Latest research in football - week 12 - 2013

#1 How Effective are Exercise-Based Injury Prevention Programmes for Soccer Players? : A Systematic Review.
Authors: van Beijsterveldt AM, van der Horst N, van de Port IG, Backx FJ.
Reference:  Sports Med. 2013 Mar 8. [Epub ahead of print]
Summary: The purpose of the manuscript was to systematically study the evidence on preventive exercise-based training programmes to reduce the incidence of injuries in soccer. The quality of the studies were assessed using the PEDro scale and studies were included if (1) randomized controlled trials or controlled clinical trials; (2) primary outcome of the study is the number of soccer injuries and/or injury incidence; (3) intervention focusing on a preventive training programme, including a set of exercises aimed at improving strength, coordination, flexibility or agility; and (4) study sample of soccer players. A final of six studies involved a total of 6,099 participants and the results were contradictory. Two of the six studies reported a statistical significant reduction in injuries overall. Four of the six studies described an overall preventive effect, although the effect of one study was not statistically significant. Three studies of high, moderate and low quality described a significant preventive effect. The authors concluded that effectiveness of exercise-based programmes to prevent soccer injuries is not scientifically robust with the contradicting finding, however, some reasons for the contradictory findings could be different study samples (gender, age) in the included studies, differences between the intervention programmes implemented (training content, -frequency and -duration) and compliance with the programme. More research is needed.


#2 Alteration in basal redox state of young male soccer players after a six-month training programme
Authors: Zivkovic V, Lazarevic P, Djuric D, Cubrilo D, Macura M, Vuletic M, Barudzic N, Nesic M, Jakovljevic V.
Reference: Acta Physiol Hung. 2013 Mar;100(1):64-76. doi: 10.1556/APhysiol.100.2013.1.6.
Summary:  The purpose of the study was to determine the effects of a six-month training programme on basal redox status of young male soccer players. 26 male youth soccer players (12-13 years) participated in a six-month training programme and were compared to 26 age-matched non-athletes that did not participate in the training process. Oxidative stress markers (lipid peroxidation (measured as TBARS), nitrites (NO2-), superoxide anion radical (O2-), hydrogen peroxide (H2O2), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) level) were obtained from blood samples before and after six-month of training. After six months, the levels of TBARS and NO2- were significantly increased, while the O2- and H2O2 remained unchanged. However, SOD and CAT activity increased, while GSH decreased. The authors concluded that a carefully prepared training programme could strengthen most components of antioxidant defence systems and regular training does not promote oxidative stress.


#3 Relationship between measures of aerobic fitness, speed and repeated sprint ability in full and part time youth soccer players
Authors: Gibson N, Currie J, Johnston R, Hill J.
Reference: J Sports Med Phys Fitness. 2013 Feb;53(1):9-16.
Summary: The primary purpose of the study was to investigate the relationship between repeated sprint ability (RSA) involving changes in direction, short linear sprinting and aerobic capacity in young elite soccer players. The secondary purpose was to assess any differences in performance of these assessments between players of different age groups. Thirty-two male adolescent soccer players belonging to the same elite club academy were assessed for RSA comprising 6 x 40m efforts interspersed by 25s recovery, linear sprinting speed over 15m, and aerobic capacity via the YYIE2 assessment. The performances showed a significant correlation between the YYIE2 and RSA total time, RSA fastest sprint and RSA percentage decrement. There were significant differences between age groups for distance covered in the YYIE2, RSA total time and RSA fastest sprint. The authors concluded that RSA assessment over 40m, incorporating changes of direction, appear to be significantly correlated with YYIE2 performance in young elite level soccer players. Additionally, an increase in the YYIE2 and the RSA was seen with age, but not in linear sprinting. These results have implications for the design of assessment protocols for young elite soccer players of different ages.


#4 Side-to-Side Differences in the Lower Leg Muscle-Bone Unit in Male Soccer Players
Authors: Anliker E, Sonderegger A, Toigo M.
Reference: Med Sci Sports Exerc. 2013 Mar 6. [Epub ahead of print]
Summary: The purpose of the study was to characterize side-to-side differences in the lower leg muscle-bone unit between the non-dominant leg (NL) and the dominant leg (DL) using maximum voluntary forefoot ground reaction force (Fm1LH) during multiple one-legged hopping (m1LH), and tibial bone mass and geometry measured by peripheral quantitative computed tomography (pQCT). Male soccer players (N=66) with a age range 12-18 years performed m1LH to determine Fm1LH acting on the forefoot during landing for the NL and DL separately. pQCT scans were obtained to assess bone structural variables at 4, 14, 38 and 66% tibia length and calf muscle cross-sectional area at the 66%-site. Participants displayed significant side-to-side differences in bone mass and geometry at 4, 14 and 38% of tibia length, with higher values in NL relative to DL and most evident at the 14%-site. However, no statistical significant asymmetries were found for Fm1LH between the two legs. In addition, the relationship between Fm1LH and vBMC14% was strong for both NL and DL, but side-to-side differences in Fm1LH (ΔFm1LH) and side-to-side differences in vBMC14% (ΔvBMC14%) were not related. The authors concluded that in contrast the mechanostat theory, ΔFm1LH and ΔvBMC14% did not differ in proportion to each other. Furthermore, the authors stated that it appears that playing soccer is a well-balanced activity with respect to Fm1LH. However, the NL contributes to the supporting of the action of the DL, which result in a more pronounced loading experienced by the tibia for the NL relative to the DL, leading to the observed higher bone strength values for the NL.


#5 Evidence of cognitive dysfunction after soccer playing with ball heading using a novel tablet-based approach
Authors: Zhang MR, Red SD, Lin AH, Patel SS, Sereno AB.
Reference: PLoS One. 2013;8(2):e57364. doi: 10.1371/journal.pone.0057364. Epub 2013 Feb 27.
Summary: The question arises whether frequent head-to-ball contact cause cognitive dysfunctions and brain injury to soccer players? The study was designed to examine the impact of ball-heading among high school female soccer players and examined both direct, stimulus-driven, or reflexive point responses (Pro-Point) as well as indirect, goal-driven, or voluntary point responses (Anti-Point), thought to require cognitive functions in the frontal lobe. The results showed that soccer players were significantly slower than controls in the Anti-Point task but displayed no difference in Pro-Point latencies, indicating a disruption specific to voluntary responses. The authors suggested that even subconcussive blows in soccer can result in cognitive function changes that are consistent with mild traumatic brain injury of the frontal lobes.


#6 Soccer Skill Development in Talented Players
Authors: Huijgen BC, Elferink-Gemser MT, Ali A, Visscher C.
Reference: Int J Sports Med. 2013 Mar 4. [Epub ahead of print]
Summary: The purpose of the study was to gain insight into the development of soccer-specific skills and whether differences between talented players exist on the Loughborough Soccer Passing Test (LSPT). Two scores can be derived from the LSPT: 1) execution time: time to complete 16 passes (speed) and 2) skill performance time: execution time including bonus and penalty time for accuracy. The study comprised 2 parts. The first one was a quasi-longitudinal design with 270 talented players (aged 10-18 years) performing the LSPT in which a multilevel modelling was applied. The second part described differences between those players allowed to continue in the development program (selected, N = 269) and players who were forced to leave (de-selected, N = 50). The longitudinal data showed that the predicted execution time improved significantly from age 10-18 years for ~18%. Skill performance time was predicted to improve approximately 32% for the same timeframe. Interestingly, the selected players significantly outscored de-selected players only on skill performance time, but not on execution time. The authors concluded that already in high-level youth soccer, the combination of speed and accuracy in soccer skills might be more important than speed alone.


#7 Isokinetic Strength Responses to Season-long Training and Competition in Turkish Elite Soccer Players
Authors: Eniseler N, Sahan C, Vurgun H, Mavi HF.
Referemce: J Hum Kinet. 2012 Mar;31:159-68. doi: 10.2478/v10078-012-0017-5. Epub 2012 Apr 3.
Summary: The purpose of this study was to evaluate the seasonal changes in isokinetic strength of 14 Turkish professional soccer players over their 24-week soccer season. Peak torque of knee extensor and flexor muscles were measured using a Biodex at angular velocities of 60°/s, 300°/s and 500°/s and the players were tested at the beginning and end of the competitive season. At the end of the training period, players' knee strength changed significantly at 500°/s angular velocities. In addition the training affected the H/Q ratio improving the dominant as well as non-dominant leg at 500°/s significantly. In addition significant bilateral strength improvements for knee flexors were also observed at 500°/s. The authors concluded that usual daily soccer training and weekly competition might produce changes in knee strength at high angular velocities.


#8 Evolution of Perceived Cohesion and Efficacy over the Season and their Relation to Success Expectations in Soccer Teams
Authors: Marcos FM, Sánchez-Miguel PA, Sánchez-Oliva D, Alonso DA, García-Calvo T.
Reference: J Hum Kinet. 2012 Oct;34:129-38. doi: 10.2478/v10078-012-0072-y. Epub 2012 Oct 23.
Summary: The purpose of the study was to examine the evolution of players' perception of cohesion and efficacy over the season and their relation with success expectations. 146 youth male soccer players between 15 and 19 years of age participated in this study and diverse instruments were used to measure cohesion, perceived efficacy, and success expectations. The result showed that expectations of single players that did not match the team's final performance will experience a negative evolution of their levels of perceived cohesion and efficacy, whereas players whose expectations at the start of the season match the team's final performance in the classification will maintain their degree of perceived cohesion and efficacy. The authors concluded that coaches and sport psychologists should attempt to clarify the players' basic goals of the season to create expectations that match what is expected from the team.


#9 Validity and reproducibility of the sargent jump test in the assessment of explosive strength in soccer players
Authors: de Salles PG, Vasconcellos FV, de Salles GF, Fonseca RT, Dantas EH.
Reference: J Hum Kinet. 2012 Jun;33:115-21. doi: 10.2478/v10078-012-0050-4. Epub 2012 Jul 4.
Summary: The purpose of this study was to check the validity and the intra- and inter-evaluators reproducibility of the Sargent Jump Test. Forty-five soccer players were randomly selected from different clubs competing in the local soccer championship. All players performed one test on the same jump platform model Jumptest and two independent Sargent Jump Tests assessed by the same evaluator. Two days later, another Sargent Jump Test was performed simultaneously assessed by 2 evaluators. In all tests, three jumps were performed and the highest one was used for further data analysis. Sargent Jump Test scores were compared to those from the jump platform (considered as gold standard). The intraclass correlation coefficients (ICC) to evaluate intra- and inter-evaluator reproducibility were high resulting in permission to conclude that the Sargent Jump Test is a valid and reproducible instrument for measuring the explosive strength in homogeneous groups.


#10 The role of situational variables in analysing physical performance in soccer
Author: Lago-Peñas C.
Reference: J Hum Kinet. 2012 Dec;35:89-95. doi: 10.2478/v10078-012-0082-9. Epub 2012 Dec 30.
Summary: Performance analysis in sport is used to investigate the performance of teams and players across different sports. Research within this area, especially when focussing on the determinants of success, has grown rapidly in the last few years. During this time, the role of a new concept, 'situational variables' has emerged. This term includes the different game and situational conditions that may influence performance at a behavioural level. Given that soccer is dominated by strategic factors, it is reasonable to suggest that situational variables of match status (i.e. whether the team is winning, losing or drawing), quality of opposition (strong or weak), and match location (i.e. playing at home or away) may somehow influence the teams' and players' activities. These situational variables need to be analyzed in depth to understand their influence in team sports. The aim of this article was to examine the independent and interactive effects of situational variables on physical performance in elite soccer. The view that professional soccer players regulate their physical efforts according to the specific demands of individual matches and periods of the game is offered. In support of this argument results from recent studies are presented. Implications of this perspective for match analyst and coaches for evaluating performance are also considered.


#11 The Use of Match Statistics that Discriminate Between Successful and Unsuccessful Soccer Teams
Authors: Castellano J, Casamichana D, Lago C.
Reference: J Hum Kinet. 2012 Mar;31:139-47. doi: 10.2478/v10078-012-0015-7. Epub 2012 Apr 3.
Summary: The purpose of the study was to identifying variables best discriminating between winning, drawing and losing teams from three football World Cups (2002, 2006, 2010). 177 matches were included and two categories of variables were studied: 1) those related to attacking play: goals scored, total shots, shots on target, shots off target, ball possession, number of off-sides committed, fouls received and corners; and 2) those related to defence: total shots received, shots on target received, shots off target received, off-sides received, fouls committed, corners against, yellow cards and red cards. The analysis of these matches revealed the following: (a) the variables related to attacking play that best differentiated between winning, drawing and losing teams were total shots, shots on target and ball possession; and (b) the most discriminating variables related to defence were total shots received and shots on target received. The authors concluded that winning, drawing and losing of national teams may be discriminated from one another on the basis of variables such as ball possession and the effectiveness of their attacking play.


#12 A comparison of physiological responses to various intermittent and continuous small-sided games in young soccer players
Author: Köklü Y.
Reference: J Hum Kinet. 2012 Mar;31:89-96. doi: 10.2478/v10078-012-0009-5. Epub 2012 Apr 3.
Summary: The purpose of this study was to investigate physiological responses to various intermittent (int) and continuous (con) small-sided games (SSGs) - including 2-a-side, 3-a-side, and 4-a-side games - in youth male soccer players. Twenty soccer players participated in this study and underwent anthropometric measurements followed by the YoYo intermittent recovery test. Measured variables were heart rate (HR), percentage of maximum HR (%HRmax), and blood lactate concentration (LA). The results demonstrated that the 3-a-side SSGint and SSGcon measurements were significantly higher than the 2-a-side and 4-a-side games in terms of HR and %HRmax, whereas the 2-a-side SSGint and SSGcon resulted in higher LA responses compared to other SSG types. The study results also demonstrated that SSGint and SSGcon are similar in terms of physiological responses except for 2-a-side game LA responses. As a conclusion the authors stated that both SSGint and SSGcon could be used for the physiological adaptations required for soccer specific aerobic endurance.


#13 The effect of immediate post-training active and passive recovery interventions on anaerobic performance and lower limb flexibility in professional soccer players
Authors: Rey E, Lago-Peñas C, Casáis L, Lago-Ballesteros J.
Reference: J Hum Kinet. 2012 Mar;31:121-9. doi: 10.2478/v10078-012-0013-9. Epub 2012 Apr 3.
Summary: The purpose of the study was to determine the effectiveness of active (12 min submaximal running and 8 min of static stretching) vs. passive recovery (20 min sitting on a bench) interventions performed immediately after a training session on anaerobic performances (CMJ, 20 m sprint and Balsom agility test) and lower limb flexibility, measured 24 hours after the training. 31 professional soccer players participated in this study and player's anaerobic performances and lower limb flexibility were measured pre- and post-intervention. The intervention consisted of a standardized soccer training during which heart rate and RPE were recorded to evaluate the training load and a randomly assigned recovery strategy, either active recovery or passive recovery. No significant differences between groups were observed in heart rate and RPE. The only significant differences between active and passive recovery was seen in CMJ, in which active recovery participants scored significantly greater compared to the passive recovery group.


#14 Comparison of a new test for agility and skill in soccer with other agility tests
Authors: Kutlu M, Yapıcı H, Yoncalık O, Celik S.
Reference: J Hum Kinet. 2012 Jun;33:143-50. doi: 10.2478/v10078-012-0053-1. Epub 2012 Jul 4.
Summary: The purpose of this study was to a) develop a novel test to measure run, shuttle run and directional change agility, and soccer shots on goal with decision making and b) to compare it with other agility tests. Multiple comparisons and assessments were conducted, including test-retest, Illinois, Zig-Zag, 30 m, Bosco, T-drill agility, and Wingate peak power tests. 113 Turkish amateur and professional soccer players and tertiary-level students participated in the study. Test-retest and inter-tester reliability testing measures were conducted with athletes. The correlation coefficient of the new test was .88 and no significant difference between the test- re-test results was observed. ANOVA results revealed a significant difference between the T-drill agility and power test results for soccer players. The authors concluded that the new agility and skill test is an acceptable and reliable test when considering test-retest reliability and inter-rater reliability.


#15 Leadership power perceptions of soccer coaches and soccer players according to their education
Author: Konter E.
Reference: J Hum Kinet. 2012 Oct;34:139-46. doi: 10.2478/v10078-012-0073-x. Epub 2012 Oct 23.
Summary: The purpose of this study was to analyze the leadership power perceptions of soccer coaches and soccer players according to their educational levels. Data were collected from 165 male soccer coaches and 870 male soccer players. Adapted versions of the "Power in Soccer Questionnaire-Other", the "Power in Soccer Questionnaire-Self" and an "information form" were used for data collection, and collected data were analyzed by the Kruskal-Wallis and the Mann-Whitney Tests. Analysis of the Power in Soccer Questionnaire-Other revealed significant differences between soccer players' level of education and their perception of Coercive Power, and no significant differences related to Referent Power, Legitimate Power and Expert Power. Analysis of the Power in Soccer Questionnaire-Self also revealed the only significant difference between coaches' level of education and their perception of Legitimate Power, and no significant differences with regard to others. Different perception of leadership powers between coaches and players might create communication and performance problems in soccer.


#16 A review on the effects of soccer small-sided games
Authors: Aguiar M, Botelho G, Lago C, Maças V, Sampaio J.
Reference: J Hum Kinet. 2012 Jun;33:103-13. doi: 10.2478/v10078-012-0049-x. Epub 2012 Jul 4.
Summary: The purpose was to evaluate the effectiveness of small-sided games as a conditioning stimulus. Available studies indicate that physiological responses (e.g. heart rate, blood lactate concentration and rating of perceived exertion), tactical and technical skill requirements can be modified during small-sided games by altering factors such as the number of players, the size of the pitch, the rules of the game, and coach encouragement. However, because of the lack of consistency in small-sided games design, player fitness, age, ability, level of coach encouragement, and playing rules in each of these studies, it is difficult to make accurate conclusions on the influence of each of these factors separately.


#17 The effect of fatigue on kicking velocity in soccer players
Authors: Ferraz R, van den Tillaar R, Marques MC.
Reference: J Hum Kinet. 2012 Dec;35:97-107. doi: 10.2478/v10078-012-0083-8. Epub 2012 Dec 30.
Summary: The purpose of the study was to evaluate the effect of acute fatigue on ball velocity from instep kicks. Ten adult amateur football players with sufficient football experience performed maximal instep kicks before and after the implementation of an intensive, intermittent and repeated exercise protocol. A significant decrease in ball velocity after just one round of the fatigue circuit was observed. However, after the third circuit ball velocity increased and after the fifth circuit maximal ball velocity increased yet again (compared to the second circuit) and was not significantly different from before commencement of the fatigue protocol. The results partly confirmed the hypothesis of the negative influence of fatigue upon ball velocity in soccer kicking, demonstrating also some variability in the presented values of ball velocity perhaps theoretically accounted for by the general governor model.


#18 The relationship between the yo-yo tests, anaerobic performance and aerobic performance in young soccer players
Authors: Karakoç B, Akalan C, Alemdaroğlu U, Arslan E.
Reference: 2012 Dec;35:81-8. doi: 10.2478/v10078-012-0081-x. Epub 2012 Dec 30.
Summary: The purposes of this study was to determine the relationship between performance in the Yo-Yo intermittent recovery test level 1 (YIRT1), the Yo-Yo intermittent recovery test level 2 (YIRT2) and the Yo-Yo endurance test (continuous) (YET) with maximal oxygen uptake (VO2max) and Wingate anaerobic performance (WaNT) test in youth soccer players, aged 15 years. A treadmill test (TRT) was used to assess VO2max pre- and post-test. The Yo-Yo tests showed significant higher HRmax values compared to the TRT, but moderate correlations between VO2max and YIRT 1-2 performances were seen. Furthermore, there was only a weak relationship between VO2max and YET performance and a moderate, but significant negative correlations, between performance in the YIRT2 and peak power measured in the WaNT. A moderate negative correlation was found between performance in the YIRT2 and Fatigue index (FI). The authors concluded that the YIRT2 may be a more suitable field test for determining both aerobic and anaerobic performance in soccer players.


#19 Integrating the Internal and External Training Load in Soccer
Authors: Akubat I, Barrett S, Abt G.
Reference: Int J Sports Physiol Perform. 2013 Mar 8. [Epub ahead of print]
Summary: The purpose of the study was to assess the relationships of fitness in soccer players with a novel integration of internal and external training load (TL). Ten amateur soccer players performed a lactate threshold (LT) test followed by a soccer simulation (BEAST90mod). The results from the LT test were used to determine vLT, vOBLA, VO2max and the heart rate-blood lactate profile for calculation of internal TL (iTRIMP). The total distance (TD) and high intensity distance (HID) covered during the BEAST90mod was measured using GPS technology that allowed measurement of performance and external TL. The internal TL was divided by the external TL to form iTRIMP:TD and iTRIMP:HID ratios. Results revealed that vLT, vOBLA and vO2max were not significant related to TD or HID. iTRIMP:HID significantly correlated with vOBLA and iTRIMP:TD showed a significant correlation with vLT. The authors concluded that integrated use of ratios may help in the assessment of fitness, as performance alone showed no significant relationships with fitness.


#20 Evaluation of how different implementation strategies of an injury prevention programme (FIFA 11+) impact team adherence and injury risk in Canadian female youth football players: a cluster-randomised trial
Authors: Steffen K, Meeuwisse WH, Romiti M, Kang J, McKay C, Bizzini M, Dvorak J, Finch C, Myklebust G, Emery CA
Reference: Br J Sports Med. 2013 Mar 13. [Epub ahead of print]
Summary: The purpose of the study was to evaluate different delivery methods of an effective injury prevention programme (FIFA 11+) on adherence and injury risk among female youth football teams.
During the 4-month 2011 football season, coaches and 13-year-old to 18-year-old players from 31 tier 1-3 level teams were introduced to the 11+ through either an unsupervised website ('control') or a coach-focused workshop with ('comprehensive') and without ('regular') additional supervisions by a physiotherapist. Team and player adherence to the 11+, playing exposure, history and injuries were recorded. Teams in the comprehensive and regular intervention groups demonstrated adherence to the 11+ programme of 85.6% and 81.3% completion of total possible sessions, compared to 73.5% for teams in the control group. These differences were not statistically significant, after adjustment for cluster by team, age, level and injury history. Compared to players with low adherence, players with high adherence to the 11+ had a 57% lower injury risk. However, adjusting for covariates, this between-group difference was not statistically significant. The authors concluded that a coach workshop, coach-led delivery of the FIFA 11+ was equally successful with or without the additional field involvement of a physiotherapist. Proper education of coaches during an extensive preseason workshop was more effective in terms of team adherence than an unsupervised delivery of the 11+ programme to the team.


#21 Effect of various warm-up protocols on jump performance in college football players
Authors: Pagaduan JC, Pojskić H, Užičanin E, Babajić F.
Reference: J Hum Kinet. 2012 Dec;35:127-32. doi: 10.2478/v10078-012-0086-5. Epub 2012 Dec 30.
Summary: The purpose of this study was to identify the effects of warm-up strategies on countermovement jump performance. Twenty-nine male college football players underwent a control (no warm-up) and (6) different warm-up conditions: 1. general warm-up; 2. general warm-up with dynamic stretching; 3. general warm-up, dynamic stretching and passive stretching; 4. passive static stretching; 5. passive static stretching and general warm-up; and, 6. passive static stretching, general warm-up and dynamic stretching. Countermovement jump performance was measured after each intervention or control. Results revealed a significant difference on warm-up strategies. A general warm-up and a general warm-up with dynamic stretching posted the greatest gains among all interventions. However, no warm-up and passive static stretching displayed the least results in countermovement jump performance. The authors concluded that countermovement jump performance preceded by a general warm-up or a general warm-up with dynamic stretching posted superior gains in countermovement jump performance.