Examination of the myoelectric activity of back muscles during random vibration – methodical approach and first results

Blüthner, R.; Seidel, H.; Hinz, B.

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Volume 16, Supplement 1 , Pages S25-S30, 2001

Examination of the myoelectric activity of back muscles during random vibration – methodical approach and first results

Department of Occupational Health, Federal Institute for Occupational Safety and Health, Group AM 4.3, Biological Effects of Vibration and Noise Nöldnerstr. 40-42 D-10317 Berlin, Germany

Abstract

Objective. To elaborate methods for an elimination of artefacts and the analysis of the relationship between random whole-body vibration and electromyographic responses of back muscles.

Design. A procedure involving wavelets and digital filtering has been used for the removal of artefacts from the electromyogram during whole-body vibration.

Background. Back muscle forces contribute essentially to the whole-body vibration-induced spinal load. The electromyogram can help to estimate these forces during whole-body vibration.

Methods. 38 subjects were exposed to identical random low-frequency whole-body vibration. Artefacts caused by the electrocardiogram in the electromyogram were identified by appropriate wavelets and eliminated in the time-domain. After averaging the individual high-pass filtered and rectified undistorted electromyograms across subjects, the transfer function from seat acceleration to the average electromyogram was determined and used for the prediction of the electromyogram.

Results. A sufficient procedure involving wavelets and digital filtering has been elaborated for the removal of artefacts from the electromyogram of back muscles during whole-body vibration. A systematic relationship between random vibration and back muscle-response was obtained and described. The transfer function suggests two different reflex-mechanisms – one elicited below, the other above 4 Hz.

Conclusions. The approach of analysing and predicting the muscle-response to random vibration by using the transfer function seems to be promising and could be a valuable tool for the future calculation of muscle forces as an input to active models.

Relevance

The knowledge of the extent and timing of the back muscle-response to random whole-body vibration is relevant for an improved evaluation of whole-body vibration with respect to health.

Keywords: EMG, Back, Vibration, ECG, Artefact, Wavelet, Transfer function