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Potentiation of `late' responses evoked in muscles during effort
  1. A. R. M. Upton1,
  2. A. J. McComas1,
  3. R. E. P. Sica2
  1. National Hospital for Nervous Diseases, Maida Vale, London
  2. The Regional Neurological Centre, Newcastle General Hospital, Newcastle upon Tyne


    A study has been made of the effect of voluntary contraction on the `late' responses which can be recorded in muscles after indirect stimulation. Two late responses have been described of which the first was shown to consist mainly of a potentiated H-reflex. The potentiation of this wave was greatest in the abductor pollicis brevis muscle and depended largely on `direct' descending pathways to motoneurones. In addition, a later evoked muscle response appeared during effort; the nature of this wave was uncertain. Simple formulae have been devised to express the excitability of motoneurones to inputs from muscle nerves during effort.

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    • 1 Present address: Neurology Section, McMaster University Medical Centre, Hamilton 16, Ontario.

    • 2 Present address: Hospital Ramos Mejia, Buenos Aires, Argentina.