nils-herrmann/clean_scirepeval huggingface dataset:
Mechanical difference of left ventricle between rabbits of myocardial infarction and hypertrophy.
Venue: Journal of biomechanics

The analysis of cardiac wall stress is of importance to understand the development of heart failure (HF). The aim of the study is to carry out the cardiac mechanics analysis to show the changes of left ventricular (LV) wall stresses after LV hypertrophy (LVH) and myocardial infarction (MI). Here, LVH and MI were generated in rabbit hearts through the transverse aortic constriction (TAC) and the distal left circumflex (LCx) artery ligation operations, respectively. Physiological and CT measurements were carried out at postoperative 2 and 4 weeks, based on which a finite element (FE) model was developed to perform the mechanics computation. We found a gradual increase of end-diastolic myofiber stress in free wall and interventricular septum of LVH and MI (higher stress in the free wall than the septum). In the interventricular septum, the 4-weeks LVH group has the highest ED myofiber stresses (11.378 ± 3.022 kPa), while the 4-weeks MI group has the highest ED myofiber stresses (13.494 ± 2.835 kPa) in the free wall. LVH increased myocardial volume (3.49 ± 0.07 and 4.52 ± 0.26 ml at postoperative 2 and 4 weeks) while MI increased LV volume (from 2.75 ± 0.29 to 4.19 ± 0.27 ml). LVH and MI had different distributions of local myofiber stress.
A new anisotropic soft tissue model for elimination of unphysical auxetic behaviour.
Venue: Journal of biomechanics

Auxetic behaviour, the unphysical transverse expansion during uniaxial tension, is a common and undesirable feature of classical anisotropic hyperelastic constitutive models for soft tissue. In this study we uncover the underlying mechanism of such behaviour; high levels of in-plane compaction occurs due to increasing tension in strain-stiffening fibres, leading to unphysical out-of-plane expansion. We demonstrate that auxetic behaviour is primarily influenced by the ratio of fibre to matrix stiffness, and is accentuated by strain-stiffening fibres in a constant stiffness matrix (e.g., the widely used neo-Hookean matrix with exponentially stiffening fibres). We propose a new bilinear strain stiffening fibre and matrix (BLFM) model which allows close control of the fibre-matrix stiffness ratio, thereby robustly eliminating auxetic behaviour. We demonstrate that our model provides accurate prediction of experimentally observed out-of-plane compaction, in addition to stress-stretch anisotropy, for arterial tissue subjected to uniaxial tension testing.
Center of pressure predicts Intra-limb compensatory patterns that shift demands away from knee extensors during squatting.
Venue: Journal of biomechanics

The persistence of knee extensor moments deficits following anterior cruciate ligament reconstruction (ACLr) may be attributed to difficulty quantifying inter- and intra-limb compensations clinically. Force plate derived center of pressure (CoPpos) and vertical force (vGRF) may provide valuable information regarding limb and joint loading impairments in this group. This study aimed to determine the: 1) relationship between measures CoPpos and intra-limb extensor moment distribution during a squat, and 2) utility of using CoPpos and vGRF to estimate knee extensor moment deficits post-ACLr. Twenty-four individuals, 142 ± 22.5 days post-ACLr, performed bilateral squats. Ankle (aEXT), knee (kEXT) and hip (hEXT) extensor moments were calculated using three-dimensional kinematics and GRF. Moments, CoPpos and vGRF were identified at peak kEXT. Intra-limb moment distribution was characterized using hEXT/kEXT and aEXT/kEXT ratios. Linear regressions analyzed relationships between CoPpos and hEXT/kEXT and aEXT/kEXT. Stepwise regressions determined if between-limb CoPpos ratio predicted between-limb ratios of hEXT/kEXT and aEXT/kEXT. Stepwise regression determined if between-limb CoPpos and vGRF ratios predicted between-limb kEXT ratio. Results found that CoPpos predicts intra-limb moment distribution (hEXT/kEXT and aEXT/kEXT); more anterior CoPpos related to higher moments at the hip and ankle relative to the knee. In addition, between-limb CoPpos ratio predicts between-limb ratio of hEXT/kEXT and aEXT/kEXT ratios. Together between-limb CoPpos (52%) and vGRF (18%) ratios explained 70% of the variance in between-limb kEXT ratios (R2 = 0.70, p < 0.001). These data suggest that force plate derived CoPpos and vGRF may be important for detection of knee extensor moment deficits in individuals post-ACLr.
Progressive deformation-induced degradation of knee articular cartilage and osteoarthritis.
Venue: Journal of biomechanics

Articular cartilage (AC) is a dense connective tissue in the diarthrodial joints. Osteoarthritis is a disease associated with progressive changes in the tissue structure which affects mechanical properties of the tissue. Experimental studies show that abnormal/excessive mechanical loading or changes in biochemical composition can alter the structure which leads to degradation and loss of stiffness. In this study, deformation-induced degradation of human knee articular cartilage is investigated by conducting excessive deformations and inspecting progressive changes in mechanical properties of the tissue. Evolution of the properties is formulated to predict the amount of damage and consequently to connect the loss of stiffness to the grade of osteoarthritis. It is shown that, for tensile strains up to almost 15%, the tissue may recover its initial properties without permanent damage but for higher deformations degradation is expected. The proposed model is not confined to tension as the evolution laws are expressed in a 3D framework. The model predicts higher thresholds for compression and shear (25-30%) which is in good correlation with experimental investigations. It is concluded that, modelling the alterations of mechanical properties can be an effective method for predicting degradation of the AC under excessive loading and its connection to the associated diseases.
Large-deformation strain energy density function for vascular smooth muscle cells.
Venue: Journal of biomechanics

Vascular tissue exhibits marked mechanical nonlinearity when exposed to large strains. Vascular smooth muscle cells (VSMCs) are the most prevalent cell type in the artery wall, but it is unclear how much of the vessel nonlinearity is attributable to VSMCs. Here, we used cellular microbiaxial stretching (CμBS) to measure the large-strain mechanical properties of individual VSMCs. We find that the mechanical properties of VSMCs with native-like architectures are highly anisotropic, due to their highly aligned actomyosin cytoskeletons, and that inhibition of actomyosin contraction with rho-associated kinase inhibitor HA-1077 results in nearly isotropic material properties. We further find that when VSMCS are exposed to large strains (up to 60% stretch), the cells' stress-strain behavior is surprisingly linear. Finally, we modified a previously published Holzapfel-Gasser-Ogden type strain energy density function to characterize individual VSMCs, to account for the observed large-deformation linearity. These data have important implications in the development of models of vascular mechanics and mechanobiology.
Blood flow simulations in patient-specific geometries of the carotid artery: A systematic review.
Venue: Journal of biomechanics

Computational Fluid Dynamics (CFD) and Fluid-Structure Interaction (FSI) are currently widely applied in the study of blood flow parameters and their alterations under pathological conditions, which are important indicators for diagnosis of atherosclerosis. In this manuscript, a systematic review of the published literature was conducted, according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, on the simulation studies of blood flow in patient-specific geometries of the carotid artery bifurcation. Scopus, PubMed and ScienceDirect databases were used in the literature search, which was completed on the 3rd of August 2020. Forty-nine articles were included after the selection process and were organized in two distinct categories: the CFD studies (36/49 articles), which comprise only the fluid analysis and the FSI studies (13/49 articles), which includes both fluid and Fluid-Structure domain in the analysis. The data of the research works was structured in different categories (Geometry, Viscosity models, Type of Flow, Boundary Conditions, Flow Parameters, Type of Solver and Validation). The aim of this systematic review is to demonstrate the methodology in the modelling, simulation and analysis of carotid blood flow and also identify potential gaps and challenges in this research field.
Balance control during stair descent on compliant surface is associated with knee flexor and ankle plantar flexor strength in older adults.
Venue: Journal of biomechanics

Balance and lower limb strength deficits are associated with a high incidence of falls in older adults. This study investigated the association between balance control during and after stair descent onto a compliant surface and lower limb strength. Thirty-five women and 14 men participated in this study. Stair descent time, mean center of pressure velocity in anteroposterior and mediolateral direction during stair descent (CoP VAP and CoP VML), and CoP velocity in the first 5 s of restabilization phase (CoP V5) were evaluated. Bilateral strength of the knee flexors and extensors, and ankle plantar and dorsal flexors was evaluated. Spearman correlation analysis with Bonferroni correction yielded a significant association between the strength of the knee flexors on the trailing limb and stair descent time in women (r = 0.502, p = 0.002, R2 = 0.246). The same analysis in men revealed a significant association between the strength of the knee flexors on the trailing limb and CoP VAP (r = -0.820, p < 0.001, R2 = 0.280) and CoP VML (r = -0.697, p = 0.006, R2 = 0.359). The strength of the ankle plantar flexors on the trailing limb was significantly associated with stair descent time (r = 0.684, p = 0.007, R2 = 0.429) and CoP VAP (r = -0.723, p = 0.003, R2 = 0.408) in men. Stair descent balance control is associated with knee flexion strength on trailing limb in women, and with ankle plantar flexion and knee flexion strength on the same limb in men.
A patient-specific modelling method of blood circulatory system for the numerical simulation of enhanced external counterpulsation.
Venue: Journal of biomechanics

Lumped parameter model (LPM) is a common numerical model for hemodynamic simulation of human's blood circulatory system. The numerical simulation of enhanced external counterpulsation (EECP) is a typical biomechanical simulation process based on the LPM of blood circulatory system. In order to simulate patient-specific hemodynamic effects of EECP and develop best treatment strategy for each individual, this study developed an optimization algorithm to individualize LPM elements. Physiological data from 30 volunteers including approximate aortic pressure, cardiac output, ankle pressure and carotid artery flow were clinically collected as optimization objectives. A closed-loop LPM was established for the simulation of blood circulatory system. Aiming at clinical data, a sensitivity analysis for each element was conducted to identify the significant ones. We improved the traditional simulated annealing algorithm to iteratively optimize the sensitive elements. To verify the accuracy of the patient-specific model, 30 samples of simulated data were compared with clinical measurements. In addition, an EECP experiment was conducted on a volunteer to verify the applicability of the optimized model for the simulation of EECP. For these 30 samples, the optimization results show a slight difference between clinical data and simulated data. The average relative root mean square error is lower than 5%. For the subject of EECP experiment, the relative error of hemodynamic responses during EECP is lower than 10%. This slight error demonstrated a good state of optimization. The optimized modeling algorithm can effectively individualize the LPM for blood circulatory system, which is significant to the numerical simulation of patient-specific hemodynamics.
From perviousness to permeability, modelling and measuring intra-thrombus flow in acute ischemic stroke.
Venue: Journal of biomechanics

Thrombus permeability determines blood flow through the occluding thrombus in acute ischemic stroke (AIS) patients. The quantification of thrombus permeability is challenging since it cannot be directly measured nor derived from radiological imaging data. As a proxy of thrombus permeability, thrombus perviousness has been introduced, which assesses the amount of contrast agent that has penetrated the thrombus on single-phase computed tomography angiography (CTA). We present a method to assess thrombus permeability rather than perviousness. We follow a three-step approach: (1) we propose a theoretical channel-like structure model describing the thrombus morphology. Using Darcy's law, we provide an analytical description of the permeability for this model. According to the channel-like model, permeability depends on the number of channels in the thrombus, the radius of the occluded artery, and the void fraction representing the volume available for the blood to flow; (2) we measure intra-thrombus blood flow and velocity on dynamic CTA; and (3) we combine the analytical model with the dynamic CTA measurements to estimate thrombus permeability. Analysis of dynamic CTA data from 49 AIS patients showed that the median blood velocity in the thrombus was 0.58 (IQR 0.26-1.35) cm/s. The median flow within the thrombus was 3.48 · 10-3 (IQR 1.71 · 10-3-9.21 · 10-3) ml/s. Thrombus permeability was of the order of 10-3-10-5 mm2, depending on the number of channels in the thrombus. The channel-like thrombus model offers an intuitive way of modelling thrombus permeability, which can be of interest when studying the effect of thrombolytic drugs.
Sports bra but not sports footwear decreases breast movement during walking and running.
Venue: Journal of biomechanics

Running is a modality that has a large number of adepts, including women. Therefore, it is important to understand how sportswear can help women, with special attention to the breast movement. The aim of this study was to analyse the effect of different combinations of breast support and footwear on the breast movement during walking and running. Twenty women performed treadmill walking (5 km/h) and running (7 and 10 km/h) combining different footwear (barefoot, minimalist, and traditional) and breast support conditions (bare breast, everyday bra, and sports bra). Three-dimensional data from breast and trunk markers were tracked for 10 stride cycles. Relative breast displacement was calculated and derived for velocity. An interaction effect was observed between support, footwear, and speed conditions. The bare breast conditions presented differences from the other conditions in the majority of the kinematic variables, presenting higher breast displacement and velocity values. On the other hand, the sports bra conditions presented the lowest values for the kinematics variables. In the vertical component of breast displacement during running (10 km/h) we verified that the sports bra presented reductions of 56% and 43% in relation to the bare breast and everyday bra conditions, respectively. Despite this, no differences were found between footwear within each breast support condition. A sports bra is efficient to decrease breast movement. In addition, neither of the tested footwear was able to decrease these movements.
Novel isodamping dynamometer accurately measures plantar flexor function.
Venue: Journal of biomechanics

Isokinetic dynamometers are the gold standard tools used to assess in vivo joint and muscle function in human subjects, however, the large size and high cost of these devices prevents their widespread use outside of traditonal biomechanics labs. In this study, we developed a mobile dynamometer to allow for field measurements of joint level function. To ensure subject safety, we designed a new "isodamping" dynamometer that acted as passive energy sink which constrains velocity by forcing incompressible oil through an orifice with an adjustable diameter. We validated the performance of this device by testing plantar flexor function in six healthy adults on both a commercial isokinetic dynamometer and this novel device at three velocities/damper settings and at three different effort levels. During maximal effort contraction, measurements of peak moment and velocity at peak moment of the novel device and the commercial device were strongly correlated along the predicted quadratic line (R2 > 0.708, p ≤ 0.008). The setting of the damper prescribed the relationship between peak moment and velocity at peak moment across all subjects and effort levels (R2 > 0.910, p < 0.001). The novel device was significantly smaller (0.75 m2 footprint), lighter (30 kg), and lower cost (~$2,200 US Dollars) than commercial devices compared to commercially-available isokinetic dynamometers (5.95 m2 footprint, 450 kg, and ~$40,000 US Dollars respectively).
A joint kinematics driven model of the pelvic soft tissue artefact.
Venue: Journal of biomechanics

When skin-markers trajectories are used in human movement analysis, compensating for their relative movement with respect to the underlying bone (soft tissue artefact, STA) is essential for accurate bone-pose estimation; information about the artefact is required in the form of a mathematical model. Such model, not available for pelvic artefacts, could allow pelvic STA compensation in routine gait analysis by embedding it in skeletal kinematics estimators and developing ad-hoc optimization problems for the estimate of subject-specific model parameters. It was developed as driven by adjacent body segment kinematics. Model architecture feasibility was tested; its compensation effectiveness was assessed evaluating the error in pelvic orientation after removing the modelled artefact from the measured one. Five volunteers with a wide body mass range (BMI: 22-37) underwent MRI scans to reconstruct subject-specific pelvic digital bone models. Multiple anatomical calibrations performed in different static postures, as occurring during walking and star-arc movements, registering the bone-models with points digitized through stereophotogrammetry over pelvic bony prominences, allowed to define the relevant poses of a pelvis-embedded anatomical coordinate system. Such approach allowed to measure STAs over several pelvic anatomical landmarks, for each posture and subject. Model parameters were estimated by minimizing the least squares difference between measured and modelled STAs. The measured STAs were appropriately modelled with subject-specific calibrations, both in terms of shape (correlation coefficient: median [inter-quartile-range]: 0.72 [0.36]) and amplitude (root mean square residual: 3.0 [3.2] mm). Consequently, the overall error in pelvic orientation vector (5.1 [4.4] deg) was reduced after removing the modelled artefacts (2.5 [1.9] deg).
Evaluating the mechanical response of novel synthetic femurs for representing osteoporotic bone.
Venue: Journal of biomechanics

Osteoporosis is a disease prevalent in older adults, characterized by high porosity in bone and subsequent decrease in fracture resistance. This demographic is also the population that most frequently receives devices such as hip implants. However, high porosity complicates surgery and reduces the fixation and effectiveness of orthopaedic devices, which are typically designed using cadaveric specimens from the general population. Synthetic bones are also used in the design of such devices but need to represent the properties of the patient population. Thus, the mechanical response of two iterations of novel synthetic femurs were evaluated for their ability to represent osteoporotic cadaveric specimens and were tested and compared against cadaveric specimens across four loading modes. The first iteration had reduced density and wall thickness compared to standard models and was typically too rigid or too stiff to be a feasible alternative to cadaveric specimens. The second iteration, with similarly reduced wall thickness and further reduced density, was quite representative, with no statistical differences identified against the cadaveric specimens in any loading mode, except in screw pullout. Such a model can provide a foundation for the development of orthopaedic devices better suited to osteoporotic bone, potentially improving surgical outcomes, reducing medical expense, and improving quality of life for patients.
Using the loading response peak for defining gait cycle timing: A novel solution for the double-belt problem.
Venue: Journal of biomechanics

Split-belt treadmills (SBTM) contain force plates under each belt that measure ground reaction force (GRF). Initial contact (IC) detection for each gait cycle obtained from the GRF is used for calculating temporal gait parameters (e.g., gait variability, step time, stride time). Occasionally, the participant steps with one leg on the contralateral belt (i.e., crossing) making the IC undetectable and the calculation of temporal gait parameters are compromised. We term this the double-belt problem (DBP).



here we developed a complementary detection method using the loading response peak (LRP), anchor point for calculating gait parameters.



we used GRF gait data from twenty adults (age 56.45 ± 4.81 y; 6 males) who walked on an SBTM. First, we used no-crossing gait periods free of the DBP to calculate stride time, step time, and stride time to stride time coefficient of variation and evaluated the true error and the normalized true error of the LRP detection method. Then, we used multiple comparisons between no-crossing data and crossing data.



we found that normalized errors (in comparison to the IC method) are ≤5.1%. Strong correlations were found between gait parameters computed based on the two detection methods (Intraclass correlation coefficient ≥0.97; p ≤ 0.001).



detecting gait cycle timing based on the LRP detection method is reliable for estimating temporal gait parameters, demonstrating high correspondence with the gold standard IC detection method.
Eccentric exercise and delayed onset muscle soreness reduce the variability of active cervical movements.
Venue: Journal of biomechanics

People with acute neck pain commonly present with restricted neck movement. However, it is unknown whether the presence of acute pain affects the quality of neck movement, specifically neck movement variability. We examined the effects of acute neck muscle soreness induced via eccentric exercise in healthy volunteers, on the variability of neck movement by examining changes in parameters of the helical axis during active neck movements. An experimental, single-arm repeated measures study recruited 32 healthy participants, male and female, aged between 18 and 55 years. Repetitive active neck movements (flexion-extension, bilateral lateral flexion and bilateral rotation) were performed at different speeds, either at full range of motion (RoM) or restricted to 45° RoM at baseline, pre-exercise (T0), immediately following eccentric neck exercise (T1), 24 h (T2) and 48 h post-exercise (T3). The mean distance (MD) and mean angle (MA) parameters of the helical axis were extracted to quantify movement variability. MD, measured during movements performed at full RoM, reduced significantly at T2 compared to T0 (P = 0.001) regardless of direction or speed of movement. MA was significantly lower at T2 and T3 compared to T1 (P = 0.029 and P = 0.033, respectively). When RoM was restricted to 45°, significantly lower MD values were observed at T3 compared to T1 (P = 0.034), and significantly lower MA values were measured at T3 compared to T0, T1 and T2 (all P < 0.0001). This study uniquely demonstrates that neck movement variability is reduced immediately after, 24 h and 48 h after eccentric exercise, indicating that acute neck muscle soreness modifies the quality of neck movement.