Daniel Leyhr

Talent identification (TI) is a topic of ongoing discussion across several fields, particularly in sport (Parra-Martinez & Wai, 2023). In sporting contexts, TI has been defined as the process of re...

Handball decisions in the penalty area remain one of the most controversial topics in professional association football, yet they are underexplored in sports science. The purpose of this research was to establish a foundation for understanding the controversy by examining its underlying causes. Two video-based studies quantified how key stakeholders interpret handball incidents and how closely these interpretations align with Union of European Football Associations (UEFA) guidelines. Study 1 involved referees active in German men’s professional football ( n = 154) who judged 30 incidents. Study 2 repeated the procedure with professional coaches ( n = 31) and players ( n = 46) using 18 incidents. Outcomes were Accuracy (accordance with UEFA), Strictness (percentage of incidents deemed punishable), Consensus (within- and between-group agreement), and Reasoning (primary reason for a decision). Referees reached 84.0% Accuracy, which differed by role, performance level, and handball category. Strictness among referees was lower compared to UEFA (42.9% vs. 50%). Coaches and players demonstrated lower Accuracy (63.8% and 67.5%) and Strictness (36.0% and 33.9%) than referees, resulting in significant differences in Consensus across Stakeholder Groups in 11 out of 18 incidents. Reasoning also diverged as referees preferred Naturalness, whereas coaches and players emphasised Avoidability and Impact. These findings reveal systematic differences between governing body guidelines, referee decision-making, and practitioner expectations. The results can inform educational measures and discussions on potential revisions to the handball law. Clearer and more objective criteria, jointly agreed by key stakeholders, are required to improve the consistency and acceptance of handball decisions.

The current study was designed to explore: (a) profiles of perceived autonomy, competence, and relatedness among National Collegiate Athletic Association coaches; (b) differences in these profiles based on coaches’ sex, Division, and coaching role; and (c) associations between coaches’ profile-affiliation and use of different coping functions. N = 1,218 National Collegiate Athletic Association Division I and II coaches from multiple sports participated in the research. Latent profile analysis (Bayesian information criterion = 17,078, Entropy = .83) revealed five profiles: “Moderately High Need Satisfaction/Moderately Low Need Frustration,” “Average Need Satisfaction/Average Need Frustration,” “Low Autonomy and Relatedness Satisfaction/High Autonomy and Relatedness Frustration,” “Low Competence Satisfaction/High Competence Frustration,” and “Low Need Satisfaction/High Need Frustration.” There were significant differences in participants’ profile-affiliation based on their sex ( p < .05), but not their role and Division. Multivariate analysis of variance indicated significant variations in participants’ use of problem-, emotion-, and avoidance-focused coping based on their profile ( p < .001).

Differences in biological maturity status (BMS) during puberty may advantage biologically older players within selection processes. This study examined maturity-related differences across multi-stage selection procedures, playing positions, and the relationship between BMS and team performance within the German Football Association's U15 national selection tournaments. Anthropometric measurements were collected from N = 695 male regional association team players (M = 14.1 ± 0.3 years), and BMS was assessed via skeletal age using the BAUSport™ ultrasound device. When compared to players' expected BMS, a significant large pre-selection bias was observed favouring players with higher BMS to get selected for a regional association team (M = 15.1 ± 1.0, d = 1.19, p < .001). Positional analyses revealed significant differences in BMS (η² = .14, p < .001) with goalkeepers, defenders, and forwards being biologically older than midfielders. Team performance (points achieved) showed a strong positive correlation with BMS (r_s = .71, p < .001). Significant small advantages in maturity-related variables were found for players selected for the extended U15 youth national team squad (0.17 ≤ d ≤ 0.23; p < .05). Position-specific analysis of selection status revealed medium-to-large effects in forwards and goalkeepers with respect to BMS. The findings highlight the critical influence of BMS in multi-stage selection processes and underscore the need for position-specific considerations to ensure fair and developmentally appropriate talent promotion.

Background/Objectives: Assessment of a novel deep-learning (DL)-based T1w volumetric interpolated breath-hold (VIBE_DL) sequence in breast MRI in comparison with standard VIBE (VIBE_Std) for image quality evaluation. Methods: Prospective study of 52 breast cancer patients examined at 1.5T breast MRI with T1w VIBE_Std and T1 VIBE_DL sequence. T1w VIBE_DL was integrated as an additional early non-contrast and a delayed post-contrast scan. Two radiologists independently scored T1w VIBE _Std/DL sequences both pre- and post-contrast and their calculated subtractions (SUBs) for image quality, sharpness, (motion)–artifacts, perceived signal-to-noise and diagnostic confidence with a Likert-scale from 1: Non-diagnostic to 5: Excellent. Lesion diameter was evaluated on the SUB for T1w VIBE_Std/_DL. All lesions were visually evaluated in T1w VIBE_Std/_DL pre- and post-contrast and their subtractions. Statistics included correlation analyses and paired t-tests. Results: Significantly higher Likert scale values were detected in the pre-contrast T1w VIBE_DL compared to the T1w VIBE_Std for image quality (each p < 0.001), image sharpness (p < 0.001), SNR (p < 0.001), and diagnostic confidence (p < 0.010). Significantly higher values for image quality (p < 0.001 in each case), image sharpness (p < 0.001), SNR (p < 0.001), and artifacts (p < 0.001) were detected in the post-contrast T1w VIBE_DL and in the SUB. SUB_DL provided superior diagnostic certainty compared to SUB_Std in one reader (p = 0.083 or p = 0.004). Conclusions: Deep learning-enhanced T1w VIBE_DL at 1.5T breast MRI offers superior image quality compared to T1w VIBE_Std.

Female players have largely been neglected in soccer‐specific talent research. Particularly, prospective studies examining the predictive validity of multidimensional performance factors for different selection levels—especially players' success in adulthood—remain scarce. This prospective cohort study investigated the predictive validity of multidimensional performance factors for the future success of U15 female players (N = 264) participating in the German Football Association's Talent Development program. All players' kicking, tactical, and psychosocial skills, as well as endurance capacity, were evaluated subjectively. They also completed five objective motor tests (sprint, agility [CODS], dribbling, ball control, and juggling). Players' future success was based on their selection for the U17 Bundesliga (43.6% selection rate), U17 Youth National Team (6.4%), and Women's Bundesliga (i.e., professional level in adulthood; 6.1%). Univariate analyses examined performance differences in each predictor between selected and nonselected players. Multivariate analyses determined whether objective predictors, subjective predictors, or a combination thereof offered the best prediction. Univariate results indicate the predictive validity of both assessments, revealing a trend toward larger effect sizes for higher selection levels and differences in predictor relevance. Multivariate models showed that adding subjective to objective predictors led to an increase in explained variance for participation in the U17 Bundesliga (Nagelkerke's R² = 16%) and Women's Bundesliga (31%), but not U17 Youth National Team (18%). Sprint performance reached significance across models, whereas the sole significant subjective predictor was tactical skills regarding participation in the Women's Bundesliga. Overall, these findings support the practical value of both assessments, which can likely be increased further via more distinct coach ratings.

In the ever-growing body of evidence on relevant talent predictors in soccer, goalkeepers (GKs) remain vastly underrepresented. Therefore, this large-scale prospective study was designed to investigate the predictive validity of objectively tested motor attributes and subjectively rated position-specific skills on GKs' selection into a youth academy (YA) three seasons after data collection. GKs across four age groups (U12-U15; N = 3431) who are part of the German Football Association's talent development program completed five motor tests assessing general speed abilities and position-independent technical skills. GK-specific technical and tactical skills, and GKs' overall performance level, were subjectively assessed via coach ratings. Univariate analyses performed separately for each age group confirmed the predictive validity of the motor tests (Mdn(d) = 0.35), evaluations of GK-specific skills (Mdn(d) = 0.68), and ratings of GKs' overall performance level (Mdn(Φ) = 0.21). Multivariate analyses demonstrated that considering all predictors in combination revealed explanatory power for a YA selection (.13 ≤ Nagelkerke's R² ≤ .22), with at least one significant objective and subjective predictor. Yet, except for participants in U14, only one GK-specific predictor reached significance indicating limiting additional explanatory power from other subjectively rated variables. Overall, the findings indicate benefits from the combined consideration of position-independent and GK-specific attributes as predictors of goalkeeping talent.

The objective of this study was to evaluate a high-resolution deep-learning (DL)-based diffusion-weighted imaging (DWI) sequence for breast magnetic resonance imaging (MRI) in comparison to a standard DWI sequence (DWI_Std) at 1.5 T. It is a prospective study of 38 breast cancer patients, who were scanned with DWI_Std and DWI_DL. Both DWI sequences were scored for image quality, sharpness, artifacts, contrast, noise, and diagnostic confidence with a Likert-scale from 1 (non-diagnostic) to 5 (excellent). The lesion diameter was evaluated on b 800 DWI, apparent diffusion coefficient (ADC), and the second subtraction (SUB) of the contrast-enhanced T1 VIBE. SNR was also calculated. Statistics included correlation analyses and paired t-tests. High-resolution DWI_DL offered significantly superior image quality, sharpness, noise, contrast, and diagnostic confidence (each p < 0.02)). Artifacts were significantly higher in DWI_DL by one reader (M = 4.62 vs. 4.36 Likert scale, p < 0.01) without affecting the diagnostic confidence. SNR was higher in DWI_DL for b 50 and ADC maps (each p = 0.07). Acquisition time was reduced by 22% in DWI_DL. The lesion diameters in DWI b 800_DL and _Std and ADC_DL and _Std were respectively 6% lower compared to the 2nd SUB. A DL-based diffusion sequence at 1.5 T in breast MRI offers a higher resolution and a faster acquisition, including only minimally more artefacts without affecting the diagnostic confidence.

Prior clustering approaches of soccer players have employed a variety of methods based on various data categories, but none of them have focused on clustering by career paths characterized through a time series analysis of yearly performance quality. Therefore, this study aims to propose a methodology how a career path can be represented as a time series of a player’s seasonal qualities and then be clustered with players that have a similar career path. The underlying data focuses on soccer players from the five largest European soccer nations (Big-5). This allows for the identification of different types of career paths of players and the investigation of significant disparities between career paths among the Big-5 nations. In line with our proposed methodological approach, we identified and interpreted 13 different clusters of player career paths. These range from the cluster with the highest player quality scores to the pattern comprising players with the weakest scores. Further, the detected clusters show significant differences regarding variables of soccer players’ early career phase in adolescence (e.g., age of debut in professional soccer, years spent in a youth academy). The presented approach might represent a first step for stakeholders in soccer to get an objective insight in players’ career by utilizing mainly freely available data sources.

Purpose: The aim of the present study was to investigate the influence of players' relative age, maturation-related characteristics, and motor performance tests on two different stages of talent selection (regional and national level) in youth elite basketball. Methods: Relative age, maturation-related variables (height, weight, maturity offset, maturity timing) and motor performance (Countermovement jump, Standing long jump, Modified agility T-test, Linear sprint 20 m) of N = 68 male youth basketball players (M_age = 14.39 ± 0.28 years) were assessed during the initial selection tournament for the German U15 national team. Pre-selection biases regarding relative age and maturity timing on the regional level were investigated utilizing one-sample t-tests. Differences in relative age, maturation-related characteristics and motor performance between players selected (n = 27) and non-selected (n = 41) for the youth national team were examined via independent samples' t-tests and logistic regression analyses. Results: Strong pre-selection biases toward early-born and early-maturing players were confirmed on the regional level. Significant advantages in height and weight and higher values in maturity offset and maturity timing were found for selected players. Among the motor variables, only Countermovement jump performance was significantly better in selected players. When controlling for relative age and biological maturation regression models including motor performance variables did not significantly discriminate players' selection status. Conclusion: Coaches working in national, but also preceding selection stages (regional and club level) should raise their awareness to relative age and biological maturation when evaluating players' potential and current (motor) performance.