Surface Electromyography Decomposition And Muscle Fatigue Research Of Upper Extremity In Stroke Patients

Surface electromyography (sEMG) is the weak signal generated during themuscular activity and detected from skin by surface electrodes. Since the advantageof been non-invasive, sEMG decomposition is more and more widely used in thediagnosis of diseases such as tremor paralysis myasthenia gravis, myotonia andamyotrophia in neuromuscular system for clinical application. Decomposition ofsEMG is the reverse process of the formation. By this decomposition procedure,waveforms, recruitment and firing patterns of motor unit action potentials (MUAPs)can be acquired. Using the idea of template matching, this paper finished thedecomposition of single channel sEMG through clustering and separation byapplying Gap Statistic algorithm based on fuzzy K-means and generalizedcross-correlation which calculate the time delay.Patients usually suffer from hemiparalysis after stroke, and it’s particularlyimportant for the patients’ physical rehabilitation and the improvement of their lifequality to take timely and effective rehabilitation therapy. Feature extraction in timeand frequency domain can reflect the motor functional status of the muscle fromelectro-neurophysiology. This paper studies sEMG features of stroke patients’ upperextremities during activities. It’s found out that the mean power frequency (MPF) ofdeltoideus medius and extensor digitorum communis between patients in differentBrunnstrom recovery stage is significantly different. The MPF of patients in latterstages decreases slower than that in earlier stages and the tendency is much moresimilar to normal subjects, which illustrates that with the conduct of rehabilitationtherapy, muscular fatigue resistance ability of stroke patients has been significantlyimproved.It’s found that with the occurrence of muscular fatigue, MPF of sEMG tends to decrease. Research suggested that this phenomenon is related to the decline ofperipheral nerve conduction velocity and the decrease of MUAP firing frequency.And this paper do the sEMG decomposition of stroke patients during lateral armrising and metacarpophalangeal joint flexion and extension for the study of MUAPfiring frequency changes in the movement. Comparison of the MU involved and theMUAP firing patterns between the first and the last movements is conducted, andfinds out that as the motion conducted, MUAP firing frequency decreasescorresponding to the muscle fatigue proceeds.The activities of motor units are under the unified control of central nervoussystems. Research result of this paper validates that with the improvement ofrecovery stage, the movement control ability of the central nervous system isstrengthened, the motion process becomes more stable, and the muscular fatigueresistance ability been improved. It’s also confirmed that MUAP firing patterns ofpatients in different stages acquired by sEMG decomposition can be thequantitative assessment of central nervous system functional status during therehabilitation training.