Stability analyses of human walking could be used to prevent falling by improving stability with assistive or restorative devices. Traditionally, walking stability measures have been defined by logical assumptions about what causes falls. However, the current trend in stability research is toward the use of non-traditional measures based on the idea that human walking is a nonlinear system.
This study compares emerging non-traditional stability measures, Lyapunov exponents and Floquet multipliers, and a traditional measure, mean standard deviation. The study was conducted in two phases including the analyses of: (1) healthy walking with constraints; and (2) brace and FES-based interventions for multiple sclerosis.
Results showed that (1) the Lyapunov exponents were the most sensitive measure across constraints and assistive devices; (2) traditional and non-traditional measures did not reveal the same stability effects of the imposed constraints and devices; and (3) there was significant intersubject variability for all constraints and measures.