Multi-joint movements with reversal in Parkinson's disease: Kinematics and electromyography

Subjects with Parkinson's disease (PD) presented difficulties in the performance of multi-joint movements. The purpose of the study was to determine whether the slowness of such movements was caused by the generation of non-linear trajectories and/or by a reduction or a deficit in the modulation of EMG activity. Nine healthy subjects and 10 subjects with PD performed multi-joint movements involving elbow and shoulder with reversal towards three targets in the sagittal plane without any constraint. The movement kinematics were calculated using X and Y coordinates of the markers positioned on the joints. EMG signals were recorded for the muscles related to these movements. The results revealed that subjects with PD presented a lower linear speed and the differences between them and healthy subjects increased with target distance. The trajectory was found to be linear and both groups of subjects had few errors in the targets despite the slower muscle activity in subjects with PD. Another interesting finding was the EMG pattern of subjects with PD. They showed a difficulty in modulating the activity of agonists and antagonists during the different movement phases. The low speed movements of PD subjects were attributable to the low EMG activity and difficulty in modulating the bursts of muscle activity.