Effect of Bilateral Contraction of Proximal Arm Muscle on Electromyographic Activity in Hemiplegic Patients

ABSTRACT

OBJECTIVE: Reaction time is known to be longer for bilateral activities than for unilateral ones. However, bilateral isometric training is a common technique for motor recovery in relatively early stage of recovery following stroke. Moreover, few studies elucidated the response time of proximal arm muscle. This study was designed to investigate the effects of bilateral shoulder abduction on electromyographic (EMG) timing in hemiplegic subjects. METHOD: EMG signal of 18 subjects with hemiplegia was recorded during isometric contraction of shoulder abductor along the audible beep. Each subject performed three sets of contraction unilateral contraction of each side and simultaneous bilateral contraction. EMG parameters included initiation delay, termination delay, and root mean square (RMS). RESULTS: When subjects performed bilateral contraction simultaneously, initiation and termination delays and RMS of paretic arm significantly increased in the affected arm than nonaffected side. Compared with unilateral contraction, initiation and termination delays did not differ significantly although RMS was significantly reduced. In addition, side-to-side difference of termination delay significantly decreased. CONCLUSION: These results demonstrated that bilateral isometric training of proximal arm muscle could be performed for motor recovery after stroke with no compromise of movement timing. Furthermore, movement control would be expected to be enhanced.