Abstract
Dexterous hitting movement, which requires continuous and variable input-output transformation, was examined from the viewpoints of preprogrammed control and a dynamical system with external temporal input as a continuous control model. The movements of forehand and backhand tennis strokes were observed kinematically under two conditions: when the same input pattern was repeated, and when two different input patterns were switched stochastically. Analysis of the time when movement was initiated and the relative timing revealed that different outputs corresponded to the same input under the switching input condition. This result does not seem to support a preprogrammed control model. On the other hand, the analysis based on a dynamical system confirmed two different excited attractors corresponding to two inputs under the periodic condition, and the transition between these two attractors under the switching input condition. This suggests that dexterity can be understood as a dynamical system with external temporal input.
