Search Results (48)

In ultra-cold narrow-window drilling, pipe connection causes flow-path switching as the main circulation is interrupted and bypass circulation is established, breaking the initial relative pressure balance of the whole wellbore and inducing asymmetric transient variations in flow distribution, annular friction, and bottomhole pressure response, thereby increasing the risks of wellbore instability, lost circulation, and kicks. To address the poor pressure-control accuracy, long non-productive time, and inadequate low-temperature adaptability of conventional drilling technologies in the Irkutsk block of Russia, this study developed and field-tested an integrated all-electric managed pressure drilling (MPD) and cold-resistant continuous circulation system (CCS). Existing conventional technologies often suffer from high communication latency and hydraulic freezing in extreme cold environments, leading to uncoordinated pressure compensation. To overcome these limitations, the scientific novelty of this work lies in proposing a transient pressure rebalancing mechanism that effectively suppresses the asymmetric pressure disturbances induced by topological flow path switching. Methodologically, the proposed system was validated through a comprehensive industrial field test. An improved Herschel–Bulkley temperature–pressure coupled model was established to dynamically calculate full wellbore annular pressure loss. Furthermore, a dedicated hardware adapter module utilizing multi-protocol conversion was integrated to achieve a communication delay of less than 8 ms, enabling high frequency coordinated pressure regulation. Field results demonstrate that compared to the delayed responses of conventional systems, the proposed integrated approach successfully maintained a dynamic backpressure tracking error within ±0.069 MPa under extreme conditions of −38 °C and a narrow pressure window of 0.08 g/cm³. The rapid suppression of asymmetric transient responses prevented any lost circulation, kicks, or wellbore collapse. These findings highlight the significant advantages of the integrated system in maintaining pressure field stability, thereby providing a robust and innovative engineering solution for complex well interventions. Full article

With society’s ever-growing concern for animal welfare, the equestrian industry has focused on passing and enforcing new rules to protect the main athlete, the horse. In jumping, courses go by quickly, with judges using the occurrence of conflict behaviours to assess any welfare breach. This study aimed to evaluate the overall frequency of such behaviours in Brazilian Sport Horses during elite show jumping competitions in Brazil. Conflict behaviour displays were analyzed in 120 different horse–rider pairs in jumping competitions in Brazil. All videos were observed at a slowed-down speed, with the frequency of behaviours being recorded. The observed behaviours included head shaking, tail swishing, neck hyperflexion, excessive pulling on the reins, kicking, bucking, rearing, and disobedience. All horses (100%) presented at least one type of conflict behaviour, with head shaking (100%, n = 120, IQR 3–7, range 1–18) being the most common one (p < 0.001) and tail swishing (45.83%, n = 55, IQR 1–10, range 1–29) being the second most common (p < 0.001). Most horses showed only one (41.67%, n = 50) or two (43.33%, n = 52) different types of behaviours, with few episodes of each throughout the course. Those findings were in line with studies in other disciplines, as the competition environment offers a series of challenging and stressful situations. The low levels of conflict observed in most horses indicate that the current horse welfare rules are working and must continue to be reinforced to consistently protect the horses. Full article

Elite women’s rugby has often been analysed using the male performance model as a reference, despite evidence that women’s rugby presents distinct game demands and potentially different risk profiles. This study aimed to compare the frequency of key contact-related events between elite men’s and women’s rugby. An observational, retrospective, comparative cohort study was conducted using official performance data from 135 international matches from the men’s and women’s Six Nations Championships. Variables were grouped into three categories: Open-Play, Static Phases, and Discipline. Independent samples t-tests, Mann–Whitney U tests, and Linear Discriminant Analysis were used to identify sex-based differences. The results showed that men presented a higher frequency of rucks lasting more than 6 s (p < 0.001), whereas no significant differences were found in total tackles (p = 0.378) or total rucks (p = 0.634). In Static Phases, women’s teams recorded significantly more scrums (p < 0.001). In Discipline, women conceded fewer free kicks (p = 0.003) but received more red cards (p = 0.020). In conclusion, elite women’s rugby shares some open-play characteristics with the men’s game but differs in scrum frequency and disciplinary profile, supporting the existence of a distinct contact and risk exposure profile that should be considered when designing training and prevention strategies. Full article

Objectives: Post-activation performance enhancement (PAPE) has been explored for its potential to improve performance in combat sports. This part II of the systematic review and meta-analysis investigated the acute effects of PAPE protocols on sport-specific performance outcomes and evaluated the influence of moderating variables, specifically competitive level and training experience. Methods: A PRISMA-guided search (2010–2024) identified 13 studies examining PAPE in combat sports athletes. Inclusion criteria required human trials using defined PAPE protocols and evaluating sport-specific tests, primarily the Frequency Speed of Kick Test (FSKT-10) and the Taekwondo-Specific Agility Test (TSAT). A random-effects meta-analysis (Hedges’ g) was conducted on data from 176 athletes. Results: The meta-analysis revealed a profound moderating effect of training status on PAPE responsiveness. For the FSKT-10, amateur athletes demonstrated large, significant improvements (g = 1.28, p < 0.001), whereas elite athletes showed trivial, non-significant changes (g = 0.11, p = 0.357). Similarly, athletes with <6 years of training experience exhibited substantially larger enhancements in both FSKT-10 (g = 1.60) and TSAT agility (g = −1.64) compared to their more experienced (>6 years) counterparts (g = 0.42 and g = −0.65, respectively). Furthermore, dynamic and biomechanically specific conditioning activities (e.g., repeated high-intensity techniques) were most effective at driving sport-specific potentiation. Conclusions: PAPE protocols may enhance acute sport-specific performance when utilizing dynamic, highly specific conditioning activities. However, a possible “ceiling effect” may blunt this potentiation in elite and highly experienced athletes, suggesting a potential need for highly individualized priming strategies at the top competitive levels, specifically in taekwondo. Full article

Martial arts have evolved from self-defense practices into structured competitive sports that demand high levels of neuromotor control, where improper execution remains a major source of injury. This study evaluates lower-limb control during the execution of the karate lateral kick using videogrammetry biomechanical analysis. Three participants were recorded during regular training sessions and selected according to their level of expertise. Each participant performed lateral kicks at three predefined distances (close, comfortable, and long), selected based on common training practice and individual biomechanical considerations. Videogrammetry data were generated using Kinovea version 0.9.5 software to extract sagittal ankle trajectories. Statistical analyses were carried out in MATLAB version 2025b using spatial coordinates to obtain kinematic data on the practitioner’s performance. The results revealed skill-dependent differences in movement control, characterized by temporal evolution of kinematic variables and their corresponding time–frequency representations. Novice practitioners exhibited limited control during the raising and recovery phases, despite reaching the target. In contrast, expert practitioners demonstrated consistent posture, controlled acceleration during impact, and stable limb trajectories during descent. These observations provide a foundation for data-driven classification of kick execution quality and outline potential applications in supervised learning, real-time feedback systems, and injury risk reduction during karate training. Full article

This study examined differences in finishing techniques and positional contexts across three temporal windows in the Ultimate Fighting Championship (2003–2004, 2013–2014, and 2023–2024), revealing differences consistent with a shift from greater diversity to a specialized and systematized model. Analysis of 906 finalized bouts demonstrated a marked concentration of submission finishes, with rear naked choke increasing from 15.8% to 46.8% (p ≤ 0.001), while back control was the dominant positional context (45.5%, p ≤ 0.001). In striking-based finishes, punches maintained prevalence, evolving from 77.4% (2003–2004) to 86.1% (2023–2024, p ≤ 0.001), whereas kicks declined from 20.5% to 11.3% (p ≤ 0.001). Submissions increased from 37.0% to 52.0% of all finalized bouts (p ≤ 0.001). These findings indicate a growing emphasis on specific finishing techniques, with modern mixed martial arts demonstrating increased distributional concentration in the methods used to finalize bouts. The increased frequency of certain techniques (e.g., rear naked choke and punches) among finalized fights may reflect strategic preferences, training priorities, or rule-driven changes in technique effectiveness, but cannot be interpreted as evidence of inherent technical superiority without additional data on success rates or efficiency metrics. Our data suggest that contemporary fighters have developed more direct and systematized approaches to finishing fights, reflecting the evolution of training methodologies and competitive strategies. Full article

Objective: to clarify differences in the intermuscular coherence of core muscles during side kicks among male Sanda athletes at varying skill levels, particularly in critical frequency bands; to reveal the association between neuromuscular coordination mechanisms and technical proficiency; and to provide methodological references for quantitative analysis of combat sports techniques. Methods: Thirty-six male Sanda athletes were divided into professional (n = 18) and amateur (n = 18) groups based on athletic ranking and training duration. Surface electromyographic (EMG) signals from 15 core muscles and kinematic data were synchronously recorded using a wireless EMG system and a high-speed camera. Signal processing extracted root mean square amplitude (RMS) and integral EMG (iEMG). Muscle coordination was quantified via time-frequency coherence analysis across alpha (8–15 Hz), beta (15–30 Hz), and gamma (30–50 Hz) bands. Results: The professional group exhibited significantly higher RMS and iEMG values in most core muscles (e.g., rectus femoris RMS: 0.298 ± 0.072 vs. 0.214 ± 0.077 mV, p < 0.001). Regarding intermuscular coherence, the professional group demonstrated significantly superior coherence in the α, β, and γ bands for key muscle pairs, including upper limb–swing leg, support leg–swing leg, and upper limb–support leg. Notable differences were observed in pairs such as external oblique–rectus femoris (alpha band: 0.039 ± 0.012 vs. 0.032 ± 0.011, p < 0.01) and right rectus femoris–biceps femoris (beta band: 0.033 ± 0.010 vs. 0.023 ± 0.007, p < 0.01). Conclusions: The fundamental difference in side kick technique among Sanda athletes lies in neuromuscular control strategies and muscle coordination efficiency. Sensor-based intermuscular coherence analysis provides an objective quantitative indicator for distinguishing technical proficiency, offering a scientific basis for optimizing training and extending the methodological framework for technique assessment in combat sports. Full article

Foot gesture recognition using a continuous-wave (CW) radar requires implementation on edge hardware with strict latency and memory budgets. Existing structured and unstructured pruning pipelines rely on iterative training–pruning–retraining cycles, increasing search costs and making them significantly time-consuming. We propose a NAS-guided bisection hybrid pruning framework on foot gesture recognition from a continuous-wave (CW) radar, which employs a weighted shared supernet encompassing both block and channel options. The method consists of three major steps. In the bisection-guided NAS structured pruning stage, the algorithm identifies the minimum number of retained blocks—or equivalently, the maximum achievable sparsity—that satisfies the target accuracy under specified FLOPs and latency constraints. Next, during the hybrid compression phase, a global L1 percentile-based unstructured pruning and channel repacking are applied to further reduce memory usage. Finally, in the low-cost decision protocol stage, each pruning decision is evaluated using short fine-tuning (1–3 epochs) and partial validation (10–30% of dataset) to avoid repeated full retraining. We further provide a unified theory for hybrid pruning—formulating a resource-aware objective, a logit-perturbation invariance bound for unstructured pruning/INT8/repacking, a Hoeffding-based bisection decision margin, and a compression (code-length) generalization bound—explaining when the compressed models match baseline accuracy while meeting edge budgets. Radar return signals are processed with a short-time Fourier transform (STFT) to generate unique time–frequency spectrograms for each gesture (kick, swing, slide, tap). The proposed pruning method achieves 20–57% reductions in floating-point operations (FLOPs) and approximately 86% reductions in parameters, while preserving equivalent recognition accuracy. Experimental results demonstrate that the pruned model maintains high gesture recognition performance with substantially lower computational cost, making it suitable for real-time deployment on edge devices. Full article

Background: Transcranial Magnetic Stimulation (TMS) has been employed in athletes from various sports to enhance performance; however, no data have focused on its effects in mixed martial arts (MMA). This study investigated the effects of intermittent theta-burst stimulation (iTBS), an alternative modality of TMS, on motor performance and plasma oxidative-stress biomarkers of ten male mixed martial arts (MMA) athletes. Methods: A randomized controlled trial was conducted with ten professional MMA athletes (aged 18–35 years). Participants were assigned to the experimental (iTBS) or placebo groups. Baseline and post-intervention performance were assessed using the Multiple Frequency Speed of Kick Test (MFSKT) and a Progressive Speed Kick Test (PSKT). Plasma biomarkers of oxidative stress, including thiols, total antioxidant capacity, 8-isoprostane, and carbonylated proteins, were measured before and after the performance tests in both groups. The iTBS was applied to the left primary motor cortex at an 80 motor threshold for the experimental group and at sub-threshold levels for the placebo group. A two-way ANOVA for paired groups, followed by Bonferroni post-hoc tests, were used to analyze the repeated measures, with the significance level set at p < 0.05. Results: The findings revealed significant improvements on the MFSKT [25.4 (±1.2) kicks vs. 20.8 (±1.4) kicks] and the PSKT [27.6 (±1.5) vs. 22.4 (±1.7) kicks] in the iTBS group vs. placebo, respectively. No significant differences were observed between the groups in terms of the serum redox balance biomarkers pre- and post-test, suggesting a limited impact on redox homeostasis despite performance enhancement. The placebo group showed no notable changes in either test or biomarker levels. Conclusions: These results highlight the improved physical performance in MMA athletes without altering redox biomarkers in the blood—emphasizing its applicability for neuromodulation in sports. Full article

Penalty shootouts often decide major football tournaments, making the analysis of spatial symmetry and shot patterns crucial for performance optimization. This study analyzed 212 decisive penalty kicks in elite men’s football to explore spatial patterns and asymmetries in execution, as well as their relationship with performance effectiveness. An observational methodology was used, combining temporal pattern detection (T-patterns) and chi-square tests to examine associations between contextual, spatial, and outcome-related variables. Results showed that the most frequently targeted area was left-down (28.3%), with a success rate of 71.7%. Additionally, central zones exhibited particularly high accuracy (ranging from 88.9% to 100%) despite their low usage frequency. Differences were also observed in the distribution of shots between left- and right-footed players, both in frequency and effectiveness, although these were not significant. The findings suggest the presence of strategic tendencies and functional spatial asymmetries, which may have implications for specialized training in high-pressure scenarios. These insights can guide targeted training strategies for both kickers and goalkeepers and encourage further research on decision-making and spatial behavior under extreme pressure. Full article

Background. In taekwondo (TKD), high-intensity actions—particularly kicks and rapid changes of direction—are key determinants of sport-specific performance. Kinetic vari-ables derived from unloaded countermovement jumps (CMJs) are employed as proxies of neuromuscular efficiency. However, most studies have examined the link between CMJ outputs and TKD using jump height alone in sport-specific tasks. Objective. To determine the associations between unloaded CMJ-derived kinetic variables and sport-specific performance, identifying key determinants of repeated high-intensity kicking capacity and change-of-direction ability. Methods. Fifteen national-team athletes (nine men, six women; 18–27 years) completed unloaded CMJ testing (Day 1) and, after 48 h, the Taekwondo-Specific Agility Test (TSAT) and the Multiple Frequency Speed of Kick Test (FSKTMULT) (Day 2). Results. For FSKTMULT, jump height (r = 0.545–0.746), take-off velocity (r = 0.548–0.799), and mean power (r = 0.602–0.799) were positively correlated with the number of kicks across all sets (p = 0.001–0.044). Stepwise regression identified mean power as the sole significant predictor, explaining 32–46% of the variance across sets. For TSAT, time correlated negatively with mean power (r = −0.678, p = 0.008), mean force (r = −0.536, p = 0.048), and RFD (0–30%) (r = −0.655, p = 0.011). Mean power and mid-propulsion impulse (30–60%) jointly explained 72.8% of the variance in TSAT time (R² = 0.728, p < 0.001). Conclusions. Unloaded CMJ mean power and mid-propulsion impulse (30–60%) emerge as proxies of neuromuscular efficiency linked to sport-specific perfor-mance, supporting their use for athlete monitoring and targeted training. Full article

Downhole kick is one of the most severe safety hazards in deep and ultra-deep well drilling operations. Traditional monitoring methods, which rely on surface flow rate and fluid level changes, are limited by their delayed response and insufficient sensitivity, making them inadequate for early warning. This study proposes a real-time monitoring technique for gas content in drilling fluid based on the attenuation principle of Ba-133 γ-rays. By integrating laboratory static/dynamic experiments and Geant4-11.2 Monte Carlo simulations, the influence mechanism of gas–liquid two-phase media on γ-ray transmission characteristics is systematically elucidated. Firstly, through a comparative analysis of radioactive source parameters such as Am-241 and Cs-137, Ba-133 (main peak at 356 keV, half-life of 10.6 years) is identified as the optimal downhole nuclear measurement source based on a comparative analysis of penetration capability, detection efficiency, and regulatory compliance. Compared to alternative sources, Ba-133 provides an optimal energy range for detecting drilling fluid density variations, while also meeting exemption activity limits (1 × 10⁶ Bq) for field deployment. Subsequently, an experimental setup with drilling fluids of varying densities (1.2–1.8 g/cm³) is constructed to quantify the inverse square attenuation relationship between source-to-detector distance and counting rate, and to acquire counting data over the full gas content range (0–100%). The Monte Carlo simulation results exhibit a mean relative error of 5.01% compared to the experimental data, validating the physical correctness of the model. On this basis, a nonlinear inversion model coupling a first-order density term with a cubic gas content term is proposed, achieving a mean absolute percentage error of 2.3% across the full range and R² = 0.999. Geant4-based simulation validation demonstrates that this technique can achieve a measurement accuracy of ±2.5% for gas content within the range of 0–100% (at a 95% confidence interval). The anticipated field accuracy of ±5% is estimated by accounting for additional uncertainties due to temperature effects, vibration, and mud composition variations under downhole conditions, significantly outperforming current surface monitoring methods. This enables the high-frequency, high-precision early detection of kick events during the shut-in period. The present study provides both theoretical and technical support for the engineering application of nuclear measurement techniques in well control safety. Full article

This study proposes an enhanced derivative control strategy, named $PI$-$D^{\AE }$, designed to overcome key limitations of the derivative ($D$) term, such as noise amplification, derivative kick $(D$-$k)$, and tuning difficulties. These issues often arise in high-frequency or rapidly changing systems, in which traditional PID controllers struggle. The proposed solution introduces a novel adaptive exponent algorithm (Æ) that dynamically modulates the $D$ term based on the evolving relationship between system output and setpoint. This yields the $PI$-$D^{\AE }$ controller, which adapts in real time to changing conditions. The results show significant performance improvements. Simulation results on two systems demonstrate that $PI$-$D^{\AE }$ achieves a 90% faster response time, a 35% reduction in peak time, and a 100% improvement in settling time compared with conventional PID controllers, all while maintaining a near-zero steady-state error even under external disturbances. Unlike more-complex alternatives such as fuzzy logic, neural networks, or sliding mode control, $PI$-$D^{\AE }$ retains the simplicity and robustness of PID, avoiding high computational costs or intricate setups. This adaptive exponent strategy offers a practical and scalable enhancement to classical PID, improving performance and robustness without added complexity, and thus provides a promising control solution for real-world applications in which simplicity, adaptability, and reliability are essential. Full article

Objectives: Taekwondo performance is influenced by a complex and dynamic interplay of physical, nutritional, and psychological factors, all of which contribute to competitive success. However, the gender-specific relationships among these factors in young high-performance athletes remain understudied. This study aimed to fill in this knowledge gap. Methods: A cross-sectional study was conducted with 35 elite taekwondo athletes (male: n = 20, female: n = 15, age: 13 ± 1 years). Participants underwent anthropometric assessments, dietary evaluations, and psychological skill assessments during an 8-week training camp before the World Taekwondo Championships. Physical performance was assessed using the Frequency Speed of Kick Test (FSKT_mult) and the Taekwondo-Specific Agility Test (TSAT). Statistical analyses included independent t-tests, correlation analyses, and regression models. Results: Males exhibited significantly higher fat-free mass (FFM: 42.8 ± 2.9 kg vs. 36.3 ± 1.6 kg, p < 0.001), skeletal muscle mass (SMM: 31.1 ± 2.2 kg vs. 28.2 ± 1.6 kg, p < 0.001), and energy intake (32.4 ± 4.6 kcal/kg vs. 29.3 ± 3.1 kcal/kg, p = 0.032) than females. Males also had greater dietary intakes of vitamin A, vitamin C, magnesium, and iron (all p < 0.05). There were no gender differences in any psychological attributes associated with emotional intelligence, sport success perception, and mental toughness. Although the total kick count in the FSKT_mult was similar for male and female taekwondo athletes (100.2 ± 4.6 vs. 97.5 ± 5.9 kicks, p = 0.139), males outperformed females in round 4 (19.4 ± 1.1 vs. 18.6 ± 1.4 kicks, p = 0.048) and round 5 (18.2 ± 1.0 vs. 17.2 ± 1.0 kicks, p = 0.007) of this test, suggesting higher physical performance maintenance during the test. Regression models indicated that body mass (β = 0.901, p < 0.001) and calcium intake (β = 0.284, p = 0.011) predicted performance in males, while body mass (β = 1.372, p < 0.001), protein intake (β = 0.171, p = 0.012), and emotional regulation (β = 0.174, p = 0.012) were key predictors in females. Conclusions: These findings highlight the importance of an integrated approach to training, nutrition, and psychological preparation in optimizing taekwondo performance. While males and females demonstrated similar psychological resilience and total kick output in a taekwondo-specific test, males exhibited superior endurance in later test rounds of this test. Performance optimization in young elite taekwondo athletes may require the implementation of gender-specific training and nutrition strategies, emphasizing body weight control and calcium intake for males and protein intake for females. Full article

The present study investigated the effect of inter-limb asymmetry and bilateral indexes (BLIs) in power performance, assessed by squat jump (SJ) and countermovement jump (CMJ), on sport-specific anaerobic performance. Forty-eight taekwondo athletes (24 males and 24 females; mean ± SD, age: 19.8 ± 2.1 years) performed randomly, in separate sessions, SJ and CMJ tests using the right, left, and both legs to determine the asymmetry and BLI, the 10 s Frequency Speed of Kick Test (FSKT_10s), and its multiple version (FSKT_mult). FSKT_10s was positively correlated with CMJ asymmetry (ρ = 0.299, p = 0.039, low) and SJ BLI (r = 0.596, p < 0.001, large), and negatively correlated with CMJ BLI (r = −0.472, p = 0.001, moderate). Similarly, FSKT_mult was positively correlated with SJ BLI (ρ = 0.632, p < 0.001, large), and negatively correlated with CMJ BLI (ρ = −0.532, p < 0.001, large). CMJ and SJ BLI explained 45.9% of the variance of the FSKT_10s performance, whilst they explained 55.7% of the variance of FSKT_mult performance. These results highlight the importance of managing both interlimb asymmetry and bilateral deficit indexes to achieve better performance by improving the strength of the non-dominant leg and using exercises that are performed bilaterally despite unilateral movements being predominant in taekwondo, which can potentially enhance the effectiveness in sport-specific actions Full article