Kinematic and myoelectric analysis of skill acquisition: II. 150cm subject group.

This experiment was conducted as a direct variation of a previous report. All electromyographic (EMG) and kinematic procedures were identical to those reported earlier; however, a new sample of 23 subjects practiced the shoulder flexion taken at a different subject-to-target distance (150cm) in an effort to establish whether similarities or differences existed between this and the previously developed model of skill acquisition. The criterion measure was again significantly altered during the learning sequence, and the majority of learning occurred within the first few trials. Kinematic and myoelectric measurements followed patterns similar to those reported in the previous model. To develop and maintain accuracy at the task, the subjects in the 150cm group found it necessary to decrease the projectile angle (19%), decrease the movement time (20%), an increase in the velocity of the limb at ball release (50%). Myoelectric activity commensurate with these kinematic changes included the following: 1) a considerable overall increase in total electrical activity for all muscles; 2) increases in premovement muscular activity for all muscles; 3) alterations in muscle firing order; and 4) replacement of variables representing total electric output by temporal variables later in the practice sessions. As indicated by the performance score, the added subject-to-target distance increased the difficulty of the task. Empirical observation concludes that the pattern of skill improvement was essentially similar for both groups.