Object release under varying task constraints in children with hemiplegic cerebral palsy.

Considerable attention has been given in recent years to fingertip force coordination during grasping and lifting small objects in children with cerebral palsy (CP). However, little is known about the children's ability to replace and release an object from grasp. The present study examined the coordination of fingertip forces during replacement and release of an object from grasp under varying task constraints in the involved hand of 15 children (10 males, five females, age range 7 to 14 years) with hemiplegic CP and in the non-dominant hand of 15 age-matched, typically-developing children (seven males, eight females). Participants released an object, instrumented with force transducers and held with a precision grip, onto a stable surface and onto an unstable surface (requiring higher accuracy) at self-paced and fast-as-possible speeds. Temporal and force measures were recorded and the dependent measures were tested using analyses of variance. Results showed that force coordination was impaired in children with hemiplegia, resulting in prolonged and uncoordinated replacement and release of the object (p<0.05). Differences between controls and children with hemiplegia were greater when speed and accuracy constraints were imposed (i.e. task performance was affected by these constraints to a greater extent in the children with CP, p<0.05). Impairments in temporal coordination of object release were also observed in the non-involved hand under all conditions (p<0.05). These results provide additional information about impaired hand function in children with hemiplegic CP. Clinical implications of these findings are discussed.