Intracellular action potential generation and extinction strongly affect the sensitivity of M-wave characteristic frequencies to changes in the peripheral parameters with muscle fatigue.

Changes in muscle fibre propagation velocity (MFPV) and shape of intracellular action potentials (IAPs) accompany peripheral muscle fatigue. We have shown through mathematical simulations that the effects of IAP generation and extinction reduced the sensitivity of the mean (fmean) and median (fmed) frequency of M-wave power spectra to individual changes in MFPV. Due to the differences in weighting of the spectral components used for calculation of the characteristic frequencies, the highest spectral components of the M-wave affected the fmean more than the fmed. These components are related to the M-wave leading edge that reflects the IAP depolarization phase. They reduced the sensitivity of the spectral moment of order 1 to individual changes in MFPV and increased its sensitivity to IAP changes. Since the changes of the IAP depolarization phase during the final stages of peripheral muscle fatigue affected the fmean more, the range of the relative reductions of the fmean and fmed were approximately the same under combined changes in IAP and MFPV. The sensitivities of M-wave characteristic frequencies depended also on the electrode arrangement and position as well as on the length of active muscle fibres.

[1]  J Hanson,et al.  The effects of repetitive stimulation on the action potential and the twitch of rat muscle. , 1974, Acta physiologica Scandinavica.

[2]  Roberto Merletti,et al.  Motor unit recruitment strategies investigated by surface EMG variables. , 2002, Journal of applied physiology.

[3]  N. Dimitrova,et al.  Interpretation of EMG changes with fatigue: facts, pitfalls, and fallacies. , 2003, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[4]  L. Arendt-Nielsen,et al.  The relationship between mean power frequency of the EMG spectrum and muscle fibre conduction velocity. , 1985, Electroencephalography and clinical neurophysiology.

[5]  G Rau,et al.  The presence of unknown layer of skin and fat is an obstacle to a correct estimation of the motor unit size from surface detected potentials. , 2002, Electromyography and clinical neurophysiology.

[6]  O. A. Nikitin,et al.  Neither high-pass filtering nor mathematical differentiation of the EMG signals can considerably reduce cross-talk. , 2002, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[7]  R. Kadefors,et al.  An electromyographic index for localized muscle fatigue. , 1977, Journal of applied physiology: respiratory, environmental and exercise physiology.

[8]  H C LUETTGAU,et al.  The effect of metabolic inhibitors on the fatigue of the action potential in single muscle fibres , 1965, The Journal of physiology.

[9]  G V Dimitrov,et al.  Effect of parameters altering with muscle fibre functional state on power spectra of spatially filtered extracellular potentials. , 2001, Journal of medical engineering & technology.

[10]  K. Häkkinen,et al.  Effects of fatigue and recovery on electromyographic and isometric force- and relaxation-time characteristics of human skeletal muscle , 2004, European Journal of Applied Physiology and Occupational Physiology.

[11]  G V Dimitrov,et al.  Amplitude-related characteristics of motor unit and M-wave potentials during fatigue. A simulation study using literature data on intracellular potential changes found in vitro. , 2002, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[12]  D F Stegeman,et al.  Muscle fatigue in McArdle's disease. Muscle fibre conduction velocity and surface EMG frequency spectrum during ischaemic exercise. , 1990, Brain : a journal of neurology.

[13]  C. Juel,et al.  Muscle action potential propagation velocity changes during activity , 1988, Muscle & nerve.

[14]  C. D. De Luca,et al.  Myoelectric signal conduction velocity and spectral parameters: influence of force and time. , 1985, Journal of applied physiology.

[15]  A Forster,et al.  Changes in muscle fiber conduction velocity, mean power frequency, and mean EMG voltage during prolonged submaximal contractions , 1989, Muscle & nerve.

[16]  G V Dimitrov,et al.  Estimate of M-wave changes in human biceps brachii during continuous stimulation. , 2005, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[17]  L.H. Lindstrom,et al.  Interpretation of myoelectric power spectra: A model and its applications , 1977, Proceedings of the IEEE.

[18]  L. Hammarström,et al.  AUTORADIOGRAPHIC STUDIES ON THE DISTRIBUTION OF C14‐LABELLED ASCORBIC ACID AND DEHYDROASCORBIC ACID , 1966 .

[19]  E. Änggård,et al.  Biological Effects of an Unsaturated Trihydroxy Acid (PGF2α) from Normal Swine Lung Prostaglandin and Related Factors 13 , 1963 .

[20]  M. Naeije,et al.  Relation between EMG power spectrum shifts and muscle fibre action potential conduction velocity changes during local muscular fatigue in man , 1982, European Journal of Applied Physiology and Occupational Physiology.

[21]  J Hanson,et al.  Changes in the action potential and contraction of isolated frog muscle after repetitive stimulation. , 1971, Acta physiologica Scandinavica.

[22]  R. Merletti,et al.  Electrically evoked myoelectric signals. , 1992, Critical reviews in biomedical engineering.

[23]  H. Westerblad,et al.  Action potential fatigue in single skeletal muscle fibres of Xenopus. , 1987, Acta physiologica Scandinavica.

[24]  C. D. De Luca,et al.  Frequency Parameters of the Myoelectric Signal as a Measure of Muscle Conduction Velocity , 1981, IEEE Transactions on Biomedical Engineering.

[25]  Roberto Merletti,et al.  On-Line Monitoring of the Median Frequency of the Surface EMG Power Spectrum , 1985, IEEE Transactions on Biomedical Engineering.

[26]  T. W. Van Weerden,et al.  Relationship between average muscle fibre conduction velocity and EMG power spectra during isometric contraction, recovery and applied ischemia , 2004, European Journal of Applied Physiology and Occupational Physiology.

[27]  N A Dimitrova,et al.  Longitudinal variations of characteristic frequencies of skeletal muscle fibre potentials detected by a bipolar electrode or multi-electrode. , 2001, Journal of medical engineering & technology.

[28]  Knaflitz,et al.  Myoelectric manifestations of fatigue in voluntary and electrically elicited contractions. , 1990, Journal of applied physiology.

[29]  R. Fitts,et al.  Fatigue from high- and low-frequency muscle stimulation: Role of sarcolemma action potentials , 1986, Experimental Neurology.

[30]  G V Dimitrov,et al.  Bipolar recording of potentials generated by excitable fibres in a volume conductor. , 1977, Agressologie: revue internationale de physio-biologie et de pharmacologie appliquees aux effets de l'agression.

[31]  G V Dimitrov,et al.  Fundamentals of power spectra of extracellular potentials produced by a skeletal muscle fibre of finite length. Part II: Effect of parameters altering with functional state. , 1998, Medical engineering & physics.

[32]  R. Merletti,et al.  Surface EMG signal processing during isometric contractions. , 1997, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[33]  Lars Arendt-Nielsen,et al.  Muscle fibre conduction velocity, mean power frequency, mean EMG voltage and force during submaximal fatiguing contractions of human quadriceps , 2004, European Journal of Applied Physiology and Occupational Physiology.

[34]  G. Hagg,et al.  Interpretation of EMG spectral alterations and alteration indexes at sustained contraction. , 1992 .

[35]  T. Masuda,et al.  Relationships between muscle fibre conduction velocity and frequency parameters of surface EMG during sustained contraction , 1983, European Journal of Applied Physiology and Occupational Physiology.

[36]  Z C Lateva,et al.  Anatomical and electrophysiological determinants of the human thenar compound muscle action potential , 1996, Muscle & nerve.

[37]  E Stalberg,et al.  Propagation velocity in human muscle fibers in situ. , 1966, Acta physiologica Scandinavica. Supplementum.

[38]  Kurt Jørgensen,et al.  Myo-electric fatigue manifestations revisited: power spectrum, conduction velocity, and amplitude of human elbow flexor muscles during isolated and repetitive endurance contractions at 30% maximal voluntary contraction , 2005, European Journal of Applied Physiology and Occupational Physiology.

[39]  P. Gatev,et al.  Changes in the parameters of human single muscle fiber potentials with consecutive discharges , 1982, Experimental Neurology.

[40]  G V Dimitrov,et al.  Fundamentals of power spectra of extracellular potentials produced by a skeletal muscle fibre of finite length. Part I: Effect of fibre anatomy. , 1998, Medical engineering & physics.

[41]  N. Dimitrova,et al.  Precise and fast calculation of the motor unit potentials detected by a point and rectangular plate electrode. , 1998, Medical engineering & physics.

[42]  R. Merletti,et al.  Advances in processing of surface myoelectric signals: Part 1 , 1995, Medical and Biological Engineering and Computing.

[43]  L. Lindstrom,et al.  Muscular fatigue and action potential conduction velocity changes studied with frequency analysis of EMG signals. , 1970, Electromyography.

[44]  C L Vaughan,et al.  Spectral compression of the electromyographic signal due to decreasing muscle fiber conduction velocity. , 2000, IEEE transactions on rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society.

[45]  K. Jørgensen,et al.  Changes in conduction velocity, median frequency, and root mean square-amplitude of the electromyogram during 25% maximal voluntary contraction of the triceps brachii muscle, to limit of endurance , 2004, European Journal of Applied Physiology and Occupational Physiology.

[46]  T. Sadoyama,et al.  Frequency analysis of surface EMG to evaluation of muscle fatigue , 2004, European Journal of Applied Physiology and Occupational Physiology.

[47]  L. Gerilovsky,et al.  Changes in the muscle fibre extracellular action potentials in long-lasting (fatiguing) activity , 2004, European Journal of Applied Physiology and Occupational Physiology.

[48]  K. Jørgensen,et al.  Modification of myo-electric power spectrum in fatigue from 15% maximal voluntary contraction of human elbow flexor muscles, to limit of endurance: reflection of conduction velocity variation and/or centrally mediated mechanisms? , 2004, European Journal of Applied Physiology and Occupational Physiology.