People with physical impairments often have asymmetric gait. To evaluate if their overall symmetry is improving during intervention, there needs to be a simple metric that can help classify gait patterns that includes multiple measures of gait asymmetry. The Combined Gait Asymmetry Metric presented here is based on the Mahalanobis distance of multiple step parameters. We tested able-bodied subjects with perturbations that involve a change in leg length, the addition of ankle weights, and a combination of both perturbations. The Mahalanobis distances are calculated from perfect symmetry to all points in the data to analyze the effects of the different perturbations. The metric demonstrates how an overall view of symmetry can give a better perspective of asymmetry than only looking at a few individual parameters. This metric is straightforward and can be extended to include large numbers of spatiotemporal, kinematic, and kinetic parameters that more completely evaluate a change in gait symmetry.
A kinetic shape (KS) is a smooth two- or three-dimensional shape that is defined by its predicted ground reaction forces as it is pressed onto a flat surface. A KS can be applied in any mechanical situation where position-dependent force redirection is required. Although previous work on KSs can predict static force reaction behavior, it does not describe the kinematic behavior of these shapes. In this article, we derive the equations of motion for a rolling two-dimensional KS (or any other smooth curve) and validate the model with physical experiments. The results of the physical experiments showed good agreement with the predicted dynamic KS model. In addition, we have modified these equations of motion to develop and verify the theory of a novel transportation device, the kinetic board, that is powered by an individual shifting their weight on top of a set of KSs.
A Kinetic Shape has a physical and continuous curve with a changing radius that is exactly defined by its kinetic behavior. A Kinetic Shape curve is defined by specifying the force applied to the Kinetic Shape and the force with which the Kinetic Shape subsequently reacts at ground contact. This concept allows for predictable, position-dependent, and purely mechanical force redirection which make it broadly applicable. Kinetic Shapes have been previously used in several applications to predict the redirection of forces applied to the shape into ground reaction forces. Here, we analyze various ways 2D Kinetic Shapes interact and show how different mechanical force-based computational operations can be performed using these interconnected Kinetic Shapes, which we call Kinetic Shape Systems.
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