Search Results (2,214)

Optimizing the neuromechanical determinants of explosive performance remains a key objective in sports science. This study compared the effects of an eight-week movement-pattern-based training program (MPT) with an isometric strength training protocol (ITG) on countermovement jump (CMJ) mechanics in competitive track and field athletes. Thirty-four athletes (19 men, 15 women) with ≥7 years of training experience were randomly allocated to the MPT or ITG. Pre- and post-intervention assessments were conducted using dual force plates to evaluate jump height, musculotendinous stiffness, concentric and eccentric impulses, contraction time, eccentric-to-concentric force ratio, and rate of force development (RFD). The MPT elicited significant gains in stiffness (Δ = +840.94 ± 1302.21 N/m; p = 0.002), maintained concentric peak force, and reduced contraction time (Δ = –64.53 ± 190.32 ms; p = 0.01), suggesting improved elastic efficiency and neuromuscular timing. Conversely, ITG was associated with reductions in concentric peak force (Δ = –66.18 ± 77.45 N; p = 0.003) and stiffness (Δ = –691.94 ± 1414.41 N/m) and an increase in the eccentric-to-concentric force ratio (Δ = +1.99%; p = 0.006). The RFD changes were inconsistent across both groups. These findings indicate that dynamic multi-joint training confers superior neuromechanical adaptations compared to isolated isometric loading. From a performance perspective, programming strategies should prioritize movement-specific dynamic tasks to enhance the explosive qualities critical for sprinting, jumping, and multidirectional field sports. Full article

Background/Objectives: National Football League (NFL) American football players are exposed to osteoarthritis risk factors of obesity and high joint loads. We sought to examine the association between total body mass (TBM), lean body mass (LBM), body fat percentage (BF%), and normalized compressive knee joint reaction forces (JRFcomp), peak knee adductor moments (KAM), and vertical ground reaction forces (vGRF) in NFL draft-eligible players during a high-speed run. Methods: A total of 125 participants ran a single trial at 5.5–6.5 m/s for 5 s on an instrumented treadmill. Bilateral vGRF and knee joint kinetics were calculated using inverse dynamics. Body composition was assessed using bioelectrical impedance. Results: LBM demonstrated significant moderate associations with vGRF (left, r(123) = −0.56, p < 0.001; right, r(123) = −0.60, p < 0.001) and low-to-negligible associations with KAM (left, r(123) = −0.20, p = 0.026; right, r(123) = −0.30, p < 0.001) and JRFcomp (left, r(123) = −0.39, p = 0.020; right, r(123) = −0.38, p = 0.015), respectively. TBM showed significant moderate negative associations with vGRF (left, r(123) = −0.56, p < 0.001; right, r(123) = −0.61, p < 0.001) and low-to-negligible associations with KAM (left, r(123) = −0.21, p = 0.021; right, r(123) = −0.28, p = 0.002) and JRFcomp (left, r(123) = −0.39, p < 0.001; right, r(123) = −0.37, p < 0.001), respectively. BF% showed significant low-to-negligible negative associations with JRFcomp (left, r(123) = −0.21, p < 0.001; right, r(123) = −0.22, p < 0.001) and vGRF (left, r(123) = −0.39, p < 0.001; right, r(123) = −0.41, p < 0.001), respectively, and no significant associations with KAM, p > 0.05. The heavier group exhibited significantly lower normalized JRFcomp, and vGRF, p < 0.05. Conclusions: Heavier, but not fatter, players attenuate knee loads. Dampening may be a short-term protective strategy for joints of heavier players. Full article

This study uses the CREATE^TM-AV/Kestrel simulation software to model a towed jumper scenario using standard aircraft settings to quantify paratrooper stability and risk of contact during static line airborne operations. The focus areas of this study include a review of the technical build-up, which includes aircraft, paratrooper and static line modeling, plus preliminary functional checkouts executed to verify simulation performance. This research and simulation development effort is driven by the need to meet the analysis demands required to support the US Army Personnel Airdrop with static line length studies and the North Atlantic Treaty Organization (NATO) Joint Airdrop Capability Syndicate (JACS) with airdrop interoperability assessments. Each project requires the use of various aircraft types, static line lengths and exit procedures. To help meet this need and establish a baseline proof of concept (POC) simulation, simulation setups were developed for a towed jumper from both the C-130J and C-17 using a 20-ft static line to support US Army Personnel Airdrop efforts. Concurrently, the JACS is requesting analysis to support interoperability testing to help qualify the T-11 parachute from an Airbus A400M Atlas aircraft, operated by NATO nations. Due to the lack of an available A400M geometry, the C-17 was used to demonstrate the POC, and plans to substitute the geometry are in order when it becomes available. The results of a nominal Computational Fluid Dynamics (CFD) simulation run using a C-17 and C-130J will be reviewed with a sample of the output to help characterize performance differences for the aircraft settings selected. The US Army Combat Capabilities Development Command Soldier Center (DEVCOM-SC) Aerial Delivery Division (ADD) has partnered with the US Air Force Academy (USAFA) High Performance Computing Research Center (HPCRC) to enable Modeling and Simulation (M&S) capabilities that support the Warfighter and NATO airdrop interoperability efforts. Full article

Background: This study investigated sex differences in foot arch structure and function, and their impact on postural control and energy flow during dynamic tasks. Findings aim to inform sex-specific training, movement assessment, and injury prevention strategies. Methods: A total of 108 participants (53 males and 55 females) underwent foot arch morphological assessments and performed a sit-to-stand (STS). Motion data were collected using an infrared motion capture system, three-dimensional force plates, and wireless surface electromyography. A rigid body model was constructed in Visual3D, and joint forces, segmental angular and linear velocities, center of pressure (COP), and center of mass (COM) were calculated using MATLAB. Segmental net energy was integrated to determine energy flow across different phases of the STS. Results: Arch stiffness was significantly higher in males. In terms of postural control, males exhibited significantly lower mediolateral COP frequency and anteroposterior COM peak velocity during the pre-seat-off phase, and lower COM displacement, peak velocity, and sample entropy during the post-seat-off phase compared to females. Conversely, males showed higher anteroposterior COM velocity before seat-off, and greater anteroposterior and vertical momentum after seat-off (p < 0.05). Regarding energy flow, males exhibited higher thigh muscle power, segmental net power during both phases, and greater shank joint power before seat-off. In contrast, females showed higher thigh joint power before seat-off and greater shank joint power after seat-off (p < 0.05). Conclusions: Significant sex differences in foot arch function influence postural control and energy transfer during STS. Compared to males, females rely on more frequent postural adjustments to compensate for lower arch stiffness, which may increase mechanical loading on the knee and ankle and elevate injury risk. Full article

With the continuous improvement of the prefabricated modular technology system, the prefabricated subway station structures are widely used in underground engineering projects. However, prefabricated subway stations in soft soil can suffer significant adverse effects under seismic action. In order to study the seismic performance of a prefabricated subway station, this work is based on an actual project of a subway station in soft soil. And the nonlinear static and dynamic coupling two-dimensional finite element models of cast-in-place structures (CIPs), assembly splicing structures (ASSs), and assembly monolithic structures (AMSs) are established, respectively. The soil-structure interaction is considered, and different peak ground accelerations (PGA) are selected for incremental dynamic analysis. The displacement response, internal force characteristics, and structural damage distribution for three structural forms are compared. The research results show that the inter-story displacement of the AMS is slightly greater than that of the CIP, while the inter-story displacement of the ASS is the largest. The CIP has the highest internal force in the middle column, the ASS has the lowest internal force in the middle column, and the AMS is between the two. The damage to the CIP is concentrated at the bottom of the middle column and sidewall. The AMS compression damage moves upward, but the tensile damage mode is similar to the CIP. The ASS can effectively reduce damage to the middle column and achieve redistribution of internal force. Further analysis shows that the joint splicing interface between cast-in-place and prefabricated components is the key to controlling the overall deformation and seismic performance of the structure. The research results can provide a theoretical basis for the seismic design optimization of subway stations in earthquake-prone areas. Full article

Background: Post-traumatic joint contracture (PTJC) remains one of the most prevalent and challenging complications arising from musculoskeletal trauma or surgical intervention. Conventional treatment modalities are largely reactive and address symptoms after onset, yet provide limited efficacy once contracture has developed. In contrast, pharmacological strategies targeting the underlying inflammatory and fibrotic pathways offer a promising strategy for preventing the development of PTJC altogether. Methods: A total of 26 male Sprague Dawley rats underwent standardized knee trauma followed by immobilization for a duration of two weeks. Rats were randomized into two groups. The experimental group (n = 13) received bosentan at a dosage of 50 mg/kg twice daily throughout the immobilization period. The control group (n = 13) received a placebo instead. Joint mobility was quantitatively assessed by measuring the contracture angle (CA) and resistance to extension. In addition, posterior joint capsule tissues were harvested for histological analysis and subjected to quantitative PCR (qPCR) to quantify the expression of profibrotic genes, including α-Sma, Il-6, Tgf-β1, Nfκ-b, Ctgf. Results: Bosentan had no relevant effect on the biomechanics of the contracture compared to the placebo group. The contracture angle was comparable between the groups (86.8° ± 14.1°, 84.8° ± 11.1°). Similarly, the force required to achieve knee joint extension was comparable between the groups. Gene expression analysis also provided no evidence of reduced expression of pro-inflammatory or profibrotic genes. Histological assessments revealed no change in the absolute or relative number of myofibroblasts, or in the number of vessels, in the posterior joint capsules of the rats treated with bosentan. Compared to the control group, the number of myofibroblasts significantly increased in both the bosentan and control groups (p < 0.001, one-way ANOVA). Conclusion: Bosentan’s purported antifibrotic properties do not appear to confer a preventative effect on the development of PTJC. These findings suggest that, despite its potential in modulating fibrosis, bosentan does not mitigate the progression of the fibrotic condition. Furthermore, the involvement of endothelin-1 (ET-1) in the pathophysiology of PTJC remains yet to be fully understood, warranting further investigation. Full article

This study investigates the application of laser spot welding to join protective housing components in the automotive electronics industry. The PBT GF 30 components were joined using two primary configurations: a purely overlapping joint and a top-overlap joint, both autogenous (i.e., without filler material). To complement the experimental analysis, a numerical model, previously validated for a simpler joint configuration, was adapted and applied to configurations beyond the overlapping and top-overlap joint, more representative of practical automotive industry components. The results demonstrated that butt-overlap joints exhibited significantly higher strength (85% increase) than purely overlapping joints. This enhancement is attributed to the combined effect of normal and shear stresses in the top-overlap configuration, whereas purely overlapping joints rely solely on shear stress. The validated numerical model accurately predicted the experimental results, including displacement and force values. While minor deviations were observed, the numerical model’s predictions converged within the average experimental values and standard deviation, demonstrating that such a model can be used to precisely design laser-welded joints for similar applications. Full article

This study presents the design and evaluation of a dexterous prosthetic hand featuring five fingers, ten independently actuated joints, and four passively driven joints. The hand’s dexterity is enabled by a novel rigid–flexible coupled finger mechanism that incorporates a 1-active–1-passive joint configuration, which can enhance the dexterity of traditional rigid actuators while achieving a human-like workspace. Each finger is designed with a specific degree of rotational freedom to mimic natural opening and closing motions. This study also elaborates on the mapping of eight-channel electromyography to finger grasping force through improved TCN, as well as the control algorithm for grasping flexible objects. A functional prototype of the prosthetic hand was fabricated, and a series of experiments involving adaptive grasping and handheld manipulation tasks were conducted to validate the effectiveness of the proposed mechanical structure and control strategy. The results demonstrate that the hand can stably grasp flexible objects of various shapes and sizes. This work provides a practical solution for prosthetic hand design, offering promising potential for developing lightweight, dexterous, and highly anthropomorphic robotic hands suitable for real-world applications. Full article

Magnetic surgical instruments are primarily driven by magnetic force and/or micro-motors. When micro-motors are used to drive motion, they are typically installed near the manipulator joints, resulting in a larger manipulator size due to the presence of micro-motors. We designed a magnetic anchored and cable-driven surgical forceps, which separates micro-motors from the manipulator through cables. The cables are responsible for transmitting motion and force from micro-motors to the manipulator. This design enables the integration of relatively large motors (diameter: 8 mm) while maintaining a compact overall diameter of the manipulator (diameter: 10 mm). This is beneficial for improving the flexibility of the manipulator and facilitating the coordination between surgical instruments. The manipulator of the magnetic anchored and cable-driven surgical forceps has three degrees of freedom (DoFs): pitch, yaw and clamping. A magnetic attraction experiment was conducted to measure the magnetic force on the magnetic surgical forceps with the variation of abdominal skin thickness. The results indicate that at a distance of 20 mm, the magnetic force exerted on the magnetic surgical forceps is 5.86 N, with a maximum vertical load capacity of 5.13 N. Additionally, an ex vivo experiment was conducted to validate the practicality of the magnetic anchored and cable-driven surgical forceps prototype. Full article

Background: Hand function is critical for daily living, occupational performance, and sports. Optimal training approaches for healthy adults remain unclear. Objective: To evaluate the effects of hand-focused strength and proprioceptive training on grip strength, pinch strength, manual dexterity, maximum voluntary contraction, joint position sense, and force sense in healthy younger and older adults. Methods: PubMed, Google Scholar, Semantic Scholar, Web of Science, Cochrane CENTRAL and registers were searched until July 2025 for randomized controlled trials (RCTs) involving adults (≥18 years) without upper limb dysfunction. Studies with clinical populations, single-session interventions, or lacking pre–post outcome data were excluded. Risk of bias was assessed using the Cochrane RoB 2 tool. Random-effects meta-analyses (Hedges’ g) pooled pre–post change score differences for each outcome; subgroup analyses examined age, training type, and comparator. Results: Twenty-two RCTs (n = 1017 participants; 19–78 years) met the inclusion criteria. Strength and proprioceptive training produced a small-to-moderate improvement in grip strength (g = 0.44, 95% CI [0.23–0.64], 95%PI [–0.09, 0.96]) and a large improvement in manual dexterity (g = 1.11, 95% CI [0.52–1.71], 95%PI [–0.01, 2.23]). Effects on pinch strength were positive but non-significant (g = 0.63, 95% CI [–0.09–1.35], 95%PI [–1.38, 2.63]) and showed substantial heterogeneity. Moderator analyses indicated greater effects in older adults (g = 0.97) compared to younger adults (g = 0.18). Strength-only protocols showed significant effects, while combined protocols yielded smaller, non-significant effects; however, the difference between them was not statistically significant. Effects were also larger when compared with passive controls than with untrained hands. Limitations: Evidence quality was limited by high risk of bias, measurement variability, and small study numbers for some outcomes. Conclusions: Strength-focused hand training, particularly in older adults, yields meaningful improvements in grip strength and dexterity. Further high-quality RCTs are needed for under-studied outcomes. Full article

Forward head posture and altered scapular alignment are associated with musculoskeletal dysfunctions and impaired physical performance. However, the relationship between postural alignment indices and physiological function in young adults remains unexplored. A total of 54 healthy participants (mean age: 21.88 ± 2.06 years) were evaluated. Craniovertebral angle (CVA) and scapular index were measured as indicators of postural alignment. Upper trapezius muscle tone was assessed using the MyotonPRO device. Pulmonary function parameters, including the forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁)/FVC, were measured using spirometry. Balance control was evaluated using the Tetrax system, and cervical proprioception was assessed using joint position error (JPE) tests. CVA showed statistically significant but weak correlations with the muscle tone (r = −0.191), weight distribution index in the eyes-open condition (r = −0.199), and cervical flexion JPE (r = −0.198) and a positive correlation with FVC (r = 0.251) (p < 0.05). Scapular index showed a positive correlation with FEV₁/FVC (r = 0.241) and a negative correlation with balance control (r = −0.213) (p < 0.05). Improved postural alignment, as reflected by a higher CVA and scapular index, was associated with reduced muscle tone, enhanced pulmonary function, better balance control, and more accurate cervical proprioception. Full article

This paper deals with static stability in planar grasps of an object by multiple fingers. Differently from previous research, we focus on the case that each finger has redundant links and joints. Based on contact constraints between the object and fingers, the relationships among displacements of object’s pose, contact positions, and joint positions are formulated. Using the constraints, the redundant joints are reduced to independent parameters. The relationship between the displacement and reaction torque of each joint is modeled as a linear spring, and potential energy of the grasp is formulated. Not only for frictionless sliding contact but also for pure rolling contact, we derive stable conditions on the contact positions and joint positions. Based on the conditions, partially differentiating the potential energy, a wrench (force and moment) vector and a stiffness matrix applied to the object by each finger are derived. Summing up the wrenches and matrices of all the fingers, we obtain a wrench vector and a stiffness matrix of the grasp, and we evaluate the grasp stability. Because of our analytical formulation, grasp parameters such as local curvatures at contact points, joint stiffnesses, etc., are explicitly included in the derived matrices. Partially differentiating the wrenches and matrices by the grasp parameters, we clarify effects of the parameters on the stability. Moreover, the difference between the frictionless sliding contact and pure rolling contact is derived in the wrench vector and the stiffness matrix. Using numerical examples, we validate our analysis. Full article

Scaffolds are temporary structures that workers usually use during building or repair work. These structures can be built in different shapes and types depending on the type of joints to which the beams and columns of the scaffolds are connected. Due to their temporary nature, they are very sensitive to vibration under dynamic or static actions, and this causes many accidents and unstable behaviours in them. This unstable behaviour has different reasons, including bracing conditions and slenderness of the columns, stiffness of joints and anchors, imperfections in the construction, damage and corrosion due to climate change, etc. This article aims to reanalyse the mechanical properties of scaffold joints and anchors and obtain some critical factors in the overall stability of the mentioned structures, including load-bearing capacity, initial stiffness, energy absorption, and ductility. To this aim, some recent research on scaffolds has been summarised and discussed, and then the failure mode and mechanical behaviour of the scaffolds in different types of scaffold joints and anchors have been estimated and considered from previous studies. Moreover, some mechanical properties, including ductility, initial stiffness, and energy absorption, have been estimated and developed based on the force-displacement curves of previous studies. The results highlight the crucial importance of the mechanical properties and behaviour of anchors and joints in estimating the behaviour and stability of scaffolds. The results also revealed that determining the mechanical characteristics of the mentioned elements can have a significant influence on the optimisation and design of scaffolds more accurately and predictably. Moreover, determining the mechanical properties of the anchors and joints can enhance our insights and understanding of how the mentioned parameters can improve the behaviour, stability, and safety of the scaffold structures. Full article

As a flagship low-carbon transition zone in China, the Yangtze River Delta (YRD) faces challenges in synergizing green innovation efficiency (GIE) and urban ecological resilience (UER). This study establishes a dual-system evaluation framework to quantify their coupling coordination degree (CCD) across the 41 cities of the YRD from 2010 to 2023 using coupling coordination modeling, Geodetector, as well as Geographically and Temporally Weighted Regression (GTWR). Key findings reveal the following: (1) Temporally, GIE surged from 0.252 to 0.692, while UER rose steadily from 0.228 to 0.395. This joint improvement elevated the CCD from mildly discordant to primary coordination. (2) Spatially, an east–high, west–low gradient defined three regional typologies: coastal clusters with high coupling and intermediate coordination; the Yangtze River corridor with high coupling yet only primary coordination; and inter-provincial border zones with low coupling and low coordination. In these border zones, administrative fragmentation resulted in a CCD that was 10–23% lower than that of inland regions. (3) Mechanistically, the green innovation driving force and policy synergy degree were the dominant promoters. In contrast, urban expansion pressure and rigid ecological regulation exhibited spatially heterogeneous effects, with their overall inhibitory impacts most pronounced in highly urbanized coastal cores and inland industrial transition zones. The findings may serve as a practical case reference for tailoring governance strategies in global mega-city regions pursuing synergistic low-carbon transitions. Full article

Osteoarthritis is a prevalent and disabling condition in companion dogs, yet existing treatments are primarily symptomatic and limited by safety concerns. EF-M2, a defined derivative of vitamin D-binding protein, selectively biases macrophages toward an anti-inflammatory phenotype in vitro. We conducted a randomised, double-blind, placebo-controlled trial (IMPAWS-OA-1) in 60 client-owned dogs with naturally occurring hip or elbow osteoarthritis. Animals were allocated to subcutaneous EF-M2 (0.1 µg/kg) given thrice weekly or twice weekly, or to saline placebo for four weeks, followed by four weeks off-drug. The primary endpoint was change in Canine Brief Pain Inventory–Pain Severity Score (CBPI-PSS) at Day 28. EF-M2 produced dose–frequency-dependent benefits: LS-mean ΔPSS was −2.11 for thrice weekly, −1.42 for twice weekly, and −0.54 for placebo (arm effect p < 0.001). Objective measures showed parallel improvements in peak vertical force and accelerometery. Serum biomarkers confirmed macrophage repolarisation (ARG1/iNOS ratio, IL-10 increase, TNF-α decrease), correlating with clinical response. Adverse events were infrequent and mild, with no excess over placebo. In conclusion, EF-M2 achieved clinically meaningful pain relief, functional gains, and biomarker shifts without safety signals, establishing first-in-species proof that targeted macrophage modulation may be a viable disease-modifying approach for canine osteoarthritis. Full article