A statistical approach to time frequency analysis of SEMG

The aim of this study was to examine the influence of various external factors on the time-frequency (TF) content of surface electromyography (SEMG). The paper reports on a study of various factors like the level of muscle contraction, gender of the subject and inter electrode distance. A group of ten healthy subjects (five males and five females) performed isometric elbow flexions of the right arm at 20, 50 and 80% of their maximal voluntary contraction (MVC). The SEMG signal was recorded using surface electrodes placed at a distance of 18 and 36 mm over the biceps brachii muscle. WVD was used to extract the time frequency (TF) information of the signal and instantaneous frequency (IF) of the signal was extracted. Statistical analysis was performed on the IF values to determine the influence of each of the factors on the signal. The analysis indicates that there is a variation in the SEMG recordings for subjects based on gender, change of inter electrode distance and the level of muscle contraction. The IF at 50% was the highest compared with 20% and 80% MVC, while 20% was the lowest.