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Techniques to quantify postural stability usually rely on the evaluation of only two variables, that is, two coordinates of COP. However, by using three variables, that is, three components of acceleration vector, it is possible to describe human movement more precisely. For this purpose, a single three-axis accelerometer was used, making it possible to evaluate 3D movement by use of a novel method, convex polyhedron (CP), together with a traditional method, based on area of the confidence ellipse (ACE). Ten patients (Pts) with cerebellar ataxia and eleven healthy individuals of control group (CG) participated in the study. The results show a significant increase of volume of the CP (CPV) in Pts or CG standing on foam surface with eyes open (EO) and eyes closed (EC) after the EC phase. Significant difference between Pts and CG was found in all cases as well. Correlation coefficient indicates strong correlation between the CPV and ACE in most cases of patient examinations, thus confirming the possibility of quantification of postural instability by the introduced method of CPV.

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AbstractQuantification of upper extremity movement is a common objective in both research and clinical practice. Currently, methods based on angle-angle diagrams, also called cyclograms, seem to be promising. Nevertheless, compared to the study of lower limbs, the concept of angle-angle diagrams has not been systematically used to study upper limb movements during walking. The paper describes two examples of new methods based on angle-angle diagrams for application in rehabilitation and assistive robotics. The cyclograms represent information about the relationship between the angles and their changes over time. We used cyclograms as patterns for learning artificial neural networks and predicting the movement of upper-limb. Together with artificial intelligence, cyclograms offer wide scope of application in prosthesis control systems. Using bilateral cyclogram, the information about the relationship between the right and left arm joint angles is used to evaluate the symmetry of movements. The method based on the orientation of the bilateral cyclogram can be used as an additional method for determining the symmetry of movements of the upper limbs or exo-prosthesis.