title: Estimation of quasi-stiffness of the human hip in the stance phase of walking.
abstract: This work presents a framework for selection of subject-specific quasi-stiffness of hip orthoses and exoskeletons, and other devices that are intended to emulate the biological performance of this joint during walking. The hip joint exhibits linear moment-angular excursion behavior in both the extension and flexion stages of the resilient loading-unloading phase that consists of terminal stance and initial swing phases. Here, we establish statistical models that can closely estimate the slope of linear fits to the moment-angle graph of the hip in this phase, termed as the quasi-stiffness of the hip. Employing an inverse dynamics analysis, we identify a series of parameters that can capture the nearly linear hip quasi-stiffnesses in the resilient loading phase. We then employ regression analysis on experimental moment-angle data of 216 gait trials across 26 human adults walking over a wide range of gait speeds (0.75-2.63 m/s) to obtain a set of general-form statistical models that estimate the hip quasi-stiffnesses using body weight and height, gait speed, and hip excursion. We show that the general-form models can closely estimate the hip quasi-stiffness in the extension (R(2) = 92%) and flexion portions (R(2) = 89%) of the resilient loading phase of the gait. We further simplify the general-form models and present a set of stature-based models that can estimate the hip quasi-stiffness for the preferred gait speed using only body weight and height with an average error of 27% for the extension stage and 37% for the flexion stage.
authors.affiliation: School of Engineering and Applied Science, Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Kamran
authors.initials: K
authors.lastname: Shamaei
authors.affiliation: Joint Department of Biomedical Engineering, North Carolina State University and University of North Carolina at Chapel Hill, Raleigh, North Carolina, United States of America.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Sawicki
authors.affiliation: School of Engineering and Applied Science, Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Dollar
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology; D006615:Hip / Q000033:anatomy & histology / Q000502:physiology*; D006621:Hip Joint / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009989:Orthotic Devices; D016059:Range of Motion, Articular / Q000502:physiology; D012044:Regression Analysis; D016138:Walking / Q000502:physiology*