title: Characterization of the mechanomyographic signal of three different muscles and at different levels of isometric contractions.
abstract: OBJECTIVE
  Lateral (X) and longitudinal (Y) mechanical oscillations of muscle fibers that take place during muscular contraction seem to contain information additionally to the myoelectric activity, which can contribute to the interpretation of some muscle gradation force mechanisms. However, no previous study was found that had investigated the relationship between the muscle force and features associated to the mechanomyographic (MMG) signal obtained by means of a biaxial accelerometer in three different muscles. Therefore, the aim of this study was to evaluate the relationship between the force output at different load levels (20% to 100%) of the maximum voluntary isometric contraction (%MVIC) and the two signals supplied by a biaxial accelerometer and, in addition, the so-called resultant (R) acceleration signal derived from the two signals mentioned previously. Twenty seven male volunteers participated in this study.
  
  
  METHODS
  The force output related to the right biceps brachii, soleus and gastrocnemius medialis muscles was studied by means of linear regression models fit to log-transformed of the root mean square (RMS) values of the MMG signals in X, Y, and R axes versus each %MVIC. The phase angle of R acceleration (PhaseR) and anthropometric data were also considered.
  
  
  RESULTS
  The angular coefficient a and the antilog of y-intercept b from the log-transformed of MMG data values versus force output were able to distinguish partially motor unit strategies during isometric contractions in the three muscles studied.
  
  
  CONCLUSIONS
  The findings suggest that biaxial accelerometer seems to be an interesting approach in the assessment of muscle contraction properties.
authors.affiliation: Laboratório de Instrumentação Biomédica (LIB) - PEB/COPPE/UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
authors.forename: Bruno
authors.initials: B
authors.lastname: Jotta
authors.affiliation: Laboratório de Instrumentação Biomédica (LIB) - PEB/COPPE/UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.|Departamento de Biociências da Atividade Física - EEFD/UFRJ Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Cavalcanti Garcia
authors.affiliation: Laboratório de Instrumentação Biomédica (LIB) - PEB/COPPE/UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Visintainer Pino
authors.affiliation: Laboratório de Instrumentação Biomédica (LIB) - PEB/COPPE/UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
authors.forename: Marcio Nogueira
authors.initials: MN
authors.lastname: De Souza
mesh_terms: D000054:Acceleration; D000328:Adult; D001132:Arm; D001696:Biomechanical Phenomena; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007866:Leg; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000502:physiology*; D009213:Myography / Q000706:statistics & numerical data*; D012815:Signal Processing, Computer-Assisted; D016474:Weight-Bearing / Q000502:physiology; D055815:Young Adult