nils-herrmann/clean_scirepeval huggingface dataset:
Dispersion of shoulder helical axes during upper limb movements after muscle fatigue.
Venue: Journal of biomechanics

Shoulder complex control of motion is influenced by neuromuscular function and can be quantified through the analysis of helical axes (HAs) dispersion. Muscle fatigue is a variable able to influence neuromuscular control, altering muscle activation timing and proprioception. The aim of the study was to describe shoulder complex HAs dispersion after muscle fatigue during upper limb movements of young healthy subjects. Thirty healthy right-handed volunteers (age 23.2 ± 2.6 years) were asked to perform a test made up of 15 humerothoracic flexion and rotation movements using both upper limbs in two different recording sessions. After each session, muscles of the tested movement were fatigued in isometric condition at dominant side. After fatigue, subjects repeated the test. Kinematics was recorded by an optoelectronic system and HAs dispersion was computed using Mean Distance (MD) and Mean Angle (MA) for the entire Range of Motion (RoM) and in portions of RoM. After fatigue of shoulder flexion muscles, greater MD (p = 0.001) and MA (p = 0.019) were found on the dominant side. After fatigue of shoulder rotation muscles, greater MD and MA were found on the dominant (p = 0.002 for MD; p = 0.047 for MA) and non-dominant (p = 0.038 for MD; p = 0.019 for MA) sides. Independently of fatigue, greater MA was found in portions of RoM with higher external resistance torque in flexion and rotation tasks. Muscle fatigue increases shoulder complex HAs dispersion, probably due to alteration in neuromuscular control. This data should be considered when exercise involving upper arms are proposed to subjects undergoing fatigue.
Comprehensive description of sit-to-stand motions using force and angle data.
Venue: Journal of biomechanics

A normative description of a motion details the necessary and sufficient criteria to identify that motion. It equips researchers with a shared lexicon for describing their research and, in this way, adoption of a normative description facilitates communication within the research community. Although there is an abundance of descriptions of sit-to-stand movement, there is not a commonly accepted normative description of sit-to-stand; study-specific descriptions are commonplace. This work evaluates the breadth of existing sit-to-stand descriptions using new experimental data from 15 healthy young adults standing from a 46 cm chair. Our goal is to develop a normative description of the sit-to-stand motion that is in harmony with the literature. After aligning experimental data to seat-off (the one sit-to-stand event with a clear definition), events defining the start of sit-to-stand, seat-off, and the end of sit-to-stand are identified using a density-based clustering method. Then, the intermediary events of start of seat unloading, end of momentum transfer, and beginning of stabilization are determined while maintaining consistent sequencing and biomechanical meaning. These six events of sit-to-stand are determined from trunk, hip, knee, and ankle angle data and vertical ground reaction forces. The events are in greatest accordance with the descriptions of sit-to-stand introduced by Schenkman et al. (1990) and Kralj et al. (1990), and the event timings are in alignment with the findings of other researchers. The proposed description of healthy sit-to-stand promotes consistency in the description of this motion and adoption of this description will promote effective communication in sit-to-stand research.
Three-dimensional architecture of rabbit M. soleus during growth.
Venue: Journal of biomechanics

Muscle architecture has a significant influence on the mechanical properties of skeletal muscles. Important parameters include the fascicle length, the angle of pennation, the physiological cross-sectional area (PCSA) as well as aponeurosis and tendon dimensions. During growth, skeletal muscles have to react to an increasing body mass and size demanding adaptations in muscle dimensions. Investigations of muscle architectural changes during growth are sparse, and existing studies often confine their scope to specific parameters or regions of the muscle. For this cross-sectional study, we determined the entire three-dimensional fascicle architecture of rabbit M. soleus via manual digitization. To this end, the investigations covered nine rabbits in the age-range between 29 days and 109 days. Fascicle length, muscle belly length, and aponeurosis length increased by 40%, 107%, and 111%, respectively. As the pennation angle remained almost constant and the contribution of fascicle length growth to muscle belly growth was minor, the increase in muscle mass primarily led to an increase in PCSA (462%), which required a similar increase in aponeurosis area (434%). Results gain new insight into the build-up of rabbit M. soleus and reveal that increases in muscle belly length are primarily connected to increases in aponeurosis length (83%). Contributions from fascicle length increase (17%) only play a minor role.
Quantification of spatiotemporal parameter behavior during walking speed transitions.
Venue: Journal of biomechanics

The biomechanics of constant speed walking have been well quantified, but little is known about transitions between walking speeds. Spatiotemporal behavior (step time, length, and speed) has been investigated in starting, stopping, and walking to running transitions, but speed transitions during walking have yet to be investigated. This study quantified the spatiotemporal parameter behavior during walking speed transitions with a range of magnitudes (or differences between pre- and post-transition normalized speeds ranging from 0.03 to 0.13, or approximately 1.18 m/s to 1.58 m/s). 23 healthy adults walked on a treadmill at five different constant speeds for one minute each to establish a baseline. They then performed walking speed transitions, in which they walked on the treadmill as it randomly changed between the five speeds. Linear mixed effect models showed that subjects converged to slightly different post-transition step time and step length averages than established in the constant speed baseline, but the differences are likely too small to be meaningful (on the order of 0.01 s and 0.01 m). When diverging from the pre-transition speed, subjects either diverged in only step time (with step length remaining the same), only step length (with step time remaining the same), or both step time and step length to reach the post-transition speed, with the behavior strongly tied to the magnitude of the speed transition (p<0.001). Step time often overshot the new value before converging. The number of steps required for each parameter to converge increased with increasing transition magnitude (p<0.001) and was consistently higher at all magnitudes for speed than step time and length (p<0.001). In summary, transition magnitude affected the spatiotemporal behavior during walking speed transitions. Further, step time, length, and speed all exhibited slightly different divergence and convergence behavior during transitions.
Classification of runners' performance levels with concurrent prediction of biomechanical parameters using data from inertial measurement units.
Venue: Journal of biomechanics

Identification of runner's performance level is critical to coaching, performance enhancement and injury prevention. Machine learning techniques have been developed to measure biomechanical parameters with body-worn inertial measurement unit (IMU) sensors. However, a robust method to classify runners is still unavailable. In this paper, we developed two models to classify running performance and predict biomechanical parameters of 30 subjects. We named the models RunNet-CNN and RunNet-MLP based on their architectures: convolutional neural network (CNN) and multilayer perceptron (MLP), respectively. In addition, we examined two validation approaches, subject-wise (leave-one-subject-out) and record-wise. RunNet-MLP classified runner's performance levels with an overall accuracy of 97.1%. Our results also showed that RunNet-CNN outperformed RunNet-MLP and gradient boosting decision tree in predicting biomechanical parameters. RunNet-CNN showed good agreement (R2 > 0.9) with the ground-truth reference on biomechanical parameters. The prediction accuracy for the record-wise method was better than the subject-wise method regardless of biomechanical parameters or models. Our findings showed the viability of using IMUs to produce reliable prediction of runners' performance levels and biomechanical parameters.
Application of level-set method in simulation of normal and cancer cells deformability within a microfluidic device.
Venue: Journal of biomechanics

Application of microfluidic systems for the study of cellular behaviors has been a flourishing area of research in the past decade. In the process of probing cell biomechanics the passage of a cell through a narrow microchannel or a small pore has attracted much attention during the recent years. And the study of cellular deformability and transportability using these systems with enhanced resolution and accuracy has opened a new paradigm for high-throughput characterization of both healthy and diseased cell populations.Here we use the level-set method to explore the relationship between the transit time and mechanical properties of normal white blood cells (WBCs) and breast cancer epithelial cells (MCF7) under different microenvironmental parameters (i.e., pressure difference, cell size, effective cell surface tension, constriction size and taper angle) in a 2-D computational domain by considering the cell as a viscous drop. The novel biomechanical relations are obtained for each cell type by the Response Surface Method (RSM), relating microenvironmental parameters to the dimensionless entry time of the normal and cancer cells. Our results revealed that MCF7 cells show asignificantly different behavior (a bifurcating behavior when the pressure difference of inlet/outlet increases) in regards to the dimensionless entry time as a function of microchannel taper angle in comparison with the WBC. These results suggest that the microenvironmental parameters have a significant effect on the transportability of the cells and different cells have different behaviors in response to a specific microenvironmental parameter. Finally, it can be claimed that this method can be also utilized to distinguish between benign and cancerous cells or even to probe tumor heterogeneity toward high throughput cell cytometry.
An individualized gait pattern prediction model based on the least absolute shrinkage and selection operator regression.
Venue: Journal of biomechanics

Gait pattern prediction is an essential function of individualized motion control of the lower-limb exoskeleton. This paper presents a novel gait pattern prediction model based on the least absolute shrinkage and selection operator (LASSO) regression. Gait data were collected from one hundred and twenty healthy young adults (78 males and 42 females), who were instructed to walk back and forth on a 12-meter-long walking platform while having their heel strike coinciding with the beat of a metronome. The lower-limb joint (i.e., the hip, knee and ankle) angular kinematics were segmented, resampled and transformed into Fourier coefficients. The LASSO regression model with age, gender and 14 anthropometric parameters as prediction variables was trained and used to estimate the Fourier coefficients which were then applied in the lower-limb joint angle trajectory reconstruction. The results showed that the root mean square errors between the actual and predicted joint angle trajectories ranged from 3.41° to 4.55°. The parameters of the linear fit method further revealed the waveform similarity between the actual and predicted joint angle time series. These results suggested that the proposed model was able to accurately predict lower-limb joint kinematics during gait. Application of the proposed model can help resolve the overfitting problem, and provides a new solution to individualized gait pattern prediction.
Inverse solution of corneal material parameters based on non-contact tonometry: A comparative study of different constitutive models.
Venue: Journal of biomechanics

Assessing the biomechanical properties of the cornea in vivo is important for predicting the outcome of refractive surgery, and for controlling the risk of postoperative complications. In this study, we examined the impact of corneal mechanical properties (nonlinearity and anisotropy) on the inverse solution of corneal material parameters based on the non-contact tonometry ("air puff") test. Finite element models with different constitutive models (linear-elastic, isotropic hyperelastic, and fiber-dependent) were established to simulate the non-contact tonometry test. The results showed that the corneal nonlinear mechanical property and fiber distribution had significant effects on the corneal deflection profile. These findings may help in constructing an appropriate inverse solution strategy when using the inverse finite element method and in identifying individual differences in the corneal matrix shear modulus and fiber stiffness.
The relationship between alignment, function and loading in total knee replacement: In-vivo analysis of a unique patient population
Venue: Journal of biomechanics

The purpose of this study was to quantify the effect of total knee replacement (TKR) alignment on in-vivo knee function and loading in a unique patient cohort who have been identified as having a high rate of component mal-alignment. Post-TKR (82.4 ± 6.7 months), gait analysis was performed on 25 patients (27 knees), to calculate knee kinematics and kinetics. For a step activity, video fluoroscopic analysis quantified in-vivo implant kinematics. Frontal plane lower-limb alignment was defined by the Hip-Knee-Ankle angle (HKA) measured on long leg static X-rays. Transverse plane component rotation was calculated from computed tomography scans. Sagittal plane alignment was defined by measuring the flexion angle of the femoral component and the posterior tibial slope angle (PTSA). For gait analysis, a more varus HKA correlated with increased peak and dynamic joint kinetics, predicting 47.6% of Knee Adduction Angular Impulse variance. For the step activity, during step-up and single leg loaded, higher PTSA correlated with a posterior shift in medial compartment Anterior-Posterior (AP) translation. During step-down, higher PTSA correlated with reduced lateral compartment AP translation with a posterior shift in AP translation in both compartments. A more varus HKA correlated with a more posterior medial AP translation and inter-component rotation was related to transverse plan range of motion. This in-vivo study found that frontal plane lower-limb alignment had a significant effect on joint forces during gait but had minimal influence on in-vivo implant kinematics for step activity. PTSA was found to influence in-vivo TKR translations and is therefore an important surgical factor.
Trunk stiffness decreases and trunk damping increases with experimental low back pain.
Venue: Journal of biomechanics

Movement adaptations to low back pain (LBP) are believed to protect the painful area. Increased trunk stiffness and decreased trunk damping have been shown in people with recurrent LBP. However, no study has examined these properties using external force perturbations to the trunk during acute LBP when protective adaptations might be expected to have most relevance. Adaptations to an acute painful stimulus via unilateral injection of hypertonic saline into the right longissimus muscle were assessed using a trunk force perturbation paradigm and a mass-spring-damper model to describe effective trunk dynamical properties. Equal weights (15% body weight) were connected to the front and back of the trunk via a cable. Either one was dropped at random to perturb the trunk. Effective trunk dynamical properties were estimated in fourteen males (mean (standard deviation) age 25 (6) years) assuming that trunk movement can be modelled as a second order linear system. Effective trunk dynamical properties were compared before, during and after the experimentally induced painful period. Estimates of effective trunk stiffness (K) decreased and damping (B) increased during pain compared to both before ([mean contrast, 95% CI] K: -403 [-651 to -155] Nm-1, B: 28 [9-50] Nms-1) and after (K: -324 [-58 to -591] Nm-1, B: 20 [4-33] Nms-1) the experimentally induced painful period. We interpret our results to show that, when challenged by a step force perturbation, a healthy system adapts to noxious input by controlling trunk velocity rather than trunk displacement, in contrast to observations during remission from recurrent clinical LBP.
Racial differences in gait mechanics.
Venue: Journal of biomechanics

The effect of race has rarely been investigated in biomechanics studies despite racial health disparities in the incidence of musculoskeletal injuries and disease, hindering both treatment and assessment of rehabilitation. The purpose of this study was to test the hypothesis that racial differences in gait mechanics exist between African Americans (AA) and white Americans (WA). Ninety-two participants (18-30 years old) were recruited with equal numbers in each racial group and sex. Self-selected walking speed was measured for each participant. 3D motion capture and force plate data were recorded during 7 walking trials at regular and fast set speeds. Step length, step width, peak vertical ground reaction force, peak hip extension, peak knee flexion, and peak ankle plantarflexion were computed for all trials at both set speeds. Multivariate and post-hoc univariate ANOVA models were fit to determine main and interaction effects of sex and race (SPSS V26, α = 0.05). Self-selected walking speed was slower in AA (p = 0.004, ƞp2 = 0.088). No significant interactions between race and sex were identified. Males took longer steps (regular: p < 0.001, ƞp2 = 0.288, fast: p < 0.001, ƞp2 = 0.193) and had larger peak knee flexion (regular: p = 0.007, ƞp2 = 0.081, fast: p < 0.001, ƞp2 = 0.188) and ankle plantarflexion angles (regular: p = 0.050, ƞp2 = 0.044, fast: p = 0.049, ƞp2 = 0.044). Peak ankle plantarflexion angle (regular: p = 0.012, ƞp2 = 0.071, fast: p < 0.001, ƞp2 = 0.137) and peak hip extension angle during fast walking (p = 0.007, ƞp2 = 0.083) were smaller in AA. Equivalency in gait measures between racial groups should not be assumed. Racially diverse study samples should be prioritized in the development of future research and individualized treatment protocols.
Development of a hip joint mathematical model to assess implanted and non-implanted hips under various conditions.
Venue: Journal of biomechanics

While total hip arthroplasty does generally improve patient quality of life, current systems can still yield atypical forces, premature component wear, and abnormal kinematics compared to native joints. Specifically, common complications include instability, separation, sliding, and edge loading within the hip joint. Unfortunately, evaluating potential solutions to these issues can be costly and time-consuming. Fortunately, mathematical modeling is an accurate and efficient tool that can be used to evaluate potential solutions. A forward dynamics mathematical model of the hip allows users to virtually insert a hip implant into a theoretical patient and observe the predicted postoperative mechanics. The objective of this study is therefore to develop, validate, and use a fully functional forward solution mathematical model that allows for a comparison between various hip implant designs and a determination of factors leading to in vivo hip separation, instability, and edge loading. The model presented herein has been validated kinetically against telemetric data and kinematically against fluoroscopic data. It was determined through this research that shifting of the joint rotation center during total hip arthroplasty has the potential to yield postoperative instability, and surgical errors can exacerbate these outcomes. However, the relationships between subject-specific joint shifting and hip instability are extremely complex, and therefore it becomes essential for surgeons to focus on implanting components as accurately as possible to minimize these risks.
Time-course of axial residual strain remodeling and layer-specific thickening during aging along the human aorta.
Venue: Journal of biomechanics

Detailed estimation of axial residual strains in the human aorta is necessary when performing biomechanical analyses of physiologic functions and pathologic conditions. We recently published such data for autopsied aortas and the present aim was to measure axial residual stretches at different wall depths, along with layer thicknesses on images borrowed from that work. Residual stretches at the external surface and medial-adventitial interface increased along the aorta's ascending course, decreased along its descending course, and increased from the diaphragm toward the iliac arteries. Residual stretches at the intimal-medial interface and internal surface decreased down the distal one-third of the aorta. A continuous decrease in medial thickness was witnessed along the vessel, whereas intimal and adventitial thickness remained fairly stable. At some axial locations, smaller were the axial residual stretches of the outer than those of the other quadrants, with minor differences in layer-specific thicknesses among quadrants. Adventitial thickness did not vary with age, while the intima and media thickened considerably with different time-courses. The observed intimal thickening solely between young (≤40 yr) and middle-aged subjects (40-60 yr) is consistent with the increased circumferential residual stretches previously established by our group between those subject groups and the minimal further increase in old subjects (≥60 yr). The observed medial thickening between middle-aged and old subjects was accompanied by decreased axial residual stretches that were not seen between young and middle-aged subjects. These observations suggest distinct roles for the intima and media in determining circumferential and axial residual stretches that merit further attention.