Latest research in football - week 10 - 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 Hormonal responses during two different concurrent-training trials in youth elite soccer players: does changing the organisation of training impact the hormonal response to concurrent exercise?
Reference: J Sports Med Phys Fitness. 2017 Feb 22. doi: 10.23736/S0022-4707.17.07198-5. [Epub ahead of print]
Authors: Enright K, Morton J, Iga J, Drust B
Summary: There are no data describing the acute hormonal responses to concurrent- training programmes in youth elite soccer players. Therefore, the aim of this study was to describe the total testosterone (T), cortisol (C), and growth hormone (hGH) responses during two same-day concurrent-training (CT) trials in elite soccer players. Thirteen youth elite players (age: 17.0±0.2 yrs; height, 1.80±0.07 m; body mass, 73.1±5.7 kg; VO2 max, 64.4± from an English premier league soccer club completed two CT trials. 'Trial 1' (CT1); E (10.30h) followed by S (14.00h) and Trial 2 (CT2); strength-training (S) 09.00h followed by a soccer-specific endurance-training session (E) at 10.30h. Venous blood samples were collected at 5 time-points around training and food intake (T1; 08.00h, T2; 09.45h, T3; 12.30h, T4; 13.45h and T5; 15.15h) and analysed for T (nmol/L) and C (nmol/L) and hGH (ug/L). There was no main effects found between exercise conditions for any hormones (T; P=0.22, C; P=0.07, hGH; P=0.21). Effect size analysis revealed a moderate effect for T at T3 (ES=0.63, CT1; 18.4±3.8, CT2; 15.7±4.7 nmol/L-1). A moderate effect for T area under the curve (AUC) was observed between conditions (CT1; 300±76 versus CT2; 244 ± 81 [AU]; ES=0.71). A moderate effect was apparent for C concentrations T4 in (ES=-0.95, CT1; 230±69, CT2; 314±105 nmol/L-1). Moderate effect sizes were observed at T3 and T4 (ES=0.82, CT1; 1.28±1.17, CT2; 0.47±0.75, ES=0.72, CT1; 0.11±0.05, CT2; 0.07±0.06 ug/L-1 respectively). A moderate effect for hGH AUC was observed between trials (CT1; 14±11 versus CT2; 5±9; [AU], ES=-1.08). The organisation of the concurrent-training protocols used in this study has a negligible impact upon the acute T, C and hGH in youth elite soccer players.

#2 The periodization of resistance training in soccer players: changes in maximal strength, lower extremity power, body composition, and muscle volume
Reference: J Sports Med Phys Fitness. 2017 Feb 22. doi: 10.23736/S0022-4707.17.07129-8. [Epub ahead of print]
Authors: Barjaste A, Mirzaei B
Summary: The purpose of this study was to investigate the effect of 12-weeks traditional periodized resistance training on some physical capacities of soccer players. Eighteen amateur soccer players with very little experience in resistance training voluntarily participated in this study. Subjects were assigned into two groups; Experimental (EX) group (n: 10) that conducted a traditional linear periodized resistance training program and a control (C) group (n: 8) that did not participate in any resistance training. Periodized resistance training in two mesocycles was used in this study: general or anatomical adaptation phase (6 wk, 65%-75% of 1RM, eleven exercises in each session) and maximal strength phase (6 wk, 85%-95% of 1RM, three to four exercises in each session). One Repetition Maximum (1RM) strength in lower and upper body, Vertical Jump (VJ) height, Body Composition, and Muscle Volume were measured at three different time points; baseline, after general phase, and after maximal strength phase. The average of the increase in 1RM all exercises in general phase was greater than the maximal strength phase, on average 29.38% and 9.67% respectively (P≤0.05). Also, the Percentage of change in VJ height in general phase was greater than the maximal strength phase (11.93% vs 3.97% respectively) (P≤0.05). The results of this study indicated that muscle strength and explosive performance in players with the little experience in resistance training can be significantly improved with the completion of general phase of resistance training periodization using moderate loads.

#3 Nonlinear sprint performance differentiates professional from young soccer players
Reference: J Sports Med Phys Fitness. 2017 Feb 22. doi: 10.23736/S0022-4707.17.07116-X. [Epub ahead of print]
Authors: Cardoso de Araujo M, Baumgart C, Freiwald J, Hoppe MW
Summary: Linear and nonlinear sprinting activities are relevant physical capacities in soccer. This study aimed (1) to compare linear and nonlinear sprint performance between professional and young soccer players and (2) to investigate relationships between both sprint types. Sixty-eight German male elite field soccer players were grouped based on age as professional (PRO, n = 20), under-23 (U23, n = 16), under-19 (U19, n = 18), and under-17 (U17, n = 14). All players were tested for 30 m linear (split-times at 5, 10, and 20 m) and 22 m nonlinear sprint performance. In linear sprint, PRO players were moderately to very largely faster than U17 players at all distances and also than U19 players at 20 m (effect size [ES] = 0.90-2.06, p ≤ 0.04). U23 players were moderately to largely faster than U17 players at 5 and 10 m (ES = 0.93-1.74, p ≤ 0.04). In nonlinear sprint, PRO players were moderately to largely faster than all other groups (ES = 1.04-1.84, p ≤ 0.02). Moderate to large correlations were found between linear and nonlinear sprint performance for all players (r = 0.48-0.50, p < 0.01). Within groups, moderate to large correlations were evident only for PRO at 5-20 m (r = 0.45-0.61, p ≤ 0.05) and U23 at 30 m (r = 0.55, p = 0.03). The findings indicate that nonlinear sprint performance is a key physical capacity in professional soccer. Therefore, training programs should focus to increase this capacity in younger players. Furthermore, linear and nonlinear sprint performance should be independently tested and trained in elite players.

#4 Sex Differences in Anthropometrics and Heading Kinematics Among Division I Soccer Athletes
Reference: Sports Health. 2017 Mar/Apr;9(2):168-173. doi: 10.1177/1941738116678615. Epub 2016 Nov 15.
Authors: Bretzin AC, Mansell JL, Tierney RT, McDevitt JK
Summary: Soccer players head the ball repetitively throughout their careers; this is also a potential mechanism for a concussion. Although not all soccer headers result in a concussion, these subconcussive impacts may impart acceleration, deceleration, and rotational forces on the brain, leaving structural and functional deficits. Stronger neck musculature may reduce head-neck segment kinematics. The relationship between anthropometrics and soccer heading kinematics will not differ between sexes. The relationship between anthropometrics and soccer heading kinematics will not differ between ball speeds. Division I soccer athletes (5 male, 8 female) were assessed for head-neck anthropometric and neck strength measurements in 6 directions (ie, flexion, extension, right and left lateral flexions and rotations). Participants headed the ball 10 times (25 or 40 mph) while wearing an accelerometer secured to their head. Kinematic measurements (ie, linear acceleration and rotational velocity) were recorded at 2 ball speeds. Sex differences were observed in neck girth ( t = 5.09, P < 0.001), flexor and left lateral flexor strength ( t = 3.006, P = 0.012 and t = 4.182, P = 0.002, respectively), and rotational velocity at both speeds ( t = -2.628, P = 0.024 and t = -2.227, P = 0.048). Neck girth had negative correlations with both linear acceleration ( r = -0.599, P = 0.031) and rotational velocity at both speeds ( r = -0.551, P = 0.012 and r = -0.652, P = 0.016). Also, stronger muscle groups had lower linear accelerations at both speeds ( P < 0.05). There was a significant relationship between anthropometrics and soccer heading kinematics for sex and ball speeds.

#5 The effects of "Prevent Injury and Enhance Performance Program" in a female soccer team
Reference: J Sports Med Phys Fitness. 2017 Feb 21. doi: 10.23736/S0022-4707.17.07024-4. [Epub ahead of print]
Authors: Rodriguez C, Echegoyen S, Aoyama T
Summary: The purpose of this study is to evaluate the changes of muscle strength in lower limbs and knee valgus alignment using the Prevent Injury and Enhance Performance Program (PEP program) to prevent ACL injuries in female soccer players during an entire season. A longitudinal and prospective study was done in twenty female soccer players at the Universidad Nacional Autónoma de México, from a senior team. During 24 weeks the training program was applied three times a week as a part of the team workouts. Video analysis of dynamic knee valgus alignment and maximal strength of quadriceps, hamstrings and gastrocnemius were evaluated pre and post training. Quadriceps and hamstring strength increased on the right pelvic limb (p<0.001). In addition the quadriceps/hamstrings ratio decreased from 3.38 to 2.3 in the right side, and from 1.99 to 1.09 in the left side. The mechanics of jump improved in 20% of the female soccer players. Muscle strength in quadriceps and hamstrings increased in right pelvic limb (p<0.001), and the quadriceps/hamstrings ratio decreased from 3.38 to 2.3 in right side and from 1.99 to 1.09 in left side. Although injuries did not decrease during this period no ACL injury was registered. Until now there are no reports about muscle strength and jump technique assessment with the application of the PEP program. The neuromuscular training and muscle balance are important to prevent ACL injuries. We advise that this program is integrated to women ́s soccer training.

#6 Soccer-related performance in eumenorrheic Tunisian high-level soccer players: effects of menstrual cycle phase and moment of day
Reference: J Sports Med Phys Fitness. 2017 Feb 21. doi: 10.23736/S0022-4707.17.06958-4. [Epub ahead of print]
Authors: Tounsi M, Jaafar H, Aloui A, Souissi N
Summary: This study aimed to examine the combined effects of menstrual cycle phase and moment of day on female soccer players' performances in the five-jump test (5JT), the repeated shuttle- sprint ability test (RSSA), and the Yo-Yo intermittent recovery test level 1 (YYIRT1). Eleven eumenorrheic Tunisian high-level soccer players volunteered to participate. Each subject individually participated in three testing periods: one in the early follicular phase (menses), one in the late follicular phase, and another in the luteal phase. In each period, two test sessions were conducted: one at 07:30 h and another at 17:30 h. The testing routines included the 5JT, the RSSA, and the YYIRT1. None of the measured variables were altered due to menstrual cycle phase (all P > 0.05). Mean time during RSSA was significantly lower in the afternoon session compared to the morning session (8.48 ± 0.27 s and 8.77 ± 0.34 s, respectively, P < 0.001), while 5JT performance was significantly higher in the afternoon compared to the morning (9.08 ± 0.58 m and 8.60 ± 0.56 m, respectively, P < 0.001). Soccer-specific endurance as well as jumping and repeated sprinting ability of Tunisian female high-level soccer players are not affected due to menstrual cycle phase neither in the morning nor in the afternoon.

#7 Neuroplus biofeedback improves attention, resilience, and injury prevention in elite soccer players
Reference: Psychophysiology. 2017 Feb 21. doi: 10.1111/psyp.12847. [Epub ahead of print]
Authors: Rusciano A, Corradini G, Stoianov I
Summary: Performance and injury prevention in elite soccer players are typically investigated from physical-tactical, biomechanical, and metabolic perspectives. However, executive functions, visuospatial abilities, and psychophysiological adaptability or resilience are also fundamental for efficiency and well-being in sports. Based on previous research associating autonomic flexibility with prefrontal cortical control, we designed a novel integrated autonomic biofeedback training method called Neuroplus to improve resilience, visual attention, and injury prevention. Herein, we introduce the method and provide an evaluation of 20 elite soccer players from the Italian Soccer High Division (Serie-A): 10 players trained with Neuroplus and 10 trained with a control treatment. The assessments included psychophysiological stress profiles, a visual search task, and indexes of injury prevention, which were measured pre- and posttreatment. The analysis showed a significant enhancement of physiological adaptability, recovery following stress, visual selective attention, and injury prevention that were specific to the Neuroplus group. Enhancing the interplay between autonomic and cognitive functions through biofeedback may become a key principle for obtaining excellence and well-being in sports. To our knowledge, this is the first evidence that shows improvement in visual selective attention following intense autonomic biofeedback.

#8 Relative Age, Maturation and Physical Biases on Position Allocation in Elite-Youth Soccer
Reference: Int J Sports Med. 2017 Feb 20. doi: 10.1055/s-0042-119029. [Epub ahead of print]
Authors: Towlson C, Cobley S, Midgley AW, Garrett A, Parkin G, Lovell R
Summary: This study assessed the contribution of relative age, anthropometry, maturation, and physical fitness characteristics on soccer playing position (goalkeeper [GK], central-defender [CD], lateral-defender [LD], central-midfield [CM], lateral-midfielder [LM], and forward [FWD]) for 465 elite-youth players (U13-U18's). U13-14 CD were relatively older than LD and CM (likely small effects). CD and GK were generally taller and heavier (likely small to very-likely moderate effects) than other players at each developmental stage and were advanced maturers at U13-14 (very-likely small to likely moderate effects). GK had inferior agility (very-likely small to likely moderate effects), endurance (very-likely small to likely moderate effects), and sprint capacities (likely small-moderate effects) vs. outfield positions at U13-14, but deficits in anaerobic phenotypes were diminished in U15-16 and U17-18. Position specific fitness characteristics were distinguished at U15-16 (likely small) and U17-18 (likely moderate), where LM were faster than their central counterparts. In summary, relative age, maturation and anthropometric characteristics appear to bias the allocation of players into key defensive roles from an early development stage, whereas position-specific physical attributes do not become apparent until the latter stages of talent development in outfield players. Given the inter-individual trajectories of physical development according to biological maturation, playing position allocation might be considered 'plastic' by selectors, until complete-maturity is achieved.

#9 The intra- and inter-reliability of the soccer injury movement screen (SIMS)
Reference: Int J Sports Phys Ther. 2017 Feb;12(1):53-66.
Authors: McCunn R, Aus der Funten K, Govus A, Julian R, Schimpchen J, Meyer T
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Summary: The growing volume of movement screening research reveals a belief among practitioners and researchers alike that movement quality may have an association with injury risk. However, existing movement screening tools have not considered the sport-specific movement and injury patterns relevant to soccer. The present study introduces the Soccer Injury Movement Screen (SIMS), which has been designed specifically for use within soccer. Furthermore, the purpose of the present study was to assess the intra- and inter-rater reliability of the SIMS and determine its suitability for use in further research. The study utilized a test-retest design to discern reliablility. Twenty-five (11 males, 14 females) healthy, recreationally active university students (age 25.5 ± 4.0 years, height 171 ± 9 cm, weight 64.7 ± 12.6 kg) agreed to participate. The SIMS contains five sub-tests: the anterior reach, single-leg deadlift, in-line lunge, single-leg hop for distance and tuck jump. Each movement was scored out of 10 points and summed to produce a composite score out of 50. The anterior reach and single-leg hop for distance were scored in real-time while the remaining tests were filmed and scored retrospectively. Three raters conducted the SIMS with each participant on three occasions separated by an average of three and a half days (minimum one day, maximum seven days). Rater 1 re-scored the filmed movements for all participants on all occasions six months later to establish the 'pure' intra-rater (intra-occasion) reliability for those movements. Intraclass correlation coefficient (ICC) values for intra- and inter-rater composite score reliability ranged from 0.66-0.72 and 0.79-0.86 respectively. Weighted kappa values representing the intra- and inter-rater reliability of the individual sub-tests ranged from 0.35-0.91 indicating fair to almost perfect agreement. Establishing the reliability of the SIMS is a prerequisite for further research seeking to investigate the relationship between test score and subsequent injury. The present results indicate acceptable reliability for this purpose; however, room for further development of the intra-rater reliability exists for some of the individual sub-tests.

#10 Effects of a small-sided game-based training programme on repeated sprint and change of direction abilities in recreationally-trained football players
Reference: J Sports Med Phys Fitness. 2017 Feb 21. doi: 10.23736/S0022-4707.17.07044-X. [Epub ahead of print]
Authors: Bujalance-Moreno P, Garcia-Pinillos F, Latorre-Roman PA
Summary: The purpose of the study was to examine the effects of 6-week periodized small-sided game (SSG) training intervention on change of direction [COD], sprint and repeated sprint ability [RSA] in recreational male football players. Twenty-three young football players (age: 20.86 years) were randomized in a control group (n = 11) and an experimental group (n = 12). The SSG programme was included in the experimental group's training sessions. The players completed two variations of a SSG (i.e. 2 vs. 2 and 4 vs. 4 players) during intervention. To examine the changes in physical performance after the 6-week periodized SSG training intervention, all players were tested 6 weeks apart (i.e. pre-test and post-test) in sprint, COD ability test, and RSA shuttle test. A 2x2 ANOVA showed that 6-week SSG training intervention induced significant improvements (P<0.05, ES>0.7) in COD ability test, and variables related to both sprint test and RSA in the experimental group, whereas the control group remained unchanged (P≥0.05, ES<0.4). Regarding the response to the RSA test - in terms of BLa, both the experimental group (P=0.001, ES=1.270) and the control group (P=0.010, ES=0.939) increased BLa after the intervention. The current study indicates that a 6-week SSG-based training programme could improve decisive parameters in performance in football, such as COD, RSA and sprint in recreationally trained football players.

#11 Risk factors of anterior cruciate ligament injury in football players: a systematic review of the literature
Reference: Muscles Ligaments Tendons J. 2016 Feb 12;6(4):480-485. doi: 10.11138/mltj/2016.6.4.480.
Authors: Volpi P, Bisciotti GN, Chamari K, Cena E, Carimati G, Bragazzi NL
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Summary: The ACL lesion represents one of the most dramatic injuries in a sportsman's career. There are many injury risk factors related to intrinsic, or non-modifiable, and extrinsic, or modifiable, factors. In literature at today current evidence suggests that ACL injury risk is multifactorial and involves biomechanical, anatomical, hormonal and neuromuscular factors. The purpose of the study was to perform a systematic review of the literature concerning the ACL injury risk factors in soccer. The injury risk factors show a low level of evidence, further studies in the field are needed.

#12 ACL injury in football: a literature overview of the prevention programs
Reference: Muscles Ligaments Tendons J. 2016 Feb 12;6(4):473-479. doi: 10.11138/mltj/2016.6.4.473.
Authors: Bisciotti GN, Chamari K, Cena E, Carimati G, Volpi P
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Summary: The ACL prevention programs are addressed to the control and/or modification of the so-called "modifiable risk factors". All these programs focus on different intervention strategies aimed to decrease the ACL injury risk, particularly in female athletes population. The purpose of the study was to furnish an overview of the most used ACL injury prevention program through a narrative review. In literature there are many reports on prevention programs whose common denominator is the proper alignment of the lower limb joints and proper motor control during movements that are considered at risk for ACL integrity, as the landing phase after a jump. Nevertheless, some programs would appear more effective than others. In any cases a major problem remains the lack of sufficient compliance in respect of prevention programs. Finally, it is important to remember that the ethiology of ACL injuries is multifactorial. For this reason a prevention program able to prevent all the risk situations is utopian.

#13 Where biomedicalisation and magic meet: Therapeutic innovations of elite sports injury in British professional football and cycling
Reference: Soc Sci Med. 2017 Feb 9;178:136-143. doi: 10.1016/j.socscimed.2017.02.011. [Epub ahead of print]
Authors: Faulkner A, McNamee M, Coveney C, Gabe J
Summary: Injury is a conspicuous feature of the practice and public spectacle of contemporary elite sports. The paper argues that the 'biomedicalisation' thesis (medico-industrial nexus, techno-scientific drivers, medical optimisation, biologisation, the rise of evidence and health surveillance) goes some way to capturing the use in elite sports injury of some highly specialised mainstream therapies and some highly maverick biological therapies, which are described. Nevertheless, these main strands of biomedicalisation do not capture the full range of these phenomena in the contexts of sports medicine and athletes' practices in accessing innovative, controversial therapies. Drawing on multi-method qualitative research on top-level professional football and cycling in the UK, 2014-2016, we argue that concepts of 'magic' and faith-based healing, mediated by notions of networking behaviour and referral systems, furnish a fuller explanation. We touch on the concept of 'medical pluralism', concluding that this should be revised in order to take account of belief-based access to innovative bio-therapies amongst elite sportspeople and organisations.

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