QUANTIFICATION OF THE STATIC LOAD COMPONENT IN MUSCLE WORK USING NONLINEAR FILTERING OF SURFACE EMG

Prolonged static strain on the muscles of the neck-shoulder region is believed to be linked to the development of musculoskeletal problems. To quantify the static strain on the basis of EMG, the level as well a s the duration of the muscle load should be analysed on temporal basis . In this paper, some methods for the temporal analysis of EMG recordi ngs are proposed with an aim of quantifying the long-term static strai n on the muscle. The use of nonlinear median prefilters for decomposin g the EMG activity according both to amplitude level and duration of t he activity at different levels is proposed. The prefiltering methods were also evaluated using laboratory studies. The main aim of the stud ies was to compare the estimation errors between EMG and force for dif ferent types of prefilters especially when the static load component w as analysed. The average estimation error for sequences having a durat ion longer than 1 s was found to be 8% of MVC in the case of trapezius muscle and 14% of MVC in the case of biceps brachii muscle. Linear re lation was found on the basis of linear least squares curve fitting to give the largest correlation coefficients between EMG and force, when the static load component was analysed.