Ia presynaptic inhibition after muscle twitch in the arm

Maurizio Inghilleri, Cinzia Lorenzano, Francesca Gilio, Francesca Pedace, Stefano Romeo, Mario Manfredi, Alfredo Berardelli

Research output: Contribution to journalArticlepeer-review


Contraction of upper limb muscles in healthy subjects was used to investigate presynaptic inhibition at spinal level. The H reflex recorded in the forearm flexor muscles in response to median nerve stimulation was depressed in amplitude from 400 ms to 1 s after a muscle twitch induced by transcranial stimulation, root stimulation, direct biceps stimulation, and triceps tendon tap. Stimulation of the cutaneous branch of musculocutaneous nerve, ipsilateral triceps and contralateral biceps, and biceps tendon tap did not alter H-reflex size. Forearm flexor H-reflex amplitude is therefore related to changes in proprioceptive inflow secondary to the biceps muscle twitch. Root and direct muscle stimulation both failed to reduce the size of the motor evoked potential (MEP) after transcranial magnetic stimulation, suggesting that the inhibition acts at presynaptic level. Attenuation of H- reflex amplitude was related to the size of the muscle twitch and was less pronounced during an isometric twitch than during free joint movement. Our results suggest that the biceps muscle twitch produces long-lasting inhibition of the Ia afferents from forearm flexor muscles. This is an important and a simple mechanism for suppressing proprioceptive input during movement. (C) 2000 John Wiley and Sons, Inc.

Original languageEnglish
Pages (from-to)748-752
Number of pages5
JournalMuscle and Nerve
Issue number5
Publication statusPublished - May 2000


  • Heteronymous inhibition
  • Muscle twitch
  • Presynaptic inhibition
  • Transcranial magnetic stimulation

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)


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