nils-herrmann/clean_scirepeval huggingface dataset:
Stability control in older adults with asymmetrical load carrying when stepping down a curb.
Venue: Journal of biomechanics

We investigated the effect of asymmetric load carrying using different bag types with the dominant and non-dominant hands on upper limb coordination, walking adaptations, and stability control in a curb-descend task in older adults. Fourteen participants walked on a pathway with a 16-cm curb located in the middle. They walked without a load or asymmetrically carrying a load corresponding to 7% of their body mass. The weight was placed in two different bags (with and without strap) and carried by the dominant and non-dominant hands. The upper limb coordination analysis showed that the anti-phase pattern between right and left shoulder reduced considerably due to the almost motionless shoulder of the side carrying the load. The spatial-temporal walking parameters and curb negotiation variables were unaffected by load carriage. The margin of stability (MoS) was unchanged by load transportation in the AP direction. In the ML direction, taking the bag on the same side of the foot contacting the floor increased the MoS; however, when the load was incorporated into the COM model, the MoS did not differ anymore from the control condition. The changes in interlimb coordination reflected a strategy to prevent unexpected movements of the bag that could threaten body stability. Healthy older adults were able to predict the consequences of carrying a load and kept the MoS constant. They compensated for the disturbance caused by the transport of a relatively moderate load and performed the descending curb task successfully.
Influence of multiple sclerosis on dynamic gait stability.
Venue: Journal of biomechanics

Falls are a serious health threat for people with multiple sclerosis (MS). Dynamic gait stability has been identified as a key risk factor of falls. The development of effective interventions for preventing falls requires a sound understanding of how MS affects dynamic gait stability. The purpose of the study was to compare dynamic gait stability within the framework of Feasible Stability Region between people with and without MS during level walking at a self-selected speed. Twenty adults with MS and 25 age- and sex-matched healthy individuals were recruited. Dynamic gait stability at touchdown and liftoff on both the strong and weak sides was assessed as the primary outcome measurement. Spatiotemporal gait parameters, including step times, step length, step frequency, and foot landing angle, were determined as explanatory variables. People with MS exhibited lower stability at both gait events bilaterally than their healthy counterparts. The lower stability was mainly attributable to the slower gait speed in MS than in the healthy control. To compensate for the dynamic gait stability deficit resulting from the slow gait speed, individuals with MS adopted a short step length to shift the center of mass motion state closer to the feasible stability region. For people with MS, the stability value was higher on the weak side than on the strong side at touchdown, but not liftoff. The findings from this study could provide insight into the impact of MS on the control of dynamic gait stability.
Lower limb biomechanics before and after anterior cruciate ligament reconstruction: A systematic review.
Venue: Journal of biomechanics

This review aimed to synthesise the findings of literature that have assessed the changes in lower limb biomechanics following anterior cruciate ligament (ACL) reconstructive surgery. Systematic searches of CINHAL, MEDLINE, SCOPUS, and SPORTDiscus databases were run. All included studies had presented biomechanical variables pre- and post-surgery for the same participants. Articles were categorised by the analysed movement, and effect sizes were calculated. Fifty-four studies met the inclusion criteria, providing data on gait (n = 31), balance (n = 12), joint position sense (n = 5), stair ambulation (n = 4), pivoting (n = 6), and landing (n = 5). Measures of balance performance and joint position sense showed improvements from pre- to post-surgery. Changes in joint kinematics were inconsistent between studies, however increased knee flexion excursion, and reduced tibial anterior translation and internal rotation post reconstruction were identified. Joint kinetics reduced in magnitude in the early stages after surgery (≤5 weeks), then increased later in recovery (≥24 weeks). Risk of bias assessment identified most articles had a moderate or high risk (low = 5; moderate = 21; high = 11) resulting from participant retention and surgical intervention differences. The results of the review identified that although lower limb biomechanics did alter following reconstruction, few variables provided consistent results across studies and tasks. The low methodological quality of some articles may have contributed to these inconsistent findings. Alternatively, differences across studies may have resulted from individual coping strategies of participants that have previously been suggested to be present before reconstructive surgery, and future research should look to explore individual coping strategies to ACL reconstruction.
Synergies in the ground reaction forces and moments during double support in curb negotiation in young and older adults.
Venue: Journal of biomechanics

Falls that occur while negotiating steps are a leading cause of death in older adults. Although recent efforts have improved understanding of the mechanics and control of stepping behaviors, the double support phase during stepping is understudied. Therefore, we quantified the stability of the resultant forces and moments acting on the body during this phase. These quantities determine the movement of the body, and therefore, their stability is essential for successful stepping behavior. We measured the ground reaction variables (GRVs) under both feet as healthy young (n = 10) and older adults (n = 10) stepped up and down a curb. We employed the uncontrolled manifold method to evaluate the hypotheses that the GRVs covary to stabilize the resultant force and moment in the three coordinate directions. Robust stabilization of the resultant forces and moments was observed while stepping up. However, while stepping down, the stability of the resultant moment was prioritized over that of the resultant forces in the vertical and the anterior-posterior directions, and the stability of the resultant medio-lateral force was prioritized over that of the resultant anterior-posterior force. The salience of stabilizing whole-body angular momentum and medio-lateral motion during locomotion is well known, but their prioritization during adaptive gait is a novel result and is possibly related to the higher likelihood of falling during descent (versus ascent). Finally, contrary to our expectations, we observed no age differences in our stability indices, indicating that healthy aging does not diminish the stability of the resultant forces and moments.
Evaluation of musculoskeletal modelling parameters of the shoulder complex during humeral abduction above 90°.
Venue: Journal of biomechanics

Based on electromyographic data and force measurements within the shoulder joint, there is an indication that muscle and resulting joint reaction forces keep increasing over an abduction angle of 90°. In inverse dynamics models, no single parameter could be attributed to simulate this force behaviour accordingly. The aim of this work is to implement kinematic, kinetic and muscle model modifications to an existing model of the shoulder (AnyBody™) and assess their single and combined effects during abduction up to 140° humeral elevation. The kinematics and the EMG activity of 10 test subjects were measured during humeral abduction. Six modifications were implemented in the model: alternative wrapping of the virtual deltoid muscle elements, utilization of a three element Hill model, strength scaling, motion capture driven clavicle elevation/protraction, translation of the GH joint in dependency of the acting forces and an alteration of the scapula/clavicle rhythm. From the six modifications, 16 different combinations were considered. Parameter combinations with the Hill model changed the resultant GH joint reaction force and led to an increase in force during abduction of the humerus above 90°. Under the premise of muscle activities and forces within the GH joint rising after 90° of humeral abduction, we propose that the Hill type muscle model is a crucial parameter for accurately modelling the shoulder. Furthermore, the outcome of this study indicates that the Hill model induces the co-contraction of the muscles of the shoulder without the need of an additional stability criterion for an inverse dynamics approach.
Lower knee extensor and flexor strength is associated with varus thrust in people with knee osteoarthritis.
Venue: Journal of biomechanics

Varus thrust during walking is common in people with knee osteoarthritis (OA) and can increase the risk of disease progression. Lower limb muscle strength, particularly isokinetic strength, may play a role in varus thrust. The purpose of this study was to investigate the relationships between varus thrust and isokinetic strength knee extensors and flexors in people with and without knee OA . Data from participants with (n = 28) and without (n = 68) knee OA were used. All participants underwent gait analysis during walking at a self-selected pace. Isokinetic knee extensor and flexor strength were measured at 60°/s and 120°/s. Varus thrust was measured using peak knee adduction velocity and knee adduction excursion during the first half of stance. Multiple linear regression was used to examine relationships between strength and varus thrust in the two groups separately while adjusting for age, sex, walking speed, and static alignment. In those with knee OA, knee extensor (Model R2 = 27.0%) and flexor torque (Model R2 = 28.5%) at 60°/s were negatively associated with peak adduction velocity. No other associations were seen between strength and varus thrust measures in the OA group. No associations were seen in the control group. Lower isokinetic knee extensor and flexor muscle at 60°/s strength is related to greater magnitude of varus thrust in individuals with knee OA but not in those without OA. Isokinetic strength deficits may be involved in varus thrust.
Validity and reliability of force-velocity outcome parameters in flywheel squats.
Venue: Journal of biomechanics

Our study was designed to check the reliability of force-velocity (F-v) relationship outcome measures using flywheel (FW) squats. The main objectives at the primary level were to test intra-session reliability of mechanical parameters for ten equidistant FW loads, and at the secondary level, to test reliability and validity of the F-v relationship outcome measures in case any possible reduction in used loads and number of loads - compared to the 10-load method as a reference - is administered. Twenty-six subjects performed two sets of five squats with FW loads in the range 0.025-0.25 kg∙m2. Averaging six consecutive repetitions obtained ICC2.k > 0.9 for mean force and mean velocity results. Consecutively averaged parameters at the primary level showed excellent inter-set reliability (ICC2.1 > 0.9). The inverse F-v relationship was strong (R2 = 0.96). At the secondary level, Bland-Altman statistics showed decreasing bias and limits of agreement in combination with more loads. Theoretical maximal force and power showed smaller bias as F-v slope and theoretical maximal velocity for three loads or more. Four loads (0.025, 0.075, 0.225 and 0.25 kg∙m2) lowered bias to a 5% in relation to the reference F-v slope. In conclusion, six repetitions are required to obtain trustworthy force and velocity results. The results will contribute to standardising the methodology for assessing the mechanical capacities of leg muscles using FW resistance. Moreover, assessing individual F-v profile with reduced protocol may be a less fatiguing tool for prescribing exercise intensity and for assessing training adaptations.
Estimating upper extremity joint loads of persons with spinal cord injury walking with a lower extremity powered exoskeleton and forearm crutches.
Venue: Journal of biomechanics

Lower extremity powered exoskeletons with crutch support can provide upright mobility to persons with complete spinal cord injury (SCI); however, crutch use for balance and weight transfer may increase upper extremity (UE) joint loads and injury risk. This research presented the first exoskeleton-human musculoskeletal model to estimate upper extremity biomechanics, driven by 3D motion data of persons with complete SCI walking with an exoskeleton and crutch assistance. Forearm crutches instrumented with strain gauges, force plates, and a 3D motion capture system were used to collect kinematic and kinetic data from five persons with complete SCI while walking with the ARKE exoskeleton. Model output estimated participant upper extremity kinematics, kinetics, and crutch forces. Compared to inverse dynamic biomechanical crutch model studies of persons with incomplete SCI, exoskeleton users walked with more anterior trunk tilt and twice the shoulder flexion angle. Anterior tilt increased forces and moments at the crutch, shoulder, and elbow. Crutch floor contact periods were 30-40% longer, resulting in upper extremity joint impulses 5 to 12 times greater than previously reported. Reducing UE joint loading is important to reduce overuse injuries associated with ambulatory assistive devices. Incorporating a variable assist ankle joint or more experience with exoskeleton walking may reduce UE joint loads, and minimise injury risk. Study outcomes provide a quantitative understanding of UE dynamics during exoskeleton walking that can be used to improve device design, training, and rehabilitation.
Algorithm to compute muscle excitation patterns that accurately track kinematics using a hybrid of numerical integration and optimization.
Venue: Journal of biomechanics

Forward dynamic simulation is used to examine the causal relationships between muscle excitation patterns and human movement. The computed muscle control (CMC) algorithm computes a set of muscle excitations for a movement using proportional-derivative control. However, errors between experimental and simulated kinematics may cause rapid movements. Herein, we propose a novel algorithm, i.e., hybrid computed muscle control (HCMC), which uses a hybrid of numerical integration and optimization to compute muscle excitation patterns that accurately track kinematics, even for rapid movements. We compared the muscle excitation patterns and accuracies of the kinematics simulated by HCMC and CMC using synthetic and experimental data. Two simple musculoskeletal models were used. The synthetic data were generated for three repetitive movements from the rest position to the flexed position (the hip, knee, and ankle underwent 10°, 20°, and 10° plantar flexion, respectively) and back to the rest position for various times. Experimental data were obtained for a subject running at 220 steps/min. The maximum errors in all kinematics calculated using the HCMC algorithm were extremely lower than those calculated using CMC algorithm (HCMC: 0.04-0.07° [synthetic data] and 0.00-0.03° [experimental data]; CMC: 1.04-2.41° [synthetic data] and 0.48-2.50 [experimental data]). For rapid movements, muscle excitations estimated using HCMC occurred early and without delay than those estimated using CMC. The HCMC algorithm can provide muscle excitation patterns that accurately track kinematics and may be useful for perturbation studies using forward dynamic simulation of joints characterized by a low range of motion during rapid movements.
Detecting changes in postural sway.
Venue: Journal of biomechanics

Postural sway has been identified as a valid marker for assessing the presence of a concussion and monitoring return to activity progression. Instrumented balance assessments have shown to be more reliable in detecting postural sway. However, many sports medicine programs cannot afford to purchase a force plate system to objectively assess postural sway and changes, which may occur due to a head injury. The purpose of this study was to determine if the C3Logix™ application can detect postural sway with the same degree of accuracy as the VSR Sport™ by NeuroCom®. Forty-five Division I Lacrosse players, consisting of 27 males and 18 females, participated in this study. Participants completed the Stability Evaluation Test (SET) on the VSR Sport™ while simultaneously completing the same balance assessment via the C3Logix™ application. The balance assessment consisted of three stances (double leg, single leg, tandem stance) on two surfaces (firm & foam) for a total of six trials. A Pearson correlation was used to determine the correlation between the postural sway velocity values from the VSR Sport™ and ellipse volume values from the C3Logix™ application. Each of the stances on both the firm and foam surface was found to have a strong correlation, suggesting the C3Logix™ application is a valid alternative to postural assessments on a force plate.
Numerical investigation of the impact of Kenenisa Bekele's cooperative drafting strategy on its running power during the 2019 Berlin marathon.
Venue: Journal of biomechanics

In this paper we examined the aerodynamic drag and the resulting decrease of power output associated with the drafting positions used by Kenenisa Bekele at the 2019 Berlin marathon. Examination of videos of the race revealed three different positions adopted by Bekele directly behind a frontline of three runners. These drafting positions were numerically studied using CFD simulations performed with the RANS equations and the SST k-ω model. Depending on his position behind the pacers, our analyses indicated that Bekele's drafting strategy resulted in reductions of 38.5-57.3% of the drag resistance and aerodynamic power. In terms of metabolic power, Bekele's drafting positions yielded an estimated 1.91-2.84% reduction compared to the calculated metabolic power of 1427.89 W (or equivalent metabolic power relative to body mass of 25.50 W/kg) that Bekele would have developed if he had run alone at the same speed of 5.75 m.s-1.
Natural arrangement of micro-strips reduces shear strain in the locust cuticle during power amplification.
Venue: Journal of biomechanics

As one of the key components in power amplification of locust, semi-lunar process (SLP) cuticle has five different portions where its portion II stores a large amount of strain energy when locusts kick. The SLP portion II is composed of regular chitin micro-strips that non-uniformly arranged in its transverse plane. However, it is still unknown whether the natural arrangement of micro-strips affects the power amplification of the SLP cuticle. To address this, SLP portion II samples of adult locusts were mechanically tested along three orthogonal directions, corresponding to the length, width, and thickness axes of the micro-strips, respectively. Four different arrangements of micro-strips in the portion II were compared using finite element method. It was found that the micro-strip set of the portion II is orthotropic elastic and its elastic modulus is maximal in the length axis of the micro-strip. The inclusion of the micro-strips offers more strain energy than the isotropic portion II (without micro-strips). Compared to the horizontally- and vertically-arrangements of the micro-strips, their natural arrangement does not affect the strain energy but reduces the in-plane shear strain in the portion II. This research helps us deeply understand the power amplification mechanism of locusts and may guide optimization of catapult device design in bioinspired robots.
Sex differences in postures of the upper body during a simulated work task performed above shoulder level.
Venue: Journal of biomechanics

The aim of this study was to evaluate if there are sex differences in postures of upper arm, upper back, head and neck after muscle fatigue induced by a simulated work task, requiring upper arm movements performed above shoulder level. Nineteen females and 18 males were evaluated. Upper arm elevation, upper back, head and neck forward flexion postures were recorded using digital inclinometers. The first and the last cycles of the task were considered as pre- and post-fatigue periods, respectively. For both periods, Amplitude Probability Distribution Function (APDF) was calculated for 10th, 50th and 90th percentiles, as well as the angular ranges between the 5th and 95th percentiles (APDF5-95 range). The APDF5-95 range for upper arm elevation was higher with fatigue, but with a higher increase for males. After fatigue, there was also a decrease in the upper arm elevation, with a larger decrease in males for the 10th and 50th percentiles. For head and neck, females showed higher APDF5-95 ranges than males, regardless of the task period evaluated. After muscle fatigue, males adopted more neutral postures of the upper arm than females. Furthermore, females showed more non-neutral postures for head and neck. These findings suggest that the kinematic strategies adopted by females and males during a simulated work task are different and may predispose females to a higher risk of developing work-related musculoskeletal disorders of the neck.
Modeling of braided stents: Comparison of geometry reconstruction and contact strategies.
Venue: Journal of biomechanics

Braided stents are self-expandable devices widely used in many different clinical applications. In-silico methods could be a useful tool to improve the design stage and preoperative planning; however, numerical modeling of braided structures is not trivial. The geometries are often challenging, and a parametric representation is not always easily achieved. Moreover, in the literature, different options have been proposed to handle the contact among the wires, but an extensive comparison of these modeling techniques is missing.In this work, both the geometry and contact issues are discussed. Firstly, an effective strategy based on parametric equations to draw complex braided geometries is illustrated and exploited to build three beam meshes resembling commercial devices. Secondly, three finite element simulations (bending, crimping and confined release) were carried out to compare simplified contact techniques involving connector elements with the more realistic but computationally expensive option based on the general contact algorithm, which has already been validated in the literature through comparisons with experimental results. Both local (stress distribution) and global quantities (forces/displacements) were analyzed.The results obtained using the connectors are significantly affected by wire interpenetrations and over-constraint.The percentage errors reached considerably high values, exceeding 100% in the confined release test and 50% in the remaining cases study. Moreover, the errors do not show uniform trends but vary according to the stent geometry, boundary conditions, connector type and investigated entity, suggesting that it is not possible to replace the use of the general contact algorithm with simplified approaches.