Background: The distribution of muscle fiber conduction velocity (MFCV)estimated from surface myoelectric signals differs depending on the recording electrode locations. Itis assumed in this study that the irregular values of MFCV may be estimated around the end-plate zoneand the fiber endings due to effect of unique interference property of myoelectric signals, and its hypothesisis confirmed experimentally and numerically in consideration of the waveform characteristics of surfacemyoelectric signals. Material/Methods: In experimental study, the surface myoelectric signals are recordedby array electrodes during voluntary isometric contraction in biceps brachii muscle. In the numericalstudy, the surface myoelectric signals in consideration of the interference property of some motor unitactivities are calculated from the current dipole model which simulated the firing features of musclefiber from end-plate zone to fiber endings. MFCV is estimated by the technique of cross-correlation.Maximum correlation coefficient (R[sub]xy[/sub](T[sub]s[/sub])) and amplitude ratio (AMP[sub]ratio[/sub]) are used to evaluate similarityand attenuation rate between traveling signals. Results: In both results of experimental and numericalstudies, the MFCV significantly increase when both R[sub]xy[/sub] (T[sub]s[/sub]) and AMP[sub]ratio[/sub] decrease around the end-platezone and fiber endings although three parameters denote constant values in the locations other than theend-plate zone and the fiber endings. The high correlativity is recognized between the experimental andnumerical data for MFCV, R[sub]xy[/sub] (T[sub]s[/sub]), and AMP[sub]ratio[/sub]. Conclusions: Therefore, it is demonstrated byexperimental and theoretical studies that MFCV, R[sub]xy[/sub] (T[sub]s[/sub]), and AMP[sub]ratio[/sub] are influenced by irregularwaveform properties depending on both positions of the end-plate and fiber endings.

Keywords: Action Potentials, Isometric Contraction - physiology, Models, Neurological, Motor Endplate - physiology, Muscle Fibers, Skeletal - physiology, Neural Conduction - physiology