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

Relationships between strength, sprint, and jump performance in well-trained youth soccer players

Research has demonstrated a clear relationship between absolute and relative strength and sprint and jump performance in adult athletes; however, this relationship in younger athletes has been less extensively studied. The aim of this study, therefore, was to determine the relationships between strength, sprint, and jump performances in well-trained youth soccer players. Thirty-four young male soccer players (17.2 ± 0.6 years; body mass, 72.62 ± 7.42 kg; height, 179.27 ± 6.58 cm) performed a predicted maximal squat test, 20-m sprints, squat jumps (SJs), and countermovement jumps (CMJs). Absolute strength showed the strongest correlations with 5-m sprint times (r = -0.596, p < 0.001, power = 0.99), SJ height (r = 0.762, p < 0.001, power = 1.00), and CMJ height (r = 0.760, p < 0.001, power = 1.00), whereas relative strength demonstrated the strongest correlation with 20-m sprint times (r = -0.672, p < 0.001, power = 0.99). The results of this study illustrate the importance of developing high levels of lower-body strength to enhance sprint and jump performance in youth soccer players, with stronger athletes demonstrating superior sprint and jump performances.

Long-term strength training effects on change-of-direction sprint performance

The requirement profiles for sports such as soccer, football, tennis, and rugby demonstrate the importance of strength and speed-strength abilities, in addition to other conditional characteristics. During a game, the athletes complete a large number of strength and speed-strength actions. In addition to the linear sprints, athletes perform sprints while changing the direction (change-of-direction sprint [COD]). Therefore, this study aims to clarify the extent to which there is a strength training intervention effect on COD. Further, this investigation analyzes the possible correlations between the 1-Repetition Maximum/body mass (SREL) in the front and back squats and COD. The subjects (n = 112) were at pretest between 13 and 18 years of age and were divided into 2 groups with 4 subgroups (A = under 19 years of age, B = under 17 years of age, and C = under 15 years of age). For approximately 2 years, 1 group (control group [CG]) only participated in routine soccer training, and the other group (strength training group [STG]) participated in an additional strength training program with the routine soccer training. Additionally, the performances in the COD of 34 professional soccer players of the first and second divisions in Germany were measured as a standard of high-level COD. For the analysis of the performance development within a group and pairwise comparisons between 2 groups, an analysis of variance with repeated measures was calculated with the factors group and time. Relationships between the COD and SREL were calculated for the normal distributed data using a plurality of bivariate correlations by Pearson. Our data show that additional strength training over a period of 2 years significantly affects the performance in the COD. The STG in all subcohorts reached significantly (p < 0.05) faster times in the COD than did the CG. The STG amounted up to 5% to nearly 10% better improvements in the 10-m sprint times compared with that of the CG. Furthermore, our data show significant (p < 0.05) moderate to high correlations (r = -0.388 to -0.697) between the SREL and COD. Our data show that a long-term strength training improves the performance of the COD. Therefore, a long-term resistance training is recommended as early as in childhood and adolescence.

Effect of countermovement on power-force-velocity profile

PURPOSE

To study the effect of a countermovement on the lower limb force-velocity (F-v) mechanical profile and to experimentally test the influence of F-v mechanical profile on countermovement jump (CMJ) performance, independently from the effect of maximal power output (P max).

METHODS

Fifty-four high-level sprinters and jumpers performed vertical maximal CMJ and squat jump (SJ) against five to eight additional loads ranging from 17 to 87 kg. Vertical ground reaction force data were recorded (1,000 Hz) and used to compute center of mass vertical displacement. For each condition, mean force, velocity, and power output were determined over the entire push-off phase of the best trial, and used to determine individual linear F-v relationships and P max. From a previously validated biomechanical model, the optimal F-v profile maximizing jumping performance was determined for each subject and used to compute the individual mechanical F-v imbalance (Fv IMB) as the difference between actual and optimal F-v profiles.

RESULTS

A multiple regression analysis clearly showed (r(2) = 0.952, P < 0.001, SEE 0.011 m) that P max, Fv IMB and lower limb extension range (h PO) explained a significant part of the interindividual differences in CMJ performance (P < 0.001) with positive regression coefficients for P max and h PO and a negative one for Fv IMB.

CONCLUSION

Compared to SJ, F-v relationships were shifted to the right in CMJ, with higher P max, maximal theoretical force and velocity (+35.8, 20.6 and 13.3%, respectively). As in SJ, CMJ performance depends on Fv IMB, independently from the effect of P max, with the existence of an individual optimal F-v profile (Fv IMB having an even larger influence in CMJ).

Acceleration and sprint profiles of a professional elite football team in match play

The aim of this study was to characterise the acceleration and sprint profiles of elite football match play in one Norwegian elite football team (Rosenborg FC). Fifteen professional players in five playing positions took part in the study (n = 101 observations). Player movement was recorded during every domestic home game of one full season (n = 15) by an automatic tracking system based on microwave technology. Each player performed 91 ± 21 accelerations per match, with a lower number in the second compared with the first half (47 ± 12 vs. 44 ± 12). Players in lateral positions accelerated more often compared to players in central positions (98.3 ± 20.5 vs. 85.3 ± 19.5, p < 0.05). Average sprint distance was 213 ± 111 m distributed between 16.6 ± 7.9 sprints, with no differences between first (106 ± 60 m, 8.2 ± 4.2 sprints) and second halves (107 ± 72 m, 8.3 ± 4.8 sprints). Players in lateral positions sprinted longer distances (287 ± 211 m vs. 160 ± 76 m, p < 0.05) and tended to sprint more often (21.6 ± 7.8 vs. 13.0 ± 5.7, p = 0.064) compared to players in central positions. We found more walking and less of the more intense activities during the last third of the season compared to the first. The main finding in this study was that Norwegian elite players had substantially less number of accelerations and fewer but longer sprints than previous studies reported for higher-ranked leagues. Also, less high-intensity activity was found towards the end of the season. Ultimately, these data provide useful information for the fitness coach (1) in planning of position-specific football training and (2) to avoid the decline in high-intensity activities the last third of the competitive season.

The Back Squat and the Power Clean: Elicitation of Different Degrees of Potentiation

Purpose:

To compare the acute effects of back squats and power cleans on sprint performance.

Methods:

Thirteen elite junior rugby league players performed 20-m linear sprints before and 7 min after 2 different conditioning activities or 1 control condition. The conditioning activities included 1 set of 3 back squats or power cleans at 90% 1-repetition maximum. A 2 × 2 repeated-measures ANOVA was used to compare preconditioning and postconditioning changes in sprint performance.

Results:

Both the back-squat and power-clean conditioning activities demonstrated a potentiation effect as indicated by improved sprint time (back squat: P = .001, ES = –0.66; power cleans: P = .001, ES = –0.92), velocity (back squat: P = .001, ES = 0.63; power cleans: P = .001, ES = 0.84), and average acceleration over 20 m (back squat: P = .001, ES = 0.70; power cleans: P = .001, ES = 1.00). No potentiation effect was observed after the control condition. Overall, the power clean induced a greater improvement in sprint time (P = .042, ES = 0.83), velocity (P = .047, ES = 1.17), and average acceleration (P = .05, ES = 0.87) than the back squat.

Conclusions:

Back-squat and power-clean conditioning activities both induced improvements in sprint performance when included as part of a potentiation protocol. However, the magnitude of improvement was greater after the power cleans. From a practical perspective, strength and conditioning coaches should consider using power cleans rather than back squats to maximize the performance effects of potentiation complexes targeting the development of sprint performance.

Effect of football or strength training on functional ability and physical performance in untrained old men

The effects of 16 weeks of football or strength training on performance and functional ability were investigated in 26 (68.2 ± 3.2 years) untrained men randomized into a football (FG; n = 9), a strength training (ST; n = 9), or a control group (CO; n = 8). FG and ST trained 1.6 ± 0.1 and 1.5 ± 0.1 times per week, respectively, with higher (P < 0.05) average heart rate (HR) (∼140 vs 100 bpm) and time >90%HRmax (17 vs 0%) in FG than ST, and lower (P < 0.05) peak blood lactate in FG than ST (7.2 ± 0.9 vs 10.5 ± 0.6 mmol/L). After the intervention period (IP), VO₂ max (15%; P < 0.001), cycle time to exhaustion (7%; P < 0.05), and Yo-Yo Intermittent Endurance Level 1 performance (43%; P < 0.01) were improved in FG, but unchanged in ST and CO. HR during walking was 12% and 10% lower (P < 0.05) in FG and ST, respectively, after IP. After IP, HR and blood lactate during jogging were 7% (P < 0.05) and 30% lower (P < 0.001) in FG, but unchanged in ST and CO. Sit-to-stand performance was improved (P < 0.01) by 29% in FG and 26% in ST, but not in CO. In conclusion, football and strength training for old men improves functional ability and physiological response to submaximal exercise, while football additionally elevates maximal aerobic fitness and exhaustive exercise performance.

Strength, power, and speed qualities in English junior elite rugby league players

The aim of this study was to compare strength, power, and speed characteristics of elite junior English rugby league forwards and backs. A squad of males under 20's (n = 24; age 18.70 ± 0.90 years; body mass 86.4 ± 9.93 kg; height 178.47 ± 6.97 cm) players from a Super League team performed a range of assessments, including 10-, 20-, and 40-m sprints; vertical jump; and 1 repetition maximum (1RM) bench press and 1-RM back squat. Independent t-tests revealed no significance between body mass and height (180.13 ± 7.65 cm, 176.83 ± 6.10 cm; p > 0.05) or body mass (90.08 ± 11.72 kg, 82.75 ± 6.28 kg; p > 0.05) for the forwards and backs, respectively. Backs were significantly quicker over the 10-m sprints (1.99 ± 0.60 seconds, 2.06 ± 0.10 seconds; p = 0.011), 20-m sprints (3.26 ± 0.70 seconds, 3.39 ± 0.17 seconds; p = 0.002), and 40-m sprints (5.55 ± 0.13 seconds, 5.80 ± 0.26 seconds; p = 0.0001) compared with the forwards. No significant difference (p > 0.05) was observed for the vertical jump performances between the forwards (50.58 ± 7.06 cm) and the backs (50.60 ± 5.02 cm). In addition, forwards demonstrated a higher 1RM bench press and 1RM back squat (110.00 ± 15.8 kg and 140.21 ± 26.21 kg) compared with the backs (101.67 ± 9.13 kg and 132.71 ± 9.38 kg), although this was not statistically significant (p > 0.05); when expressed relative to body mass the differences between forwards and backs was reduced further for both bench press (1.22 ± 0.10 kg/kg, 1.23 ± 0.08 kg/kg, respectively; p > 0.05) and back squat (1.61 ± 0.13 kg/kg, 1.56 ± 0.20 kg/kg, respectively; p > 0.05). In addition, relative squat strength demonstrated moderate inverse correlations between relative squat strength sprint times (r = -0.45, -0.46, and -0.44; p < 0.01) across 10, 20, and 40 m, respectively. These findings highlight the importance of maximizing squat strength in academy rugby league athletes and highlight that differences in sprint performance between positions may be attributable to the differences in relative strength levels between positions.

Fitness testing of tennis players: how valuable is it?

In tennis, sport-specific technical skills are predominant factors, although a complex profile of physical performance factors is also required. The fitness test batteries assist in examining tennis players' capabilities for performance at different levels in the laboratory as well as in the field, in the junior or elite level. While laboratory tests can be, and are, used to evaluate basic performance characteristics of athletes in most individual sports, in a more specific approach, field-based methods are better suited to the demands of complex intermittent sports like tennis. A regular test battery performed at different periods of the year allows to obtain an individual's performance profile, as well as the ability to prescribe individual training interventions. Thus, the aim of the present review was to describe and evaluate the different physical tests recommended and used by practitioners, sports scientists and institutions (national tennis federations).

Importance of muscle power variables in repeated and single sprint performance in soccer players

This study examined the relationship between lower body power and repeated as well as single sprint performance in soccer players. The performance of nineteen male soccer players was examined. The first testing session included the countermovement jump (CMJL) and the progressive full squat (FSL), both with external loads. Power in the CMJL and FSL was measured with each load that was lifted. The second session included a protocol of 40-m repeated sprints with a long recovery period (2 min). The number of sprints executed until there was a 3% decrease in performance for the best 40-m sprint time was recorded as a repeated sprint index (RSI). The RSI was moderately associated with power output relative to body mass in the CMJL and FSL (r = 0.53/0.54, p ≤ 0.05). The most and least powerful players (determined by FSL) showed significant differences in the RSI (9.1 ± 4.2 vs. 6.5 ± 1.6) and 10 m sprint time (p ± 0.01). Repeated and single sprints are associated with relatively lower body power in soccer players.

Different loading schemes in power training during the preseason promote similar performance improvements in Brazilian elite soccer players

The present study investigated the effects of 2 different power training loading schemes in Brazilian elite soccer players. Thirty-two players participated in the study. Maximum dynamic strength (1RM) was evaluated before (B), at midpoint (i.e., after 3 weeks; T1), and after 6 weeks (T2) of a preseason strength/power training. Muscle power, jumping, and sprinting performance were evaluated at B and T2. Players were randomly allocated to 1 of 2 training groups: velocity-based (VEL: n = 16; age, 19.18 ± 0.72 years; height, 173 ± 6 cm; body mass, 72.7 ± 5.8 kg) or intensity-based (INT: n = 16; age, 19.11 ± 0.7 years; height, 172 ± 4.5 cm; body mass, 71.8 ± 4.6 kg). After the individual determination of the optimal power load, both groups completed a 3-week traditional strength training period. Afterward, the VEL group performed 3 weeks of power-oriented training with increasing velocity and decreasing intensity (from 60 to 30% 1RM) throughout the training period, whereas the INT group increased the training intensity (from 30 to 60% 1RM) and thus decreased movement velocity throughout the power-oriented training period. Both groups used loads within ±15% (ranging from 30 to 60% 1RM) of the measured optimal power load (i.e., 45.2 ± 3.0% 1RM). Similar 1RM gains were observed in both groups at T1 (VEL: 9.2%; INT: 11.0%) and T2 (VEL: 19.8%; INT: 22.1%). The 2 groups also presented significant improvements (within-group comparisons) in all of the variables. However, no between-group differences were detected. Mean power in the back squat (VEL: 18.5%; INT: 20.4%) and mean propulsive power in the jump squat (VEL: 29.1%; INT: 31.0%) were similarly improved at T2. The 10-m sprint (VEL: -4.3%; INT: -1.6%), jump squat (VEL: 7.1%; INT: 4.5%), and countermovement jump (VEL: 6.7%; INT: 6.9%) were also improved in both groups at T2. Curiously, the 30-m sprint time (VEL: -0.8%; INT: -0.1%) did not significantly improve for both groups. In summary, our data suggest that male professional soccer players can achieve improvements in strength- and power-related abilities as a result of 6 weeks of power-oriented training during the preseason. Furthermore, similar performance improvements are observed when training intensity manipulation occurs around only a small range within the optimal power training load.

Barefoot Running: The Effects of an 8-Week Barefoot Training Program

Background:

It has been proposed that running barefoot can lead to improved strength and proprioception. However, the duration that a runner must train barefoot to observe these changes is unknown.

Hypothesis:

Runners participating in a barefoot running program will have improved proprioception, increased lower extremity strength, and an increase in the volume or size of the intrinsic musculature of the feet.

Study Design:

Randomized controlled trial; Level of evidence, 2.

Methods:

In this 8-week study, 29 runners with a mean age of 36.34 years were randomized into either a control group (n = 10) who completed training in their regular running shoes or to an experimental barefoot group (n = 14). Pretraining tests consisted of a volumetric measurement of the foot followed by a strength and dynamic balance assessment. Five subjects completed the pretests but did not complete the study for reasons not related to study outcomes. Participants then completed 8 weeks of training runs. They repeated the strength and dynamic balance assessment after 8 weeks.

Results:

Significant changes from baseline to 8 weeks were observed within the barefoot group for single-leg hop (right, P = .0121; left, P = .0430) and reach and balance (right, P = .0029) and within the control group for single–left leg hop (P = .0286) and reach and balance (right, P = .0096; left, P = .0014). However, when comparing the differences in changes from baseline to 8 weeks between the barefoot and control groups, the improvements were not significant at the .05 level for all measures.

Conclusion:

Although statistically significant changes were not observed between the pre- and posttest evaluations in strength and proprioception with the 8-week low-intensity barefoot running regimen, this does not necessarily mean that these changes do not occur. It is possible that it may take months or years to observe these changes, and a short course such as this trial is insufficient.

Fatigue-induced balance impairment in young soccer players

CONTEXT

Although balance is generally recognized to be an important feature in ensuring good performance in soccer, its link with functional performance remains mostly unexplored, especially in young athletes.

OBJECTIVE

To investigate changes in balance induced by fatigue for unipedal and bipedal static stances in young soccer players.

DESIGN

Crossover study.

SETTING

Biomechanics laboratory and outdoor soccer field.

PATIENTS OR OTHER PARTICIPANTS

Twenty-one male soccer players (age = 14.5 ± 0.2 years, height = 164.5 ± 5.6 cm, mass = 56.8 ± 6.8 kg).

INTERVENTION(S)

Static balance was assessed with postural-sway analysis in unipedal and bipedal upright stance before and after a fatigue protocol consisting of a repeated sprint ability (RSA) test (2 × 15-m shuttle sprint interspersed with 20 seconds of passive recovery, repeated 6 times).

MAIN OUTCOME MEASURE(S)

On the basis of the center-of-pressure (COP) time series acquired during the experimental tests, we measured sway area, COP path length, and COP maximum displacement and velocity in the anteroposterior and mediolateral directions.

RESULTS

Fatigue increased all sway values in bipedal stance and all values except COP velocity in the mediolateral direction in unipedal stance. Fatigue index (calculated on the basis of RSA performance) was positively correlated with fatigue/rest sway ratio for COP path length and COP velocity in the anteroposterior and mediolateral directions for nondominant single-legged stance.

CONCLUSIONS

Fatigued players exhibited reduced performance of the postural-control system. Participants with better performance in the RSA test appeared less affected by balance impairment, especially in single-legged stance.

Does an in-Season 6-Week Combined Sprint and Jump Training Program Improve Strength-Speed Abilities and Kicking Performance in Young Soccer Players?

The aim of this study was to examine the effect of a six-week combined jump and sprint training program on strength-speed abilities in a large sample of youth competitive soccer players. It was hypothesized that the experimental training group would enhance their jumping and sprinting abilities. Enhancement of kicking performance was also hypothesized due to an expected increase in explosive strength established by a plyometric and sprinting regimen. Fifty-two young male soccer players playing at the national level (aged 13.4 ± 1.4 years, body mass 53.4 ± 11.7 kg, body height 1.66 ± 0.11 m) took part in the study. Half of the group underwent the plyometric and sprint training program in addition to their normal soccer training, while the other half was involved in soccer training only. The plyometric training group enhanced their running (+1.7 and +3.2%) and jumping performance (+7.7%) significantly over the short period of time, while the control group did not. Furthermore, both groups increased their kicking velocity after just six weeks of training (+3.3 vs. 6.6%). The findings suggest that a short in-season 6-week sprint and jump training regimen can significantly improve explosive strength in soccer-specific skills and that these improvements can be transferred to soccer kicking performance in terms of ball speed.

The development, retention and decay rates of strength and power in elite rugby union, rugby league and American football: a systematic review

BACKGROUND AND AIM

Strength and power are crucial components to excelling in all contact sports; and understanding how a player's strength and power levels fluctuate in response to various resistance training loads is of great interest, as it will inevitably dictate the loading parameters throughout a competitive season. This is a systematic review of training, maintenance and detraining studies, focusing on the development, retention and decay rates of strength and power measures in elite rugby union, rugby league and American football players.

SEARCH STRATEGIES

A literature search using MEDLINE, EBSCO Host, Google Scholar, IngentaConnect, Ovid LWW, ProQuest Central, ScienceDirect Journals, SPORTDiscus and Wiley InterScience was conducted. References were also identified from other review articles and relevant textbooks. From 300 articles, 27 met the inclusion criteria and were retained for further analysis. STUDY QUALITY: Study quality was assessed via a modified 20-point scale created to evaluate research conducted in athletic-based training environments. The mean ± standard deviation (SD) quality rating of the included studies was 16.2 ± 1.9; the rating system revealed that the quality of future studies can be improved by randomly allocating subjects to training groups, providing greater description and detail of the interventions, and including control groups where possible.

DATA ANALYSIS

Percent change, effect size (ES = [Post-Xmean - Pre-Xmean)/Pre-SD) calculations and SDs were used to assess the magnitude and spread of strength and power changes in the included studies. The studies were grouped according to (1) mean intensity relative volume (IRV = sets × repetitions × intensity; (2) weekly training frequency per muscle group; and (3) detraining duration. IRV is the product of the number of sets, repetitions and intensity performed during a training set and session. The effects of weekly training frequencies were assessed by normalizing the percent change values to represent the weekly changes in strength and power. During the IRV analysis, the percent change values were normalized to represent the percent change per training session. The long-term periodized training effects (12, 24 and 48 months) on strength and power were also investigated.

RESULTS

Across the 27 studies (n = 1,015), 234 percent change and 230 ES calculations were performed. IRVs of 11-30 (i.e., 3-6 sets of 4-10 repetitions at 74-88% one-repetition maximum [1RM]) elicited strength and power increases of 0.42% and 0.07% per training session, respectively. The following weekly strength changes were observed for two, three and four training sessions per muscle region/week: 0.9%, 1.8 % and 1.3 %, respectively. Similarly, the weekly power changes for two, three and four training sessions per muscle group/week were 0.1%, 0.3% and 0.7 %, respectively. Mean decreases of 14.5% (ES = -0.64) and 0.4 (ES = -0.10) were observed in strength and power across mean detraining periods of 7.2 ± 5.8 and 7.6 ± 5.1 weeks, respectively. The long-term training studies found strength increases of 7.1 ± 1.0% (ES = 0.55), 8.5 ± 3.3% (ES = 0.81) and 12.5 ± 6.8% (ES = 1.39) over 12, 24 and 48 months, respectively; they also found power increases of 14.6% (ES = 1.30) and 12.2% (ES = 1.06) at 24 and 48 months.

CONCLUSION

Based on current findings, training frequencies of two to four resistance training sessions per muscle group/week can be prescribed to develop upper and lower body strength and power. IRVs ranging from 11 to 30 (i.e., 3-6 sets of 4-10 repetitions of 70-88% 1RM) can be prescribed in a periodized manner to retain power and develop strength in the upper and lower body. Strength levels can be maintained for up to 3 weeks of detraining, but decay rates will increase thereafter (i.e. 5-16 weeks). The effect of explosive-ballistic training and detraining on pure power development and decay in elite rugby and American football players remain inconclusive. The long-term effects of periodized resistance training programmes on strength and power seem to follow the law of diminishing returns, as training exposure increases beyond 12-24 months, adaptation rates are reduced.

Vertical jump performance in Italian male and female national team soccer players

The aim of this study was to examine the validity of vertical jump (VJ) performance variables in elite-standard male and female Italian soccer players. One hundred eighteen national team soccer players (n = 56 men and n = 62 women) were tested for countermovement (CMJ) and squatting jump (SJ) heights. The stretch-shortening cycle efficiency (SSCE) was assessed as percentage of CMJ gain over SJ ([INCREMENT]CMJ-SJ), difference (CMJ-SJ), and ratio (CMJ:SJ). Results showed significant sex difference in SJ and CMJ. Differences in SSCE were mainly in the absolute variables between sexes. Cutoff values for CMJ and SJ using sex as construct were 34.4 and 32.9 cm, respectively. No competitive level differences in VJ performance were detected in the male players. Female national team players showed VJ performance higher than the under 17 counterpart. The results of this study showed that VJ performance could not discriminate between competitive levels in male national team-selected soccer players. However, the use of CMJ and SJ normative data may help strength and conditioning coaches in prescribing lower limb explosive strength training in elite soccer players. In this, variations in VJ performance in the range of approximately 1 cm may be regarded as of interest in tracking noncasual variation in elite-standard soccer players.

Effects of applied training loads on the aerobic capacity of young soccer players during a soccer season

The aim of this study was to examine the effects of applied training loads on the aerobic capacity, speed, power, and speed endurance of young soccer players during 1 soccer season. The participants in the study were 19 young male soccer players (age: 16.61 ± 0.31 years; weight: 64.28 ± 6.42 kg; height: 176.58 ± 5.98 cm). The players completed 150 training sessions and 54 games over the course of 1 soccer season. The training intensity was divided into 4 categories: (a) aerobic performance (61% of the total training duration), (b) mixed aerobic-anaerobic performance (34%), (c) anaerobic lactate performance (3%), and (d) anaerobic nonlactate performance (2%). No significant changes in the V[Combining Dot Above]O2max were observed throughout the season. The players' power level and speed endurance increased significantly with the coincident decrements in their 5-m sprint time. The applied training loads, including 1 high-intensity training session of small-sided games performed during a competitive season, did not significantly change the aerobic capacity of the young soccer players. However, the participants did maintain their V[Combining Dot Above]O2max at the elite level. The first squad players (FSPs) reached the highest level of aerobic fitness in the middle of the season, whereas substitute players (SPs) at the end of the season. Moreover, the V[Combining Dot Above]O2max in FSP was significantly higher (p < 0.003) than in SP in the middle of the season.

Avaliação da simetria e descarga de peso entre os membros inferiores de atletas de futebol da categoria de base

INTRODUÇÃO: A avaliação instrumentada dos saltos verticais informa sobre as capacidades funcionais e variáveis neuromusculares, auxiliando no atendimento dos atletas. Essencial dar atenção maior para as categorias de base, pois contém fases importantes do desenvolvimento dos atletas que serão o futuro do esporte. Objetivo: Avaliar as características funcionais e neuromusculares de atletas de futebol da categoria de base, no desempenho em saltos verticais. METODOLOGIA: Foram avaliados atletas de futebol com idade entre 15 e 17 anos. Foram realizados em duas plataformas de força os seguintes saltos verticais: salto em agachamento, salto em contramovimento, salto pliométrico de 40 cm de altura. Para análise das variáveis das forças concêntrica, excêntrica, impacto e altura dos saltos utilizou-se a prova estatística de Shapiro-Wilk, descrição das variáveis em média e desvio padrão, considerando quando p < 0,05. RESULTADOS: Dos 30 atletas avaliados, obtivemos: três goleiros (10%), cinco zagueiros (16,7%), um lateral (3,3%), três volantes (10%), 12 meio-campistas (40%) e seis atacantes (20%). A categoria sub-17 apresentou maiores resultados comparada a categoria sub-15. Maior altura de salto do contramovimento em relação ao salto em agachamento (p < 0,05) e ao pliométrico (p > 0,05). Sem diferença na força concêntrica entre as categorias e os tipos de saltos. Maior força de impacto no contramovimento. Maior força em membro inferior direito em todos os saltos e variáveis de força. CONCLUSÕES: Encontramos assimetria entre os membros inferiores, podendo correlacionar com um déficit de potência muscular, má desaceleração do movimento e erros biomecânicos. Fatores predisponentes a lesões musculoesqueléticas, os quais podem ser prevenidos. A avaliação instrumentada da força através desses testes pode subsidiar os profissionais do clube como uma ferramenta de trabalho, capaz de aprimorar o treinamento, preparação e reabilitação. Entretanto, são necessárias mais pesquisas, de forma que momentos distintos da idade e da temporada do atleta sejam avaliados.

Analysis of lower limb asymmetries by isokinetic and vertical jump tests in soccer players

Assessment of lower extremity bilateral asymmetries in soccer players is important for both injury prevention and performance. The purpose of this investigation was to compare isokinetic knee extensor assessment of asymmetry with a more specific countermovement jump (CMJ). Forty-six Brazilian male professional soccer players participated in this study. The maximal power, maximal force and impulse were determined during CMJ and the total work and peak torque at 60, 180, and 300°·s during isokinetic leg extension, separately for each leg. Factor analysis was performed for all investigated variables, and the diagnostic concordance between different criteria was analyzed by McNemar's χ test. The factor analysis showed that the isokinetic and CMJ tests were widely independent methods for the assessment of bilateral differences. Concordance of the diagnostic information could only be found between the maximal force during CMJ and the total work and peak torque at 180 and 300°·s during isokinetic leg extension. Impulse and maximal power during CMJ on a double force platform appear to be appropriate additional variables for the identification of bilateral differences. Therefore, it might be pertinent to perform, in addition to isokinetic assessment, a vertical jump test on a force platform to assure widespread and reliable diagnostic information.

Analysis of balance, rapidity, force and reaction times of soccer players at different levels of competition

In the present study we analyzed 12 physical parameters, namely force, static and dynamic balance (both quantified by means of 4 parameters each), rapidity, visual reaction times and acoustic reaction times, over 185 subjects. 170 of them played soccer in teams enrolled in all the ten different Italian soccer leagues. Results show that 6 parameters (out of the 12 analyzed) permit to identify and discriminate top-level players, among those showing the same training frequency. The other parameters are strictly related to training frequency or do not discriminate among players or control subjects (non-athletes), such as visual and acoustic reaction times. Principal component analysis permits to identify 4 clusters of subjects with similar performances, thus representing a useful instrument to characterize the overall ability of players in terms of athletic characteristics, on the basis of their location on the principal component parameters plane.

Influence of lumbar spine extension on vertical jump height during maximal squat jumping

The purpose of this study was to determine the influence of lumbar spine extension and erector spinae muscle activation on vertical jump height during maximal squat jumping. Eight male athletes performed maximal squat jumps. Electromyograms of the erector spinae were recorded during these jumps. A simulation model of the musculoskeletal system was used to simulate maximal squat jumping with and without spine extension. The effect on vertical jump height of changing erector spinae strength was also tested through the simulated jumps. Concerning the participant jumps, the kinematics indicated a spine extension and erector spinae activation. Concerning the simulated jumps, vertical jump height was about 5.4 cm lower during squat jump without trunk extension compared to squat jump. These results were explained by greater total muscle work during squat jump, more especially by the erector spinae work (+119.5 J). The erector spinae may contribute to spine extension during maximal squat jumping. The simulated jumps confirmed this hypothesis showing that vertical jumping was decreased if this muscle was not taken into consideration in the model. Therefore it is concluded that the erector spinae should be considered as a trunk extensor, which enables to enhance total muscle work and consequently vertical jump height.

Yo-Yo intermittent recovery test performances within an entire football league during a full season

The study examined Yo-Yo intermittent recovery level 2 (YYIR2) and submaximal YYIR1 test performances in 172 male semi-professional football players (age; 25.8 ± 4.1 years) representing all teams in a top league at pre-season, start-season, mid-season and end-season. YYIR2 performance was 847 ± 227 m (±SD) at pre-season and rose (P < 0.05) by 128 ± 113 m to 975 ± 205 m at start of season and further (P < 0.05) by 59 ± 102 m to 1034 ± 211 m at mid-season. Submaximal YYIR1 HR was 90.9 ± 4.2% HR(max) at pre-season, which was higher (P < 0.05) than at start, mid and end of season (87.0 ± 3.9, 85.9 ± 4.1 and 87.0 ± 3.7% HR(max), respectively). Peak YYIR2 performance and minimum YYIR1 HR were 1068 ± 193 m and 85.1 ± 3.8% HR(max), respectively, with ~50% of the players peaking at mid-season. Top-teams and middle-teams had higher (P < 0.05) peak YYIR2 scores (1094 ± 205 and 1121 ± 152 m, respectively) than bottom-teams (992 ± 185 m). YYIR2 performance was 16% higher (P < 0.05) and YYIR1 HR was 1.4% HR(max) lower (P < 0.05) for regular players than non-regular players at pre-season and remained lower (P < 0.05) throughout the season. Central defenders had poorer (P < 0.05) YYIR performances compared to other positional roles. In conclusion, YYIR performances are highly variable within a football league over a season and are influenced by league ranking, regularity of competitive play and playing position.

New genetic model for predicting phenotype traits in sports

PURPOSE

The aim of the current study was to construct a genetic model with a new algorithm for predicting athletic-performance variability based on genetic variations.

METHODS

The influence of 6 polymorphisms (ACE, ACTN-3, BDKRB2, VDR-ApaI, VDR-BsmI, and VDR-FokI) on vertical jump was studied in top-level male Italian soccer players (n = 90). First, the authors calculated the traditional total genotype score and then determined the total weighting genotype score (TWGS), which accounts for the proportion of significant phenotypic variance predicted by the polymorphisms. Genomic DNA was extracted from saliva samples using a standard protocol. Genotyping was performed using polymerase chain reaction (PCR).

RESULTS

The results obtained from the new genetic model (TWGS) showed that only 3 polymorphisms entered the regression equation (ACTN-3, ACE, and BDKRB2), and these polymorphisms explained 17.68-24.24% of the vertical-jump variance. With the weighting given to each polymorphism, it may be possible to identify a polygenic profile that more accurately explains, at least in part, the individual variance of athletic-performance traits.

CONCLUSIONS

This model may be used to create individualized training programs based on a player's genetic predispositions, as well as to identify athletes who need an adapted training routine to account for individual susceptibility to injury.

Physical characteristics and abilities of junior elite male and female handball players

This study first aimed to examine strength, speed, and jumping abilities in 29 male and 29 female junior elite handball players and second to compare Under-18 and Under-16 players in the selected parameters. The players were chosen by the Norwegian Handball Federation, and all were tested in strength (squat and bench press), speed (10-, 30-, and 6 × 30-m repeated sprint ability), and jumping abilities (countermovement jump and squat jump [SJ]). Anthropometric qualities were also measured. Independent t-tests were applied to reveal possible mean differences between the U-18 and U-16 players within each sex. No significant differences in anthropometry were observed between the U18 and U16 players within either sex. Furthermore, we did not observe any significant between group differences among the male players in any of the tested performance parameters. On average, however, the U16 male (n = 14) players performed better in all the tests compared with in the U18 (n = 15) male players. Similarly, we did not find any significant differences in test performances between U18 female players and U16 female players. Still, a few trends (p ≤ 0.1) were observed because female U18 (n = 14) players were found to sprint faster on both 10 and 30 m and to jump higher in SJ vs. female U16 (n = 15) players. The empirical findings do not confirm the hypothesis of pubertal development and muscle growth leading to taller and heavier U18 players. Furthermore, we expected U18 players to perform better in all the tests when compared with U16 players. Again, the data did not substantiate this, although female U18 players tended to perform better in sprint and SJ compared with the U16 players.

Association of short-passing ability with athletic performances in youth soccer players

Purpose

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.

Methods

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.

Results

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.

Conclusion

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.

Neuromuscular function, hormonal and redox status and muscle damage of professional soccer players after a high-level competitive match

The main aim was to analyse the impact of an official match on hormonal and redox status, muscle damage and inflammation and neuromuscular function. Seven high-level male soccer players from the same team performed an official match and data were collected 72 h before, 24, 48 and 72 h post-match. Plasma testosterone/cortisol ratio (T/C), creatine kinase (CK), superoxide dismutase (SOD), glutathione peroxidase (GPX) and reductase (GR) activities, myoglobin (Mb), C-reactive protein (CRP), uric acid (UA), protein sulfhydryls (-SH), malondialdehyde (MDA) concentrations and total antioxidant status (TAS) were measured. Sprint, jump and change of direction performance, and maximal isokinetic knee extension and flexion were obtained as neuromuscular functional parameters. Cortisol increased and T/C decreased until 48 h recovery (P < 0.05). Mb, CRP and -SH (P < 0.05) increased at 24 h and CK, TAS, SOD and MDA (P < 0.05) increased up to 48 h recovery. GR increased and GPX decreased at 24 h recovery (P < 0.05). Jump performance decreased 24 h post-match (P < 0.05), but no significant alterations in sprint, change of direction and muscle strength were observed. In conclusion, an official match resulted in changes in plasma biomarkers until 48 h of recovery period, without major impact on performance.

Using balance training to improve the performance of youth basketball players

The aim of this study was to evaluate the effectiveness of 12 weeks of balance training to improve the balance and vertical jump abilities of young basketball players. Twenty-three players from two teams in the Under Fifteen Basketball Excellence category participated in the study. Participants were divided into two training groups: balance training (BAL, n = 11) and isotonic training (ISO, n = 12). Both groups were tested for balance and vertical jumps at the beginning of the competitive season and at the end of 12 weeks of specific training programme. All of the tests were performed in sustained bipodalic and monopodalic (both right and left) positions. The results showed that players who participated in balance training for 12 weeks, compared to players who trained with isotonic machines, exhibited a significantly increase in balance (bipodalic 28.3 %; right 41.4 %; left 45.8 %; p < 0.01) and muscular power (bipodalic 8.1 %; right 13.5 %; left 12.5 %; p < 0.01) as measured through a vertical jump. In conclusion, balance training using unstable boards was an effective training method for improving balance and the vertical jump, which is a basketball-specific action that frequently occurs in this sport.

Short-term training effects of vertically and horizontally oriented exercises on neuromuscular performance in professional soccer players

PURPOSE

The aim of this study was to compare the effects of 2 strength and conditioning programs involving either purely vertically oriented or combining vertically and horizontally oriented exercises on soccer-relevant performance variables (ie, acceleration, jumping ability, peak power, and endurance).

METHODS

Twenty-two professional male soccer players were randomly assigned to 2 training groups: vertical strength (VS, n = 11) and vertical and horizontal strength (VHS, n = 11). Players trained 2 times per week during all the preseason (5 wk) and 3 weeks of the competitive season. The effect of the training protocols was assessed using double-and single-leg vertical countermovement jumps (CMJ), half-squat peak power (PP), sprint performance over 5 and 15 m, and blood lactate concentration at selected running speeds.

RESULTS

Both groups obtained significant improvements in PP (P < .05; ES = 0.87 and 0.80 for VS and VHS, respectively) and small practical improvements in 5-m- (P < .05; ES = 0.27 and 0.25 for VS and VHS, respectively) and 15-m-sprint time (P < .05; ES = 0.19 and 0.24 for VS and VHS, respectively). The CMJ performance showed a small improvement (P < .05, ES = 0.34) only in the VHS group. Submaximal aerobic-fitness changes were similar in both groups (P < .05; ES = 1.89 and 0 .71 for VS and VHS, respectively).

CONCLUSION

This study provided a small amount of practical evidence for the consideration of preseason training protocols that combine exercises for vertical- and horizontal-axis strength development in professional male soccer players. Further studies using more aggressive training protocols involving horizontally oriented conditioning exercises are warranted.