Experimental Brain Research

, Volume 235, Issue 2, pp 389–400

Variability in spatio-temporal pattern of trapezius activity and coordination of hand-arm muscles during a sustained repetitive dynamic task

  • Afshin Samani
  • Divya Srinivasan
  • Svend Erik Mathiassen
  • Pascal Madeleine
Research Article

DOI: 10.1007/s00221-016-4798-y

Cite this article as:
Samani, A., Srinivasan, D., Mathiassen, S.E. et al. Exp Brain Res (2017) 235: 389. doi:10.1007/s00221-016-4798-y

Abstract

The spatio-temporal distribution of muscle activity has been suggested to be a determinant of fatigue development. Pursuing this hypothesis, we investigated the pattern of muscular activity in the shoulder and arm during a repetitive dynamic task performed until participants’ rating of perceived exertion reached 8 on Borg’s CR-10 scale. We collected high-density surface electromyogram (HD-EMG) over the upper trapezius, as well as bipolar EMG from biceps brachii, triceps brachii, deltoideus anterior, serratus anterior, upper and lower trapezius from 21 healthy women. Root-mean-square (RMS) and mean power frequency (MNF) were calculated for all EMG signals. The barycenter of RMS values over the HD-EMG grid was also determined, as well as normalized mutual information (NMI) for each pair of muscles. Cycle-to-cycle variability of these metrics was also assessed. With time, EMG RMS increased for most of the muscles, and MNF decreased. Trapezius activity became higher on the lateral side than on the medial side of the HD-EMG grid and the barycenter moved in a lateral direction. NMI between muscle pairs increased with time while its variability decreased. The variability of the metrics during the initial 10 % of task performance was not associated with the time to task termination. Our results suggest that the considerable variability in force and posture contained in the dynamic task per se masks any possible effects of differences between subjects in initial motor variability on the rate of fatigue development.

Keywords

Fatigue development High-density electromyogram Functional connectivity 

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Afshin Samani
    • 1
  • Divya Srinivasan
    • 2
    • 3
  • Svend Erik Mathiassen
    • 3
  • Pascal Madeleine
    • 1
  1. 1.Laboratory for Ergonomics and Work-related Disorders, Physical Activity and Human Performance Group - SMI, Department of Health Science and TechnologyAalborg UniversityAalborg EastDenmark
  2. 2.Department of Industrial and Systems EngineeringVirginia Polytechnic Institute and State UniversityBlacksburgUSA
  3. 3.Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, Faculty of Health and Occupational StudiesUniversity of GävleGävleSweden

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