Inter-limb asymmetries are common in soccer players and are frequently monitored in high-performance settings; however, their expression across different flywheel-based strength exercises, movement phases, and over time remains unclear. This study aimed to (i) compare inter-limb power asymmetry magnitudes across multiple unilateral flywheel exercises and between concentric (CON) and eccentric (ECC) phases, and (ii) describe changes in these asymmetries over an 8-week period of routine soccer training, stratified by baseline asymmetry magnitude. The present study was designed as an observational and descriptive study. Twenty-one professional male soccer players completed two testing sessions separated by eight weeks. Players performed six unilateral flywheel exercises targeting hip- and knee-dominant quadriceps (Qhip, Qknee), hip- and knee-dominant hamstrings (Hhip, Hknee), adductors (ADD), and abductors (ABD). For each exercise and limb, the repetition with the highest CON mean power and its consecutive ECC phase were selected for analysis. Inter-limb asymmetry (%) was calculated for mean and peak power in both phases. Across exercises, ECC asymmetries were generally greater than CON asymmetries, with the largest values observed for Qknee peak power (CON: 12.86 ± 11.04%; ECC: 27.60 ± 13.65%) and Hknee peak power (CON: 10.45 ± 11.26%; ECC: 24.01 ± 20.46%). Exercise-specific patterns were evident, with generally weak associations between asymmetries across tasks. Over time, players classified with higher baseline asymmetry (≥10%) presented lower values at follow-up in several outcomes (particularly ECC-related measures), whereas players with lower baseline asymmetry (<10%) showed small increases or remained stable; These between-group patterns should be interpreted cautiously, as they may be more strongly influenced by regression to the mean and measurement variability than by underlying physiological changes. Overall, inter-limb power asymmetries assessed with flywheel technology were phase- and exercise-specific in this professional soccer sample. These descriptive findings may help contextualize phase-specific and multi-exercise asymmetry monitoring in professional soccer settings.

Background/Objectives: Power indices may provide valuable information for performance and injury prevention in soccer players, so increasing the knowledge about them seems essential. Therefore, this study aimed to establish limb-specific normative values for flywheel-derived power indices in professional soccer players, while accounting for limb performance or ability, to explore the relationships between power indices across variables and to compare the power outcomes related to these indices between injured and non-injured players within four months post-assessment. Methods: Twenty-two male professional soccer players (age: 26.6 ± 4.6 years; competitive level: Belgian second division) were recruited from a single elite-tier club to participate in this cross-sectional diagnostic study. Participants underwent a standardized assessment protocol, executed in a rotational inertial device, comprising six unilateral exercises focused on the lower limbs: hip-dominant quadriceps (Qhip), knee-dominant quadriceps (Qknee), hip-dominant hamstrings (Hhip), knee-dominant hamstrings (Hknee), adductor (Add), and abductor (Abd). The testing session incorporated a randomized, counterbalanced design, with each exercise comprising two sets of eight maximal concentric–eccentric repetitions per limb. Leg dominance was operationally defined as the self-reported preferred limb for ball-striking tasks. Power indices were calculated from these exercises. Results: No significant differences in flywheel-derived power indices were found between limbs or between injured and non-injured players. However, significant correlations between indices were found in all power variables, with the Qhip:Qknee and Hhip:Hknee concentric ratios emerging as the most clinically actionable biomarkers for rapid screening. Conclusions: These results suggest the necessity of including more variables for injury prediction. Moreover, power indices could be considered based on the classification of limbs as “strong” or “weak”.

Introduction and Objective. The purpose of the study was to analyze the differences in locomotor profiles in professional football players and their relationship with performance in jumping and maximum oxygen consumption (VO₂max). Methodology. 23 players from the Second Division of the Belgian league (27.6 ± 4.2 years old; 182.5 ± 6 cm; 77.29 ± 7.16 kg) performed the countermovement jump test (CMJ), a 30-meter sprint and the 30-15 IFT test to estimate VO₂max. Players are classified in Speed, Hybrid and Endurance profiles. Results. The descriptive analyzes showed the highest values ​​of maximum aerobic speed (VAM) in the Endurance profile (5.98 ± 0.29), maximum sprint speed (MSS) in the Speed ​​profile (9.59 ± 0.49), anaerobic speed reserve (ASR) (3.96 ± 0.21) and CMJ also in the Speed ​​profile (40.55 ± 5.97), while the VO₂max was higher in the Resistance profile (58.57 ± 2.95). The CMJ showed a significant contribution to the variation of the VAM in resistance players (Spearman's rho = -0.804; p = 0.029), and in the Velocity group the VO₂max was strongly associated with the VAM (Spearman's = 0.872; p = 0.054) and the MSS (Spearman's = 0.900; p = 0.083). Conclusions. The results suggest that locomotor profiles are linked to specific neuromuscular and aerobic attributes. Individualized training based on locomotor characteristics can improve performance by enhancing specific strengths. Additional investigations are recommended to examine the long-term effects of personalized interventions on physical profiles and football performance.

Background: Soccer performance is largely dependent on high-intensity, unilateral actions such as sprints, jumps, and changes of direction. These demands can lead to strength and power differences between limbs, highlighting the importance of individualised assessment in professional players. Rotational inertial devices offer a valuable method to evaluate and train these mechanical variables separately for each leg. The aim of this study was twofold: (a) to characterise the mechanical variables derived from several lower-body strength exercises performed on rotational inertial devices, all targeting the same muscle group; and (b) to compare the mechanical variables between the dominant and non-dominant leg for each exercise. Methods: Twenty-six male professional soccer players (age = 26.3 ± 5.1 years; height = 182.3 ± 0.6 cm; weight = 75.9 ± 5.9 kg; body mass index = 22.8 ± 1.1 kg/m2; fat mass percentage = 9.1 ± 0.6%; fat-free mass = 68.8 ± 5.3 kg), all belonging to the same professional Belgian team, voluntarily participated in this study. The players completed a single assessment session consisting of six unilateral exercises (i.e., quadriceps hip, hamstring knee, adductor, quadriceps knee, hamstring hip, and abductor). For each exercise, they performed two sets of eight repetitions with each leg (i.e., dominant and non-dominant) in a randomised order. Results: The quadriceps hip exercise resulted in higher mechanical values compared to the quadriceps knee exercise in both limbs (p < 0.004). Similarly, the hamstring hip exercise produced greater values across all variables and limbs (p < 0.004), except for peak force, where the hamstring knee exercise exhibited higher values (p < 0.004). The adductor exercise showed higher peak force values for the dominant limb (p < 0.004). The between-limb comparison revealed differences only in the abductor exercise (p < 0.004). Conclusions: These findings suggest the necessity of prioritising movement selection based on targeted outcomes, although it should be considered that the differences between limb differences are very limited.

The purpose of this study was to compare the change of Body Composition (BC) (height, weight, body fat percentage and muscle mass) as a function of the trimester and category in a sample of young soccer players. Data collection was performed in five consecutive seasons (2016–2021). The sample consisted of 741 young male football players of different categories (Under 14 year old (U14), U15, U16, U17 and U18) belonging to a high-performance football academy. Considering the trimestral change of all the raw anthropometrics variables a set of new variables called the trimestral change in percentage (TC) of each raw variable was computed. Two-way repeated measures ANOVA (including the raw anthropometric variables as dependent and trimester and the age-category as independent) revealed differences for the anthropometric variables (p value < 0.001 in all cases), concluding that the effect of trimester reaches conventional levels of statistical significance. The trimester by age in contrast was significant (p < 0.05) in all raw variables except for the height. Considering the TC variables, the variable height-TC showed an increase (p value < 0.05) while the variable muscle mass-TC was near the significative value (p = 0.09). In this case the interaction trimester by age category was not significative (p > 0.05 in all cases). It seems that height suffers more changes in the first trimester but the weight, body fat percentage and muscle mass changes more in the second and third trimester. It is important to modulate the training load according to the trimester-specific response, although these improvements may vary according to factors such as genetics, diet, sleep and the specific training.

The pre-season plays a crucial role in the preparation of professional football players, as it allows for an extensive focus on training sessions compared to the more congested schedules during the in-season period, especially in professional football leagues. This study aimed to describe the workload during a 6-week pre-season in Belgian professional football players and to analyse and compare the workloads for players in each microcycle according to several variables of external workload (e.g., distance covered at some velocities). Seventeen male Belgian professional football players competing in the second division of the Belgian league system participated in the study. Throughout the 6 weeks, the players were closely monitored during both training sessions and friendly matches using Global Positioning System (GPS) devices. Several parameters, including total distance covered and distance at different velocities, were recorded. Accelerating and decelerating distances, as well as the number of sprints, were also captured. Statistical analysis was based on a repeated measures ANOVA, percentage dynamics, and effect size calculations. The results obtained showed a progressive increase in the distance travelled at different intensities from week 1 (i.e., lower values) to week 3 (i.e., higher values), with reductions in these values in week 6, prior to the start of the official competition. Similarly, the peak of accelerations and decelerations were observed in week 2 and week 3, with decrements at the end of the pre-season period. This comprehensive investigation attempts to shed light on the effects and dynamic changes in external workload during the crucial pre-season, contributing valuable insights for coaches and practitioners in football conditioning and training programs, especially concerning optimal preparation for the beginning of the league’s season.

This study aimed at evaluate the effects of strength training with inertial devices on the performance and body composition of female professional futsal players, and the subsequent detraining period. Eleven players from a first division Spanish league participated in six weeks of supervised training, followed by four weeks of strength training cessation. Specific on-court training was maintained throughout. Body fat percentage decreased after the intervention and remained low after detraining. Jump performance increased after the intervention and after detraining. Sprint performance was improved in the 5-, 10- and 20-meter distances only after the intervention. Velocity and power outcomes during the squat exercise showed significant improvement after the intervention and after detraining. Six weeks of twice-weekly strength training using inertial devices could be an optimal way to improve performance and body composition. These improvements were maintained after a four-week detraining period, during which the players only trained on the futsal court.

(1) The purpose of this study was to compare the percentages of quarterly change for each of the variables analysed (height, weight, body fat percentage and muscle mass) as a function of the quarter in a sample of adolescent football players. (2) The sample consisted of young male football players of different categories belonging to a high-performance football academy, (more than 5 years in football and have spent 1 full year at the academy). (3) Two-way repeated measures ANOVA revealed for the anthropometric variable, P_value

Objective: The objective of this study was to analyze the effect of playing several friendly matches on consecutive days affects neuromuscular fatigue evaluated with countermovement jump (CMJ), session rate of perceived effort (sRPE) and wellness in young male soccer players. Participants: Forty-four young male soccer players from Under 16 (U16) (N= 23; age: 14.70 ± 0.48 years) and U19 (N= 19; age: 17.63 ± 0.52 years) participated in this study. Method: The evaluation of CMJ and Wellness was carried out pre-and post-match. sRPE was recorded 30 minutes after the end of each game. Effect sizes (ES) were calculated using Cohen’s and statistical significance was set at p < 0.05. Results: [U16 group]: differences between CMJ values after the last match and first (p < 0.001) and second (p < 0.001) matches. Differences in fatigue, soreness and stress (p<0.05) were observed. [U19 group]: Differences in CMJ were observed when baseline values were compared with post-match values (p < 0.001) and also when the last match were compared to the first (p < 0.001) and the second (p < 0.001) matches. We only noticed differences between the second and third matches were observed in sleep, stress and humor variables (p < 0.05). Conclusion: In this scenario of competitive tournaments in young players, it is important for fitness coaches to propose practical solutions for reducing the accumulation of fatigue, since this could influence the state of well-being and physical performance of players, and the possible increase on injuries. Key words: Soccer, Muscle Fatigue, Questionarie, Evaluation, Intensity Workload.

The present study aimed to examine the influence of leg dominance on the change of direction (COD) performance. In this study participated 94 healthy young highly trained male soccer players belonging from two categories (n = 27 vs. n = 67; 14.81 ± 0.40 vs. 16.64 ± 1.25 years of age; 170.61 ± 5.61 vs. 173.73 ± 7.19 cm of height; 64.74 ± 8.44 vs. 66.70 ± 7.95 kg of weight, for U16 and U18, respectively). Fitness assessments were performed two times in a period of three months, and included: (1) anthropometry measures, (2) 30–15 IFT, (3) 10-m sprint test, (4) 505-COD test, 90° COD test and cross-over hop test. A paired sample t-test was performed to evaluate the asymmetries at the intragroup level in each of the COD’s tests. A symmetry index was used to analyse the asymmetries between categories, and an independent sample t-test was used to compare the variability between the two categories in each of the three tests performed. The effect size was also evaluated. Analysis demonstrated that evidence a trend for a better performance with the preferred leg in the cross-over hop and 505-COD tests, and with the non-dominant leg in the 90° COD. However, in the intragroup analysis, only the 505-COD test registered differences, and no differences were notice din the intergroup comparison. Only in the 505-COD test the percentage of variability (CV) was statistically significant (7.03 ± 4.18% vs. 4.03 ± 2.02% from U16 and U18, respectively). In sum, bilateral differences were noticed in the intragroup comparison, although only in 505-COD test the leg dominance showed to influence performance. In the intergroup analysis any difference was noticed between age categories.

Abstract Background The postural stability seems to be important in the physical development of the soccer player and the specific tasks related to the game. In addition, it is related to the injury risk and therefore, with the injury prevention and retraining processes. In this context, the Y Balance Test (YBT) is presented as a tool to assess dynamic postural control. Objective This study aimed to explore the differences and possible correlations in the YBT scores and inter-limb asymmetry for anterior (ANT), posteromedial (PM) and posterolateral (PL) directions by category and field position in soccer players. Methods 173 males soccer players aged between 14 and 33 years old agreed to participate. Five categories and six field position were considered in this study. A standardised protocol was used at multiple clubs during the pre-season assessment of musculoskeletal function in soccer players. All the players performed the Y Balance Test (YBT) (official YBT Kit), assessing the dominant and non-dominant leg for three YBT directions (anterior-AN, posteromedial-PM and posterolateral-PL), inter-limb asymmetry and composite score. Results For AN, amateur and semiprofessional obtained the highest values for Dominant and Non-Dominant legs (Rangemean = 101.8–109.4%) and the lowest level in PRO players (mean: 62.0%). Concerning PM-PL, semiprofessional (Rangemean = 126.4–132.7%, dominant and non-Dominant respectively), followed by professional and amateur reported higher scores compared to youth categories. Inter-limb asymmetry showed higher values in lower age categories. The best composite scores were detected in semiprofessionals (Rangemean = 113.3–126.7% for dominant and Rangemean = 113.8–129.7% for non-Dominant leg), compared with the rest of the categories and for each field position evaluated. Conclusion Comparisons between field-positions revealed that centre-backs were worse than wingers and forwards. In order to explain variations in dynamic balance between competitive levels within the same age-group, special considerations about training programmes and related co-variables should be considered.

The aim of the present paper was to determine the relationship between linear sprinting and jump performance, dynamic balance and change of direction on young soccer players. Ninety-four healthy young highly trained male soccer players belonging to the same high-performance academy agreed to participate in the study [twenty-seven soccer players U16 (14.8 ± 0.4 years; height: 170.6 ± 5.6 cm; body mass 64.7 ± 8.4 kg)] and [sixty-seven soccer players U19 (16.6 ± 1.3 years; height: 173.7 ± 7.2 cm; body mass 66.7 ± 8.0 kg)]. Participants completed 3 testing sessions, 7 days apart. Data from a CMJ, Crossover Hop Test, 10-m sprint test, 505 COD tests and the 90° COD test were collected. Moderate correlations were found in some of the cases (r values were between 0.2 and 0.5 in all cases, being p < 0.05), indicating that linear sprinting, jumping performance and dynamic balance are influential factors in agility but are not the main limiting factor. The highest correlation was found between the cross-over hop test and the 505 COD test (r = 0.44; p < 0.001). The main evidence from the current study suggested that linear sprinting, jumping performance and dynamics balance are determinants of COD, namely explaining the variations in such a skill. The current study revealed that short-distance sprint and jumping performance significantly explain the variations of COD performance on young soccer players.

The trend in recent years of wanting to perfect strategies and tactical approaches has led football to evolve into new approaches that allow for much deeper and more rigorous strategic plans to be analyzed and developed. For this, methods such as the game model have been established, which aims to establish the key game patterns of a team in order to develop a structure that identifies and defines the characteristics of a team. The objective of this work is to carry out a case study that analyzes the game model of a professional soccer team in Germany by visualizing all its league games (n = 25) before COVID-19 and using a descriptive methodology, establishing 2 criteria and 4 elements of analysis. The results indicate, in general terms, that the team analyzed is a team marked by a combinative pattern of offensive play, which tries to unbalance the rival by progression through the central area of the field and which, at a defensive level, is defined as a team that tries to recover the ball as soon as possible, covering the interior corridors, being able to conclude how through a case study we can analyze and study the characteristics of a soccer team.

La tendencia en los últimos años de querer perfeccionar las estrategias y planteamientos tácticos ha hecho que el fútbol evolucione hacia nuevos enfoques que permitan analizar y elaborar planes estratégicos mucho más profundos y rigurosos. Para ello se han establecido planes estratégicos como el modelo de juego, el cual pretende establecer los patrones de juego claves de un equipo con el objetivo de poder desarrollar una estructura que identifique y defina los rasgos de un equipo. Este trabajo tiene como objetivo realizar un estudio caso que analice el modelo de juego de un equipo de fútbol profesional de Alemania mediante la visualización de todos sus partidos de liga (n=25) antes del COVID-19 y utilizando una metodología descriptiva, estableciéndose 2 criterios y 4 elementos de análisis. Los resultados indican, en líneas generales, que el equipo analizado es un equipo marcado por un patrón combinativo de juego ofensivo, que trata de desequilibrar al rival mediante progresión por la zona central del campo y que a nivel defensivo se define por ser un equipo que intenta recuperar el balón lo antes posible, tapando los pasillos interiores, pudiéndose concluir cómo a través de un estudio caso podemos analizar y estudiar las características de un equipo de fútbol. Abstract: The trend in recent years of wanting to perfect strategies and tactical approaches has led football to evolve into new approaches that allow for much deeper and more rigorous strategic plans to be analyzed and developed. For this, methods such as the game model have been established, which aims to establish the key game patterns of a team in order to develop a structure that identifies and defines the characteristics of a team. The objective of this work is to carry out a case study that analyzes the game model of a professional soccer team in Germany by visualizing all its league games (n = 25) before COVID-19 and using a descriptive methodology, establishing 2 criteria and 4 elements of analysis. The results indicate, in general terms, that the team analyzed is a team marked by a combinative pattern of offensive play, which tries to unbalance the rival by progression through the central area of ​​the field and which, at a defensive level, is defined as a team that tries to recover the ball as soon as possible, covering the interior corridors, being able to conclude how through a case study we can analyze and study the characteristics of a soccer team.

In this study we try to observe, code and analyze the performance that different tactical systems offer to a professional soccer team. Through the observational method and the use of the SWOT analysis tool, the use of the game systems of the matches carried out before the covid19 (n = 25) of the 19-20 season is analyzed. Performance-related variables were analyzed taking into account the gaming system used and its context, in addition to performing a SWOT that would allow obtaining data on strategic factors of each system. The game systems were (1-4-2-2-2; 1-3-1-4-2; 1-3-4-3; 1-3-4-1-2; 1-4-2- 3-1). The 1-4-2-2 system was the most used (52%), it achieved more victories (57.14%), more draws (50%), most used as a visitor (46.15%) and at home (58.33%). The 3-defense game system prevailed when the rival used a striker (54.55%) and at the offensive level a system with two forwards was used 83% of times against a defense of 3. We can conclude that the analyzed team obtained a high performance After using a wide variety of game systems, obtaining advantages in competition that the SWOT tool helps us to collect in a simple, economical and efficient way.

The objective of this study was to evaluate the effects of a combined plyometrics and sled training carried out two days a week for 8 weeks. 60 young male soccer players were distributed in 4 groups (Under U16) [Experimental Group (U16 Exp, n=15) and Control Group (U16 Cont, n=15); and (Under19) [U19 Exp, (n=15) and U19 Cont, (n=15)]. The jump with countermovement (CMJ) was evaluated with Chronojump-Boscosystem® and the time in seconds (sec) in the 10, 20, and 40 m split with FitLight Trainer®. Was calculated a level of significance of p≤0.05, the effect size (ES) and % change. Both experimental groups improved from pre-to pots-test in CMJ [U16Exp (p<0.02) and U19Exp (p<0.01)] and the 10, 20, and 40 m splits [U16Exp (p<0.02, p<0.03, and p<0.01, respectively) and U19Exp (p<0.02, p<0.02, and p<0.01, respectively)]. Therefore, the combination of football and plyometric and resisted methods can be used for a general development of the neuromuscular capacities of young soccer players. Resumen. El objetivo fue evaluar los efectos de un entrenamiento combinado de pliometría y arrastres realizado 2 días en semana durante 8 semanas. 60 jugadores jóvenes de fútbol fueron distribuidos en 4 grupos (Cadete (CAD) [Grupo Experimental (CADExp n= 15) y Grupo Control (CADCont n= 15)] y (Juvenil (JUV) [JUVExp n= 15 y JUVCont n= 15]. Se evaluó el salto con contramovimiento (CMJ) con Chronojump-Boscosystem® y el tiempo en segundos (seg) en los tramos de 10, 20, y 40 m con FitLight Trainer®. Se calculó en nivel de significación p≤0.05, tamaño del efecto (TE) y % de cambio. Los grupos experimentales mejoraron del pre al pots-test en CMJ [CADExp (p<0.02) y JUVExp (p<0.01)] y los tramos de 10, 20, y 40 m [CADExp (p<0.02, p<0.03, p<0.01, respectivamente) y JUVExp (p<0.02, p<0.02, p<0.01, respectivamente)]. Por tanto, la combinación de fútbol y métodos pliométricos y resistidos puede utilizarse para un desarrollo general de las capacidades neuromusculares de los futbolistas jóvenes.

Purpose: The purpose of this study was to examine the effects of 15 weeks (2/week) of two different resistance training (RT) programs [the self-load group (SG) vs. the overload group (OG)] on selected measures of physical performance in young male soccer players. Methods: The countermovement jump (CMJ), aerobic endurance (VO2 max), and body composition [body mass (BM), height (H), body fat percentage (% BF), and lean mass (LM)] were measured before and after the 15-week RT interventions. Subjects were randomized to treatments: 1. SG [age = 15.34 ± 1.34 years]; 2. OG [age = 16.28 ± 1.21 years]. Results: The level of significance set for the study (p ≤ 0.05). Within-group analysis did report significant differences in all variables for the SG (p = 0.008 to 0.001; ES = -0.33 to 1.41, small to large) as in the OG (p = 0.001; ES = 0.82 to 1.30, large). Between-groups analysis reported differences in CMJ (F = 4.32; p = 0.004) for the OG. Conclusion: The main findings of this study indicated that RT with and without external load was effective in improving the measures of physical performance in young soccer players, with special attention to jumping ability, where the OG group was more effective. Furthermore, there is no interference to aerobic endurance. It is recommended that soccer coaches implement RT without external load in the early stages of training or in players with late maturation development and in those soccer clubs with limited material resources.

La obesidad es una enfermedad que lidera el disfuncionamiento de numerosos órganos. El alto contenido adiposo conlleva a un estado inflamatorio crónico y las reservas suficientes para la hipertrofia de los adipocitos. Si se combina el efecto del covid‑19 con la obesidad su severidad incrementa. Ambos resultados combinados son enormemente peligrosos y disminuyen la esperanza de vida. Incluso, la atención a las personas con obesidad en los hospitales se ve perjudicada, lo que difículta su cuidado y requiere de más personal. Las necesidades de ventilación mecánica de las personas con obesidad son previsiblemente incrementadas y esto puede ser crucial, ya que no todos los hospitales disponen de este material. Por tanto, ejercitarse mediante la combinación del entrenamiento de fuerza y de resistencia gana otra razón en estos días para combatir el virus. Añadir una restricción calórica también es otro factor clave para conseguir efectos significativos.