nils-herrmann/clean_scirepeval huggingface dataset:
Effects of the soft tissue artefact on the hip joint kinematics during unrestricted activities of daily living.
Venue: Journal of biomechanics

Soft tissue artefact (STA) affects the kinematics retrieved with skin marker-based motion capture, and thus influences the outcomes of biomechanical models that rely on such kinematics. In order to be compensated for, the effects of STA must be characterized across a broad sample population and for different motion activities. In this study, the error introduced by STA on the kinematics of the hip joint and of its individual components, and on the location of the hip joint center (HJC) was quantified for fifteen THA subjects during overground gait, stair descent, chair rise and putting on socks. The error due to STA was computed as the difference between the kinematics measured with motion capture and those measured simultaneously with moving fluoroscopy, a STA-free X-ray technique. The main significant effects of STA were: underestimation of the hip range of motion for all four activities, underestimation of the flexion especially during phases of the motion with higher flexion, overestimation of the internal rotation, and lateral misplacement of the HJC mostly due to the functional calibration. The thigh contributed more to the STA error than the pelvis. The STA error of the thigh appeared to be correlated with the hip flexion angles, with a varying degree of linearity depending on the activity and on the phase of the motion cycle. Future kinematic-driven STA compensation models should take into account the non-linearity of the STA error and its dependency of the phase of the motion cycle.
Does kinematic gait quality improve with functional gait recovery? A longitudinal pilot study on early post-stroke individuals.
Venue: Journal of biomechanics

Typical clinical gait outcomes mostly focus on function; only sparse information exists on gait quality, i.e. symmetry or more natural gait patterns. It remains unclear whether functional gait recovery improves with gait quality, or whether these are two independent processes. The objective of this observational pilot study is to examine whether the gait quality improves with gait function (i.e. speed) over the course of early recovery. Full lower body gait kinematics were measured longitudinally in a clinical environment using wearable inertial measurement units. We recorded six individuals with subacute stroke (<1 month) for a total of 56 physical therapy sessions over the initial recovery stage of 12 weeks. We examined relations between gait symmetry in spatiotemporal, limb and joint kinematic parameters compared to gait function. We observed that overall gait symmetry improved with walking speed, but limb and joint kinematic parameters remained asymmetric at the maximum level of recovery (both p < 0.01). We also found that limb kinematic parameters (R2 = 41.9%) of the impaired side was preferentially associated with functional gait recovery over joint kinematics (R2 = 33.1%). These data suggest that our pilot cohort did not achieve "true" gait recovery despite achieving typical measures of recovery in gait speed and spatiotemporal symmetry. These initial results illustrate the multifaceted nature of recovery and justify further research on monitoring gait quality with a larger clinical study, providing insight for more effective training regimens.
Optimization of muscle activation schemes in a finite element neck model simulating volunteer frontal impact scenarios.
Venue: Journal of biomechanics

Neck muscle activation is increasingly important for accurate prediction of occupant response in automotive impact scenarios and occupant excursion resulting from active safety systems such as autonomous emergency braking. Muscle activation and optimization in frontal impact scenarios using computational Human Body Models have not been investigated over the broad range of accelerations relevant to these events. This study optimized the muscle activation of a contemporary finite element model of the human head and neck for human volunteer experiments over a range of frontal impact severities (2 g to 15 g). The neck muscles were grouped as flexors and extensors, and optimization was undertaken for each group based on muscle activation level and activation time. The boundaries for optimization were defined using data from the literature and a preliminary parametric study. A linear polynomial method was used to optimize the model head kinematics to the volunteer experiments for each impact severity. The optimized models predicted muscle activation to increase with higher impact severities, and improved the average cross-correlation by 35% (0.561-0.755) relative to the Maximum Muscle Activation (MMA) scheme in the original model. Importantly, a newly proposed Cocontraction Muscle Activation (CMA) scheme for maintaining the head in a neutral posture provided a 23% on average improvement in correlation compared to the MMA scheme. In conclusion, this study identified a new scheme to obtain more accurate response kinematics across multiple impact severities in computational Human Body Models as well as contributing to the understanding of muscle influence during frontal impact scenarios.
Classification of tracheal stenosis in children based on computational aerodynamics.
Venue: Journal of biomechanics

Tracheal stenosis is a health condition in which local narrowing of the upper trachea can cause breathing difficulties and increased incidence of infection, among other symptoms. Occurring most commonly due to intubation of infants, tracheal stenosis often requires corrective surgery. It is challenging to determine the most effective surgical strategy for a given patient as current clinical methods used to assess tracheal stenosis are simplistic and subjective, and are not rigorously based on aerodynamic considerations. This paper summarizes a non-invasive approach based on computational fluid dynamics (CFD) and medical imaging to establish relationships between trachea anatomy and inspiration performance. Though patient-specific CFD analysis has gained recent popularity, an objective of this study is to computationally formulate dimensionless analytical correlations between anatomy and performance that are applicable to any member of a class of patients and that can be interpreted within the context of the Myer-Cotton stenotic airway classification system. These correlations can provide aerodynamics-based insight for the development of more robust stenosis evaluation methods and may allow for time-efficient assessment of corrective surgical strategies.
Mechanical adaptions of collective cells nearby free tissue boundaries.
Venue: Journal of biomechanics

Mechanical adaptions of cells, including stiffness variation, cytoskeleton remodeling, motion coordination, and shape changing, are essential for tissue morphogenesis, wound healing, and malignant progression. In this paper, we take confluent monolayers of Madin-Darby canine kidney (MDCK) and mouse myoblast (C2C12) cells as model systems to probe how cells collectively adapt their mechanical features in response to a free tissue boundary. We show that the free boundary not only can trigger unjamming transition but also induces cell fluidization nearby the boundary. The Young's moduli of cells near the boundary are found to be much lower than those of interior cells. We demonstrate that the stiffness of cells in monolayers with a free tissue boundary exhibits negative dependence on the projected cell area, in contrast to previous studies where cells were found to stiffen as cellular area increases in a confluent MDCK monolayer without boundary. In addition, the free tissue boundary may activate cell remodeling, rendering volume enlargement and cell-specified cytoskeleton organization. Our study emphasizes the important role of geometrical boundary in regulating biomechanical properties of cell aggregates.
Determining the impacts of venoarterial extracorporeal membrane oxygenation on cerebral oxygenation using a one-dimensional blood flow simulator.
Venue: Journal of biomechanics

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is a mechanical system that provides rapid and short-term support for patients with cardiac failure. In many patients, pulmonary function is also impaired, resulting in poorly-oxygenated cardiac outflow competing against well-oxygenated VA-ECMO outflow, a condition known as North-South syndrome. North-South syndrome is a primary concern because of its potential to cause cerebral hypoxia, which has a critical influence on neurological complications often seen in this patient population. In order to reduce ischemic neurological complications, it is important to understand how clinical decisions regarding VA-ECMO parameters influence blood oxygenation. Here, we studied the impacts of flow rate and cannulation site on oxygenation using a one-dimensional (1D) model to simulate blood flow. Our model was initially tested by comparing blood flow results to those observed from experimental work in VA-ECMO patients. The 1D model was combined with a two-phase flow model to simulate oxygenation. Additionally, the influence of various other clinician-tunable parameters on oxygenation in the common carotid arteries (CCAs) were tested, including, blood viscosity, cannula position within the insertion artery, heart rate, and systemic vascular resistance (SVR), as well as geometrical changes such as arterial radius and length. Our results indicated that blood oxygenation to the brain strongly depended on the cannula insertion site and the VA-ECMO flow rate with a weaker but potentially significant dependence on arterial radius. During femoral cannulation, VA-ECMO flow rates greater than ~4.9L/min were needed to perfuse the CCAs. However, axillary and central cannulation began to perfuse the CCAs at significantly lower flow (~1L/min). These results may help explain the incidence of cerebral hypoxia in this patient population and the common need to change cannulation strategies during treatment to address this clinical problem. While this work describes patient-averaged results, determining these relationships between VA-ECMO parameters and cerebral hypoxia is an important step towards future work to develop patient-specific models that clinicians can use to improve outcomes.
Free-leg side elevation of pelvis in single-leg jump is a substantial advantage over double-leg jump for jumping height generation.
Venue: Journal of biomechanics

In single-leg jumps, humans achieve more than half the jumping height that they can reach for double-leg jumps. Although this bilateral deficit in jumping has been believed to be due to the reduction of leg extensor force/work exertions, we hypothesised that the three-dimensional biomechanical differences between double-leg and single-leg jumps also influence the bilateral deficit in jumping. Here, we show the substantial effect of the elevation of the pelvic free-leg side in single-leg squat jumps on the bilateral deficit in jumping in addition to extensor force reduction. We collected the kinematic and ground reaction force data during single-leg and double-leg squat jumps from ten male participants using motion capture systems and force platforms. We determined the components of the mechanical energy directly contributing to the height of the centre of mass due to segment movement. The energy due to rotations of the foot, shank, thigh, and pelvis were significantly greater in single-leg squat jumps than in double-leg squat jumps. The magnitudes of the difference in energy between single-leg and double-leg squat jumps due to the pelvis (0.54 ± 0.22 J/kg) was significantly larger than that due to any other segment (<0.30 J/kg). This indicates that pelvic elevation in single-leg jump is a critical factor causing bilateral deficit in jumping, and that humans generate the jumping height with a single leg not just by an explosive leg-extension but also by synchronous free-leg side elevation of the pelvis. The findings suggest that this pelvic mechanism is a factor characterising human single-leg jumps.
Adversarial autoencoder for visualization and classification of human activity: Application to a low-cost commercial force plate.
Venue: Journal of biomechanics

The ability to visualize and interpret high dimensional time-series data will be critical as wearable and other sensors are adopted in rehabilitation protocols. This study proposes a latent space representation of high dimensional time-series data for data visualization. For that purpose, a deep learning model called Adversarial AutoEncoder (AAE) is proposed to perform efficient data dimensionality reduction by considering unsupervised and semi-supervised adversarial training. Eighteen subjects were recruited for the experiment and performed two sets of exercises (upper and lower body) on the Wii Balance Board. Then, the accuracy of the latent space representation is evaluated on both sets of exercises separately. Data dimensionality reduction with conventional Machine Learning (ML) and supervised Deep Learning (DL) classification are also performed to compare the efficiency of AAE approaches. The results showed that AAE can outperform conventional ML approaches while providing close results to DL supervised classification. AAE approaches for data visualization are a promising approach to monitor the subject's movements and detect adverse events or similarity with previous data, providing an intuitive way to monitor the patient's progress and provide potential information for rehabilitation tracking.
Comprehensive analysis of effective reflection distance and its association with wave reflection strength under diverse hemodynamic conditions in anesthetized dogs.
Venue: Journal of biomechanics

Pressure wave reflection is associated with cardiovascular risk. The conceptual distance to a theoretical major reflection site, termed effective reflection distance (ERD), has been associated with aging and augmentation index (AIx) clinically. However, it remains unclear whether and how ERD varies and associates with AIx when the hemodynamic condition is acutely perturbed in a patient. The objective of this study was to address this issue in rigorously controlled animal experiments. In 13 anesthetized dogs, we measured arterial pressure, aortic flow and femoral arterial flow, while altering the hemodynamic condition over wide ranges by administering zatebradine (bradycardic agent), nitroprusside (vasodilator), noradrenaline (vasoconstrictor), dobutamine (inotrope), and dextran (volume-expander). Using the measured data, we determined ERD based on an arterial model comprising a tube with a complex frequency-dependent load (ERDTL), which has been considered a physiologically valid model. We also determined ERD based on wave separation (ERDWSA) and pressure-based analyses (ERDAW). ERDTL was shortened significantly in response to nitroprusside or dobutamine infusion, and was significantly and negatively associated with AIx in multiple regression analysis using pooled data. ERDWSA or ERDAW did not necessarily correlate with ERDTL in terms of responses to drug administration or association with AIx. In conclusion, under diverse hemodynamic conditions, ERDTL changes sensitively and shows physiologically reasonable association with AIx. This result substantiates the importance of paying close attention to medications during clinical analysis of wave reflection. Caution is required when using ERDWSA or ERDAW as an alternative to ERDTL.
Intraoperative testing of passive and active state mechanics of spastic semitendinosus in conditions involving intermuscular mechanical interactions and gait relevant joint positions.
Venue: Journal of biomechanics

In cerebral palsy (CP) patients suffering pathological knee joint motion, spastic muscle's passive state forces have not been quantified intraoperatively. Besides, assessment of spastic muscle's active state forces in conditions involving intermuscular mechanical interactions and gait relevant joint positions is lacking. Therefore, the source of flexor forces limiting joint motion remains unclear. The aim was to test the following hypotheses: (i) in both passive and active states, spastic semitendinosus (ST) per se shows its highest forces within gait relevant knee angle (KA) range and (ii) due to intermuscular mechanical interactions, the active state forces elevate. Isometric forces (seven children with CP, GMFCS-II) were measured during surgery over a range of KA from flexion to full extension, at hip angle (HA) = 45° and 20°, in four conditions: (I) passive state, (II) individual stimulation of the ST, simultaneous stimulation of the ST (III) with its synergists, and (IV) also with an antagonist. Gait analyses: intraoperative data for KA = 17-61° (HA = 45°) and KA = 0-33° (HA = 20°) represent the loading response and terminal swing, and mid/terminal stance phases of gait, respectively. Intraoperative tests: Passive forces maximally approximated half of peak force in condition II (HA = 45°). Added muscle activations did increase muscle forces significantly (HA = 45°: on average by 42.0% and 72.5%; HA = 20°: maximally by 131.8% and 123.7%, respectively in conditions III and IV, p < 0.01). In conclusion, intermuscular mechanical interactions yield elevated active state forces, which are well above passive state forces. This indicates that intermuscular mechanical interactions may be a source of high flexor forces in CP.
Biomechanical differences during ascent on regular stairs and on a stairmill.
Venue: Journal of biomechanics

Stair climbing is an intense physical activity and requires large range of motion at the joints, adequate muscle strength, and balance control. A powered stairmill, integrated with a gait rehabilitation device, can potentially be used for training those who have difficulty climbing stairs. In order to assess the effectiveness of such an approach, it is necessary to understand the similarities and differences in walking on regular stairs and on a stairmill. We have conducted an experiment to compare the differences in kinematics and muscle activations during climbing on regular stairs and a stairmill. Twelve subjects participated in this study. They first walked on regular stairs five times and then performed a one-minute continuous walking on a stairmill. The results showed several important differences. During continuous walking on a stairmill, when compared to regular stairs, there was (i) an increase in the percentage of stance phase during a walking cycle, (ii) a higher angle of plantarflexion of the ankle during the transition from stance phase to swing phase, and (iii) a decrease in muscle activation of the tibialis anterior during swing phase. These differences would provide additional insights into the design of future rehabilitation systems and to interpret human data obtained from stairmills.
Assessing changes in attitudes toward engineering and biomechanics resulting from a high school outreach event.
Venue: Journal of biomechanics

National Biomechanics Day aims to introduce students to the emerging field of biomechanics and improve their perception of engineering and engineers. This quantitative study examines participants' attitude changes following one such event. By prioritizing increasing excitement and engagement over teaching content, we anticipate that students' opinions of engineering and biomechanics will improve following the event. Pre- and post-test surveys consisting of Likert scale and semantic differential (SD) items assessed changes in three key areas: self-identity as a scientist and engineer, attitudes toward engineering, and attitudes toward biomechanics. Based on unpaired and paired student responses, we found significant gains in all three areas. Students agreed more strongly with statements regarding whether they saw themselves as scientists and engineers, and they had improved attitudes toward engineering in general and biomechanics specifically. The SD scales also reflected improved opinions of both science and biomechanics. These more positive attitudes could eventually lead to more students recruited to study a variety of engineering disciplines, ultimately addressing the ongoing national shortage of qualified engineers.
The consequences of dehydration-hydration on bone anisotropy and implications on the sublamellar organization of mineralized collagen fibrils.
Venue: Journal of biomechanics

In this study, the effect of dehydration-hydration based sublamellar dimensional change on bone anisotropy was used as a tool to understand sublamellar organization of mineralized collagen fibrils. Bone consists of hydroxyapatite, Type I Collagen, mucopolysaccharides and bone fluid, which associates with bone constituents and improves the mechanical properties of bone. Knowing that dehydration causes dimensional changes comparable to those observed in the mechanical testing of a bone sample, here, the dehydrated organic component of lamellar bone was modelled to contract towards the mineral, forming a contraction vector as the surface normal of the mineral plate. The amount of dehydration based contraction in rotated collagen fibrils was calculated for two models of sublamellar arrangements, namely A and B, where the mineral plate of the 0° (axial, [0 0 1]) sublamellar collagen fibril was oriented respectively along either (0 1 0) or (0 0 1) planes. Projections of sublamellar contraction vectors were denoted as u, v and w displacements at 10°-20°-30° angles and summed to give the lamellar total. Using the total displacements, anisotropy ratios of properties in directions parallel (W) versus perpendicular (U or V) to the osteonal axis were calculated. With dehydration, the osteonal lamellae in Model A (behaving as positive Poisson's ratio material) may display maximal planar expansion (at 1.4%) and peraxial contraction (-0.24%), which may even cause sample warping. The large variation in the wet and dry bone anisotropy ratios of the models demonstrates the effect of collagen orientation on bone mechanics.
The impact of ankle-foot-orthosis (AFO) use on the compensatory stepping response required to avoid a fall during trip-like perturbations in young adults: Implications for AFO prescription and design.
Venue: Journal of biomechanics

Ankle-foot-orthoses (AFOs) are commonly prescribed to treat foot drop and enhance walking in fall-prone individuals (e.g. stroke). AFOs improve static balance but AFO-users are still at high fall risk. To our knowledge, no one has studied the biomechanical effect of AFO-use on the compensatory stepping response required to avoid falling during dynamic conditions such as trip, the leading cause of falls. The objective of this study is to evaluate the impact of a semi-rigid thermoplastic AFO on the compensatory stepping response in young healthy individuals following trip-like treadmill perturbations. We found that the AFO on the stepping leg (AFO-step) decreased trunk stability (increased trunk angle and angular velocity), shortened the compensatory step length, and reduced dynamic stability (smaller COM-BOS). AFO on the support leg (AFO-support) was only marginally different from the No-AFO condition. Detrimental changes in compensatory stepping response (e.g. decreased trunk stability) were linearly correlated to diminished propulsive impulse of the step. In summary, AFO-use on the stepping leg is associated with impaired compensatory stepping response (e.g. reduced trunk stability) and decreased propulsive impulse in young adults. It is important to note that AFO-use enhances static stability and decreases the probability of a trip/stumble occurring indicating they are important for fall prevention. Still, our results suggest that AFO-use may impair the compensatory stepping response after a trip/stumble has occurred and may suggest that preserving plantarflexion function may support the compensatory stepping response. Further study of these devices and their impact on compensatory stepping response in fall-prone individuals is warranted.