Dataset Information

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.

SUBMITTER: Shamaei K

PROVIDER: S-EPMC3857237 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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

Shamaei Kamran K Sawicki Gregory S GS Dollar Aaron M AM

PloS one 20131209 12

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 ...[more]

PMID: 24349136

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Project description:We sought to evaluate the effects of the application of torque pulses to the hip and knee joint via a robotic exoskeleton in the context of training propulsion during walking. Based on our previous study, we formulated a set of conditions of torque pulses applied to the hip and knee joint associated with changes in push-off posture, a component of propulsion. In this work, we quantified the effects of hip/knee torque pulses on metrics of propulsion, specifically hip extension (HE) and normalized propulsive impulse (NPI), in two experiments. In the first experiment, we exposed 16 participants to sixteen conditions of torque pulses during single strides to observe the immediate effects of pulse application. In the second experiment, we exposed 16 participants to a subset of those conditions for 200 strides to quantify short-term adaptation effects. During pulse application, NPI aligned with the expected modulation of push-off posture, while HE was modulated in the opposite direction. The timing of the applied pulses, early or late stance, was crucial, as the effects were often in the opposite direction when changing timing condition. Extension torque applied at late stance increased HE in both experiments - range of change in HE: (2.9 ± 0.4 deg, 7.7 ± 1.0 deg), . The same conditions resulted in a negative change in NPI only in the single pulse experiment - change in NPI for knee torque: -3.0 ± 0.4 ms, - and no significant change for hip torque. Also, knee extension and flexion torque during early and late stance, respectively, increased NPI during single pulse application - range of change in NPI: (3.8, 4.6) ± 0.8 ms, . During repeated pulse application, NPI increased for late stance flexion torque - range of change in NPI: (4.5 ± 0.7 ms, 4.8 ± 0.8 ms), , but not late stance extension torque. After exposure, we observed positive after-effects in HE in three conditions - range of change in HE: (2.0 ± 0.3 deg, 3.7 ± 0.7 deg) - and significant positive after-effects in NPI for early stance flexion torques - change in NPI: (2.7 ± 0.6 ms, ). These results indicate that positive propulsive after-effects can be achieved through repeated exposure to torque pulses.

Dataset Information

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

Publications

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

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