Associations between force-velocity-power profile in sprinting and ballistic lower limb tests in adolescent elite footballers

This study investigated the relationships between performance and force-velocity (F-v) parameters obtained from a ballistic lower limb (BLL) and a 30-m sprint test in 24 adolescent elite footballers (13.2-15.1 years old). In the BLL test, normal ground reaction force and velocity were recorded by two force plates and a linear encoder, respectively, and take-off velocity (vto) at 0% of body mass was considered as performance. In the 30-m sprint test, raw velocity-time data were measured using a radar, and 5, 10 and 30 m sprint times using a timing gate system. Theoretical maximal force (F0), velocity (v0) and power (Pmax) were determined using the Samozino's method. All sprint times were significantly correlated with vto (p = 0.004 to p < 0.001; -0.57 to -0.72), but no significant correlation was found between the respective F-v parameters ;(p = 0.152 to 0.913). As both tests assess explosive performance, players who can produce a high vto will also perform best in short sprints. However, the F-v discrepancies highlight the complementarity of these tests: the BLL test minimises the coordination and technical influences that can affect sprint performance in adolescents.

Jump Squat Vs. Resisted Sprint Training Programs Applied to Elite Youth Soccer Players: Effects on Sprint and Power-Related Performance

ABSTRACT

Loturco, I, Pereira, LA, Mercer, VP, Oliveira, LP, Zanetti, V, Lima, L, Bastos, T, Moura, TBMA, and McGuigan, MR. Jump squat vs. resisted sprint training programs applied to elite youth soccer players: effects on sprint and power-related performance. J Strength Cond Res 38(12): 2107-2113, 2024-This study examined the effectiveness of 2 different and widely used training programs on the sprint and power-related performance of youth soccer players. Two distinct training strategies-vertically oriented jump squats (JSs) or horizontally oriented resisted sprints (RSs)-were executed under the same absolute loading conditions (i.e., 30% of the athletes' body mass [BM]) during a 4-week preseason period. Training schemes, loading intensities (based on %BM), and the number of experimental sessions were designed in conjunction with the soccer club's coaching staff, considering the calendar, available resources, and regular training programs. Twenty-five under-17 soccer players performed a series of speed, power, and jump tests before and after 10 resisted training sessions, consisting solely of loaded JS or RS. Overall, neither group (i.e., JS or RS training groups) exhibited any improvement in linear sprint and change-of-direction (COD) speed. Conversely, vertical jumping ability and peak velocity in the loaded JS increased significantly only in the JS group, which may positively affect players' performance and training prescription during short soccer preseasons. Given the challenges in enhancing sprint speed among soccer players during preseasons (and even over the competitive season), coupled with the limited effectiveness of RS in improving sprinting, COD, and jumping capabilities within congested and short training phases (i.e., ≤4 weeks), the regular use of RS training methods during these phases may be highly questionable. Coaches should carefully consider these critical limitations and potential disadvantages when designing neuromuscular training programs for soccer players during the preparatory phases of the annual training season.

A systematic review of resistance training methodologies for the development of lower body concentric mean power, peak power, and mean propulsive power in team-sport athletes

This study aimed to systematically review training methods prescribed to develop lower-body power, determine their effectiveness for the development of lower-body mechanical power and their implementation in an annual training cycle amongst team-sport athletes. The absolute and relative outcome values of concentric mean power, peak power and mean propulsive power were extracted from 19 studies. Outcomes were assessed using baseline to post intervention percent change, effect sizes, and the level of evidence concerning the method's effectiveness. A thorough analysis of the literature indicated that, based on the high level of evidence, traditional (e.g., strength training alone) and combination training (e.g., complex and contrast) methods should be considered. Further, optimal load and velocity-based training can be implemented if coaches have access to the appropriate equipment to monitor movement velocity and mechanical power in every session. This is of particular importance in periods of the season where high volumes of technical-tactical training and congested fixture periods are present. Also, flywheel, eccentric overload and weightlifting methods have been shown to be effective although the level of evidence is low. Future research should expand on current training practices whilst adequately reporting actual training loads from sport-specific training and games alongside strength-power training protocols.

Exploring countermovement jump variables across competitive levels and playing positions in futsal

Introduction

The aims of this study were to compare several countermovement jump (CMJ) kinetic variables between professional (PRO) and semi-professional (SEMI-PRO) futsal players and examine the differences amongst playing positions.

Methods

CMJ performance from 56 male futsal players (25.2 ± 4.8 years; weight: 74.4 ± 6.4 kg) was analysed. Players were separated into PRO (n = 29; 27.0 ± 4.4 years; 75.4 ± 6.0 kg) and SEMI-PRO (n = 27; 22.7 ± 4.3 years; 73.1 ± 6.8 kg), and according to playing position: defenders (n = 16; 25.4 ± 3.7 years; 75.2 ± 6.0 kg), wingers (n = 26; 23.5 ± 4.5 years; 72.0 ± 6.9 kg), and pivots (n = 14; 28.0 ± 5.6 years; 77.8 ± 4.3 kg). Linear mixed models and effect sizes were used for the analyses based on the mean of two jumps for each variable.

Results

PRO players presented a deeper center of mass (COM) displacement (p = 0.002, ES = 0.83), greater eccentric (Ecc) absolute (p = 0.019, ES = 0.61) and relative peak power (p = 0.046, ES = 0.52), and achieved greater Ecc peak velocities (p = 0.004, ES = 0.76) when compared to SEMI-PRO. Non-significant and trivial-to-small differences were observed in all the other CMJ variables according to the competitive level and playing position.

Discussion

Ecc capabilities (i.e., deeper COM displacement, greater Ecc absolute and relative peak power, and peak velocity) during vertical jump seem to differentiate PRO and SEMI-PRO players. However, CMJ variables do not discriminate amongst playing positions in futsal players.

The effect of high-intensity plyometric training on anaerobic performance parameters: a pilot study in U17 elite A league

The aim of this study was to examine the effects of high-intensity plyometric training (HIPT) on some parameters in elite soccer players in the U17. Volunteer soccer players were randomly divided into two groups according to their positions: the regular training (RT) group (age: 16.71 ± 0.47 years; stature: 163.46 ± 3.31 cm; body weight: 61.04 ± 1.59 kg) and the HIPT group (age: 16.64 ± 0.50 years; stature: 165.60 ± 3.03 cm; body weight: 59.76 ± 1.92 kg), and each group included five defenders, five midfielders, and four attackers. While the RT group did only routine soccer training, the HIPT group performed high-intensity plyometric training three days a week in addition to routine soccer training. In the study, body weight, stature, sprint (10 m, 30 m, and 40 m), jump (standing long jump, right and left-limb triple hop) and 5-0-5 change of direction speed test measurements of the soccer players were taken. Skewness and Kurtosis values obtained from the pre-test and post-test measurements were calculated to test whether the normality assumption of the study was met. A mixed measure two-way ANOVA test was used to determine the difference between the pre-test and post-test. The significance was set as p < 0.05. The results indicated that 8-week high- intensity plyometric training provided more improvement in measured performance parameters than routine soccer training. As a result, when the data obtained is examined, it can be said that HIPT had better values in sprint, jump, and change of direction parameters, so plyometric training was more beneficial for anaerobic parameters than routine soccer training in children. It is recommended that the trainers make their plans considering these results.

The development of physical characteristics in adolescent team sport athletes: A systematic review

BACKGROUND

Physical development during adolescence is crucial for athletes in team sports, as it prepares them for the high sport demands at the senior level. While physical development in non-athletes are well-documented, a comprehensive understanding of adolescent athletes' development, including the potential effects of team sports participation and training load, is lacking.

OBJECTIVES

The study aimed to investigate the development of physical characteristics in team sport athletes during adolescence (12-20 years) and explore the impact of training load.

METHODS

A systematic search of the databases PubMed, SPORTDiscus and Web of Science were conducted combining keywords related to physical characteristics, youth athletes, team sport and study design. Criteria for inclusion were: (1) team sport athletes aged 12-20 years, (2) cross-sectional or longitudinal designs investigating physical characteristics, (3) comparisons across different age groups, (4) peer-reviewed original article, (5) written in English, and (6) available results from physical testing. Results were normalized and weighted based on sample size.

RESULTS

176 eligible articles were identified. The results showed consistent annual improvement in most physical characteristics from 12 to 16 years for both sexes (e.g., boys: lower body strength 14.3%; intermittent endurance 11%; countermovement jump height 6.7%; change of direction 2.8%; 30 m sprint 3.6%, and girls: lower body strength 9.4%; intermittent endurance 12.1%; countermovement jump 4.7%; change of direction 3.3%; 30 m sprint 1.9%). Only 4 studies investigated the effect of training load on physical development.

CONCLUSIONS

Although both sexes consistently improved through adolescence, girls tended to have less pronounced physical development compared to boys, likely due to lower increase in lean mass and limb length. The existing evidence do not definitively establish whether team sports participation, compared to studies examining non-athletes, or training load have an additive effect on physical development during this period.

Mixed Training Programs Applied to Young Soccer Players: Effects on Speed-Power Abilities

We compared the effects of two 4-week strength-power-speed training protocols on physical performance of young soccer players. Twenty-three highly trained under-20 soccer players were randomly allocated to two mixed-training groups: 1) "traditional" (TRAD: n=11), comprising vertically oriented strength-power exercises and linear sprints; or 2) "multidirectional" (MULTI: n=12), combining vertically and horizontally oriented strength-power exercises, linear sprints, and change-of-direction (COD) drills. Squat jump (SJ) and countermovement jump, 2) linear sprint, COD speed, and 3) jump-squat (JS) and hip-thrust (HT) power tests were performed pre- and post-training. Differences were determined using a two-way ANOVA with repeated measures and "target scores" were used to detect real changes in performance. No group-time interactions were found for any of the variables (p>0.05). Significant increases (p<0.05) in 20-m sprint velocity, JS- and HT-power were found in both groups, and in SJ in TRAD. Individual analyses revealed a greater number of meaningful changes in zig-zag velocity in MULTI while most players in TRAD displayed meaningful increases in SJ height. In conclusion, both training protocols resulted in similar adaptations but, at the individual level, it appears that MULTI protocol is superior to improve COD ability while TRAD should be preferred to maximize vertical jumping capabilities during short soccer pre-seasons.

The use of sand as an alternative surface for training, injury prevention and rehabilitation in English professional football and barriers to implementation: a cross-sectional survey of medical staff

PURPOSE

The purpose of the present study was to investigate the use of sand as an alternative surface for training, injury prevention and rehabilitation interventions in English professional football. A Secondary aim was to explore the potential barriers to implementation.

MATERIALS AND METHODS

All 92 teams from the male English professional football pyramid during the 2021-22 season were eligible to take part. A cross-sectional survey of the medical personnel (one per club) was conducted between June 2021 and December 2021 based on the RE-AIM framework. A total of 58 respondents (63% of all clubs) completed the survey.

RESULTS AND CONCLUSIONS

Only 18 (31%) of the clubs surveyed used sand-based interventions across the last 3 seasons. Respondents felt sand-based interventions would be effective at improving physiological gains (median 4, interquartile range [IQR] 4-5) and as part of injury prevention and rehabilitation strategies (4, IQR 3-4) but were indifferent in relation to its potential to improve sporting performance (3, IQR 3-4). Barriers to implementation of sand-based interventions within wider football were a lack of facilities, lack of awareness of its potential benefits, lack of high-quality evidence and the surface not being specific to the sport. Medical staff also did not perceive that coaches' positively viewed sand interventions as a training or injury management strategy.

Effects of a Short-Term Detraining Period on the Strength Deficit and Functional Performance of Highly Trained Soccer Players

ABSTRACT

Loturco, I, Grazioli, R, Veeck, F, Nakamura, FY, Inácio, M, Schons, P, Preissler, A, Pinto, RS, Pereira, LA, McGuigan, MR, and Cadore, EL. Effects of a short-term detraining period on the strength deficit and functional performance of highly trained soccer players. J Strength Cond Res 37(10): 2058-2063, 2023-The aim of this study was to examine the effects of a 4-week detraining period on the neuromuscular performance of highly trained soccer players. Pre and post detraining, 18 adult soccer players (age: 27 ± 4.9 years; height: 180.2 ± 7.1 cm; body mass [BM]: 78.9 ± 7.6 kg) performed vertical jumps, 20-m linear sprints, curve sprint and change of direction speed tests, and a progressive loading test in the half-squat exercise with loads corresponding to 50, 100, and 150% of the players' BM to assess the peak-force (PF), mean power (MP), and strength-deficit (SDef). Pre and post differences in the variables of interest were analyzed using paired t -tests and effect sizes (ES). No significant changes were detected for vertical jumping height and sprint times. Higher PF at 50 and 100% BM and lower SDef were shown when comparing pre- and postassessments (ES = 0.66, 0.68, 0.55; p = 0.018, 0.016, and 0.046, respectively). The MP at 50 and 100% BM increased significantly after the detraining phase (ES = 0.56, 0.82; p = 0.049 and 0.007, respectively). The results indicate that these athletes were able to maintain and achieve satisfactory levels of performance after a short period of training cessation. Interestingly, some strength- and power-derived parameters improved significantly after short-term detraining, which may have important implications for training programs aimed at maximizing speed and power performance. It is recommended that coaches test their players not only at the beginning but also at the end of the season, to better evaluate variations in performance and thus create more efficient and tailored training strategies.

Speed Training Practices of Brazilian Olympic Sprint and Jump Coaches: Toward a Deeper Understanding of Their Choices and Insights (Part II)

This is the second article in a three-article collection regarding the plyometric, speed, and resistance training practices of Brazilian Olympic sprint and jump coaches. Here, we list and describe six out of the ten speed training methods most commonly employed by these experts to enhance the sprinting capabilities of their athletes. Maximum speed sprinting, form running, resisted sprinting, overspeed running, uphill and downhill running, and sport-specific movement methods are critically examined with reference to their potential application in different sport contexts. In an era when sprint speed is of critical importance across numerous sports, practitioners can employ the methods outlined here to design efficient training programs for their athletes.

Sprint and Jump Training on Sand vs. Grass Surfaces: Effects on the Physical Performance of Young Soccer Players

ABSTRACT

Pereira, LA, Freitas, TT, Zabaloy, S, Ferreira, RCA, Silva, ML, Azevedo, PHSM, and Loturco, I. Sprint and jump training on sand versus grass surfaces: effects on the physical performance of young soccer players. J Strength Cond Res 37(9): 1828-1833, 2023-The aims of this study were to (a) examine the effects of a 6-week sand training program including both sprint and jump exercises on the speed-related and vertical jump performance of elite young soccer players and (b) compare the changes induced by a sand training scheme with those induced by a similar training program (in volume, intensity, and exercise types) performed on grass. Twenty-four under-20 soccer players were randomly allocated to 2 training groups, as follows: "sand" ( n = 12) or "grass" ( n = 12) groups. Athletes performed squat and countermovement jumps, linear sprints, and Zigzag change-of-direction speed tests at pre-, mid- (after 6 training sessions), and postintervention (after 12 training sessions). Both groups exhibited similar increases in the vertical jump and Zigzag performance after the 6-week training period ( p values ranging from 0.0001 to 0.025; effect size ranging from 1.05 to 3.78, for main effect of time). No significant changes were detected for the linear sprint velocity for both the groups ( p values ranging from 0.079 to 1.00; effect size ranging from 0.07 to 0.65, for main effect of time). In summary, training on sand or grass surfaces resulted in similar improvements in the physical performance of elite young soccer players. This study confirms the current evidence on the effectiveness of both soft and harder training surfaces in improving the sprint and jump performance of team-sport athletes.

Effects of horizontal compared to vertical-based plyometric jump training on semi-professional soccer player's performance

This study aimed to compare the effects of horizontal (HJ) and vertical (VJ)-based plyometric jump training on male semi-professional soccer player's performance (e.g., change-of-direction speed [5-0-5 test]; 10-m, 20-m, and 30-m linear sprint speed). A parallel-study design was conducted. Participants were organized into HJ (n = 10) or VJ (n = 9) during 12 weeks. Measures of athletic performance were obtained in four phases: (i) before and (ii) end of the pre-season, (iii) during (weeks 7th), and (iv) after the intervention. The within-group analysis revealed that both HJ and VJ improved change of direction ([Formula: see text] = 27.783; p < 0.001 ([Formula: see text] = 21.635; p < 0.001),), 10-m linear sprint time ([Formula: see text] = 28.576; p < 0.001), 20-m linear sprint time ([Formula: see text] = 28.969, p < 0.001), and 30-m linear sprint time ([Formula: see text] = 26.143; p < 0.001). Similarly, the VJ-group also imposed significant changes on 5-0-5 time, 10-m linear sprint time ([Formula: see text] = 25.787; p < 0.001), 20-m linear sprint time ([Formula: see text] = 24.333, p < 0.001), and 30-m linear sprint time ([Formula: see text] = 22.919; p < 0.001). Between-group analysis revealed no significant differences in any of the assessment moments. HJ and VJ plyometric jump training are effective for improving the change-of-direction and a linear sprint of semi-professional players with no difference between types of intervention.

Kinetic and kinematic changes during resisted sprinting due to towing three common parachute sizes

BACKGROUND

Different sized parachutes may alter applied resistance during parachute towing (PT), changing results of resisted sprint training interventions. Thus, it was hypothesized that there may be significant net anteroposterior ground reaction force and impulse differences due to parachute size towed.

METHODS

Fifteen male sprinters completed control and PT sprints over a 50 m force platform system. Estimated aerodynamic drag, ground reaction forces and kinematic differences during the maximum speed phase were compared between control (no parachute) and PT trials with small (0.39 m²), medium (0.54 m²) and large (0.72 m²) parachutes, using One-way ANOVA (significance set at P<0.050) with Tukey's HSD post-hoc (critical Q value = 3.746) tests.

RESULTS

No significant (P>0.050) step length, step frequency, propulsive mean force, vertical mean force, or vertical impulse differences between trials. There was a significant anteroposterior impulse difference (P<0.001, Q=4.574) between small and medium PT, but no differences between medium and large PT. Compared to the control trial, all PT trials increased anteroposterior net mean force (P<0.001), anteroposterior net impulse (P<0.001), and propulsive impulse (P<0.001). However, only PT with the large parachute significantly reduced running speed (P<0.050, Q=3.792), braking mean force (P<0.050, Q=4.130) and braking impulse (P<0.001, Q=5.987), compared to the control trial.

CONCLUSIONS

A large parachute may be most effective for PT (compared to control trial) to overload the body during the maximum speed phase in a single session.

IMPROVEMENT OF SPEED AND EXPLOSIVE STRENGTH IN SOCCER PLAYERS

ABSTRACT Introduction: Besides good physical condition, soccer players should also possess good technical and psychological abilities. Physical fitness is a crucial factor in the competitive ability improvement of soccer players. Objective: Explore the improvement of running speed and explosive strength in soccer players. Methods: We selected 30 soccer players by random sampling. Individuals were randomly divided into experimental and control groups. Members of both groups participated in daily physical activities, and speed and strength training was added to the experimental group through a protocol with regular exercises. The athletes trained for ten weeks. The speed and explosiveness of the athletes were measured before and after the test. A mathematical and statistical analysis was made of the data collected. Results: There were significant differences in running speed and explosiveness strength in the athletes of the experimental group compared to the control group in the 30-meter dash, long jump, and Illinois run. Conclusion: Speed and strength exercises can significantly improve the running speed of athletes, and increase the muscular explosive force and physical agility of soccer players. The speed and strength exercises developed in this paper are consistent with the technical characteristics of soccer. These results can lay the foundation for future daily training planning and project work in soccer teams. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Effects of Maturation Stage on Sprinting Speed Adaptations to Plyometric Jump Training in Youth Male Team Sports Players: A Systematic Review and Meta-Analysis

Purpose

To determine the effects of maturation stage (eg, classified in the same intervention protocol as early-, and late-mature) on linear sprinting speed adaptations to plyometric jump training (PJT) in youth (aged <18 years) male team sports players.

Patients and Methods

Eligibility criteria was determined based on PICOS: (P) healthy youth male team sport players classified in the same intervention protocol in ≥2 maturation-related categories, based on a recognized maturation stage-determination method, including (but not limited to) Tanner stage; peak height velocity (eg, Mirwald method); radiography-based method (eg, Fels method); (I) athletes exposed to PJT with a minimum of 4 weeks duration; (C) athletes non-exposed to PJT (non-dedicated intervention, ie, only field-based regular training) or performing a parallel intervention not-related with PJT organized by maturation levels; (O) sprinting speed (eg, time, maximal sprint speed) measured in any linear sprint test trajectories before and after the intervention; (S) only randomized controlled and/or parallel trials. Searches were conducted on December 2021 in EMBASE, PubMed, Scopus, SPORTDiscus and Web of Science, restricted to Portuguese, Spanish and English languages, with no restrictions regarding publication date, and no filters applied. The PEDro scale was used to assess the risk of bias in the included studies. Meta-analysis was computed using the inverse variance random-effects model. The significance level was set at p < 0.05.

Results

The search identified 1219 titles. From those, four studies were selected for qualitative and quantitative synthesis. Four studies provided data for sprinting performance, involving 10 experimental and 8 control groups showing a small effect of trained participants on sprinting performance (ES = 0.31; p = 0.064; I2 = 41.3%) when compared to controls. No significant moderator effect was noted for somatic maturity (p = 0.473 between groups).

Conclusion

PJT had no significant effect on sprinting performance, although the inclusion criteria partially may explain that.

Variations of the Locomotor Profile, Sprinting, Change-of-Direction, and Jumping Performances in Youth Soccer Players: Interactions between Playing Positions and Age-Groups

The purpose of this study was two-fold: (i) analyze the variations of locomotor profile, sprinting, change-of-direction (COD) and jumping performances between different youth age-groups; and (ii) test the interaction effect of athletic performance with playing positions. A cross-sectional study design was followed. A total of 124 youth soccer players from five age-groups were analyzed once in a time. Players were classified based on their typical playing position. The following measures were obtained: (i) body composition (fat mass); (ii) jump height (measured in the countermovement jump; CMJ); (iii) sprinting time at 5-, 10-, 15-, 20-, 25- and 30-m; (iv) maximal sprint speed (measured in the best split time; MSS); (v) COD asymmetry index percentage); (vi) final velocity at 30-15 Intermittent Fitness Test (VIFT); and (vii) anaerobic speed reserve (ASR = MSS - VIFT). A two-way ANOVA was used for establishing the interactions between age-groups and playing positions. Significant differences were found between age-groups in CMJ (p < 0.001), 5-m (p < 0.001), 10-m (p < 0.001), 15-m (p < 0.001), 20-m (p < 0.001), 25-m (p < 0.001), 30-m (p < 0.001), VIFT (p < 0.001), ASR (p = 0.003), MSS (p < 0.001), COD (p < 0.001). Regarding variations between playing positions no significant differences were found. In conclusion, it was found that the main factor influencing changes in physical fitness was the age group while playing positions had no influence on the variations in the assessed parameters. In particular, as older the age group, as better was in jumping, sprinting, COD, and locomotor profile.

Exploring the Use of Player Load in Elite Soccer Players

BACKGROUND

The aims of this study were to (1) analyze the distribution of the player load (PL_TOTAL) in 3 axes of movement (PL_AP, anterior-posterior; PL_ML, medial-lateral; PL_V, vertical) during elite soccer matches, (2) investigate the effect of playing position on PL-related variables, and (3) explore the association between PL_TOTAL and distance covered by the players.

HYPOTHESIS

Despite different load distribution between axes of movement, PL_TOTAL might be used as a body load indicator for all playing positions.

STUDY DESIGN

Longitudinal study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Data were collected from elite soccer players using WIMU Pro tracking systems, which included inertial sensors.

RESULTS

The axis of movement had a significant effect on the distribution of the load (P < 0.001; conditional R² = 0.91), with the greatest contribution from the PL_V (P < 0.001; d = 5.41-5.86). Moreover, no effect of playing position on PL_TOTAL, PL_V, PL_ML, or PL_AP was observed (P > 0.05). Finally, a large correlation was found between PL_TOTAL and distance covered, and the linear mixed model showed that distance may be predicted by the PL_TOTAL (conditional R² = 0.81; P < 0.001).

CONCLUSION

Differences in load distribution were based on the axis of movement, although playing position had no effect on any variable. The selection of either distance covered, which is representative of a 2-dimensional analysis, or PL_TOTAL, which is representative of a 3-dimensional analysis, may be adequate for monitoring locomotor demands or accelerometer-derived load.

CLINICAL RELEVANCE

Training strategies that focus on the vertical component of match play should be adopted. In addition, given that PL_TOTAL is an accelerometry-based metric, which combines the accelerations in anterior-posterior, medial-lateral, and vertical planes, strength and conditioning coaches may use this parameter as a measure of total body load.

Assessing Inter-Limb Asymmetries in Soccer Players: Magnitude, Direction and Association with Performance

In this study, we aimed to analyze the magnitude and direction of inter-limb asymmetries in ankle dorsiflexion range of motion (ROM), power (using iso-inertial devices), and a neuromuscular skill (change of direction). Secondarily, we aimed to determine the relationship between inter-limb asymmetry scores for each test and also between these scores and the scores for the different performance tests. Sixteen semiprofessional male soccer players (age: 25.38 ± 6.08 years; body height: 1.78 ± 0.64 m; body mass: 79.5 ± 14.9 kg) participated in this study. We calculated inter-limb asymmetries using five tests: ankle dorsiflexion ROM, change of direction (COD 180º), and iso-inertial resistance tasks in the open (leg extension strength (LE), leg curl strength (LC)) and closed (crossover step (CRO)) kinetic chain. Our results showed that asymmetry magnitudes differed between all tests with highest inter-limb asymmetries displayed during iso-inertial overloading. In addition, we observed that the direction of asymmetries varied depending on the test-specificity, and that the CRO asymmetries had a negative association with LE and CRO performance. These findings highlight the independent nature of asymmetries and that CRO could be an appropriate test to detect asymmetries related with the performance of soccer-specific actions (such as changes of direction). Practitioners are encouraged to use multiple tests to detect existing inter-limb differences according to the specific characteristics of each sport.

Effects of a Congested Fixture Period on Speed and Power Performance of Elite Young Soccer Players

PURPOSE

To investigate the effects of a match-congested period on straight and curve sprint performance, change of direction (COD) speed and deficit, vertical jumping ability, and half-squat (HS) mean propulsive power (MPP) output in young soccer players.

METHODS

A total of 15 under-20 elite male soccer players participated in 14 matches over 8 weeks. The following assessments were performed before and after the congested fixture period: squat and countermovement jumps, 17-m linear sprint, curve sprint test for the "good" (CSGS) and "weak" (CSWS) sides, modified 17-m Zigzag test, and HS MPP. Magnitude-based inferences and a paired t test were used to analyze pre-post changes in the assessed variables.

RESULTS

Very likely (P < .05) decreases were noticed in 17-m sprint velocity (effect size [ES] [90% confidence limit; CL], -0.56 [-0.32 to -0.81]) and CSGS (ES [90% CL], -0.72 [-0.40 to 1.03]) after the 8-week period. A possible but nonsignificant impairment was revealed in CSWS (ES [90% CL], -0.18 [0.03 to -0.39]), and countermovement jump (ES [90% CL], -0.21 [-0.54 to 0.12]). Zigzag velocity (ES [90% CL], -2.90 [-2.45 to -3.36]) and COD deficit (ES [90% CL], 0.86 [0.52 to 1.20]) were almost certainly and significantly (P < .05) reduced and increased, respectively, after the match-congested period. An almost certain and significant (P < .05) reduction was found in HS MPP (ES [90% CL], -1.18 [-0.76 to -1.61]).

CONCLUSIONS

Straight and curve sprint velocity, COD speed and deficit, and HS MPP were impaired after the match-congested period. Vertical jump height was possibly decreased. Seasonal phases comprising high volumes of soccer-specific training and competition seem to be detrimental to speed-power qualities in under-20 elite soccer players.

Curve Sprint in Elite Female Soccer Players: Relationship with Linear Sprint and Jump Performance

The aim of this study was to examine the associations between linear sprint, curve sprint (CS), change of direction (COD) speed, and jump performance in a sample of 17 professional female soccer players. All athletes performed squat and countermovement jumps, single leg horizontal triple jumps, 17 m linear sprints, CS tests, and a 17 m Zigzag COD test. A Pearson product–moment test was performed to determine the relationships among the assessed variables. The significance level was set at p < 0.05. Nearly perfect associations (r > 0.9) were found between linear and CS velocities. Players faster in linear sprints and CS exhibited greater COD deficits. No significant associations were found between COD deficit and either body mass or sprint momentum. Jumping ability was significantly correlated with linear sprint and CS performance, but not to COD performance. These findings may be used by coaches and practitioners to guide testing and training prescriptions in this population. The associations observed here suggest that training methods designed to improve linear sprint and CS velocities may benefit from the implementation of vertically and horizontally oriented plyometric exercises.

Physical and Physiological Match-Play Demands and Player Characteristics in Futsal: A Systematic Review

Futsal, also known as five-a-side indoor soccer, is a team-sport that is becoming increasingly popular. In fact, the number of futsal-related investigations is growing in recent years. This review aimed to summarize the scientific literature addressing the match-play demands from the following four dimensions: time-motion/external load analysis and physiological, neuromuscular, and biochemical responses to competition. Additionally, it aimed to describe the anthropometric, physiological, and neuromuscular characteristics of elite and sub-elite male futsal players, contemplating the differences between competition levels. The literature indicates that elite futsal players cover greater total distance with higher intensities and perform a greater number of sprints during match-play when compared to sub-elite players. The physiological demands during competition are high (average intensity of ≥85% maximal heart rate and ~80% maximum oxygen uptake [VO2max]), with decrements between the two halves. Research suggests that neuromuscular function decreased and hormonal responses increased up to 24 h after the match. Considering anthropometric characteristics, players present low percentage of body fat, which seems commonplace among athletes from different on-court positions and competition levels. Elite players display greater values and at VO2max with respect to sub-elite competitors. Little is known regarding elite and sub-elite futsal players' neuromuscular abilities (strength, jumping, sprinting, and change of direction [COD]). However, it appears that elite players present better sprinting abilities compared to lower-level athletes. Futsal players aiming to compete at the highest level should focus on developing maximal speed, lower-body power and strength, aerobic capacity, and lean muscle mass.

Short-Term Detraining Does Not Impair Strength, Speed, and Power Performance in Elite Young Soccer Players

This study aimed to examine the effects of short-term detraining on the strength, speed, and jump capacities of under-20 soccer players. Twenty-four elite under-20 soccer players from the same professional club were assessed pre and post 26 days of detraining. The measurements were performed in the following order: countermovement jump (CMJ); 10 m linear sprint velocity; and one-repetition maximum test (1RM) in the horizontal leg-press exercise. To analyze the differences between pre- and post-tests, a paired T-test was applied. The significance level was set as p < 0.05. Soccer players exhibited a significant increase in CMJ performance (p = 0.02) and no significant differences in 10 m sprint velocity and 1RM leg-press were found after the short-term training cessation (p = 0.61; p = 0.55, respectively). We demonstrated that a short-term detraining period was capable of promoting a significant increase in the vertical jump height without inducing negative effects on the strength and speed capabilities of elite under-20 soccer players. Practitioners and sport scientists should be aware of these findings to program more effective training strategies at the beginning of the subsequent training cycle.

Multidirectional sprints in soccer: are there connections between linear, curved, and change-of-direction speed performances?

BACKGROUND

The aim of this study was to investigate the relationships between linear sprint, curve sprint (CS) and change of direction (COD) abilities and vertical jump performance in elite young soccer players.

METHODS

Twenty-nine players from the same soccer club participated in this study. On the same day, athletes performed countermovement jump (CMJ), 17-m linear sprint (with a 10-m split time), CS (for both sides) and COD tests. A Pearson product moment correlation was performed to determine the associations between the assessed variables. Significance level was set at P<0.05.

RESULTS

Linear sprint was significantly related to CS (r ranging from 0.67 and 0.76; P<0.05) but not to COD performance (r=0.23 and 0.33 for 10- and 17-m, respectively; P>0.05). CS ability (for both good and weak sides) was significantly associated with COD performance (r=0.60 and 0.54, respectively; P<0.05). CMJ height was significantly correlated with both linear and CS velocities (r varying between 0.50 and 0.68; P<0.05), but not with COD velocity (r=0.37; P>0.05).

CONCLUSIONS

Based on these findings, it is possible to suggest that training strategies designed to improve vertical jumping capacity may potentially improve both linear and curvilinear sprint abilities. Moreover, increases in COD velocity may also produce positive changes in CS performance.

A Novel Strategy to Determine the 1-Repetition Maximum in the Jump Squat Exercise

Loturco, I, McGuigan, MR, Rodríguez-Rosell, D, Pereira, LA, and Pareja-Blanco, F. A novel strategy to determine the 1-repetition maximum in the jump squat exercise. J Strength Cond Res XX(X): 000-000, 2020-This study aimed to determine the maximum relative load of the half-squat (HS; i.e., % HS 1-repetition maximum [1RM]) that can be used in its ballistic variation, namely, the jump squat (JS) exercise, and to examine whether this reference value varies in subjects with different strength levels. In total, 186 elite athletes from 10 distinct sport disciplines participated in this study. A progressive loading test up to HS 1RM was performed during the competitive phase of the season for all athletes. Mean propulsive velocity and propulsive phase duration were also assessed during the 1RM test. Athletes were divided into 3 distinct subgroups: "low," "middle," and "high" strength levels, based on their relative HS 1RM values (kg·kg). A 1-way analysis of variance was used to compare the variables assessed between the groups. Significance level was set at p < 0.05. The high group demonstrated the highest relative HS 1RM values, followed by the middle and low groups (all p < 0.05). No significant differences were observed between the groups for the remaining variables (p > 0.05). It was observed that at 86.0 ± 5.4% 1RM, the full concentric action can already be considered as entirely propulsive in the HS exercise for all subjects, independent of their strength levels. Therefore, this relative strength value may be used as a reference for the 1RM in the JS exercise.