Force control during human bouncing gaits

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Title: Force control during human bouncing gaits
Author: Yen, Jasper Tong-Biau
Abstract: Every movement has a goal. For reaching, the goal is to move the hand to a specific location. For locomotion, however, goals for each step cycle are unclear and veiled by the automatic nature of lower limb control. What mechanical variables does the nervous system "care" about during locomotion? Abundant evidence from the biomechanics literature suggests that the force generated on the ground, or endpoint force, is an important task variable during hopping and running. Hopping and running are called bouncing gaits for the reason that the endpoint force trajectory is like that of bouncing on a pogo stick. In this work, I captured kinematics and kinetics of human bouncing gaits, and tested whether structure in the inherent step-to-step variability is consistent with control of endpoint force. I found that joint torques covary from step to step to stabilize only peak force. When two limbs are used to generate force on the ground at the same time, individual forces of the limbs are not stabilized, but the total peak force is stabilized. Moreover, passive dynamics may be exploited during forward progression. These results suggest that the number of kinetic goals is minimal, and this simple control scheme involves goals for discrete times during the gait cycle. Uncovering biomechanical goals of locomotion provides a functional context for understanding how complex joints, muscles, and neural circuits are coordinated.
Type: Dissertation
Date: 2011-04-01
Publisher: Georgia Institute of Technology
Subject: Spring-mass model
Uncontrolled manifold
Motor control
Locomotion Regulation
Human locomotion
Motor ability
Ground reaction force (Biomechanics)
Department: Biomedical Engineering
Advisor: Committee Chair: Chang, Young-Hui; Committee Member: Liu, Karen; Committee Member: Nichols, T. Richard; Committee Member: Prilutsky, Boris; Committee Member: Ting, Lena
Degree: PhD

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