nils-herrmann/clean_scirepeval huggingface dataset:
Hip fracture risk functions for elderly men and women in sideways falls.
Venue: Journal of biomechanics

Falls among the elderly cause a huge number of hip fractures world-wide. The objective is to generate hip fracture force risk functions for elderly women and men in sideways falls which can be used for determining effectiveness of fall prevention measures as well as for individual assessment of fracture risk at the clinics. A literature survey was performed and ten publications were identified who contained several hundred individual femoral neck fracture forces in sideways fall for both elderly women and men. Theoretical distributions were tested for goodness of fit against the pooled dataset with the Anderson-Darling test (AD-test) and root mean square errors (RMSE) were extracted. According to the AD-test, a Weibull distribution is a plausible model for the distribution of hip fracture forces. A simple, exponential two-parameter Weibull function was therefore proposed, having a RMSE below 2.2% compared to the experimental distribution for both men and women. It was demonstrated that elderly women only can endure nearly half the proximal femur force for 5 and 10% fracture risk as elderly men. It should be noted though, that women were found to have significantly lesser body height and body weight which would produce less impact force during falls from standing height. The proposed sex-specific hip fracture risk functions can be used for biomechanically optimizing hip protectors and safety floors and for determining their effectiveness as a fall prevention measure.
Relationships between lower limbs fatigability threshold and postural control in obese adults.
Venue: Journal of biomechanics

The objective of this study was to investigate the effect of obesity on markers of neuromuscular fatigability of ankle muscles and their potential relationships with postural control capacities. Two groups: non-obese control group (CG; n = 15; age = 40.1 ± 13.9 years; BMI = 23.9 ± 2.8 kg/m2) and obese group (OG; n = 15; age = 44.2 ± 12.4 years; BMI = 42.2 ± 5.2 kg/m2), performed two postural tasks with and without vision in order to collect parameters of center of pressure (CoP) displacements; area (cm2), velocity (mm/s), length (cm) and the ratio length/area. Fatigability was estimated during 60 repeated maximal voluntary contractions of plantar (PF) and dorsal flexors (DF). The maximal force, critical force (Fcr) presenting the asymptote of the force-time evolution and rate of the force decrease (τ) were extracted. Results reported that CoP parameters were higher in OG compared to CG in all postural tasks (p < 0.05). Fcr of PF and DF were 39% and 28% lower respectively in OG compared to CG (p < 0.05). Only τ of PF was 12% lower in OG (p < 0.05). Fcr of PF was negatively correlated with the ratio length/area in OG in all postural tasks (r = 0.86 and r = 0.85, respectively, p < 0.05). We concluded that obesity is associated with a decreased Fcr of ankle muscles expressing the intensity threshold above which fatigue develops drastically. We also revealed that decreased fatigability threshold particularly that of PF, could partly explain postural control alterations in obese adults.
On the in vivo systolic compressibility of left ventricular free wall myocardium in the normal and infarcted heart.
Venue: Journal of biomechanics

Although studied for many years, there remain continued gaps in our fundamental understanding of cardiac kinematics, such as the nature and extent of heart wall volumetric changes that occur over the cardiac cycle. Such knowledge is especially important for accurate in silico simulations of cardiac pathologies and in the development of novel therapies for their treatment. A prime example is myocardial infarction (MI), which induces profound, regionally variant maladaptive remodeling of the left ventricle (LV) wall. To address this problem, we conducted an in vivo fiduciary marker-based study in an established ovine model of MI to generate detailed, time-evolving transmural in vivo volumetric measurements of LV free wall deformations in the normal state, as well as up to 12 h post-MI. This was accomplished using a transmural array of sonomicrometry crystals that acquired fiducial positions at ∼250 Hz with a positional accuracy of ∼0.1 mm, covering the entire infarct, border, and remote zones. A convex-hull method was used to directly calculate the Jacobian J(t)=Δv(t)/ΔVED from sonocrystal positions over the entire cardiac cycle, where ΔV is the volume of each convex polyhedral at end diastole (ED) (typically ∼1 cc). We demonstrated significant in vivo compressibility in normal functioning LV free wall myocardium, with JES=0.85±0.07 at end systole (ES). We also observed substantial regional variations, with the largest reduction in local myocardial tissue volume during systole in the base region accompanied by substantial transmural gradients. These patterns changed profoundly following loss of perfusion post-MI, with the apical region showing the greatest loss of volume reduction at ES. To verify that the sonocrystals did not affect local volumetric measurements, JES measures were also verified by non-invasive magnetic resonance imaging, exhibiting very similar changes in regional volume. We note that while our estimates of regional compressibility were in close agreement with the values previously reported for large animals, ranging from 5% to 20%, the direct, comprehensive measurements of wall compressibility presented herein improved on the limitations of previous reports. These limitations included dependency on the small local volumes used for analysis and often indirect measurement of compressibility. Our novel findings suggest that proper accounting for the myocardial effective compressibility at the ∼1 cc volume scale can improve the accuracy of existing kinematic indices, such as wall thickening and axial shortening, and simulations of LV remodeling following MI.
Effect of anthropometry scaling on the response of the piper child scalable human body model subject to pelvic impact.
Venue: Journal of biomechanics

The Open Source PIPER child scalable human body model was publicly released in April 2017 () along with frontal and side impact validation conditions. The objective of this paper is to investigate the effect of anthropometry scaling on the response of the model in side pelvic impact. Three setups from two published studies were used: (1) a lateral drop test (2) a greater trochanter impact with a rigid pendulum (3) a pelvis side impact with a flat surface. The first study used scaling assumption developed for crash test dummy design (setups 1 and 2) and the second performed tests on post mortem human surrogates. The baseline 6 years old child model was scaled using a model morphing methodology to match the stature and weight of the surrogates used in the two published studies. Overall, the main trends observed in the three setups can be approached using the baseline model. Although the model morphing did not account for specific skeletal dimensions, it reduced some of the discrepancies between model response and reference for the drop test and flat plate impact. However, it had little effect on the pendulum test. In that case, the model response was in the corridor at low speed but above at higher speeds. Possible reasons for this difference should be further investigated.
Reliability of recurrence quantification analysis of postural sway data. A comparison of two methods to determine recurrence thresholds.
Venue: Journal of biomechanics

Ageing affects balance control resulting in a greater amplitude of sway and alterations in structure of the sway time series. Recurrence quantification analysis (RQA) has been used to determine the structure of center-of-pressure (CoP; a measure that reflects standing postural control) data as a means to quantify how CoP repeats itself / recurs below a certain threshold. This study aimed to determine how the method of threshold determination, below which a recurrence is defined, affects the within-session reliability of RQA in an elderly population. Within-session reliability of RQA of CoP motion in the anterior-posterior and mediolateral directions was assessed in 267 individuals (>65 years old) when standing on firm or foam surface with eyes open or closed for each of two recurrence threshold methods. One threshold method sets the recurrence threshold level such that the recurrence rate is fixed to 5%, the other method sets the recurrence threshold based on 27% of the mean distance between all points from which recurrences are quantified. Reliability across four 30-s balance trials within each of four balance conditions (firm vs. foam, eyes open vs. closed) was determined using intra-class correlation, standard error of measurement and minimal detectable change. ICCs were better, the standard error of measurement and minimal detectable change were smaller when the recurrence threshold was set to 5% using the fixed recurrence threshold. Fixing recurrence rate improves the within session reliability of RQA and could increase sensitivity to identify fall risk.
Individuals with unilateral transtibial amputation exhibit reduced accuracy and precision during a targeted stepping task.
Venue: Journal of biomechanics

Accurate foot placement is important for dynamic balance during activities of daily living. Disruption of sensory information and prosthetic componentry characteristics may result in increased locomotor task difficulty for individuals with lower limb amputation. This study investigated the accuracy and precision of prosthetic and intact foot placement during a targeted stepping task in individuals with unilateral transtibial amputation (IUTAs; N = 8, 47 ± 13 yrs), compared to the preferred foot of control participant's (N = 8, 33 ± 15 yrs). Participants walked along a 10-metre walkway, placing their foot into a rectangular floor-based target with dimensions normalised to a percentage of participant's foot length and width; 'standard' = 150% x 150%, 'wide' = 150% x 200%, 'long' = 200% x 150%. Foot placement accuracy (relative distance between foot and target centre), precision (between-trial variability), and foot-reach kinematics were determined for each limb and target, using three-dimensional motion capture. A significant foot-by-target interaction revealed less mediolateral foot placement accuracy for IUTAs in the wide target, which was significantly less accurate for the intact (28 ± 12 mm) compared to prosthetic foot (16 ± 14 mm). Intact peak foot velocity (4.6 ± 0.8 m.s-1) was greater than the prosthetic foot (4.5 ± 0.8 m.s-1) for all targets. Controls were more accurate and precise than IUTAs, regardless of target size. Less accurate and precise intact foot placement in IUTAs, coupled with a faster moving intact limb, is likely due to several factors including reduced proprioceptive feedback and active control during prosthetic limb single stance. This could affect activities of daily living where foot placement is critical, such as negotiating cluttered travel paths or obstacles whilst maintaining balance.
Incorporating subject-specific geometry to compare metatarsal stress during running with different foot strike patterns.
Venue: Journal of biomechanics

Stress fracture of the second metatarsal is a common and problematic injury for runners. The choice of foot strike pattern is known to affect external kinetics and kinematics but its effect on internal loading of the metatarsals is not well understood. Subject-specific models of the second metatarsal can be used to investigate internal loading in a non-invasive manner. This study aimed to compare second metatarsal stress between habitual rearfoot and non-rearfoot strikers during barefoot running, using a novel subject-specific mathematical model, including accurate metatarsal geometry. Synchronised force and kinematic data were collected during barefoot overground running from 20 participants (12 rearfoot strikers). Stresses were calculated at the plantar and dorsal periphery of the midshaft of the metatarsal using a subject-specific beam theory model. Non-rearfoot strikers demonstrated greater external loading, bending moments and compressive forces than rearfoot strikers, but there were no differences in peak stresses between groups. Statistical parametric analysis revealed that non-rearfoot strikers had greater second metatarsal stresses during early stance but that there was no difference in peak stresses. This emphasises the importance of bone geometry when estimating bone stress and supports the suggestion that external forces should not be assumed to be representative of internal loading.
Portable, automated foot progression angle gait modification via a proof-of-concept haptic feedback-sensorized shoe.
Venue: Journal of biomechanics

Modifying the foot progression angle (FPA) is a non-pharmacological, non-surgical treatment option for knee osteoarthritis, however current widespread adoption has been limited by the requirement of laboratory-based motion capture systems. We present the first customized haptic feedback-sensorized shoe for estimating and modifying FPA during walking gait, which includes an electronic inertial and magnetometer module in the sole for estimating FPA, and two vibration motors attached to the medial and lateral shoe lining for providing vibrotactile feedback. Feasibility testing was performed by comparing FPA performance while wearing the haptic feedback-sensorized shoe with the training targets. Participants performed five walking trials with five randomly-presented FPA targets (10° toe-in, 0°, 10° toe-out, 20° toe-out, and 30° toe-out) of 2 min each on a treadmill. Overall average FPA performance error across all conditions was 0.2 ± 4.1°, and the overall mean absolute FPA performance error across all conditions was 3.1 ± 2.6°. Reducing the size of the no-feedback window resulted in less performance error during walking. This study demonstrates that a novel haptic feedback-sensorized shoe can be used to effectively train FPA modifications. The haptic feedback-sensorized shoe could potentially be used for FPA gait modification outside of specialized camera-based motion capture laboratories as a conservative treatment for knee osteoarthritis or other related clinical applications requiring FPA assessment and modification in daily life.
A solution method for predictive simulations in a stochastic environment.
Venue: Journal of biomechanics

Predictive gait simulations currently do not account for environmental or internal noise. We describe a method to solve predictive simulations of human movements in a stochastic environment using a collocation method. The optimization is performed over multiple noisy episodes of the trajectory, instead of a single episode in a deterministic environment. Each episode used the same control parameters. The method was verified on a torque-driven pendulum swing-up problem. A different optimal trajectory was found in a stochastic environment than in the deterministic environment. Next, it was applied to gait to show its application in predictive simulation of human movement. We show that, unlike in a deterministic model, a nonzero minimum foot clearance during swing is predicted by a minimum-effort criterion in a stochastic environment. The predicted amount of foot clearance increased with the noise amplitude.
Experimental thermal analysis of a novel prosthetic socket along with silicone and PCM liners.
Venue: Journal of biomechanics

Prosthetic liners and sockets insulate a residual limb, causing excessive heat, sweating, skin irritation and maceration. Circulation of a fluid through the socket wall has been shown to have positive cooling effects on the internal surface of the socket, i.e. skin temperature. Moreover, Phase Change Materials (PCMs) have been recognized as a practical method for cooling garments. These materials, such as water or many synthesized polymers, have a high latent heat and their application within a prosthetic liner allows for absorbing heat from the limb for retaining a constant temperature. In this study, a novel prosthetic socket has been designed and prototyped to investigate the interactive effects of fluid circulation and PCM materials on thermal comfort of prosthetic sockets. The results indicate a statistically significant difference (p-value < 0.001) in the duration a PCM liner can retain the appropriate skin temperature, compared to regular silicone liners. Likewise, the presence of air circulation within the socket wall was shown to have statistically significant influences (p-value = 0.018) on providing the efficient cooling effects compared to regular sockets. Hence, incorporating circulation cooling mechanisms along with PCM liners as proposed in this study holds a promising solution to enhance the thermal comfort of prosthetic socket systems.
Inter-joint coordination during obstacle crossing in people with diabetic neuropathy.
Venue: Journal of biomechanics

Sensori-motor deficit due to diabetic peripheral neuropathy (DPN) alters the quality of obstacle-crossing which may increase the risk of falling. The aim of this study was to compare inter-joint coordination (IJC) during obstacle-crossing between people with DPN and healthy controls. Fifteen DPN and 15 healthy people crossed over obstacles with heights of 10% and 20% of the subject's leg length. The mean absolute relative phase (MARP) and deviation phase (DP) of both leading and trailing limbs were used to calculate the phase dynamic and variability of IJC. Furthermore, correlation between Berg Balance Scale (BBS), Fall Efficacy Scale (FES-I), Timed Up and Go (TUG) and MARP, DP were assessed in DPN group. There was no significant interaction between group and obstacle height on measured variables. However, Group had significant main effect on DP of hip-knee in leading limb (p < 0.05). Additionally, the main effects of the obstacle's height were significant on MARP of hip-knee of trailing limb (p < 0.01) and knee-ankle in leading limb (p < 0.05). FES-I was significantly correlated to hip-knee and knee-ankle MARPs of leading limb for crossing over 20% and knee-ankle MARP for crossing over 10% height obstacle (r = 0.68, 0.69, 0.59, respectively, p < 0.05). This score was also significantly correlated with hip-knee DP of both trailing and leading limbs when crossing 10% obstacle (r = 0.59, 0.57, respectively, p < 0.05). In conclusion, IJC during obstacle-crossing was less variable and more out-of-phase, as a result of DPN and obstacle height, respectively. Moreover, when crossing over lower obstacles, fear of falling is related to IJC dynamics and variability of more proximal segment, especially in the leading limb.
The effect of preterm birth, recurrent laryngeal nerve lesion, and postnatal maturation on hyoid and thyroid movements, and their coordination in infant feeding.
Venue: Journal of biomechanics

Movements of the hyoid and thyroid are critical for feeding. These structures are often assumed to move in synchrony, despite evidence that neurologically compromised populations exhibit altered kinematics. Preterm infants are widely considered to be a neurologically compromised population and often experience feeding difficulties, yet measuring performance, and how performance matures in pediatric populations is challenging. Feeding problems are often compounded by complications arising from surgical procedures performed to ensure the survival of preterm infants, such as damage to the recurrent laryngeal nerve (RLN) during patent ductus arteriosus correction surgery. Here, we used a validated infant pig model for infant feeding to test how preterm birth, postnatal maturation, and RLN lesion interact to impact hyoid and thyroid excursion and their coordination. We filmed infant pigs when feeding using videofluorscopy at seven days old (1-2 months human equivalent) and 17 days old (6-9 months human equivalent) and tracked movements of the hyoid and thyroid on both days. We found that preterm birth impacted the coordination between hyoid and thyroid movements, but not their actual excursion. In contrast, excursion of the two structures increased with postnatal age in term and preterm pigs. RLN lesion decreased thyroid excursion, and primarily impacted hyoid movements by increasing variation in hyoid excursion. This work demonstrates that RLN lesion and preterm birth have distinct, but pervasive effects on feeding performance in infants, and suggest that interventions targeted towards reducing dysphagia should be prescribed based off the etiology driving dysphagia, rather than the prognosis of dysphagia.
Biomechanical comparison of squatting and "optimal" supine birth positions.
Venue: Journal of biomechanics

In obstetric science, it is unknown whether the inherent biomechanical features of the squatting position can be achieved and/or transposed to the supine birth position. In this study Biomechanical features of the squatting position were compared with 2 hyperflexed supine positions for giving birth. Thirteen pregnant women past the 32 weeks of gestational age not in labor were assessed first in the squatting position with the feet flat on the floor, then in the hyperflexed supine position, and finally in the optimal supine position "crushing" the hand of the caregiver onto the bed. For each position, the flexion of the spine associated with the plane of the external conjugate (ANGce) and the pelvis, hip flexion, and abduction were quantified using an optoelectronic motion capture system. A non-invasive strain-gauge-based measuring system was used to track the lumbar curve. An optimal position was defined with a flat lumbar spine and a pelvic inlet plane perpendicular to the lumbar spine (ANGce = 0° ± 5°). For the 13 participants, hip flexion, hip abduction, and the lumbar curve did not differ significantly for the three positions (squatting position, hyperflexed supine position, and OS) in the post-hoc analyses. The optimal supine position induced an ANGce closer to the perpendicular plane than the squatting position (p = 0.002). In the squatting position or in hyperflexed supine position positions, none of the subjects fulfilled the two conditions considered necessary to reach the optimal position. The squatting position was not significantly different from the supine hyperflexed supine position with or without voluntary lordosis correction.
Foot contact identification using a single triaxial accelerometer during running.
Venue: Journal of biomechanics

The analysis of in-field biomechanics data typically requires the identification of foot contact. Existing techniques to identify foot contact using accelerometers offer a viable option for identifying foot contact in the field. However, these techniques often require the placement of additional accelerometers or the identification of impact peaks, which can be difficult when peaks are low. Using resultant tibial acceleration to identify foot contact may overcome these limitations. The purpose of this study was to develop a new technique for identifying time of foot contact during rearfoot strike running from a single triaxial accelerometer placed on the distal tibia. Additionally, we sought to establish the concurrent validity of this new technique. An algorithm to identify foot contact from a local minimum in the resultant tibial acceleration waveform was developed and tested in nineteen rearfoot strike runners. Foot contact determined from the resultant tibial acceleration occurred 2.3 ± 4.7 ms earlier than foot contact determined from vertical ground reaction force, with 95% limits of agreement of -6.8 to 11.5 ms. The difference between the two methods was less than 10 ms for 183 out of 190 foot contacts. These findings compare favorably to previous techniques for identifying foot contact using accelerometers. Additionally, this technique can also be used when peak tibial accelerations are low. We recommend this technique to identify foot contacts in the field, particularly when some peak values are expected to be low.