Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but not Corticospinal Pathways

Trevor S. Barss, David F. Collins, Dylan Miller, Amit N. Pujari* (Corresponding Author)

*Corresponding author for this work

Research output: Working paper


The aim of this study was to investigate whether indirect upper limb vibration (ULV) modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0±15.7 vs 18.4±11.2 % Mmax; p<0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (−1.50 ± 2.1 % Mmax) to ULV (−1.73 ± 2.2 % Mmax; p<0.05). There was no significant effect of ULV on MEP amplitude (p>0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc).
Original languageEnglish
Number of pages23
Publication statusPublished - 15 Oct 2020

Bibliographical note

Support for this research was provided by Churchill Travelling Fellowship through Winston Churchill Memorial Trust (to ANP) and a Campus Alberta Neuroscience Postdoctoral Fellowship (TSB). The vibration stimulation device used in this work was supported by funding from the Scottish Funding Council, UK (SFC) (to ANP).
The authors wish to acknowledge the participants for their contributions during data acquisition.


  • Indirect vibration
  • upper limb vibration
  • H-reflex
  • cutaneous reflex
  • motor evoked potential
  • electromyography
  • transcranial magnetic stimulation
  • sensorimotor integration


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