Improvement of arm movement patterns and endpoint control depends on type of feedback during practice in stroke survivors.

BACKGROUND: A major challenge in stroke rehabilitation is restoration of arm motor function. Therapy-induced improvements in arm function may occur via restoration of premorbid movement patterns (recovery) or development of compensatory movement strategies. However, it is unclear whether the learning benefits of practice might be enhanced by incorporating different forms of feedback, focusing on movement outcomes or on specific arm movement patterns. OBJECTIVE: To determine if manipulation of attentional focus by providing either knowledge of results (KR) feedback, focusing on movement outcomes, or knowledge of performance (KP) feedback, focusing on arm movement patterns during repetitive practice of a pointing movement, may lead to arm motor recovery. METHODS: Twenty-eight chronic stroke survivors were randomly assigned to 2 groups that practiced 10 sessions of 75 pointing movements. During practice, groups received either 20% KR about movement precision or faded (26.6% average) KP about arm joint movements. A nondisabled control group (n = 5) practiced the same task with KR. RESULTS: Motor patterns recovered only in KP, as evidenced by immediate and long-term increases in joint range, better interjoint coordination in early movement phases, and generalization of gains. Improvements in clinical impairment and function were related to decreases in compensation (trunk rotation) and recovery of interjoint coordination in mid-movement phases. CONCLUSIONS: In stroke survivors, when the learners' attention was directed to the movements themselves (KP), motor improvements reflect recovery compared to when attention was directed toward movement outcomes (KR).

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.

Interjoint coordination dynamics during reaching in stroke.

A technique is described that characterizes the dynamics of the interjoint coordination of arm reaching movements in healthy subjects (n=10) and in patients who had sustained a left-sided cerebrovascular accident (n=18). All participants were right-handed. Data from the affected right arm of patients with stroke were compared with those from the right arm of healthy subjects. Seated subjects made 25 pointing movements in a single session. Movements were made from an initial target located ipsilaterally to the right arm beside the body, to a final target located in front of the subject in the contralateral arm workspace. Kinematic data from the finger, wrist, elbow, both shoulders and sternum were recorded in three dimensions at 200 Hz with an optical tracking system. Analysis of interjoint coordination was based on the patterns of temporal delay between rotations at two adjacent joints (shoulder and elbow). The data were reduced to a single graph (Temporal Coordination or TC index) integrating the essential temporal characteristics of joint movement (the angular displacements, velocities and timing). TC segments, duration and amplitude, were analysed. The analysis was sensitive to the differences in interjoint coordination between healthy subjects and patients with arm motor deficits. In patients, the temporal coordination between elbow and shoulder movements was disrupted from the middle to the end of the reach. More specifically, in mid-reach, all patients had difficulty coordinating elbow flexion with shoulder horizontal adduction. In addition, patients with severe arm hemiparesis had difficulty changing elbow movement direction from flexion to extension and in coordinating this change with shoulder movement. At the end of the reach, patients with severe hemiparesis had deficits in the execution of elbow extension while all patients had impaired coordination of elbow extension and shoulder horizontal adduction. In addition, active ranges of joint motions were significantly decreased in the stroke compared to the healthy subjects. Finally, TC analysis revealed significant relationships between specific aspects of disrupted interjoint coordination and the level of motor impairment, suggesting that it may be a useful tool in the identification of specific movement coordination deficits in neurological impaired populations that can be targeted in treatment for arm motor recovery.

Compensatory strategies for reaching in stroke.

A major prerequisite for successful rehabilitation therapy after stroke is the understanding of the mechanisms underlying motor deficits common to these patients. Studies have shown that in stroke patients multijoint pointing movements are characterized by decreased movement speed and increased movement variability, by increased movement segmentation and by spatial and temporal incoordination between adjacent arm joints with respect to healthy subjects. We studied how the damaged nervous system recovers or compensates for deficits in reaching, and correlated reaching deficits with the level of functional impairment. Nine right-hemiparetic subjects and nine healthy subjects participated. All subjects were right-hand dominant. Data from the affected arm of hemiparetic subjects were compared with those from the arm in healthy subjects. Seated subjects made 40 pointing movements with the right arm in a single session. Movements were made from an initial target, for which the arm was positioned alongside the trunk. Then the subject lifted the arm and pointed to the final target, located in front of the subject in the contralateral workspace. Kinematic data from the arm and trunk were recorded with a three-dimensional analysis system. Arm movements in stroke subjects were longer, more segmented, more variable and had larger movement errors. Elbow-shoulder coordination was disrupted and the range of active joint motion was decreased significantly compared with healthy subjects. Some aspects of motor performance (duration, segmentation, accuracy and coordination) were significantly correlated with the level of motor impairment. Despite the fact that stroke subjects encountered all these deficits, even subjects with the most severe motor impairment were able to transport the end-point to the target. All but one subject involved the trunk to accomplish this motor task. In others words, they recruited new degrees of freedom typically not used by healthy subjects. The use of compensatory strategies may be related to the degree of motor impairment: severely to moderately impaired subjects recruited new degrees of freedom to compensate for motor deficits while mildly impaired subjects tended to employ healthy movement patterns. We discuss the possibility that there is a critical level of recovery at which patients switch from a strategy employing new degrees of freedom to one in which motor recovery is produced by improving the management of degrees of freedom characteristic of healthy performance. Our data also suggest that stroke subjects may be able to exploit effectively the redundancy of the motor system.