EMG frequency content changes with increasing force and during fatigue in the quadriceps femoris muscle of men and women.

The purpose of this study was to determine the effect of gender on changes in electromyographic (EMG) signal characteristics of the quadriceps muscles with increasing force and with fatigue. A total of fourteen healthy adults (seven men, seven women) participated in the study. Subjects had to perform isometric ramp contractions in knee extension with the force gradually increasing from 0 to 100% of the maximal voluntary contraction (MVC) in a 6-s period. Subjects then performed a fatigue task, consisting of a sustained maximum isometric knee extension contraction held until force decreased below 50% of the pre-fatigue MVC. Subjects also performed a single ramp contraction immediately after the fatigue task. The Root Mean Square (RMS) amplitude, mean power frequency (MPF) and median frequency (MF) of EMG signals obtained from the vastus lateralis, vastus medialis and rectus femoris were calculated at nine different force levels from the ramp contractions (10, 20, 30, 40, 50, 60, 70, 80 and 90% MVC), as well as every 5 s during the fatigue task. The main results were a more pronounced increase in EMG RMS amplitude for the three muscles and in MPF for the VL muscle with force in men compared with women. No significant effect of gender was found with regards to fatigue. These observations most likely reflect a moderately greater type II fiber content and/or area in the VL muscle of men compared to that of women.

[1]  C J De Luca,et al.  Recruitment threshold and muscle fiber conduction velocity of single motor units. , 1991, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[2]  J Lexell,et al.  Distribution of different fibre types in human skeletal muscles. 2. A study of cross-sections of whole m. vastus lateralis. , 1983, Acta physiologica Scandinavica.

[3]  V. Edgerton,et al.  Muscle fibre type populations of human leg muscles , 1975, The Histochemical Journal.

[4]  J. Lexell,et al.  Variability in muscle fibre areas in whole human quadriceps muscle: how to reduce sampling errors in biopsy techniques. , 1989, Clinical physiology.

[5]  C J De Luca,et al.  pH-induced effects on median frequency and conduction velocity of the myoelectric signal. , 1991, Journal of applied physiology.

[6]  T. Masuda,et al.  Fibre conduction velocity and fibre composition in human vastus lateralis , 2004, European Journal of Applied Physiology and Occupational Physiology.

[7]  M. Solomonow,et al.  Motor unit recruitment strategy of knee antagonist muscles in a step-wise, increasing isometric contraction , 2004, European Journal of Applied Physiology and Occupational Physiology.

[8]  B Gerdle,et al.  Dependence of the mean power frequency of the electromyogram on muscle force and fibre type. , 1991, Acta physiologica Scandinavica.

[9]  M. Johnson,et al.  Data on fibre size in thirty-six human muscles. An autopsy study. , 1973, Journal of the neurological sciences.

[10]  D. Sale,et al.  Gender differences in strength and muscle fiber characteristics , 1993, European Journal of Applied Physiology and Occupational Physiology.

[11]  Jessica Elert,et al.  The influences of muscle fibre proportions and areas upon EMG during maximal dynamic knee extensions , 2000, European Journal of Applied Physiology.

[12]  M Solomonow,et al.  Electromyogram power spectra frequencies associated with motor unit recruitment strategies. , 1990, Journal of applied physiology.

[13]  J. Lexell,et al.  Variability in muscle fibre areas in whole human quadriceps muscle. How much and why? , 1989, Acta physiologica Scandinavica.

[14]  A. Mannion,et al.  The Influence of Muscle Fiber Size and Type Distribution on Electromyographic Measures of Back Muscle Fatigability , 1998, Spine.

[15]  C. Bouchard,et al.  Skeletal muscle histochemical and biochemical characteristics in sedentary male and female subjects. , 1985, Canadian journal of physiology and pharmacology.

[16]  M. Johnson,et al.  Data on the distribution of fibre types in thirty-six human muscles. An autopsy study. , 1973, Journal of the neurological sciences.

[17]  M. Harmon,et al.  Endurance capacity of untrained males and females in isometric and dynamic muscular contractions , 2004, European Journal of Applied Physiology and Occupational Physiology.

[18]  M W Weiner,et al.  Mechanisms of human muscle fatigue. Quantitating the contribution of metabolic factors and activation impairment. , 1995, Advances in experimental medicine and biology.

[19]  C. Håkansson.  Conduction velocity and amplitude of the action potential as related to circumference in the isolated fibre of frog muscle. , 1956, Acta physiologica Scandinavica.

[20]  D. Gravel,et al.  Changes in the electromyographic spectrum power distribution caused by a progressive increase in the force level , 2004, European Journal of Applied Physiology and Occupational Physiology.

[21]  D. Downham,et al.  Distribution of different fibre types in human skeletal muscles Fibre type arrangement in m. vastus lateralis from three groups of healthy men between 15 and 83 years , 1983, Journal of the Neurological Sciences.

[22]  C. Bouchard,et al.  Human variation in skeletal muscle fiber-type proportion and enzyme activities. , 1989, The American journal of physiology.

[23]  Simon C. Gandevia,et al.  Fatigue : neural and muscular mechanisms , 1995 .

[24]  B Gerdle,et al.  Do the fibre-type proportion and the angular velocity influence the mean power frequency of the electromyogram? , 1988, Acta physiologica Scandinavica.

[25]  D. Pincivero,et al.  Influence of contraction intensity, muscle, and gender on median frequency of the quadriceps femoris. , 2001, Journal of applied physiology.

[26]  B Gerdle,et al.  Is the mean power frequency shift of the EMG a selective indicator of fatigue of the fast twitch motor units? , 1992, Acta physiologica Scandinavica.

[27]  A G Crenshaw,et al.  The relationships between EMG and muscle morphology throughout sustained static knee extension at two submaximal force levels. , 1997, Acta physiologica Scandinavica.

[28]  G. Street.  Biomechanics IX-B , 1985 .

[29]  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.

[30]  B Gerdle,et al.  EMG: a non-invasive method for determination of fibre type proportion. , 1987, Acta physiologica Scandinavica.

[31]  S Karlsson,et al.  The mean frequency of the EMG of the knee extensors is torque dependent both in the unfatigued and the fatigued states. , 1994, Clinical physiology.

[32]  D. Gravel,et al.  EMG power spectra of elbow extensors during ramp and step isometric contractions , 2004, European Journal of Applied Physiology and Occupational Physiology.

[33]  C. D. De Luca,et al.  Effects of muscle fiber type and size on EMG median frequency and conduction velocity. , 1995, Journal of applied physiology.