Comparison of complexity of EMG signals between a normal subject and a patient after stroke--a case study.

An innovative method to quantitatively assess the motor function of upper extremities for post-stroke patients is proposed. A post-stroke patient and a normal subject were recruited to conduct a special performance of voluntary elbow flexion and extension by following a sinusoidal trajectory from 30° to 90° at 6 different peak angular velocities in a horizontal plane. During the test, the elbow angle and subject's electromyographic (EMG) signal (biceps brachii and triceps brachii) were recorded simultaneously. Fuzzy approximate entropy (fApEn) was applied to analyze the EMG signals. The results showed observable differences in fApEn when the control and the patient (unaffected and affected arms) were compared, and an uptrend of fApEn was detected with the increase in the tracking velocities in both the normal individual and patient (unaffected and affected arm). The fApEn values, which are a measure of complexity of EMG, could be used for the quantitative evaluation of the deficiencies of motor control induced by stroke.