Latest research in football - week 34 - 2014

#1 Arthroscopic excision of bone fragments in a neglected fracture of the lateral process of the talus in a junior soccer player
Reference: Arthrosc Tech. 2014 May 12;3(3):e331-4. doi: 10.1016/j.eats.2014.01.014. eCollection 2014.
Authors: Funasaki H, Kato S, Hayashi H, Marumo K.
Summary: Fractures of the lateral process of the talus are uncommon and often overlooked. Typically, they are found in adult snowboarders. We report the case of an 11-year-old male soccer player who complained of lateral ankle pain after an inversion injury 6 months earlier. He did not respond to conservative treatment and thus underwent arthroscopic excision of fragments of the talar lateral process. The ankle was approached through standard medial and anterolateral portals. A 2.7-mm-diameter 30° arthroscope was used. Soft tissues around the talus were cleared with a motorized shaver, and the lateral aspect of the talar process was then visualized. The lateral process presented as an osseous overgrowth, and a loose body was impinged between the talus and the calcaneus. The osseous overgrowth was resected piece by piece with a punch, and the loose body was removed en block. The patient returned to soccer 5 weeks after the operation. This case exemplifies 2 important points: (1) This type of fracture can develop even in children and not only in snowboarders. (2) Arthroscopic excision of talar lateral process fragments can be accomplished easily, and return to sports can be achieved in a relatively short time.


#2 Anthropometric and Physiological Profiling of Youth Soccer Goalkeepers
Reference: Int J Sports Physiol Perform. 2014 Aug 12. [Epub ahead of print]
Authors: Rebelo-Gonçalves R, Coelho-E-Silva MJ, Severino V, Tessitore A, Figueiredo AJ.
Summary: Studies focused on position-related characteristics of young soccer players often ignore the goalkeepers. The aim of this study was to examine the effect of playing position on anthropometry, physiological attributes, soccer skills and goal orientation across adolescence. One hundred and forty five soccer players aged 11-19 years who were assessed in training experience, body size, maturation, physiological parameters, soccer skills and goal orientation. Factorial ANOVA was used to test the effect of age group, playing position and respective interaction terms, while analysis of variance was used to compare goalkeepers versus outfield players in middle (U-13 & U-15) and late (U-17 & U-19) adolescence. Discriminant analysis was used to identify the variables that contributed explaining playing positions. Age group was a consistent source of variation for all variables except task and ego orientations. Fat mass, agility, endurance, dribbling speed, shooting accuracy and passing were affected by the gradient derived from the classification between goalkeepers and outfield players. It was possible to correctly classify the playing position based on fat-free mass and three manipulative skills in younger players, and on four skills in U-17 & U-19 soccer players. Future research should include longitudinal information to improve our understanding of the factors that contribute to distinguish goalkeepers from outfield players.


#3 Pre-Match Salivary IgA in Soccer Players From the 2014 World Cup Qualifying Campaign
Reference: Int J Sports Physiol Perform. 2014 Aug 12. [Epub ahead of print]
Authors: Morgans R, Owen A, Doran D, Drust B, Morton JP.
Summary: The purpose was to monitor resting salivary secretory immunoglobulin A (SIgA) levels in international soccer players during the short-term training period that precedes international match play. In a repeated measure design, saliva samples were obtained from thirteen outfield soccer players who participated in the training camps preceding 7 games (5 home and 2 away) of the 2014 FIFA World Cup qualifying campaign. Samples were obtained daily for four days preceding each game (and analyzed for SIgA using the IPRO Oral Fluid Collection System) at match day (MD) minus 1 (MD-1), minus 2 (MD-2), minus 3 (MD-3) and minus 4 (MD-4). SIgA displayed a progressive decline (P = 0.01) during the 4-day training period (MD-4: 365 ± 127 μg.mL-1; MD-3: 348 ± 154 μg.mL-1; MD-2: 290 ± 138 μg.mL-1; MD-1: 256 ± 90 μg.mL-1) such that MD-1 values were significantly lower (P = 0.01) than both MD-4 and MD-3. Ninety-five % confidence intervals for the differences between MD-1 and MD-4 (95% CI = -191 to - 26) and MD-1 and MD-3 (95% CI = -155 to - 28). Data demonstrate that a short-term soccer training camp in preparation for international competition induces detectable perturbations to mucosal immunity. Future studies should monitor SIgA (as a practical and non-invasive measurement of immunity) alongside internal and external measures of training load in an attempt to strategically individualize training and nutritional strategies that may support optimal preparation for high-level competition.


#4 Effects of a Very Congested Match Schedule on Body Load Impacts, Accelerations, and Running Measures in Youth Soccer Players
Reference: Int J Sports Physiol Perform. 2014 Aug 12. [Epub ahead of print]
Authors: Arruda AF, Carling C, Zanetti V, Aoki MS, Coutts AJ, Moreira A.
Summary: The aim of this study was to analyze the effects of a very congested match schedule on the total distance covered (TD), high-intensity running distance (HIR), and frequency of accelerations and body load impacts (BLI) performed in a team of Under-15 soccer players (n=10; 15.1±0.2 yr, 171.8±4.7 cm, 61±6.0 kg) during an international youth competition. Using Global Positioning Systems, player performances were repeatedly monitored in five matches performed over 3 successive days. Significant differences were observed between matches (p < 0.05) for the frequency of accelerations per minute, BLI and BLI per minute. No differences were observed for the TD covered and TD run per minute, number of high-intensity runs, distance covered in HIR and per minute, peak running speed attained, or frequency of accelerations. The frequency of accelerations per minute decreased across the competition while BLI were higher during the final compared to all other matches. These results suggest that BLI and acceleration might be used as an alternative means for representation of the external load during congested match schedules rather than measures related to running speed or distance covered.


#5 The Effect of Ankle Taping to Restrict Plantar Flexion on Ball and Foot Velocity During an Instep Kick in Soccer
Reference: J Sport Rehabil. 2014 Aug 12. [Epub ahead of print]
Authors: Sasadai J, Urabe Y, Maeda N, Shinohara H, Fujii E.
Summary: Posterior ankle impingement syndrome (PAIS) is a common disorder in soccer players and ballet dancers. In soccer players, it is caused by the repetitive stress of ankle plantar flexion due to instep kicking. Protective ankle dorsal flexion taping is recommended with the belief that it prevents posterior ankle impingement. However, the relationship between the ankle taping and ball kicking performance remains unclear. The objective was to demonstrate the relationship between the restriction of ankle taping and performance of an instep kick in soccer. Eleven male university soccer players participated in this study. The subjects' ankle plantar flexion was limited by taping. Four angles of planter flexion (0°, 15°, 30°, and without taping) were formed by gradation limitation. The subjects performed maximal instep kicks at each angle. The movements of the kicking legs and the ball were captured using 3 high-speed cameras at 200 Hz. The direct liner transformation method was used to obtain 3D coordinates using a digitizing system. Passive ankle plantar flexion angle, maximal plantar flexion angle at ball impact, ball velocity and foot velocity were measured. The data were compared among 4 conditions using repeated measures ANOVA and the correlations between ball velocity and foot velocity, and between ball velocity and toe velocity were calculated. Ankle dorsal flexion taping could gradually limit both passive plantar flexion and plantar flexion at the impact. Furthermore, limitation of 0° and 15° reduced the ball velocity generated by instep kicks. Plantar flexion limiting taping at 30° has a potential to avoid posterior ankle impingement without decreasing the ball velocity generated by soccer instep kicks.


#6 Comparing Tactical Behaviour of Soccer Players in 3 vs. 3 and 6 vs. 6 Small-Sided Games
Reference: J Hum Kinet. 2014 Jul 8;41:191-202. doi: 10.2478/hukin-2014-0047. eCollection 2014.
Authors: Silva B, Garganta J, Santos R, Teoldo I
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120453/pdf/jhk-41-191.pdf
Summary: The present study aimed to compare players' tactical behaviour in 3 vs. 3 and 6 vs. 6 soccer small-sided games (SSGs). The sample comprised 3,482 tactical actions performed by 18 U-11 youth soccer players from a Portuguese club, in 3 vs. 3 and 6 vs. 6 SSGs. All participants played eight minutes in both situations and field size was adapted according to the number of players involved (30 m × 19.5 m for 3 vs. 3 and 60 m × 39 m for 6 vs. 6). The System of Tactical Assessment in Soccer (FUT-SAT) was used for data collection and analyses. Descriptive analysis was conducted to verify frequencies and percentages of the variables assessed. The chi-squared (χ(2)) test was performed to compare the frequencies of the variables between 3 vs. 3 and 6 vs. 6 SSGs and Standardized Residuals (e) were used to examine the influence of the frequency of one or more variables within 3 vs. 3 and 6 vs. 6 SSGs. Data treatment was performed through SPSS for Windows®, version 18.0. Results indicated that players displayed safer behaviours in 6 vs. 6 SSG and more aggressive behaviours in 3 vs. 3 SSG. Findings can aid coaches and teachers to develop different players' tactical skills according to the chosen SSG (3 vs. 3 or 6 vs. 6) form.


#7 Effect of number of touches and exercise duration on the kinematic profile and heart rate response during small-sided games in soccer
Reference: J Hum Kinet. 2014 Jul 8;41:113-23. doi: 10.2478/hukin-2014-0039. eCollection 2014.
Authors: Casamichana D, Suarez-Arrones L, Castellano J, Román-Quintana JS
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120444/pdf/jhk-41-113.pdf
Summary: This study aimed to examine the effect of exercise duration and the number of touches allowed during possession on time-motion characteristics and the physiological responses of soccer players in 6 vs. 6 small-sided games (SSGs) lasting 12 minutes. The analysis divided each game into two 6-min periods and we compared two formats: free play (SSGFP) vs. a maximum of two touches per individual possession (SSG2T). Participants were 12 semi-professional players (age: 22.7±4.3 years; body height: 177.5±4.9 cm; body mass: 74.9±6.3 kg) and the following variables were measured by means of heart rate monitors and GPS devices: mean heart rate (HRmean), time spent in each exercise intensity zone, total distance covered, total distance covered in different speed zones, number of accelerations at different intensities, maximum speed reached, player load, and the work-to-rest ratio. The results showed that in SSGFP there was a decrease in the intensity of physical parameters during the second 6-min period (6-12 min), whereas this decrease was not observed when a maximum of two touches per individual possession was allowed. During the second period (6-12 min) of SSG2T there was an increase in HRmean and in the time spent in high exercise intensity zones, but these differences were not observed in SSGFP. The value of these findings for soccer coaches is that they illustrate how different technical, tactical or conditioning objectives could be addressed by altering the length and format of the SSG used in training.