Latest research in football - week 48 - 2015

#1 Effect of different types of shoes on balance among soccer players
Reference: Muscles Ligaments Tendons J. 2015 Oct 20;5(3):208-213.
Atuhors: Notarnicola A, Maccagnano G, Pesce V, Tafuri S, Mercadante M, Fiore A, Moretti B
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4617223/pdf/208-213.pdf
Summary: In soccer, balance ability is important to reduce non-contact injuries. The effect of footwear on balance is poorly understood in this sport. Soccer boots and futsal trainers need to guarantee a good grip on compliant surfaces. Running shoes are designed to reduce friction on rigid su rfaces. The purpose of the present study was to investigate these types of shoes on balance ability. Twenty-four healthy male volunteers were recruited from amateur soccer teams. They were ask to perform the BESS (Balance Error Scoring System) test to measure the number of instability episodes in 6 conditions: double-leg, single-leg, and tandem stances on firm and foam surfaces. Anova with factor (several shoes) and Bonferroni were used to compare the means of two subtotal scores (firm and foam surface) and the final total score (BESS). The three shoe models led to greater stability than when the subject was barefoot (p=0.001). Only on the firm surface the soccer boots were statistically better than futsal trainers (p=0.009). The lack of stability while barefoot could be explained by the fact that with shoes there is a greater surface area, which produces a sensory filter that leads to posture modifications to improve stability. The greater stability, that was found in the three types of footwear, could be guaranteed by the design to reduce friction (for running shoes) and by the presence of studs (for soccer boots and futsal trainers).


#2 Knee stability, athletic performance and sport-specific tasks in non-professional soccer players after ACL reconstruction: comparing trans-tibial and antero-medial portal techniques
Reference: Muscles Ligaments Tendons J. 2015 Oct 20;5(3):175-180.
Authors: Tudisco C, Bisicchia S, Cosentino A, Chiozzi F, Piva M
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4617217/pdf/175-180.pdf
Summary: A wrong position of bone tunnels, in particular on the femur, is one of the most frequent causes of a failed anterior cruciate ligament (ACL) reconstruction. Several studies demonstrated that drilling the femoral tunnel through the antero-medial portal (AMP) allows a more anatomical placement on the lateral femoral condyle and higher knee stability, compared to trans-tibial (TT) technique. The aim of this study was to retrospectively evaluate two groups of soccer players operated on for ACL reconstruction according to either one of these two techniques. Two groups of non-professional soccer players operated on for a single bundle ACL reconstruction with hamstrings autograft using either a TT (20 patients) or an AMP (23 patients) technique were retrospectively evaluated with KT-1000 arthrometer, manual pivot shift test, isokinetic test, the incremental treadmill-running test, athletic and sport specific tasks, and knee scores (IKDC, Lysholm and KOOS). The AMP group showed better results at pivot shift test and KOOS, but lower flexion angles at single leg squat test. There were no differences in all the other considered outcomes. The better rotational stability of the knee achieved in AMP group did not lead to significantly better clinical and functional results in our patients.


#3 Anthropometric factors related to sprint and agility performance in young male soccer players
Reference: Open Access J Sports Med. 2015 Nov 5;6:337-342.
Authors: Mathisen G, Pettersen SA
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4640228/pdf/oajsm-6-337.pdf
Summary: The purpose of the study was to investigate the relationship between anthropometrics and sprint and agility performance and describe the development of sprint (acceleration) and agility performance in 10- to 16-year-old male soccer players. One hundred and thirty-two participants were divided into three age groups, 10-12 years (mean 10.8±0.50), 13-14 years (mean 13.9±0.50), and 15-16 years (mean 15.5±0.24), with assessment of 20 m sprint with 10 m split time and agility performance related to body height and body mass within groups. In the 10- to 12-year-olds, there were no significant correlations between height, weight, and the performance variables, except for body mass, which was correlated to 10-20 m sprint (r=0.30). In the 13- to 14-year-olds, body height was significantly correlated with 10 m sprint (r=0.50) and 20 m sprint (r=0.52), as well as 10-20 m sprint (r=0.50) and agility performance (r=0.28). In the 15- to 16-year-old group, body height was correlated to 20 m (r=0.38) and 10-20 m (r=0.45) sprint. Body mass was significantly correlated to 10 m spring (r=0.35) in the 13- to 14-year-olds, as well as 20 m (r=0.33) and 10-20 m (r=0.35) sprint in the 15- to 16-year-olds. Height and body mass were significantly correlated with sprint performance in 13- to 16-year-old male soccer players. However, the 10- to 12-year-olds showed no significant relationship between sprint performance and anthropometrics, except for a small correlation in 10-20 m sprint. This may be attributed to maturation, with large differences in body height and body mass due to different patterns in the growth spurt. The agility performance related to anthropometrics was insignificant apart from a moderate correlation in the 13- to 14-year-olds.


#4 Analysis of Jumping-Landing Manoeuvers after Different Speed Performances in Soccer Players
Reference: PLoS One. 2015 Nov 24;10(11):e0143323. doi: 10.1371/journal.pone.0143323. eCollection 2015.
Authors: Daneshjoo A, Abu Osman NA, Sahebozamani M, Yusof A
Download link: http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0143323&representation=PDF
Summary: Running at high speed and sudden change in direction or activity stresses the knee. Surprisingly, not many studies have investigated the effects of sprinting on knee's kinetics and kinematics of soccer players. Hence, this study is aimed to investigate indices of injury risk factors of jumping-landing maneuvers performed immediately after sprinting in male soccer players. Twenty-three collegiate male soccer players (22.1±1.7 years) were tested in four conditions; vertical jump (VJ), vertical jump immediately after slow running (VJSR), vertical jump immediately after sprinting (VJFR) and double horizontal jump immediately after sprinting (HJFR). The kinematics and kinetics data were measured using Vicon motion analyzer (100Hz) and two Kistler force platforms (1000Hz), respectively. For knee flexion joint angle, (p = 0.014, η = 0.15) and knee valgus moment (p = 0.001, η = 0.71) differences between condition in the landing phase were found. For knee valgus joint angle, a main effect between legs in the jumping phase was found (p = 0.006, η = 0.31), which suggests bilateral deficit existed between the right and left lower limbs. In brief, the important findings were greater knee valgus moment and less knee flexion joint angle proceeding sprint (HJFR & VJFR) rather than no sprint condition (VJ) present an increased risk for knee injuries. These results seem to suggest that running and sudden subsequent jumping-landing activity experienced during playing soccer may negatively change the knee valgus moment. Thus, sprinting preceding a jump task may increase knee risk factors such as moment and knee flexion joint angle.


#5 A systematic review and meta-analysis of dropout rates in youth soccer
Reference: Percept Mot Skills. 2015 Nov 23. [Epub ahead of print]
Authors: Møllerløkken NE, Lorås H, Pedersen AV
Summary: Despite the many benefits of involvement in youth sports, participation in them declines throughout childhood and adolescence. The present study performed a systematic review and meta-analysis of 12 studies reporting dropout rates in youth soccer, involving a total of 724,036 youths ages 10-18 years from five countries. The mixed effects meta-regression analyses took into account age and sex as statistical moderators of dropout rate. Potential articles were identified through computerized searches of the databases PubMed, MedLine, Embase, and SportDiscus up until August 2014, without any further time limit. Based on results reported in the 10 included articles, the annual weighted mean dropout rate is 23.9% across the included cohorts. Meta-regression indicated that annual dropout rates are stable from the ages of 10-19 years, with higher rates for girls (26.8%) compared to boys (21.4%). The present study suggests that youth soccer players are prone to dropout rates in which close to one-fourth of players leave the sport annually, which appears to be a consistent finding across ages 10-18 years.


#6 Testosterone Concentration and Lower Limb Power Over an Entire Competitive Season in Elite Young Soccer Players
Reference: J Strength Cond Res. 2015 Dec;29(12):3380-5. doi: 10.1519/JSC.0000000000000993.
Authors: Arruda AF, Aoki MS, Freitas CG, Spigolon LM, Franciscon C, Moreira A.
Summary: The aim of this study was to investigate salivary T changes and its relationship with power performance over a 1-year competitive season in elite under 15 (U15) and under 17 (U17) soccer players. Soccer players were recruited from 1 soccer club that has been participated in the main state and national leagues for these age groups. The soccer players were divided into 2 age categories (U15, n = 16 and U17, n = 23). A resting saliva sample was taken to determine T level, and power was assessed using the countermovement jump test with a bar of 30% of body mass on the athletes' shoulders on 3 occasions (T1: beginning of the competitive season, T2: end of the regular season, and T3: end of the playoffs). There was a decrease in T concentration at the end of the competitive season (T3) as compared with the beginning of the season (T1) for both age categories (p ≤ 0.05). Conversely, power performance parameters were increased for both age groups (U15: mean power and relative mean power and U17: peak power, mean power, relative peak power, and relative mean power; p ≤ 0.05). No significant correlation was identified between the relative changes in T concentration and power performance in both groups. The findings of this study suggest that T changes and power changes are not related.


#7 Acute effects of instrument assisted soft tissue mobilization vs. foam rolling on knee and hip range of motion in soccer players
Reference: J Bodyw Mov Ther. 2015 Oct;19(4):690-6. doi: 10.1016/j.jbmt.2015.04.010. Epub 2015 May 5.
Authors: Markovic G
Summary: The aim of the present investigation was to evaluate the acute effects of foam rolling (FR) and a new form of instrument-assisted soft tissue mobilization (IASTM), Fascial Abrasion Technique ™ (FAT) on hip and knee range of motion in soccer players. Twenty male soccer players randomly allocated into FR and FAT group (n = 10 each). Passive knee flexion and straight leg raise tests were measured before, immediately after and 24 h after intervention (FR or FAT). The FR group applied a 2-min quadriceps and hamstrings rolling, while FAT group received a 2-min application of FAT to the quadriceps and hamstrings muscles. Both groups significantly improved knee and hip ROM (p < 0.05), with higher gains observed in FAT group (10-19% vs. 5-9%). At 24 h post-treatment, only FAT group preserved most of the gains in ROM (7-13%; p < 0.05). These results support the use of the newly developed IASMT, Fascial Abrasion Technique ™ and FR for increasing lower extremity ROM of athletes.


#8 Technical performance and match-to-match variation in elite football teams
Reference: J Sports Sci. 2015 Nov 27:1-10. [Epub ahead of print]
Authors: Liu H, Gómez MA, Gonçalves B, Sampaio J
Summary: Recent research suggests that match-to-match variation adds important information to performance descriptors in team sports, as it helps measure how players fine-tune their tactical behaviours and technical actions to the extreme dynamical environments. The current study aims to identify the differences in technical performance of players from strong and weak teams and to explore match-to-match variation of players' technical match performance. Performance data of all the 380 matches of season 2012-2013 in the Spanish First Division Professional Football League were analysed. Twenty-one performance-related match actions and events were chosen as variables in the analyses. Players' technical performance profiles were established by unifying count values of each action or event of each player per match into the same scale. Means of these count values of players from Top3 and Bottom3 teams were compared and plotted into radar charts. Coefficient of variation of each match action or event within a player was calculated to represent his match-to-match variation of technical performance. Differences in the variation of technical performances of players across different match contexts (team and opposition strength, match outcome and match location) were compared. All the comparisons were achieved by the magnitude-based inferences. Results showed that technical performances differed between players of strong and weak teams from different perspectives across different field positions. Furthermore, the variation of the players' technical performance is affected by the match context, with effects from team and opposition strength greater than effects from match location and match outcome.


#9 Factors associated with playing football after anterior cruciate ligament reconstruction in female football players
Reference: Scand J Med Sci Sports. 2015 Nov 21. doi: 10.1111/sms.12588. [Epub ahead of print]
Authors: Fältström A, Hägglund M, Kvist J
Summary: This study investigated whether player-related factors (demographic, personality, or psychological factors) or the characteristics of the anterior cruciate ligament (ACL) injury were associated with the return to playing football in females after ACL reconstruction (ACLR). We also compared current knee function, knee related quality of life and readiness to return to sport between females who returned to football and those who had not returned. Females who sustained a primary ACL rupture while playing football and underwent ACLR 6-36 months ago were eligible. Of the 460 contacted, 274 (60%) completed a battery of questionnaires, and 182 were included a median of 18 months (IQR 13) after ACLR. Of these, 94 (52%) returned to football and were currently playing, and 88 (48%) had not returned. Multiple logistic regression analysis identified two factors associated with returning to football: short time between injury and ACLR (0-3 months, OR 5.6; 3-12 months OR 4.7 vs reference group > 12 months) and high motivation. Current players showed higher ratings for current knee function, knee-related quality of life, and psychological readiness to return to sport (P < 0.001). Undergoing ACLR sooner after injury and high motivation to return to sports may impact a player's return to football after ACLR.


#10 Large eccentric strength increase using the Copenhagen Adduction exercise in football: A randomized controlled trial
Reference: Scand J Med Sci Sports. 2015 Nov 21. doi: 10.1111/sms.12585. [Epub ahead of print]
Authors: Ishøi L, Sørensen CN, Kaae NM, Jørgensen LB, Hölmich P, Serner A
Summary: Hip adductor injuries are frequent in football, and players with low adductor strength appear to be at increased risk of injury. High adductor muscle activity has been shown in the Copenhagen Adduction exercise (CA); however, an associated strength gain has not been investigated. This study aims to examine the eccentric hip adduction strength (EHAD) gain using the CA in-season. Two U-19 sub-elite football teams, including 24 football players, were randomized to either an 8-week supervised progressive training program in addition to the usual training (intervention) or to continue training as usual (control). EHAD, eccentric hip abduction strength (EHAB), and side-bridge endurance were measured using reliable test procedures at baseline and follow-up by a blinded tester. There was a significant interaction between group and time on EHAD, EHAB, and EHAD/EHAB ratio (P < 0.025). The intervention group demonstrated a 35.7% increase in EHAD (P < 0.001); a 20.3% increase in EHAB (P = 0.003), and 12.3% increase in EHAD/EHAB ratio (P = 0.019). No significant within-group differences were found in the control group (P > 0.335). Compliance was 91.25%, and median muscle soreness ranged from 0 to 2. The CA implemented in-season with an 8-week progressive training program elicited a large significant increase in EHAD, EHAB, and EHAD/EHAB ratio.