nils-herrmann/clean_scirepeval huggingface dataset:
Tricuspid annulus cinching force under pulmonary hypertensive right ventricle conditions: An ex vivo study.
Venue: Journal of biomechanics

This study investigates the force required to reduce or "cinch" the tricuspid annulus under elevated right ventricular pressures, commonly seen in patients with pulmonary hypertension. Tricuspid regurgitation affects 1.6 million Americans. Approximately 43% of patients who undergo tricuspid valve repair to correct tricuspid regurgitation will develop residual pulmonary hypertension, putting them at risk for developing increased right ventricle pressures. Previous studies have quantified the forces required to cinch the tricuspid annulus by only pressurizing the right ventricle, leaving out forces from the pressurized left ventricle and septal wall unaccounted for. This study pressurized both left and right ventricles of 10 porcine hearts to their normal physiological pressures of 110 mmHg and 30 mmHg respectively, then increased right ventricular pressures to mimic moderate and severe pulmonary hypertension. A suture was anchored around the free wall of the tricuspid annulus with the free end attached to a force transducer. The force transducer was mounted on a slider system which pulled the suture at regular intervals. The cinching force on the tricuspid annulus was quantified with each annular reduction by simulating peak systole condition in both ventricles. The data was compared with only the right ventricle pressurized as previous studies did. There were significant differences in required cinching forces with each increase in right ventricular pressure and between trials that pressurized both ventricles versus only the right ventricle, suggesting adoption of this physiologically improved protocol. We also found with increased cinching of the tricuspid annulus, notable changes occur in the mitral annulus.
Effects of age and locomotor demand on foot mechanics during walking.
Venue: Journal of biomechanics

Older adults exhibit reductions in push-off power that are often attributed to deficits in plantarflexor force-generating capacity. However, growing evidence suggests that the foot may also contribute to push-off power during walking. Thus, age-related changes in foot structure and function may contribute to altered foot mechanics and ultimately reduced push-off power. The purpose of this paper was to quantify age-related differences in foot mechanical work during walking across a range of speeds and at a single fixed speed with varied demands for push-off power. 9 young and 10 older adults walked at 1.0, 1.2, and 1.4 m/s, and at 1.2 m/s with an aiding or impeding horizontal pulling force equal to 5% BW. We calculated foot work in Visual3D using a unified deformable foot model, accounting for contributions of structures distal to the hindfoot's center-of-mass. Older adults walked while performing less positive foot work and more negative net foot work (p < 0.05). Further, we found that the effect of age on mechanical work performed by the foot and the ankle-foot complex increased with increased locomotor demand (p < 0.05). Our findings suggest that during walking, age-related differences in foot mechanics may contribute to reduced push-off intensity via greater energy loss from distal foot structures, particularly during walking tasks with a greater demand for foot power generation. These findings are the first step in understanding the role of the foot in push-off power deficits in older adults and may serve as a roadmap for developing future low-cost mobility interventions.
Reconstructing an accelerometer-based pelvis segment for three-dimensional kinematic analyses during laboratory simulated tasks with obstructed line-of-sight.
Venue: Journal of biomechanics

Close interface between humans and inanimate objects (furniture, assistive devices, and external loads) can obstruct line-of-sight in biomechanics studies that utilize optoelectronic motion capture systems. This specific problem is frequently encountered with the pelvis segment. This study sought to compare joint and pelvis angles computed from a pelvis-fixed local coordinate system (LCS) that was constructed from optically tracked pelvis landmarks (gold standard) and landmarks derived from angular deviations calculated from triaxial accelerometer data. One participant performed seven tasks: sitting, forward bend, sit-to-stand-to-sit, forward lunge, symmetrical squat, asymmetrical squat, and gait. The root mean square error (RMSE) and coefficient of determination (R2) were examined for the pelvis, lumbar spine, and hip joint angles calculated using the standard and accelerometer-based methods for creating a LCS. The RMSE values for global pelvis angles ranged from 2.2° (gait; R2 = 0.47) to 4.9° (sit-to-stand-to-sit; R2 = 0.98), 0.6° (sitting; R2 = 0.88) to 7.4° (gait; R2 = 0.39), and 1.5° (forward bend; R2 = 0.99) to 2.9° (sit-to-stand-to-sit; R2 = 0.99) for motion about the X, Y, and Z axes, respectively. The magnitude of error observed for adjacent joint motion was lowest about the Z axis for all tasks. In conclusion, the accelerometer-based LCS offers an alternative method for computing pelvis and adjacent joint angles without the reliance on a visual line-of-sight. For motion about the X and Y axes, time-series data derived with the accelerometer-based method may be less representative of discrete events, particularly for gait and lunging tasks.
Effect of fatigue loading and rest on impact strength of rat ulna.
Venue: Journal of biomechanics

Stress fracture is a common injury among athletes and military personnel and is associated with fatigue-initiated damage and impact loading. The recovery of bending strength has been shown to be a function of the rest days allowed after fatigue loading in rodents and the aim of this study was to investigate if similar results would occur under impact conditions. In this study, cyclic axial compression load was applied in vivo on the right forelimbs while left forelimbs served as controls. Two rest groups were used: one day of rest and seven days of rest. Afterwards, all ulnae were scanned using micro-Computed Tomography followed by impact testing. The micro-CT scan confirmed the formation of woven bone on loaded ulnae after seven days rest. The peak impact force was 37.5% higher in the control (mean = 174.96 ± 33.25 N) specimens compared to the loaded bones (mean = 130.34 ± 22.37 N). Fourier-transformed infrared spectroscopy analyses suggested no significant change of chemical composition in the cortical region between the loaded and control ulnae, but woven bone region had lower carbonate and amide I content than contralateral controls (p < 0.05). We find that cyclic fatigue loading had a negative effect on bone's impact response. Bones that experienced fatigue loading became less stiff, weaker, and more prone to fracture when subjected to impact. The formation of woven bone after seven days of rest did not restore the stiffness upon impact and confirm that rest time is crucial to the recovery of fatigue damage.
Prediction of mechanical properties of trabecular bone in patients with type 2 diabetes using damage based finite element method.
Venue: Journal of biomechanics

Type-2 diabetic (T2D) and osteoporosis (OP) suffered patients are more prone to fragile fracture though the nature of alteration in areal bone mineral density (aBMD) in these two cases are completely different. Therefore, it becomes crucial to compare the effect of T2D and OP on alteration in mechanical and structural properties of femoral trabecular bone. This study investigated the effect of T2D, OP, and osteopenia on bone structural and mechanical properties using micro-CT, nanoindentation and compression test. Further, a nanoscale finite element model (FEM) was developed to predict the cause of alteration in mechanical properties. Finally, a damage-based FEM was proposed to predict the pathological related alteration of bone's mechanical response. The obtained results demonstrated that the T2D group had lower volume fraction (-18.25%, p = 0.023), young's modulus (-23.47%, p = 0.124), apparent modulus (-37.15%, p = 0.02), and toughness (-40%, p = 0.001) than the osteoporosis group. The damage-based FE results were found in good agreement with the compression experiment results for all three pathological conditions. Also, nanoscale FEM results demonstrated that the elastic and failure properties of mineralised collagen fibril decreases with increase in crystal size. This study reveals that T2D patients are more prone to fragile fracture in comparison to OP and osteopenia patients. Also, the proposed damage-based FEM can help to predict the risk of fragility fracture for different pathological conditions.
The assessment of center of mass and center of pressure during quiet stance: Current applications and future directions.
Venue: Journal of biomechanics

This perspective article provides a brief review of our understanding of how center of pressure (CoP) and center of mass (CoM) are traditionally utilized to measure quiet standing and how technological advancements are allowing for measurements to be derived outside the confines of a laboratory setting. Furthermore, this viewpoint provides descriptions of what CoP and CoM outcomes may reflect, a discussion of recent developments in selected balance outcomes, the importance of measuring instantaneous balance outcomes, and directions for future questions/research. Considering the enormous number and cost of falls annually, conclusions drawn from this perspective underscore the need for more cohesive efforts to advance our understanding of balance performance. As we refine the technology and algorithms used to portably assess postural stability, the question of which measurement (i.e. CoP or CoM) to utilize seems to be highly dependent on the question being asked. Further, the complexity of the question appears to span multiple disciplines and cultivate exploration of the intrinsic mechanisms of stability. Recently developed multi-dimensional methods for assessing balance performance may provide additional insight into balance, improving our ability to predict balance impairments and falls outside the laboratory and in the clinic. However, additional work will be necessary to understand the clinical significance and predictive capacity of these outcomes in various fall-prone populations.
Machine learning for rapid estimation of lower extremity muscle and joint loading during activities of daily living.
Venue: Journal of biomechanics

Joint contact and muscle forces estimated with musculoskeletal modeling techniques offer useful metrics describing movement quality that benefit multiple research and clinical applications. The expensive processing of laboratory data associated with generating these outputs presents challenges to researchers and clinicians, including significant time and expertise requirements that limit the number of subjects typically evaluated. The objective of the current study was to develop and compare machine learning techniques for rapid, data-driven estimation of musculoskeletal metrics from derived gait lab data. OpenSim estimates of patient joint and muscle forces during activities of daily living were simulated using laboratory data from 70 total knee replacement patients and used to develop 4 different machine learning algorithms. Trained machine learning models predicted both trend and magnitude of estimated joint contact (mean correlation coefficients ranging from 0.93 to 0.94 during gait) and muscle forces (mean correlation coefficients ranging from 0.83 to 0.91 during gait) based on anthropometrics, ground reaction forces, and joint angle data. Patient mechanics were accurately predicted by recurrent neural networks, even after removing dependence on key subsets of predictor features. The ability to quickly estimate patient mechanics from derived measurements of movement has the potential to broaden the impact of musculoskeletal modeling by enabling faster assessment in both clinical and research settings.
Evaluation of affine fiber kinematics in porcine tricuspid valve leaflets using polarized spatial frequency domain imaging and planar biaxial testing.
Venue: Journal of biomechanics

Collagen fibers are the primary load-bearing microstructural constituent of bodily soft tissues, and, when subjected to external loading, the collagen fibers reorient, uncrimp, and elongate. Specific to the atrioventricular heart valve leaflets, the collagen fiber kinematics form the basis of many constitutive models; however, some researchers claim that modeling the affine fiber kinematics (AFK) are sufficient for accurately predicting the macroscopic tissue deformations, while others state that modeling the non-affine kinematics (i.e., fiber uncrimping together with elastic elongation) is required. Experimental verification of the AFK theory has been previously performed for the mitral valve leaflets in the left-side heart; however, this same evaluation has yet to be performed for the morphologically distinct tricuspid valve (TV) leaflets in the right-side heart. In this work, we, for the first time, evaluated the AFK theory for the TV leaflets using an integrated biaxial testing-polarized spatial frequency domain imaging device to experimentally quantify the load-dependent collagen fiber reorientations for comparison to the AFK theory predictions. We found that the AFK theory generally underpredicted the fiber reorientations by 3.1°, on average, under the applied equibiaxial loading with greater disparity when the tissue was subjected to the applied non-equibiaxial loading. Furthermore, increased AFK errors were observed with increasing collagen fiber reorientations (Pearson coefficient r = -0.36, equibiaxial loading), suggesting the AFK theory is better suited for relatively smaller reorientations. Our findings suggest the AFK theory may require modification for more accurate predictions of the collagen fiber kinematics in the TV leaflets, which will be useful in refining modeling efforts for more accurate TV simulations.
How does bone strain vary between the third metacarpal and the proximal phalangeal bones of the equine distal limb?
Venue: Journal of biomechanics

Strain parameters at injury prone sites of the equine third metacarpal (MC3) and proximal phalangeal (P1) bones were investigated with the aim of improving understanding of injury pathogenesis. We hypothesized that dorsal principal and shear strain patterns, magnitudes and directions would differ from proximal-to-distal; and would be similar from medial-to-lateral across each bone. Unilateral limbs from nine equine cadavers were instrumented with rosette strain gauges during limb loading to 10,500 N. Gauges were attached at seven dorsal sites: middle MC3, distal MC3 (medial, middle, lateral) and proximal P1 (medial, middle, lateral). Outcome measures were analysed with repeated measures analysis of variance. Distal MC3 had the greatest, and proximal P1 the smallest magnitude of minimum principal and shear strains. Directions of maximum and minimum principal strain were similar at the middle and distal MC3 sites with a 20-40° direction difference compared to proximal P1. The patterns of strain magnitude and direction were similar from medial-to-lateral on distal MC3 but varied in pattern and magnitude among the P1 sites. Overall, as load reached maximum, direction of minimum principal strain became more axial in orientation, converging from opposite directions between bones, potentially maximising stability of the distal limb. The difference in strain parameters and strain ratio for adjacent anatomic sites on distal MC3 and proximal P1 was not anticipated, in light of the anatomic congruity of the metacarpophalangeal joint. Based on the predominance of shear strain across proximal P1, shear forces are likely the predominant biomechanical contributor to sagittal fractures of P1.
The curvature peaks of the trajectory of the body centre of mass during walking: A new index of dynamic balance.
Venue: Journal of biomechanics

During walking, falling is most likely to occur towards the side of the supporting lower limb during the single stance. Timely lateral redirection of the centre of mass (CoM) preceding the no-return position is necessary for balance. We analysed the curvature peaks (the inverse of the radius of curvature) of the three-dimensional path of the CoM during the entire stride. Twelve healthy adults walked on a force-sensorized treadmill at constant velocities from 0.4 to 1.2 m s-1, in 0.2 m s-1 increments. The three-dimensional displacements of the CoM, the muscular power sustaining the CoM motion with respect to the ground, and the efficiency of the pendulum-like transfer of the CoM were computed via the double integration of the ground reaction forces. The curvatures of the CoM trajectory were measured (Frenet-Serret formula). During the single stance, the curvature showed a bell-shaped increment, lasting a few tenths of a millisecond, and peaking at 365-683 m-1 (radius of 2.7-1.4 mm, respectively), the higher the walking velocity. The CoM was redirected towards the swinging lower limb. The curvature increment was sustained by muscle-driven braking of the CoM. Smoother increments of curvature (peaking at approximately 37-150 m-1), further orienting the CoM towards the leading lower limb, were observed during the double stance. The peaks of the curvatures were symmetric between the two sides. The high curvature peaks during the single stance may represent an index of dynamic balance during walking. This index might be useful for both rehabilitation and sports training purposes.
Bilateral in vivo neuromechanical properties of the triceps surae and Achilles tendon in runners and triathletes.
Venue: Journal of biomechanics

Inter-limb differences in Achilles tendon mechanical, material and morphological properties have previously been described in non-athletes and attributed to the preferential use of a given limb. Achilles tendon overuse tendon injury generally initiate unilaterally and alters triceps surae activation and Achilles tendon properties. The investigation of inter-limb differences in muscle activation and tendon properties may provide directions for injury prevention in habitual runners. In this study triceps surae and Achilles tendon properties were investigated bilaterally in habitual runners during unilateral maximal isometric contractions. Morphological, mechanical and material Achilles tendon properties were assessed using isokinetic dynamometry, motion capture and ultrasonography while triceps surae activation strategies were assessed using electromyography. Lower limb preference was assessed for inter-limb comparisons using the Waterloo questionnaire. Zero and one-dimensional statistical analysis and Cohen's d were employed to investigate possible inter-limb differences. Inter-limb associations in Achilles tendon properties and intra-limb associations between triceps surae activations were assessed using Pearson's correlation coefficients. No differences were observed between the preferred and non-preferred limb in terms of triceps surae muscle activation amplitude and Achilles tendon properties. However, intra-limb association among triceps surae activation ratios were not identical between limbs. Runners and triathletes present similar Achilles tendons properties between limbs, and thus initial observations of unilateral changes in the Achilles tendon properties might be used as a strategy to prevent the onset of overuse tendon injury. The non-similar associations within activation ratios between limbs should be further explored since triceps surae activation strategies may alter loading of the Achilles tendon.
Effects of back-support exoskeleton use on trunk neuromuscular control during repetitive lifting: A dynamical systems analysis.
Venue: Journal of biomechanics

Back-support exoskeletons (BSEs) are a promising ergonomic intervention to mitigate the risk of occupational low back pain. Although growing evidence points to the beneficial effects of BSEs, specifically in reducing low-back physical demands, there is limited understanding of potential unintended consequences of BSE use on neuromuscular control of the trunk during manual material handling (MMH). We quantified the effects of two passive BSEs (BackX™ AC and Laevo™ V2.5) on trunk dynamic stability and movement coordination during a repetitive lifting task. Eighteen participants (gender-balanced) completed four minutes of repetitive lifting in nine different conditions, involving symmetric and asymmetric postures when using the BSEs (along with no BSE as a control condition). Maximum Lyapunov exponents (short-term: λmax-s; long-term: λmax-l) and Floquet multipliers (FMmax) were respectively calculated to quantify the local dynamic and orbital stability of thorax and pelvis trajectories. Thorax-pelvis segmental coordination was also quantified using the continuous relative phase. Wearing the Laevo™ significantly increased λmax-s for the pelvis (by ~ 8%) and FMmax for the thorax and pelvis (by ~ 5-10%). Use of either BSE decreased the in-phase coordination pattern for the thorax-pelvis coupling (by ~ 15%). These results suggest that BSE use can compromise neuromuscular control of the trunk, and caution should thus be used in selecting a suitable BSE for use in a given MMH task. Future work is needed, however, to assess the generalizability of different BSE design approaches in terms of unintended short-term and long-term effects on trunk neuromuscular control.
Different types of foot orthoses effect on gait mechanics in patients with rheumatoid arthritis.
Venue: Journal of biomechanics

Foot orthoses are a first line conservative treatment for foot impairments in patients with rheumatoid arthritis (RA), however their effect on gait mechanics is poorly understood. We aimed to compare changes in lower limb and foot mechanics between two types of commonly used foot orthoses (FO) with a control. Twenty-seven patients with rheumatoid arthritis participated in this crossover study. Two different types of FO (a medially wedged custom-made FO and a prefabricated FO with a metatarsal dome, respectively), were compared against a control insole. During gait, lower limb mechanics were analyzed using 3D motion capture, force plates, and an in-shoe pressure system. Inverse dynamics models were created in the Anybody Modeling System to calculate joint angles and joint moments during gait. Gait variables were analyzed using statistical parametric mapping. Compared to the control, the prefabricated FO had limited effect on gait mechanics. Compared to the control the custom-made FO reduced ankle plantarflexion moment with 0.4 %body weight * body height (BW * BH) between 66 and 76% of stance and ankle eversion moment was reduced 0.16% BW*BH between 3 and 40% of stance. Furthermore, it also reduced the average forefoot plantar pressure by 9 kPa between 20 and 62% of stance compared to the control. Changes in foot pressure distribution, joint moments and angles were most pronounced for custom-made FO compared to the prefabricated FO. The findings suggest that patients with RA and foot impairments may benefit more from an individualized FO strategy, if the aim of the treatment is to alter gait mechanics. (NCT03561688).