Muscle fatigue in myophosphorylase deficiency: power spectral analysis of the electromyogram

It has been postulated that the power spectral shift in the surface EMG during fatigue is due to accumulation of muscle lactate. This hypothesis has been directly tested by measuring such shift in 3 patients with myophosphorylase deficiency who performed sustained isometric contractions of the quadr...

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Published inElectroencephalography and clinical neurophysiology Vol. 57; no. 4; pp. 330 - 335
Main Authors Mills, K.R, Edwards, R.H.T
Format Journal Article
LanguageEnglish
Published Shannon Elsevier Ireland Ltd 01.04.1984
Amsterdam Elsevier
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ISSN0013-4694
1872-6380
DOI10.1016/0013-4694(84)90155-X

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Summary:It has been postulated that the power spectral shift in the surface EMG during fatigue is due to accumulation of muscle lactate. This hypothesis has been directly tested by measuring such shift in 3 patients with myophosphorylase deficiency who performed sustained isometric contractions of the quadriceps muscle. It was found that the spectral shift in these patients was greater than that in normal subjects, rendering lactate as a cause of this phenomenon very unlikely. The mechanism of excessive fatiguability in myophosphorylase deficiency is thought to be due to failure of excitation of the muscle membrane; further support for this postulate is provided and it is contended that accumulation of extracellular potassium ions may explain the phenomena of spectral shift in normals and myophosphorylase deficient patients and the excessive fatiguability in the latter. L'hypothèse que la modification de la puissance spectrale de l'EMG de surface pendant la fatigue était due à l'accumulation d'acide lactique a été avancée. Cette hypothèse a été directement éprouvée en mesurant de telles modifications chez 3 patients déficients en myophosphorylase, qui effectuaient des contractions isométriques soutenues du quadriceps. On a trouvé que la modification du spectre chez ces patients était plus grande que chez les sujets normaux, ce qui rend imporbable l'hypothèse du lactate en tant que cause de ce phénomène. Le mécanisme de la fatigabilité excessive dans les cas de déficits en myophosphorylase est, pense-t-on un défault d'excitation de la membrane musculaire. Des arguments supplémentaires sont fournis, et qui suggèrent que cést l'accumulation d'ions potassium extracellulaires qui pourrait expliquer la modification du spectre chez les sujets normaux et chez les sujets déficitaires en myophosphorylase, ainsi que l'excessive fatigabilité.
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ISSN:0013-4694
1872-6380
DOI:10.1016/0013-4694(84)90155-X