ABSTRACT
Impairment of upper limb function is a common problem following hemiplegic stroke. The aim of this study is to assess the extent of aberrant co-contraction of agonist/antagonist muscles during voluntary movement of the paretic upper extremity and its relation to motor abilities assessed by motor scales. Twenty post-stroke hemiparetic patients were evaluated. Modified Ashworth Scale was used as a measure of spasticity. Upper limb motor impairment was assessed with the Fugl-Meyer motor assessment scale [FMS]. Integrated electromyographic activities [IEMG] of wrist extensors and flexors were simultaneously recorded during isometric wrist extension [WE] and were simultaneously recorded during isometric wrist flexion [WF]. The degree of co-contraction and the strength of contraction were assessed. Co-contraction was calculated as ratio of antagonist to agonist IEMG. Strength of contraction was calculated as ratio of affected to non-affected IEMG. The affected and the non-affected side were compared. Significant differences were found between the affected and the unaffected sides regarding the measured parameters. The degree of co-contraction was significantly greater in the affected limb during WE [p<0.001] and WE [p<0.001] and was found to correlate significantly with FMS during WE [r=-0.847. p<0.001] and WF [r=-0.736, p<0.001]. The degree of co-contraction measured during WE and WF correlated with the degree of spasticity [r=0.841, p<00.01 and r=0.480, p<0.001 respectively]. It was also found to correlate with strength of contraction of wrist extensors [r=-0.654, p=0.002] and flexors [r=-0.737, p<0.001]. Co-contraction is a manifest phenomenon in pa relic upper extremity. Its degree correlates significantly with motor impairment. Antagonist co-contraction can contribute, in part, to weak agonist activity further contributing to impaired functional abilities of post-stroke hemiparetic patients