Latest research in football - week 45 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Combined Power Band Resistance Training on Sprint Speed, Agility, Vertical Jump Height, and Strength in Collegiate Soccer Players
Reference: Int J Exerc Sci. 2020 Aug 1;13(4):950-963.  eCollection 2020.
Authors: Edgar T Katushabe, Mark Kramer
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Summary: Soccer involves explosive physical actions requiring strength, power, and agility for optimal performance. Such attributes may be trained several ways, of which power-band resistance training has received limited attention regarding the potential for performance improvement in soccer players. This study serves to determine the effect of power-band resistance training on 1-repetition maximal (1RM) strength, speed, standing vertical jump (SVJ) height, and agility of collegiate soccer players. Seventeen male players (age: 20.47 ± 1.85 years, height: 1.77 ± 0.08 m, mass: 70.49 ± 4.15 kg) were matched and randomly allocated into either a conventional resistance group (CON, n = 8), or a power-band resistance training group (EXP, n = 9). Following a 6-week intervention, participants were re-assessed relative to their baseline values, showing improvements in 1RM squat mass (CON: +31.57%; EXP: +34.61%), 1RM deadlift mass (CON: +15.44%; EXP: +13.72%), and SVJ height (CON: +4.15%; EXP: +6.35%). Power-band resistance training produced greater results compared to conventional training in 1RM squat mass, even when between-group baseline values were controlled for (ANCOVA, F(1,14)=5.32, p = 0.037, η2p=.28). No other between-group differences were evident, showing no clear methodological superiority. Power-band resistance training shows potential as an effective training methodology compared to conventional resistance training to improve performance variables in university soccer players.

#2 Perception of Affordances in Soccer: Kicking for Power Versus Kicking for Precision
Reference: Res Q Exerc Sport. 2020 Sep 14;1-9.  doi: 10.1080/02701367.2020.1812494. Online ahead of print.
Authors: Alper Tunga Peker, Veysel Böge, George Bailey, Jeffrey B Wagman, Thomas A Stoffregen
Summary: We investigated youth soccer players' perception of affordances for different types of kicks. In the Power task, players judged the maximum distance they could kick the ball. In the Precision task, players judged how close to a designated target line they could kick the ball. Following judgments, players performed each task. Both judgments and performance were assessed immediately before and immediately after players competed in a regulation soccer match, thereby permitting us to assess possible effects of long-term experience on perceptual sensitivity to short-term changes in ability. We compared players from two league groups: U16 (mean age = 15.45 years, SD = 0.52 years) versus U18 (mean age = 17.55 years, SD = 0.52 years). As expected, for the Power task actual kicking ability was greater for the U18 group (p < .05). In statistically significant interactions, we found that judgments of Power kicking ability differed before versus after match play, but only for the U16 group. We found no statistically significant effects for the Precision task. We identified interactions between long-term and short-term soccer experience which revealed that the effects of long-term experience on affordance perception were not general. Two additional years of playing experience (in the U18 group, relative to the U16 group) did not lead to an overall improvement in the perception of kicking-related affordances. Rather, variation in long-term experience was associated with changes in affordance perception which were situation-specific, being manifested only after playing a soccer match, and not before.

#3 Comparisons of Accelerometer Variables Training Monotony and Strain of Starters and Non-Starters: A Full-Season Study in Professional Soccer Players
Reference: Int J Environ Res Public Health. 2020 Sep 9;17(18):E6547. doi: 10.3390/ijerph17186547.
Authors: Hadi Nobari, Rafael Oliveira, Filipe Manuel Clemente, Jose Carmelo Adsuar, Jorge Pérez-Gómez, Jorge Carlos-Vivas, João Paulo Brito
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Summary: The purpose of this study was two-fold: (1) to describe weekly average values for training monotony (TM) and training strain (TS) and their variations across the full soccer season, based on the number of accelerations and decelerations; (2) to analyze the differences between starter and non-starter players on weekly average TM and TS values for the pre-season and three in-season periods. In total, 21 professional soccer players were evaluated over 48 weeks during the full-season. The TM and TS were calculated based on the number of accelerations and decelerations at zone 1, zone 2 and zone 3, respectively. The results revealed that starters presented higher values compared to non-starters throughout the full season for all variables analyzed (all, p < 0.05). Generally, there were higher values in the pre-season. Specifically, accelerations at zones 1, 2 and 3 revealed moderate to very large significance of the starters compared to non-starters over the full-season. Decelerations at zone 1, 2 and 3 presented moderate to nearly optimally significant greater weekly averages for starters compared to non-starters during the full season. In conclusion, the TM and TS values were higher for starters compared to non-starters through the full-season, which confirms that the training session does not provide a sufficient load to non-starter soccer players during the full-season.

#4 Anxiety and Depressive Symptoms During the COVID-19 Emergency Period: A Comparative Cross-Sectional Study in Professional Football
Reference: Clin J Sport Med. 2020 Sep 15. doi: 10.1097/JSM.0000000000000886. Online ahead of print.
Authors: Vincent Gouttebarge, Imtiaz Ahmad, Margo Mountjoy, Simon Rice, Gino Kerkhoffs
Summary: The primary objective of our study was to establish the prevalence of anxiety and depressive symptoms among professional football (ie, soccer; hereinafter "football") players during the COVID-19 emergency period, drawing comparisons with players assessed before exposure to the COVID-19 emergency period. A total of 468 female (mean age: 22.8 years) and 1134 male (mean age: 26.0 years) players participated in this study. The non-COVID-19 comparison group consisted of 132 female (mean age: 23.1 years) and 175 male (mean age: 24.8 years) professional footballers. Anxiety symptoms were measured with the validated Generalized Anxiety Disorder 7 and depressive symptoms with the validated Patient Health Questionnaire 9. Both instruments have been widely used in both clinical and research settings among different populations, showing excellent psychometric properties. During the COVID-19 emergency period, the 2-week prevalence of symptoms consistent with a diagnosis of generalized anxiety disorder and depression was 18.2% and 21.6%, respectively, among female professional footballers and 15.5% and 12.9%, respectively, among male players. The 2-week prevalence of anxiety and depressive symptoms among professional footballers was significantly higher during the COVID-19 emergency period than before the global pandemic (P < 0.01). Differences were most pronounced for those worried about the playing future. The COVID-19 emergency period is associated with increased symptoms of anxiety and depression in professional footballers, especially among those worried about their future as players.

#5 Deconstructing celebratory acts following goal scoring among elite professional football players
Reference: PLoS One. 2020 Sep 16;15(9):e0238702. doi: 10.1371/journal.pone.0238702. eCollection 2020.
Authors: Assaf Lev, Yair Galily, Omer Eldadi, Gershon Tenenbaum
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Summary: Goal celebration in sport is mostly spontaneous and is manifested via vocal expressions and bodily gestures aimed at communicating emotions. The aim of this study is to deconstruct the celebratory acts among elite professional football players in the European Champions League following scoring a goal, and to capture the multiple acts and functions of the celebrations. In examining the 2018/19 season of the European Champions League tournament, we draw attention to the players' celebrations and their corresponding social and individual functions. All goals/celebrations (K = 366) were used for the analyses. To analyze the goal celebration acts, a socio-psychological model was established which is comprised of several theories. To describe the goal celebration acts across the competition stages (e.g., preliminary and final), match location (i.e., home or away), time phase (0-15, 15-45, 45-75, 75-90, 90+ minutes), scoring mode (i.e., prior to the goal, after the goal), and players' continent origin (Europe, Africa, Asia, South/Central, and North America), the number and percent of all the celebratory acts were counted and presented in their respective mode (i.e., single, double, and team). The main findings indicate that (a) most of the goal celebration acts were performed interactively by the scoring player and his teammates, (b) the interactive modes of celebration lasted longer than the modes which were performed non-interactively, (c) the celebration lasted longer following goal scoring in the final stage than in the preliminary stage, (d) the celebration duration lasted the longest time when the goal was scored during the overtime phase (90+ min) of the final but not the preliminary stage, and (e) players from Africa and South America demonstrated religious acts more than their European counterparts. We assert that our conceptual model enables the categorization of a variety of personal and social meanings to the celebrations on the field during the most thrilling moments of the game.

#6 Passing Networks and Tactical Action in Football: A Systematic Review
Reference: Int J Environ Res Public Health. 2020 Sep 11;17(18):E6649. doi: 10.3390/ijerph17186649.
Authors: Sergio Caicedo-Parada, Carlos Lago-Peñas, Enrique Ortega-Toro
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Summary: The aim of this study is to examine the most significant literature on network analyses and factors associated with tactical action in football. A systematic review was conducted on Web of Science, taking into account the PRISMA guidelines using the keyword "network", associated with "football" or "soccer". The search yielded 162 articles, 24 of which met the inclusion criteria. Significant results: (a) 50% of the studies ratify the importance of network structures, quantifying and comparing properties to determine the applicability of the results instead of analyzing them separately; (b) 12.5% analyze the process of offensive sequences and communication between teammates by means of goals scored; (c) the studies mainly identify a balance in the processes of passing networks; (d) the variables allowed for the interpretation of analyses of grouping metrics, centralization, density and heterogeneity in connections between players of the same team. Finally, a systematic analysis provides a functional understanding of knowledge that will help improve the performance of players and choose the most appropriate response within the circumstances of the game.

#7 Effect of football activity and physical fitness on information processing, inhibitory control and working memory in adolescents
Reference: BMC Public Health. 2020 Sep 14;20(1):1398. doi: 10.1186/s12889-020-09484-w.
Authors: Ryan A Williams, Simon B Cooper, Karah J Dring, Lorna Hatch, John G Morris, Caroline Sunderland, Mary E Nevill
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Summary: Whilst an acute bout of exercise has been shown to enhance subsequent cognition, including in adolescents, the effects of team games (of which Football is the most popular) has received little attention. Therefore, this study examined: the effect of an acute bout of outdoor Football activity on information processing, inhibitory control, working memory and circulating brain-derived neurotrophic factor (BDNF) in adolescents; the effect of physical fitness on cognition and; the moderating effect of physical fitness on the acute exercise responses. Following familiarisation, 36 adolescents (16 girls) took part in two trials (60-min Football and 60-min seated rest) separated by 7-d in a counterbalanced, crossover design. Information processing and inhibitory control (Stroop Test), and working memory (Sternberg Paradigm) were assessed 30-min before exercise/rest and immediately, 45- and 90-min post-exercise/rest. Capillary blood samples were obtained before exercise/rest and up to 120-min post-exercise/rest. The median split of distance covered on the MSFT was used to divide the group into high- and low-fit groups. Performance on the cognitive function tasks was similar between Football and seated rest (trial*time interactions; all p > .05). However, the high-fit group had overall quicker response times on both levels of the Stroop Task and all three levels of the Sternberg Paradigm (main effect of fitness; all p < .001). Furthermore, the exercise-cognition relationship was moderated by physical fitness, with improvements in working memory response times seen post-exercise, only in the high-fit group (trial*time*fitness interaction, p < .05). Circulating BDNF was unaffected by the Football activity and physical fitness (p > .05). The present study shows that higher levels of physical fitness are beneficial for cognitive function and provides novel evidence that an ecologically valid, and popular, form of exercise is beneficial for working memory following exercise, in high-fit participants only.

#8 Game format alters the physiological and activity demands encountered during small-sided football games in recreational players
Reference: J Exerc Sci Fit.  2021 Jan;19(1):40-46. doi: 10.1016/j.jesf.2020.05.001. Epub 2020 May 28.
Authors: Emilija Stojanović, Nenad Stojiljković, Ratko Stanković, Aaron T Scanlan, Vincent J Dalbo, Zoran Milanović
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Summary: Conditioning in the form of football small-sided games (SSG) is being increasingly utilized as a health-promoting and performance-enhancing activity. The aim of this study was to quantify and compare the physiological responses and activity demands encountered during 3-a-side, 4-a-side, and 5-a-side football SSG in recreational players. Heart rate, blood lactate (BLa), rating of perceived exertion (RPE) and activity demands were measured across 2 × 20-min football sessions played on a 40 × 20-m pitch in 12 recreationally active college students. Data were collected over a period of two weeks using a repeated-measures crossover design. Mean heart rate was higher (moderate) during 5-a-side than 4-a-side (p = 0.02) and 3-a-side SSG (p < 0.001). BLa tended to be higher (small) in 3-a-side compared to 4-a-side (p = 0.12) and 5-a-side SSG (p = 0.46). The total distance covered was lower (large) during 5-a-side than 4-a-side SSG (p = 0.02), while the total number of accelerations (p = 0.01) and decelerations (p = 0.02) were higher (large) during 5-a-side than 4-a-side SSG. These data suggest: 1) 5-a-side SSG require a greater intermittent workload and exacerbated HR responses; 2) 4-a-side SSG require more sustained activity (distance); and 3) 3-a-side SSG result in higher BLa compared to other SSG formats. The observed intermittent workload and exacerbated HR response in 5-a-side SSG were likely due to greater turnover rates with more frequent interceptions. Sustained activity in 4-a-side SSG might be underpinned by format-specific structures permitting optimal team work, while isolated guarding of players in 3-a-side SSG may have exacerbated BLa responses.

#9 The prevalence of non-contact muscle injuries of the lower limb in professional soccer players who perform Salah regularly: a retrospective cohort study
Reference: J Orthop Surg Res. 2020 Sep 24;15(1):440. doi: 10.1186/s13018-020-01955-5.
Authors: Eduard Bezuglov, Oleg Talibov, Mikhail Butovskiy, Anastasiya Lyubushkina, Vladimir Khaitin, Artemii Lazarev, Evgeny Achkasov, Zbigniew Waśkiewicz, Thomas Rosemann, Pantelis T Nikolaidis, Beat Knechtle, Nicola Maffulli
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Summary: The present study assessed the prevalence of non-contact muscle injuries of the lower limbs, including hamstring injuries, in professional Russian soccer players who regularly perform Salah, an obligatory Muslim prayer performed 5 times a day. Using a retrospective cohort study design, 68 professional male soccer players (excluding goalkeepers), 34 of whom were Muslims regularly performing Salah (exposure group) and 34 were randomly chosen non-Muslim players (control group), were included in the study. The groups were similar in their playing leagues, field positions, age (27 ± 3.1 vs 28 ± 4.2 years), and body mass index (22 ± 1.2 vs 23 ± 0.92 kg/m2). The incidence of hamstring injury was significantly lower in the exposure group (2 vs 14, p = 0.0085). A declining trend for the number of muscle injuries (either hamstring or not) was observed in the exposure group (11 vs 27, p = 0.0562). Two players in the exposure group and 11 in the control group (p = 0.0115, OR 0.1307, 95% CI 0.0276 to 0.5698) suffered a hamstring injury, with no statistically significant difference in the occurrence of other injuries. The total amount of the training and play days missed because of hamstring and other muscle injuries was significantly lower in the exposure group (24 vs 213 days, p = 0.0043, and 200 vs 344 days, p = 0.0066, respectively). The prevalence of non-contact muscle injuries, including hamstring injuries, was lower in professional Russian soccer players who regularly performed Salah.

#10 Effects of Tetraselmis chuii Microalgae Supplementation on Ergospirometric, Haematological and Biochemical Parameters in Amateur Soccer Players
Reference: Int J Environ Res Public Health. 2020 Sep 21;17(18):E6885. doi: 10.3390/ijerph17186885.
Authors: Víctor Toro, Jesús Siquier-Coll, Ignacio Bartolomé, María C Robles-Gil, Javier Rodrigo, Marcos Maynar-Mariño
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Authors: This study aimed to analyse the effects of Tetraselmis chuii (TC) microalgae supplementation during thirty days on ergospirometric, haematological and biochemical parameters in amateur soccer players. Thirty-two amateur soccer players divided into a control group (CG; n = 16; 22.36 ± 1.36 years; 68.36 ± 3.53 kg) and a supplemented group (SG; n = 16; 22.23 ± 2.19 years; 69.30 ± 5.56 kg) participated in the double-blind study. SG ingested 200 mg of the TC per day, while CG ingested 200 mg per day of lactose powder. Supplementation was carried out for thirty days. The participants performed a maximal treadmill test until exhaustion. The ergospirometric values at different ventilatory thresholds and haematological values were obtained after the test. Heart rate decreased after supplementation with TC (p < 0.05). Oxygen pulse, relative and absolute maximum oxygen consumption increased in SG (pre vs. post; 19.04 ± 2.53 vs. 22.08 ± 2.25; 53.56 ± 3.26 vs. 56.74 ± 3.43; 3.72 ± 0.35 vs. 3.99 ± 0.25; p < 0.05). Haemoglobin and mean corpuscular haemoglobin increased in SG (pre vs. post; 15.12 ± 0.87 vs. 16.58 ± 0.74 p < 0.01; 28.03 ± 1.57 vs. 30.82 ± 1.21; p < 0.05). On the other hand, haematocrit and mean platelet volume decreased in SG (p < 0.05). TC supplementation elicited improvements in ergospirometric and haematological values in amateur soccer players. TC supplementation could be valuable for improving performance in amateur athletes.

#11 Area per player in small-sided games to replicate the external load and estimated physiological match demands in elite soccer players
Reference: PLoS One. 2020 Sep 23;15(9):e0229194. doi: 10.1371/journal.pone.0229194. eCollection 2020.
Authors: Andrea Riboli, Giuseppe Coratella, Susanna Rampichini, Emiliano Cé, Fabio Esposito
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Summary: The current study determined the area-per-player during small- or large-sided games with or without goalkeeper that replicates the relative (m·min-1) total distance, high-intensity running distance, sprint distance and metabolic power covered during official matches. Time-motion analysis was performed on twenty-five elite soccer-players during 26 home-matches. A total of 2565 individual samples for SSGs using different pitch sizes and different number of players were collected and classified as SSGs with (SSG-G) or without goalkeeper (SSG-P). A between-position comparison was also performed. The area-per-player needed to replicate the official match demands was largely higher in SSG-G vs SSG-P for total distance [187±53 vs 115±35 m2, effect size (ES): 1.60 95%CI 0.94/2.21], high-intensity running distance [262±72 vs 166±39 m2, ES: 1.66(0.99/2.27)] and metabolic power [177±42 vs 94±40, ES: 1.99(1.31/2.67)], but similar for sprint distance [(316±75 vs 295±99 m2, ES: 0.24(-0.32/0.79)] with direction of larger area-per-player for sprint distance > high-intensity running > total distance ≌ metabolic power for both SSG-G and SSG-P. In SSG-G, forwards required higher area-per-player than central-defenders [ES: 2.96(1.07/4.35)], wide-midfielders [ES: 2.45(0.64/3.78)] and wide-defenders [ES: 3.45(1.13/4.99)]. Central-midfielders required higher area-per-player than central-defenders [ES: 1.69(0.20/2.90)] and wide-midfielders [ES: 1.35(-0.13/2.57)]. In SSG-P, central defenders need lower area-per-player (ES: -6.01/-0.92) to overall replicate the match demands compared to all other positions. The current results may be used to gain knowledge of the SSGs relative to the match demands. This imply manipulating SSGs using higher or lower ApP, the presence of the goalkeeper or design specific rules to increase or decrease the position-specific demands with respect to the desired external load outcomes.

#12 Effects of an Initial Muscle Strength Level on Sports Performance Changes in Collegiate Soccer Players
Reference: Sports (Basel). 2020 Sep 15;8(9):E127. doi: 10.3390/sports8090127.
Authors: Ai Ishida, Kyle Rochau, Kyle P Findlay, Brandon Devero, Marco Duca, Michael H Stone
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Summary: The purposes of this study were to investigate effects of partial block periodized strength training on physical performance and to examine relationships between initial muscle strength measured with isometric mid-thigh pull (IMTP) and performance changes after 7 weeks of strength training. Seventeen collegiate male soccer players participated. Initial muscle strength was determined using IMTP while physical performance included 10 m and 20 m sprints and static vertical jump with a polyvinyl chloride pipe (SJ0), 20 kg barbell (SJ20), and barbell loaded to 40 kg bar (SJ40). Performance testing was performed at three points: before first week (baseline), fourth week (T1), and seventh week (T2). Statistically small to moderate changes were found from baseline to T2 in peak power (PP; p < 0.001, ES = 0.49), net impulse (NI; p < 0.001, ES = 0.49), peak velocity (PV; p < 0.001, ES = 0.62), allometrically scaled PP (PPa; p < 0.001, ES = 0.62) in SJ20 and jump height (JH) in SJ40 (p < 0.001, ES = 0.36). Moderate to large correlations were found between isometric peak force and the changes from baseline to T2 in SJ20 PP (p = 0.04, r = -0.49), SJ20 PF (p = 0.03, r = -0.52), PPa (p = 0.04, r = -0.50), and SJ20 allometrically scaled peak force (p = 0.04, r = -0.49). Properly structured strength training maximizes task-specific physical performance. Initial muscle strength negatively affects the magnitudes of adaptations to physical performance.

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