Latest research in football - week 21 - 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 Are European Soccer Players Worth More If They Are Born Early in the Year? Relative Age Effect on Player Market Value
Reference: Int J Environ Res Public Health. 2020 May 9;17(9). pii: E3301. doi: 10.3390/ijerph17093301.
Authors: Perez-Gonzalez B, Fernandez-Luna A, Castillo D, Burillo P
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Summary: The relative age effect (RAE) consists of the lower presence of members of an age group born in the months furthest from the age cut-off date established. In youth soccer, it is known that because of this effect the birth dates of more players in a team are closer to the cutoff of 1 January. These older players, due to their physical and psychological advantages, are more likely to be identified as talent. This study aimed to examine whether RAE can be identified in professional players of the top five European soccer leagues (Spain, Italy, England, Germany, and France) and to assess its influence on the perceived market value of the players. Market value data for 2577 players were obtained from the Transfermarkt database. A significant RAE was produced in all leagues (p < 0.05). However, this bias did not affect the market value of the professional elite soccer players examined here. Our observations indicate that, while the identification and promotion of talent at young ages are often biased by RAE, once players have reached the professional stage, the market value assigned to them is based more on factors other than their date of birth.

#2 Weekly Load Variations of Distance-Based Variables in Professional Soccer Players: A Full-Season Study
Reference: Int J Environ Res Public Health. 2020 May 9;17(9). pii: E3300. doi: 10.3390/ijerph17093300.
Authors: Clemente FM, Silva R, Castillo D, Los Arcos A, Mendes B, Afonso J
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Summary: The aim of this study was two-fold: (1) to analyze the variations of acute load, training monotony, and training strain among early (pre-season), mid (first half of season), and end season (second half of season) periods; (2) to compare these training indicators for playing positions in different moments of the season. Nineteen professional players (age: 26.5 ± 4.3 years; experience as professional: 7.5 ± 4.3 years) from a European First League team participated in this study. The players were monitored daily over a 45-week period for the total distance (TD), distance covered (DC) at 14 km/h-1 or above (DC > 14 km/h), high-speed running above 19.8 km/h-1 (HSR) distance, and number of sprints above 25.2 km/h-1. The acute load (sum of load during a week), training monotony (mean of training load during the seven days of the week divided by the standard deviation of the training load of the seven days), and training strain (sum of the training load for all training sessions and matches during a week multiplied by training monotony) workload indices were calculated weekly for each measure and per player. Results revealed that training monotony and training strain for HSR were meaningfully greater in pre-season than in the first half of the in-season (p ≤ 0.001; d = 0.883 and p ≤ 0.001; d = 0.712, respectively) and greater than the second half of the in-season (p ≤ 0.001; d = 0.718 and p ≤ 0.001; d = 0.717). The training monotony for the sprints was meaningfully greater in pre-season than in the first half of in-season (p < 0.001; d = 0.953) and greater than the second half of in-season (p ≤ 0.001; d = 0.916). Comparisons between playing positions revealed that small-to-moderate effect sizes differences mainly for the number of sprints in acute load, training monotony, and training strain. In conclusion, the study revealed that greater acute load, training monotony, and training strain occurred in the pre-season and progressively decreased across the season. Moreover, external defenders and wingers were subjected to meaningfully greater acute load and training strain for HSR and number of sprints during the season compared to the remaining positions.

#3 'Soccer toe': Chronic physeal injury of the great toe metatarsal in a skeletally immature child - A case report
Reference: SA J Radiol. 2020 Apr 22;24(1):1834. doi: 10.4102/sajr.v24i1.1834. eCollection 2020.
Authors: Schapiro A, Laor T
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Summary: Chronic physeal stress injuries in children can result from ongoing, repetitive compression, distraction and/or shear forces during sports-related activity, and manifest as physeal widening on imaging. We present an 11-year-old soccer athlete with focal physeal widening of her great toe metatarsal and postulate that ongoing or repetitive stress from soccer play may manifest as this imaging appearance. We suggest that recognition of this entity in growing children might explain pain, if present, and guide conservative treatment.

#4 How Training Tools Physically Linking Soccer Players Improve Interpersonal Coordination
Reference: J Sports Sci Med. 2020 May 1;19(2):245-255. eCollection 2020 Jun.
Authors: Yokoyama K, Tabuchi N, Araújo D, Yamamoto Y
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Summary: Interpersonal coordination is an important skill for promoting collective behavior in team sports. This study tested the impact of two types of tools in facilitating triadic coordination. 16 males aged under 12 years were divided into four groups with similar skill levels and average ages. Each group performed a three-versus-one ball passing task under three conditions: a one-elastic-band tool linking the three players, a three-elastic-bands tool linking the three players, and without a tool linking the three players. The dependent variables were ball passing frequency, frequency and amplitude of inner angles of the triangle formed by the players, and duration of the synchronized patterns of the inner angles. The results show that neither tool increased ball-passing frequency or the duration of synchronized patterns. However, both tools increased the frequency of inner angles, and the three-elastic-bands tool decreased the amplitude of inner angles. From these results, we conclude that elastic-band tools affect spatial and temporal triadic formation by means of haptic and visual information. Specifically, compared with the one-elastic-band tool, the three-elastic-bands tool stabilizes the triadic spatial formation. We also explore the implications for how these tools can be used in practice.

#5 A Low-Glycemic Index, High-Fiber, Pulse-Based Diet Improves Lipid Profile, but Does Not Affect Performance in Soccer Players
Reference: Nutrients. 2020 May 6;12(5). pii: E1324. doi: 10.3390/nu12051324.
Authors: Mizelman E, Chilibeck PD, Hanifi A, Kaviani M, Brenna E, Zello GA
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Summary: Pulses (i.e., lentils, chickpeas, beans, peas) are low-glycemic index, high-fiber foods that are beneficial for improving blood lipids. Young soccer players typically have low dietary fiber intake, perhaps because of concerns regarding gastro-intestinal problems during exercise performance. Twenty-seven (17 females) soccer players were randomized to receive a pulse-based diet or their regular diet for four weeks in a cross-over study and evaluated for changes in blood lipids and athletic performance, with 19 (22 ± 6y; 12 females) completing the study (eight participants withdrew because of lack of time). Women increased high density lipoproteins (+0.5 ± 0.7 vs. -0.6 ± 0.3 mmol/L; p < 0.01) and reduced total cholesterol to high density lipoprotein ratio (-2.4 ± 2.9 vs. +2.6 ± 2.2; p < 0.01) on the pulse-based vs. regular diet, respectively, while there were no differences between diet phases in men. Athletic performance assessed by distance covered during games by a global positioning system was not significantly different during the pulse-based vs. regular diet (9180 ± 1618 vs. 8987 ± 1808 m per game; p = 0.35). It is concluded that a pulse-based diet can improve blood lipid profile without affecting athletic performance in soccer players.

#6 Women's Football: An Examination of Factors That Influence Movement Patterns
Reference: J Strength Cond Res. 2020 May 13. doi: 10.1519/JSC.0000000000003638. [Epub ahead of print]
Authors: Griffin J, Larsen B, Horan S, Keogh J, Dodd K, Andreatta M, Minahan C
Summary: The popularity and professionalism of women's football has increased in conjunction with participation rates over the last 10 years, with projected female participation rates to double worldwide by 2026. Scientific interest has also increased, in part due to Fédération Internationale de Football Association now allowing global positioning system (GPS) units to be worn during all competitive matches, resulting in investigations into the match demands of women's football. Therefore, the purpose of the present review is to provide a summary of the literature specific to the movement patterns of women's football matches. Contemporary scientific investigation using GPS match data has led to a greater understanding of the movement patterns of football. Greater emphasis has been placed on high-speed running and sprinting during matches because of the strong link to scoring opportunities and being a distinguishing factor between international and national along with elite and subelite competition levels. Further research, however, is warranted in regard to accelerations and decelerations, given the high metabolic and mechanical loads and contribution to high-speed running and sprinting. With an influx of research into the movement patterns of match-play, investigators have begun to examine factors affecting match performance such as positional demands, age, level of competition, opponent, scoreline, and phase of the game. An understanding of the factors that influence match demands is vital to ultimately be able to understand the effects on performance and how manipulating these factors may improve football performance and reduce the risk of injury.

#7 Influence of Academic Performance, Level of Play, Sports Success, and Position of Play on the Motivation of the Young Football Player
Reference: Int J Environ Res Public Health. 2020 May 12;17(10). pii: E3374. doi: 10.3390/ijerph17103374.
Authors: Ureña-Lopera C, Morente-Oria H, Chinchilla-Minguet JL, Castillo-Rodríguez A
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Summary: Motivation in athletes is a state that fluctuates due to multiple factors that can, in turn, negatively or positively influence sports performance. The aim of this study was twofold, being, on the one hand, to analyze the motivation of soccer players of developmental age in two different contexts (training time (baseline) and the precompetitive time) depending on the category, sports success and playing position, and, on the other hand, to find relations of the motivation dimensions with the academic performance and physical characteristics of the soccer players. One hundred and forty-one under 16 (U16) soccer players were selected (age: 14.7 ± 0.5; height: 170.4 ± 7.2 cm; weight: 61.6 ± 10.0 kg). Data on academic performance, physical and socio-demographic characteristics were recorded, and in two differentiated moments, the motivation dimensions, both in training and in competition. The results showed that the general motivation decreases with the competition, and in particular, the intrinsic motivation, where the precompetitive evaluation is lower than the basal, in both categories (p < 0.05). In addition, demotivation is explained by 10.2%, 19.8%, and 23.9% by fat mass, by academic performance, and by category, respectively; and the extrinsic motivation of external regulation is explained in 26.0% by the academic performance factor (p < 0.01). U16 soccer players show lower levels of motivation at moments prior to the sports competition, and these dimensions of motivation are explained by the category, academic performance, and fat mass.

#8 Acute Effects of a Single Football Training or Match on Passive Hip Rotation Range of Motion in Semi-Professional Football Players: A Pilot Study
Reference: Medicina (Kaunas). 2020 May 10;56(5). pii: E228. doi: 10.3390/medicina56050228.
Authors: De-la-Cruz-Torres B, Abuín-Porras V, Blanco-Morales M, de-la-Cueva-Reguera M, Calvo-Lobo C, López-López D, Romero-Morales C
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Summary: The repetitive loading forces generated during football activities may induce alterations in the hip rotation range of motion (ROM) in players. The objective of this study was to evaluate the acute effects of a training and a match on bilateral passive hip rotation ROM in both lower limbs in soccer. Twenty-eight male players were divided into two groups: 14 players (28 limbs) with normal bilateral hip rotation ROM (NH group) and 14 players (28 limbs) with restricted bilateral hip ROM (RH group). Passive bilateral hip rotation ROM was measured, by goniometer, before and after training or a match. Internal-rotation ROM (ROMIR), external-rotation ROM (ROMER), total ROM (ROMTOT) and relative internal rotation (ROMREL) were calculated. The NH group did not show substantial changes in hip ROM after a training nor a match. After a training session, only the RH group exhibited a substantial increase in ROMIR, ROMER and ROMTOT. After a match, only the RH group exhibited a substantial increase in ROMER and ROMTOT and exhibited a substantial decrease in ROMREL. Comparing both groups, there were significant differences within ROM changes for ROMER and ROMTOT after training and for ROMER and ROMREL after a match. Despite the small sample size of the present study, the findings indicate that a single football activity leads to significant changes in hip rotation ROM in players with restricted bilateral hip external-rotation ROM. However, these changes did not reach reference cut-off scores.

#9 Responsiveness of Device-Based and Self-Report Measures of Physical Activity to Detect Behavior Change in Men Taking Part in the Football Fans in Training (FFIT) Program
Reference: J Meas Phys Behav. 2020 Mar;3(1):67-77. doi: 10.1123/jmpb.2019-0018.
Authors: Donnachie C, Hunt K, Mutrie N, Gill JMR, Kelly P
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Summary: The capacity of physical activity (PA) measures to detect changes in PA within interventions is crucial. This is the first study to examine the responsiveness of activPAL3™ and the International Physical Activity Questionnaire (IPAQ; Short Form) in detecting PA change during a 12-week group-based, men-only weight management program-Football Fans in Training (FFIT). Participants wore an activPAL3™ and completed the IPAQ pre- and post-program (n = 30). Relationships between change scores were assessed by Spearman's correlations. Mean or median changes in PA were measured using paired samples t-tests and Wilcoxon signed-rank tests. Responsiveness to change was assessed utilizing Standardized Response Mean (SRM). Both device-based and self-report measures demonstrated significant changes pre-post intervention, although these changes were not significantly correlated. The SRM values for changes in activPAL3™ metrics were: 0.54 (MET-mins/day); 0.53 (step counts/day); and 0.44 (MVPA/day), indicating a small to medium responsiveness to change. SRM values for changes in IPAQ scores were: 0.59 (for total PA mins/day); 0.54 (for total MET-mins/day); 0.59 (for walking MET-mins/day); 0.38 (for vigorous MET-mins/day); and 0.38 (for moderate MET-mins/day), revealing a small to medium responsiveness to change. These findings reveal that two commonly used device-based and self-report measures demonstrated responsiveness to changes in PA. While inclusion of both device-based and self-report measures is desirable within interventions it is not always feasible. The results from this study support that self-reported measures can detect PA change within behavioral interventions, although may have a tendency to overestimate changes compared with device-based measures on absolute values, but not standardized response values.

#10 Physical Fitness, Body Composition, and Adherence to the Mediterranean Diet in Young Football Players: Influence of the 20 mSRT Score and Maturational Stage
Reference: Int J Environ Res Public Health. 2020 May 7;17(9). pii: E3257. doi: 10.3390/ijerph17093257.
Authors: Manzano-Carrasco S, Felipe JL, Sanchez-Sanchez J, Hernandez-Martin A, Gallardo L, Garcia-Unanue J
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Summary: This study aimed to analyze the differences in physical fitness variables, body composition, and adherence to the Mediterranean diet according to the cardiorespiratory fitness and the maturational stage in young football players. A total of 194 male football players (aged 8-16) from three football sport schools participated in this study. Data on cardiorespiratory fitness (the 20-m shuttle run test), anthropometric measurements, handgrip strength, respiratory capacity (forced spirometry), and adherence to the Mediterranean diet (KIDMED questionnaire) were collected. Players were divided into two groups depending on their maturational stage (prepubertal n = 127 and pubertal n = 67). The results show a direct relationship between low levels of cardiorespiratory fitness and body mass index, as well as body fat and leg fat. Similarly, players with lower cardiorespiratory fitness presented higher values of handgrip strength in the prepubertal state. On the other hand, improvements in respiratory values were observed in the pubertal state with the rest of the parameters when the cardiorespiratory fitness was increased. Therefore, the promotion of recreational football that encourage and develop cardiorespiratory fitness is a key factor and can be used as an effective sport activity to promote physical fitness and healthy habits in children and adolescents as well as within the population that is already physically active.

#11 Purposeful Heading in Youth Soccer: Time to Use Our Heads
Reference: J Orthop Sports Phys Ther. 2020 May 22;1-8. doi: 10.2519/jospt.2020.9680. Online ahead of print.
Authors: Kerry Peek, James M Elliott , Andrew Gardner
Summary: Repeated purposeful heading in soccer has come under increased scrutiny as concerns surrounding the association with long-term neurodegenerative disorders in retired players continues to grow. Whilst a causal link between heading and brain health has not been established, the 'Precautionary Principle' supports the notion that soccer governing bodies and associations should consider implementing pragmatic strategies, which can reduce head impact during purposeful heading in youth soccer whilst this relationship is being investigated. This viewpoint discusses the current evidence to support low-risk head impact reduction strategies during purposeful heading to protect young developing players; and how such strategies could be implemented now while research and debate continues on this topic.

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