Shoulder electromyography-based indicators to assess manifestation of muscle fatigue during laboratory-simulated manual handling task

Abstract

Muscle fatigue is a risk factor for developing shoulder musculoskeletal disorders. The aim of this study was to identify shoulder electromyographic indicators that are most indicative of muscle fatigue during a laboratory simulated manual handling task. Thirty-two participants were equipped with electromyographic electrodes on 10 shoulder muscles and moved boxes for 45-minutes. The modified rate of perceived exertion (mRPE) was assessed every 5-minutes and multivariate linear regressions were performed between myoelectric manifestation of fatigue (MMF) and the mRPE scores. During a manual handling task representative of industry working conditions, spectral entropy, median frequency, and mobility were the electromyographic indicators that explained the largest percentage of the mRPE. Overall, the deltoids, biceps and upper trapezius were the muscles that most often showed significant changes over time in their electromyographic indicators. The combination of these three indicators may improve the accuracy for the assessment of MMF during manual handling.

Practitioner Summary: To date, muscle fatigue has primarily been assessed during tasks done to exhaustion, which are not representative of typical working conditions. During a manual handling task representative of industry working conditions, EMG-derived spectral entropy, and median frequency, both extracted from time-frequency analysis, and mobility extracted from time domain, were the best indicators of the manifestation of muscle fatigue.

Keywords:

• Biomechanics Entropy Median frequency Time-frequency analysis Shoulder

Acknowledgements

We would like to thank Élodie Monga-Dubreuil for her help in collecting data, the volunteers for their participation in the study.

Author contributions

EG was responsible for the data analyses and drafted the manuscript. RM was involved in the design of the study, the data collection and provided significant feedback on the analysis of the study. JB was involved in the design of the study and provided critical revision of manuscript for intellectual content. JDM provided critical revision of manuscript for intellectual content. MB and FDM, the lead scientists, helped in all facets of the project. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The present research was financially supported by The Institut de recherche Robert-Sauvé en santé et sécurité du travail (IRSST) [Grant number: #2014-0045], and the Canadian Institutes of Health Research [Grant number: #MFE-146666].