nils-herrmann/clean_scirepeval huggingface dataset:
Evaluating cost function criteria in predicting healthy gait.
Venue: Journal of biomechanics

Accurate predictive simulations of human gait rely on optimisation criteria to solve the system's redundancy. Defining such criteria is challenging, as the objectives driving the optimization of human gait are unclear. This study evaluated how minimising various physiologically-based criteria (i.e., cost of transport, muscle activity, head stability, foot-ground impact, and knee ligament use) affects the predicted gait, and developed and evaluated a combined, weighted cost function tuned to predict healthy gait. A generic planar musculoskeletal model with 18 Hill-type muscles was actuated using a reflex-based, parameterized controller. First, the criteria were applied into the base simulation framework separately. The gait pattern predicted by minimising each criterion was compared to experimental data of healthy gait using coefficients of determination (R2) and root mean square errors (RMSE) averaged over all biomechanical variables. Second, the optimal weighted combined cost function was created through stepwise addition of the criteria. Third, performance of the resulting combined cost function was evaluated by comparing the predicted gait to a simulation that was optimised solely to track experimental data. Optimising for each of the criteria separately showed their individual contribution to distinct aspects of gait (overall R2: 0.37-0.56; RMSE: 3.47-4.63 SD). An optimally weighted combined cost function provided improved overall agreement with experimental data (overall R2: 0.72; RMSE: 2.10 SD), and its performance was close to what is maximally achievable for the underlying simulation framework. This study showed how various optimisation criteria contribute to synthesising gait and that careful weighting of them is essential in predicting healthy gait.
The effects of knee pain on knee contact force and external knee adduction moment in patients with knee osteoarthritis.
Venue: Journal of biomechanics

Knee osteoarthritis (OA) is a major cause of knee pain, leading to physical dysfunction. External knee adduction moment (KAM), a surrogate measure of knee contact force (KCF) in the medial compartment, is related to knee pain, but the association between KCF and pain severity remains unclear. This study aimed to reveal the differences in KCF due to pain severity. Twenty-eight patients with knee OA were evaluated knee symptoms including pain severity via the Knee Society Score. Based on the median symptom score, 17 points in this study, subjects were classified as having Mild symptomatic OA (n = 15) and Severe symptomatic OA (n = 13). Subjects walked three times at a comfortable speed along a six-meter walkway, and we calculated KAM during the stance phase. KCF magnitude and distribution were also computed using the subject-specific musculoskeletal model, considering physical characteristics such as the femorotibial angle measured by X-ray. No differences in physical characteristics such as femorotibial angle and gait speed were found by symptom severity, whereas KAM and medial KCF at minimum and second peak in Severe symptomatic OA patients were significantly greater than those in Mild symptomatic OA. A significant medial shift of KCF in Severe symptomatic OA was also seen at first peak and minimum. Severe symptomatic OA had a greater medial KCF and medial shift of KCF. Detailed evaluations of KCF magnitude and distribution in addition to KAM would provide crucial information on knee contact force in relation to symptom severity.
Using deep neural networks for kinematic analysis: Challenges and opportunities.
Venue: Journal of biomechanics

Kinematic analysis is often performed in a lab using optical cameras combined with reflective markers. With the advent of artificial intelligence techniques such as deep neural networks, it is now possible to perform such analyses without markers, making outdoor applications feasible. In this paper I summarise 2D markerless approaches for estimating joint angles, highlighting their strengths and limitations. In computer science, so-called "pose estimation" algorithms have existed for many years. These methods involve training a neural network to detect features (e.g. anatomical landmarks) using a process called supervised learning, which requires "training" images to be manually annotated. Manual labelling has several limitations, including labeller subjectivity, the requirement for anatomical knowledge, and issues related to training data quality and quantity. Neural networks typically require thousands of training examples before they can make accurate predictions, so training datasets are usually labelled by multiple people, each of whom has their own biases, which ultimately affects neural network performance. A recent approach, called transfer learning, involves modifying a model trained to perform a certain task so that it retains some learned features and is then re-trained to perform a new task. This can drastically reduce the required number of training images. Although development is ongoing, existing markerless systems may already be accurate enough for some applications, e.g. coaching or rehabilitation. Accuracy may be further improved by leveraging novel approaches and incorporating realistic physiological constraints, ultimately resulting in low-cost markerless systems that could be deployed both in and outside of the lab.
Asymmetric velocity profiles in Paralympic powerlifters performing at different exercise intensities are detected by functional data analysis.
Venue: Journal of biomechanics

Asymmetries compromise performance in powerlifting and Paralympic powerlifting, but its quantification can be complex. Previous studies consider average or peak values to quantify asymmetries, however this approach does not consider the pattern of movement like velocity profiles. Here we demonstrate that conducting a functional analysis of variance (FANOVA) permits to quantify asymmetries in bench press performance by Paralympic powerlifting at different submaximal intensities. Kinematic data were collected from 10 Paralympic powerlifting athletes performing in bench press at submaximal intensities (50% and 90% of the one-repetition maximum). Linear velocity was quantified considering mean values and the entire waveform. Mean values were compared by analysis of variance (ANOVA) and the waveforms were compared by FANOVA. FANOVA identified asymmetry profiles that ANOVA did not recognize at the highest intensity, which is the closest to a competition. This way, FANOVA can bring advantages to the analysis of competitive performance. FANOVA data analysis identifies asymmetries at higher intensity of effort considering the whole pattern of movement. Therefore, we consider that the FANOVA's approach may benefit the biomechanical assessment of the Paralympic powerlifting.
Flow diverter modeled as heterogeneous and anisotropic porous medium: Simulation, experimental validation and case analysis.
Venue: Journal of biomechanics

Simulation of flow diverter (FD) treated aneurysm can evaluate treatment efficacy and aid treatment planning. However, explicit modeling of thin wires of FD impose extremely high demand of computational resources and time, which limit its use in time-sensitive presurgical planning. One alternative approach is to model FD as homogenous porous medium, which saves time but with compromise in accuracy. We proposed a new method to model FD as heterogeneous and anisotropic porous medium whose properties were determined from local porosity. The new method was validated by comparing with PIV measurement from an in-vitro phantom. Simulation result was in good agreement with experimental measurement. Four patient cases were further analyzed to compare the new method with the homogenous porous media method. Results showed that in patient cases with curved artery, new method was preferred over the homogenous method, as the assumption of homogenous porosity led to overpredicted flow reduction effect by as much as 87.9%, which may lead to overoptimistic decision making and poor prognosis. Our new method can provide timely and accurate simulation to aid in the treatment planning of aneurysms.
The effect of rotational speed on ankle-foot orthosis properties.
Venue: Journal of biomechanics

Ankle-foot orthoses (AFOs) are devices that support ankle motion. An AFO's sagittal plane rotational stiffness can affect gait kinematics. Because AFOs are often made from viscoelastic materials, their properties may vary at different walking speeds. The influence of rotational speed on AFO properties has not been thoroughly investigated. Therefore, the purpose of this study was to determine the impact of rotational speed on AFO stiffness about the ankle. We tested a sample of one thermoplastic off-the-shelf AFO and two 3-D printed carbon fiber enforced nylon AFOs. Each AFO's dynamic resistance torque was measured as it was flexed at five speeds (5-100 °/s) using a custom-built measurement apparatus. We compared loading stiffness, neutral angle, and energy dissipation parameters for each AFO across speeds. Parameter values were generally greater at higher speeds. These effects were statistically significant for all AFOs (p≤0.002). However, differences in AFO stiffness and neutral angle across speeds were quite small (<0.6 Nm/° and <2.2 °). Changes in the thermoplastic AFO's stiffness were lower than the minimum detectable difference. Energy dissipation, as indicated by hysteresis area, increased by up to 6.3 J (about 250%) at the highest speed. This demonstrates that AFO flexion speed can influence the properties of different AFOs over the range typically achieved in human walking. Future work should assess whether the observed small variations of stiffness and neutral angle have a clinically meaningful impact on user performance, as well as explore effects of angular speed on a variety of AFO materials and designs.
Physiological articular contact kinematics and morphological femoral condyle translations of the tibiofemoral joint.
Venue: Journal of biomechanics

The changes of tibiofemoral articular cartilage contact locations during knee activities represent a physiological functional characteristic of the knee. However, most studies reported relative motions of the tibia and femur using morphological flexion axes. Few data have been reported on comparisons of morphological femoral condyle motions and physiological tibiofemoral cartilage contact location changes. This study compared the morphological and physiological kinematic measures of 20 knees during an in vivo weightbearing single leg lunge from full extension to 120° of flexion using a combined MRI and dual fluoroscopic imaging system (DFIS) technique. The morphological femoral condyle motion was measured using three flexion axes: trans-epicondylar axis (TEA), geometric center axis (GCA) and iso-height axis (IHA). At low flexion angles, the medial femoral condyle moved anteriorly, opposite to that of the contact points, and was accompanied with a sharp increase in external femoral condyle rotation. At 120° of flexion, the morphological measures of the lateral femoral condyle were more posteriorly positioned than those of the contact locations. The data showed that the morphological measures of femoral condyle translations and axial rotations varied with different flexion axes and did not represent the physiological articular contact kinematics. Biomechanical evaluations of the knee joint motion should include both morphological and physiological kinematics data to accurately demonstrate the functionality of the knee.
Individual acceleration-speed profile in-situ: A proof of concept in professional football players.
Venue: Journal of biomechanics

Assessing football players' sprint mechanical outputs is key to the performance management process (e.g. talent identification, training, monitoring, return-to-sport). This is possible using linear sprint testing to derive force-velocity-power outputs (in laboratory or field settings), but testing requires specific efforts and the movement assessed is not specific to the football playing tasks. This proof-of-concept short communication presents a method to derive the players' individual acceleration-speed (AS) profile in-situ, i.e. from global positioning system data collected over several football sessions (without running specific tests). Briefly, raw speed data collected in 16 professional male football players over several training sessions were plotted, and for each 0.2 m/s increment in speed from 3 m/s up to the individual top-speed reached, maximal acceleration output was retained to generate a linear AS profile. Results showed highly linear AS profiles for all players (all R2 > 0.984) which allowed to extrapolate the theoretical maximal speed and accelerations as the individual's sprint maximal capacities. Good reliability was observed between AS profiles determined 2 weeks apart for the players tested, and further research should focus on deepening our understanding of these methodological features. Despite the need for further explorations (e.g. comparison with conceptually close force-velocity assessments that require, isolated and not football-specific linear sprint tests), this in-situ approach is promising and allows direct assessment of football players within their specific acceleration-speed tasks. This opens several perspectives in the performance and injury prevention fields, in football and likely other sprint-based team sports, and the possibility to "test players without testing them".
Margins of stability of persons with transtibial or transfemoral amputations walking on sloped surfaces.
Venue: Journal of biomechanics

Gait is a complex motor skill. However, most falls in humans occur during gait, and people with lower limb amputation have an increased risk of falls. Thus, this study evaluated the stability of persons with unilateral amputation by quantifying the margin of stability (MoS) during gait, to contribute to understanding the strategies adopted by these people to reduce falls. The participants were divided into 3 groups: persons with transtibial amputations (n = 12, 32.27 ± 10.10 years, 76.9 ± 10.3 kg, 1.74 ± 0.06 m); persons with transfemoral amputations (n = 13, 32.21 ± 8.34 years, 72.55 ± 10.23 kg, 1.73 ± 0.05 m); and controls (n = 15, 32.2 ± 10.17 years, 75.4 ± 9.25 kg, 1.75 ± 0.05 m), who walked for 4 min on a level and sloped (8% down and up) treadmill. The pelvic and foot marker kinematic data were used to estimate the center of mass and base of support, and from these, the MoS was estimated. Although both groups of persons with amputations showed higher values for the ML MoS than did the control group (transtibial: 8.81 ± 1.79, 8.97 ± 1.74, 8.79 ± 1.76, transfemoral: 10.15 ± 2.03, 10.60 ± 1.98, 10.11 ± 1.75, control: 8.13 ± 1.30, 7.18 ± 1.85, 8.15 ± 1.57, level, down, and up, respectively), only the transfemoral group presented a significant higher value compared to the control group. Our findings suggest that the documented limitations in persons with amputations, especially with transfemoral amputation, are exacerbated in situations that require more skills, such as walking on sloped surfaces, triggering protective mechanisms.
Can gait kinetic data predict femoral bone mineral density in elderly men and women aged 50 years and older?
Venue: Journal of biomechanics

This retrospective study was conducted to investigate the correlation between kinetic gait parameters and femoral bone mineral density (BMD) in elderly subjects aged 50 years and older that could walk independently. Four hundred and twenty-six subjects (158 men and 258 women; mean age 68.7 years, standard deviation (SD) 7.9 years) were included in the study. BMDs (g/cm2) of the femoral neck, trochanter, shaft, and total proximal femur were collected. Kinetic data including maximum hip power and hip power-time integral was obtained from a three-dimensional gait analysis with self-selected walking speed. Correlation between BMDs of proximal femur and gait kinetic data was analyzed. Multiple regression analysis was also performed to identify factors significantly associated with BMD. Correlation between BMD and hip kinetic data was not prominent in elderly men. In women, BMD was significantly correlated with hip kinetic data. Hip power-time integral showed greater correlation with BMD than maximum hip power during gait in elderly women. Age (p < 0.001), weight (p = 0.007) and hip power-time integral (p = 0.008) were significant factors associated with femoral neck BMD, and these factors explained 25.4% of femoral neck BMD. In conclusion, the association between the mechanical load and BMD in the different sexes provokes future research into these issues. The effects of various types of exercises on BMD should be investigated more precisely using a gait analysis tool.
Effects of head tilt on squeeze-bottle nasal irrigation - A computational fluid dynamics study.
Venue: Journal of biomechanics

Nasal irrigation is a widely recognized treatment for several sinonasal diseases. However, there is a lack of clear evidence-based guidelines for optimal irrigation delivery to improve lavage and topical drug delivery. This study uses computational fluid dynamics (CFD) to assess the effects of different head tilt positions on sinonasal coverage, residence time and shear stresses in squeeze-bottle nasal irrigation. A sinonasal cavity computational model was constructed from a high-resolution CT scan of a healthy, 25-year-old Asian female. The Volume of Fluid method was used to track the interface between the two immiscible fluids (air and water). The direction of gravity was varied to simulate different head tilt-positions (0° Straight, 45° Forward, 45° Left, 45° Right and 45° Backward) during nasal irrigation with 150 mL liquid via a squeeze bottle through the left nostril for 2 s with a 0.1 s acceleration/deceleration time. The results showed that the 45° backward head tilt position was the most effective in delivering irrigation to the ethmoid, frontal and sphenoid sinuses. Altering head tilt had minimal impact on irrigation delivery to the maxillary sinuses. Maximum wall shear stresses seen in localized areas of the sinus mucosa varied significantly with different head tilt angles. However, the difference in mean wall shear stress on the sinus surfaces was marginal with changing head tilt position. The findings suggest that an optimized head tilt position can be identified to improve liquid irrigation to targeted sinuses, as per treatment requirements (lavage and topical drug delivery).
Numerical modeling of bare and polymer-covered braided stents using torsional and tensile springs connectors.
Venue: Journal of biomechanics

Computational modeling of braided stents using the finite element (FE) method has become an essential tool in the design and development of these medical devices. One of the most challenging issues in such a task is representing in an accurate manner the interaction between the interlacing wires. With the goal of achieving a compromise between accuracy and computational affordability, we propose a new approach consisting in using 1D FE formulations equipped with torsional springs at the crossover points of the wires. In the case of covered braided stents, the model is enriched with a set of tensile springs (defined in the longitudinal direction), aimed at capturing the stiffening effect of the polymeric membrane. The predictive capabilities of the proposed model are evaluated using data of our own experimental tests, as well as data from other tests in the literature. The simulations demonstrate that the proposed model is able to predict the (markedly nonlinear) behavior of stents when subjected to radial and axial cycle loads, with errors at the end of the compression stage ranging from 0.5% to 10% in all cases.
A progressive-individualized midstance gait perturbation protocol for reactive balance assessment in stroke survivors.
Venue: Journal of biomechanics

Restoration of balance control is a primary focus of rehabilitation after a stroke. The study developed a gait perturbation, treadmill-based, balance assessment protocol and demonstrated that it can be used to quantify improvements in reactive balance responses among individuals post-stroke. The protocol consists of a sequence of fifteen 90-second treadmill walking trials, with a single perturbation applied during the middle third of each trial. Gait was perturbed by rapid acceleration-deceleration of the treadmill belt at mid-stance of the unaffected leg during a randomly selected gait cycle. The initial perturbation magnitude was based on the participant's maximum walking speed and increased or decreased in each trial, based on success or failure of recovery, as determined from an instrumented harness. The protocol was used before and after a 10-week period of therapy in twenty-four stroke survivors. Outcomes included maximum recoverable perturbation (MRP), self-selected gait speed, levels progressed through the algorithm, and falls versus recoveries.Participants were able to take recovery steps in response to the perturbation. Twelve participants completed the full assessment protocol before and after the therapeutic intervention. After the intervention, they had fewer falls and more recoveries (p < 0.001), progressed through more algorithm levels (p = 0.043), had a higher MRP (p = 0.005), and had higher gait speeds. The protocol was found to be feasible in stroke survivors with moderate gait deficits. The data supports the conclusion that this protocol can be used in clinical research to quantify improvements in balance during walking.
Activation patterns of shoulder internal and external rotators during pure axial moment generation across a postural range.
Venue: Journal of biomechanics

Musculoskeletal risk is mediated by body posture, especially for static tasks. Workstations that require non-neutral postures can lead to increased load, muscular fatigue and injury risk. However, demands during simple axial rotation tasks are not well-defined. The purpose of this study is to quantify the muscular activity of during static axial rotation in a range of postures. Eighteen participants performed 76 axial rotation exertions in varying combinations of humeral elevation angles (30°-60°-90°-120°-150°), plane of elevation (30°-60°-90°-120°) and exertion intensity (20-40%). Six unilateral (right) muscles (pectoralis major (clavicular and sternal), posterior deltoid, teres major, infraspinatus, latissiumus dorsi) were monitored using surface electromyography (EMG). EMG was normalized and integrated over 2 s. The influences of elevation, plane, and intensity on activity levels were then tested with a 3-way ANOVAs (p < .05). During internal rotation, activity was highest at low elevation/high plane combinations for the internal rotators, but at high elevation/low plane combinations for the external rotators. During the 40% intensity exertions, activity levels were highest at lower elevations for internal rotator but at high elevations for the external rotators. During external rotation, as the degree of elevation increased, the activity of the external rotator muscles also increased while internal rotators were unaffected. Humeral muscles responsible for axial rotation are influenced by arm posture during axial rotation exertions. High elevation and plane combinations resulted in high demands for external rotator muscles and this should be considered for job design and injury risk.