Effects of combined strength and kick coordination training on soccer kick biomechanics in amateur players

The aim of this study was to examine the effect of a soccer (strength and technique) training program on kinematics and electromyographic (EMG) muscle activity during a instep kick. Ten amateur soccer players (aged 19.9+/-0.4 years, body mass 74.8+/-9.1 kg, height 177.4+/-6.7 cm) constituted the experimental group (EG) whereas 10 players (age 21.6+/-1.3 years, weight 71.5+/-6.7 kg, height 175.2+/-3.4 cm) served as controls (CG). The EG followed a 10-week soccer-specific training program combining strength and technique exercises. All participants performed an instep soccer kick using a two-step approach while three-dimensional data and EMG from six muscles of swinging and support legs were recorded prior to and after training. Maximum isometric leg press strength, 10-m sprint performance and maximum speed performance on a bicycle ergometer were also measured. Analysis of variance designs with repeated measures showed that the EG improved significantly (P<0.05) maximum ball speed, the linear velocity of the foot, ankle and angular velocity of all joints during the final phase of the kick. Training had insignificant effects on EMG values, apart from an increase in the averaged EMG of the vastus medialis whereas maximum isometric strength and sprint times significantly improved after training (P<0.05). The present results suggest that the application of the training programs using soccer-specific strength exercises would be particularly effective in improving of soccer kick performance.     

Comparison of standing balance between female collegiate dancers and soccer players

STUDY DESIGN: This study was designed as a comparison study of two cohorts. OBJECTIVES: The hypothesis of this study was that soccer players and dancers have different balance abilities and that these differences could be objectively measured using center of pressure measurements. BACKGROUND: Center of pressure (COP) measurements are reproducible and have been validated in the literature for assessing standing balance. The literature does not provide sensitive enough techniques for discriminating between two groups of athletes with excellent standing balance. METHODS AND MEASURES: A Matscan pressure mat (Tekscan, Boston, MA) was used to compare COP change variability between 32 female collegiate soccer players and 32 dancers. COP was used to calculate sway index, center acquisition time, sway path length and sway velocity as measures of standing balance. RESULTS: The dancers had significantly better balance scores (p<0.05) in 5 of 20 balance tests. Results for the remaining 15 balance tests were not significantly different. CONCLUSION: These data show that standing balance characteristics of dancers and soccer players can be objectively measured using COP data. Dancers have certain standing balance abilities that are better than those of soccer players. The COP measurements in this study can be used as a tool in future studies investigating standing balance in different groups of athletes.     

Dynamic balance is impaired after a match in young elite soccer players

PurposeThe aim of this study is to assess the effect of actual match effort on dynamic balance abilities in young elite soccer players.MethodsSeventeen Under 15 male players who compete at national level participated in the study. Their dynamic balance was assessed by having them jump starting with both feet on the ground in a standing position and land on one foot only. Their vertical time to stabilization (vTTS) and postural sway were calculated before and after 35 min of an unofficial match. Postural sway was assessed on the basis of center-of-pressure (COP) trajectories. Parameters considered were sway area, COP displacements in the antero-posterior (AP) and medio-lateral (ML) directions and COP path length.ResultsAfter the match, a significant increase in vTTS (p = 0.007) COP path length (p = 0.001) and COP displacements in ML (p < 0.001) was observed. Such effects involve both non-dominant (vTTS, path length) and dominant limb (COP displacements).ConclusionsThe physical effort associated with the match induces significant impairments of players' dynamic balance abilities. On the basis of such findings, coaches might consider integrating training sessions with specific balance exercises as well as performing injury-prevention routines even when players are fatigued, to better adapt them to match conditions.     

Knee isokinetic muscle strength and balance ratio in female soccer players of different age groups: a cross-sectional study

ABSTRACT

Background: As a consequence of years of soccer training and sexual maturation, there is an increase in lower body muscle mass and strength especially in the knee extensors and flexors muscles. In this context, the lack of knee joint stability, resulting from strength imbalance between knee extensor and flexors muscles, has been associated with knee injuries. The aim of this study was to compare the knee flexor and extensor muscle peak torque, average power, contralateral deficit, conventional and functional balance ratios of female soccer players from different age groups.

Methods: Sixty-six female soccer players were divided into four groups: under 13 (U13), under 15 (U15), under 17 (U17) years old and professional (PRO). Flexor and extensor knee muscle strength in concentric and eccentric actions of both limbs were assessed using isokinetic dynamometer.

Results: For the dominant limb, the knee concentric extensor muscles peak torques, assessed at 60 and at 240 deg/sec, and the average power of U15 group were significantly higher than U13 group. Extensor muscle average power of the PRO group was higher than U17. Dominant knee flexor average power of U15 was significantly higher than the U13 group. Peak torque at 60 deg/sec and 240 deg/sec and average power of the PRO group were higher than the U17 group. No differences were found regarding the eccentric action for flexor and extensor muscles. Conventional and functional balance ratios were similar among all age group, except for U13, which presented higher values than the U15 group for the dominant limb.

Conclusions: The greatest improvement in muscular performance occur when the athlete starts practicing soccer (after U13) and when they become professional (after U17) and the balance ratios, and muscle balance ratios remain stable in all age groups, although they are below the recommended level in the literature, which may increase the risk for lower limb injury.     

Isokinetic strength training program for muscular imbalances in professional soccer players

The aim of the study was to investigate the effect of a muscular training program on soccer players’ performance of which initially appeared imbalances or deficits. The study was conducte on 68 professional soccer players (age, 24.1±5.7 years; weight, 76.8±5.7 kg; height, 1.82±7 cm) participating in the championship of the first Greek national division over 2 years. During the preparation period, all the players performed an isokinetic test of knee flexors and extensors (60° s⁻¹ and 180° s⁻¹). These initial measurements detected muscular imbalances or deficits in 27 players (40%). The 27 players followed a specific isokinetic training program for 2 months, 3 times per week. After completion of the isokinetic training program, the 68 players repeated the isokinetic test. The analysis revealed significant differences between the pre-and post-training measures at both angular velocities in peak torque values, in differences from one limb to the other, and in peak torque ratios for flexors and extensors. Consequently, the application of this specific isokinetic training program can restore imbalances in knee muscle strength efficiently.     

Tibia and fibula fractures in soccer players

We performed a retrospective review of 31 athletes who sustained a fracture of the lower leg from a direct blow while playing soccer. Fifteen fractures involved both the tibia and fibula, 11 only the tibia, and 5 only the fibula. Information was collected using a standardized questionnaire. The mean follow-up from the time of injury was 30 months. Injuries typically occurred in young, competitive athletes during game situations. The mechanisms were broadly classified into several categories: contact during a slide tackle (13, 42%), a collision with the goalkeeper (8, 26%), two opposing players colliding while swinging for a loose ball (7, 23%), or a player being kicked by a standing opponent (3, 10%). The majority of fractures (26, 90%) occurred while the athletes were wearing shin guards. The point of impact was with the shin guard prior to the fracture in 16 cases (62%). Return to competitive soccer averaged 40 weeks for combined tibia and fibula fractures, 35 weeks for isolated tibia fractures, and 18 weeks for isolated fibula fractures. Injuries were associated with a high incidence of major complications (12 out of 31, 39%), especially in concurrent tibia and fibula fractures (8 out of 15, 50%). These findings suggest that lower leg fractures in soccer players are serious injuries, often necessitating a prolonged recovery time. In addition, this study questions the ability of shin guards to protect against fractures. Received: 1 March 1998 Accepted: 10 August 1998     

Injury prevention behaviour in community-level soccer players

Objective: To adapt and pilot test a method for undertaking routine surveillance of injury prevention behaviour in community-level soccer. Design: Surveillance system using a cohort design. Methods: Simple random samples were drawn from the player registration databases of two soccer federations. All players aged 13 years or over who intended to play in a school or club competition during the 2006 winter season were eligible. The cohort consisted of 687 male and 193 female players. The players were contacted each week and asked about their adherence to nationally recommended injury prevention measures. Results: No more than 20% of players completed any form of pre-season screening. Almost all players warmed-up for player-matches (97%) and player-training sessions (93%). Eighty-one percent of players undertook some form of physical conditioning on at least one occasion in the off-season. Very few players (13%) reported receiving instruction on tackling technique pre-season. Shin-guards were worn in 99% of matches. For 61% of match injury events, the injured player continued to play after the injury occurred and in 65% of these cases, the player reported that in hindsight they should not have returned to play. Conclusions: The results provide a baseline measure of injury prevention behaviour in community-level soccer players. Future research, employing comparable surveillance methods, could be used to monitor progress on adherence to the injury prevention measures canvassed in this study.     

Postural balance impairment in Tunisian second division soccer players with groin pain: A case-control study

ObjectiveTo compare postural balance outcomes between soccer players with and without groin pain (GP).DesignCase-control study.SettingLaboratory.ParticipantsFifty-four soccer players, 27 with GP (GP group: GPG) and 27 healthy ones (control group: CG).Main outcome measuresStatic and dynamic postural balance were assessed with a force platform and Y-balance test (Y-BT), respectively. Hip abduction, internal rotation (IR), external rotation (ER) and total rotation (TR) of both limbs were evaluated.ResultsThe GPG exhibited significant higher centre of pressure values in the bipedal posture only on the foam surface in eyes opened and closed compared to controls. Besides, they had lower anterior, posteromedial and posterolateral reach distances and composite Y-BT score on the injured limb (IL) compared to non-injured limb (NIL) and dominant-limb (DL) of the CG. Moreover, they showed lower abduction, IR, ER, and TR on the IL compared to NIL and DL.ConclusionsDynamic unipedal postural balance disorder could be one of the limiting factors of performance in soccer players with non-time loss GP. Hence, postural balance data in these players could enable sport coaches and physical therapists to better understand the mechanisms contributing for performance decrease.     

Modelling developmental changes in repeated-sprint ability by chronological and skeletal ages in young soccer players

This study investigated the influence of chronological (CA) and skeletal ages (SA), anthropometry, aerobic endurance and lower limb explosive strength on developmental changes in repeated-sprint ability (RSA) in soccer players aged 11-17 years. Participants were annually followed over 5 years, resulting in 366 measurements. Multilevel regression modelling analysed longitudinal data aligned by CA and SA (Model 1 and 2, respectively). After diagnosing for multicollinearity, it was possible to predict RSA with 2-level hierarchical models [Model 1 (CA as Level 2 predictor): Log-Likelihood=1?515.29, p<0.01; Model 2 (SA as Level 2 predictor): Log-Likelihood=1?513.89, p<0.01]. Estimating sum of sprints for young soccer players are given by equations: sum of sprints=84.47?-?1.82×CA?+?0.03×CA2?-?0.05×aerobic endurance?-?0.10×lower limb explosive strength -?0.09×fat-free mass?+?0.13×fat mass (Model 1); 73.58?-?0.43×SA?-?0.05×aerobic endurance?-?0.10×lower limb explosive strength?-?0.08×fat-free mass?-?0.45×training experience?+?0.13×fat mass (Model 2). The models produced performance curves that may be used to estimate individual performance across adolescent years. Finally, the validity of each model was confirmed based on corresponding measurements taken on an independent cross-sectional sample.     

Explosive strength in female 11-on-11 versus 7-on-7 soccer players

Lower limbs strength capacity in female soccer players is poorly addressed. The aim of this study was to evaluate explosive strength in 7-on-7 (7FP) and 11-on-11 (11FP) female players and its possible changes at 3 different checkpoints of the competitive season. Thirteen 11FP of mean age 22.0 years) and twenty-six 7FP (of mean age 23.6 years) were enrolled. Vertical jump capacity was determined by means of squat jump (SJ) and counter movement jump (CMJ) tests in 3 different periods (September 2005, December 2005, April 2006). No significant differences were observed in SJ elevation or CMJ elevation between the two groups at any time point, and there were no significant changes over time. However, 7FPs tended to have higher explosive performance during SJ compared to 11FPs, and they had a significantly lower elastic recoil index at all three evaluations. This may be due to the characteristics of 7-on-7 soccer, in which the neuromuscular and explosive strength demands are higher than those of 11-on-11 soccer. Such requirements, though increasing muscular explosive performance, also increase the rigidity of the lower limb extensor apparatus.     

Plantar pressure asymmetry and risk of stress injuries in the foot of young soccer players

BackgroundAsymmetries in the magnitude of plantar pressure are considered a risk factor for stress fracture of the fifth metatarsal in soccer athletes.ObjectiveTo investigate the presence of plantar pressure asymmetries among young soccer athletes.DesignObservational.SettingLaboratory.ParticipantsThirty young adolescents divided into a soccer player group (n = 15) or a matched control group (n = 15).Main outcome measuresMean plantar pressure was determined for seven different regions of the foot. Data were compared between the preferred and non-preferred foot, and between the groups, during barefoot standing on a pressure mat system.ResultsHigher pressure was found in the hallux, 5th metatarsal and medial rearfoot of the non-preferred foot in the young soccer players. These asymmetries were not observed in the control group. Magnitudes of plantar pressure did not differ between the groups.ConclusionYoung soccer players present asymmetries in plantar pressure in the hallux, 5th metatarsal and medial rearfoot, with higher pressure observed in the non-preferred foot.     

Determinants of concussion diagnosis,symptomology, and resolution time in U.S. high school soccer players

ABSTRACT

Determinants of concussion diagnosis, symptomology, and other sequelae have not been examined in high school soccer players. Using a sample of soccer-related head/neck injuries from the NATION Surveillance Program, we evaluated potential determinants (sex, injury history, injury mechanism, setting) of concussion characteristics. A total of 378 head/neck injuries were recorded, and 189 (50.0%) injuries from this sample, resulted in a concussion diagnosis. Odds of concussion diagnosis were 84% higher among female players compared with their male counterparts, and over two-fold higher in game settings compared with practice settings. We also observed several significant symptom dependencies, such as higher odds of difficulty concentrating (OR = 5.84, 95% CI = [2.99, 11.42]) given concurrent light sensitivity. Furthermore, we identified injury mechanism as a determinant of concussion symptom resolution time. Our results suggest that determinants of soccer-related concussions and their sequelae are multifactorial, and extend the existing literature with the potential to inform clinical practice.