint starts used by high-level male soccer players

Reference: Heliyon. 2021 Jun 18;7(6):e07333. doi: 10.1016/j.heliyon.2021.e07333. eCollection 2021 Jun.

Authors: Takahiko Sato, Yusuke Fukuhara, Tadao Isaka

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8239737/pdf/main.pdf

Summary: From standing in a parallel stance, two common techniques for sprint starts are forward and false steps. In the forward step technique, athletes take a first step in the sprinting direction; in the false step technique, the first step is in the opposite direction to the sprinting direction. Although the false step technique, including a redundant step, has generally been considered as an inferior technique, athletes habitually use it to start sprinting in a forward direction. The present study aimed to clarify which step technique is habitually used by high-level male soccer players when they start sprinting in a backward or a sideward direction. From a stationary standing position, 15 male soccer players were instructed to sprint backward and rightward three times each, and the step techniques used to start sprinting were recorded. In the backward sprint start trials, 2 trials were done using the forward step technique and 43 using the false step technique. In the rightward sprint start trials, 27 trials were done using the forward step technique and 18 using the false step technique. While the false step technique was used significantly more than the forward step technique in the backward sprint start trials (p < 0.001), no significant difference was found between the use of either technique in the rightward sprint start trials (p = 0.18). The results demonstrate that high-level male soccer players habitually use the false step technique in a backward sprint start and use both techniques with similar frequencies in a sideward sprint start.

 

Tue

21

Dec

2021

Load Monitoring Practice in Elite Women Association Football

The description of current load monitoring practices may serve to highlight developmental needs for both the training ground, academia and related industries. Therefore, this study aims to provide a first overview of the current load monitoring practices in elite women’s football.

Mon

20

Dec

2021

Higher risk of ACL rupture in amateur football compared to professional football

Anterior cruciate ligament (ACL) injuries are a common severe type of football injury at all levels of play. A football-specific ACL registry providing both prospective ACL injury data according to the skill level and risk factors for vACL injury is lacking in the literature.

Mon

13

Dec

2021

Latest research in football - week 38 - 2021

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 FIFA 11+ Shoulder Injury Prevention Program Was Effective in Reducing Upper Extremity Injuries Among Soccer Goalkeepers: A Randomized Controlled Trial

Reference: Am J Sports Med. 2021 Jun 17;3635465211021828.  doi: 10.1177/03635465211021828. 

Authors: Wesam Saleh A Al Attar, Oliver Faude, Mario Bizzini, Saud Alarifi, Hosam Alzahrani, Raed S Almalki, Riyadh G Banjar, Ross H Sanders

Summary: Soccer is one of the most popular sports worldwide. Goalkeepers are more likely to injure their upper limbs, particularly their shoulders, than outfield players. To reduce upper extremity injuries, the FIFA 11+ Shoulder Injury Prevention Program (FIFA 11+S) was developed. The purpose of this study was to assess the effectiveness of the FIFA 11+S program in reducing the incidence of upper extremity injuries among amateur soccer goalkeepers. A total of 726 goalkeepers, who were blinded to study intent, were randomly assigned to the experimental group (n = 360) or control group (n = 366). The experimental group was instructed to perform the FIFA 11+S program before all training sessions for 1 season (6 months). The control group was instructed to continue performing their usual routine warm-up program before training sessions for 1 season. Primary outcomes included the incidence of upper extremity injury and incidence of mechanism, type, and severity of injury measured using injury risk ratios (IRR); compliance with the experimental and control interventions was also recorded. A total of 50 injuries (0.62 injuries per 1000 exposure-hours) were reported in the experimental group, and 122 injuries (1.94 injuries/1000 hours) were reported in the control group. The FIFA 11+S program reduced the total number of upper extremity injuries by 68% (IRR = 0.32 [95% CI, 0.27-0.34]) compared with the usual warm-up. The FIFA 11+S program reduced the incidence of contact injury (IRR = 0.30 [95% CI, 0.25-0.31]), noncontact injury (IRR = 0.40 [95% CI, 0.35-0.43]), initial injury (IRR = 0.34 [95% CI, 0.29-0.36]), recurrent injury (IRR = 0.20 [95% CI, 0.17-0.21]), and overuse injury (IRR = 0.40 [95% CI, 0.35-0.43]). Participants in the experimental group demonstrated a significant decrease in injuries of minor (IRR = 0.32 [95% CI, 0.27-0.34]) and moderate severity (IRR = 0.33 [95% CI, 0.29-0.35]) compared with the control group. We noted no difference in compliance between the experimental and control groups (80% vs 73%, respectively; P = .92). The FIFA 11+S program resulted in 50% fewer upper extremity injuries among soccer goalkeepers, compared with a regular warm-up.

 

 

#2 Blood and performance adaptations to individual training load in professional soccer: a team study

Reference: J Sports Med Phys Fitness. 2021 Jun 17.  doi: 10.23736/S0022-4707.21.12690-8. Online ahead of print.

Authors: Vincenzo Rago, Italo Leo, Arcano Marrocco, Riccardo Izzo, Cristoforo Filetti

Summary: The aim of this study was to describe seasonal changes in iron storage, hormonal status and functional capacity in relation to accumulated training load in a professional male soccer team. Resting blood samples, countermovement jump (CMJ) and aerobic capacity (45-15 test) were collected over a 6-month period from the start of the preparatory period to the middle-season (E1 to E4) in a professional male soccer team (n=15 outfield players). External training load was regularly quantified using a wearable 10-Hz global positioning system. One player systematically showed reduced iron storage throughout the season (ferritin<110 μg·l-1, hemoglobin<14 g·dl-1). No significant differences in blood and performance parameters were observed throughout the season (P>0.05). However, accumulated total distance and high-intensity distance (above maximal aerobic speed) from E1 to E3 were negatively correlated to changes in haematocrit, hemoglobin and red blood cells (r=-0.85 to -0.67; P<0.05) and positively to changes in ferritin (r=0.63-0.69; P<0.05). Additionally, high-intensity distance covered between E1 and E3 was negatively correlated to changes in testosterone concentrations (r [95%CI]=-0.71 [-0.93; -0.15]; P=0.021). Resting blood parameters and functional capacity of male soccer players appeared to be stable throughout the early competitive period. However, iron storage and hormonal status are likely to be affected by accumulated high-intensity activity performed during practice and competition. Practitioners involved with GPS-based TL monitoring could consider the accumulated amount of high-intensity activity to inform medical staffs about possible changes in oxygen-carrying capacity and anaerobic overtraining.

 

 

#3 Pre- and post-match hop test outcomes in soccer players returning to performance after lower extremity injury

Reference: J Sports Med Phys Fitness. 2021 Jun 17.  doi: 10.23736/S0022-4707.21.12576-9. Online ahead of print.

Authors: Astrid Vereijken, Inne Aerts, Emiel van Trijffel, Bruno Tassignon, Jo Verschueren, Romain Meeusen 

Summary: Most soccer injuries concern the lower extremity with a higher injury rate during the second half of matches. In advising safe return to sport, hop tests are usually assessed at the point of return to sport under non-fatigued conditions. No studies exist investigating hop test outcomes before and after a match in soccer players returning to performance after lower extremity injury and non-injured teammates. The objective is to assess differences in hop test outcomes before and after a match in and between soccer players returning to performance after lower extremity injury and their non-injured teammates. A repeated-measures design was used to measure outcomes on five hop tests before and after a soccer match. For analyzing differences in hop tests before and after a match, paired sample t-tests were used. Independent t-tests were used to analyze differences between soccer players after injury and non-injured teammates. Effect sizes were calculated using Cohen's d. Hop tests were completed by 61 amateur soccer players after injury and 121 non-injured teammates. Differences in hop tests before and after the match within both groups had negligible to small effect sizes (d=0.00-0.49), except for the figure of 8 and 30 seconds side hop in the injured leg of RTPf soccer players (d=0.56 and d=0.71 respectively). Differences between both groups were negligible to small (d=0.00-0.36). Soccer players returning to performance after a lower extremity injury showed similar scores on hop tests than their non-injured teammates. More demanding sport-specific performance test and measurement of quality of movement are additionally recommended for safe return to sport decision-making.

 

 

#4 A Novel Approach to Training Monotony and Acute-Chronic Workload Index: A Comparative Study in Soccer

Reference: Front Sports Act Living. 2021 May 31;3:661200.  doi: 10.3389/fspor.2021.661200. eCollection 2021.

Authors: José Afonso, Fábio Yuzo Nakamura, Rui Canário-Lemos, Rafael Peixoto, Cátia Fernandes, Tomás Mota, Miguel Ferreira, Rafaela Silva, Armando Teixeira, Filipe Manuel Clemente 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8200417/pdf/fspor-03-661200.pdf

Summary: Load is a multifactorial construct, but usually reduced to parameters of volume and intensity. In the last decades, other constructs have been proposed for assessing load, but also relying on relationships between volume and intensity. For example, Foster's Training Monotony has been used in athletes' load management simply by computing mean weekly load divided by its standard deviation, often multiplied by session rate of perceived exertion. Meanwhile, the Acute to Chronic Workload Ratio (ACWR) has been debated by the sport scientists as a useful monitoring metric and related to so-called injury prevention. None of these models includes parameters that are representative of training specificity, namely load orientation. The aim of this study is to present broader conceptual approaches translated by new indices for assessing Intraweek Training Monotony (ITM) and Acute to Chronic Workload Index (ACWI) while incorporating load orientation, session duration and weekly density (frequency normalized) in addition to parameters related to proxies of external and/or internal load. Our ITM and Foster's Training Monotony were similar in terms of average values, but very different for individualized analysis, illustrating how average values may be deceiving. While Foster's model provided clusters of values, ITM provided more scattered, individualized data. ACWI and ACWR provided very distinct qualitative information, and the two models were uncorrelated. Therefore, the models incorporating training load orientation presented in this study provide distinct and not redundant information when compared to previous models. More importantly, ITM and ACWI are metrics that are compatible to each other and might fit to coaches' monitoring targets in the short and medium terms, respectively. Because our models include several parameters, including load orientation, we contend that might provide a more complete monitoring tool. However, we suggest they are used for intraindividual comparisons and not so strongly for interindividual comparisons.

 

 

#5 Premature Professionalisation or Early Engagement? Examining Practise in Football Player Pathways

Reference: Front Sports Act Living. 2021 Jun 7;3:660167.  doi: 10.3389/fspor.2021.660167. eCollection 2021.

Authors: Liam Sweeney, Dan Horan, Áine MacNamara

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8215134/pdf/fspor-03-660167.pdf

Summary: There is a growing debate, both in the academic and sporting worlds, about the most appropriate pathway for high potential young players in sport. In this regard, there has been a considerable focus on the age of selection into structured talent development pathways and the nature of the experience once players have been recruited. Given the economic and reputational currency associated with developing professional footballers in particular, it is unsurprising that professional football clubs continue to invest significant financial resources into their academy structures. Understandably, this recruitment policy has attracted substantial attention within the media and research community, with ethical concerns arising surrounding the impact early selection may have on the welfare and the experiences of the young players within the pathway. The aim of this perspective article was to critically consider the research underpinning the early engagement practises of football clubs and the extent to which, and how, the pathway can provide players with the most appropriate starting point for their development. This evidence points to the need to look beyond the prevalent 'early specialisation vs. diversification' debate in youth sport towards a consideration of an early engagement perspective that reflects the biopsychosocial influences on talent development and the socio-political environment that influences decisions. We provide practical recommendations focused on the quality of the early engagement experience.

 

 

#6 What Will We Do? The Action Plan From a Brazilian Professional Football Club Youth Academy Facing the COVID-19 Pandemic

Reference: Front Sports Act Living. 2021 Jun 7;3:589459.  doi: 10.3389/fspor.2021.589459. eCollection 2021.

Authors: Murilo Dos Reis Morbi, Annie Rangel Kopanakis, Pau Mateu, Billy Graeff, Renato Francisco Rodrigues Marques

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8215199/pdf/fspor-03-589459.pdf

Summary: In 2020, the world was affected by the COVID-19 pandemic, which remains a major challenge for most countries today. In Brazil, football clubs' youth academies have faced a disruption of their regular activities. In order to study how the learning cultures of a Brazilian professional football club youth academy have been changed, and the alternatives created by the club's staff within this context, this perspective article aims to analyze how they have structured the Under-15 (U15) team learning culture during social isolation due to the COVID-19 pandemic. Through document and thematic analysis on a Brazilian professional football club's youth academy program, we promoted a dialogue between the process of adaptation to remote theoretical-tactical teaching with the learning theory proposed by Hodkinson and collaborators. The main theme of analysis of this study was the remote structure of the theoretical-tactical learning and physical training. Challenged with the need to transpose face-to-face activities into a learning culture based on remote communication, the U15 team coaching staff created a process to prescribe physical training, and to teach and discuss football tactical issues with young players during the period of social isolation. This perspective article shows that it is possible for sports institutions to create programs for the development of young athletes within the social isolation/distancing context, considering both theoretical-tactical learning and physical training processes. The adaptation to remote environments as structures for the learning culture seems a challenge, but is also a good alternative for young players to develop their interpretation and perception of football theoretical-tactical issues.

 

 

#7 Decision-making to stop or continue playing after football injuries - A systematic video analysis of 711 injury situations in amateur football

Reference: Eur J Sport Sci. 2021 Jun 23;1-17.  doi: 10.1080/17461391.2021.1943717. Online ahead of print.

Authors: Krutsch Volker, Oberhauser Julia, Krutsch Werner, Loose Oliver, Weber Johannes, Kerschbaum Maximilian, Lang Siegmund, Koch Matthias, Alt Volker, Worlicek Michael

Summary: Scientific injury registration via video analysis is lacking in amateur football. The purpose of this study was to analyse match injury situations with a focus on the decisions made by players and referees after sustaining a football trauma. In a retrospective cohort study, traumatic injuries sustained in any of the 305 matches of the highest amateur level (4th league) in Germany in the 2015-16 season were assessed by means of video analysis and a standardised video protocol. In total, 711 traumatic incidents at 919 different body regions had been recorded. The three most frequently injured body regions were the ankles (34.1%), the head (17.5%) and the knees (17.0%). 90% (n=156) of head injuries were direct contact injuries, this percentage was significantly higher than that of contact injuries on ankle (68.4%; p<0.001) or knee (52.6%; p=0.001). Referees decided on foul play significantly more often in case of knee injuries (57.1%; p=0.002) or ankle injuries (64.5%; p<0.001) than in head injuries (39.8%). Only 26.1% of players with a head injury opted for substitution, which was lower than after ankle (27.8%; p=0.78) and knee injuries (34.0%; p=0.13). In conclusion, amateur football is associated with a considerable number of injury situations that are followed by match interruptions and the substitution of players. Players and referees decided to continue playing more often after a head injury than after an injury to other body regions. An advanced education programme on the risks and management of head injuries in football is required to prevent long-term health consequences.

 

 

#8 Fitness assessment in talented football referees: an academy based longitudinal field-study

Reference: J Sports Med Phys Fitness. 2021 Jun 22.  doi: 10.23736/S0022-4707.21.12293-5. Online ahead of print.

Authors: Carlo Castagna, Alejo P Leguizamón, Susana C Póvoas

Summary: This study aim was to profile physical fitness in talented football referees (FR) with performance relevant field-tests across time. Thirty-eight male FR (age 28±1.5 years, height 178±5.1 cm, body mass 69.0±7.34 kg, body fat 17.2±2.87%) were observed for 15 months. Endurance was assessed with the Yo-Yo Intermittent Recovery Test level 1 (YYIR1) and repeated sprint ability (RSA) with 5x30m line-sprints with 30s recovery (5x30m). Long sprint endurance (LSA) and change of direction ability (COD) evaluated with novel field-tests. FR was tested six times (every three months) during the study. YYIR1 performance showed large increments across testing occasions. Sprint time in the COD largely and significantly decreased across the testing occasions. Very large associations were reported between 5x30m and LSA tests grand mean (r=0.89, 0.78-0.94, P<0.0001). A nearly perfect (r=0.97, 0.94-0.99, P<0.0001) association was observed between 5x30m best sprint and 5x30m grand means. The results of this study revealed ability-related variations in performance across time. The effect of training and competitions on the determinism of physical fitness in refereeing seem plausible. Interestingly, sprint endurance tests shared a very large variance proposing tests interchangeability and mutual physiological demands. This study information provides useful information for the development of sound field-tests batteries in talented FR.

 

 

#9 Concussion in European professional football: a view of team physicians

Reference: BMJ Open Sport Exerc Med. 2021 Jun 3;7(2):e001086.  doi: 10.1136/bmjsem-2021-001086. eCollection 2021.

Authors: Vincent Gouttebarge, Imtiaz Ahmad, Zafar Iqbal, Emmanuel Orhant, Craig Rosenbloom, Kristof Sas, Gino M M J Kerkhoffs

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8183281/pdf/bmjsem-2021-001086.pdf

Summary: The objective was to explore the view and thoughts of physicians working in professional football about several aspects (eg, education and use of video footages) likely to enhance concussions' recognition and on-field management. An observational study based on a cross-sectional design by means of an electronic survey was conducted among physicians working for a professional football club in Belgium, England or France. A total of 96 physicians (95% male; mean age: 44 years) completed the survey. Nearly all participants (95%) were in favour of informational sessions about concussion for players or technical staff. Only 5%-10% of the participants mentioned that they had felt pressured by the technical staff or players not to substitute a player with a (potential) concussion. Most participants were in favour of an additional permanent concussion substitution and a temporary concussion substitution. Four out of five participants reported that the availability of instant video footages (side-line) would ease the recognition of concussion. A better recognition and on-field management of concussions in professional football can only be achieved with a holistic approach, including adequate laws of the football game and protocols. Especially, regular education of players and technical staff should be made mandatory while the medical teams should be provided side-line with instant video footages.

 

 

#10 Conservative Treatment of the Fifth Metatarsal Bone Fractures in Professional Football Players Using Platelet-Rich Plasma

Reference: Foot Ankle Spec. 2021 Jun 18;19386400211017368. doi: 10.1177/19386400211017368.

Authors: Eduard Bezuglov, Andrey Zholinsky, Gleb Chernov, Vladimir Khaitin, Evgeniy Goncharov, Zbigniew Waśkiewicz, Ekaterina Barskova, Artemii Lazarev

Summary: Injuries of the metatarsal bones in football are relatively rare and in most cases are localized in the fifth metatarsal. The gold standard of the diagnosis of fractures in this area can be X-rays, which in most cases allows verifying the diagnosis. The treatment tactics depend on the localization of the fracture according to Lawrence and Botte's classification: 3 zones of localization are distinguished. Fractures located in zones 2 and 3 belong to a high-risk group due to delayed consolidation and nonunion and therefore athletes are most often treated with osteosynthesis using intramedullary screws. The minimal recovery time for this type of treatment is at least 8 weeks. This report describes 7 cases of the fifth metatarsal bone fractures, located in zones 2 and 3 in professional football players who were treated with an immobilization boot, cryotherapy, nutritional supplements of calcium and vitamin D, and local injections of platelet-rich plasma, which contains numerous growth factors. The deadline for returning to regular training activities was 43 to 50 days, and there was no relapse of damage within 6 months of follow-up. 

 

 

#11 Covid-19: Deaths in Brazil near half a million as controversial football tournament gets under way

Reference: BMJ. 2021 Jun 15;373:n1539.  doi: 10.1136/bmj.n1539.

Authors: Luke Taylor

Download link: https://www.bmj.com/content/bmj/373/bmj.n1539.full.pdf

 

 

#12 External Training Load Monitoring and the Impact on Training Load Management in Collegiate Male Soccer Players

Reference: J Strength Cond Res. 2021 Jun 17.  doi: 10.1519/JSC.0000000000004080. Online ahead of print.

Authors: Jacob R Gdovin, Riley Galloway, Lorenzo S Tomasiello, Michael Seabolt, Robert Booker

Summary: Soccer is a physically demanding sport within the National Collegiate Athletic Association and continuously increases in popularity. To ensure athletes are adequately prepared for weekly physical stressors, coaches can use global positioning system technology to monitor external workloads and exercise intensity. These data can subsequently help coaches and practitioners better implement individualized training programs to ensure athletes are properly balancing the overreaching and overtraining paradigm. Therefore, the purpose of this observational study was to retrospectively analyze 3 consecutive seasons of external workload (total and high intensity distance) and injury data, which were derived from all training sessions and matches in 46 Division-I collegiate male soccer players. A coach's interpretation sought to provide practical insight into the functionality behind load management and how it prepares athletes for the physical stressors placed on them throughout a season. Two separate 3 × 3 repeated measures ANOVAs were conducted to determine differences between total distance and distance at high-intensity with an alpha level set at 0.05. Total distance between preseason and in-season (p = 0.003), acute high-intensity distance (p < 0.001), and chronic high-intensity distance (p < 0.001) yielded significant differences. These results conclude the demands of each athlete change weekly and between seasons. It is recommended that sport coaches and practitioners develop individualized training programs by workload monitoring while considering variables such as a team's style of play, experience, position, role within a program, training intensity, and the length of time between conditioning sessions, practices, and matches.

 

 

#13 Talent Identification in Youth Soccer: Prognosis of U17 Soccer Performance on the Basis of General Athleticism and Talent Promotion Interventions in Second-Grade Children

Reference: Front Sports Act Living. 2021 Jun 4;3:625645.  doi: 10.3389/fspor.2021.625645. eCollection 2021.

Authors: Andreas Hohmann, Maximilian Siener

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8212928/pdf/fspor-03-625645.pdf

Summary: Several talent identification programs in elementary school have implemented motor diagnostics to introduce children to groups of sports, like game sports, or even to particular sports like soccer. However, as in most other sports, in youth soccer, the predictive value of such early testing is still unclear. This prospective study evaluated the midterm prognostic validity of generic motor performance tests. The sample consisted of male second-grade children, which had received a recommendation to participate in soccer. The talent screening campaign was a basic check comprising two anthropometric parameters, five physical fitness, and three motor competence diagnostics of the German Motor Test 6-18. The test data were collected from the participating elementary school classes of the years 2010 to 2014. The soccer competition performance of those children having completed the age of at least 15 years (n = 502) up to the end of the season 2019/2020 (2020, September 30) was recorded. This group of U17 players was then assigned individually to five different competition levels. The prognostic validity of the physical and physiological tests was determined using ANOVAs, odds ratios, and a regression path analysis. All diagnostic methods exhibited medium-to-high prognostic validity over the 8 year time span from the talent screening to the later soccer competitions in the adolescent age groups. For later success in soccer on the province level, the 6-min run (OR = 4.28), dynamic balance (OR = 4.04), and 20-m sprint (OR = 2.46), as well as the participation in the training center of the German Soccer Federation (OR = 5.67) and the diversity of club sport activities (OR = 3.56), were of particular importance.

 

 

#14 Acute effects of whole-body vibrations on the fatigue induced by multiple repeated sprint ability test in soccer players

Reference: J Sports Med Phys Fitness. 2021 Jun 22.  doi: 10.23736/S0022-4707.21.12349-7. Online ahead of print.

Authors: Giuseppe Annino, Vincenzo Manzi, Paolo Buselli, Bruno Ruscello, Fabrizio Franceschetti, Cristian Romagnoli, Franco Cotelli, Maurizio Casasco, Elvira Padua, Ferdinando Iellamo

Summary: We tested the hypothesis that Whole Body Vibration (WBV) positively affects the fatigue process ensuing from repeated bouts of maximal efforts, as induced by repeated sprints ability (RSA). Eleven male soccer players performed three sets of six repeated shuttle sprints (40 metres). Eleven male soccer players (age 23,6±4,5 years) were cross-randomized to perform WBW before RSA and during the recovery between sets (WBV-with) or to warm-up and passive recovery between sets (WBV-without). The effects of WBV were quantified by sprint time (ST) and blood lactate concentration (LA), collected up to 15th min after completion of tests. ST during RSA showed a better maintenance of performance in the WBV-with compared to WBV-without condition in all three sets, reaching a statistical significance between-groups during the 2nd and 3rd set (P< 0.05). No significant differences in ST over the sets were detected in WBVwith, whereas a significant decrease was observed in the WBV-without condition (P<0.001). LA recovered significantly faster from the 9th to 15th minute of recovery in WBV-with as compared to WBV-without (P<0.05). These findings would indicate that WBV performed during recovery between RSA sets is capable of delaying the onset of muscle fatigue resulting in a better maintenance of sprint performance.

 

 

#15 Goal Side Selection of Penalty Shots in Soccer: A Laboratory Study and Analyses of Men's World Cup Shoot-Outs

Reference: Percept Mot Skills. 2021 Jun 23;315125211025412.  doi: 10.1177/00315125211025412. 

Authors: Mauro R Pereira, Geoffrey R Patching

Download link: https://journals.sagepub.com/doi/pdf/10.1177/00315125211025412

Summary: Penalty kicks in soccer provide a unique scenario in which to examine human choice behavior under competitive conditions. Here, we report two studies examining the tendency for soccer kickers to select the goal side with the largest area to the left or right of the goalkeeper's veridical midline, when the goalkeeper stands marginally off-center. In Study I participants viewed realistic images of a soccer goal and goalkeeper with instructions to choose the left or right side of the goalmouth to best score a goal. We systematically displaced the goalkeeper's position along the goal line; and, to simulate changes in the kicker's viewing position, we systematically displaced the lateral position of the goalmouth in each image. While, overall, participants tended to choose the left over the right goal side, this preference was modulated by the goalkeeper's position relative to the center of the goal and jointly on the lateral position of the goalmouth relative to the participants' body midline. In Study II we analyzed 100 penalty shots from men's world cup shoot-outs between the years 1982 to 2018. Again, we found a small tendency for kickers to aim the ball to the left goal side, but with barely any modulating effect of changes in the goalkeeper's position and no effect of changes in the kicker's position. In contrast to earlier claims that a goalkeeper may benefit by standing marginally to the left or right of the center of the goal to influence the direction of the kicker's shot, our findings suggest that this is probably not a good strategy in elite football competitions.

 

 

#16 When do soccer players experience the most demanding passages of match play? A longitudinal study in a professional team

Reference: Res Sports Med. 2021 Jun 23;1-11.  doi: 10.1080/15438627.2021.1943390. Online ahead of print.

Authors: José M Oliva-Lozano, Helena Martínez-Puertas, Víctor Fortes, José M Muyor

Summary: This study analysed the periods in which the most demanding passages (MDP) of play occurred during professional soccer matches, considering different criterion variables and investigating the effect that the playing position had on the MDP-of-play occurrence for each criterion variable. The MDP of play were calculated based on five criterion variables: distance covered (DIS), sprinting distance (SPD), high-metabolic load distance (HMLD), and the total of high-intensity accelerations and decelerations (ACCHIGH and DECHIGH). The results showed that the first period of the match (0'-15') was the interval with the highest frequency (i.e., the greatest % of cases) in which the players achieved the MDP of play for all the variables (DIS= 38.9%; SPD= 28.4%; HMLD= 37.7%; ACCHIGH= 54.3%; DECHIGH= 48.8%). The playing position had no significant effect on MDP-of-play occurrence in any variable (likelihood ratio, LR= 15.88-32.05; p > 0.05; effect size, ES= 0.01-0.04), except for the DIS covered (LR= 32.05; p= 0.04; ES= 0.05), in which the most frequent MDP for the full backs occurred within the second period of the match (15'-30'). In conclusion, the first periods of the matches usually elicited the MDP of play and these periods need to be trained to prevent injuries and optimize performance.

 

 

#17 Agility testing in amateur soccer: A pilot study of selected physical and perceptual-cognitive contributions

Reference: PLoS One. 2021 Jun 24;16(6):e0253819.  doi: 10.1371/journal.pone.0253819. eCollection 2021.

Authors: Stefan Altmann, Rainer Neumann, Sascha Härtel, Gunther Kurz, Thorsten Stein, Alexander Woll

Download link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0253819

Summary: The purpose of this study was to examine the relationships of physical and perceptual-cognitive factors with agility performance in amateur soccer players. Fifteen male amateur soccer players (age, 24.5 ± 1.9 years) completed a linear-sprint test with splits at 5 m, 10 m, and 30 m, a change-of-direction test of 12 m with 2 pre-planned directional changes of 45° at 2 m and 7 m, and a soccer-specific agility test with same movement pattern as the change-of-direction test but with the inclusion of a human stimulus performing passing movements. Additionally, the perceptual-cognitive deficit (agility performance minus change-of-direction performance) was calculated. In relation to agility performance, linear-sprint performance showed large relationships, which were higher with increasing sprint distance (5 m, r = 0.57; 10 m, r = 0.59; 30 m, r = 0.69), change-of-direction performance a very large relationship (r = 0.77), and the perceptual-cognitive deficit a large relationship (r = 0.55). The findings of this study highlight the relatively high contribution of both physical (i.e., linear-sprint and change-of-direction performance) and perceptual-cognitive factors (i.e., perceptual-cognitive deficit) in relation to soccer-specific agility performance at an amateur level. Consequently, such elements might be recommended to be included in training programs aimed at improving agility performance at this playing level. Moreover, the here introduced perceptual-cognitive deficit allows for a convenient and likewise thorough analysis of agility performance. Future studies should investigate the effects of both physically and perceptual-cognitive oriented training interventions on agility performance, which is considered a key element for success in soccer.

 

 

#18 Using multiple machine learning algorithms to classify elite and sub-elite goalkeepers in professional men's football

Reference: Sci Rep. 2021 Nov 22;11(1):22703. doi: 10.1038/s41598-021-01187-5.

Authors: Mikael Jamil, Ashwin Phatak, Saumya Mehta, Marco Beato, Daniel Memmert, Mark Connor

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8609025/pdf/41598_2021_Article_1187.pdf

Summary: This study applied multiple machine learning algorithms to classify the performance levels of professional goalkeepers (GK). Technical performances of GK's competing in the elite divisions of England, Spain, Germany, and France were analysed in order to determine which factors distinguish elite GK's from sub-elite GK's. A total of (n = 14,671) player-match observations were analysed via multiple machine learning algorithms (MLA); Logistic Regressions (LR), Gradient Boosting Classifiers (GBC) and Random Forest Classifiers (RFC). The results revealed 15 common features across the three MLA's pertaining to the actions of passing and distribution, distinguished goalkeepers performing at the elite level from those that do not. Specifically, short distribution, passing the ball successfully, receiving passes successfully, and keeping clean sheets were all revealed to be common traits of GK's performing at the elite level. Moderate to high accuracy was reported across all the MLA's for the training data, LR (0.7), RFC (0.82) and GBC (0.71) and testing data, LR (0.67), RFC (0.66) and GBC (0.66). Ultimately, the results discovered in this study suggest that a GK's ability with their feet and not necessarily their hands are what distinguishes the elite GK's from the sub-elite.

 

 

#19 Position specific physical performance and running intensity fluctuations in elite women's football

Reference: Scand J Med Sci Sports. 2021 Nov 26.  doi: 10.1111/sms.14105. Online ahead of print.

Authors: A K Winther, I Baptista, S Pedersen, M B Randers, D Johansen, P Krustrup, S A Pettersen

Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.14105

Summary: The purpose of the present study was to investigate the physical performance of elite female football players during match play along with transient alterations in running performance following 1- and 5-min univariate peak periods. 54 elite female players from four top-level Norwegian teams were monitored for one season (n = 393 match observations), and physical performance data collected using STATSport GPS APEX. Results revealed significant differences in physical performance between the positions during full match play, particularly between wide and central players. Both full backs (FBs) and wide midfielders (WMs) covered more total distance (TD), high-speed running distance (HSRD), and sprint distance (SpD) than center backs (CBs) (p < 0.05-0.001), while WMs also covered more HSRD than both central midfielders (CMs) (p < 0.01) and forwards (FWs) (p < 0.05), and more acceleration -and deceleration distance (Accdist and Decdist ) than both CBs and CMs (p < 0.01-0.001). A similar pattern was observed for the peak period analysis, with FBs and WMs covering more SpD in peak 1 min than CBs and CM (p < 0.001) and more SpD in peak 5-min than CBs, CMs, and FWs (p < 0.001). Irrespective of the variable analyzed, greater distances were covered during the peak 5-min period than in the next-5 and mean 5-min periods (p < 0.001). Significant (p < 0.001), but small to trivial (Cohen's Dz : 0.07-0.20), decreases in distance covered were also observed for each variable following each univariate peak 5-min period. In conclusion, practitioners should account for differences in physical performance when developing training programs for female football players and be aware of transient reductions in physical performance following univariate peak 1- and 5-min periods. Specifically, the very high intensity in 1-min peak periods adds support to the principal of executing speed endurance activities during training to mirror and be prepared for the physical demands of match play.

 

 

#20 The Differentiate Effects of Resistance Training With or Without External Load on Young Soccer Players' Performance and Body Composition

Reference: Front Physiol. 2021 Nov 5;12:771684.  doi: 10.3389/fphys.2021.771684. eCollection 2021.

Authors: Moisés Falces-Prieto, Eduardo Sáez de Villarreal-Sáez, Javier Raya-González, Francisco Tomás González-Fernández, Filipe Manuel Clemente, Georgian Badicu, Eugenia Murawska-Ciałowicz

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8602856/pdf/fphys-12-771684.pdf

Summary: The purpose of this study was to examine the effects of 15 weeks (2/week) of two different resistance training (RT) programs [the self-load group (SG) vs. the overload group (OG)] on selected measures of physical performance in young male soccer players.  The countermovement jump (CMJ), aerobic endurance (VO2 max), and body composition [body mass (BM), height (H), body fat percentage (% BF), and lean mass (LM)] were measured before and after the 15-week RT interventions. Subjects were randomized to treatments: 1. SG [age = 15.34 ± 1.34 years]; 2. OG [age = 16.28 ± 1.21 years].  The level of significance set for the study (p ≤ 0.05). Within-group analysis did report significant differences in all variables for the SG (p = 0.008 to 0.001; ES = -0.33 to 1.41, small to large) as in the OG (p = 0.001; ES = 0.82 to 1.30, large). Between-groups analysis reported differences in CMJ (F = 4.32; p = 0.004) for the OG. The main findings of this study indicated that RT with and without external load was effective in improving the measures of physical performance in young soccer players, with special attention to jumping ability, where the OG group was more effective. Furthermore, there is no interference to aerobic endurance. It is recommended that soccer coaches implement RT without external load in the early stages of training or in players with late maturation development and in those soccer clubs with limited material resources.

 

 

#21 Toward Automatically Labeling Situations in Soccer

Reference: Front Sports Act Living. 2021 Nov 3;3:725431.  doi: 10.3389/fspor.2021.725431. eCollection 2021.

Authors: Dennis Fassmeyer, Gabriel Anzer, Pascal Bauer, Ulf Brefeld

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8595941/pdf/fspor-03-725431.pdf

Summary: We study the automatic annotation of situations in soccer games. At first sight, this translates nicely into a standard supervised learning problem. However, in a fully supervised setting, predictive accuracies are supposed to correlate positively with the amount of labeled situations: more labeled training data simply promise better performance. Unfortunately, non-trivially annotated situations in soccer games are scarce, expensive and almost always require human experts; a fully supervised approach appears infeasible. Hence, we split the problem into two parts and learn (i) a meaningful feature representation using variational autoencoders on unlabeled data at large scales and (ii) a large-margin classifier acting in this feature space but utilize only a few (manually) annotated examples of the situation of interest. We propose four different architectures of the variational autoencoder and empirically study the detection of corner kicks, crosses and counterattacks. We observe high predictive accuracies above 90% AUC irrespectively of the task.

 

 

#22 The relationships between knee extensors/ flexors strength and balance control in elite male soccer players

Reference: PeerJ. 2021 Nov 16;9:e12461. doi: 10.7717/peerj.12461. eCollection 2021.

Authors: Robert Śliwowski, Jakub Marynowicz, Łukasz Jadczak, Monika Grygorowicz, Paweł Kalinowski, Thierry Paillard

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8603814/pdf/peerj-09-12461.pdf

Summary: Strength and balance are important factors for soccer players to be successful. This study's aim was to determine the relationship between lower-limb muscle strength and balance control in elite male soccer players (n = 77). Concentric isokinetic strength (peak torque of quadriceps (PT-Q) and hamstrings (PT-H), hamstrings/quadriceps (H/Q) ratio) was measured for the dominant and non-dominant leg at angular velocities of 60°s-1and 240°s-1, as well as the total work for extensors (TW-Q) and flexors (TW-H) for both legs (at an angular velocity of 240°s-1only). Balance score (BAL score) was used for unilateral assessment of balance control using a Delos Postural System Test measurement tool. Hierarchical multiple regression analyses were performed to predict balance control using isokinetic knee strength performance for dominant and non-dominant legs. Final modelling included peak torque of hamstrings at 240°s-1 and peak torque of the quadriceps at 240°s-1 for the non-dominant leg (R 2 = 19.6%; p ≤ 0.001) and only peak hamstring torque at 240°s-1 for the dominant leg (R 2 = 11.3%; p = 0.003) as significant predictors of balance score. Findings indicate that balance control is widely influenced by peak hamstring torque and peak quadriceps torque at high angular velocity particularly in the non-dominant leg i.e., the supporting leg in soccer players.

 

 

#23 Elite Youth Soccer Players' Sources and Types of Soccer Confidence

Reference: Sports (Basel). 2021 Oct 22;9(11):146.  doi: 10.3390/sports9110146.

Authors: Iain Greenlees, Aimee Parr, Sarah Murray, Esther Burkitt

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8617682/pdf/sports-09-00146.pdf

Summary: Sport confidence is a psychological characteristic considered vital for youth soccer players to possess. However, only limited research has explored the types and sources of sport confidence important to elite youth performers in professional soccer academies. Semi-structured interviews were conducted with 11 academy footballers (aged 10 or 11). Abductive hierarchical content analysis identified types of confidence to include achievement, skill execution, psychological factors, superiority to opposition and tactical awareness. Key sources of confidence identified by players were performance accomplishments, coaching, social support, and preparation. Even though the dimensions reported were similar to previous research, a number of unique sub-themes of confidence sources emerged, including pre-training/competition emotions, coach and team-mate feedback. The results demonstrate the importance of considering maturation levels and context when seeking to understand and develop confidence in youth performers.

 

 

#24 Is the Integration of Additional Eccentric, Balance and Core Muscles Exercises into a Typical Soccer Program Effective in Improving Strength and Postural Stability?

Reference: Sports (Basel). 2021 Oct 25;9(11):147.  doi: 10.3390/sports9110147.

Authors: Konstantinos Dafkou, Chrysostomos Sahinis, Athanasios Ellinoudis, Eleftherios Kellis

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8622779/pdf/sports-09-00147.pdf

Summary: Soccer teams integrate specific exercises into their typical workout programs for injury prevention. The purpose of this study was to investigate whether the incorporation of a brief and supplementary training program that involves eccentric, balance, and core exercises into the weekly soccer schedule can cause positive neuromuscular adaptations. Twenty-one soccer players were randomly allocated to either a training (n = 11) or a control group (n = 10). All players followed their teams' typical program, consisting of 4-5 soccer-specific sessions plus 1 match, weekly. Training group players additionally performed biweekly, hamstring eccentric, balance, and core stability exercises for 8 weeks. Isokinetic concentric and eccentric peak torque (PT) of the hamstrings and quadriceps, changes in the center of pressure (COP) during a 30 s single-leg stance, and a supine bridge (trunk stability) test were assessed before and after the intervention. After the intervention, a 27% increase in hamstring concentric PT and a 33% reduction in COP sway in the stance test, were observed for the training group only (p < 0.05). These improvements were significant only for the non-dominant leg. Furthermore, the control group displayed an increase in COP sway during the bridge test compared to baseline values (p < 0.05), which reflects a deterioration in postural balance over time. Consequently, incorporating small doses of hamstring eccentric, proprioception, and core stability exercises into a typical training program of youth soccer players improves strength and postural balance in the non-dominant leg, as well as core muscle performance.

 

 

#25 Differences in Squat Jump, Linear Sprint, and Change-of-Direction Performance among Youth Soccer Players According to Competitive Level

Reference: Sports (Basel). 2021 Oct 27;9(11):149.  doi: 10.3390/sports9110149.

Authors: Michael Keiner, Andreas Kapsecker, Tobias Stefer, Björn Kadlubowski, Klaus Wirth

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8624564/pdf/sports-09-00149.pdf

Summary: The aim of this investigation was to analyze significant differences in performance depending on the level of play (elite vs. amateur) in youth soccer players (under 17 years. old (U17) and U19). A cross-sectional study was conducted, and 45 elite and amateur male youth soccer players (16.56 ± 0.9 years old) were evaluated in their performances in squat jump (SJ), 10 m linear sprint (LS), 20 m LS, 505 agility test (505) and Illinois agility test (IAT). Differences in performances were analyzed with a 2 × 2 MANOVA, post-hoc ANOVAs, and Hedges' g (g) for pairwise comparisons of subgroups (level of play and age group). This investigation showed that the elite player performance was significantly (p < 0.05) better in all performance tests than amateur players in both age groups. Interestingly, this investigation showed that the more complex the target exercise, the larger the effect sizes for group differences (SJ: g = 0.64-1.18, LS: g = 0.05-2.23, change-of-direction (COD): g = 3.01-6.84). The SJ, LS, 505, and IAT may prove useful in talent selection test batteries to separate between competitive levels in youth soccer players.

 

Fri

10

Dec

2021

Differences in worst-case scenarios calculated by fixed length and rolling average methods in professional soccer match-play

Differences in worst-case scenarios calculated by fixed length and rolling average methods in professional soccer match-play.

Thu

09

Dec

2021

The dominant leg is more likely to get injured in soccer players

The purpose of this systematic review with meta-analysis is to examine the relationship between limb dominance and soccer injuries.

Thu

02

Dec

2021

Latest research in football - week 37 - 2021

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 Nationwide Subjective and Objective Assessments of Potential Talent Predictors in Elite Youth Soccer: An Investigation of Prognostic Validity in a Prospective Study

Reference: Front Sports Act Living. 2021 May 28;3:638227. doi: 10.3389/fspor.2021.638227. eCollection 2021.

Authors: Oliver Höner, Dennis Murr, Paul Larkin, Robert Schreiner, Daniel Leyhr 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8193982/pdf/fspor-03-638227.pdf

Summary: Recent studies have provided empirical evidence on the prognostic relevance of objective performance diagnostics in the soccer talent identification and development process. However, little is known about the prognostic validity of coaches' subjective evaluations of performance. This study evaluated objective and subjective assessments within a nationwide talent development program and addressed motor, perceptual skill, and personality-related performance factors. Male players (N = 13,869; M age = 12.59 ± 1.07 years) from the age groups U12 to U15 of the German soccer talent development program participated in this study. Participants completed an objective motor diagnostic (sprint, agility, dribbling, ball control, juggling) and were subjectively rated by their coaches (kicking skills, endurance, individual tactical skills, psychosocial skills). All nine predictors were assessed with sufficient psychometric properties (α ≥ 0.72; except dribbling and ball control: α ≥ 0.53). Players' success three seasons later was operationalized by achieving professional youth academy level or not (success rate, 9%). Independent-samples t-tests analyzed univariate mean group comparisons between future selected and non-selected players. Logistic regression models examined the multivariate prognostic validity of all assessments by predicting success with subjective (model 1), objective (model 2), and both groups of predictors (model 3). Confirming the univariate prognostic validity, future selected outperformed non-selected players regarding all predictors (each p < 0.001, except for agility in U15: p < 0.01). Tactical skills, kicking skills, and sprint were of highest predictive value (d ≥ 0.61 in each age group). Multivariate results provided empirical evidence for the subjective (7% ≤ Nagelkerke's R 2 ≤ 11%; each p < 0.001) and objective (8% ≤ Nagelkerke's R 2 ≤ 13%; each p < 0.001) assessments' prognostic validity. However, model 3 revealed the best statistical explanatory power in each age group (0.15 ≤ Nagelkerke's R 2 ≤ 0.20; p < 0.001). In this combined assessment model, sprint, tactical skills, and dribbling were found to be the most predictive variables. In conclusion, this study reinforces the call for multidimensional diagnostics integrating objective and subjective assessments. Future research is needed to address the demands for longitudinal analyses of subjective ratings, the integration of biological maturation, and empirical evidence for female soccer.

 

 

#2 Sprint Mechanical Characteristics of Female Soccer Players: A Retrospective Pilot Study to Examine a Novel Approach for Correction of Timing Gate Starts

Reference: Front Sports Act Living. 2021 May 28;3:629694.  doi: 10.3389/fspor.2021.629694. eCollection 2021.

Authors: Jason D Vescovi, Mladen Jovanović

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8192793/pdf/fspor-03-629694.pdf

Summary: The purpose of this study was to compare model estimates of linear sprint mechanical characteristics using timing gates with and without time correction. High-level female soccer players (n = 116) were evaluated on a 35-m linear sprint with splits at 5, 10, 20, 30, and 35 m. A mono-exponential function was used to model sprint mechanical metrics in three ways: without a time correction, with a fixed (+0.3 s) time correction, and with an estimated time correction. Separate repeated-measures ANOVAs compared the sprint parameter estimates between models and also the residuals between models. Differences were identified between all modeled sprint mechanical metrics; however, comparable estimates to the literature occurred when either time correction was used. Bias for both time-corrected models was reduced across all sprint distances compared to the uncorrected model. This study confirms that a time correction is warranted when using timing gates at the start line to model sprint mechanical metrics. However, determining whether fixed or estimated time corrections provide greater accuracy requires further investigation.

 

 

#3 Physiological Monitoring Detected Changes During Women's Soccer Anterior Cruciate Ligament Injury

Reference: Cureus. 2021 May 4;13(5):e14838. doi: 10.7759/cureus.14838.

Authors: John P Detherage, Jon G Divine, Michael A Donaworth, Thomas G Palmer, Joshua A Hagen, Kimberly A Hasselfeld, Marsha Eifert-Mangine, Robert E Mangine, Joseph F Clark, Brian M Grawe

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8191855/pdf/cureus-0013-00000014838.pdf

Summary: A growing number of studies utilizing wearable technologies are examining the influence of the autonomic nervous system (ANS) on intense training, recovery, and injury risk. Exercise biometric (EB) data were collected on collegiate, female soccer players during a preseason camp. One player sustained an anterior cruciate ligament (ACL) injury. Baseline anthropometric and EB data were compared to non-injured, position-matched teammates. All players had similar baseline testing. The injured athlete had a higher body mass index (BMI) and slower vision reaction time (RT). On the day of her injury (DOI), relative percentage heart rate recovery (tHRR) between intense training sets was calculated. Relative percentage tHRR was much lower for the injured athlete, indicating reduced recovery between training sets immediately prior to the injury. Also on DOI, the injured athlete had a lower glomerular filtration rate (GFR). In addition to BMI and RT differences, the lower relative percentage tHRR and GFR on the DOI observed for the injured athlete may reflect an imbalanced ANS recovery, and potentially to risk factors leading to her ACL injury.

 

 

#4 Female Adolescent Soccer Players Utilize Different Neuromuscular Strategies Between Limbs During the Propulsion Phase of a Lateral Vertical Jump

Reference: Int J Sports Phys Ther. 2021 Jun 2;16(3):695-703.  doi: 10.26603/001c.22134.

Authors: Matthew D DeLang, Joseph P Hannon, Shiho Goto, James M Bothwell, J Craig Garrison

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8169019/pdf/ijspt_2021_16_3_22134.pdf

Summary: Multiplanar dynamic stability is an important unilateral function in soccer performance but has been scarcely examined in female soccer players. The lateral vertical jump task assesses unilateral functional performance, and energy generation contribution examines how each joint (hip, knee, ankle) contributes to the vertical component of the vertical jump phase to measure inter- and intra-limb differences. The purpose was to examine dominant versus non-dominant limb performance using energy generation contribution of the hip, knee, and ankle during the vertical jump component of the lateral vertical jump. Seventeen healthy, adolescent female soccer players (age 13.4±1.7 years; height 160.6±6.0 cm; mass 53.1±8.2 kg) participated. Quadriceps strength was measured via isokinetic dynamometry. Energy generation contribution (measured from maximal knee flexion to toe off) and vertical jump height were measured during the vertical component of the lateral vertical jump. There was no significant difference between limbs for quadriceps strength (p=0.64), jump height (p=0.59), or ankle energy generation contribution (p=0.38). Energy generation contribution was significantly greater in the dominant hip (dominant 29.7±8.6%, non-dominant 18.4±6.3%, p<0.001) and non-dominant knee (dominant 22.8±6.8%, non-dominant 36.2±8.5%, p<0.001). High demand on coordination and motor control during the lateral vertical jump and inherent limb dominance may explain different intra-limb strategies for task performance despite jump height symmetry. Non-dominant affinity for stability and dominant compensatory performance may neutralize potential asymmetries. Implications for symmetry in observable outcomes such as jump height must consider underlying internal asymmetries. Symmetrical findings on functional tasks have underlying internal asymmetries observed here in female adolescent soccer players. The lateral vertical jump may highlight these internal asymmetries (hip- versus knee-dominant movement strategies) due to the high coordinative demand to perform the task. Clinicians should be cognizant of underlying, potentially inherent, asymmetries even when observing functional symmetry in a task. 

 

 

#5 Biomechanical Changes During a 90º Cut in Collegiate Female Soccer Players With Participation in the 11+

Reference: Int J Sports Phys Ther. 2021 Jun 2;16(3):671-680.  doi: 10.26603/001c.22146.

Authors: Celeste Dix, Amelia Arundale, Holly Silvers-Granelli, Adam Marmon, Ryan Zarzycki, Lynn Snyder-Mackler

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8168994/pdf/ijspt_2021_16_3_22146.pdf

Summary: Valgus collapse and high knee abduction moments have been identified as biomechanical risk factors for ACL injury. It is unknown if participation in the 11+, a previously established, dynamic warm-up that emphasizes biomechanical technique and reduces ACL injury rates, reduces components of valgus collapse during a 90º cut. The aim was to determine whether participation in the 11+ during a single soccer season reduced peak knee abduction moment and components of valgus collapse during a 90º cut in collegiate female soccer players. Forty-six participants completed preseason and postseason motion analysis of a 90º cut. During the season, 31 players completed the 11+ and 15 players completed their typical warm-up (control group). Peak knee abduction moment, components of valgus collapse (hip adduction, internal rotation, and knee abduction angles), and a novel measure of knee valgus collapse were analyzed with repeated-measures ANOVAs to determine differences between preseason and postseason. Smallest detectable change (SDC) and minimal important difference (MID) values were applied to contextualize results. There was a significant main effect of time for non-dominant knee valgus collapse (p=0.03), but decreases in non-dominant knee valgus collapse only exceeded the SDC in the intervention team. Clinically meaningful decreases in knee valgus collapse may indicate a beneficial biomechanical effect of the 11+. Participation in the 11+ may lower ACL injury risk by reducing valgus collapse during a 90º cut.

 

 

#6 Are Soccer and Futsal Affected by the Relative Age Effect? The Portuguese Football Association Case

Reference: Front Psychol. 2021 May 28;12:679476. doi: 10.3389/fpsyg.2021.679476. eCollection 2021.

Authors: Pedro Figueiredo, André Seabra, Marta Brito, Marta Galvão, João Brito

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8194498/pdf/fpsyg-12-679476.pdf

Summary: A better understanding of the relative age effect (RAE) in youth will increase the awareness of the need for reducing the bias of (de)selection. Thus, we investigated the RAE in youth female and male soccer and futsal players in Portugal, using nationwide data. Birthdates of 5,306 female and 126,285 male soccer players, and 2,437 female and 23,988 male futsal players (U7-U19), registered in Portugal during the season 2019-2020, and Portuguese National teams (from U15 to AA soccer teams and from U17 to AA futsal teams) were analyzed. Data were categorized into age groups and certification levels [no certification, basic football training center, football school, and training institution] of the respective clubs/academies. Birthdates were stratified from the start of the selection year using quartiles (Q) and semesters (S). Differences between the observed and expected birthdate distributions were analyzed using chi-square statistics, and RAEs were calculated using odds ratios (OR). In both soccer and futsal, female players, in the age category U9, RAEs were found (Q1 vs. Q4, OR: 1.49 and 1.84, respectively). In male soccer, differences in the birthdate distribution were observed in all age categories (U7-U19) with significant OR between all comparisons (Q and S). In contrast, an over-representation of young male futsal players (Q1 vs. Q4) was observed only in the age categories U7 and U9 (OR: 1.54 and 1.34, respectively). The stratification by certification level showed a significant RAE for all certification levels in male soccer players. In contrast, in male futsal players, the RAE was significant only in clubs and academies with the highest level. For National teams, the RAE was more pronounced in male soccer, particularly in the U16 and U17 (OR: 9.84 and 12.36, respectively). Data showed a RAE in female and male youth soccer and futsal, particularly in male, younger age categories, and in clubs and academies having a higher certification level, which could be accompanied by a loss of valuable elite players during the youth phase of their careers. Thus, adjustments in the systems and structure of talent identification are recommended to prevent RAE-related discrimination in youth soccer and futsal.

 

 

#7 Relationships between RPE-derived internal training load parameters and GPS-based external training load variables in elite young soccer players

Reference: Res Sports Med. 2021 Jun 14;1-16.  doi: 10.1080/15438627.2021.1937165. Online ahead of print.

Authors: Vicente de Dios-Álvarez, David Suárez-Iglesias, Sara Bouzas-Rico, Pello Alkain, Adrián González-Conde, Carlos Ayán-Pérez

Summary: This study aimed to identify the GPS-based external training load variables that influence the internal training loads (RPE-derived parameters: RPE and session RPE - sRPE), and generate a model to predict GPS-based external load variables from RPE and perceived wellness values. Training load data for 21 elite young players were collected over 72 training sessions and 23 matches from the same competitive season, and 564 observations (training sessions, 462; matches, 102) were analysed. Considering all observations (training sessions and matches), significant moderate and large correlations (p < 0.01) were detected between RPE values and EL measures. The correlation between the GPS outcomes with both the RPE and sRPE values was higher during training sessions than during matches. Moreover, increased RPE and perceived wellness measures had a significant positive effect on external load variables (p < 0.001). The present work provides preliminary evidence of the utility of the RPE and sRPE method to quantify the training loads in young soccer players since most of the GPS-based EL indicators were moderate to highly correlated with the RPE-derived parameters. Additionally, EL variables may be estimated when combining perceived IL and subjective wellness indicators in young soccer players.

 

 

#8 Dietary and Ergogenic Supplementation to Improve Elite Soccer Players' Performance

Reference: Ann Nutr Metab. 2021 Jun 11;1-7.  doi: 10.1159/000516397. Online ahead of print.

Authors: Haniel Fernandes

Download link: https://www.karger.com/Article/Pdf/516397

Summary: Soccer is an extremely competitive sport, where the most match important moments can be defined in detail. Use of ergogenic supplements can be crucial to improve the performance of a high-performance athlete. Therefore, knowing which ergogenic supplements are important for soccer players can be an interesting strategy to maintain high level in this sport until final and decisive moments of the match. In addition, other supplements, such as dietary supplements, have been studied and increasingly referenced in the scientific literature. But, what if ergogenic supplements were combined with dietary supplements? This review brings some recommendations to improve performance of soccer athletes on the field through dietary and/or ergogenic supplements that can be used simultaneously. Soccer is a competitive sport, where the match important moments can be defined in detail. Thus, use of ergogenic supplements covered in this review can improve performance of elite soccer players maintaining high level in the match until final moments, such as creatine 3-5 g day-1, caffeine 3-6 mg kg-1 BW around 60 min before the match, sodium bicarbonate 0.1-0.4 g kg-1 BW starting from 30 to 180 min before the match, β-alanine 3.2 and 6.4 g day-1 provided in the sustained-release tablets divided into 4 times a day, and nitrate-rich beetroot juice 60 g in 200 mL of water (6 mmol of NO3- L) around 120 min before match or training, including a combination possible with taurine 50 mg kg-1 BW day-1, citrulline 1.2-3.4 g day-1, and arginine 1.2-6 g day-1. Key Messages: Soccer athletes can combine ergogenic and dietary supplements to improve their performance on the field. The ergogenic and dietary supplements used in a scientifically recommended dose did not demonstrate relevant side effects. The use of various evidence-based supplements can add up to further improvement in the performance of the elite soccer players.

 

 

#9 Assessment of diet quality and physical activity of soccer players aged 13 to 16, from the Principality of Asturias, Spain

Reference: An Pediatr (Engl Ed). 2021 Jun 9;S2341-2879(21)00103-4.  doi: 10.1016/j.anpede.2020.05.015.

Authors: María Del Mar Fernández-Álvarez, Rubén Martín-Payo, Edurne Zabaleta-Del-Olmo, Rebeca García-García, Marcelino Cuesta, Xana Gonzalez-Méndez

Download link: https://reader.elsevier.com/reader/sd/pii/S2341287921001034?token=BDBAB195C9E3C1E26CF51DBA05992A25D63B536D01EB6D524BE01FCB2254A689733AC96F6D1836DDD09F83853C7B3789&originRegion=eu-west-1&originCreation=20210626152303

Summary: Diet and physical activity are factors that have key roles in childhood overweight and obesity prevention. Appropriate assessment of these factors is an essential task in public health. The main aims of the study are to assess body composition, physical activity, and adherence to Mediterranean diet of soccer players, aged 13 to 16 years old in Asturias, Spain. It also aims to evaluate the relationships between diet, physical activity, body composition, and personal characteristics. A cross-sectional descriptive survey approach was used involving children (n = 303) with a mean age of 14.15 years (SD = 1.06), and using the KIDMED and PAQ-A questionnaires to assess adherence to Mediterranean diet and level of physical activity, respectively. Body composition was represented using the participants' body mass index. Approximately 23.1% of the participants were overweight or obese. With regards to adherence to Mediterranean diet, 54.8% of the participants had medium adherence, while 8.9% had low adherence. PAQ-A mean score was 2.69 (SD = 0.47). Excess weight was associated with being a goalkeeper (P = .001), higher PAQ-A (P = .011), and lower KIDMED scores (P = .032). Correlation analysis showed an inverse association between age and PAQ-A score (r = -0.122), and a direct association between KIDMED and PAQ-A scores (r = 0.152). Participants had an adequate level of physical activity. However, they had an obesogenic profile similar to that of their age population, who were not soccer players. Actions to improve adherence to healthy diet practices are highly recommended.

 

 

#10 Heading in Football: Incidence, Biomechanical Characteristics and the Association with Acute Cognitive Function-A Three-Part Systematic Review

Reference: Sports Med. 2021 Jun 15.  doi: 10.1007/s40279-021-01492-z. Online ahead of print.

Authors: Robert McCunn, Florian Beaudouin, Katy Stewart, Tim Meyer, John MacLean

Summary: There is growing concern surrounding the role of repetitive sub-concussive head impacts, such as football heading, on brain health. Three questions were addressed while only considering studies that observed heading exposure directly: (1) how frequently does heading occur within football training and matches, (2) what are the biomechanical characteristics of heading, and (3) is cognitive function affected by heading? This review followed the steps described in the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Electronic databases including MEDLINE and SPORTDiscus were searched from the earliest entry to July 2020. Studies that reported independently quantified heading exposure, biomechanical characteristics of heading or the relationship between heading and cognitive function were included. Data were extracted and used to populate summary tables with reference to each research question. Heading incidence ranged between one to nine headers per player per match. The number of headers observed in small-sided games during training varied depending on the exact format used but generally speaking ranged between zero to one per player per game. The three most commonly reported biomechanical variables were head acceleration, head rotational velocity and overall movement kinematics during the heading action. Average head acceleration ranged from approximately four to 50 g. Nine out of 12 included studies did not observe a negative impact on cognitive test performance following exposure to heading and while three did, these negative effects were limited to specific outcome measures: reaction time and memory function. The current weight of evidence summarised herein does not support the notion that heading is deleterious to cognitive performance in the short term; however, this conclusion is tentative due to methodological shortcomings in the existing evidence base.

 

 

#11 Effect of playing position, passage duration and starting status on the most demanding passages of match play in professional football

Reference: Res Sports Med. 2021 Jun 14;1-10.  doi: 10.1080/15438627.2021.1937163. Online ahead of print.

Authors: Isabel Martín-Fuentes, José M Oliva-Lozano, Víctor Fortes, José M Muyor

Summary: The aims of this research were to analyse the effect that different playing positions, passage durations and starting status had on the most demanding passages (MDP) of play in professional football matches. Players were categorized by positions and the MDP of distance (DIS), high-speed running distance (HSRD) and sprinting distance (SPD) were analysed for four passage durations (1, 3, 5 and 10 minutes). The results indicated that DIS (p < 0.001), HSRD (p < 0.001) and SPD (p < 0.001) covered per minute decreased as the passage durations increased for all positions. Regarding the playing position, it had a significant effect on the DIS (p < 0.001), HSRD (p < 0.001) and SPD (p < 0.001) covered. In addition, although the results reported that the starting status had no significant effect on the DIS (p = 0.36) covered, it had a statistically significant effect on the HSRD (p = 0.01) and SPD (p < 0.001) covered. Coaching and medical departments should consider the impact that these variables have on players' performance when designing training drills aimed at preparing the player for the competitive demands.

 

 

#12 Impact of Scoring First on Match Outcome in the Chinese Football Super League

Reference: Front Psychol. 2021 May 28;12:662708. doi: 10.3389/fpsyg.2021.662708. eCollection 2021.

Authors: Tianbiao Liu, Antonio García-de-Alcaraz, Hai Wang, Ping Hu, Qiu Chen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8194256/pdf/fpsyg-12-662708.pdf

Summary: The aim of this study was to explore the effect of scoring first on match outcomes in the Chinese Football Super League (CSL). A total of 1,116 matches in which at least one goal was scored from the 2014 to 2018 seasons were collected. Match outcomes, absolute goal differences, the minute of the first goal, match locations, and teams' budgets were analyzed. A team's budget was measured in terms of a team's value at the beginning of the season, and teams were clustered into two groups (high and low budget with means of 50.77 and 13.77 million dollars, respectively). A descriptive analysis was conducted, and two generalized linear models (a multinomial logit model and a Poisson model; p < 0.05) were applied. The results showed a favorable outcome for the team that scored first both in match outcome and goal difference. Regarding the teams that scored first, 66.31% won their matches, 20.70% achieved a draw, and 12.99% lost. Specifically, home teams were more likely to win (13.42%) and less likely to lose (9.52%) or draw (3.90%) than away teams. Home teams also had a higher likelihood of obtaining a larger goal difference. Higher budget teams were more likely to win (14.90%) and less likely to lose (9.75%) or draw (5.14%) than low-budget teams. Additionally, for each minute, the team scores closer to the end of the match, and the average probability of winning increased by 0.0028. These findings can guide the strategies of coaches in different match scenarios according to the match location and the opponent's quality.

 

 

#13 Design and Validation of an Observational System for Penalty Kick Analysis in Football (OSPAF)

Reference: Front Psychol. 2021 May 28;12:661179. doi: 10.3389/fpsyg.2021.661179. eCollection 2021.

Authors: Guilherme de Sousa Pinheiro, Vitor Bertoli Nascimento, Matt Dicks, Varley Teoldo Costa, Martin Lames

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8194359/pdf/fpsyg-12-661179.pdf

Summary: The analysis of penalty kick has played an important role in performance analysis. The study aims are to get formal feedback on the relevance of variables for penalty kick analysis, to design and validate an observational system; and to assess experts' opinion on the optimum video footage in penalty kick analysis. A structured development process was adopted for content validity, reliability and agreement on video usage. All observational variables included in OSPAF showed Aiken's V values above the cut-off (for 5-scale V> 0.64; for 2-scale = V > 0.75; p < 0.05). Cohen's Kappa resulted in mean intra- and inter-rater reliability values of 0.90 and 0.86, respectively. It is recommended to combine at least three different viewing angles (V = 0.90; p = 0.006) with standardization of video quality (V = 0.95; p = 0.006). Changing the viewing angles may influence the observer perception (V = 0.86; p = 0.006). The aerial and pitch-level viewing angle behind the penalty taker and pitch-level viewing angle behind the goalkeeper were indicated as most appropriate for observational analysis (V = 0.97; p = 0.01). The OSPAF met all requirements of instrument validation. It may be recommended as basis of future observational systems on penalty kicks.

 

 

#14 Pursuing Collective Synchrony in Teams: A Regime-Switching Dynamic Factor Model of Speed Similarity in Soccer

Reference: Psychometrika. 2021 Jun 18. doi: 10.1007/s11336-021-09782-1. Online ahead of print.

Authors: Daniel M Smith, Theodore A Walls

Summary: Collective synchrony refers to the simultaneous occurrence of behavior, cognition, emotion, and/or physiology within teams of three or more persons. It has been suggested that collective synchrony may emanate from the copresence of team members, from their engagement in a shared task, and from coordination enacted in pursuit of a collective goal. In this paper, a regime-switching dynamic factor analytical approach is used to examine interindividual similarities in a particular behavioral measure (i.e., speed) in a collegiate soccer team. First, the analytical approach is presented didactically, including the state space modeling framework in general, followed by the regime-switching dynamic factor model in particular. Next, an empirical application of the approach is presented. Speed similarity (covariation in speed, operationalized in two ways: running cadence and distance covered) during competitive women's soccer games is examined. A key methodological aspect of the approach is that the collective is the unit of analysis, and individuals vary about collective dynamics and their evolution. Reporting on the results of this study, we show how features of substantive interest, such as the magnitude and prevalence of behavioral similarity, can be parameterized, interpreted, and aggregated. Finally, we highlight several key findings, as well as opportunities for future research, in terms of methodological and substantive aims for advancing the study of collective synchrony.

 

 

#15 Total numbers and in-hospital mortality of patients with myocardial infarction in Germany during the FIFA soccer world cup 2014

Reference: Sci Rep. 2021 Jun 17;11(1):11330.  doi: 10.1038/s41598-021-90582-z.

Authors: Karsten Keller, Lukas Hobohm, Volker H Schmitt, Martin Engelhardt, Philip Wenzel, Felix Post, Thomas Münzel, Tommaso Gori, Birgit Friedmann-Bette

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8211804/pdf/41598_2021_Article_90582.pdf

Summary: Environmental stress like important soccer events can induce excitation, stress and anger. We aimed to investigate (i) whether the FIFA soccer world cup (WC) 2014 and (ii) whether the soccer games of the German national team had an impact on total numbers and in-hospital mortality of patients with myocardial infarction (MI) in Germany. We analyzed data of MI inpatients of the German nationwide inpatient sample (2013-2015). Patients admitted due to MI during FIFA WC 2014 (12th June-13th July2014) were compared to those during the same period 2013 and 2015 (12th June-13th July). Total number of MI patients was higher during WC 2014 than in the comparison-period 2013 (18,479 vs.18,089, P < 0.001) and 2015 (18,479 vs.17,794, P < 0.001). WC was independently associated with higher MI numbers (2014 vs. 2013: OR 1.04 [95% CI 1.01-1.07]; 2014 vs. 2015: OR 1.07 [95% CI 1.04-1.10], P < 0.001). Patient characteristics and in-hospital mortality rate (8.3% vs. 8.3% vs. 8.4%) were similar during periods. In-hospital mortality rate was not affected by games of the German national team (8.9% vs. 8.1%, P = 0.110). However, we observed an increase regarding in-hospital mortality from 7.9 to 9.3% before to 12.0% at final-match-day. Number of hospital admissions due to MI in Germany was 3.7% higher during WC 2014 than during the same 31-day period 2015. While in-hospital mortality was not affected by the WC, the in-hospital mortality was highest at WC final.

 

 

#16 The effects of hydration status and ice-water dousing on physiological and performance indices during a simulated soccer match in the heat

Reference: J Sci Med Sport. 2021 May 24;S1440-2440(21)00138-9.  doi: 10.1016/j.jsams.2021.05.013.

Authors: Courteney L Benjamin, Yasuki Sekiguchi, Margaret C Morrissey, Cody R Butler, Erica M Filep, Rebecca L Stearns, Douglas J Casa

Summary: The aim was to assess the effects of hydration status and ice-water dousing on physiological and performance parameters. Twelve athletes (mean[M] ± standard deviation[SD]; age, 20 ± 1 years; height, 174 ± 8 cm; body mass, 72.1 ± 11.0 kg; VO2max 53.9 ± 7.3 mL⋅kg-1⋅min-1) completed four trials (euhydrated without dousing, hypohydrated without dousing, euhydrated with dousing, and hypohydrated with dousing), which involved intermittent treadmill running (five 15-minute bouts) in the heat (M ± SD; ambient temperature, 34.7 ± 2.1 °C; relative humidity, 46 ± 3%; wet-bulb globe temperature, 28.0 ± 0.4 °C). Participants also completed four cognitive, power, agility, reaction time, and repeated sprint performance tests throughout each trial. Heart rate (HR) and rectal temperature (Trec) were measured continuously. Repeated measures ANOVAs were performed to assess differences between physiological and performance variables. Alpha was set at ≤0.05, a priori. Data are reported as mean difference ± standard error (MD ± SE). HR was significantly lower in euhydrated trials compared to hypohydrated trials, irrespective of dousing (8 ± 2 bpm; p = 0.001). Dousing did not significantly impact HR (p = 0.455) and there was no interaction between hydration and dousing (p = 0.893). Trec was significantly lower in euhydrated trials compared to hypohydrated trials (0.39 ± 0.05 °C, p < 0.001), with no effect from dousing alone (p = 0.113) or the interaction of hydration and dousing (p = 0.848). Dousing resulted in improved sprint performance (11 ± 3 belt rotations, p = 0.007), while hydration status did not (p = 0.235). Athletes should aim to maintain euhydration during exercise in the heat for improved physiological function and cooling with ice-water dousing elicits additional performance benefits.

 

 

#17 Football as an Alternative to Work on the Development of Social Skills in Children with Autism Spectrum Disorder with Level 1

Reference: Behav Sci (Basel). 2021 Nov 19;11(11):159.  doi: 10.3390/bs11110159.

Authors: Jose Maria Lopez-Diaz, Nerea Felgueras Custodio, Inmaculada Garrote Camarena

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8614793/pdf/behavsci-11-00159.pdf

Summary: Given the characteristics of people with Autism Spectrum Disorder, it is evident the difficulties they show in the development of social skills. The scarce participation of people with Autism Spectrum Disorder in group sports can be taken as a reference. The aim of this study was to analyse the impact of football on the development of social skills in children with Autism Spectrum Disorder. In order to measure the sporting impact, it was necessary to implement a football training programme with the intention of evaluating different social skills. Thirteen children participated in the programme, all of them with a diagnosis of Autism Spectrum Disorder and with a severity level of 1. The study was based on a pre-experimental, pre-test/post-test design. Non-parametric tests were used for the statistical analysis, applying the Wilcoxon test. Two specific tools on social skills were used for data collection. The results showed a generalised improvement in the dimensions linked to the social skills assessed. This highlights the possibility of considering group sport as an alternative to be taken into account to work on and enhance social skills in children with Autism Spectrum Disorder.

 

 

#18 FIFA 11+ Kids program effects on jump kinetics in soccer players - A randomized controlled clinical trial

Reference: Res Sports Med. 2021 Nov 26;1-12.  doi: 10.1080/15438627.2021.2010204. Online ahead of print.

Authors: Vitória A Teixeira, Thiago M Queiroz, Isadora V Leão, Lucas D G Innecco, Erica L Marcelino, Daniel F M Lobato

Summary: This study aimed to analyse the effects of the FIFA 11+ Kids programme on jump kinetics in soccer players. Twenty-four athletes (aged 9-11 years) were randomly allocated to the following groups: 1) the FIFA 11+ Kids programme (FT, n = 12), and 2) control training (CT, n = 12). Kinetic assessments of vertical jump (VJ), drop landing (DL), and anterior jump + maximum vertical jump (AJ) were performed on a force platform before and after eight weeks of training. Post-intervention impulse peak force and maximum impulse force (VJ) were significantly greater than the baseline values in the FT group (P < 0.001). Post-intervention landing peak force values for the first and second landings (DL) were significantly greater than the baseline values in the FT group (P = 0.01 and P = 0.05, respectively). Post-intervention landing peak force in the first landing (AJ) was significantly greater than the baseline values in the FT group (P = 0.005). The FT was effective in improving the impulsion performance during VJ. However, it increased the landing forces during DL and VJ.

 

 

#19 The Intra- and Inter-Rater Reliability of a Hip Rotation Range-of-Motion Measurement Using a Smartphone Application in Academy Football (Soccer) Players

Reference: Sports (Basel). 2021 Oct 26;9(11):148.  doi: 10.3390/sports9110148.

Authors: Paul Spork, James O'Brien, Morris Sepoetro, Maximilian Plachel, Thomas Stöggl

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8623895/pdf/sports-09-00148.pdf

Summary: The clinical assessment of hip rotation range-of-motion (ROM) is important for managing hip and groin injuries in footballers. Previously published reliability studies on hip ROM have employed protocols that are difficult to replicate under everyday clinical conditions. This single trial, intra- and inter-rater reliability study included 41 male academy football (soccer) players, aged 14-15 years, from one European football academy. Passive hip internal rotation (IR) and external rotation (ER) ROM were measured in supine with hip and knee flexed to 90°. The ROM was determined using a smartphone application, with the smartphone attached to the lower leg. The tests were performed on two separate occasions, one week apart, by two different physiotherapists and on both sides (left and right hips). Reliability was evaluated using Intra-Class Correlation Coefficients (ICCs) and Minimal Detectable Change (MDC). Hip IR and ER ROM displayed moderate to good intra-rater agreement (ICCs 0.54-0.75), with MDCs ranging from 10.9° to 16.4°. Inter-rater reliability displayed poor to moderate reliability (ICCs 0.33-0.75), with MDCs ranging from 11.7° to 16.5°. A hip rotation ROM test using a smartphone application and a protocol closely reflecting everyday clinical conditions displayed moderate to good intra-rater reliability and poor to moderate inter-rater reliability. Due to the high MDCs, the practical applicability of this test procedure is limited and further refinement is necessary.

 

 

#20 The neurological risks of playing association football

Reference: JRSM Open. 2021 Nov 18;12(11):20542704211055558.  doi: 10.1177/20542704211055558. eCollection 2021 Nov.

Authors: Oliver C Cockerell, Natalie Iino Hayes, Richard Sylvester

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8609100/pdf/10.1177_20542704211055558.pdf

Summary: The present study aims to provide a narrative review of the literature surrounding concussion and head injury in football and its clarity in evaluating the risk of long-term neurological disease. Epidemiological studies have shown correlations between participation in professional football and increased incidence of neurodegenerative disease and there have been reports of chronic traumatic encephalopathy (CTE) in the brains of former players in autopsy. These findings have been assumed by some to be the result of repetitive brain injury from head injuries and/or from heading the ball over a player's career. Data linking increased heading exposure with dementia is conflicting, and studies are limited by the reliance on retrospection and undocumented reports of concussion. It remains unclear whether CTE is unique to sportsmen or a variant of dementia pathology endemic in the population. Although logically appealing, there is no current evidence that heading is the cause of neurodegeneration amongst footballers and risks should be balanced by the protective mental and physical benefits of the sport. Physicians have an important role in providing balanced views in this emotive and controversial area.

 

Wed

01

Dec

2021

Distance Between Players During a Soccer Match: The Influence of Player Position

We analyse the proximity between professional players during a soccer match. Specifically, we are concerned about the time a player remains at a distance to a rival that is closer than 2m, which has a series of consequences, from the risk of contagion during a soccer match to the understanding of the tactical performance of players during the attacking/defensive phases.

Tue

30

Nov

2021

Predictive Strength of Contextual and Personal Variables in Soccer Players’ Goal Orientations

This study aimed to examine the relationships among a set of psychological variables (perceived motivational climate, goal orientation, self-determined motivation and personality) in male and female footballers.

Fri

26

Nov

2021

Latest research in football - week 36 - 2021

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 Influence of Social Support and Ability Perception on Coping Strategies for Competitive Stress in Soccer Players: The Mediating Role of Cognitive Assessment

Reference: Front Psychol. 2021 May 25;12:554863.  doi: 10.3389/fpsyg.2021.554863. eCollection 2021.

Authors: Zhao Dai, Qiang Liu, Wenhui Ma, Chengwei Yang

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8185028/pdf/fpsyg-12-554863.pdf

Summary: The aim was to explore the effect of social support and ability perception on stress coping strategies for competitive stress, and to reveal the mediating effects of primary and secondary evaluation, so as to further improve the theoretical model of stress coping in soccer players. A total of 331 male athletes from 22 teams in the Chengdu Middle School Campus Football League were taken as survey samples, and surveys were conducted on their stress experience, social support, ability perception, cognitive assessment, and coping strategies for competition stress. SPSS 21.0 and AMOS 21.0 statistical analysis software were used. Descriptive statistics, correlation analysis, exploratory factor analysis (EFA), and confirmatory factor analysis (CFA) were used to process the obtained data.  Positive primary assessment acted as a full mediator in the relationship between social support and secondary assessments, and negative primary assessment acted as a partial mediator in the relationship between competence perception and secondary assessments; Secondary assessment played a partial mediating role between positive primary assessment and positive coping strategies, and a full mediating role between negative primary assessment and positive coping strategies; Secondary assessments played the mediator neither between social support and a coping strategy for stress nor competence perception and a coping strategy for stress; (4) Positive primary assessment, positive negative assessment, and secondary assessment all had significant positive benefits for positive coping. Still, the impact of positive primary assessment on positive coping was significantly better than negative primary assessment and secondary assessment.  The coping strategy for the competitive stress model proposed by this study has a very good fit for the causal model. It can be used to explain the observed data from soccer players in middle schools. The primary and secondary assessments play different roles in the model. The combination of problem focuses and emotional focus on the positive stress coping strategy is suitable in the field of competitive sports. Still, the relevant research results need to be further explored and verified in the future.

 

 

#2 The Efficacy of Heat Acclimatization Pre-World Cup in Female Soccer Players

Reference: Front Sports Act Living. 2021 May 25;3:614370.  doi: 10.3389/fspor.2021.614370. eCollection 2021.

Authors: César M P Meylan, Kimberly Bowman, Trent Stellingwerff, Wendy A Pethick, Joshua Trewin, Michael S Koehle

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8185056/pdf/fspor-03-614370.pdf

Summary: The efficacy of a 14-day field-based heat acclimatization (HA) training camp in 16 international female soccer players was investigated over three phases: phase 1: 8 days moderate HA (22. 1°C); phase 2: 6 days high HA (34.5°C); and phase 3: 11 days of post-HA (18.2°C), with heart rate (HR), training load, core temp (T c), and perceptual ratings recorded throughout. The changes from baseline (day-16) in (i) plasma volume (PV), (ii) HR during a submaximal running test (HRex) and HR recovery (HRR), and (iii) pre-to-post phase 2 (days 8-13) in a 4v4 small-sided soccer game (4V4SSG) performance were assessed. Due to high variability, PV non-significantly increased by 7.4% ± 3.6% [standardized effect (SE) = 0.63; p = 0.130] from the start of phase 1 to the end of phase 2. Resting T c dropped significantly [p < 0.001 by -0.47 ± 0.29°C (SE = -2.45)], from day 1 to day 14. Submaximal running HRR increased over phase 2 (HRR; SE = 0.53) after having decreased significantly from baseline (p = 0.03). While not significant (p > 0.05), the greatest HR improvements from baseline were delayed, occurring 11 days into phase 3 (HRex, SE = -0.42; HRR, SE = 0.37). The 4v4SSG revealed a moderate reduction in HRex (SE = -0.32; p = 0.007) and a large increase in HRR (SE = 1.27; p < 0.001) from pre-to-post phase 2. Field-based HA can induce physiological changes beneficial to soccer performance in temperate and hot conditions in elite females, and the submaximal running test appears to show HRex responses induced by HA up to 2 weeks following heat exposure.

 

 

#3 Age at Nomination Among Soccer Players Nominated for Major International Individual Awards: A Better Proxy for the Age of Peak Individual Soccer Performance?

Reference: Front Psychol. 2021 May 24;12:661523. doi: 10.3389/fpsyg.2021.661523. eCollection 2021.

Authors: Geir Oterhals, Håvard Lorås, Arve Vorland Pedersen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182689/pdf/fpsyg-12-661523.pdf

Summary: Individual soccer performance is notoriously difficult to measure due to the many contributing sub-variables and the variety of contexts within which skills must be utilised. Furthermore, performance differs across rather specialised playing positions. In research, soccer performance is often measured using combinations of, or even single, sub-variables. All too often these variables have not been validated against actual performance. Another approach is the use of proxies. In sports research, the age of athletes when winning championship medals has been used as a proxy for determining their age of peak performance. In soccer, studies have used the average age of players in top European leagues or in the Champions League to determine the age of individual peak performance. Such approaches have methodological shortcomings and may underestimate the peak. We explore the use of a new proxy, the age at nomination for major individual awards, to determine the average age at peak individual soccer performance. A total of 1,981 players nominated for major awards from 1956 to 2019 were included, and a subset of 653 retired players was extracted, thus including players' complete careers. Players' average ages at nomination, at their first nomination, and at their last ever nomination were calculated, and differences across playing positions were calculated together with changes over time in the average age at peak. Based on our proxy, the age of individual peak soccer performance occurs around 27-28 years, varying across playing positions from 26 to 31 years. A player's first peak, on average, seems to coincide with known peaks of physiological variables; their last-ever peak occurs long after physiological performance has started to decline, indicating that the decline can be compensated for by other variables. The peak age is higher than previously reported for soccer; however, it is similar to those in other team ball sports. The average age at peak performance has increased over time, especially in the last decade. Our approach of using proxies for unearthing information about hidden features of otherwise immeasurable complex performance appears to be viable, and such proxies may be used to validate sub-variables that measure complex behaviour.

 

 

#4 Construct validity of age at predicted adult height and BAUS skeletal age to assess biological maturity in academy soccer

Reference: Ann Hum Biol. 2021 Mar;48(2):101-109.  doi: 10.1080/03014460.2021.1913224.

Authors: Ludwig Ruf, Sean Cumming, Sascha Härtel, Anne Hecksteden, Barry Drust, Tim Meyer

Summary: The assessment of biological maturity status plays an important role in talent identification and development programs. The aim was to compare age at predicted adult height and BAUS skeletal age as indicators of biological maturity status in youth soccer players using a construct-validity approach. Participants were 114 players from the U12 to U17 age groups of a professional youth soccer academy. Maturity status was determined via percentage of predicted adult height based upon the Khamis-Roche method (somatic maturity) and assessed via the SonicBone BAUSTM system (skeletal maturity). Convergent and known-groups validity were evaluated between maturity assessment methods and by comparing maturity-related selection biases across age groups. Although maturity status indicators were largely interrelated (r = .94, 95%CL 0.91-0.96), concordance (κ = 0.31 to 0.39) and Spearman's rank-order correlations (ρ = 0.45-0.52) of classification methods were moderate. A selection bias towards early maturing players emerged in the U14 age group which remained relatively consistent through to the U17 age group. Results confirm the construct-validity of both methods to assess biological maturity status although further validation relative to established indicators of biological maturity is needed. Furthermore, caution is also warranted when interpreting maturity status classification methods interchangeably given the poor concordance between classification methods.

 

 

#5 Toward Improved Triadic Functioning: Exploring the Interactions and Adaptations of Coaches, Parents and Athletes in Professional Academy Soccer Through the Adversity of COVID-19

Reference: Front Psychol. 2021 May 19;12:609631.  doi: 10.3389/fpsyg.2021.609631. eCollection 2021.

Authors: James Maurice, Tracey J Devonport, Camilla J Knight

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8170100/pdf/fpsyg-12-609631.pdf

Summary: On March 23rd, 2020, elite soccer academies in the UK closed in compliance with the government enforced lockdown intended to contain the COVID-19 pandemic. This forced parents, players, and coaches to reconsider how they interacted with, and supported, one another. The aims of the present study were (a) to explore the perceptions of players, parents, and coaches (i.e., the athletic triangle) regarding how they interacted and collaborated with one another during the COVID-19 pandemic to support wellbeing and performance, and; (b) to identify opportunities to enhance workings of those within the athletic triangle resulting from adaptions made following enforced lockdown. Using an interpretive description methodology, semi-structured interviews were conducted with five coaches, six players, and six parents from an English elite academy soccer club. Interviews were analyzed using thematic analysis. Findings highlighted (a) the importance of support and the different means of communication used between members of the athletic triangle to facilitate such support; (b) the increased understanding of each member of the athletic triangle, leading to enhanced relationships, and; (c) how members of the athletic triangle adapted practice to facilitate relationship development during the pandemic and beyond. The identification of these considerations has implications for coach and parent education initiatives to allow for optimal functioning of the athletic triangle as elite academy soccer clubs return from lockdown. These include (a) the importance of continued communication between coach, athlete and parent; (b) increasing understanding of each individual within the athletic triangle; and (c) utilizing key interpersonal and technological skills learnt during the lockdown to further facilitate engagement within the athletic triangle.

 

 

#6 Post-exercise Recovery Methods Focus on Young Soccer Players: A Systematic Review

Reference: Front Physiol. 2021 May 20;12:505149. doi: 10.3389/fphys.2021.505149. eCollection 2021.

Authors: Julio Calleja-González, Juan Mielgo-Ayuso, Álvaro Miguel-Ortega, Diego Marqués-Jiménez, Miguel Del Valle, Sergej M Ostojic, Jaime Sampaio, Nicolás Terrados, Ignacio Refoyo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8173167/pdf/fphys-12-505149.pdf

Summary: Prescription of post-match or post-training recovery strategies in young soccer players is a key point to optimize soccer performance. Considering that the effectiveness of recovery strategies may present interindividual variability, scientific evidence-based recovery methods and protocols used in adults are possibly not applicable to young soccer players. Therefore, the current systematic review primarily aimed to present a critical appraisal and summary of the original research articles that have evaluated the effectiveness of recovery strategies in young male soccer players and to provide sufficient knowledge regarding the effectiveness of the recovery methods and strategies. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines until November 31, 2020, using the next data bases: WOS, PubMed, Cochrane Library, Evidence Database (PEDro), Evidence Based Medicine (EBM) Search review, EMBASE, and Scopus. There were no filters applied.  A total of 638 articles were obtained in the initial search. After the inclusion and exclusion criteria, the final sample was 10 articles focusing on recovery in young male players. Neuromuscular performance can be recovered using WVB but not with SS, and water immersion protocols may also be useful, but their positive effects are not significant, and it is unable to distinguish the best water immersion method; match running performance maintenance may be achieved using water immersion protocols but no other recovery methods have been investigated; EIMD and inflammatory responses could be positively affected when water immersion and AR are applied, although SS seems to be ineffective; perceptual responses also seem to be better with CWI and WVB, but contradictory results have been found when AR is applied, and SS had no positive impact. Finally, it is important to consider that AR strategies may modify HR response and soccer-specific performance.

 

 

#7 Soccer player activity prediction model using an internet of things-assisted wearable system

Reference: Technol Health Care. 2021 May 27.  doi: 10.3233/THC-213010. Online ahead of print.

Authors: Lei Wu, Juan Wang, Long Jin, K Marimuthu

Summary: Soccer is one of the world's most successful sports with several players. Quality player's activity management is a tough job for administrators to consider in the Internet of Things (IoT) platform. Candidates need to predict the position, intensity, and path of the shot to look back on their results and determine the stronger against low shot and blocker capacities. In this paper, the IoT-assisted wearable device for activity prediction (IoT-WAP) model has been proposed for predicting the activity of soccer players. The accelerometer built wearable devices formulates the impacts of multiple target attempts from the prevailing foot activity model that reflect a soccer player's characteristics. The deep learning technique is developed to predict players' various actions for identifying multiple targets from the differentiated input data compared to conventional strategies. The Artificial Neural Network determines a football athlete's total abilities based on football activities like transfer, kick, run, sprint, and dribbling. The experimental results show that the suggested system has been validated from football datasets and enhances the accuracy ratio of 97.63%, a sensitivity ratio of 96.32%, and a specificity ratio of 93.33% to predict soccer players' various activities.

 

 

#8 Soccer, concussions, and safety: Perceptions of parents of youth soccer participants

Reference: J Safety Res. 2021 Jun;77:255-262.  doi: 10.1016/j.jsr.2021.03.008. Epub 2021 Mar 29.

Authors: Sungwon Kim, Daniel P Connaughton

Summary: The rate of concussions in youth soccer is among the highest of all youth sports. Parents play an important role in caring for their children and making decisions regarding whether they should participate in a sport, such as soccer, where concussions are well known. This study examined parental perceptions regarding: (a) coaches' role in concussion management, (b) heading restriction policies, and (c) overall concussion risk and participation issues. Online surveys were completed by 419 parents of youth soccer players who participated in the largest U.S. youth soccer programs nationwide. Findings indicated 44.5% of the respondents had considered keeping their children from playing organized soccer and 47.2% were concerned about a potential decline in youth soccer participation due to concussions. Nearly 69% of responding parents agreed that heading should be banned for participants 10 years old or younger, while 56.5% thought heading should not be limited for participants 13 or older. Only 35% of parents were very confident about their child's coach's ability to properly identify concussions and remove those suspected of a concussion from play. Parents' socioeconomic status (SES), soccer coaching and playing experience, and previous history of concussion(s) were key predictors of greater perceived risk about concussions. Findings from this study shed light on parents' perceptions about concussions and related safety issues in youth soccer. Understanding what parents believe about concussions is vital to preserve youth soccer participation and can be used to strengthen education and policies that promote a safer environment for youth sport participants. Practical Applications: Youth soccer coaches can benefit from stronger, comprehensive educational efforts at the league/club level. Additionally, parents of youth athletes who are in the lower SES communities should be targeted to receive concussion safety information and/or interventions that would improve their knowledge, attitude, and practices regarding concussion safety.

 

 

#9 Effects of 14-weeks betaine supplementation on pro-inflammatory cytokines and hematology status in professional youth soccer players during a competition season: a double blind, randomized, placebo-controlled trial 

Reference: Soc Sports Nutr. 2021 Jun 5;18(1):42.  doi: 10.1186/s12970-021-00441-5.

Authors: Hadi Nobari, Jason M Cholewa, Jorge Pérez-Gómez, Alfonso Castillo-Rodríguez

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8180114/pdf/12970_2021_Article_441.pdf

Summary: Systemic elevations in pro-inflammatory cytokines are a marker of non-functional over reaching, and betaine has been shown to reduce the secretion of pro-inflammatory cytokines in vitro. The aim of this study was to investigate the effects of betaine supplementation on tumor necrosis factor alpha (TNF-α), interleukins-1 beta (IL-1β), - 6 (IL-6) and the complete blood cell (CBC) count in professional youth soccer players during a competitive season. Twenty-nine soccer players (age, 15.5 ± 0.3 years) were randomly divided into two groups based on playing position: betaine group (BG, n = 14, 2 g/day) or placebo group (PG, n = 15). During the 14-week period, training load was matched and well-being indicators were monitored daily. The aforementioned cytokines and CBC were assessed at pre- (P1), mid- (P2), and post- (P3) season. Significant (p < 0.05) group x time interactions were found for TNF-α, IL-1β, and IL-6. These variables were lower in the BG at P2 and P3 compared to P1, while IL-1β was greater in the PG at P3 compared to P1 (p = 0.033). The CBC count analysis showed there was significant group by time interactions for white blood cells (WBC), red blood cells (RBC), hemoglobin (Hb), and mean corpuscular hemoglobin concentration (MCHC). WBC demonstrated increases at P3 compared to P2 in PG (p = 0.034); RBC was less at P3 compared to P1 in BG (p = 0.020); Hb was greater at P2 compared to P1, whilst it was less at P3 compared to P3 for both groups. MCHC was greater at P3 and P2 compared to P1 in BG, whereas MCHC was significantly lower at P3 compared to P2 in the PG (p = 0.003). The results confirmed that 14 weeks of betaine supplementation prevented an increase in pro-inflammatory cytokines and WBC counts. It seems that betaine supplementation may be a useful nutritional strategy to regulate the immune response during a fatiguing soccer season.

 

 

#10 Assessment of Muscle Volume Using Magnetic Resonance Imaging (MRI) in Football Players after Hamstring Injuries

Reference: Eur J Sport Sci. 2021 Jun 10;1-17.  doi: 10.1080/17461391.2021.1942226. Online ahead of print.

Authors: Nils Mühlenfeld MD, Ida Bo Steendahl, Daniel P Berthold MD, Tim Meyer MD, Thomas Hauser MD, Nils Wagner MD, Anna-Lena Sander MD, Ingo Marzi MD, Benjamin Kaltenbach MD, Ibrahim Yel MD, Thomas Vogl MD, Katrin Eichler MD

Summary: Muscle injuries of the hamstrings are among the most frequent in football and a main cause for significant time away from training and competition. The purpose of this study was to prospectively evaluate the loss of muscle volume in recreational football players three and six weeks after initial trauma. We hypothesized that significant muscle volume loss occurs within 6 weeks after the initial injury event. Twenty recreational football players (mean-age=25 ± 4years; mean-height=181 ± 8cm; mean-weight=81 ± 10kg) with type3a (minor partial muscle tear) and type3b (moderate partial muscle tear) injuries were included. Muscle volume was determined using established methods for the hamstrings and the quadriceps femoris muscle within 3 days and after 3 and 6 weeks following the initial injury. The injured hamstrings lost 6.5% (mean=64cm3(95%CI=31-98cm3),p<0.001), the healthy hamstrings lost 2.1% (mean=21cm3(3-44cm3),p=0.096) of muscle volume after six weeks. The quadriceps in the injured leg lost 3.8% (mean=78cm3(51-104cm3),p<0.001) and 4.5% (83cm3(45-121cm3),p<0.001) in the healthy leg. Muscle volume loss inversely correlated with activity levels in the healthy leg for the quadriceps (r=0.96(0.90-0.98);R2=0.92;p<0.001) and the hamstrings (r=0.72(0.40-0.88);R2=0.51;p<0.001), as well as the quadriceps in the injured leg (r=0.70(0.37-0.87);R2=0.49;p<0.001), but not the injured hamstrings. Muscle volume ratio of hamstrings to quadriceps in the control limb was 0.52 ± 0.06 and 0.53 ± 0.06 in the injured leg. The rehabilitation period of six weeks did not have a relevant negative or a positive effect on ratios. Significant muscle volume loss in the upper thigh occurs in recreational soccer players within three, and within six weeks after a hamstring injury and lies between 2 and 7%.

 

 

#11 Ticks on the turf: investigating the presence of ixodid ticks on and around football fields in Germany

Reference: Exp Appl Acarol. 2021 Jun 9.  doi: 10.1007/s10493-021-00628-0. Online ahead of print.

Authors: Olaf Kahl, Daniel Kämmer, Ingrid Bulling, Martin Komorek, Christof von Eiff, Claudius Malerczyk

Download link: https://link.springer.com/content/pdf/10.1007/s10493-021-00628-0.pdf

Summary: Ixodes ricinus is the most abundant tick species and an important vector of pathogens in Germany and in large parts of Europe. A few other ixodid tick species, e.g., Dermacentor reticulatus, may also be of eco-epidemiological relevance. As ticks are not only found in natural but also in suburban areas (parks, gardens), the present study investigated whether ticks occur on and near football grounds thus posing a potential risk to players and visitors. Thirty-two football grounds from all 16 German federal states were selected, mainly situated adjacent to a green area (forest, park). Ticks were collected by the conventional flagging method in spring 2018, and nymphs and adults were counted and morphologically determined. Altogether 807 nymphal and adult ticks were collected from 29 football grounds: 714 I. ricinus, 64 Ixodes inopinatus, 2 Ixodes frontalis, 24 Ixodes sp. ticks, and 3 D. reticulatus. Ixodes inopinatus was found in 13 out of 16 German states. Three ticks were even found on the turf of two football fields. It can be concluded that ticks occur quite frequently and sometimes in high abundance near football grounds situated close or adjacent to a forest or a park.

 

 

#12 Finding Neymar: The Role of Colour in the Detection and Discrimination of Football Kits

Reference: Perception. 2021 Jun 9;3010066211019370.  doi: 10.1177/03010066211019370. Online ahead of print.

Authors: Liam Burnell, Peter Thompson

Download link: https://journals.sagepub.com/doi/pdf/10.1177/03010066211019370

Summary: Association Football (hereafter football) is a fast-moving sport in which rapid decisions need to be made; where are other players, are they on my team? Two experiments investigated how kit variations affect the search of teammates. Experiment 1 confirmed that discriminability is slower when playing in crossed kits (e.g., red shirts-blue shorts vs. blue shirts-red shorts), versus uniform kits (e.g., all red vs. all blue). Experiment 2 found that there is significant confusion when both teams wear the same-coloured shorts. Based on these findings, we suggest changes to the Laws of the game concerning kit colours.

 

 

#13 Load Monitoring Practice in European Elite Football and the Impact of Club Culture and Financial Resources

Reference: Front Sports Act Living. 2021 May 20;3:679824. doi: 10.3389/fspor.2021.679824. eCollection 2021.

Authors: Kobe C Houtmeyers, Jos Vanrenterghem, Arne Jaspers, Ludwig Ruf, Michel S Brink, Werner F Helsen

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8173105/pdf/fspor-03-679824.pdf

Summary: Load monitoring is considered important to manage the physical training process in team sports such as Association Football. Previous studies have described the load monitoring practices of elite English football clubs and clubs with an established sports-science department. An examination of a broader international sample is currently not available. In addition, previous research has suggested factors that may improve the implementation of load monitoring practices, such as a strong club belief on the benefit of evidence-based practice (EBP) and high club financial resources. However, no study has examined yet the actual impact of these factors on the monitoring practices. Therefore, this study aims (1) to provide an overview of load monitoring practices in European elite football and (2) to provide insight into the differences in implementation between clubs by examining the impact of the club beliefs on the benefit of EBP and the club financial resources. An online survey, consisting of multiple choice and Likert scale questions, was distributed among sports-science and sports-medicine staff (n = 99, 50% response rate). Information was asked about the types of data collected, collection purposes, analysis methods, and staff involvement. The results indicated that external load data (e.g., global navigation satellite system, accelerometer…) was collected the most whilst respondents also indicated to collect internal load (e.g., heart rate, rating of perceived exertion…) and training outcome data (e.g., aerobic fitness, neuromuscular fatigue…) for multiple purposes. Considerable diversity in data analysis was observed suggesting that analysis is often limited to reporting the gathered data. Sports-science staff were responsible for data collection and analysis. Other staff were involved in data discussion to share decision-making. These practices were positively impacted by a stronger club belief on the benefit of EBP and greater financial resources. Creating an organizational culture, characterized by a strong belief on the benefit of EBP, is important to increase the impact of load monitoring. However, the actual potential may still be largely determined by financial resources. High-level clubs could therefore play a leading role in generating and sharing knowledge to improve training practices and player health.

 

 

#14 Reliability, validity, and maturation-related differences of frontal and sagittal plane landing kinematic measures during drop jump and tuck jump screening tests in male youth soccer players

Reference: Phys Ther Sport. 2021 May 28;50:206-216. doi: 10.1016/j.ptsp.2021.05.009. Online ahead of print.

Authors: Francisco Javier Robles-Palazón, Iñaki Ruiz-Pérez, Jon L Oliver, Francisco Ayala, Pilar Sainz de Baranda

Download link: https://reader.elsevier.com/reader/sd/pii/S1466853X21000900?token=CC5594794C0BA774F02926F24815E5404256437FB4FF25462DE76D16E32AF7BA7A7E4874337104AC561887ADAA92947E&originRegion=eu-west-1&originCreation=20210619112817

Summary: The aim was to determine the inter-rater and intra-rater reliability of frontal and sagittal plane landing kinematic measures during drop jump (DVJ) and tuck jump (TJA) tasks in male youth soccer players, to assess the concurrent validity between DVJ and TJA tests, and to evaluate the ability of both tasks to detect differences between players' stage of maturation. 223 male youth soccer players participated. Frontal plane knee projection angles (FPPA), and hip (HF), knee (KF) and ankle (AF) flexion angles at initial contact (IC) and peak flexion (PF) (i.e., the deepest landing position) in the sagittal plane were assessed. Good-to-excellent inter- and intra-rater reliability (ICC > 0.75; TEMST < 0.3; CVTE < 5%) for the FPPA, HF and KF during DVJ and TJA tasks were found. A low concurrent validity between DVJ and TJA measures was reported. Differences by maturity status (BF10 > 10; error < 10; δ > 0.6) were only identified for the TJA. Pre-PHV group reported higher FPPA, HF-IC, HF-PF, and KF-IC values, as well as lower AF-IC than post-PHV. Pre-PHV also displayed greater HF-IC and KF-IC than circa-PHV group. Although both tests are reliable, the TJA might be viewed as a more informative tool given it shows greater FPPA and can also detect differences by maturity status.

 

Thu

25

Nov

2021

Win, Draw, or Lose? GPS-Based Variables’ Effect on the Match Outcome: A Full-Season Study on an Iranian Professional Soccer Team

The aim of the study was to determine the between-match and between-halves match variability of various Global Positioning System (GPS) variables and metabolic power average (MPA) in competitions, based on the match results obtained by professional soccer players over a full season.

Tue

23

Nov

2021

Match-related physical performance in professional soccer: Position or player specific?

The purpose of this study was to examine to what extent the physical match performance of professional soccer players is both position and player specific.

Fri

29

Oct

2021

Latest research in football - week 35 - 2021

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 Effects of including endurance and speed sessions within small-sided soccer games periodization on physical fitness

Reference: Biol Sport. 2021 Jun;38(2):291-299.  doi: 10.5114/biolsport.2021.99325. Epub 2020 Oct 22.

Authors: Daniel Castillo, Javier Raya-González, Hugo Sarmento, Filipe Manuel Clemente, Javier Yanci

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8139358/pdf/JBS-38-99325.pdf

Summary: The main aim of this study was to analyse the effects of including additional speed and endurance sessions during small-sided games (SSG) training periodization on physical fitness in professional soccer players. Sixteen outfield players (age = 25.6 ± 7.6 years) who competed in the First Division of a European League participated in this study. Players were randomly assigned to perform only the SSG periodization (G-SSG group) or to add endurance and speed training contents to the SSG (ES-SSG group). Before and after the 6-week experimental period, a Yo-Yo Intermittent Recovery Test level 1 (YYIR1) and a 40 m sprinting test were performed. Rating of perceived exertion (RPE) was also measured after each training session. The G-SSG group showed a large improvement in the YYIR1 performance (p = 0.018-0.028; ES = 0.521-0.576) after the training programme, whereas no significant changes were observed for the ES-SSG group (p = 0.763-1.000; ES = 0.000-0.014). In addition, no significant differences (p > 0.05, ES = 0.005-361, trivial to small) in sprint performance at 5 and 10 m intervals up to 40 m were observed at post-training in comparison to pre-training evaluation in G-SSG and ES-SSG groups. No significant differences (p > 0.05) between groups were observed at baseline in the YYIR1 test. The 6-week SSG training supported with only six endurance and speed training sessions was no more effective than well-organized SSG alone for improving running endurance in professional soccer players.

 

 

#2 Performance and reference data in the jump squat at different relative loads in elite sprinters, rugby players, and soccer players

Reference: Biol Sport. 2021 Jun;38(2):219-227.  doi: 10.5114/biolsport.2020.98452. Epub 2020 Aug 31.

Authors: Irineu Loturco, Michael R McGuigan, Tomás T Freitas, Pedro L Valenzuela, Lucas A Pereira, Fernando Pareja-Blanco

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8139350/pdf/JBS-38-98452.pdf

Summary: The aims of this study were to compare the outcomes and provide reference data for a set of barbell mechanical parameters collected via a linear velocity transducer in 126 male sprinters (n = 62), rugby players (n = 32), and soccer players (n = 32). Bar-velocity, bar-force, and bar-power outputs were assessed in the jump-squat exercise with jump-squat height determined from bar-peak velocity. The test started at a load of 40% of the athletes' body mass (BM), and a load of 10% of BM was gradually added until a clear decrement in the bar power was observed. Comparisons of bar variables among the three sports were performed using a one-way analysis of variance. Relative measures of bar velocity, force, and power, and jump-squat height were significantly higher in sprinters than in rugby (difference ranging between 5 and 35%) and soccer (difference ranging between 5 and 60%) players across all loads (40-110% of BM). Rugby players exhibited higher absolute bar-power (mean difference = 22%) and bar-force (mean difference = 16%) values than soccer players, but these differences no longer existed when the data were adjusted for BM (mean difference = 2.5%). Sprinters optimized their bar-power production at significantly greater relative loads (%BM) than rugby (mean difference = 22%) and soccer players (mean difference = 25%); nonetheless, all groups generated their maximum bar-power outputs at similar bar velocities. For the first time, we provided reference values for the jump-squat exercise for three different bar-velocity measures (i.e., mean, mean propulsive, and peak velocity) for sprinters, rugby players, and soccer players, over a wide range of relative loads. Practitioners can use these reference values to monitor their athletes and compare them with top-level sprinters and team-sport players.

 

 

#3 Effect of formation, ball in play and ball possession on peak demands in elite soccer

Reference: Biol Sport. 2021 Jun;38(2):195-205.  doi: 10.5114/biolsport.2020.98450. Epub 2020 Sep 1.

Authors: Andrea Riboli, Marco Semeria, Giuseppe Coratella, Fabio Esposito

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8139352/pdf/JBS-38-98450.pdf

Summary: This study examined the most demanding passages of match play (MDP) and the effects of playing formation, ball-in-play (BiP) time and ball possession on the 1-min peak (1-minpeak) demand in elite soccer. During 18 official matches, 305 individual samples from 223 Italian Serie A soccer players were collected. MDP and 1-minpeak were calculated across playing position (central defenders, wide defenders, central midfielders, wide midfielders, wide forwards and forwards). Maximum relative (m·min-1) total distance (TD), high-speed running (HSR), very high-speed running (VHSR), sprint (SPR), acceleration/deceleration (Acc/Dec), estimated metabolic power (Pmet) and high-metabolic load (HML) distance were calculated across different durations (1-5, 10, 90 min) using a rolling method. Additionally, 1-minpeak demand was compared across playing formation (3-4-1-2, 3-4-2-1, 3-5-2, 4-3-3, 4-4-2), BiP and ball/no-ball possession cycles. MDP showed large to verylarge [effect-size (ES): 1.20/4.06] differences between 1-minpeak vs all durations for each parameter. In 1-minpeak, central midfielders and wide midfielders achieved greater TD and HSR (ES:0.43/1.13) while wide midfielders and wide forwards showed greater SPR and Acc/Dec (ES:0.30/1.15) than other positions. For VHSR, SPR and Acc/Dec 1-minpeak showed fourfold higher locomotor requirements than 90-min. 1-minpeak for Acc/Dec was highest in 4-3-3 for forwards, central and wide midfielders. 1-minPeak was lower during peak BiP (BiPpeak) for HSR, VHSR and Acc/Dec (ES: -2.57/-1.42). Comparing with vs without ball possession, BiPpeak was greater (ES: 0.06/1.48) in forwards and wide forwards and lower (ES: -2.12/-0.07) in central defenders and wide defenders. Positional differences in MDP, 1-minpeak and BiPpeak were observed. Soccer-specific drills should account for positional differences when conditioning players for the peak demands. This may help practitioners to bridge the training/match gap.

 

 

#4 Session-to-session variations in external load measures during small-sided games in professional soccer players

Reference: Biol Sport. 2021 Jun;38(2):185-193. doi: 10.5114/biolsport.2020.98449. Epub 2020 Aug 28.

Authors: Saeid Younesi, Alireza Rabbani, Filipe Manuel Clemente, Hugo Sarmento, António J Figueiredo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8139343/pdf/JBS-38-98449.pdf

Summary: The aims of this study were 1) to analyse session-to-session variations in different external load measures and 2) to examine differences in within-session intervals across different small-sided game (SSG) formats in professional players. Twenty professional soccer players (mean ± SD; age 28.1 ± 4.6 years, height 176.7 ± 4.9 cm, body mass 72.0 ± 7.8 kg, and body fat 10.3 ± 3.8%) participated in 3v3, 4v4, and 6v6 SSGs under different conditions (i.e., touch limitations and presence of goalkeepers vs. free touch and ball possession drill) over three sessions. Selected external load measures-including total distance (TD), high-intensity running (HIR, distance covered > 14.4 km.h-1), high-speed running (HSR, distance covered > 19.8 km.h-1), and mechanical work (MW, accelerations and deceleration > 2.2 m.s2)-were recorded using GPS technology during all SSG sessions. Small to large standardized typical errors were observed in session-to-session variations of selected measures across SSGs. TD.min-1 showed less variability, having a coefficient of variation (CV) of 2.2 to 4.6%, while all other selected external load measures had CV values ranging from 7.2% to 29.4%. Trivial differences were observed between intervals in TD.min-1 and HIR.min-1 for all SSGs, as well as in HSR.min-1 and MW.min-1 for most SSG formats. No reductions or incremental trends in session-to-session variations were observed when employing touch limitations or adding goalkeepers. The increased noise observed in higher speed zones (e.g., high-speed running) suggests a need for more controlled, running-based conditional drills if the aim is greater consistency in these measures.

 

 

#5 Effects of 1 vs. 2 sessions per week of equal-volume sprint training on explosive, high-intensity and endurance-intensive performances in young soccer players

Reference: Biol Sport. 2021 Jun;38(2):175-183.  doi: 10.5114/biolsport.2020.97675. Epub 2020 Aug 31.

Authors: Hamza Marzouki, Ibrahim Ouergui, Nidhal Doua, Nebil Gmada, Anissa Bouassida, Ezdine Bouhlel

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8139356/pdf/JBS-38-97675.pdf

Summary: The study aimed to evaluate the effects of 1 vs. 2 sessions per week of equal-volume sprint training on explosive, high-intensity and endurance-intensive performances among young soccer players. Thirty-six young male soccer players were randomly divided into 2 experimental groups that performed either a single weekly sprint training session (ST1, n = 18, age: 17.2 ± 0.8 years) or two weekly sprint training sessions (ST2, n = 18; age: 17.1 ± 0.9 years) of equal weekly and total volume, in addition to their regular soccer training regimen. Linear sprinting (10 m, 20 m, 30 m, and flying 10 m), T-test agility, countermovement jump (CMJ) and maximal oxygen consumption were assessed one week before (T1), in the middle (T2) and immediately after the 10 weeks of training (T3). A large magnitude and statistically significant main effect for time was found in all the assessed variables after both training interventions (all p < 0.001; ES ≥ 0.80). No main effect was observed between the 2 groups at any time in linear sprinting, T-test or CMJ test (p > 0.05; ES < 0.20). A significant interaction effect (F = 4.05; p = 0.04, ES = 0.21) was found for maximal oxygen consumption with ST2 inducing better performance than ST1 (p = 0.001; ES = 1.11). Our findings suggested that the two sprint training frequencies were effective in enhancing explosive, high-intensity and endurance-intensive performances. However, it is recommended for coaches and fitness coaches to use a biweekly sprint training modality as it was found to be more effective in improving endurance-intensive performance.

 

 

#6 The first, second, and third most demanding passages of play in professional soccer: a longitudinal study

Reference: Biol Sport. 2021 Jun;38(2):165-174. doi: 10.5114/biolsport.2020.97674. Epub 2020 Aug 25.

Authors: José M Oliva-Lozano, Víctor Fortes, José M Muyor

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8139346/pdf/JBS-38-97674.pdf

Summary: The study aimed to compare the physical demands required during the first, second, and third most demanding passages (MDP) of play considering the effect of playing position, type of passage, and passage duration. A longitudinal study for three mesocycles was conducted in a professional soccer team competing in LaLiga123. Tracking systems collected total distance covered (DIS), high-speed running distance (HSRD), sprinting distance (SPD), total of high-intensity accelerations (ACCHIGH), and total of high-intensity decelerations (DECHIGH). The results confirmed that a significant effect of the type of passage (first, second or third MDP of play) on DIS (F(1.24, 178.89) = 115.53; p = 0.01; ηp2 = 0.45), HSRD (F(1.35, 195.36) = 422.82; p = 0.01; ηp2 = 0.75), SPD (F(1.43, 206.59) = 299.99; p = 0.01; ηp2 = 0.68), ACCHIGH (F(1.45, 209.38) = 268.59; p = 0.01; ηp2 = 0.65), and DECHIGH (F(1.45, 209.38) = 324.88; p = 0.01; ηp2 = 0.69) was found. In addition, a significant interaction between playing position, type and duration of the passage was observed in DIS (F(12.60, 453.47) = 1.98; p = 0.02; ηp2 = 0.05) and ACCHIGH (F(13.99, 503.78) = 1.92; p = 0.03; ηp2 = 0.06). In conclusion, significant differences in physical demands between the first, second, and third MDP of play were observed. However, there were some cases (DIS and ACCHIGH) in which no significant differences were found between these passages. Therefore, coaches should consider not only the magnitude of these peak intensity periods (e.g., distance covered per minute) but also the number of passages that players may experience during match play.

 

 

#7 Mucoid degeneration of the posterior cruciate ligament in a college soccer player: a case report

Reference: J Med Case Rep. 2021 Jun 3;15(1):284.  doi: 10.1186/s13256-021-02893-4.

Authors: Ryo Kanto, Hiroshi Nakayama, Tomoya Iseki, Shintaro Onishi, Ryo Iwakura, Shinichi Yoshiya, Toshiya Tachibana

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8173834/pdf/13256_2021_Article_2893.pdf

Summary: To the best of our knowledge, arthroscopic treatment for symptomatic mucoid degeneration of the posterior cruciate ligament in young athletes has not been reported before. An 18-year-old Asian male college soccer player presented with a 3-month history of right knee pain without episodes of trauma. Despite conservative treatment over the preceding 3 months, his symptoms persisted. Physical examination of the right knee revealed full range of motion, though posterior knee pain was induced when the knee approached full flexion. On ligament examination, posterior sagging and Lachman test were negative, and no clinical finding indicative of ligament insufficiency was noted. Magnetic resonance imaging showed a diffusely thickened posterior cruciate ligament with increased signal intensity on the T2-weighted sequence. A few intact fibers were observed with continuous margin from origin to insertion. Based on the patient's history and the magnetic resonance imaging findings, we suspected mucoid degeneration of the posterior cruciate ligament as the cause of the patient's symptoms. Since conservative treatment had failed to relieve the symptoms, arthroscopic treatment was indicated. Arthroscopic examination revealed yellowish crumbly tissues along the thickened posterior cruciate ligament. Tension and bulk of the posterior cruciate ligament were well preserved. Curettage of degenerative tissue and decompression of the posterior cruciate ligament resulted in symptom relief without instability of the knee joint. The patient returned to play at 3 months. At 12 months, postoperative magnetic resonance imaging showed no evidence of recurrence and indicated that the remaining posterior cruciate ligament was thicker than before the surgery. At 2 years follow-up, the patient remained asymptomatic and could play soccer at the same level as before the onset of pain.

 

 

#8 Testosterone, cortisol, vitamin D and oxydative stress and their relationships in professional soccer players

Reference: J Sports Med Phys Fitness. 2021 Jun 1. doi: 10.23736/S0022-4707.21.12094-8. Online ahead of print.

Authors: Michele Abate, Luigi DI Carlo, Giulio Cocco, Antonino Cocco, Vincenzo Salini

Summary: The testosterone/cortisol ratio has been used in sport physiology to evaluate the balance between anabolism and catabolism; its decrease below 30% has been considered a marker of overtraining. In this framework recent studies in soccer players have investigated the relationships between testosterone, cortisol, vitamin D and reactive oxygen species, but with unconvincing results. The aim of the present study was to evaluate the behavior of such biological parameters and their relationships both in winter (the season of championship) and in summer (off-competition season), characterized by different homeostatic situations. Twenty-seven professional male football players (Second Italian Division), were studied. Blood levels of free testosterone, cortisol, vitamin D and reactive oxygen species were evaluated in August (pre-season training) and in February, in the midseason. A comparison between these two periods was performed and for each of them the relationships between the biological parameters were evaluated. Blood levels of testosterone were higher during summer whereas those of cortisol were higher in winter. Vitamin D levels were higher in summer; in this season a positive significant relationship between vitamin D and testosterone was observed (p=0.001), but not in winter (p=0.592). Reactive oxygen species were higher in winter; in this season a significant positive relationship between these substances and cortisol was observed (0.000), but not in summer (p=0.325). In professional soccer players it was found a positive relationship between vitamin D and testosterone in summer and between reactive oxygen species and cortisol in winter. However the question whether such results are genuine cause-effect relationships or mere casual or spurious statistical correlations is still unsolved. As matter of fact, such results could be dependent from other determinants which might drive the aforementioned biological parameters in the same direction. These conclusions must be considered valid only in relation to the experimental conditions (training workload, diet and sun exposure) of the present study.

 

 

#9 Relationship of regional and whole body morphology to vertical jump in elite soccer players: a data-driven approach

Reference: J Sports Med Phys Fitness. 2021 Jun 1. doi: 10.23736/S0022-4707.21.12323-0. Online ahead of print.

Authors: Tindaro Bongiovanni, Alessio Rossi, F Marcello Iaia, Angela DI Baldassarre, Giulio Pasta, Paolo Manetti, Giampietro Alberti, Athos Trecroci

Summary: This study aimed to analyse the relationship of regional and whole body morphology to vertical jump performance and to compare the morphological features outlining high and low performers in professional soccer players. Twenty-one male soccer players were recruited. Whole and regional (upper and lower limbs) features were obtained in the form of body dimensional measurements. Then, all players were tested for vertical jump performance. A data-driven approach was used to group players according to their jump performance parameters (high vs low). The regional morphological features presented higher correlations with vertical jump than whole body features. High and low performers were significantly different among upperand lower-limb morphology. No differences were observed among whole body features. These findings indicate that, rather than the whole body, the use of morphological features linked to specific body regions may ensure a better interpretation of the soccer players' physical potential in jump performance.

 

 

#10 The role of pre-season health characteristics as injury risk factors in female adolescent soccer players

Reference: J Phys Ther Sci. 2021 May;33(5):439-443. doi: 10.1589/jpts.33.439. Epub 2021 May 15.

Authors: Brent Harper, Adrian Aron, Emmanuel John

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8165364/pdf/jpts-33-439.pdf

Summary: Determine if female adolescent soccer players with a history of concussion, impaired K-D scores, and pre-season subjective complaints of neck pain, dizziness, and headache were predisposed to additional risk of musculoskeletal or concussive injury during 10-weeks of competitive play. [Participants and Methods] Twenty-three female high school soccer athletes provided concussion history and reported pre-season subjective complaints. K-D testing was performed pre and postseason. During the 10-week season, all injuries, preventing participation in practice or game, were recorded. [Results] Six reported a history of concussion. Of those six, three injuries were reported, including two concussions and a hamstring strain. Baseline K-D scores were worse in athletes that had two or more pre-season subjective factors compared to those that did not have any. Moderate positive correlations were found between a history of concussion and the number of injuries and a history of concussion and K-D post-test scores. [Conclusion] Findings indicate that pre-season subjective factors of neck pain, dizziness and headache, history of concussion, and K-D potentially increased injury risk. Combining pre-season metrics both at baseline and during the course of the season may assist in better injury risk screening in-season or indicate suboptimal function due to cumulative effects.

 

 

#11 The relation between neck strength and psychological distress: preliminary evidence from collegiate soccer athletes

Reference: Concussion. 2021 May 14;6(2):CNC91. doi: 10.2217/cnc-2020-0023.

Authors: Tara Porfido, Nicola L de Souza, Allison M Brown, Jennifer F Buckman, Brian D Fanning Jr, James S Parrott, Carrie Esopenko

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8162191/pdf/cnc-06-91.pdf

Summary: The aim was to examine whether neck strength and symmetry are associated with psychological function in athletes with exposure to repetitive head impacts. Collegiate soccer (n = 29) and limited/noncontact (n = 63) athletes without a history of concussion completed the Brief Symptom Inventory 18 and assessments of isometric neck strength. Neck strength symmetry was calculated as the difference in strength between opposing muscle groups. The results demonstrated that lower neck strength was associated with more symptoms of anxiety, whereas asymmetry in neck strength was associated with more symptoms of somatization and depression in soccer athletes only. These preliminary results suggest that greater neck strength/symmetry is related to better psychological function in athletes who have higher exposure to repetitive head impacts.

 

 

#12 Short-Term Periodized Programming May Improve Strength, Power, Jump Kinetics, and Sprint Efficiency in Soccer

Reference: J Funct Morphol Kinesiol. 2021 May 24;6(2):45. doi: 10.3390/jfmk6020045.

Authors: Ai Ishida, S Kyle Travis, Michael H Stone

Download link: https://www.mdpi.com/2411-5142/6/2/45/htm

Summary: The purpose of this study was to examine if short-term periodized programming may improve strength, power, jump kinetics, and sprint efficiency in soccer. Seventeen players (19.6 ± 1.6 yrs; 73.8 ± 8.2 kg; 1.77 ± 0.6 m) were divided into two groups based on mean isometric midthigh pull peak force (IPF) (stronger and weaker) and squat jump (SJ) peak power (PP) (higher power and lower power). Eight weaker players were included in the lower power group, while six stronger players were included in the higher power group. Block periodization was adopted to design strength training consisting of 3-week strength endurance and 4-week maximum strength blocks. Performance data included SJ with polyvinyl chloride pipe (SJ0), 20 kgs bar (SJ20), and 40 kgs (SJ40) bar and 20 m sprint across three time points (baseline: TB; post-block 1: T1; post-block 2: T2). Stronger group showed significant increases from TB to T2 in SJ20 peak power (PP), net impulse, and allometrically-scaled PP (p = 0.005 to 0.01, ES = 0.32 to 0.49). Weaker group demonstrated moderate to large increases from TB to T2 in SJ20, allometrically-scaled peak force (PF), PP, and allometrically-scaled PP (p = <0.001 to 0.04, ES = 1.41 to 1.74). Lower power group showed significant increases from TB to T2 in SJ20 allometrically-scaled PF, net impulse, PP, and allometrically-scaled PP (p = <0.001 to 0.026, ES = 1.06 to 2.01). Weaker and less powerful soccer players can benefit from strength-focused training to improve loaded SJ kinetics associating with force production.

 

 

#13 A Comparison of Match Demands Using Ball-in-Play versus Whole Match Data in Professional Soccer Players of the English Championship

Reference: Sports (Basel). 2021 May 26;9(6):76. doi: 10.3390/sports9060076.

Authors: Dylan Mernagh, Anthony Weldon, Josh Wass, John Phillips, Nimai Parmar, Mark Waldron, Anthony Turner

Download link: https://www.mdpi.com/2075-4663/9/6/76/htm

Summary: This is the first study to report the whole match, ball-in-play (BiP), ball-out-of-play (BoP), and Max BiP (worst case scenario phases of play) demands of professional soccer players competing in the English Championship. Effective playing time per soccer game is typically <60 min. When the ball is out of play, players spend time repositioning themselves, which is likely less physically demanding. Consequently, reporting whole match demands may under-report the physical requirements of soccer players. Twenty professional soccer players, categorized by position (defenders, midfielders, and forwards), participated in this study. A repeated measures design was used to collect Global Positioning System (GPS) data over eight professional soccer matches in the English Championship. Data were divided into whole match and BiP data, and BiP data were further sub-divided into different time points (30-60 s, 60-90 s, and >90 s), providing peak match demands. Whole match demands recorded were compared to BiP and Max BiP, with BiP data excluding all match stoppages, providing a more precise analysis of match demands. Whole match metrics were significantly lower than BiP metrics (p < 0.05), and Max BiP for 30-60 s was significantly higher than periods between 60-90 s and >90 s. No significant differences were found between positions. BiP analysis allows for a more accurate representation of the game and physical demands imposed on professional soccer players. Through having a clearer understanding of maximum game demands in professional soccer, practitioners can design more specific training methods to better prepare players for worst case scenario passages of play.

 

 

#14 Sleep Quality in Chilean Professional Soccer Players

Reference: Int J Environ Res Public Health. 2021 May 29;18(11):5866. doi: 10.3390/ijerph18115866.

Authors: Carlos Jorquera-Aguilera, Guillermo Barahona-Fuentes, María José Pérez Peña, María Mercedes Yeomans Cabrera, Álvaro Huerta Ojeda

Download link: https://www.mdpi.com/1660-4601/18/11/5866/htm

Summary: Recent research has shown that good sleep quality has a positive effect on physical performance. However, sleep quality in Chilean professional soccer players is unknown. The purpose of this study was to determine sleep quality in Chilean professional soccer players. It was a cross-sectional, explanatory study with observable variables. The sample consisted of 94 Chilean male soccer players belonging to four professional clubs. The main variable was the Sleep Quality Index, evaluated through the Pittsburgh questionnaire (Spanish version). After estimating sleep quality individually, the four professional soccer clubs' comparison was performed through a one-factor ANOVA. The Pearson test was used to relate the questionnaire variables; the significance level was p < 0.05. In the global analysis of the Pittsburgh Sleep Quality Index, a value of 4.75 ± 2.29 on a scale of 0-21 was observed, with no significant differences between the clubs evaluated (p > 0.05). Based on the results obtained, Chilean male professional soccer players present good sleep quality. However, the high values of "sleep latency" and "sleep disturbances" are indicators that should be worked on by the multidisciplinary team of each professional club. They should develop strategies to improve sleep hygiene, encourage good sleep, and fall asleep efficiently.

 

 

#15 Relationship between Respiratory Muscle Function and Postural Stability in Male Soccer Players: A Case-Control Study

Reference: Healthcare (Basel). 2021 May 29;9(6):644. doi: 10.3390/healthcare9060644.

Authors: Felipe León-Morillas, Carlos Lozano-Quijada, Miguel Ángel Lérida-Ortega, Martha Cecilia León-Garzón, Alfonso Javier Ibáñez-Vera, Silvana Loana de Oliveira-Sousa

Download link: https://www.mdpi.com/2227-9032/9/6/644/htm

Summary: The important role of postural stability in exercise performance has been determined by several authors. Despite this, few studies have analyzed the relationship between respiratory muscles' strength and postural stability in athletes. For this reason, the aim of this study was to investigate the relationship between postural stability and respiratory muscles' function in male soccer players. A case-control study was conducted over twenty-eight healthy men (18 soccer players; 10 non-athletes). Inspiratory muscle strength (MIP) and respiratory resistance (MVV) were obtained through a digital spirometer. Stability variables were obtained in standing position on a stabilometric platform and in open and closed eyes conditions. The area and length of the center of pressures and displacements in the X and Y range were analyzed. Pearson's coefficient was used to measure the linear correlation between MIP, MVV and stabilometric variables. In the soccer players' group, MIP and MIP % predictive were inversely correlated with length (r = -0.535 and r = -0.585; p < 0.05) and X range (r = -0.527 and r = -0.560; p < 0.05), whereas MVV was directly correlated with length (r = 0.606; p < 0.01) and Y range (r = 0.558; p < 0.05). Our results show that the greater the inspiratory muscle strength, the less displacement of the pressure center, while at higher respiratory rates there is greater displacement.

 

Wed

27

Oct

2021

Effects of Match Location, Opposition and Match Outcome on Running Performance in a Portuguese Professional Football Team

The aim of this study was to analyze the effects of match location, quality of opposition and match outcome on match running performance according to playing position in a Portuguese professional football team.

Tue

26

Oct

2021

Quantifying Accelerations and Decelerations in Elite Women Soccer Players during Regular In-Season Training as a Training Load Index

Accelerations (ACC) and decelerations (DEC) are important actions in soccer. We aimed to investigate whether ACC and DEC were good indicators of the variation of training loads. Changes in the training load were monitored during two different selected weeks (considered a “low week” and a “heavy week”) during the in-season.

Fri

22

Oct

2021

Latest research in football - week 34 - 2021

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 Understanding gender differences in professional European football through machine learning interpretability and match actions data

Reference: Sci Rep. 2021 May 24;11(1):10805.  doi: 10.1038/s41598-021-90264-w.

Authors: Marc Garnica-Caparrós, Daniel Memmert

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8144211/pdf/41598_2021_Article_90264.pdf

Summary: After the great success of the Women's World Cup in 2019, several platforms have started identifying the reasons for gender inequality in European football. Even though these inequalities emerge from a variety of key aspects in the modern sport, we focused on the game and evaluated the main differential features of European male and female football players in match actions data under the assumption of finding significant differences and established patterns between genders. A methodology for unbiased feature extraction and objective analysis is presented based on data integration and machine learning explainability algorithms. Female ([Formula: see text]) and male ([Formula: see text]) data points were collected from event data and categorized by game period and player position. We set up a supervised classification pipeline to predict the gender of each player by looking at their actions in the game. The comparison methodology did not include any qualitative enrichment or subjective analysis to prevent biased data enhancement or gender-related processing. The pipeline included three representative binary classification models; A logic-based Decision Trees, a probabilistic Logistic Regression and a multilevel perceptron Neural Network. Each model tried to draw the differences between male and female data points, and we extracted the results using machine learning explainability methods to understand the underlying mechanics of the models implemented. The study was able to determine pivotal factors that differentiate each gender performance as well as disseminate unique patterns by gender involving more than one indicator. Data enhancement and critical variables analysis are essential next steps to support this framework and serve as a baseline for further studies and training developments.

 

 

 

#2 The effect of approach velocity on pelvis and kick leg angular momentum conversion strategies during football instep kicking

Reference: J Sports Sci. 2021 May 25;1-10.  doi: 10.1080/02640414.2021.1929008. Online ahead of print.

Authors: Simon Augustus, Penny E Hudson, Neal Smith

Summary: During football instep kicking, whole-body deceleration during the final stride has been associated with greater kick leg angular momentum and enhanced foot and ball velocities, but the influence of approach velocity on these mechanisms is unknown. This study assessed how approach velocity affects momentum conversion strategies of experienced players performing fast and accurate kicks. Eleven semi-professional footballers performed instep kicks from self-selected (3.34 ± 0.43 m/s), fast (3.71 ± 0.33 m/s) and slow (2.77 ± 0.32 m/s) approaches. Kicking motions and ground reaction forces under the support leg were captured using 3D motion analysis (1000 Hz). The players responded to perturbations in approach velocity by using the support leg to regulate whole-body deceleration and create ideal conditions for co-ordinated pelvic and kick leg momentums during the downswing. Further, the pelvis was key for generating transverse momentum at the kick leg, but the participants displayed distinctly different pelvis transverse rotation strategies. Identification of these inter-individual strategies may provide a basis for technical and strength training practices to be tailored for individual players. Future research might investigate if training practices that expose footballers to varying approach velocities of between 2.5 and 4.0 m/s promotes development of movement strategies that are robust to perturbations in approach conditions.

 

 

#3 Competitive anxiety or Coronavirus anxiety? The psychophysiological responses of professional football players after returning to competition during the COVID-19 pandemic

Reference: Psychoneuroendocrinology . 2021 May 14;129:105269.  doi: 10.1016/j.psyneuen.2021.105269. Online ahead of print. 

Authors: Amir Hossien Mehrsafar, Ali Moghadam Zadeh, José Carlos Jaenes Sánchez, Parisa Gazerani

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8118697/pdf/main.pdf

Summary: This study aimed to examine the relationship between competitive anxiety, fear/anxiety of COVID-19, and autonomic and endocrine stress responses in professional football players after returning to competition during the COVID-19 pandemic. Ninety male professional football players (age: 26.33 ± 2.48 yr) volunteered to participate in this study, which included an official competition. Psychophysiological responses, including the Fear of COVID-19 Scale, the Coronavirus Anxiety Scale, and the Competitive State Anxiety Inventory-2 Revised, were collected 30 min before the competition. In addition, salivary alpha-amylase (sAA) and salivary cortisol (sCort) were collected at 8 a.m. and 15 min before the competition. The main findings, based on the Pearson correlation, showed significant positive correlations between COVID-19 anxiety and somatic competitive anxiety (p = 0.01), cognitive competitive anxiety (p = 0.01), and competition response of sCort and sAA (p = 0.01). Moreover, fear of COVID-19 was positively correlated with COVID-19 anxiety (p = 0.01). On the contrary, the awakening response of sCort and sAA was not found to be correlated with psychological parameters (all p > 0.05). The analysis also indicated that there was no significant correlation between self-confidence with other psychological and physiological variables (all p > 0.05). The regression analysis showed that cognitive anxiety was a relevant predictor for the competition response of sCort and sAA (p < 0.05). Moreover, COVID-19 anxiety was the only predictor of somatic and cognitive anxiety (p < 0.05). The present study provides the first preliminary evidence that COVID-19 anxiety and competitive anxiety might pose a negative impact on the athletic performance of professional football players during COVID-19 pandemic competitions. Thus, research is needed to build a strategy to reduce the psychophysiological stress related to COVID-19 and competition response.

 

 

#4 Association of the British Athletic Muscle Injury Classification and anatomic location with return to full training and reinjury following hamstring injury in elite football

Reference: BMJ Open Sport Exerc Med. 2021 May 10;7(2):e001010. doi: 10.1136/bmjsem-2020-001010. eCollection 2021.

Authors: Ricky Shamji, Steven L J James, Rajesh Botchu, Kent A Khurniawan, Gurjit Bhogal, Alison Rushton

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8112435/pdf/bmjsem-2020-001010.pdf

Summary: The relationship between hamstring muscle injuries (HMIs) that involve the intramuscular tendon and prolonged recovery time and increased reinjury rate remains unclear in elite footballers. To determine the association of time to return to full training (TRFT) and reinjury of HMIs using the British Athletic Muscle Injury Classification (BAMIC) and specific anatomical injury location in elite-level football players. The electronic medical records of all players at an English Premier League club were reviewed over eight consecutive seasons. All players who sustained an acute HMI were included. Two experienced musculoskeletal radiologists independently graded each muscle using the BAMIC, categorised each injury location area (proximal vs middle vs distal third and proximal vs distal tendon) and reported second muscle involvement. TRFT and reinjury were recorded. Out of 61 HMIs, the intramuscular tendon (BAMIC 'c') was involved in 13 (21.3%). HMI involving the intramuscular tendon ('c') had a mean rank TRFT of 36 days compared with 24 days without involvement (p=0.013). There were 10 (16.4%) reinjuries with a significant difference of 38.5% reinjury rate in the group with intramuscular tendon injury ('c') and 12.5% in the group without (p=0.031). TRFT and reinjury involving a second muscle was statistically significantly higher than without. Most of the HMIs to the biceps femoris with reinjury (5 out of 9) were in the distal third section related to the distal tendon site involving both the long and short head. TRFT in HMI involving the intramuscular tendon ('c') of the Biceps femoris is significantly longer with significantly higher reinjury rate compared with injuries without, in elite football players. The finding that most reinjures of the biceps femoris occurring in the distal third muscle at the distal tendon site, involving both the long and short head, merits further investigation.

 

 

#5 The Effect of a Tailored Intervention on Female Soccer Players' Hydration Status

Reference: J Hum Kinet. 2021 Mar 31;78:131-140.  doi: 10.2478/hukin-2021-0047. eCollection 2021 Mar.

Authors: Kristien Van Campenhout, Laurent Chapelle, Tom Deliens, Eva D'Hondt, Peter Clarys

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120958/pdf/hukin-78-131.pdf

Summary: Numerous studies have reported that athletes' pre-training/-game hydration status is of concern. Up to now, only two cohort studies have examined the effect of an intervention aimed at improving pretraining/-game hydration status; however, without including a control group. Therefore, the aim of this quasi-experimental study was to examine whether and to what extent an individually tailored intervention focused on the benefits of being optimally hydrated before training or game would alter the hydration status of female soccer players. Two teams of young adult female soccer players were allocated to an intervention (n = 22; 19.8 ± 3.0 years) or a control group (n = 15; 22.8 ± 4.0 years). Players in the intervention group received an individually tailored intervention, based on Urine Specific Gravity (USG) measurements, which took place in between two training weeks. Before each training and match play, a urine sample was collected to determine players' hydration status. Mixed modelling was applied to assess within and between differences in hydration status over time. The pre-training/-game hydration status of the intervention group improved significantly, with players' mean USG-value decreasing from 1.013 ± 0.001 g/mL to 1.008 ± 0.002 g/mL (p = 0.005). In contrast, the mean USG-value in the control group increased significantly from 1.012 ± 0.002 g/mL to 1.016 ± 0.002 g/mL (p = 0.023), indicating a deterioration of their pre-training/-game hydration status. The individually tailored intervention did show a positive effect even though female soccer players in the present study were already reasonably well hydrated before the start of the intervention.

 

 

#6 Does Youth Soccer Players' Group Cooperation Improve when Pitch, Goal, and Team Size are Reduced?

Reference: J Hum Kinet. 2021 Mar 31;78:151-160.  doi: 10.2478/hukin-2021-0035. eCollection 2021 Mar.

Authors: Antonio García-Angulo, Enrique Ortega-Toro, José María Giménez-Egido, Aurelio Olmedilla, Alexandre García-Mas 4, José Manuel Palao 5

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120978/pdf/hukin-78-151.pdf

Summary: The aim of this study was to analyse the effects of the modification of the pitch size, goal size, and the number of players per team on the level of cooperation in youth soccer players (U-12). A quasi-experimental design was implemented to measure the effects of the changes in the number of players per team (8-a-side vs. 5-a-side), goal size (6 x 2 m vs. 3 x 2 m), and field size (58 x 38 m vs. 38 x 20 m) on the cooperation. Four soccer teams under-12 (n = 48 players) participated in three tournaments (standard rules; proposed rules; standard rules). The five variables of cooperation were measured using the "Sports Cooperation Questionnaire": conditional cooperation, cooperation with the coach, disposition of unconditional cooperation, situational cooperation with teammates, and situational cooperation outside the field of play. Players presented the same level of cooperation in conditional cooperation, situational cooperation with teammates, and situational cooperation outside the field of play with both types of rules. The modification of rules involved a reduction of the cooperation with the coach and a disposition of unconditional cooperation. The causes of the reduction may be related to players' adaptation to new tactical dispositions and game situations. Future studies are needed of player's cooperation and different competition rules in youth sports.

 

 

#7 Influence of Pitch Size on Short-Term High Intensity Actions and Body Impacts in Soccer Sided Games

Reference: J Hum Kinet. 2021 Mar 31;78:187-196.  doi: 10.2478/hukin-2021-0037. eCollection 2021 Mar.

Authors: Daniel Castillo, Javier Raya-González, Javier Yanci, Filipe Manuel Clemente

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120965/pdf/hukin-78-187.pdf

Summary: The aim of this study was to compare external training loads between small-sided games (SSGs) and largesided games (LSGs) in soccer players. Twenty outfield soccer players (14.8 ± 0.6 years old) who competed in the Spanish U16 Provincial Division and belonged to the same team participated in the study. The soccer sided games were played at different individual interaction space (IIS) per player (i.e., SSG = 100 m2 and LSG = 200 m2) and were disputed in the same format (five-a-side plus goalkeepers) on two different pitch sizes (i.e., 38 x 26 vs. 53 x 37 m) defending an official soccer-goal. The sided games' duration was 4 bouts of 6 min with 2 min rest intervals between bouts. The results of this study showed no meaningful differences in the total distance and intensity of accelerations and decelerations between SSGs and LSGs except for the lower distance covered at medium intensity (2.5 - 4 m·s-2) observed during LSGs (-10.2%; ES (effect size): -0.51). Players registered greater sprints, maximum velocity (Velmax) and body impacts at different intensities (i.e., I5-6g, I6-6.5g, I6.5-7g, I7-8g, I8-10g,) in LSGs in comparison to SSGs. These findings suggest that an increase in the pitch size (i.e., IIS per player) can induce higher external loads for soccer players.

 

 

#8 The influence of randomness on goals in football decreases over time. An empirical analysis of randomness involved in goal scoring in the English Premier League

Reference: J Sports Sci. 2021 May 24;1-16.  doi: 10.1080/02640414.2021.1930685. Online ahead of print.

Authors: Fabian Wunderlich, Alessandro Seck, Daniel Memmert

Summary: Performance analysis in football predominantly focuses on systematic contributions to success, thus neglecting the role of randomness. The present paper pursues a direct approach to quantify and analyse randomness in football by identifying random influences in the goal scoring process. The dataset includes all matches from the seasons 12/13 to 18/19 of the English Premier League, adding up to a total of 7,263 goals, that were checked for the occurrence of six variables of random influence. Additionally, the influence of nine situational variables was investigated. Results show that randomness was present for almost 50% of all goals. Moreover, it was demonstrated that the proportion of random goals decreased over the seven seasons (p < .001), is more pronounced for weaker teams (p < .05) as well as if the current scoreline is a draw (p < .05) and depends on the match situation (open play, freekick, corner, penalty). An improved understanding of randomness in football has important implications for both researchers and practitioners. Performance analysts should acknowledge randomness as a crucial factor to distinguish clearly between performance and success. Coaches could even consider the conscious creation of uncontrollable situations as a possible tactic to provoke random influences on goal scoring.

 

 

#9 Individual acceleration-speed profile in-situ: A proof of concept in professional football players

Reference: J Biomech. 2021 May 15;123:110524. doi: 10.1016/j.jbiomech.2021.110524. Online ahead of print.

Authors: Jean-Benoit Morin, Yann Le Mat, Cristian Osgnach, Andrea Barnabò, Alessandro Pilati, Pierre Samozino, Pietro E di Prampero

Summary: Assessing football players' sprint mechanical outputs is key to the performance management process (e.g. talent identification, training, monitoring, return-to-sport). This is possible using linear sprint testing to derive force-velocity-power outputs (in laboratory or field settings), but testing requires specific efforts and the movement assessed is not specific to the football playing tasks. This proof-of-concept short communication presents a method to derive the players' individual acceleration-speed (AS) profile in-situ, i.e. from global positioning system data collected over several football sessions (without running specific tests). Briefly, raw speed data collected in 16 professional male football players over several training sessions were plotted, and for each 0.2 m/s increment in speed from 3 m/s up to the individual top-speed reached, maximal acceleration output was retained to generate a linear AS profile. Results showed highly linear AS profiles for all players (all R2 > 0.984) which allowed to extrapolate the theoretical maximal speed and accelerations as the individual's sprint maximal capacities. Good reliability was observed between AS profiles determined 2 weeks apart for the players tested, and further research should focus on deepening our understanding of these methodological features. Despite the need for further explorations (e.g. comparison with conceptually close force-velocity assessments that require, isolated and not football-specific linear sprint tests), this in-situ approach is promising and allows direct assessment of football players within their specific acceleration-speed tasks. This opens several perspectives in the performance and injury prevention fields, in football and likely other sprint-based team sports, and the possibility to "test players without testing them".

 

 

#10 Collective states and their transitions in football

Reference: PLoS One. 2021 May 24;16(5):e0251970.  doi: 10.1371/journal.pone.0251970. eCollection 2021.

Authors: Mitchell Welch, Timothy M Schaerf, Aron Murphy

Download link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0251970

Summary: Movement, positioning and coordination of player formations is a key aspect for the performance of teams within field-based sports. The increased availability of player tracking data has given rise to numerous studies that focus on the relationship between simple descriptive statistics surrounding team formation and performance. While these existing approaches have provided a high-level a view of team-based spatial formations, there is limited research on the nature of collective movement across players within teams and the establishment of stable collective states within game play. This study draws inspiration from the analysis of collective movement in nature, such as that observed within schools of fish and flocking birds, to explore the existence of collective states within the phases of play in soccer. Order parameters and metrics describing group motion and shape are derived from player movement tracks to uncover the nature of the team's collective states and transitions. This represents a unique addition to the current body of work around the analysis of player movement in team sports. The results from this study demonstrate that sequences of ordered collective behaviours exist with relatively rapid transitions between highly aligned polar and un-ordered swarm behaviours (and vice-versa). Defensive phases of play have a higher proportion of ordered team movement than attacking phases, indicating that movements linked with attacking tactics, such as player dispersion to generate passing and shooting opportunities leads to lower overall collective order. Exploration within this study suggests that defensive tactics, such as reducing the depth or width to close passing opportunities, allows for higher team movement speeds and increased levels of collective order. This study provides a novel view of player movement by visualising the collective states present across the phases of play in football.

 

 

#11 Applying the Input-Process-Outcome Model to Team Learning in Sport Sciences: An Exploratory Qualitative Study on Twenty Soccer Players

Reference: J Hum Kinet. 2021 Mar 31;78:251-262. doi: 10.2478/hukin-2021-0040. eCollection 2021 Mar.

Authors: Thibault Kérivel, Cyril Bossard, Gilles Kermarrec

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120967/pdf/hukin-78-251.pdf

Summary: In sport science literature, referring to the Input-Process-Outcome (IPO) model, few studies demonstrated links between team training and team learning despites several calls for empirical studies. Thus, this study aimed at exploring systemically the building process of the interpersonal coordination by focusing on (1) a specific antecedent (i.e., video feedback during practice), (2) the influence of this antecedent on the team learning process, and (3) outcomes from this process as shared cognitive contents. Thus, this study was original by examining empirically the IPO model in a sport-training context. Our study showed that Input influenced the specific learning Process during practice (five processes) and video feedback sessions (five processes) and produced Outcomes (six typical shared cognitive contents). Finally, results are discussed in relation to team learning processes theoretically identified in the literature and an IPO soccer model adapted to team learning in a soccer context is proposed.

 

 

#12 Structure of the training program during the Covid-19 confinement in Spanish professional football: A coach survey

Reference: Phys Sportsmed. 2021 May 24.  doi: 10.1080/00913847.2021.1932633. Online ahead of print.

Authors: Iván Asín-Izquierdo, Luis Gutiérrez-García, Juan Carlos Zapardiel, Marcos Chena

Summary: COVID-19 has produced an exceptional situation for sport due to confinement and restrictions. The usual training programs and competition have been interrupted in world football, requiring an adaptation of training to the new situation. The aim was to describe and analyze the training programs carried out during the COVID-19 forced confinement in men´s professional football in Spain. The sample consisted of thirty-six coaches representing thirty-six professional men's soccer teams in the Spanish first and second division. Training programs developed during confinement prioritized conditioning and functional emphasis, in addition to general and non-specific resistance training, due to contextual limitations. The structure of training during the COVID-19 confinement was limited by contextual circumstances. This study has made possible to record the training and strategies used in professional football during a confinement due to a worldwide state of alarm, with the aim of resuming competitive activity in the best possible conditions.

 

Thu

21

Oct

2021

The Influence of the Coach’s Autonomy Support and Controlling Behaviours on Motivation and Sport Commitment of Youth Footballers

The aim of this cross-sectional study was to analyse the influence of young soccer players’ perception of their coach’s autonomy-supportive and controlling behaviours on the satisfaction and frustration of their basic psychological needs (BPN) and sport commitment.

Wed

20

Oct

2021

The Role of Parental Involvement in Youth Sport Experience: Perceived and Desired Behaviour by Male Soccer Players

The aims of this cross-sectional study were to assess the perceived and desired parental involvement by children and to examine their satisfaction or dissatisfaction with any specific behaviour.

Tue

19

Oct

2021

Latest research in football - week 33 - 2021

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 Contrasting Learning Psychology Theories Applied to the Teaching-Learning-Training Process of Tactics in Soccer

Reference: Front Psychol. 2021 May 4;12:637085. doi: 10.3389/fpsyg.2021.637085. eCollection 2021.

Authors: Grégory Hallé Petiot, Rodrigo Aquino, Davi Correia da Silva, Daniel Vieira Barreira, Markus Raab

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8129189/pdf/fpsyg-12-637085.pdf

Summary: Research in sport pedagogy and its applied recommendations are still characterized by a contrast between the different learning theories from psychology. Traditional theories and their corresponding approaches to the specific case of teaching and learning "how to play [team sports like soccer]" are subject to compatibilities and incompatibilities. We discuss how behaviorism as an approach to teaching the game shows more incompatibilities with the nature of tactical actions when compared to constructivism. As coaches strive to teach the game and make their players and team perform, we argue that teaching the game requires teaching approaches that will help develop their way to play (i.e., tactical behavior) without taking away their autonomy and adaptiveness. The teaching-learning-training process for playing the game should then be conducted to harmonize the characteristics of the contents, the context, and the individual(s) at hand. We provide two illustrated examples and portray how the recommended approaches fit key contents of the game that are observed in the tactical behavior. We finally argue that the coherent design of games provides minimal conditions to teaching approaches, and that such a design should be a priority when elaborating the learning activities along the player development process. As a conclusion, the interactionist theory is the one that best serves the teaching of the game and the development of tactical behavior. We therefore defend that its principles can help coaches tailor their own strategy to teach the game with the many tools.

 

 

#2 Soccer goalkeeper expertise identification based on eye movements

Reference: PLoS One. 2021 May 19;16(5):e0251070. doi: 10.1371/journal.pone.0251070. eCollection 2021.

Authors: Benedikt W Hosp, Florian Schultz, Oliver Höner, Enkelejda Kasneci

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8133470/pdf/pone.0251070.pdf

Summary: By focusing on high experimental control and realistic presentation, the latest research in expertise assessment of soccer players demonstrates the importance of perceptual skills, especially in decision making. Our work captured omnidirectional in-field scenes displayed through virtual reality glasses to 12 expert players (picked by DFB), 10 regional league intermediate players, and13 novice soccer goalkeepers in order to assess the perceptual skills of athletes in an optimized manner. All scenes were shown from the perspective of the same natural goalkeeper and ended after the return pass to that goalkeeper. Based on the gaze behavior of each player, we classified their expertise with common machine learning techniques. Our results show that eye movements contain highly informative features and thus enable a classification of goalkeepers between three stages of expertise, namely elite youth player, regional league player, and novice, at a high accuracy of 78.2%. This research underscores the importance of eye tracking and machine learning in perceptual expertise research and paves the way for perceptual-cognitive diagnosis as well as future training systems.

 

 

#3 Influence of Laboratory Index on match performance. A comparison study to evaluate physical performance in professional soccer players of an Italian Elite Team

Reference: Eur Rev Med Pharmacol Sci. 2021 May;25(9):3444-3452. doi: 10.26355/eurrev_202105_25825.

Authors: M Pieri, M A Perrone, A Imbrogno, F Tomassetti, R Colombo, L Leone, S Aguzzetti, S Tecce, G Merra, A Bernardini, G Calugi

Download link: https://www.europeanreview.org/wp/wp-content/uploads/3444-3452.pdf

Summary: It was hypothesized that activity exercise at professional levels could lead to an increase in metabolic levels and a decrease in performance parameters. These trends are explained by physical activity as a cellular stressor. We used an algorithm, Laboratory Index which evaluates salivary cortisol, CK and d-ROMs, collected previously from elite Italian soccer players, compared to InStat Index. The last one estimates analytically the athlete's performance in soccer pitch, applying the Heath Maps. A good agreement between the two Index was obtained, especially for two players, who showed an ideal combined trend. We would investigate the clinical and activity profile of soccer players with the aim of providing information for the development of training strategies. Also, the performances, during training and match time, are an objective evaluation of the athlete's physical preparation. As a consequence, the combination of two Index could be used for a new approach to the sports world.

 

 

#4 Do exercise-based prevention programmes reduce non-contact musculoskeletal injuries in football (soccer)? A systematic review and meta-analysis with 13 355 athletes and more than 1 million exposure hours

Reference: Br J Sports Med . 2021 May 17;bjsports-2020-103683. doi: 10.1136/bjsports-2020-103683.

Authors: Italo Ribeiro Lemes, Rafael Zambelli Pinto, Vitor N Lage, Bárbara A B Roch, Evert Verhagen, Caroline Bolling, Cecilia Ferreira Aquino, Sérgio T Fonseca, Thales R Souza

Download link: https://bjsm.bmj.com/content/bjsports/early/2021/05/16/bjsports-2020-103683.full.pdf

Summary: The aim of this systematic review was to investigate the effect of exercise-based programmes in the prevention of non-contact musculoskeletal injuries among football players in comparison to a control group. MEDLINE, EMBASE, CENTRAL, CINAHL, PEDro and SPORTDiscus databases were searched from the earliest record to January 2021. Studies were eligible if they (1) included football players aged 13 years or older, (2) used exercise-based programmes as intervention, (3) presented the number of non-contact musculoskeletal injuries (ie, defined as any acute sudden onset musculoskeletal injury that occurred without physical contact) and exposure hours for each group, and (4) had a control group (eg, usual training, minimal intervention, education). All types of exercise-based prevention programmes were eligible for inclusion. Risk of bias for each included study and overall quality of evidence for the meta-analysis were assessed. Ten original randomised controlled trials with 13 355 football players and 1 062 711 hours of exposure were selected. Pooled injury risk ratio showed very low-quality evidence that exercise-based prevention programmes reduced the risk of non-contact musculoskeletal injuries by 23% (0.77 (95% CI 0.61 to 0.97)) compared with a control group. Exercise-based prevention programmes may reduce the risk of non-contact musculoskeletal injuries by 23% among football players. Future high-quality trials are still needed to clarify the role of exercise-based programmes in preventing non-contact musculoskeletal injuries among football players.

 

 

#5 When and how do elite soccer players sprint in match play? A longitudinal study in a professional soccer league

Reference: Res Sports Med. 2021 May 17;1-12.  doi: 10.1080/15438627.2021.1929224. Online ahead of print.

Authors: José M Oliva-Lozano, Víctor Fortes, José M Muyor

Summary: The aims of this study were to examine the periods in which the maximum speed actions occurred during elite soccer matches and analyse these actions considering the effect of playing position and different contextual variables. Performance-related variables (VMAX: maximum speed; Vo: starting speed; SPD: sprinting distance; ACCMAX: maximum acceleration; DECMAX: maximum deceleration) and sprint-related contextual variables (trajectory, ball possession, role, field area in which the action occurred) from each maximum speed action were collected. The first 15 minutes of each match half elicited most maximum speed actions (44.6% of cases), regardless of playing position (likelihood ratio, LR=13.95; p=0.95). However, playing position had a significant effect on the role of the action (Chi-Squared, χ2=50.68; p=0.001) and the field area in which the sprint occurred (χ2=26.54; p=0.001). Regarding the effect of different contextual variables on the sprint-related performance variables, no significant effect from any contextual variable on ACCMAX, DECMAX or Vo was found (p > 0.05). Nevertheless, the contextual variables had a significant effect on SPD (from ball possession: sprints without ball > sprints with ball; trajectory: non-linear sprints > linear sprints; role: offensive sprints > defensive sprints) and VMAX (from ball possession: sprints without ball > sprints with ball; playing position: midfielders < other positions).

 

 

#6 A new approach to quantify angles and time of changes-of-direction during soccer matches

Reference: PLoS One. 2021 May 17;16(5):e0251292.  doi: 10.1371/journal.pone.0251292. eCollection 2021.

Authors: Tomohiro Kai, Shin Hirai, Yuhei Anbe, Yohei Takai

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8128237/pdf/pone.0251292.pdf

Summary: Soccer players frequently perform change-of-directions (CODs) at various speeds during matches. However, tracking systems have shown limitations to measure these efforts. Therefore, the aim of the present study was to propose a new approach to measure CODs using a local positioning system (LPS), and clarify position-related difference in profile of CODs by using the approach. The x- and y-coordinate data for each soccer player were measured with a local positioning system. Speed, acceleration, jerk, and direction of speed were derived from the coordinate data. Based on accelerations of above 2 m/s2, the onsets and ends of CODs derived from jerk were identified (COD duration). Changes of direction of speed (θCOD) were determined for the corresponding period. Six collegiate male soccer players performed CODs according to 13 set angles (0-180°; every 15°) so that differences between θCOD and set angle could be determined (Exp. 1). Relative frequency distributions of θCOD and number of CODs were determined in 79 collegiate and amateur male soccer players during 9 soccer matches (Exp. 2). In Exp. 1, θCOD was positively related to set angle (r = 0.99). Each θCOD was smaller than the corresponding set angle, and the difference became greater with increasing COD angle. In Exp. 2, The number of CODs in a match was 183 ± 39 across all positions. There were no significant position-related differences in the number of CODs. The duration of a COD was 0.89 ± 0.49 s across all positions. The relative frequency distribution of θCOD revealed that the number of CODs at 0-15° and 105-135° tended to be higher than those at other angles during soccer matches. Further, θCOD was affected by the speed at the onset of COD during soccer matches (Exp. 2). The current findings demonstrate that θCOD derived from direction of speed and jerk may be a new indicator for evaluating COD during soccer matches.

 

 

#7 A daytime 40-min nap opportunity after a simulated late evening soccer match reduces the perception of fatigue and improves 5-m shuttle run performance

Reference: Res Sports Med. 2021 May 17;1-14.  doi: 10.1080/15438627.2021.1917400. Online ahead of print.

Authors: Hsen Hsouna, Omar Boukhris, David W Hill, Raouf Abdessalem, Khaled Trabelsi, Achraf Ammar, Khadijah Irandoust, Nizar Souissi, Morteza Taheri, Omar Hammouda, Cain C T Clark, Tarak Driss, Hamdi Chtourou 

Summary: The effect of a 40-min nap opportunity was investigated during the day following a late evening simulated soccer match. Twelve male amateur soccer players (23 ± 3 years; 77.3 ± 5.3 kg; 1.76 ± 0.04 m) performed the Loughborough-intermittent-shuttle test at 21h00 and the following day they completed the sleepiness scale after either a nonap (N0) or 40-min nap (N40) opportunity that began at 14h00. At 17h00, participants performed the 5-m shuttle run test (5mSRT) (6 × 30-s with 35-s in-between; best distance (BD) and total distance (TD) were calculated). After performing the 5mSRT, they provided their rating of the perceived exertion (RPE) and rated their muscle soreness. Sleepiness scores were significantly lower in N40 in comparison with N0 (P < 0.05). A significant increase of TD (+64.5 m) and BD (+9.6 m) after N40 compared to N0 was observed (P < 0.05). The improved performance was associated with reduced levels of muscle soreness and lower RPE. In conclusion, a daytime 40-min nap opportunity after a late evening simulated soccer match improves short-term repetitive maximal performance in soccer players, and has positive effects on perception of sleepiness, muscle soreness, and RPE.

 

 

#8 Reliability of a novel dynamic test of postural stability in high-level soccer players

Reference: Heliyon. 2021 Apr 21;7(4):e06647. doi: 10.1016/j.heliyon.2021.e06647. eCollection 2021 Apr.

Authors: Paul E Beelen, Ricardo Okhuijsen, Maarten R Prins, Arnold Huurnink, Tim Hordijk, Christiaan Kruiswijk, Edwin A Goedhart, Peter van der Wurff, Peter A Nolte, Jaap H van Dieën, Idsart Kingma

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8093417/pdf/main.pdf

Summary: Postural stability of athletes is commonly tested with single-leg stance (SLS) tests. However, for this population, these tests are insufficiently challenging to achieve high sensitivity. Therefore, a new dynamic SLS test based on standardized translational surface perturbations was developed. This study aimed to assess reliability, sensitivity to learning effects, and internal and concurrent validity of this novel test. Healthy soccer players (21 females, 21 males) performed 2 test sessions. Each session consisted of 2 trials. For one trial, the participant performed a 30-seconds, unperturbed SLS on each leg, followed by 12 platform perturbations per leg. Intraclass Correlation Coefficients (ICC) and correlations between outcomes were calculated for the Center of Pressure speed (CoPs) and Time To Stabilization (TTS). ANOVA was used to assess learning effects. CoPs and TTS showed a fair reliability between sessions (ICC = 0.73-0.76). All variables showed improvement over time within and between sessions (all p < 0.01) and were moderately correlated with CoPs during unperturbed SLS (r = 0.39-0.56). Single-leg dynamic postural stability testing through standardized horizontal platform perturbations yielded sufficiently reliable CoPs and TTS outcome measures in soccer players. The moderate correlations with unperturbed SLS support concurrent validity, but also indicates that the new test captures aspects of postural stability that differ from the conventional, unperturbed SLS test.

 

 

#9 Effect of COVID-19 Lockdown on Young Egyptian Soccer Players

Reference: Glob Pediatr Health. 2021 May 8;8:2333794X211012980. doi: 10.1177/2333794X211012980. eCollection 2021.

Authors: May Fouad Nassar, Mohamed Farouk Allam, Mennatallah Osama Shata

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8114258/pdf/10.1177_2333794X211012980.pdf

Summary: The present study was designed to highlight the physical and psychological health hazards that a young Egyptian soccer team faced during the first COVID-19 wave lockdown. The study included 37 young Egyptian male soccer players. History taking and anthropometric measurements were taken. Two questionnaires were filled covering the athletes'` sleep habits and quality of life (QoL). Finally, the mothers were asked to fill in a questionnaire concerned with depression, anxiety, and stress. More than 50% of the enrolled athletes gained weight during the lockdown especially those without compliance to home exercises. The mothers' anxiety score correlated positively with the increased body mass index (BMI) of the athletes. The athletes mean QoL Score worsened significantly and significant negative correlation was found between the increased BMI and the change of QoL. The increased BMI was significantly reported among the athletes who didn't do home exercises and had a negative correlation with their QoL change throughout the lockdown. The mothers' anxiety had a possible reflection on their youngsters' weight gain. These findings highlight the need for weight control when outdoors physical activity is restricted during pandemics with better compliance to home exercising schedules and less screen time.

 

 

#10 Effects of eccentric exercises on improving ankle dorsiflexion in soccer players

Reference: BMC Musculoskelet Disord. 2021 May 26;22(1):485. doi: 10.1186/s12891-021-04337-y.

Authors: Iris Femmigje Lagas, Duncan E Meuffels, Edwin Visser, Floor P Groot, Max Reijman, Jan A N Verhaar, Robert-Jan de Vos

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157442/pdf/12891_2021_Article_4337.pdf

Summary: The purpose of this study was to determine the effect of targeted eccentric calf muscle exercises compared to regular training on ankle dorsiflexion in healthy adolescent soccer players with a decreased ankle dorsiflexion. Male adolescent players (aged 14-21 years) from two professional soccer clubs were evaluated with the Weight Bearing Dorsiflexion Lunge Test (WBDLT) at baseline and after 12 weeks of this prospective controlled study. One club served as the control group and the other as the intervention group. Players with decreased ankle dorsiflexion (WBDLT) ≤ 10 cm) performed stretching and eccentric calf muscle exercises three times per week next to regular training in the intervention group, and performed only regular training in the control group. Primary outcome was the between-group difference in change in WBDLT between baseline and 12 weeks. Of 107 eligible players, 47(44 %) had a decreased ankle dorsiflexion. The WBDLT (± standard deviation) increased in the intervention group from 7.1 (± 1.8) to 7.4 (± 2.4) cm (95 % Confidence Interval (CI)[-0.493 to 1.108], p = 0.381) and in the control group from 6.1 (± 2.4) to 8.2 (± 2.9) cm (95 % CI [1.313 to 2.659], p < 0.001). The difference in change of WBDLT between both groups was statistically significant (95 % CI [-2.742 to -0.510], p = 0.005). Targeted eccentric calf muscle exercises do not increase ankle dorsiflexion in healthy adolescent soccer players. Compared to regular training, eccentric exercises even resulted in a decreased calf muscle flexibility.

 

 

#11 Altered Knee Laxity and Stiffness in Response to a Soccer Match Simulation in Players Returning to Sport Within 12 Months After Anterior Cruciate Ligament Reconstruction

Reference: Am J Sports Med. 2021 May 26;3635465211013020. doi: 10.1177/03635465211013020.

Authors: Stefano Nuccio, Luciana Labanca, Jacopo Emanuele Rocchi, Pier Paolo Mariani, Paola Sbriccoli, Andrea Macaluso

Summary: The acute effects of exercise on anterior knee laxity (AKL) and anterior knee stiffness (AKS) have been documented in healthy participants, but only limited evidence has been provided for athletes cleared to return to sports after anterior cruciate ligament (ACL) reconstruction (ACLR). The purpose was to determine if 45 minutes of a soccer match simulation lead to acute changes in AKL and AKS in soccer players returning to sport within 12 months after ACLR. We hypothesized that the reconstructed knee of the ACLR group would exhibit an altered response to sport-specific exercise. A total of 13 soccer players cleared to return to sport after ACLR and 13 healthy control soccer players matched for age, physical activity level, limb dominance, and anthropometric characteristics were recruited. To assess the effects of a standardized soccer match simulation (Soccer Aerobic Field Test [SAFT45]) on AKL and AKS, an arthrometric evaluation was carried out bilaterally before and immediately after SAFT45. To conduct a comprehensive examination of the force-displacement curve, the absolute and side-to-side difference (SSD) values of both AKL and AKS were extracted at 67, 134, and 200 N. The ACLR and control groups showed similar AKL and AKS at baseline (P > .05). In response to SAFT45, laxity increased bilaterally at all force levels by 14% to 17% only in the control group (P < .025). Similarly, AKS at 134 and 200 N decreased in response to SAFT45 only in the control group (10.5% and 20.5%, respectively; P < .025). After SAFT45, the ACLR group had 1.9 and 2.5 times higher SSDs of AKS at 67 and 134 N compared with the control group, respectively (P < .025), as well as a 1.9 times higher SSD of AKS at 134 N compared with baseline (P = .014). Soccer players at the time of return to sport after ACLR showed an altered mechanical response to a sport-specific match simulation consisting of bilaterally unchanged AKL and AKS.

 

 

#12 Effect of the FIFA 11+ soccer specific warm up programme on the incidence of injuries: A cluster-randomised controlled trial

Reference: PLoS One. 2021 May 24;16(5):e0251839.  doi: 10.1371/journal.pone.0251839. eCollection 2021.

Authors: Assuman Nuhu, Jennifer Jelsma, Kim Dunleavy, Theresa Burgess

Download link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0251839

Summary: Soccer players incur injuries that typically affect their performance. Injuries are caused by intrinsic and extrinsic factors that call for multifactorial preventive interventions. The study examines the impact of the FIFA 11+ warm up programme on the incidence and severity of injuries in second division soccer players in Rwanda. Twelve teams (309 players) were randomised in the intervention group and 12 teams (317 players) in the control group using a cluster randomized controlled trial with teams as the unit of randomization. Intervention group teams implemented the FIFA 11+ soccer specific warm-up programme during training and matches at least three times a week over seven months of the Rwandan soccer season. Control group teams continued with usual warm up exercises. The primary outcome of this study was the overall incidence of training and match injuries. Injuries, training and match exposure as well as severity categories were recorded per the F-MARC guidelines. A lower proportion of players sustained injuries in the intervention group (52%) compared to the control group (63%) (Odd ratio: 0.7; 95%CI: 0.5-0.9). A significantly lower rate ratio was observed in the intervention group for overall (RR = 0.6; 95%CI: 0.5-0.8) and match (RR = 0.6; 95%CI: 0.5-0.8) injuries. Compliance to the injury prevention programme was 77%. In the intervention group, the incidence of injury was similar across all teams and across the medium and highly compliant teams. There was a statistically significant 55% and 71% reduction of the rate of moderate and severe injuries in the intervention group respectively. The 11+ warm up injury prevention programme resulted in a significant reduction in the odds of sustaining injuries. In addition, injuries sustained were less severe. The programme should be rolled out to all teams in Rwanda and may well result in a decrease in the incidence and severity of injury in similar contexts.

 

 

#13 Pre-season in soccer: a paradox between a high volume of technical/tactical training and improvement in the neuromuscular performance of elite women soccer players

Reference: J Sports Med Phys Fitness. 2021 May 24. doi: 10.23736/S0022-4707.21.12427-2. Online ahead of print.

Authors: Ronaldo Kobal, Leonardo Carvalho, Cesar C Abad, Bruno Faust, Marcelo Rossetti, Tiemi Saito, Rafael R Klosterhoff, Eduardo O De Souza, Renato Barroso

Summary: There is a paradox between the development of strength-power abilities and the high volume of technical/tactical training in elite soccer players during the pre-season. This concurrent effect between aerobic and neuromuscular training regimes induce impairment in power performance. This study aimed to investigate the effect of an equalized program of strength-power training (4-5 sessions/week) and soccer training (4-6 sessions/week) in power and aerobic performance during 8-weeks of pre-season in elite women soccer players. Vertical jumps [squat jump (SJ); countermovement jump (CMJ)] and Yo-Yo intermittent recovery level 1 test (YOYO-R1) were assessed pre- and post pre-season. A paired sample t-test was used to compare differences between pre and post pre-season (Δ%). The level of significance was established at p ≤ 0.05. The women soccer players improved the SJ (p<0.001; Δ%=12), CMJ (p<0.001; Δ%=8.5), and YOYO-R1 (p<0.001; Δ% =28.5). There was a body recomposition observed, lower body fat (p = 0.004; Δ%=15), higher fat free mass (p = 0.001; Δ%=5). Our results demonstrated that it is possible to develop aerobic and power abilities of elite women soccer players during pre-season using an equalized ratio of soccer training and strength-power training schedules.

 

 

#14 Effects of a Competitive Soccer Match on Jump Performance and Interlimb Asymmetries in Elite Academy Soccer Players

Reference: J Strength Cond Res. 2021 Jun 1;35(6):1707-1714. doi: 10.1519/JSC.0000000000002951.

Authors: Tom Bromley, Anthony Turner, Paul Read, Jason Lake, Sean Maloney, Shyam Chavda, Chris Bishop

Summary: The purpose of this study was to investigate the effects of a competitive soccer match on jump performance and interlimb asymmetries over incremental time points during a 72-hour period. Fourteen elite adolescent players from a professional English category 3 academy performed single-leg countermovement jumps pre, post, 24-, 48-, and 72-hour post-match on a single force platform. Eccentric impulse, concentric impulse, peak propulsive force, jump height, peak landing force, and landing impulse were monitored throughout. Interlimb asymmetries were also calculated for each metric as the percentage difference between limbs. Significant negative changes (p < 0.05) in jump performance were noted for all metrics at all time points, with the exception of jump height. Interlimb asymmetries were metric-dependent and showed very large increases, specifically post-match, with a trend to reduce back toward baseline values at the 48-hour time point for propulsive-based metrics. Asymmetries for landing metrics did not peak until the 24-hour time point and again reduced toward baseline at 48-hour time point. This study highlights the importance of monitoring distinct jump metrics, as jump height alone was not sensitive enough to show significant changes in jump performance. However, interlimb asymmetries were sensitive to fatigue with very large increases post-match. More frequent monitoring of asymmetries could enable practitioners to determine whether existing imbalances are also associated with reductions in physical performance or increased injury risk.

 

Mon

18

Oct

2021

Comparison of Three Eccentric Overload Training Strategies on Power Output and Interlimb Asymmetry in Youth Soccer Players

The present study compared the effects of performing the lateral squat exercise in three different formats from eccentric overload training on concentric/eccentric peak/mean power and inter-limb asymmetries in young soccer players.

Thu

14

Oct

2021

Intra-Season Variations in Workload Parameters in Europe’s Elite Young Soccer Players

The main purpose of the current study was to compare the within-season variations of workload, training duration, acute/chronic workload ratio (ACWR), training monotony and training strain (TS) through session rating perceived exertion (s-RPE) between starters and non-starters.

Wed

13

Oct

2021

Latest research in football - week 32 - 2021

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 Aerodynamics of the newly approved football for the English Premier League 2020-21 season

Reference: Sci Rep. 2021 May 5;11(1):9578.  doi: 10.1038/s41598-021-89162-y.

Authors: Takeshi Asai, Sungchan Hong

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8100144/pdf/41598_2021_Article_89162.pdf

Summary: Footballs are typically constructed with 32 panels. Recently, the number of panels has been successively reduced to 14, 8, and 6 panels, and official balls have been adopted with complex panel shapes and aerodynamics that differ from those of 32-panel balls. The official ball for the 2020-21 season of the English Premier League comprises just four panels with a complex panel shape and surface groove design; however, its aerodynamics have not yet been clarified. This study aims to clarify the aerodynamic characteristics (drag, side force, lift force, their deviations, and critical Reynolds number) of the new 4-panel ball (Flight 2020, Nike) in comparison to a 6-panel ball (Tsubasa 2020, Adidas) and conventional 32-panel ball (Pelada 2020, Molten) using a wind tunnel test, surface design measurement, and a simple 2D flight simulation. The results showed that Flight 2020 has greater surface roughness and smaller critical Reynolds number than Pelada 2020 and Tsubasa 2020, resulting to its marginally greater drag force in the supercritical region, and slightly smaller fluctuations of the side and lift forces. Furthermore, Flight with a symmetrical orientation exhibits a significantly higher drag coefficient in the supercritical region, suggesting its greater air resistance during flight under this condition.

 

 

#2 Rehabilitation and successful return to play of a 17-year old elite soccer player with juvenile osteochondritis dissecans trochlear groove lesion of the knee: A case report

Reference: Res Sports Med. 2020 Dec 1;1-10.  doi: 10.1080/15438627.2020.1853543. Online ahead of print.

Authors: Gareth Thomas, Matt Greig

Summary: This case summarizes the rehabilitation and return to play management of a 17-year-old elite male soccer player who required surgical stabilization of an Osteochondritis Dissecans (OCD) lesion of the trochlea groove. Trochlea groove lesions represent <1% of OCD cases, resulting in limited evidence to inform practice. The case was initially identified as antalgic running gait, and at this point the player revealed progressively worsening knee pain (over preceding 2 months) which presented as patellofemoral pain with a small knee effusion and quadriceps atrophy present on assessment. No improvement in symptoms after 2 weeks of unloading (no running) and traditional patellofemoral treatment prompted magnetic resonance imaging and computed tomography scans to inform surgical intervention. We present a summary of the four-stage rehabilitation process defined by objective assessments, resulting in a successful return-to-play 24 weeks post-surgery. This case advocates consideration of OCD in the assessment of persistent knee pain in young athletes.

 

 

#3 M. Biceps Femoris Long Head Architecture and Sprint Ability in Youth Soccer Players

Reference: Int J Sports Physiol Perform. 2021 May 5;1-9.  doi: 10.1123/ijspp.2020-0726. Online ahead of print.

Authors: Paul Ritsche, Thomas Bernhard, Ralf Roth, Eric Lichtenstein, Martin Keller, Sabrina Zingg, Martino V Franchi, Oliver Faude

Summary: Hamstring muscle architecture may be associated with sprint performance and the risk of sustaining a muscle injury, both of which increase during puberty. In this study, we investigated the m. biceps femoris long head (BFlh) cross-sectional area (ACSA), fascicle length (FL) and pennation angle (PA), and sprint performance as well as their relationship in under 13 to 15 youth soccer players. We measured 85 players in under-13 (n = 29, age = 12.5 [0.1] y, height = 155.3 [6.2] cm, weight = 43.9 [7.6] kg), under-14 (n = 25, age = 13.5 [0.3] y, height = 160.6 [7.7] cm, weight = 47.0 [6.8] kg), and under-15 (n = 31, age = 14.4 [0.3] y, height = 170.0 [7.7] cm, weight = 58.1 [8.8] kg) teams. We used ultrasound to measure BFlh ACSA, FL and PA, and sprint tests to assess 10- and 30-m sprint time, maximal velocity (vmax), and maximal acceleration (αmax). We calculated Pearson r to assess the relationship between sprint ability and architectural parameters. All muscle architectural parameters increased from the under-13 to the under-15 age group (BFlh ACSA = 37%, BFlh FL = 11%, BFlh PA = 8%). All sprint performance parameters improved from the under-13 to under-15 age categories (30-m time = 7%, 10-m time = 4%, vmax = 9%, αmax = 7%). The BFlh ACSA was correlated with 30-m sprint time (r = -.61 (95% compatibility interval [CI] [-.73, -.45]) and vmax (r = .61, 95% CI [.45, .72]). A combination of BFlh ACSA and age best predicted 30-m time (R² = .47 [.33, .62]) and 10-m time (R² = .23 [.08, .38]). Muscle architectural as well as sprint performance parameters increase from the under-13 to under-15 age groups. Even though we found correlations for all assessed architectural parameters, BFlh ACSA was best related to the assessed sprint parameters.

 

 

#4 Evaluating the effects of oral contraceptive use on biomarkers and body composition during a competitive season in collegiate female soccer players

Reference: J Appl Physiol (1985). 2021 May 6.  doi: 10.1152/japplphysiol.00818.2020. Online ahead of print.

Authors: Brittany N Bozzini, Bridget A McFadden, Kirsty J Elliott-Sale, Paul A Swinton, Shawn M Arent

Summary: High training demands throughout the competitive season in female collegiate soccer players have been shown to induce changes in biomarkers indicative of stress, inflammation, and reproduction, which may be exacerbated in athletes using oral contraceptives (OCs). The purpose was to compare biomarkers and body composition between OC-using and non-using (CON) female soccer players throughout a competitive season. Female collegiate soccer players were stratified into two groups based on their reported OC use at the start of pre-season (OC: n=6; CON: n=17). Prior to the start of pre-season and immediately post-season, athletes underwent a battery of performance tests. Blood draws and body composition assessments were performed prior to pre-season, on weeks 2, 4, 8, and 12 of the season, and post-season. Area-under-the-curve ratios (OCAUC:CONAUC) indicated the OC group were exposed to substantially higher levels of sex-hormone binding globulin (AUCratio=1.4, probability=p>0.999), total cortisol (1.7; p>0.999), c-reactive protein (5.2; p>0.999), leptin (1.4; p=0.990), growth hormone (1.5; p=0.97), but substantively lower amounts ofestradiol (0.36; p<0.001),progesterone (0.48; p=0.008), free testosterone (0.58; p<0.001), follicle-stimulating hormone (0.67; p<0.001) and creatine kinase (0.33, p<0.001) compared with the CON across the season. Both groups increased fat free mass over the season, but CON experienced a greater magnitude of increase along with decreased body fat percentage. Although similar training loads were observed between groups over the season, the elevated exposure to stress, inflammatory, and metabolic biomarkers over the competitive season in OC users may have implications on body composition, training adaptations, and recovery in female athletes.

 

 

#5 Effect of a simple core muscle training program on trunk muscle strength and neuromuscular control among pediatric soccer players

Reference: J Exp Orthop. 2021 May 6;8(1):36.  doi: 10.1186/s40634-021-00353-y.

Authors: yRyotaro Kumahara, Shizuka Sasaki, Eiji Sasaki, Yuka Kimura, Yuji Yamamoto, Eiichi Tsuda, Yasuyuki Ishibashi

Download link: https://jeo-esska.springeropen.com/track/pdf/10.1186/s40634-021-00353-y.pdf

Summary: The purpose of this study was to examine the effect of simple core muscle training (CMT) program on trunk muscle strength and neuromuscular control among pediatric athletes. Forty-nine male soccer players (mean age, 10.8 years) participated. The CMT program had three components (bench, side bench, and Nordic hamstrings) and was performed at least three times weekly for a year. Trunk flexion/extension muscle strength and the K/H ratio (determined by dividing knee separation distance by hip separation distance during drop-jump test and used as an index of lower limb valgus alignment) were measured, and the Y balance test (YBT) was performed before and after intervention. This study did not include the pure control group among the same team. To consider the effect of CMT on trunk muscle strength due to physical growth, we used the data of trunk muscle strength from the local cohort study previously conducted in our institution. One hundred participants who matched the age, height, body weight, and body mass index of the training group was designated as a control group. In the training group, the trunk flexion/extension strength significantly increased at 6 months (p < 0.001, p < 0.001, respectively) and 12 months (p < 0.001, p < 0.001, respectively) compared to initial value. The K/H ratio at initial contact and maximum knee flexion phase significantly increased at 6 months (p < 0.001 and p < 0.001, respectively); however, it did not increase at 12 months (p = 0.384 and p = 0.070, respectively) compared to the initial value. In the YBT, the maximized reach distance in each direction significantly increased after intervention on both the dominant and non-dominant sides, except in the posteromedial direction on the non-dominant foot. Compared to the control group, although there was no significant difference in trunk flexion/extension strength at baseline (p = 0.141 and p = 0.390, respectively), the training group showed significantly higher trunk flexion/extension muscle strength at 12 months (p < 0.001 and p < 0.001, respectively). The CMT program increased trunk muscle strength and improved dynamic balance among pediatric male athletes.

 

 

#6 Increased occurrence of ACL injuries for football players in teams changing coach and for players going to a higher division

Reference: Knee Surg Sports Traumatol Arthrosc. 2021 May 13.  doi: 10.1007/s00167-021-06604-w.

Authors: Alexander Sandon, Werner Krutsch, Volker Alt, Magnus Forssblad 

Download link: https://link.springer.com/content/pdf/10.1007/s00167-021-06604-w.pdf

 

 

#7 The porous high-press? An experimental approach investigating tactical behaviours from two pressing strategies in football

Reference: J Sports Sci. 2021 May 13;1-12.  doi: 10.1080/02640414.2021.1925424. Online ahead of print.

Authors: Benedict Low, Robert Rein, Dominik Raabe, Sebastian Schwab, Daniel Memmert

Summary: The aim of this study was to analyse footballers' tactical behaviours from their position data, as an effect of two contrasting pressing strategies, high-press defending and deep-defending, using a trial-based experimental approach. Sixty-nine youth footballers participated in this 11 versus 11 study, performing 72 trials of attack versus defence, in a counterbalanced crossover study design. Players' position data were captured using a local positioning system, and processed to calculate measures of inter-team distance, trial duration, distance to nearest opponent, dispersion, team length, team width, team shape, space control gain, inter-line distance, and individual area. This was augmented by the notational analyses of passes. The findings showed that using a high-press defending strategy leads to: closer inter-team distance; larger dispersion, due to a longer team length; and larger inter-line distances between defenders, midfielders, and forwards. The resulting effects on the attacking team include reduced ball possession time; larger individual areas for attacking midfielders and forwards; longer team length; and more penetrative passes performed. Some differences in marking behaviour were also observed. Consequently, the study recommends that high-press defending be used sparingly due to these trade-offs.

 

 

#8 Illustrating changes in landscapes of passing opportunities along a set of competitive football matches

Reference: Sci Rep. 2021 May 7;11(1):9792.  doi: 10.1038/s41598-021-89184-6.

Authors: Luis Ignacio Gómez-Jordana, Rodrigo Amaro E Silva, João Milho, Angel Ric, Pedro Passos

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8105376/pdf/41598_2021_Article_89184.pdf

Summary: This study aims to illustrate the landscape of passing opportunities of a football team across a set of competitive matches. To do so positional data of 5 competitive matches was used to create polygons of pass availability. Passes were divided into three types depending on the hypothetical threat they may pose to the opposing defense (penetrative, support, and backwards passes). These categories were used to create three heatmaps per match. Moreover, the mean time of passing opportunities was calculated and compared across matches and for the three categories of passes. Due to the specificity of player's interactive behavior, results showed heatmaps with a variety of patterns. Specifically the fifth match was very dissimilar to the other four. However, characterizing a football match in terms of passing opportunities with a single heatmap dismisses the variety of dynamics that occur throughout a match. Therefore, three temporal heatmaps over windows of 10 min were presented highlighting on-going dynamical changes in pass availability. Results also display that penetrative passes were available over shorter periods of time than backward passes that were available shorter than support passes. The results highlight the sensibility of the model to different task constrains that emerge within football matches.

 

 

#9 Hip apophyseal injuries in soccer players: can MRI findings be useful to define when to return to play?

Reference: Skeletal Radiol. 2021 May 10.  doi: 10.1007/s00256-021-03797-6. Online ahead of print.

Authors: Andre Fukunishi Yamada, Andrea Puchnick, Frederico Roberto Pollack Filho, Erica Narahashi, Gustavo Gonçalves Arliani, Alberto de Castro Pochini, Artur da Rocha Correa Fernandes

Summary:  The aim was to describe magnetic resonance imaging (MRI) findings in professional soccer players with acute apophyseal injury of the hip and to assess their relationship with return to sports. Adolescent soccer players with diagnosis of apophyseal injury in the anterosuperior and anteroinferior iliac spine were retrospectively evaluated between 2008 and 2016. All athletes underwent hip MRI examination within 4 days after onset of clinical complaint. Images were independently analyzed by two radiologists. Medical records were reviewed to obtain clinical data. Mean displacement of the apophysis was 4.8 ± 4.6 mm. Bone edema was present in 82% of athletes and muscular edema in 41%. The mean time to return to sports was 37.3 ± 14.7 days. The difference between the measurements of the two radiologists was close to zero with agreement limits below 1.0 mm (p < 0.001). There was a significant correlation between displacement of the apophysis and return to sports, as well as between both and the presence of muscular edema. A displacement of the apophysis of 3.0 mm might serve as a parameter to predict return to sports/activity before 40 days, with a sensitivity of 92% and specificity of 96%, considering conservative physiotherapy treatment. Displacement of the apophysis and presence of muscular edema evaluated by MRI showed a significant correlation with return to sports in athletes with acute apophyseal injuries of the anterosuperior and anteroinferior iliac spines.

 

 

#10 Monitoring Individual Sleep and Nocturnal Heart Rate Variability Indices: The Impact of Training and Match Schedule and Load in High-Level Female Soccer Players

Reference: Front Physiol. 2021 Apr 26;12:678462.  doi: 10.3389/fphys.2021.678462. eCollection 2021.

Authors: Júlio A Costa, Pedro Figueiredo, Fábio Y Nakamura, António Rebelo, João Brito

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8110215/?report=reader

Summary: The purpose was to describe individual sleep habits and nocturnal heart rate variability (HRV) responses, and to explore intra-individual associations of workload with sleep and nocturnal HRV indices in high-level female soccer players throughout a 2-week competitive period. The study followed a descriptive, observational design. Thirty-four high-level female soccer players (aged 20.6 ± 2.3 years) wore wrist actigraph units and heart rate (HR) monitors during night-sleep to record objective sleep and HRV data throughout 14 days [six evening-time training sessions (ET), six rest-days (RD), and two match-days (MD)]. During each ET and MD, exercise HR (HRexe), %HRpeak, training impulse (TRIMP), session rating of perceived exertion (s-RPE) and perceived ratings of wellbeing were monitored. After ET, a higher number of players (17-22) slept less than 7 h/night, in contrast to the remaining days (i.e., MD and RD), but only 1-6 players had a sleep efficiency < 75%. The coefficient of variation (CV) for sleep duration and sleep efficiency ranged between 9-22% and 2-11%, respectively. A small negative within-subject correlation was found between TRIMP and sleep duration [r = -0.25 (-0.36; -0.12); P < 0.001] and sleep efficiency [r = -0.20 (-0.32; -0.08); P = 0.004]. A moderate and small negative within-subject correlation was found between s-RPE and sleep duration [r = -0.43 (-0.53; -0.32); P < 0.001] and sleep efficiency [r = -0.17 (-0.30; -0.05); P = 0.02]. Nocturnal HRV for the time-domain analyses ranged from 4.1 (3.9; 4.3) to 4.4 (4.1; 4.6) ln[ms], and for the frequency-domain analyses ranged from 6.3 (5.9; 6.7) to 7.5 (7.1; 7.9) ln[ms2]. CV for time-domain HRV ranged from 3 to 23%, and from 4 to 46% for the frequency-domain. Higher CV fluctuations in time- and frequency-domain HRV were particularly observed in four players. Overall, this study highlights the individual variability of sleep and nocturnal HRV indices, indicating that sleep duration may be affected by training and match schedules and workloads. Training and matches workload were not associated with nocturnal HRV in high-level female soccer players.

 

 

#11 Variations in Head Impact Rates in Male and Female High School Soccer

Reference: Med Sci Sports Exerc. 2021 Jun 1;53(6):1245-1251. doi: 10.1249/MSS.0000000000002567.

Authors: Colin M Huber, Declan A Patton, Divya Jain, Christina L Master, Susan S Margulies, Catherine C McDonald, Kristy B Arbogast

Summary: Repetitive head impacts in soccer have been linked to short-term neurophysiological deficits, and female soccer players have higher concussion rates than males. These findings have inspired investigation into gender differences in head impact exposure and how head impact rate contributes to the cumulative effect of head impact exposure on neurological outcomes. Various periods of exposure have been used to calculate head impact rates, including head impacts per season, game, and player-hour. The aim of this study was to apply different methodological approaches to quantify and compare head impact rates by gender for two seasons of high school varsity soccer. Video review was used to confirm all events recorded by a headband-mounted impact sensor and calculate playing time for all players. Impact rates were calculated per athlete exposure (presence and participation) and per player-hour (scheduled game time, individual play time, and absolute time). Impact rates per athlete exposure ranged from 2.5 to 3.2 for males and from 1.4 to 1.6 for females, and impact rates per player-hour ranged from 2.7 to 3.8 for males and from 1.0 to 1.6 for females. The exposure calculation method significantly affected head impact rates; however, regardless of approach, the head impact rate for males was higher, up to threefold, than for females. Individual head impact exposure varied substantially within a team with one in five players experiencing no impacts. Overall, the gender differences found in this study indicate that males experience higher head impact exposure compared with females. Future studies are needed to understand potential clinical implications of variability in head impact exposure and reconcile higher female concussion rates with the reduced head impact rates presented herein.

 

 

#12 Off-training physical activity and training responses as determinants of sleep quality in young soccer players

Reference: Sci Rep. 2021 May 13;11(1):10219.  doi: 10.1038/s41598-021-89693-4.

Authors: Nuno Mateus, Juliana Exel, Bruno Gonçalves, Anthony Weldon, Jaime Sampaio

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8119450/

Summary: This study aimed to quantify and assess the relationship of young soccer players' off-training physical activity (PA) and training responses on sleep quality. Eleven adolescent soccer players (13 ± 0.5 years old) were monitored during weekdays for four consecutive weeks, throughout soccer practice days. Off-training PA and sleep quality were assessed using 100 Hz tri-axial accelerometers and training responses analyzed using 20 Hz global positioning measurement units. A cluster analysis classified all cases into three different dimensions, (1) off-training PA, (2) training responses and (3) sleep quality. For each dimension, the most important variables for classifying the cases into clusters were sedentary PA and moderate-to-vigorous PA; total distance covered and impacts; and sleep onset latency and sleep fragmentation index, respectively. Afterwards, a correspondence analysis was used to identify whether off-training PA and training responses affected sleep quality. Results exposed that high to medium off-training PA combined with medium to high training responses may have decreased sleep quality. Conversely, no correspondence was observed between off-training PA and training responses, with higher sleep quality. This study emphasizes the importance of sports organizations adopting a holistic approach to youth soccer players' development, that appropriately considers the inter-relationship between lifestyle, performance and health-related information.

 

 

#13 Systematic Video Analysis of Anterior Cruciate Ligament Injuries in Professional Female Soccer Players

Reference: Am J Sports Med. 2021 May 14;3635465211008169.  doi: 10.1177/03635465211008169. 

Authors: Simona Lucarno, Matteo Zago, Matthew Buckthorpe, Alberto Grassi, Filippo Tosarelli, Rebecca Smith, Francesco Della Villa

Summary: Female soccer players are particularly susceptible to anterior cruciate ligament (ACL) injuries, accounting for 16% to 43% of the injury burden during the season. Despite the advancements in injury prevention programs, the rate of ACL injuries continues to rise. The purpose was to provide a comprehensive description of the mechanisms, situational pattern, and biomechanics of ACL injuries in women's soccer. We identified 57 consecutive ACL injuries that occurred in matches of 6 top female leagues across 3 seasons (2017-2020). A total of 35 (61%) injury videos were analyzed for the mechanism and situational pattern, while biomechanical analysis was possible in 29 cases. Three independent reviewers evaluated each video. The distribution of ACL injuries according to month, timing within the match, and field location at the time of injury was also reported. In the 35 injury videos, there were 19 (54%) noncontact injuries, 12 (34%) indirect contact injuries, and 4 (11%) direct contact injuries. We identified 3 main situations in players who suffered a noncontact/indirect contact injury: (1) pressing and tackling (n = 18), (2) regaining balance after kicking (n = 7), and (3) being tackled (n = 4). Biomechanical analysis indicated multiplanar mechanisms with frequent knee valgus loading (88%). Additionally, 64% of injuries occurred in the first half of matches and most frequently within the first 30 minutes. Female athletes showed remarkable similarities with elite male players in terms of the ACL mechanism and situational pattern of injury, and 88% of injuries involved no direct contact to the knee, with noncontact injuries being highly prevalent. Injuries occurred during 3 main situations, with accompanying alterations in multiplanar biomechanics. Interventions aimed at reducing ACL injuries in women's soccer should consider high-intensity defensive play at the beginning of a match. Instruction in the 3 main situations should be applied alongside appropriate neuromuscular training interventions.

 

Tue

12

Oct

2021

Fascial therapy, strength exercises and taping in soccer players with recurrent ankle sprains: A randomized controlled trial

The objective was to evaluate the effectiveness of a fascial therapy and strength training program, combined with kinesiotaping, in improving ankle range of motion, pain, strength and stability in footballers with recurrent sprains.

Mon

11

Oct

2021

The Influence of Menstrual Cycle on Bioimpedance Vector Patterns, Performance, and Flexibility in Elite Soccer Players

This study aimed to examine whether menstrual cycle affects body composition and bioimpedance vector analysis (BIVA) patterns, jumping and sprinting ability and flexibility in elite soccer players.

Fri

08

Oct

2021

UEFA Champions League Pre-Match Warm-Up Sevilla FC

Thanks to a friend I was able to attend the UEFA Champions League match Wolfsburg vs. Sevilla and I recorded the warm-ups of the teams.

 

Below are parts from Sevilla FC.

Thu

07

Oct

2021

Neuromuscular Performance and Training Workload Over an In-Season Mesocycle in Elite Young Soccer Players

The purpose of this study was to assess neuromuscular performance capabilities over an in-season mesocycle in early career professional soccer players and examine the relationship with training workload.

Wed

06

Oct

2021

The effect of core stability-based corrective exercises on gait parameters in elite footballers with Middle Crossed Syndrome

The aim of this study was to investigate the effect of eight weeks of core stability based corrective exercises, on gait parameters in elite soccer players diagnosed with middle crossed syndrome.

Tue

05

Oct

2021

Latest research in football - week 31 - 2021

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 Monitoring Accumulated Training and Match Load in Football: A Systematic Review

Reference: Int J Environ Res Public Health.  2021 Apr 8;18(8):3906.  doi: 10.3390/ijerph18083906.

Authors: José E Teixeira, Pedro Forte, Ricardo Ferraz, Miguel Leal, Joana Ribeiro, António J Silva, Tiago M Barbosa, António M Monteiro

Download link: https://www.mdpi.com/1660-4601/18/8/3906/htm

Summary: Training load monitoring has become a relevant research-practice gap to control training and match demands in team sports. However, there are no systematic reviews about accumulated training and match load in football. Following the preferred reporting item for systematic reviews and meta-analyses (PRISMA), a systematic search of relevant English-language articles was performed from earliest record to March 2020. The search included descriptors relevant to football, training load, and periodization. The literature search returned 7972 articles (WoS = 1204; Pub-Med = 869, SCOPUS = 5083, and SportDiscus = 816). After screening, 36 full-text articles met the inclusion criteria and were reviewed. Eleven of the included articles analyzed weekly training load distribution; fourteen, the weekly training load and match load distribution; and eleven were about internal and external load relationships during training. The reviewed articles were based on short-telemetry systems (n = 12), global positioning tracking systems (n = 25), local position measurement systems (n = 3), and multiple-camera systems (n = 3). External load measures were quantified with distance and covered distance in different speed zones (n = 27), acceleration and deceleration (n = 13) thresholds, accelerometer metrics (n = 11), metabolic power output (n = 4), and ratios/scores (n = 6). Additionally, the internal load measures were reported with perceived exertion (n = 16); heart-rate-based measures were reported in twelve studies (n = 12). The weekly microcycle presented a high loading variation and a limited variation across a competitive season. The magnitude of loading variation seems to be influenced by the type of week, player's starting status, playing positions, age group, training mode and contextual variables. The literature has focused mainly on professional men; future research should be on the youth and female accumulated training/match load monitoring.

 

 

#2 Home-Advantage during COVID-19: An Analysis in Portuguese Football League

Reference:  Int J Environ Res Public Health. . 2021 Apr 4;18(7):3761.  doi: 10.3390/ijerph18073761.

Authors: Rui Matos, Diogo Monteiro, Raul Antunes, Diogo Mendes, João Botas, João Clemente, Nuno Amaro

Download link: https://www.mdpi.com/1660-4601/18/7/3761/htm

Summary: Covid-19 pandemic forced, at the final rounds of 2019-2020 season, in many different sport leagues worldwide, teams to play without an audience. Therefore, the present paper aims to compare the home advantage score in the last ten rounds in 2019-2020 season with the first 24 rounds in same season using Pollard's (1986) and Matos et al.'s (2020) methods. In addition, comparisons across different seasons (2016-2017; 2017-2018; 2018-2019 and 2019-2020) using the same methods were also analyzed. Results showed no differences (p > 0.05) between first 24 rounds and the last 10 in 2019-2020 season as well as in the 3 previous seasons. With Pollard's method, no differences (p > 0.05) were also found among those four seasons on global (all 34 rounds) home advantage. However, a significance difference between 2017-2018 and 2019-2020 (p < 0.05) was founded using Matos et al.'s (2020) method, which is an indicator of the importance of using complementary methods when analyzing the same realities. Overall, despite what might be expectable from recent findings, the lack of an audience in the last 10 rounds of Portuguese Football League 2019-2020 season, due to COVID-19 pandemic, did not affect home advantage. Therefore, future studies could try to analyze other different variables in Portuguese Football League, such as referees' behaviors, rules changing (e.g., the possibility of making five substitutions, instead of three), crowd dimension and density as well as include variables about odds as forecasts in football being played without crowds.

 

 

#3 A 2D video-analysis scoring system of 90° change of direction technique identifies football players with high knee abduction moment

Reference: Knee Surg Sports Traumatol Arthrosc. 2021 Apr 29.  doi: 10.1007/s00167-021-06571-2.

Authors: Francesco Della Villa, Stefano Di Paolo, Dario Santagati, Edoardo Della Croce, Nicola Francesco Lopomo, Alberto Grassi, Stefano Zaffagnini

Download link: https://link.springer.com/content/pdf/10.1007/s00167-021-06571-2.pdf

Summary: Abnormal joint biomechanics and poor neuromuscular control are modifiable risk factors for Anterior Cruciate Ligament (ACL) injury. Although 3D motion capture is the gold standard for the biomechanical evaluation of high-speed multidirectional movements, 2D video analysis is a growing-interest alternative because of its higher cost-effectiveness and interpretability. The aim of the present study was to explore the possible association between a 2D evaluation of a 90° change of direction (COD) and the KAM measured with gold standard 3D motion analysis. Thirty-four competitive football (soccer) players (age 22.8 ± 4.1, 18 male and 16 females) were enrolled. Each athlete performed a series of pre-planned 90° COD at the maximum speed possible in a laboratory equipped with artificial turf. 3D motion analysis was recorded using 10 stereophotogrammetric cameras, a force platform, and three high-speed cameras. The 2D evaluation was performed through a scoring system based on the video analysis of frontal and sagittal plane joint kinematics. Five scoring criteria were adopted: limb stability (LS), pelvis stability (PS), trunk stability (TS), shock absorption (SA), and movement strategy (MS). For each criterion, a sub-score of 0/2 (non-adequate), 1/2 (partially adequate), or 2/2 (adequate) was attributed to the movement, based on objective measurements. The intra-rater and inter-rater reliability were calculated for each criterion and the total score. The Knee Abduction Moment (KAM) was extracted from the 3D motion analysis and grouped according to the results of the 2D evaluation. Excellent intra-rater reliability (ICC > 0.88) and good-to-excellent inter-rater reliability (ICC 0.68-0.92) were found. Significantly higher KAM was found for athletes obtaining a 0/2 score compared to those obtaining a 2/2 score in all the sub-criteria and the total score (20-47% higher, p < 0.05). The total score and the LS score showed the best discriminative power between the three groups. The 2D video-analysis scoring system here described was a simple and effective tool to discriminate athletes with high and low KAM in the assessment of a 90° COD and could be a potential method to identify athletes at high risk of non-contact ACL injury.

 

 

#4 The effect of motor control training according to the Kinetic Control concept on the back pain of female football players

Reference: J Back Musculoskelet Rehabil. 2021 Apr 23.  doi: 10.3233/BMR-200226. Online ahead of print.

Authors: Kamil Zaworski, Krystyna Gawlik, Anna Krȩgiel-Rosiak, Joanna Baj-Korpak

Summary: Due to a significant burden associated with training sessions and matches, female football players often suffer from lumbar pain. Physical exercise is considered an effective form of therapy for this condition. The exercises in the Kinetic Control concept are one of the forms of motor control training. The aim of the study was to evaluate the effectiveness of motor control training according to the Kinetic Control concept on the level of lumbar spine pain, degree of disability, functional level and load distribution of lower limbs in football players. The study included 18 football players, randomly divided into two study groups: A - female players implementing their training plan with additional Kinetic Control training (n= 9) and B (control) - female players implementing their training plan only (n= 9). Pain intensity was measured using Visual Analogue Scale (VAS) and Laitinen's questionnaire. Functional disability was assessed using Oswestry Disability Index (ODI) and Back Pain Functional Scale (BPFS). The asymmetry index was assessed in a balance test with open and closed eyes and a countermovement jump (CMJ). There was a significant statistical difference between the groups (p< 0.05) in measurements using VAS, ODI and BPFS, in favor of group A. Asymmetry index values in tests on the dynamometer platform did not differ significantly between the groups (p> 0.05). A statistically significant correlation was found between the asymmetry index score in the closed-eye balance test (r= 0.567, p= 0.049) and the CMJ landing phase (r= 0.641, p= 0.033), and the level of pain measured using VAS. Motor control training in the Kinetic Control concept reduced the pain symptoms of the lumbar spine and the degree of disability and increased the functional level in football female players.

 

 

#5 Dose-Response Relationships between Training Load Measures and Physical Fitness in Professional Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 19;18(8):4321.  doi: 10.3390/ijerph18084321.

Authors: Saeid Younesi, Alireza Rabbani, Filipe Manuel Clemente, Rui Silva, Hugo Sarmento, António José Figueiredo

Download link: https://www.mdpi.com/1660-4601/18/8/4321/htm

Summary: The aim of this cohort study was two-fold: (i) to analyze within-group changes of final velocity in a 30-15 intermittent fitness test (VIFT), final velocity in a Vameval test (Vvameval), 20-m sprint and countermovement jump (CMJ); (ii) to explore the relationships between VIFT and Vvameval outcomes and their changes with internal and external loads. Twenty-two professional soccer players (mean ± SD; age 27.2 ± 3.4 years, height 174.2 ± 3.6 cm, body mass 69.1 ± 6.4 kg, and body fat 10.4 ± 4.1%, 3.1 ± 1.5 years in the club) participated in this study. External and internal loads were obtained using global positioning system, heart rate and rate of perceived effort (sRPE) after each training session. Players were assessed in CMJ, 20-m sprint, Vameval and 30-15 intermittent fitness test, before and after the observed period. Very large relationships were observed between VIFT and Vameval for pre- (r = 0.76), post (r = 0.80) and pooled-data (r = 0.81). Vvameval showed less sensitivity (-22.4%, [-45.0 to 9.4]), ES -0.45 [-1.05 to 0.16]) than VIFT. ∆VIFT had unclear associations with all sRPE, but had moderate correlations with objective internal and external measures, while, ∆Vvameval varied between large and very large relationships with all sRPE, but had unclear associations with all other selected training loads. Objective internal and external loads may be used to track aerobic power related changes from VIFT.

 

 

#6 Effects of Recreational Small-Sided Soccer Games on Bone Mineral Density in Untrained Adults: A Systematic Review and Meta-Analysis

Reference: Healthcare (Basel). 2021 Apr 13;9(4):457.  doi: 10.3390/healthcare9040457.

Authors: Filipe Manuel Clemente, Rodrigo Ramirez-Campillo, Hugo Sarmento, Daniel Castillo, Javier Raya-González, Thomas Rosemann, Beat Knechtle

Download link: https://www.mdpi.com/2227-9032/9/4/457/htm

Summary: This systematic review with meta-analysis was conducted to assess the effects of small-sided games (SSG)-based training programs on bone mineral density (BMD) in untrained adults. The data sources utilized were Cochrane, Embase, Medline (PubMed), Scopus, SPORTDiscus, and Web of Science. The study eligibility criteria were: (i) untrained adults (>18 years old) of any sex, with or without a noncommunicable disease; (ii) SSG-based programs with a minimum duration of four weeks and no restrictions regarding frequency (number of sessions per week); (iii) passive or active control groups; (iv) pre-post values of BMD; (v) only randomized controlled trials; and (vi) only original and full-text studies written in English. The database search initially yielded 374 titles. From those, nine articles were eligible for the systematic review and meta-analysis. The age of included population varied from a minimum of 20 and a maximum of 71 years old. Non-significant differences between SSG and passive and active control groups on total BMD (ES = 0.14; p = 0.405 and ES = 0.28; p = 0.05, respectively). Meanwhile, significant differences in favor of SSGs vs. passive and control groups were detected, evidencing an improvement of BMD in lower limbs of the adult population for both sexes (ES = 0.26; p = 0.05 and ES = 0.28; p = 0.156, respectively). As conclusions, SSGs can be used as a non-pharmacological alternative to increase the BMD in the lower limbs despite having no significant impact on total body BMD. Careful generalization should be done of the level of heterogeneity.

 

 

#7 Examination of the Sprinting and Jumping Force-Velocity Profiles in Young Soccer Players at Different Maturational Stages

Reference: Int J Environ Res Public Health. 2021 Apr 27;18(9):4646.  doi: 10.3390/ijerph18094646.

Authors: Luis Miguel Fernández-Galván, Daniel Boullosa, Pedro Jiménez-Reyes, Víctor Cuadrado-Peñafiel, Arturo Casado

Download link: https://www.mdpi.com/1660-4601/18/9/4646/htm

Summary: The aim was to determine the relationships among components of the force-velocity (F-V) profiles in jumping and sprinting, with both biological and chronological ages in 89 young soccer players belonging to categories from U10 to U18. Participants performed countermovement jumps (CMJ) and 20-m sprint tests. F-V components assessed were associated with both maturity offset and chronological age, using correlation and multiple linear regression analyses. Horizontal (i.e., maximal theoretical force [F0] and velocity [V0], maximal power [Pmax] and F-V slope) and vertical (i.e., [F0] and [Pmax]) F-V components displayed very large correlations (i.e., 0.79 ≤ r ≤ 0.92) with both chronological age and maturity offset. The combination of sprinting Pmax and training experience and jumping F0 and training experience explained up to 94% of the variances in maturity offset and chronological age. Furthermore, similar correlations were found between sprinting and jumping performances, and components of the F-V profiles, and both maturity offset and chronological age. Identification of vertical jump and sprint mechanical determinants may assist in strengthening those components of the F-V profile which are weaker throughout the training process. Sprinting and jumping capabilities can be indistinctly monitored with respect to their chronological age or maturity offset in young soccer players.

 

 

#8 Dynamic Knee Alignment and Pelvic Balance: Comparison Regarding Gender in Young Soccer Athletes

Reference: Rev Bras Ortop (Sao Paulo). 2021 Apr;56(2):175-180.  doi: 10.1055/s-0040-1721361. Epub 2021 Apr 26.

Authors: Flaviano Moreira da Silva, Denis Bordoni Canêz, Andressa Rodeghiero Madeira, Gustavo Dias Ferreira

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8075638/pdf/10-1055-s-0040-1721361.pdf

Summary: The aim was to evaluate knee alignment in the frontal plane and pelvic balance during the step-down test in female and male soccer players.  Cross-sectional study carried out with male and female soccer players from under-15 and under-17 teams of a professional club in Southern Brazil. The step-down test was performed, filmed with a video camera, and evaluated according to the angular measurements obtained during movement using the Kinovea software (open source), version 0.8.24. The sample consisted of 38 individuals, 19 males and 19 females. Female athletes had a greater varus angle (9.42° ± 1.65°) compared to male athletes (3.91° ± 2.0°; p = 0.04). There was no difference regarding the unilateral pelvic drop between the groups. In addition, the association between the hip-related pelvic drop and the projection angle on the frontal plane of the knee was weak in both genders. Even though the pelvic drop was observed in both genders, young female athletes had greater varus knee angles on the step-down test, which require greater attention to minimize the risk of injury.

 

 

#9 High and highly bonded: Fused football fans who use cocaine are most likely to be aggressive toward rivals

Reference: Int J Drug Policy. 2021 May 3;103263.  doi: 10.1016/j.drugpo.2021.103263. Online ahead of print.

Authors: Martha Newson

Summary: Cocaine use among British football fans has yet to be quantified, despite its association with football-related aggression by the media. Identity fusion, a potent form of social bonding, is a well-established predictor of fan violence, which has never been investigated in relation to stimulant use. British football fans (n = 1486) completed a self-selected online survey about how bonded they were to their club and fellow fans, their cocaine use, and aggressive behavior toward rival fans over the prior 12-months. Fans reported more cocaine use than the national average (6.19%). Of fans who attended stadia matches, 1.08% had used cocaine in stadia, and 30.05% had witnessed other fans take cocaine at matches. Fans who used cocaine reported significantly more aggression toward rivals than fans who did not. Cocaine and identity fusion significantly interacted, such that highly 'fused' cocaine users were especially likely to have behaved aggressively toward their rivals. Men were more fused and more aggressive than women. Football mirrors wider society, be it in social issues or drug use. The widespread availability of cheap but high purity cocaine may be associated with fan aggression, especially among fans who are highly bonded to their clubs and fellow fans.

 

 

#10 Drilling under the COVID-19 pandemic: A diary study of professional football players' mental health and workout performance

Reference: Stress Health. 2021 May 4.  doi: 10.1002/smi.3059.

Authors: Shuhua Sun, Stephen X Zhang, Asghar Afshar Jahanshahi, Mehdi Jahanshahi

Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1002/smi.3059

Summary: There is little research examining how individuals' daily experience during a pandemic affects their daily mental health status and work performance. To address this knowledge gap, we invoke conservation of resources theory to propose a resource-based framework explaining how individuals' daily COVID-19 intrusive experience affects their daily mental health status (depression and anxiety) and work performance via its effect on daily psychosocial resource loss and gain; We further examine whether their supervisors' daily visionary leadership behaviour alleviates the adverse impacts of daily COVID-19 intrusive experience. Results, based on daily diary data from 139 football players (or soccer players) at 15 professional football clubs over 5 days during the COVID-19 pandemic, provided support for our predictions. Our study extends the literature by providing previously undocumented evidence on daily within-person variations in mental health status and work performance during a pandemic and by offering theory-driven insights into the mediating and moderating mechanisms involved in within-person variations.

 

 

#11 The effects of training on hormonal concentrations and physical performance of football referees

Reference: Physiol Rep. 2021 Apr;9(8):e14740.  doi: 10.14814/phy2.14740.

Authors: Antonella Muscella, Erika Stefàno, Santo Marsigliante

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8087984/pdf/PHY2-9-e14740.pdf

Summary: As no study has explored the impact of physical stress on hypothalamic-pituitary-gonadal axis hormones over a long period, the purpose of this study was to determine the effects of the football season period on plasma cortisol and testosterone concentrations and referee's physical performances. Physical tests and plasma cortisol and testosterone concentrations were assayed before the beginning of the training period, just after the training period, at the middle of the season, and at the end of the season, in 29 male football referees and 30 healthy control subjects. Results showed significant differences in hormone concentrations at the four-time points evaluated. Plasma cortisol increased during the first training period from 15.8 ± 3.8 to 21.7 ± 5.1 µg/dl (p < 0.001), then decreased during the season and at the end of it was 18.7 ± 2.4 µg/dl. Before the beginning of the training period, plasma testosterone concentration was 386.1 ± 58.8 ng/dl; after the training period, it increased to 572.2 ± 88.1 ng/dl (p < 0.001) and then returned to baseline levels at the end of the season. Between the start of the training period and the end of the season, significant differences were observed in physical performances of referees. Plasma cortisol and testosterone levels significantly (p < 0.0001 for both) correlated with Yo-Yo intermittent recovery test level 1 (YYIRT1) and maximal oxygen consumption (VO2max ) at the end of the training period. In the middle season, plasma testosterone concentration only significantly (p < 0.0001) correlated with YYIRT1 and VO2max . These data underline the importance of set up training protocols that present the prospective to favor positive physiological adaptations.

 

 

#12 SARS-CoV-2 serological assay and viral testing: a report of professional football setting

Reference: Postgrad Med J. 2021 Apr 30;postgradmedj-2021-140176.  doi: 10.1136/postgradmedj-2021-140176. 

Authors: Bahar Hassanmirzaei, Zohreh Haratian, Ali Ahmadzadeh Amiri, Amir Ahmadzadeh Amiri, Navid Moghadam

Download link: https://pmj.bmj.com/content/postgradmedj/early/2021/04/29/postgradmedj-2021-140176.full.pdf

Summary: PCR is the current standard test for the diagnosis of SARS-CoV-2 infection. However, due to its limitations, serological testing is considered an alternative method for detecting SARS-CoV-2 exposure. In this study, we measured the level of SARS-CoV-2 IgM and IgG antibodies of male professional football players and compared the results with the standard PCR test to investigate the association between the two tests. Participants were male professional football players and team officials. Nasopharyngeal swabs and peripheral blood samples were collected for the PCR and serological tests, respectively. Also, previous records of COVID-19 testing and symptoms were gathered. Those with previous positive PCR tests who tested negative for the second time were considered to be recovered patients. Of the 1243 subjects, 222 (17.9%) were seropositive, while 29 (2.3%) tested positive for the SARS-CoV-2 PCR test. Sixty percent of symptomatic cases with a negative PCR were found to be seropositive. The mean level of IgM was significantly higher in PCR-positive and symptomatic subjects, whereas the recovered cases showed significantly higher levels of IgG. Our study revealed an inconsistency of results between the two tests; therefore, although application of serological assays alone seems insufficient in diagnosing COVID-19 disease, the findings are beneficial in the comprehension and the management of the disease.

 

 

#13 Physical Demands of Women's Soccer Matches: A Perspective Across the Developmental Spectrum

Reference: Front Sports Act Living. 2021 Apr 16;3:634696.  doi: 10.3389/fspor.2021.634696. eCollection 2021.

Authors: Jason D Vescovi, Elton Fernandes, Alexander Klas

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8085412/pdf/fspor-03-634696.pdf

Summary: Female soccer players are exposed to specific physical demands during matches, which vary according to the standard of play. Existing studies have largely focused on quantifying the distances covered for professional and international level players. This approach is limited in scope regarding the broader aspects around physical demands and is detached from development pathway models. An understanding of the demands across all standards will provide valuable insights about appropriate player development and help ensure physical readiness for the demands of the sport. The aim of this perspective paper is to describe the physical demands experienced during women's soccer matches across the developmental spectrum. A combination of evidence from the literature and data from the author's research (JDV) is presented. Specifically highlighted are the trends for locomotor distances, acceleration and deceleration frequency, and metabolic power metrics for youth (≤U17), college (NCAA/U20), professional (domestic) and international standards of women's soccer. In addition, the changes in match demands between levels of play are used to help illustrate gaps that must be overcome in order to successfully achieve physical readiness to compete at higher levels. The evidence demonstrates the importance of training appropriate attributes to prepare female soccer players who are striving to play at progressively higher standards.

 

Mon

04

Oct

2021

Match running performance in Brazilian professional soccer players: comparisons between successful and unsuccessful teams

This study aimed to compare the match running performance between bottom (BR)- and top-ranked (TopR) teams (4 each) in professional soccer players over the 2020 season of the Brazilian National 2nd Division League. This study verified the independent and interactive effects of playing position and contextual factors on running outputs between these teams.

Fri

01

Oct

2021

Match running performance in Brazilian professional soccer players: comparisons between successful and unsuccessful teams

This study aimed to compare the match running performance between bottom- and top-ranked teams (4 each) in  professional soccer players over the 2020 season of the Brazilian National 2nd Division League. This study verified the independent and interactive effects of playing position and contextual factors on running outputs between these teams.

Wed

22

Sep

2021

Latest research in football - week 30 - 2021

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 Phase Angle Is Related to 10 m and 30 m Sprint Time and Repeated-Sprint Ability in Young Male Soccer Players

Reference: Int J Environ Res Public Health.  2021 Apr 21;18(9):4405.  doi: 10.3390/ijerph18094405.

Authors: Priscila Custódio Martins, Anderson Santiago Teixeira, Luiz Guilherme Antonacci Guglielmo, Juliana Sabino Francisco, Diego Augusto Santos Silva, Fábio Yuzo Nakamura, Luiz Rodrigo Augustemak de Lima

Download link: https://www.mdpi.com/1660-4601/18/9/4405/htm

Summary: The aim was to examine the association between phase angle (PhA) and bioelectrical impedance vector analysis (BIVA) and components of physical performance in male youth soccer players. Sixty-two players from two professional soccer academies were recruited. Electrical bioimpedance was used to obtain the PhA and BIVA. Body fat (BF) and lean soft tissue mass (LSTM) were measured by dual-energy X-ray absorptiometry. All players completed physical tests including the standing long jump (SLJ), Carminatti's test (peak speed at the end of the test, PST-CAR), 10 m and 30 m straight-line sprints, and repeated-sprint ability (RSA) test (RSAbest and RSAmean times). Adjusting for chronological age, BF, and LSTM, multiple regression analysis outputs showed that PhA remained inversely related to RSAmean (β = -0.362; p < 0.001), RSAbest (β = -0.239; p = 0.020), 10 m (β = -0.379; p = 0.012), and 30 m (β = -0.438; p < 0.001) sprint times, while the association with PST-CAR and SLJ performance were statistically non-significant. In addition, BIVA showed that differences in confidence ellipses were found between athletes in the reference population and the study sample (p < 0.05). The tolerance ellipses indicated that the athletes in the present study had more total body water (TCW) and lower proportions of intracellular water (ICW) to extracellular water (ECW). The reference population had more TCW and ICW/ECW. Our results suggest that young soccer players with higher PhA values, indicating better cell integrity and functionality, have better performance in typical anaerobic running activities, such as sprinting speed and RSA performance, adjusted to age and body composition characteristics.

 

 

#2 Match Analysis of Soccer Refereeing Using Spatiotemporal Data: A Case Study

Reference: Sensors (Basel). 2021 Apr 5;21(7):2541.  doi: 10.3390/s21072541.

Authors: Bruno Gonçalves, Diogo Coutinho, Bruno Travassos, João Brito, Pedro Figueiredo

Download link: https://www.mdpi.com/1424-8220/21/7/2541/htm

Summary: This case study explored how spatiotemporal data can develop key metrics to evaluate and understand elite soccer referees' performance during one elite soccer match. The dynamic position of players from both teams, the ball and three elite referees allowed to capture the following performance metrics: (i) assistant referees: alignment with the second last defender; (ii) referee: referee diagonal movement-a position density was computed and a principal component analysis was carried to identify the directions of greatest variability; and (iii) referee: assessing the distance from the referee to the ball. All computations were processed when the ball was in-play and separated by 1st and 2nd halves. The first metric showed an alignment lower than 1 m between the assistant referee and the second last defender. The second metric showed that in the 1st half, the referee position ellipsis area was 548 m2, which increased during the 2nd half (671 m2). The third metric showed an increase in the distance from the referee to the ball and >80% of the distance between 5-30 m during the 2nd half. The findings may be used as a starting point to elaborate normative behavior models from the referee's movement performance in soccer.

 

 

#3 Comparative Analysis of Soccer Performance Intensity of the Pre-Post-Lockdown COVID-19 in LaLiga™

Reference: Int J Environ Res Public Health. 2021 Apr 1;18(7):3685.  doi: 10.3390/ijerph18073685.

Authors: Abraham García-Aliaga, Moisés Marquina, Antonio Cordón-Carmona, Manuel Sillero-Quintana, Alfonso de la Rubia, Ignacio Refoyo Román 

Download link: https://www.mdpi.com/1660-4601/18/7/3685/htm

Summary: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) forced a stoppage in the 2019/2020 season of LaLiga™, possibly influencing performance indicators in the return to competition. Therefore, here, we evaluated whether the stoppage due to the coronavirus 2019 disease (COVID-19) lockdown influenced physical performance compared to the start of LaLigaTM in terms of high-intensity efforts. Using a semi-automatic, multiple-camera system, running activities during 22 matches were analyzed. We compared the first 11 matches of the season (pre-lockdown) with the 11 matches just after the restart of LaLiga™ (post-lockdown). The results showed higher (p < 0.05) performance in the pre-lockdown period compared with the post-lockdown period, including in medium-speed running (14.1-21 km/h), high-speed running (21.1-24 km/h), and sprinting speed running distances (>24 km/h). However, the number of accelerations/min and decelerations/min were significantly higher during the post-lockdown period. Therefore, we conclude that the stoppage due to the COVID-19 lockdown generated lower physical performance in the post-lockdown period compared with the pre-lockdown period, most likely due to the accumulation of matches (congested schedules).

 

 

#4 Effectiveness of the FIFA 11+ Referees Injury Prevention Program in reducing injury rates in male amateur soccer referees

Reference: Scand J Med Sci Sports. 2021 Apr 29.  doi: 10.1111/sms.13983. Online ahead of print.

Authors: Wesam Saleh A Al Attar, Mario Bizzini, Fahad Alkabkabi, Nasser Alshamrani, Saud Alarifi, Hosam Alzahrani, Hussain Ghulam, Eman Aljedaani, Ross H Sanders

Summary: The Fédération International de Football Association (FIFA) 11+ Referees Injury Prevention Program (FIFA 11+ Referees Program) is a structured warm-up program specially designed to prevent injuries in soccer referees. However, its effectiveness has yet to be fully documented in the literature. Therefore, the purpose of this study was to investigate the effectiveness of the FIFA 11+ Referees Program in reducing injury rates among soccer referees. A cluster randomized controlled trial was conducted. Two hundred male amateur soccer referees (mean±SD age, 31.6±4.1 years) participated in this study. Participants were randomly allocated to the experimental and control groups. The experimental group performed the FIFA 11+ Referees Program as a warm-up during training sessions at least twice a week, and the control group performed their usual warm-ups. The participants were followed up for one season. The outcome measures were the incidence of overall injury, initial injury, recurrent injury, injury mechanism, and injury severity (primary), and the rate of adherence to the intervention program (secondary). A total of 24 injuries were reported among 100 referees in the control group in 16606 hours of exposure (1.45 injuries/1000 exposure hours), and a total of nine injuries were reported across 100 referees within the experimental group in 17834 exposure hours (0.50 injuries/1000 exposure hours). The Injury Risk Ratio (IRR) was 0.35 (95% CI 0.26 to 0.45). The results indicated that the FIFA 11+ Referees Program effectively reduced injuries in the experimental group by 65% compared to the control group.

 

 

#5 The Influence of Playing Formation on Physical Demands and Technical-Tactical Actions According to Playing Positions in an Elite Soccer Team

Reference: Int J Environ Res Public Health. 2021 Apr 14;18(8):4148.  doi: 10.3390/ijerph18084148.

Authors: José Luis Arjol-Serrano, Miguel Lampre, Adrián Díez, Daniel Castillo, Fernando Sanz-López, Demetrio Lozano

Download link: https://www.mdpi.com/1660-4601/18/8/4148/htm

Summary: The aim of this study was to examine the differences in the physical demands and technical-tactical actions encountered by soccer players between two playing formations (1-4-2-3-1 and 1-4-4-2) for each playing position. Twenty-three professional male soccer players who played 31 official matches participated in this study. Players were classified according to their playing position: central defenders (CD), wide defenders (WD), central midfielders (CM), wide midfielders (WM), offensive midfielders (OM) and forwards (FW). The physical demands were collected as total distance (TD), distance covered in different speed thresholds, and number of accelerations and decelerations. Also, the technical-tactical variables were recorded. The results showed that the 1-4-2-3-1 playing formation demanded decelerations between 2-4 m·s2 (p = 0.027; ES = 0.26) in comparison with 1-4-4-2 for all players. Likewise, forwards (FW) and central midfielders (CM) registered higher physical demands playing with the 1-4-2-3-1 compared to the 1-4-4-2 formation. Regarding the technical-tactical actions, they showed differences between the playing positions of the two playing formations. The findings suggest coaches prescribe specific training programs based on the influence of the playing formation and playing position on the physical demands and technical-tactical actions encountered by players during official match-play.

 

 

#6 Muscle Damage and Performance after Single and Multiple Simulated Matches in University Elite Female Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 14;18(8):4134.  doi: 10.3390/ijerph18084134.

Authors: Tai-Ying Chou, Kazunori Nosaka, Trevor C Chen

Download link: https://www.mdpi.com/1660-4601/18/8/4134/htm

Summary: The present study aimed to compare changes in muscle damage and performance parameters after playing single versus multiple soccer matches to examine fixture congestion effects on performance. Twelve elite female university soccer players performed single, three and six consecutive 90-min bouts of the Loughborough Intermittent Shuttle Test (LIST) with ≥12-weeks between conditions in a pseudo-randomized order. Heart rate, blood lactate, rating of perceived exertion and covering distance in each LIST were examined. Changes in several types of muscle damage (e.g., maximal voluntary isometric torque of the knee extensors: MVC-KE) and performance measures (e.g., Yo-Yo Intermittent Recovery Test level 1: YYIR1) were taken before each LIST, 1 h, and 1-5 d after the last LIST. The total distance covered during the LIST was shorter (p < 0.05) in the 2nd-3rd, or 2nd-6th LISTs when compared with the 1st LIST. Changes (p < 0.05) in all measures were observed after the LIST, and the greatest changes were observed after the six than after the three LISTs followed by one LIST (e.g., largest changes in MVC-KE: -26 > -20 > -14%; YYIR1: -31 > -26 > -11%). Many of the variables did not recover to the baseline for 5 d after six LISTs. These suggest that fixture congestion induces greater muscle damage and performance decline than a single match.

 

 

#7 Comparison Between Soccer and Basketball of Bone Bruise and Meniscal Injury Patterns in Anterior Cruciate Ligament Injuries

Reference: Orthop J Sports Med. 2021 Apr 14;9(4):2325967121995844.  doi: 10.1177/2325967121995844. eCollection 2021 Apr.

Authors: Huijuan Shi, Li Ding, Yanfang Jiang, Haocheng Zhang, Shuang Ren, Xiaoqing Hu, Zhenlong Liu, Hongshi Huang, Yingfang Ao

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8050764/pdf/10.1177_2325967121995844.pdf

Summary: The varying effectiveness of anterior cruciate ligament (ACL) injury prevention programs between soccer and basketball may be due to differences in sport-specific injury mechanisms. Bone bruise patterns may provide information regarding injury mechanisms. The aim was to compare bone bruise and meniscal injury patterns for ACL injuries sustained in soccer versus basketball. Clinical notes, operative reports, and magnetic resonance imaging scans were reviewed for patients who sustained a noncontact ACL rupture while playing soccer or basketball between August 2016 and August 2018. The presence, location, and signal intensity of bone bruises on the tibia and femur were documented, and patterns were classified according to the location of the bone bruise in the lateral-medial direction. The meniscal and bone bruise injury patterns and the specific bone bruise locations were compared between the soccer and basketball groups. Overall, 138 patients were included (56 with soccer-related and 82 with basketball-related ACL injury). No significant difference between the groups was observed in bone bruise patterns (P = .743) or meniscal injury patterns (P = .952). Bone bruise on the lateral side only of both the femur and the tibia was the most common pattern in both soccer (41.9%) and basketball (47.0%) groups; the most common meniscal injury type was an isolated lateral meniscal injury in both soccer (50.0%) and basketball (45.0%) groups. For patients with bone bruises on both the lateral and the medial sides of both the femur and the tibia (BF+BT), the bone bruise signal intensity on the lateral side of the femur (P < .001) and tibia (P = .009) was significantly higher than that on the medial side for both groups. The bone bruises on the lateral side of the femur (P < .001) and tibia (P = .002) were significantly more anterior than those on the medial side for patients with the BF+BT pattern. No significant differences in bone bruise location or meniscal injury type were detected when comparing ACL injuries sustained during soccer versus basketball. The study results suggest a similar biomechanical loading pattern for ACL injuries in these sports.

 

 

#8 Distribution of Plantar Pressure in Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 15;18(8):4173. doi: 10.3390/ijerph18084173.

Authors: Arletta Hawrylak, Anna Brzeźna, Krystyna Chromik

Download link: https://www.mdpi.com/1660-4601/18/8/4173/htm

Summary: The aim of this study was to evaluate differences in the static and dynamic distribution of foot pressure on the ground and to investigate the relationships between body mass index (BMI) and mean variables of plantar pressure between soccer players and their non-athlete peers. The study involved 18 first-division Polish soccer players and 30 non-athlete physiotherapy students. The research experiment was conducted using the FreeMed platform. Basic descriptive statistics were calculated to summarize the variables. Additionally, in the static and dynamic tests, Spearman's rank correlations between body mass index (BMI) and plantar load were calculated. Statistically significant differences between groups were observed in the loading of the dominant limb. A statistically significant correlation between BMI and loading of both limbs was found in the static test and between BMI and loading of the dominant limb in the dynamic test. The baropodometric mat used in our study helped determine the plantar pressure distribution of soccer players and their non-athlete peers. Correlation analysis revealed that BMI was only associated with the mean plantar pressure of the dominant limb in the control group. Further research on a larger group of athletes is needed to determine how much sporting activity may affect the development to modifications within feet in soccer players.

 

 

#9 Motor Performance in Male Youth Soccer Players: A Systematic Review of Longitudinal Studies

Reference: Sports (Basel). 2021 Apr 19;9(4):53.  doi: 10.3390/sports9040053.

Authors: Maryam Abarghoueinejad, Adam D G Baxter-Jones, Thayse Natacha Gomes, Daniel Barreira, José Maia

Download link: https://www.mdpi.com/2075-4663/9/4/53/htm

Summary: The aim of this systematic review was to identify and synthesize the available information regarding longitudinal data addressing young soccer players' motor performance changes. Following the Preferred Reporting Items for Systematic and Meta-analyses (PRISMA) statement, literature searches were performed in three databases: PubMed, ISI Web of Science and SCOPUS. The following descriptors were used: football, soccer, youth, young, player, athlete, physical performance, motor performance, longitudinal. The inclusion criteria were original articles in English with longitudinal data of young males (aged 10-18 years), with the aim to investigate motor performance serial changes. The initial search returned 211 records, and the final sample comprised 32 papers. These papers covered the European continent, and used mixed and pure longitudinal design with variation in sample size and age range. The reviewed studies tended to use different tests to assess the motor performance and aimed to identify changes in motor performance in several ways. In general, they indicated motor performance improvements with age, with a marked influence of biological maturity, body composition, and training stimuli. This review highlights the need for coaches and stakeholders to consider players' motor performance over time whilst considering biological maturation, biological characteristics, and training stimuli.

 

 

#10 Can Rules in Technical-Tactical Decisions Influence on Physical and Mental Load during Soccer Training? A Pilot Study

Reference: Int J Environ Res Public Health. 2021 Apr 19;18(8):4313. doi: 10.3390/ijerph18084313.

Authors: Tomás García-Calvo, Juan José Pulido, José Carlos Ponce-Bordón, Miguel Ángel López-Gajardo, Israel Teoldo Costa, Jesús Díaz-García

Download link: https://www.mdpi.com/1660-4601/18/8/4313/htm

Summary: This study aimed to analyze the effects of rules limitations in pass decisions during soccer tasks on physical and mental load reported by players. Participants were 40 semiprofessional Spanish soccer players (Mage = 22.40, SD = 2.25) from two male teams. Two training sessions with four tasks (same tasks with different score system: two maintaining ball possession games with goalkeepers, and two maintaining ball possession games) in counterbalanced order between teams were completed. To achieve a goal during limitation tasks, a minimum number of players had to participate in the passes before the goal. Internal (perceived effort and heart rate) and external physical load (distances), mental load (validated adaptation of the NASA-TXL) and fatigue (VASfatigue) were quantified. Paired t-test and magnitude-based inference were conducted. The results showed significantly higher mean speeds (p < 0.01), effort perception (p < 0.001), and mental fatigue (very likely positive) during possession games with restrictions. Additionally, performance satisfaction obtained significantly higher values with goalkeepers and pass restrictions (very likely positive). External physical load showed no significant differences between situations. The influence of mental fatigue on internal load and the complexity of the tasks could explain these results. Coaches can use this information to manipulate the training load in ecological conditions.

 

 

#11 Association between Training Load and Well-Being Measures in Young Soccer Players during a Season

Reference: Int J Environ Res Public Health. 2021 Apr 22;18(9):4451. doi: 10.3390/ijerph18094451.

Authors: Hadi Nobari, Ana Ruivo Alves, Hamed Haghighi, Filipe Manuel Clemente, Jorge Carlos-Vivas, Jorge Pérez-Gómez, Luca Paolo Ardigò

Download link: https://www.mdpi.com/1660-4601/18/9/4451/htm

Summary: This study aimed to analyze the correlations among weekly (w) acute workload (wAW), chronic workload (wCW), acute/chronic workload ratio (wACWR), training monotony (wTM), training strain (wTS), sleep quality (wSleep), delayed onset muscle soreness (wDOMS), fatigue (wFatigue), stress (wStress), and Hooper index (wHI) in pre-, early, mid-, and end-of-season. Twenty-one elite soccer players (age: 16.1 ± 0.2 years) were monitored weekly on training load and well-being for 36 weeks. Higher variability in wAW (39.2%), wFatigue (84.4%), wStress (174.3%), and wHI (76.3%) at the end-of-season were reported. At mid-season, higher variations in wSleep (59.8%), TM (57.6%), and TS (111.1%) were observed. Moderate to very large correlations wAW with wDOMS (r = 0.617, p = 0.007), wFatigue, wStress, and wHI were presented. Similarly, wCW reported a meaningful large association with wDOMS (r = 0.526, p < 0.001); moderate to very large associations with wFatigue (r = 0.649, p = 0.005), wStress, and wHI. Moreover, wTM presented a large correlation with wSleep (r = 0.515, p < 0.001); and a negatively small association with wStress (r = -0.426, p = 0.003). wTS showed a small to large correlation with wSleep (r = 0.400, p = 0.005) and wHI; also, a large correlation with wDOMS (r = 0.556, p = 0.028) and a moderate correlation with wFatigue (r = 0.343, p = 0.017). Wellness status may be considered a useful tool to provide determinant elite players' information to coaches and to identify important variations in training responses.

 

 

#12 External Loads in Under-12 Players during Soccer-7, Soccer-8, and Soccer-11 Official Matches

Reference: Int J Environ Res Public Health. 2021 Apr 26;18(9):4581.  doi: 10.3390/ijerph18094581.

Authors: Mario Sanchez, Rodrigo Ramirez-Campillo, Daniel Hernandez, Manuel Carretero, Jesus Maria Luis-Pereira, Javier Sanchez-Sanchez

Download link: https://www.mdpi.com/1660-4601/18/9/4581/htm

Summary: The aim of this study was to compare the external loads (i.e., displacement distances and velocities) of 10-11 years-old soccer players during Soccer-7 (i.e., seven-a-side), Soccer-8 (i.e., eight-a-side), and Soccer-11 (i.e., eleven-a-side) official matches. Male athletes (n = 133; age, 10.9 ± 0.8 years) were measured during official matches for total distance (TD), relative distance (Drel), maximal velocity (Vmax), acceleration (ACC), deceleration (DEC), and absolute and relative distance covered at different velocities. Data during matches were collected using a Global Positioning System unit. Greater TD was recorded during Soccer-11 compared to Soccer-7 and Soccer-8 (p < 0.01), and greater Drel during Soccer-11 compared to Soccer-8 (p < 0.05). Absolute ACC was greater during Soccer-11 compared to Soccer-7 (p < 0.01), although relative values for %ACC and %DEC were greater during Soccer-7 and Soccer-8 compared to Soccer-11 (p < 0.01). Globally, results show that Soccer-11 matches induce greater external loads compared to Soccer-7 and Soccer-8 matches. Current results may help coaches and soccer-related organizers to plan more suited soccer competitions for young players, with lower external loads.

 

 

#13 Exploring the Determinants of Repeated-Sprint Ability in Adult Women Soccer Players

Reference: Int J Environ Res Public Health. 2021 Apr 26;18(9):4595. doi: 10.3390/ijerph18094595.

Authors: Lillian Gonçalves, Filipe Manuel Clemente, Joel Ignacio Barrera, Hugo Sarmento, Francisco Tomás González-Fernández, Markel Rico-González, José María Cancela Carral

Download link: https://www.mdpi.com/1660-4601/18/9/4595/htm

Summary: This study aimed to explore the main determinants of repeated-sprint ability (RSA) in women soccer players considering aerobic capacity, sprinting performance, change-of-direction, vertical height jump, and hip adductor/abductor isometric strength. Twenty-two women soccer players from the same team participating in the first Portuguese league were observed. Fitness assessments were performed three times during a 22-week cohort period. The following assessments were made: (i) hip abductor and adductor strength, (ii) squat and countermovement jump (height), (iii) change-of-direction test, (iv) linear sprinting at 10- and 30-m, (v) RSA test, and (vi) Yo-Yo intermittent recovery test level 1. Positive moderate correlations were found between peak minimum RSA and adductor and abductor strength (r = 0.51, p < 0.02 and r = 0.54, p < 0.01, respectively). Positive moderate correlations were also found between peak maximum RSA and adductor and abductor strength (r = 0.55, p < 0.02 and r = 0.46, p < 0.01, respectively). Lastly, a moderate negative correlation was found between fatigue index in RSA and YYIR1 test performance (r = -0.62, p < 0.004). In conclusion, abductor and adductor isometric strength-based coadjutant training programs, together with a high degree of aerobic endurance, may be suitable for inducing RSA in female soccer players.

 

 

#14 High Specialization among Female Youth Soccer Players Is Associated with an Increased Likelihood of Serious Injury

Reference: Med Sci Sports Exerc. 2021 Apr 28. doi: 10.1249/MSS.0000000000002693. Online ahead of print.

Authors: Michelle Xiao, Jacie L Lemos, Calvin E Hwang, Seth L Sherman, Marc R Safran, Geoffrey D Abrams

Summary: The purpose was to assess the associations between serious injury (> 3-month time loss) and level of specialization among high-level female soccer players and to compare the specialization and college commitment ages of female youth soccer players to Division I college and professional soccer athletes. Youth, college, and professional female soccer players in the United States playing in the top league at each level were recruited to complete an anonymous online survey. The survey collected information about player demographics, soccer specialization and training patterns, history of serious injuries from soccer, and perceptions surrounding soccer specialization. Comparisons between groups were performed using 2-sample t-tests, chi-squared analyses, and multiple logistic regression models controlling for differences in age. A p-value of less than 0.05 was set as significant. A total of 1,018 (767 youth, 251 college/professional) athletes completed the survey. Serious injuries affected 23.6% of youth and 51.4% of college/professional athletes. Anterior cruciate ligament (ACL) tears were more prevalent in college/professional players compared to youth athletes (18.3% vs 4.0%; p < 0.001). Highly specialized youth athletes (66.5%) were more likely to have sustained a serious injury from soccer compared to athletes with low specialization (Odds Ratio (OR) = 2.28 [1.38-3.92]; p=0.008) but not moderate specialization (OR = 1.37 [0.83-2.27]; p=0.43). A higher proportion of youth athletes specialized at a young age (< 10 years) compared to college/professional players (44.2% vs 25.9%; p < 0.001). High specialization in female youth soccer players is associated with an increased likelihood of sustaining a serious injury. Current youth soccer players are specializing earlier and committing to play college soccer at a younger age compared to when current college and professional players did.

 

Fri

17

Sep

2021

The Coaches’ Efficacy Expectations of Youth Soccer Players with Different Maturity Status and Physical Performance

This study aimed to report possible anthropometrical and physical performance differences between youth soccer players with different maturity status and to report the coaches’ expectations, hypothesizing that coaches would expect more from players with advanced maturity.

Wed

15

Sep

2021

Coach Encouragement During Soccer Practices Can Influence Players’ Mental and Physical Loads

This study analyzed the influence of the coaches’ encouragement on the mental and physical load in soccer practices.

Tue

14

Sep

2021

Latest research in football - week 29 - 2021

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 Do hip and groin muscle strength and symptoms change throughout a football season in professional male football players? A prospective cohort study with repeated measures

Reference: J Sci Med Sport. 2021 Apr 10;S1440-2440(21)00083-9.  doi: 10.1016/j.jsams.2021.03.019. 

Authors: P van Klij, R Langhout, A M C van Beijsterveldt, J H Stubbe, A Weir, R Agricola, Y Fokker, A B Mosler, J H Waarsing, J Verhaar, I Tak 

Download link: https://www.jsams.org/action/showPdf?pii=S1440-2440%2821%2900083-9

Summary: Groin injuries are common in professional male football and result in significant complaints, time-loss and cost. We aimed to study: 1. Normal values of hip muscle strength and self-reported hip and groin function (Hip And Groin Outcome Score (HAGOS)). 2. Changes in these values throughout the season. 3. If previous (groin) injuries, leg dominance or league were associated with these outcome measures. 313 professional male football players (11 clubs) participated. Player characteristics and previous injuries were registered. Hip muscle strength (hand-held dynamometer) and HAGOS measurements were done at the start, middle and end of the season. Data from 217 players were analysed. Adduction strength (mean±standard deviation, Nm/Kg) was 3.40±0.72 (start), 3.30±0.65 (mid) and 3.39±0.74 (end) (p=0.186). Abduction strength was 3.45±0.67, 3.14±0.57 and 3.28±0.61 (p<0.001). Adduction/abduction ratio was 1.00±0.21, 1.07±0.22 and 1.05±0.23 (p<0.001). Statistically, the HAGOS-subscale 'Pain' (median [interquartile range]) deteriorated slightly during the season (p=0.005), especially from mid-season (97.5 [90.6-100.0]) to end-of-season (95.0 [87.5-100.0]) (p=0.003). Other subscale scores remained unchanged between time points; 85.7 (symptoms), 100.0 (daily living), 96.9 (sports and recreation) 100.0, (physical activities) and 90.0 (quality of life). Previous injuries were associated with lower HAGOS-scores. Dominant legs had higher abduction strength (p<0.001) and lower adduction/abduction ratio (p<0.001). No differences between leagues were found for hip muscle strength and HAGOS-scores. In Dutch male professional football players, hip muscle strength and HAGOS-scores remained relatively stable throughout the season. Pain increased slightly, which while statistically significant, was not clinically relevant.

 

 

#2 Influence of the artificial turf certification on physical performance and muscle damage in football players (QUALTURF PROJECT)

Reference: Sci Rep. 2021 Apr 21;11(1):8625.  doi: 10.1038/s41598-021-88192-w.

Authors: Javier Sanchez-Sanchez, Jose Luis Felipe, Antonio Hernandez-Martin, David Viejo-Romero, Vicente Javier Clemente-Suarez, Leonor Gallardo, Jorge Garcia-Unanue

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8060304/pdf/41598_2021_Article_88192.pdf

Summary: This study aimed to analyse the influence of the FIFA Quality PRO certification of artificial turf pitches on the physical, physiological performance and muscle damage in soccer players. Fifteen healthy male players (21.2 ± 1.4 years; 178.2 ± 4.3 cm; 79.1 ± 8.3 kg) from a university football team were selected to participate in the research. Mechanical properties related to surface-player interaction were assessed on the two surfaces selected for this study. A randomized design was used and the players performed the Ball-sport Endurance and Sprint Test (BEAST90) on the different artificial turf fields. Average time of the 20 m sprints was longer on the FIFA Quality Pro surface than on the non-certified pitch (+ 0.13 s; p < 0.05; CI 95% - 0.01 to 0.27; ES: 0.305). The players' perceived effort was higher in the first (+ 2.64; p < 0.05; CI 95% 0.92 to 4.35; ES: 1.421) and the second half (+ 1.35; p < 0.05; CI 95% - 0.02 to 2.72; ES: 0.637) of the test on the FIFA Quality Pro field. Comparative analysis between surfaces showed no significant differences in the time spent in each of the heart rate zones and higher concentrations of CK (+ 196.58; p > 0.05; CI 95% 66.54 to 326.61; ES: 1.645) were evidenced in the non-certified pitch surface. In response to a simulated match protocol, markers of post-exercise muscle damage may be reduced on accredited artificial turf fields. These insights can provide the opportunity to maximize the efficiency of training sessions and reduce the risk of injury during the season.

 

 

#3 Safety and Effects of Football in Skeletal Metastatic Prostate Cancer: a Subgroup Analysis of the FC Prostate Community Randomised Controlled Trial

Reference: Sports Med Open. 2021 Apr 20;7(1):27.  doi: 10.1186/s40798-021-00318-6.

Authors: Eik Dybboe Bjerre, Sarah Weller, Mads Hvid Poulsen, Søren Sørensen Madsen, Rie Dybboe Bjerre, Peter Busch Østergren, Michael Borre, Klaus Brasso, Julie Midtgaard

Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-021-00318-6.pdf

Summary: Skeletal metastatic disease excludes many cancer patients from participating in exercise and physical activity due to safety concerns. Empirical evidence from high-quality trials is warranted to guide clinicians and patients.The aim was to evaluate the safety and potential benefits of high-impact aerobic exercise in patients with prostate cancer with skeletal metastases. Exploratory subgroup analysis of a pragmatic, multicentre, parallel randomised controlled trial. The trial recruited 214 patients from five hospital urological departments in Denmark. Patients with prostate cancer with skeletal metastases (n = 41). Six months of football training twice weekly at a local club or usual care. Both groups received brief information on physical activity recommendations at the time of randomisation. Safety, defined as falls, fractures and hospital admissions were used as outcome measures. Effects were evaluated on the primary outcome (prostate cancer-specific quality of life) and secondary outcomes (lean body mass, fat mass, hip and spine bone mineral density, and general physical and mental health). The original trial comprised 214 participants, 41 of whom had skeletal metastases at enrolment. Of these, 22 were allocated to football and 19 to usual care. The trial retention rate was 95% at 12 weeks and 88% at 6 months. Football participants attended 13 sessions on average at 12 weeks and 23 at 6 months. There were two falls, one in each group after 6 months, and no fractures. There were four unplanned hospital admissions in the study period, all four in the usual care group. Statistically significant between-group difference was observed in the primary outcome change in prostate cancer-specific quality of life at 12 weeks (7.6 points [95% CI 0.5 to 15.0]; P = 0.038). No statistical changes were found in the secondary outcomes. The analysis showed that football training was safe in patients with skeletal metastatic prostate cancer and significantly improved quality of life. Larger analyses and/or trials are warranted to confirm the safety of exercise more broadly in cancer patients with skeletal metastatic disease.

 

 

#4 Physical Activity Levels of Adult Virtual Football Players

Reference: Front Psychol. 2021 Mar 26;12:596434.  doi: 10.3389/fpsyg.2021.596434. eCollection 2021.

Authors: Ana M Pereira, Evert Verhagen, Pedro Figueiredo, André Seabra, António Martins, João Brito

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8044777/pdf/fpsyg-12-596434.pdf

Summary: Esports, including virtual football, are a worldwide phenomenon. Yet, little is known about the physical activity levels of individuals engaged in virtual football game play. Therefore, we aimed to perform a preliminary evaluation of the levels of physical activity, sedentarism, and habits of physical training of adults engaged with virtual football in Portugal. This was a cross-sectional investigation based on a structured online survey using the International Physical Activity Questionnaire (IPAQ) and a set of questions regarding habits of physical training. The participants (n = 433) reported spending a median of 5,625 MET-min⋅week-1 being physically active. Still, the participants spent 320 min/day sitting, and 150 min/day practicing virtual football. According to the IPAQ scores, high physical activity levels were reported by 84.5% of the participants, and 87.1% were considered physically active considering the WHO guidelines on physical activity and sedentary behavior. Overall, 60.0% of the participants reported planning their own physical training. Maintaining or improving overall physical health was one of the main reasons for doing physical training (66.7%), with only 6.1% responding being active to improve virtual football performance. Overall, the results showed that virtual football players accomplished the standard recommendations for physical activity, with high levels of physical activity, and encompassing regular physical training focused mostly on health promotion, rather than improved virtual football performance.

 

 

#5 Staying on the ball during COVID-19 pandemic: impact on training modalities in football players

Reference: J Sports Med Phys Fitness. 2021 Apr 19.  doi: 10.23736/S0022-4707.21.12256-X. Online ahead of print.

Authors: Dominik Schüttler, Wolfgang Hamm, Simone Krammer, Julius Steffen, Eileen Deuster, Michael Lauseker, Florian Egger, Tim Meyer, Stefan Brunner

Summary: COVID-19 pandemic has affected worldwide sports competitions and training in both amateur and professional leagues. We thus aimed to investigate changes in different training modalities in elite and amateur football players following COVID-19 lockdown in March 2020. In this cross-sectional study we applied a Likert scale-based questionnaire with 20 items to quantify and classify time spent at standard training methods in 47 professional and 54 amateur football players from 12 Austrian clubs before and during lockdown.  Additionally, McLean score was calculated to assess perceived training fatigue. Weekly amount of training time at endurance exercises (cycling) increased in both professional (37.5 [IQR 46.5] min/week vs. 187.5 [IQR 127.5] min/week, p<0.001), and amateur players (0.0 [IQR 45.0] min/week vs. 37.5 [IQR 112.5] min/week, p=0.015) during COVID-19 lockdown. Time on diverse muscle strengthening workouts was significantly elevated in both cohorts. Total training time at ball declined for professionals (from 472.5 [IQR 150] min/week to 15.0 [IQR 112.5] min/week, p<0.001) and amateurs (from 337.5 [IQR 285] min/week to 0.0 [IQR 37.5] min/week, p<0.001). Videoguided training was intensified in both groups (p<0.001 each). Location shifted from football fields and gyms to home and outdoors. Overall McLean score remained unchanged in amateurs (p=0.42) while elite players showed a trend towards an increase (p=0.056). COVID-19 lockdown compromised football training, especially training concepts with ball. Consequently, resulting changes in exercise loads and muscular burden might impact susceptibility for injuries and impair performances especially in amateur players, especially as they lacked training supervision and professional training plans. Minimum effective dose of training workload in order to maintain endurance- and neuromuscular-related performance parameters should be prescribed.

 

 

#6 Modulators of Change-of-Direction Economy After Repeated Sprints in Elite Soccer Players

Reference: Int J Sports Physiol Perform. 2021 Apr 19;1-7.  doi: 10.1123/ijspp.2020-0740. Online ahead of print.

Authors: Filippo Dolci, Andrew E Kilding, Tania Spiteri, Paola Chivers, Ben Piggott, Andrew Maiorana, Nicolas H Hart

Summary: The purpose was to investigate the acute effect of repeated-sprint activity (RSA) on change-of-direction economy (assessed using shuttle running economy [SRE]) in soccer players and explore neuromuscular and cardiorespiratory characteristics that may modulate this effect. Eleven young elite male soccer players (18.5 [1.4] y old) were tested on 2 different days during a 2-week period in their preseason. On day 1, lower-body stiffness, power and force were assessed via countermovement jumps, followed by an incremental treadmill test to exhaustion to measure maximal aerobic capacity. On day 2, 2 SRE tests were performed before and after a repeated-sprint protocol with heart rate, minute ventilation, and blood lactate measured. Pooled group analysis indicated no significant changes for SRE following RSA due to variability in individual responses, with a potentiation or impairment effect of up to 4.5% evident across soccer players. The SRE responses to RSA were significantly and largely correlated to players' lower-body stiffness (r = .670; P = .024), and moderately (but not significantly) correlated to players' force production (r = -.455; P = .237) and blood lactate after RSA (r = .327; P = .326). In summary, SRE response to RSA in elite male soccer players appears to be highly individual. Higher lower-body stiffness appears as a relevant physical contributor to preserve or improve SRE following RSA.

 

 

#7 Male collegiate soccer athletes with severe ankle laxity display increased knee abduction during side-cutting tasks compared to those with only perceived ankle instability

Reference: Res Sports Med. 2021 Apr 20;1-10.  doi: 10.1080/15438627.2021.1917407. Online ahead of print.

Authors: Shun Kunugi, Takashi Koumura, Ryota Myotsuzono, Akihiko Masunari, Naruto Yoshida, Shumpei Miyakawa, Naoki Mukai

Summary: This study aimed to examine lower limb kinematics during a side-cutting task in male collegiate soccer athletes with severe ankle laxity. Forty-seven participants with a history of ankle sprains and perceived ankle instability were categorized into non-laxity (n = 17), laxity (n = 19), and severe laxity (n = 11) groups using stress radiography tests. Three-dimensional kinematic data during the stance phase of a 45° side-cutting task were analysed. The frontal plane kinematics of the knee significantly differed between the three groups (p < 0.05). The severe laxity group exhibited a greater abduction angle than the non-laxity group (p < 0.05). The horizontal and sagittal plane kinematics of the rearfoot differed between the three groups during the end of the stance phase (p < 0.05). Our data suggest that collegiate soccer athletes with both perceived ankle instability and severe ankle laxity exhibit greater knee abduction movement during a 45° side-cutting task compared to those with only perceived ankle instability.

 

 

#8 Hamstring and Quadriceps Muscle Strength in Youth to Senior Elite Soccer: A Cross-Sectional Study Including 125 Players

Reference: Int J Sports Physiol Perform. 2021 Apr 22;1-7.  doi: 10.1123/ijspp.2020-0713. Online ahead of print.

Authors: Lasse Ishøi, Kasper Krommes, Mathias F Nielsen, Kasper B Thornton, Per Hölmich, Per Aagaard, Juan J J Penalver, Kristian Thorborg

Summary: Increasing age, high quadriceps strength, and low hamstring muscle strength are associated with hamstring strain injury in soccer. The authors investigated the age-related variation in maximal hamstring and quadriceps strength in male elite soccer players from under-13 (U-13) to the senior level. A total of 125 elite soccer players were included from a Danish professional soccer club and associated youth academy (first tier; U-13, n = 19; U-14, n = 16; U-15, n = 19; U-17, n = 24; U-19, n = 17; and senior, n = 30). Maximal voluntary isometric force was assessed for the hamstrings at 15° knee joint angle and for the quadriceps at 60° knee joint angle (0° = full extension) using an external-fixated handheld dynamometer. Hamstring-to-quadriceps strength (H:Q) ratio and hamstring and quadriceps maximal voluntary isometric force levels were compared across age groups (U-13 to senior). Senior players showed 18% to 26% lower H:Q ratio compared with all younger age groups (P ≤ .026). Specific H:Q ratios (mean [95% confidence interval]) were as follows: senior, 0.45 (0.42-0.48); U-19, 0.61 (0.55-0.66); U-17, 0.56 (0.51-0.60); U-15, 0.59 (0.54-0.64); U-14, 0.54 (0.50-0.59); and U-13, 0.57 (0.51-0.62). Hamstring strength increased from U-13 to U-19 with a significant drop from U-19 to the senior level (P = .048), whereas quadriceps strength increased gradually from U-13 to senior level. Elite senior soccer players demonstrate lower H:Q ratio compared with youth players, which is driven by lower hamstring strength at the senior level compared with the U-19 level combined with a higher quadriceps strength. This discrepancy in hamstring and quadriceps strength capacity may place senior-level players at increased risk of hamstring muscle strain injuries.

 

 

#9 A case of an injured calcaneus secundarius in a professional soccer player

Reference: BMC Musculoskelet Disord. 2021 Apr 22;22(1):374.  doi: 10.1186/s12891-021-04246-0.

Authors: Kepka Sabrina, Morel Marc, Garnier Franck, Pietra François, Marjanovic Nicolas, Zeller Pascal, Bilbault Pascal, Kremer Stéphane, Bierry Guillaume 

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8063446/pdf/12891_2021_Article_4246.pdf

Summary: The calcaneus secundarius (CS) is an accessory ossicle of the anterior facet of the calcaneus and is usually asymptomatic. This accessory bone can be frequently mistaken for a fracture of the anterior process of the calcaneus. Few reports of symptomatic CS have been published, and physicians need to be familiar with imaging strategies when encountering chronic ankle pain or in case of suspicion of fracture of the anterior process of the calcaneus. We describe the case of symptomatic CS in a professional soccer player injured during a match. First, computed tomography showed a large CS. Second, magnetic resonance imaging (MRI) demonstrated synchondrosis between the CS and the calcaneus, as well as edema (high MR T2 signal) within it, corresponding to posttraumatic edema. The patient was successfully treated with nonsteroidal anti-inflammatory drugs and physiotherapy; no surgical management was necessary. At the 4-week follow-up, he was pain-free and returned to activity. This case illustrates the role of imaging for the diagnosis of CS in cases of acute pain of the foot. CT, as well as MRI, helped to confirm the diagnosis of CS traumatized synchondrosis, which can be mistaken for a fracture.

 

 

#10 Effects of sprint distance and repetition number on energy system contributions in soccer players

Reference: J Exerc Sci Fit. 2021 Jul;19(3):182-188.  doi: 10.1016/j.jesf.2021.03.003. Epub 2021 Apr 1.

Authors: Süleyman Ulupınar, Serhat Özbay, Cebrail Gençoğlu, Emerson Franchini, Necip Fazıl Kishalı, İzzet İnce

Summary: This study aims to compare the effect of sprint distance and repetition number on performance, physiological responses, and energy systems contributions. Eighteen male university league soccer players (age: 19.9 ± 1.6 years, height: 177.9 ± 4.7 cm, body mass: 72.4 ± 6.3 kg, percentage body fat: 8.9 ± 1.8, training experience: 7.4 ± 1.6 years) completed two different repeated sprint protocols: 20 × 20 m (20 × 20) and 10 × 40 m (10 × 40) with 15s and 30s rest intervals, respectively. Oxygen uptake (VO2) were measured during the rest, exercise, and recovery phases. Rest and peak blood lactate concentrations were determined. Using VO2 and lactate values, the energy system contributions were calculated using a mono-exponential model and mathematical calculations. Energy systems contributions and total energy expenditure (TEE) were calculated both for the entire protocol (overall) and for the sprints only. Ratings of perceived exertion (RPE), peak and mean heart rate (HR) responses were significantly higher in the 20 × 20 whereas lactate response was higher in the 10 × 40. TEE was similar between the 10 × 40 (586.3 ± 60.8 kJ) and 20 × 20 (595.6 ± 57.5 kJ). For overall estimations, the 10 × 40 and 20 × 20 presented similar results of oxidative (47.5 ± 5.4 vs 45.7 ± 5.1 kJ min-1) and phosphagen (44.7 ± 5.4 vs (42.9 ± 4.8 kJ min-1) systems contributions whereas glycolytic contribution was higher in the 10 × 40 (15.5 ± 2.2 vs 12.8 ± 2.3 kJ min-1). For sprints only estimation, the phosphagen (257.6 ± 31.5 vs 225.2 ± 28.2 kJ min-1), glycolytic (89.4 ± 13.4 vs 67.3 ± 12.5 kJ min-1), and oxidative (76.9 ± 6.9 vs 72.0 ± 7.9 2 kJ min-1) systems contributions were higher in the 10 × 40. Although HR and RPE responses were higher in the 20 × 20, phosphagen (during sprints) and glycolytic (during both sprints and overall protocol) were higher in the 10 × 40 protocol. Therefore, the 10 × 40 protocol seems more reasonable for developing or evaluating the anaerobic systems.

 

 

#11 A Goal Scoring Probability Model for Shots Based on Synchronized Positional and Event Data in Football (Soccer)

Reference: Front Sports Act Living. 2021 Mar 29;3:624475.  doi: 10.3389/fspor.2021.624475. eCollection 2021.

Authors: Gabriel Anzer, Pascal Bauer

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8056301/pdf/fspor-03-624475.pdf

Summary: Due to the low scoring nature of football (soccer), shots are often used as a proxy to evaluate team and player performances. However, not all shots are created equally and their quality differs significantly depending on the situation. The aim of this study is to objectively quantify the quality of any given shot by introducing a so-called expected goals (xG) model. This model is validated statistically and with professional match analysts. The best performing model uses an extreme gradient boosting algorithm and is based on hand-crafted features from synchronized positional and event data of 105, 627 shots in the German Bundesliga. With a ranked probability score (RPS) of 0.197, it is more accurate than any previously published expected goals model. This approach allows us to assess team and player performances far more accurately than is possible with traditional metrics by focusing on process rather than results.

 

 

#12 Internal, external and repeated-sprint demands in small-sided games: A comparison between bouts and age groups in elite youth soccer players

Reference: PLoS One. 2021 Apr 28;16(4):e0249906.  doi: 10.1371/journal.pone.0249906. eCollection 2021.

Authors: Richard Hauer, Paul Störchle, Bettina Karsten, Harald Tschan, Arnold Baca

Download link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0249906

Summary: This study investigated the activity profile during small-sided games (SSG) in elite youth soccer players. Internal load (IL) including heart rate (HR) and external load (EL) such as distance covered in different speed-zones (SZ) were collected from forty-eight players of three different teams (U15, U16, U18). The investigation included a total of eighteen 5vs.5 SSGs, each consisting of four 2-minute bouts on a 40x32m pitch during spring season. Total group results (n = 48) showed a reduction in total-distance (p = 0.001; [Formula: see text] = 0.12), high-intensity-running (p = 0.009; [Formula: see text] = 0.09), and low-intensity-running distance (p = 0.028; [Formula: see text] = 0.07) between bouts. Similarly, a reduction in the number of both acceleration-low (p = 0.001; [Formula: see text] = 0.12) and deceleration-high (p = 0.003; [Formula: see text] = 0.11) values was observed. Additionally, time spent in HR-zones 3 and 4 (p≤0.007; [Formula: see text] ≥ 0.10), increased, with a reduction in HR-zone 1 (p = 0.000, [Formula: see text] = 0.25). Age group comparison showed less distance covered in SZ 1 (p≤0.000; [Formula: see text] = 0.56) and greater deceleration-high values (p≤0.038; [Formula: see text] = 0.32) in U15 players compared to other age groups. Further, U15 showed lower values in low-intensity-running compared to U18 (p = 0.038; [Formula: see text] = 0.22). No age-related differences were found for IL and repeated sprint ability (RSA) values. The higher EL in younger age groups should be taken into account when implementing soccer specific SSGs. In addition, HRmean values between 80-85% of HRmax and RSA numbers, which are similar to match-play data, indicate SSGs as an effective training tool to prepare youth soccer athletes for the demands of competition.

 

 

#13 Experience of cold-water immersion on recovery efficiency after soccer match

Reference: Tunis Med. 2021 Feb;99(2):252-258.

Authors: Mostafa Farkhari Babak, Mohammad Mosaferi Ziaaldini, Attarzadeh Hoseini Seyyed Reza

Summary: immersion in cold-water is one of the most common recovery and rehabilitation techniques among athletes. However, several factors such as shocking induced by cold water can affect the effectiveness of this technique. The aim of this study was to investigate the effect of 4 weeks cold water habituation on the effectiveness of CWI recovery technique on muscle damage and function indices of young soccer players. Twenty young men with no previous experience of CWI participated in this study. Output power and RSADec of subjects were measured. The subjects then performed a simulated soccer test and, after collecting blood samples, were immediately immersed in 15 ° C water for 15 minutes. Twenty-four hours later blood sampling and functional tests were repeated. Subjects then were divided randomly into two groups of exercise with CWI recovery and exercise with passive recovery. After four weeks, the blood sampling and performance tests repeated like the pre-test.

Results: The CWI had no significant effect on serum levels of AST and LDH before and after 4 weeks of CWI (P> 0.05). Also, there was no significant difference in power output and RSADec after CWI before and after cold water habituation (P> 0.05). It seems that the experience of recovering by immersion in cold-water has no effect on the effectiveness of this method. Therefore, soccer coaches and athletes should think more about using this recovery method.

 

 

#14 Intra- and Inter-week Variations of Well-Being Across a Season: A Cohort Study in Elite Youth Male Soccer Players

Reference: Front Psychol. 2021 Apr 9;12:671072.  doi: 10.3389/fpsyg.2021.671072. eCollection 2021.

Authors: Hadi Nobari, Maryam Fani, Filipe Manuel Clemente, Jorge Carlos-Vivas, Jorge Pérez-Gómez, Luca Paolo Ardigò

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