title: Applicability of the coactivation method in assessing synergies of the scapular stabilizing muscles.
abstract: OBJECTIVE
  This study investigated the feasibility of quantifying the coactivation levels in the evaluation of synergisms of the scapular stabilizing muscles during the elevation and lowering of the arms. This method, which quantifies the overlapping area of the normalized electromyographic (EMG) activity, could be applicable in assessing such muscular synergies.
  
  
  METHODS
  Both shoulders of 10 healthy volunteers were assessed. The coactivation of 3 synergic muscular groups (upper, middle and lower trapezius; upper trapezius and serratus anterior; middle trapezius and serratus anterior) and the isolated electromyographic activity of each muscle were analyzed.
  
  
  RESULTS
  Analysis of variance revealed that the coactivation values between the synergic groups were different from the isolated levels of each respective muscle for both movements (24.42 < F < 40.12; df=6; p < 0.001). The coactivation values of all groups during elevation were different from those during the lowering of the arms (13.31 <F < 959.92; df=1; p <or= 0.002), with progressive increases in EMG activity during the elevation and decreases during the lowering of the arms.
  
  
  CONCLUSIONS
  The significant differences in EMG activity between the isolated and the coactivation methods indicated that the coactivation method was adequate to assess the scapular muscular synergies.
authors.affiliation: Department of Physical Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Christina Danielli Coelho de Morais
authors.initials: CD
authors.lastname: Faria
authors.forename: Luci Fuscaldi
authors.initials: LF
authors.lastname: Teixeira-Salmela
authors.forename: Pollyanna Figueiredo
authors.initials: PF
authors.lastname: Gomes
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000886:Anthropometry; D001132:Arm / Q000502:physiology; D015992:Body Mass Index; D015331:Cohort Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009985:Orthopedics / Q000379:methods; D011336:Probability; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D055815:Young Adult