Effects of muscle fiber type and size on emg median frequency and conduction velocity. Kupa, E. J., S. H. Roy, S. C. Kandarian, and C. J. De Luca. NeuroMuscular Research Center, Boston University, Boston, MA 02215, Sargent College of Allied Health Professions, Department of Health Sciences, Boston, MA 02215
APStracts 2:0074A, 1995.
This paper describes an in vitro method for comparing surface-detected EMG median frequency and conduction velocity parameters with histochemical measurements of muscle fiber-type composition and cross-sectional area (CSA). EMG signals were recorded during electrically elicited tetanic contractions from rat soleus, extensor digitorum longus and diaphragm muscles placed in an oxygenated Krebs bath. Fibers were typed as slow oxidative (SO), fast oxidative glycolytic (FOG), and fast glycolytic (FG) based on histochemical enzyme stains. Muscles with a greater percentage of FG and FOG fibers exhibited greater initial values of median frequency and conduction velocity as well as a greater reduction in these variables over the course of the contraction. Regression indicated that fiber-type composition could be predicted based on two median frequency parameters. A weighted measure of muscle fiber CSA was found to be linearly related to both initial median frequency and conduction velocity. The results of this study suggest that median frequency and conduction velocity parameters recorded during a muscular contraction are related to muscle fiber-type composition and muscle fiber CSA. 

Received 15 August 1994; accepted in final form 13 February 1995.
APS Manuscript Number A863-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  7 March 1995.