Antiphasic electromyographic activities between biarticular arm muscles reflects improved two joint arm movement performaces in stroke patients

Antiphasic electromyographic (EMG) activities between biarticular arm muscles are indispensable for smooth performance. In the case of two-joint arm movement in a planar horizontal plane, elbow and shoulder joint movements were achieved by the biceps brachii (BB) and the triceps brachii muscles (TB). To our knowledge, however, no conclusions have been reached concerning the antiphasic EMG activities between biarticular arm muscles during two-joint arm movements in stroke patients and the effects of training in paretic upper limbs. The objective of this study was to investigate whether or not the antiphasic EMG activities with the BB and the TB muscles were restored in stroke patients by repetitive two-joint arm movements. Three stroke patients performed point-to-point movement (PTP) and circle-drawing (Circle) tasks 20 minutes daily for 10 days. The movement velocity and achievement periods increased after training for the same duration. After the training, antiphasic EMG activities between the BB and the TB appeared. The increased movement velocities played a major contribution in increasing the antiphasic EMG activities and improving positional precision. These results suggested that stroke patients could achieve motor performance to move their wrists fast and precisely by practicing a two-joint arm movement, especially, circle drawing.