Effects of maturation on myotonometric parameters and their predictors of athletic performance in elite youth soccer players.

The aim of the present study was to investigate the variations in individual muscle stiffness across different maturation stages (i.e., peak height velocity [PHV]) in elite youth soccer players and to explore the associations between lower limb muscle stiffness and performance in sprinting (10, 20, and 40 m sprint), maneuverability (9-3-6-3-9 m sprint test), and jumping (countermovement jump [CMJ]). A total of 131 elite youth soccer players aged 12-18 years, volunteered to participate in the study and were divided into pre-PHV (n = 21), mid-PHV (n = 33), and post-PHV (n = 80). Muscle stiffness of the rectus femoris (RF) and biceps femoris (BF) muscles was assessed using a MyotonPRO. Results showed that players in the pre-PHV stage had lower stiffness in the BF and RF muscles compared to mid-PHV (p < 0.001; effect size [ES] = moderate to large) and post-PHV players (p < 0.001; ES = moderate to large). It was also observed that the mid-PHV group had lower stiffness levels in their RF muscle compared to the post-PHV group (p < 0.001; ES = small). Significant correlations were found between BF and RF stiffness and sprint (p < 0.001) and maneuverability (p < 0.001) performance. RF stiffness showed a significant positive correlation with CMJ (p < 0.05), suggesting that greater lower body stiffness is beneficial for athletic performance in youth soccer players. The findings highlighting the importance of considering training methods that increase muscular stiffness, particularly in relation to the RF muscle, to optimize athletic performance.

Effects of Different Recovery Duration on External and Internal Load Measures during Bouts of Small-Sided Games.

The aim of this study was to analyse the effects of different recovery times between bouts of small-sided games (SSG) on external and internal load variables in semi-professional soccer players. Sixteen male semi-professional soccer players performed three 4 vs. 4 + goalkeeper SSG training sessions, each with different recovery bout duration: short (1 min) (SSG1), medium (2 min) (SSG2), and long (4 min) (SSG4). Time motion and neuromuscular measures were collected during all SSGs, in addition, the rating of perceived exertion (RPE) was determined at the end of the last bout of each SSG. Results showed a significant increase in the total number of accelerations (p = 0.016, ES = 0.97, large) and decelerations (p = 0.022, ES = 0.81, large) in SSG4 compared to SSG1. In terms of the internal load, SSG2 showed significantly higher RPE values (p = 0.011, ES = 1.00, large) in comparison with SSG1. If the sessions' focus is on neuromuscular training, longer recovery times between SSG bouts should be used. Conversely, if the aim is to reach a higher total and running distance at different intensities, a 2-min recovery period between bouts may be more appropriate.

Application of arbitrary and individualized load quantification strategies over the weekly microcycle in professional soccer players.

The aims of this study were to: (a) determine the differences in external load quantification between arbitrary and individual speed thresholds over the weekly microcycle in professional soccer players, and (b) analyse the association between internal load and different external load quantification strategies (ELQSs). Ten professional outfield players were monitored during training sessions and official matches using 10 Hz GPS devices over a 6-week in-season period. The absolute and relative ("R" before the distance category) distances covered were calculated for the following external load variables: medium-intensity running distance (MIR), high-intensity running (HIR), sprint distance (SD), and very high-intensity running (VHIR). Individualized thresholds were determined based on maximal sprinting speed (MSS) and the last speed achieved during the 30-15 Intermittent Fitness Test (VIFT) of each player. In terms of match-day workload, significant differences (p < 0.05) were observed between arbitrary and individualized strategies (i.e., MSS and VIFT) for the distance covered in MIR, HIR, SD, VHIR, RHIR, RSD, and RVHIR. The MSS strategy compared to arbitrary thresholds revealed significant differences (p < 0.05) for distance covered in HIR, RHIR, and VHIR during all training sessions. The present results showed that arbitrary thresholds lead to underestimation of external load absolute and relative metrics compared to the MSS strategy throughout the microcycle. The VIFT strategy mainly revealed differences in external load quantification regarding MD compared to arbitrary thresholds. Individualized speed threshold strategies did not achieve better associations with internal load measures in comparison with arbitrary thresholds in professional soccer players.

Do small-sided games prepare players for the worst-case scenarios of match play in elite young soccer players?

The aim of the study was to determine whether the physical performance of young soccer player during various small sided games (SSGs) underloads, replicates or overloads the requirements of the worst-case scenarios (WCS) during match play. A total of 521 SSGs' individual observations and 15 different formats of SSGs with different areas per player (ApP) (ApP100: < 100; ApP200: ranged from 101 to 200; ApP300: > 201, all in m2 · player-1) were taken into consideration. Whole (90-min average; OM) and 15-, 5- and 1-min worst-case scenarios (WCS15, WCS5 and WCS1, respectively) were analysed. Total distance covered relative (m · min-1) (TDCR), high-speed distance relative (m · min-1) (HSDR), very high-speed distance relative (m · min-1) (VHSDR) and sprint distance relative (m · min-1) (SDR), player load relative (PLR) and both total (ACCR) and high intensity relative accelerations (n · min-1) (ACCHR) were collected. All external load measures analysed were significantly higher in WCS1 compared to WCS of longer duration and SSGs with different ApP (p < 0.001). The analysis demonstrated interactions between game type and player positions (p < 0.001) for TDCR, VHSDR, PLR and ACCHR. The SSG formats did not sufficiently stimulate the WCS for locomotor demands (VHSDR and SDR). SSGs played on an ApP100 overestimated the mechanical values compared to WCS15 and WCS5. The analysed SSG formats did not sufficiently stimulate players to cope with all external load demands that occurred during WCS1. This study provides useful information for practitioners on the heightened impact of different SSG formats on external load in relation to the WCS of competitive match play.

Effectiveness of short vs. long-distance sprint training on sprinting and agility performance in young soccer players.

The purpose of this study was to examine the effects of short sprint-distance training (SST) compared with long sprint-distance training (LST), matched for the total session training volume, on short-, medium- and long-distance sprint performance and agility in young soccer players. Eighteen U19 male players (age: 17.1 ± 0.7 years; height: 178.0 ± 6.3 cm, body mass: 69.4 ± 6.6 kg) were randomly assigned to SST (n = 9) or LST (n = 9) group. The intervention programs were performed 2 times a week over 6 weeks. Before and after training period, 5 m, 10 m, 20 m, 30 m and 40 m sprint, and agility were assessed. Within-group analysis showed significant improvements (p ≤ 0.001) in 5 m, 10 m, 20 m, 30 m and 40 m sprint from pretest to posttest in SST (9.2%, 6.6%, 5.3%, 2.9%, and 2.5%, respectively) and LST (10.5%, 8.5%, 6.5%, 5.1%, and 4.7%, respectively). Players in both SST and LST also showed significant enhancements in agility from pretest to posttest. In the between-groups analysis, there were no differences between the sprint training groups (SST vs. LST) in any variable (p > 0.05). In conclusion, the findings of this study indicate that both sprint training distances used seem to be effective to improve soccer-specific performance measures. However, due to the better percentage changes obtained by LST group in all fitness variables, this method could be considered as preferred method.

Tensiomyographic Assessment of Contractile Properties in Elite Youth Soccer Players According to Maturity Status.

Little is known about how muscle contractile properties are affected by biological maturation in elite youth soccer players. This study aimed to determine the effects of maturation on contractile properties of rectus femoris (RF) and biceps femoris (BF) muscles assessed by tensiomyography (TMG) and provide reference values for elite youth soccer players. One hundred twenty-one elite youth soccer players (14.98 ± 1.83 years; 167.38 ± 10.37 cm; 60.65 ± 11.69 kg) took part in the study. The predicted peak height velocity (PHV) was used in order to establish players' maturity status (Pre-PHV, n = 18; Mid-PHV, n = 37; Post-PHV = 66). Maximal radial displacement of the muscle belly, contraction time, delay time, and contraction velocity for RF and BF muscles were recorded. One-way ANOVA showed no significant differences between PHV groups for any tensiomyography variables in RF and BF muscles (p > 0.05). Our results established that maturity status did not show a significant effect in mechanical and contractile properties on RF and BF muscles evaluated by TMG in elite youth soccer players. These findings and reference values can be useful for strength and conditioning coaches of elite soccer academies in order to optimize the evaluation of neuromuscular profiles.

The seven phases of match status differentiate the running performance of soccer players in UEFA Champions League.

The purpose of this research was to investigate the running performance of professional soccer players in relation to seven phases which resulted in the changing or maintaining the match status in the UEFA Champion League games during season 2020/2021. Moreover, we aimed to define which match status phases occur at the earliest stage of regular game time. This study involved professional soccer players from 24 teams participating in the group stage of UEFA Champions League in season 2020/21. The match status was divided into seven phases that result in changing or maintaining the match outcome: DW (Drawing to Winning); LD (Losing to Drawing); WW (Winning to Winning); DD (Drawing to Drawing); LL (Losing to Losing); DL (Drawing to Losing); WD (Winning to Drawing). Such running performance variables as: total distance covered (TDC) and distance covered in high-intensity running (HIR) were analyzed. Players participating in the UEFA Champions League matches cover the longest TDC in DW, DL and DD phases. TDC in these stages was between 111 and 123 m min-1. The highest HIR was recorded during phases: DW, DL and LL (range between 9.91 and 10.82 m min-1). In contrast, the lowest total distance and distance in HIR is covered during WD phase (only 105.57 ± 1.89 m min-1 and 7.34 m min-1 respectively). On average, phases resulting in the change of the match status occur during the first half, while all phases maintaining the result in the second half. Coaching staffs should consider registering and analysing the physical match performance in relation to described seven match status phases. Such information allows to prepare team-specific training drills, that players should perform more often in order to change or maintain the status of the game.

Changes of physical match performance after the COVID-19 lockdown in professional soccer players according to their playing position.

The aim of this study was to evaluate the impact of the pandemic lockdown, which included training cessation and home-based training, on physical performance in professional soccer players from the Polish Ekstraklasa according to their playing position. The research was based on 3137 players' individual match performance observations during the 2019/2020 season divided into before (26 matchdays) and after (11 matchdays) lockdown periods. The data were collected using the computerised multiple-camera optical tracking system TRACAB (ChryronHego VID, New York, NY) with a sampling frequency of 25 Hz. Independently of playing position, a significant (p < 0.001) reduction in season resumption metrics of total distance (-0.9%), jogging (-1.6%), running (-3.4%) and high-speed running (-2.5%), with a contemporaneous increase in walking distance (1.4%), was noted in relation to pre-lockdown performance. A reduction in high-speed running was observed in central defenders (p < 0.05), central midfielders (p < 0.01) and forwards (p < 0.05). No significant decrease in sprinting or maximal running velocity was observed. The COVID-19 lockdown negatively influenced the physical performance in professional soccer players.

The effect of mid-season coach turnover on running match performance and match outcome in professional soccer players.

The aim of this research was to examine the physical match performance and match outcome before and after coach turnover in professional soccer teams compared with a control group containing coaches working continuously for 3 consecutive seasons. Analysed data included 325 performances of teams led by dismissed coaches (DC), 313 of teams led by new coaches (NC), and 580 of teams led by unchanged coaches (UnC). Variables, such as average number of collected points, total distance (TD), total distance per minute (TD/min), high-speed running (HSR), sprinting and number of high-intensity runs (NHIR), were analysed in the last 15 games of DC and 15 matches of NC. These periods were divided into 3 blocks out of 5 matches (5-match blocks). NC collected a significantly higher number of points than DC (p = 0.015), whereas average points collected by UNC were significantly greater than DC (p < 0.001 and NC (p = 0.012). TD and TD/min for DC were significantly lower (p < 0.001) compared with both NC and UnC, whereas significant differences in HSR (p = 0.003) and NHIR (p = 0.03) were identified between DC and NC. The current study reported that mid-season coach turnover may result in short-term improvement in team results and physical match performance. However, this effect disappears after a period of approximately 5 games.

Why Percussive Massage Therapy Does Not Improve Recovery after a Water Rescue? A Preliminary Study with Lifeguards.

The aim of this study was to analyze the effects of percussive massage therapy (PMT) on lifeguards' recovery after a water rescue, in comparison with passive recovery. Methods: A quasi-experimental crossover design was conducted to compare passive recovery (PR) and a PMT protocol. A total of 14 volunteer lifeguards performed a simulated 100 m water rescue and perceived fatigue and blood lactate were measured as recovery variables after the rescue and after the 8-min recovery process. Results: There were no differences between PMT and PR in lactate clearance (p > 0.05), finding in both modalities a small but not significant decrease in blood lactate. In perceived fatigue, both methods decreased this variable significantly (p < 0.001), with no significant differences between them (p > 0.05). Conclusions: PMT does not enhance recovery after a water rescue, in comparison with staying passive. Despite PMT appearing to be adequate for recovery in other efforts, it is not recommended for lifeguards' recovery after a water rescue.

Does Vibration Foam Roller Influence Performance and Recovery? A Systematic Review and Meta-analysis.

BACKGROUND: Foam rolling has been extensively investigated, showing benefits in performance and recovery. Recently, vibration has been added to foam rollers, with hypothesized advantages over conventional foam rollers. However, there is no systematic evidence in this regard. OBJECTIVE: To carry out a systematic review and meta-analysis about the effects of vibration foam roller (VFR) on performance and recovery. METHODS: A systematic search was conducted in PubMed/MEDLINE, Web of Science and SportDiscus according to the PRISMA guidelines. The outcomes included performance (jump, agility and strength) and recovery variables (blood flow, pain and fatigue) measured after an intervention with VFR. The methodological quality was assessed with the PEDro scale. A random-effects model was used to perform the meta-analysis. RESULTS: Initially, 556 studies were found and after the eligibility criteria 10 studies were included in the systematic review and 9 in the meta-analysis. There was no significant effects on jump performance (SMD = 0.14 [95% CI - 0.022 to 0.307]; p = 0.101; I2 = 1.08%) and no significant beneficial effects were reported on isokinetic strength (SMD = 0.16 [95% CI - 0.041 to 0.367]; p = 0.117; I2 = 9.7%). Recovery appears to be enhanced after VFR interventions, but agility does not seem to increase after VFR interventions. CONCLUSION: This systematic review and meta-analysis suggest that VFR could have great potential for increasing jump performance, agility, strength and enhancing recovery. Further research is needed to confirm the effects of VFR on performance and recovery. Trial Registration This investigation was registered in PROSPERO with the code CRD42021238104.

Small-sided games in female soccer players: a systematic review.

INTRODUCTION: This systematic review aimed to analyze the literature on small-sided games (SSGs) from a physiological and physical perspective in female soccer players. EVIDENCE ACQUISITION: A systematic review of Web of Science, PubMed, Scopus and SPORTDiscus was performed according to PRISMA (Preferred, Reporting Items for Systematic reviews and Meta-Analysis) Guidelines. Studies informed about physical and/or, physiological-responses during SSGs played by young and/or adult amateur and/or professional female soccer players were included. Information regarding study information, population, intervention data, instruments, variables analyzed, and outcomes were elucidated. EVIDENCE SYNTHESIS: The search returned 2944 records. After screening against set criteria, a total of 13 manuscripts were fully reviewed. The present review grouped studies according to the three following age categories taking sample's mean age into account: Under-19 as young players and senior female players (>19 years old). The most common topics of analysis were: 1) player number; 2) pitch area and game surface; 3) sex differences; and 4) training regimens. CONCLUSIONS: This review provides useful information on the complex relationship between technical, physical and physiological interactions in SSGs and how manipulating these types of variables can improve the soccer training process.

Effects of Copenhagen Adduction Exercise on the Architectural Characteristics of Adductors in U-17 Male Soccer Players: A Randomized Controlled Trial.

Groin injuries are one of the most prevalent in male soccer players, especially due to the hip adductor muscles' weakness which is considered as a risk factor in these injuries. The Copenhagen adduction (CA) exercise has been demonstrated to increase the strength of adductor muscles, but its effects on the architectural characteristics of adductor muscles have not been studied yet. This study aimed to analyze the effects of the CA exercise on the muscle thickness of the adductors. Twelve male U-17 soccer players were randomized into two groups: the control group with no intervention and the experimental group with an intervention based on an eight-week training with CA exercise. The muscle thickness of adductors was measured before and after the intervention using ultrasound imaging. A significant increase in muscle thickness was found in both control (p = 0.002) and experimental group (p < 0.001), but the experimental group did not show additional effects in comparison with the control group. In conclusion, an 8-week CA exercise intervention does not increase the muscle thickness of adductors in U-17 soccer players more than their regular training.

[Perception, knowledge and education for drowning prevention in adolescent.] / Percepciones, conocimientos y educación para la prevención del ahogamiento en adolescentes.

OBJECTIVE: Drowning is a major problem of public health in Spain, with a high number of deaths. The main strategy to address it is prevention, going through knowledge and education. The aim of this study was to analyze from a public health perspective a) the knowledge of young participants from 14 to 16 years old about drowning prevention, swimming skills and risks on the beach and b) to evaluate a pilot program with educational video for drowning prevention due to rip currents. METHODS: For this purpose, a three-phase study was carried out: (1) application of a questionnaire to identify bath habits, risk perception in relation to rip currents and swimming level, (2) evaluation of a video for the identification of rip current risk and (3) evaluation of the assimilation of the visualized content one month after the intervention. 120 adolescents participated in this study during march, april and may, 2019. A descriptive analysis and comparisons with Chi-Square were performed in SPSS. RESULTS: 120 adolescents participated in this study during March, April and May, 2019. 96.7% knew how to swim, but 44.1% had a basic level. More than half of the participants did not know rip currents or did not identify them in swimming areas. The video achieves the assimilation of concepts related to rip currents and drowning prevention. CONCLUSIONS: These findings suggest that adolescents have a lack of knowledge about rip currents and are not able to identify safe swimming areas. The use of health communication strategies based on the interests and profiles of young people have shown an improvement in the perception of risks at beaches on the sample studied.

OBJETIVO: El ahogamiento es un problema de salud pública en España, con un gran número de muertes. La principal estrategia para abordarlo es la prevención, que debe pasar por el conocimiento y la educación de las personas. El objetivo de este estudio fue analizar desde la perspectiva de salud pública: a) los conocimientos de adolescentes entre 14 y 16 años sobre prevención del ahogamiento, habilidades de natación y riesgos en la playa y b) evaluar un programa piloto de formación mediante un video educativo para prevenir ahogamiento por corrientes de resaca. METODOS: Se realizó un estudio en tres fases: (1) aplicación de un cuestionario para identificar los hábitos de baño, la percepción del riesgo con relación a las corrientes de resaca y el nivel de natación, (2) evaluación de un programa formativo mediante un vídeo y (3) evaluación de la asimilación del contenido visualizado tras un mes. 120 adolescentes participaron en este estudio durante los meses de marzo, abril y mayo del 2019. Se realizó un análisis estadístico descriptivo y de comparaciones mediante la prueba Chi-Cuadrado con el programa SPSS. RESULTADOS: El 96,7% sabían nadar, pero 44,1% tenían un nivel básico. Más de la mitad no conocían las corrientes de resaca o no las identificaron en zonas de baño. La intervención educativa mediante un vídeo logró mejorar el conocimiento. CONCLUSIONES: Los adolescentes tienen una falta de conocimiento sobre las corrientes de resaca y no son capaces de identificar zonas de baño seguras. El uso de estrategias de comunicación para la salud, basadas en los intereses y perfiles de personas jóvenes han mostrado una mejora en la percepción de los riesgos en las playas en la muestra estudiada.

Acute Effects of Foam Rolling on Blood Flow Measured by Ultrasonography in Soccer Players.

ABSTRACT: Alonso-Calvete, A, Padrón-Cabo, A, Lorenzo-Martínez, M, and Rey, E. Acute Effects of Foam Rolling on Blood Flow Measured by Ultrasonography in Soccer Players. J Strength Cond Res 35(11): 3256-3259, 2021-In recent years, foam rolling (FR) has become a popular device for recovery to increase range of motion and decrease pain after sport practice and competition. However, there is little evidence about the underlying physiological effects of FR, specifically in blood flow parameters. Thus, the aim of this study was to analyze acute effects of FR on blood flow parameters (maximal velocity and maximal volume) measured by Doppler ultrasonography in soccer players. Twelve soccer players were assessed in 3 different situations: pre-FR intervention, immediately after FR intervention, and 30 minutes after FR intervention. The femoral artery was measured in the dominant leg with subjects in horizontal lying position. Before the intervention, subjects completed one familiarization session with FR. The FR intervention consisted of 2 sets, each with 45 seconds of FR and 15 seconds of rest between sets with a high-density foam roller in quadriceps, hamstrings, and iliotibial band. Results showed a significant increase in both maximal velocity (p < 0.001; effect size [ES] = 0.81) and maximal volume (p = 0.001; ES = 1.73) after intervention in comparison with pretest, but after 30 minutes, there were no significant differences. Therefore, this increase of the blood flow could promote important advantages for postexercise recovery, suggesting an acute effect that may contribute to the understanding of local physiological mechanism of FR.

Follicular phase of menstrual cycle is related to higher tendency to suffer from severe injuries among elite female futsal players.

OBJECTIVE: To describe the injury incidence according to each phase of menstrual cycle (MC) in professional futsal players along two consecutive season and, secondly, to compare the injury incidence and frequency between different phases of the MC. DESIGN: Prospective cohort study. SETTINGS: Elite futsal players. PARTICIPANTS: 179 players. MAIN OUTCOME MEASURE: Players were registered along two consecutive seasons. RESULTS: 191 injuries were reported throughout both seasons. The injury incidence was 30.63 days-off during the follicular phase, 23.6 during ovulatory phase and 17.59 days-off in luteal phase, showing higher incidence during the follicular phase. No statistical differences (p > 0.05) were reported for any variable comparing among the three phases of MC. CONCLUSIONS: This study suggests the relevance to track the MC, but reduces its possible relationship or influence on the injury distribution during each phase of the MC. The knowledge of injury incidence, burden and etiology is a key factor to design injury prevention programs with the focus on the most common injuries, where MC could be included as a complementary factor.

The Influence of COVID-19 Pandemic Lockdown on the Physical Performance of Professional Soccer Players: An Example of German and Polish Leagues.

The purpose of this study was to investigate whether the in-season pandemic lockdown influenced physical match performance in professional soccer players who participated in the competition of German Bundesliga and Polish Ekstraklasa. The data from 306 games for German Bundesliga and 296 games for Polish Ekstraklasa were divided into before- and after-lockdown periods. The physical performance of German Bundesliga teams after the 63-day COVID-19 lockdown did not differ significantly from that in the first part of the season. In contrast, Polish Ekstraklasa teams, after the 81-day lockdown, displayed significantly shorter total distances (p < 0.001), shorter high-intensity running distances (p = 0.03), and fewer high-intensity actions (p = 0.02). Moreover, when the effective playing time was considered, teams covered significantly less relative total distance (p < 0.001) and relative high-intensity running distance (p = 0.02). The results of the current study suggest that physical performance during the matches of the German Bundesliga was not influenced by the COVID-19 lockdown, contrary to those of the Polish Ekstraklasa. This difference could have been caused by different break lengths and different restrictions implemented in these countries during the pandemic lockdown.

Talent Selection Strategies and Relationship With Success in European Basketball National Team Programs.

There is limited knowledge of the talent selection strategies used by national sporting organizations to identify and develop talented players in basketball. Therefore, we aimed to explore differences in selection strategies between European youth basketball national team (NT) programs, and how they relate to the program's success. Specifically, we examined differences in the number of youth NT players and within-country variance in the 1988-1999 generations between 38 countries (n men = 38, women = 32). Further, we tested if the number of youth NT players and within-country variance was related to the NTs senior ranking, youth ranking, and youth-to-senior player promotion, using generalized Bayesian multilevel models. We further checked the moderating effect of the amount of licensed basketball players in each country. On average, 15.6 ± 2.0 male and 12.4 ± 1.8 female players were selected per generation. Over a third of the NTs consistently selected a higher or lower number of players than the average, with a difference of 8.1 players (95% CI [5.8, 10.8]) for men and 7.6 players (95% CI [5.4, 10.0]) for women between the countries with the highest and lowest average. When licensed players were used as moderator, the differences decreased but did not disappear, in both genders. There was an above 99.3% probability that a higher number of players was positively related to higher men's senior and youth rankings, and women's youth ranking. Within countries, generations with a higher number of youth players generated more senior players, with a probability of 98.4% on the men's, and 97.3% on the women's side. When licensed players were used as moderator, the probabilities for these relationships remained largely unaffected, apart from women's youth ranking, which sank to 80.5%. In conclusion, the selection strategy in basketball NT programs varies between European countries and selecting a higher number of players possibly relates to better long-term performance and more players promoted to the senior NTs. These findings show that talent development programs should make conscious decisions about their selection strategies as it can affect their success.

Effects of Plyometric Training with Agility Ladder on Physical Fitness in Youth Soccer Players.

The aim of this study was to assess the effects of plyometric training with an agility ladder on components of physical fitness in youth soccer players. A total of twenty male under-13 soccer players were randomly assigned to a plyometric training group with an agility ladder (n=10) or a control group (n=10). Before and after training intervention linear sprint test (5 m, 10 m, 20 m), vertical jump ability (squat jump, countermovement jump and countermovement jump with arms), agility test, and slalom dribble test were assessed. The plyometric training with agility ladder was applied two times per week over six weeks. Data were analyzed using linear mixed model. The plyometric training group showed significant improvements (p<0.001) from pre-test to post-test in countermovement jump, countermovement jump with arms, and slalom dribble test. In the control group, no significant enhancements were obtained in all performance tests (p>0.05). The between-group analysis showed significant differences in countermovement jump with arms (p=0.03), but no significant differences (p>0.05) were found in squat jump, countermovement jump, sprint, agility test, and slalom dribble test. In conclusion, the short-term plyometric training with agility ladder seems to be ineffective and not time-efficient to improve physical fitness in youth soccer players. However, the interpretation of these results must be understood within the sample size limitations.

Analysis of Physical and Technical Performance of Substitute Players in Professional Soccer.

Current soccer scientific literature is scarce with regard to examining the technical performance of substitute players. Purpose: This study aimed to analyze the physical and technical performance of substitute players versus those who completed the entire match or were replaced and also examine the performance of substitutes across different playing positions. Method: The sample was composed of 6,631 match observations from 431 professional soccer players competing in the German Bundesliga during the season 2018-2019. These observations were divided into three groups: entire match (n = 3,807), replaced (n = 1,412), and substitutes (n = 1,412). Linear mixed models were adjusted to compare the performance of the three groups independently of playing position and separately for each position (central defenders, fullbacks, central midfielders, wide midfielders, and attackers). Results: Substitute players showed higher total distance covered (effect sizes [ES]: 0.99-1.06), number of sprints (ES: 0.60-0.64), and number of fast runs (ES: 0.83-0.91) relative to playing time than replaced and entire match players. The differences in technical performance between groups varied according to playing position. Substitute central defenders showed less possession (ES: 0.39-0.41), touches (ES: 0.47-0.57), and passes (ES: 0.54-0.59) but higher defensive performance (ES: 0.51-0.54) than replaced and entire match players. Substitutes in midfield and attack positions displayed more possession (ES: 0.22-0.47), touches (ES: 0.27-0.37), and shots (ES: 0.22-0.28) than replaced and entire match players. Conclusion: This study has shown that substitutes are able to improve the performance of the players who completed the entire match or were replaced in both physical and some technical variables depending on playing position.