Latest research in football - week 53 - 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 Relationship between movement dysfunctions and sports injuries according to gender of youth soccer player
Reference: J Exerc Rehabil. 2020 Oct 27;16(5):427-431. doi: 10.12965/jer.2040650.325. eCollection 2020 Oct.
Authors: Ki-Hoon Lim, Tae-Beom Seo, Young-Pyo Kim
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Summary: The purpose of this study is to investigate relationship between movement dysfunctions and sports injuries according to gender of youth soccer player. Thirty-eight middle school soccer players participated in this study and they were divided into male (n=19) and female (n=19) groups. The Functional Movement Screen (FMS) and the Quadriceps-angle (Q-angle) during single-leg squat were analyzed for identifying imbalance and asymmetry of the body, and sports injury questionnaire was examined for 6 months after FMS test. The number of sports injuries did not show significant difference between youth male and female soccer athletes. In FMS results, the scores of overhead squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, and rotary stability and the total scores were no significant differences between gender, but the score for the trunk stability push-up was significantly higher in male group than female group. There was no significant difference of Q-angle values between the left and right legs, but Q-angle value between youth male and female groups significantly showed interaction. Therefore, the present data suggested that FMS and Q-angle during single-leg squat might be indicators to predict and/or prevent sports injury in youth male and female soccer players.

#2 Can Small-side Games Provide Adequate High-speed Training in Professional Soccer?
Reference: Int J Sports Med. 2020 Nov 11. doi: 10.1055/a-1293-8471. Online ahead of print.
Authors: Jose Asian-Clemente, Alberto Rabano-Muñoz, Borja Muñoz, Jesus Franco, Luis Suarez-Arrones
Summary: The aim was to compare the running activity in official matches with that achieved in two small-sided games, designed with the same relative area per player but with different constraints and field dimensions, aiming to stimulate high-speed and very-high-speed running. Seventeen young professional players played one 5 vs. 5+5 with 2 floaters, varying in terms of whether there was a change of playing area (SSGCA) or not change (SSGNC). Running activity was monitored using GPS and the following variables were recorded: total distance covered; high-speed distance (18-21 km·h-1); very high-speed distance (>21 km·h-1); peak speed; accelerations and decelerations between 2-3 m·s-2 and above 3 m·s-2. SSGCA achieved statistically higher total distance, high-speed, peak speed and number of accelerations and decelerations than SSGNC (large to small magnitude). Both drills showed statistically greater high speed, number of accelerations and decelerations than official matches (large to small magnitude). Moreover, SSGCA exhibited statistically more total distance and distance at higher speed than official matches (moderate and small magnitude, respectively). In contrast, official matches showed statistically higher peak speeds than both training tasks and more very high speed than SSGNC (large and moderate magnitude, respectively). Coaches could use SSGCA to promote greater running activity in soccer players.

#3 Concussions in Soccer: An Epidemiological Analysis in the Pediatric Population
Reference: Orthop J Sports Med. 2020 Oct 21;8(10):2325967120951077. doi: 10.1177/2325967120951077. eCollection 2020 Oct.
Authors: Kiran Chatha, Taylor Pruis, Carlos Fernandez Peaguda, Eric Guo, Sandra Koen, Danielle Malone, Vani Sabesan
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Summary: As the popularity of youth soccer has increased in the United States, more attention has been focused on the effect of concussion injuries, with recent debate on whether heading should be disallowed. There is little evidence examining the epidemiology of these injuries. The purpose of this study was to examine the prevalence and incidence of youth soccer-related concussions. We hypothesized that concussion rates will correlate with increased participation in youth soccer. The National Electronic Injury Surveillance System was used to collect data on concussion injuries that occurred during soccer in pediatric patients from 2008 through 2016. Soccer-related concussion injuries were identified using specific codes and were analyzed for variation in disposition. The types of contact were categorized into player-to-player, head-to-ball, player-to-post, and player-to-ground contacts. Contact types related to hospitalization were subanalyzed. A weighted total of 3285 concussion injuries were identified during the study period, with an average of 386 concussions each year. The average age was 13.5 years, and there were no differences seen in incidence between the sexes. The overall incidence of concussion injuries increased (r = 0.789), while hospitalizations decreased (r = -0.574). The most common cause of concussion was found to be player-to-player contact, followed by head-to-ground contact and then head-to-ball contact. Subanalysis showed that 13% of hospitalizations were due to head-to-ball contact, compared with 39% and 44% due to player-to-player contact and head-to-ground contact, respectively. The relative risk of hospitalization from a concussion due to head-to-ball contact was 7.06 compared with 22.60 due to head-to-ground contact. The incidence of concussion in youth soccer has been increasing over the past decade as predicted, given the growing participation rates in both male and female soccer players. The most common cause of concussion was player-to-player contact, and the majority of concussions resulting in hospitalization occurred because of head-to-ground contact.

#4 Acute Physiological Responses to High-Intensity Resistance Circuit Training vs. Traditional Strength Training in Soccer Players
Reference: Biology (Basel). 2020 Nov 7;9(11):E383. doi: 10.3390/biology9110383.
Authors: Cristian Marín-Pagán, Anthony J Blazevich, Linda H Chung, Salvador Romero-Arenas, Tomás T Freitas, Pedro E Alcaraz
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Summary: The aim of this study was to evaluate and compare the cardiorespiratory and metabolic responses induced by high-intensity resistance circuit-based (HRC) and traditional strength (TS) training protocols. Ten amateur soccer players reported to the laboratory on four occasions: (1) protocol familiarization and load determination; (2) maximal oxygen consumption test; (3) and (4) resistance training protocols (HRC and TS), completed in a cross-over randomized order. In both protocols, the same structure was used (two blocks of 3 sets × 3 exercises, separated by a 5-min rest), with only the time between consecutive exercises differing: TS (3 min) and HRC (~35 s, allowing 3 min of local recovery). To test for between-protocol differences, paired t-tests were applied. Results showed that oxygen consumption and heart rate during HRC were 75% and 39% higher than TS, respectively (p < 0.001). After the training sessions, blood lactate concentration at 1.5, 5 and 7 min and excess post-exercise oxygen consumption were higher in HRC. The respiratory exchange ratio was 6.7% greater during HRC, with no between-group differences found post-exercise. The energy cost of HRC was ~66% higher than TS. In conclusion, HRC training induces greater cardiorespiratory and metabolic responses in soccer players and thus may be a time-effective training strategy.

#5 Exploring the Relationship Between Participation in an Adult-women's Soccer League and Intimate Partner Violence in Rural Kenya
Reference: J Interpers Violence. 2020 Nov 1;886260520969241. doi: 10.1177/0886260520969241. Online ahead of print.
Authors: Francis Barchi, Samantha C Winter, Daniel Mbogo, Bendettah Thomas, Brittany Ammerman
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Summary: Rates of intimate partner violence (IPV) against women in Sub-Saharan Africa are among the highest of any region in the world. Empirical studies on the effectiveness of IPV-prevention programs in Africa, though few, suggest that successful programs have emphasized community-level engagement and attitudinal change around gender roles. This study explored the relationship between adult women's participation in an all-women's soccer league and IPV in rural Kenya. Nikumbuke Project is a health- and literacy-based program for 702 women in Kwale County, Kenya, that also hosts a women's soccer league. A total of 684 Nikumbuke members completed surveys for this study, 543 of whom identified as having had a partner in the preceding 12 months and were included in this analysis. Participants in the study were, on average, in their late 30s, married with 4-6 children, a primary education or less, and no source of formal employment. Logistic regression models examined the association between a woman's participation in the soccer league and the odds that she would have experienced recent IPV, controlling for other covariates. Women who played on soccer teams had 59% lower odds of reporting physical IPV in the preceding 12 months and approximately 43% lower odds of reporting any form of IPV during the same period compared to women who did not play soccer. Support of more gender-equitable norms was associated with lower odds of all forms of recent violence. More research is needed to identify the underlying reasons for these observed effects and to determine the presence of a causal or temporal relationship between adult women's sports and IPV-risk reduction. Nonetheless, findings from this study point to a novel IPV intervention in communities that might otherwise be resistant to more overt attempts to address gender-based violence (GBV) or where social service agencies with the capacity for IPV-prevention programming may be limited.

#6 The Acute Effects of Cognitive-Based Neuromuscular Training and Game-Based Training on the Dynamic Balance and Speed Performance of Healthy Young Soccer Players: A Randomized Controlled Trial
Reference: Games Health J. 2020 Nov 9. doi: 10.1089/g4h.2020.0051. Online ahead of print.
Authors: Murat Emirzeoğlu, Özlem Ülger
Summary: The aim of this study was to investigate the acute effects of cognitive and game-based trainings (GBT) on dynamic balance (DB) and speed performance (SP) in healthy young soccer players. Forty-nine male soccer players were divided into three groups: cognitive-based neuromuscular training (CBNT; n = 16; age = 16.93 ± 1.18 years; body mass index [BMI] = 21.37 ± 1.57 kg/m2) group, GBT (n = 17; age = 17.05 ± 1.39 years; BMI = 21.10 ± 0.97 kg/m2) group, and control group (n = 16; age = 16.75 ± 1.12 years; BMI = 21.95 ± 1.36 kg/m2). The athletes in CBNT and GBT groups took part in one session lasting 1 hour. The Star Excursion Balance Test and the Speed Dribbling Test were used to evaluate DB and SP, respectively. The measurements were taken just before and after the trainings. Statistical analysis of the study was performed using SPSS 22.0 software (Statistical Package for Social Sciences, Inc., Chicago, IL). The Paired Student's t-test and Wilcoxon test were used. For in-group evaluation the ANOVA test was used for comparisons between the three groups. The Tukey's test was used for post hoc analysis. DB significantly improved in all directions in the GBT group (P < 0.05). Also, significant improvements were observed in DB in all directions except anterior, anterolateral, and anteromedial in the CBNT group, and except anterior, medial, and anteromedial directons in the control group (P < 0.05). SP significantly developed just in the CBNT and GBT groups (P = 0.001, P = 0.003, respectively). CBNT and GBT improved the DB of soccer players by 9.6% and 9.5%, respectively. Also, trainings improved the SP by 3.1% and 2.6%, respectively. CBNT and GBT are promising trainings that can improve DB and SP of healthy young soccer players.

#7 Characterization of On-Field Head Impact Exposure in Youth Soccer
Reference: J Appl Biomech. 2020 Nov 3;1-7. doi: 10.1123/jab.2020-0071. Online ahead of print.
Autors: Brian T Tomblin, N Stewart Pritchard, Tanner M Filben, Logan E Miller, Christopher M Miles, Jillian E Urban, Joel D Stitzel
Summary: The objective of this research was to characterize head impacts with a validated mouthpiece sensor in competitive youth female soccer players during a single season with a validated mouthpiece sensor. Participants included 14 youth female soccer athletes across 2 club-level teams at different age levels (team 1, ages 12-13 y; team 2, ages 14-15 y). Head impact and time-synchronized video data were collected for 66 practices and games. Video data were reviewed to characterize the type and frequency of contact experienced by each athlete. A total of 2216 contact scenarios were observed; heading the ball (n = 681, 30.7%) was most common. Other observed contact scenarios included collisions, dives, falls, and unintentional ball contact. Team 1 experienced a higher rate of headers per player per hour of play than team 2, while team 2 experienced a higher rate of collisions and dives. A total of 935 video-verified contact scenarios were concurrent with recorded head kinematics. While headers resulted in a maximum linear acceleration of 56.1g, the less frequent head-to-head collisions (n = 6) resulted in a maximum of 113.5g. The results of this study improve the understanding of head impact exposure in youth female soccer players and inform head impact exposure reduction in youth soccer.

#8 Residual deficits in reactive strength indicate incomplete restoration of athletic qualities following anterior cruciate ligament reconstruction in professional soccer players
Reference: J Athl Train. 2020 Nov 5. doi: 10.4085/169-20. Online ahead of print.
Authors: Paul J Read, William T Davies, Chris Bishop, Sean Mc Auliffe, Mathew G Wilson, Anthony N Turner
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#9 Prediction of Somatotype from Bioimpedance Analysis in Elite Youth Soccer Players
Reference: Int J Environ Res Public Health. 2020 Nov 5;17(21):8176. doi: 10.3390/ijerph17218176.
Authors: Francesco Campa, Catarina N Matias, Pantelis T Nikolaidis, Henry Lukaski, Jacopo Talluri, Stefania Toselli
Summary: The accurate body composition assessment comprises several variables, causing it to be a time consuming evaluation as well as requiring different and sometimes costly measurement instruments. The aim of this study was to develop new equations for the somatotype prediction, reducing the number of normal measurements required by the Heath and Carter approach. A group of 173 male soccer players (age, 13.6 ± 2.2 years, mean ± standard deviation; body mass index, BMI, 19.9 ± 2.5 kg/m2), members of the academy of a professional Italian soccer team participating in the first division (Serie A), participated in this study. Bioelectrical impedance analysis (BIA) was performed using the single frequency of 50 kHz and fat-free mass (FFM) was calculated using a BIA specific, impedance based equation. Somatotype components were estimated according to the Heath-Carter method. The participants were randomly split into development (n = 117) and validation groups (n = 56). New anthropometric and BIA based models were developed (endomorphy = -1.953 - 0.011 × stature2/resistance + 0.135 × BMI + 0.232 × triceps skinfold, R2 = 0.86, SEE = 0.28; mesomorphy = 6.848 + 0.138 × phase angle + 0.232 × contracted arm circumference + 0.166 × calf circumference - 0.093 × stature, R2 = 0.87, SEE = 0.40; ectomorphy = -5.592 - 38.237 × FFM/stature + 0.123 × stature, R2 = 0.86, SEE = 0.37). Cross validation revealed R2 of 0.84, 0.80, and 0.87 for endomorphy, mesomorphy, and ectomorphy, respectively. The new proposed equations allow for the integration of the somatotype assessment into BIA, reducing the number of collected measurements, the instruments used, and the time normally required to obtain a complete body composition analysis.

#10 Potential prognostic factors for hamstring muscle injury in elite male soccer players: A prospective study
Reference: PLoS One. 2020 Nov 9;15(11):e0241127. doi: 10.1371/journal.pone.0241127. eCollection 2020.
Authors: Ismet Shalaj, Masar Gjaka, Norbert Bachl, Barbara Wessner, Harald Tschan, Faton Tishukaj
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Summary: Hamstring injuries remain the most common injury type across many professional sports. Despite a variety of intervention strategies, its incidence in soccer players playing in the UEFA Champions League has increased by 4% per year over the last decade. Test batteries trying to identify potential risk factors have produced inconclusive results. The purpose of the current study was to prospectively record hamstring injuries, to investigate the incidence and characteristics of the injuries, and to identify possible risk factors in elite male soccer players, playing in the Kosovo national premier league. A total of 143 soccer players from 11 teams in Kosovo were recruited. To identify possible prevalent musculoskeletal or medical conditions a widespread health and fitness assessment was performed including isokinetic strength testing, Nordic hamstring strength test, functional tests, and a comprehensive anamnesis surveying previous hamstring injuries. On average 27.9% of the players sustained at least one hamstring injury with three players suffering bilateral strains with the re-injury rate being 23%. Injured players were significantly older and heavier and had a higher body mass index compared to non-injured ones (p < 0.05). There was a lower passing rate in the Nordic hamstring strength test and a higher injury incidence among the previously injured players compared to non-injured ones (p < 0.05). Except for hamstring/quadriceps ratio and relative torque at 60°/sec (p < 0.05) for dominant and non-dominant leg, there were no other significant differences in isokinetic strength regardless of the angular velocity. No differences were observed for functional tests between cohorts. Regression analysis revealed that age, Nordic hamstring strength test, previous injury history, and isokinetic concentric torque at 240°/sec could determine hamstring injuries by 25.9%, with no other significant predicting risk factors. The battery of laboratory and field-based tests performed during preseason to determine performance related skills showed limited diagnostic conclusiveness, making it difficult to detect players at risk for future hamstring injuries.

#11 Perceptions of Stress of Swedish Volunteer Youth Soccer Coaches
Reference: Sports (Basel). 2020 Nov 3;8(11):E146. doi: 10.3390/sports8110146.
Authors: Krister Hertting, Stefan Wagnsson, Karin Grahn
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Summary: The work of a coach can be stressful, and little is known about how volunteer coaches in child and youth soccer perceive stress. Therefore, the overall aim of this study was to explore perceptions of stress among Swedish volunteer youth soccer coaches. An online questionnaire was distributed to 1514 soccer coaches of which 688 (78% men and 22% women; 4% < 30 years, 34% 31-40 years; 57% 41-50 years and 5% > 51 years) with non-profit positions responded. Findings indicate that participants in general do not feel excessively stressed by being a volunteer youth soccer coach (M = 2.20; SD = 0.93; Min = 1; Max = 5), and no significant differences in perceived stress level were found based on gender, age, ethnicity, educational level or occupation. Multiple regression analysis showed that demands from employment (β = 0.24, p < 0.001), difficulty catching up with the family (β = 0.22, p < 0.001), not having enough time to plan activities (β = 0.13, p < 0.001), feeling pressured when selecting the team (β = 0.09, p = 0.013) and own demands to achieve good results (β = 0.07, p = 0.045), significantly contributed to perceptions of stress among the investigated youth sport coaches. The results shed light on the important aim that sport clubs develop holistic strategies when recruiting and retaining coaches and for other functions concerning child and youth soccer teams.

#12 Differences in physical fitness after an 8-week preseason training among elite football players aged 17-19 years
Reference: J Exerc Rehabil. 2020 Oct 27;16(5):442-449. doi: 10.12965/jer.2040598.299. eCollection 2020 Oct.
Authors: Hojun Lee, Chang-Hwa Joo
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Summary: There may be an optimal period of time to maximize the improvement of physical fitness during adolescence. The aim of this study was to examine the magnitude of changes in physical fitness after 8 weeks of preseason training according to chronological ages after the age at peak high velocity. Thirty male young football players from an elite football team (U-16, n=10; U-17, n=10; U-18, n=10) participated in the study. The players completed an 8-week general preseason football training and participated in the pre- and posttests to measure physical fitness. The 8-week preseason training improved the power of all young players (P<0.05). The 20-m sprint performance was improved by training in U-16 and U-18 (P<0.05), but no changes were found in the U-17 group (P>0.05). Significant differences were found in the arrowhead left in U-16 and U-18 (P<0.05) after training; however, no difference was observed in U-17 (P>0.05). Coordination was enhanced further in U-16 and U-17 (P<0.05) compared with that in U-18 (P>0.05). The performance of repeated sprints and Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) were similar between pre- and posttraining in all age groups (P>0.05). Collectively, the results emphasized the importance of systematic and scientific training methods to improve the fitness levels of young football players in the preseason training period. Moreover, training to improve coordination in young football players is effective at younger ages.

#13 What Do Football Players Look at? An Eye-Tracking Analysis of the Visual Fixations of Players in 11 v 11 Elite Football Match Play
Reference: Front Psychol. 2020 Oct 16;11:562995. doi: 10.3389/fpsyg.2020.562995. eCollection 2020.
Authors: Karl Marius Aksum, Lukas Magnaguagno, Christian Thue Bjørndal, Geir Jordet
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Summary: Current knowledge of gaze behavior in football has primarily originated from eye-tracking research in laboratory settings. Using eye-tracking with elite players in a real-world 11 v 11 football game, this exploratory case study examined the visual fixations of midfield players in the Norwegian premier league. A total of 2,832 fixations by five players, aged 17-23 years (M = 19.84), were analyzed. Our results show that elite football midfielders increased their fixation duration when more information sources became available to them. Additionally, participants used shorter fixation durations than previously reported in laboratory studies. Furthermore, significant differences in gaze behavior between the attack and defense phases were found for both areas of interest and fixation location. Lastly, fixation locations were mainly on the ball, opponent, and teammate category and the player in possession of the ball. Combined, the results of this study enhance the knowledge of how elite footballers use their vision when playing under actual match-play conditions. They also suggest that laboratory designs may not be able to capture the dynamic environment that footballers experience in competition.

#14 Effects of a 10 vs. 20-Min Injury Prevention Program on Neuromuscular and Functional Performance in Adolescent Football Players
Reference: Front Physiol. 2020 Oct 15;11:578866. doi: 10.3389/fphys.2020.578866. eCollection 2020.
Authors: Anna Lina Rahlf, Cornelius John, Daniel Hamacher, Astrid Zech
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Summary: Regular injury prevention training is not only effective in reducing sports injury rates, but also in improving neuromuscular and performance-related variables. However, it is currently unknown if this effect can be modified by varying the training dosage. The objective was t compare the effects of two injury prevention programmes with a different training duration on neuromuscular control and functional performance in adolescent football players. 342 (15.4 ± 1.7 years) male football players from 18 teams were initially included. The teams were cluster-randomized into two intervention groups. Both groups performed an injury prevention program twice a week during one football season (10 months) using the same exercises but a different duration. One intervention group (INT10, n = 175) performed the program for 10 min, while the other intervention group (INT20, n = 167) for 20 min. At the beginning and end of the season, balance control (Balance Error Scoring System = BESS), jump performance (Squat Jump, Countermovement Jump) and flexibility (Sit and Reach Test, ankle flexibility, hip flexibility) tests were performed. For the final analysis, nine teams with 104 players were considered. Significant group by time interactions were found for the sit and reach test (p < 0.001) and ankle flexibility (p < 0.001) with higher improvements in the INT20 group. Improvements over the period of one season but no group differences were found for the BESS, Squat Jump and hip flexibility. Within a single training session, performing structured neuromuscular training with a longer duration is more effective than a shorter duration for improving lower extremity flexibility.

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