Abstract - Computational method to evaluate ankle postural stiffness with ground reaction forces

Zhiming Ji, PhD; Thomas Findley, MD, PhD; Hans Chaudhry, PhD; Bruce Bukiet, PhD

Departments of Mechanical Engineering, Biomedical Engineering, and Mathematical Sciences, New Jersey Institute
of Technology, Newark, NJ; War-Related Illness and Injury Study Center, Department of Veterans Affairs (VA)
Medical Center, East Orange, NJ

Abstract — We examined an existing method for evaluating postural sway based on force-plate technology. Through an improved mathematical model of postural dynamics, we propose a new method, which better evaluated postural sway and, in addition, computed ankle moment and ankle postural stiffness directly from the measured ground reaction forces. An example is detailed that demonstrates the utility of this approach. The proposed method does not involve filtering or numerical integration and considers the platform inclination. Results from normal subjects show a linear relation between the ankle moment and the sway angle during quiet standing.

Key words: ankle postural stiffness, postural stability, quiet standing.

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