Ability to adjust reach extent in the hemiplegic arm

Insufficient information exists about the ability of hemiparetic patients to adjust reach extent during early recovery from stroke. Further knowledge may suggest guidance for therapy intervention. The objective of this study was to investigate the ability of hemiparetic subjects to adjust reach extent within 6 months after stroke.

Repeated-measures design experiment with two factors-group and target position.

Physiotherapy department.

Nine hemiparetic and nine age- and gender-matched healthy subjects.

Participants performed 15 reaching movements in the sagittal plane, five to each target of 8, 13 and 18 cm from the starting position.

Motion analysis was used to collect information on the kinematic variables of distance moved, movement duration, peak velocity, average velocity and the timing of peak velocity. These variables were compared between the different target positions and between groups.

The stroke group demonstrated a longer movement duration, lower peak and average velocity, and a later time to peak velocity compared with the healthy group. In response to the change in target position, both groups increased peak velocity for each increase in target position with no significant increase in movement duration, and showed a longer deceleration phase for the 18-cm target position. There was no significant difference between scaling of distance moved and peak velocity to target position between the groups. However, stroke subjects tended to overshoot the closer target and undershoot the more distant targets. The mean difference between groups was 12 mm [95% confidence interval (CI): -17 to 50] for the 8-cm position, 5mm (95% CI: -34 to 23) for the 13-cm position, and 9 mm (95% CI: -39 to 22) for the 18-cm position. The difference in peak velocity between each target position was smaller in the stroke subjects compared with the healthy subjects. The mean difference between groups was 103 mm/second (95% CI: -171 to -34) for the 8-cm position, 157 mm/second (95% CI: -231 to -82) for the 13-cm position, and 171 mm/second (95% CI: -262 to -80) for the 18-cm position.

Some aspects of the movement organisation of stroke subjects were similar to that of healthy subjects. However, stroke subjects showed errors in adjusting reach extent and velocity appropriately for different distances.