Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players

Effects of an electrostimulation training program on strength, jumping, and kicking capacities in soccer players

The present study investigated the influence of a 5-week electrostimulation (EMS) training program on muscular strength, kicking velocity, sprint, and vertical jump performance in soccer players. Twenty amateur soccer players participated in the study, 10 in the electrostimulated group and the remaining 10 in a control group. Electrostimulation was applied on the quadriceps muscles over 5 weeks. Subjects were tested before, during (wk-3), and after (wk-5) the EMS training program. Maximal voluntary contraction using different contraction mode (i.e., eccentric, concentric, and isometric), vertical jump height, sprint running for 10 m, and ball speed were examined. We observed an increase in isometric and eccentric maximal knee extension torques and also a gain in ball speed performance without run up at wk-3. After 5 weeks of EMS training, eccentric, isometric, and concentric torques and ball speed had significantly improved. It appeared appropriate to conduct EMS training during at least 3 weeks to observe beneficial effects in specific soccer skills such as ball speed.

Positional role and competitive-level differences in elite-level men's basketball players

The purpose of the present study was to compare the physical attributes of elite men's basketball players according to age and specific individual positional roles. Forty-five players from 3 national basketball teams (Under-18 years, Under-20 years, and Senior) were measured for anthropometry (height, body mass, percentage body fat), explosive power (5 jumps and vertical jump), speed (5-m, 10-m, and 30-m sprint), agility (T-test), strength (bench press and squat 1 repetition maximum [1RM]), and intermittent high-intensity endurance performance (Yo-Yo intermittent recovery test [Yo-Yo IR1]). Data on match frequency, training routines, and playing experience were also collected. Under-18 players were significantly (p < 0.05) shorter and lighter than both Senior and Under-20 players but showed higher (p < 0.05) percentage body fat. Under-20 and Senior players were faster and had better explosive-power and agility (p < 0.05) performances than Under-18 players. Bench press and squat 1RMs were higher in Senior players (p < 0.05) compared with the other groups. There were significant difference in the Yo-Yo IR1 performance among groups (Senior > Under-20 > Under-18, p < 0.05). Centers and power forwards were the tallest and the heaviest (p < 0.05). The Yo-Yo IR1 performance was higher (p < 0.01) in point guards than in centers. Point guards showed also better agility and 5- and 10-m performances. Power forwards and centers were stronger than the rest of players' positions in the bench press 1RM (p < 0.01). These results showed the existence of age and positional role differences in fitness performance in men's basketball. Differences were particularly evident in intermittent high-intensity endurance and agility performance. Sprint training possibly should be individualized when dealing with positional roles in elite men's basketball. Strength and conditioning coaches should use Yo-Yo IR1 to assess specific endurance in players of different age and positional role.

Performance and physiological responses to repeated-sprint and jump sequences

In this study, the performance and selected physiological responses to team-sport specific repeated-sprint and jump sequence were investigated. On four occasions, 13 team-sport players (22 ± 3 year) performed alternatively six repeated maximal straight-line or shuttle-sprints interspersed with a jump ([RS(+j), 6 × 25 m] or [RSS(+j), 6 × (2 × 12.5 m)]) or not ([RS, 6 × 25 m] or [RSS, 6 × (2 × 12.5 m)]) within each recovery period. Mean running time, rate of perceived exertion (RPE), pulmonary oxygen uptake (V(O)₂), blood lactate ([La](b)), and vastus lateralis deoxygenation ([HHb]) were obtained for each condition. Mean sprint times were greater for RS(+j) versus RS (4.14 ± 0.17 vs. 4.09 ± 0.16 s, with the qualitative analysis revealing a 82% chance of RS(+j) times to be greater than RS) and for RSS(+j) versus RSS (5.43 ± 0.18 vs. 5.29 ± 0.17 s; 99% chance of RSS(+j) to be >RSS). The correlation between sprint and jump abilities were large-to-very-large, but below 0.71 for RSSs. Jumps increased RPE (Cohen's d ± 90% CL: +0.7 ± 0.5; 95% chance for RS(+j) > RS and +0.7 ± 0.5; 96% for RSS(+j) > RSS), V(O)₂(+0.4 ± 0.5; 80% for RS(+j) > RS and +0.5 ± 0.5; 86% for RSS(+j) > RSS), [La](b) (+0.5 ± 0.5; 59% for RS(+j) > RS and +0.2 ± 0.5; unclear for RSS(+j) > RSS), and [HHb] (+0.5 ± 0.5; 86% for RS(+j) > RS and +0.5 ± 0.5; 85% for RSS(+j) > RSS). To conclude, repeated- sprint and jump abilities could be considered as specific qualities. The addition of a jump within the recovery periods during repeated-sprint running sequences impairs sprinting performance and might be an effective training practice for eliciting both greater systemic and vastus lateralis physiological loads.

A mathematical model of neuromuscular adaptation to resistance training and its application in a computer simulation of accommodating loads

A large corpus of data obtained by means of empirical study of neuromuscular adaptation is currently of limited use to athletes and their coaches. One of the reasons lies in the unclear direct practical utility of many individual trials. This paper introduces a mathematical model of adaptation to resistance training, which derives its elements from physiological fundamentals on the one side, and empirical findings on the other. The key element of the proposed model is what is here termed the athlete's capability profile. This is a generalization of length and velocity dependent force production characteristics of individual muscles, to an exercise with arbitrary biomechanics. The capability profile, a two-dimensional function over the capability plane, plays the central role in the proposed model of the training-adaptation feedback loop. Together with a dynamic model of resistance the capability profile is used in the model's predictive stage when exercise performance is simulated using a numerical approximation of differential equations of motion. Simulation results are used to infer the adaptational stimulus, which manifests itself through a fed back modification of the capability profile. It is shown how empirical evidence of exercise specificity can be formulated mathematically and integrated in this framework. A detailed description of the proposed model is followed by examples of its application-new insights into the effects of accommodating loading for powerlifting are demonstrated. This is followed by a discussion of the limitations of the proposed model and an overview of avenues for future work.

Can common measures of core stability distinguish performance in a shoulder pressing task under stable and unstable conditions?

The primary purpose of this study was to determine whether a range of static core stability (CS) measures could distinguish shoulder press performance in unstable vs. stable conditions. Thirty resistance-trained men gave informed consent to participate in this study. One-repetition maximum strength (from < 6 repetitions) was predicted in the seated shoulder dumbbell press performed in unstable (Swiss ball[SB]) and stable (back-support bench) environments. Three CS muscle endurance tests were performed, with 4 CS ratios also calculated. The degree of strength decrement, referred to as the instability strength level (ISL), was calculated by dividing the predicted 1RM Unstable score by the 1RM Stable score. All subjects were categorized as high (ISL > 0.90), moderate (0.85 < or = ISL < or = 0.90), or low (ISL < 0.85). Between-group differences for the high- and low-ISL groups were assessed using analysis of variance and effect sizes. Pearson product moment correlations were then performed to examine the relationships between the CS measures and the ISL for the entire group. No significant between-group differences (p = 0.132-0.999) or large effect sizes were observed for any of the CS measures. Trunk flexion endurance was the only CS measure significantly correlated to the ISL (r = 0.477). In line with muscular strength research, these results suggest that CS exhibits relatively high levels of task specificity and that CS performance in static single-joint exercises may not be highly related to that in more dynamic multijoint activities. Core stability training (with or without a SB) may therefore only lead to significant improvements in functional dynamic performance if the postures, mode and velocity of contraction performed in training, are similar to the competitive tasks.

Relationship between strength characteristics and unweighted and weighted vertical jump height

PURPOSE

To investigate the relationship between maximum strength and differences in jump height during weighted and unweighted (body weight) static (SJ) and countermovement jumps (CMJ).

METHODS

Sixty-three collegiate athletes (mean +/- SD; age= 19.9 +/- 1.3 y; body mass = 72.9 +/- 19.6 kg; height = 172.8 +/- 7.7 cm) performed two trials of the SJ and CMJ with 0 kg and 20 kg on a force plate; and two trials of mid-thigh isometric clean pulls in a custom rack over a force plate (1000-Hz sampling). Jump height (JH) was calculated from flight time. Force-time curve analyses determined the following: isometric peak force (IPF), isometric force (IF) at 50, 90, and 250 ms, and isometric rates of force development (IRFD). Absolute and allometric scaled forces, [absolute force/(body mass(0.67))], were used in correlations.

RESULTS

IPF, IRFD, F50(a), F50, F90, and F250 showed moderate/strong correlations with SJ and CMJ height percent decrease from 0 to 20 kg. IPF(a) and F250(a) showed weak/moderate correlations with percent height decrease. Comparing strongest (n = 6) to weakest (n = 6): t tests revealed that stronger athletes (IPF(a)) performed superior to weaker athletes.

CONCLUSION

Data indicate the ability to produce higher peak and instantaneous forces and IRFD is related to JH and to smaller differences between weighted and unweighted jump heights. Stronger athletes jump higher and show smaller decrements in JH with load. A weighted jump may be a practical method of assessing relative strength levels.

In-season effect of short-term sprint and power training programs on elite junior soccer players

The aim of this study was to examine the effects of 2 in-season short-term sprint and power training protocols on vertical countermovement jump height (with or without arms), sprint (Sprint-15m) speed, and agility (Agility-15m) speed in male elite junior soccer players. Twenty highly trained soccer players (age 18.3 +/- 0.6 years, height 177 +/- 4 cm, body mass 71.4 +/- 6.9 kg, sum skinfolds 48.1 +/- 11.4 mm), members of a professional soccer academy, were randomly allocated to either a CONTRAST (n = 10) or SPRINT (n = 10) group. The training intervention consisted of 6 supervised training sessions over 7 weeks, targeting the improvement of the players' speed and power. CONTRAST protocol consisted of alternating heavy-light resistance (15-50% body mass) with soccer-specific drills (small-sided games or technical skills). SPRINT training protocol used line 30-m sprints (2-4 sets of 4 x 30 m with 180 and 90 seconds of recovery, respectively). At baseline no difference between physical test performance was evident between the 2 groups (p > 0.05). No time x training group effect was found for any of the vertical jump and Agility-15m variables (p > 0.05). A time x training group effect was found for Sprint-15m performance with the CONTRAST group showing significantly better scores than the SPRINT group (7.23 +/- 0.18 vs. 7.09 +/- 0.20 m.s, p < 0.01). In light of these findings CONTRAST training should be preferred to line sprint training in the short term in young elite soccer players when the aim is to improve soccer-specific sprint performance (15 m) during the competitive season.

Reliability, Usefulness, and Validity of a Repeated Sprint and Jump Ability Test

Purpose:

Two studies involving 122 handball players were conducted to assess the reliability, usefulness, and validity of a repeated shuttle-sprint and jump ability (RSSJA) test. The test consisted of 6 × (2 × 12.5-m) sprints departing on 25 s, with a countermovement jump performed during recovery between sprints.

Methods:

For the reliability and usefulness study, 14 well-trained male handball players performed the RSSJA test 7 d apart. Reliability of the test variables was assessed by the typical error of measurement, expressed as a coefficient of variation (CV). The minimal changes likely to be “real” in sprint time and jump power were also calculated. For the validity study, players of seven teams (national to international levels, women and men) performed the RSSJA test.

Results:

CV values for best and mean sprint time were 1.0% (90% CL, 0.7 to 1.6) and 1.0% (90% CL, 0.7 to 1.4). CV values for best and mean jump peak power were 1.7% (90% CL, 1.2 to 2.7) and 1.5% (90% CL, 1.1 to 2.5). The percent sprint and jump decrements were less reliable, with CVs of 22.3% (90% CL, 15.7 to 38.3) and 34.8% (90% CL, 24.2 to 61.8). Minimal changes likely to be “real” for mean sprint time and jumping peak power were -2.6% and 4.8%. Qualitative analysis revealed that the majority of between-team differences were rated as “almost certain” (ie, 100% probability that the true differences were meaningful) for mean sprint and jump performances.

Conclusion:

The RSSJA test is reliable and valid to assess repeated explosive effort sequences in team sports such as handball. Test results are likely to be representative of gender and competition level; thus the test could be used to discriminate across playing standards and monitor fitness levels.

Efeito ergogênico de uma bebida esportiva cafeinada sobre a performance em testes de habilidades específicas do futebol

O consumo de cafeína tem demonstrado promover efeitos ergogênicos sobre a performance de atletas de esportes coletivos. O objetivo do presente estudo foi comparar o efeito de uma bebida esportiva cafeinada (BEC) frente a uma bebida carboidratada comercial (BCC) sobre a performance durante a execução de testes físico-motores de habilidades específicas do futebol. Os atletas foram submetidos a dois testes, salto vertical (Sargent Jump) e teste de agilidade (Illinois Agility Test), que foram executados antes e após as partidas durante as quais foram consumidas BEC (7% de carboidratos (CHO), concentração de cafeína correspondente a 250mg.l-1) ou BCC (sem cafeína, 7% de CHO). Os resultados demonstraram que BEC aumentou significantemente (p < 0,01) a altura atingida no salto em relação ao momento anterior ao seu consumo e em comparação com a BCC (p = 0,02). BCC não promoveu aumento na potência de membros inferiores. Tanto BEC (p = 0,62) quanto BCC (p = 0,93), não aumentaram a agilidade no teste realizado após a partida em comparação com o realizado anteriormente. Ambas as bebidas não foram capazes de melhorar o desempenho na execução do teste de agilidade após a partida (p = 0,95). O consumo de BEC proporcionou um efeito ergogênico para jogadores de futebol, aumentando a potência de membros inferiores relacionada com a força explosiva. Contudo, quanto à agilidade não foi possível identificar vantagens no desempenho.

Effects of SAQ Training and Small-Sided Games on Neuromuscular Functioning in Untrained Subjects

Purpose:

The main objective of this study was to investigate the efficacy of both programmed (speed, agility, and quickness; SAQ) and random (small-sided games; SSG) conditioning methods on selected neuromuscular and physical performance variables.

Methods:

Twenty volunteers (21.1 ± 4.0 y, 1.71 ± 0.09 m, 66.7 ± 9.9 kg; mean ± SD) completed the study. The study design used two physically challenging periodized experimental conditions (SAQ and SSG conditions) and a non exercise control condition (CON). Participants engaged in 12.2 ± 2.1 h of directed physical conditioning. All participants had at least 24 h of recovery between conditioning sessions, and each 1-h session included 15 min of general warm-up and a 45-min exercise session. Participants completed a battery of tests (15-m sprint, isokinetic flexion/extension, depth jump) before and following the training program.

Results:

There was a 6.9% (95% CI: -4.4 to 18.3) greater improvement in 5-m acceleration time and 4.3% (95% CI: -0.9 to 9.5) in 15-m mean running velocity time for the SAQ group compared with the SSG group. In addition, increases in maximal isokinetic concentric strength for both the flexor and extensor muscles, with the exception of 180 °/s flexion, were greater in the SAQ than SSG condition. The SAQ group also showed 19.5% (95% CI: -11.2 to 50.2) greater gain in reactive strength (contact time depth jump) and 53.8% (95% CI: 11.2 to 98.6) in mean gastrocnemius medialis activity in comparison with SSG.

Conclusions:

SAQ training should benefit the physical conditioning programs of novice players performing invasion games.

Physiological profile of Asian elite youth soccer players

The purposes of this study were to provide information about the physiological characteristics of Asian elite youth soccer players (a) for strength and conditioning specialists to design training program based on players' physiological characteristics and b) for coach to design an appropriate play tactic. Sixteen Chinese elite youth male players (height: 173 +/- 5.2 cm; weight: 64.2 +/- 8.1 kg; and age: 16.2 +/- 0.6 years) from the U-17 national team participated in the following tests in the current study: (a) maximal vertical jump, (b) isokinetic muscular strength tests of knee joint at angular velocities of 60, 120, 180, 240, and 300 degrees x s, (c) maximal oxygen consumption (VO2max), (d) 1 repetition maximum (1RM) strength test, and (e) 30-m sprint. Compared with European and African players, Asian youth players have less jump height and shorter body height. They also have poor performance in isokinetic muscular strength of quadriceps and hamstrings (especially at high speed), VO2max, 1RM strength test, sprint starts, and 20- to 30-m sprints. A specialized training in jumping performance, high-speed movement, muscular strength at high contraction speed, endurance running, short distance sprint (i.e., 5 m), and 20- to 30-m sprints are recommended for Asian elite youth soccer players (or players with similar physique and ability).

Functional performance, maximal strength, and power characteristics in isometric and dynamic actions of lower extremities in soccer players

The purposes of the present study were to determine muscle strength and power output characteristics in a group of professional soccer players and to identify their relationships with 2 functional performance tests (vertical jumping height and 15-m sprint time). Maximal strength and power indices attained against different loads in barbell back squat exercise, isometric maximal force of the knee extensor and plantar flexor muscles, isokinetic peak torque of the knee extensors muscles, vertical jumping height in squat and counter-movement jumps, and 15-m sprint time tests were assessed in 21 semiprofessional soccer players (age 20 +/- 3.8 years). Correlation analyses were performed to examine the relationship between each of these measures. The main results of the present study were that (a) maximal power in concentric half-squat exercise was attained with a load of 60% of 1 repetition maximum, representing 112% of body weight; (b) the performance in the functional tests selected was significantly related with all the half-squat variables measured, especially with loads of 75-125% of body weight; and (c) low to nonsignificant correlations were found between functional tests performance and isometric and isokinetic muscle strength measures. It was concluded that in semiprofessional soccer players (a) isometric and isokinetic muscle strength assessed in an open kinetic chain were not movement-specific enough to predict performance during a more complex movement, such as jump or sprint and (b) concentric half-squat exercise was principally related with the functional tests selected when it was performed against external loading within the range of the load in case of which the maximal power output was attained.

Efeitos do treinamento neuromuscular na aptidão cardiorrespiratória e composição corporal de atletas de voleibol do sexo feminino

As respostas do organismo humano submetido a estímulos diversos, mensuradas através de parâmetros de performance, têm sido objeto de estudo a fim de aprimorar os métodos de treinamento. O objetivo deste estudo foi investigar os efeitos do treinamento neuromuscular na capacidade cardiorrespiratória e composição corporal de atletas de voleibol. Foram avaliadas 11 mulheres, antes e após 12 semanas de treinamento, referente à fase preparatória do ciclo anual de treinamento. O protocolo experimental constou de avaliação da composição corporal (percentual de gordura, massa magra e a gordura corporal) e da aptidão cardiorrespiratória por meio de ergoespirometria em esteira rolante com protocolo contínuo e carga crescente, na qual se determinaram o consumo máximo de oxigênio, a frequência cardíaca máxima, o limiar anaeróbio, a frequência cardíaca do limiar anaeróbio e a velocidade do limiar anaeróbio. O treinamento teve frequência de cinco dias por semana dividido em duas sessões: uma de treinamento de força e outra de treinamento técnico e tático. Após o período estudado ocorreram aumentos (p < 0,05) no consumo máximo de oxigênio (6,5%), no limiar anaeróbio (17,5%), na velocidade do limiar (15,3%) e redução (p < 0,05) na frequência cardíaca máxima (-3,1%). Também houve redução (p < 0,05) no percentual de gordura (-8,2%), na gordura corporal (-7,4%) e aumento (p < 0,05) na massa magra (3,2%). Conclui-se que o treinamento neuromuscular realizado na fase preparatória de treinamento contribuiu para o aumento da capacidade cardiorrespiratória e massa magra e para redução do percentual de gordura e a gordura corporal das atletas de voleibol.

Leg muscles design: the maximum dynamic output hypothesis

It is well known that both individual muscle and muscle groups produce maximum power against particular external loads. Within the present review, we propose the hypothesis that the lower-limb muscles of physically active individuals are predominantly designed to provide the maximum dynamic output (MDO; assessed as power and momentum) in rapid movements like jumping and sprinting against the load imposed by the weight and the inertia of their own body. The evidence supporting the MDO hypothesis can be found in some general considerations (e.g., certain evolutionary aspects, muscular system design in animals, effects of athletic training) as well as in recent experimental findings. Specifically, here we show that the optimal load for the power and momentum production in vertical jumping in habitually active individuals (but not in strength/power-trained athletes) could be the subject's own body. This also implies that the performance of rapid movements corresponds to body-size-independent MDO of the lower-limb muscles. If supported by future research, MDO hypothesis could 1) provide a theoretical framework for relating both structure and function of the muscular system and for understanding long-term adaptation of the muscular system; 2) suggest that rapid movements, such as vertical jumps, performed without external load could be used for the assessment of MDO (power and momentum) of lower limbs in nonathletic population; and 3) simplify the assessment of physical abilities and neuromuscular function in general through the usage of simple and relatively inexpensive physical performance tests based on natural rapid movements.

Single-leg assessment of postural stability and knee functional outcome two years after anterior cruciate ligament reconstruction

OBJECTIVE

To analyse postural stability and the single-leg hop for distance in subjects 2 years after anterior cruciate ligament reconstruction (ACLR), in comparison with an age- and activity-matched control group.

DESIGN AND SETTING

Subjects reported to a sports medicine or athletic training research laboratory for testing.

SUBJECTS

Twenty-six subjects having undergone ACLR and 26 age- and activity-matched controls were selected to participate in this study. An arthroscopically-assisted, central, one-third bone-patellar tendon procedure was used to repair the ACLs.

MEASUREMENTS

One-leg stance postural stability was measured with the NeuroCom Balance Master platform system. We recorded the single-leg hop for distance as an objective measure of function.

RESULTS

We found a significant difference (p<0.05) between the ACLR and control subjects in terms of the one-leg stance sway velocity (knee fully extended) on the operated side.

CONCLUSIONS

After ACLR (mean time postoperatively: 24+/-1 months), single-leg hop for distance score was normal, when compared with the contralateral limb. Our results indicate that 2 years after surgery, single-limb postural stability in the ACLR group differed significantly from that in the control group. The persistence of poor stability control may be correlated to an impairment in proprioception.

Performance-determining physiological factors in the luge start

In luge, the start is a performance-determining factor. Athletes spend several months in the off-season training to improve starting performance. The aim of this study was to evaluate the influence of different physiological factors on the luge start and identify an appropriate physiological test battery. Thirteen male members of the Austrian national luge team were recruited. All participants completed a test battery that consisted of tests for balance, jumping, isometric truck flexion and extension strength, leg strength, hand grip strength, isometric bench pull and bench press strength, flexibility, and a luge start simulator. Regression analyses of fitness variables and starting speeds revealed relationships (P at least 0.049) except for flexibility, isometric trunk flexion strength, and isometric leg strength at a knee angle of 100 degrees (P at best 0.069). Results showed that a single variable (isometric bench pull strength) explained most of the variance in maximum push-off speed (R2 = 0.750) and suggest that any test battery should include bench pull, trunk extension, and grip strength tests. Bench pull performance might also be a useful tool in the recruitment of athletes.

Differences in thigh muscularity and dynamic torque between junior and senior soccer players

The aim of the present study was to examine differences in thigh muscularity and dynamic torque between elite junior (15.7 +/- 0.2 years) and senior (22.6 +/- 2.4 years) soccer players. Cross-sectional areas of the total muscle compartment, quadriceps femoris, and hamstrings + adductors were determined using magnetic resonance imaging. Knee extension and flexion torque were also measured at 1.05 and 3.14 rad . s(-1). Neither junior nor senior players showed significant differences in cross-sectional area or torque between the dominant and non-dominant leg. The quadriceps femoris and hamstrings + adductors were significantly greater in the senior than junior players at all thigh-slice sites. The percentage of quadriceps femoris to total muscle compartment was significantly higher in the junior than the senior players, and the corresponding value of hamstrings + adductors was significant in the reverse direction. The senior players showed greater torque than the juniors regardless of motion and velocity, even in terms of torque relative to the product of the cross-sectional area and height. The present results indicate that (1) senior players are characterized by the predominant development of hamstrings and adductors and a higher dynamic torque relative to muscle size, and (2) elite soccer players did not show asymmetry in terms of the muscularity or dynamic torque of the thigh muscles irrespective of age.

Fitness determinants of success in men's and women's football

In this study, we examined gender and age differences in physical performance in football. Thirty-four elite female and 34 elite male players (age 17 +/- 1.6 to 24 +/- 3.4 years) from a professional football club were divided into four groups (n=17 each) according to gender and competitive level (senior males, senior females, junior males, and junior females). Players were tested for specific endurance (Yo-YoIR1), sprint over 15 m (Sprint-15 m), vertical jump without (CMJ) or with (ACMJ) arm swing, agility (Agility-15 m), and ball dribbling over 15 m (Ball-15 m). The Yo-YoIR1 and Agility-15m performances showed both a gender and competitive level difference (P < 0.001). Senior and junior males covered 97 and 153% more distance during the Yo-YoIR1 than senior and junior females, respectively (P < 0.001). Gender but not age differences were found for Sprint-15 m performance (P < 0.001). No difference in vertical jump and Ball-15 m performances were found between senior and junior males (P > 0.05). More marked gender differences were evident in endurance than in anaerobic performance in female players. These results show major fitness differences by gender for a given competitive level in football players. It is suggested that training and talent identification should focus on football-specific endurance and agility as fitness traits in post-adolescent players of both sexes.

Self-reported psychological characteristics as risk factors for injuries in female youth football

Identifying and understanding injury risk factors are necessary to target the injury-prone athlete and develop injury prevention measurements. The influence of psychological factors on injuries in football is poorly documented. The purpose of this 8-month prospective cohort study therefore was to examine whether psychological player characteristics assessed by a self-administered questionnaire represent risk factors for injury. At baseline, female football players (14-16 years) were asked to complete a detailed questionnaire covering player history, previous injuries, perception of success and motivational climate, life stress, anxiety and coping strategies. During the 2005 season, a total of 1430 players were followed up to record injuries. A history of a previous injury [odds ratio (OR)=1.9 (1.4; 2.5), P<0.001] increased the risk of a new injury to the same region. There were significant differences in disfavor for previously injured compared with non-injured players for ego orientation (P=0.007), perception of a performance climate (P=0.003) and experienced stressful life events (P<0.001). However, only high life stress (P=0.001) and perception of a mastery climate (P=0.03) were significant risk factors for new injuries. In conclusion, a perceived mastery climate and a high level of life stress were significant predictors for new injuries in a cohort of young female football players.

Evaluating sprinting ability, density of acceleration, and speed dribbling ability of professional soccer players with respect to their positions

The aim of this study is to evaluate sprinting ability, density of acceleration, and speed dribbling ability of professional soccer players with respect to their positions.A total of 243 professional soccer players were examined. These soccer players are playing in different leagues of Turkey. The F-MARC test battery, which was designed by FIFA, was used for soccer players. We did not find any statistical differences for 30-m sprint test and four-line sprint test values with respect to positions of soccer players (p > 0.05). On the other hand, there was a statistical difference for speed dribbling test values in terms of positions of soccer players (p < 0.05). It was found that the test values of defense players, midfielders, and forwards were better than the test values of goalkeepers (p < 0.05). In conclusion, this study, which was done during the training season, shows that there is a similarity between the abilities of professional soccer players for 30-m sprint and four-line sprint tests. Therefore, it is believed that there must be fast players in all positions in terms of sprint ability. There is a similarity among defenders, midfielders, and forwards in terms of speed dribbling ability; in contrast, the speed dribbling ability of goal keepers is different from the players in those three positions. Although there are many more speed dribbling exercises within the training programs of defenders, midfielders, and forwards, the speed dribbling ability test is not used much for goal keepers. Correspondingly, speed dribbling ability is not a specific indicator for goal keepers, and this test should not be used for the choice of goalkeepers.

The five-jump test for distance as a field test to assess lower limb explosive power in soccer players

The 5-jump test (5JT) was proposed to evaluate lower limb explosive power of athletes competing in various disciplines. Although 5JT performance is usually expressed in absolute terms as the overall distance covered (i.e., in meters), subject size can play a significant role in the performance. The aims of the present study were to test the relationship of 5JT absolute performance with laboratory tests for explosive power and to develop performance notations useful to improve the diagnostic value of 5JT. Fifteen elite soccer players, members of the Under-23 Tunisian national team, were tested for 5JT, force platform vertical jumping (squat jump [SJ] and arm-aided countermovement jump [Arm-CMJ]), and concentric isokinetic leg extension/flexion (90 degrees x s(-1) and 240 degrees x s(-1)). 5JT performance was expressed in absolute terms (meters), relative to leg length (5JT-relative) and with body mass-dependent notations (Body mass x 5JT, 5JT-body mass). 5JT performance was significantly correlated with SJ height and scaled (W x kg) peak power (0.72 and 0.77, respectively, p < 0.01). 5JT-relative values were significantly related to SJ and Arm-CMJ height (0.61 and 0.71, respectively, p < 0.05) and scaled peak power (0.57 and 0.59, respectively, p < 0.05). 5JT-body mass revealed significantly related of SJ (0.82, p < 0.0001) and Arm-CMJ peak power (0.54, p < 0.05) and to SJ and Arm-CMJ peak force (0.67 and 0.65, respectively p < 0.05). 5JT-relative and 5JT-body mass correlated significantly with knee extensors 240 degrees x s(-1) (0.60, p < 0.05) and knee flexors 90 degrees x s(-1) (0.67, p < 0.01) isokinetic acceleration time, respectively. The results of this study suggest that the 5JT may be regarded as an explosive strength diagnostic tool under field conditions in elite soccer players. The use of performance notation accounting for body size differences may improve the diagnostic ability of 5JT.

Muscular strength, functional performances and injury risk in professional and junior elite soccer players

Muscle strength and anaerobic power of the lower extremities are neuromuscular variables that influence performance in many sports activities, including soccer. Despite frequent contradictions in the literature, it may be assumed that muscle strength and balance play a key role in targeted acute muscle injuries. The purpose of the present study was to provide and compare pre-season muscular strength and power profiles in professional and junior elite soccer players throughout the developmental years of 15-21. One original aspect of our study was that isokinetic data were considered alongside the past history of injury in these players. Fifty-seven elite and junior elite male soccer players were assigned to three groups: PRO, n=19; U-21, n=20 and U-17, n=18. Players benefited from knee flexor and extensor isokinetic testing consisting of concentric and eccentric exercises. A context of lingering muscle disorder was defined using statistically selected cut-offs. Functional performance was evaluated throughout a squat jump and 10 m sprint. The PRO group ran faster and jumped higher than the U-17 group (P<0.05). No significant difference in isokinetic muscle strength performance was observed between the three groups when considering normalized body mass parameters. Individual isokinetic profiles enabled the identification of 32/57 (56%) subjects presenting lower limb muscular imbalance. Thirty-six out of 57 players were identified as having sustained a previous major lower limb injury. Of these 36 players, 23 still showed significant muscular imbalance (64%). New trends in rational training could focus more on the risk of imbalance and implement antagonist strengthening aimed at injury prevention. Such an intervention would benefit not only athletes recovering from injury, but also uninjured players. An interdisciplinary approach involving trainers, a physical coach, and medical staff would be of interest to consider in implementing a prevention programme.