nils-herrmann/clean_scirepeval huggingface dataset:
Mechanical behavior of biomimetically mineralized collagen matrix using the polymer - induced liquid precursor process.
Venue: Journal of biomechanics

Biomimetic mineralization is a promising technique in biomedical applications. To understand the mechanical behavior of biomimetically mineralized collagen material (BMC), we examined the composition and structure of the mineral deposition in BMCs mineralized by the polymer-induced liquid precursor (PILP) process and applied wide angle x-ray scattering (WAXS) with in situ tensile testing to investigate the mineral-to-tissue co-deformation in the material. We found that the PILP process is able to achieve good biomimetic mineralization in bulk collagen matrix. Compositionally, the mineral deposition showed high crystallinity with no carbonation. However, the morphology of extrafibrillar mineral deposition and the preferential crystal orientation were different from natural bone. Further, the Young's modulus and mineral-to-tissue co-deformation ratio of the BMC were significantly lower than both natural bone and partially demineralized bone with similar mineral volume fraction. It was concluded that while biomimetic mineralization can achieve good mineral deposition volume in the BMC, the mechanical behavior of the material was different from natural bone.
Positioning and baby devices impact infant spinal muscle activity.
Venue: Journal of biomechanics

Infant positioning in daily life, particularly in relation to active neck and back muscles, may affect spinal development, psychosocial progression, and motor milestone achievement. Yet the impact of infant body position on muscle activity is unknown. The objective of this study was to evaluate neck and back muscle activity of healthy infants in common positions and baby devices. Healthy full-term infants (n = 22, 2-6 months) participated in this experimental study. Daily sleep and positioning were reported by caregivers. Cervical paraspinal and erector spinae muscle activity was measured using surface electromyography (EMG) in five positions: lying prone, lying supine, held in-arms, held in a baby carrier, and buckled into a car seat. Mean filtered EMG signal and time that muscles were active were calculated. Paired t-tests were used to compare positions to the prone condition. Caregivers reported that infants spent 12% of daily awake time prone, 43% in supine-lying baby gear, and 44% held in-arms or upright in a baby carrier. Infants exhibited highest erector spinae activity when prone, and lowest cervical paraspinal muscle activity in the car seat. No differences were found between in-arms carrying and babywearing. This first evaluation of the muscle activity of healthy infants supports the importance of prone time in infants' early spinal development because it promotes neck and back muscle activity. Carrying babies in-arms or in baby carriers may also be beneficial to neck muscle development, while prolonged time spent in car seats or containment devices may be detrimental to spinal development.
Total knee arthroplasty reduces knee extension torque in-vitro and patellofemoral arthroplasty does not.
Venue: Journal of biomechanics

Patients often have difficulty recovering knee extension strength post total knee arthroplasty (TKA), and that may reflect alteration of the mechanics including geometry and rollback kinematics, so the purpose of this work was to explore this by comparing the knee extension torque (KET) of the native knee, TKA and patellofemoral arthroplasty (PFA) in response to quadriceps tension. Eight fresh-frozen knees were mounted in a knee extension rig with quadriceps loading and tibial extension torque measurement. Each knee was subject to four conditions: native knee, PFA, cruciate-retaining (CR) and posterior-stabilized (PS) TKA. The KET was measured from 120° to 0° knee flexion. Data were analyzed using one-way ANOVA and post-hoc paired t-tests. The native KET was lowest in terminal extension and 70-100° flexion, and maximal at 20-30° flexion. PFA produced the greatest KET (p < 0.008) compared with native, CR- and PS-TKA, at 30-40° flexion. CR- and PS-TKA had lower KET across 0-50° flexion (p < 0.001 across 0-30°), falling to 25% of the native knee KET or the PFA at full extension. PFA had the highest KET in early flexion possibly due to increased trochlear offset and/or preservation of the cruciate mechanism, so PFA may be more beneficial during the functional range of motion. The claimed benefits of PS- over CR-TKA in deep flexion were not detected. Both CR- and PS-TKAs led to lower KET than the native and PFA knee states across 0-50° flexion. This mechanical effect may help to explain clinical findings of knee extension weakness post-TKA.
Time-scale mechanical behaviors of locust semi-lunar process cuticles under power amplification for rapid movements.
Venue: Journal of biomechanics

The semi-lunar process (SLP) is a key component in the power amplification of locusts to achieve rapid movements. Its mechanical properties determine the amount of the power amplification and the subsequent locomotion performance. As previously reported, the SLP cuticle endures physiological dynamic loadings. However, the time-scale mechanical properties of the SLP are still unknown, especially under stress relaxation and cyclic loadings. In this paper, the SLP cuticles of adult desert locusts (Schistocerca gregaria) were studied using stress relaxation and cyclic tests, with loadings corresponding to the physiological loading conditions of the power amplification. The SLP cuticle was found to show pronounced stress relaxation behavior with the resultant force and an evident time shift between the maximal displacement and the maximal resultant force. The number of loading cycles before mechanical failure (life cycle number) increases when the SLP cuticle is cyclically loaded by a lower stress level. Moreover, the failure strength of the SLP at low cycles equals the physiological stress level in the power amplification, implying that the healing of the cuticle might contribute to the successful performance of numerous jumps in the course of the adult locust life. This study not only deepens our understanding of the power amplification mechanism of locust locomotion but also provides valuable knowledge for the design optimization of bioinspired jumping robots and elastic energy storage devices.
Body coordination during sit-to-stand in blind and sighted female children.
Venue: Journal of biomechanics

Detecting coordination pattern and coordination variability help us to find how joints organize collaboratively to perform sit-to-stand (STS) under restricted visual input. This experiment aimed to compare the coordination of the trunk, hip, knee, and ankle and its variability between individuals with long- and short-term restricted visual input during STS. Forty-five female children participated in this study, including fifteen congenitally blind (CB) children and 30 healthy children. The healthy children were divided randomly into two groups: one group in which the participants were instructed to keep their eyes open (EO) and another to keep their eyes closed (EC) for 20 min before the test. In the standing phase, CB children had a decreased ankle-knee vector angle on the nondominant (ND) side compared to that of healthy children. In the sagittal plane, a small coefficient-of-correspondences (CoC) was observed at seat-off (hip-trunk CoC on the dominant (D) side and ankle-hip CoC on the ND side) and in the preparation phase (ankle-hip CoC on the ND side and bilateral hip CoC). In the frontal plane (at the end: ankle-knee, in the standing phase: bilateral hip) a high CoC was observed (in the standing phase: knee-trunk CoC on the D side). The EC group had smaller CoCs at initiation event (knee-trunk and bilateral knee CoCs on both sides), the end event (ankle-knee and ankle-hip CoCs on the ND side), and in the standing phase (bilateral hip CoC) in the frontal plane than the other groups. The findings reveal that vector and CoC variables are altered because of long- and short-term restricted visual data and should be a focus in rehabilitation programs.
Effects of nucleus pulposus location on spinal loads and joint centers of rotation and reaction during forward flexion: A combined finite element and Musculoskeletal study.
Venue: Journal of biomechanics

The mechanical environment of the intervertebral disc and spinal loads are intimately associated with low back pain (LBP) caused by mechanical load. The cause and effect relationship between postures and pain has been therapeutically investigated and widely used to guide patient care. Shift of the nucleus pulposus (NP) inside the intervertebral disc when the spine changes posture in the sagittal plane, known also as NP migration, has been observed and quantified in in-vivo studies. However, the effects of this phenomenon on biomechanics of the disc and the surrounding spinal structures has not been investigated. This study aimed to quantify the effects of the NP location in a moderate flexion posture on spinal load and load-sharing using a Finite Element (FE) model of the L4-L5 functional spinal unit (FSU) driven by muscle forces, reaction forces, ligament forces and disc moment predicted by a Musculoskeletal (MSK) model of the trunk. The results showed that intradiscal pressure (IDP) and compressive force are sensitive to the nucleus location while the effects on the center of rotation (CoR), center of reaction (CTR) and moment rotation curves were negligible. Also, our findings revealed that FE models should consider the effects of NP location during bending to predict more realistic results as the nucleus displacement caused by disc bulge predicted by these models is much smaller than the real shift observed in in-vivo. In addition, this study confirmed that position of the rigid joint in MSK models that fix this latter to the CoR, must be modelled carefully for more accurate muscle forces and spinal loads prediction.
In-home neurogaming: Demonstrating the impact of valid gesture recognition method on high volume kinematic outcomes.
Venue: Journal of biomechanics

The process of cleaning motion capture data of aberrant points has been described as "the bane of motion capture operators". Yet, managing the high volume kinematic data generated through in-home neurogames requires data quality control that, executed insufficiently, jeopardizes accuracy of outcomes. To begin to address this issue at the intersection of biomechanics and "big data", we performed a secondary analysis of a neurogame, evaluating gesture count as well as shoulder and elbow joint angle outcomes calculated from kinematic data in which valid gestures were identified through 3 methods: visual review of regions of interest by an expert (BP); manufacturer-recommended data smoothing (MS); and automated methods (AI). We hypothesized that upper extremity kinematic outcomes from BP would be matched by AI but not MS methods. From one person with post-stroke hemiparesis, upper-extremity kinematic data were collected for 6 days over 2 weeks using a Microsoft Kinect™-based neurogame. We calculated gesture count, shoulder angle, and elbow angle outcomes from data managed using BP, MS, and AI methods. BP identified 1929 valid gestures total over 6 days which was different than the other two methods (p = 0.0015). In contrast, the AI algorithm with best precision identified 4372 and MS identified 4459 valid gestures. Furthermore, angle outcomes calculated from AI and MS methods resulted in different values than BP (p < 0.001 for 5 of 6 variables). More research is needed to automate treatment of high volume, low quality motion data to support investigation of motion associated with in-home rehabilitation neurogames.
Importance of toe flexor strength in vertical jump performance.
Venue: Journal of biomechanics

This study investigated whether toe flexor strength and foot arch height were related to force components during the ground contact phase in vertical jump performance. The toe flexor strength, foot arch height and vertical jump performance were studied in 31 healthy young men. For the measurement of toe flexor strength, participants explosively exerted maximum force on a toe grip dynamometer. The maximum isometric force (Fmax) and the rate of force development (RFD) of the toe flexor strength were evaluated. Foot arch height was assessed as the distance between the navicular tuberosity and the floor. Fmax and foot arch height were normalized by body mass (rFmax) and height, respectively. Three types of vertical jumps without arm swing were performed on a force plate: a squat jump (SJ), a countermovement jump (CMJ), and a rebound jump (RJ). Fmax, rFmax and RFD of the toe flexor strength were positively correlated with the vertical jump height in the SJ (r = 0.408, r = 0.452, r = 0.514) and CMJ (r = 0.377, r = 0.444, r = 0.548) and the rebound jump index in the RJ (r = 0.549, r = 0.582, r = 0.575); however, foot arch height was not correlated with the vertical jump performance, and it was only significantly correlated with the minimum ground reaction force relative to body weight during the unloading phase of the CMJ (r = -0.366). These results suggest that the toe flexor strength is an important parametre for enhancing the jump performance.
Extending the center of pressure to incorporate handhold forces: Derivation and sample application.
Venue: Journal of biomechanics

Measures describing movement of the center of pressure (CoP) are frequently used to characterize postural control. Estimates of CoP often focus on forces that individuals exert in a single plane through the feet (standing on force plates). However, balance may also be supported by forces other than those developed at the feet, especially when walkers, handrails, and other aids are used. In these cases, it is common to neglect the contributions of handheld supports. Here, we derive and apply equations for an extended CoP that incorporates handhold forces. We then examine the influence of CoP definition (i.e., including or ignoring handhold forces) on common metrics (path length; RMS and maximum excursion; average and maximum velocity) for 12 younger adults with a handrail located lateral to the participants' dominant hand. Participants attempted balance recovery in response to a range of small, medium and large forward and backward platform translations. Significant interactions between perturbation magnitude and CoP definition were found for most metrics. Notably, the interaction of CoP definition and perturbation magnitude significantly affected path length (p-values < 0.001). Post-hoc analyses revealed larger CoP path length when handrail forces were incorporated in CoP estimates compared to ignoring handrail forces at medium (backward: 59.9 vs. 19.0% height; forward: 70.5 vs 22.4% height) and large perturbation magnitudes (backward: 69.9 vs 22.4% height; forward: 103.5 vs 24.6% height). Incorporation of hand forces in CoP calculations can present a different view of postural balance control than relying on a feet-only CoP. This measure could be useful in assessing balance control tasks that involve the use of handrails or hand-held mobility devices.
Propulsion biomechanics do not differ between athletic and nonathletic manual wheelchair users in their daily wheelchairs.
Venue: Journal of biomechanics

The purpose of this study was to investigate whether athletic and nonathletic manual wheelchair users (MWU) display differences in kinetic and kinematic variables during daily wheelchair propulsion. Thirty-nine manual wheelchair users (athletic n = 25; nonathletic n = 14) propelled their own daily living wheelchair on a roller ergometer at two submaximal speeds for three minutes (1.11 m s-1 and 1.67 m s-1). A 10 camera Vicon motion capture system (Vicon, Motion Systems Ltd. Oxford, United Kingdom) collected three-dimensional kinematics of the upper limbs and thorax at 200 Hz during the final minute of each propulsion trial. Kinetics, kinematics and kinematic variability were compared between athletic and nonathletic groups. Kinematic differences were investigated using statistical parametric mapping. Athletic MWU performed significantly greater physical activity per week compared to nonathletic MWU (920 ± 601 mins vs 380 ± 147 mins, respectively). However, no significant biomechanical differences between athletic and nonathletic MWU were observed during either propulsion speed. During the 1.11 m s-1 trial wheelchair users displayed a stroke frequency of 53 ± 12 pushes/min and a contact angle of 92.5 ± 16.2°. During the 1.67 m s-1 trial the mean stroke frequency was 64 ± 22 pushes/min and contact angle was 85.4 ± 13.6°. Despite the hand being unconstrained during the recovery phase the magnitude of joint kinematic variability was similar across both glenohumeral and scapulothoracic joints during recovery and push phases. To conclude, although athletic MWU participate in more physical activity per week they adopt similar strategies to propel their daily living wheelchair. Investigations of shoulder pain and dailywheelchair propulsion do not need to distinguish between athletic and nonathletic MWU.
Functional tooth mobility in young pigs.
Venue: Journal of biomechanics

Mobility is a fundamental characteristic of mammalian teeth, and has been widely used to determine individual tooth prognosis. However, the direction and extent of tooth movement under functional loads are unknown. This study investigated maxillary molar mobility, alveolar bending, and periodontal space (PDL) fluid pressure during mastication and masseter muscle contraction in young pigs, along with PDL space measurements. Twelve three-month-old farm pigs were instrumented with some or all of the following: (1) ultrasonic crystals, one implanted into the pulp chamber of a deciduous maxillary molar and additional crystals glued onto its buccal and palatal alveolar plates; (2) rosette strain gauges affixed to the buccal and palatal of alveolar ridges; (3) a pressure transducer inserted into palatal alveolar bone facing the PDL. Tooth mobility, alveolar bending, and fluid pressure were simultaneously recorded during unrestrained feeding and subsequent masseter muscle stimulation. The PDL widths were measured using micro-CT. The results indicate that during the power stroke of mastication, (1) the molar displaced buccally and apically (192 ± 95 µm) regardless of the side of chewing; (2) compressive bone strain was greater on the buccal than on the palatal alveolar plate; and (3) PDL pressure increased during the power strok (3.63 ± 0.80 kPa). Masseter contraction produced similar results but with generally lower values. The PDL widths were larger than the range of tooth mobility, and showed no correlation with the mobility. Thus occlusal function causes buccal tipping and intrusion of maxillary molars with concomitant compression of the buccal alveolar plate and raised pressure within the PDL space.
The effect of anteroposterior perturbations on the control of the center of mass during treadmill walking.
Venue: Journal of biomechanics

Shifts of the center of pressure (CoP) through modulation of foot placement and ankle moments (CoP-mechanism) cause accelerations of the center of mass (CoM) that can be used to stabilize gait. An additional mechanism that can be used to stabilize gait, is the counter-rotation mechanism, i.e., changing the angular momentum of segments around the CoM to change the direction of the ground reaction force. The relative contribution of these mechanisms to the control of the CoM is unknown. Therefore, we aimed to determine the relative contribution of these mechanisms to control the CoM in the anteroposterior (AP) direction during a normal step and the first recovery step after perturbation in healthy adults. Nineteen healthy subjects walked on a split-belt treadmill and received unexpected belt acceleration perturbations of various magnitudes applied immediately after right heel-strike. Full-body kinematic and force plate data were obtained to calculate the contributions of the CoP-mechanism and the counter-rotation mechanism to control the CoM. We found that the CoP-mechanism contributed to corrections of the CoM acceleration after the AP perturbations, while the counter-rotation mechanism actually counteracted the CoM acceleration after perturbation, but only in the initial phases of the first step after the perturbation. The counter-rotation mechanism appeared to prevent interference with the gait pattern, rather than using it to control the CoM after the perturbation. Understanding the mechanisms used to stabilize gait may have implications for the design of therapeutic interventions that aim to decrease fall incidence.
Universality of vortex ring decay in the left ventricle.
Venue: Journal of biomechanics

We present clinical measurements and a theoretical model for the decay of the left ventricular (LV) vortex ring. Previous works have postulated that the formation of the vortex ring downstream of the mitral annulus is affected by LV diastolic impairment. However, no previous works have considered how the strength of the vortex ring will decay inside the ventricle after its formation. Although the vortex ring formation relates to the very initial stage of the filling, the decay process is governed by a large portion of the diastolic time and will be affected by the interaction of the ventricle walls and the vortex ring. Here we used in-vivo measurements and presented a mechanistic model to calculate the evolution of the vortex ring strength and predict the rate of vortex ring decay within the left ventricle. The results demonstrated the actual circulation decay rate was universal, remaining nearly unchanged across all subjects of varying LV geometry or diastolic function. Furthermore, using the model-predicted circulation decay rate, differentiation between normal and abnormal filling was observed.
Development of a novel geometrically-parametric patient-specific finite element model to investigate the effects of the lumbar lordosis angle on fusion surgery.
Venue: Journal of biomechanics

The success of lumbar interbody fusion, the key surgical procedure for treating different pathologies of the lumbar spine, is highly dependent on determining the patient-specific lumbar lordosis (LL) and restoring sagittal balance. This study aimed to (1) develop a personalized finite element (FE) model that automatically updates spinal geometry for different patients; and (2) apply this technique to study the influence of LL on post-fusion spinal biomechanics. Using an X-Ray image-based algorithm, the geometry of the lumbar spine (L1-S1) was updated using independent parameters. Ten subject-specific nonlinear osteoligamentous FE models were developed based on pre-operative images of fusion surgery candidate patients. Post-operative FE models of the same patients were consequently created. Comparison of the obtained results from FE models with pre- and post-operation functional images demonstrated the potential value of this technique in clinical applications. A parametric study of the effect of LL was conducted for cases with zero LL angle, positive LL angles (+6° and +12°) and negative LL angles (-3° and -6°) on fused level (L4-L5), resulting in a total of 50 fusion simulation models. The average range of motion, intradiscal pressure, and fiber strain at adjacent levels were significantly higher with decreased LL during different directions except axial rotation. This study demonstrates that the LL alters both the intersegmental motion and load-sharing in fusion, which may influence the initiation and rate of adjacent level degeneration. This personalized FE platform provides a practical, clinically applicable approach for the analyses of the biomechanical changes associated with lumbar spine fusion.