Search Results (175)

This study investigates the under-explored contribution of internal radial stress to macroscopic gravitational potentials. We utilize a novel, precision-damped torsion balance apparatus designed to isolate and measure gravitational perturbations induced by radial stress within rapidly rotating macroscopic masses, rigorously controlling for acoustic, thermal, and electromagnetic variables. Our findings document an anisotropic mechanical influence along the plane of rotation that exceeds standard weak-field gravitational predictions. The measured apparatus potential exhibits a kinematic scaling (∝ω⁴) consistent with a linear torsion spring responding to an underlying quadratic (ω²) driving force. While active Herzan leveling, counter-rotating geometry, and precision balancing successfully eliminated bulk frame-drag and mechanical vibration, this atmospheric baseline study concedes that the persistent ω² force may still be masked by complex, non-linear fluid dynamic asymmetries. Consequently, this paper establishes a ‘Stage 1’ methodological baseline, mapping the absolute limits of atmospheric testing and defining the engineering prerequisites for future high-vacuum gravitational extractions. Isolating this residual force in a future high-vacuum environment is imperative. Should such testing confirm the signal is gravitationally sourced, this anisotropy suggests a potential coupling between the internal stress-energy tensor and the local spacetime metric that is not fully accounted for in standard linear approximations. If this phenomenological stress-metric coupling can be isolated and shown to scale macroscopically, it could theoretically provide a non-linear mechanism for observed rotational gravitational symmetry breaking. The speculative astrophysical implications of such a coupling are also discussed. Full article

Background: Curve sprinting in the 200 m dash entails distinct biomechanical requirements under strenuous anaerobic conditions that differ from sprinting on the straightway. This study aimed to examine possible relationships between anaerobic biomarkers (specifically, peak post-test blood lactate concentration; BLa) and step kinematic asymmetry, stance-phase biomechanics, and spring–mass model (SMM) variables at the curve-to-straight transition during a 200 m sprint. Methods: Sixteen adult male club- and national-level sprinters performed a maximal 200 m sprint test in this exploratory cross-sectional study. Kinematical data were recorded for the first step immediately after the geometric end of the curve, and peak BLa was measured at 3, 5, and 7 min post-test. Based on data normality, differences in inter-limb step parameters were examined using a paired t-test or Wilcoxon signed-rank test. Pearson’s and Kendall’s correlation coefficients evaluated the relationships between BLa and the biomechanical variables (significance level: a = 0.05). Results: Peak BLa was 16.16 ± 2.61 mmol/L and demonstrated no significant correlation (p > 0.05) with sprint time (24.89 ± 1.24 s). Only stride and step frequency during the outer-to-inner leg step was correlated (p < 0.05) with BLa. Furthermore, the step initiated by the outer leg had a larger length (p < 0.05) compared to the step length generated from the inner leg. Conclusions: These findings stem from the different roles between legs while handling the centripetal force requirements during curve sprinting. The outer leg generated a longer step to facilitate curve-to-straight transition, whereas the inner leg functioned primarily to stabilize and steer the body. Full article

The Timed Up and Go (TUG) test is widely used to assess functional mobility in Parkinson’s disease (PD), although total test duration may overlook phase-specific biomechanical alterations. This cross-sectional study investigated whether phase-specific analysis of the instrumented TUG (iTUG) could identify candidate biomechanical markers characterizing differences among early-stage PD subgroups and healthy controls. Seventy-nine participants (38 PD, 41 controls) performed four iTUG trials in the OFF-medication state. Movement data were collected using synchronized inertial measurement units and optoelectronic motion capture systems. The iTUG was segmented into six phases, and temporal, spatiotemporal, variability, and multisegmental kinematic parameters were analyzed. Participants with PD at modified Hoehn and Yahr (mH&Y) stage 2 performed the iTUG more slowly than controls (p < 0.001), mainly due to impairments during walking (p = 0.012) and turning. Turning was the only phase that distinguished controls from individuals with PD at mH&Y stages 1–1.5 (p = 0.015), who also showed increased elbow asymmetry (p = 0.009). Participants with PD at mH&Y stage 2 exhibited broader differences, including increased double-support time, shorter stride length, lower walking speed, reduced frontal-plane control, and reduced trunk, elbow, hip, and ankle motion, whereas gait variability did not differ significantly between groups. Sagittal trunk ROM on the less affected side was the only variable that significantly differed between the two PD subgroups. These findings suggest that phase-specific iTUG analysis may reveal candidate biomechanical markers associated with mH&Y stage and functional mobility impairment and support sensor-based assessment for objective characterization of functional mobility in PD. Full article

Imaging underpins the diagnosis and structural staging of osteonecrosis of the femoral head (ONFH) but does not directly quantify functional impairment during weight-bearing walking. We developed a subject-level ONFH classification framework using multilevel gait features acquired with wearable inertial measurement units (IMUs). Thirty healthy controls and 21 participants with imaging-confirmed ONFH completed self-paced walking trials recorded at 100 Hz. Gait cycles were segmented from bilateral foot-contact events, normalized to 120 points, and represented as 17-channel kinematic waveforms, 22-dimensional cycle-level scalar features, and 7-channel dynamic absolute asymmetry waveforms. These inputs were encoded by CNN–CBAM–BiLSTM, multilayer perceptron, and one-dimensional convolutional branches, respectively, and fused at the feature level. Evaluation used 51-fold leave-one-subject-out cross-validation, training-fold-only preprocessing, within-subject probability averaging, and five predefined random seeds. The five-seed ensemble achieved an accuracy of 0.9412, sensitivity of 0.8571, specificity of 1.0000, F1-score of 0.9231, and area under the receiver operating characteristic curve of 0.9556. Ablation analysis identified the scalar-feature vector as the principal source of incremental performance; the dynamic asymmetry branch contributed complementary information only in the complete model. These findings provide preliminary evidence for further evaluation of wearable gait-based ONFH classification in independent cohorts and objective functional assessment. Full article

Wearable inertial measurement units (IMUs) offer an accessible alternative to optical motion capture (MoCap) gait analysis, but their performance in Progressive Supranuclear Palsy (PSP) requires validation. We assessed the concurrent validity of IMU-derived versus MoCap-derived gait metrics and static postural sway in 30 patients with PSP using Bland–Altman analysis, Intraclass Correlation Coefficients (ICC), and Spearman rank correlations. Finally, we assessed equivalence using the Two one-sided tests (TOST) procedure. Multivariable linear regression was used to determine whether clinical severity, as measured by the PSP Rating Scale (PSPRS), independently predicted absolute IMU measurement error while controlling for patient age and gait velocity. IMUs demonstrated excellent between-system agreement for parameters such as cadence (100.76 ± 11.42 vs. 100.52 ± 11.59) and cycle time (1.21 ± 0.15 vs. 1.22 ± 0.15; ICC > 0.98), despite a systematic underestimation of gait velocity (p < 0.05). Agreement significantly diminished for micro-phases (e.g., single/double support times) and spatial asymmetry. Interestingly, the TOST procedure revealed that only sagittal and transverse trunk kinematics were equivalent between systems, with all other measures failing to find equivalency. For static sway, the IMU demonstrated strong rank-order correspondence for tracking relative postural instability (ρ = 0.82, p < 0.05). Multivariable analysis revealed that higher PSPRS scores are independently associated with greater between-system discrepancies in support phases and pelvic and trunk kinematics (p < 0.05), irrespective of reduced gait speed. These findings highlight the need to develop disease-specific algorithms, rather than relying on normative commercial models, to establish reliable digital biomarkers for monitoring progressive motor decline. Full article

Microprocessor-controlled knee prostheses (MPKs) face limited accessibility in resource-constrained environments due to high implementation costs and excessive power consumption associated with complex actuators. This study examines the technical feasibility of a low-cost electronically controlled pneumatic knee (ECPK) that combines structural mechanics with minimal electronic control. A functional decoupling strategy was implemented: stance-phase stability is provided by passive kinematic locking of a four-bar linkage over the near-extended stance range, while a lightweight feedforward controller driven by a single joint-axis Hall sensor segments the gait cycle continuously, updates its speed estimate once per step, and adjusts the valve only for swing-phase damping. From the stance duration of the preceding steps, this controller presets the pneumatic valve orifice to compensate for mechanical response delays, so that link rotation speed is regulated semi-actively without powered actuation. System integration and control viability were evaluated in a single-case feasibility study (N = 1), in which the ECPK was compared within subject with a commercial mechanical prosthesis after a 4-week adaptation period. Despite a 400 g distal mass penalty, the semi-active control algorithm was associated with a smaller increase in step-length asymmetry at the highest speed tested. Furthermore, net oxygen cost was lower with the ECPK during high-speed walking. Because the conditions were compared at unmatched self-selected speeds and the ECPK condition reached a respiratory exchange ratio (RER) of 1.13, this observation is hypothesis-generating. Coupling passive four-bar stance stability with minimal electronic swing regulation is therefore a viable engineering basis for accessible prostheses, and the present study establishes its technical feasibility rather than its clinical effectiveness. Full article

To address the persistent challenges in optimizing the transmission performance of crank-rocker mechanisms—namely, the inaccuracies of local static evaluation models, the non-linear coupling constraints among multiple objectives, and the difficulties of navigating discontinuous and restricted solution spaces—this paper proposes a multi-objective collaborative design methodology grounded in kinematic and dynamic analysis. First, full-cycle mathematical models for transmission efficiency and transmission inertia are established, explicitly quantifying the impact of quick-return characteristics on inertial forces. Second, targeting the maximization of transmission efficiency alongside the minimization of transmission inertia and kinematic asymmetry, an adaptive multi-objective genetic algorithm is developed. Using a bearing life testing machine as the engineering baseline, virtual prototype simulations and multi-load physical bench tests are conducted to validate the proposed approach. Post-optimization results indicate that the full-cycle average transmission efficiency of the mechanism surges significantly from 73.6% to 91.96%, while the transmission inertial force is drastically curtailed by 72.28%. Concurrently, the advance-to-return time ratio, an indicator of kinematic asymmetry, is reduced to 1.0229. Additionally, the torque fluctuations at the output shaft are notably mitigated, and the overall operational noise level is reduced by 4 to 6 dB. This research provides a highly effective theoretical and engineering paradigm for achieving the globally collaborative optimum of planar mechanisms under complex physical constraints. Full article

Background/Objectives: Previous studies have shown that excess body weight influences plantar pressure. However, the specific impact of Body Mass Index (BMI) on dynamic pressure distribution during different phases of walking, as well as its effect on load symmetry between the feet, requires further investigation. This study aimed to evaluate the effects of varying BMI categories on dynamic plantar pressure, spatiotemporal gait parameters, and load symmetry. Methods: A retrospective analysis of pre-existing records from 300 adults (2017–2025) classified as normal weight, overweight, and obese was conducted. Dynamic plantar pressure, contact time, and gait speed across four stance phases were assessed using baropodometric platforms. Bilateral differences were evaluated via the symmetry index (SI). Results: Overweight and obese individuals exhibited higher plantar pressures and prolonged contact times, particularly during the forefoot contact phase (FFCP) ($p$ < 0.001). Gait speed decreased inversely with BMI across all phases. Despite these kinematic adaptations, BMI-related load asymmetry occurred only during the initial contact phase (ICP) ($p$ < 0.001), restoring stability in subsequent phases. Conclusions: Excess body mass is associated with targeted mechanical overload of the forefoot rather than uniform stress across the foot. To manage inertia and maintain symmetry, individuals with high BMI may adopt spatiotemporal strategies that reduce speed and extend double support, potentially prioritizing stability over propulsive efficiency. These findings suggest that orthotic interventions for individuals with high BMI may benefit from prioritizing forefoot offloading, although prospective studies are needed. Full article

The single-leg countermovement jump (SL CMJ) is widely used to assess limb-specific neuromuscular function, with interpretation commonly centred on inter-limb asymmetry. However, contextualising unilateral performance relative to bilateral capacity remains less clearly defined. This retrospective cross-sectional study aimed to develop exploratory descriptive benchmarks for SL CMJ kinetic, kinematic, and temporal variables expressed as a percentage of bilateral CMJ performance in a heterogeneous athletic cohort. A total of 348 athletes completed bilateral and unilateral CMJs using dual force plate sampling at 1000 Hz. The best trials were selected using the modified reactive strength index (mRSI), and averaged unilateral variables were expressed relative to bilateral potential. Unilateral-to-bilateral transfer was non-uniform across metric domains. Median relative jump height and the mRSI were 44.8% and 39.4%, respectively, whereas median average relative braking and propulsive force values were 76.0% and 75.4%, respectively. Gross impulse measures were retained to a greater extent than power- and rate-dependent variables, while temporal metrics showed prolonged unilateral phase durations. Exploratory sex-based analyses indicated trivial-to-small differences in selected variables; however, these findings should be interpreted cautiously because of unequal group sizes and the descriptive nature of the dataset. These results provide broad exploratory percentile benchmarks that may help practitioners contextualise SL CMJ performance relative to bilateral execution. However, the values should not be interpreted as universal clinical thresholds, injury-risk markers, or sport-specific normative standards without consideration of sex, sport discipline, competitive level, injury history, and longitudinal athlete context. Full article

Background. Visual biofeedback (BF) and rhythmic metronome stimulation (RMS) are used for correction of stroke gait. To determine the feasibility of improving gait reciprocity using BF technology combined with RMS. Methods. Patients with subacute stroke in the Main group (n20 patients) underwent a course of BF training targeting the reciprocity parameter by RMS (9 sessions) plus standard rehabilitation. The Control group (n = 20) received standard rehabilitation only. Biomechanical gait analysis covering spatiotemporal, kinematic, and EMG parameters, as well as clinical scale assessments, was performed before and after the rehabilitation. Results. At baseline and at the end of rehabilitation, the Main group showed a functionally more severe condition on the DGI and TUG scales (p < 0.05). Both groups displayed a typical picture of hemiparetic gait with asymmetry of biomechanical, kinematic, and EMG parameters. By the end of rehabilitation, the Main group showed a positive trend in the reciprocity parameter that did not reach statistical significance. In the Control group, no changes in the parameter were observed. Conclusions. A short-term (9-session) course of BF training did not produce a statistically significant improvement in the reciprocity parameter and requires confirmation in a powered randomized trial. Full article

Background/Objectives: To characterize clinical values obtained from a digital jaw tracking system during the functional assessment of mandibular movements in patients undergoing prosthetic rehabilitation. Methods: Ten patients undergoing prosthetic rehabilitation were included. Mandibular movements were recorded using the Zebris JMA Jaw Tracking System and measurements including maximum mouth opening, lateral excursions, protrusion, and condylar path length. Descriptive analyses were performed. Quantitative parameters were summarized as mean ± standard deviation and range and compared with normative values reported in the literature. Results: Ten participants completed mandibular kinematics registration (8 female, 2 male). Considerable interindividual variability was observed across all parameters. Mean maximum opening was 38.19 ± 10.99 mm (range 22.5–59.6 mm), mean protrusion 5.79 ± 4.47 mm (range 3.0–17.8 mm), mean right lateral excursion 6.56 ± 3.06 mm, and mean left lateral excursion 4.90 ± 2.11 mm. Lateral asymmetry was identified in 5 out of 10 patients. Bilateral condylar path length asymmetry had a mean of 3.59 ± 1.89 mm. Conclusions: Values obtained through the jaw tracking system demonstrated considerable interindividual variability in this prosthetic rehabilitation population. These preliminary findings support the need for further research to characterize normative kinematic values in this specific population and to evaluate the clinical impact of integrating jaw tracking data into prosthetic planning workflows. Full article

Joint statistical learning enables interacting individuals to form shared representations, but prior research has primarily focused on homogeneous dyads with equivalent expertise. Real-world interactions often involve knowledge asymmetries, yet it remains unclear how novices implicitly acquire statistical regularities from expert partners via sensorimotor signals. This study investigated whether novices can implicitly extract sequence regularities to enhance joint statistical learning and compared two candidate mechanisms, action feedback versus action visibility. Using a modified serial reaction time task across three experiments, we found that novices paired with trained experts exhibited significantly steeper declines in reaction time compared to those paired with pseudo-experts. Moreover, expert-paired novices demonstrated a pronounced quadratic trajectory, indicating sequence-specific learning. Experiment 2 revealed that the absence of immediate action feedback eliminated this sequence-specific interference effect in novices, highlighting the critical role of shared perceptual outcomes in the implicit transmission of task regularities. Conversely, Experiment 3 showed that the absence of visual access to the expert’s physical movements attenuated neither the novices’ general sequence acquisition nor their sequence-specific interference effect. These findings extend the Theory of Event Coding framework to asymmetric social contexts by demonstrating that effect-based coding, rather than direct kinematic observation, drives implicit behavioral facilitation in joint action. Full article

Honeybee (Apis mellifera) flight and vertical locomotion were investigated using high-speed imaging and schlieren flow visualization. Free-flight recordings were analyzed to extract wingbeat frequency, projected stroke amplitude, wingtip trajectories, and membrane deformation. The wingtip trajectory exhibited a pronounced asymmetry between upstroke and downstroke, suggesting a dominant role of the downstroke in thrust production. Significant membrane deformation was observed near stroke reversal, indicating strong wing flexibility and dynamic modulation of wing shape during flapping. A novel support-based framework was introduced to characterize vertical locomotion through the support polygon formed by leg contact points and the displacement of its centroid relative to the body. This movement function quantified changes in support distribution and revealed adaptive leg-contact strategies during wall climbing. Schlieren visualization provided qualitative evidence of wingtip vortex formation, although finer wake structures remained difficult to resolve. These findings provide new experimental observations of honeybee flight kinematics and introduce a quantitative framework for analyzing vertical locomotion using support redistribution metrics. Full article

Background/Objectives: Previous studies have measured a limited number of biomechanical parameters during medical rehabilitation of an anterior cruciate ligament (ACL) rupture. This study aimed to quantitatively assess changes in gait biomechanics, knee function, and lower-extremity muscle activity during after ACL reconstruction. Methods: The study included 32 patients after arthroscopic ACL reconstruction. The patients were divided into three groups based on postoperative time points: 0.5 year (12 men), 1 year (7), and over 1 year (9). Gait analysis at both self-selected and fast speeds was performed using an inertial system. Statistical analysis was performed using rank models and full-factorial orthogonal designs. Results: After 0.5 year, the timing of the gait cycle at self-selected speed was within the control group’s range and showed no significant asymmetry. With increasing speed, a decrease in knee joint range of motion was observed in the 0.5 year and 1-year groups, without achieving a full physiological increase in range of motion at long-term follow-up. Multivariate analysis revealed the greatest biomechanical imbalance during fast walking at one year and a phase-dependent effect of time after surgery, speed, and limb status on kinematics and EMG, particularly in the quadriceps. Conclusions: Basic temporal gait parameters during self-selected walking were within the control range by 0.5 year, but load-dependent knee kinematic and EMG abnormalities persisted. The knee joint’s response to increased loads remained impaired for at least one year. The persistence of phase-specific compensatory changes in kinematics and muscle activity at later stages can be assessed using exercise testing. Full article

Dense underwater aquaculture poses significant challenges for intelligent image processing because asymmetric occlusion, turbidity, aeration-like bubbles, and motion blur frequently degrade fish contours and quasi-periodic scale textures. These disturbances often cause conventional detectors to miss detections, merge bounding boxes, experience feature collapse, and exhibit unstable counting. To address this problem, we propose DenseFish-v13, a symmetry-aware NMS-free YOLOv13-Mamba framework for dense underwater fish detection and bio-kinematic behavior recognition. The framework integrates a Bio-Harmonic Frequency Gate to preserve biological texture patterns while suppressing bubble-like frequency noise, a Bi-directional Multi-scale Wavelet Mamba backbone for global occlusion-aware structure recovery, and an asymmetry-aware density repulsion strategy to separate highly overlapping fish instances during bipartite matching. In addition, a lightweight Bio-Kinematic Behavior Head converts continuous detections into interpretable trajectory descriptors for behavior-state recognition. Experiments on the Dense-Aqua benchmark, constructed from public aquaculture datasets, show that DenseFish-v13 achieves 64.8% mAP@50:95 and a Counting MAE of 3.7 on the overall test set, while reaching 64.2% mAP@50:95 and a Counting MAE of 4.1 on the extreme-density split. Under a strong synthetic bubble perturbation, the model shows only a 1.3 percentage-point drop in mAP and maintains 125 FPS on Jetson Orin NX. These results demonstrate its effectiveness in robust, real-time underwater aquaculture monitoring. Full article