Assessment and training of synergies with an arm rehabilitation robot

Patients with moderate to severe hemiparesis following stroke often show abnormal muscle coactivation and a loss of interjoint coordination in the hemiparetic limb. These abnormal stereotypic movement patterns are known in clinical rehabilitation as abnormal secondary torques or synergies. In the beginning of a rehabilitation process the patients often train inside those synergistic patterns, what helps to restore some functionality, but makes it more difficult to break out of them later. Preliminary tests in our lab showed, that there is no precise test to characterize short term alteration in abnormal coupling between different joints. Therefore, a new assessment tool has been developed and implemented on the arm rehabilitation robot ARMin. A special synergy training program has been assembled and evaluated with one patient. The new assessment method showed to be appropriate for a qualitative measurement of abnormal couplings. After training, the patient's dominant synergy pattern were reduced.