[Changes in the muscle fiber conduction velocity (MFCV) due to the masticatory muscle development. 1. Preliminary...

The purpose of this study was to investigate the methods involved in observing the muscle fiber conduction velocity (MFCV) both in the masseter muscle and the m. biceps brachii in healthy persons. Three adults were the subjects in this study, none of whom had any gnathofacial dysfunction. The EMG activities were recorded from the m. biceps brachii with the arm bent at right angles and the masseter muscle in the intercuspal position, in both muscles during 50% of maximum voluntary isometric contraction on the habitual side. Three types of surface electrodes were used. Type 1. the disc type electrodes array arranged straight, Type 2. the disc type electrodes array arranged independently, Type 3. the strip type surface electrodes array arranged straight. The EMG activities preamplified at three conditions of time constant, e.g., 0.003, 0.01, 0.03 sec on m. biceps brachii were analyzed through a personal computer system and a FFT analyser. The conduction velocity was calculated by the cross-correlation method. The results obtained in this study were as follows: 1) No differences in the MFCV between the time constant were noticed. 2) The electrode array arranged straight was effective in the measurement of the MFCV in adults and in particular the strip type series electrodes array arranged straight was the most effective to measure the MFCV in the masseter muscle. 3) The average MFCV of the m. biceps brachii and the masseter muscle were 4.13 +/- 0.29 m/sec and 14.28 +/- 1.21 m/sec respectively.