nils-herrmann/clean_scirepeval huggingface dataset:
Multiscale characterization of ovariectomized rat femur.
Venue: Journal of biomechanics

Estrogen deficiency activates bone resorbing cells (osteoclasts) and to a lesser extent bone forming cells (osteoblasts), resulting in a gap between resorption and formation that leads to a net loss of bone. These cell activities alter bone architecture and tissue composition. Thus, the objective of this study is to examine whether multiscale (10-2 to 10-7 m) characterization can provide more integrated information to understand the effects of estrogen deficiency on the fracture risk of bone. This is the first study to examine the effects of estrogen deficiency on multiscale characteristics of the same bone specimen. Sprague-Dawley female rats (6 months old) were obtained for a bilateral ovariectomy (OVX) or a sham operation (sham). Micro-computed tomography of rat femurs provided bone volumetric, mineral density, and morphological parameters. Dynamic mechanical analysis, static elastic and fracture mechanical testing, and nanoindentation were also performed using the same femur. As expected, the current findings indicate that OVX reduces bone quantity (mass and bone mineral density) and quality (morphology, and fracture displacement). Additionally, they demonstrated reductions in amount and heterogeneity of tissue mineral density (TMD) and viscoelastic properties. The current results validate that multiscale characterization for the same bone specimen can provide more comprehensive insights to understand how the bone components contributed to mechanical behavior at different scales.
Mechanical fatigue of whole rabbit-tibiae under combined compression-torsional loading is better explained by strained volume than peak strain magnitude.
Venue: Journal of biomechanics

The mechanical fatigue behavior of whole bone is poorly defined, particularly for the combined loading modes that occur in vivo. The purpose of this study was to quantify the fatigue life of whole rabbit-tibiae under cyclic uniaxial compression and biaxial (compression and torsion) loading, and to explore the relationship between fatigue life and specimen-specific finite element (FE) predictions of stress/strain. Twelve tibiae were tested cyclically until failure across a range of uniaxial-compressive loads. Another twenty-two tibiae were separated into three groups and loaded biaxially; peak compressive load was constant in all three groups (50% ultimate force) but torsion was varied (0%, 25%, or 50% of ultimate torque). FE models with heterogeneous linear-elastic material properties were developed from computed tomography. We assessed peak stress/strain and stressed/strained volume based on principal stress/strain, as well as von Mises and pressure modified von Mises criteria. A logarithmic (r2 = 0.68; p < 0.001) relationship was observed between uniaxial-compressive load and fatigue life. Biaxial tests demonstrated that fatigue life decreased with superposed torsion (p = 0.034). Strained volume, based on a maximum principal strain or pressure modified von Mises strain criteria, were strong predictors of fatigue life under both uniaxial (r2 = 0.73-0.82) and biaxial (r2 = 0.59-0.60) loads, and these outperformed equivalent peak stress- and strain-based measures. Our findings highlight the importance of evaluating strain distributions, rather than peak stress or strain, to predict the fatigue behavior or whole bone, which has important implications for the study of stress fracture.
Age-related compensation: Neuromusculoskeletal capacity, reserve & movement objectives.
Venue: Journal of biomechanics

The prevention, mitigation and treatment of movement impairments, ideally, requires early diagnosis or identification. As the human movement system has physiological and functional redundancy, movement limitations do not promptly arise at the onset of physical decline. A such, prediction of movement limitations is complex: it is unclear how much decline can be tolerated before movement limitations start. Currently, the term 'homeostatic reserve' or 'physiological reserve' is used to refer to the redundancy of the human biological system, but these terms do not describe the redundancy in the muscle architecture of the human body. The result of functional redundancy is compensation. Although compensation is an early predictor of movement limitations, clear definitions are lacking and the topic is underexposed in literature. The aim of this article is to provide a definition of compensation and emphasize its importance. Compensation is defined as an alteration in the movement trajectory and/or altering muscle recruitment to complete a movement task. Compensation for capacity is the result of a lack in neuromusculoskeletal reserve, where reserve is defined as the difference between the capacity (physiological abilities of the neuromusculoskeletal system) and the task demand. Compensation for movement objectives is a result of a shift in weighting of movement objectives, reflecting changing priorities. Studying compensation in biomechanics requires altered protocols in experimental set-ups, musculoskeletal models that are not reliant on prescribed movement, and inclusion of alternative movement objectives in optimal control theory.
The effects of a simple optical clearing protocol on the mechanics of collagenous soft tissue.
Venue: Journal of biomechanics

Optical clearing of biological tissues improves imaging depth for light transmission imaging modalities such as two-photon microscopy. In studies that investigate the interplay between microstructure and tissue-level mechanics, mechanical testing of cleared tissue may be useful. However, the effects of optical clearing on soft tissue mechanics have not been investigated. Thus, we set out to quantify the effects of a simple and effective optical clearing protocol on the mechanics of soft collagenous tissues using ovine mitral valve anterior leaflets as a model system. First, we demonstrate the effectiveness of an isotonic glycerol-DMSO optical clearing protocol in two-photon microscopy. Second, we evaluate the mechanical effects of optical clearing on leaflets under equibiaxial tension in a dependent study design. Lastly, we quantify the shrinkage strain while traction-free and the contractile forces while constrained during clearing. We found the optical clearing protocol to improve two-photon imaging depth from ~100 μm to ~500-800 μm, enabling full-thickness visualization of second-harmonic generation, autofluorescent, and fluorophore-tagged structures. Under equibiaxial tension, cleared tissues exhibited reduced circumferential (p < 0.001) and radial (p = 0.009) transition stretches (i.e. stretch where collagen is recruited), and reduced radial stiffness (p = 0.031). Finally, during clearing we observed ~10-15% circumferential and radial compressive strains, and when constrained, ~2mN of circumferential and radial traction forces. In summary, we suggest the use of this optical clearing agent with mechanical testing be done with care, as it appears to alter the tissue's stress-free configuration and stiffness, likely due to tissue dehydration.
The torque-frequency relationship is impaired similarly following two bouts of eccentric exercise: No evidence of a protective repeated bout effect.
Venue: Journal of biomechanics

High-intensity eccentric exercise can lead to muscle damage and weakness. The 'repeated bout effect' (RBE) can attenuate these impairments when performing a subsequent bout. The influence of eccentric exercise-induced muscle damage on low-frequency force production is well-characterized; however, it is unclear how eccentric exercise and the RBE affect torque production across a range of stimulation frequencies (i.e., the torque-frequency relationship). We investigated the influence of an initial (Bout 1) and repeated bout (Bout 2) of eccentric exercise on the elbow flexor torque-frequency relationship. Eleven males completed two bouts of high-intensity eccentric elbow flexions, 4 weeks apart. Torque-frequency relationships were constructed at baseline and 0.5, 24, 48, 72, 96, and 168 h following both bouts via percutaneous stimulation at 1, 6, 10, 20, 30, 40, 50, and 100 Hz. Serum creatine kinase activity, self-reported muscle soreness, and isometric maximum voluntary contraction torque indirectly inferred the presence of muscle damage following Bout 1, and attenuation of muscle damage following Bout 2. Torque amplitude at all stimulation frequencies was impaired 30 min following eccentric exercise, however, torque at lower (1-10 Hz) and higher frequencies (40-100 Hz) recovered within 24 h while torque across the middle frequency range (20-30 Hz) recovered by 48 h. No between-bout differences were detected in absolute or normalized torque at any stimulation frequency, indicating no protective RBE on the elbow flexor torque-frequency relationship.
Stable to unstable differences in force-velocity-power profiling during chest presses and squats.
Venue: Journal of biomechanics

Despite several studies investigating the effect of instability resistance exercises on neuromuscular performance, the force-velocity-power characteristics of muscles involved in lifting tasks and the underlying mechanisms have not been fully explored. This study investigates power-velocity and force-velocity relationships during resistance exercises performed on stable and unstable surfaces with different weights. A group of 63 physically active young men performed chest presses on the bench and Swiss ball, and squats on the firm surface and BOSU ball with weights from 20 kg to at least 85% of one-repetition maximum. Peak and/or mean values of power, velocity and force were analyzed. Results showed significantly lower peak power and force during chest presses on the Swiss ball as opposed to the bench at lower velocities (147.6 W and 176.0 N at 1.1 m·s-1, 108.7 W and 126.4 N at 1.3 m·s-1, 112.0 W and 72.7 N at 1.5 m·s-1; all at p < 0.01). Their values produced at lower velocities were also significantly lower during squats on the BOSU ball when compared to the firm surface (232.2 W and 257.1 N at 1.1 m·s-1, 228.2 W and 173.3 N at 1.2 m·s-1, 245.1 W and 156.8 N at 1.3 m·s-1, 254.5 W and 113.5 N at 1.4 m·s-1; all at p < 0.05). These significant differences between power produced during stable and unstable resistance exercises at lower velocities (or at higher loads) have to be taken into account in sports that require production of a high force in a short time. Because of the variable loading patterns under unstable conditions, it is necessary to quantify the optimal exercise load for each individual athlete.
Variable stiffness foot design and validation.
Venue: Journal of biomechanics

Energy storing and returning prosthetic feet are commonly prescribed. Research has demonstrated advantages to use these types of prosthetic feet. However, their stiffness in the sagittal plane is fixed and cannot adapt to different walking tasks and user preference. In this paper, we propose a novel prosthetic foot design capable of modulating its stiffness in the sagittal plane. The Variable Stiffness Ankle unit (VSA) is mounted on a commercially available prosthetic foot. The stiffness of the foot is adjusted with a lightweight servo motor controlled wirelessly. The stiffness change is accomplished by moving the supports points on the glass fiber leaf spring of the VSA ankle unit. We described the design and characterized changes in ankle stiffness using a mechanical test bench. A novel method was used to capture mechanical test data using a six degree of freedom load cell, allowing us to contrast mechanical and biomechanical data. A transtibial unilateral amputee performed level ground walking on an instrumented treadmill. The VSA prosthetic foot exhibited ankle stiffness change in the mechanical test bench. Ankle stiffness changes were also confirmed during the biomechanical analysis. Future work will involve additional subjects. The VSA prosthetic foot could improve user satisfaction and help prosthetist to fine tune prosthetic feet during fittings.
Anticipatory postural adjustments in forward and backward single stepping: Task variability and effects of footwear.
Venue: Journal of biomechanics

A single step is usually preceded by the so-named anticipatory postural adjustments (APAs). These are normally described through the observation of the trajectory of the center of pressure (CoP). Even though, external factors such as stepping direction and footwear are known to modify APAs, quantitative investigations regarding their relevant effects are understudied in the literature. Therefore, this study aims at characterizing APAs patterns prior to forward and backward stepping when performed either in barefoot or shod condition and explores their variability. Twenty-eight young healthy volunteers participated in the study. CoP trajectories were recorded using a force plate and relevant spatio-temporal parameters extracted (i.e. duration, amplitude, and mean speed). Results showed distinct effects of both direction of the step and footwear on APAs: the first mainly induces variations of APAs along the anteroposterior direction, whereas the latter in the mediolateral direction. In addition, variability indices exhibited lower values for the APAs along the mediolateral axis which was affected by neither footwear nor direction of the step. This study extends previous literature by revealing significant direction X footwear interactions on APAs. Furthermore, regardless of these factors, the medio-lateral strategy is still well preserved, highlighting the prioritization of balance control over motor performance. In conclusion, both direction and footwear have a major effect on postural preparation therefore both factors should be included when evaluating APAs in real-life condition.
Effect of increasing speed on whole-body angular momentum during stepping in the elderly.
Venue: Journal of biomechanics

Recent evidence suggests that older adults may have difficulty controlling whole-body angular momentum (H) during volitional stepping, which could impose a major challenge for balance control and result in potential falls. However, it is not known if and how H is influenced by speed when stepping. This study aimed to investigate the effect on H of increasing speed during step initiation in older adults. Twenty-seven healthy individuals over 60 were enrolled in the current study and were instructed to perform a series of step initiations with their dominant leg under two speed conditions: at preferred speed and as fast as possible. Two force plates and a motion-capture system were used to record H and the components of the net external moment (moment arms and ground reaction forces) during the double support and step execution phases of stepping. Results revealed that increasing speed of stepping affected H differently in both stepping phases and in the different planes. H ranges in all three planes increased with speed during the double support phase. During the step execution phase, while H ranges in frontal and transversal planes decreased, sagittal plane H range significantly increased with speed. This increased H range in the sagittal plane, which may result from the task demands, could impose a greater challenge for balance control in the elderly.
Brain microvascular damage linked to a moderate level of strain induced by controlled cortical impact.
Venue: Journal of biomechanics

Cerebral blood vessels play an important role in brain metabolic activity in general and following traumatic brain injury (TBI) in particular. However, the extent to which TBI alters microvessel structure is not well understood. Specifically, how intracranial mechanical responses produced during impacts relate to vascular damage needs to be better studied. Therefore, the objective of this study was to investigate the biomechanical mechanisms and thresholds of brain microvascular injury. Detailed microvascular damage of mouse brain was quantified using Arterial Spin Labeling (ASL) magnetic resonance imaging (MRI) and ex vivo Serial Two-Photon Tomography (STPT) in seven mice that had undergone controlled cortical impact. Mechanical strains were investigated through finite element (FE) modeling of the mouse brain. We then compared the post-injury vessel density map with FE-predicted strain and found a moderate correlation between the vessel length density and the predicted peak maximum principal strains (MPS) (R2 = 0.52). High MPS was observed at the impact regions with low vessel length density, supporting the mechanism of strain-triggered microvascular damage. Using logistic regression, the MPS corresponding to a 50% probability of injury was found to be 0.17. Given the literature reporting MPS of over 0.2 in the human brain for mild TBI/concussion cases, it is highly recommended to consider microvascular damage when investigating mild TBI/concussion in the future.
Kinematic 3-D motion analysis of shoulder resurfacing hemiarthroplasty - An objective assessment method.
Venue: Journal of biomechanics

Shoulder replacement is indicated in the treatment of pain due to osteoarthritis. Few studies have objectively assessed range of motion (RoM) gains at different post-operative time points. This is a prospective 3D motion analysis study to objectively quantify RoM changes at multiple time points following shoulder resurfacing arthroplasty (SRA) for primary gleno-humeral osteoarthritis, comparing it with clinically measured RoM. Clinical assessment, Visual Analog Scale (VAS) pain score, Constant-Morley (CS) and Oxford Shoulder Score (OSS) were recorded. Motion analysis was performed for RoM and three activities of daily living tasks (ADL), pre-operatively and post-operatively at 4 and 12 months. Nineteen shoulders in fifteen patients were included. The mean age was 72 years (range 52-84). There were significant improvements in external and internal rotation, ability to place the hand behind the head and reach the fifth lumbar vertebra, at 4 months on clinical examination and kinematic analysis with no further improvements at 12 months. There was significant improvement in abduction at 4 months with further improvement at 12 months, which was significantly more than noted on clinical assessment. In contrast, kinematic analysis showed a reduction in flexion between 4 and 12 months, while clinically there appeared to be an improvement between these time periods. This is the first study to prospectively utilise objective kinematic 3-D motion analysis in addition to clinical measurements and outcome scores, to investigate the outcome of resurfacing arthroplasty at multiple time points after surgery, providing an understanding into the trends of change in these parameters.
Aortic aneurysms and dissections: Unmet needs from physicians and engineers perspectives.
Venue: Journal of biomechanics

The treatment of aortic disease is complex, requiring cardiothoracic and vascular surgeons to make pre-, post- and intraoperative decisions directly influencing patient survival and well-being. Despite tremendous advancement in vascular surgery and endovascular techniques in the last two decades, along with the abundance of research in the field, many unmet needs and unanswered questions remain. Tight collaboration between engineers and physicians is a keystone in translating new tools, techniques, and devices into practice. Here, we have gathered our perspective, as physicians and engineers, in several pressing issues associated with the diagnosis and treatment of aortic aneurysms and dissection, referring to the current knowledge and practice, signifying unmet needs as well as future directions.
Hemodynamic performance limits of the neonatal Double-Lumen cannula.
Venue: Journal of biomechanics

Venovenous extracorporeal membrane oxygenation (VV-ECMO) is the preferred surgical intervention for patients suffering from severe cardiorespiratory failure, also encountered in SARS-Cov-2 management. The key component of VV-ECMO is the double-lumen cannula (DLC) that enables single-site access. The biofluid dynamics of this compact device is particularly challenging for neonatal patients due to high Reynolds numbers, tricuspid valve location and right-atrium hemodynamics. In this paper we present detailed findings of our comparative analysis of the right-atrial hemodynamics and salient design features of the 13Fr Avalon Elite DLC (as the clinically preferred neonatal cannula) with the alternate Origen DLC design, using experimentally validated computational fluid dynamics. Highly accurate 3D-reconstructions of both devices were obtained through an integrated optical coherence tomography and micro-CT imaging approach. Both cannula configurations displayed complex flow structures inside the atrium, superimposed over predominant recirculation regimes. We found that the Avalon DLC performed significantly better than the Origen alternative, by capturing 80% and 94% of venous blood from the inferior and superior vena cavae, respectively and infusing the oxygenated blood with an efficiency of more than 85%. The micro-scale geometric design features of the Avalon DLC that are associated with superior hemodynamics were investigated through 14 parametric cannula configurations. These simulations showed that the strategic placement of drainage holes, the smooth infusion blood stream diverter and efficient distribution of the venous blood capturing area between the vena cavae are associated with robust blood flow performance. Nevertheless, our parametric results indicate that there is still room for further device optimization beyond the performance measurements for both Avalon and Origen DLC in this study. In particular, the performance envelope of malpositioned cannula and off-design conditions require additional blood flow simulations for analysis.
In vivo articular contact pattern of a total wrist arthroplasty design.
Venue: Journal of biomechanics

Total wrist arthroplasty (TWA) designs suffer from relatively high complication rates when compared to other arthroplasties. Understanding the contact pattern of hip and knee replacement has improved their design and function; however, the in vivo contact pattern of TWA has not yet been examined and is thus the aim of this study. We hypothesized that the center of contact (CoC) is located at the geometric centers of the carpal component and radial component in the neutral posture and that the CoC moves along the principal arcs of curvature throughout primary anatomical motions. Wrist motion and implant kinematics of six patients with the Freedom® total wrist implant were studied during various tasks using biplanar videoradiography. The location of the CoC of the components was investigated by calculating distance fields between the articular surfaces. We found the CoC at the neutral posture was not at the geometric centers but was located 3.5 mm radially on the carpal component and 1.2 mm ulnarly on the radial component. From extension to flexion, the CoC moved 10.8 mm from dorsal to volar side on the carpal component (p < 0.0001) and 7.2 mm from volar to dorsal on the radial component (p = 0.0009). From radial to ulnar deviation, the CoC moved 12.4 mm from radial to ulnar on the carpal component (p < 0.0001), and 5.6 mm from ulnar to radial on the radial component (p = 0.009). The findings of this study may eventually improve TWA success by advancing future designs through a more accurate understating of their kinematic performance in vivo.