nils-herrmann/clean_scirepeval huggingface dataset:
Foot flexibility confounds the assessment of triceps surae extensibility in children with spastic paresis during typical physical examinations.
Venue: Journal of biomechanics

Accurate assessment of the talo-crural (ankle) joint angle at physical examination is important for assessing extensibility of m. triceps surae (TS) in children with spastic cerebral paresis (SCP). The main aim of this study was to quantify foot flexibility during standardized measurements of TS muscle-tendon complex extensibility (i.e. based on foot-sole rotation) in SCP children, and typical developed (TD) ones. Additionally, we aim to define a method that minimizes the confounding effects of foot flexibility on estimates of talo-crural joint angles and TS extensibility. Children, aged 6-13 years, with SCP (GMFCS I-III, n = 13) and TD children (n = 14) participated in this study. Externally applied -1 Nm, 0 Nm, 1 Nm and 4 Nm dorsal flexion foot plate moments were imposed. Resulting TS origin-insertion lengths, foot sole (φFoSo) rotations, and changes in talo-crural joint angle (φTaCr) were measured. Foot flexibility was quantified as Δ(φTaCr -φFoSo) between the 0 Nm and 4 Nm dorsal flexion conditions. In both groups, φFoSo rotations of approximately 20° were observed between 0 Nm and 4 Nm dorsal flexion, of which about 6° (≈30%) was related to foot flexibility. Foot flexibility correlated to φFoSo (r = 0.69) but not to φTaCr (r = 0.11). For φFoSo no significant differences were found between groups at 4 Nm. However, for SCP children the mean estimate of φTaCr was 4.3° more towards plantar flexion compared to the TD group (p < 0.05). Normalized TS lengths show a higher coefficient of correlation with φTaCr (r2 = 0.82) than with φFoSo (r2 = 0.60), indicating that TS lengths are better estimated by talo-cural joint angles. In both SCP and TD children aged 6-13 year, estimates of TS length and extensibility based on foot sole assessments are confounded by foot flexibility. Assessments of TS extensibility at physical examination will be more accurate when based on measurements of talo-crural joint angles.
Temporal kinematic differences throughout single and double-leg forward landings.
Venue: Journal of biomechanics

Screening methods for anterior cruciate ligament (ACL) injuries often involve double-leg landings, though the majority of ACL injuries occur during single-leg landings. Differences in kinematic temporal characteristics between single-leg and double-leg landings are poorly understood. The purpose of this study was to examine discrete and temporal kinematics associated with functional valgus collapse during single-leg and double-leg landings (LANDSL and LANDDL). Three-dimensional kinematics were obtained during the landing phases of LANDSL and LANDDL in ninety participants (45 females: 20.1 ± 1.7 yr, 165.2 ± 7.6 cm, 68.6 ± 13.1 kg; 45 males: 20.7 ± 2.0 yr, 177.7 ± 8.5 cm, 82.8 ± 16.3 kg). Peak joint angles and time series curves for frontal and transverse plane hip and knee kinematics were analyzed with an RMANOVA (discrete variables) and Statistical Parametric Mapping (SPM) paired t-tests (time series). LANDSL elicited greater knee abduction than LANDDL from 0 to 35% (0-73 ms) but greater knee adduction from 54 to 100% (112-207 ms). Peak knee abduction was 2.0° greater during LANDDL than during LANDSL (p < .001). LANDSL elicited greater hip adduction than LANDDL from 2 to 33% (4-69 ms) and greater hip abduction from 49 to 100% (102-207 ms). Peak hip adduction was 4.6° greater during LANDSL than during LANDDL (p < .001). LANDSL elicited less knee internal rotation from 0 to 3% and greater hip internal rotation from 52 to 75% of the landing phase. Peak transverse plane joint angles did not differ between tasks. During the time frame in which ACL injuries are thought to occur, LANDSL elicited frontal plane knee and hip movement consistent with risky biomechanics. Researchers and clinicians should be cognizant of how a chosen screening task alters observed kinematic effects.
Does variability in motor output at individual joints predict stride time variability in gait? Influences of age, sex, and plane of motion.
Venue: Journal of biomechanics

Old age is associated with variability in gait motor output, particularly in females, and is linked to fall risk. However, little is known about how older age and sex affect variability in the outputs of individual joints, and how these variabilities contribute to the collective gait output. Healthy adults aged 18-99 years (N = 102, 57 females) completed six trials of straight walking at self-selected speed. Stride time variability (coefficient of variation) and variabilities of lower limb tridimensional joint angles (standard deviations: SD) were calculated. Age * Sex (A * S) mixed models were conducted on all measures and year-by-year rates of change were subsequently estimated. Correlations and stepwise linear regression analyses were computed between joint angular variabilities and stride time variability. Each year of age was associated with 0.022% higher stride time variability (A: p = .002), 0.07° lower variability in peak ankle dorsiflexion (A: p = .004), 0.002-0.098° higher variability in mean ankle inversion/eversion, mean pelvic obliquity, and pelvic rotation range of motion (A: p < .05), and 0.024° higher variability in knee flexion/extension range of motion in males (A * S: p = .003). Higher variability in mean ankle and hip flexion/extension and in mean ankle inversion/eversion correlated with (ρ = 0.211-0.336; ps < 0.05) and independently predicted higher stride time variability (ps < 0.05), together explaining 21.9% of variance. Results suggest that higher stride time variability with older age may be produced by a shift from sagittal plane variability to frontal plane variability at the ankle.
Hip extensor fatigue alters hip and knee coupling dynamics during single-limb step-downs: A randomized controlled trial.
Venue: Journal of biomechanics

Impaired hip muscle function may cause movement coordination deficits that increase lower extremity injury risks. We examined whether hip and knee coordination is altered during single-limb step-downs following a hip extensor fatigue protocol. Forty participants in this randomized controlled trial performed 20 single-limb step-downs before and after completing either a fatigue protocol or a sham fatigue protocol. Means and SDs of sagittal and frontal plane hip and knee kinematics were measured. Nonlinear measures of coupled hip and knee coordination were examined with cross recurrence quantification analyses. Pre- to post-fatigue change scores were analyzed inferentially (α = 0.05). The fatigue protocol induced 22.2% strength reduction in the fatigue group, versus 4% reduction in the sham group. Neither the magnitude nor variability in sagittal and frontal plane hip and knee kinematics changed following the fatigue protocol (P > .05, small effect sizes). Participants in the fatigue group, however, performed post-fatigue step-downs with greater cross determinism (P = .046, effect size = 0.71) and mean line (P = .038, effect size = 0.74) in sagittal plane hip and frontal plane knee coupling, whereas participants in the sham-control group performed step-downs with reductions in those measures. In the fatigued state, participants performed repeated step-downs with subtle increases in cross determinism and cross mean line, which implies they performed the task with greater predictability of hip and knee coupling and less adaptability. The findings may provide insight into coupled movement patterns and their reflection of motor control.
Deformable link segment analysis for prosthetic foot-ankle components: Kinematics.
Venue: Journal of biomechanics

Approaches in the literature for estimating prosthetic foot-ankle power typically require calculating the segment deformation velocity. This, in turn, necessitates approximating the segment angular velocity. Methods can be distinguished by the way in which a segment is defined and the assumptions used for estimating the segment angular velocity. However, isolating foot-ankle performance from overall prosthetic system performance is limited by uncertainties in the definition of angular velocity of a deformable segment. A deformable link segment (DLS) analysis is proposed that provides a means for estimating deformation velocity of a deformable segment without first approximating the angular velocity: the deformation velocity and angular velocity are solved simultaneously at each instant during the stance phase of gait. DLS analysis was compared to two approaches in the literature: the distal foot (DF) model and the unified deformable (UD) segment model during over-ground walking for three trans-tibial prosthesis users. DLS and UD segment estimates of deformation velocity were comparable when applied to the UD segment. Furthermore, DLS analysis enables modelling of deformable prosthetic foot-ankle components separately from other prosthetic componentry. The method is proposed as a rigorous approach to estimating angular velocity and deformation velocity of passive prosthetic foot-ankle components for subsequent calculation of deformation power and energy performance of these devices.
Application of the Gait Deviation Index in the analysis of post-stroke hemiparetic gait.
Venue: Journal of biomechanics

Due to the complexity and volume of kinematic data from 3-dimensional gait analysis, the Gait Deviation Index (GDI) was introduced as a summary measure providing a global picture of gait kinematic data, however previously it was not validated as an outcome measure in individuals after stroke. The present study investigated the concurrent validity of the GDI as an outcome measure of gait defects at a chronic stage of recovery post-stroke, through comparisons with conventional measures of gait. Those enrolled included 65 individuals after stroke and 65 healthy individuals without gait disorders, matched for age and gender. The kinematic gait parameters were measured using a movement analysis system. Walking speed, walking distance, number of steps, self-reliant mobility, cadence, step length, and single support time were evaluated. Strong correlation was found between cadence and mGDI as well as GDI for the affected leg (0.7 ≤ |R| < 0.9; p < 0.001). Moderate correlations were found between walking speed, number of steps, step length affected leg and mGDI as well as GDI for the affected leg (0.5 ≤ |R| < 0.7; p < 0.001). Low correlations were found between walking distance, self-reliant mobility, single support time affected leg and mGDI as well as GDI for the affected leg (0.3 ≤ |R| < 0.5; p < 0.001; p < 0.005). The findings confirm the concurrent validity of the GDI, but only for the affected leg and mGDI in post-stroke patients. On the other hand, the GDI for unaffected leg may be useful in efforts to identify any compensatory mechanisms developing in post-stroke gait patterns.
Effects of segment masses and cut-off frequencies on the estimation of vertical ground reaction forces in running.
Venue: Journal of biomechanics

The purpose of this study is to examine the effect of the body's mass distribution to segments and the filtering of kinematic data on the estimation of vertical ground reaction forces from positional data. A public dataset of raw running biomechanics was used for the purposes of the analysis, containing recordings of twenty-eight competitive or elite athletes running on an instrumented treadmill at three different speeds. A grid-search on half of the trials was employed to seek the values of the parameters that optimise the approximation of biomechanical loads. Two-way ANOVAs were then conducted to examine the significance of the parameterised factors in the modelled waveforms. The reserved recordings were used to validate the predictive accuracy of the model. The cut-off filtering frequencies of the pelvis and thigh markers were correlated to running speed and heel-strike patterns, respectively. Optimal segment masses were in agreement with standardised literature reported values. Root mean square errors for slow running (2.5 m/s) were on average equal to 0.1 (body weight normalized). Errors increased with running speeds to 0.13 and 0.18 for 3.5 m/s and 4.5 m/s, respectively. This study accurately estimated vertical ground reaction forces for slow-paced running by only considering the kinematics of the pelvis and thighs. Future studies should consider configuring the filtering of kinematic inputs based on the location of markers and type of running.
Active arm swing and asymmetric walking leads to increased variability in trunk kinematics in young adults.
Venue: Journal of biomechanics

Fall induced injuries are a leading cause for occupational injuries with the majority originating from challenging same-level walking surfaces. Despite current perturbation and fall prevention paradigms, occupational fall prevalence remains stable. Typically, these paradigms do not account for arm swing which has been demonstrated to affect the center of mass' movement during walking. This study examined the effect of different arm swing on postural control during symmetric and asymmetric walking. Fifteen healthy young adults (age = 23.4 ± 2.8) walked symmetrically and asymmetrically with three arm motions (normal, held, and active) on a split-belt treadmill CAREN Extended-System (Motek Medical, Amsterdam, NL). Mean, standard deviation and maximal values of trunk linear and angular velocity, and whole-body angular momentum were calculated in all three axes; additionally, step length, time and width mean and Coefficient of Variation, Margin of Stability and Harmonic Ratios were calculated. Compared to normal and held conditions, active arm increased trunk linear and angular velocity standard deviation, max velocity values, mean step length and time, as well as the Coefficient of Variation for step length, time, and width. Furthermore, whole-body angular momentum increased as a function of arm swing amplitude. Active arm swing further reduced Harmonic Ratios in the mediolateral and anteroposterior directions. Asymmetric walking increased average step time, and width as well as increased the Coefficient of Variation for step length and time but reduced left average step length and step width Coefficient of Variation. Further, asymmetric walking increased mediolateral Margin of Stability and reduced anteroposterior and mediolateral Harmonic Ratios. Finally, results demonstrated that actively increasing arm swing increases trunk linear and angular velocity variability in healthy young adults during symmetric and asymmetric treadmill walking. Findings may be due to active arm swing and asymmetric walking causing a disproportional contribution to trunk and center of mass movement causing participants to modify their base of support to maintain stability.
The biomechanics of concussive helmet-to-ground impacts in the National Football league.
Venue: Journal of biomechanics

This paper presents a detailed characterization of helmet-to-ground impacts in the National Football League. Video analysis was performed for 16 head-to-ground impacts that caused concussions. Average resultant closing velocity was 8.3 m/s at an angle nearly 45° to the surface. Preimpact rotational velocity of the helmet ranged from negligible to as high as 54.1 rad/s. Helmet impacts were concentrated on the posterior and lateral aspects. To study the interaction in greater detail, a helmeted anthropomorphic test device (ATD) was launched over a football field and fell to the ground in various impact conditions. Substantial decoupling between the helmet and the head was observed, such that the head rebounded within the helmet and underwent changes in linear and rotational motion greater than those of the helmet. Vertical helmet rebound was also observed; the helmet underwent a change in vertical velocity on average 24% greater than the vertical component of its closing velocity. Frictional interaction between the helmet and the ground surface caused the helmet to undergo an average horizontal change in velocity of 57% of the horizontal component of its closing velocity. Finally, the duration of a helmet-to-ground impact was generally in the range of 15 - 30 ms, suggesting that the impact surface provides little ride-down. Lengthening this duration could be beneficial both by reducing the peak linear and rotational acceleration and by shifting the impact toward a time regime where brain strain is related to rotational acceleration rather than rotational velocity.
Walking assistance using crutches: A state of the art review.
Venue: Journal of biomechanics

Crutches are one of the most common ambulatory assistive devices. Using crutches encourages more physical activity than many other assistive devices, which has long-term health benefits. Recent advances have led to improvements in performance, but using crutches remains slower than normal walking, are energetically inefficient, cause additional strain on upper extremities, and often result in abrasions on the skin. Further improvements to address these deficiencies are needed but require an understanding of the crutch users' disabilities, different crutch gait patterns, associated biomechanics, and how the crutch design interacts with the user. It is important that research studies and designs take into account parameters from multiple ways of measuring performance in order for impaired users to achieve effective crutch walking. Many existing studies of crutches only analyze a subset of quantitative variables, so the overall impact of a design or modification is not fully assessed or comparable to other designs. Another important aspect is the user; each crutch type has specific characteristics that need to match the user's ability, physical fitness, and gait pattern. Pain and injuries on upper extremities should also be considered as an important factor in long-term users. A search was done to find research papers and related patents focusing on crutch design and usage. Papers that studied one or more of the following topics were included: effects of crutches on the gait parameter, types of crutch walking patterns, improving walking efficiency through crutch design, and identifying the important components when studying a gait. This review paper summarizes the effects of existing crutch types and gives guidelines for how future studies should comprehensively evaluate design changes. This paper includes an overview of crutch gait walking patterns, users, the components and measurements of crutch studies, and advancements of crutch designs.
Development of a two-dimensional dynamic model of the foot-ankle system exposed to vibration.
Venue: Journal of biomechanics

Workers in mining, mills, construction and some types of manufacturing are exposed to vibration that enters the body through the feet. Exposure to foot-transmitted vibration (FTV) is associated with an increased risk of developing vibration-induced white foot (VIWFt). VIWFt is a vascular and neurological condition of the lower limb, leading to blanching in the toes and numbness and tingling in the feet, which can be disabling for the worker. This paper presents a two-dimensional dynamic model describing the response of the foot-ankle system to vibration using four segments and eight Kelvin-Voigt models. The parameters of the model have been obtained by minimizing the quadratic reconstruction error between the experimental and numerical curves of the transmissibility and the apparent mass of participants standing in a neutral position. The average transmissibility at five locations on the foot has been optimized by minimizing the difference between experimental data and the model prediction between 10 and 100 Hz. The same procedure has been repeated to fit the apparent mass measured at the driving point in a frequency range between 2 and 20 Hz. Monte Carlo simulations were used to assess how the variability of the mass, stiffness and damping matrices affect the overall data dispersion. Results showed that the 7°-of-freedom model correctly described the transmissibility: the average transmissibility modulus error was 0.1. The error increased when fitting the transmissibility and apparent mass curves: the average modulus error was 0.3. However, the obtained values were reasonable with respect to the average inter-participant variability experimentally estimated at 0.52 for the modulus. Study results can contribute to the development of materials and equipment to attenuate FTV and, consequently, lower the risk of developing VIWFt.
Biomechanical contribution of the alar ligaments to upper cervical stability.
Venue: Journal of biomechanics

Acute and chronic whiplash-associated disorders pose a significant healthcare burden due to chronic pain, which is associated with upper cervical instability resulting from ligamentous injury. No standard measure exists for diagnosing alar ligament injury and imaging findings vary widely. Multiple physical examination maneuvers are used to diagnose alar ligament injury including the C2 Spinous Kick, Flexion-Rotation, and Bending-Rotation tests. The objective of the current study was to determine the mechanical contribution of the alar ligaments to upper cervical stability and quantify the biomechanical changes seen during simulated clinical examinations after alar ligament injury. Eight cadaveric C0-C3 specimens were evaluated using a robotic testing system. Range of motion and moment at the end of intact specimen replay were the primary outcomes. Clinical examinations were simulated by rotation through two axes as performed during physical examination. Intact, unilateral and bilateral alar ligament injury states were tested. Unilateral alar ligament injury led to significant increases in lateral bending (12.0 ± 7.2%, p < 0.05), axial rotation (4.1 ± 2.4%, p < 0.05), and flexion-extension (5.3 ± 4.3%, p < 0.05) compared with intact specimens. The alar ligaments also contributed to resistance to intact motion in extension (13.4 ± 6.6%, p < 0.05), flexion (4.4 ± 2.2%, p < 0.05), axial rotation (19.3 ± 2.7%, p < 0.05), and lateral bending (16.0 ± 2.8%, p < 0.05). The C2 Spinous Kick Test showed the largest percentage change (-23.0 ± 14.8%), and the Bending- Test towards the side of injury significantly increased axial rotation by the largest absolute magnitude (5.5° ± 5.1°). Overall, quantifiable changes to motion measured during simulated physical examinations were found, but the ability of a clinician to feel these changes remains unknown.
A feasibility study of deep learning for predicting hemodynamics of human thoracic aorta.
Venue: Journal of biomechanics

Numerical analysis methods including finite element analysis (FEA), computational fluid dynamics (CFD), and fluid-structure interaction (FSI) analysis have been used to study the biomechanics of human tissues and organs, as well as tissue-medical device interactions, and treatment strategies. However, for patient-specific computational analysis, complex procedures are usually required to set-up the models, and long computing time is needed to perform the simulation, preventing fast feedback to clinicians in time-sensitive clinical applications. In this study, by using machine learning techniques, we developed deep neural networks (DNNs) to directly estimate the steady-state distributions of pressure and flow velocity inside the thoracic aorta. After training on hemodynamic data from CFD simulations, the DNNs take as input a shape of the aorta and directly output the hemodynamic distributions in one second. The trained DNNs are capable of predicting the velocity magnitude field with an average error of 1.9608% and the pressure field with an average error of 1.4269%. This study demonstrates the feasibility and great potential of using DNNs as a fast and accurate surrogate model for hemodynamic analysis of large blood vessels.