2017 Volume 13 Issue 1 Pages 13-21
The hypothesis in this study was tested by conducting EMG experiments comparing the variability in muscle activity during repetitive reaching movements in hemiplegic patients and healthy subjects. The present study investigated the characteristics of reaching movements in hemiplegic patients using the variability in average electromyogram (EMG) value. We studied 21 right-handed stroke patients with left-sided hemiparesis and 14 right-handed healthy control subjects. Post-stroke patients (hemiplegic group) and normal subjects (control group) repeated a reaching movement 10 times. The variability in average EMG value of each muscle was defined as the average standard deviation of the average rectified values (nARV-SDave). During the reaching movements, the nARV-SDave values was significantly higher in the hemiparesis group than in the control group for the biceps and triceps brachii (P < 0.05). In the hemiparesis group, significant negative correlations between the variability in nARV-SDave values and the Fugl-Meyer assessment scores were observed in all muscle types (rs = −0.46 to −0.76; P < 0.05, P < 0.01). This study identified a direct relationship between the variability in muscle activity and the severity of motor function deficit in post-stroke patients. The selective impact on the biceps and triceps were related to the nature of the reaching task.