Search Results (581)

This study aimed to examine age- and maturity-related differences in anthropometric characteristics, body composition, functional movement, and field-based physical performance among U14–U19 male youth soccer players. Seventy academy players completed anthropometric and body composition assessments, the Functional Movement Screen, a 30-m linear sprint, the Illinois Agility Test with and without the ball to assess change-of-direction speed (CODs), a standing long jump, and the Yo-Yo Intermittent Recovery Test Level 1. Biological maturation was estimated using the Mirwald equation. Age-category differences were examined using one-way ANOVA or Welch’s ANOVA, as appropriate. Associations between variables were assessed using Pearson’s correlation coefficient, while multivariable linear regression models were used to examine the independent associations of chronological age and maturity offset with physical performance outcomes. Significant age-category differences were observed in estimated age at peak height velocity (F(4, 65) = 5.12, η² = 0.240), maturity offset (F(4, 65) = 45.12, η² = 0.735), body height (F(4, 32.15) = 5.01, η² = 0.319), body weight (F(4, 65) = 15.47, η² = 0.488), skeletal muscle mass (F(4, 65) = 16.36, η² = 0.502), 30-m sprint time (F(4, 65) = 27.97, η² = 0.633), CODs without a ball (F(4, 65) = 16.52, η² = 0.504), standing long jump (F(4, 65) = 11.39, η² = 0.412), and endurance test performance (F(4, 30.21) = 16.47, η² = 0.408; all p < 0.01). The U14 players generally demonstrated less favorable performance than the older age categories. Interestingly, no significant age-category differences were observed in body fat percentage, Functional Movement Screen total score, or CODs with the ball. In the regression analyses, maturity offset was significantly associated only with standing long jump performance (β = 0.496, p = 0.012), but the association did not remain significant after Holm correction. The reported age-category values may provide preliminary benchmarks for evaluating youth academy soccer players, but they should be interpreted alongside maturity status and individual developmental characteristics. Future studies could complement field-based testing with biomechanical and treadmill-based laboratory assessments to provide a more comprehensive evaluation of age- and maturity-related performance. Full article

Background: Volleyball court roles impose distinct physical demands, yet multi-domain position-specific profiles of elite female players are scarce. This study compared anthropometric characteristics and field-test physical performance across five positions. Methods: Fifty players (10 per position: setter, libero, outside hitter, opposite, middle blocker) from the Turkish Sultans League (2024–2025) completed anthropometry and a field-test battery (countermovement, block and spike jumps, standing long jump, drop jump, reactive strength index, seated chest-pass and overhead medicine-ball throws, Davies test, 10 m sprint, Yo-Yo IR1). One-way ANOVA, Games–Howell post hoc tests, partial η², Cohen’s d and Benjamini–Hochberg correction (nineteen omnibus tests; 180 pairwise contrasts corrected across the complete contrast set) were applied. Results: Fourteen outcomes remained significant, with large effects (η² = 0.29–0.62, p ≤ 0.003) for height, standing reach, mass, BMI, circumferences, all three vertical jumps, reactive strength index, both throws and Yo-Yo IR1 distance. Waist-to-hip ratio, standing long jump and 10 m sprint did not differ, but were underpowered for small-to-moderate effects rather than equivalent. Middle blockers and opposites were tallest, with the greatest jumping and throwing outputs; setters and liberos were smallest, and setters—but not liberos—covered significantly more Yo-Yo IR1 distance than the three attacking positions; outside hitters were intermediate. After adjustment for stature, the vertical-jump and reactive-strength differences persisted; whereas, the medicine-ball throw and Yo-Yo IR1 differences did not. Conclusions: Elite female volleyball players display distinct positional profiles in body size, vertical jumping and reactive strength, with outside hitters intermediate on most outcomes. Estimated VO₂max is an indirect proxy derived from Yo-Yo IR1 distance and is not interchangeable with gas-exchange measurement; all pairwise contrasts and applied recommendations are exploratory and require prospective validation. Full article

We develop a PDE-constrained optimization framework for calibrating a regime-switching Heston–Merton model to S&P 500 index option prices. The model features two latent Markov regimes modulating stochastic volatility parameters and compound Poisson jumps, capturing the stylized fact that market volatility clusters differently during normal and crisis periods. Using real data from the Federal Reserve Economic Data (FRED) database covering July 2016 to July 2026 (2609 business days), we identify crisis regimes via VIX thresholds and estimate transition probabilities. Our empirical analysis reveals that crisis regimes exhibit 3.78 times higher long-run variance, 1.60 times higher vol-of-vol, and 113 times higher jump intensity compared to normal regimes. We derive the full adjoint system for the forward PIDE, including the previously undocumented jump operator adjoint and Markov-switching generator adjoint, and demonstrate that the adjoint method reduces per-iteration PDE solves from order-P to 2 regardless of parameter dimensionality. A panel calibration exercise demonstrates superior in-sample fit (${\mathrm{RMSE}}_{\mathrm{IV}}=1.24$ vol points) versus the nested Heston (2.87), Bates (2.31), and Black–Scholes (19.46) models. Out-of-sample Diebold–Mariano tests confirm statistically significant forecasting gains at the 1% level. The Feller condition is satisfied in both regimes. Full article

Background: The growing inclusion of students with developmental disabilities (SWDs) in mainstream physical education (PE) highlights the need for teaching approaches that support participation while maintaining educational effectiveness. This study examined the effects of a 12-week para-volleyball program on motor abilities in students without developmental disabilities (SWDDs). Methods: A total of 217 fifth- and sixth-grade primary school students were assigned to an experimental group (n = 110), in which students participated in a 12-week para-volleyball program, and a control group (n = 107), in which students followed the regular PE curriculum. Anthropometric characteristics and motor abilities, such as explosive strength, agility, and aerobic capacity, were assessed before and after the intervention using standardized field tests. Results: The experimental group showed significantly greater improvements in agility and explosive strength than the control group. Specifically, agility test performance improved by 0.92 s (p < 0.001, ηp² = 0.16), and standing long jump distance increased by 10.60 cm (p < 0.001, ηp² = 0.17). No significant effects were found for aerobic capacity (p > 0.05) or body composition, while flexibility improved only in the control group (+4.41 cm, p < 0.001). Conclusions: A 12-week para-volleyball program significantly improved agility and explosive strength in primary school students compared to standard PE. These findings suggest that para-volleyball is an effective tool for developing motor abilities and promoting inclusive PE. Full article

This paper develops a generalized autoregressive conditional heteroskedasticity–mixed data sampling model with continuous and jump components (GARCH-MIDAS-CJ). It aligns the continuous–jump (CJ) decomposition of realized volatility with the long-run–short-run multiplicative structure. The model places block-smoothed daily continuous variation in the long-run mixed-data-sampling term and demeaned jump variation in the short-run Glosten–Jagannathan–Runkle GARCH (GJR-GARCH) recursion. Using high-frequency data for the Standard & Poor’s 500 (S&P 500), we find a positive jump coefficient under both the Corsi–Pirino–Renò (CPR) and Andersen–Bollerslev–Dobrev (ABD) decompositions, supported by one-sided Wald, boundary-adjusted likelihood-ratio, and parametric-bootstrap tests. Relative to return- and realized-measure benchmarks, the forecasting value of the CJ allocation is competitive for multi-day and cumulative variance forecasts and in high-volatility periods, whereas established benchmarks can perform better for one-day and low-volatility forecasts. Under the CPR decomposition, the $h=22$ average cumulative forecasts reduce the mean squared error (MSE) and QLIKE relative to the aggregate-realized-variance benchmark by 8.2% and 3.3%, respectively. One-day-ahead value-at-risk (VaR) results are strongest at the 1% and 0.5% tails; the 5% forecasts have exceedance rates above the nominal level. Across alternative information-timing conventions, forecast windows, and United States equity assets, the clearest gains remain concentrated at multi-day horizons, although their magnitude varies across settings. The findings support a persistence-based allocation of continuous and jump variation within the GARCH-MIDAS structure. Full article

In long-distance subsea pipelines, pipeline inspection gauge (PIG) speed fluctuations under complex operating conditions can cause a mismatch between the sampling frequency and the operating state. This mismatch may compromise the integrity of defect detection signals. To address this problem, this study proposes an adaptive sampling method for in-line inspection of pipeline data based on multi-sensor fusion and a spatial sampling interval model predictive controller (SSI-MPC). The impact of PIG velocity fluctuations on defect detection signal integrity was analyzed, and a multi-sensor velocity fusion estimation model based on Kalman filtering was established to fuse inertial measurement unit (IMU) acceleration data with cumulative displacement information from the odometer. The sampling frequency adjustment was formulated as a spatial sampling interval tracking problem, and an SSI-MPC controller was developed. The effectiveness of the proposed method was verified through comparative simulations with fixed-time sampling and odometer-based equidistant sampling. The results indicate that SSI-MPC adaptive sampling more effectively restores the key quantitative features of defect detection signals under velocity-jump and high-speed conditions. The RSE and RAE of the defect detection signals are controlled within 3.44% and 2.10%, respectively. Compared with fixed-time sampling, the proposed method reduces the detection signal data volume by 39.37%. Full article

Objectives: The main purpose of this exploratory study was to examine differences between high-performing (HP) and low-performing (LP) female taekwondo athletes in body composition, lower extremities power, and knee extension/flexion isokinetic torque. A secondary aim was to explore how body composition, torque, and power relate to performance in the multiple frequency speed of kick test (FSKT_MULT). Methods: Twenty-six female taekwondo athletes (age: 18.0 ± 2.8 years; body mass: 58.1 ± 9.9 kg; height: 166.0 ± 0.05 cm) participated in the study. Athletes were classified as high performers (HP) or low performers (LP) based on their total score in the FSKT_MULT. Measurements included body composition assessed with dual-energy X-ray absorptiometry, countermovement jump (CMJ), standing long jump (LJ), and isokinetic knee extension and flexion at 60°/s and 240°/s. Results: High performers completed significantly more kicks during the first FSKT_MULT set than low performers (19.8 ± 1.1 vs. 18.0 ± 0.9 kicks; p = 0.001). They also showed higher trunk lean mass (p = 0.038), greater total lean mass (p = 0.036), and better standing long jump performance (p = 0.016). Mean and peak knee-flexion torque at 60°/s were higher in HP compared to LP. When all athletes were analyzed as one group, moderate-to-large correlations were observed between FSKT_MULT performance and body composition, as well as knee extension and flexion torque at both 60°/s and 240°/s. Conclusions: These findings indicate that high-performing female taekwondo athletes are stronger and generate greater power than low performers. Lean mass and knee extension and flexion torque showed moderate associations with FSKT_MULT performance. Full article

Positioning jumps are a primary cause of trajectory discontinuities in urban canyon environments, severely hindering the widespread adoption of autonomous vehicles. This paper proposes a CNN-GRU fusion-based method for correcting such positioning jumps. A complete 15-dimensional error-state extended Kalman filter (EKF) framework is established to analyze the jump generation mechanisms from three perspectives—pseudorange distortion, inertial drift, and filter gain divergence—thereby justifying the use of inertial measurement unit (IMU) time-series data for anomaly prediction. An end-to-end mapping model is further constructed, in which a one-dimensional convolutional neural network (CNN) extracts cross-channel spatial features from multi-axis inertial data, while a gated recurrent unit (GRU) captures long-term temporal error evolution. A hysteresis navigation quality factor and a piecewise Huber loss function are incorporated to enable hierarchical adaptive optimization. Experimental results demonstrate that the proposed method reduces the positioning root mean square error (RMSE) from 1.24 m to 0.70 m, achieves a jump suppression rate of 43.5%, and maintains a single-frame inference latency of 11.8 ms, meeting the real-time requirements for future autonomous driving localization. Full article

Background: Physical fitness is an important marker of health and development during early childhood. However, data describing fitness characteristics of preschool children from Central and Eastern Europe remain limited. This study examined age-related trends, sex differences, and associations with BMI-for-age z-scores (BMI SDS) in selected components of the PREFIT battery in Czech preschool children. Methods: A cross-sectional study was conducted in 40 children aged 3–6 years (19 girls and 21 boys) attending a public kindergarten in the Czech Republic. Physical fitness was assessed using four selected PREFIT components: handgrip strength, standing long jump, 4 × 10 m shuttle run, and one-leg stance. Associations with age, sex, and BMI SDS were analyzed using linear regression models. Results: Physical fitness was significantly associated with age across all assessed components (all p < 0.001). Sex differences were generally small, although boys demonstrated moderately higher handgrip strength than girls. After adjustment for age and sex, higher BMI SDS was associated with lower handgrip strength, poorer standing long-jump performance, and longer shuttle-run times, whereas no significant association was observed for one-leg stance performance. Conclusions: Selected PREFIT components were successfully implemented in a real-world kindergarten setting and were sensitive to age-related differences in physical fitness. Age showed the strongest and most consistent associations with fitness performance, while BMI SDS was independently associated with selected fitness outcomes. Larger multi-site and longitudinal studies are needed to establish population-specific reference values and to clarify the role of early physical fitness in later health and development. Full article

Natural gas production from mature fields is progressively shifting toward low-rate wells operating near their economic limit, creating challenges for long-term asset management. This study proposes an integrated stochastic decision-support framework combining Arps decline curve analysis, a calibrated Schwartz Type-I mean-reverting jump-diffusion model, Monte Carlo simulation, and Bellman dynamic programming to optimize marginal dry gas well management. The framework evaluates pipeline commercialization and a hybrid strategy integrating on-site electricity generation, while incorporating monetized environmental externalities associated with CO₂ emissions from gas combustion and potential post-abandonment CH₄ emissions. Application to the Mareógrafo 100 well in Mexico shows that the environmentally adjusted Bellman policy yields a mean NPV of USD 34.84 thousand, exceeding the comparable pipeline-only and hybrid strategies. Internalizing environmental costs reduces the mean optimal NPV by 46.6% relative to the economic-only formulation, while the mean abandonment time is approximately 200 days. Sensitivity analysis identifies electricity price, natural gas price, and pipeline distance as the dominant profitability drivers. The proposed framework provides a transferable methodology for jointly evaluating commercialization, environmental externalities, and abandonment decisions in mature dry gas fields under uncertainty. Full article

The Anatolian Caracal Optimization Algorithm (ACOA), a swarm-based optimization approach inspired by nature, approximately describes the characteristic hunting strategy of the Anatolian caracal, shaped by its superior auditory–visual perception and extraordinary agility, using mathematical models. The algorithm structures this process into three main stages by integrating and modifying established search mechanisms within a sequential framework: (i) wide-area scanning (exploration), which supports a broad exploration of the solution space through prey-focused movements; (ii) tracking–approach, which uses Brownian (continuous, small steps) and Lévy (occasional long jumps) movements to support the transition from exploration to exploitation; and (iii) predatory leap (exploitation), which represents the Anatolian caracal’s jump with a dimensionless projectile-inspired formulation and supports the refinement of candidate solutions. ACOA has been benchmarked across the CEC 2017, CEC 2019, CEC 2020, and CEC 2022 test suites, including unimodal and multimodal functions with fixed and varying dimensions, as well as real-world engineering design problems, for a total of 131 functions. It has been compared against 11 recent and well-known optimization algorithms. The best mean performance is achieved by ACOA in 111 out of 131 cases. In terms of stability, consistently low standard deviation is maintained by ACOA across the majority of the evaluated functions, indicating a strong reproducibility of the obtained solutions across independent runs. These findings indicate that the proposed three-stage framework provides a competitive exploration–exploitation behavior and can offer effective and stable solutions for a wide range of benchmark and engineering optimization problems. Full article

A novel distributed Transmission-Only Vector Network Analyzer (TVNA) based on two Six-Port Reflectometers (SPRs) is experimentally verified. The prototype distributed SPR-TVNA measures $S_{21}$ and operates with two independent RF sources, allowing the two ports of the Device Under Test (DUT) to be widely separated with no common cables coming to a central location. Using the distributed SPR-TVNA allows for measurements of, e.g., distantly separated antennas, or taking grain bin imaging measurements that would otherwise require long coaxial cables. A key issue of these large DUTs is accurate measurement of the through-measurement, $S_{21}$. The distribution (separation) of the two RF sources in the SPR-VNA requires novel procedures to obtain accurate results. The results are confirmed using simulations and experiments, with the experimental results obtained using custom-built hardware. While, in theory, a full VNA can measure $S_{11}$ and $S_{22}$, which is confirmed through simulation, the experimental results show significant errors in $S_{11}$ and $S_{22}$. We thus call the current device a Transmission-Only VNA. The fundamental math of the SPR-VNA means there is a ±180° phase uncertainty that must be solved, e.g., via a wide-band sweep looking for phase jumps. The experimental $S_{21}$ measurements of the prototype show maximum errors of 1.5 dB in magnitude and 6 degrees in phase over a bandwidth of 0.6–1.2 GHz. Full article

Physical ability testing is an essential part of police education, as fitness assessments indicate students’ preparedness for police work. Clear documentation and reporting of test protocols and measurement properties are essential for interpreting, evaluating, and comparing the usefulness of different test batteries. Therefore, this scoping review aimed to map the fitness tests used in police education programs internationally, including reporting standards of test protocols, reliability, validity, and sex-based test specificity, thereby providing insight into the physical abilities considered important for police work. The main searches were conducted in the databases CINAHL, PubMed, SPORTDiscus, and Web of Science. The database search yielded 1323 articles, of which 92 met the inclusion criteria. An additional nine articles were included through citation and hand searching. Of the 101 studies, 95 used an average of 4–5 general fitness tests, and 29 included work-related police tests. Test protocols were generally well documented across studies. However, only a few studies included in this review assessed test–retest reliability, and only a limited number of studies, whose primary aim was to validate the tests, evaluated test validity. The most commonly used assessments were upper-body and core muscular endurance (60 s push-up, maximum pull-up, and 60 s sit-up tests), upper-body muscular strength (hand-grip test), lower-body power (standing long jump, and vertical jump tests), and aerobic capacity (20 m multistage fitness, 2400 m Cooper, and 12 min Cooper tests. Only 19 studies reported sex-specific performance standards, including differences in test execution, scoring systems, VO_2max estimation, or time limits. The findings indicate that tests of upper-body muscular endurance and strength, lower-body power, and aerobic capacity are among the most frequently measured physical abilities in police education programs internationally, while also highlighting the need for more standardized reporting of test protocols, reliability, and validity. Full article

(1) Background: French contrast training (FCT) enhances sports performance, but its long-term efficacy in elite basketball players remains unclear. This study compared FCT and traditional strength training (TST) on jump performance and lower-limb strength. (2) Methods: Sixteen elite basketball players (age 22.4 ± 1.4 years; 14 male, 2 female) were randomly assigned to 8 weeks of FCT (n = 8) or TST (n = 8). The TST protocol consisted of barbell back squat, barbell Bulgarian split squat, conventional deadlift, and barbell hip thrust (4 sets of 8, 6, 4, 4 repetitions at 80%, 95%, 90%, 90% of one-repetition maximum [1RM]; 2–3 min inter-set rest). Assessments included countermovement jump (CMJ) kinetics, CMJ with arm swing (CMJA), running CMJ, running single-leg CMJ, and back squat 1RM, analyzed via repeated-measures ANOVA. (3) Results: A significant Group × Time interaction favored FCT for maximal relative force (p = 0.007, ηp² = 0.41): FCT increased 6.80% (Cohen’s d = 1.55), TST decreased 2.41% (d = −0.36). Significant time effects (p < 0.001–0.044) occurred for CMJA, running CMJ, flight height, reactive strength index, and back squat 1RM, with large improvements in both groups (e.g., back squat 1RM: FCT +30.45%, d = 2.89; TST +26.77%, d = 2.34). The interaction for average power approached significance (p = 0.053, ηp² = 0.24). No other interactions were significant. (4) Conclusions: Both FCT and TST improved performance, but FCT yielded superior gains in maximal relative force. Limitations include small sample (n = 16), mixed-gender composition, short 8-week intervention, and lack of retention testing. Full article

Creatine monohydrate is well supported as an ergogenic aid in adults, but age-specific evidence in adolescent athletes remains limited. This critical narrative review examined performance, safety, dosing, and responsible-use considerations. PubMed/MEDLINE was the primary source; citation tracking, the Cochrane Library, ClinicalTrials.gov, Google Scholar, and Semantic Scholar were used through 19 June 2026. The core athletic synthesis included 17 primary studies: five Tier 1 studies with direct adolescent samples, eleven Tier 2 age-adjacent or mixed-age studies, and one Tier 4 adult study retained for contextual interpretation. Across soccer, swimming, basketball, rehabilitation, and resistance-training settings, controlled studies reported possible task-specific improvements in selected power, repeated-sprint, jumping, technical, and rehabilitation outcomes, whereas other outcomes were unchanged and some favorable findings were limited to within-group analyses. Short-term controlled studies and a 32-week mixed-age cohort did not identify a consistent clinically important safety signal within the protocols studied; however, safety monitoring was often secondary and the evidence remains underpowered for uncommon or long-term events. Creatine monohydrate should therefore be neither routinely recommended nor categorically prohibited in adolescent athletes. Any consideration represents a precautionary, individualized risk-management approach—not a validated adolescent protocol—and should be food-first, family-involved, professionally supervised, and accompanied by product-quality control and planned reassessment. Full article