nils-herrmann/clean_scirepeval huggingface dataset:
Stability-normalised walking speed: A new approach for human gait perturbation research.
Venue: Journal of biomechanics

In gait stability research, neither self-selected walking speeds, nor the same prescribed walking speed for all participants, guarantee equivalent gait stability among participants. Furthermore, these options may differentially affect the response to different gait perturbations, which is problematic when comparing groups with different capacities. We present a method for decreasing inter-individual differences in gait stability by adjusting walking speed to equivalent margins of stability (MoS). Eighteen healthy adults walked on a split-belt treadmill for two-minute bouts at 0.4 m/s up to 1.8 m/s in 0.2 m/s intervals. The stability-normalised walking speed (MoS = 0.05 m) was calculated using the mean MoS at touchdown of the final 10 steps of each speed. Participants then walked for three minutes at this speed and were subsequently exposed to a treadmill belt acceleration perturbation. A further 12 healthy adults were exposed to the same perturbation while walking at 1.3 m/s: the average of the previous group. Large ranges in MoS were observed during the prescribed speeds (6-10 cm across speeds) and walking speed significantly (P < 0.001) affected MoS. The stability-normalised walking speeds resulted in MoS equal or very close to the desired 0.05 m and reduced between-participant variability in MoS. The second group of participants walking at 1.3 m/s had greater inter-individual variation in MoS during both unperturbed and perturbed walking compared to 12 sex, height and leg length-matched participants from the stability-normalised walking speed group. The current method decreases inter-individual differences in gait stability which may benefit gait perturbation and stability research, in particular studies on populations with different locomotor capacities.
Comparison of posturographic outcomes between two different devices.
Venue: Journal of biomechanics

The Interactive Balance System (IBS), a posturography device for assessing posture control, is widely used in clinical and rehabilitation settings. However, data on the validity of the device are unavailable. Fluctuations of the center of pressure (COP) were measured in 24 healthy participants (age: 29 ± 5 (mean ± SD) years, 12 females) synchronously using the IBS, which was rigidly mounted on a Kistler platform. Four different bipedal conditions were examined: eyes open or closed on stable or soft surfaces. Time series were compared using congruity (CON, proportion of the measurement time during which values of both devices changed similarly in direction), whereas IBS-specific postural outcomes were correlated with traditional postural control outcomes of the Kistler force platform. The time-displacement curves showed similar shapes for CON (>0.9) for each of the four standing conditions without differences between male and female participants (P > 0.39). The path length results of both devices showed very high linear associations, explaining on average 92% (medio-lateral) or 96% (anterior-posterior) of the common variance. The Kistler path length of the anterior-posterior direction revealed nearly perfect linear associations with the stability index of the IBS (r2 > 0.99). The results of this study indicate that the IBS provides valid posturographic results. Since the medial-lateral and anterior-posterior trajectories of the IBS can be used to calculate COP fluctuations, comparisons between different measurement systems are possible.
The differences in sagittal plane whole-body angular momentum during gait between patients with hemiparesis and healthy people.
Venue: Journal of biomechanics

Regulation of whole-body angular momentum (WBAM) is essential for maintaining dynamic balance during gait. Patients with hemiparesis frequently fall toward the anterior direction; however, whether this is due to impaired WBAM control in the sagittal plane during gait remains unknown. The present study aimed to investigate the differences in WBAM in the sagittal plane during gait between patients with hemiparesis and healthy individuals. Thirty-three chronic stroke patients with hemiparesis and twenty-two age- and gender-matched healthy controls walked along a 7-m walkway while gait data were recorded using a motion analysis system and force plates. WBAM and joint moment were calculated in the sagittal plane during each gait cycle. The range of WBAM in the sagittal plane in the second half of the paretic gait cycle was significantly larger than that in the first and second halves of the right gait cycle in the controls (P = 0.015 and P = 0.011). Furthermore, multiple regression analysis revealed the slower walking speed (P < 0.001) and larger knee extension moment on the non-paretic side (P = 0.003) contributed to the larger range of WBAM in the sagittal plane in the second half of the paretic gait cycle. Our findings suggest that dynamic stability in the sagittal plane is impaired in the second half of the paretic gait cycle. In addition, the large knee extension moment on the non-paretic side might play a role in the dynamic instability in the sagittal plane during gait in patients with hemiparesis.
In vivo ankle joint kinematics from dynamic magnetic resonance imaging using a registration-based framework.
Venue: Journal of biomechanics

In this paper, we propose a method for non-invasively measuring three-dimensional in vivo kinematics of the ankle joint from a dynamic MRI acquisition of a single range-of-motion cycle. The proposed approach relies on an intensity-based registration method to estimate motion from multi-plane dynamic MRI data. Our approach recovers not only the movement of the skeleton, but also the possibly non-rigid temporal deformation of the joint. First, the rigid motion of each ankle bone is estimated. Second, a four-dimensional (3D+time) high-resolution dynamic MRI sequence is estimated through the use of the log-euclidean framework for the computation of temporal dense deformation fields. This approach has been then applied and evaluated on in vivo dynamic MRI data acquired for a pilot study on six healthy pediatric cohort in order to establish in vivo normative joint biomechanics. Results demonstrate the robustness of the proposed pipeline and very promising high resolution visualization of the ankle joint.
An assessment of the information lost when applying data reduction techniques to dynamic plantar pressure measurements.
Venue: Journal of biomechanics

Data reduction techniques are commonly applied to dynamic plantar pressure measurements, often prior to the measurement's analysis. In performing these data reductions, information is discarded from the measurement before it can be evaluated, leading to unkonwn consequences. In this study, we aim to provide the first assessment of what impact data reduction techniques have on plantar pressure measurements. Specifically, we quantify the extent to which information of any kind is discarded when performing common data reductions. Plantar pressure measurements were collected from 33 healthy controls, 8 Hallux Valgus patients, and 10 Metatarsalgia patients. Eleven common data reductions were then applied to the measurements, and the resulting datasets were compared to the original measurement in three ways. First, information theory was used to estimate the information content present in the original and reduced datasets. Second, principal component analysis was used to estimate the number of intrinsic dimensions present. Finally, a permutational multivariate ANOVA was performed to evaluate the significance of group differences between the healthy controls, Hallux Valgus, and Metatarsalgia groups. The evaluated data reductions showed a minimum of 99.1% loss in information content and losses of dimensionality between 20.8% and 83.3%. Significant group differences were also lost after each of the 11 data reductions (α=0.05), but these results may differ for other patient groups (especially those with highly-deformed footprints) or other region of interest definitions. Nevertheless, the existence of these results suggest that the diagnostic content of dynamic plantar pressure measurements is yet to be fully exploited.
Does the condylar lift-off method or the separation method better detect loss of contact between tibial and femoral implants based on analysis of single-plane radiographs following total knee arthroplasty?
Venue: Journal of biomechanics

Loss of contact between the femoral and tibial implants following total knee arthroplasty (TKA) has been related to accelerated polyethylene wear and other complications. Two methods have been used to detect loss of contact in single-plane fluoroscopy, the condylar lift-off method and the separation method. The objectives were to assess the ability of each method to detect loss of contact.



TKA was performed on ten cadaveric knee specimens. Tibial force was measured in each compartment as specimens were flexed from 0° to 90° while internal-external and varus-valgus moments were applied. Single-plane radiographs taken simultaneously with tibial force were analyzed for loss of contact using the two methods. Receiver operating characteristic (ROC) and optimum threshold distances were determined.



For the lift-off method and the separation method, the areas under the ROC curves were 0.89 vs 0.60 for the lateral compartment only and 0.81 vs 0.70 for the medial compartment only, respectively. For the lift-off method, the optimum threshold distances were 0.7 mm in the lateral compartment only and 0.1 mm in the medial compartment only but the false positive rate for the medial compartment only almost doubled. For both compartments jointly, the areas under the ROC curves decreased to 0.70 and 0.59 for the lift-off and separation methods, respectively.



When detecting loss of contact using single-plane fluoroscopy, the lift-off method is useful for the lateral compartment only but not for the medial compartment only and not for both compartments jointly. The separation method is not useful.
Validity and reliability of peak tibial accelerations as real-time measure of impact loading during over-ground rearfoot running at different speeds.
Venue: Journal of biomechanics

Studies seeking to determine the effects of gait retraining through biofeedback on peak tibial acceleration (PTA) assume that this biometric trait is a valid measure of impact loading that is reliable both within and between sessions. However, reliability and validity data were lacking for axial and resultant PTAs along the speed range of over-ground endurance running. A wearable system was developed to continuously measure 3D tibial acceleration and to detect PTAs in real-time. Thirteen rearfoot runners ran at 2.55, 3.20 and 5.10 m·s-1 over an instrumented runway in two sessions with re-attachment of the system. Intraclass correlation coefficients (ICCs) were used to determine within-session reliability. Repeatability was evaluated by paired T-tests and ICCs. Concerning validity, axial and resultant PTAs were correlated to the peak vertical impact loading rate (LR) of the ground reaction force. Additionally, speed should affect impact loading magnitude. Hence, magnitudes were compared across speeds by RM-ANOVA. Within a session, ICCs were over 0.90 and reasonable for clinical measurements. Between sessions, the magnitudes remained statistically similar with ICCs ranging from 0.50 to 0.59 for axial PTA and from 0.53 to 0.81 for resultant PTA. Peak accelerations of the lower leg segment correlated to LR with larger coefficients for axial PTA (r range: 0.64-0.84) than for the resultant PTA per speed condition. The magnitude of each impact measure increased with speed. These data suggest that PTAs registered per stand-alone system can be useful during level, over-ground, rearfoot running to evaluate impact loading in the time domain when force platforms are unavailable in studies with repeated measurements.
Lung injury risk assessment during blast exposure.
Venue: Journal of biomechanics

Blast pulmonary trauma are common consequences of modern war and terrorism action. To better protect soldiers from that threat, the injury risk level when protected and unprotected must be assessed. Knowing from the literature that a possible amplification of the blast threat would be provided by some thoracic protective systems, the objective is to propose an original approach to correlate a measurable parameter on a manikin with a pulmonary risk level. Using a manikin whose response is correlated with the proposed tolerance limits should help in the evaluation of thoracic protective system regarding injury outcomes. A database including lung injury data from large mammals have been created, allowing the definition of iso-impulse tolerance limits from no lung injury to severe ones (∼60% of ecchymosis). As the use of this metric is not sufficient to evaluate the performance of protective systems on a manikin, the iso-impulse tolerance limits were associated with the thoracic response of post-mortem swine under blast loading. It was found that the lung injury threshold in terms of incident impulse is 58.3 kPa·ms, corresponding to a chest wall peak of acceleration/velocity/displacement of 7350 m/s2, 3.7 m/s and 6.4 mm respectively. Lung injuries are considered as severe (30-60% of ecchymosis) when the incident impulse exceed 232.8 kPa·ms, leading to a chest wall peak of acceleration/velocity/displacement of 79.7 km/s2, 14.7 m/s and 30.1 mm respectively. The defined lung tolerance limits are valid for a 50 kg swine (unprotected) exposed side-on to the blast threat and against a wall.
The effect on conventional gait model kinematics and kinetics of hip joint centre equations in adult healthy gait.
Venue: Journal of biomechanics

The Conventional Gait Model (CGM) needs to benefit from large investigations on localization of the hip joint centre (HJC). Incorrect positions from the native equations were demonstrated (Sangeux et al., 2014; Harrington et al., 2007). More accurate equations were proposed but their impact on kinematics and kinetic CGM outputs was never evaluated. This short communication aims at examining if adoption of new HJC equations would alter standard CGM outputs. Sixteen able bodied participants underwent a full 3-D optoelectronic gait analysis followed by a 3-D ultrasound localization of their hips. Data were processed through the open source python package pyCGM2 replicating kinematic and kinetic processing of the native CGM. Compared with 3D ultrasound location, Hara equations improved the accuracy of sagittal plane kinematics (0.6°) and kinetics (0.02 N m kg-1) for the hip. The worst case participant exhibited Harrington's equations reached a deviation of 3° for the sagittal kinematics. In the coronal plane, Hara and Harrington equations presented similar differences (1°) for the hip whilst Davis equations had the largest deviation for hip abduction (2.7°) and hip abductor moment (0.10 N m kg-1). Both Harrington and Hara equations improved the CGM location of the HJC. Hara equations improved results in the sagittal plane, plus utilise a single anthropometrics measurement, leg length, that may be more robust. However, neither set of equations had significant effect on kinematics. We reported some effects on kinetics, particularly in the coronal plane, which warrant caution in interpreting outputs using different sets of equations.
Biophysical properties of cells for cancer diagnosis.
Venue: Journal of biomechanics

Biophysical properties associated with the microenvironment of a tumor has been recognized as an important modulator for cell behaviour and function. Particularly, tissue rigidity is important during tumor carcinogenesis as it affects the tumor's ability to metastasis. Multiple downstream pathways are affected with a difference in rigidity of the extracellular matrix. The insight into tumor mechanosignalling represents a promising field that may lead to novel approaches for cancer diagnostics. Measurement of rigidity of the extracellular matrix or the tissue is a potential diagnostics approach for cancer detection. Altered extracellular matrix states persist for a long period of time and have lower heterogeneity compared to protein or genetic markers, therefore are more reliable as biomarkers. On the other hand, measurement of different kinase associated proteins or transcripts provide an early insight into potential transition of cells towards metastasis. Co-localization of transcriptional factors like YAP/TAZ provide an insight to determine if the cells are undergoing metastatic changes. This review explains the unique biophysical properties of the tumor microenvironment that present the potential targets for the diagnosis of cancer.
Biomechanical evaluation of walking and cycling in children.
Venue: Journal of biomechanics

Physical activity in children is important as it leads to healthy growth due to physiological benefits. However, a physiological benefit can be partially negated by excessive or unphysiological loads within the joints. To gain an initial understanding into this, the present study sought to compare joint loading between walking and cycling in children. With institutional ethical approval, 14 pre-pubertal children aged 8-12 walked on an instrumented treadmill and cycled on a stationary ergometer. Two methods were used to match physiological load. Cardiovascular loads between walking and cycling were matched using heart rate. Metabolic load was normalised by matching estimates of oxygen consumption. Joint reaction forces during cycling and walking as well as joint moments were derived using inverse dynamics. Peak compressive forces were greater on the knees and ankles during walking than during cycling. Peak shear peak forces at the knee and ankle were also significantly larger during walking than during cycling, independent of how physiological load was normalised. For both cycling conditions, ankle moments were significantly smaller during cycling than walking. No differences were found for knee moments. At equivalent physiological intensities, cycling results in less joint loading than walking. It can be speculated that for certain populations and under certain conditions cycling might be a more suitable mode of exercise than weight bearing activities to achieve a given metabolic load.
The impact of increased femoral antetorsion on gait deviations in healthy adolescents.
Venue: Journal of biomechanics

Increased femoral antetorsion leads to several gait deviations, and amongst others, an increased knee flexion was reported in mid and terminal stance. Therefore, the purpose of this retrospective study was to identify gait deviations caused by increased femoral antetorsion and to perform subgroup analyses based on sagittal knee kinematics. Patients with isolated, CT confirmed increased femoral antetorsion (n = 42) and age-matched typically developing children (TDC, n = 17) were included in this study. Patients were referred to gait analysis because of gait abnormalities going along with an increased femoral antetorsion ≥30°. Kinematic and kinetic data were recorded during 3D gait analysis and three valid gait cycles were analyzed. Principal component (PC) analysis was used to achieve data transformation. A linear mixed model was used to estimate the group effect of PC-scores of retained PCs explaining 90% of the cumulative variance. Group effects of PC-scores revealed that patients walked with more flexed hips and greater anterior pelvic tilt throughout the gait cycle. Knee flexion was increased in patients during mid and terminal stance. Increased frontal plane knee and hip joint moments were found for patients compared to TDC. Furthermore, dividing patients into two subgroups based on their sagittal knee kinematics showed that kinematic gait deviations were more pronounced in patients with higher femoral antetorsion, while deviations in joint moments were more pronounced in patients with lower femoral antetorsion. Increased femoral antetorsion showed alterations in all lower limb joints and may be not only a cosmetic problem. Therefore, 3D gait analysis should be used for clinical management and operative treatment should be considered depending on severity of gait deviations.
Experiments on dynamic behaviour of a Dacron aortic graft in a mock circulatory loop.
Venue: Journal of biomechanics

Dacron grafts are currently used for the surgical treatment of aortic aneurysm and acute dissection, two otherwise fatal pathologies when aortic wall rupture occurs. While Dacron is chosen for aortic grafts because of characteristics such as biocompatibility and durability, few data are available about the dynamic response of Dacron prosthetic devices and about their side effects on the cardiovascular system. In this study, a Dacron graft was subjected to physiological flow conditions in a specifically-developed mock circulatory loop. Experiments were conducted at different physiological pulsation-per-minute rates. Results show that, in comparison to an aortic segment of the same length, the prosthesis is extremely stiffer circumferentially, thus limiting the dynamical radial expansion responsible for the Windkessel effect in human arteries. The prosthesis is instead excessively compliant in the axial direction and develops preferentially bending oscillations. This very different dynamic behaviour with respect to the human aorta can alter cardiovascular pressure and flow dynamics resulting in long-term implant complications.
Head mounted displays for capturing head kinematics in postural tasks.
Venue: Journal of biomechanics

Tracking head motion in a simple, portable and accurate manner during performance of postural tasks in a virtual reality environment could have important implications for investigating normal and pathological head kinematics. We investigated concurrent validity of head tracking of two Head Mounted Displays (HMDs), Oculus Rift and HTC Vive, vs. a gold-standard motion capture system (Qualisys). Head kinematics of N = 20 healthy young adults was quantified during static and dynamic postural tasks. While wearing the Oculus Rift or HTC Vive, participants observed moving stars (static tasks) or a flying ball (dynamic task). Head kinematics were recorded simultaneously by the Rift or Vive and Qualisys camera system. We calculated head directional path, acceleration in 6 directions and volume of translation movement. Intra-Class Correlations (ICC) and 95% Limits of agreement were calculated. Most ICC values were around 0.9 with several at 0.99 indicating excellent agreement between the HMDs and Qualisys. Weaker agreement was observed for vertical displacement during a static task and moderate agreement was observed pitch and yaw displacement during a dynamic task. A negative bias of a small magnitude (indicating more movement in VR) was observed for most variables in static tasks, while a positive bias was observed for most variables in the dynamic task (indicating less movement in VR). Our results generally support the concurrent validity of Oculus Rift and HTC Vive head tracking during static and dynamic standing tasks in healthy young adults. Specific task- and direction-dependent differences should be considered when planning measurement studies using these novel tools.