Search Results (1,708)

Objective: Analyze physical fitness variables and body composition to define patterns or similarities in performance using principal component analysis. Materials and Methods: Sixty-eight players participated in the study, divided into three groups according to their age: Under-13 (n = 23), Under-15 (n = 27) and Under-17 (n = 18). A comparative cross-sectional study was performed. The variables analyzed were squat jump, countermovement jump, countermovement jump with arms, hamstring strength, COD-Timer 5-0-5, COD-Timer 5 + 5, speed (5, 10, 15 m), and running anaerobic sprint test. Body composition variables were skinfold thickness, diameters, and circumferences. Results: For the squat jump, 10.4% of the variability in speed (η² = 0.104) and 12.5% of the variability in jump height (η² = 0.125) are explained by category, both with moderate effect sizes. For the countermovement jump, 10.8% of the variability in speed (η² = 0.108) and 13.2% of the variability in jump height (η² = 0.132) are explained by category, both with moderate effects. For the running anaerobic sprint test power test, a large effect size was determined for each of the six times, indicating that at least 57.4% of the variability in time is explained by category. Conclusions: Two control groups were identified according to category (Under-13, Under-15, Under-17), revealing that principal component 1 and principal component 2 were significant in the performance of anthropometric variables such as residual mass, bi-styloid diameter, arm span, and residual mass, and physical variables, specifically related to COD-Timer 5 + 5, COD-Timer 5-0-5, and speed. Full article

This paper presents a multimodal sensing approach for fine-grained soccer action recognition using synchronized mm-wave FMCW radar and multiview RGB cameras. A TI IWR1443BOOST FMCW radar and three Sony IMX296 global-shutter cameras were used to record seven soccer-related actions in different movement directions in an outdoor environment. Range–Doppler radar processing is applied to extract global mel features and CFAR-localized block representations of mel and radar spectrogram features to capture both coarse and fine micro-Doppler characteristics. Camera features are derived from bounding box, HOG, optical flow, and pose estimations. Classification is performed using logistic regression as the classical model and various deep models. Performance is evaluated using cross-validation. Radar alone achieved moderate performance (0.897 F1_macro using TCN), successfully identifying coarse motion but showing limited separability for dribbling-based actions. Camera-only models achieve near-perfect accuracy (≥0.997 F1_macro using 1D-CNN), with the confusion matrices being nearly perfectly diagonal already. The best performance is obtained from a cross-modal transformer with multiple cameras (0.998 F1_macro). These results demonstrate that a camera by itself performs strongly for the action recognition task but also that radar–camera fusion can improve robustness and enhance the discrimination of finer soccer player movements for outdoor analytics and player monitoring applications. Full article

Background: Calcaneus secundarius (CS) is an accessory ossicle located at the anterior aspect of the calcaneus and is typically an incidental and asymptomatic radiographic finding. However, it may become symptomatic following trauma or repetitive mechanical stress and can mimic anterior calcaneal process fracture or tarsal coalition, leading to diagnostic confusion. The presence of multiple independent CS ossicles represents a rare morphological variant and a potential source of diagnostic ambiguity. Methods: We report the case of a 19-year-old male soldier who presented with progressive anterior foot pain following soccer activity without a clearly identifiable traumatic event. Radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) were performed to evaluate the underlying pathology. Results: CT demonstrated two separate, well-corticated accessory ossicles adjacent to the anterior calcaneal process without bony continuity. MRI revealed focal bone marrow edema (BME) at the calcaneus–ossicle interface, suggesting mechanical irritation at the fibrous connection. Due to persistent symptoms and concordant imaging findings, surgical excision was performed, resulting in immediate pain relief and return to full daily and sports activities without recurrence at the 1-year follow-up. Conclusions: Multiple CS ossicles may produce fragment-like imaging appearances and increase the risk of misdiagnosis. Recognition of characteristic imaging features, particularly well-corticated ossicles and focal BME at the ossicle–calcaneus interface, together with clinical correlation, is essential for accurate diagnosis and appropriate management in patients with persistent anterior foot pain. Full article

The purpose of this study was to examine associations between lower-limb mechanical strength, phase-oriented composite strength indices, generalized neuromuscular activation, and maximal soccer ball kicking speed in trained athletes. Twenty-five male soccer players (age: 20.64 ± 2.50 years; height: 179.28 ± 4.27 cm; body mass: 75.80 ± 9.41 kg) participated in this cross-sectional study. Isometric ankle and knee joint torques were assessed using an isokinetic dynamometer, and joint-specific and phase-oriented cross-joint composite indices were computed to represent integrated strength capacity across the kinetic chain. Neuromuscular activation was evaluated via surface electromyography during a standardized squat jump task. Ball-kicking speed was measured using Doppler radar during maximal instep kicks. Associations were analyzed using Pearson correlation coefficients (p ≤ 0.05) with false discovery rate correction for multiple comparisons. In unadjusted analyses, moderate positive correlations were observed for several ankle torque variables and composite ankle strength indices, while swing-phase composite measures demonstrated moderate correlations (r = 0.43–0.55). Knee strength indices and sEMG variables showed no significant relationships. However, none of the variables remained statistically significant after FDR correction, suggesting limited independent explanatory value of isolated isometric strength and non-task-specific neuromuscular activation assessed during a standardized squat jump for maximal kicking performance. Full article

The aim of the current study was to examine whether weekly dynamic stress load (DSL) volume could be associated with competition internal and external load outcomes in professional soccer players. Weekly DSL volume was recorded across standardized one-match microcycles. Match outcomes included total distance covered (TDC), high-speed running distance (HSRD), sprint distance (SPRD), high-intensity accelerations (HIACC), high-intensity decelerations (HIDEC), high-metabolic-load distance (HMLD), time spent > 85% of maximum heart rate (HRmax), and Edwards training impulse (Edwards’ TRIMP). Analyses of our results revealed that higher weekly DSL volume was associated with greater time > 85%HRmax in the first half (β = 0.00647; p = 0.002) and second half (β = 0.00764; p = 0.026). In the second half, weekly DSL was negatively associated with HSRD (β = −0.3068; p < 0.001) and SPRD (β = −0.0619; p < 0.001), and positively with HMLD (β = 0.3532; p = 0.002). Across the full match, weekly DSL was negatively associated with TDC (β = −0.5080; p = 0.002), HSRD (β = −0.4159; p < 0.001), SPRD (β = −0.0988; p < 0.001), HIACC (β = −0.0265; p = 0.003), and Edwards’ TRIMP (β = −0.2251; p = 0.001). Weekly DSL volume may represent an important monitoring tool providing useful information for practitioners aiming to manage fatigue and support competition performance maintenance; however, these findings should be interpreted cautiously until confirmed in larger samples. Full article

This study examined the influence of the follicular (FP) and luteal phases (LP) of the menstrual cycle on sweat rate, estimated sweat sodium concentration, heart rate, hydration status, fluid intake, and perceived exertion in first-division university female football players. A small sample of eight athletes completed two monitored training sessions, one in each estimated-menstrual phase, following a repeated-measures field-based design under habitual training conditions. Sweat rate was determined using pre- to post-exercise body mass changes and microfluidic sweat patches, while estimated sweat sodium concentration was obtained via wearable colorimetric sensors. Heart rate was continuously monitored, hydration status was assessed using urine specific gravity, fluid intake was recorded, and perceived exertion was evaluated using the Borg CR-10 scale. Sweat rate was significantly higher during LP compared with FP (0.83 ± 0.20 vs. 0.55 ± 0.25 L·h⁻¹, p = 0.026), alongside greater estimated sweat sodium concentration (695 ± 305 vs. 404 ± 159 mg·L⁻¹, p = 0.031) and higher perceived exertion (4.63 ± 1.41 vs. 3.13 ± 0.83, p = 0.021). Fluid intake was also significantly greater during LP (0.99 ± 0.19 vs. 0.49 ± 0.25 L, p < 0.001). No significant differences were observed for urine specific gravity, mean heart rate, or total body mass change (p > 0.05). These findings suggest that the luteal phase may be associated with higher thermoregulatory and perceptual responses during football training, highlighting the potential importance of menstrual cycle-informed hydration and training management strategies in female athletes. Full article

This study examined the within-session (same-day) test–retest reliability of heart rate (HR) and parasympathetic modulation, assessed using the root mean square of successive differences (RMSSD), across exercise and recovery phases in trained soccer players. Twenty-seven male soccer players (age: 24.9 ± 3.7 years) completed a standardized soccer training session. HR and RMSSD were recorded using an ECG-based chest-strap monitor at rest, pre-exercise, and at ~10–20 min, 1 h, and 3 h post-exercise. At each time point, two consecutive 5 min seated recordings were obtained under identical conditions. Test–retest reliability was evaluated using intraclass correlation coefficients (ICC_(3,1)), standard error of measurement (SEM), coefficient of variation (CV%), minimal detectable change (MDC₉₅), paired-samples t-tests, and Hedges’ g effect sizes. HR demonstrated excellent reliability across all time points (ICC = 0.980–0.994; SEM = 0.87–1.25 bpm; CV% = 1.33–3.70%). RMSSD showed excellent reliability at rest (ICC = 0.944) and pre-exercise (ICC = 0.918), moderate reliability during early recovery (~10–20 min; ICC = 0.551), and good reliability at 1 h (ICC = 0.826) and 3 h post-exercise (ICC = 0.873). No significant systematic differences were observed between test and retest measurements (all p > 0.05), and effect sizes were trivial. These findings indicate that within-session reliability of HR remains consistently high across exercise and recovery phases, whereas RMSSD reliability varies according to measurement timing, particularly during early recovery. Full article

This study examined whether different body fat percentages (BF%) may influence performance, physiological responses, and fatigue in professional soccer players during a simulated soccer game protocol on a treadmill. Twenty professional male soccer players were categorized in higher (HBF%) and lower (LBF%) body fat percentage groups [HBF% > 11.5%; n = 11, BF% = 14.2 ± 2, LBM = 65.3 ± 8 kg, age = 22.7 ± 4 years, height = 177 ± 7 cm, weight = 76 ± 9 kg, V̇O₂max = 60.1 ± 4.5]; [LBF% < 11.5%, n = 9; BF% = 8.1 ± 1, LBM = 65.9 ± 5 kg, age = 20.1 ± 3 years, height = 179 ± 4 cm, weight = 72 ± 5 kg, V̇O₂max = 61.6 ± 4). Players underwent a simulated soccer game protocol on a treadmill. Cardiometabolic and hormonal responses, and fuel oxidation and performance, were evaluated. At baseline, apart from the BF% variable (p < 0.0001), the groups did not differ in any other physiological or physical characteristic (p > 0.05). There were no differences between the groups in any performance or biological parameters evaluated (p > 0.05), except for plasma glucose, which was higher in the HBF% group at rest and during the soccer game protocol (p < 0.05). In conclusion, the theory of a uniform ideal (~10 ± 2%) of BF% in elite soccer is not supported by the present study. This study suggests that when muscle mass and fitness levels of the soccer players are maintained at high levels during the competitive period, BF% represents a highly individualized characteristic rather than a uniform target across players. However, a higher BF% increased resting and exercising blood glucose concentrations, even in highly trained professional soccer players, without concomitant effects on metabolism or fuel oxidation during match play. Full article

Background/Objectives: The aim of this study was to describe seasonal trends in match-average External Load (EL) variables across three (2022/23, 2023/24, 2024/25) consecutive competitive seasons in a Hungarian professional second-division soccer team (Gyirmót FC Győr), using the Catapult Vector S7 Global Navigation Satellite System (GNSS). Specifically, Average Distance (AD; m), Average Player Load^TM (PL; AU), and Acceleration–Deceleration Efforts (>2 m·s⁻²) (ADE) were examined. The study aimed to provide descriptive reference values and characterize seasonal variation in match EL demands within a professional second-division context. Methods: A descriptive seasonal comparison was conducted based exclusively on aggregated match average EL values. The unit of analysis was the match, with each match contributing one aggregated value per variable derived from players who completed the full match. A total of 94 matches were included (2022/23: N = 38; 2023/24: N = 29; 2024/25: N = 27); matches with red cards were excluded. EL data were collected using a 10 Hz Catapult Vector S7 GNSS. Results: The median AD decreased continuously from the 2022/23 season (10.210 m) to the 2024/25 season (9.795 m). The median PL decreased from 1002 (2022/23 and 2023/24) to 846 in the 2024/25 season. The median ADE decreased from 220.8 (2022/23) to 199.0 (2024/25). Conclusions: Lower values were observed across match EL variables, with the most pronounced reduction in PL. These findings provide descriptive reference values and may support the interpretation of seasonal variation in match EL demands in professional second-division soccer. Full article

Background: Global positioning system (GPS) technology is widely used to quantify external training load (ETL) in youth soccer. Despite its extensive application in training and match contexts, considerable heterogeneity is present in the selection, definition, and interpretation of GPS-derived variables, limiting comparability between studies and practical implementation by coaches. Objective: This narrative review aimed to summarize and critically evaluate the current literature on GPS-based ETL monitoring in youth soccer players, with a focus on commonly used variables, methodological considerations, and practical applications in training and match contexts. Methods: A narrative literature search was conducted using PubMed, SPORTDiscus, and Scopus databases. Peer-reviewed studies published in English between the years of 2012 and 2025 were included. Data were extracted on participant characteristics, GPS technology, monitored ETL variables, and contextual settings. Results: The 34 reviewed studies primarily reported total distance (TD; m), high-speed running distance (HSR; m), sprint distance (SD; m), distance per minute (m·min⁻¹), peak speed (km·h⁻¹), and acceleration- and deceleration-based (ACC, DEC; count) ETL variables. Substantial variability was observed in speed thresholds, acceleration definitions, and data processing methods. Positional roles, training formats (e.g., small-sided games), and seasonal phase influenced ETL demands, although methodological inconsistencies limited cross-study comparisons. Conclusion: GPS technology provides valuable insights into the ETL demands of youth soccer. The lack of standardized variable definitions and thresholds remains a major limitation. Greater methodological consistency and clearer reporting standards are required to enhance the practical usefulness of GPS monitoring for coaches in youth soccer. Full article

Introduction: Monitoring training load is essential in elite soccer to optimize performance and reduce injury risk. The training-to-match load ratio (TMr) has emerged as a useful metric to contextualize training demands relative to competitive match exposure. The objective of this study was to compare daily and accumulated TMr between starters and non-starters over a professional season, considering microcycle day and playing position. Methods: Twenty players (Tier 3) from a professional team were monitored during a full competitive season (30 microcycles; 144 training sessions; 30 matches). External load variables, namely total distance (TD), high-speed distance (HSD), sprint distance (SPD), high metabolic load distance (HMLD), acceleration (ACC) and deceleration (DCC), were collected using 10 Hz GPS devices (STATSports). Daily and microcycle TMr were calculated relative to each player’s maximal match value registered during a full competitive period. Linear mixed-effects models examined the effects of starting status, microcycle day, and playing position. Results: Linear mixed models revealed significant three-way interactions (status × day × position) for locomotor variables: TD (F = 3.36, p < 0.001), HSD (F = 2.49, p < 0.001), and SPD (F = 3.37, p < 0.001). Starters accumulated higher loads on match day, whereas non-starters showed higher TMr on MD + 1 and MD + 2. Position-specific differences emerged during acquisition sessions (i.e., MD − 5 to MD − 3), particularly for wide midfielders (WMs) and central defenders (CDs). No significant three-way interactions were observed for ACC, DCC, or HMLD absolute loads (p > 0.05), nor for any accumulated microcycle TMr metrics (p > 0.05). Conclusions: TMr effectively differentiates preparation strategies between starters and non-starters. Although “top-up conditioning” sessions increase early-week relative loads for non-starters, position-specific variations–particularly in mechanical variables during acquisition sessions–highlight the need for individualized load prescription. Full article

Background: Small-sided games (SSG) and running-based high-intensity interval training (HIIT) are commonly used in soccer conditioning to improve aerobic fitness and performance. Although both modalities induce high cardiovascular stress, their acute neuromuscular, perceptual, and cognitive responses remain incompletely understood when examined within the same cohort. This study compared the acute physical, psychophysiological, and cognitive responses to SSG and Tabata-type HIIT in amateur male soccer players. Methods: Thirty-two male amateur players (n = 32; age: 20.53 ± 1.65 years) completed a counterbalanced within-subject crossover design. Participants performed a 4v4 SSG protocol and a running-based Tabata-HIIT protocol (8 × 20 s, 10 s recovery) on separate days (48 h apart). Countermovement jump (CMJ), squat jump (SJ), 20-m sprint, agility t-test, heart rate, perceived exertion (Borg CR-10), mental effort, and cognitive performance (d2 test) were assessed pre- and post-exercise. Parametric variables were analyzed using 2 × 2 repeated-measures ANOVA (time × protocol; η²p), and non-parametric data were analyzed using Friedman and Wilcoxon tests (r) (p < 0.05). Results: Both protocols elicited similar cardiovascular responses (~90% HR_max). A significant protocol × time interaction was observed for CMJ (p < 0.001), showing a decline after Tabata-HIIT, whereas performance was maintained after SSG. No inter-protocol differences were found for SJ, sprint, or agility. Perceived exertion and mental effort during recovery were higher following Tabata-HIIT (p < 0.05). Cognitive performance improved after both protocols (p < 0.001), with no between-protocol differences. Conclusions: Despite comparable cardiovascular load, Tabata-HIIT was associated with greater acute neuromuscular and perceptual strain, whereas SSG preserved neuromuscular performance. Perceptual and mental responses may therefore differ despite similar physiological intensity, which may inform soccer training prescription. Full article

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. Full article

This study aimed to identify distinct lactate kinetic phenotypes in professional soccer players using unsupervised machine learning and determine their relationship with maximal running velocity (V_max) through explainable artificial intelligence methods. A total of 361 professional male soccer players from the First Division participated in the study. Incremental treadmill tests measured lactate concentrations at five standardized velocities, alongside VO_2max, V_max, lactate threshold (LT), and anaerobic threshold (AT) parameters. Three distinct lactate kinetic phenotypes emerged: Economical Aerobic (n = 216), Balanced Metabolic (n = 19), and High Producer (n = 126). The Economical Aerobic phenotype demonstrated superior performance metrics compared to High Producer (V_max: 15.85 ± 0.85 km/h; VO_2max: 56.20 ± 4.26 mL/kg/min; p < 0.001). Initial multicollinearity assessment revealed notable collinearity among all 10 candidate predictors (VIF > 10; maximum VIF = 10.75 for V_AT), necessitating rigorous feature selection. Ridge regression with 4 selected features (V_AT, VO_2max, 9.5 km/h lactate, 14 km/h lactate) achieved moderate but statistically significant predictive performance: 10-fold cross-validation R²= 0.392 ± 0.147 (permutation test p = 0.001). Standardized coefficients identified V_AT (β = 0.399) as the dominant predictor, followed by VO_2max (β = 0.253), 9.5 km/h lactate (β = 0.107), and 14 km/h lactate (β = −0.066). Lactate kinetic phenotyping reveals position-independent metabolic profiles with potentially meaningful performance associations in professional soccer. The Economical Aerobic phenotype demonstrates performance advantages associated with superior anaerobic threshold capacity. These exploratory findings suggest that individualized training strategies based on metabolic phenotype rather than playing position alone warrant further investigation, with potential applications for talent identification, training periodization, and return-to-play protocols pending prospective validation. Full article

Objective: This randomized controlled trial aimed to investigate how volume-matched unilateral and bilateral jump training affects physical performance in prepubertal and pubertal male youth soccer players and to examine whether maturational status influences these training adaptations. Methods: Sixty-five male soccer players (age 10.5 ± 2.9 years; height 136.7 ± 17.8 cm; body mass 32.8 ± 8.6 kg; maturity offset −1.6 ± 1.0 years) completed an 8-week training program (two sessions/week). Participants were randomly assigned to a bilateral jump group (n = 22), unilateral jump group (n = 22), or control group (n = 21). Performance was evaluated in a single testing session, which included horizontal jump tests (bilateral standing long jump and single-leg hop distance), linear sprint tests over 10 m (acceleration) and 30 m (maximal sprint performance) using timed trials, and change-of-direction (COD) ability assessed via a standardized timed COD test. Results: Significant main effects of time, maturation, and time × group interactions were observed for all outcomes (p ≤ 0.013). A maturation × group interaction was found for bilateral jump performance (p = 0.045), a group effect for 10 m sprint time (p = 0.015), and a time × maturation × group interaction for COD performance (p < 0.001). Both training groups had improved jump performance (jump distance) and 10 m sprint time across maturity levels, while no changes were observed in the control group. For 30 m sprint time, improvements were observed in both training groups in prepubertal players, whereas only the unilateral group showed improvements in pubertal players. COD performance (completion time) improved in the unilateral group at both maturity levels and in the bilateral group at the pubertal level. Conclusions: Structured jump training enhances horizontal jump distance, sprint performance, and COD ability in youth soccer players. Adaptations appear to be influenced by training modality and maturation, although these effects may vary depending on the specific performance task. Full article