VARIABILITY OF SOME SEMG PARAMETER ESTIMATES WITH ELECTRODE LOCATION

Muscular action potential conduction velocity (CV) and mean power freq uency (MPF) are commonly used parameters to describe the surface elect romyographic signal (SEMG). The discrepancies concerning the behavior and interpretation of these main parameters in the literature have mot ivated this work. Our objective was to evaluate within- and between-in dividual reproducibility, sensitivity and variation of CV and MPF depe nding on the electrode location with respect to various contraction mo dalities. The results present evidence for significant influence of el ectrode location on CV and MPF, not only in their initial values but a lso in their changes during fatiguing efforts. This influence appears to be subject-dependent. This variability seems to be essentially due to the relative displacements of myotendinous and neuromuscular juncti ons with respect to the electrode set. Moreover, this study shows that MPF can be seen as force-dependent under certain conditions and that the CV-MPF relationship is strongly influenced by methodological facto rs. In conclusion, it seems irrelevant to derive reliable SEMG paramet er estimates without considering electrode location. There is a strong need for proper standardization based on anatomical and methological aspects before attempting any individual characterization. Finally, we suggest a procedure for assessment of measurement quality. (C) 1998 E lsevier Science Ltd. All rights reserved.