title: Mechanomyogram and electromyogram analyses during isometric contraction in human masseter muscle.
abstract: OBJECTIVE
  To investigate the relationship between mechanomyogram (MMG), electromyogram (EMG) and bite force during isometric contraction of the human masseter muscle.
  
  
  METHODS
  Data were obtained from 16 healthy Japanese males (Mean age: 25.6 +/- 2.3 years). The measuring device for MMG consisted of an amorphous sensor and a small magnet. The bite force, MMG and EMG signals were recorded simultaneously during isometric contraction of the masseter muscle. The subjects were instructed to perform 0, 5, 10, 20, 30, 40, 50, and 60% maximal voluntary contractions (MVC) for 20 seconds. The average rectified value (ARV) for MMG and EMG were calculated from 1 to 5 second samples. The median frequency of the power spectrum (MFPS) for MMG and EMG were determined with the use of a fast Fourier transformation algorithm.
  
  
  RESULTS
  The mean ARV for MMG increased up to 20% MVC and then gradually decreased at the higher force levels. The mean ARV for EMG increased with bite force in a monotonic fashion. The mean MFPS for MMG clearly increased up to 10% MVC and then gradually increased. On the other hand, the mean MFPS for EMG clearly increased up to 10% MVC, but then gradually decreased with bite force.
  
  
  CONCLUSIONS
  These findings suggest that the MMG analysis combined with the EMG may be a more useful method for evaluating the status of the masseter muscle.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Kyushu University, Fukuoka, Japan. ioi@dent.kyushu-u.ac.jp
authors.forename: Hideki
authors.initials: H
authors.lastname: Ioi
authors.forename: Makoto
authors.initials: M
authors.lastname: Kawakatsu
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nakata
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakasima
authors.forename: Amy L
authors.initials: AL
authors.lastname: Counts
mesh_terms: D000328:Adult; D001732:Bite Force; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008280:Magnetics / Q000295:instrumentation; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D009213:Myography / Q000295:instrumentation*; D014732:Vibration