Dystonic bradykinesia is thought to be related to a loss of the selectivity of the motor command, and in particular its diffusion to antagonist groups. If this hypothesis is correct, we expect to observe abnormal co-activation of antagonist groups at the distal level. Because of the postural component of dystonia, we also expect to see an undue diffusion of the motor command to proximal muscles. Finally, we will look for signs of mirror movements indicating perturbations of inter-hemispheric motor inhibition.