Search Results (2,231)

Accurately capturing muscle behavior remains a challenging task in computational biomechanics, primarily due to the nonlinear response, anisotropy, and time-dependent characteristics of muscle tissue. In this context, finite element methods have proven to be a suitable framework for representing such complex mechanical behavior. Among the available constitutive approaches, Hill’s three-element model continues to be widely adopted, largely because it offers a reasonable balance between physiological interpretability and computational efficiency. In this work, a parametric and sensitivity-oriented analysis of the Hill three-element muscle model is performed within a finite element formulation originally proposed by Kojić, Mijailović, and Zdravković (1998) and implemented in the PAK software environment. The analysis considers five key parameters, which are varied independently: the stiffness parameter of the series elastic element (α), the corresponding stress scaling parameter (β), the modulus of the parallel elastic element (E), the activation level (a), and the length ratio constant (k). To enable comparison between parameters of different physical nature, normalized sensitivity indices are used. The results show that the activation parameter a has the strongest influence on active force generation, with an increase of 36.4% at the highest considered activation level. In contrast, parameters α and β primarily affect the behavior of the series elastic component, with variations on the order of ±15–18%. It can also be observed that the influence of individual parameters depends on the deformation regime. At lower deformation levels, the response is mainly governed by the parameter E, while α and β become more relevant in the intermediate nonlinear range. At higher deformation levels, the activation parameter a becomes dominant. From a modeling perspective, these findings suggest a structured approach to parameter calibration in Hill-type finite element models. In addition, they provide further insight into the sensitivity characteristics of such formulations within computational biomechanics. Full article

The objective of this study was to evaluate the effects of dietary Allium mongolicum Regel essential oil (AMO) supplementation on growth performance, carcass traits, meat quality, and muscle amino acid profile in finishing lambs. A total of twenty male Dorper × Han crossbred lambs (body weight = 32.5 ± 2.5 kg, 4–4.5 months old) were randomly allocated into two dietary treatments (n = 10 per group): a control group fed a basal diet (roughage to concentrate ratio of 45:55) or an AMO group supplemented with 56 mg/d of AMO per lamb. The trial consisted of a 15-day adaptation period followed by a 60-day experimental period. At the end of the trial, six lambs were randomly selected from each group for slaughter. Samples of the longissimus thoracis (LT) muscle were collected to determine meat quality traits, proximate composition, and amino acid profiles. Supplementation increased average daily gain by 6.6% and improved feed conversion ratio by 4.6% (p < 0.05), whereas feed intake and final body weight were not affected (p > 0.05). In LT, GR tissue depth and loin muscle area were increased (p < 0.05). Drip loss was reduced (p < 0.05), whereas proximate composition, cooking loss, and shear force remained unchanged (p > 0.05). The hydrolyzed amino acid composition and protein nutritional value of LT were not affected (p > 0.05). However, total free amino acid (FAA), total essential FAA, and the concentrations of free leucine, isoleucine, lysine, valine, phenylalanine, tyrosine, alanine, glutamic acid, glycine, and cysteine were increased by supplementation (p < 0.05). Moreover, flavor-related FAA, including umami-, sweet-, and bitter/sweet/sulfurous-related FAA were also increased by supplementation (p < 0.05). These results indicate that AMO improves growth efficiency and enhances LT meat quality, particularly by increasing flavor-related FAA, without altering protein nutritional characteristics. Full article

Humanoid robots operating near humans require short protective reaction times in physical human–robot interaction (pHRI). Safety standards distinguish between quasi-static and transient contact. This paper quantifies the reaction timing of a compliant pneumatic artificial muscle (PAM) mechanism under controlled preload conditions. Measurements were performed at 10 N, 50 N, and 100 N preload using synchronised load-cell force, PAM pressure, actuator position, and force-sensitive resistor (FSR) signals. Reaction timing was evaluated relative to the FSR-defined contact onset, at which the controller issued the pressure-release command. The force trace reached its first post-contact peak within 15–20 ms after onset, while the pressure peak occurred within 5–15 ms. A 90% recovery of the post-contact force excursion was achieved within 40–50 ms, whereas the corresponding pressure excursion required 155–180 ms. These timing results quantify reaction latency in PAM-actuated humanoid joints and support multi-modal sensing for robust onset localisation and mitigation monitoring in both ISO/TS 15066 contact types. Full article

Background: Astragali radix is a traditional herb known for its antioxidant, anti-inflammatory, and immunomodulatory properties and has gained attention for its potential to support post-exercise recovery. However, the effects of long-term supplementation coupled with resistance training are not well understood. Methods: Twenty-four moderately active participants were recruited and randomly assigned to the Astragali radix supplementation (ASTRA, n = 13) or placebo (PLA, n = 11) group. All participants underwent 8 weeks of regular resistance training (3 sessions/week) and 2 weeks of intensified training (6 sessions/week). Results: Before (BAS), after 8 weeks of resistance training (RT), and at the end of the intensified training (IT), knee extensors’ maximal voluntary isometric contraction torque (MVIT), and leg press and leg extension one repetition max (1RM) were measured. Blood samples were collected to analyze inflammatory markers and testosterone. From BAS to after RT, MVIT, 1RM leg press, and 1RM leg extension increased in both ASTRA and PLA, with no differences between groups. After IT, MVIT, 1RM leg press and 1RM leg extension decreased in both ASTRA and PLA. CPK levels and myoglobin concentration increased while cortisol decreased significantly from BAS to IT, but no group differences were detected. TNF-α and IL-6 showed significant time × supplementation interactions, with lower values after IT in ASTRA compared to PLA. Conclusions: Astragali radix supplementation did not lead to additional benefits in muscle during the period of resistance training, nor did it prevent the decline in force following the intensified training period. However, Astragali radix supplementation prevented the increase in some inflammatory biomarkers, specifically TNF-α and IL-6, during the intensified period of training. Full article

Coronary artery bypass grafting (CABG) using the autologous saphenous vein (SV) remains widely performed for obstructive atherosclerosis; however, vein graft disease drives recurrent ischaemia through early thrombosis and progressive intimal hyperplasia, and accelerated atherosclerosis developing within the grafts. Extracellular vesicles (EVs) are membrane-bound particles that transfer proteins, lipids, and microRNAs between cells. They modulate endothelial dysfunction, vascular smooth muscle cell phenotypic switching, inflammation, and coagulation, which are core processes in vein graft remodelling. Arterialisation exposes the vein to abrupt rises in shear stress, cyclic stretch, and intraluminal pressure. These forces increase EV release and reshape EV cargo in experimental systems, suggesting a potential mechanism for amplifying early graft injury which warrants direct investigation in vein tissue. This review synthesises current evidence for cell-specific EV contributions from ECs, vascular smooth muscle cells, platelets, and macrophages, and appraises EV-associated microRNAs with biomarker potential relevant to graft failure pathways. We also review therapeutic strategies that may modulate EV signalling including antiplatelet therapy, statins, KCa3.1 inhibition, and pro-reparative mesenchymal stromal cell-derived EVs. No published clinical studies evaluate EV-based biomarkers specifically for saphenous vein graft patency, and none prospectively predict saphenous graft failure. CABG provides a well-defined time zero event that enables longitudinal sampling and risk stratification. Prospective studies linking EV phenotypes and miRNA signatures to imaging-defined graft outcomes are needed to support clinical translation. Full article

Background/Objectives: Muscle strength is a key determinant of functional capacity in older adults. However, measures such as handgrip strength may not fully reflect multi-joint force production, and the relevance of the Isometric Mid-Thigh Pull (IMTP) for functional and cardiorespiratory outcomes remains unclear. This study examined the associations between IMTP-derived peak force and functional and submaximal cardiorespiratory variables in independent older women. Methods: This cross-sectional study included 21 independent older women (72.6 ± 6.9 years). Maximal isometric strength (IMTP and handgrip), functional performance (TUG, 30-CST, 30-ACT), and submaximal cardiorespiratory variables were assessed. Associations were examined using Pearson’s correlation coefficients with false discovery rate (FDR) correction (q = 5%). Results: Absolute IMTP peak force was significantly related to handgrip strength (r = 0.77; q = 0.001) and PVT1 (r = 0.67; q = 0.007). Relative IMTP peak force was related to relative handgrip strength (r = 0.71; q = 0.002), VO₂VT2 (r = 0.60; q = 0.02), and inversely to COP (r = −0.56; q = 0.03). No significant relationships were observed with TUG, 30-ACT, or most cardiorespiratory variables. Conclusions: IMTP-derived peak force was related to selected neuromuscular and submaximal cardiorespiratory variables, but not to functional performance measures. These findings suggest that the IMTP may provide complementary information on neuromuscular status, although further studies are required. Full article

How do ryanodine receptors (RyRs) open simultaneously to trigger the contraction of whole myofibrils within a large skeletal muscle cell? One possible answer is the uniformity of mechanosensitive RyRs, which is mechanically forced by the neighboring environment, including proteins. Here, we review papers addressing this proposed “mechanical sarcoplasmic reticulum (SR) paradigm”. Crystals of the molecular complexes comprising RyR and L-type voltage-gated Ca²⁺ channels were observed at the T-tubule/SR junction in situ using cryo-electron tomography. Observations of the SR vesicles isolated from rabbit and scallop cross-striated muscles using negative staining and transmission electron microscope raised a hypothesis of dynamic rearrangement of the Ca²⁺-ATPase (ATPase) molecules in response to cytoplasmic calcium concentration, as follows: (i) At a low calcium concentration where the ratio of operating ATPase molecules to the total molecules is at a submaximal level, the ATPase molecules form, at least in part, their cylindrical crystals in the SR membrane with the help of ATP; this results in the elongation of the SR vesicles. (ii) High concentrations of calcium, at which the ratio of operating ATPase molecules is maximal, reversibly collapse the ATPase crystals to transform the elongated vesicles into round forms comprising tightly attached crystal patches. These data further lead to the idea that the reversible growth of cylindrical ATPase crystals provides a dynamic crystalline network, which acts as an “SR membrane-endoskeletal motor” to manipulate the SR movement. The possibility of interactions between ATPase crystals and neighboring RyR crystals is also discussed. Full article

A distinct typing interface using surface electromyography (sEMG) can facilitate silent, hands-free typing by interpreting muscle activity in relation to specific keystrokes. Character-level recognition poses greater challenges than coarse gesture recognition because it is sensitive to subtle temporal variations and overlapping muscle dynamics. Temporal features are essential for typing recognition because keypresses may differ in duration, force, and accompanying hand movements across users. This paper proposes TransTCNet, a two-stage deep neural network architecture with a causal convolutional layer for learning local features and a transformer-based component for learning long-range temporal interactions. We evaluated our network on a publicly available 26-class typing sEMG dataset acquired from 19 individuals. The model achieved a validation accuracy of 96.53%, exceeding the baseline models. Our study revealed generalization among participants, and the AUC values were also high (>0.994) across all classes. The model was highly reliable and exhibited high prediction confidence (>0.9), enabling us to achieve a high training accuracy (97.86%) for real-time filtering decisions. TransTCNet could be suitable for wearable and edge devices due to its efficient architecture and low inference cost. The model’s ability to consistently decode fine-grained neuromuscular signals across users makes it well-suited for real-time applications such as adaptive user interfaces, virtual and augmented reality, prosthetic control, and communication systems. Full article

The foot arch functions as a dynamic biomechanical system, maintained by the integrated actions of bones, ligaments, and muscles. A large body of clinical evidence indicates that, in addition to congenital foot deformities, acquired variations in the foot arch caused by factors such as poor gait, aging, weight, or injury can significantly affect quality of life. Early intervention upon detection of foot arch changes can help mitigate progression and prevent further deterioration. Despite the availability of multimodal sensor-integrated running platforms for gait analysis, such systems are inherently bulky and not conducive to routine walking measurement. To overcome the above limitations, this study employed a flexible plantar pressure insole with an integrated accelerometer and a dedicated acquisition circuit to capture plantar pressure and acceleration data. This smart insole system acquires plantar data, performs feature extraction via time–domain and wavelet analysis, and then employs machine learning to classify the foot arch type as a normal foot, flatfoot, or high-arched. A Random Forest classifier was then established to categorize foot arch types based on the collected data, which integrates numerous decision trees through bootstrap aggregation and random feature selection, with final classification determined by majority voting. A total of 30 volunteers participated, including 11 with normal arches, 11 with flat feet, and 8 with high arches. Compared with support vector machine, K nearest neighbors, and decision tree, the Random Forest achieved the highest recognition accuracy of 92%. This system reveals the patterns of plantar pressure distribution and acceleration fluctuations during walking across three foot arches and demonstrates that wavelet entropy can effectively quantify the changes in signal complexity included in foot arch differences. Compared with laboratory force plates, this system features lower cost and a smaller form factor, making it suitable for real-time monitoring. This system can lay the technical foundation for personalized foot orthopedics and health monitoring. Full article

(1) Background: This study aims to investigate the differences in body composition, muscle strength, and power between young karate athletes from different competitive disciplines. (2) Methods: The study sample consisted of 131 participants (69 boys and 62 girls) aged 10–14 years divided into three groups: kata (n = 48), kumite (n = 40), and athletes competing in both disciplines (n = 43). The set of variables included 1 anthropometric variable, 6 variables for assessing body composition (InBody 270), 8 variables for assessing handgrip strength (handgrip strength test, Fmax, RFD, absolute and relative, both hands), and 3 variables for assessing lower limb muscle power (force plate, CMJ height and power). Of the statistic analysis, MANOVA and ANOVA, along with MANCOVA and ANCOVA were performed. (3) Results: The adjusted results revealed significant general differences between groups (from p = 0.005 to p = 0.009). Regarding body composition, kumite athletes are taller, have greater body mass, body water, proteins, minerals, and muscle mass content than kata athletes and athletes specialized in both disciplines (from p = 0.002 to p = 0.045). The young karate athletes specialized in kumite competition exhibit higher levels of absolute handgrip muscle strength, rate of force development, and absolute lower limb muscle power than kata athletes and athletes specialized in both disciplines (from p = 0.002 to p = 0.041). There were no significant differences in any measured parameters between kata athletes and young karate athletes specialised in both disciplines. (4) Conclusions: The results are associated with higher values of body composition, muscle strength, and power in kumite athletes compared to kata athletes and athletes competing in both disciplines. Full article

Caragana korshinskii is an underutilized non-grain feed resource. This study investigated the optimal dietary inclusion level of fermented Caragana korshinskii for Mongolian lambs by assessing growth performance, antioxidant status, meat quality, fatty acid and amino acid profiles, and rumen microbiota. Thirty-six lambs were fed diets containing 0%, 10%, 15%, or 20% fermented Caragana korshinskii replacing Leymus chinensis hay for 105 days after a 10 d adaptation period. The 10% group exhibited higher final body weight, average daily gain, feed intake, and carcass weight (p < 0.05). All supplemented groups showed elevated serum T-AOC and reduced MDA (p < 0.05); furthermore, 10% supplementation increased CAT, and 10% and 15% supplementation increased SOD (p < 0.05). Meat quality improved in the 10% and 15% groups, with lower water loss, shear force, drip loss, L*, and b* (p < 0.05; p < 0.01), and higher a* (p < 0.05). Muscle nutrients remained unchanged. Amino acid alterations included increased Glu (all groups), Thr, Ile (15%, 20%), Leu (20%), and variable changes in Asp. Fatty acid analysis revealed higher C18:0, PUFA, C18:2n6c, C18:3n3 in 10% (p < 0.05; p < 0.01), but lower PUFA and C18:3n3 in the 15% and 20% groups (p < 0.05). Rumen 16S sequencing revealed higher abundances of Thermodesulfobacteriota, Methanobacteriota, Methanobrevibacter (10%, 20%), Xylanibacter, Succiniclasticum (15%, 20%), and lower Rikenellaceae_RC9_gut_group (20%) (p < 0.05; p < 0.01). Correlations linked rumen microbes to meat-related fatty acids and amino acids. In conclusion, supplementation with 10% fermented Caragana korshinskii optimally enhanced lamb growth, health, and meat quality through modulation of the rumen microbiota. Full article

This study evaluated the effects of scallion white and ginger extracts on stress indicators, gene expression, tissue structure, and muscle quality in crucian carp during transportation. Compared with the control group, ginger extract effectively alleviated long-term transportation stress (48 h), as evidenced by lower levels of glucose and lactate dehydrogenase activity, along with reduced pathological damage in gill, liver, and muscle tissues. Consequently, muscle quality parameters including shear force, glycogen content, and inosine monophosphate levels were notably improved. These improvements were associated with the suppression of heat shock responses, inflammation, and apoptosis, supported by the downregulation of hsp70, il-6, caspase 3, caspase 8 and bax gene expression. Similar trends were observed in the scallion white extract group, though its anti-stress effects and muscle quality enhancement were comparatively weaker. The findings suggest that natural extracts offer a promising approach to mitigating stress and improving muscle quality during live fish transportation. Full article

Background: Respiratory muscle strength (RMS) is a critical factor influencing athletic performance, particularly in high-intensity or prolonged activities. RMS encompasses inspiratory (IMs) and expiratory muscles (EMs), which differ in anatomical structure, fiber composition, and responsiveness to training. Methods: This pilot interventional within-subject study investigated the effects of two resistive respiratory muscle training (RMT) protocols on RMS and small airway function in eight physically active adults (two females, six males). Maximal inspiratory (MIP) and expiratory pressures (MEP), along with pulmonary function tests (PFTs), were measured using the Airofit PRO™ device and spirometry before and after two consecutive 7-day training protocols, with a 2-day break between interventions. The workload was progressively increased by lengthening the duration of forced inhalation and exhalation, while keeping the air resistance constant. Results: Results demonstrated significant improvements in MEP across both protocols and after a 10-day washout period (p < 0.001–0.03), whereas MIP showed no significant changes (p = 0.19–0.66). Moderate transient improvements were observed in small airway flow (MEF25%) following the first protocol (ES = 0.62), which regressed after the second. Conclusions: These outcomes suggest differential responsiveness of respiratory muscles to RMT; EMs, characterized by a higher proportion of fast-twitch type II fibers and a predominantly passive role in normal breathing, respond rapidly to short-duration, high-intensity forced expiration training through neuromuscular adaptations. Conversely, IMs, dominated by slow-twitch type I fibers, require longer-duration, higher-load training to elicit meaningful adaptations, explaining the limited changes in MIP. Small airway function appeared minimally trainable due to structural and physiological constraints, with short-term improvements likely reflecting effort-dependent factors rather than lasting adaptations. Finally, RMT can selectively enhance EM performance through appropriately designed short-duration, high-intensity interventions, while IMs may necessitate prolonged or higher-load stimuli. The findings highlight the importance of targeted training strategies, individualized to muscle fiber composition and functional demands, to optimize respiratory performance. Future research should investigate longer interventions, larger diverse cohorts, and precise measurement methods to further elucidate RMT’s effects on both respiratory muscles and small airway function. Full article

Background/Objectives: Sciatica secondary to lumbar disc herniation is a common cause of chronic radicular pain and functional disability. Since the sciatic nerve is involved in the motor and sensory innervation of the foot, it is important to evaluate the potential distal biomechanical alterations it produces. Evidence regarding the effect of radicular pain on kinetic parameters remains limited and heterogeneous. The aim of this study was to describe gait characteristics in people with chronic unilateral radicular pain due to non-traumatic lumbar or lumbosacral disc herniation and to compare kinetic differences between the affected and unaffected limbs. Methods: A cross-sectional analytical observational study was conducted in 41 patients who met the inclusion criteria. Dynamic baropodometric assessment was performed using the Footscan^® system. The analysis focused on kinetic parameters, including surface area, pressure, and maximum force, as well as spatiotemporal variables comprising stance time, step time, step length, and plantar push-off mechanics. Demographic data, Foot Posture Index (FPI) scores, and muscle strength were also recorded. Results: According to patient reports, the left foot was the most severely affected. Significant differences in muscle strength were found between the affected and unaffected limbs. However, no significant differences were observed in any of the kinetic or spatiotemporal parameters evaluated. Conclusions: Patients with unilateral sciatica due to lumbar disc herniation showed reduced muscle strength in the affected limb with no significant differences in kinetic or spatiotemporal gait parameters, suggesting compensatory mechanisms. Full article

This study aimed to evaluate breed-specific differences in meat quality, nutritional compo sition, and volatile flavor compounds of beef, and to discuss their implications for animal breeding and health. Longissimus dorsi muscles were collected from four cattle breeds—Dabieshan cattle (DBS), local water buffalo (LWB), Simmental (SM), and Angus (AG)—with six animals per breed, all reared under identical feeding conditions. Meat quality parameters (color, cooking loss, shear force, and water-holding capacity), proximate composition, fatty acid and amino acid profiles, and volatile compounds were analyzed using standardized methods. Significant breed effects were observed for most traits (p < 0.05). DBS exhibited the highest intramuscular fat content (2.9%) and total fatty acid concentration, along with favorable proportions of unsaturated fatty acids (MUFA + PUFA) and abundant flavor volatiles (aldehydes and ketones). LWB showed superior water-holding capacity, lowest cooking loss, and the highest total amino acid content, including essential amino acids, along with a higher PUFA/SFA ratio. SM and AG had intermediate meat quality traits, with AG displaying lower lightness (L*) and better tenderness than SM. Notably, LWB and DBS presented higher levels of nutritionally beneficial fatty acids (e.g., C18:3n3) and amino acids (e.g., glutamic acid). Breed significantly influences meat quality and nutritional composition. DBS and LWB offer distinct advantages in fat deposition, amino acid profile, and potential health benefits. These findings provide preliminary insights for selective breeding programs aiming to improve meat quality and meet consumer preferences. The observed compositional differences—such as lower saturated fatty acids in LWB and higher intramuscular fat in DBS—may offer nutritional advantages from a dietary perspective, although direct health benefits were not assessed. The results also underscore the importance of preserving indigenous cattle genetic resources for sustainable animal production. Full article