A new gait parameterization technique by means of cyclogram moments: Application to human slope walking

A new parameterization technique for the systematic characterization of human walking gait in diverse external conditions is proposed in this work. By parameterization we mean a quantitative expression of certain gait descriptors as the function of an external parameter, such as the ground slope. The mathematical quantities derived from the geometric features of the hip-knee cyclograms are the main gait descriptors considered in this study. We demonstrate that these descriptors, expressed in a general setting as the geometric moments of the cyclogram contours, can meaningfully reflect the evolution of the gait kinematics on different slopes. We provide a new interpretation of the cyclogram perimeter and discover two potential invariants of slope-walking gait. Experimental slope-walking data obtained at 1° interval within the range of −13 to +13° (±23.1%) on a variable-inclination treadmill was used in this study. The parameterization procedure presented here is general in nature and may be employed without restriction to any closed curve such as the phase diagram, the moment-angle diagram, and the velocity–velocity curves of human gait. The technique may be utilized for the quantitative characterization of normal gait, global comparison of two different gaits, clinical identification of pathological conditions and for the tracking of progress of patients under rehabilitation program.