Latest research in football - week 9 - 2014

#1 Multidimensional performance characteristics in selected and deselected talented soccer players
Authors: Huijgen BC, Elferink-Gemser MT, Lemmink KA, Visscher C.
Reference: Eur J Sport Sci. 2014 Feb;14(1):2-10. doi: 10.1080/17461391.2012.725102. Epub 2012 Sep 27.
Summary: The present study examined whether performance characteristics discriminated between selected and deselected players in talent development programmes. This examination was carried out in talented soccer players, aged 16-18 years using objective measurement instruments. Four domains of multidimensional performance characteristics (physiological, technical, tactical and psychological) were assessed by using a test battery consisting of soccer-specific field tests and questionnaires. Multivariate analyses of covariance revealed that the physiological characteristics peak and repeated shuttle sprint, the technical characteristics of peak and repeated shuttle dribble and the tactical characteristic of 'positioning and deciding', significantly differed between the selected (n=76) and deselected players (n=37), with selected players performing better (P<0.05). Discriminant function analysis showed that the combination of the technical characteristic 'peak dribbling', the tactical characteristic 'positioning and deciding' and the physiological characteristic of 'peak sprinting' classified 69% of talented players correctly. In conclusion, the decisions made by the investigated clubs to either select or deselect players in their talent development programme, whom were aged 16-18 years, were mostly discriminated by aspects of the players' technical, tactical and physiological skill performances. Sports research can play an essential role in investigating the club's perception of important performance characteristics in talented players.


#2 Home advantage in Greek football
Authors: Armatas V1, Pollard R.
Reference: Eur J Sport Sci. 2014 Mar;14(2):116-22. doi: 10.1080/17461391.2012.736537. Epub 2012 Oct 30.
Summary: Home advantage as it relates to team performance at football was examined in Superleague Greece using nine seasons of game-by-game performance data, a total of 2160 matches. After adjusting for team ability and annual fluctuations in home advantage, there were significant differences between teams. Previous findings regarding the role of territorial protection were strengthened by the fact that home advantage was above average for the team from Xanthi (P =0.015), while lower for teams from the capital city Athens (P =0.008). There were differences between home and away teams in the incidence of most of the 13 within-game match variables, but associated effect sizes were only moderate. In contrast, outcome ratios derived from these variables, and measuring shot success, had negligible effect sizes. This supported a previous finding that home and away teams differed in the incidence of on-the-ball behaviours, but not in their outcomes. By far the most important predictor of home advantage, as measured by goal difference, was the difference between home and away teams in terms of kicked shots from inside the penalty area. Other types of shots had little effect on the final score. The absence of a running track between spectators and the playing field was also a significant predictor of goal difference, worth an average of 0.102 goals per game to the home team. Travel distance did not affect home advantage.


#3 The effectiveness of shin guards used by football players
Authors: Tatar Y, Ramazanoglu N, Camliguney AF, Saygi EK, Cotuk HB.
Reference: J Sports Sci Med. 2014 Jan 20;13(1):120-7. eCollection 2014.
Summary: In football, injuries from opponent contact occur commonly in the lower extremities. FIFA the world's governing body for football requires players to wear shin guards. The aim of this study was to compare the protective effectiveness of polypropylene based shin guards with custom-made carbon fiber ones. Three commercial polypropylene shin guards (Adidas Predator™, Adidas UCL™, and Nike Mercurial™) and two custom-made carbon fiber shin guards were examined. The experimental setup had the following parts: 1) A pendulum attached a load cell at the tip (CAS Corp., Korea) and a fixed prosthetic foot equipped with a cleat to simulate an attacker's foot. 2) An artificial tibia prepared by condensed foam and reinforced by carbon fibers protected with soft clothing. 3) A multifunctional sensor system (Tekscan Corp., F-Socket System, Turkey) to record the impact on the tibia. In the low impact force trials, only 2.79-9.63 % of the load was transmitted to the sensors. When comparing for mean force, peak force and impulse, both carbon fiber shin guards performed better than the commercial ones (Adidas Predator™, Adidas UCL™, and Nike Mercurial™) (p = 0.000). Based on these same parameters, the Nike Mercurial™ provided better protection than the Adidas Predator™ and the Adidas UCL™ (p = 0.000). In the high impact force trials, only 5.16-10.90 % of the load was transmitted to the sensors. For peak force and impulse, the carbon fiber shin guards provided better protection than all the others. Carbon fiber shin guards possess protective qualities superior to those of commercial polypropylene shin guards. Key PointsShin guards decrease the risk of serious injuries. Carbon shin guards provide sufficient protection against high impact forces. Commercially available Polypropylene based shin guards do not provide sufficient protection against high impact forces.


#4 An exploration of pre-performance routines, self-efficacy, anxiety and performance in semi-professional soccer
Authors: Hazell J, Cotterill ST, Hill DM.
Reference: Eur J Sport Sci. 2014 Feb 24. [Epub ahead of print]
Summary: Whilst much research has suggested a positive link between pre-performance routines (PPRs) and performance, the specific mechanisms of the process have yet to be understood fully. It has been suggested that the PPR may influence performance through lowering the athlete's anxiety, and/or increasing their self-efficacy, but to date this has not specifically been explored in detail. As a result the aim of the current study was to explore the impact of specific individualised PPRs on performance, anxiety and self-efficacy in semi-professional soccer players. Participants were 20 male semi-professional soccer players (M = 19.45, SD = 2.81) recruited from clubs in England. Adopting a repeated measure design, players were tested on performance, anxiety, and self-efficacy pre- and post a 7-day intervention period in which the participants learnt a new PPR. The data were analysed using factorial mixed measures analysis of variance (ANOVAs), with the results revealing a significant difference in somatic anxiety for the experimental group and a decrease in performance for the control group. The study provides further support for the suggestion that the PPR can enhance performance by reducing experiences of anxiety prior to performance.


#5 High intensity interval training every second week maintains VO2max in soccer players during off-season
Authors: Slettaløkken G1, Rønnestad BR.
Reference: J Strength Cond Res. 2014 Feb 20. [Epub ahead of print]
Summary: Reduced endurance training among semi-professional soccer players during off-season may have negative effect on game performance during the competition season. This negative effect can be prevented by adding high-intensity interval training (HIT) to normal activity. In the present study we want to compare two different frequencies of HIT (5 bouts of 4 min on 87-97% peak heart rate) session on maintenance of aerobic fitness among semi-professional soccer players during a six week off-season period. Seventeen male players at second and third highest soccer division in Norway participated. The subjects were randomized into one HIT session every second week (HIT 0.5) or one HIT session per week (HIT 1). All participants performed a 20-m shuttle run test and a maximal oxygen uptake (VO2max) test on treadmill before and after the training intervention. VO2max (HIT 0.5 63.4±5.9 mL·kg·min, HIT 1 65.6±2.1 mL·kg·min) and 20-m shuttle run performance (HIT 0.5 2335±390 m, HIT 1 2531±106 m) were not different between the groups before the training intervention. VO2max was maintained after the training intervention in both HIT 0.5 and HIT 1(64.0±5.9 mL·kg·minand 64.3±1.3 mL·kg·min, respectively). There was a reduction in distance covered during the 20-meter shuttle run test in HIT 1 and when groups were pooled (-7.9±5.7% and -6.4±7.9%, respectively, p <0.05). In conclusion, HIT 1 did not maintain VO2max better than HIT 0.5 when added to normal off-season activity. However, performance in 20-m shuttle run, which is a more soccer specific fitness test than VO2max test, was slightly reduced when both groups was pooled.


#6 Effects of two types of trunk exercises on balance and athletic performance in youth soccer players
Authors: Imai A, Kaneoka K, Okubo Y, Shiraki H.
Reference: Int J Sports Phys Ther. 2014 Feb;9(1):47-57.
Summary: Many athletes perform trunk stabilization exercises (SE) and conventional trunk exercises (CE) to enhance trunk stability and strength. However, evidence regarding the specific training effects of SE and CE is lacking and there have been no studies for youth athletes. Therefore, the purpose of this study was to investigate the training effects of SE and CE on balance and athletic performance in youth soccer players. Twenty-seven male youth soccer players were assigned randomly to either an SE group (n = 13) or CE group (n = 14). Data from nineteen players who completed all training sessions were used for statistical analyses (SE, n = 10; CE, n = 9). Before and after the 12-week intervention program, pre- and post-testing comprised of a static balance test, Star Excursion Balance Test (SEBT), Cooper's test, sprint, the Step 50, vertical jump, and rebound jump were performed. After pre-testing, players performed the SE or CE program three times per week for 12 weeks. A two-way repeated-measures ANOVA was used to assess the changes over time, and differences between the groups. Within-group changes from pre-testing to post-testing were determined using paired t-tests. Statistical significance was inferred from p < 0.05. There were significant group-by-time interactions for posterolateral (p = 0.022) and posteromedial (p < 0.001) directions of the SEBT. Paired t-tests revealed significant improvements of the posterolateral and posteromedial directions in the SE group. Although other measurements did not find group-by-time interactions, within-group changes were detected indicating significant improvements in the static balance test, Cooper's test, and rebound jump in the only SE group (p < 0.05). Vertical jump and sprint were improved significantly in both groups (p < 0.05), but the Step 50 was not improved in either group (p > 0.05). Results suggested that the SE has specific training effects that enhance static and dynamic balance, Cooper's test, and rebound jump.


#7 Fatigue-Induced Balance Impairment in Young Soccer Players
Reference: J Athl Train. 2014 Feb 25. [Epub ahead of print]
Authors: Pau M, Ibba G, Attene G.
Summary:  Although balance is generally recognized to be an important feature in ensuring good performance in soccer, its link with functional performance remains mostly unexplored, especially in young athletes. The objective of the study was to investigate changes in balance induced by fatigue for unipedal and bipedal static stances in young soccer players. Twenty-one male soccer players (age = 14.5 ± 0.2 years, height = 164.5 ± 5.6 cm, mass = 56.8 ± 6.8 kg). Static balance was assessed with postural-sway analysis in unipedal and bipedal upright stance before and after a fatigue protocol consisting of a repeated sprint ability (RSA) test (2 × 15-m shuttle sprint interspersed with 20 seconds of passive recovery, repeated 6 times). On the basis of the center of pressure (COP) time series acquired during the experimental tests, we measured sway area, COP path length, and COP maximum displacement and velocity in the anteroposterior and mediolateral directions. Fatigue increased all sway values in bipedal stance and all values except COP velocity in the mediolateral direction in unipedal stance. Fatigue index (calculated on the basis of RSA performance) was positively correlated with fatigue/rest sway ratio for COP path length and COP velocity in the anteroposterior and mediolateral directions for nondominant single-legged stance. Fatigued players exhibited reduced performance of the postural-control system. Participants with better performance in the RSA test appeared less affected by balance impairment, especially in single-legged stance.


#8 Dynamics of the support leg in soccer instep kicking
Authors: Inoue K, Nunome H, Sterzing T, Shinkai H, Ikegami Y.
Reference: J Sports Sci. 2014 Feb 28. [Epub ahead of print]
Summary: We aimed to illustrate support leg dynamics during instep kicking to evaluate the role of the support leg action in performance. Twelve male soccer players performed maximal instep kicks. Their motions and ground reaction forces were recorded by a motion capture system and a force platform. Moments and angular velocities of the support leg and pelvis were computed using inverse dynamics. In most joints of the support leg, the moments were not associated with or counteracting the joint motions except for the knee joint. It can be interpreted that the initial knee flexion motion counteracting the extension joint moment has a role to attenuate the shock of landing and the following knee extension motion associated with the extension joint moment indirectly contributes to accelerate the swing of kicking leg. Also, appreciable horizontal rotation of the pelvis coincided with increase of the interaction moment due to the hip joint reaction force on the support leg side. It can be assumed that the interaction moment was the main factor causing the pelvis counter-clockwise rotation within the horizontal plane from the overhead view that precedes a proximal-to-distal sequence of segmental action of the swing leg.


#9 Time-motion analysis of acceleration demands of 4v4 small-sided soccer games played on different pitch sizes
Authors: Hodgson C, Akenhead R, Thomas K.
Reference: Hum Mov Sci. 2014 Feb;33:25-32. doi: 10.1016/j.humov.2013.12.002. Epub 2014 Jan 11.
Summary: We aimed to quantify the time-motion characteristics and technical demands of small-sided soccer games (SSGs) played on small, medium and large pitches using a high frequency non-differential global positioning system (NdGPS) that allowed assessment of acceleration and deceleration patterns. Eight male soccer players competed in SSGs comprising 4×4min quarters (3min recovery) on small (30×20m) medium (40×30m) and large (50×40m) pitch sizes. Time motion analysis using a NdGPS positioning system quantified distance covered sprinting (⩾6.7ms(-1)), high speed running (⩾5.8ms(-1)) and low (1-2ms(-2)), medium (2-3ms(-2)) and high (>3ms(-2)) acceleration. The frequency of common technical actions (passing, turning, dribbling, shooting, tackling, heading and interceptions) was performed using a hand notation system. SSGs played on medium and large pitches had a greater physical demand than on small pitches, with significantly more distance covered in all movement categories. Total distance covered in acceleration categories ranged from 230±111 (small pitch) to 356±72m (medium pitch). The small pitch imposed a greater technical demand on players (more passes, shots and tackles) compared to medium and large pitches. The study provides novel data demonstrating the acceleration patterns observed in SSGs are relatively greater than those observed during professional match play. Thus SSGs might offer a "density" type conditioning stimulus. Practitioners should be aware that changes in pitch size impact both the physical and technical demands of SSGs.