Author/Editor		Korošec, Dean
Title		Parametric time-varying spectrum and its application to SEMG signals
Type		članek
Source		In: Kokol P, Zupan B, Stare J, et al, editors. Medical informatics Europe '99. Amsterdam: IOS press,
Publication year		1999
Volume		str. 385-90
Language		eng
Abstract		Frequency spectrum of surface electromyographic signals (SEMGs) exhibits a non-stationary nature even in case of constant level isometric muscle contractions. This changes are related to muscle fatigue processes and can be evaluated by methods for estimation of timevarying (TV) spectrum. We describe a two estimation techniques: sliding window approach and decompostion of linear model coeficients trajectories. Drawback of the first is its large variance which causes unrealistic abrupt changes in the curve of Qverall dynamics, calculated either as the second derivative of the MF or as the ARMA distance between subsequent linear models forming the TV parametric spectrum. We demonstrate, that the second method is more appropriate for description of a slowly changing spec- trum of surface EMG signals. Dynamics measures obtained from this estimation are proposed as an indication of the fatigue process character.
Descriptors		ELECTROCARDIOGRAPHY ISOMETRIC CONTRACTION MUSCLE FATIGUE LINEAR MODELS