Arm reaching improvements with short-term practice depend on the severity of the motor deficit in stroke

The effects of short-term, constant practice on the kinematics of a multi-joint pointing movement were studied in the hemiparetic arm of 20 chronic patients with unilateral left cerebro-vascular accident (CVA) and in 10 age- and sex-matched healthy individuals. Practice consisted of a single session of 70 pointing movements made with the right arm. Movements were made from a target located beside the body to one in the contralateral workspace, in front of the body. Vision of the final hand position was allowed after every 5th trial. At the beginning of practice, stroke patients made slower, less precise and more segmented movements, characterised by smaller active ranges of elbow and shoulder motion, disrupted elbow-shoulder coordination, as well as greater trunk movement compared with healthy subjects. With practice, healthy subjects and some patients made faster and more precise movements. These tendencies were revealed only after many repetitions (up to 55 for those with severe hemiparesis), whereas changes in healthy individuals occurred after fewer trials (approximately 20). In addition, the patients decreased movement segmentation with practice. In healthy subjects, faster movement times may be attributed to better shoulder/elbow movement timing in the first half of the reach, whereas improvement of precision was not correlated with any changes in the movement variables. In patients, improvements were accomplished differently depending on arm motor severity. For some patients with mild-to-moderate clinical symptoms, practice resulted in better timing of shoulder/elbow movements with less trunk rotation in middle to late reach. Patients with more severe impairment also improved shoulder/elbow movement timing in mid-reach but used more compensatory trunk rotation. The results suggest that even one session of repetitive practice of a multi-joint pointing task leads to improvements in movement performance-based outcome measures, but the mechanisms of improvement may vary with the individual's level of motor impairment.