Upper limb neurorehabilitation in patients with stroke using haptic device system: Reciprocal bi-articular muscle activities reflect as a result of improved circle-drawing smoothness

Purpose. Muscular co-contraction resulted in corrected elbow and shoulder joint stiffness; however, this correction neither ameliorated endpoint oscillation nor assisted in the execution of smooth two-joint arm movements. We hypothesised that the reacquisition of smooth arm movements became synonymous with the restoration of time-domain reciprocal electromyographic (EMG) activities in biarticular arm muscles. The purpose of this study was to investigate whether or not the restored reciprocal EMG activities in biarticular arm muscles reflected improved smooth motor performance in patients with stroke after 10 days of two-joint arm-movement training. Methods. Three male patients with sub-acute stroke with left-arm paralysis performed circle-drawing tasks using a haptic device system for upper limb neuromuscular rehabilitation. Results. After the training, the movement velocities and achievement periods increased with the enhancement of the reciprocal EMG activities in biarticular arm muscles, and there was less jerkness in movement after training for the same duration. Conclusions. Patients with stroke could achieve smooth motor performance with the restoration of the reciprocal EMG activities in biarticular arm muscles. Therefore, the reciprocal EMG activities in biarticular arm muscles in response to circle drawing would be an index for the progressive improvements of smooth motor functions in the upper limbs.