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Tendon-driven continuum robot kinematic models are frequently computationally expensive, inaccurate due to unmodeled effects, or both. In particular, unmodeled effects produce uncertainties that arise during the robot’s operation that lead to variability in the resulting geometry. We propose a novel solution to these issues through the development of a Gaussian mixture kinematic model. We train a mixture density network to output a Gaussian mixture model representation of the robot geometry given the current tendon displacements. This model computes a probability distribution that is more representative of the true distribution of geometries at a given configuration than a model that outputs a single geometry, while also reducing the computation time. We demonstrate uses of this model through both a trajectory optimization method that explicitly reasons about the workspace uncertainty to minimize the probability of collision and an inverse kinematics method that maximizes the likelihood of occupying a desired geometry.

Purpose: Most shoulder pathologies are associated with altered scapular kinematics which is mentioned as scapular dyskinesis. Scapular mobility, especially in upward rotation, measurement is essential for diagnosis and treatment. Easy-to-use, clinically applicable 2-dimensional (2-D) measurements would show excellent intra-tester reliability. To quantify intra-tester reliability for measuring scapular upward rotation in individuals with scapular dyskinesias, the landmark palpation with a video annotation tool was used.

Methods: Ten participants with scapular dyskinesis were recruited. Scapular upward rotation was measured at rest, 30°, 60°, 90°, and 120° of humeral elevation in the coronal plane both raising and lowering phases. Two trials were conducted for each arm position randomly, and an assessor took the pictures throughout. The video annotation tool (2-D Kinovia program) was used for measuring scapular upward rotation angles between days. The intra-tester reliability of scapular upward rotation was calculated.

Results: This measurement technique demonstrated excellent intra-tester reliability (ICC${}_{3,1}$ = 0.98), range 0.96–0.99, and standard error of measurement was less than 1°.

Conclusions: The findings demonstrated that using this technique to measure scapular upward rotation was reliable in subjects with scapular dyskinesis.

This study compares the prosthetic gait asymmetry in transfemoral amputees with varied femoral lengths to able-bodied participants in terms of temporal-spatial parameters and joint kinematics. Sixteen young and active transfemoral amputees with short and long residual limbs were divided into two groups and subjected to three-dimensional quantitative motion analysis through high definition optoelectronic cameras and force platform. The prosthetic gait of amputees was compared with those of 15 participants with normal gait to analyze the asymmetry. There was a significant difference in temporal-spatial gait parameters between the amputee groups in terms of intact limb stride length and swing time ($p<0.005$). The gait of amputees with long femoral lengths was with comparatively higher mean step length (0.31 versus 0.35m), velocity (0.48 versus 0.44m/s), and cadence (73.58 versus 66.62 steps/min) compared to short residual limbs, however these results are nonsignificant ($p>0.05$). Amputees and able-bodied participants differed significantly for all measured parameters ($p<0.05$). The amputees with short residual limbs had more variation in sagittal plane hip flexion at initial contact than long amputees and able-bodied subjects. Amputees with longer residual limbs demonstrated peak swing prosthetic hip flexion closer to able-bodied individuals. The frontal pelvic obliquity and sagittal pelvic tilt revealed more variance among amputees with shorter residual limbs than longer ones. This study will aid in identifying the underlying mechanism of gait asymmetry in transfemoral amputees in relation to residual femoral length and hence will pave a path for improving the knee and foot prosthetic components.

The objective was to investigate the effects of running shoes with midsole hollow structure span and height on the biomechanics of the lower limbs during running. We collected 21 adults with running habits who wore two pairs of running shoes with different midsole hollow structures and ran at a speed of 3.3m/s on a force-measuring treadmill. The lower limb kinematics, ground reaction force (GRF) and lower limb muscle activation characteristics were simultaneously captured by a motion capture system, a 3D force treadmill, and a surface electromyography (sEMG) system. Paired t-tests were performed on data for the two shoe conditions that fit the normal distribution assumptions; otherwise, Wilcoxon signed-rank tests were used. The statistical parameter mapping (SPM) technology was used for the analysis of 1D parameters of kinematic, dynamic, and sEMG activation characteristics. The result showed that the time to the peak impact force at touchdown of Hollow shoe2 was significantly increased ($P<0.01$), the maximum loading rate ($P<0.01$) and average loading rate ($P<0.05$) were significantly reduced, braking time ($P<0.05$), push time ($P<0.05$), contact time ($P<0.01$) of Hollow shoe2 were significantly increased compared with Hollow shoe1. Hollow shoe2 push phase of the tibialis anterior muscle activation characteristics was significantly lower (SPM, $P<0.05$) than Hollow shoe1. Our conclusion is that running shoes offer the solution as they have the advantage of the complex structure of the hollow midsole.