nils-herrmann/clean_scirepeval huggingface dataset:
Basic inertial quantities including multi-segment trunk of fit, young males obtained based on personalized data.
Venue: Journal of biomechanics

Up to now several researchers use values of basic inertial quantities of human body parts obtained for old cadavers. Taking into account the trunk researchers presented this body part often as one segment only and rarely as few-segment part. The purpose of this study was obtaining values of basic inertial quantities of body parts including five parts of the trunk for young, fit living males. Thirty young, fit males (age: 24 ± 4 years, height: 179 ± 6 cm, body mass: 74 ± 7 kg) were directly measured (circumferences and skin-fat folds) and photographed in order to use these data for Clauser et al. (parts of extremities) and Erdmann's (parts of trunk) methods for estimation of mass and location of centres of mass of body parts. These methods take into account personal data for estimating inertial quantities. Relative mass (according to the mass of the whole body) of trunk parts (sum of thorax + abdomen + pelvis but without shoulder girdle) of subjects investigated in this work was similar to that obtained by Dempster for old cadavers. Relative mass differed for shoulders and for lower extremities. Old subjects for both lower extremities had around 31-32% of the whole body mass and young subjects had almost 37%. Procedure for obtaining location of the whole body centre of mass for graphical method (summation of mas) was presented. Obtained data are very important for analyses of arched trunk, e.g. in high jumping, pole vault jumping, rhythmic gymnastics of young, fit athletes and also for models of young passengers in car-crash tests, for ergonomics and medical analyses and other purposes.
Propulsive joint powers track with sensor-derived angular velocity: A potential tool for lab-less gait retraining.
Venue: Journal of biomechanics

Lower propulsive joint powers, particularly at the ankle, are often observed in older compared to young adults. Interventions to increase joint powers often require labs with motion capture and force treadmill technology. Translating these interventions out of the lab requires identifying portable measures that track (i.e., strongly correlate with) changes in joint powers. The purpose of this study was to determine if kinematics collected using inertial measurement units (IMUs) correlate with propulsive joint powers calculated using inverse dynamics. We collected data simultaneously with motion capture, force plates, and IMU sensors as young and older adults walked at varying speeds overground in a laboratory. Hip, knee, and ankle joint powers were calculated using inverse dynamics and positive peaks in the second half of stance were identified as the propulsive powers of interest. Raw IMU gyroscope data were oriented to a functional medial-lateral axis and peaks in the second half of stance were identified for segment (thigh, shank, foot) and joint (hip, knee, ankle) angular velocities. Pearson correlation coefficients were calculated between peak joint powers and peak angular velocities. We identified significant (all p < 0.001) correlations between hip joint power and hip and thigh angular velocities (r = 0.80-0.83) and between ankle joint power and ankle, shank, and foot angular velocities (r = 0.77-0.89). Correlation strength was similar between young and older adults and between segment and joint angular velocities. These results suggest that changes in joint powers longitudinally or over the course of an intervention could be tracked using a minimal set of wearable sensors.
The effects of general fatigue induced by incremental exercise test and active recovery modes on energy cost, gait variability and stability in male soccer players.
Venue: Journal of biomechanics

The aerobic endurance is considered an important physiological capacity of soccer players which is examined by Incremental Exercise Test (IET). However, it is not clear how general fatigue induced by IET influences physiological and biomechanical gait features in soccer players and how players recover optimally at post-IET. Here, the effect of general fatigue induced by IET on energy cost, gait variability and stability in soccer players was investigated. To identify an optimal recovery mode, the effect of walking at Preferred Walking Speed (PWS), running at Individual Ventilation Threshold (IVT) (two active recovery modes), and Rest (a passive recovery mode) on aforementioned features were studied. Nine male players walked 4-min at PWS on a treadmill prior IET (PreT), which was followed by four 4-min walking trials (PosT-0, 1, 2, and 3) with three 4-min recovery intervals (PWS, IVT, or Rest) between them, in three sessions (one for each recovery mode) in a random order. Energy cost, gait variability and stability were examined at PreT (baseline), and at PosT-0, 1, 2, and 3 (intervals of respectively 0-4, 8-12, 16-20, 24-28 min at post-IET). Gait variability was assessed by the standard deviation of trunk angle and gait stability was assessed by the local dynamic stability of trunk angular velocity. Gait stability was not affected by IET, despite increases in gait variability and energy cost. Different from IVT, PWS and Rest recovery modes reduced energy cost at post-IET. Gait variability and energy cost recovered at PosT-1 and PosT-2, suggesting that 8-12 and 16-20 min recovery intervals, respectively, were required for returning to their baselines. No preference for active over passive recovery was found in terms of gait variability and energy cost.
Elucidating failure mechanisms in human femurs during a fall to the side using bilateral digital image correlation.
Venue: Journal of biomechanics

An improved understanding of the mechanical properties of human femurs is a milestone towards a more accurate assessment of fracture risk. Digital image correlation (DIC) has recently been adopted to provide full-field strain measurements during mechanical testing of femurs. However, it has typically been used to measure strains on the anterior side of the femur, whereas in both single-leg-stance and sideways fall loading conditions, the highest deformations result on the medial and lateral sides of the femoral neck. The goal of this study was to measure full-field deformations simultaneously on the medial and lateral side of the femoral neck in a configuration resembling a fall to the side. Twelve female cadaver femurs were prepared for DIC measurements and tested in sideways fall at 5 mm/s displacement rate. Two pairs of cameras recorded the medial and lateral side of the femoral neck, and deformations were calculated using DIC. The samples exhibited a two-stage failure: first, a compressive collapse on the superolateral side of the femoral neck in conjunction with peak force, followed by complete femoral neck fracture at the force drop following the post-elastic phase. DIC measurements corroborated this observation by reporting no tensile strains above yield limit for the medial side of the neck up to peak force. DIC measurements registered onto the bone micro-architecture showed strain localizations in proximity of cortical pores due to, for instance, blood vessels. This could explain previously reported discrepancies between simulations and experiments in regions rich with large pores, like the superolateral femoral neck.
Passive load-deformation properties of human temporal muscle.
Venue: Journal of biomechanics

The passive load-deformation properties of the human temporal muscle applicable to computer simulations of the human head or the comparison of the temporal muscle to other graft materials are unexplored to date and it is unclear, if these properties depend on age, sex, post-mortem interval or body side. Eighty-eight fresh temporal muscle samples from 69 human cadavers (age range 4 months - 94 years) were investigated in a quasi-static tensile setup. For comparative reasons, 20 age-matched human temporal muscle fascia and scalp samples were tested in the same manner as the temporal muscle. Human temporal muscle showed an elastic modulus of 1.58 ± 0.64 MPa, an ultimate tensile strength of 0.26 ± 0.11 MPa and a strain at maximum force of 26.21 ± 12.48%. These parameters were independent of sex (p > 0.88), side (p > 0.92) and post-mortem interval (p > 0.09). All passive load-deformation parameters of the human temporal muscle differed from temporal muscle fascia and scalp except for the strain at maximum force of the temporal muscle and scalp. Significantly different load-deformation properties of the human temporal muscle from temporal muscle fascia and scalp indicate the need for a separate simulation of these soft tissue layers in computational head models to reflect lifelike conditions. Contrary to other tissues such as scalp or temporal muscle fascia the biomechanical temporal muscle properties in head models may not require adjustments for sex, side and age based on the here-presented findings.
Estimating ankle torque and dynamics of the stabilizing mechanism: No need for horizontal ground reaction forces.
Venue: Journal of biomechanics

Changes in human balance control can objectively be assessed using system identification techniques in combination with support surface translations. However, large, expensive and complex motion platforms are required, which are not suitable for the clinic. A treadmill could be a simple alternative to apply support surface translations. In this paper we first validated the estimation of the joint stiffness of an inverted pendulum using system identification methods in combination with support surface translations, by comparison with the joint stiffness calculated using a linear regression method. Second, we used the system identification method to investigate the effect of horizontal ground reaction forces on the estimation of the ankle torque and the dynamics of the stabilizing mechanism of 12 healthy participants. Ankle torque and resulting frequency response functions, which describes the dynamics of the stabilizing mechanism, were calculated by both including and excluding horizontal ground reaction forces. Results showed that the joint stiffness of an inverted pendulum estimated using system identification is comparable to the joint stiffness estimated by a regression method. Secondly, within the induced body sway angles, the ankle torque and frequency response function of the joint dynamics calculated by both including and excluding horizontal ground reaction forces are similar. Therefore, the horizontal ground reaction forces play a minor role in calculating the ankle torque and frequency response function of the dynamics of the stabilizing mechanism and can thus be omitted.
Calibration of the shear wave speed-stress relationship in in situ Achilles tendons using cadaveric simulations of gait and isometric contraction.
Venue: Journal of biomechanics

It has been shown that shear wave speed is directly dependent on axial stress in ex vivo tendons. Hence, a wave speed sensor could be used to track tendon loading during movement. However, adjacent soft tissues and varying joint postures may affect the wave speed-load relationship for intact tendons. The purpose of this study was to determine whether the proportional relationship between squared wave speed and stress holds for in situ cadaveric Achilles tendons, to evaluate whether this relationship is affected by joint angle, and to assess potential calibration techniques. Achilles tendon wave speed and loading were simultaneously measured during cadaveric simulations of gait and isometric contractions performed in a robotic gait simulator. Squared wave speed and axial stress were highly correlated during isometric contraction at all ankle postures (R2avg = 0.98) and during simulations of gait (R2avg = 0.92). Ankle plantarflexion angle did not have a consistent effect on the constant of proportionality (p = 0.217), but there was a significant specimen-angle interaction effect (p < 0.001). Wave speed-based predictions of tendon stress were most accurate (average RMS error = 11% of maximum stress) when calibrating to isometric contractions performed in a dorsiflexed posture that resembled the posture at peak Achilles loading during gait. The results presented here show that the linear relationship between tendon stress and squared shear wave speed holds for a case resembling in vivo conditions, and that calibration during an isometric task can yield accurate predictions of tendon loading during a functional task.
Simulated lesions representative of metastatic disease predict proximal femur failure strength more accurately than idealized lesions.
Venue: Journal of biomechanics

Metastatic disease in bone is characterized by highly amorphous and variable lesion geometry, with increased fracture risk. Assumptions of idealized lesion geometry made in previous finite element (FE) studies of metastatic disease in the proximal femur may not sufficiently capture effects of local stress/strain concentrations on predicted failure strength. The goal of this study was to develop and validate a FE failure model of the proximal femur incorporating artificial defects representative of physiologic metastatic disease. Data from 11 cadaveric femur specimens were randomly divided into either a training set (n = 5) or a test set (n = 6). Clinically representative artificial defects were created, and the femurs were loaded to failure under offset torsion. Voxel-based FE models replicating the experimental setup were created from the training set pre-fracture computed tomography data. Failure loads from the linear model with maximum principal strain failure criterion correlated best with the experimental data (R2 = 0.86, p = 0.024). The developed model was found to be reliable when applied to the test dataset with a relatively low RMSE of 46.9 N, mean absolute percent error of 12.7 ± 17.1%, and cross-validation R2 = 0.88 (p < 0.001). Models simulating realistic lesion geometry explained an additional 26% of the variance in experimental failure load compared to idealized lesion models (R2 = 0.62, p = 0.062). Our validated automated FE model representative of physiologic metastatic disease may improve clinical fracture risk prediction and facilitate research studies of fracture risk during functional activities and with treatment interventions.
Modified vector coding analysis of trunk and lower extremity kinematics during maximum and sub-maximum back squats.
Venue: Journal of biomechanics

The back squat is a complex movement with significant demands on the lower extremities and trunk to raise an external load. The back squat is simultaneously an open and closed kinetic chain movement that requires coordination of the entire body for successful completion of the lift. Therefore, this study aimed to examine coordination of the thigh and shank, trunk and thigh, and the hip and knee during the concentric phase of maximum, supra-maximum (at 105% max), and sub-maximum (at 80% max) back squats. Fourteen resistance trained adults participated in this study. Maximum back squat loads were determined using a previously determined progressive load protocol. Motion capture of the trunk and lower extremities and ground reaction force data were recorded during all squats. Angle-angle plots and modified vector coding were performed to analyze segment and joint coupling angles and knee-hip moments. Overall, the concentric phase of back squats depict a transition from early knee dominance to hip dominance as the system ascends. Interestingly, all squats presented with coupling of thigh-rising and trunk-falling. Based on the angle-angle plots and the modified vector coding results, the prolonged coupling of trunk falling and thigh rising likely resulted in too large of a moment arm for the external load for the participants to overcome during Supramax conditions.
Effect of random variation of input and various daily activities on wear in a hip joint simulator.
Venue: Journal of biomechanics

The ISO 14242-1 standard specifies fixed, simplified, sinusoidal motion and double-peak load cycles for wear testing of total hip prostheses. In order to make the wear simulation more realistic, random variation was added for the first time to the motion and load control signals of a hip joint simulator. For this purpose and for the simulation of various daily activities, computer-controlled, servo-electric drives were mounted on a biaxial hip simulator frame and successfully introduced. Random variation did not result in a statistically significant difference in the wear factor of large diameter VEXLPE liners compared with fixed sinusoidal waveforms. However, level walking according to biomechanical literature surprisingly resulted in a 134 per cent higher, and jogging in a 57 per cent lower wear factor compared with the fixed sinusoidal waveforms. These wear phenomena were likely to be caused by a variation in the lubrication conditions and frictional heating. Simplified motion waveforms may result in an underestimation of wear in walking.
An experimental and computational investigation of the material behaviour of discrete homogenous iliofemoral and carotid atherosclerotic plaque constituents.
Venue: Journal of biomechanics

An enhanced understanding of the structure and mechanical behavior of atherosclerotic plaque can potentially provide key guidance for clinical intervention and vascular device design. This study presents an investigation of morphological and mechanical properties of iliofemoral (n = 8) and carotid (n = 22) atherosclerotic plaque constituents. μCT analysis is used characterize the content and morphology of calcifications in excised plaques. Calcified particles contribute a significant proportion of the average plaque volume (7.6% carotid; 19.1% iliofemoral), and on average over 50% of this volume (53.7 ± 18.6% carotid; 61.7 ± 15% iliofemoral) is accounted for by the largest individual particle found in the plaque. Fibrous tissue and calcifications were isolated for mechanical testing. Unconfined compression testing of isolated calcifications uncovered viscoelastic behavior. Tensile stress relaxation uncovered viscoelastic behavior in fibrous atherosclerotic samples. Iliofemoral fibrous samples were found to be statistically significantly stiffer (*p < 0.05) than carotid fibrous samples. Results show isolated calcifications are approximately two orders of magnitude stiffer than non-calcified fibrous tissue. The results from this study advance the current understanding of plaque mechanics and suggest that computational simulation of angioplasty procedures should incorporate a discrete representation of atherosclerotic plaque constituents.
Effect of foods on selected dynamic parameters of mandibular elevator muscles during symmetric incisal biting.
Venue: Journal of biomechanics

The paper focuses on research that enables the relationship between food and selected mechanical parameters do be determined. The main aim of the study was to designate, depending on the food: (1) the work of a single muscle (i.e. masseter, medial pterygoid, temporalis), and (2) the energy balance of mandibular elevator muscles based on the dynamic patterns of muscles. In turn, the indirect goal was to determine: (1) the muscle contraction, and (2) the average muscle contraction velocity based on the specified kinematic parameters, i.e. incisal biting velocity and incisal biting time. A hybrid model, consisting of a phenomenological model of the masticatory system and a behavioural model of incisal biting, was used in the calculations. The phenomenological model was based on an anatomically and physiologically normal mandible and healthy muscles, while the behavioural model was represented by the dynamic patterns of food. Calculations showed that muscle force is an important, but not the only, parameter that enables the quantitative and qualitative assessment of the functioning of the mandibular elevator muscles during symmetric incisal biting. Based on the obtained results, it can be stated that the dynamic patterns of muscles are a very important parameter, because on their basis, among others, muscle contraction, contraction time, work, and energy can be determined. The conducted calculations and analyses showed that the above-mentioned parameters depend on the mechanical properties of food (the dynamic patterns of food).
Mechanical work performed by distal foot-ankle and proximal knee-hip segments during anticipated and unanticipated cutting.
Venue: Journal of biomechanics

Side-step cutting is a common evasive maneuver which is typically performed without prior anticipation. Studies quantifying joint work and its inter-joint proportions in cutting have not accounted for work done by the foot, even though this segment has been shown to be an important source of mechanical work in walking, running, and landing. The aims of this study were to: (1) quantify the magnitude of foot work performed and provide a more precise account of percentage joint work during cutting, and (2) examine the effect, a lack of anticipation had on these variables. Three-dimensional motion capture with forceplates were used to assess the cutting behaviour of 17 healthy participants. All participants performed a 45° cut with an approach speed of 4 m/s. Hip, knee, and ankle joint work were calculated using inverse dynamics; whilst foot work was quantified using the Unified-Deformable foot method. The foot contributed up to 12.45% and 3.09% of total limb negative and positive work, respectively. Unanticipated cutting significantly reduced ankle positive work (-0.09 J/kg [95% CI -0.13 to -0.06], P < 0.001) and significantly reduced percentage ankle positive work (-2.17% [95% CI -3.47 to -0.86], P = 0.001). The foot performs as much negative work as the hip but had only a minor contribution to positive work during cutting. Anticipation had a negligible influence on joint work and its inter-joint proportions. The foot should not be neglected in understanding whole-body dynamics during cutting, with greater understanding of its function potentially useful for informing athletic footwear design and cutting technique modification.
A comparison of currently available optoelectronic motion capture systems.
Venue: Journal of biomechanics

The measurement of human motion relies heavily on the ability of the optoelectronic motion capture systems to accurately measure retroreflective marker positions. Marker position accuracy is largely dependent on the optical characteristics of the camera system and algorithms implemented in the tracking software. In 1999, Richards critically reviewed multiple camera systems and each of their ability to generate the same marker coordinate positions under different field tests. Field tests were designed utilizing what became to be known as the Standard Assessment of Motion System Accuracy (SAMSA) device. The SAMSA test results indicated that some systems outperformed others and accuracy varied depending on the test. In the subsequent 20 years, motion capture technology has significantly improved. Therefore, we aimed to replicate the tests from 1999 using current, higher-resolution motion capture systems and current calibration techniques. Reference marker distances were established utilizing a FaroArm 3D digitizer (FARO technologies). The modern cameras field test performance showed nearly a three-fold improvement in agreement with the reference measure compared to their 1999 predecessors. No systems' absolute marker distance measured greater than 0.5 mm from the FaroArm measurement and no systems' maximum error exceeded 1.0 mm. Given the consistency in accuracy reported by all the systems included in the current assessment, it's reasonable to assume that the current systems would eliminate errors associated with system hardware/software as an obstacle to sharing data between laboratories.