Principles for learning single-joint movements.

The previous paper in this series showed that changes both within and between experimental sessions can be understood in the framework of the dual-strategy hypothesis of motor control, with a modification sometimes required for the timing of the antagonist muscle. The present paper extends these findings by determining how practicing movements at one distance generalizes to changes in performance at other distances. Five subjects made elbow flexion movements over five different distances (pretest). They then performed 1400 movements (seven sessions of ten blocks of 20 trials) at only one of those distances. The subjects then repeated the flexion movements over the five different distances (posttest). On the posttest, subjects decreased their average movement time by 20 ms. In addition, their movements became less variable. The electromyographic pattern of the faster movements was characterized by a more rapidly rising electromyogram, for three of the subjects, and an antagonist latency that decreased. [ABSTRACT FROM AUTHOR]