Validity of electromyograms and tension as a means of motor unit number estimation

The purpose of this study was to validate three different techniques for obtaining motor unit number estimates of the rat medial gastrocnemius muscle. These consisted of two electromyographic techniques using unprocessed and digitally averaged unitary muscle action potentials, and one mechanical technique. We also injected subunit B of cholera toxin into this muscle and counted the number of spinal motor neurons labeled by the toxin. Our results revealed that a motor unit number estimate obtained by using the unprocessed unitary muscle action potential was statistically different from the actual number of motor neurons. The other two motor unit number estimates, however, were not statistically different from the actual motor neuron number. These two methods thus seem more appropriate than the first electromyographic method for obtaining an accurate motor unit number estimate. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20, 552–560, 1997.

[1]  W F Brown,et al.  Multiple point electrical stimulation of ulnar and median nerves. , 1976, Journal of neurology, neurosurgery, and psychiatry.

[2]  H. Iwamoto,et al.  Influence of aging and the motor unit type on the inverse relationship between the refractory period and the conduction velocity of the alpha motor nerve fibers , 1995, Muscle & nerve.

[3]  M J Campbell,et al.  Electrophysiological estimation of the number of motor units within a human muscle , 1971, Journal of neurology, neurosurgery, and psychiatry.

[4]  C A Laszlo,et al.  A review of techniques employed to estimate the number of motor units in a muscle , 1990, Muscle & nerve.

[5]  Keisuke Arasaki,et al.  WS-22-2 Validity of EMG and tension as means of motor unit number estimation (MUNE) , 1995 .

[6]  T J Doherty,et al.  Determinants of mean motor unit size: Impact on estimates of motor unit number , 1993, Muscle & nerve.

[7]  W. Brown,et al.  Methods for estimating numbers of motor units in biceps‐brachialis muscles and losses of motor units with aging , 1988, Muscle & nerve.

[8]  Maximal and minimal motor nerve conduction velocities determined by a collision method: correlation with axonal conduction velocity of type-identified motor units , 1992, Journal of the Neurological Sciences.

[9]  A. Eisen,et al.  The motor unit profile of the rat soleus in experimental myopathy and reinnervation , 1974, Neurology.

[10]  J F Yang,et al.  Methods for estimating the number of motor units in human muscles , 1990, Annals of neurology.

[11]  J. Stephens,et al.  Study of human motor unit contractions by controlled intramascular microstimulation , 1976, Brain Research.

[12]  G. Wieneke,et al.  Estimation of the number of motor units based on macro-EMG. , 1988, Journal of neurology, neurosurgery, and psychiatry.

[13]  M. Abercrombie.  Estimation of nuclear population from microtome sections , 1946, The Anatomical record.

[14]  Y. Lamarre,et al.  Electrophysiological and anatomical estimation of the number of motor units in the monkey extensor digitorum brevis muscle. , 1977, Journal of neurology, neurosurgery, and psychiatry.

[15]  A. McComas,et al.  Motor unit estimation: Anxieties and achievements , 1995, Muscle & nerve.

[16]  R. Burke,et al.  Medial gastrocnemius motor nucleus in the rat: Age‐related changes in the number and size of motoneurons , 1988, The Journal of comparative neurology.