Abstract
A new method is proposed, based on the pole phase angle (PPA) of a second-order autoregressive (AR) model, to track spectral alteration during localised muscle fatigue when analysing surface myo-electric (ME) signals. Both stationary and non-stationary, simulated and real ME signals are used to investigate different methods to track spectral changes. The real ME signals are obtained from three muscles (the right vastus lateralis, rectus femoris and vastus medialis) of six healthy male volunteers, and the simulated signals are generated by passing Gaussian white-noise sequences through digital filters with spectral properties that mimic the real ME signals. The PPA method is compared, not only with spectra-based methods, such as Fourier and AR, but also with zero crossings (ZCs) and the first AR coefficient that have been proposed in the literature as computer efficient methods. By comparing the deviation (dev), in percent, between the linear regression of the theoretical and estimated mean frequencies of the power spectra for simulated stationary (s) and non-stationary (ns) signals, in general, it is found that the PPA method (devs=4.29; devns=1.94) gives a superior performance to ZCs (dvs=8.25) and the first AR coefficient (4.18<devs<21.8; 0.98<devns<4.36) but performs slightly worse than spectra-based methods (0.33<devs<0.79; 0.41<devns<1.07). However, the PPA method has the advantage that it estimates spectral alteration without calculating the spectra and therefore allows very efficient computation.
Similar content being viewed by others
References
Akaike, H. (1974): ‘A new look at the statistical model identification’,IEEE Trans. Autom. Control, AC-19, pp. 716–723
Auger, F., Flandrin, P., Gonçalvés, P., andLemoine, O. (1996): ‘Time-frequency toolbox: for use with MATLAB (Centre National De La Recherche Scientifique, France)
Basmajian, J., andDe Luca, C. J. (1985): ‘Muscles alive: their functions revealed by electromyography, 5th edn’, (Williams & Wilkins, Baltimore, MD)
Bigland-Ritchie, B. (1981): ‘EMG/Force relations and fatigue of human voluntary contractions’,Exerc. Sport Sci. Rev.,9, pp. 75–88
Burg, J. P. (1972): ‘The relationship between maximum entropy spectra and maximum likelihood spectra’,Geophysics,37, pp. 375–376
De Luca, C. J. (1979): ‘Physiology and mathematics of myoelectric signals’,IEEE Trans., BME-26, pp. 313–325
De Luca, C. J. (1997): ‘The use of surface electromyography in biomechanics’,J. Appl. Biomech.,13, pp. 135–163
Gerdle, B., andFugl-Meyer, A. R. (1992): ‘Is the mean power frequency shift of the EMG a selective indicator of fatigue of the fast twitch motor units?’,Acta Physiol Scand.,145, pp. 129–138
Graupe, D., andCline, W. K. (1975): ‘Functional separation of EMG signals via ARMA identification methods for prosthesis control purposes’,IEEE Trans. Syst. Man Cybern., SMC-5, pp. 252–259
Hannan, E. J., andQuinn, B. G. (1979): ‘The determination of the order of an autoregression’,J. Royal. Statist. Soc.,41, pp. 190–195
Hagg, G. (1992): ‘Interpretation of EMG spectral alterations and alteration indexes at sustained contraction,J. Appl. Physiol.,73, pp. 1211–1217
Inbar, G. F., andNoujaim, A. E. (1984): ‘On surface EMG spectral characterization and its application to diagnostic classification’,IEEE Trans., BME-31, pp. 597–604
Karlsson, S., Erlandson, B. E., andGerdle, B. (1994): ‘A personal computer-based system for real-time analysis of surface EMG signals during static and dynamic contractions’,J. Electromyogr. Kinesiol.,4, pp. 170–180
Karmen, G., andCaldwell, G. E. (1996): ‘Physiology and interpretation of the electromyogram’,J. Clin. Neurophysiol.,13, pp. 366–384
Kiryu, T., De Luca, C. J., andSaitoh, Y. (1994): ‘AR modelling of myoeletric interference signals during a ramp contraction’,IEEE Trans., BME-41, pp. 1031–1038
Kuo, R., andLi, H. (1985): ‘Reduced-order autoregressive modelling for center-frequency estimation’,Ultrason. Imaging,7, pp. 244–251
Kupa, E. J., Roy, S. H., Kandarian, S. C., andDe Luca, C. J. (1995): ‘Effects of muscle fiber type and size on EMG median frequency and conduction velocity’,J. Appl. Physiol.,79, pp. 23–32
Lindström, L., andMagnusson, R. (1977): ‘Interpretation of myoelectric power spectra: A model and its applications’,Proc. IEEE,65, pp. 653–662
Ljung, L. (1987): ‘System identification: theory for the user’ (Prentice-Hall, Inc., New Jersey)
Lysne, D., andTjøstheim, D. (1987): ‘Loss of spectral peaks in autoregressive spectral estimation’,Biometrika,74, pp. 200–206
Martin, R. D. (1980): ‘Robust estimation of autoregressive models’,in Brillinger, D. R., andTiao, G. C. (Eds.): Directions in time series’ (Institute of Mathematical Statistics Publication, Haywood, CA), pp. 228–254
Merletti, R., Knaflitz, M., andDe Luca, C. J. (1992): ‘Electrically evoked myoelectric signals’,CRC Crit. Rev. Biomed. Eng.,19, pp. 293–340
Merletti, R., Gulisashvili, A., andLo Conte, L. R. (1995): ‘Estimation of shape characteristics of surface muscle signal spectra from time domain data’,IEEE Trans., BME-42, pp. 769–776
Merletti, R., andLo Conte, L. R. (1995): ‘Advances in processing of surface myoelectric signals: Part 1’,Med. Biol. Eng. Comput.,33, pp. 362–372
Paiss, O., andInbar, G. F. (1987): ‘Autoregressive modeling of surface EMG and its spectrum with application to fatigue’,IEEE Trans., BME-34, pp. 761–770
Percival, D. B., andWalden, A. T. (1993): ‘Spectral analysis for physical applications’ (Cambridge University Press)
Priestley, M. B. (1981): ‘Spectral analysis and time series’, (Academic Press, London)
Rissanen, J. (1983): ‘A universal prior for the integers and estimation by minimum description length’,Ann. Statist.,11, pp. 417–431
Saltzberg, B., Burton, W. D., Barlow, J. S., andBurch, R. (1985): ‘Moments of the power spectral density estimated from samples of the autocorrelation function (a robust procedure for monitoring changes in the statistical properties of lengthy nonstationary time series such as the EEG)’,Electroenceph. Clin. Neurophysiol.,61, pp. 89–93
Saltzberg, B. (1986): ‘An efficient formula for estimating the generalized moments of the power spectral density (PSD) without computing the Fourier transform’,IEEE Trans., BME-33, pp. 1134–1136
Shwedyk, E., Balasubramanian, R., andScott, R. (1977): ‘A nonstationary model for the electromyogram’,IEEE Trans., MEB-24, pp. 417–424
Wretling, M., Gerdle, B., andHenriksson-Larsen, K. (1987): ‘EMG: A non-invasive method for determination of fiber type proportion’,Acta Physiol. Scand.,131, pp. 627–628
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Karlsson, S., Yu, J. Estimation of surface electromyogram spectral alteration using reduced-order autoregressive model. Med. Biol. Eng. Comput. 38, 520–527 (2000). https://doi.org/10.1007/BF02345747
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02345747