Alterations in spike amplitude distribution of the surface electromyogram post-stroke

We examined surface electromyogram (EMG) characteristics during voluntary isometric activation of the first dorsal interosseous (FDI) muscle in stroke survivors. Five stroke subjects participated in the study. They were instructed to generate isometric contraction at different force levels. The recording was performed in both paretic and contralateral muscles using a matched force protocol. Comparisons of the spike amplitude distribution of the surface EMG signals were made between paretic and contralateral muscles. For a given contraction level, a widened or narrowed spike amplitude distribution was observed in paretic muscles of stroke subjects. Such differences may be induced by degeneration of some spinal motoneurons and/or disorganization of motor unit control properties after stroke.