nils-herrmann/clean_scirepeval huggingface dataset:
Impact of transversal calf muscle loading on plantarflexion.
Venue: Journal of biomechanics

Muscle compression commonly occurs in daily life (for instance wearing backpacks or compression garments, and during sitting). However, the effects of the compression on contraction dynamics in humans are not well examined. The aim of the study was to quantify the alterations of contraction dynamics and muscle architecture in human muscle with external transverse loads. The posterior tibialis nerve of 29 subjects was stimulated to obtain the maximal double-twitch force of the gastrocnemius muscle with and without transverse compression that was generated using an indentor. The muscle architecture was determined by a sonographic probe that was embedded within the indentor. Five stimulations each were conducted at 5 conditions: (1) pretest (unloaded), (2) indentor loading with 2 kg, (3) 4.5 kg, (4) 10 kg, and (5) posttest (unloaded). Compared to the pretest maximal force decreased by 9%, 13% and 16% for 2 kg, 4.5 kg and 10 kg, respectively. The half-relaxation time increased with increased transverse load whereas the rate of force development decreased from pretest to 2 kg and from 4.5 kg to 10 kg. The lifting height of the indentor increased with transverse load from 2 kg to 4.5 kg but decreased from 4.5 kg to 10 kg. Increases in pennation during the twitches were reduced at the highest transverse load. The results demonstrate changes of the contraction dynamics due to transversal muscle loading. Those alterations are associated with the applied pressure, changes in muscle architecture and partitioning of muscle force in transversal and longitudinal direction.
Validity of a novel method to measure vertical oscillation during running using a depth camera.
Venue: Journal of biomechanics

Recent advancements in low-cost depth cameras may provide a clinically accessible alternative to conventional three-dimensional (3D) multi-camera motion capture systems for gait analysis. However, there remains a lack of information on the validity of clinically relevant running gait parameters such as vertical oscillation (VO). The purpose of this study was to assess the validity of measures of VO during running gait using raw depth data, in comparison to a 3D multi-camera motion capture system. Sixteen healthy adults ran on a treadmill at a standard speed of 2.7 m/s. The VO of their running gait was simultaneously collected from raw depth data (Microsoft Kinect v2) and 3D marker data (Vicon multi-camera motion capture system). The agreement between the VO measures obtained from the two systems was assessed using a Bland-Altman plot with 95% limits of agreement (LOA), a Pearson's correlation coefficient (r), and a Lin's concordance correlation coefficient (rc). The depth data from the Kinect v2 demonstrated excellent results across all measures of validity (r = 0.97; rc = 0.97; 95% LOA = -8.0 mm - 8.7 mm), with an average absolute error and percent error of 3.7 (2.1) mm and 4.0 (2.0)%, respectively. The findings of this study have demonstrated the ability of a low cost depth camera and a novel tracking method to accurately measure VO in running gait.
Is the sheep a suitable model to study the mechanical alterations of disc degeneration in humans? A probabilistic finite element model study.
Venue: Journal of biomechanics

Intervertebral disc degeneration is one major source of low back pain, which because of its complex multifactorial nature renders the treatment challenging and thus necessitates extensive research. Experimental animal models have proven valuable in improving our understanding of degenerative processes and potentially promising therapies. Currently, the sheep is the most frequently used large animal in vivo model in intervertebral disc research. However, despite its undoubted value for investigations of the complex biological and cellular aspects, to date, it is unclear whether the sheep is also suited to study the mechanical aspects of disc degeneration in humans. A parametric finite element (FE) model of the L4-5 spinal motion segment was developed. Using this model, the geometry and the material properties of both the human and the ovine spinal segment as well as different appearances of disc degeneration can be depicted. Under pure and combined loads, it was investigated whether degenerative changes to both the human and the ovine model equivalent caused the same mechanical response. Different patterns of degeneration resulted in large variations in the ranges of motion, intradiscal pressure, ligament and facet loads. In the human, but not in the ovine model, all these results differed significantly between different degrees of degeneration. This FE model study highlighted possible differences in the mechanical response to disc degeneration between human and ovine intervertebral discs and indicates the necessity of further, more detailed, investigations.
Muscle volume reconstruction from several short magnetic resonance imaging sequences.
Venue: Journal of biomechanics

The gold standard to determine muscle morphological parameters is magnetic resonance imaging (MRI). To measure large muscles like the vastus lateralis (VL) in one sequence, scanners with a large field of view (FOV) and a high flux density are needed. However, large scanners are expensive and not always available. The purpose of the current study was to develop a marker-based approach to reconstruct the VL from several separate MRI sequences, acquired with a low-field MRI scanner. The VL muscle of 21 volunteers was marked at one-third and two-third of thigh length using fish oil capsules. Three consecutive MRI sequences (i.e. proximal, medial and distal part) of the thigh were captured between the markers and the muscle insertion and origin. After a manual segmentation of the VL the muscle was reconstructed using the developed approach. The muscle volume, maximal anatomical cross-sectional area and length were 715.1 ± 93.4 cm3, 34.0 ± 4.0 cm2 and 34.4 ± 2.2 cm respectively. The procedure showed an average error between 0.9% and 2.2% for the reconstructed muscle volume, the averaged RMSD between the cross-sectional areas of two overlapping sequences were between 0.80 ± 0.71 cm2 and 0.88 ± 0.78 cm2. The proposed approach provides an appropriate accuracy for muscle volume assessment, as the estimated error for muscle volume calculation was quite small. The reconstruction quality depends mainly on the proper marker attachment and identification, as well as the spatial resolution of the image sequences. We are confident that the presented method can be used in most investigations regarding muscle morphology.
Analysis of the main passive soft tissues associated with adult acquired flatfoot deformity development: A computational modeling approach.
Venue: Journal of biomechanics

Adult acquired flatfoot deformity (AAFD) is a pathology with a wide range of treatment options. Physicians decide the best treatment based on their experience, so the process is entirely subjective. A better understanding of soft tissue stress and its contribution in supporting the plantar arch could help to guide the clinical decision. Traditional experimental trials cannot consistently evaluate the contribution of each tissue. Therefore, in this research a 3-Dimensional FE foot model was reconstructed from a normal patient in order to measure the stress of the passive stabilizers of the arch, and its variation in different scenarios related with intermediate stages of AAFD development. All bones, the plantar fascia (PF), cartilages, plantar ligaments and the spring ligament (SL) were included, respecting their anatomical distribution and biomechanical characteristics. An AAFD evaluation scenario was simulated. The relative contribution of each tissue was obtained comparing each result with a normal case. The results show that PF is the main tissue that prevents the arch elongation, while SL mainly reduces the foot pronation. Long and short plantar ligaments play a secondary role in this process. The stress increment on both PF and SL when one of two fails suggests that these tissues complement each other. These findings support the theory that regards the tibialis posterior tendon as a secondary actor in the arch maintenance, compared with the PF and the SL, because this tendon is overstretched by the hindfoot pronation around the talonavicular joint. This approach could help to improve the understanding of AAFD.
External sensory-motor cues while managing unexpected slippages can violate the planar covariation law.
Venue: Journal of biomechanics

This study was aimed at investigating the intersegmental coordination of six older adults while managing unexpected slippages delivered during steady walking, and wearing an Active Pelvis Orthosis (APO). The APO was setup either to assist volunteers at the hip levels during balance loss or to be transparent. The Planar Covariation Law (PCL) of the lower limb elevation angles was the main tool used to assess the intersegmental coordination of both limbs (i.e., the perturbed and unperturbed ones). Results revealed that, after the onset of the perturbation, elevation angles of both limbs do not covary, a part from the robot-mediated assistance. These new evidences suggest that external sensory-motor cues can alter the temporal synchronization of elevation angles, thus violating the PCL.
Numerical simulations of cell flow and trapping within microfluidic channels for stiffness based cell isolation.
Venue: Journal of biomechanics

Analysis of rare cells in heterogenous mixtures is proven to be beneficial for regenerative medicine, cancer treatment and prenatal diagnostics. Scarcity of these cells, however, makes the isolation process extremely challenging. Efficiency in cell isolation is still low and therefore, novel cell isolation strategies with new biomarkers need exploration. In this study, we investigated the feasibility of using the mechanical stiffness difference to detect and isolate the rare cells from the surrounding cells without labelling them. Fluid and solid mechanics simulations have shown that cell isolation can be performed at high efficiency using stiffness-based isolation. Accuracy of the numerical simulations is established using microfluidic flow chamber experiments.
Ankle intrinsic stiffness changes with postural sway.
Venue: Journal of biomechanics

In standing, the human body is inherently unstable and its stabilization requires constant regulation of ankle torque, generated by a combination of ankle intrinsic properties, peripheral reflexes, and central contributions. Ankle intrinsic stiffness, which quantifies the joint intrinsic properties, has been usually assumed constant in standing; however, there is strong evidence that it is highly dependent on the joint torque, which changes significantly with sway in stance. In this study, we examined how ankle intrinsic stiffness changes with postural sway during standing. Ten subjects stood on a standing apparatus, while subjected to pulse perturbations of ankle position. The mean torque of a short period before the start of each pulse was used as a measure of background torque. Responses with similar background torques were grouped together and used to estimate the parameters of an intrinsic stiffness model. Stiffness estimates were normalized to the critical stiffness and the background torque was transformed to the center of pressure location. We found that in most subjects, the normalized stiffness increased linearly with the movement of center of pressure towards the toes, with an average slope of 2.11 ± 0.80 1/m·rad. This modulation of ankle intrinsic stiffness seems functionally appropriate, since the intrinsic stiffness increases quickly, as the center of pressure moves toward the toes and the limits of stability. These large changes of ankle intrinsic stiffness with postural sway must be incorporated in any model of stance control.
Hinged ankle braces do not alter knee mechanics during sidestep cutting.
Venue: Journal of biomechanics

Lateral ankle sprains are common injuries in quick, dynamic movements and are caused by rapid ankle inversion. Ankle braces are used to reduce ankle inversion, while allowing normal plantar and dorsiflexion ranges of motion. Knee injuries, such as anterior cruciate ligament injuries, are also common in dynamic movements. It is important to understand how ankle braces affect injury risk at other proximal joints. There is limited and conflicting results on how ankle braces affect knee mechanics during these types of movements. Additionally, it is unknown if sex differences exist when using an ankle brace. Therefore, the purpose of this study was to determine the effects of a hinged ankle brace and sex during a 45° cutting movement. Three-dimensional kinematics and ground reaction forces were collected using a motion capture system and force plate on ten men and eight women during cutting trials. 2 × 2 repeated measures ANOVAs were used to detect differences in ground reaction forces, as well as knee and ankle kinematics between brace conditions and sex (p < 0.05). The brace condition exhibited greater initial contact ankle dorsiflexion (p = 0.011), decreased peak ankle inversion (p < 0.01), and increased vertical loading rate (p = 0.040). Females performed the cutting movement with less initial contact (p = 0.019) and peak knee flexion (p = 0.023) compared to males. Ankle bracing had no impact on the observed sex differences. Females exhibited decreased knee flexion compared to males, which has been well documented in the literature. The use of an ankle braces reduced ankle injury risk variables while not adversely impacting knee mechanics during a 45° sidecutting movement.
The concept of margins of stability can be used to better understand a change in obstacle crossing strategy with an increase in age.
Venue: Journal of biomechanics

The purpose of the current study was to use the margins of stability (MoS) to investigate how older adults choose between minimizing the risk of a forward fall when crossing an obstacle and the ease of maintaining forward progression during the steps taken behind the obstacle. In the current study 143 community-dwelling older adults aged between 55 and 83 years old, were divided into three age groups based on tertials of age. All participants were asked to complete five trials of obstacle walking and five trials of normal walking. For the trials of normal walking, the main difference between groups was that MoS at initial contact was lower in the older age groups. For the trials of obstacle crossing the MoS at the instants of obstacle crossing with both the leading and trailing limb became smaller with an increase in age. This result might imply that older people choose to use a strategy during obstacle crossing that results in smaller chance of falling forward if an obstacle was struck. A negative consequence of this more conservative strategy was a smaller MoS at the instants of initial contact after crossing the obstacle, thus a larger chance of a backward fall. These findings provide more insight into the regulation of stability during obstacle crossing and specifically in the differences in strategy between younger and older people, and therefore these results might be used for further research to investigate whether obstacle crossing strategies are trainable in older adults, which could be used as advisory programs aimed at fall prevention and/or engagement in an active lifestyle.
Computational investigation of the Laplace law in compression therapy.
Venue: Journal of biomechanics

This study aims to use computational methods for elucidating the effect of limb shape on subgarment and subcutaneous pressures, stresses and strains. A framework was built that generates computational models from 3D arm scans using a depth sensing camera. Finite Element Analysis (FEA) was performed on the scans taken from 23 lymphoedema patients. Subgarment pressures were calculated based on local curvature for each patient and showed a large variability of pressure across each arm. Across the cohort an average maximum subgarment pressure of 5100 Pa was found as opposed to an intended garment pressure of 2500 Pa. Subcutaneous results show that stresses/strains in the adipose tissues more closely follow the subgarment pressures than in the stiffer skin tissues. Another novel finding was that a negative axial gradient in subgarment pressure (from wrist to elbow) consistently led to positive axial gradients for the Von Mises stresses in the adipose tissues; a phenomenon caused by a combination of arm shape and the stiffness ratio between skin and adipose tissues. In conclusion, this work fills a knowledge gap in compression therapy in clinical practice and can inform garment design or lead to optimal treatment strategies.
Hypersensitivity of trunk biomechanical model predictions to errors in image-based kinematics when using fully displacement-control techniques.
Venue: Journal of biomechanics

Recent advances in medical imaging techniques have allowed pure displacement-control trunk models to estimate spinal loads with no need to calculate muscle forces. Sensitivity of these models to the errors in post-imaging evaluation of displacements (reported to be ∼0.4-0.9° and 0.2-0.3 mm in vertebral displacements) has not yet been investigated. A Monte Carlo analysis was therefore used to assess the sensitivity of results in both musculoskeletal (MS) and passive finite element (FE) spine models to errors in measured displacements. Six static activities in upright standing, flexed, and extended postures were initially simulated using a force-control hybrid MS-FE model. Computed vertebral displacements were subsequently used to drive two distinct fully displacement-control MS and FE models. Effects of alterations in the reference vertebral displacements (at 3 error levels with SD (standard deviation) = 0.1, 0.2, and 0.3 mm in input translations together with, respectively, 0.2, 0.4, and 0.6° in input rotations) were investigated on the model predictions. Results indicated that outputs of both models had substantial task-dependent sensitivities to errors in the measured vertebral translations. For instance, L5-S1 intradiscal pressures (IDPs) were considerably affected (SD values reaching 1.05 MPa) and axial compression and shear forces even reversed directions as translation errors increased to 0.3 mm. Outputs were however generally much less sensitive to errors in measured vertebral rotations. Accounting for the accuracies in image-based kinematics measurements, therefore, it is concluded that the current measured vertebral translation errors at and beyond 0.1 mm are too large to drive biomechanical models of the spine.
Human crawling performance and technique revealed by inertial measurement units.
Venue: Journal of biomechanics

Human crawling performance and technique are of broad interest to roboticists, biomechanists, and military personnel. This study explores the variables that define crawling performance in the context of an outdoor obstacle course used by military organizations worldwide to evaluate the effects of load and personal equipment on warfighter performance. Crawling kinematics, measured from four body-worn inertial measurement units (IMUs) attached to the upper arms and thighs, are recorded for thirty-three participants. The IMU data is distilled to four metrics of crawling performance; namely, crawl speed, crawl stride time, ipsilateral limb coordination, and contralateral limb coordination. We hypothesize that higher performance (as identified by higher crawl speeds) is associated with more coordinated limbs and lower stride times. A cluster analysis groups participants into high and low performers exhibiting statistically significant differences across the four performance metrics. In particular, high performers exhibit superior limb coordination associated with a "diagonal gait" in which contralateral limbs move largely in-phase to produce faster crawl speeds and shorter crawl stride times. In contrast, low performers crawl at slower speeds with longer crawl stride times and less limb coordination. Beyond these conclusions, a major contribution of this study is a method for deploying wearable IMUs to study crawling in contextually relevant (i.e. non-laboratory) environments.
Construct validation of lower limb segmental excursion as a measure of potential risk for lower limb injury in Division I women's basketball players.
Venue: Journal of biomechanics

The region of limb stability (ROLS) is an inertial sensor-based measure of static knee joint stability, defined by thigh and shank movements of the supporting limb during single limb stance. Changes in thigh and shank movements and/or symmetry differences between limbs may predict risk of injury to the less stable limb or the need for rehabilitation. In this study, construct validity of the ROLS metrics was examined in twelve Division I women's basketball players during pre-season in preparation for their exercise training program. The subjects were categorized based on their injury history during the season: (Group 1) No reported injuries throughout the season, (Group 2) lower limb injury that did not result in missing any games, and (Group 3) lower limb injury that resulted in missing both practice and the remainder of their season. Significant differences were found in ROLS metrics at pre-season between Group 3 and other groups in a prospective cohort study (p < 0.05). Study findings provided pilot data for supporting ROLS as a measure of postural stability impairment and potential risk for lower limb injury in athletes.
Dynamic balance during running using running-specific prostheses.
Venue: Journal of biomechanics

Running is beneficial for physical, social, and emotional health, and participating in physical activity, including running, is becoming more popular for people with an amputation. However, this population has a greater risk of falling relative to people without an amputation, which may be a barrier to running. Understanding how dynamic balance is maintained during running is important for removing this barrier. To investigate dynamic balance, we quantified whole-body angular momentum in eight people with a unilateral transtibial amputation (TTA) using running-specific prostheses (RSPs) compared to eight people without TTA during running at 2.5, 3.0, and 3.5 m/s. People with TTA had greater ranges of whole-body angular momentum compared to people without TTA in the frontal and sagittal planes (p < 0.01). These greater ranges resulted from smaller peak medial, lateral, and braking ground reaction forces from the amputated leg compared to the intact leg and people without TTA. Reduced RSP mass relative to the biological leg also influenced whole-body angular momentum as evidenced by smaller ranges of amputated leg angular momentum compared to the intact leg in the frontal and sagittal planes. Smaller amputated leg angular momentum corresponded with smaller contralateral arm angular momentum in the sagittal plane (p < 0.01). People with TTA maintain balance during running with altered muscle coordination and prosthesis characteristics. Restoring mediolateral force generation through prosthetic design advances may help in regulating the frontal plane component of whole-body angular momentum for people with TTA, with potential to improve their ability to maintain balance during running.