EMG normalization: considerations of the literature for muscular function evaluation

Abstract

Introduction: Different intrinsic and extrinsic factors may affect the electrical muscular activity using the electromyography (EMG). To minimize this effect, the normalization of the EMG is suggested. However, it is not clear the advantages and disadvantages of each EMG normalization method when applied in different patients (symptomatic and asymptomatic). Objectives: To review and discuss the main methods of normalization of the EMG signal for evaluation of the motor function in different individuals. Methods: This revision included scientific papers since 1984, available on Medline databases. Seventeen articles, being two with symptomatic patients and two of revision, were selected for the critical review. Conclusion: The choice of a normalization technical is based on intra-and inter-individual variability. One method more suitable to reduce the biological variability is of a sub-maximal voluntary contraction, used as reference on EMG normalization. However, using this method there is a lack of information corresponding to the level of muscle activation required for the task in relation to the maximal capacity of individual.