MUSCLE ELECTRIC-ACTIVITY .2. ON THE FEASIBILITY OF MODEL-BASED ESTIMATION OF EXPERIMENTAL CONDITIONS IN ELECTROMYOGRAPHY

From regular one-channel registrations of single muscle fiber action p otential no measures on the recording configuration can be derived. Wh en multichannel recordings are made, experimental parameters such as t he distance between muscle fiber and needle electrode can be estimated . With the help of a volume conductor model, the single fiber activity at each of the electrodes can be predicted as a function of the recor ding conditions. Within known physical and physiological constraints s uch a model approach can be inverted (the inverse model) and used to e stimate basic experimental conditions. From eight simultaneous single fiber action potential recordings we estimated (a) the distance betwee n fiber and needle, (b) the axial position of the needle with respect to the muscle fiber, (c) a factor related to the muscle tissue anisotr opy, and (d) a factor combining the muscle fiber diameter and the effe ctive muscle tissue conductivity. With the help of a model describing the influence of the needle shaft it is made plausible that the needle inhomogeneity influences the results of the proposed procedure.