Quantification of force abnormalities during passive and active-assisted upper-limb reaching movements in post-stroke hemiparesis

We evaluated a method for measuring abnormal upper-limb motor performance i n post-stroke hemiparetic subjects, A servomechanism (MIME) moved the forea rm in simple planar trajectories, directly controlling hand position and fo re:arm orientation, Design specifications are presented, along with system performance data during an initial test of 13 stroke subjects with a wide r ange of impairment levels, Performance of subjects was quantified by measur ing the forces and torques between the paretic limb and the servomechanism as the subjects relaxed (passive); or attempted to generate force in the di rection of movement (active). During passive movements, the more severely i mpaired subjects resisted movement, producing higher levels of negative wor k than less-impaired subjects and neurologically normal-controls, During ac tive movements, the more severely impaired subjects produced forces with la rger directional errors, and were less efficient in producing work, These m etrics had significant test-retest repeatability. These motor performance m etrics can potentially detect smaller within-subject changes than motor fun ction scales, This method could complement currently used measurement tools for the evaluation of subjects during recovery-from stroke, or during ther apeutic interventions.