Impaired force coordination during object release in children with hemiplegic cerebral palsy.

Recent studies on hand motor control in children with cerebral palsy (CP) have focused on the coordination of fingertip forces during the grasping and lifting of objects. However, little is known about the ability to replace and release an object from grasp, a function that is just as important for fine dexterity. The present study examines the coordination of fingertip forces during the replacement and release of an object (either 200 g or 400 g) from grasp in 14 children (aged between 7 and 13 years) with hemiplegic CP and in 14 age-matched typically developing children. The results indicate that children with hemiplegic CP abruptly replaced the object but had a prolonged and uncoordinated release of the grasp. Unlike what was seen in the control children, the grip and load forces decreased sequentially in the children with CP. However, all the children could appropriately scale the rate of force decrease based on somatosensory weight-related information from the ongoing lift. The results provide further information about the impaired hand skills in children with hemiplegic CP.