Search Results (71)

Background. Recent advances in data systematization have enabled the development of machine learning models to evaluate performance in elite sports; however, studies are needed to analyze the performance of professional players in relation to their playing position. Objective. To analyze the performance of professional soccer players who competed between 2017 and 2024 by applying a multilevel classification approach that integrates different machine learning algorithms. Materials and Methods. We analyzed 9088 player-seasons from professional players during the 2017–2024 seasons. These data were extracted from standardized databases on sports performance analysis belonging to the following leagues: LaLiga (Spain), Premier League (England), Bundesliga (Germany), Serie A (Italy), and Ligue 1 (France). The final sample, distributed by performance level, was as follows: elite players (n = 1818; 20%), mid-level players (n = 2727; 30%), and low-level players (n = 4543; 50%). The average age of the players analyzed was 26.1 ± 4.0 years, distributed across three outfield playing positions: center backs (CB), central midfielders (CM), and strikers (ST); goalkeepers were excluded because the dataset contains no goalkeeper-specific performance metrics. Results. Under a leakage-controlled protocol (the label-defining indicators were excluded from the predictors and the train/test split preceded all preprocessing), a linear model (logistic regression) achieved the best overall performance (mean macro-F1 = 0.729), ahead of ensemble and kernel-based methods; this indicates that, once target leakage is removed, the classification does not require non-linear models. Strikers (ST) were the most separable position (best macro-F1 = 0.818, area under the receiver operating characteristic curve [AUC-ROC] = 0.948) and center backs (CB) the most difficult (macro-F1 = 0.602, AUC-ROC = 0.791), with midfielders (CM) intermediate (macro-F1 = 0.770, AUC-ROC = 0.916). Conclusions. The results confirmed that performance structures differ substantially depending on the position in the field, supporting the use of position-specific analytical strategies. In this context, the combination of position-stratified dimensionality reduction, handling of imbalance, and explainable artificial intelligence allowed for the identification of interpretable performance patterns associated with the profiles of elite, mid-level, and low-level players. Full article

The aim of the present study was to examine the potential effects of circadian rhythmicity on specific external load metrics in professional male soccer players. Twenty players, members of a Greek Super League team, participated in the study. Data were collected from twenty match-day-minus-one (MD-1) training sessions, performed either in the morning (10:30 h, n = 10) or afternoon (15:00 h, n = 10). All sessions followed identical structure, volume, and intensity, ensuring internal validity. The external load metrics examined were total distance (TD), high-speed running (HSR; >19.8 km/h), high-intensity-acceleration count (HIACC; >3 m/s²), high-intensity-deceleration count (HIDEC; <−3 m/s²), and sprint distance (SD; >25.2 km/h). Statistical analysis was conducted using paired t-tests with Bonferroni correction for multiple comparisons (α = 0.01). Our results revealed significantly higher TD, HSR, HIACC, and HIDEC values (p < 0.01) during morning sessions compared to afternoon, suggesting a diurnal pattern favoring morning performance. No significant difference was found for SD (p > 0.01) despite the observed tendency for higher morning-values. These findings support the notion that time of day influences training output and that habitual morning training may lead to improved physical performance due to training-induced adaptations. Since in elite soccer even minor changes in performance could be decisive for the outcome of a competition, accounting for circadian factors in training planning could be crucial for competition performance. Full article

This study investigates the performance characteristics of U18 semi-professional soccer players by examining both technical load (TL) and physical load (PL) variables across various playing positions during the 2021/2022 Spanish Football U18 National League Championship. Methods: Principal Component Analysis (PCA) was employed to simplify the dataset, which comprised 246 match records from 49 athletes (mean age 17.9 ± 0.7 years; height ~177.6 ± 6.3 cm; body mass ~72.0 ± 7.2 kg) across ten matches. This analytical approach aimed to facilitate a deeper understanding of player performance dynamics. Results: Kaiser–Meyer–Olkin (KMO) values varied across positions (technical load: 0.20–0.93; physical load: 0.27–0.91). This indicates acceptable sampling adequacy for several positional models, but low adequacy for others; therefore, results for positions with low-KMO values should be interpreted cautiously. Factor analysis for both technical and physical load variables identified two components each, explaining substantial total variance (technical load: 63.75–86.65%; and physical load: 71.74–88.92% across position), with significantly high factor correlations (p < 0.001). The findings further indicate that players occupying defensive positions, such as goalkeepers and center-backs, generally exhibit lower levels of physical intensity and technical engagement compared to their counterparts in more dynamic roles, including full-backs, wingers, and forwards. The latter groups demonstrate higher involvement in high-intensity running and offensive actions. Conclusions: The observed performance patterns highlight the necessity for tailored training programs that align with the specific demands of each playing position. This approach is expected to optimize individual player performance and enhance overall tactical efficiency. Furthermore, the study underscores the importance of developing individualized conditioning strategies that address the unique physical and technical requirements inherent to each role on the field. This analytical approach using PCA provides a more structured and data-driven understanding of these positional differences, reinforming the need for tailored training programs and individualized conditioning strategies. Full article

Background: Despite the high prevalence of adductor injury in soccer, there is limited injury-specific predictive modeling to identify common risk factors. The objective of this study was to create an adductor strain prediction model utilizing injury, game, and performance data collected from a cohort of professional Major League Soccer (MLS) players. Methods: We identified potential risk factors for soft tissue, non-contact adductor strain using a predictive machine learning model framework. Performance and injury data were collected between the 2019 to 2022 seasons of one professional MLS team. We utilized Random Forest (RF) machine learning models with Synthetic Minority Oversampling (SMOTE) to predict soft tissue, non-contact adductor strain injury amongst the cohort. Features chosen to be implemented in the model included injury, game, and performance data. Results: From the four models constructed in this study, the best performing model included Catapult Global Position System (GPS)/Internal Measurement Unit (IMU), strength, injury, and game data using a weekly structure determined by F1 score. Multiple models indicated that not having a previous injury lowers the odds of a future injury in the following week or month. Forwards had greater odds of injury whereas defenders had lower odds of injury. Greater hamstring max force lowered odds of injury whereas a greater amount of change of direction efforts increased the odds of injury in the following week or month. Adductor-to-abductor max strength ratio showed conflicting results regarding the odds of future injury. Conclusions: Through the utilization of RF and SMOTE, we were able to successfully predict adductor injuries in an MLS cohort utilizing injury, game, and performance metrics. Validation in a larger cohort would be highly recommended before utilizing the findings of this study in the design of injury prevention protocols. Full article

Background: Muscle injuries are among the main problems in professional soccer, affecting player availability and team performance. Countermovement jump (CMJ) variables have been proposed as indicators of injury risk and for detecting strength imbalances, although their use is less explored than isokinetic assessments. Unlike previous studies based solely on linear statistics, this research integrates biomechanical data with machine learning approaches, providing a novel perspective for injury prediction in elite soccer. Objective: To examine the association between CMJ variables and muscle injury risk during a competitive season, considering injury incidence and effective playing minutes. It was hypothesized that specific CMJ asymmetries would be associated with a higher injury risk, and that machine learning algorithms could accurately classify players according to their injury status. Methods: Forty-one professional soccer players (18 women, 23 men) from national league teams (Chile) were assessed during preseason using force platforms. Non-contact muscle injuries and playing minutes were recorded over 10 months after the CMJ evaluations. Analyses included two-way ANOVA (sex × injury status) and machine learning algorithms (Logistic Regression, Decision Tree, K-Nearest Neighbors [KNN], Random Forest, Gradient Boosting [GB]). Results: Significant sex differences were observed in most variables (p < 0.05 and η_p² > 0.11), except peak force and peak power asymmetry. For injury status, only peak force asymmetry differed, while sex × injury interactions were found in peak power and left peak power. KNN (Accuracy = 87% and CI 95% = 71% to 96%) and GB (Accuracy = 84% and CI 95% = 68% to 94%) achieved the best classification performance between injured and non-injured players. Conclusions: CMJ did not show consistent statistical differences between injured and non-injured groups. However, machine learning models, particularly KNN and GB, demonstrated high predictive accuracy, suggesting that injuries are a complex phenomenon characterized by non-linear patterns. These findings highlight the potential of combining CMJ with machine learning approaches for functional monitoring and early detection of injury risk, though validation in larger cohorts is required before establishing clinical thresholds and preventive applications. Full article

Background: Oral health (OH) seems to be relevant for the number of sick and injured days (NSID), missing matches (MM) and secondarily for the physical performance (PP). Aim: The objective was to clarify possible associations between OH, NSID, and PP for elite soccer players. Methods: Thirty-nine male athletes (age: 24.6 ± 4.2 years, age range: 17–34 years) from a third league professional soccer team were examined concerning several dental parameters (decayed, missing, and filled teeth, DMFT; periodontal screening index, PSI; approximal plaque index, API; papillary bleeding index, PBI) and PP parameters. The PP diagnostic contains grip strength, posturography, jump and sprint tests, and an endurance test on treadmill. Furthermore, the number of sick and injured days and missing matches was collected and assessed over four seasons. Results: We could not find any relevant (r > 0.7) correlations between sick and injured days or missing matches and variables of different dimensions (OH, PP). The soccer players showed a remarkable level of oral health (missing teeth, MT: 0.18 ± 0.56), jumping performance (44.5 ± 5.42 cm), and grip strength (53.7 ± 7.02 kg). The endurance capacity (velocity at 4 mmol/L lactate threshold, v4: 14.9 ± 1.11 km/h) was on an average level, whereas the levels of postural stability (stability indicator, ST: 20.0 ± 4.55) and sprinting performance (10 m sprint: 1.79 ± 0.09 s) were comparatively low. Only five players (13%) reported that oral health had ever had a negative impact on his physical performance. Two players (5%) reported currently tooth pain and six players (15%) bleeding gums or grinding teeth. Conclusions: Based on the high level of dental health, it was difficult to prove any relationships between OH and the NSID/MM or PP. Nevertheless, it seems that young soccer players benefit particularly from improved oral health programs. The excellent dental care appears to have a positive effect on general health and physical performance in soccer. Full article

Comprehensive weekly load data appears relatively absent in the literature for the professional female soccer population. This exploratory observational study quantified the weekly training, match, and total loads experienced in a professional soccer team and compared these loads according to player role. Data were collected over a full season from 22 players competing in the Australian national A-League Women’s soccer competition. Internal (session-rating of perceived exertion load [session-RPE load]) and external load (total and relative values for total and high-speed running [HSR] distance) data were acquired during on-field training sessions and matches. Players were categorized as starters (started the match) or non-starters (used as a substitute in the match) within each week. Linear mixed models and effect size analyses were used to compare weekly loads between player roles. Weekly match and total load analyses revealed higher (p < 0.001, moderate-to-very large effects) duration, total distance, total HSR distance, and session-RPE load in starters than non-starters. In contrast, relative total and HSR distance in matches were higher (p < 0.001, moderate-to-large effects) in non-starters than in starters. These data provide an initial reference for the weekly loads in this competition, highlighting disparities between player roles that should be considered when developing training and preparation plans. Given the recruitment of a single team and small sample size, future research should extend upon this study to further strengthen the evidence base in this population. Full article

Background/Objectives: The role of body composition in sports performance has been widely studied, particularly in soccer. Understanding how anthropometric characteristics impact movement efficiency and neuromuscular performance is crucial for optimizing player performance. This study examined the relationship between body composition and locomotor performance in elite soccer players. Methods: Thirty-six male soccer players from the Mexican National Team participated in the study, where body composition was assessed using surface anthropometry. Players underwent tests to measure countermovement jump (CMJ) performance, sprinting speed, maximum acceleration, and distance covered during two games of the CONCACAF Nations League quarterfinals. Correlation matrices were created to identify the most significant associations, followed by generalized linear models (GLMs) to associate body composition variables with performance metrics. Results: Anthropometric profile tables were created by playing position. Higher body fat percentage (%BF) was associated with lower performance. Specifically, higher %BF was associated with slower sprint speed (B = −0.74 m/s, p < 0.001) and shorter distance covered (B = −4.86 m/min, p < 0.001). Conversely, greater muscularity, reflected by corrected girth values for the thigh and calf, was associated with improved CMJ performance. Thigh corrected girth was positively associated with concentric mean force (B = 48.85 N, p < 0.001), and calf corrected girth was positively associated with peak power (B = 240.50 W, p < 0.001). These findings underscore the importance of low body fat and high lean mass for efficient movement. Conclusions: The results highlight the critical role of body composition in enhancing soccer performance, particularly for explosive movements like jumps, sprints, and accelerations. This study suggests that monitoring and optimizing body composition should be a central focus of nutrition, training, and conditioning strategies, adapted to the specific positional demands of professional soccer. Full article

Background: Oral health (OH) has been linked to overall health status and common physical performance (PP). Aim: The objective was to compare the OH and PP of two third league professional team players from different sports (soccer, ice hockey). Methods: Twenty-nine professional soccer players (mean ± standard deviation; age: 24.3 ± 4.1 years) and twenty-one ice hockey players (age: 27.7 ± 3.6 years) were investigated regarding several dental scores (DMFT, PSI, API, PBI) by one calibrated examiner. The PP diagnostic includes measurement of grip strength as well as postural stability and regulation using posturography. Results: Concerning dental scores, relevant sport-specific differences for PSI (1 vs. 2; p < 0.001), API (29 vs. 48; p = 0.001), and PBI (14 vs. 42; p < 0.001) in favor of soccer players were found. Ice hockey players reported significantly more tension of the temporomandibular joint (p = 0.004) and showed lower readiness for regular check-ups (p < 0.001) and additional oral hygiene (p = 0.045). In contrast, ice hockey players were more balanced and displayed a higher level of weight distribution (p < 0.001), especially in the anterior-posterior direction (p = 0.002). Conclusions: Based on more intensive oral hygiene and dental care, the investigated professional soccer players showed partially better OH conditions compared to the ice hockey players examined. In summary, the OH and PP results reflect the different sport-specific requirements and related training impacts on athletes. Full article

As powerful actions commonly proceed goal scoring opportunities within soccer, enhancing powerful actions could be essential to optimize performance. There is a large body of evidence supporting the positive associations between maximal isometric mid-thigh pull force-generating qualities and jump performance. Objectives: The purpose of this study was to determine if relative maximal isometric force production can discriminate between higher- and lower-performing jumpers among professional and semi-professional soccer players. As such, it was hypothesized that stronger players would have a greater jump performance than weaker players. Methods: An observational cross-sectional research design was used to assess ballistic and isometric force production of the lower limbs across players from four professional and semi-professional soccer clubs during the pre-season period. Seventy-six professional male lower-league soccer players (mass: 82.5 ± 8.2 kg; height: 1.80 ± 0.07 m; age: 25.8 ± 4.3 years) performed three trials of the countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) using force plates. Players were categorized as strong and weak using the group’s average IMTP relative peak force (33.41 N/kg). A series of one-way Bayesian independent t-tests were performed to determine the difference between strong and weak groups. Results: A large magnitude of difference was observed between strong and weak players for relative peak force (d [95% CI] = 2.53 [2.017–∞]), with strong evidence supporting the hypothesis (BF₁₀ = 2.698 × 10⁺¹⁴). There was moderate evidence to support the hypothesis that strong players (n = 37) had a greater modified reactive strength index (mRSI) and relative average braking force in comparison to weaker players (n = 39). All other evidence was weak, with trivial-to-small differences (d = 0.10–0.42) for jump height, jump momentum, propulsive force, force at minimum displacement, time to take off, and countermovement depth. Conclusions: Maximal relative strength has implications on jump performance, albeit not on the jump outcome. Stronger players performed the CMJ more efficiently when observing the mRSI, with a shorter time to take off, while producing greater average relative forces during the braking phase. This could have potential implications in the sporting environment when performing jumping tasks, where they can achieve a similar outcome over a shorter duration. Full article

Adductor strains are prevalent injuries in professional soccer. The purpose of this study is to identify further evidence of characteristics associated with adductor injury. MLS and other worldwide leagues have differing styles of play warranting further investigation of injury mechanisms. A descriptive cohort study was conducted with a single professional team in the MLS. Injury data was collected between the 2016 to 2022 seasons to characterize adductor injury. Player position type, age, previous injury, and mechanism(s) of injury (MOI) were assessed to understand the injured population. Generalized estimating equations (GEEs) were utilized to assess the odds of future injury among the injured and non-injured populations. Adductor strains (n = 30) made up 15.5% of all soft-tissue, lower extremity injuries (n = 194) in a single MLS cohort. These injuries were the second most common defined soft-tissue, non-contact injury after hamstring strains (26.4%) and before quadricep strains (11.9%). Among the position types, 28% of defenders, 25% of goalkeepers, 21.4% of forwards, and 20.5% of midfielders experienced at least one adductor strain. The MOI most responsible for these injuries were overuse (30%), change of direction (26.7%), running (13.3%), and kicking (10%). Athletes with previous adductor injury had 167.2 times the odds of adductor injury in a future half-season compared to non-injured athletes. The findings from this study provide further descriptive evidence of player position types and mechanisms related to adductor strain. Insights into the nature of injury within an MLS team and support of previous evidence shows the prevalence of adductor injuries in elite soccer players. Full article

This study explores market value depreciation among soccer players across the top five European leagues, addressing a critical gap in the sports finance literature by focusing on post-prime valuation dynamics. Leveraging a dataset from the 2023/2024 season, player market values and attributes sourced from Transfermarkt and Sportmonks were analyzed using league-specific multilinear regression models. The findings reveal a consistent decline in market values beginning at age 27, with notable variation across leagues. The German Bundesliga demonstrates the steepest depreciation rates, suggesting shorter career peaks or distinct market dynamics. In contrast, the Italian Serie A and Spanish La Liga exhibit the slowest depreciation rates, preserving player value for older athletes longer than other leagues. The English Premier League and French Ligue 1 show moderate depreciation, with the Premier League’s decline closely aligning with Ligue 1 and diverging less from other leagues than traditionally assumed. These results challenge preconceived narratives about league-specific player valuations and offer empirical insights into the transfer market. By providing a nuanced understanding of depreciation trends, this study can inform strategic decisions for agents, managers, and clubs, particularly in optimizing contract negotiations, transfer strategies, and long-term asset management in professional football. Full article

Background and Objectives: This study analyzes the effects of proprioceptive training on the physical fitness and soccer-specific technical skills of young professional soccer players. Materials and Methods: Twenty-eight male professional soccer players from the Türkiye Football Federation’s Third League, aged 20.46 ± 1.60 years (average), participated voluntarily. Body composition was assessed with the Inbody270 bioelectrical impedance analyzer, while agility and maximal VO₂ cardiorespiratory fitness were measured using the ChronoJump smartspeed mat. Soccer-specific technical skill assessments were also conducted. Data were analyzed using SPSS 22, with paired sample t-tests for comparisons, Cohen’s d test for effect size, and repeated measures two-way ANOVA for interaction effects (group × time). Eta squared (η²) values were reported for effect size. A 95% confidence level and p = 0.05 were used. Results: Proprioceptive training significantly improved body fat percentage (p < 0.05; η² = 0.006) and soccer-specific technical skills, including free juggling (p < 0.05; η² = 0.302), alternating foot juggling (p < 0.05; η² = 0.271), right foot juggling (p < 0.05; η² = 0.250), and shooting performance (p < 0.05; η² = 0.513). Conclusions: A 12-week proprioceptive training program, when incorporated into soccer practice, significantly enhances soccer-specific technical skills and reduces body fat percentage. Full article

Objectives: This study uniquely examines the evolution of match running performance in official matches over four consecutive seasons (2019/2020–2022/23) within Spain’s top two professional soccer leagues (LaLiga). By analyzing differences between competitive league standards (First Division vs. Second Division), this research provides critical insights into how competition levels influence physical performance trends over time. Methods: A total of 6784 match observations were recorded from 95 teams competing in the First and Second Divisions (LaLiga). Performance metrics included total distance (TD), high-speed running (HSR, >21 km·h⁻¹), very high-speed running (VHSR, 21.1–24 km·h⁻¹), sprint distance (Sprint, >24 km·h⁻¹), the number of HSR efforts (Nº. Sprints > 21 km·h⁻¹), and sprint efforts (Nº. Sprints > 24 km·h⁻¹), all analyzed using a computerized tracking system (TRACAB, ChyronHego, New York, NY, USA). Results: The primary findings indicated significantly higher match running performance in First Division matches compared to Second Division matches across all variables (p < 0.001). Furthermore, match running performance significantly increased over the four seasons in both leagues, with notably higher values during the 2021/22 and 2022/23 seasons for all physical performance metrics (p < 0.001). Conclusions: This study contributes to understanding the temporal evolution of soccer match performance across competition levels. The findings emphasize the importance of periodic performance monitoring and adapting training loads increasing high-intensity distances to align with escalating physical demands in modern soccer, offering valuable guidance for coaches and performance analysts. Full article

Background/Objectives: Studies focused on the soccer goalkeeper position in training and official matches are scarce. The present study aimed to analyze the external load during training sessions and official matches in semi-professional goalkeepers. Methods: Data from goalkeepers (n = 6) from the youth ranks of a professional team belonging to the first Spanish soccer league have been used. The sample is made up of a total of 758 data collected during all the training and competitions carried out by the analyzed teams that made up the squad during the 2021/2022 and 2022/2023 seasons. A descriptive and inferential analysis was carried out based on the category (Youth B or Youth C) and the sports context (training or competition). Results: The results showed significant differences depending on the category (average time to feet left, average time to feet right, total jumps, total dives, total left dives, total right dives, high metabolic load distance (HMLD), and high metabolic power efforts (HMPE)), and the sport context (average time to feet right, total jumps, total dives, total left dives, total right dives, total distance, distance 18–21 km/h, distance 21–24 km/h, Dec 2–3, efforts, and HMLD). Conclusions: The EL of the GKs shows differences regarding the category and the context. Therefore, it is necessary to analyze and determine the threshold of each player considering different variables related to the external and internal load to individualize the training tasks and prevent injuries due to overload. Full article