Latest research in football - week 51 - 2014

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

Following studies were retrieved for this week:

#1 Effects of the Workplace Health Promotion Activities Soccer and Zumba on Muscle Pain, Work Ability and Perceived Physical Exertion among Female Hospital Employees
Reference: PLoS One. 2014 Dec 10;9(12):e115059. doi: 10.1371/journal.pone.0115059. eCollection 2014.
Authors: Barene S, Krustrup P, Holtermann A
Download link: http://www.plosone.org/article/fetchObject.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0115059&representation=PDF
Summary: This 40-week workplace physical training RCT investigated the effect of soccer and Zumba, respectively, on muscle pain intensity and duration, work ability, and rating of perceived exertion (RPE) during work among female hospital employees. 107 hospital employees were cluster-randomized into two training groups, and a control group. The training was conducted outside working hours as two-three 1-h sessions per week for the first 12 weeks, and continued as one-two 1-h sessions per week for the last 28 weeks. Muscle pain intensity and duration, work ability, and RPE during work were measured at baseline and after 12 and 40 weeks. After 12 weeks, both the soccer (-1.9, 95% CI, -3.0, -0.8, P = 0.001) and the Zumba group (-1.3, 95% CI, -2.3, -0.3, P = 0.01) reduced the pain intensity (on a scale from 0 to 10) in the neck-shoulder region (eta squared = 0.109), whereas only the soccer group (-1.9, 95% CI, -3.2, -0.7, P = 0.002, eta squared = 0.092) showed a reduction after 40 weeks referencing the control group. After 40 weeks, both the soccer (-16.4 days, 95% CI, -29.6, -3.2, P<0.02) and the Zumba group (-16.6 days, 95% CI, -28.9, -4.2, P<0.01) reduced the pain duration during the past 3 months in the neck-shoulder region (eta squared = 0.077). No significant effects on intensity or duration of pain in the lower back, RPE during work or work ability were found. The present study indicates that workplace initiated soccer and Zumba training improve neck-shoulder pain intensity as well as duration among female hospital employees.

#2 The influence of playing surface on physiological and performance responses during and after soccer simulation
Reference: Eur J Sport Sci. 2014 Dec 9:1-8. [Epub ahead of print]
Authors: Stone KJ, Hughes MG, Stembridge MR, Meyers RW, Newcombe DJ, Oliver JL.
Summary: The aim of this study was to investigate the effect of playing surface on physiological and performance responses during and in the 48 h after simulated soccer match play. Blood lactate, single-sprint, repeated-sprint and agility of eight amateur soccer players were assessed throughout a 90-min soccer-simulation protocol (SSP) completed on natural turf (NT) and artificial turf. Counter-movement jump, multiple-rebound jump, sprint (10 m, 60 m), L-agility run (L-AR), creatine kinase (CK) and perception of muscle soreness (PMS) were measured before, immediately after, 24 h and 48 h after exercise. Analyses revealed significant changes in blood lactate and single-sprint performance (both P < 0.05) during the SSP but with no significant differences between surfaces. Conversely, repeated-sprint performance demonstrated an interaction effect, with reductions in performance evident on NT only (P < 0.05). Whilst L-AR and 10-m sprint performance remained unchanged, 60-m sprint and multiple-rebound jump performance were impaired, and PMS and CK were elevated immediately following the SSP (all P < 0.05) but with no surface effects. Although performance, CK and PMS were negatively affected to some degree in the 48 h after the SSP, there was no surface effect. For the artificial and natural surfaces used in the present study, physiological and performance responses to simulated soccer match play appear to be similar. Whilst a potential for small differences in performance response exists during activity, surface type does not affect the pattern of recovery following simulated match play.

#3 Effects of velocity-based resistance training on young soccer players of different ages
Reference: J Strength Cond Res. 2014 Dec 5. [Epub ahead of print]
Authors: González-Badillo JJ, Pareja-Blanco F, Rodríguez-Rosell D, Abad-Herencia JL, Del Ojo-López JJ, Sánchez-Medina L.
Summary: This study aimed to analyze the effect of velocity based-resistance training (RT) with moderate load and few repetitions per set combined with jumps and sprints on physical performance in young soccer players of different ages. A total of 44 elite youth soccer players belonging to three teams participated in this study: an under-16 team (U16, n = 17) and an under-18 team (U18, n = 16) performed maximal velocity RT program for 26 weeks in addition to typical soccer training, whereas an under-21 team (U21, n = 11) did not perform RT. Before and after the training program all players performed: 20-m running sprint (T20); countermovement jump (CMJ); a progressive isoinertial loading test in squat to determine the load which players elicited ∼1 m·s (V1LOAD); and an incremental field test to determine maximal aerobic speed (MAS). U16 showed significantly (P = .000) greater gains for V1LOAD than U18 and U21 (100/0/0%). Only U16 showed significantly (P = .01) greater gains than U21 (99/1/0%) for CMJ height. U18 obtained a likely better effect on CMJ performance than U21 (89/10/1%). The beneficial effects on T20 between groups were unclear. U16 showed a likely better effect on MAS than U21 (80/17/3%), whereas the rest of comparisons were unclear. The changes in CMJ correlated to the changes in T20 (r = -.49) and V1LOAD (r = .40). In conclusion, velocity-based RT with moderate load and few repetitions per set seems to be an adequate methodology to improve the physical performance in young soccer players.

#4 Neuro-mechanical and metabolic adjustments to the repeated anaerobic sprint test in professional football players
Reference: Eur J Appl Physiol. 2014 Dec 7. [Epub ahead of print]
Authors: Brocherie F, Millet GP, Girard O.
Summary: This study aimed to determine the neuro-mechanical and metabolic adjustments in the lower limbs induced by the running anaerobic sprint test (the so-called RAST). Eight professional football players performed 6 × 35 m sprints interspersed with 10 s of active recovery on artificial turf with their football shoes. Sprinting mechanics (plantar pressure insoles), root mean square activity of the vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) muscles (surface electromyography, EMG) and VL muscle oxygenation (near-infrared spectroscopy) were monitored continuously. Sprint time, contact time and total stride duration increased from the first to the last repetition (+17.4, +20.0 and +16.6 %; all P < 0.05), while flight time and stride length remained constant. Stride frequency (-13.9 %; P < 0.001) and vertical stiffness decreased (-27.2 %; P < 0.001) across trials. Root mean square EMG activities of RF and BF (-18.7 and -18.1 %; P < 0.01 and 0.001, respectively), but not VL (-1.2 %; P > 0.05), decreased over sprint repetitions and were correlated with the increase in running time (r = -0.82 and -0.90; both P < 0.05). Together with a better maintenance of RF and BF muscles activation levels over sprint repetitions, players with a better repeated-sprint performance (lower cumulated times) also displayed faster muscle de- (during sprints) and re-oxygenation (during recovery) rates (r = -0.74 and -0.84; P < 0.05 and 0.01, respectively). The repeated anaerobic sprint test leads to substantial alterations in stride mechanics and leg-spring behaviour. Our results also strengthen the link between repeated-sprint ability and the change in neuromuscular activation as well as in muscle de- and re-oxygenation rates.

#5 Quality of functional movement patterns and injury examination in elite-level male professional football players
Reference: Acta Physiol Hung. 2014 Dec 6:1-9. [Epub ahead of print]
Authors: Zalai D, Panics G, Bobak P, Csáki I, Hamar P
Summary: The purpose of this study is to examine the quality of functional movement patterns among one of Hungary's first league soccer clubs, where the elite male football players (N = 20) utilize the well-established Functional Movement Screen™ (FMS) system; a comprehensive functional program designed to determine and identify the quality of movement and the greatest risk factors for non-contact injuries. Furthermore, an additional purpose of this program is to examine injuries over the course of 6 competitive months. Focusing on the mechanisms of injuries and their causes in the lower extremities during this period is one of the key objectives. Over the course of 6 months we found significant differences between ankle injuries and the FMS Hurdle Step exercise (p < 0.05), and the FMS Deep Squat exercise and knee and hip injuries (p < 0.05). The FMS pre-screening system found lower limb asymmetry present in 40% of the participants. The authors believe that the importance of preventative measures and structural sport specific pre-screening cannot be overemphasized, and that there is a growing need for further transparent research in this field in order to be more effective with regard to programs dedicated to injury prevention and the enhancement players' physical performance.

#6 A situated analysis of football goalkeepers’ experiences in critical games situations
Reference: Percept Mot Skills. 2014 Dec 2. [Epub ahead of print]
Authors: Villemain A, Hauw D
Summary: This study described elite football (soccer) goalkeepers' activity and performance in critical game situations. The 11 best French players (M age = 15.5 yr., SD = 0.5) participated in the study. Interviews focused on goalkeepers' experiences were conducted to identify meaningful events involved in failed actions. Players formulated 23 critical game situations. Verbatim encoding using a thematic analysis indicated that four main categories (coming off the line, goal-line clearance, one-on-one, and diving) represented the most critical situations encountered during matches. The relations among experience and action, inner states, background, attention contents, and intentions were elucidated. The discussion is grounded on the properties of such critical game situations and their implications for improving goalkeepers' performance.

#7 Effects of long-term football training on the expression profile of genes involved in muscle oxidative metabolism
Reference: Mol Cell Probes. 2014 Nov 28. pii: S0890-8508(14)00061-9. doi: 10.1016/j.mcp.2014.11.003. [Epub ahead of print]
Authors: Alfieri A, Martone D, Randers MB, Labruna G, Mancini A, Nielsen JJ, Bangsbo J, Krustrup P, Buono P
Summary: We investigated whether long-term recreational football training affects the expression of health-related biochemical and molecular markers in healthy untrained subjects. Five untrained healthy men trained for 1 h 2.4 times/week for 12 weeks and 1.3 times/week for another 52 weeks. Blood samples and a muscle biopsy from the vastus lateralis were collected at T0 (pre intervention) and at T1 (post intervention). Gene expression was measured by RTqPCR on RNA extracted from muscle biopsies. The expression levels of the genes principally involved in energy metabolism (PPARγ, adiponectin, AMPKα1/α2, TFAM, NAMPT, PGC1α and SIRT1) were measured at T0 and T1. Up-regulation of PPARγ (p < 0.0005), AMPKα1 (p < 0.01), AMPKα2 (p < 0.0005) and adiponectin was observed at T1 vs T0. Increases were also found in the expression of TFAM (p < 0.001), NAMPT (p < 0.01), PGC1α (p < 0.01) and SIRT1 (p < 0.01), which are directly or indirectly involved in the glucose and lipid oxidative metabolism. Multiple linear regression analysis revealed that fat percentage was independently associated with NAMPT, PPARγ and adiponectin expression. In conclusion, long-term recreational football training could be a useful tool to improve the expression of muscle molecular biomarkers that are correlated to oxidative metabolism in healthy males.

#8 Practice and play in the development of German top-level professional football players
Reference: Eur J Sport Sci. 2014 Dec 2:1-10. [Epub ahead of print]
Authors: Hornig M, Aust F, Güllich A.
Summary: This study examined the developmental sporting activities of 52 German football first Bundesliga professionals (including 18 senior national team members) and 50 fourth to sixth league amateur players. They reported their volumes of organised football practice/training, including its "microstructure" (proportions of physical conditioning, skill exercises and playing forms), non-organised leisure football play and engagement in other sports through their career, respectively. Analyses revealed that the Bundesliga professionals performed moderate amounts of organised football practice/training throughout their career. They accumulated 4264 (mean value) hours over ~16 years before debuting in 1st Bundesliga; senior National Team debut was preceded by 4532 hours (mean) over ~17 years. Within the "microstructure" of organised practice/training, the proportion of playing forms developed from ~52% (childhood) to ~45% (adolescence) and ~40% (adulthood) and physical conditioning from ~13% to ~14% and ~23%. Outside organised involvement, these players engaged in extensive non-organised leisure football play making ~68%, ~54% and ~9% of all football involvement. Subsuming organised and non-organised football, ~86% (childhood), ~73% (adolescence) and ~43% (adulthood) of all activity was game play (exclusive matchplay). National Team differed from amateurs in more non-organised leisure football in childhood, more engagement in other sports in adolescence, later specialisation, and in more organised football only at age 22+ years. Relative to numerous other studies, these players performed less organised practice, particularly less physical conditioning, but greater proportions of playing activities. The findings are discussed relative to the significance of playing forms and variable involvements and are reflected against the deliberate practice and Developmental Model of Sport Participation (DMSP) frameworks.

#9 Prevalence of genital anomalies in young football players
Reference: An Pediatr (Barc). 2014 Nov 27. pii: S1695-4033(14)00388-9. doi: 10.1016/j.anpedi.2014.07.007. [Epub ahead of print] [Article in Spanish]
Authors: Mónaco M, Verdugo F, Bodell M, Avendaño E, Til L, Drobnic F
Summary: The purpose of genital examination (GE) during the Pre-participation Physical Examination (PPE) is to identify the state of maturity, and rule out any genital pathology. To describe genital anomalies (GA) and estimate the awareness of GE in young football players. A descriptive, cross-sectional study was conducted in 280 elite football players from the results of PPE over two seasons. There was a detection rate of 5.4% GA, with varicocele being 3.2%, and of which only 13% were aware of their condition. Although this study shows a low incidence of genital abnormality in the study population, only 13% were aware of the GE prior to assessment. These findings demonstrate a low incidence of GA in this population. While GE is recommended during PPE, it is not a routine practice performed by family doctors or sports medicine specialists. This article attempts to raise awareness of the importance of GE in PPE as a preventive health strategy.

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