Journal of Biomechanics

Altered walking mechanics in individuals with obesity can contribute to knee osteoarthritis. The gait deviations may become more pronounced during obstacle crossing. In women, body fat distribution may further influence knee load, especially when excess fat accumulates in the thighs and hips. However, relatively little is known about how regional fat distribution affects gait in women with obesity. This study investigated how obesity and, among women, different fat distributions (Apple: more abdominal fat; Pear: more lower-limb fat) influence knee biomechanics during walking with and without obstacle crossing. Participants were 15 controls without obesity (NB) and 27 with obesity (OB). Within female participants, 10 without obesity (fNB) were compared with 20 with obesity, stratified by waist-hip ratio (Apple:10, Pear:10). Speed-adjusted statistical parametric mapping applied a general linear model (NB vs. OB) and an analysis of covariance (fNB vs. Apple vs. Pear). OB exhibited a significantly greater late-stance knee extension moment than NB across all tasks, and this difference persisted among fNB, Apple, and Pear in obstacle tasks (p<0.05). OB walked with reduced knee flexion during the early-stance leading limb after crossing a medium-height obstacle (p=0.048) and a high-height obstacle (p=0.008) compared to NB. There were significant body-shape effects (p<0.05), and post-hoc comparisons confirmed that Pear had lower knee angles than fNB in both leading-limb conditions after crossing medium- and high-height obstacles (p=0.008 and p=0.001, respectively). These findings suggest that obstacle crossing helps illuminate how excess weight influences knee biomechanics, and how regional fat distribution modulates the degree of this alteration.

Balance is fundamental to mobility and independence, yet it remains difficult to measure in a way that is both clinically meaningful and feasible for widespread adoption. There is a need for more quantitative, objective, and accessible balance assessments. To this end, we created the Stanford Balance Level Evaluation (StaBLE), a battery of 18 balance-challenging tasks and accompanying digital performance metrics computed from video that aimed to capture widely ranging balance abilities across 180 participants. We validated the StaBLE score against existing clinical scales and found that it correlated with age ({rho} = -0.76, p<0.001), the Activities-Specific Balance Confidence Scale ({rho} = 0.60, p<0.001), a Mini-Balance Evaluation Systems Test task ({tau}=0.55, p<0.001), 4-Stage Balance Test ({tau} = 0.55, p<0.001), and Short Physical Performance Battery ({tau} =0.57, p<0.001). StaBLE overcame ceiling effects in these existing scales and had a different underlying distribution for those identified at risk of falling and not (KS: 0.67, p<0.001). To reduce the time it takes to perform the test, we identified subsets of balance tasks that best predicted the StaBLE score across different populations. Together, our dataset, balance assessment protocol, and performance-based score demonstrate the validity of digital measures of balance.

Marker-based optical motion capture remains the gold standard for kinematic analysis across biomechanical research. However, when tracking dynamic movements, severe occlusions often create missing data and noisy signals that require time-consuming manual cleaning. Existing automated methods usually rely on predefined skeleton models or need massive training datasets for machine learning solutions. This study presents the AMP: an automated marker based motion capture processing pipeline. The AMP is a fully analytical approach that uses hierarchical algorithms including 1) rigid-body constraint, 2) Kalman Filter state estimation and 3) kinematic pattern match to label markers and fill data gaps without manual human intervention. First, the algorithm identifies and removes mislabeling markers before any data scrubbing. During the data cleaning process, our hierarchical algorithm uses a translation-based step to track segments even when there are insufficient donor markers to form a full rigid body. To reconstruct missing marker trajectories, the pipeline initially uses Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) interpolation for short marker gaps. However, the PCHIP creates massive spatial errors during long occlusions, the system automatically switches to rigid-body tracking for gaps over 40 ms. Results showed the pipeline drastically reduced processing time compared to manual human expert methods by 73.5%. In addition, the AMP kept spatial errors within 10 mm of the manual ground truth. By using this combined hierarchical approach to match marker processing accuracy, the pipeline provides a fast, general-purpose tool that fully automates data cleaning and saves hours of manual effort.

Introduction: Knee muscle coactivation is elevated after anterior cruciate ligament reconstruction (ACLR), contributing to altered joint loading and post-traumatic osteoarthritis. Existing methods average coactivation within predefined gait phases and require priori designation of muscles roles, limiting the resolution for when differences occur. Objective: Characterize knee joint coactivation and dynamics throughout gait in individuals with ACLR using statistical parametric mapping. Methods: Ten individuals with unilateral ACLR and ten healthy matched controls performed overground walking at their preferred speed, while kinematics, kinetics, and electromyography of the quadriceps, hamstring, and gastrocnemius muscles were recorded. Coactivation was quantified using time-varying, multi-muscle coactivation, and was compared using a one-tailed statistical parametric mapping (SPM) t-test. Knee joint angle, angular speed, and moment were compared using SPM Hotelling's T2 tests with Bonferroni-adjusted post hoc comparisons (= 0.05). Results: Coactivation was greater in the ACLR group at 0.01%-6.14%, 35.23%-40.94%, 69.73-71.99%, 72.12-77.31%, 77.89-78.05%, and 94.63%-95.87% (p < 0.0001) of stride. The ACLR group also demonstrated greater knee internal-external rotation angle at 0.01%-47.34%, 52.14%-61.87%, and 66.47%-100% (p <0.0001) and lower knee flexion angle at 55.79%-65.93% (p = 0.004) of stride, than healthy controls. Finally, a smaller knee flexion-extension moment was observed in the ACLR group at 57.43%-62.18% (p = 0.005) of stride. Conclusions: Coactivation after ACLR is elevated at loading response, late mid-stance, terminal stance and early push-off phase. Greater coactivation was observed during weight-acceptance phases, whereas lower knee moments characterized initial swing. These alterations are localized rather than uniformly distributed, supporting phase-targeted rehabilitation.

Conventional clinical assessment of upper limb kinematics relies on goniometry or visual estimation, methods that provide limited information on multi-segment 3D kinematics and can have poor inter-rater reliability. Inertial measurement units (IMUs) represent a viable alternative; however, extracting anatomically meaningful joint angles from skin-mounted sensors remains challenging owing to sensor-to-segment misalignment, soft-tissue artefact, and suboptimal orientation estimation under dynamic conditions. This study developed and validated a multi-segment IMU-based framework for upper limb kinematic assessment, addressing three stages of the measurement pipeline: (i) sensor fusion gain optimisation as a function of task mean segment angular velocity; (ii) accuracy of an anatomical landmark registration-based alignment method; and (iii) comparative evaluation of landmark-based alignment against manual and neutral-pose alignment approaches. Twenty participants with typical shoulder function performed clinical and functional upper limb tasks, recorded simultaneously with an optoelectronic motion capture system and six IMUs tracking the thorax, clavicle, scapula, humerus, forearm, and hand. Orientation estimation used a gradient-descent complementary filter with velocity-dependent gain modulation. Sensor-to-segment alignment was achieved via manual, neutral-pose, and landmark registration methods. Mean sensor orientation errors ranged from 1.5 to 3 degrees across segments/tasks and increased with angular velocity. Landmark registration produced substantially lower joint angle errors than manual and neutral-pose alignment across all joints (root mean square error range: 3.7-7.8 degrees; manual: 8.3-24.2 degrees; neutral: 15.5-35.5 degrees). These results indicate that IMU-derived kinematic accuracy is context-dependent, varying with joint and movement type, suggesting that accuracy should be established for the specific movements and joints relevant to each clinical application.

Arterial stiffness and endothelial dysfunction are non-traditional risk markers after stroke, yet reliability and minimal detectable change (MDC) of pulse wave velocity (PWV) and flow-mediated dilation (FMD) have not been established. We examined test-retest reliability and MDC of carotid-femoral (cfPWV), carotid-radial (crPWV), and femoral-dorsalis pedis PWV (ffPWV), and absolute and relative brachial artery FMD in people >12 months post-stroke. Seventeen individuals (n=4(24%) females; 63.9{+/-}8.6 years; 4.5{+/-}2.8 years post-stroke) completed two bilateral assessments of PWV via applanation tonometry and FMD via duplex ultrasound within one week. Intraclass correlation coefficients (ICC2,1) were calculated via two-way random-effects models, and MDC derived at 68%, 90%, and 95% confidence levels. We found good-to-excellent reliability for cfPWV in paretic (ICC2,1=0.85; 95%CI:0.59,0.95) and non-paretic (ICC2,1=0.94; 95%CI:0.82,0.98) limbs, with MDC95% values of 2.23 and 1.68 m/s, respectively. crPWV and ffPWV exhibited poor reliability bilaterally (ICC2,1=0.12-0.33). Relative FMD showed-moderate reliability for paretic (ICC2,1=0.50; 95%CI:-0.20,0.85) and non-paretic (ICC=0.59; 95%CI:0.04,0.84) limbs, with MDC95% values of 6.88% and 7.65%, respectively. Reliability for absolute FMD was poor (ICC2,1=0.11-0.44). These findings support cfPWV as a reliable vascular assessments in individuals >12 months post-stroke, and provide stroke-specific MDC values to guide interpretability in future trials.

Crank length affects the geometry of the bicycle-rider system and influences the motion of the lower limb throughout the pedal cycle. Conventional crank selection has largely relied on rider stature and mechanical power, yet mechanical power and cycling economy remain remarkably insensitive to crank length across a broad range. Yet, elite cyclists and triathletes increasingly adopt shorter cranks, particularly in disciplines where aerodynamic drag strongly affects cycling performance. However, the mechanisms that connect crank length to mechanical power and aerodynamic drag remain unclear. Here we show that crank length couples rider anthropometry, hip kinematics, and aerodynamic drag. Population anthropometry of 6,068 individuals reveals that stature alone poorly predicts personalized crank length, while geometric analysis identifies a nearly linear relationship between crank length and minimum lower hip angle: a 10-mm reduction in crank length increases hip-angle margin by approximately 1.42 degrees with little mechanical penalty. This geometric freedom permits more flexion of the torso and a more aerodynamic posture; the resulting aerodynamic advantage grows rapidly with cycling speed because aerodynamic power scales with velocity cubed. Data from 150 elite cyclists and triathletes support this shift toward shorter cranks, with triathletes adopting shorter relative crank lengths than cyclists. Our results establish crank length as a personalized design variable that connects lower-limb geometry to aerodynamics. These insights enable personalized crank selection, integrated rider-bicycle design, and performance optimization for the increased aerodynamic demands of high-speed cycling.

Objective: The aim of the current study was to evaluate the feasibility of a multi-channel distributed wearable ultrasound (D-WUS) system capable of simultaneously probing dynamic muscle activity across multiple anatomical sites to assess neuromuscular coordination during physical activity. Methods: Twenty NCAA Division I women athletes (8 with prior knee injury) performed countermovement jumps (CMJs) on dual force plates while wearing a four-channel D-WUS system targeting the vastus lateralis (VL) and vastus medialis oblique (VMO) in both limbs. Real-time M-mode ultrasound data were processed using a composite factorization approach integrating nonnegative matrix factorization and principal component analysis (CF-PCA) to extract dominant muscle-contraction patterns. Correlation and timing metrics between VL and VMO were compared across injury status. Results: CMJ performance metrics (jump height, RSImod) did not differ between groups (p > 0.05). However, D-WUS revealed significant differences in muscle coordination in the right limb: VL-VMO correlation (p = 0.029) and timing symmetry (p = 0.019) were reduced in participants with prior knee injury; left-limb differences were not significant. Right-limb timing symmetry was negatively correlated with SMFA score (rho = -0.48, p = 0.033). Functional survey scores (SMFA) also differed significantly (p = 0.001), while VISA-P scores did not. Conclusion: These preliminary findings provide feasibility-level evidence that distributed wearable ultrasound can detect limb-specific neuromuscular coordination differences not reflected in force-plate biomechanics, motivating larger prospective studies to establish reliability and clinical utility. Significance: With further validation, this approach may offer a scalable, objective means of monitoring muscle contraction during rehabilitation.

Background: Ascending thoracic aortic aneurysm (ATAA) is characterized by progressive biomechanical remodeling that is incompletely captured by maximum aortic diameter. The relationships between age, sex, aortic valve phenotype (BAV vs TAV), and aneurysmal mechanics remains incompletely understood. Methods: Ascending aortic specimens from 54 patients undergoing elective ATAA repair were evaluated. Biaxial testing quantified Green strain and local stiffness at membrane tensions of 60 and 120 N/m. Opening angle was used to assess circumferential residual stress and stretch. Associations with age were evaluated using Pearson correlations, and differences between sex and valve phenotype were also explored. Multivariable linear regression models including age, sex, and valve phenotype were used to evaluate their adjusted associations with each mechanical outcome. Results: Increasing age was associated with increased local stiffness and reduced Green strain and remained the strongest determinant of biaxial mechanical properties after adjustment. Compared with tricuspid aortic valve specimens, BAV specimens exhibited lower Green strain together with lower local stiffness. Females demonstrated greater Green strain in unadjusted analyses; however, after adjustment, sex remained associated only with longitudinal Green strain at 60 N/m. None of the evaluated clinical characteristics consistently explained opening angle or residual stretch. Conclusions: Age was the predominant clinical determinant of biaxial mechanical remodeling in ATAA, whereas valve phenotype demonstrated selective associations and sex contributed comparatively little after adjustment. Circumferential residual stress appeared largely independent of these clinical characteristics, suggesting that residual stress and biaxial mechanics capture complementary aspects of aneurysmal remodeling.

BackgroundTrunk flexor and extensor measurement tools are useful for measuring progress throughout the identification, treatment and management of spinal pathologies. Handheld dynamometry is popular amongst clinicians due to its convenience. However, poor standardisation of the testing position can lead to suboptimal intra-rater reliability, which consequently reduces the validity of the results. The VALD ForceFrame Strength Testing System is a portable and standardized hybrid strength-assessment system that quantifies strength and power outputs. ObjectiveThis study aims to assess the test-retest reliability of isometric trunk flexion and extension strength using the ForceFrame testing technology. MethodsA total of 29 healthy participants undertook two testing sessions, each requiring them to perform maximal isometric trunk flexion and extension using the ForceFrame. Test re-test reliability was assessed using the Intraclass Correlation Coefficient (ICC), and the standard error of measure (SEM) was used to calculate the minimum detectable change. ResultsExcellent reliability was observed for both trunk flexion (ICC 0.92; 95% CI 0.83-0.96) and extension (ICC 0.93; 95% CI 0.86-0.97) tests, and the minimum detectable changes observed were 71.35N and 101.20N, respectively. ConclusionsThe results from this study suggest that the VALD force frame offers clinicians a reliable method of assessing change in trunk flexor and extensor strength.

Introduction: The femoropopliteal artery undergoes substantial axial compression, bending, torsion, and pinching during limb flexion. When an implanted stent does not accommodate these deformations, repetitive biomechanical mismatch may alter the vascular response to implantation and contribute to restenosis. We tested whether designing a peripheral stent to better accommodate physiologic limb-flexion deformation reduces the subsequent inflammatory and neointimal response. Methods: A nitinol stent was developed using multi-objective computational optimization to maintain arterial apposition while reducing wall stress and luminal pinching during physiologic deformation. Sixteen Yucatan minipigs were studied in independent 3- and 6-month cohorts (n=8 each). Each animal received the optimized stent in one limb and a commercial stent with representative biomechanical behavior contralaterally. CTA quantified in vivo limb-flexion deformation, while CT and histology assessed stenosis, neointimal accumulation, inflammatory-cell burden, SMA-positive tissue, and extracellular-matrix composition. Results: The optimized stent accommodated greater axial shortening than the commercial comparator at both 3 months (11.2{+/-}2.7% vs. 6.6{+/-}2.1%, p=0.003) and 6 months (13.7{+/-}4.4% vs. 6.8{+/-}2.3%, p=0.004). Intimal hyperplasia volume was lower with the optimized stent at 3 months (227.5{+/-}85.2 vs. 350.0{+/-}130.5 mm3, p=0.002) and 6 months (183.6{+/-}46.2 vs. 261.2{+/-}60.6 mm3, p=0.001), with significantly lower maximum, mean, and median stenosis at both timepoints. At 3 months, macrophage and total inflammatory-cell counts were 51% and 45% lower, respectively, with the optimized stent. Histologic tissue area was 28% lower at 3 months and 12% lower at 6 months. SMA-positive tissue fraction was higher with the optimized stent at both timepoints, whereas elastin, glycosaminoglycan, and collagen fractions were similar between devices. Discussion: Improved accommodation of limb-flexion deformation was associated with a smaller inflammatory and neointimal response to stent implantation through 6 months, while overall neointimal matrix composition remained largely unchanged. These findings provide in vivo evidence that biomechanical compatibility with the dynamic lower-limb environment can influence vascular healing and should be considered a mechanistic design criterion for peripheral artery stents.

To correct lower limb length discrepancies, orthopedic surgeons often perform limb lengthening procedures. These procedures involve directly lengthening a primary bone (e.g., femur), which also stretches the muscles and tendons spanning the elongation site. Limb lengthening procedures improve lower-limb length symmetry, often at the expense of chronic joint-level decrements. For example, knee joint range of motion and strength does not always return to pre-surgery values following femur lengthening. These joint-level decrements governed by altered muscle force-length characteristics, but it is unestablished how human muscles remodel during surgical limb lengthening. Here, we characterized bilateral human vastus lateralis fascicle force-length profiles following femur lengthening. At 2.2 {+/-} 1.7 years (Avg {+/-} SE) post-initial surgery, the lengthened limb's vastus lateralis fascicles were longer, effectively stiffer, and weaker than the contralateral limb. The lengthened limb's vastus lateralis fascicles were 38 mm longer (Avg) than that of the contralateral limb, even though the lengthened limb's femur was only 31 mm longer (Avg). The onset of vastus lateralis fascicle passive force production began at 22% shorter (Avg) operating lengths in lengthened versus contralateral limb muscles. Additionally, vastus lateralis peak active force production was 34% less (Avg) in the lengthened versus contralateral limbs, and in-series quadriceps tendon stiffness was not stiffer in lengthened limbs. These data suggest that active muscle tissues lengthen more than passive muscle tissues following limb lengthening, effectively creating stiffer muscles. Years after limb lengthening, patient muscles exhibit numerous differences in their force-length properties versus that of natural growth, likely contributing to impaired joint-function.

Background: Knee osteoarthritis (OA) is characterized by progressive joint degradation and altered gait biomechanics. Inter-limb load asymmetry during daily living tasks may accelerate joint deterioration, particularly when combined with physical fatigue. This study investigates the relationship between daily physical fatigue and inter-limb load asymmetry patterns during functional activities in individuals with unilateral knee OA. Objective: To evaluate the impact of fatigue on inter-limb load asymmetry and joint loading rates during daily living tasks in patients with unilateral knee osteoarthritis, and to identify biomechanical and clinical factors associated with load distribution patterns. Methods: One hundred eighteen participants with unilateral knee OA (mean age 62.6 (SD 7.4) years, BMI 29.9 (SD 4.2) kg/m2) completed biomechanical assessments during non-fatigued and fatigued conditions. Ground reaction force measurements were obtained during functional tasks including stair climbing, sit-to-stand transitions, and level walking. Load asymmetry was quantified as the inter-limb difference in peak vertical ground reaction forces. Statistical analysis was conducted using Python (v3.9), including paired t-tests, analysis of variance, and linear regression modeling. Results: Participants demonstrated significantly increased load asymmetry under fatigue conditions (mean difference 8.7% (SD 12.3) %, p < 0.001). Fatigue-induced asymmetry was task-dependent, with stair negotiation showing the greatest increase (11.2% (SD 14.1) %). Peak loading rates on the affected knee were inversely correlated with time-to-peak load during fatigued conditions (r = -0.68, p < 0.001). Disease severity (WOMAC score) and age significantly predicted asymmetry changes (R2 = 0.52, p < 0.001). Conclusions: Physical fatigue exacerbates inter-limb load asymmetry in unilateral knee OA, potentially accelerating joint degeneration. Task-specific interventions targeting fatigue management and load redistribution may improve long-term outcomes. Future longitudinal studies should examine the temporal relationship between acute biomechanical changes and progressive structural joint damage. Keywords: Knee osteoarthritis, load asymmetry, fatigue, biomechanics, ground reaction forces, functional tasks.

Background: Hypertension is a major risk factor for type B aortic dissections and rupture, with guidelines recommending systolic blood pressure (SBP) control below 130 mmHg to improve outcomes. While post-TEVAR blood pressure is often managed with a focus on mean SBP, little is known about temporal hemodynamic patterns and their association with surgical success. This study investigates blood pressure and heart rate (HR) time-series metrics within 24 hours post-TEVAR and their predictive potential for outcomes. Methods: Blood pressure (n = 560) and HR (n = 680) time-series data from 31 patients were analyzed alongside preoperative aortic geometry metrics. Exploratory data analysis identified correlations between BP variability and outcomes. Stationarity tests were performed on time-series data to assess statistical properties. Logistic regression models incorporating hemodynamic metrics, along with CT-derived features, were used to predict TEVAR outcomes. Results: Successful outcomes correlated with greater diastolic blood pressure variability and strictly stationary SBP. Logistic regression models combining these metrics along with heart rate standard deviation and preoperative aortic geometry achieved 96.67% 5-fold cross-validation accuracy in predicting outcomes. Conclusion: Post-TEVAR behaviors of hemodynamic variables are critical predictors of TEVAR success, with higher DBP standard deviation and strict stationarity of SBP significantly associated with favorable outcomes. These findings highlight the importance of hemodynamic variability and stationarity in optimizing post-TEVAR patient care.

Targeted stepping requires coordinating limb transport, preparatory postural adjustments, and accurate foot placement while maintaining balance under competing speed and accuracy demands. Although Fitts' law robustly describes speed-accuracy trade-offs (SATs) in upper-limb movements, its applicability to whole-body stepping remains unclear due to additional postural and visuomotor constraints. This study investigates how instructional emphasis and spatial demands modulate SAT regulation and pre-step postural dynamics during stepping. Twenty-four healthy young adults will perform a multidirectional stepping task across two directions (0 degrees and 45 degrees) and two distances (45% and 80% of leg length) under three instruction conditions: Fast, Accurate, and Fast & Accurate. Kinematic and force-plate data will quantify movement time, foot-placement error, and pre-step center-of-pressure dynamics. We hypothesize that instructional emphasis and increased postural demands will systematically alter stepping strategies and produce deviations from classical Fitts-type scaling, particularly during diagonal stepping.

Background: Safely walking through complex environments requires the use of visual information to plan and regulate steps, while managing competing cognitive demands. Age-related changes in visual control of gait and executive function may contribute to unsafe stepping behaviour, particularly under cognitive load. Route previewing may support visual motor planning, but its effects under dual task conditions in older adults are not well understood. Research Question: Does cognitive dual tasking influence gait and gaze behaviour during adaptive walking in older adults, and does previewing the walking route before gait initiation mitigate these effects? Methods: Thirty nine community dwelling older adults (Mage=73.4 years, SD=8.1; 14 male) completed four adaptive walking conditions, combining single and dual-task walking with and without previewing. Per condition, participants completed six trials across different 8-m long coloured walking routes. Gait characteristics were assessed using an instrumented walkway and video-analysis, while gaze behaviour was recorded using mobile eye tracking. Cognitive load was manipulated using a serial subtraction task. Gait and gaze outcomes were evaluated using linear mixed effects models. Results: Dual task performance significantly increased stepping errors, cross-steps, and double limb support, while reducing stride length (p < .001). It also significantly increased the number and duration of task irrelevant fixations (p < .001). After previewing, participants exhibited more efficient gaze behaviour, as evidenced by looking further ahead (larger forward gaze transitions) and fewer irrelevant gaze fixations (p < .002). Significant Task-by-Preview interactions revealed that previewing mitigated the negative effects of dual-tasking on stepping errors and cross steps (p < .001). Significance: Route previewing prior to gait initiation attenuates negative effects of cognitive load on adaptive gait in older adults, likely by supporting visual motor planning. These findings highlight the potential value of simple visual planning interventions for improving adaptive gait in older adults.

The COVID-19 pandemic led to significant disruptions in cardiovascular care and reductions in physical activity, but little is known about how exercise patterns changed after this period. This study assessed changes in weekly aerobic and strength training activity between 2020 and 2022 amongst adults aged 18 years or older who reported one or more cardiovascular diseases or risk factors. This study used National Health Interview Survey data from 2020 and 2022. Adjusted differences for moderate-to-vigorous physical activity (MVPA) were calculated using a linear regression model and for strength sessions using a Poisson regression, adjusting for sex and age. Changes in these outcomes were then stratified by age and sex subgroups. The weighted study population included 182,783,008 (standard error, +/-3,334,337) adults in 2020 and 185,388,060 (SE, +/-3,285,161) adults in 2022. Between 2020 and 2022, the overall weekly MVPA increased from 244.2 (SE, +/-4.5) minutes to 266.3 (SE, +/-5.7) minutes (adjusted difference, +22.1 [SE, +/-6.92] minutes). There were no statistically significant changes in the number of strength session per week overall or among sex and age subgroups. Across sex and age subgroups, increases in weekly MVPA were entirely concentrated among males and younger adults. The recovery from pandemic era reductions in aerobic and strength exercise training was uneven amongst demographic subgroups, which aligns with concurrent persistent disruptions in cardiovascular care.

The human pancreas secretes digestive fluid that flows through an extensive ductal network before emptying into the duodenum. However, little is known about how hydrodynamic forces influence pancreatic function and development. We hypothesized that pancreatic cells respond to physiological levels of fluid shear stress. In this study, we developed a microfluidic system featuring reversible sealing between the device layer and the cell culture substrate, enabling (1) conventional open-well cell culture prior to fluid shear stress application and (2) selective patterning of proteins and cells for migration studies. Channel dimensions were chosen to support 24-hour perfusion using standard syringe pumps. Using this platform, we investigated effects of physiological shear stress levels representing basal and activated pancreatic function (2, 8 and 33 mPa) on human iPSC-derived pancreatic progenitor cells. Pancreatic progenitor cells exhibit graded sensitivity to shear stress at the transcriptomic level. Specifically, shear stress upregulated expression of cell cycle-related gene sets; endocrine-associated genes including NEUROG3; and Notch receptor ligands (DLL1, DLL3) in a magnitude-dependent manner. The exposure to unidirectional fluid flow also resulted in a reduction in YAP1 protein content, decreased WWTR1 gene expression, and downregulation of YAP/TAZ target genes. Furthermore, barrier-based migration assays under shear stress revealed that cell patches expanded their boundaries both along and against the flow, with greater distance in the direction of flow. Our system and findings may help lay the foundation for understanding biophysical regulation of developmental processes in a physiologically important, yet hard-to-access, epithelial model system.

Background: Transthoracic echocardiography (TTE) remains the gold standard for assessing left ventricular (LV) diastolic dysfunction (DD), but noninvasive alternatives are needed to overcome geometric and acoustic limitations. 4D-Flow MRI enables comprehensive assessment of intraventricular pressure differences (IVPDs) and flow propagation velocity (VP). We aimed to evaluate 4D-Flow-derived IVPDs and VP in patients with hypertrophic cardiomyopathy (HCM). Methods: Thirty-eight HCM patients and 38 age- and sex-matched healthy controls underwent TTE and 4D-Flow MRI. Spatiotemporal maps of velocity and IVPDs, decomposed into inertial and convective components, were derived along the main inflow streamline from the mitral valve to the apex. Peak early filling rate (PEFR) was used to normalize IVPDs and VP. Results: While absolute peak flow rates were comparable, HCM patients exhibited significantly faster VP (100.4 vs. 60.2 cm/s, p < 0.01) and higher positive early E IVPD (1.40 vs. 0.92 mmHg, p < 0.01) compared to controls. Normalizing IVPDs by PEFR amplified group differences, revealing a markedly increased flow-normalized E-IVPD (5.13 vs. 2.94 x 103 mmHg.ml1.s, p < 0.001) and deeper reverse ER IVPD (-6.06 vs. -4.61 x 103 mmHg.ml1.s, p < 0.01) in HCM. These differences were primarily driven by the inertial components. Multivariable analysis demonstrated that ER IVPD is independently determined by PEFR and the TTE E/E' ratio (r = 0.65, p < 0.001). Conclusions: 4D-Flow MRI-derived, flow-normalized IVPDs and propagation velocity provide robust, noninvasive markers of altered LV chamber stiffness and impaired diastolic filling in HCM, offering deeper 3D hemodynamic insights into diastolic dysfunction.

Purpose: The aims of this study were to develop an externally validated deep learning vascular segmentation model for digital enhancement of vertebral artery dissection detection on CTA and to assess clinical utility of the model through a paired crossover reader study. Materials and Methods: This retrospective, IRB-approved study conducted from September 2024 to July 2026 included an internal training cohort of 84 manually segmented CTAs plus 17 CTAs from the RSNA Intracranial Aneurysm Challenge (101 CTAs total) and an external testing cohort of 40 CTAs (22 positive, 18 negative for vertebral artery dissection). A nnU-Net (version 2) model was trained using five-fold cross-validation with the entire training cohort. Technical performance was evaluated using the Dice similarity coefficient (DSC). A two-part crossover reader study included 10 readers who assessed diagnostic accuracy, confidence, and interpretation time with and without segmentation-based augmentation. Statistical analyses included McNemar's exact test (accuracy) and Wilcoxon signed-rank test (confidence, time), with P < .05 considered significant. Results: The model achieved a DSC of 0.96 (SD 0.01). In the reader study, diagnostic accuracy was lower with augmentation than without (0.72 vs 0.84, P < 0.001), while confidence (3.98 vs 3.96, P = .77) and interpretation time (137.3 vs 166.7 seconds, P = .54) did not differ significantly. Subjectively, 7 of 10 readers reported they would use the tool routinely in acute or trauma settings. Conclusion: Although the deep learning model demonstrated accurate segmentation of vascular structures, further validation is needed to establish its utility for enabling accurate diagnosis of VAD in fast-paced clinical settings.