Latest research in football - week 18 - 2017

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 Perceptions of football players regarding injury risk factors and prevention strategies
Reference: PLoS One. 2017 May 1;12(5):e0176829. doi: 10.1371/journal.pone.0176829. eCollection 2017.
Authors: Zech A, Wellmann K
Download link:
Summary: Current approaches regarding injury prevention focus on the transfer of evidence into daily practice. One promising approach is to influence attitudes and beliefs of players. The objective of this study was to record player's perceptions on injury prevention. A survey was performed among players of one German high-level football (soccer) club. 139 professional and youth players between age 13 and 35 years completed a standardized questionnaire (response rate = 98%). It included categories with (1) history of lower extremity injuries, (2) perceptions regarding risk factors and (3) regularly used prevention strategies. The majority of players (84.2%) had a previous injury. 47.5% of respondents believe that contact with other players is a risk factor, followed by fatigue (38.1%) and environmental factors (25.9%). The relevance of previous injuries as a risk factor is differently perceived between injured (25%) and uninjured players (0.0%). Nearly all players (91.5%) perform stretching to prevent injuries, followed by neuromuscular warm up exercises (54.0%). Taping is used by 40.2% of previously injured players and 13.6% of players without a history of injuries. In conclusion, the perception of risk factors and performed preventive strategies are inconsistent with scientific evidence. Future transfer strategies should incorporate the players beliefs and attitudes.

#2 A unique opportunity to use football to improve birth registration awareness and completeness in Nigeria
Reference: Br J Sports Med. 2017 Apr 28. pii: bjsports-2016-097404. doi: 10.1136/bjsports-2016-097404. [Epub ahead of print]
Authors: Makinde OA, Odimegwu CO, OlaOlorun FM
Download link:

#3 More Than the Win: The Relation between Appetitive Competition Motivation, Socialization, and Gender Role Orientation in Women's Football
Reference: Front Psychol. 2017 Apr 13;8:547. doi: 10.3389/fpsyg.2017.00547. eCollection 2017.
Authors: Meyer-Parlapanis D, Siefert S, Weierstall R
Download link:
Summary: The ability to produce peak performance plays a decisive role in the success of athletes in competitive contest situations. Levels of appetitive competition motivation (ACM), i.e., the desire to defeat an opponent independent of secondary reinforcing factors, were assessed in professional female football/soccer players in the premier and regional leagues, using club level as the measurement of sport success. Furthermore, the influence of social environments predominantly encouraging masculine and competitive play behavior and the players' perceptions of their own gender role orientations were investigated. Ninety female football players from the German premier league (44) and regional leagues (46) participated (age: M = 24, SD = 5 years). Questionnaires ascertaining ACM and self-perceptions of gender via gender-role stereotypes, childhood play behavior and style of upbringing were utilized. Premier league athletes showed a significantly greater inclination toward direct sporting confrontations. Almost 50% of the variance in ACM between the premier and regional league athletes was determined by modern upbringing style and the development of gender roles not corresponding to classic female gender stereotypes. The results emphasize the significance of ACM as an important facet in competitive sports and illustrate the influence of socialization on athletic performance.

#4 The influence of successive matches on match-running performance during an under-23 international soccer tournament: The necessity of individual analysis
Reference: J Sports Sci. 2017 May 12:1-7. doi: 10.1080/02640414.2017.1325511. [Epub ahead of print]
Authors: Varley MC, Di Salvo V, Modonutti M, Gregson W, Mendez-Villanueva A
Summary: This study investigated the effects of successive matches on match-running in elite under-23 soccer players during an international tournament. Match-running data was collected using a semi-automated multi-camera tracking system during an international under-23 tournament from all participating outfield players. Players who played 100% of all group stage matches were included (3 matches separated by 72 h, n = 44). Differences in match-running performance between matches were identified using a generalised linear mixed model. There were no clear effects for total, walking, jogging, running, high-speed running and sprinting distance between matches 1 and 3 (effect size (ES); -0.32 to 0.05). Positional analysis found that sprint distance was largely maintained from matches 1 to 3 across all positions. Attackers had a moderate decrease in total, jogging and running distance between matches 1 and 3 (ES; -0.72 to -0.66). Classifying players as increasers or decreasers in match-running revealed that match-running changes are susceptible to individual differences. Sprint performance appears to be maintained over successive matches regardless of playing position. However, reductions in other match-running categories vary between positions. Changes in match-running over successive matches affect individuals differently; thus, players should be monitored on an individual basis.


#5 Effects of Sex and Event Type on Head Impact in Collegiate Soccer
Reference: Orthop J Sports Med. 2017 Apr 24;5(4):2325967117701708. doi: 10.1177/2325967117701708. eCollection 2017 Apr.
Authors: Reynolds BB, Patrie J, Henry EJ, Goodkin HP, Broshek DK, Wintermark M, Druzgal TJ
Download link:
Summary: The effects of head impact in sports are of growing interest for clinicians, scientists, and athletes. Soccer is the most popular sport worldwide, but the burden of head impact in collegiate soccer is still unknown. The purpose of the study was to quantify head impact associated with practicing and playing collegiate soccer using wearable accelerometers. Mastoid patch accelerometers were used to quantify head impact in soccer, examining differences in head impact as a function of sex and event type (practice vs game). Seven female and 14 male collegiate soccer players wore mastoid patch accelerometers that measured head impacts during team events. Data were summarized for each athletic exposure, and statistical analyses evaluated the mean number of impacts, mean peak linear acceleration, mean peak rotational acceleration, and cumulative linear and rotational acceleration, each grouped by sex and event type. There were no differences in the frequency or severity of head impacts between men's and women's soccer practices. For men's soccer, games resulted in 285% more head impacts than practices, but there were no event-type differences in mean impact severity. Men's soccer games resulted in more head impacts than practices across nearly all measured impact severities, which also resulted in men's soccer games producing a greater cumulative impact burden. Similar to other sports, men's soccer games have a greater impact burden when compared with practices, and this effect is driven by the quantity rather than severity of head impacts. In contrast, there were no differences in the quantity or severity of head impacts in men's and women's soccer practices. These data could prompt discussions of practical concern to collegiate soccer, such as understanding sex differences in head impact and whether games disproportionately contribute to an athlete's head impact burden.

#6 Prognostic factors for musculoskeletal injury identified through medical screening and training load monitoring in professional football (soccer): a systematic review
Reference: Br J Sports Med. 2017 May 10. pii: bjsports-2017-097827.1. doi: 10.1136/bjsports-2017-097827.1. [Epub ahead of print]
Authors: Hughes T, Sergeant JC, Parkes M, Callaghan M
Summary: The purpose was to identify prognostic factors and models for spinal and lower extremity injuries in adult professional/elite football players from medical screening and training load monitoring processes. The MEDLINE, AMED, EMBASE, CINAHL Plus, SPORTDiscus electronic bibliographic databases and the Cochrane Database of Systematic Reviews were searched from inception to July 2016. Searches were limited to original research, published in peer reviewed journals of any language. The Quality in Prognostic Studies (QUIPS) tool was used for appraisal and the modified GRADE approach was used for synthesis. Prospective and retrospective cohort study designs of spinal and lower extremity injury incidence were found from populations of adult professional/elite football players, between 16 and 40 years. Non-football or mixed sports were excluded. 858 manuscripts were identified. Removing duplications left 551 studies, which were screened for eligibility by title and abstract. Of these, 531 studies were not eligible and were excluded. The full text of the remaining 20 studies were obtained; a further 10 studies were excluded. 10 studies were included for appraisal and analysis, for 3344 participants. Due to the paucity and heterogeneity of the literature, and shortcomings in methodology and reporting, the evidence is of very low or low quality and therefore cannot be deemed robust enough to suggest conclusive prognostic factors for all lower limb musculoskeletal injury outcomes identified. No studies were identified that examined spinal injury outcomes or prognostic models.


#7 Solid Organ Laceration in an Adolescent Soccer Player: A Case Report
Reference: Med Sci Sports Exerc. 2017 May 9. doi: 10.1249/MSS.0000000000001316. [Epub ahead of print]
Authors: Visenio M, Buesing K, Moffatt K
Summary: Pediatric solid organ lacerations are a relatively uncommon but potentially dangerous injury that must be addressed urgently once recognized. Seen most often during recreational or team sports, they usually occur after a blunt deceleration mechanism to the abdomen or flank. Depending on the severity of injury, solid organ laceration may not be immediately apparent clinically. This emphasizes the importance of sideline witnessing and evaluation, acting quickly once symptoms develop, and placing importance on safe sporting technique. Additionally, management has changed over time to favor medical management for minor injuries, with laparotomy reserved for high-grade or hemodynamically unstable lacerations. Awareness of solid organ laceration in pediatric populations is more important than ever as they are beginning to appear in younger adolescents. Here we present a case of a 14-year-old girl sustaining a grade IV liver laceration while playing contact team sports.

#8 Modulation of isometric quadriceps strength in soccer players with transcranial direct current stimulation: a crossover study
Reference: J Strength Cond Res. 2017 May 9. doi: 10.1519/JSC.0000000000001985. [Epub ahead of print]
Authors: Vargas VZ, Baptista AF, Pereira GOC, Pochini AC, Ejnisman B, Santos MB, Joao SMA, Hazime FA
Summary: The aim of this study was to evaluate the effect of transcranial direct current stimulation (tDCS) on the maximum isometric muscle contraction (MVIC) of the knee extensors in soccer players at the pre-professional level. Twenty female soccer players aged 15 to 17 years (mean = 16.1; SD = 0.9) with 5.2 ± 2.6 years of training were randomly divided into two groups to receive either active or sham tDCS in a single session (2 mA; 0.057mA/cm). The MVIC of the knee extensors was evaluated in both lower limbs by manual dynamometry in five sets of contractions divided into four blocks: (0) pre-stimulation, (1) during tDCS, (2) 30 minutes post-tDCS, and (3) 60 minutes post-tDCS. After an interval of seven days, the groups were evaluated again, and the type of initial stimulation was inverted between participants. The MVIC of the knee extensors increased significantly during active tDCS (MD = 0.4; IC = 0.1 to 0.8 N/Kg), 30 minutes post-active tDCS (MD = 0.9; IC 0.4 to 1.4 N/Kg), and 60 minutes post-active tDCS (MD = 1.0; IC 0.3 to 1.6 N/Kg) but not for sham tDCS. Our conclusion was that tDCS temporarily increases isometric quadriceps strength in adolescent female soccer players, which may be useful for both strength training and rehabilitation.

#9 Match outcome and sprinting activities in match play by elite German soccer players
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07352-2. [Epub ahead of print]
Authors: Andrzejewski M, Chmura P, Konefal M, Kowalczuk E, Chmura J
Summary: The aim of the study was to examine the ways playing positions and match outcome (i.e. win, draw, loss) affect the sprint distance covered and the number of sprints performed by German Bundesliga soccer players. Match performance data were collected from 350 soccer players competing in the German Bundesliga during the 2014/2015 domestic season. A total of 4393 individual match observations were undertaken on outfield players. The analysis was carried using the Impire AG motion analysis system with records of all movements of players in all the 306 matches. The recorded variables included total sprint distance covered and the total number of sprints in offensive and defensive play. The conformity assessment was carried out with the Shapiro-Wilk test (p ≤ 0.01). To compare mean values of the examined variables a two-way ANOVA was used. The differences between pairs of means were verified with Fisher's LSD. The analysis of the covered sprint distance and the number of performed sprints showed that central defenders and full-backs covered shorter distances in won matches than in lost matches (p ≤ 0.05). Furthermore, forwards and wide midfielders covered significantly longer sprint distances in won matches than in lost matches (p ≤ 0.05). The match outcome may be viewed as a measure of performance accomplishment and, hence, it may influence the sprinting efforts made by players.

#10 Soccer training: high-intensity interval training is mood disturbing while small sided games ensure mood balance
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07292-9. [Epub ahead of print]
Authors: Selmi O, Haddad M, Majed L, Ben Khalifa W, Hamza M, Chamari K
Summary: The aim of the study was to compare the effects of high-intensity intermittent training (HIIT) versus small-sided games (SSG) in soccer on both the physiological responses and the mood state of players. Sixteen professional soccer players took part in the study (age: 24.1±0.9 years). Testing of players was conducted on separate days in a randomized and counter-balanced order (each training session: 28-min: 4x4 minutes work with 3-min of passive recovery in-between). Effort: HIIT: intermittent 15-s runs at 110% maximal aerobic speed with 15-s of passive recovery in-between. SSG: 4 versus 4 players on a 25x35m pitch size with full-involvement play. Psychological responses before- and after- each training-session were assessed using the profile of mood-state (POMS: Tension, Depression, Anger, Vigor, Fatigue, and Confusion). The players' heart rate (HR) was continuously measured, whereas ratings of perceived exertion (RPE) and blood lactate concentration ([La]) were collected ~3-min after each training-session. HIIT and SSG showed no significant difference in HR, RPE and [La] responses. The HIIT compared with SSG resulted in: an increased total mood disturbance (p<0.001), tension (p<0.05), fatigue (p<0.01) and a decreased vigor (p<0.001). Both HIIT and SSG sessions induced similar physiological responses, in contrast, HIIT produced a mood disturbance while SSG ensured mood balance. Practitioners could choose between these two exercises according to the objective of their training, keeping in mind the mood-related advantages of the SSG shown in the present study.

American Football
#1 Return to Play and Decreased Performance After Anterior Cruciate Ligament Reconstruction in National Football League Defensive Players
Reference: Am J Sports Med. 2017 May 1:363546517703361. doi: 10.1177/0363546517703361. [Epub ahead of print]
Authors: Read CR, Aune KT, Cain EL Jr, Fleisig GS
Summary: Anterior cruciate ligament (ACL) injuries occur commonly in football. Recent work has reported ACL reconstruction (ACLR) as one of several orthopaedic procedures with unfavorable outcomes for professional athletes. The performance impact to defensive players after surgery has not been quantified. The purpose was to quantify the effect of ACLR on the performance of defensive players by comparing them to a cohort of matched controls as well as to measure the effect of ACLR on athletes' career length in the National Football League (NFL). Thirty-eight NFL defensive players with a history of ACLR from 2006 to 2012 were identified. For each injured player, a matched control player was identified. Demographic and performance statistics were collected from the online NFL player database. Players who returned after ACLR (n = 23) were compared with players who did not return (n = 15) using t tests and chi-squared analyses. Similarly, players who returned after ACLR (n = 23) were compared with their matched controls with t tests and chi-squared analyses. Two-way repeated-measures analysis of variance was utilized to test for significant differences between performance before and after the season of the injury for the players in the ACLR group who returned (n = 23) and for their matched controls. Kaplan-Meier analysis was performed to test for differences in the rate of retirement between the groups. For all analyses, P values <.05 were considered significant. Approximately 74% (28/38) of athletes who underwent ACLR returned to play at least 1 NFL game, and 61% (23/38) successfully returned to play at least half a season (ie, 8 games). Athletes in the ACLR group who returned retired from the NFL significantly sooner and more often after surgery than their matched controls. In the seasons leading up to their injury, athletes who successfully returned to play started a greater percentage of their games (81%) and made more solo tackles per game (3.44 ± 1.47) compared with athletes in the ACLR group who did not return to play (54% and 1.82 ± 1.17, respectively) and compared with healthy control players (52% and 1.77 ± 1.19, respectively). After the season of surgery, athletes in the ACLR group who returned to play decreased to 57% games started and 2.38 ± 1.24 solo tackles per game, while their matched controls suffered no significant decreases. Players who successfully returned were above-average NFL players before their injury but comparatively average after their return.

#2 Return to Play After Revision Anterior Cruciate Ligament Reconstruction in National Football League Players
Reference: Orthop J Sports Med. 2017 Apr 4;5(4):2325967117698788. doi: 10.1177/2325967117698788. eCollection 2017.
Authors: Okoroha KR, Kadri O, Keller RA, Marshall N, Cizmic Z, Moutzouros V
Download link:
Summary: National Football League (NFL) players who undergo anterior cruciate ligament (ACL) reconstruction have been shown to have a lower return to play (RTP) than previously expected. However, RTP in the NFL after revision ACL reconstruction (RACLR) is not well defined. The purpose of this study is to determine the RTP of NFL players after RACLR and evaluate factors that predict RTP. Our hypothesis was that more experienced and established players would be more likely to RTP after RACLR. A total of 24 NFL players who underwent RACLR between 2007 and 2014 were reviewed and evaluated. Return to NFL play, time to return, seasons and games played prior to and after revision surgery, draft status, and demographic data were collected. Overall RTP was determined, and players who did RTP were compared with those unable to RTP. Data were also compared with control players matched for age, position, size, and experience. After RACLR, 79% (19/24) of NFL players returned to NFL regular-season play at an average of 12.6 months. All players who were drafted in the first 4 rounds, played in at least 55 games, or played 4 seasons of NFL play prior to injury were able to RTP. Players drafted in the first 4 rounds of the NFL draft were more likely to RTP than those who were not (odds ratio, 0.1; 95% CI, 0.01-1.00; P = .05). Those who returned to NFL play played in significantly less games and seasons after their injury than before (P = .01 and P = .01, respectively). However, these values did not differ when compared with matched controls (P = .67 and P = .33). NFL players who RTP after RACLR do so at a similar rate but prolonged time period compared with after primary ACL reconstruction. Athletes who were drafted in earlier rounds were more likely to RTP than those who were not. Additionally, player experience prior to injury is an important factor when predicting RTP after RACLR.

#3 The Effect of Subcritical Bone Loss and Exposure on Recurrent Instability After Arthroscopic Bankart Repair in Intercollegiate American Football
Reference: Am J Sports Med. 2017 May 1:363546517704184. doi: 10.1177/0363546517704184. [Epub ahead of print]
Authors: Dickens JF, Owens BD, Cameron KL, DeBerardino TM, Masini BD, Peck KY, Svoboda SJ
Summary: There is no consensus on the optimal method of stabilization (arthroscopic or open) in collision athletes with anterior shoulder instability. The purpose was to examine the effect of "subcritical" bone loss and football-specific exposure on the rate of recurrent shoulder instability after arthroscopic stabilization in an intercollegiate American football population. Fifty intercollegiate football players underwent primary arthroscopic stabilization for anterior shoulder instability and returned to football for at least a single season. Preoperatively, 32 patients experienced recurrent subluxations, and 18 patients experienced a single or recurrent dislocation. Shoulders with glenoid bone loss >20%, an engaging Hill-Sachs lesion, an off-track lesion, and concomitant rotator cuff repair were excluded from the study. The primary outcome of interest was the ability to return to football without subsequent instability. Patients were followed for time to a subsequent instability event after return to play using days of exposure to football and total follow-up time after arthroscopic stabilization. Fifty consecutive patients returned to American football for a mean 1.5 seasons (range, 1-3) after arthroscopic stabilization. Three of 50 (6%; 95% CI, 1.3%-16.5%) patients experienced recurrent instability. There were no subsequent instability events after a mean 3.2 years of military service. All shoulders with glenoid bone loss >13.5% (n = 3) that underwent arthroscopic stabilization experienced recurrent instability upon returning to sport, while none of the shoulders with <13.5% glenoid bone loss (n = 47) sustained a recurrent instability event during football ( X2 = 15.80, P < .001). Shoulders with >13.5% glenoid bone loss had an incidence rate of 5.31 cases of recurrent instability per 1000 athlete-exposures of football. In 72,000 athlete-exposures to football with <13.5% glenoid bone loss, there was no recurrent instability. Significantly more anchors were used during the primary arthroscopic stabilization procedure in patients who experienced multiple preoperative instability events ( P = .005), and lesions spanned significantly more extensive portions along the circumference of the glenoid ( P = .001) compared with shoulders having a single preoperative instability event before surgical stabilization. Arthroscopic stabilization of anterior shoulder instability in American football players with <13.5% glenoid bone loss provides reliable outcomes and low recurrence rates.

The Training Manager -