Postural adjustments during internally triggered perturbations: anticipatory responses
during arm movements
Problems in initiating postural muscle activity prior to voluntary muscle activity are present
in children with unilateral spastic CP. Nashner et al. (1983) performed experiments in
which they asked children with unilateral spastic CP to push or pull on a handle while
standing. They found that there was a lack of preparatory postural activity prior to the arm
movement for the hemiparetic side, compared to the normal side in the children with cerebral
palsy. Onset of contraction in postural muscles in the trunk and leg of the intact side preceded
contraction onset in the prime movers of the arm. In contrast, in the hemiparetic side, muscle
contraction onset in the arm preceded that of the postural muscles of the leg (Nashner
et al. 1983).