ABSTRACT
Muscles within and surrounding the ankle-foot complex contain active and passive elements that are important during walking. However, the net effect of these active and passive muscular elements could create a system that can be mimicked by a prosthesis using purely passive elastic elements under appropriate conditions. Davis and DeLuca
and Mesplay
have examined the
quasi
-
stiffness
of the ankle during walking by creating and analyzing ankle moment vs. ankle dorsiflexion curves. Davis and DeLuca
did not report on the effects of speed on
quasi-stiffness
properties and Mesplay
examined the effects of changing cadence on the ankle moment-angle curve with one subject. The term
quasi-stiffness
used here, as suggested by Latash and Zatsiorsky,
refers to the slope of the ankle moment vs. ankle dorsiflexion curve and is used because measurements are not performed at equilibrium and because the exact
nature of the moments are not known. Palmer
studied sagittal plane ankle moment vs. ankle dorsiflexion curves during various stages of the gait cycle and concluded that an augmented system would be needed to replicate the behavior of the ablebodied ankle at most walking speeds. The work described in this chapter aims at examining the behavior of the able-bodied ankle joint during walking at various speeds. Understanding the quasi-stiffness of the able-bodied ankle during walking could help in the development of biomimetic ankle-foot prostheses, i.e., artificial limbs that mimic the biological human ankle and foot complex. Knowledge of quasistiffness behavior at different speeds could assist in creating prostheses that can adapt as prosthesis users change their walking speed.
