Average Moment Research Articles

Study of the crawler crane stability affected by the length of compensating ropes and platform rotation angle in the mode of movement with payload

Payload uncontrolled oscillations arising during movement of a loaded self-propelled crawler crane at a construction site were reduced by equipping the crane with two additional compensating ropes equal in length and connecting the rotating platform to the load gripping device. This also increased the stability of the entire system. The stability margin moment was used to evaluate the crane stability at individual tipping axes of the crawler support contour. While moving along a random microrelief surface, under the varied length of the compensating ropes and the platform rotation angle, the length reduction increased the mathematical expectation of the stability margin moment for the most loaded lateral tipping axis. The smallest values of the stability margin moment were obtained at the platform rotation angle close to 90 degrees, with the crane stability index being most affected by the compensating rope length. At a zero platform rotation angle, the compensating rope length effect on the stability at the most loaded lateral axis was insignificant. The regression equation of the average stability margin moment affected by the compensating rope length and the platform rotation angle was obtained. The results can be used in the design of advanced self-propelled cable electric crawler cranes.

Source characterizations of the New Cairo earthquake, Egypt

The New Cairo region was hit by a moderate size earthquake (Mw = 4.18) on midday Monday, 31st December 2018 that was felt throughout the greater Cairo region without any reported damage. The source mechanism solution and moment tensor inversion exhibit a normal fault with a minor strike-slip component. The NW-fault plane is the preferred rupture plane consistent with the geological and tectonic settings of the region. The dynamic source parameters have calculated, assuming a simplified circular source model, by using displacement spectra. The obtained source parameters are included average seismic moment is 2.41E+15 N-m, rupture radius of 0.46 Km, stress drop is 10.9 MPa, relative displacement is 0.012 cm, and energy releases are 1.2E+18 Erg. According to “Scholz” (1990), the studied earthquake might be considered as an intraplate type-(II) earthquake that related to plate boundaries. In the present study, the thermal infrared data is used to derive Land Surface Temperature (LST) as a precursory analysis for this earthquake. The results indicated that there was a correlation between LST with precursor seismic activity before the time of the New Cairo earthquake occurrence.

First measurement of the total gravitational quadrupole moment of a black widow companion

ABSTRACT We present the first measurement of the gravitational quadrupole moment of the companion star of a spider pulsar, namely the black widow PSR J2051–0827. To this end, we have re-analysed radio timing data using a new model that is able to account for periastron precession caused by tidal and centrifugal deformations of the star as well as by general relativity. The model allows for a time-varying component of the quadrupole moment, thus self-consistently accounting for the ill-understood orbital period variations observed in these systems. Our analysis results in the first detection of orbital precession in a spider system at $\dot{\omega } = -68{_{.}^{\circ}}6_{-0{_{.}^{\circ}}5}^{+0{_{.}^{\circ}}9}$ yr−1 and the most accurate determination of orbital eccentricity for PSR J2051–0827 with e = (4.2 ± 0.1) × 10−5. We show that the variable quadrupole component is about 100 times smaller than the average quadrupole moment $\bar{Q} = -2.2_{-1}^{+0.6} \times 10^{41} \ {\rm kg\,m^2}$. We discuss how accurate modelling of high-precision optical light curves of the companion star will allow its apsidal motion constant to be derived from our results.

Multiplicity moments using Tsallis statistics in high-energy hadron–nucleus interactions

The study of higher-order moments of a distribution and its cumulants constitute a sensitive tool to investigate the correlations between the particle produced in high-energy interactions. In our previous work, we have used the Tsallis [Formula: see text] statistics, NBD, Gamma and shifted Gamma distributions to describe the multiplicity distributions in [Formula: see text]-nucleus and [Formula: see text]-nucleus fixed target interactions at various energies ranging from [Formula: see text][Formula: see text]GeV to 800[Formula: see text]GeV. In this study, we have extended our analysis by calculating the moments using the Tsallis model at these fixed target experiment data. By using the Tsallis model, we have also calculated the average charged multiplicity and its dependence on energy. It is found that the average charged multiplicity and moments predicted by the Tsallis statistics are in much agreement with the experimental values and indicates the success of the Tsallis model on data from visual detectors. The study of moments also illustrates that KNO scaling hypothesis holds good at these energies.

Chemical Inhibition of the Replication Stress Response Causes DNA Damage and Delayed Regeneration in S. mediterranea

S. mediterranea is a planarian with extensive regenerative ability which requires substantial cell division. However, DNA replication stress occurs every cell division and must be resolved. From yeast to man, an evolutionarily conserved DNA replication stress response (RSR) is essential for life. The RSR is a signal transduction pathway regulated by Ataxia telangiectasia and Rad3‐related kinase (ATR) and Checkpoint 1 kinase (CHK1) to respond to replication stress. However, the RSR has not been established in planarian nor do we know if it functions in regeneration. We hypothesize that ATR may be essential for regeneration. Preliminary results show reduced regenerative ability in the presence of hydroxyurea (HU), a replication stress inducing agent. However, low concentrations (2mM) did not attenuate regeneration, indicating that ATR and the RSR may be present and able to overcome replication stress. To test this, we treated amputated tails with HU, ATR inhibitor (ATRi), and a combination of both. In 2mM HU, tails regenerated similarly to control. We observed only a one day delay in regeneration with ATRi alone. However, ATRi and 2mM HU in combination prevented planarian regeneration completely. In addition, replication stress was confirmed through comet assays, which quantified levels of DNA damage within each planarian experimental group. The ATRi and 2mM HU combination group exhibited the highest average comet tail moment. These synergistic effect suggests that ATR is significant in the response to replication stress during regeneration. Additionally, inhibition of CHK1, another kinase in the RSR pathway, exhibited similar tail moment values with ATRi. Future experiments will allow us to support the presence of CHK1 and its important role in resolving replication stress. Further, determining the importance of RSR genes in planarian will elucidate the conserved components and allow us to understand how ATR and the RSR contributes to the incredible regenerative abilities in planarian.Support or Funding InformationUST Committee for Student ResearchAlvarado Sanchez LabJim Jenkin for S. mediterraneaDepartment of Education HSI‐STEM grantUST Biology Smith ChairUST Biology Department

INFLUENCE OF LOWER EXTREMITY STATIC ALIGNMENT ON DYNAMIC KNEE VALGUS IN ADOLESCENTS FOLLOWING ACL RECONSTRUCTION

Background:Dynamic limb valgus, particularly high knee abduction moments, are a known risk factor for anterior cruciate ligament (ACL) injury. High knee abduction moments may result from poor static anatomic limb alignment, faulty biomechanics, or a combination of both. The distinction is important because anatomic limb alignment is difficult to change, while dynamic factors can be addressed through neuromuscular or biomechanical training.Hypothesis/Purpose:This study assessed the influence of static (lower extremity anatomic alignment) and dynamic (kinematic and kinetic) factors on external knee abduction moments during side-step cutting in uninjured adolescent athletes.Methods:This retrospective study included 43 adolescents with recent unilateral ACL reconstruction (mean age 15.3 years, SD 2.0, range 10-21; 17/43 female; 3-12 months post-surgery, mean 6.5, SD 2.1). Frontal plane hip to ankle imaging (EOS) was used to measure mechanical axis deviation (perpendicular distance from the center of the femoral condyles to the mechanical axis line connecting the center of the femoral head to the center of the talar dome) and tibial-femoral angle. Femoral anteversion was measured during physical examination. 3D motion capture provided lower extremity kinematics and kinetics during quiet standing and during the loading phase (initial contact to peak knee flexion) of an anticipated 45° side-step cut, with 2-3 trials per limb averaged for analysis. Relationships among imaging, static motion capture, and dynamic motion capture measures were investigated using correlation, and backward stepwise linear regression was used to evaluate potential predictors of average dynamic knee abduction moment.Results:Dynamic knee abduction moment was best predicted by a combination of dynamic measures: knee and hip abduction, external knee rotation, lateral trunk lean towards the planting foot, and ankle inversion during cutting (Table 1.1). Although EOS frontal plane tibial-femoral angle was correlated with dynamic knee abduction moment (r=0.24, p=0.02), no static/anatomic variables entered the model once the dynamic measures were included.Conclusion:Knee abduction moments during side-step cutting were related to dynamic factors reflecting frontal plane trunk, hip, knee, and ankle motion, as well as external knee rotation. Static (anatomic) lower limb alignment did not influence knee abduction moments once these dynamic factors were considered. Knee abduction moments and ACL injury risk are therefore not dictated by anatomic alignment and can be altered through neuromuscular/biomechanical training.Table 1.1.Multivariable prediction of average knee abduction moment during cutting (R2=0.69) βPDynamic ankle eversion-0.35<0.001Dynamic knee external rotation0.69<0.001Dynamic hip abduction0.180.004Dynamic trunk contralateral lean0.170.007Dynamic knee abduction0.39<0.001

S. mediterranea Ataxia telangiectasia and Rad3‐related kinase (SmedATR) May be Required to Prevent DNA Replication Stress

DNA replication is an important mechanism involved in cellular processes like reproduction, repair, and regeneration. S. mediterranea, a planarian with an amazing regenerative ability, goes through continuous rounds of cell division. Consequently, DNA replication stress occurs with each cell division and must be resolved. From yeast to man, The DNA replication stress response (RSR) is evolutionarily conserved and necessary for life among organisms. The RSR is a signal transduction pathway regulated by Ataxia telangiectasia and Rad3‐related kinase (ATR) and Checkpoint 1 kinase (CHK1) to respond to replication stress, including DNA damage. However, the RSR has not yet been established in the planarian and its involvement in regeneration is currently unknown. We hypothesize that ATR may be essential in replication by preventing and resolving DNA damage. Regeneration experiments were conducted and results indicated that the regenerative ability of planaria were reduced in the presence of hydroxyurea (HU), a replication stress inducing agent. Low HU concentrations (2mM) had similar phenotypic results to the control which suggests that ATR and the RSR may be present in this low dosage to overcome the replication stress. However, when treated with a combination of 2mM HU and ATR inhibitor (ATRi), planarian regeneration was severely hindered. To confirm replication stress shown phenotypically in the regeneration experiments, comet assays were performed to quantify the levels of DNA damage in each experimental group. The ATRi and 2mM HU combination group exhibited the highest average comet tail moment, a parameter used to measure the amounts of fragmented DNA within each planarian cell. The synergistic effects of ATR in combination with HU suggest that ATR is significant in the response to replication stress during regeneration. Additionally, inhibition of CHK1, another kinase in the RSR pathway exhibited similar tail moment values as ATRi. Future experiments will allow us to support the presence of CHK1 and its important role in resolving replication stress. Determining the importance of RSR genes in planarian will elucidate the conserved components and allow us to understand how ATR and the RSR contributes to the incredible regenerative abilities in planarian.Support or Funding InformationUST Committee for Student Research Alvarado Sanchez Lab, Stowers Institute for Medical Research Jim Jenkin for S. mediterranea Department of Education HSI‐STEM grant UST Biology Smith Chair UST Biology Department

Effects of age, speed, and step length on lower extremity net joint moments and powers during walking.

During walking older adults' gait is slower, they take shorter steps, and rely less on ankle and more on knee and hip joint moments and powers compared to young adults. Previous studies have suggested that walking speed and step length are confounds that affect joint moments and powers. Our purpose was to examine the effects of walking speed and step length manipulation on net joint moments and powers in young and older adults. Sixteen young and 18 older adults completed walking trials at three speeds under three step length conditions as marker position and force platform data were captured synchronously. Net joint moments were quantified using inverse dynamics and were subsequently used to compute net joint powers. Average extensor moments at each joint during the stance phase were then computed. Older adults displayed greater knee extensor moment compared to young adults. Older adults showed trends (p<.10) of having lower ankle and higher hip moments, but these differences were not statistically significant. Average ankle, knee, and hip extensor moments increased with speed and step length. At the fast speed, older compared to young adults generated lower average ankle power (p=.003) and showed a trend (p=.056) of exerting less average moment at the ankle joint. Age-associated distal-to-proximal redistribution of net joint moments was diminished and not statistically significant when the confounding effects of walking speed and relative step length were controlled. These findings imply that age-related distal-to-proximal redistribution of joint moments may influence the different speeds and step lengths chosen by young and older adults.

An atomistic simulation study investigating the effect of varying network structure and polarity in a moisture contaminated epoxy network

Absorbed moisture is a frequent contributor to performance loss in polymer-based composite structures operating in nearly all environments. However, the fundamental mechanisms that govern water-polymer interaction remain poorly understood. In this molecular dynamics study, the polarity and internal structure of an epoxy-based composite matrix was varied through manipulation of crosslink density. A commonly used epoxy-hardener combination (DGEBA- DETA) was chosen and four different models were created with crosslinking density of 20%, 51%, 65% and 81% respectively. The results indicate that the increase in crosslinking leads to a greater availability of polar sites with a concomitant rise in available free volume. The rise in network polarity aids the hydrogen bonding interactions between the absorbed water and the composite matrix, but the greater availability of free volume also allows water molecules to cluster together through mutual hydrogen bonding activity. This results in a subsequent decrease in moisture interaction with polar sites at very high crosslink densities. It was also found that the diffusivity and average dipole moment of the absorbed moisture are correlated with the state of water molecules and that a greater percentage of network-bonded molecules tends to lower both of these quantities. These results are consistent with previously published experimental results which have contemplated the dual nature of water molecules in an epoxy network. The results also highlight the potential of leveraging this phenomenon for non-destructive inspection of the physical and chemical state of a polymer network.

Capturing the Effects of Explicit Waters in Implicit Electrostatics Modeling: Qualitative Justification of Gaussian-Based Dielectric Models in DelPhi.

Our group has implemented a smooth Gaussian-based dielectric function in DelPhi (J. Chem. Theory Comput. 2013, 9 (4), 2126-2136) which models the solute as an object with inhomogeneous dielectric permittivity and provides a smooth transition of dielectric permittivity from surface-bound water to bulk solvent. Although it is well-understood that the protein hydrophobic core is less polarizable than the hydrophilic protein surface, less attention is paid to the polarizability of water molecules inside the solute and on its surface. Here, we apply explicit water simulations to study the behavior of water molecules buried inside a protein and on the surface of that protein and contrast it with the behavior of the bulk water. We selected a protein that is experimentally shown to have five cavities, most of which are occupied by water molecules. We demonstrate through molecular dynamics (MD) simulations that the behavior of water in the cavity is drastically different from that in the bulk. These observations were made by comparing the mean residence times, dipole orientation relaxation times, and average dipole moment fluctuations. We also show that the bulk region has a nonuniform distribution of these tempo-spatial properties. From the perspective of continuum electrostatics, we argue that the dielectric "constant" in water-filled cavities of proteins and the space close to the molecular surface should differ from that assigned to the bulk water. This provides support for the Gaussian-based smooth dielectric model for solving electrostatics in the Poisson-Boltzmann equation framework. Furthermore, we demonstrate that using a well-parametrized Gaussian-based model with a single energy-minimized configuration of a protein can also reproduce its ensemble-averaged polar solvation energy. Thus, we argue that the Gaussian-based smooth dielectric model not only captures accurate physics but also provides an efficient way of computing ensemble-averaged quantities.

Performance of torsionally eccentric RC wall frame buildings designed to DDBD under bi-directional seismic excitation

The seismic performance of a class of reinforced concrete eccentric wall frame buildings under bi-directional ground motion excitation is investigated. For this purpose, four and eight-storey RC buildings comprising structural walls, flat-plates and gravity columns, having different strength and stiffness eccentricity and torsional restrain, are designed in accordance with the Direct Displacement Based Design (DDBD) method for damage control. The structures are analysed under static and dynamic inelastic response, considering ten ground motion record pairs, three intensity levels and different angles of incidence. Several global and local engineering demand parameters, namely, inter-storey drift, slab rotation, member plastic rotations and wall internal forces are evaluated and compared with the DDBD limits. It is shown that ground motion directionality effects are small, and the average drift and wall moment profiles are within DDBD predictions and, often, considerably lower than DDBD demanded. However, wall shear force and local inelastic demands are underpredicted by both DDBD and static inelastic analyses and, more significantly so, for the torsionally flexible structures.

Effect of Asymmetry on Biomechanical Characteristics During 180° Change of Direction.

Thomas, C, Dos'Santos, T, Comfort, P, and Jones, PA. Effect of asymmetry on biomechanical characteristics during 180° change of direction. J Strength Cond Res 34(5): 1297-1306, 2020-The aim of this study was to explore the effect of asymmetry on biomechanical characteristics during two 180° change of direction (CoD) tasks (505 and modified 505 [505mod]). Fifty-two male (n = 24; age = 22.1 ± 4.8 years; height = 1.78 ± 0.06 m; body mass = 76.9 ± 10.8 kg) and female (n = 28; age = 19.1 ± 1.7 years; height = 1.67 ± 0.06 m; body mass = 60.4 ± 7.4 kg) team-sport players were recruited for this investigation. Three-dimensional motion data using 10 Qualisys Oqus 7 infrared cameras (240 Hz) and ground reaction force (GRF) data from 2 AMTI force platforms (1,200 Hz) were collected to analyze penultimate contacts (PEN) and final foot contacts. A series of repeated-measures analysis of variance were used to examine for differences in each dependent variable. Significant differences existed between dominant (D) and nondominant (ND) limbs for knee abduction angle (KAA) during 505mod (p = 0.048), while significant differences existed for peak horizontal and vertical GRF (vGRF) (p < 0.001) during 505. For both tasks, the PEN involved significantly greater peak vGRF, hip flexion angles, hip extensor moments, knee flexion angles, and knee extensor moments, but lower average vGRF, horizontal GRF, and peak ankle extensor moments. For 505, the ND limb involved significantly greater peak vGRF, but the opposite was revealed for peak horizontal GRF. For 505mod, the D limb involved significantly greater KAAs. Finally, there was a significant interaction (group × limb) for peak horizontal GRF ratio during 505. For both tasks, there was no interaction or main effects for time to completion. Therefore, it appears asymmetry influences GRFs and KAAs, but not completion time during 180° CoD in team-sport players.

Corticomotor Excitability of Gluteus Maximus Is Associated with Hip Biomechanics During a Single-Leg Drop-Jump

The purpose of this study was to determine the association between corticomotor excitability (CME) of gluteus maximus (GM) and hip biomechanics during a single-leg drop-jump task. Thirty-two healthy individuals participated. The slope of the input-output curve (IOC) obtained from transcranial magnetic stimulation was used to assess CME of GM. The average hip extensor moment and peak hip flexion angle during the stance phase of the drop jump task was calculated. The slope of the IOC of GM was found to be a predictor of the average hip extensor moment (r2 = 0.18, p = 0.016) and peak hip flexion angle (r2 = 0.20, p = 0.01). Our results demonstrate that greater functional use of the hip was associated with enhanced descending neural drive of GM.

Preasymptotic Taylor dispersion: evolution from the initial condition

Although the process of hydrodynamic dispersion has been studied for many years, the description of solute spreading at early times has proved to be challenging. In particular, for some kinds of initial conditions, the solute evolution may exhibit a second moment that decreases (rather than increases, as is typically observed) in time. Most classical approaches would predict a negative effective hydrodynamic dispersion coefficient for such a situation. This creates some difficulties: not only does a negative dispersion coefficient lead to a violation of the second law of thermodynamics, but it also creates a mathematically ill-posed problem. We outline a set of four desirable qualities in a well-structured theory of unsteady dispersion as follows: (i) positivity of the dispersion coefficient, (ii) non-dependence upon initial conditions, (iii) superposability of solutions and (iv) convergence of solutions to classical asymptotic results. We use averaging to develop an upscaled result that adheres to these qualities. We find that the upscaled equation contains a source term that accounts for the relaxation of the initial configuration. This term decreases exponentially fast in time, leading to correct asymptotic behaviour while also accounting for the early-time solute dynamics. Analytical solutions are presented for both the effective dispersion coefficient and the source term, and we compare our upscaled results with averaged solutions obtained from numerical simulations; both averaged concentrations and spatial moments are compared. Error estimates are quantified, and we find good correspondence between the upscaled theory and the numerical results for all times.

Earthquake Stress Drops From Dynamic Rupture Simulations Constrained by Observed Ground Motions

AbstractStress drop characterizing dynamics of earthquake rupture propagation has various definitions and measures with a yet unclear mutual relationship. We aim to reconcile this discrepancy by analyzing synthetic dynamic rupture models generated by random sampling of the model space of spatially heterogeneous dynamic rupture parameters. An ensemble of ~1,600 dynamic models, with waveforms statistically fitting empirical Ground Motion Prediction Equations, is treated as a synthetic event database. The events exhibit various magnitudes, degrees of complexity, and realistic ω−2 spectral decay of their average moment rates. While the variability of the stress drop Δτe estimated from the moment rates agrees with real data studies ( , the true static stress drops Δτs evaluated directly from the dynamic models exhibit larger values and lower variability ( ). Our study suggests that the disagreement between various stress drop definitions is related to the source model approximation and not to any particular data processing.

Validitas dan Praktikalitas Modul Larutan Penyangga Berbasis Inkuiri Terbimbing Dilengkapi Soal-Soal Tipe HOTS

This research development aims were to create and determine validity and practicality categories of buffer solution module based on guided inquiry equipped with HOTS type problems. This research was a Research and Development with Plomp development model. Instrument used was module validity and practicality questionnaire. Module was validated by 5 validators. Practicality was determined by providing a questionnaire to 2 chemistry teachers and 51 students of class XII MIPA SMAN 8 Padang. The data obtained were analysed with the Kappa Cohen formula. The result of the research obtained average kappa moment value validity (0,90), average kappa moment value practicality of teacher response (0,93) and the practicality of student response (0,84). This result showed that the module which has been developed was very valid and practical to used in learning

Shell design from planar pre-stressed structures

The interplay between mechanics and geometry is used to construct a theoretical framework able to describe the class of three-dimensional objects that can be fabricated from suitable planar designs by using relaxation of pre-strains/stress in ultra-thin films. Small deformations and large rotations are used here to model the elastic relaxation into various three-dimensional shapes. Over the kinematics associated with the designed mid-surface, a small perturbation of Love–Kirchhoff type is considered in order to deduce the design plate-to-shell equations for orthotropic materials with an important pre-stress/strain heterogeneity. The resulting equations for the efforts average and efforts moments provide the supplementary equations to compute the in-plane pre-strain/stress. In particular, for materials with a weak material transversal heterogeneity the moments equations involve only the thickness, the curvature tensor, and the pre-strain/stress moments. Special attention is devoted to materials that can be obtained by layer-by-layer crystal growth (molecular beam epitaxy), which posses an in-plane isotropic pre-strain. We have found that a rectangular plate could relax both into a cylindrical surface or on a part of a sphere in which case it should have a small diameter with respect to the sphere radius. In both cases, the theoretical estimates have been compared with the experimental realizations and finite-element numerical computations and we found very good agreement among all of them. In addition, for the cone geometry we found that the design is not possible from an isotropic pre-stress with an in-plane homogeneity. However, the 3D finite-element computation of the relaxed surface with a (necessary) non-isotropic pre-stress obtained from the theoretical estimates matches remarkably well the designed conical surface.

Effects of load carriage on biomechanical variables associated with tibial stress fractures in running

BackgroundMilitary personnel are required to run while carrying heavy body-borne loads, which is suggested to increase their risk of tibial stress fracture. Research has retrospectively identified biomechanical variables associated with a history of tibial stress fracture in runners, however, the effect that load carriage has on these variables remains unknown. Research questionWhat are the effects of load carriage on running biomechanical variables associated with a history of tibial stress fracture? MethodsTwenty-one women ran at 3.0 m/s on an instrumented treadmill in four load carriage conditions: 0, 4.5, 11.3, and 22.7 kg. Motion capture and ground reaction force data were collected. Dependent variables included average loading rate, peak absolute free moment, peak hip adduction, peak rearfoot eversion, and stride frequency. Linear mixed models were used to asses the effect of load carriage and body mass on dependent variables. ResultsA load x body mass interaction was observed for stride frequency only (p = 0.017). Stride frequency increased with load carriage of 22.7-kg, but lighter participants illustrated a greater change than heavier participants. Average loading rate (p < 0.001) and peak free moment (p = 0.015) were greater in the 22.7-kg condition, while peak rearfoot eversion (p ≤ 0.023) was greater in the 11.3- and 22.7-kg conditions, compared to the unloaded condition. Load carriage did not affect peak hip adduction (p = 0.67). SignificanceParticipants adapted to heavy load carriage by increasing stride frequency. This was especially evident in lighter participants who increased stride frequency to a greater extent than heavier participants. Despite this adaptation, running with load carriage of ≥11.3-kg increased variables associated with a history of tibial stress fracture, which may be indicative of elevated stress fracture risk. However, the lack of concomitant change amongst variables as a function of load carriage may highlight the difficulty in assessing injury risk from a single measure of running biomechanics.

Kinematic analysis of motor learning in upper limb body-powered bypass prosthesis training.

Motor learning and compensatory movement are important aspects of prosthesis training yet relatively little quantitative evidence supports our current understanding of how motor control and compensation develop in the novel body-powered prosthesis user. The goal of this study is to assess these aspects of prosthesis training through functional, kinematic, and kinetic analyses using a within-subject paradigm compared across two training time points. The joints evaluated include the left and right shoulders, torso, and right elbow. Six abled-bodied subjects (age 27 ± 3) using a body-powered bypass prosthesis completed the Jebsen-Taylor Hand Function Test and the targeted Box and Blocks Test after five training sessions and again after ten sessions. Significant differences in movement parameters included reduced times to complete tasks, reduced normalized jerk for most joints and tasks, and more variable changes in efficiency and compensation parameters for individual tasks and joints measured as range of motion, maximum angle, and average moment. Normalized jerk, joint specific path length, range of motion, maximum angle, and average moment are presented for the first time in this unique training context and for this specific device type. These findings quantitatively describe numerous aspects of motor learning and control in able-bodied subjects that may be useful in guiding future rehabilitation and training of body-powered prosthesis users.

Commonly reported isokinetic parameters do not reveal long-term strength deficits of the Triceps surae complex following operative treatment of Achilles tendon rupture

Isokinetic strength assessments are common outcome measures following operatively treated Achilles tendon (AT) ruptures. However, there is a lack of clarity on whether commonly reported outcome measures (such as peak joint moment) are sufficient to describe the extent of long-term functional deficits following AT rupture and repair. The present study conducted a comprehensive isokinetic evaluation of the Triceps surae complex in 12 participants who previously underwent AT rupture and repair. Testing occurred 4.4 (±2.6) years following surgery, and consisted of maximal isokinetic strength assessments of the plantarflexors at two angular velocities (30 and 60°∙s−1) with the knee in flexed and straight positions. Differences between injured and non-injured limbs were tested through discrete and statistical parametric mapping analysis. Average joint moment showed significant main effects between injured and non-injured limbs, but common isokinetic parameters such as peak moment and angle of peak moment did not. The normalised moment curves showed a significant main effect of limb, angular velocity and knee joint position on joint moment throughout different portions of the range of motion. Temporal analysis revealed a significantly greater ability of the non-injured limb to sustain plantarflexor moments across a range of testing conditions. Participants who had undergone operative treatment of AT ruptures did not display inter-limb differences in discrete isokinetic strength outcomes that are often used in the literature. Instead, temporal analyses were required to highlight the reduced capacity of the injured limb to generate end-range joint moments and to sustain higher levels of joint moment for longer periods.