Latest research in football - week 5 - 2015

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 Periodisation and Physical Performance in Elite Female Soccer Players
Reference: Int J Sports Physiol Perform. 2015 Jan 22. [Epub ahead of print]
Authors: Mara JK, Thompson KG, Pumpa KL, Ball NB.
Summary: The purpose of the study was to investigate the variation in training demands, physical performance and player wellbeing across a female soccer season. Seventeen elite female players wore GPS tracking devices during every training session (n = 90) throughout one national league season. Intermittent high-speed running capacity, 5, 15 and 25m sprint testing were conducted at the beginning of preseason, end of preseason, midseason and end of season. In addition, subjective wellbeing measures were self-reported daily by players over the course of the season. Time over 5m was lowest at the end of preseason (mean = 1.148s, SE = 0.017s), but then progressively deteriorated to the end of the season (p < 0.001). Sprint performance over 15m improved by 2.8% (p = 0.013) following preseason training; while 25m sprint performance peaked at midseason, with a 3.1% (p = 0.05) improvement from the start of preseason, before declining at the end of season (p = 0.023). Training demands varied between phases with total distance and high-speed distance greatest during preseason before decreasing (p < 0.001) during the early and late season phases. Endurance capacity and wellbeing measures did not change across training phases. Monitoring training demands and subsequent physical performance in elite female soccer players allow coaches to ensure training periodisation goals are being met, and related positive training adaptations are being elicited.

#2 Association Between Ball-Handling Versus Defending Actions and Acute Noncontact Lower Extremity Injuries in High School Basketball and Soccer
Reference: Am J Sports Med. 2015 Jan 16. pii: 0363546514564541. [Epub ahead of print]
Authors: Monfort SM, Comstock RD, Collins CL, Onate JA, Best TM, Chaudhari AM
Summary: High school-sponsored athletic programs currently provide more than 7.7 million students in the United States with health and societal benefits, but they also inherently increase the risk of students sustaining a sports injury. Understanding risk factors that predict injuries in sports is an essential first step to addressing the problem in this population. The purpose of the study was to determine the role of offensive versus defensive actions in noncontact lower extremity injury rates in high school basketball and soccer in both boys' and girls' sports. Noncontact lower extremity injury data were collected from academic years 2005-2006 through 2011-2012 for boys' and girls' basketball and soccer through the surveillance tool High School RIO (reporting information online). The injuries in this subset of the database occurred over a total of 6.4 million athlete-exposures. Significant differences in overall lower extremity injury rates were found when comparing ball-handling and defending actions in basketball (rate ratio [RR], 1.36; 95% CI, 1.08-1.73; P = .009), but no appreciable difference was observed in soccer (RR, 0.89; 95% CI, 0.70-1.12; P = .31). Female participants had higher injury rates than did males for both ball-handling and defending actions for both sports (P < .05). Only girls' soccer showed significant differences in the odds ratio (OR) of defending to ball-handling injury rates between competition and practice (OR, 1.88; 95% CI, 1.01-3.48; P = .047). The injury rate differences observed in this study between offensive and defensive actions suggest that investigating potential differences between sport-specific tasks may provide a more complete understanding of injury mechanisms.

#3 Effects of plyometric and sprint training on physical and technical skill performance in adolescent soccer players
Reference: J Strength Cond Res. 2015 Jan 29. [Epub ahead of print]
Authors: Sáez de Villarreal E, Suarez-Arrones L, Requena B, Haff GG, Ferrete C
Summary: The purpose was to determine the influence of a short-term combined plyometric and sprint training (9-weeks) within regular soccer practice on explosive and technical actions of pubertal soccer players during the in-season. Twenty-six players were randomly assigned to 2 groups; control group (CG) (soccer training only), and combined group (CombG) (plyometric+acceleration+dribbling+shooting). All players trained soccer four times per week and the experimental groups supplemented the soccer training with a proposed plyometric-sprint training program for 40 minutes (two days per weeks). 10-m sprint, 10-m agility with and without ball, CMJ and Abalakov vertical jump, ball-shooting speed and Yo-Yo IE test were measured before and after training. The experimental group followed a 9-week plyometric and sprint program (i.e., jumping, hurdling, bouncing, skipping, and footwork) implemented before the soccer training. Baseline-training results showed no significant differences between the groups in any of the variables tested. No improvement was found in the control group, however, meaningful improvement was found in all variables in the experimental group: CMJ (ES=0.9), Abalakov vertical jump (ES=1.3), 10-m sprint (ES=0.7-0.9), 10-m agility (ES=0.8-1.2) and ball-shooting speed (ES=0.7-0.8). A specific combined plyometric and sprint training within regular soccer practice improved explosive actions compared to conventional soccer training only. Therefore, the short-term combined program had a beneficial impact on explosive actions, such as sprinting, change of direction, jumping and ball-shooting speed which are important determinants of match-winning actions in soccer performance. Therefore, we propose modifications to current training methodology for pubertal soccer players to include combined plyometric and speed training for athlete preparation in this sport.

#4 A non-randomised experimental feasibility study into the immediate effect of three different spinal manipulative protocols on kicking speed performance in soccer players
Reference: Chiropr Man Therap. 2015 Jan 13;23(1):1. doi: 10.1186/s12998-014-0046-3. eCollection 2015.
Authors: Deutschmann KC, Jones AD, Korporaal CM
Download link:
Summary: The most utilized soccer kicking method is the instep kicking technique. Decreased motion in spinal joint segments results in adverse biomechanical changes within in the kinematic chain. These changes may be linked to a negative impact on soccer performance. This study tested the immediate effect of lumbar spine and sacroiliac manipulation alone and in combination on the kicking speed of uninjured soccer players. This 2010 prospective, pre-post experimental, single-blinded (subject) required forty asymptomatic soccer players, from regional premier league teams, who were purposively allocated to one of four groups (based on the evaluation of the players by two blinded motion palpators). Segment dysfunction was either localized to the lumbar spine (Group 1), sacroiliac joint (Group 2), the lumbar spine and sacroiliac joint (Group 3) or not present in the sham laser group (Group 4). All players underwent a standardized warm-up before the pre-measurements. Manipulative intervention followed after which post-measurements were completed. Measurement outcomes included range of motion changes (digital inclinometer); kicking speed (Speed Trac™ Speed Sport Radar) and the subjects' perception of a change in kicking speed. SPSS version 15.0 was used to analyse the data, with repeated measures ANOVA and a p-value <0.05 (CI 95%). Lumbar spine manipulation resulted in significant range of motion increases in left and right rotation. Sacroiliac manipulation resulted in no significant changes in the lumbar range of motion. Combination manipulative interventions resulted in significant range of motion increases in lumbar extension, right rotation and right SI joint flexion. There was a significant increase in kicking speed post intervention for all three manipulative intervention groups (when compared to sham). A significant correlation was seen between Likert based-scale subjects' perception of change in kicking speed post intervention and the objective results obtained. This pilot study showed that lumbar spine manipulation combined with SI joint manipulation, resulted in an effective intervention for short-term increases in kicking speed/performance. However, the lack of an a priori analysis, a larger sample size and an unblinded outcome measures assessor requires that this study be repeated, addressing these concerns and for these outcomes to be validated.

#5 Comparison of inflammatory responses and muscle damage indices following a soccer, basketball, volleyball and handball game at an elite competitive level
Reference: Res Sports Med. 2015;23(1):59-72. doi: 10.1080/15438627.2014.975814.
Authors: Souglis A, Bogdanis GC, Giannopoulou I, Papadopoulos Ch, Apostolidis N
Summary: Inflammatory responses and muscle damage indices were compared between four popular team sports at an elite level. Seventy two male elite players of four team sports: soccer (n = 18), basketball (n = 18), volleyball (n = 18) and handball (n = 18), completed an official match, while 18 non-athletes served as controls. Blood samples were drawn before, immediately after and 13 and 37 h post-match. Soccer produced the greatest increase in inflammatory cytokines (tumor necrosis factor-alpha and interleukin-6), which were increased by 3-4 fold immediately after the game, as well as in C-reactive protein, which was increased by threefold in the next morning after the match. Metabolic stress (urea, ammonia and cortisol) and muscle damage indices (creatine kinase and lactate dehydrogenase) were also higher after soccer, with creatine kinase responses being almost 2-3 times higher than the other sports. Volleyball showed the smallest increase in inflammation and muscle damage markers compared with the other three sports.

#6 The between-match variability of peak power output and Creatine Kinase responses to soccer match-play
Reference: J Strength Cond Res. 2015 Jan 26. [Epub ahead of print]
Authors: Russell M, Northeast J, Atkinson G, Shearer DA, Sparkes W, Cook CJ, Kilduff L
Summary: Post-match assessments of peak power output (PPO) during countermovement jumps and Creatine Kinase (CK) concentrations are common markers of recovery status in soccer players. Yet, the impact of soccer match-play on recovery in the 48 h after competition is unclear and the between-match variability of these responses has not been examined. Fourteen reserve team players from an English Premier League club were examined over 1-4 matches per player. CK and PPO were measured before, 24 h and 48 h after each match. Data were analyzed with within-subjects linear mixed models. Compared with the pre-match baseline, PPO was 237±170 W and 98±168 W lower at 24 h and 48 h, respectively (P≤0.005) and CK was elevated (+24 h: +334.8±107.2 μ·L, +48 h: +156.9±121.0 μ·L; both P≤0.001) after match-play. These responses were consistent across the different matches and playing positions (P>0.05). Within-subjects correlations between PPO and CK were significant (r=-0.558; P≤0.005). The between-match variability of PPO was 10.9%, 11.0% and 9.9% respectively at baseline, +24 h and +48 h whereas for CK the variability was 41.7%, 30.0% and 34.3%, respectively. These findings highlight that greater than 48 h is needed to restore metabolic and performance perturbations following soccer match-play and that CK demonstrates greater between-match variability than PPO. Such information is likely to be of interest to those responsible for the design of training schedules in the days following a match and sports scientists whose responsibilities include the monitoring of recovery status in soccer players.

#7 Effects of Static Stretching and Playing Soccer on Knee Laxity
Reference: Clin J Sport Med. 2015 Jan 30. [Epub ahead of print]
Authors: Baumgart C, Gokeler A, Donath L, Hoppe MW, Freiwald J
Summary: This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint. Thirty-one athletes were randomly assigned into a stretching (26.9 ± 6.2 years, 1.77 ± 0.09 m, 67.9 ± 10.7 kg) and a control group (27.9 ± 7.4 years, 1.75 ± 0.08 m, 72.0 ± 14.9 kg). Thirty-one amateur soccer players in an additional soccer group (25.1 ± 5.6 years, 1.74 ± 0.10 m, 71.8 ± 14.8 kg). All participants had no history of knee injury requiring surgery and any previous knee ligament or cartilage injury. The stretching group performed 4 different static stretching exercises with a duration of 2 × 20 seconds interspersed with breaks of 10 seconds. The soccer group completed a 90-minute soccer-specific training program. The control group did not perform any physical activity for approximately 30 minutes. Anterior tibial translation was measured with the KT-1000 knee arthrometer at forces of 67 N, 89 N, and maximal manual force (Max) before and after the intervention. There was a significant increase in ATT after static stretching and playing soccer at all applied forces. Maximal manual testing revealed a mean increase of ATT after static stretching of 2.1 ± 1.6 mm (P < 0.0005) and after playing soccer of 1.0 ± 1.5 mm (P = 0.001). The ATT increase after static stretching at 67 and 89 N is significantly higher than in controls. At maximum manual testing, significant differences were evident between all groups. Static stretching and playing soccer increase ATT and may consequently influence mechanical factors of the anterior cruciate ligament. The ATT increase after static stretching was greater than after playing soccer. The observed increase in ATT after static stretching and playing soccer may be associated with changes in kinesthetic perception and sensorimotor control, activation of muscles, joint stability, overall performance, and higher injury risk.

#8 Effect of high-intensity training on speed and agility performance in 10-year-old soccer players
Reference: J Sports Med Phys Fitness. 2015 Jan-Feb;55(1-2):25-9.
Authors: Mathisen G, Pettersen SA
Summary: The aim of the present study was to assess the effect of short-burst high intensity training on speed and agility performance in 10-year-old male soccer players. Pretest posttest experimental design. A training group (TG) (N.=20; age 10.5 SD±0.2), followed an 8 week intervention program, and with an corresponding control group (CG) (N.=12; age 10.4 SD±0.2). Brower Timing System (USA) were used to record split and completion time. One way analysis of variance (ANOVA), two tailed paired t-test and Pearson's correlation r were used in statistical analyses. All analyses were performed using SPSS version 19.0. Findings from the present study showed significant improvement in agility performance (7.8%) and 20 m sprint (1.8%) (P<0.05). No significant performance increase was obtained in the CG. Furthermore the correlation between 10 m sprint and agility was r=0.40 and between 20 m sprint and agility performance r=0.58 (P<0.05). These results demonstrate that short-burst high intensity training increase speed and agility performance in 10-year-old male soccer players. The results also indicate a common variance between straight line sprinting and agility performance.

#9 The alpha-actinin-3 R577X polymorphism and physical performance in soccer players
Reference: J Sports Med Phys Fitness. 2015 Feb 4. [Epub ahead of print]
Authors: Coelho D, Pimenta E, Rosse I, Veneroso C, Becker L, Carvalho MR, Pussieldi G, Silami-Garcia E
Summary: The aim of this study was to investigate the association between ACTN3 genotype (RR, RX, and XX) and physical performance of 138 adult, professional, U--20 and U--17 years Brazilian first--division soccer players. The following three parameters were investigated: first, speed, using a 30--m sprint test with speed measured at 10 m, 20 m, and 30 m; second, muscular strength, using counter--movement--jump and squat jump tests; and third, aerobic endurance using the Yo--Yo endurance test. The athletes were ranked in ascending order according to their performance in each test. after which they were divided into quartiles and clustered according to genotype and allele frequency. The X 2 was used to compare the genotype frequencies (RR, RX and RR) and allele frequencies (R and X) within and between the different quartiles of performance rating. No significant differences were observed in genotypic or allelic frequencies between different performance ratings. The ACTN3 genotype was not associated to any of the physical performance parameters. This information should be noted with care, because, besides physical capacity, there are other factors, like tactical knowledge, that interfere with performance in sport, considering that expertise is multifactorial.

The Training Manager -