Posturo-kinetic capacity in the disabled

''Normal movements'' in atypical populations address the question of postural control: Voluntary movement is a perturbation of body balance and cannot be executed without a convenient counterperturbation. Despite a change in the postural program in relation to the impairment (Parkinson's disease, paraplegia), the performance level is decreased. Movements are not ''normal,'' owing to a reduction in posturokinetic capacity.