Independent control of initial kinematics and terminal oscillations of rapid positioning movements.

Human subjects performed rapid elbow flexions to visual targets. Subjects were instructed to modulate characteristics of the endpoint oscillations while attempting to hold constant the amplitude and duration of the movement itself. Independent control of the initial kinematics and the frequency of terminal oscillations was observed. The view that positioning movements may be subserved by either a two-stage or time-series control system is supported.