Influence of accuracy constraints on bimanual coordination during a goal-directed task in children with hemiplegic cerebral palsy.

Previously we found that children with hemiplegic cerebral palsy (CP) have impaired bimanual coordination compared to typically developing children during a functional drawer-opening task. However, performance of the task under time constraints (fast-as-possible) facilitated better bimanual coordination for these children. Accuracy is another important task constraint that could influence the coordination of the two hands during such tasks. The effect of accuracy constraints on bimanual coordination in children with hemiplegic CP is not well understood. In the present study, children were asked to reach forward and open a drawer with one hand and then activate a light switch inside the drawer with the contralateral hand. Task accuracy constraints (different handles and switch sizes) were manipulated in order to determine their effect on upper extremity coordination. Eleven children with hemiplegic CP (age 8-16 years) and eleven age-matched typically developing children participated in this study. The results show that higher accuracy constraints prolong the total movement completion time for both groups of children. However, children with hemiplegic CP demonstrated less sequential movement with a higher accuracy constraint (a smaller knob handle) than a lower accuracy constraint (a larger loop handle). Nevertheless, presentation of both higher accuracy constraints (handle and switch) at the same time was detrimental to their performance. These influences of task constraints were similar regardless of which hand was used to open the drawer. The results suggest that performance may not be linearly related to the constraints, and in some cases "more is not better".