Latest research in football - week 15 - 2013

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 Performance effects of 6 weeks of anaerobic production training in junior elite soccer players
Authors: Ingebrigtsen J, Shalfawi SA, Tønnessen E, Krustrup P, Holtermann A.
Reference: J Strength Cond Res. 2013 Apr 1. [Epub ahead of print]
Summary: This study investigates the performance effects of a six-week biweekly anaerobic speed endurance production training among junior elite soccer players. Sixteen junior elite soccer players aged 16, were tested in Yo-Yo Intermittent Recovery test level 2 (IR2), 10 m and 35 m sprints, 7x35 m Repeated Sprint Ability (RSA) tests, Counter Movement Jump (CMJ) and Squat Jump (SJ) tests, and randomly assigned into either a control group performing their normal training schedule, which included four weekly soccer training sessions of ∼90 min, or a training group performing anaerobic speed endurance production training twice weekly for six weeks in addition to their normal weekly schedule. The authors found that the intervention group significantly improved their performance in the Yo-Yo IR2 and 10 m sprint time. No significant performance changes were found in the control group. Significant between-group pre- to post-test differences were found for 10 m sprint times. No significant changes were observed in 35 m sprint times, RSA, or jump performances. The present results indicate that short-term anaerobic production training is effective for improving acceleration and intermittent exercise performance among well-trained junior elite players.


#2 Monitoring Training in Elite Soccer Players: Systematic Bias between Running Speed and Metabolic Power Data
Authors:  Gaudino P, Iaia FM, Alberti G, Strudwick AJ, Atkinson G, Gregson W.
Reference: Int J Sports Med. 2013 Apr 2. [Epub ahead of print]
Summary: The study investigated measurements of high-intensity activity during field-based training sessions in elite soccer players of different playing positions. Agreement was appraised between measurements of running speed alone and predicted metabolic power derived from a combination of running speed and acceleration. Data was collected during a 10-week phase of the competitive season from 26 English Premier League outfield players using global positioning system technology. High-intensity activity was estimated using the total distance covered at speeds >14.4 km/h (TS) and the equivalent metabolic power threshold of >20 W/kg (TP), respectively. The authors selected 0.2 as the -minimally important standardised difference between methods. Mean training session TS was 478±300 m vs. 727±338 m for TP (p<0.001). This difference was significant greater for central defenders (~ 85%) vs. wide defenders and attackers (~ 60%). The difference between methods also significantly decreased as the proportion of high-intensity distance within a training session increased. The authors concluded that the high-intensity demands of soccer training are underestimated by traditional measurements of running speed alone, especially in training sessions or playing positions associated with less high-intensity activity. Estimations of metabolic power better inform the coach as to the true demands of a training session.

#3 Relationships between strength, sprint and jump performance in well trained youth soccer players
Authors: Comfort P, Stewart A, Bloom L, Clarkson B.
Reference: J Strength Cond Res. 2013 Mar 28. [Epub ahead of print]
Summary: Research has demonstrated a clear relationship between absolute and relative strength and sprint and jump performance in adult athletes; however, this relationship in younger athletes has been less extensively studied. The purpose of this study, therefore, was to determine the relationships between strength, sprint and jump performances in well-trained youth soccer players. Thirty-four young male soccer players with the age of 17 performed a predicted maximal squat test, twenty meter sprints, squat jumps and countermovement jumps. Absolute strength showed the strongest correlations with 5m sprint times (r -0.596, p<0.001, power = 0.99), squat jump height (r 0.762, p<0.001, power = 1.00) and CMJ height (r 0.760, p<0.001, power = 1.00), whereas relative strength demonstrated the strongest correlation with 20m sprint times (r -0.672, p<0.001, power = 0.99). The results of this study illustrates the importance of developing high levels of lower body strength in order to enhance sprint and jump performance in youth soccer players, with stronger athletes demonstrating superior sprint and jump performances.

#4 High adherence to a neuromuscular injury prevention programme (FIFA 11+) improves functional balance and reduces injury risk in Canadian youth female football players: a cluster randomised trial
Authors: Steffen K, Emery CA, Romiti M, Kang J, Bizzini M, Dvorak J, Finch CF, Meeuwisse WH.
Reference: Br J Sports Med. 2013 Apr 4. [Epub ahead of print]
Summary: The purpose of the cluster-randomised controlled trial was to assess whether different delivery methods of an injury prevention programme (FIFA 11+) to coaches could improve player performance, and to examine the effect of player adherence on performance and injury risk. During the 2011 football season (May-August), coaches of 31 tiers 1-3 level teams were introduced to the 11+ through either an unsupervised website or a coach-focused workshop with and without additional on-field supervisions. Playing exposure, adherence to the 11+, and injuries were recorded for female 13-year-old to 18-year-old players. Performance testing included the Star Excursion Balance Test (SEBT), single-leg balance, triple hop and jumping-over-a-bar tests. Complete preseason and postseason performance tests were available for 226 players. Compared to the unsupervised group, single-leg balance and the anterior direction of the SEBT improved significantly in the on-field supervised group of players, while 2-leg jumping performance decreased. However, significant improvements in 5 of 6 reach distances in the SEBT were found, favoring players who highly adhered to the 11+. Also, injury risk was lower for those players. Different delivery methods of the FIFA 11+ to coaches influenced players' physical performance minimally. However, high player adherence to the 11+ resulted in significant improvements in functional balance and reduced injury risk.

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