Increased muscular fatigue in patients with neurogenic muscle weakness: quantification and pathophysiology.

The strength of maximum voluntary contraction (MVC) and muscular fatigue measured from ankle dorsiflexors and knee extensors of 15 patients with neurogenic muscle weakness was compared with those of 20 healthy subjects. Muscle weakness, defined as the failure to generate the expected force, was determined by two methods: (1) manual muscle testing and (2) measurement of MVC using a force transducer. Muscle strength was then quantified as the MVC in Newtons (N)/kg body weight. The percent decrease in both MVC (the Fatigue Index [FI]), and rectified-integrated electromyogram (RIEMG) at the end of 60sec of sustained MVC were computed. There were three main findings. (1) Muscle strength was significantly (p less than 0.001) reduced in both muscles of the patient group: in ankle dorsiflexors, means = 1.62 +/- 0.7N/kg vs 4.8 +/- 0.5N/kg; in knee extensors, means = 3.2 +/- 1.8N/kg vs 7.8 +/- 1.5N/kg. (2) Fatigue was significantly greater (p less than 0.01) in the patient group: for ankle dorsiflexors, means = 50 +/- 15% vs 34 +/- 13%; and for knee extensors, means = 62 +/- 17% vs 46 +/- 15%. There was a negative correlation between muscle strength and FI of only the knee extensors of the patients (r = -0.88, p less than 0.001). (3) The mean decline in RIEMG of the two muscles combined was also significantly greater (p less than 0.001) in the patient group (means = 48 +/- 16% vs 2 +/- 11%).(ABSTRACT TRUNCATED AT 250 WORDS)

[1]  R. Edwards,et al.  Human muscle function and fatigue. , 2008, Ciba Foundation symposium.

[2]  H. Milner-Brown,et al.  Muscle membrane excitation and impulse propagation velocity are reduced during muscle fatigue , 1986, Muscle & nerve.

[3]  B. Sakmann,et al.  Membrane properties underlying spontaneous activity of denervated muscle fibres , 1974, The Journal of physiology.

[4]  P. Tesch.  Muscle fatigue in man. With special reference to lactate accumulation during short term intense exercise. , 1980, Acta physiologica Scandinavica. Supplementum.

[5]  Miller Rg,et al.  Muscle strengthening through electric stimulation combined with low-resistance weights in patients with neuromuscular disorders. , 1988 .

[6]  D. Jones,et al.  Fatigue in human metabolic myopathy. , 2008, Ciba Foundation symposium.

[7]  W. Engel,et al.  The histographic analysis of human muscle biopsies with regard to fiber types , 1969, Neurology.

[8]  H. Milner-Brown,et al.  Quantifying human muscle strength, endurance and fatigue. , 1986, Archives of physical medicine and rehabilitation.

[9]  R. Miledi,et al.  Failure of neuromuscular propagation in rats , 1958, The Journal of physiology.

[10]  W. Engel,et al.  The histographic analysis of human muscle biopsies with regard to fiber types , 1969, Neurology.

[11]  J. Griffin,et al.  Sequential isokinetic and manual muscle testing in patients with neuromuscular disease. A pilot study. , 1986, Physical therapy.

[12]  R. H. Adrian,et al.  Reconstruction of the action potential of frog sartorius muscle , 1973, The Journal of physiology.

[13]  Julie Whelan,et al.  Human muscle fatigue: physiological mechanisms. , 1981, Ciba Foundation symposium.

[14]  R. Westgaard.  Influence of activity on the passive electrical properties of denervated soleus muscle fibres in the rat. , 1975, The Journal of physiology.

[15]  Dynamic properties of partially denervated muscle , 1979, Annals of neurology.

[16]  R. Stein,et al.  Contractile and electrical properties of human motor units in neuropathies and motor neurone disease , 1974, Journal of neurology, neurosurgery, and psychiatry.

[17]  D. Jones,et al.  Muscle fatigue due to changes beyond the neuromuscular junction. , 1981, Ciba Foundation symposium.

[18]  L. Hermansen,et al.  Effect of metabolic changes on force generation in skeletal muscle during maximal exercise. , 2008, Ciba Foundation symposium.

[19]  C. Krarup,et al.  Post-tetanic mechanical tension and evoked action potentials in McArdle's disease , 1977, Journal of neurology, neurosurgery, and psychiatry.

[20]  R. Adams,et al.  Principles of Neurology , 1996 .

[21]  R. Edwards.  Studies of muscular performance in normal and dystrophic subjects. , 1980, British medical bulletin.

[22]  K. Mills,et al.  Muscle fatigue in myophosphorylase deficiency: power spectral analysis of the electromyogram. , 1984, Electroencephalography and clinical neurophysiology.

[23]  B. Bigland-ritchie,et al.  Excitation frequency and muscle fatigue: Mechanical responses during voluntary and stimulated contractions , 1979, Experimental Neurology.

[24]  G. Vrbóva,et al.  Responses of muscles of patients with Duchenne muscular dystrophy to chronic electrical stimulation. , 1986, Journal of neurology, neurosurgery, and psychiatry.

[25]  A. McComas,et al.  Neuromuscular function in limb girdle dystrophy. , 1985, Journal of neurology, neurosurgery, and psychiatry.

[26]  H. Barbeau,et al.  A Preliminary Study of Dynamic Muscle Function in Hereditary Ataxia , 1980, Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques.

[27]  H. Milner-Brown,et al.  Muscle strengthening through high-resistance weight training in patients with neuromuscular disorders. , 1988, Archives of physical medicine and rehabilitation.