Estimation of quasi-stiffness of the human hip in the stance phase of walking

• Published in: PloS one Vol. 8; no. 12; p. e81841
• Main Authors: Shamaei, Kamran, Sawicki, Gregory S, Dollar, Aaron M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09.12.2013; Public Library of Science (PLoS)
• Subjects: Adult; Adults; Analysis; Biomechanical Phenomena; Biomechanics; Body weight; Dynamic tests; Engineering schools; Exoskeleton; Exoskeletons; Female; Gait; Gait - physiology; Hip; Hip - anatomy & histology; Hip - physiology; Hip joint; Hip Joint - anatomy & histology; Hip Joint - physiology; Humans; Inverse dynamics; Kinematics; Laboratories; Male; Materials science; Mathematical models; Mechanical engineering; Models, Statistical; Orthoses; Orthotic Devices; Parameter identification; Physiology; Prostheses; R&D; Range of Motion, Articular - physiology; Regression Analysis; Rehabilitation; Research & development; Researchers; Statistical analysis; Statistical models; Stiffness; Studies; Unloading; Walking; Walking - physiology; United States > US; Connecticut
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0081841

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.