nils-herrmann/clean_scirepeval huggingface dataset:
Carbon dioxide hydrate as a recovery tool after fatigue of the plantar flexors.
Venue: Journal of biomechanics

This study investigated the effects of cooling the triceps surae with carbon dioxide hydrate (CDH), which is a gas hydrate, a crystalline structure belonging to the clathrates, on the recovery from muscle fatigue. Thirty-six healthy young men were equally and randomly assigned to an ICE group, a CDH group, or a non-cooling (NON) group. All participants performed 80 maximal voluntary isometric contractions (MVCs) of the plantar flexors as a fatiguing task. MVC torque and voluntary activation were determined before, immediately after, and 20 min after the fatiguing task. Evoked torque was similarly assessed except for immediately after the task. In the ICE and CDH groups, the triceps surae was cooled for 5 min using ice and CDH, starting 5 min after the fatiguing task, respectively. The MVC torque and voluntary activation were higher in order of before >20 min after >immediately after the fatiguing task regardless of group, and those time-course changes did not differ between the groups. A decrease in the evoked torque from before to 20 min after the fatiguing task was observed in the ICE and NON groups but not in the CDH group. These results suggest that cooling muscle with CDH can facilitate recovery from peripheral muscle fatigue. This may be due to an increase in blood flow caused by carbon dioxide contained within the CDH, and indicates the potential of CDH as a recovery tool after fatiguing exercise.
A sensitive data analysis approach for detecting changes in dynamic postural stability.
Venue: Journal of biomechanics

Understanding the mechanisms of instability can aid in reducing fall risk. As a sensitive measure of fall risk, the distance between the center of pressure (COP) and center of mass (COM) is currently assessed through discrete points assumed to represent physiological important fall mechanisms. However, it is unclear if these discrete points are appropriate measures of fall risk. Statistical parametric mapping (SPM) is a waveform analysis technique that removes this possibly biased a priori approach. Sixteen healthy young adults (8 males, 8 females; Age: 29 ± 3.6 years, Height: 1.7 ± 0.9 m, Mass: 75 ± 16 kg) performed two tasks that disturbed dynamic stability: voluntary stepping at different step lengths, and forward perturbations at different accelerations. COP-COM distance magnitudes were extracted during the first step in both tasks at discrete points typically assessed in previous research. Discrete point analysis (DPA) was performed on these discrete points and SPM analysis was completed on the COP-COM distance waveform. The results from the study found that SPM analysis identified equivalent significant differences to DPA and identified additional significant differences elsewhere in the COP-COM distance waveform that were not able to be detected by DPA. Two key advantages from using SPM: (1) reduction of possibly biased a priori selection, and (2) increased efficiency and reduced time-cost in data post-processing as inherent variability can limit the detection of discrete points resulting in identifying physiologically different discrete points across trials. This study suggests the use of SPM as a sensitive data analysis approach in detecting fall risk as an alternative to DPA.
Collective cell migration and residual stress accumulation: Rheological consideration.
Venue: Journal of biomechanics

Stress generation during collective cell migration represents one of the key factors which influence the configuration of migrating cells, viscoelasticity of multicellular systems and their inter-relation. Local generation of stress (normal and shear) is significant even in 2D. Normal stress is primarily accumulated within a core region of migrating cell clusters during their movement through the dense environment and during the collisions of migrating cell clusters caused by uncorrelated motility. Shear stress can be significant within perturbed boundary layers around migrating clusters. Cells are more sensitive to the action of shear stress compared with normal stress. Shear stress of a few Pa significantly influences cell state. Prior studies have shown that collectively migrating cells move in such a way to minimize this stress, but it has not yet been determined how cells effectively minimize it. Deeper insight into possible cell mechanisms for minimizing undesirable shear stress would be of great importance because it may help to direct morphogenesis, accelerate wound healing or prevent cancer invasion. In the proposed model three primary mechanisms in which cells may reduce shear are given: decreasing speed, tissue thickening, and/or reducing slip effects. Suggestions obtained from the proposed model indicate a need for further experimental studies that will reveal whether the heterogeneity in the cell-cell adhesion types correlates well with the stiffness inhomogeneity, or changes in the adhesion clustering, cytoskeletal linkage or some other modification to the adhesion complex (adherens junctions or tight junctions) are occurring to influence overall adhesive strength.
Characterizing forearm muscle activity in university-aged males during dynamic radial-ulnar deviation of the wrist using a wrist robot.
Venue: Journal of biomechanics

Functioning as wrist stabilizers, the wrist extensor muscles exhibit higher levels of muscle activity than the flexors in most distal upper-limb tasks. However, this finding has been derived mostly from isometric or wrist flexion-extension protocols, with little consideration for wrist dynamics or radial-ulnar wrist deviations. The purpose of this study was to assess forearm muscle activity during the execution of dynamic wrist radial-ulnar deviation in various forearm orientations (pronation/supination). In 12 healthy university-aged males, surface electromyography (EMG) was recorded from eight muscles of the dominant arm: flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), extensor digitorum (ED), biceps brachii (BB) and triceps brachii (TB). While grasping a handle, participants performed dynamic radial-ulnar deviation using a three-degrees-of-freedom wrist manipulandum. The robotic device applied torque to the handle, in either a radial or ulnar direction, and in one of three forearm postures (30° supinated/neutral/30° pronated). Results indicated that forearm posture influenced the muscles acting upon the hand (FDS/ED), whereas movement phase (concentric-eccentric) and torque direction influenced nearly every muscle. The ECR demonstrated the greatest task-dependency of all forearm muscles, which is possibly reflective of forearm muscle lines of action. Co-contraction ratios were much higher in radial trials than ulnar (Radial: 1.20 ± 0.78, Ulnar: 0.28 ± 0.18, P < 0.05), suggesting greater FCU and ECU contribution to wrist joint stability in radial-ulnar movement. These findings highlight a greater complexity of wrist extensor function than has previously been reported in isometric work.
A single Inertial Measurement Unit on the shank to assess the Shank-to-Vertical Angle.
Venue: Journal of biomechanics

The Shank-to-Vertical Angle (SVA) is a commonly used parameter to describe orthotic alignment. 3D gait analysis (3DGA) or 2D video analysis are usually used to assess the SVA, but are not always feasible in clinical practice. As an alternative, an Inertial Measurement Unit (IMU) attached and aligned to the shank might be used. This study aimed to investigate the validity, inter-rater reliability and optimal location of a single IMU on the shank to assess the SVA. Thirteen healthy participants (7 m/6f, mean age: 45 ± 18 years) were recorded during quiet standing and barefoot walking using a 3D motion capture system and, simultaneously, with IMUs on the shank. The IMUs were anatomically placed and aligned at two different locations, i.e. anterior, in line with the tibial tuberosity and midline of the ankle (anterior IMU), and lateral, in line with the lateral epicondyle and lateral malleolus (lateral IMU). For each participant, the IMUs were placed by two different researchers. A paired t-test, Bland Altmann analysis (mean difference, repeatability coefficient) and intraclass correlation coefficient (ICC) between the 3DGA and both IMUs, and between raters, was performed. Although validity and reliability of the lateral IMU was low, good validity and inter-rater reliability was found for the anterior IMU (Rater1: mean difference: -0.7 ± 2.1, p = 0.27; ICC = 0.83 and Rater2: mean difference: -0.4 ± 1.9, p = 0.46; ICC = 0.86). Hence, a single IMU placed at the anterior side of the shank is a valid and reliable method to assess the SVA during standing and walking in healthy adults.
On the application of entropic half-life and statistical persistence decay for quantification of time dependency in human gait.
Venue: Journal of biomechanics

Entropic half-life (ENT½) and statistical persistence decay (SPD) was recently introduced as measures of time dependency in stride time intervals during walking. The present study investigated the effect of data length on ENT½ and SPD and additionally applied these measures to stride length and stride speed intervals. First, stride times were collected from subjects during one hour of treadmill walking. ENT½ and SPD were calculated from a range of stride numbers between 250 and 2500. Secondly, stride times, stride lengths and stride speeds were collected from subjects during 16 min of treadmill walking. ENT½ and SPD were calculated from the stride times, stride lengths and stride speeds. The ENT½ values reached a plateau between 1000 and 2500 strides whereas the SPD increased linearly with the number of included strides. This suggests that ENT½ can be compared if 1000 strides or more are included, but only SPD obtained from same number of strides should be compared. The ENT½ and SPD of the stride times were significantly longer compared to that of the stride lengths and stride speeds. This indicates that the time dependency is greater in the motor control of stride time compared to that of stride lengths and stride speeds.
Collagen bundling and alignment in equibiaxially stretched human amnion.
Venue: Journal of biomechanics

We study irreversible collagen arrangement processes in ex-vivo human amnions subjected to inflation tests, which simulate the mechanical conditions prior to and during the initiation of labor uterine contractions. The investigation is focused on the center of the membrane where the stresses are maximal and equibiaxial. Second harmonic generation reveals an unexpected collagen rearrangement in the compact layer that is responsible for the structural integrity of the fetal membrane. The observed bundling and alignment of the collagen fibers indicate a deviation from the expected equibiaxial stress state. The statistical analysis of the fiber orientations provides information on two driving forces for collagen alignment: microscale flaws and macroscale deviation from the equibiaxial strain. As the pressure increases, the macroscale effect becomes dominant, and a high density of fibers that are aligned along a specific direction is observed. A model that explains these observations and relates them to the material properties is presented. The results of this study indicate that a temporal increase in intrauterine pressure or uterine cervix dilatation causes irreversible changes in collagen molecular connections that may lead to biological changes, such as the initiation of term and preterm labor.
Physiological and biomechanical effects on the human musculoskeletal system while carrying a suspended-load backpack.
Venue: Journal of biomechanics

Many people need to carry heavy loads in a backpack to perform occupational, military, or recreational tasks. Suspended-load backpacks have been shown to reduce dynamic peak forces acting on the body and lower an individual's metabolic cost during walking. However, little is known about the physiological and biomechanical effects of a suspended-load backpack on the human musculoskeletal system. The goal of this study was to determine the impact of different types of backpacks on metabolic cost, joint kinetics, gait kinematics, and muscle activity while individuals carried the same load of 15 kg at a walking speed of 5 km/h and running speed of 7 km/h on an instrumented treadmill. A group of six healthy participants participated in experiments in which two different backpacks were worn under three different conditions: suspended-load backpack working condition (SLB_ON), suspended-load backpack locking condition (SLB_OFF), and ordinary backpack condition (ORB). The results showed that carrying the backpack in the SLB_ON condition can reduce lower limb muscle activities and biological joint work while decreasing the metabolic cost by 15.25 ± 4.21% and 8.81 ± 2.46% during walking and 12.53 ± 2.39% and 6.99 ± 2.37% during running compared to carrying the backpack in the SLB_OFF and the ORB conditions, respectively. However, the SLB_ON condition may cause increased shoulder strain and dynamic stability and balance problems. These results suggest that the control of load movement in a suspended-load backpack should be considered when locomotion performance is optimized in future studies.
Soft tissue artifact causes underestimation of hip joint kinematics and kinetics in a rigid-body musculoskeletal model.
Venue: Journal of biomechanics

Rigid body musculoskeletal models have been applied to study kinematics, moments, muscle forces, and joint reaction forces in the hip. Most often, models are driven with segment motions calculated through optical tracking of markers adhered to the skin. One limitation of optical tracking is soft tissue artifact (STA), which occurs due to motion of the skin surface relative to the underlying skeleton. The purpose of this study was to quantify differences in musculoskeletal model outputs when tracking body segment positions with skin markers as compared to bony landmarks measured by direct imaging of bone motion with dual fluoroscopy (DF). Eleven asymptomatic participants with normally developed hip anatomy were imaged with DF during level treadmill walking at a self-selected speed. Hip joint kinematics and kinetics were generated using inverse kinematics, inverse dynamics, static optimization and joint reaction force analysis. The effect of STA was assessed by comparing the difference in estimates from simulations based on skin marker positions (SM) versus virtual markers on bony landmarks from DF. While patterns were similar, STA caused underestimation of kinematics, range of motion (ROM), moments, and reaction forces at the hip, including flexion-extension ROM, maximum internal rotation joint moment and peak joint reaction force magnitude. Still, kinetic differences were relatively small, and thus they may not be relevant nor clinically meaningful.
Patient-specificity of scapular orientation measurements using an acromion marker cluster with multiple calibration poses.
Venue: Journal of biomechanics

The purpose of this study was to understand how each calibration pose affects scapular orientations measured by an Acromion Marker Cluster during scapular plane arm elevation performed by patients who had been pre-operatively indicated for Reverse Total Shoulder Arthroplasty. Eight pre-operative Reverse Total Shoulder Arthroplasty patients participated in this study while optical motion capture measured kinematics, specifically scapulothoracic angles and angular displacements, vs. humerothoracic elevation. The angle measurements were compared across the static calibration poses used to calculate them within-patient with One Dimensional Statistical Parametric Mapping paired t-tests and across-patients with a series of Sign Tests. The study uncovered patient-specificity in the effects of the Acromion Marker Cluster calibration pose on scapulothoracic angles and near linear offsets between the scapulothoracic upward rotation angles. The scapulothoracic upward rotation angular displacement measurements across calibration poses were within 5° of each other, suggesting nearly linear offsets between upward rotation angle measurements from each calibration pose. The Sign Tests revealed that using the Neutral calibration pose estimated significantly greater scapulothoracic protraction angles during arm elevation than did using the Hand to Back Pocket calibration pose (p = 0.02). Scapulothoracic protraction and posterior tilt measurements were near linear offsets between calibration poses only when humerothoracic elevation was less than 50°. Results encourage patient-specific and humerothoracic elevation-specific methods to combine calibration poses and the development of standards to report scapulothoracic orientations derived from using an Acromion Marker Cluster with multiple calibration poses.
Rapid increase in intradiscal pressure in porcine cervical spine units negatively impacts annulus fibrosus strength.
Venue: Journal of biomechanics

Vertebral endplate fracture is generally accepted to occur as a result of excessive, typically rapid, pressure developed within the intervertebral disc. Clinical evidence of disc disorders later in life following endplate fracture suggests that the disc is also impacted by the fracture event. There is an abundance of evidence to indicate that loss of disc pressure at the time of fracture alters annulus fibrosus loading which could impact disc health long-term. However, little is known regarding the isolated impact of the rapid disc pressurization during the fracture event. This study sought to determine if rapid disc pressurization impacts mechanical properties of the annulus. Intervertebral discs of porcine cervical functional spine units (FSU) were pressurized via rapid injection of hydraulic fluid (standard motor oil). FSUs were subsequently grouped according to whether the pressurization resulted in endplate fracture ('fracture'; n = 9) or not ('non-fracture'; n = 13). Annular tensile properties and lamellar adhesion strength were quantified for both fractured and non-fractured samples. A third group was also examined in which FSUs did not undergo the pressurization protocol ('control'; n = 10). Annular tensile properties were not found to be statistically different between the three conditions (p > 0.05). Lamellar adhesion strength, in contrast, was found to be, on average, 53% lower in specimens which were pressurized compared to control, non-pressurized samples (p = 0.03). Further, no statistical differences in adhesion strength was found between fractured and non-fractured pressurized samples (p = 0.990) indicating that rapid pressurization , and not the presence of an endplate fracture, impacted the mechanical properties of the annulus. Decreased lamellar adhesion strength increases the potential of delamination, which can lead to disc disorders.
The use of a single sacral marker method to approximate the centre of mass trajectory during treadmill running.
Venue: Journal of biomechanics

The three-dimensional trajectory of the body's centre of mass (COM) is useful to determine a number of biomechanical outcomes in running research. Previous studies have used the COM to calculate measures such as overstriding, vertical stiffness, and vertical oscillation. The COM is traditionally computed using the segmental analysis method, though this is expensive and time-consuming owing to the need for a full-body marker set. The purpose of this study was to determine whether the COM trajectory can be approximated by a single sacral marker during running. Seventy-one participants underwent a biomechanical running analysis on a treadmill utilizing a full-body marker set. Marker trajectories from the sacral marker and from the COM calculated using the segmental analysis method were compared over the entire gait cycle by computing intraclass correlation coefficient (ICC) and root-mean-square error. Paired t-tests were used to determine if the positions differed in mediolateral, anteroposterior, and vertical directions at three gait events (initial contact, midstance, and toe-off). The trajectories from the two methods exhibited a similar pattern in vertical and anteroposterior directions throughout the gait cycle, displaying strong correlations in these directions (ICC = 0.98 ± 0.01 and 0.83 ± 0.07). Our results suggest that a single sacral marker is a valid proxy for COM trajectory in vertical and anteroposterior directions at key events during the stance phase of running in a female recreational population. Researchers can therefore use a single sacral marker to estimate COM trajectory, rather than a full-body marker set, saving on both time and supplies.
Long-term use of minimal footwear in older adult women with knee osteoarthritis: Mechanisms of action in the knee adduction moment.
Venue: Journal of biomechanics

Studies have shown the short- and long-term effects of wearing minimalist footwear in reducing knee loads in patients with knee osteoarthritis (OA). This study aimed to investigate the mechanisms underpinning the reduction in external knee adduction moment (EKAM) in older adult women who wore this type of footwear through a randomized controlled trial. Fifty-six participants with medial compartment knee OA were equally allocated to either an intervention group (IG) that wore minimalist footwear (Moleca®) or to a control group (CG) that continued regular clinical treatment for OA for six months. The influence of lower limb joint kinematics and joint frontal moments, center of pressure displacement, and foot progression angle in predicting the reduction of EKAM were assessed after a six-month intervention. Surprisingly, none of the seven independent variables predicted the first peak EKAM in the multiple regression model for the IG. For the CG, the increase of one unit in the first peak of the hip adduction moment resulted in a 1.01 units increase in the first peak EKAM. Additionally, a one-unit reduction in the ankle eversion angle resulted in an increase of 0.16 units in the percent change in the first peak EKAM. Thus, wearing the Moleca® shoe for six months helped the participants keep a natural gait pattern without increasing the hip moment or the ankle inversion angle compared to the women who did not wear the Moleca® footwear.
Computational modeling of the strength of the ascending thoracic aortic media tissue under physiologic biaxial loading conditions.
Venue: Journal of biomechanics

Type A Aortic Dissection (TAAD) is a life-threatening condition involving delamination of ascending aortic media layers. While current clinical guidelines recommend surgical intervention for aneurysm diameter > 5.5 cm, high incidence of TAAD in patients below this diameter threshold indicates the pressing need for improved evidence-based risk prediction metrics. Construction of such metrics will require the knowledge of the biomechanical failure properties of the aortic wall tissue under biaxial loading conditions. We utilized a fiber-level finite element based structural model of the aortic tissue to quantify the relationship between aortic tissue strength and physiologically relevant biaxial stress state for nonaneurysmal and aneurysmal patient cohorts with tricuspid aortic valve phenotype. We found that the model predicted strength of the aortic tissue under physiologic biaxial loading conditions depends on the stress biaxiality ratio, defined by the ratio of the longitudinal and circumferential components of the tissue stress. We determined that predicted biaxial tissue strength is statistically similar to its uniaxial circumferential strength below biaxiality ratios of 0.68 and 0.69 for nonaneurysmal and aneurysmal cohorts, respectively. Beyond this biaxiality ratio, predicted biaxial strength for both cohorts reduced drastically to a magnitude statistically similar to its longitudinal strength. We identified fiber-level failure mechanisms operative under biaxial stress state governing aforementioned tissue failure behavior. These findings are an important first step towards the development of mechanism-based TAAD risk assessment metrics for early identification of high-risk patients.