Comparison of Spectral and Entropic Measures for Surface EMG Time Series: A Pilot Study
This material was based on work partially supported by the College of Graduate Studies at Cleveland State University, Cleveland, Ohio , and by a Cottrell College Science Award from the Research Corporation (grant CC6768), Tucson, Arizona.
The electromyographic (EMG) spectral measures of back muscle fatigue do not consistently demonstrate endurance levels for patients with or without low back pain (LBP). This study compared the differences between nonlinear analysis of surface EMG time series and the power spectrum analysis in subjects with and without LBP. The variance of the EMG signal was calculated during a 1-second interval, and the Shannon (information) entropy of the time series was used to quantify the degree of "noisiness" of the signal. The spectral quantities poorly correlated with a clinical diagnosis of LBP; however, surface EMG time series from subjects without LBP demonstrated larger values of entropy than those from subjects with LBP.