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 P P