Coordination between reaching and grasping in patients with hemiparesis and healthy subjects.

OBJECTIVE

To investigate the coordination of reach-to-grasp components in hemiparetic and healthy subjects.

DESIGN

Split-plot repeated-measures design with 3 factors (group, object size, movement speed).

SETTING

Movement laboratory.

PARTICIPANTS

Twelve hemiparetic and 12 age-matched healthy subjects.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We used motion analysis to collect information on the kinematic variables of movement duration, peak velocity, peak deceleration, and maximum aperture, and the time of peak velocity, peak deceleration, and maximum aperture expressed as a percentage of movement duration during 32 reaching movements by each subject. We examined the coordination between the 2 components in 2 ways. First, we investigated the correlation between time of hand opening and start of hand transport, and between time of maximum aperture and time of peak deceleration. Second, we compared movements at preferred and fast speeds (manipulation of transport component) and to 2 different-sized cups (manipulation of grasp component).

RESULTS

Both groups demonstrated a temporal coupling between grasp and transport components at the start of the reach and at the time of maximum aperture. Both groups increased the aperture of grasp for larger cups and increased the maximum grip aperture, and had a shorter deceleration phase for faster movements. The deceleration phase of the hemiparetic patients was longer than that of the healthy subjects, however, and the components were not as tightly coupled.

CONCLUSIONS

The hemiparetic patients, who had a moderate amount of functional recovery, were similar to healthy subjects in their ability to control reach-to-grasp components. Their performance was not as skilled, however.