Robot-assisted rehabilitation has only recently begun to be applied to improvement of hand function after stroke. In a preliminary study, involving 4 post-stroke subjects, more than 2 years following the stroke, we have been able to show that 8 weeks of robot-assisted training leads to changes in patterns of arm and finger muscle activation. The patterns were quantified in terms of synchronous muscle synergies which allowed for comparison with muscle activation patterns of healthy age-matched subjects. We found that the muscle synergies of the post-stroke subjects became more similar to those of the healthy subject group following training.