The effect of shoulder position on motor evoked and maximal muscle compound action potentials of the biceps brachii

Brandon W Collins; Duane C Button

doi:10.1016/j.neulet.2017.12.019

The effect of shoulder position on motor evoked and maximal muscle compound action potentials of the biceps brachii

Neurosci Lett. 2018 Feb 5:665:206-211. doi: 10.1016/j.neulet.2017.12.019. Epub 2017 Dec 8.

Authors

Brandon W Collins¹, Duane C Button²

Affiliations

¹ Human Neurophysiology Laboratory, School of Human Kinetics and Recreation, Memorial University, St. John's, Newfoundland and Labrador, Canada.
² Human Neurophysiology Laboratory, School of Human Kinetics and Recreation, Memorial University, St. John's, Newfoundland and Labrador, Canada; BioMedical Sciences, Faculty of Medicine, Memorial University, St. John's, Newfoundland and Labrador, Canada. Electronic address: dbutton@mun.ca.

PMID: 29229395
DOI: 10.1016/j.neulet.2017.12.019

Abstract

The purpose of the study was to assess the effect of shoulder position, 0° versus 90° shoulder flexion, on stimulation intensity and maximal muscle compound action potentials (M_max) and motor evoked potentials (MEP) of the biceps brachii during both rest and 10% maximum voluntary contraction (MVC). Nine participants completed two experimental sessions with four conditions. During each condition, transcranial magnetic (TMS) and Erb's point stimulation were used to elicit MEPs and M_max, respectively. During rest, the TMS intensity to elicit a MEP response (p<0.001), was significantly lower by 28.6±6.8%, in the 90° compared to the 0° position, but the stimulation intensity to elicit a M_max was not different. MEP (p<0.001) and M_max (p<0.001) amplitudes were significantly higher by 212.4±43.3% and 86.5±38.0%, respectively in the 90° compared to the 0° position. During 10% MVC the M_max stimulation intensity (p=0.022), but not TMS intensity, was significantly lower by 7.4±3.8% in the 90° compared to the 0° position. M_max (p<0.001) amplitudes were significantly higher by 92.2±20.2% in the 90° compared to the 0° position whereas MEP (p<0.001) amplitudes were significantly lower by 24.5±6.0% in the 90° compared to the 0° position. In conclusion, TMS intensity and M_max intensity were both shoulder-position and state-dependent, whereas MEP and M_max amplitudes were only shoulder position-dependent.

Keywords: Electromyography; Motor evoked potential; Transcranial magnetic stimulation.

MeSH terms

Action Potentials / physiology*
Adolescent
Adult
Arm / physiology
Evoked Potentials, Motor / physiology*
Female
Humans
Male
Motor Cortex / physiology*
Motor Neurons / physiology
Muscle Contraction / physiology
Muscle, Skeletal / physiology*
Shoulder / physiology*
Transcranial Magnetic Stimulation / methods
Young Adult