nils-herrmann/clean_scirepeval huggingface dataset:
Women with patellofemoral pain show altered motor coordination during lateral step down.
Venue: Journal of biomechanics

Patients with patellofemoral pain (PFP) present altered activation of the hip and knee muscles. Electromyography (EMG) analyses in PFP patients are usually performed individually for each muscle. However, several studies suggest that the central nervous system may modulate neural commands directed to groups of co-activated muscles, called muscle synergies. Investigating the synergistic organization in PFP will advance our knowledge of the influence of pain on muscle coordination. This study aimed to compare the motor coordination between women with and without PFP during the lateral step down (LSD). 15 women with PFP and 14 asymptomatic women underwent three-dimensional kinematics and EMG assessment during LSD. The Movement Deviation Profile (MDP) was calculated from kinematic data. Muscle synergies were extracted from EMG data of eight lower limb muscles using a non-negative factorization algorithm. Results revealed differences in MDP and an altered synergistic control between women with PFP and asymptomatic while performing the same motor gesture. Particularly, the variability accounted for (VAF) when using 3 synergies to reconstruct EMGs of the PFP group was higher than in the control group, suggesting reduced complexity of motor control in PFP. Detailed synergy analyses highlighted specific differences between groups in vastii and rectus femoris, which are muscles with a crucial role during the squat phase and the transition to rise phase of the LSD. This study shows the ability of muscle synergies analysis to reveal impaired motor coordination in PFP patients, and has the potential to be explored as a complementary tool to current clinical assessment techniques.
Stress distribution changes in growth plates of a trunk with adolescent idiopathic scoliosis following unilateral muscle paralysis: A hybrid musculoskeletal and finite element model.
Venue: Journal of biomechanics

This study aimed to investigate changes occurred in the stress distribution in the growth plates (GPs) of a trunk with adolescent idiopathic scoliosis (AIS) following unilateral muscle paralysis. We hypothesized that weakening the appropriately chosen muscles on the concave side can decelerate AIS deformity progression. Muscle forces and reaction loads were estimated by an optimization-driven musculoskeletal (MS) model of adolescents with a normal- and an AIS trunk, and then applied on the finite element model of GPs of L1 through L4. Different set patterns of 95% reduction in the strength of the concave-side longissimus thoracis pars thoracic (LGPT), multifidus lumborum (MFL), and LGPT + MFL muscles were performed in the MS models. Results of this study showed that weakening of the concave-side MFL and LGPT muscles rendered a 35% correction in the symptomatic axial rotation of the AIS spine, and a reduction of about 25% in the compressive von Mises stress on the concave side of GPs, respectively, which can decelerate the deformity progression. It was observed that unilateral muscle weakening caused a compensatory activation of the rest of muscles to retain the spine stability. The intradiscal pressures and ratio between the rotations toward either side of the scoliotic spine, found here, matched well with some recent in-vivo investigations. One of the applications of the stability-based MS model of AIS spine with unilaterally weakened muscles presented in this study is to optimize the performance of the currently used braces. To fortify the presented therapeutic approach, experiments should be done on scoliotic animals.
Do inclined sleeping surfaces impact infants' muscle activity and movement? A safe sleep product design perspective.
Venue: Journal of biomechanics

The design of inclined sleep products may be associated with an increased risk of suffocation when an infant finds themselves prone in the product. It is important to understand how different inclined sleep surface angles impact infants' muscle activity when considering a safe sleep environment. The purpose of this study was to assess muscle activity of healthy infants when they lie supine and prone on different inclined crib mattress surfaces (0° vs. 10° vs. 20°). Fifteen healthy infants were recruited for this study. Surface EMG was recorded from cervical paraspinal, abdominal, lumbar erector spinae, and triceps muscles for 60 s during supine and prone positioning. Repeated measures ANOVAs and Bonferroni post-hoc adjustments were performed to test the effect of incline angles. Paired t-tests were performed to test the effect of position (supine vs. prone). During prone lying, abdominal muscle activity increased by 33% and 71% for 10° and 20° compared to 0°, while erector spinae and triceps muscle activity decreased for 20° compared to 0°. Lumbar erector spinae and cervical paraspinal muscle activity increased by 185% and 283% for prone compared to supine lying. During prone positioning, the 20° inclined surface resulted in significantly higher muscle activity of the trunk core muscles (abdominals), which may exacerbate fatigue and contribute to suffocation if an infant cannot self-correct to the supine position. Compared to supine positioning, prone lying requires higher musculoskeletal effort to maintain a safe posture to prevent suffocation, and babies likely fatigue faster when lying prone.
Lumbar axial torque actively induces trunk axial rotation during sidestep cutting manoeuvre: Insight to expand the trunk control concept.
Venue: Journal of biomechanics

Core stability is widely recognised as 'the body's ability to maintain or resume an equilibrium position of the trunk after perturbation'. As such, large excursions of the trunk during controlled activities are believed to be the result of poor trunk control. Here, we show that the axial torque actively induces the trunk axial rotation (the thoracic rotation relative to the pelvis) rather than minimise the axial rotation during sidestep cutting. We analysed the kinematic and kinetic data of 90° sidestep cutting with maximal effort by 10 physically active men. The thorax rotated toward the objective direction prior to the pelvis, resulting in the trunk axial rotation with the peak angle of 21.0 ± 6.0°. Lumbosacral axial torque was exerted toward the objective direction during the early stance phase, and it was then exerted inversely during the late stance and flight phases, which was consistent with the increase/decrease in the trunk axial rotation velocity. In the early stance phase, the absolute integrated component of the lumbosacral axial torque for pelvic rotation (0.074 ± 0.033 Nms/kg) was significantly larger than any other integrated component. In the late stance and flight phases, the lumbosacral axial torque mainly rotated the pelvis. The results indicate that the axial torque is exerted to actively induce the trunk axial rotation rather than minimise the trunk movement, suggesting that the trunk control concept probably should include not only stabilising but also actively moving the trunk.
In situ AFM-based nanoscale rheology reveals regional non-uniformity in viscoporoelastic mechanical behavior of the murine periodontal ligament.
Venue: Journal of biomechanics

The periodontal ligament (PDL) is a critical player in the maintenance of tooth health, acting as the primary stabilizer of tooth position. Recent studies have identified two unique regions within the PDL, the 'dense collar' region and the 'furcation' region, which exhibit distinct structural and compositional differences. However, specific functional differences between these regions have yet to be investigated. We adapted an AFM-based nanoscale rheology method to regionally assess mechanical properties and poroelasticity in the mouse PDL while minimizing the disruption of the 3-dimensional native boundary conditions, and then explored tissue mechanical function in four different regions within the dense collar as well as in the furcation region. We found significant differences between the collar and furcation regions, with the collar acting as a stabilizing ligamentous structure and the furcation acting as both a compressive cushion for vertical forces and a conduit for nutrient transport. While this finding supports our hypothesis, based on previous studies investigating structural and compositional differences, we also found surprising inhomogeneity within the collar region itself. This inhomogeneity supports previous findings of a tilting movement in the buccal direction of mandibular molar teeth and the structural adaptation to prevent lingual movement. Future work will aim to understand how different regions of the PDL change functionally during biological or mechanical perturbations, such as orthodontic tooth movement, development, or aging, with the ultimate goal of better understanding the mechanobiology of the PDL function in health and disease.
Using directional statistics to test hypotheses regarding rigid body attitude: Comparison to univariate and multivariate Cardan angle tests.
Venue: Journal of biomechanics

Rigid body attitude and single-joint kinematics are typically expressed using three Cardan angles which represent rotations in anatomical planes. It was recently shown in the Biomechanics literature that Cardan angles inaccurately estimate true mean attitude due to an important mathematical inadequacy: attitude under-representation; at least four quantities are needed to unambiguously specify attitude. Directional statistics, which is the multivariate generalization of (univariate) circular statistics, solves this problem using four-dimensional unit vectors and the mathematics of hyperspherical geometry. The purpose of this study was to compare the results of directional analysis to the results of uni- and multi-variate Cardan analysis for representative joint kinematic data during gait. We analyzed hip, knee and pelvis data from three open datasets and report exemplary results for knee kinematics in v-cut vs. side shuffle tasks. We also conducted Monte Carlo simulations, using synthetic data with precisely controlled true angular effects, to systematically compare directional and Cardan analyses. Results show that directional analysis yielded considerably smaller p values (p<0.03) than Cardan analysis (p>0.055) for the exemplary dataset. Simulation results confirmed that directional analysis is considerably more powerful (i.e., much more able to detect true angular effects) than both uni- and multi-variate Cardan analysis. These results suggest that directional statistics should be used to analyse attitude, including 3D joint kinematics, to avoid false negatives.
The immediate and prolonged effects of military body armor on the relative timing of thorax and pelvis rotations during toe-touch and two-legged squat tasks.
Venue: Journal of biomechanics

Although military body armor is an effective life saver, it considerably loads more weight on the warfighters, increasing the risk of musculoskeletal injury. This study investigated the immediate and prolonged effects of wearing body armor on timing aspect of lumbo-pelvic coordination during the toe-touch (TT) and two-legged-squat (TLS) tests. A cross-over study design was used wherein twelve asymptomatic and gender-balanced individuals completed two experimental sessions with and without body armor. A session included two similar sets of tests, before and after exposure to a treadmill walk, containing a TT and a TLS test with ten cycles of fast bending and return. Reflective markers were attached on the participants to capture the kinematics of body segments in conjunction with a motion capture system. The mean absolute relative phase (MARP) and deviation phase (DP) between the thorax and pelvis were calculated for each test. The pre-walk MARP in the return was significantly larger with versus without body armor (p = 0.022), while there were no significant effects of body armor on the other outcome measures. In addition, the pre-walk MARP and DP in the bending and return, as well as the walk-induced changes in the MARP in the bending phase were significantly larger in TLS versus TT (p < 0.026). Therefore, using a body armor immediately made the lumbo-pelvic coordination less in-phase during return, but no prolonged effects were found. Further investigation is necessary to specify chances wearing a body armor increases the risk of musculoskeletal injuries in the lower back and lower extremities joints.
Anterior cruciate ligament agonist and antagonist muscle force differences between males and females during perturbed walking.
Venue: Journal of biomechanics

Anterior cruciate ligament (ACL) injuries most commonly occur following a perturbation. Perturbations make the athlete unbalanced or at loss of control, which ultimately can lead to injury. The purpose of this study was to identify differences in ACL agonist and antagonist muscle forces, between sexes, during unexpected perturbations. Twenty recreational athletes were perturbed during walking at a speed of 1.1 m/s. Motion analysis data were used to create subject-specific musculoskeletal models and static optimization was performed to calculate muscle forces in OpenSim. Statistical parametric mapping (SPM) was used to compare muscle forces between males and females during the stance phase of the perturbed cycle. Females illustrated higher ACL antagonist muscle forces (p < 0.05) and lower ACL agonist muscle forces, compared to their male counterparts. The quadriceps (QUADs) muscle group peak was about 1.4 times higher in females (35.50 ± 8.71 N/kg) than males (22.81 ± 5.83 N/kg during 57%-62% of the stance phase (p < 0.05). Females presented a larger peak of gastrocnemius (GAS) at two instances: 12.42 ± 4.5 N/kg vs. 8.10 ± 2.83 N/kg between 70% and 75% at p < 0.05 and 2.26 ± 0.55 N/kg vs. 0.52 ± 0.09 N/kg between 95% and 100% at p < 0.05. Conversely, males illustrated higher initial hamstrings (HAMS) peak of 10.67 ± 4.15 N/kg vs. 5.38 ± 1.1 N/kg between 8% and 11%. Finally, males showed almost double the soleus (SOL) peak at 30.63 ± 8.64 N/kg vs. 17.52 ± 3.62 N/kg between 83% and 92% of the stance phase at p < 0.001. These findings suggest that females may exhibit riskier neuromuscular control in unanticipated situations, like sports.
Root surface microcracks induced by orthodontic force as a potential primary indicator of root resorption.
Venue: Journal of biomechanics

Root resorption is closely related to orthodontic force and affects orthodontic treatment with high incidence; however, the mechanism governing this effect is unclear. Microcracks are associated with bone resorption and may also play an important role in root resorption. This study aimed to assess the occurrence of microcracks on the root surface induced by orthodontic force, analyze the association between force and microcrack development, and propose potential measures to reduce microcracks. Different loads (0.5, 1, or 2 N) were applied between the left first molar and anterior teeth for different durations (1, 3, 7, or 14 days) in a rabbit model. The first molar was dissected and its surface was examined using scanning electron microscopy (SEM), which revealed the presence of microcracks on the compressed side of the root apices. The number, width, and length of microcracks were all positively correlated with the load magnitude and duration. The breaking strength of the root apex was tested by using a digital force tester. In addition, a finite element (FE) model was used to analyze the stress at the root apices and the crack propagation on the root surfaces. FE analysis calculated that the regions of maximum stress at the root apices were consistent with the microcrack regions observed via SEM. These results imply that orthodontic force can directly induce the occurrence and development of microcrack, and may contribute to further root resorption. Therefore, an appropriate interval and direction of orthodontic force may help reduce microcracks and prevent root resorption.
Tibio-femoral kinematics of the healthy knee joint throughout complete cycles of gait activities.
Venue: Journal of biomechanics

Accurate assessment of 3D tibio-femoral kinematics is essential for understanding knee joint functionality, but also provides a basis for assessing joint pathologies and the efficacy of musculoskeletal interventions. Until now, however, the assessment of functional kinematics in healthy knees has been mostly restricted to the loaded stance phase of gait, and level walking only, but the most critical conditions for the surrounding soft tissues are known to occur during high-flexion activities. This study aimed to determine the ranges of tibio-femoral rotation and condylar translation as well as provide evidence on the location of the centre of rotation during multiple complete cycles of different gait activities. Based on radiographic images captured using moving fluoroscopy in ten healthy subjects during multiple cycles of level walking, downhill walking and stair descent, 3D femoral and tibial poses were reconstructed to provide a comprehensive description of tibio-femoral kinematics. Despite a significant increase in joint flexion, the condylar antero-posterior range of motion remained comparable across all activities, with mean translations of 6.3-8.3 mm and 7.3-9.3 mm for the medial and lateral condyles respectively. Only the swing phase of level walking and stair descent exhibited a significantly greater range of motion for the lateral over the medial compartment. Although intra-subject variability was low, considerable differences in joint kinematics were observed between subjects. The observed subject-specific movement patterns indicate that accurate assessment of individual pre-operative kinematics together with individual implant selection and/or surgical implantation decisions might be necessary before further improvement to joint replacement outcome can be achieved.
Introduction of dynamic rate-of-force development scaling factor in progressive drop jumps.
Venue: Journal of biomechanics

Rapid force generation across submaximal levels has been evaluated with the rate of force development scaling factor (RFD-SF) in different isometric tasks, while such measurement was still not verified in dynamic tasks. Our study was designed to evaluate the feasibility of the RFD-SF in dynamic drop jump (DJ) task (RFD-SFDJ). A total of 55 young athletes performed isometric plantarflexion at different submaximal intensities and 60 DJs (6 different drop heights). For each participant we calculated linearity (r2) and slope in isometric task (RFD-SFPF), eccentric part of DJ (RFD-SFDJ-ECC) and concentric part of DJ (RFD-SFDJ-CON), as well as average jump height (DJH) from each drop height. Our results revealed strong linear force-RFD relationship for isometric plantarflexion (r2 = 0.90 ± 0.06), eccentric (r2 = 0.87 ± 0.09) and concentric phase of DJ (r2 = 0.80 ± 0.18). Significant moderate positive correlations were calculated between RFD-SFPF and RFD-SFDJ-ECC (r = 0.311, p < 0.05) and small negative correlations between RFD-SFDJ-CON and RFD-SF (r = -0.276, p < 0.05). Significant positive moderate correlations were seen only between RFD-SFDJ-ECC and DJH from 10 cm (r = 0.459, p < 0.001) and 15 cm (r = 0.423, p < 0.01). This is the first study to introduce and confirm that RFD-SFDJ can be obtained from the multi-joint tasks (60 jumps) and still provide acceptable reliability and linear relationship. Furthermore, RFD-SFDJ may have greater practical application than RFD-SF assessed under the isometric conditions. This verification of RFD-SFDJ opens opportunities for further research regarding its practical application.
Identification of effective elastic modulus using modal analysis; application to canine cancellous bone.
Venue: Journal of biomechanics

Mechanical properties of cancellous bone is of increasing interest due to its involvement in aging pathologies and oncology. Characterization of fragile bone tissue is challenging and available methodologies include quasi-static compressive tests of small size specimens, ultrasound and indentation techniques. We hypothesized that modal analysis of flexure beams could be a complementary methodology to obtain Young modulus. The sampling methodology was adapted such that the uniqueness of the linear dynamic response was available to determine the elastic modulus from natural frequencies and mode shapes. In a first step, the methodology was validated using a synthetic bone model as control. Then, water-jet cutting allowed collecting fourteen small beam-like specimens in canine distal femurs. X-ray microtomography confirmed the microarchitecture preservation, the homogeneity and the isotropy at the specimen scale to derive effective properties. The first natural frequency in clamped-free boundary conditions was used to obtain mean values of Young modulus, which ranged from 210 MPa to 280 MPa depending on the specimen collection site. Experimental tests were rapid and reproducible and our preliminary results were in good agreement with literature data. In conclusion, beam modal analysis could be considered for exploring mechanical properties of fragile and scarce biological tissues.
Transition from double-leg to single-leg stance in the assessment of postural stability.
Venue: Journal of biomechanics

Kinematic characteristics of the double-leg stance (DLS) to a single-leg stance (SLS) transition were analyzed in a group of young adolescent girls to assess their postural stability control. Twenty volunteers participated in a single experimental session during which their postural stability was assessed based upon the center of pressure (COP) trajectories during the transitions in two typical sensory conditions: with eyes open (EO) and with eyes closed (EC). To quantify the postural control we applied Fitts' model treating the postural sway as the noise at the initial and the target setpoint control. Results showed that in young healthy subjects characteristics of the transition to either left or right single-leg stance were quite symmetrical. The postural sway at the target posture was characterized by the double increase of postural sway when tested with EO and by the almost quadrupled amount of sway in EC trials. The sway at the target resulted in the decline of the COP mean and peak velocity proportionally to the movement index of difficulty (ID). The estimated ID value increased by 74% in EC trials while the probability of instability increased to 70%. The DLS-SLS test can be recommended for clinical and laboratory assessment of postural stability.