Youth Soccer Players Research Articles

Does team size affect Scottish male academy soccer player technical, locomotor and psychosocial outcomes during age and maturity bio-banded small-sided games?

ABSTRACT The timing of the adolescent growth spurt (i.e. peak height velocity [PHV]) varies greatly, causing significant differences in maturity-related anthropometric and physical development among chronologically age-categorised youth soccer players. These differences can lead to a maturity-selection bias favouring early maturing players. Using fifty-three players from two professional Scottish soccer academies, this study examined the effects of team size (4v4, 5v5, and 6v6) and bio-banding (i.e. grouping players by maturity status) on players technical (i.e. touches, releases, possessions), physical (i.e. distance covered, accelerations/decelerations), and psychological (i.e. confidence, competitiveness, positive attitude) performance during small-sided games, using foot-mounted inertial measurement units (F-IMU) and coach observations. Data were analysed using multivariate ANOVA. During maturity-matched games, technical actions decreased as team size increased. More mature players displayed greater technical actions in 4v4 compared to 6v6. Maturity-mismatched games revealed significant technical action differences for less mature players, particularly in 4v4 formats. More mature players covered greater high-intensity distances in maturity-matched and mismatched 6v6 games. Psychological scores were higher for more mature players in smaller team sizes (4v4), whereas less mature players showed consistent psychological scores across all formats. Smaller team sizes and maturity-matched bio-banding formats enhanced technical actions and psychological characteristics, particularly for more mature players.

Lactate Profiling and the Agreement Among Various Lactate Threshold Methods in Professional and Youth Soccer Players

The lactate threshold (LT) and the associated running velocities are important markers used to define physical readiness and prescribe exercise intensity in athletes. This study examined blood LT during maximal cardiopulmonary exercise testing using four methods: visual inspection, log-to-log transformation, the Dmax method, and the 4 mmol/L fixed blood lactate accumulation (FBLA) method. The participants included 96 soccer players, comprising 52 professional (27.37 ± 5.67 years) and 44 elite youth players (16.20 ± 0.8 years). A total of 554 capillary blood lactate samples were analyzed. Bland–Altman and ICC analyses for running velocities, determined using the four LT detection methods, demonstrated poor agreement in both groups. Results indicated that the youth players had significantly (p < 0.05) higher V̇O2 max (59.89 ± 5.6 mL·kg−1·min−1) compared to the professional players (56.43 ± 4.81 mL·kg−1·min−1). However, the professional players had significantly better running performance and running economy. A two-way ANOVA revealed a main effect of playing standard, with professional players exhibiting significantly higher 4 mmol/L FBLA LT compared to youth players. A mixed-design ANOVA indicated a significant (p < 0.01) interaction, with the youth exhibiting higher lactate accumulation only after completing the 18 Km/h stage. Therefore, youth and professional players should not use the different LT concepts interchangeably. Additionally, the 4 mmol/L FBLA LT method appears to be more robust for youth soccer players.

Longitudinal performance trajectories for youth female and male soccer players: 10m-sprint percentile curves adapted to biological age

Introduction Longitudinal performance monitoring is essential in sport science for accurate talent identification and forecasting future performance. The present study applied linear mixed-effects models (LMM) to analyze the longitudinal performance development of youth soccer players, both female and male. In addition to percentile curves based on chronological age, a novel approach incorporating biological age, which accounts for maturation variability during puberty, is introduced. The incorporation of biological age, as compared to chronological age, is intended to enable a more equitable assessment of physical potential and to reduce selection bias. The goal was to create an evidence-based tool for coaches and researchers to establish realistic benchmarks, model predictions, a support athlete development. Methods A total of 33’647 10-meter sprint test results were analyzed, derived from 11’752 male and female soccer players (f = 1’112; m = 10’640) aged 9 to 20 years. To estimate biological age, the Mirwald test was used, with 18’748 measurements utilized for the analysis. These data were extracted from the Swiss Football Association’s online database, covering the period from 2014, respectively 2019 to 2024. LMM were utilized to generate performance trajectories, establish benchmarks, and produce individualized performance predictions. A practical software tool, developed as a Web-Application, was created and made accessible to facilitate individual performance forecasting based on 10-meter sprint times from previous seasons. Results The mixed model approach identified individualized longitudinal performance developments and estimated predictions of future performance based on both chronological and biological age. Percentile curves based on chronological and biological age were developed, differences could be shown and trajectories for early and late developers were established. A Web-Application tool was created and can be used on the soccer pitch to evaluate current and predict future performance. Discussion/Conclusion LMM were utilized to analyze longitudinal sport performance data, enabling the establishment of performance benchmarks and the prediction of future outcomes. By incorporating biological age into the model, the predictions account for individual differences in maturation, enhancing accuracy during critical developmental stages such as puberty. A software tool was developed to support coaches in setting realistic training goals and identifying promising soccer players, providing a more tailored and maturity-sensitive approach to athlete development and identification.

Concurrent validity of single- and dual-beam timing systems for linear and change of direction speed testing in youth soccer players

This study investigates the concurrent validity of the Sportreact single-beam timing system with a standard dual-beam system for the evaluation of linear and change of direction speed. Forty-two youth soccer players (age = 12.9 ± 1.1 years) performed linear sprints (10 and 30 m splits) and 505 Agility Test. The times were measured by both systems simultaneously. The single-beam timing system was set at a height of 64 cm from the ground, while the dual-beam system was set at 67 and 90 cm for the lower and upper beam, respectively. The results showed very high intraclass correlation coefficients for the 10 m sprint (ICC (95% CI); 0.95 (0.93–0.98)), 30 m sprint (0.99 (0.98–0.99)), and 505 Agility Test (0.98 (0.98–0.99)), with a low typical error of estimates (TEEs (%) = 2.16%, 1.12%, and 1.05%, respectively). However, TEE of 0.046 s in the 10 m sprint test overlapped the smallest worthwhile change (≈0.030 s). Bland-Altman analyses showed 95% LoA ranging from −0.086 to 0.093 s for the 10 m sprint, −0.115 to 0.106 s for the 30 m sprint, and −0.055 to 0.049 for 505 agility tests. The Sportreact single-beam timing system provides a useful tool for linear sprint (≥30 m) and change of direction speed tests only when considering heterogeneous groups but not individual athletes. However, this system should not be used interchangeably with a dual-beam systems for the assessment of linear and change of direction sprint tests in youth team sport players.

Characterization of Fitness Profiles in Youth Soccer Players in Response to Playing Roles Through Principal Component Analysis

Background/Objectives: Physical fitness in youth soccer impacts individual and team performance through the specific demands that must be met on the field. Therefore, this study aimed to characterize and identify youth soccer players with regard to the roles they play on the field. Material and Methods: A cross-sectional study was designed to characterize and identify the physical fitness levels of youth soccer players using previously validated measurement tests. A total of 36 players were evaluated (15 defenders and 24 attackers) using various physical fitness tests: Squat Jump (SJ), Countermovement Jump (CMJ), Single-leg Countermovement Jumps (SLCMJs), COD-Timer 5-0-5, Speed (5, 10, 15, and 20 m), Yo-Yo Intermittent Recovery Test Level I (YYIR1), and Running-Based Anaerobic Sprint Test (RAST). The data were confirmed using the Shapiro–Wilk test. Effect sizes were obtained using the Rank-Biserial coefficient, and, to identify the profiles of attackers and defenders, principal component analysis (PCA) was employed. Results: For the strength variables, attackers obtained better results than defenders in the variable flight time in the SJ (p = 0.03; R-b = −0.33) and contact time (%) in the SLCMJ test (p = 0.04; R-b = −0.33). Meanwhile, defenders achieved better results than attackers in the SLCMJ test for the variable flight time (%) (p = 0.01; R-b = 0.33) and breaking angle (A°) in the Nordic Hamstring (p = 0.01; R-b = 0.33). The results showed differences according to the players’ roles. Three principal components were identified for both attackers and defenders. The PC1 for attackers considered variables of strength, asymmetry, change of direction, and power. PC2 only considered strength and power variables. PC3 considered variables of strength, speed, endurance, and power. For defenders, PC1 considered strength, asymmetry, and power. PC2 analyzed variables of strength, asymmetry, change of direction and power. Finally, PC3 only grouped speed variables. Conclusions: Although youth soccer positions involve offensive and defensive roles, this study reveals differences in certain physical fitness variables. Therefore, it is necessary to tailor training tasks according to the specificity of the playing position, in line with the systems of play used and the predominance of the role that players occupy, whether in defense or attack.

Effects of Strength, Speed and Non-Specific Resistance Training on Athletic Performance And FVP Profile Characteristics of Youth Professional Soccer Players

This study explored the effects of strength-focused, speed-focused, and non-specific resistance training on the athletic performance and sprint biomechanics through force-velocity-power (FVP) profile in youth professional soccer players (age: 17.6 ± 0.9 years). In a 6-week randomized-controlled trial, 24 male participants were assigned to strength, speed, or control groups (n = 8 each). We assessed sprint performance, including sprint split times and the sprint FVP profile. Post-training, all groups showed significant enhancements in sprint times (p = 0.000-0.004, η² = 0.32-0.75) and FVP profile variables (p = 0.000-0.049; η² = 0.17-0.73). The strength group exhibited notable improvements in the maximal ratio of horizontal-to-resultant force (p = 0.026, d = 0.78) and maximal power (Phmax) (p = 0.013, d = 0.89) compared to controls. However, maximum velocity and maximum velocity at the end of acceleration phase did not significantly change in any group. These findings demonstrate that both strength and speed training significantly enhance force production capabilities in youth soccer players, influencing key FVP profile characteristics, without substantially affecting maximum velocity.

Comparing the technical and individual possession statistics of academy players across different age groups in match-play.

Youth soccer players in the UK transition into the professional game at 16 years of age. Understanding the differences between youth and professional standards can help coaches and clubs to support player development during this transition. To (i) assess the differences in technical and possession statistics between different age groups (U16, U18, U23) and outfield positions (central defender [CD], wide defender [WD], central midfielder [CM], attacking midfielder [AM], wide midfielder [WM], striker [ST]), within an English academy soccer programme, during match-play. All matches were monitored using foot-mounted inertial measurements units (F-IMU; Playermaker™) to quantify the technical (touches and releases from the feet) and individual possession statistics (Time on the ball, Time on the ball per possession) from each match. Teams were instructed to play a 1-4-3-3 formation as part of their clubs playing philosophy, with positions defined per this formation. Data were analysed using a multi-variate ANOVA Two-tailed statistical significance was accepted as p ≤ 0.05 and measures of effect size were calculated using partial eta-squared (η2). Magnitude of the effect sizes were small (0.2<ES<0.6), moderate (0.6<ES<1.2), large (1.2<ES<2) and very large (≥2). Trivial to small effect sizes were observed across age groups for both technical and possession-based statistics during match-play. Across all age groups and positions, CD`s had the highest number of technical actions (touches and releases), whereas ST`s & AM`s, had the highest amount of time in possession of the ball. Further, positional analysis showed ST`s and AM`s had moderate to large decreases in time on the ball per possession at the U23's age group in comparison to the U16 and U18's, with no technical differences observed within the same positional analysis. Attacking players (AM & ST) are required to move the ball quicker as they progress from U16 to U23's within the current English football academy. Further exploration is required to assess if these changes are context specific given requirements of those age groups.

No match, more sleep: Greater weekend catch-up sleep in youth soccer players on free weekends.

This study aimed to compare young soccer players' week and weekend sleep behaviors in two different microcycle types: with and without an official match (no sporting commitments). Twenty-three youth male players (mean±SD; age: 17.2±0.6 years) from the same U19 soccer team had their sleep objectively monitored for eight weeks. Questionnaires for subjective sleep quality, sleepiness, and to identify individual chronotype were completed at the beginning of the study. External training and match loads were monitored using global positioning systems. Overall, all players slept less than 8h throughout the study and 16 slept less than 7h. On weekdays, total sleep time (TST) was reduced (390±60min). A significant (p<0.05) main effect of the microcycle type, night of the week, and an interaction between the two were observed for TST, bedtime, and wake-up time, indicating that weekend sleep adjustments were dependent on whether a match was played or not. Specifically, weekends without a match showed higher TST (+34min, p<0.001), and later bed and wake-up times (+48min, p<0.001; and +1.06h, p<0.001; respectively) compared with weekends that included a match. While players seem to try to compensate their week sleep debt when possible, sleep adjustments were more predominant on weekends without a match, despite still relatively short sleep durations observed.

Biological maturity but not relative age biases exist in female international youth soccer players relative to the general population

Biological maturity but not relative age biases exist in female international youth soccer players relative to the general population

Prediction of talent selection in elite male youth soccer across 7 seasons: A machine-learning approach

ABSTRACT This study aimed to investigate the relative importance of parameters from several domains associated to both selecting or de-selecting players with regards to the next age group within a professional German youth soccer academy across a 7-year period. Following a mixed-longitudinal approach, physical, physiological, psychological, skill-, health-, age-, and position-related parameters were collected from 409 male players (980 datapoints) from the U12 to U19 age groups. Supervised machine learning classifiers were used to predict the selection status regarding the next age group. The XGBoost models (ROC-AUC: 0.69, F1-Score: 0.84) revealed that physical and physiological (linear sprint, change-of-direction sprint, countermovement jump, aerobic speed reserve) as well as skill-related parameters (soccer-specific skill) were most important for being selected or de-selected regarding the next age group across the entire sample and all age groups. The majority of psychological parameters (motive structure, motive attention, motive competition, cognitive flexibility) were of medium importance. No clear pattern was observed for the health-, age-, and position-related parameters. Our study provides insights into key parameters for talent selection thereby contributing to an overall talent management strategy in highly trained youth soccer players. In particular, coaches and key stakeholders might focus on physical, physiological, and skill-related parameters.

Early player transition in elite youth and first team soccer: The predictive role of sprint distance and high-intensity acceleration and deceleration attributes

Physical performance is an important determinant of elite youth soccer player development and can influence successful transition through the professional phase of the talent development pathway. In response to previous research highlighting key stakeholders’ perceptions that successful transitions within the club pathway are influenced by sprinting capacity and explosive power; this study objectively quantified the predictive value of sprint distance and high intensity acceleration and deceleration efforts on the early transition of elite, professional youth soccer players from U18 to U21, and U21 to first team squads of a Scottish Premier League club. Early transition was defined as a player progressing to the next age group (i.e., U18 to U21) prior to reaching the chronological age limits of his current squad. Retrospective physical performance data of thirty-seven players from training and competitive matches across two seasons were analysed. Results suggest that early transition is less likely for players progressing from the U21 to the first team relative to players progressing from U18 to U21. Relative sprint distance resulted in a 52% probability of early transition (OR = 0.52) with relative aggregated high intensity acceleration and deceleration efforts reflecting an increased probability of early transition (OR = 1.70) for elite youth soccer players within the club. This novel study provides a unique insight to the complexities and context-specific nature of youth soccer player development and transition. This paper challenges the subjective perceptions of key stakeholders using objective physical data of youth players who have transitioned to advanced squads.

Effects of a Short-Term Soccer Training Intervention on Skill Course Performance in Youth Players: A Randomized Study.

The aim of this study was to evaluate the effect of 11 additional soccer training sessions among youth soccer players according to their performance in a skill course. A total of 90 participants, aged 9 to 12, were randomly assigned to either an intervention group (IG) (n = 54) or a control group (CG) (n = 36) and have validated data. The trainings focused upon enhancing ball mastery and decision-making and included a combination of one vs. one situations and small-sided games (SSGs). Pre- and post-tests measured passing and dribbling skills through a skill course. The best time with additional time penalties for each dribbling and passing error was used for further analysis. An independent t-test revealed no significant differences in improvement between the two groups. However, paired t-tests revealed significant improvements for both the IG and the CG from pre- to post-test (7.9 and 3.9 s, respectively). Furthermore, no significant differences in the development of track time, cone touches, or passing errors between the groups were detected. These findings suggest that soccer players aged 9 to 12 improve their performance in a skill course through increased familiarity with the course and natural development of technical skills based on participation in soccer training and recreational soccer play. We argue that the lack of significant differences between the groups' performances can be attributed to the short duration and few sessions of the intervention, and a somehow low similarity between the skill course and the activities in the sessions.

Youth Soccer Heading Exposure and Its Effects on Clinical Outcome Measures.

Purposeful heading, in which players may use their heads to advance the ball in play, is a unique part of soccer. Clinical outcome measures used to aid in the diagnosis of a concussion have long been a cornerstone of the contemporary measurements associated with the short- and long-term effects of monitoring repetitive head impacts (RHI) and soccer heading exposure. The effects of RHI in the youth population are still unknown, therefore, the purpose of this study was to examine if heading exposure is predictive of changes in self-reported symptoms, neurocognitive functioning, gait, and balance in female youth soccer players over the course of one soccer season. Small improvements in neurocognitive functioning and gait and slight deficits in balance were observed from pre- to post-season. All changes were not clinically relevant and likely due to a practice effect. The low heading exposure in our cohort of youth soccer players was likely not enough to elicit any changes in clinical measures. In general, our clinical outcomes did not change after a season of soccer play and change scores were not predicted by heading exposure.

Influence of puberty stage in immune-inflammatory parameters in well-trained adolescent soccer-players, following 8-weeks of pre-seasonal preparation training

Aim: The immune system can experience temporary suppression following acute or prolonged strenuous exercise, potentially increasing susceptibility to infections. Young athletes, who must balance school, training, studies, and social life, may further disrupt their immune-inflammatory responses. This study aimed to investigate the effects of an 8-week pre-season training on circulating leukocyte responses in well-trained adolescent soccer-players at different stages of puberty. Methods: Thirty-six soccer players, divided into two groups based on their biological age-under sixteen (U16) and above sixteen (A16)-underwent two rounds of assessments. These included evaluations of anthropometrics, physical fitness, and immune parameters before and after an 8-week pre-season soccer training program. Results: No significant treatment or interaction effects were found for erythrocyte sedimentation rate (ESR), platelets, total leucocyte count, immune inflammation markers (IIM), weekly rating of perceived exertion, body composition, sit-and-reach flexibility, or VO2max (P &gt; 0.05). However, post-intervention neutrophil counts were increased, while lymphocyte counts decreased, and IIM levels rose in both groups (P &lt; 0.05). Neuromuscular explosiveness and strength endurance were significantly higher in the A16 group compared to the U16 group (P &lt; 0.05). Body fat was reduced, and all physical fitness parameters improved in both groups over time (P &lt; 0.05). Conclusions: The 8-week soccer-specific training program did not lead to different effects on immune-inflammatory parameters between youth soccer players at different stages of puberty. However, training adaptations, including improvements in physical fitness, were observed in both groups. This suggests that when the same training load (frequency, duration, intensity) is applied to adolescents at different stages of puberty, immune-inflammatory responses are not significantly influenced by age, but physical fitness improves regardless of puberty stage. A key limitation of this study is the lack analysis of lymphocyte subpopulations, which could provide a deeper understanding of the cellular effects of training on immune function.

Incidence and Risk Factors for Sport-Related Concussion in Female Youth Athletes Participating in Contact and Collision Invasion Sports: A Systematic Review.

The incidence and risk factors for sport-related concussion (SRC) associated with contact and collision invasion sports (CCIS) in female youth are unclear. This systematic review aimed to identify (i) the incidence of and (ii) risk factors for SRC in female youth athletes playing CCIS. A systematic search of PubMed, CINAHL, Embase, SPORTDiscus and ProQuest to 8 May, 2024 was conducted. Two reviewers independently screened articles against eligibility criteria and assessed risk of bias (Joanna Briggs Institute Critical Appraisal Tool). Aetiological or intervention studies reporting on SRC incidence or risk factors in female youth athletes (aged 13-19years and under) participating in CCIS were included. Meta-analyses were conducted to explore SRC incidence and risk factors. For each meta-analysis of SRC incidence rate, sub-group analyses were conducted by sport. Where heterogeneity was above 60% for the meta-analysis of SRC risk/protective factors, sensitivity analyses were conducted. The search yielded 4509 articles; 66 were included. Sport-related concussion incidence or risk factor data for nine CCIS were extracted. Pooled estimates revealed SRC incidence for female youth athletes in CCIS combined was 0.50/1000 match and practice hours (95% confidence interval [CI] 0.34-0.66). When examined by sport classification, SRC incidence in contact invasion sports was 0.12/1000 match and practice hours (95% CI 0.03-0.21), and in collision invasion sports was 2.08/1000 match and practice hours (95% CI 0.90-3.25). Sub-group analysis by individual sport revealed female youth soccer players had the highest overall SRC incidence rate (0.89/1000 match and practice hours, 95% CI - 0.19 to 1.97) amongst contact sports, and rugby union players had the highest overall SRC incidence rate (4.04/1000 match and practice hours, 95% CI 3.03-5.05) among collision sports. Forty-five studies (68%) reported SRC risk factor data, investigating 12 different potential risk factors. Female youth sustained over 7.5 times the rate of SRC in matches compared with practice (incidence rate ratio 7.52, 95% CI 6.32-8.95, p < 0.01) when competing in CCIS; however, considerable heterogeneity existed (I2 = 84.98%). When exploring potential risk factors, no significant difference was found in SRC rate between female youth lacrosse players wearing versus not wearing headgear (p = 0.07). No significant difference was found in SRC rates between female youth athletes competing in younger versus older age groups (incidence rate ratio 0.91, 95% CI 0.52-1.61, p = 0.48, I2 = 0.00%). Insufficient evidence was available to examine remaining risk factors. This meta-analysis revealed SRC in female youth playing CCIS was higher than previously reported, with SRC rates higher in matches than practice. Soccer had the highest SRC incidence rate for female youth athletes competing in contact invasion sports, whilst rugby union demonstrated the highest SRC incidence rates for collision invasion sports. The results of this review should be interpreted with caution given the lack of representation from some common CCIS codes. Further research is required to examine SRC risk factors in female youth athletes participating in CCIS. OSF Registration: osf.io/s573v.

Area per Player in Small-Sided Games to Estimate the External Load in Elite Youth Soccer Players

Area per Player in Small-Sided Games to Estimate the External Load in Elite Youth Soccer Players

Elastic Bands During Half-Squats as A Re-Warm-Up Strategy for Youth Soccer Players' Performance.

The study aimed to assess the immediate effects of re-warm-up strategies using half-squats with elastic looped bands on the performance of youth soccer players. A cross-over study design with repeated measures was implemented in field youth male soccer players (n = 20, age 15.7 ± 0.8 years). Following the first 45-min of match play, players were subjected to one of four re-warm-up (Re-w) interventions of equal duration: no Re-w (PAS), half-squat without elastic looped bands (SQ), half-squat with bands placed on the thighs (SQT), and half-squat with bands placed on the lower legs (SQL). These interventions were compared against a control condition (CON). The Re-w protocols were initiated 10-min after half-time, and players' performance was evaluated through vertical and horizontal jump tests, 20-m linear sprint, and T-agility test. Statistical analysis using ANOVA revealed that the SQT and SQL interventions significantly improved (p < 0.001) several performance metrics compared to the PAS and SQ conditions. These improvements were observed in squat jumps, unilateral squat jumps (both dominant and non-dominant legs), countermovement jumps, horizontal jumps, triple horizontal jumps, the 20-m linear sprint, and T-agility performance. In conclusion, SQT and SQL are equally effective to enhance performance as Re-w strategies after the 1st-half of a soccer match. However, the lack of physiological data and 2nd-half assessments suggests the need for further research to confirm the persistence of these effects.

How do young soccer players train? A 5-year analysis of weekly microcycle training load characteristics in an elite youth academy

This study aimed to describe the distribution of training load (session rating of perceived exertion (sRPE), duration, and sRPE-training load) across weekly microcycles of an elite youth academy and assess the differences between four different age groups (U15-U16-U17-U19). Training load variables were recorded during in-season training weeks over 5 competitive seasons (from 2014–15 to 2018–19, evaluating new squads for each age group each season) for a total of 456 player observations. Mixed models assessed the variability of the three load variables across the different training days of a weekly microcycle and between the four different age groups. Estimated marginal means, 95% confidence intervals (CI), and effect sizes (d) were calculated for each training day of the microcycle. The main findings were significant differences in the training load variables three and four days before the next Match Day (i.e., MD-3 and MD-4, respectively), with U15 recording lower sRPE (−2.0 AU, d = 0.43–0.72) and U19 a lower duration (−35 min, d &lt; -1.10). All age groups reduced sRPE-training load in the two days before a match, mainly due to a decrease in training duration (−160 AU &amp; −17 min respectively). Match days provided the highest training loads within the weekly microcycle, with moderate-to-large differences between the four age groups (d = 0.77, 1.16 and 1.38 for U15 vs U16-U17-U19 respectively). The low variability in sRPE values in the three central sessions of a weekly microcycle indicates that training duration is an important factor to control when aiming to manipulate within-week training loads in elite youth soccer players.

Comparative Analysis of the Physical, Tactical, Emotional, and Mood Characteristics of Under-13 Soccer Players by Performance Level.

Background and Objectives: Soccer is a sport characterized by various unpredictable situations in which physical abilities are associated with athletic performance. There are several capabilities that young soccer players must develop to adapt to the needs of the competition. This study analyzes the physical characteristics, tactical knowledge, emotional intelligence, and mood states of youth soccer players at different competitive levels. Materials and Methods: The sample consisted of 36 male soccer players with an average age of 12.65 ± 0.48 years, weight of 44.92 ± 7.49 kg, and height of 157.2 ± 0.08 cm. A cross-sectional correlational study design was selected. Inferential analysis was conducted via the RV coefficient to assess relationships between groups. Two-sample tests (Student's t test or the Mann-Whitney U test) were used to assess the distribution of the samples. Standardized mean differences (i.e., Cohen's d) were calculated as effect sizes. Results: For the yo-yo intermittent endurance test level 1, the Premier category showed higher speed (p = 0.01, d = 0.40) and superior estimated VO2max (p = 0.01, d = -0.91). The statistically significant variables included the hamstring strength exercise of the hamstrings for the angle of rupture (p = 0.04, d = -0.04, d = -0.72), the COD-Timer 5-0-5 for contact time-5-0-5 (ms) (p = 0.04, d = 0.69) and 10 m-5-0-5 (s) (p = 0.02, d = 0.79), tactical knowledge of in-game performance (p = 0.01, d = -1.19), support level (p = 0.01, d = -1.27), decision-making ability (p = 0.01, d = 0.59), melancholy (p = 0.01, d = 0.59), confusion (p = 0.01, d = 0.56), and emotional intelligence (p = 0.04, d = 0.77). The Premier category presented slightly higher averages than did category A. In the assessment of running-based anaerobic sprint test power (p < 0.05, d = 0.83) and mood states (p < 0.05, d = 0.59), players in category A presented higher results. Conclusions: The performance capacity of youth soccer players encompasses a multidimensional complexity that includes physical, tactical, emotional, and psychological aspects, which vary among players of the same age.

Energetic and Neuromuscular Demands of Unresisted, Parachute- and Sled-Resisted Sprints in Youth Soccer Players: Differences Between Two Novel Determination Methods.

The aim of this study was to analyze the differences in terms of (1) muscle activation patterns; (2) metabolic power (MP) and energy cost (EC) estimated via two determination methods (i.e., the Global Positioning System [GPS] and electromyography-based [EMG]); and (3) the apparent efficiency (AE) of 30-m linear sprints in seventeen elite U17 male soccer players performed under different conditions (i.e., unloaded sprint [US], parachute sprint [PS], and four incremental sled loads [SS15, SS30, SS45, SS60, corresponding to 15, 30, 45 and 60 kg of additional mass]). In a single testing session, each participant executed six trials (one attempt per sprint type). The results indicated that increasing the sled loads led to a linear increase in the relative contribution of the quadriceps (R2 = 0.98) and gluteus (R2 = 0.94) and a linear decrease in hamstring recruitment (R2 = 0.99). The MP during the US was significantly different from SS15, SS30, SS45, and SS60, as determined by the GPS and EMG approaches (p-values ranging from 0.01 to 0.001). Regarding EC, significant differences were found among the US and all sled conditions (i.e., SS15, SS30, SS45, and SS60) using the GPS and EMG methods (all p ≤ 0.001). Moreover, MP and EC determined via GPS were significantly lower in all sled conditions when compared to EMG (all p ≤ 0.001). The AE was significantly higher for the US when compared to the loaded sprinting conditions (all p ≤ 0.001). In conclusion, muscle activation patterns, MP and EC, and AE changed as a function of load in sled-resisted sprinting. Furthermore, GPS-derived MP and EC seemed to underestimate the actual neuromuscular and metabolic demands imposed on youth soccer players compared to EMG.