Effects of perturbations on accuracy of arm movements.

This study was carried out to test the hypothesis that the magnitude of perturbation-induced disruption of active movement depends upon the size of the active movement, with small movements being more disrupted than large ones. Human subjects performed pronating or supinating arm movements of 3 degrees, 10 degrees, and 30 degrees in a discrete visual tracking task. When the movements were briefly stopped or reversed, the resultant errors in trajectory and static position (expressed relative to the movement size) were greater for small as compared to large movements. These findings demonstrate that peripheral kinesthetic disturbances modify movement trajectory and end point error, with small movements being more affected than large movements.