To investigate how knee joint protector design affects the biomechanical characteristics of knee motion under various activities, this pilot study (n = 5) examined how knee joint protector design modulates knee biomechanics across walking, jogging, squatting, and sit-to-stand tasks using optical motion capture and AnyBody musculoskeletal modeling (FullBody_GRFPrediction). We quantified knee flexion kinematics, model-estimated joint reaction forces and moments, and model-estimated muscle activity of eight lower-limb muscles under four conditions with different levels of structural constraint: no protector (Pro.off), a conventional sleeve-type protector (Pro.a), a segmented support protector (Pro.b), and a wrapping fixation protector (Pro.c). The biomechanical protective performance of the knee joint protector was task- and phase-dependent. The results showed that Pro.a optimized muscle activation. Pro.b increased sagittal-plane design but increased joint loading and muscle activity. Pro.c induced noticeable distal compensation along the kinetic chain. The findings revealed that protector effects were task-dependent. Dynamic tasks mainly affected coronal-plane stability parameters, whereas quasi-static tasks more clearly altered sagittal load distribution. In this study, biomechanical protective performance is defined as reduced knee joint loading without disproportionate increases in model-estimated muscle activity or excessive loss of functional knee flexion range. Under this definition, greater structural constraint did not consistently produce a more favorable biomechanical profile. These results provide a feasibility baseline for task-specific protector evaluation and motivate confirmatory studies with larger cohorts and experimental validation. This study provides theoretical and methodological insights to guide future design and optimization of knee joint protectors.
First ray hypermobility is implicated in many forefoot pathologies, yet its quantitative assessment remains challenging. Instrumented methods have traditionally focused on isolated dorsal displacement of the first metatarsal, which may not reflect physiological load sharing within the forefoot. This cadaveric biomechanical study evaluated the reliability and construct validity of two arthrometer-based measures: the first ray absolute (FRAM) and relative (FRRM) mobility, respectively assessed under isolated loading of the first metatarsal and symmetrical loading of the first metatarsal and lesser metatarsals. Ten fresh-frozen cadaveric lower limb segments were tested using an automated forefoot arthrometer. Within-session reliability was quantified using intraclass correlation coefficients, standard error of measurement, and minimal detectable change. Construct validity was assessed by correlating FRAM and FRRM with a biomechanical reference construct defined as the sum of superior-inferior translations at the first tarsometatarsal and medial naviculo-cuneiform joints measured using optical motion capture. Linear mixed-effects models were used to characterise joint-level kinematic behaviour under each loading mode. FRRM demonstrated excellent within-session reliability (ICC = 1.00) and a high positive correlation with the reference construct (R = 0.70, p < 0.001). FRAM also showed excellent reliability (ICC = 0.97) but higher absolute measurement error and a moderate positive correlation with the reference construct (R = 0.63, p < 0.001). Symmetric loading engaged proximal first ray joints more effectively than isolated loading, which predominantly mobilised the first tarsometatarsal joint. These findings indicate that arthrometer-based assessment of the first ray mobility is sensitive to the loading mode and that symmetric loading provides a more biomechanically representative evaluation of the first ray mobility than traditional isolated approaches.
This study explores the combined effects of backpack loading and smartphone dual tasking on gait dynamic stability. Unlike previous separate investigations, it systematically examines their individual and interactive influences on postural stability. An experimental protocol simulated smartphone use during backpack-loaded walking. Kinematic and kinetic data from 15 female university students were collected via 3D motion capture and analyzed using inverse dynamics. An innovative computational method assessed margin of stability (MOS), investigating biomechanical mechanisms of postural instability. Smartphone tasks disrupt pelvic, lumbar, and lower limb kinetics/kinematics, reducing walking speed and increasing instability risk. Backpack loading altered knee range of motion and ankle/metatarsophalangeal moments, with 15% body weight (BW) loads showing significant destabilizing effects. Instability correlated strongly with hip, lumbar, and metatarsophalangeal parameters. Combined tasks exacerbated effects, including reduced gait velocity and the kinematic parameters and degrees of freedom variations. Both backpack loading and mobile phone dual tasking significantly altered movement characteristics, force exertion patterns, and gait stability during walking in the pelvis, hip joints, and lumbar spine, with demonstrable interaction effects between these factors. Across the pelvis, hip joints, lumbar spine, and lower extremity joints, adaptations in joint range of motion and peak moments generated distinct mechanical adjustments to compensate for attentional distraction and center-of-mass deviation induced by these combined variables.
Alterations in the contributions of paraspinal soft tissues can influence the geometric profile of the spine. This study investigated the effects of passively modeled paraspinal soft tissues (i.e., paraspinal muscles and the thoracolumbar fascia (TLF)), on lumbar segmental mobility and geometric compensation, using a credible and previously validated finite element model (FEM) of the thoracolumbar spine. The model included the vertebrae, rib cage, intervertebral discs (IVDs), pelvis, ligaments, spinal and abdominal muscles, and the TLF. The model was subjected to 30 deg and 60 deg flexion rotation with a fixed pelvic support, and an applied follower load of 1175 N, increasing by 2.4% at each segmental level. Changes in lumbar L2-S1 intervertebral rotation (IVR), lumbar and thoracic range of motion (RoM), and curvature were analyzed for cases involving removal and increased stiffening of the paraspinal muscles and the TLF. Increasing TLF stiffness reduced lumbar RoM (5.1 deg) at 60 deg flexion relative to the validated model, with compensatory increases of 3.6 deg in thoracic RoM. Increases in lumbar lordosis (3.6 deg) were proportional to increases in thoracic kyphosis (3.3 deg). Similar effects of reduced magnitude were observed in 30 deg flexion. Inverse effects were observed following TLF removal. However, no changes were observed with changes in paraspinal muscle contribution. These findings suggest that changes in TLF stiffness influence lumbar segmental mobility and drive compensatory adjustments in the spinal geometric profile.
Temporal coordination of muscle activation is a key determinant of mechanical control in functional movements such as lifting, gait, and sit-to-stand transitions. Although electromyography (EMG) research has traditionally emphasized amplitude-based measures, temporal features-including activation onset, offset, sequencing, and burst duration-provide essential insight into neuromechanical strategies governing joint moment generation, load regulation, and movement stability. This narrative review synthesizes evidence from peer-reviewed studies published between 1990 and 2025 to examine temporal muscle activation patterns across representative functional tasks. Across tasks, a consistent neuromechanical principle emerges: proximal muscle activation precedes distal force generation, supporting trunk stabilization, efficient momentum transfer, and redistribution of joint moments. During lifting, anticipatory trunk activation modulates spinal loading, whereas altered timing and increased co-contraction are associated with inefficient load sharing in low back pain. In gait, aging and pathology are characterized by prolonged distal activation and impaired push-off mechanics. Sit-to-stand transitions show a characteristic sequence initiated by tibialis anterior and trunk musculature, followed by synchronized extensor bursts at seat-off; deviations increase joint loading and reduce mechanical efficiency. These findings highlight temporal EMG patterns as biomechanically meaningful control variables for functional movement assessment.
This study presents a patient-specific parametric model of the temporomandibular joint, designed to be semi-automated, and reproducible for multiple patients. The numerical model is used to evaluate mandibular stress distribution under different interaction and loading conditions. The main contribution is to demonstrate the feasibility of an integrated, fast, and streamlined workflow for generating accurate biomechanical models tailored to each patient. The proposed method, which relies on standard clinical images complemented by artificial intelligence-assisted segmentation of bone and muscles, enables the integration of patient-specific anatomical features and mechanical variability. A finite element model of the skull, mandible, teeth, and articular disks was constructed from calibrated computed tomography data. Material properties were automatically assigned using Hounsfield units, distinguishing between cortical bone, cancellous bone, and dental tissue. Sensitivity of key modeling parameters (mesh density, material, friction coefficients, muscle force vectors) was evaluated using abaqus/standard. Hounsfield-units-driven material assignment provides a Young modulus distribution aligned with the literature, while maintaining patient specificity. Artificial intelligence-based muscle reconstruction reveals that stress fields stabilize with increased directional vector refinement, reinforcing biomechanical accuracy and confirming the necessity of multivector muscle loading. This patient-specific parametric model accurately reproduces the distribution of mandibular stresses and offers a promising tool for surgical planning, pathology simulation, and the evaluation of personalized treatment strategies.
Limb rotations of the upper arms frequently happen during daily activities, and these actions can produce significant torsional forces which aggravate patients' conditions. However, there is limited research concerning the impact of humerus rotation on the initial stability of locking plate fixation after proximal humerus fracture reconstruction. The current study conducted a biomechanics analysis to investigate this important issue. Dynamic mechanical tests with repetitive torsional loads were executed in six fracture-model specimens. The mechanical behaviors of resistance to torque, maximum torque, and energy dissipation were recorded. A new surveillance system of digital image correlation (DIC) technology was used to observe the continuous strains of the fixation system in real time. Mean resistance to torque was significantly reduced when the rotation exceeded 3.2°. Beyond 3.2° of rotation, the mean energy dissipation increased by approximately fourfold. DIC observations showed large strains concentrated around the screw holes at the proximal shaft and waist of the plate. Under our experimental conditions, we observed a marked rise in non-elastic energy dissipation beyond 3.2° of rotation, which indicated the onset of permanent construct deformation in vitro. Surgeons should remind patients that daily upper extremity torques may affect the initial rotational stability of fixation system after surgery.
The objective of this work was to develop a finite element model of the thoracolumbar spine to assess the effects of passive structures, rib cage, intervertebral disc (IVD), iliolumbar ligament (ILL), and facet cartilage-capsular ligament (FC-FCL), on segmental range of motion (RoM) and thoracolumbar curvature. The model included the vertebrae, rib cage, IVDs, and pelvis, with ligaments and the FC modeled as tension-only and compression-only spring elements, respectively. The model was subjected to 60° of flexion and 55° of extension. A simulated follower load of 1175 N was applied, increasing by 2.4% at each segmental level. Changes in lumbar intervertebral rotations (IVR), lumbar and thoracic RoM and lumbar lordotic (LLA) and thoracic kyphotic angles (TKA) were analyzed for cases involving removal of the ILL and rib cage and removing the L4-L5 and L5-S1 FC-FCL and increasing the elastic moduli of the L4-L5 and L5-S1 IVD, independently. Removing the L5-S1 FC-FCL increased segmental motion (21.7°) in extension with compensatory reductions at L4-L5 (5.5°). Increases in lumbar lordosis (7°) were proportional to increases in thoracic kyphosis (7°). Similar yet smaller effects were observed when removing the rib cage and ILL, with the inverse observed following increasing IVD stiffness. Removal of the rib cage and ligaments or changes in the stiffness of the IVD influence segmental mobility and drives compensatory adjustments in adjacent segments to maintain congruency. Understanding how these tissues affect spinal alignment may inform surgical strategies aimed at preserving or restoring tissue function to maintain spinal stability.
Due to its avascular nature, treatment of degeneration of the intervertebral disc (IVD) is typically carried out via needle injection into the inner nucleus pulposus (NP) of the disc. Proposed treatments range from small peptides with nanometer-scale diameters to hydrogel-encapsulated stem cell constructs in the hundreds of nanometers. While low permeability of the NP has been implicated as a limiting factor in fluid injection capacity, the effect on suspended particles is largely unknown. This study tested the hypothesis that increasing particle size decreases intradiscal injectate dispersion by injecting saline carrying fluorescent markers representing small molecules (SM: 1 nm diameter) along with either small beads (SB: 45-53 μm diameter) or large beads (LB: 125-150 μm diameter) into bovine caudal IVDs. Following injection, the discs were transected and imaged. While SM dispersion was consistent and covered a median of 26% of the NP area, bead behavior was varied. While discs in the SB group showed dispersion to a median of 3.8% of the NP area, LB beads were localized mostly to the needle track and covered only 0.66% of NP area. In 20% of the SB-injected discs and 30% of LB, no fluorescent beads were found in the NP. These results suggest that while small molecule treatments may be practically delivered to the NP by injection, larger (>50 μm) particles are restricted by NP pore size and will remain localized to the track left by the delivery needle.
Lumbosacral and thoracolumbar kinematics are key risk factors for lifting-related low back pain, yet their measurement is typically restricted to motion capture laboratories. Inertial measurement units (IMUs) offer the potential to quantify spine kinematics in more naturalistic settings, but the validity of IMU-based processing pipelines relative to optical motion capture (OMC) remains unclear. Nine healthy participants performed stoop, squat, free, and asymmetric lifting tasks while IMU and OMC data were simultaneously collected to evaluate the concurrent validity of two IMU pipelines: the proprietary MVN Analyze pipeline and an OpenSense pipeline using a validated OpenSim biomechanical model for lifting. Joint angles from both pipelines were compared against OMC-derived joint angles calculated using the same validated OpenSim model with one-way repeated-measures statistical parametric mapping (SPM) (α = 0.05), Bland-Altman analysis with Limits of Agreement (LoA) and 95% Confidence Intervals (CIs), and Concordance Correlation Coefficients (CCCs) with 95% CIs. Xsens MVN Analyze consistently overestimated flexion-extension at both spinal levels across all lift types (lumbosacral: RMSE ≤ 9.8°, bias ≤ -14.5°, LoA ≤ ±10°; thoracolumbar: RMSE ≤ 5.4°, bias ≤ -8.3°, LoA ≤ ±5°), with SPM confirming significant differences during the lifting and lowering phases of all lifting cycles. In contrast, processing Xsens data with OpenSense using the same biomechanical model as the OMC data yielded excellent agreement with OMC (RMSE ≤ 2.9°, bias ≤ 3°, LoA ≤ ±10°). CCC was poor to moderate, specifically in lateral bending and axial rotation planes, likely reflecting limited between-participant ROM variability. These results suggest that discrepancies are driven primarily by biomechanical model differences rather than sensor or sensor fusion limitations. Ultimately, when paired with an appropriate biomechanical model, XSens sensors show promise for practical field-based assessment of lifting biomechanics, potentially requiring only sensors at the chest and pelvis.
Optical coherence tomography has allowed in vivo recording of sound-induced vibrations of different regions within the organ of Corti complex (OCC), including the basilar membrane (BM), outer hair cell/Deiters cell (OHC/DC) region, and reticular lamina (RL). In the hook region of the gerbil cochlea, where measurements can be made with a predominantly transverse optical axis, the three regions have different and characteristic motion responses: The OHC/DC region has greater motions than the other two regions at frequencies below the best frequency (sub-BF); the RL region typically has the greatest BF peak and smallest sub-BF motion. The phase of the OHC/DC-region motion increasingly lags BM motion phase as frequency increases; the RL-region motion phase leads BM, but with a relatively small value. All three regions are compressively nonlinear in the BF peak, but only the OHC/DC region shows sub-BF compressive nonlinearity. Here, we describe the strains that arise when the motion transitions between these regions. Large strains (deformations) were observed in the OHC body close to the RL. A region of large strain can be as short as a single 2.7-μm measurement pixel, or it can extend over several pixels, with extensive strains appearing more often at 70 than at 50 dB sound pressure level. Beyond this RL region of large strain, over a distance that can exceed 20 μm, the OHC/DC region displayed nearly spatially unvarying motion; this region vibrated as a relatively rigid body. And beyond this, at sub-BF frequencies, another region of high strain was present, indicating stretching/compressing or bowing/tilting of the DC microtubular stalk.
Condylar stress fracture of the third metacarpal bone (MC3) in Thoroughbred racehorses is a common catastrophic injury and identification of horses at heightened risk remains subjective. Standing computed tomography (sCT) is a practical screening tool that enables patient-specific finite element analysis (FEA) of the distal MC3 and prediction of subchondral bone strain, as a potential objective classifier of racehorses at heightened risk. The goal of this study was to compare two independently developed sCT-based subject-specific FEA pipelines for virtual mechanical testing of the distal MC3. One pipeline models the full 3D distal MC3 (UWMSN), while the other uses a simpler approach by using single sCT slices (UMELB). Four (n=4) MC3 condyles from four Thoroughbred racehorses were selected for the study. Models were generated using both pipelines and the predicted subchondral bone strain was compared. UMELB predicted smaller subchondral strain compared to UWMSN, likely due to more limited modes of deformation. Although the UWMSN pipeline can identify elevated subchondral strain in horses with high fatigue damage, it is more labor intensive and computationally expensive. With further tuning and validation, the UMELB pipeline could be used as a simpler and faster approach for prediction of subchondral strain in the distal MC3.
Biplanar videoradiography is a validated method for measuring skeletal kinematics. However, using two x-ray source-detector pairs introduces geometric constraints that can compromise image quality. The spatial configuration of the two pairs often requires a larger object-to-image distance (OID), leading to greater magnification and geometric blur. Consequently, increased magnification can limit the effective field of view, restricting multi-joint analyses. Additionally, geometric blur degrades image quality, potentially compromising subsequent bone registrations. To address this limitation, this proof-of-concept study evaluated a monoplane stereoscopic videoradiography (MSV) configuration. MSV uses two x-ray sources captured by a single detector, enabling a smaller OID. A pseudo-dynamic experiment was conducted to assess whether MSV would achieve accurate calibration and subsequent three-dimensional (3D) bone positions. A cube and pelvis phantom were rotated 360° on a turntable in 15° increments. At each increment, positions were recorded using both conventional motion capture (MOCAP) and MSV, with MOCAP acting as the reference standard. During MSV image acquisition, a lead barrier alternately blocked one x-ray source, allowing the other to project onto the detector. Calibration was performed using a bundle adjustment technique, and 3D bone positions were calculated using radiostereometric analysis and model-based tracking and compared against MOCAP. Overall, MSV achieved sub-millimeter and sub-degree accuracy. The calibration yielded a mean residual of 0.22 mm, while rotational and translational biases ranged from 0.36-1.16° and 0.22-1.23 mm, respectively, with precisions of 0.09-0.59° and 0.18-0.58 mm. These results support the feasibility of using MSV to accurately calculate skeletal positions. This approach reduces magnification and, by extension, geometric blur, opening avenues for multi-joint analyses and improved imaging of deeper joints. Future work will focus on implementing a true asynchronous MSV acquisition to extend this approach to dynamic,in vivokinematic studies.
Approximately 80% of the world population has had, has, or will have back pain. The aim of this study is to investigate the acute and chronic effects of the synergistic application of photobiomodulation with mechanical systems on low back pain. Patients with low back pain were randomly distributed into 5 groups: 1- Vacuum therapy combined with Laser (VL); 2- Roller combined with Laser (RL); 3- Ultrasound combined with Laser (USL); 4- Punctual Laser (L); and 5- Placebo Laser (P). All treatments were performed in the posterior region of the trunk (lumbar, thoracic, and cervical), totaling 20 min, once a week for 7 sessions. Pain assessment, biomechanical measurement, kinesiological evaluation, and questionnaires to assess quality of life and well-being were performed. There were pain reduction and increased isometric strength, flexibility, and mobility, improving some aspects of life quality and well-being, especially when combined therapies were applied for rehabilitation of back pain.
Extracorporeal life support (ECLS) technology has witnessed remarkable advancements during the last decades. However, further research and development of devices are required to increase, for example, performance-efficiency, hemocompatibility, and long-term stability. All novel devices, even in early research stages, must undergo rigorous testing and evaluation. Yet, these early evaluations are often conducted under nonstandardized conditions, resulting in data difficult to compare, interpret, or translate into clinical practice. Establishing well-defined, standardized in-vitro testing protocols for all ECLS components and devices would represent a major step forward. Such protocols would improve methodological consistency and ensure reproducibility across research groups. This document, developed by an international group of ECLS experts from all disciplines in which such components are designed, developed, and applied, provides clear recommendations and standardized criteria for device testing according to international norms. Adoption of these criteria including the ways of reporting results will foster a unified approach among scientists, engineers, clinicians, and the medical device industry. Ultimately, this common framework will facilitate data interpretation, improve comparability of study results between different groups, making the review of studies more straightforward, as not every aspect of testing requires additional review and discussion, certainly favoring decision-making in the development and application of ECLS technologies.
(1) Background: Gait analysis provides quantitative information on walking patterns and has proven invaluable for assessing motor function in rehabilitation programmes. A markerless motion capture system combining computer vision techniques provides low-cost, real-time, portable gait analysis. (2) Methods: The kinematics of the knee and ankle of twenty-seven healthy volunteers were assessed using a single smartphone camera combined with the MediaPipe human pose estimation framework. The system was validated using the OPAL wearable sensor system by APDM Wearable Technologies. (3) Results: Findings showed close correspondence between the two systems for knee kinematics showing a mean absolute error of 4.10° ± 2.32° and 3.15° ± 3.10° for right and left knee flexion, respectively, and a mean absolute error of 2.30° ± 2.01° and 3.12° ± 2.63° for right and left knee extension, respectively. The mean absolute error for right and left knee range of motion was found to be 4.55° ± 3.12° and 4.15° ± 3.01°, respectively. Moreover, Bland-Altman plots indicated minimal bias (average 0.6 for flexion, average 0.47 for the extension, and 0.30 for the range of motion) and excellent correlation for knee flexion bilaterally (0.916 and 0.845 for the right and left side, respectively), with slightly lower but still satisfactory agreement for knee extension (0.862 and 0.845 for the right and left side, respectively). Conversely, ankle measurements revealed poor concordance: dorsiflexion and range of motion presented significant differences and systematic errors, while plantarflexion showed no statistical difference but weak correlation. (4) Conclusions: This study demonstrated that combining a smartphone camera with a human pose estimation framework allows for low-cost, real-time, portable gait analysis, particularly of the knee joint.
While fascicular elastic fibers have been shown to significantly affect mechanical properties of tendon in stress relaxation and ramp to failure testing, the contribution of elastin to fatigue properties has only recently been investigated. This study expanded upon recent fatigue-to-failure data in wild-type and elastin knockdown mice (Prx1Cre+;Elnfl/fl) by halting tests at 50% of cyclic fatigue (based on normalized strain) instead of completing tests to tissue failure. Following 50% fatigue loading, Achilles (AT) and tibialis anterior (TB) tendons were subjected to subsequent stress relaxation and ramp to failure testing, enabling comparison to prior properties of non-damaged tendons to determine the effects of sub-failure fatigue. Indeed, multiple properties (e.g., ultimate stress, linear modulus) were decreased following fatigue loading, especially in elastin-deficient tendons, and genotype-dependent differences in stress relaxation properties were observed. Quantitative metrics of damage (i.e., collagen denaturation and fiber kinking) were not different between wild-type and elastin knockdown tendons as observed previously following fatigue-induced failure, suggesting that tendon damage develops later in the fatigue lifecycle. In addition, results suggest that elastin mediates collagen fiber alignment more in AT than TB, providing evidence that the different effects of elastin on tendon mechanics rely on microstructural mechanisms that vary by tendon type. Results suggest that individuals with deficient or depleted elastin may experience impaired recovery following repetitive tendon loading, which could have downstream effects on subsequent damage accumulation and tissue remodeling that should be investigated further in future studies.
Osteoporosis is a prevalent systemic disease primarily affecting the skeletal system, with the spine being one of the most commonly affected areas. Numerous studies have demonstrated detrimental biomechanical effects of osteoporosis on the lumbar spine. However, its influence on adjacent SIJ remains poorly understood. This study aimed to determine how osteoporosis alters SIJ biomechanics under physiological and vibrational load. A validated, 3D finite element model of the normal lumbopelvic segment (L1-pelvis) was modified to simulate osteoporosis by decreasing bone mechanical properties. Biomechanical responses within the SIJs to both static loading (flexion, extension, lateral bending, rotation) and vibration loading (cyclic axial compression) were analyzed and compared between the normal and osteoporotic conditions. Static analysis revealed that osteoporosis significantly increased SIJ range of motion (ROM) by 20.6%-52.7% and elevated maximum von Mises stress by 30.8%-90.3% compared to the normal condition. Also, forced vibration analysis revealed a 35%-36% increase in stress amplitudes in the osteoporotic model. These alterations correlated with reduced bone stiffness, suggesting compromised joint stability. These findings demonstrate that osteoporosis adversely affects SIJ biomechanics by increasing motion and internal stress, thereby potentially elevating the risks of SIJ instability, degeneration, and subsequent joint dysfunction and pain. This study provides novel insights into the overlooked role of SIJ pathology in osteoporotic patients, emphasizing the need for targeted diagnostic and therapeutic strategies.
Left ventricular (LV) remodeling, whether occurring with somatic growth or as a chronic response to a sustained stimulus, is a primary factor underlying cardiac mechanical function. Although LV remodeling is a complex process that can be described at several levels, response variables that govern cardiac mechanics include changes in LV wall and chamber geometry, the mechanical properties of the LV myocardium, and LV structural mechanical properties such as LV chamber stiffness. We leverage two-dimensional speckle-tracking echocardiography (STE) to serially monitor key LV remodeling response variables in porcine models of LV pressure overload (LVPO), chronic exercise (CE), and the superposition of both settings (CE+LVPO), and compare changes to those occurring in age-matched referent control (RC) animals. Our findings show that over 28-days, LVPO and CE both induce hypertrophy, but passive LV myocardial stiffness increases with the former and decreases with the latter. As a net effect of geometrical and mechanical property changes, these settings induce divergent changes in LV chamber stiffness, namely, an elevation with LVPO and reduction with CE. In the CE+LVPO cohort, exercise was found to attenuate the LVPO-induced increase in LV myocardial and LV chamber stiffnesses. Data obtained were used to identify a phenomenological model of LV chamber stiffness and develop a predictive mathematical model of late changes in LV chamber stiffness based on early remodeling response variables irrespective of stimulus. Our findings support exercise in cardiac therapy and the use of STE to predict cardiac disease risk/progression.
Previous studies have shown that additional cognitive load from a secondary task can adversely affect movement performance. However, how externally provided auditory pacing influences motor and neural responses under dual-task conditions remains unclear. This study employed a repeated-measures experimental design, studying eighteen young adults (Mean age 23.5 ± 4 years) who underwent three conditions: (1) foot tapping only (single task), (2) foot tapping and a mental task (dual task), and (3) foot tapping, mental task, and auditory pacing biofeedback (dual task + biofeedback). Ankle joint movements using Xsens IMU's (Inertial Motion Units) and brain activities using EEG (electroencephalography) were measured in these three conditions. Results showed that dual tasks significantly reduced (p < 0.01) the range of motion and increased (p < 0.05) the variability of ankle joint range of motion, suggesting a decline in foot tapping performance compared to the single-task condition. The decline was accompanied by significant increases (p < 0.05) in relative high-beta power in EEG, consistent with heightened cognitive-motor demand during dual-tasking. In the dual-task + biofeedback condition, kinematic measures returned to values statistically indistinguishable from the single-task condition and response times in the cognitive task were significantly reduced, without a loss of accuracy. The relative high-beta power was also significantly reduced, compared with the dual-task condition, which may reflect increased entrainment to external cues or a reduction in cognitive load. These results support the role of auditory pacing in facilitating movement performance under dual-tasking conditions, while highlighting the need for future studies to dissociate entrainment effects from changes in cognitive workload.