Latest research in football - week 44 - 2019

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 Effect of the FIFA 11+ on Landing Patterns and Baseline Movement Errors in Elite Male Youth Soccer Players
Reference: J Sport Rehabil. 2019 Oct 18:1-8. doi: 10.1123/jsr.2018-0374. [Epub ahead of print]
Authors: Akbari H, Sahebozamani M, Daneshjoo A, Amiri-Khorasani M, Shimokochi Y.
Summary: There is no evidence regarding the effect of the FIFA 11+ on landing kinematics in male soccer players, and few studies exist regarding the evaluating progress of interventions based on the initial biomechanical profile. The aim was to investigate the effect of the FIFA 11+ program on landing patterns in soccer players classified as at low or high risk for noncontact anterior cruciate ligament injuries. Field-based functional movement screening performed at the soccer field was measured in a total of 24 elite male youth soccer players participated in this study. The intervention group performed the FIFA 11+ program 3 times per week for 8 weeks, whereas the control group performed their regular warm-up.Before and after the intervention, all participants were assessed for landing mechanics using the Landing Error Scoring System. Pretraining Landing Error Scoring System scores were used to determine risk groups. The FIFA 11+ group had greater improvement than the control group in terms of improving the landing pattern; there was a significant intergroup difference (F1,20 = 28.86, P < .001, ηp2=.591). Soccer players categorized as being at high risk displayed greater improvement from the FIFA 11+ program than those at low risk (P = .03). However, there was no significant difference in the proportion of risk category following the routine warm-up program (P = 1.000). The present study provides evidence of the usefulness of the FIFA 11+ program for reducing risk factors associated with noncontact anterior cruciate ligament injuries. The authors' results also suggest that soccer players with the higher risk profile would benefit more than those with lower risk profiles and that targeting them may improve the efficacy of the FIFA 11+ program.

#2 Neurodegenerative Disease Mortality among Former Professional Soccer Players
Reference: N Engl J Med. 2019 Oct 21. doi: 10.1056/NEJMoa1908483. [Epub ahead of print]
Authors: Mackay DF, Russell ER, Stewart K, MacLean JA, Pell JP, Stewart W
Summary: Neurodegenerative disorders have been reported in elite athletes who participated in contact sports. The incidence of neurodegenerative disease among former professional soccer players has not been well characterized. We conducted a retrospective cohort study to compare mortality from neurodegenerative disease among 7676 former professional soccer players (identified from databases of Scottish players) with that among 23,028 controls from the general population who were matched to the players on the basis of sex, age, and degree of social deprivation. Causes of death were determined from death certificates. Data on medications dispensed for the treatment of dementia in the two cohorts were also compared. Prescription information was obtained from the national Prescribing Information System. Over a median of 18 years, 1180 former soccer players (15.4%) and 3807 controls (16.5%) died. All-cause mortality was lower among former players than among controls up to the age of 70 years and was higher thereafter. Mortality from ischemic heart disease was lower among former players than among controls (hazard ratio, 0.80; 95% confidence interval [CI], 0.66 to 0.97; P = 0.02), as was mortality from lung cancer (hazard ratio, 0.53; 95% CI, 0.40 to 0.70; P<0.001). Mortality with neurodegenerative disease listed as the primary cause was 1.7% among former soccer players and 0.5% among controls (subhazard ratio [the hazard ratio adjusted for competing risks of death from ischemic heart disease and death from any cancer], 3.45; 95% CI, 2.11 to 5.62; P<0.001). Among former players, mortality with neurodegenerative disease listed as the primary or a contributory cause on the death certificate varied according to disease subtype and was highest among those with Alzheimer's disease (hazard ratio [former players vs. controls], 5.07; 95% CI, 2.92 to 8.82; P<0.001) and lowest among those with Parkinson's disease (hazard ratio, 2.15; 95% CI, 1.17 to 3.96; P = 0.01). Dementia-related medications were prescribed more frequently to former players than to controls (odds ratio, 4.90; 95% CI, 3.81 to 6.31; P<0.001). Mortality with neurodegenerative disease listed as the primary or a contributory cause did not differ significantly between goalkeepers and outfield players (hazard ratio, 0.73; 95% CI, 0.43 to 1.24; P = 0.24), but dementia-related medications were prescribed less frequently to goalkeepers (odds ratio, 0.41; 95% CI, 0.19 to 0.89; P = 0.02). In this retrospective epidemiologic analysis, mortality from neurodegenerative disease was higher and mortality from other common diseases lower among former Scottish professional soccer players than among matched controls. Dementia-related medications were prescribed more frequently to former players than to controls. These observations need to be confirmed in prospective matched-cohort studies. (Funded by the Football Association and Professional Footballers' Association.).

#3 Sport Specialization and Coordination Differences in Multisport Adolescent Female Basketball, Soccer, and Volleyball Athletes
Reference: J Athl Train. 2019 Oct;54(10):1105-1114. doi: 10.4085/1062-6050-407-18.
Authors: DiCesare CA, Montalvo A, Foss KDB, Thomas SM, Hewett TE, Jayanthi NA, Myer GD
Summary: Early sport specialization, or the participation in 1 sport year-round to the exclusion of all others, is a growing concern in youth athletics because of its possible association with musculoskeletal injury. The underlying injury risk may be the result of coordination differences that sport-specialized athletes have been speculated to exhibit relative to multisport athletes; however, little evidence exists to support or refute this notion. The aim was to examine relative hip- and knee-joint angular-motion variability among adolescent sport-specialized and multisport female adolescent athletes to determine how sport specialization may affect coordination. A total of 366 sport-specialized and 366 multisport adolescent female basketball, soccer, and volleyball players participated in this study with an drop-vertical-jump (DVJ) assessment. Average coupling-angle variability (CAV) for hip flexion and knee flexion, knee flexion and ankle flexion, hip flexion and knee abduction, knee flexion and knee abduction, knee flexion and knee internal rotation, and knee abduction and knee internal rotation. The sport-specialized group exhibited increased coupling variability in dominant-limb hip flexion and knee flexion (P = .015), knee flexion and knee abduction (P = .014), and knee flexion and knee internal rotation (P = .048) while landing during the DVJ, although they had small effect sizes (η2 = 0.010, 0.010, and 0.007, respectively). No differences were present between groups for any of the other CAV measures of the dominant limb, and no differences were found for any CAV measures of the nondominant limb (all P values > .05). Sport specialization was associated with increased variability of critical hip- and knee-joint couplings responsible for effective landing during the DVJ. Altered coordination strategies that involve the hip and knee joints may underlie unstable landings, inefficient force-absorption strategies, or greater contact forces that can place the lower extremities at risk for injury (or a combination of these).

#4 Evaluation for the effects of nutritional education on Chinese elite male young soccer players: The application of adjusted dietary balance index (DBI)
Reference: J Exerc Sci Fit. 2020 Jan;18(1):1-6. doi: 10.1016/j.jesf.2019.08.004. Epub 2019 Aug 20.
Authors: Zeng D, Fang ZL, Qin L, Yu AQ, Ren YB, Xue BY, Zhou X, Gao ZY, Ding M, An N, Wang QR
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Summary: The aim of this study was to evaluate the effect of nutrition education on Chinese elite male young soccer players through the knowledge, attitude, behavior (KAP) survey and an adjusted dietary balance index (DBI). 30 Chinese elite male young soccer players were randomly divided into two groups: lecture group (N = 15, Age: 16.7 ± 1.8 years, Height: 173.9 ± 9.0 cm; Weight: 62.4 ± 13.0 kg; Training years: 5.6 ± 2.7 years) and non-lecture group (N = 15, Age: 16.8 ± 1.7 years, Height: 175.5 ± 7.9 cm; Weight: 62.5 ± 12.3 kg; Training years: 6.2 ± 3.3). The comics book was given to the non-lecture group, while the a four-week nutritional quality education along with comic books were given to the lecture group. Before and after 4 weeks nutritional education, dietary nutritional status of both groups was assessed. The main outcome measurements included the scores for each part of the KAP survey, diet status (food-weighing method) and the dietary index in the adjusted DBI-07 system (DBI-low bound score, LBS; DBI-high bound score, HBS; and DBI-diet quality distance, DQD). In the lecture group, significant differences were found in the scores of general nutrition knowledge, sports nutrition knowledge and total scores of KAP dietary questionnaire after 4 weeks nutritional education (P < 0.01). However, there is no significant difference in dietary attitude and dietary behavior (P > 0.05) on both two groups. There is no significant change in the DBI-low bound score (LBS), DBI-high bound score (HBS) and DBI-diet quality distance (DQD) of dietary quality index (P > 0.05) in both two groups. Four weeks nutritional quality education improved the understanding of dietary nutrition among Chinese elite male young soccer players.

#5 Analysis of the Association between Running Performance and Game Performance Indicators in Professional Soccer Players
Reference: Int J Environ Res Public Health. 2019 Oct 21;16(20). pii: E4032. doi: 10.3390/ijerph16204032.
Authors: Modric T, Versic S, Sekulic D, Liposek S
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Summary: Running performance (RP) and game performance indicators (GPI) are important determinants of success in soccer (football), but there is an evident lack of knowledge about the possible associations between RP and GPI. This study aimed to identify associations between RP and GPI in professional soccer players and to compare RP and GPI among soccer playing positions. One hundred one match performances were observed over the course of half of a season at the highest level of national competition in Croatia. Players (mean ± SD, age: 23.85 ± 2.88 years; body height: 183.05 ± 8.88 cm; body mass: 78.69 ± 7.17 kg) were classified into five playing positions (central defenders (n = 26), full-backs (n = 24), central midfielders (n = 33), wide midfielders (n = 10), and forwards (n = 8). RP, as measured by global positioning system, included the total distance covered, distance covered in five speed categories (walking, jogging, running, high-speed running, and maximal sprinting), total number of accelerations, number of high-intensity accelerations, total number of decelerations, and number of high-intensity decelerations. The GPI were collected by the position-specific performance statistics index (InStat index). The average total distance was 10,298.4 ± 928.7 m, with central defenders having the shortest and central midfielders having the greatest covered distances. The running (r = 0.419, p = 0.03) and high-intensity accelerations (r = 0.493, p = 0.01) were correlated with the InStat index for central defenders. The number of decelerations of full-backs (r = -0.43, p = 0.04) and the distance covered during sprinting of forwards (r = 0.80, p = 0.02) were associated with their GPI obtained by InStat index. The specific correlations between RP and GPI should be considered during the conditioning process in soccer. The soccer training should follow the specific requirements of the playing positions established herein, which will allow players to meet the game demands and to perform successfully.

#6 Working memory capacity does not always promote dual-task motor performance: The case of juggling in soccer
Reference: Scand J Psychol. 2019 Oct 21. doi: 10.1111/sjop.12589. [Epub ahead of print]
Authors: Laurin R, Finez L
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Summary: The aim of this research was to refine our understanding of the role of working memory capacity (WMC) on motor performances that require attentional control in dual-task situations. Three studies were carried out on soccer players. Each participant had to perform a juggling task in both normal and dual-task conditions. In Study 1, the interfering task was a mental calculation test performed under time pressure (strong cognitive load). In Study 2, the interfering task was a count-down test (low cognitive load). In Study 3 an intra-individual design in which participants perform dual-tasks increasingly complex has been proposed. Results showed a positive relationship between participants' WMC and their dual-task motor performance when the cognitive load was low and a negative relationship when the cognitive load was high. This paper highlights the role of the WMC in the activation of different modes of processing and its importance on the performance in dual-task.

#7 Injury Profile of Elite Male Young Soccer Players in a Spanish Professional Soccer Club: A Prospective Study During 4 Consecutive Seasons
Reference: J Sport Rehabil. 2019 Oct 18:1-7. doi: 10.1123/jsr.2019-0113. [Epub ahead of print]
Authors: Raya-González J, Suárez-Arrones L, Navandar A, Balsalobre-Fernández C, Sáez de Villarreal E.
Summary: As the number of injuries in young soccer players increases, an epidemiological study is the first step in improving preventive strategies. The aim was to analyze the injury profile of a Spanish professional soccer club's academy during 4 consecutive seasons and to examine the injury incidence across different chronological age groups. Aggregate injury and exposure data collected during 4 consecutive seasons were collected of three hundred nine elite male young soccer players. Injuries that led to participation time missed from training and match play prospectively reported by medical or coaching staff of the club were used as outcome measures. A total of 464 time-loss injuries were observed during this study period. The overall injury incidence was 2.93 injuries per 1000 hours, with higher incidence during matches than during training (10.16 vs 2.10 injuries/1000 h; rate ratio [RR] = 0.21; 95% confidence interval [CI], 0.17-0.25; P < .05), with the U14 age group presenting the lowest injury rate (2.39 injuries/1000 h; RR = 1.15-1.57; P < .05). In terms of injury severity, moderate injuries were the most frequent (1.42 injuries/1000 h). Muscle injuries were the most common type of injuries (57.7%; 2.75 injuries/1000 h; RR = 1.84-13.4; P < .05), and hamstrings (93/268) were the most affected muscle group (0.58 injuries/1000 h; RR = 1.58-2.91; P < .05). Injury incidence showed a seasonal variation as indicated by peaks in August and October. In matches, specifically, the match period between 75 and 90 minutes showed the highest injury incidence (10.29 injuries/1000 h; RR = 1.89-6.38; P < .01). The findings of this study suggest that specific preventive strategies must be implemented to try to reduce the injury incidence in Spanish elite young soccer players attending to the characteristics of each age group.

#8 Elite Players' Perceptions of Football Playing Surfaces: A Qualitative Study
Reference: Res Q Exerc Sport. 2019 Oct 24:1-13. doi: 10.1080/02701367.2019.1660757. [Epub ahead of print]
Authors: Roberts JR, Osei-Owusu P, Mears AC, Harland AR
Summary: The decision by the International Football Association Board in 2004 to approve the use of artificial surfaces in elite football (soccer) competitions remains controversial amongst many players, managers and coaching staff. The aim of this study was to conduct a comprehensive assessment of players' opinions to better understand the influence of playing surfaces on the game of football and identify factors that may contribute to differences of opinion. Qualitative data were collected from 103 elite footballers and 21 coaching staff during a series of interviews and focus groups. A thematic analysis was conducted to identify patterns in the data. Players considered that the type and condition of a playing surface influenced ball-surface interactions, game play, tactics/strategy, footwear selection, movement, risk of injury and fatigue. Together these influence a player's perception of the suitability of a surface and also their mindset, which could ultimately affect their performance. The majority of participants in this study expressed a higher preference for natural grass over artificial turf pitches. A perceived increased risk of injury on artificial turf remains a primary concern despite a lack of supporting evidence in research studies. To address this discrepancy, the reporting of muscle soreness and the effect of constant surface switching merit further consideration. Not all participants shared the same views and player characteristics such as age, surface experience, injury history and playing style/position were found to be potential factors that could account for differences in elite players' opinions regarding the surfaces used in football.

#9 Acute effects of differential learning on football kicking performance and in countermovement jump
Reference: PLoS One. 2019 Oct 23;14(10):e0224280. doi: 10.1371/journal.pone.0224280. eCollection 2019.
Authors: Gaspar A, Santos S, Coutinho D, Gonçalves B, Sampaio J, Leite N
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Summary: The aim of this study was to identify the acute effects of a differential-learning training program on football kicking performance and countermovement jump. Twenty youth Portuguese under-15 football players participated in this study. All players were exposed to two training approaches: i) traditional, in which the players performed a total of 36 kicks in a blocked and repetitive approach; and ii) differential learning, which consisted in the 36 kicks using differential variations in each kick. Football kicking impact and velocity were assessed using a Stalker radar gun, while the kicking accuracy was assessed by aggregating the total number of points achieved during 12 kicks into a goal, which was divided into quantifiable scoring zones. Lastly, leg power was measured using a countermovement jump. Measurements were performed at baseline, post-intervention, and following a 35-minute training match. The comparisons between the baseline and post-test revealed that the differential learning approach promoted a possibly ~5% increase in the countermovement jump (small effects) and a likely ~3% increase in the average velocity (small effects) when compared with the traditional training approach. From the accuracy perspective, there was a moderate decrease from the baseline to the post-test and post-match in accurate kicks into zone 1 (centre of the goal) and a moderate decrease from the baseline to the post-match in accurate kicks into zone 5 (lateral zones at short height) in the differential intervention. In turn, a small increase in the accurate kicks into zones 4 and 6 (lateral zones of the goal and nearest to the bar, respectively) was found from the baseline to the post-match in the differential intervention. Overall, the differential learning intervention was more beneficial than a traditional training protocol with respect to acute improvements in countermovement jump performance, football kicking velocity and higher scoring zones kicking accuracy.

#10 Testing the functionality of peripheral vision in a mixed-methods football field study
Reference: J Sports Sci. 2019 Dec;37(24):2789-2797. doi: 10.1080/02640414.2019.1664100. Epub 2019 Sep 6.
Authors: Vater C, Luginbühl S, Magnaguagno L
Summary: In team sports, peripheral vision might be useful to simultaneously monitor movements of opponents and teammates. Until now, however, little is known about the perceptual-cognitive processes underlying peripheral vision in a sporting task. Therefore, we used a mixed-methods approach with in-situ decision making (3 vs. 3 situations) and retrospective verbal reports to identify perceptual strategies used for optimal information pick-up in high- and low-skilled football players. Our results show that the use of peripheral vision by central defenders depends on the position of the ball and the position of the direct opponent. Players were shown to either use a pivot strategy, whereby they frequently look at the direct opponent if he is not in the possession of the ball in addition to making saccades to monitor other players, or they employ a more direct strategy, in which gaze is anchored on this location, avoiding saccades and monitoring the other players with peripheral vision. Based on our findings we make recommendations about how these gaze strategies can be further tested in future research and how sports practice can benefit from these results.

#11 The Relationship Between Personality Traits and Muscle Injuries in Swedish Elite Male Football Players
Reference: J Sport Rehabil. 2019 Oct 18:1-6. doi: 10.1123/jsr.2018-0473. [Epub ahead of print]
Authors: Eckerman M, Svensson K, Edman G, Alricsson M.
Summary: The physical and mental demands of an elite football player are complex, which may explain why injuries are common in football. At elite level, muscle injuries of the lower-extremity are the most common among male football players, and the research hitherto is limited. The aim was to investigate whether personality traits affect the incidence of muscle injuries among male football players from the first league in Sweden. A male football team from the first league in Sweden was prospectively followed, in terms of muscle injuries of the lower-extremity during 8 seasons, between 2007 and 2015. All muscle injuries included in this study were evaluated and diagnosed with ultrasonography. Players from the team filled out the Swedish Universities Scales of Personality questionnaire. Swedish Universities Scales of Personality questionnaire consists of 91 items and is divided into 13 categories. The raw values of each scale were linearly transformed to T scores, having a mean (SD) of 50 (10). All variables were summarized with standard descriptive statistics, such as frequency, mean, and SD. As data were of interval scale and no variable distribution was severely skewed, differences between noninjured players, rarely injured players, and frequently injured players were analyzed with 1-way analysis of variance with post hoc tests by Tukey honestly significant difference test. No significant difference in personality traits were observed between noninjured players, rarely injured players, and frequently injured players regarding number of muscle injuries (P > .05). However, a trend (P = .07) was seen, where frequently injured players scored higher on stress susceptibility than rarely injured players. A player's stress susceptibility should be taken into consideration by the player, coaches, and medical staff when assessing the risk of a muscle injury. Also, preventive measures available for these players may need to be considered.

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