The purpose of this study was to describe the relationship between the delay in initiation and termination of muscle contraction and clinical measures of motor impairment and physical disability in the affected upper limb of patients with hemiparesis. Electromyographic (EMG) activity of 26 long-term survivors of stroke was recorded during isometric wrist flexion and extension. Upper limb motor impairment and disability were assessed with the Fugl-Meyer motor assessment (FMA) and arm motor ability test (AMAT), respectively. Delay in initiation and termination of muscle contraction was significantly prolonged in the paretic arm. However, the delay was not significantly affected by stroke type, stroke level, side of hemiparesis, or presence of aphasia. Delay in initiation and termination of muscle contraction correlated significantly with FMA and AMAT. Abnormally delayed initiation and termination of muscle contraction may contribute to hemiparetic upper limb motor impairment and physical disability in hemiparetic patients.
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