Frontiers in Physiology最新文献

Background: This study aimed to kinematically compare the Yop Chagi execution between novice and experienced university Taekwondo practitioners, focusing on movement efficiency.

Methods: Forty university students were allocated into two groups: Novice (n = 20; ≤6 months experience) and Experienced (n = 20; ≥3 years of competitive experience). Participants performed maximal effort side kicks targeting a pad at trochanter height. Movement was captured using two high-speed cameras (120 Hz). Kinematic variables included hip and knee joint angles at peak flexion/extension, peak angular velocities, linear velocity of the foot, and total kick execution time. Between-group differences were analysed using independent t-tests or Mann-Whitney U tests, with effect sizes (Cohen's d) reported.

Results: The experienced group demonstrated significantly larger hip abduction and knee flexion angles during the chamber phase (p < 0.01, d > 0.8), and greater knee extension at the point of impact (p < 0.01, d = 1.2) compared to novices. The experienced group also exhibited superior performance in peak hip and knee angular velocities (p < 0.01, d > 1.5), resulting in a 28% higher peak linear velocity of the foot (p < 0.001, d = 2.1). Furthermore, the total execution time was significantly shorter for the experienced group (p < 0.01, d = 1.4).

Conclusion: Experienced practitioners execute the Yop Chagi with a more efficient kinematic pattern, characterized by a larger range of motion, faster segmental velocities, and reduced execution time. These findings suggest that long-term training optimizes the proximal-to-distal kinematic sequence, enhancing kick performance.

Background: Transient left bundle branch block (LBBB) is associated with various cardiac and systemic conditions, including exercise-induced ischemia. However, normalization of baseline LBBB following exertion is a rare and poorly understood phenomenon.

Case summary: We report the case of an 83-year-old male with longstanding coronary artery disease and baseline LBBB who underwent a routine stress echocardiogram. During the recovery phase, ECG monitoring revealed normalization of LBBB with first-degree AV block. Concurrent stress echocardiography showed improved segmental and global ventricular function.

Conclusion: This case highlights a rare instance of post-exercise resolution of LBBB and suggests a possible link between exercise-induced autonomic modulation and transient improvement in conduction. Further research is warranted to explore the prognostic significance of this finding in patients with structural heart disease.

Purpose: The Tai Chi heel-kick is a slow, high-amplitude single-leg movement that places substantial demands on lower-limb coordination, dynamic balance, and controlled force transfer, and is increasingly incorporated into performance training and rehabilitation programs. This study investigated muscle synergies and activation timing differences between the left and right legs of elite Tai Chi athletes during the heel-kick and explored leg-specific neuromuscular control features by combining synergy analysis with spinal segment statistical parametric mapping (SPM).

Methods: Twelve national-level elite Tai Chi athletes were recruited. Surface electromyography (sEMG) signals were collected from key lower-limb muscles, and muscle synergies were extracted using non-negative matrix factorization (NMF). The center of activation (CoA) was calculated using circular statistics, and SPM was applied to examine activation differences across the L2-S2 spinal segments.

Results: Four to five robust muscle synergies were identified for both legs, showing high spatial similarity; however, activation timing differed, with the left-leg synergies peaking earlier and the right-leg synergies delayed. CoA analysis indicated an overall phase advance in the left leg and a phase delay in the right leg. Spinal SPM further revealed inter-limb differences during the mid-to-late phase of the movement (40%-80%), with right-leg activation concentrated in L4-S1 segments, whereas the left leg exhibited a broader distribution.

Conclusion: During the Tai Chi heel-kick, the left and right legs share similar synergy composition but differ in temporal activation patterns and spinal segmental drive, suggesting leg-specific modulation within an overall conserved modular structure. Characterizing these timing asymmetries in highly trained athletes provides a neuromuscular reference for designing Tai Chi-based training drills targeting single-leg control and side-to-side balance, and offers a potential framework for tailoring lower-limb rehabilitation exercises that require coordinated support and kicking functions.

Background: Qigong combines physical movement, breath control, and mental focus, offering potential benefits for healthy aging. Since physiological decline begins in midlife, this stage is critical for preventive intervention. The purpose of this study was to investigate the differences in acute physiological responses, including autonomic (heart rate variability) and respiratory indicators, during a single session of combined Yijinjing and Liuzijue Qigong in middle-aged adults with varying durations of practice experience (≥4 years vs. ≤6 months).

Methods: Forty adults aged 40 to 59 were included and divided into two groups based on Qigong exercise experience: an experienced group (n = 20) with ≥4 years of practice, and an inexperienced group (n = 20) with <6 months. All participants performed 20 min of fitness Qigong, following prerecorded tapes to standardize pace and posture sequence. Heart rate variability (HRV) and respiration were measured using the Biofeedback 2000x-pert system before, during, and after the session.

Results: Significant Group × Time interactions were found for SDNN (F = 5.58, p = 0.012), RMSSD (F = 20.52, p < 0.001) and LF (F = 5.47, p = 0.025). Between-group comparisons indicated that experienced group had slightly higher SDNN at rest (p = 0.039) and significantly higher RMSSD during the recovery phase (p < 0.001); no other between-group differences emerged at other phases. There was a significant Group × Time interaction for abdominal breathing depth (F = 3.911, p = 0.024) and thoracic breathing frequency (F = 4.956, p = 0.016). Between-group comparisons revealed deeper abdominal breathing during exercise and slower thoracic breathing during recovery in the experienced group.

Conclusion: Middle-aged adults with prolonged practice of Qigong exercise have improved HRV compared to those in the inexperienced group, and these improvements may be achieved through a combination of breathing adjustments with mental focus and relaxation.

Introduction: Cognitive load significantly affects neural activity, making its assessment important in neuroscience and human-computer interaction. EEG provides a noninvasive way to monitor brain responses to mental effort. This study explores EEG-based feature extraction and classification methods to accurately assess cognitive load during mental tasks.

Methods: EEG signals were recorded from all brain lobes over 4 seconds and decomposed into ten intrinsic mode functions using Empirical Fourier Decomposition (EMFD). Entropy-based features were extracted, and feature reduction was applied. Both lobe-wise and overall classifications were performed using optimized ensemble machine learning (OML) and conventional ML classifiers. The approach was evaluated on the Mental Arithmetic Task (MAT) and Spatial Transcriptomic Multi-View (STEW) datasets.

Results: The proposed EMFD-based OML framework achieved high accuracy, reaching 97.8% on the MAT dataset and 96.4% on the STEW dataset. Lobe-wise analysis showed strong performance across all brain regions, with the frontal lobe achieving the highest accuracies of 97.8% (MAT) and 96.08% (STEW).

Discussion: The findings demonstrate that EMFD combined with optimized ensemble learning effectively enhances EEG-based cognitive load detection. The consistent performance across datasets confirms the robustness of the method, while lobe-wise analysis highlights the frontal lobe's key role in cognitive processing. The proposed framework outperforms existing methods and shows strong potential for real-world cognitive monitoring applications.

Introduction: Accurate intraocular pressure (IOP) measurement is vital in glaucoma management, yet the gold standard (Goldmann applanation tonometry) is limited to seated measurements. Rebound tonometers like the Icare IC200 and the newer SK-5500B offer portability for assessing posture-induced IOP changes, but their measurement consistency requires validation. This study aims to evaluate the agreement and repeatability of IOP measurements between the SK-5500B and Icare IC200 tonometers in sitting and supine positions.

Methods: This prospective study recruited 59 subjects (97 eyes). IOP was measured in both sitting and supine positions by two masked operators using the SK-5500B and Icare IC200 tonometers in a randomized sequence. Subjects were categorized into four groups based on their baseline non-contact tonometry (NCT) readings (<10 mmHg, 10-21 mmHg, 22-30 mmHg, and >30 mmHg). Agreement was assessed using Pearson's correlation and Bland-Altman analysis. Correlation was evaluated using Pearson's correlation coefficient (r). Intra- and inter-operator repeatability were determined by within-subject standard deviation (Sw), coefficient of variation (CV), and intraclass correlation coefficient (ICC). The correlation between the device and central corneal thickness (CCT) or axial length (AL) was also analyzed.

Results: The SK-5500B and Icare IC200 showed a strong positive correlation across all conditions (both positions and both operators) (r ≥ 0.90, P < 0.0001). Bland-Altman analysis demonstrated small mean bias, but the limits of agreement were relatively wide between the two tonometers. Both tonometers exhibited excellent intra-operator (ICC ≥ 0.99) and inter-operator (ICC ≥ 0.99) repeatability. IOP measurements from both tonometers did not show a significant correlation with CCT or AL (P > 0.05).

Conclusion: Despite wide limits of agreement in Bland-Altman analysis, the SK-5500B showed good agreement and highly comparable repeatability with the Icare IC200 in both sitting and supine positions, supporting its potential as a practical clinical alternative.

Objectives: Inflammatory cytokines contribute to Implantable Cardioverter-Defibrillator/Cardiac Resynchronization Therapy with a Defibrillator (ICD/CRT-D) high-voltage intervention by promoting arrhythmias through direct cardiac effects and indirect systemic changes. The NLRP3 inflammasome can promotes arrhythmias by linking inflammation, oxidative stress, and structural changes. The aim of this study was to assess the inflammatory response in the peri-shock-period in patients with heart failure (HF) and implanted ICD/CRT-D and the initial analysis of the possible role of cytokines, NLRP3 and soluble Klotho protein in peri-shock period and the possibility of triggering arrhythmias.

Methods: The study population consisted of 50 patients with diagnosed HF and implanted ICD/CRT-D devices. Blood samples were drawn up to max. 6 h after appropriate ICD/CRT-D intervention ("intervention group") or from patients qualified for ICD/CRT-D device replacement (ERI status) and with no intervention min in the previous 3 months ("control group"). Serum concentration of TNF-α, IL-1β, IL-6, IL-10, IL-17, NLRP3 inflammasome, soluble Klotho protein and FGF-23 complete blood count, were determined in all individuals.

Results: IL-6 and IL-10 were higher after ICD/CRT-D appropriate intervention (3.3 pg/mL, 95% CI: 2.7-3.7 vs. 4.6 pg/mL, 95% CI: 2.9-14.5, p = 0.0399 and mean 7.8 pg/mL, 95% CI: 7.1-8.5 vs. 9.0 pg/mL, 95% CI: 8.1-9.9, p = 0.0321, respectively). The group was characterized by a higher number of white blood cells (WBC, 6.8 × 10³/µL, 95% CI: 6.0-7.6 vs. 9.4 × 10³/µL, 95% CI: 8.1-10.7, p = 0.0017), neutrophils (NEUTs, 4.1 × 10³/µL, 95% CI: 3.4-4.8 vs. 6.5 × 10³/µL, 95% CI: 5.3-7.7, p = 0.0007) and lower number of eosinophils (EOSs, 0.11 × 10³/µL, 95% CI: 0.10-0.16 vs. 0.03 × 10³/µL, 95% CI: 0.01-0.08, p = 0.0013). Serum concentration of soluble Klotho protein was significantly higher after device intervention (557.5 pg/mL, 95% CI: 495.5-619.5 vs. 895.2 pg/mL, 95% CI: 744.7-1,046.0, p < 0.0001), with no change in FGF-23 levels.

Conclusion: In the peri-shock period, increased IL-6 and IL-10 serum concentrations and changes in 5-diff blood count (increased neutrophils and decreased eosinophils) are observed, which may be associated with a higher risk of ventricular arrhythmia in HF patients. A significant increase in α-Klotho protein concentration, should be taken into account in the development of future diagnostic methods and indicates an important protective role in the inflammatory process.

Falls are a leading cause of injury-related hospitalization, morbidity, and mortality in older adults, with impaired postural control serving as a key predictor of fall risk. The triceps surae, and particularly the soleus, plays a central role in maintaining upright stance by generating continuous plantarflexion moments that stabilize the body's center of mass. This mini-review summarizes evidence for the neuromechanical contributions of the soleus to postural stability and how these functions decline with age. Mechanically, the soleus acts as a brace for balance, providing sustained torque through fatigue-resistant type I fibers and a compliant Achilles tendon that buffers perturbations and contributes to ankle stiffness. Age-related reductions in tendon stiffness and rate of torque development compromise these stabilizing properties, increasing fall susceptibility. When passive stiffness is insufficient, the soleus compensates through active contraction, trading energy cost of activation for joint stability. Reflexively, the soleus serves as a stabilizer of balance through strong coupling to spinal, cutaneous, vestibular, and transcortical pathways that rapidly adjust muscle activation in response to perturbations. These reflex mechanisms also degrade with aging, leading to delayed, less adaptable responses. Together, age-related mechanical and neural deterioration reduce the soleus' ability to sustain balance and contribute to fall recovery. Preserving soleus strength, tendon stiffness, and reflex adaptability through targeted neuromuscular and perturbation-based training may represent an underrecognized but effective strategy to mitigate fall risk and maintain postural control in older adults.