Article Text

PDF

Variation of motor unit size in the human extensor digitorum brevis and thenar muscles
  1. T. E. Feasby,
  2. W. F. Brown
  1. University Hospital, London, Ontario, Canada

    Abstract

    One physiological method for estimating the motor unit number in a muscle depends on dividing into the maximum compound muscle action potential, the potential average of the first few motor unit potentials excited by a motor nerve stimulus above motor threshold. To be valid, such an average unit potential size must be representative of the whole motor unit population. This assumption may not be justified. The present study has shown that there are single motor units in healthy and abnormal, thenar, and EDB motor unit populations, many times larger than any motor unit excited close to the motor threshold. This finding suggests that previously reported motor unit estimates may not only be an overestimate of the true motor unit population number, but have excluded much larger motor units with higher thresholds. Low motor unit estimates in neuropathies may result from a change in the order of activation of motor units with the appearance of larger motor units, normally of higher threshold among the first few just above the motor threshold.

    Statistics from Altmetric.com

    Footnotes

    • 1 First presented, in part, at the 8th International Congress of Electroencephalography and Clinical Neurophysiology, Marseilles, September 1973.

    Request permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.