Background and study aim The uppercut is a complex close-range punching technique that relies on efficient proximal-to-distal sequencing and coordinated kinetic chain function. In amateur boxers, insufficient joint angular velocity may compromise strike effectiveness and mechanical efficiency. The aim of this study was to examine the kinematic adaptations following an 8-week biomechanics-based training intervention during execution of the right-hand uppercut. Material and methods Twenty-four male amateur boxers (21.25 +/- 3.12 years) with 3-4 years of training experience were randomly allocated to an experimental group (EG, n = 12) and a control group (CG, n = 12). The EG completed a structured 8-week (24-session) training program targeting joint-specific angular velocity and intersegmental coordination, while the CG maintained regular training. Three-dimensional motion capture was used to quantify maximal angular velocity of the shoulder, elbow, pelvis, hip, knee, and ankle joints before and after the intervention. Intervention effects were analyzed using a two-way mixed-design ANOVA (Group & times; Time), followed by paired and independent Student's t-tests with Holm-Bonferroni correction; effect sizes were calculated using Cohen's d (p < 0.05). Results Post-intervention analysis revealed significant increases in maximal angular velocity across upper and lower body segments in the EG (p < 0.05-0.01), with moderate-to-large effect sizes (d = 0.62-1.42). These kinematic improvements were accompanied by enhanced punch force and accuracy, whereas no significant changes were observed in the CG. Conclusions An 8-week biomechanics-based training program effectively enhances joint angular velocity and kinetic chain efficiency during uppercut execution in amateur boxers. Incorporating coordination-oriented, joint-specific velocity training into combat sport conditioning programs may substantially improve strike performance.
Purpose To compare ankle proprioception and biomechanical features between individuals with chronic ankle instability (CAI) and healthy controls, and to investigate the interplay between proprioceptive deficits and biomechanical alterations in CAI.Methods Thirty-six male participants (18 CAI, 18 healthy controls) were recruited. Proprioception was evaluated using a joint position reproduction test, quantifying absolute errors. For biomechanical assessment, participants performed six single-leg hopping tests. An infrared motion-capture system (Vicon T40, 200 Hz) and a force platform (Kistler, 1,000 Hz) simultaneously captured ankle kinematics/kinetics. Ankle muscle activation was recorded via surface electromyography (Noraxon, 2,000 Hz).Results Participants with CAI demonstrated significantly greater joint position sense errors in plantarflexion (P = 0.002), dorsiflexion (P = 0.001), inversion (P = 0.011), and eversion (P = 0.022) compared with controls. Compared with healthy controls, individuals with CAI exhibited greater peak ankle inversion angles (P = 0.039), reduced peak ankle dorsiflexion angles (P = 0.029), and lower activation of the tibialis anterior (P = 0.019) and peroneus longus (P = 0.033) during single-leg landing. Correlation analyses indicated significant associations between inversion position sense errors and both peak ankle dorsiflexion angle (r = -0.584, P = 0.011) and peak ankle inversion angle (r = -0.622, P = 0.006) in the CAI group.Conclusions Individuals with CAI exhibit impaired ankle proprioception and altered biomechanical characteristics compared with healthy controls. Decreased proprioception in the ankle was correlated with biomechanical defects. These findings suggest that proprioceptive impairments may contribute to persistent biomechanical abnormalities in CAI. Comprehensive interventions targeting proprioceptive enhancement may improve ankle biomechanics in this population.
Purpose This study aimed to develop and evaluate a comprehensive physiological testing protocol for cyclists that integrates thermal imaging and near-infrared spectroscopy during standardized incremental exercise. Methods Eight trained male cyclists performed a standardized incremental cycling test under controlled conditions. After a 10-minute warm-up (1.0 W·kg⁻¹), workload increased by 0.5 W·kg⁻¹ every 3 minutes until voluntary exhaustion, followed by a 10-minute cool-down. Muscle oxygen saturation (SmO₂) of the rectus femoris was continuously recorded bilaterally using wearable near-infrared spectroscopy (Moxy Monitor), and thermal imaging of selected quadriceps muscles was conducted with a FLIR T1020 camera. Heart rate was monitored continuously. Measurements were performed after a 25-minute acclimatization period under standardized environmental conditions. Results No statistically significant differences in normalized skin temperature (Tsk) or normalized SmO₂ were observed across exercise phases after Bonferroni correction (p = 0.012). A significant positive correlation was found between exercise-induced changes in normalized Tsk and SmO₂ (ΔEX: Spearman’s r = 0.89, p << 0.017). No significant correlation was observed during the warm-up (ΔWU: r = 0.02) or recovery (ΔCD: r = 0.14) phases. Due to the small sample size (n = 8), correlations were interpreted descriptively as indicative of a physiological connection rather than causal relationships. Conclusions Increasing exercise intensity was associated with concurrent alterations in muscle oxygenation and Tsk, reflecting integrated hemodynamic and metabolic responses. The combined IRT–NIRS protocol demonstrated methodological feasibility and may provide a valid framework for multidimensional assessment of muscular responses, warranting further validation in larger cohorts.
Purpose Paravalvular leak (PVL) is a pathological condition that may arise following prosthetic mitral valve implantation and is characterized by regurgitant blood flow through a gap between the prosthetic valve ring and the native cardiac tissue. High-velocity flow jets generated within the leak region may produce elevated shear stresses capable of inducing mechanical damage to erythrocytes and subsequent hemolysis. The purpose of this study is to investigate the influence of blood viscosity, modulated by hematocrit variability, on flow characteristics and hemolytic potential in mitral PVL.Methods A computational fluid dynamics model was developed to simulate pulsatile blood flow through mitral PVL channel. The model included a time-varying left ventricular geometry, a kinematically constrained left atrium, and a simplified representation of a mechanical mitral valve with a localized paravalvular defect. Multiple physiological hematocrit levels were considered to account for viscosity variations. Non-Newtonian rheological behavior of blood was incorporated to capture shear-dependent viscosity effects.Results The simulations showed a strong dependence of shear stress on hematocrit. Increasing hematocrit led to higher effective viscosity, resulting in elevated shear stress levels within the PVL jet. A near-linear relationship between hematocrit and maximum shear stress was observed, with stress values exceeding the hemolysis threshold at higher hematocrit levels. Additionally, higher hematocrit values resulted in earlier onset of critical shear stress conditions.Conclusion The results demonstrate that hematocrit significantly influences hemodynamic conditions and hemolysis risk in mitral PVL.
Purpose To investigate the passive biomechanical effects of the thorax and passive lumbar paraspinal muscles on the stability of the kyphotic spine. Methods Patient-specific clinical CT data and a U-Net convolutional neural network were utilized to segment the lumbar paraspinal muscles. Two finite element (FE) models were developed: a composite model including the intact thorax and passive muscles (S1), and a spine-only model (S2). Axial rotation, lateral bending, and flexion-extension conditions were simulated to compare the overall spinal displacement and segmental range of motion (ROM) between the two models. Results The restriction of spinal displacement by the thorax and passive muscles demonstrated significant direction specificity: the strongest constraint occurred in axial rotation (19.6%), followed by lateral bending (8.1%) and flexion-extension (1.3%). Segmentally, changes in ROM exhibited regional heterogeneity. Under the axial rotation condition, upper thoracic (T1-T6) ROM decreased significantly (>20%), while ROM from the thoracolumbar junction downwards (T10-S) increased (1.27%–8.33%). Under lateral bending and flexion-extension conditions, ROM showed a decreasing trend across all segments (decreasing by 3.77%–14.29% and 1.39%–7.00%, respectively). Conclusions The thorax and passive paraspinal muscles significantly restrict axial rotation; however, maintaining sagittal balance relies primarily on active musculature. This anti-rotation mechanism induces a "local anchoring and distal compensation" effect, thereby increasing lower lumbar mobility. In clinical practice, conservative treatment should adopt a dual strategy of anti-rotation bracing combined with active anti-flexion muscle strengthening, while maintaining high vigilance for the risk of secondary degeneration in the lower lumbar spine.
