Properties of internal speed control and psychophysiological response during continuous forearm rotation movement.

This study investigated the properties of speed control and psychophysiological response when subjects changed movement speed internally. The task consisted of a continuous forearm rotational movement, which 14 women performed under 3 conditions, namely, (1) Preferred: the subject performed the task at a freely selected speed, (2) Slow: the subject changed the speed in two steps from preferred to a slower pace (slow, then very slow), (3) Fast: the subject changed the speed in two steps from preferred to a faster pace (fast, then very fast). Rotation speed and the coefficient of variation were measured to evaluate within-subject variability. Under the Preferred condition, there were no significant differences in rotation speed or coefficient of variation during the trials. However, under Slow and Fast conditions, the standard variation scores and coefficient of variation indicated different tendencies. Under the Fast condition, although the standard variation increased with the faster speed, the coefficient of variation decreased. On the other hand, the coefficient of variation increased under the Slow condition. Preferred speed had a significant positive relationship to the slow, very slow, fast, and very fast speeds. Heart rate (R-R interval) and EEG spectral intensity measurements showed no significant changes among the three conditions: however, respiration frequency significantly increased during Fast as compared to Preferred and Slow conditions. These results suggest that a preferred speed for continuous movement exists and that it is closely related to internal speed control as a psychological criterion. Furthermore, different movement speeds may reflect different psychophysiological responses.