Surface EMG Examination Of Abnormal Coactivation Of Upper Limb Flexors In Hemiparetic Stroke

Objective Abnormal coactivation of upper extremity flexors is often abserved on the paretic side of stroke patients while they attempt to move. The mechanisms underlying this coactivation are not well understood. Th e primary objective of this study is to investigate coactivation patterns of upper extremity flexors by comparing their surface electromyographic signals(s EMG) between stroke patients and healthy controls when they performing elbow flexion and wrist fl exion at a m aximum isometric voluntary contraction level, and to exam ine whether abnormal coactivation is re lated to motor dysfunction after stroke.Methods Eighteen stroke patients and eighteen ag e-matched healthy control subjects participated in the study. For each subject, s EMG signals were recorded simultaneously from biceps brachii and flexor carpi radialis muscles when the subject was asked to perform elbow flexion and wrist flexion task s respectively. The coactivation level for each of biceps brachii and flexor carpi radialis muscles was derived by processing their s EMG signals. Such r esultant coactivation levels were a lso compared among the unimpaired side and the im paired side of stroke subjects and the dom inant side of control subjects. Moreover, a co rrelation analysis was perform ed between the coactivation levels and clinical assessment of motor function.Results 1. Coactivation levels of wrist flexors and of elbow flexors duri ng the elbow flexion and the wrist f lexion tasks respectively were significantly higher in the paretic upper extremity than those in the unaffected side.2. For the wrist flexion tasks, coactivation levels of elbow flexor s were significantly higher in the unaffected side than those in the control group. 3. Levels of coactivation of elbow flexors dur ing the wrist flexion task were negatively correlated with both F ugl-Meyer scores and coordination scores, and were positively correlated with degrees of spasticity.Conclusion: 1. Abnormal coactivation of upper extrem ity flexors appeared in the both sides of hemiplegic patients. 2. The motor impairment of paretic upper ex tremity is associated with the abnorm al coactivation. 3. The changes of spinal pathways m ay participate in the abnor mal coactivation of elbow and wrist flexors.