Abstract
The purpose of this overall study was to investigate changes in muscle fiber conduction velocity (MFCV) and EMG power spectrum patterns in the masseter and biceps brachii muscles in children.
A total of 35 subjects who had no gnatho-facial dysfunction were the subjects in the study. The subjects were divided into four groups: 5 primary dentition (designated as G1),5 early mixed dentition (as G2),5 late mixed dentition (as G3)and 20 permanent dentition (as G4,10 females and 10 males). EMG activities were recorded from the m. biceps brachii with the arm bent at right angles and the masseter muscle in the intercuspal position during 50% of maximum voluntary contraction (MVC). Contraction levels of 10,25,50,100% MVC were also observed in 10 of the G4. EMGs recorded using the strip type surface electrodes array, in straight arrangement, were analyzed by fast fourie transformation. Four parameters were analyzed; MFCV, frequency of maximum peak (peak frequency), frequency range and strength of maximum peak (peak magnitude).
The results obtained in the present studies were summarized as follows;
1) There were no differences in MFCV at G4 between sexes, whereas the MFCV was significantly faster (p<0.01) in the masseter muscles (12.44±1.93m/s)than the biceps brachii (4.48±0.66m/s).
2) As the contraction level rose, the MFCV, peak magnitude and frequency range increased significantly in each muscle (p<0.01).
3) In the MFCV at G4 was significantly faster (p<0.05) than G1 in the masseter muscles, and those differences between each groups were clarified with the development.
As aforementioned, change of MFCV may be due to the differences of proportion of the muscle fiber types such as fast twitch and slow twitch fiber with development.
