Dynamic Stability
Stability is a critical component of both static standing balance and dynamic walking. It is characterized by the dynamic state of a system wherein the state is the multidimensional posture and movement trajectories at an instant in time. This state is stable if small disturbances are attracted toward a prescribed reference point. Otherwise, a small state disturbance may grow without bound and the observed posture will sway precipitously. Hence, a kinematic trajectory is considered Lyapunov stable if all trajectories that start sufficiently close to the reference remain close for all time. The reference trajectory may describe a static posture or it may describe a dynamic movement.
Estimates of static stability identify individuals at greatest risk of falling, but there are few studies to determine whether stability of dynamic movement can identify fall-prone individuals.Our study revealed that the fall-prone group demonstrated poorer dynamic stability than the healthy elderly and young adult groups, which supports the need for future investigations using larger population samples to study fall-prone individuals using
nonlinear dynamic analyses of movement kinematics.