Latest research in football - week 2 - 2018

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

Following studies were retrieved for this week:

#1 The Demands of Amputee Soccer Impair Muscular Endurance and Power Indices But Not Match Physical Performance
Reference: Adapt Phys Activ Q. 2018 Jan 5:1-17. doi: 10.1123/apaq.2016-0147. [Epub ahead of print]
Authors: Simim MAM, da Mota GR, Marocolo M, da Silva BVC, de Mello MT, Bradley PS
Summary: We investigated the match demands (distances covered and acute physiological responses) of amputee soccer and its impact on muscular endurance and power. Measures such as heart rate, blood lactate concentration, subjective rating of perceived exertion, and time-motion characteristics were recorded in 16 Brazilian amputee soccer players during matches. Before and after matches, players completed a battery of tests: push-ups, countermovement vertical jump performance, and medicine ball throwing. Small differences were found between the first and second half for the distance covered in total and across various speed categories. Heart rate responses, blood lactate concentrations, and peak speed did not differ between halves, and all neuromuscular performance measures decreased after the match particularly after push-ups, although the rating of perceived exertion increased markedly compared with prematches. Although match physical performances were consistent across halves, the overall demands impaired test performance, especially for upper limb and closed kinetic chain exercise.

#2 Carbohydrates for Soccer: A Focus on Skilled Actions and Half-Time Practices
Reference: Nutrients. 2017 Dec 25;10(1). pii: E22. doi: 10.3390/nu10010022.
Authors: Hills SP, Russell M
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Summary: Carbohydrate consumption is synonymous with soccer performance due to the established effects on endogenous energy store preservation, and physical capacity maintenance. For performance-enhancement purposes, exogenous energy consumption (in the form of drinks, bars, gels and snacks) is recommended on match-day; specifically, before and during match-play. Akin to the demands of soccer, limited opportunities exist to consume carbohydrates outside of scheduled breaks in competition, such as at half-time. The link between cognitive function and blood glucose availability suggests that carbohydrates may influence decision-making and technical proficiency (e.g., soccer skills). However, relatively few reviews have focused on technical, as opposed to physical, performance while also addressing the practicalities associated with carbohydrate consumption when limited in-play feeding opportunities exist. Transient physiological responses associated with reductions in activity prevalent in scheduled intra-match breaks (e.g., half-time) likely have important consequences for practitioners aiming to optimize match-day performance. Accordingly, this review evaluated novel developments in soccer literature regarding (1) the ergogenic properties of carbohydrates for skill performance; and (2) novel considerations concerning exogenous energy provision during half-time. Recommendations are made to modify half-time practices in an aim to enhance subsequent performance. Viable future research opportunities exist regarding a deeper insight into carbohydrate provision on match-day.

#3 Talent Identification and Development in Male Football: A Systematic Review
Reference: Sports Med. 2018 Jan 3. doi: 10.1007/s40279-017-0851-7. [Epub ahead of print]
Authors: Sarmento H, Anguera MT, Pereira A, Araujo D
Summary: Expertise has been extensively studied in several sports over recent years. The specificities of how excellence is achieved in Association Football, a sport practiced worldwide, are being repeatedly investigated by many researchers through a variety of approaches and scientific disciplines. The aim of this review was to identify and synthesise the most significant literature addressing talent identification and development in football. We identified the most frequently researched topics and characterised their methodologies. A systematic review of Web of Science™ Core Collection and Scopus databases was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. The following keywords were used: "football" and "soccer". Each word was associated with the terms "talent", "expert*", "elite", "elite athlete", "identification", "career transition" or "career progression". The selection was for the original articles in English containing relevant data about talent development/identification on male footballers. The search returned 2944 records. After screening against set criteria, a total of 70 manuscripts were fully reviewed. The quality of the evidence reviewed was generally excellent. The most common topics of analysis were (1) task constraints: (a) specificity and volume of practice; (2) performers' constraints: (a) psychological factors; (b) technical and tactical skills; (c) anthropometric and physiological factors; (3) environmental constraints: (a) relative age effect; (b) socio-cultural influences; and (4) multidimensional analysis. Results indicate that the most successful players present technical, tactical, anthropometric, physiological and psychological advantages that change non-linearly with age, maturational status and playing positions. These findings should be carefully considered by those involved in the identification and development of football players. This review highlights the need for coaches and scouts to consider the players' technical and tactical skills combined with their anthropometric and physiological characteristics scaled to age. Moreover, research addressing the psychological and environmental aspects that influence talent identification and development in football is currently lacking. The limitations detected in the reviewed studies suggest that future research should include the best performers and adopt a longitudinal and multidimensional perspective.

#4 Monitoring loads and non-contact injury during the transition from club to National team prior to an international football tournament: A case study of the 2014 FIFA World Cup and 2015 Asia Cup
Reference: J Sci Med Sport. 2017 Dec 20. pii: S1440-2440(17)31825-X. doi: 10.1016/j.jsams.2017.12.002. [Epub ahead of print]
Authors: McCall A, Jones M, Gelis L, Duncan C, Ehrmann F, Dupont G, Duffield R
Summary: Injured and non-injured national team footballers were compared for external and internal loads during transition from club to National team training camp. Load and injury data were collected from the same National team prior to and during training camps of 2 tournaments; World (n=17) and Asian Cups (n=16). External (number sessions) and internal (s-RPE) loads were collected 4-weeks prior to and during camps. The acute:chronic load ratio was calculated for the first week of camp based on the mean of previous 4-weeks. Respective loads and ratios were compared between injured and non-injured players for non-contact injuries occurring during camp. Seven non-contact injuries occurred during World Cup camp and 1 during Asian Cup (preventing statistical analyses). Small-to-moderate effect sizes were found for lower chronic internal loads (ES=0.57; 90% CI: 0.39-1.08) and higher acute:chronic ratio (ES=0.45; 90% CI: 0.31-0.87) for injured compared to non-injured players. Moderate-large effects (ES=0.83; 90% CI: 0.56-1.60) were evident for increased acute:chronic ratio for number of sessions in injured compared to non-injured players. However, small-moderate effect sizes were present for lower chronic training and match loads (ES=0.55; 90% CI: 0.38-1.06) in injured players prior to the World Cup camp, alongside an increased number of sessions in week 1 of camp (ES=0.47; 90% CI: 0.33-0.91). Players incurring non-contact injury during training camp prior to an international tournament performed less prior chronic external and internal load and a concomitant higher relative increase in camp, thus representing a practical marker to monitor in national teams.

#5 Ecological validity and reliability of an age-adapted endurance field test in young male soccer players
Reference: J Strength Cond Res. 2018 Jan 11. doi: 10.1519/JSC.0000000000002255. [Epub ahead of print]
Authors: Castagna C, Krustrup P, D'Ottavio S, Pollastro C, Bernardini A, Araujo Povoas SC
Summary: The purpose of this study was to examine the reliability and the association with relevant match activities (ecological validity) of an age-adapted field test for intermittent high-intensity endurance known as Yo-Yo intermittent recovery level 1 children test (YYIR1C) in young male soccer players. Twenty-eight young male outfield soccer players (age 11.1±0.9 years, height 142±4.4 cm, body mass 37.0±5.9 kg) with at least 2 years of experience in soccer competitions were tested twice using YYIR1C and an age-adapted competitive small-sided game (i.e., 9v9), 7 days apart in a random order. The YYIR1C performance showed an excellent relative (ICC=0.94) and a good absolute reliability (TEM as %CV=5.1%). Very large and significant associations were found between YYIR1C performance and match high-intensity activity (r=0.53). Large correlations were found between YYIR1C and match sprinting (r=0.42) and high-intensity metabolic power (r=0.46) distances. Match total distance was largely associated with YYIR1C (r=0.30). The results of this study showed that YYIR1C may be considered a valid and reliable field test for assessing intermittent high-intensity endurance in young male soccer players. Due to the relevance of aerobic fitness in youth soccer, future studies testing the sensitiveness of YYIR1C are necessary.

#6 A previous hamstring injury affects kicking mechanics in soccer players
Reference: J Sports Med Phys Fitness. 2018 Jan 10. doi: 10.23736/S0022-4707.18.07852-0. [Epub ahead of print]
Authors: Navandar A, Veiga S, Torres G, Chorro D, Navarro E
Summary: Although the kicking skill is influenced by limb dominance and sex, how a previous hamstring injury affects kicking has not been studied in detail. Thus, the objective of this study was to evaluate the effect of sex and limb dominance on kicking in limbs with and without a previous hamstring injury. 45 professional players (males: n=19, previously injured players=4, age=21.16 ± 2.00 years; females: n=19, previously injured players=10, age=22.15 ± 4.50 years) performed 5 kicks each with their preferred and non-preferred limb at a target 7m away, which were recorded with a three-dimensional motion capture system. Kinematic and kinetic variables were extracted for the backswing, leg cocking, leg acceleration and follow through phases. A shorter backswing (20.20 ± 3.49% vs 25.64 ± 4.57%), and differences in knee flexion angle (58 ± 10o vs 72 ± 14o) and hip flexion velocity (8 ± 0rad/s vs 10 ± 2rad/s) were observed in previously injured, non-preferred limb kicks for females. A lower peak hip linear velocity (3.50 ± 0.84m/s vs 4.10 ± 0.45m/s) was observed in previously injured, preferred limb kicks of females. These differences occurred in the backswing and leg-cocking phases where the hamstring muscles were the most active. A variation in the functioning of the hamstring muscles and that of the gluteus maximus and iliopsoas in the case of a previous injury could account for the differences observed in the kicking pattern. Therefore, the effects of a previous hamstring injury must be considered while designing rehabilitation programs to re-educate kicking movement.

#7 Physical Fitness Performance of Young Professional Soccer Players Does not Change During Several Training Seasons in A Spanish Elite Reserve Team: A Club Study, 1996-2013
Reference: J Strength Cond Res. 2018 Jan 5. doi: 10.1519/JSC.0000000000002426. [Epub ahead of print]
Authors: Los Arcos A, Martins J
Summary: The purpose of the study was to assess the changes in physical fitness performance in young professional soccer players during several training seasons in a Spanish elite reserve team. Physical test values (i.e. vertical jump test, straight line sprint test, and discontinuous and progressive submaximal running test) of 97 young professional soccer players that belonged for at least two consecutive seasons to the reserve team of a Spanish professional team from 1996 to 2013 were analyzed. A distinction was made between the soccer players that were promoted to the Spanish 1/2 Divisions (n = 38) (PFL) and those that were not (n = 59) (non-PFL) (until the end of the 2016/2017 season). Players were also classified according to their playing positions. Independently of the competitive level reached and the playing position, the variability of the fitness performance was limited (coefficient of variation <6%) and the players did not improve their fitness values [ZERO WIDTH SPACE][ZERO WIDTH SPACE](ES ≤ small) from the first to the last season in which they were enrolled in the team (after 2-4 seasons). During the last stage of training in an elite soccer academy, young professional soccer players achieve a very similar physical fitness performance when their soccer competence is evaluated, and other soccer performance factors are those which make them stand out for selection.

#8 Investigating Effects of Sex Differences and Prior Concussions on Symptom Reporting and Cognition Among Adolescent Soccer Players
Reference: Am J Sports Med. 2018 Jan 1:363546517749588. doi: 10.1177/0363546517749588. [Epub ahead of print]
Authors: Brooks BL, Silverberg N, Maxwell B, Mannix R, Zafonte R, Berkner PD, Iverson GL
Summary: There has been increasing concern regarding the possible effect of multiple concussions on the developing brain, especially for adolescent females. Hypothesis/Purpose: The objectives were to determine if there are differences in cognitive functioning, symptom reporting, and/or sex effects from prior concussions. In a very large sample of youth soccer players, it was hypothesized that (1) there would be no differences in cognitive test performance between those with and without prior concussions, (2) baseline preseason symptoms would be better predicted by noninjury factors than concussion history, and (3) males and females with prior concussions would not have differences in cognition or symptoms. Participants included 9314 youth soccer players (mean = 14.8 years, SD = 1.2) who completed preseason baseline cognitive testing, symptom reporting, and a health/injury history questionnaire from the ImPACT battery (Immediate Post-concussion Assessment and Cognitive Testing). On the basis of injury history, athletes were grouped by number of prior concussions: 0 (boys, n = 4012; girls, n = 3963), 1 (boys, n = 527; girls, n = 457), 2 (boys, n = 130; girls, n = 97), or ≥3 (boys, n = 73; girls, n = 55). The primary measures were the 4 primary cognitive scores and the total symptom ratings from ImPACT. Primary outcomes were assessed across injury groups, controlling for age, sex, learning disability, attention-deficit/hyperactivity disorder (ADHD), treatment for headaches/migraines, substance abuse, and mental health problems. Cognitive test performance was not associated with concussion history but was associated with sex, age, learning disability, ADHD, and prior mental health problems. Greater symptom reporting was more strongly associated with psychiatric problems, older age, learning disability, substance abuse, headaches, being female, and ADHD than with a history of multiple concussions. Boys and girls did not differ on cognitive scores or symptom reporting based on a history of concussion. In this very large sample of youth soccer players with prior concussion, there was no evidence of negative effects on cognition, very weak evidence of negative effects on symptom reporting, and no evidence of sex × concussion differences in cognition or symptom reporting.

#9 Breast Injuries in Female Collegiate Basketball, Soccer, Softball and Volleyball Athletes: Prevalence, Type and Impact on Sports Participation
Reference: Eur J Breast Health. 2018 Jan 1;14(1):46-50. doi: 10.5152/ejbh.2017.3748. eCollection 2018 Jan.
Authors: Smith LJ, Eichelberger TD, Kane EJ
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Summary: In 2015-2016, over 214,000 female athletes competed at the collegiate level in the United States (U.S.). The National Collegiate Athletic Association (NCAA) collects injury data; however, breast-related injuries do not have a specific reporting category. The exact sequelae of breast injury are unknown; however, a relationship between breast injury and fat necrosis, which mimics breast carcinoma, is documented outside of sports participation. Breast injuries related to motor vehicle collisions, seatbelt trauma, and blunt trauma have been reported. For these reasons, it is important to investigate female breast injuries in collegiate sports. The objectives of this study are to report the prevalence of self-reported breast injuries in female collegiate athletes, explore injury types and treatments, and investigate breast injury reporting and impact on sports participation. A cross-sectional study of female collegiate athletes at four U.S. universities participating in basketball, soccer, softball, or volleyball. Main outcome measure was a questionnaire regarding breast injuries during sports participation. Almost half of the 194 participants (47.9%) reported a breast injury during their collegiate career, less than 10% reported their injury to health personnel with 2.1% receiving treatment. Breast injuries reported by breast injuries reported by sport include softball (59.5%), basketball (48.8%), soccer (46.7%), and volleyball (34.6%). The long-term effects and sequelae of breast injuries reported by female collegiate athletes during sport play are unknown. Nearly 50% of participants had a breast injury during sports activities. Although 18.2% indicated that breast injury affected sports participation, only 9.6% of the injuries were reported to medical personnel with 2.1% receiving treatment.

American Football
#1 Can Functional Movement Assessment Predict Football Head Impact Biomechanics?
Reference: Med Sci Sports Exerc. 2017 Dec 30. doi: 10.1249/MSS.0000000000001538. [Epub ahead of print]
Authors: Ford JM, Campbell KR, Ford CB, Boyd KE, Padua DA, Mihalik JP.
Summary: The purpose was to determine functional movement assessments' ability to predict head impact biomechanics in college football players, and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance. Participants (N = 44, mass = 109.0 ± 20.8 kg, age = 20.0 ± 1.3 years) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test, and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75); moderate (50 to 75); and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors); moderate (6-7 errors); and poor (> 7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We employed random intercepts general linear mixed models to analyze our data. There were no effects of preseason movement assessment group on the two HIT System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R=0.006) or the LESS (F1,36 < 0.01 p = 0.988, R<0.001) assessments. Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.

#2 "But He's a Star Football Player!": How Social Status Influences Mock Jurors' Perceptions in a Sexual Assault Case
Reference: J Interpers Violence. 2017 Jun 1:886260517713715. doi: 10.1177/0886260517713715. [Epub ahead of print]
Authors: Pica E, Sheahan C, Pozzulo J
Summary: There have been several recent, high-profile cases in the media that have shed light on the perceived leniency in sentencing defendants in sexual assault cases. In a number of these cases, the defendant was well known within their community (e.g., Brock Turner; People v. Turner) or nationally (e.g., Ghomeshi; R v. Ghomeshi). The purpose of this study was to examine how the social status of the defendant (low vs. high), victim social status (low vs. high), victim gender (male vs. female), and the reason the victim was unconscious during the assault (consuming alcohol vs. consuming cold medicine) influenced mock jurors' decisions in a sexual assault case. Mock jurors ( N = 489) read a mock trial transcript depicting an alleged sexual assault. Mock jurors were asked to render a dichotomous verdict, continuous guilt rating, and rate their perceptions of the victim and defendant. There was no influence of the variables on mock jurors' dichotomous verdicts; however, social status influenced guilt ratings. There also was a combined influence of the defendant's social status and the reason the victim was unconscious such that when the defendant was described as low status, and the victim was unconscious due to alcohol consumption, the defendant received higher guilt ratings compared with when the victim was unconscious due to cold medicine. Moreover, the victim was perceived as having more control over the situation when the defendant was the star quarterback (i.e., high status), the victim was female, and she was unconscious due to alcohol consumption compared with cold medicine. These results suggest that victims may be blamed based on their perceived social status and other factors that may have influenced their control over the sexual assault, such as alcohol consumption.

#3 The Evolving Treatment Patterns of NCAA Division I Football Players by Orthopaedic Team Physicians Over the Past Decade, 2008-2016
Reference: Sports Health. 2018 Jan 1:1941738117745488. doi: 10.1177/1941738117745488. [Epub ahead of print]
Authors: Carver TJ, Schrock JB, Kraeutler MJ, McCarty EC
Summary: Previous studies have analyzed the treatment patterns used to manage injuries in National Collegiate Athletic Association (NCAA) Division I football players. The hypothesis is that Treatment patterns used to manage injuries in NCAA Division I football players will have changed over the study period.  The head orthopaedic team physicians for all 128 NCAA Division I football teams were asked to complete a survey containing questions regarding experience as team physician, medical coverage of the team, reimbursement issues, and treatment preferences for some of the most common injuries occurring in football players. Responses from the current survey were compared with responses from the same survey sent to NCAA Division I team physicians in 2008. Responses were received from 111 (111/119, 93%) NCAA Division I orthopaedic team physicians in 2008 and 115 (115/128, 90%) orthopaedic team physicians between April 2016 and April 2017. The proportion of team physicians who prefer a patellar tendon autograft for primary anterior cruciate ligament reconstruction (ACLR) increased from 67% in 2008 to 83% in 2016 ( P < 0.001). The proportion of team physicians who perform anterior shoulder stabilization arthroscopically increased from 69% in 2008 to 93% in 2016 ( P < 0.0001). Of team physicians who perform surgery for grade III posterior cruciate ligament (PCL) injuries, the proportion who use the arthroscopic single-bundle technique increased from 49% in 2008 to 83% in 2016 ( P < 0.0001). The proportion of team physicians who use Toradol injections prior to a game to help with nagging injuries decreased from 62% in 2008 to 26% in 2016 ( P < 0.0001). Orthopaedic physicians changed their injury treatment preferences for NCAA Division I football players over the study period. In particular, physicians have changed their preferred techniques for ACLR, anterior shoulder stabilization, and PCL reconstruction. Physicians have also become more conservative with pregame Toradol injections.

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