The continuous nature of timing reprogramming in an interceptive task.

The time course of movement timing reprogramming was examined in a task requiring temporal coincidence of the conclusion of a forehand drive with the arrival of a moving luminous target at the end of an electronic trackway. The moving target departed from one end of the trackway at a constant velocity of 2 m (.) s(-1), and for a part of the trials its velocity was increased to 3 m (.) s(-1). Target velocity was modified at different moments during stimulus displacement, producing times-to-arrival after velocity increment (TAVIs) from 100 to 600 ms. The effect of specific practice on movement reprogramming was also examined. The results showed early adjustments to the action (TAVIs = 100 - 200 ms) that seemed to be stereotyped, while feedback-based corrections were implemented only at TAVIs of 300 ms or longer. Temporal accuracy was progressively increased as longer TAVIs were provided up to 600 ms. Skill training led to an overall increment of temporal accuracy, but no effect of specific practice was found. The results indicate that timing reprogramming in interceptive actions is a continuous process limited mainly by intrinsic factors: latency to initiate more effective adjustments to the action, and rate-of-movement timing reprogramming.