Latest research in football - week 34 - 2013

#1 Incidence, Mechanisms, and Severity of Match-Related Collegiate Women's Soccer Injuries on FieldTurf and Natural Grass Surfaces: A 5-Year Prospective Study
Authors: Meyers MC.
Reference: Am J Sports Med. 2013 Aug 13. [Epub ahead of print]
Summary: Numerous injuries have been attributed to playing on artificial turf. Over the past 2 decades, however, newer generations of synthetic turf have been developed to duplicate the playing characteristics of natural grass. Although synthetic turf has been determined to be safer than natural grass in some studies, few long-term studies have been conducted comparing match-related collegiate soccer injuries between the 2 playing surfaces. The hypothesis of this study was that Collegiate female soccer athletes do not experience any difference in the incidence, mechanisms, and severity of match-related injuries on FieldTurf and on natural grass. Female soccer athletes from 13 universities were evaluated over 5 competitive seasons for injury incidence, injury category, time of injury, injury time loss, player position, injury mechanism and situation, primary type of injury, injury grade and anatomic location, field location at the time of injury, injury severity, head and lower extremity trauma, cleat design, turf age, and environmental factors. In sum, 797 collegiate games were evaluated for match-related soccer injuries sustained on FieldTurf or natural grass during 5 seasons. The results show 355 team games (44.5%) were played on FieldTurf versus 442 team games (55.5%) on natural grass. A total of 693 injuries were documented, with 272 (39.2%) occurring during play on FieldTurf and 421 (60.8%) on natural grass. Multivariate analysis per 10 team games indicated a significant playing surface effect: F2,690 = 6.435, P = .002, n - β = .904. A significantly lower total injury incidence rate (IIR) of 7.7 (95% confidence interval [CI], 7.2-8.1) versus 9.5 (95% CI, 9.3-9.7) (P = .0001) and lower rate of substantial injuries, 0.7 (95% CI, 0.5-1.0) versus 1.5 (95% CI, 1.2-1.9) (P = .001), were documented on FieldTurf versus natural grass, respectively. Analyses also indicated significantly less trauma on FieldTurf when comparing injury time loss, player position, injury grade, injuries under various field conditions and temperatures, cleat design, and turf age. The authors concluded, that although similarities existed between FieldTurf and natural grass during competitive match play, FieldTurf is a practical alternative when comparing injuries in collegiate women's soccer. It must be reiterated that the findings of this study may be generalizable to only collegiate competition and this specific artificial surface.


#2 Comparison of the physiological responses and time motion characteristics of young soccer players in small sided games: The effect of goalkeeper
Authors: Köklü Y, Sert O, Alemdaroğlu U, Arslan Y.
Reference: J Strength Cond Res. 2013 Aug 12. [Epub ahead of print]
Summary: The purpose of this study was to investigate the effect of 'with goalkeeper' (SSGwith) and 'without goalkeeper' (SSGwithout) conditions on players' physiological responses and time motion characteristics in small sided games. Sixteen young soccer players (age 16.5±1.5 years; height 175.5±5.2 cm; body mass 63.0±6.9 kg; training experience 6.3±1.3 years) participated in 2 different 2-a-side, 3-a-side and 4-a-side games: SSGwith and SSGwithout. The players underwent anthropometric measurements (height and body mass) followed by the YoYo intermittent recovery test (level 1). Then they played 2-a-side, 3-a-side, and 4-a-side SSGwith and SSGwithout soccer-specific SSGs in random order at 2-day intervals. Heart rate (HR) responses, and distance covered in different speed zones (walking (WLK, 0-6.9 km.h), low-intensity running (LIR, 7.0-12.9km.h), moderate-intensity running (MIR, 13.0-17.9 km.h) and high-intensity running (HIR, >18km.h)) were measured during the SSGs, whereas the Rating of Perceived Exertion (RPE) and Blood Lactate (La) were determined at the end of the last bout of each SSG. During the SSGwithout players showed higher %HR, La and RPE (p<0.05), greater distance covered in LIR, MIR, HIR and total distance (p<0.05) compared to the SSGwith during the 2-a-side, 3-a-side and 4-side games. The results of this study suggest that both SSGwith and SSG without could be used for the physiological adaptations required for soccer specific aerobic endurance. However, if coaches want both higher physiological responses and greater distance covered in the intensity running zone from their teams, SSG without should be organized. In addition, this study also suggests that smaller format games (i.e. 2-a-side) may promote some anaerobic adaptations for youth soccer players.


#3 The effect of prophylactic ankle support during simulated soccer activity
Authors: Forbes H, Thrussell S, Haycock N, Lohkamp M, White M.
Reference: J Sport Rehabil. 2013 Aug;22(3):170-6.
Summary: Ankle injuries are common in soccer and may result in ongoing functional deficiency. Ankle-joint prophylactic support is hypothesized to reduce the risk of injury. Analysis of the effects of prophylactic support has so far lacked application to soccer. Therefore, the purpose of this study was to illustrate the effects of tape and brace on selected proprioceptive components and range of motion (ROM) before, after, and during a soccer-match-simulation protocol. A crossover study design was used to investigate plantar-flexion (PF) ROM, inversion (INV) ROM, and joint-position sense (weight bearing and non-weight-bearing [NWBJPS]; ± °error) in tape, brace, and control conditions. Measures were gathered from the dominant leg in a biomechanics laboratory at 0, 15, 30, and 45 min of a soccer-specific aerobic field test 90-min (SAFT90) protocol. Eight healthy male subjects (age 20.5 ± 0.5 y) experienced the 3 conditions in random order with 7 d between conditions. The tape condition used an open basket-weave technique; the brace was an AirCast AirSport brace. For the control condition no prophylactic support was applied. Application of prophylactic support significantly decreased active ROM in PF and INV (P < .05), with tape performing better than the brace (0 min). Tape lost its restrictive benefits by 15 min (P < .001) and was no different than control, while the brace maintained some effect until 45 min. Application of prophylactic support increased NWBJPS performance (P < .01; 0 min); by 15 min the tape had lost its proprioceptive benefit (P < .01) compared with the brace. Our findings suggest that the clinical usefulness of ankle-joint prophylactic support is limited if the aim is to restrict ROM and improve proprioceptive capability under soccer-specific conditions. The relative benefits of each type of support need to be considered in the context of the time-specific nature of the activity.


#4 Effect of static and dynamic stretching on the diurnal variations of jump performance in soccer players
Authors: Chtourou H, Aloui A, Hammouda O, Chaouachi A, Chamari K, Souissi N.
Reference: PLoS One. 2013 Aug 5;8(8):e70534. doi: 10.1371/journal.pone.0070534. Print 2013.
Summary: The present study addressed the lack of data on the effect of different types of stretching on diurnal variations in vertical jump height - i.e., squat-jump (SJ) and countermovement-jump (CMJ). We hypothesized that dynamic stretching could affect the diurnal variations of jump height by producing a greater increase in short-term maximal performance in the morning than the evening through increasing core temperature at this time-of-day. Twenty male soccer players (age, 18.6±1.3 yrs; height, 174.6±3.8 cm; body-mass, 71.1±8.6 kg; mean ± SD) completed the SJ and CMJ tests either after static stretching, dynamic stretching or no-stretching protocols at two times of day, 07:00 h and 17:00 h, with a minimum of 48 hours between testing sessions. One minute after warming-up for 5 minutes by light jogging and performing one of the three stretching protocols (i.e., static stretching, dynamic stretching or no-stretching) for 8 minutes, each subject completed the SJ and CMJ tests. Jumping heights were recorded and analyzed using a two-way analysis of variance with repeated measures (3 [stretching]×2 [time-of-day]). The SJ and CMJ heights were significantly higher at 17:00 than 07:00 h (p<0.01) after the no-stretching protocol. These daily variations disappeared (i.e., the diurnal gain decreased from 4.2±2.81% (p<0.01) to 1.81±4.39% (not-significant) for SJ and from 3.99±3.43% (p<0.01) to 1.51±3.83% (not-significant) for CMJ) after dynamic stretching due to greater increases in SJ and CMJ heights in the morning than the evening (8.4±6.36% vs. 4.4±2.64%, p<0.05 for SJ and 10.61±5.49% vs. 6.03±3.14%, p<0.05 for CMJ). However, no significant effect of static stretching on the diurnal variations of SJ and CMJ heights was observed. Dynamic stretching affects the typical diurnal variations of SJ and CMJ and helps to counteract the lower morning values in vertical jump height.


#5 Guiding attention aids the acquisition of anticipatory skill in novice soccer goalkeepers
Authors: Ryu D, Kim S, Abernethy B, Mann DL.
Reference: Res Q Exerc Sport. 2013 Jun;84(2):252-62.
Summary: The ability to anticipate the actions of opponents can be enhanced through perceptual-skill training, though there is doubt regarding the most effective form of doing so. We sought to evaluate whether perceptual-skill learning would be enhanced when supplemented with guiding visual information. Twenty-eight participants without soccer-playing experience were assigned to a guided perceptual-training group (n = 9), an unguided perceptual-training group (n = 10), or a control group (n = 9). The guided perceptual-training group received half of their trials with color cueing that highlighted either the key kinematic changes in the kicker's action or the known visual search strategy of expert goalkeepers. The unguided perceptual-training group undertook an equal number of trials of practice, but all trials were without guidance. The control group undertook no training intervention. All participants completed an anticipation test immediately before and after the 7-day training intervention, as well as a 24-hr retention test. The guided perceptual-training group significantly improved their response accuracy for anticipating the direction of soccer penalty kicks from preintervention to postintervention, whereas no change in performance was evident at posttest for either the unguided perceptual-training group or the control group. The superior performance of the guided perceptual-training group was preserved in the retention test and was confirmed when relative changes in response time were controlled using a covariate analysis. Perceptual training supplemented with guiding information provides a level of improvement in perceptual anticipatory skill that is not seen without guidance.


#6 Comparison of somatotype values of football players in two professional league football teams according to the positions
Authors: Orhan O, Sagir M, Zorba E.
Reference: Coll Antropol. 2013 Jun;37(2):401-5.
Summary: This study compared the somatotype values of football players according to their playing positions. The study aimed to determine the physical profiles of players and to analyze the relationships between somatotypes and playing positions. Study participants were members of two teams in the Turkey Professional Football League, Gençlerbirligi Sports Team (GB) (N = 24) and Gençlerbirligi Oftas Sports Team (GBO) (N = 24). Anthropometric measurements of the players were performed according to techniques suggested by the Anthropometric Standardization Reference Manual (ASRM) and International Biological Program (IBP). In somatotype calculations, triceps, subscapular, supraspinale and calf skinfold thickness, humerus bicondylar, femur bicondylar, biceps circumference, calf circumference and body weight and height were used. Statistical analysis of the data was performed using the Graph Pad prism Version 5.00 for Windows (Graph Pad Software, San Diego California USA); somatotype calculations and analyses used the Somatotype 1.1 program and graphical representations of the results were produced. Analysis of non-parametric (two independent samples) Mann-Whitney U Test of the player data showed that there were no statistically significant differences between the two teams. The measurements indicated that, when all of the GB and GBO players were evaluated collectively, their average somatotypes were balanced mesomorph. The somatotypes of GBO goalkeepers were generally ectomorphic mesomorph; GB goalkeepers were balanced mesomorphic, although they were slightly endomorphic.


#7 The FIFA medical emergency bag and FIFA 11 steps to prevent sudden cardiac death: setting a global standard and promoting consistent football field emergency care
Authors: Dvorak J, Kramer EB, Schmied CM, Drezner JA, Zideman D, Patricios J, Correia L, Pedrinelli A, Mandelbaum B.
Reference: Br J Sports Med. 2013 Aug 12. doi: 10.1136/bjsports-2013-092767. [Epub ahead of print]
Abstract: Life-threatening medical emergencies are an infrequent but regular occurrence on the football field. Proper prevention strategies, emergency medical planning and timely access to emergency equipment are required to prevent catastrophic outcomes. In a continuing commitment to player safety during football, this paper presents the FIFA Medical Emergency Bag and FIFA 11 Steps to prevent sudden cardiac death. These recommendations are intended to create a global standard for emergency preparedness and the medical response to serious or catastrophic on-field injuries in football.