Analysis of surface Electromyography signals using ZAM based quadratic time frequency distribution

In this work an attempt has been made to analyze the surface Electromyography signals recorded during dynamic contractions using quadratic time frequency distribution. Surface EMG signals are recorded from biceps brachii muscle in 50 healthy volunteers. These signals are subjected to Zhao-Atlas-Marks based Quadratic Time-Frequency Distribution (QTFD). Instantaneous median frequency (IMDF) and instantaneous mean frequency (IMNF) are estimated from the time frequency domain. In addition, IMDF are interpolated with time by using linear regression technique. The result shows that IMDF and IMNF are distinct in fatigue and non fatigue conditions and these parameters reduce significantly in fatigue case. Further, it is observed that IMDF decreases with time.