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1.  Development of Body Composition, Hormone Profile, Physical Fitness, General Perceptual Motor Skills, Soccer Skills and On-The-Ball Performance in Soccer-Specific Laboratory Test Among Adolescent Soccer Players 
The aim of the present study was to examine the development of on-the-ball skills in soccer-specific laboratory test and to examine how traditional measures of body composition, hormone profile, physical fitness, general perceptual motor skills and soccer skills were related to performance measured in open skill environment among 10, 12, and 14-year-old regional male soccer players (n = 12/group). The measured variables were height, weight, fat, muscle mass, testosterone, 10m sprint, agility, counter movement jump, peripheral awareness, Eye- Hand-Foot coordination, passing skill, dribbling skill and on-the-ball skills (performance time and passing accuracy) in soccer-specific laboratory test. A significant main effect by age was found in all measured variables except in fat, in peripheral awareness and in passing accuracy. In discriminant analysis 63.9% (λ = 0.603, F = 4.600, p < 0.01) of the players were classified correctly based on physical fitness and general perceptual motor skills into three ability groups originally classified with performance time in soccer-specific laboratory test. Correlation co- efficient analysis with-in age groups revealed that variables associated with performance time in soccer-specific laboratory test were peripheral awareness (r = 0.72, p < 0.01) in 10-year-olds; testosterone (r = -0.70, p < 0.05), dribbling skill (r = 0.73, p < 0.01) and passing skill (r = 0.73, p < 0.01) in 12-year-olds; agility (r = 0.79, p < 0.01), counter movement jump (r = - 0.62, p < 0.01), dribbling skill (r = 0.80, p < 0.01) and passing skill (r = 0.58, p < 0. 05) in 14-year olds. Corresponding relationships with passing accuracy were weight (r = 0.59, p < 0.05), fat (r = 0.66, p < 0.05), 10m sprint (r = 0.71, p < 0.01) and countermovement jump (r = -0.64, p < 0.05) in 10-year-olds; Eye-Hand-Foot coordination (r = 0.63, p < 0.05) in 14-year- olds. The relationship between soccer-specific anticipation time and performance time in soccer- specific laboratory test was significant only in the 14-year-old age group (r = 0.76, p < 0.01). To conclude, on-the-ball skill performance in soccer-specific laboratory test improved with age and it seemed that soccer-specific perceptual skills became more and general perceptual motor skills less important with age in soccer-specific laboratory test.
Key pointsPhysical fitness characteristics and general perceptual motor skills predicted performance time of the open skill soccer-specific laboratory test in the group of 10-14 year-old regional soccer players.Before puberty the players were able to compensate weaker soccer-specific skills with better general physical performance abilities.Soccer-specific skills became more important with age and at the age of 14 the players were not able to compensate soccer-specific skills with general physical performance abilities.Beside basic ball-handling skills it also important to recognize the importance of soccer-specific perceptual skills (anticipation and reaction) as a part of successful soccer performance.
PMCID: PMC3761817  PMID: 24149780
Football,; youth,; perception,; growth,; puberty.
2.  Executive Functioning in Highly Talented Soccer Players 
PLoS ONE  2014;9(3):e91254.
Executive functions might be important for successful performance in sports, particularly in team sports requiring quick anticipation and adaptation to continuously changing situations in the field. The executive functions motor inhibition, attention and visuospatial working memory were examined in highly talented soccer players. Eighty-four highly talented youth soccer players (mean age 11.9), and forty-two age-matched amateur soccer players (mean age 11.8) in the age range 8 to 16 years performed a Stop Signal task (motor inhibition), the Attention Network Test (alerting, orienting, and executive attention) and a visuospatial working memory task. The highly talented soccer players followed the talent development program of the youth academy of a professional soccer club and played at the highest national soccer competition for their age. The amateur soccer players played at a regular soccer club in the same geographical region as the highly talented soccer players and play in a regular regional soccer competition. Group differences were tested using analyses of variance. The highly talented group showed superior motor inhibition as measured by stop signal reaction time (SSRT) on the Stop Signal task and a larger alerting effect on the Attention Network Test, indicating an enhanced ability to attain and maintain an alert state. No group differences were found for orienting and executive attention and visuospatial working memory. A logistic regression model with group (highly talented or amateur) as dependent variable and executive function measures that significantly distinguished between groups as predictors showed that these measures differentiated highly talented soccer players from amateur soccer players with 89% accuracy. Highly talented youth soccer players outperform youth amateur players on suppressing ongoing motor responses and on the ability to attain and maintain an alert state; both may be essential for success in soccer.
PMCID: PMC3954684  PMID: 24632735
3.  Effects of Small-Sided Games on Physical Conditioning and Performance in Young Soccer Players 
The purpose of this study was to examine, first, the movement actions performed during two different small-sided games and, second, their effects on a series of field endurance and technical tests. Thirty-four young soccer players (age: 13 ± 0.9 yrs; body mass: 62.3 ± 15.1 kg; height: 1.65 ± 0.06 m) participated in the study. Small-sided games included three-a-side (3 versus 3 players) and six-a-side (6 versus 6 players) games consisting of 10 bouts of 4 min duration with 3 min active recovery between bouts. Soccer player performance was evaluated using five field tests: a) 30m sprint, b) throw-in for distance, c) Illinois Agility Test, d) dribbling the ball and e) horizontal jump before, in the middle and after the implementation of both game situations. Heart rate was monitored during the entire testing session. Each game was also filmed to measure soccer movements within the game. The ANOVA analysis indicated that the three-a- side games displayed significantly higher heart rate values compared with the six-a-side games (p < 0.05). The number of short passes, kicks, tackles, dribbles and scoring goals were significantly higher during the three-a-side compared with the six-a-side game condition (p < 0. 05) while players performed more long passes and headed the ball more often during the six-a-side (p < 0.05). After the three-a-side games, there was a significant decline in sprint and agility performance (p < 0.05), while after both game conditions significant alterations in the throw-in and the horizontal jump performance were observed (p < 0.05). The results of the present study indicated that three-a-side games provide higher stimulus for physical conditioning and technical improvement than six-a-side games and their use for training young soccer players is recommended.
Key pointsThree-a-side games display higher HR compared with six-a-side games.In the three-a-side games players performed more short passes, kicks, dribbles, tackles and scored more goals compared with the six-a-side games.Impairment in endurance and field test performance was observed mainly after three-a-side games.The use of the three-a-side games to develop physical fitness and technique in young soccer players is recommended.
PMCID: PMC3763282  PMID: 24150000
Soccer; small-sided games; field tests; technical actions; intermittent exercise
4.  Shoulder injuries in soccer players 
Even though soccer is the most popular sport of the world, no review is available at present to resume the available data on shoulder injuries in soccer. The aim of this review is to report the available epidemiological data on shoulder specific injuries in soccer players and to describe the common mechanisms of shoulder injuries in soccer. Studies published through September 15, 2011, were identified by using MEDLINE, EMBASE, CINAHL and Pre-CINAHL, Pub-Med, Web of Science, and the full Cochrane Library. Reference lists of included studies were searched by hand. Studies were included if they reported on shoulder injuries in soccer players. Limits were not placed on year of publication, status of publication, or language. The journal, authors, and author affiliations of included studies were masked from 2 reviewers. We planned to perform a study on the epidemiology, mechanisms and management of shoulder injuries in elite soccer players. We also planned to use Review Manager (RevMan. Version 5 for Windows) to calculate the magnitude of treatment effect. No studies on clinical outcome of shoulder injuries in elite soccer athletes were found. No studies on the mechanism of shoulder injury in elite soccer players were found. The results of the available studies on epidemiology are reported. Despite soccer is the world’s game, few studies focused on shoulder injuries in soccer players, and therefore no definitive conclusions can be drawn. Further research is warranted to clarify the epidemiology, mechanisms and management of shoulder injuries in elite soccer players.
PMCID: PMC3536009  PMID: 23289025
soccer; sports; athletes; shoulder; injury
5.  Reducing muscle injuries and reinjuries in one italian professional male soccer team 
The incidence rate of muscle injuries and re-injuries in professional elite soccer players actually is very high and may interfere with the fate of a championship.
To investigate the effect of a two-tiered injury prevention programme on first injury and re-injury incidence in top level male soccer players.
Study design
Case Series Study.
Muscle injuries and re-injuries sustained by a group of 36 soccer player of an italian elite soccer team have been collected during 2010–2011 season. These data have been compared with those collected during the previous season in the same elite soccer team.
A total of 64 injuries occurred, 36 (56%) of which during practice and 28 (44%) during matches. Muscle injuries accounted for 31.3% of the total (n=20), 70% (n=14) of which occurred during practice and 30% (n=6) during matches.
Hamstring were the muscles most often injured (n=11) In all, 3 re-injuries occurred (15% of muscle injuries). No early re-injuries occurred. The incidence was 2.5 injuries/1000 hours and the burden was 37 days absence/1000 hours.
Through the implementation of a group and personalized injury prevention program, we were able to reduce the total number of muscle injuries and days absent because of injury, in a team of elite soccer players, as compared to the previous season. Specifically, muscle injuries accounted for 31% of all injuries, as compared to 59% of all injuries sustained by the team during the previous season. The number of injuries/1000 hours of exposure was reduced by half (from 5.6 to 2.5) and the days absent/1000 hours fell from 106 to 37.
PMCID: PMC3940507  PMID: 24596697
muscle injuries; football; prevention
6.  Effects of the 11+ and Harmoknee Warm-up Programs on Physical Performance Measures in Professional Soccer Players 
The purpose of this study was to examine the effects of the 11+ and HarmoKnee warm-up programs on performance measures in professional soccer players. Thirty-six male professional soccer players (age: 18.9 ± 1.4 years) were divided into 3 groups, the 11+, HarmoKnee and control group (n = 12 per group). The experimental groups performed the programs 3 times per week for 2 months (24 sessions), whereas the control group only performed their regular soccer training. The performance tests carried out were: 10m speed tests with and without a ball, 20m single sprint, vertical jump, Wall-Volley and Illinois agility tests. The 11+ group demonstrated significant increases from pre-to-post time points in the vertical jump (3.7%), Wall- Volley (5.4%) and Illinois agility tests (1.7%), while the HarmoKnee group showed a significant increase in Wall-Volley test, with a 5.2% increase. The repeated measures analysis revealed differences between the groups (large effect size) in the 11+ and HarmoKnee groups, compared to the control group, in 10m speed tests with and without a ball, 20m single sprint and Illinois agility tests (p < 0.05). Thus 8-weeks performing the 11+ warm-up program can enhance jump height, agility and soccer skill while the HarmoKnee program generally only improves soccer skill in young professional male soccer players.
Key PointsThe 11+ improves performance by means of Illinois agility, vertical jump and Wall-Volley tests whereas HarmoKnee improves Wall-Volley test. Incorporating 11+ as a part of the warm-up program by the young teams would be beneficial in agility, leg power and soccer skill respectively.Further modification of both programs may be required to fully realize the players' speed performance potential.Data from this research can be helpful for soccer trainers in choosing programs to enhance performances in young male professional soccer players.
PMCID: PMC3772593  PMID: 24149156
Performance; vertical jump; Illinois agility test; sprint; Wall-Volley test
7.  Does an In-Season Only Neuromuscular Training Protocol Reduce Deficits Quantified by the Tuck Jump Assessment? 
Clinics in sports medicine  2011;30(4):825-840.
Female athletes are 4–6 times more likely to suffer an ACL injury than males in comparable sports. A link between landing biomechanics and ACL injury has led to the development of injury prevention focused training protocols. It is often difficult to measure the protocols’ efficacy of different protocols on reduction of ACL injury-related factors.
The purpose of this study was to test the effects of in-season neuromuscular training on a field-based evaluation used to help identify athletes at risk for ACL injuries. The hypothesis was that the ACL injury prevention training program included with an in-season soccer program would demonstrate increased improvement in the Tuck Jump Assessment (TJA) scores at post-season follow-up testing relative to standard in-season soccer training.
Forty-nine female soccer players were tested with TJA before and after participation in either in-season injury prevention training (IN) or standard in-season soccer training (CTRL). Participants were filmed performing the TJA with digital video cameras and scored by two separate raters, each viewing randomized videos. The groups received neuromuscular training synthesized from previous protocols demonstrated to decrease ACL injury. A mixed design (2X2; group by time) repeated measures ANOVA was used to test the interaction and main effects of group (ACL intervention training in-season vs. standard soccer in-season training) and time (pre vs. post-season) on dynamic TJA scores.
There was a significant main effect of time on TJA score (p=0.04) for athletes measured at pre- and post-season. The IN group reduced measured landing and jumping deficits from 5.4 ± 1.6 to 4.9 ± 1.0 points following training. CTRL showed a 14% reduction in TJA deficit points following the soccer season.
The tested hypothesis that the in-season ACL intervention training can be utilized to reduce measured TJA deficits above and beyond a standard in-season soccer protocol was not supported. Future research is warranted to determine if a combination of intensive pre-season and reduced in-season maintenance training is optimal for improvement of dynamic movement biomechanics during the TJA and ultimately preventing ACL injuries.
PMCID: PMC3200535  PMID: 22018323
Anterior cruciate ligament injury; knee; drop vertical jump landing; young athletes; Injury Risk Assessment; Neuromuscular training outcomes
8.  Energy Expenditure and Intensity of Physical Activity in Soccer Referees During Match-Play 
The aim of this study was to determine the caloric expenditure and the intensity of physical activities performed by official soccer referees during a match expressed in Metabolic Equivalent (METs). The physical activity of referees accredited by CBF (Brazilian Confederation of Soccer) was video-recorded during twenty-nine official games of Paraná Championship (Brasil), Series A and B of the 2005/2006. Computerized video analysis was used to determine the time spent in 6 locomotor activities (standing still, walking, jogging, backwards running, running and sprint). The frequency and duration of each activity were recorded and these data were utilized to calculate the distance covered by the referee. Energy expenditure values were estimated, utilizing specific equations, from the time players spent in each motor activity. The referees observed in this study had a mean age of 38.9 ± 3.8 years, body mass of 86.1 ± 7.1 kg, stature of 1.80 ± 0.07 m and a body mass index of 26.5 ± 0.6 kg·m-2. During match-play, referees covered an average distance of 9155.4 ± 70.3 meters (8411 - 9765), with a mean energy expenditure of 734.7 ± 65 kcal. This energy expenditure was significantly reduced in the second half: 359.9 ± 6.3 vs 374.7 ± 6.6 kcal (p = 0.006), and averaged to be moderate energy intensity (5 METs) with predominant utilization of the aerobic energy system. In total, during 67% of match-play the intensity was equal or lower than 3.8 METs and in 33% it was higher than 9.8 METs. The pattern of movement observed in the present study confirms that soccer refereeing may be considered as a highly intermittent exercise mode. The high to low-intensity activity ratio may be defined as 1:7.1. In conclusion, referees officiating in professional soccer matches in Brazil should perform a physical conditioning regime that provides the stamina required at this level and consume appropriate and adequate nutrition to meet the energetic demands for match-play.
Key pointsIn order to elaborate a diet that sufficiently restores the athlete’s energy expenditure during training and/or competition, the first step would be to measure energy expenditure during activity.We observed that during officials matches soccer referees perform physical aerobic activities of low and moderate intensity, and present a significant decline in energy expenditure between the first and second half.The pattern of movement observed in the present report confirms that soccer referees, like players undertake intermittent type exercise.Nutritional habits of soccer referees must be adapted to their daily physical activities, short training periods and moderate energy intensity physical activity, on average, during match refereeing.
PMCID: PMC3761902  PMID: 24149899
Motion-analysis; referee; football; METs; oxygen consumption
9.  The Effects of Interset Rest on Adaptation to 7 Weeks of Explosive Training in Young Soccer Players 
The aim of the study was to compare the effects of plyometric training using 30, 60, or 120 s of rest between sets on explosive adaptations in young soccer players. Four groups of athletes (age 10.4 ± 2.3 y; soccer experience 3.3 ± 1.5 y) were randomly formed: control (CG; n = 15), plyometric training with 30 s (G30; n = 13), 60 s (G60; n = 14), and 120 s (G120; n = 12) of rest between training sets. Before and after intervention players were measured in jump ability, 20-m sprint time, change of direction speed (CODS), and kicking performance. The training program was applied during 7 weeks, 2 sessions per week, for a total of 840 jumps. After intervention the G30, G60 and G120 groups showed a significant (p = 0.0001 – 0.04) and small to moderate effect size (ES) improvement in the countermovement jump (ES = 0.49; 0.58; 0.55), 20 cm drop jump reactive strength index (ES = 0.81; 0.89; 0.86), CODS (ES = -1.03; -0.87; -1.04), and kicking performance (ES = 0.39; 0.49; 0.43), with no differences between treatments. The study shows that 30, 60, and 120 s of rest between sets ensure similar significant and small to moderate ES improvement in jump, CODS, and kicking performance during high-intensity short-term explosive training in young male soccer players.
Key pointsReplacing some soccer drills by low volume high-intensity plyometric training would be beneficial in jumping, change of direction speed, and kicking ability in young soccer players.A rest period of 30, 60 or 120 seconds between low-volume high-intensity plyometric sets would induce significant and similar explosive adaptations during a short-term training period in young soccer players.Data from this research can be helpful for soccer trainers in choosing efficient drills and characteristics of between sets recovery programs to enhance performances in young male soccer players.
PMCID: PMC3990881  PMID: 24790481
Biological age; explosive strength; team sports; childhood; strength training
10.  The Relationship Between Imagery Type and Collective Efficacy in Elite and Non Elite Athletes 
This study investigated the relationship between imagery function and individual perceptions of collective efficacy as a function of skill level. Elite (n = 70) and non elite (n = 71) athletes from a number of interactive team sports completed the Sport Imagery Questionnaire (SIQ) and the Collective Efficacy Inventory (CEI). Multiple hierarchical regression analysis was then used to examine which SIQ sub-scales predicted individual perceptions of collective efficacy. For the elite sample, Motivational General-Mastery (MG-M) imagery accounted for approximately 17% of the variance in collective efficacy scores. No significant predictions were observed in the non elite sample. The findings suggest MG-M imagery as a potential technique to improve levels of collective efficacy although competitive level may moderate the effectiveness of such interventions.
Key pointsAs imagery is an individual intervention, an examination of individual perceptions of collective efficacy was most appropriate.Elite athletes who use more MG-M imagery also have higher individual perceptions of collective efficacy.For non-elite athletes, none of the imagery functions tested predicted individual perceptions of collective efficacy.Performance accomplishments provided by MG-M imagery may increase individual perceptions of collective efficacy.Future research should investigate further the effects of imagery intervention programmes on collective efficacy beliefs.
PMCID: PMC3786238  PMID: 24149327
Mental rehearsal; mental skills; team confidence; self efficacy; group dynamics
11.  Creatine monohydrate supplementation on lower-limb muscle power in Brazilian elite soccer players 
Studies involving chronic creatine supplementation in elite soccer players are scarce. Therefore, the aim of this study was to examine the effects of creatine monohydrate supplementation on lower-limb muscle power in Brazilian elite soccer players (n = 14 males) during pre-season training.
This was a randomized, double-blind, placebo-controlled parallel-group study. Brazilian professional elite soccer players participated in this study. During the pre-season (7 weeks), all the subjects underwent a standardized physical and specific soccer training. Prior to and after either creatine monohydrate or placebo supplementation, the lower-limb muscle power was measured by countermovement jump performance. The Jumping performance was compared between groups at baseline (p = 0.99). After the intervention, jumping performance was lower in the placebo group (percent change = - 0.7%; ES = - 0.3) than in the creatine group (percent change = + 2.4%; ES = + 0.1), but it did not reach statistical significance (p = 0.23 for time x group interaction). Fisher’s exact test revealed that the proportion of subjects that experienced a reduction in jumping performance was significantly greater in the placebo group than in the creatine group (5 and 1, respectively; p = 0.05) after the training. The magnitude-based inferences demonstrated that placebo resulted in a possible negative effect (50%) in jumping performance, whereas creatine supplementation led to a very likely trivial effect (96%) in jumping performance in the creatine group.
Creatine monohydrate supplementation prevented the decrement in lower-limb muscle power in elite soccer players during a pre-season progressive training.
PMCID: PMC4077550  PMID: 24991195
Football; Team sports; Dietary supplement; Jumping; Athletes
12.  Vitamin D and Exercise Performance in Professional Soccer Players 
PLoS ONE  2014;9(7):e101659.
The current study had two aims. The primary purpose was to examine the association between serum vitamin D levels and the ergometric evaluation of muscle strength, aerobic capacity, and speed in professional soccer players. The secondary aim was to evaluate the effects of the soccer off-season period on serum vitamin D levels.
Sixty-seven Caucasian male soccer players (age 25.6±6.2 and height 1.81±0.08 m), members of two Greek Superleague Soccer teams and one Football-league championship team participated in this study. Exercise performance testing for the determination of squat jump (SJ), countermovement jump (CMJ), 10 (10 m) and 20 meters (20 m) sprint performance, maximal oxygen consumption (VO2max), anthropometry, and blood sampling were performed before (pre) and after (post) the six-week off-season period.
Analysis of our results showed the following: (a) a significant correlations between serum vitamin D levels and performance parameters in both pre (SJ; P<0.001, CMJ; P<0.001, VO2max; P<0.001, 10 m; P<0.001, and 20 m; P<0.001) and post (SJ; P<0.001, CMJ; P<0.001, VO2max; P = 0.006, 10 m; P<0.001, and 20 m; P<0.001) experimental sessions. (b) Vitamin D concentration increased significantly (P<0.001) following the six-week off-season period compared to baseline, while at the same time all measured performance parameters decreased (SJ; P<0.001, CMJ; P<0.001, 10 m; P<0.001, 20 m; P<0.001, VO2max; P<0.001).
Our findings suggest that vitamin D levels are associated with the ergometric evaluation of muscle strength, as expressed by SJ and CMJ, sprinting capacity, and VO2max in professional soccer players, irrespective the levels of performance. Furthermore, our data reaffirm the importance of UVB on serum vitamin D levels. Moreover, reductions in exercise training stress may also have beneficial effects on vitamin D levels, suggesting a possible association of its levels and the training-induced stress. Our results indicate a possibly bidirectional interaction between soccer performance indices and vitamin D levels.
PMCID: PMC4081585  PMID: 24992690
13.  The cardiovascular profile of soccer referees: an echocardiographic study 
During a soccer game, the cardiovascular system is severely taxed The referees must be alert and their level of fitness must be such that fatigue will not impair their decision-making. Referee's peak overall performance is usually after 40 when the performance starts to decline. We evaluated the morphological and functional cardiac profile of professional soccer referees.
Materials and methods
We submitted to a clinical and echocardiographic exam a group of 120 professional soccer referees aged 25 – 45 years, including the first division of the Italian Championship, matched with 120 soccer players, including élite soccer players. Data were compared using an unpaired Student's t test. Statistical significance was with p < 0.05.
Right ventricle dimensions (22.2 ± 3.8 vs 25.9 ± 2.4 mm) and Left Ventricular Mass Index (LVMi) (100.5 ± 45.2 vs 105.4 ± 17.3) were significantly greater in referees than in active soccer players. Left atrium dimensions (33.7 ± 8.9 vs 36.2 ± 3.1 mm), aortic root (29.7 ± 7.9 vs 32.1 ± 3 mm) and LVMi (115.1 ± 16.7 vs 134.1 ± 19.9 g/m2) were significantly greater in élite soccer players than in first-division referees.
Our investigation shows that right ventricle is greater in referees than in soccer players. The differences (left atrium, aortic root and LVMi) between first division referees and élite soccer players may derive from the different training workloads.
PMCID: PMC2259300  PMID: 18269755
14.  A non-randomised experimental feasibility study into the immediate effect of three different spinal manipulative protocols on kicking speed performance in soccer players 
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.
PMCID: PMC4310142  PMID: 25635222
Chiropractic; Manipulation; Athletic performance; Soccer
15.  A Multilevel Approach to the Path to Expertise in Three Different Competitive Settings 
The objectives of the study were to analyze the deliberate practice variables in three different youth competitive sport settings; to analyze the effects of a season-long exposure on deliberate practice variables. The study explores three contexts in two different sports, soccer and volleyball, and at two competitive levels. The athletes fulfilled the questionnaire at the beginning and at the end of the season. A multilevel analysis was performed. Forty eight boys aged 15-17 years (14 from a volleyball club; 14 from an elite volleyball centre; 20 from a professional soccer club) participated in the study. The measure was an adapted version for soccer and volleyball of the Deliberate Practice Motivation Questionnaire, which assesses two dimensions: the will to compete and the will to excel. Fewer people in the volleyball group showed a will to excel, the soccer group showed an increase in the scores. In will to compete, the three teams showed a decrease in their means. The decrease is more pronounced in the will to excel but the context effect is not significant. The biggest decrease is shown by the elite volleyball team, followed by the club teams. The findings raise questions for managers and coaches who look for physical and technical gifted young athletes and aim to develop their qualities through a careful planned training programme. The insertion in programmes that are believed to foster expertise seems to have unexpected consequences. Sport participation cannot rely exclusively on an orientation toward expertise, forgetting the autonomy of young people to set their goals.
Key PointsThe need for the adolescents to focus on game performance can be a deterrent for their own perspectives of a career or just to have fun.The crucial factor to influence the players’ answers seems to be the perspective of a rewarding professional career in sport.It is possible that young athletes, after a hard season, re-evaluate their priorities and think that their dedication to sport did not fit their initial expectations.Managers and coaches should be aware of important pedagogical implications, and the effectiveness of sport participation cannot rely exclusively on an orientation toward expertise.
PMCID: PMC3918554  PMID: 24570621
Deliberate practice; multilevel; expertise; soccer; volleyball
16.  Cardiovascular Responses, Perceived Exertion and Technical Actions During Small-Sided Recreational Soccer: Effects of Pitch Size and Number of Players 
Journal of Human Kinetics  2013;38:95-105.
The aim of this study was to determine the cardiovascular, perceived exertion and technical effects of altering pitch size and number of players in recreational soccer match-play. The further aim was to evaluate to what extent exercise intensity during various game formats corresponds to the recommended intensity level for cardiovascular fitness improvement. Ten male recreational players aged 31.7±7.6 years (mean ± SD) completed four variations of small-sided games (except for goalkeepers, 5-a-side and 7-a-side on small and large pitches) during which heart rate, perceived exertion and technical actions were evaluated. Two-way analysis of variance on repeated measures was applied to collected data. The results indicated that an average workload expressed as heart rate and percentage of heart rate reserve during 5-a-side games was higher than for 7-a-side games. The rate of perceived exertion values were moderate and similar for all formats of games. The players performed more dribbling and successful passes, but fewer unsuccessful passes during 5-a-side games. Furthermore, the number of ball possessions and unsuccessful passes was higher on a small pitch than on a large one. Consequently, the current findings suggest that, independent of pitch size, the cardiovascular demands imposed on participants increase when the game is played with fewer players. However, all formats of recreational soccer can be used as an effective activity to promote cardiovascular fitness. Finally, participants may have more chance to perform basic technical actions during 5-a-side games on small and large pitches.
PMCID: PMC3827765  PMID: 24233236
Exercise intensity; heart rate; rate of perceived exertion; notation analysis; recreational soccer
17.  Association of Short-Passing Ability with Athletic Performances in Youth Soccer Players 
This study was designed to examine the relationship between multiple short-passing ability [measured using the Loughborough Soccer Passing Test (LSPT)] and athletic performances in youth soccer players.
Forty-two young soccer players (age 14.8±0.4years) performed the LSPT, the squat-jump (SqJ), the counter movement jump (CMJ), the 30m sprints (with 5m and 20m split times also recorded), the 15m agility run (Agility-15m), the 15m ball dribbling (Ball-15m), the Illinois agility test (IAGT) and the Yo-Yo IRT Level 1 tests.
LSPT total performance (LSPT TP) showed significant positive correlation with 5m, 20m, and 30m sprint times, Agility-15m, Ball-15m and Illinois agility test (r=0.60, r=0.58, r=0.49, r=0.75, r=0.71 and r=0.72; P<0.01, respectively). Significant negative correlation were found between LSPT TP and SqJ and CMJ (r=−0.62 and r=−0.64; P<0.01, respectively). It was determined that Agility-15m, Illinois agility test and Ball-15m were the most effective factors associated with LSPT TP among other factors in multiple regression analysis.
This study showed that LSPT TP of young elite soccer players is determined by their agility abilities, thus enabling this test to be used for talent identification purposes.
PMCID: PMC3685159  PMID: 23785575
Technical Skills; Agility; Cognitive Function; Physical Fitness; Football
18.  The Effects of Injury Preventive Warm-Up Programs on Knee Strength Ratio in Young Male Professional Soccer Players 
PLoS ONE  2012;7(12):e50979.
We aimed to investigate the effect of FIFA 11+ (11+) and HarmoKnee injury preventive warm-up programs on conventional strength ratio (CSR), dynamic control ratio (DCR) and fast/slow speed ratio (FSR) in young male professional soccer players. These ratios are related to the risk of injury to the knee in soccer players.
Thirty-six players were divided into 3 groups; FIFA 11+, HarmoKnee and control (n = 12 per group). These exercises were performed 3 times per week for 2 months (24 sessions). The CSR, DCR and FSR were measured before and after the intervention.
After training, the CSR and DCR of knee muscles in both groups were found to be lower than the published normal values (0.61, 0.72, and 0.78 during 60°.s−1, 180°.s−1 and 300°.s−1, respectively). The CSR (60°.s−1) increased by 8% and FSR in the quadriceps of the non-dominant leg by 8% in the 11+. Meanwhile, the DCR in the dominant and non-dominant legs were reduced by 40% and 30% respectively in the 11+. The CSR (60°.s−1) in the non-dominant leg showed significant differences between the 11+, HarmoKnee and control groups (p = 0.02). As for the DCR analysis between groups, there were significant differences in the non-dominant leg between both programs with the control group (p = 0.04). For FSR no significant changes were found between groups.
It can be concluded that the 11+ improved CSR and FSR, but the HarmoKnee program did not demonstrate improvement. We suggest adding more training elements to the HarmoKnee program that aimed to enhance hamstring strength (CSR, DCR and FSR). Professional soccer players have higher predisposition of getting knee injuries because hamstring to quadriceps ratio were found to be lower than the average values. It seems that the 11+ have potentials to improve CSR and FSR as well as prevent knee injuries in soccer players.
PMCID: PMC3513304  PMID: 23226553
19.  A comparison of the physiological profiles of elite Gaelic footballers, hurlers, and soccer players 
Background: Gaelic football, soccer, and hurling are prominent field games in Ireland and involve participants undertaking a variety of playing tasks and skills which place various physiological demands on the participants. The aim of this study was to evaluate and compare the mid-season physiological profiles of elite players.
Methods: Physiological assessment was carried out on 29 inter-county Gaelic footballers, 30 inter-county hurlers, and 21 League of Ireland soccer players.
Results: Significant differences were reported for % body fat (p<0.05), aerobic capacity (p<0.05), flexibility (p<0.05), upper body strength (p<0.05), upper body strength endurance (p<0.05), abdominal endurance (p<0.05), and speed endurance (p<0.05), while there were no differences recorded for height, weight, or speed levels. A relatively heterogeneous body size is evident for all three sports. Soccer players had lower body fat levels, greater aerobic capacity, greater strength endurance, and greater flexibility compared to both Gaelic footballers and hurlers, possibly due to specific training and conditioning programmes or physical adaptation to match play The greater strength of both Gaelic footballers and hurlers and the superior speed endurance levels of Gaelic footballers also reflect the physical nature of the sports. Similar speed levels amongst all three sports reflect the importance of speed for performance.
Conclusions: The various physiological attributes for Gaelic football, soccer, and hurling reflect the physical requirements for success and participation in each of these field games.
PMCID: PMC1725248  PMID: 15976166
20.  The Role of Situational Variables in Analysing Physical Performance in Soccer 
Journal of Human Kinetics  2012;35:89-95.
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.
PMCID: PMC3588697  PMID: 23487326
fatigue; soccer; physical performance; situational variables
21.  An emerging paradigm: a strength-based approach to exploring mental imagery 
Mental imagery, or the ability to simulate in the mind information that is not currently perceived by the senses, has attracted considerable research interest in psychology since the early 1970's. Within the past two decades, research in this field—as in cognitive psychology more generally—has been dominated by neuroscientific methods that typically involve comparisons between imagery performance of participants from clinical populations with those who exhibit apparently normal cognitive functioning. Although this approach has been valuable in identifying key neural substrates of visual imagery, it has been less successful in understanding the possible mechanisms underlying another simulation process, namely, motor imagery or the mental rehearsal of actions without engaging in the actual movements involved. In order to address this oversight, a “strength-based” approach has been postulated which is concerned with understanding those on the high ability end of the imagery performance spectrum. Guided by the expert performance approach and principles of ecological validity, converging methods have the potential to enable imagery researchers to investigate the neural “signature” of elite performers, for example. Therefore, the purpose of this paper is to explain the origin, nature, and implications of the strength-based approach to mental imagery. Following a brief explanation of the background to this latter approach, we highlight some important theoretical advances yielded by recent research on mental practice, mental travel, and meta-imagery processes in expert athletes and dancers. Next, we consider the methodological implications of using a strength-based approach to investigate imagery processes. The implications for the field of motor cognition are outlined and specific research questions, in dynamic imagery, imagery perspective, measurement, multi-sensory imagery, and metacognition that may benefit from this approach in the future are sketched briefly.
PMCID: PMC3612690  PMID: 23554591
expertise; mental imagery; metacognition; motor cogniton; converging methods; mental practice; mental travel; mental rotation
22.  Motor Imagery and Tennis Serve Performance: The External Focus Efficacy 
There is now ample evidence that motor imagery (MI) contributes to enhance motor performance. Previous research also demonstrated that directing athletes’ attention to the effects of their movements on the environment is more effective than focusing on the action per se. The present study aimed therefore at evaluating whether adopting an external focus during MI contributes to enhance tennis serve performance. Twelve high-level young tennis players were included in a test-retest procedure. The effects of regular training were first evaluated. Then, players were subjected to a MI intervention during which they mentally focused on ball trajectory and specifically visualized the space above the net where the serve can be successfully hit. Serve performance was evaluated during both a validated serve test and a real match. The main results showed a significant increase in accuracy and velocity during the ecological serve test after MI practice, as well as a significant improvement in successful first serves and won points during the match. Present data therefore confirmed the efficacy of MI in combination of physical practice to improve tennis serve performance, and further provided evidence that it is feasible to adopt external attentional focus during MI. Practical applications are discussed.
Key PointsMotor imagery contributes to enhance tennis serve performance.Data provided evidence of the benefits of adopting an external focus of attention during imagery.Results showed significant improvement in successful first serves and won points during a real match.
PMCID: PMC3761826  PMID: 24149813
Movement imagery; motor performance; focus of attention; safety window
23.  The Relative Age Effect in Youth Soccer Players from Spain 
The purpose of this study was to identify the existence of Relative Age Effect (RAE) at youth level in both elite and amateur Spanish soccer clubs, and also to carry out an analysis providing with information on how this effect has evolved in recent years. We have obtained information on the youth teams of the 20 clubs belonging to the Spanish Professional Football League (LFP) in two separate seasons (2005-2006 and 2008-2009) as well as data on five youth academies belonging to amateur clubs. The collected data revealed an over- representation of players born in the first months of the selection year in all groups of analysis (Elite 2005-2006, Elite 2008-2009 and Amateurs), although only the Elite groups showed significant variations in birth-date distribution in relation to the Spanish population. The results showed a reduction in RAE from the 2005-2006 season to the 2008-2009 season. The following variables - playing position, the number of years each player has spent in their specific age group and the category of the team at each club were shown not to have influence on the extent of RAE.
Key pointsThere was RAE in all groups analyzed, although only the Elite groups showed significant variations in birth-date distribution in relation to the general population.RAE is more evident in the Elite groups than in the Amateur probably because of the detection process, which is more thorough in the Elite groups.Playing position, number of years in their specific age group and category of the team did not have any influence on the extent of RAE.Any attempts to prevent RAE should be based on a stable sport policy and the implication of all the stakeholders in the system. All of them should think in the development of a player as a long-term project.
PMCID: PMC3761747  PMID: 24149685
Relative age effect; season-of-birth bias; selection processes; talent identification; youth soccer
24.  Effectiveness of an injury prevention programme for adult male amateur soccer players: a cluster-randomised controlled trial 
British Journal of Sports Medicine  2012;46(16):1114-1118.
The incidence rate of soccer injuries is among the highest in sports, particularly for adult male soccer players.
To investigate the effect of the ‘The11’ injury prevention programme on injury incidence and injury severity in adult male amateur soccer players.
Study design
Cluster-randomised controlled trial.
Teams from two high-level amateur soccer competitions were randomly assigned to an intervention (n=11 teams, 223 players) or control group (n=12 teams, 233 players). The intervention group was instructed to perform The11 in each practice session during one soccer season. The11 focuses on core stability, eccentric training of thigh muscles, proprioceptive training, dynamic stabilisation and plyometrics with straight leg alignment. All participants of the control group continued their practice sessions as usual.
In total, 427 injuries were recorded, affecting 274 of 456 players (60.1%). Compliance with the intervention programme was good (team compliance=73%, player compliance=71%). Contrary to the hypothesis, injury incidences were almost equal between the two study groups: 9.6 per 1000 sports hours (8.4–11.0) for the intervention group and 9.7 (8.5–11.1) for the control group. No significant differences were found in injury severity, but a significant difference was observed in the location of the injuries: players in the intervention group sustained significantly less knee injuries.
This study did not find significant differences in the overall injury incidence or injury severity between the intervention and control group of adult male soccer players. More research is recommended, focusing on injury aetiology and risk factors in adult male amateur soccer players.
PMCID: PMC3596860  PMID: 22878257
25.  Watch me if you can: imagery ability moderates observational learning effectiveness 
Recent research has revealed similarities in brain activity during observational learning and motor execution. However, whilst action develops visual, motor and afferent representations during acquisition, action-observation has been proposed to only develop visual-spatial learning via visual representation. In addition, it has been suggested that the vividness of visual representations are determined by imagery ability. Thus, the purpose of the current investigation was to explore the possible moderating role of imagery ability in the effectiveness of observational learning. Participants (n = 40) were assessed on their imagery ability via the Vividness of Movement Imagery Questionnaire-2 (VMIQ-2) and then assigned to one of four groups; high imagery ability and observational learning (HIA-OL), low imagery ability and observational learning (LIA-OL), high imagery ability control (HIA-C) and low imagery ability control (LIA-C). Following group allocation all participants performed a pre-test consisting of five actual practice trials of a novel gymnastics routine. The HIA-OL and LIA-OL groups then participated in a 14 day observational learning intervention whilst the HIA-C and LIA-C groups acted as controls. Following this, participants performed a post test, which was identical in nature to the pre-test, before finally completing the VMIQ-2 again. Performance on both the pre-test and post test was evaluated by two qualified gymnastics judges. Results revealed that gymnastics performance increased from pre-test to post test for both the HIA-OL and LIA-OL groups. However, this effect was greater in the HIA-OL group suggesting that the relationship between observational learning and successful imitation performance is moderated by imagery ability.
PMCID: PMC3763482  PMID: 24046736
action observation; skill acquisition; motor learning; gymnastics; form tasks

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