title: Prediction of maximal surface electromyographically based voluntary contractions of erector spinae muscles from sonographic measurements during isometric contractions.
abstract: OBJECTIVE
  Currently, there are no studies combining electromyography (EMG) and sonography to estimate the absolute and relative strength values of erector spinae (ES) muscles in healthy individuals. The purpose of this study was to establish whether the maximum voluntary contraction (MVC) of the ES during isometric contractions could be predicted from the changes in surface EMG as well as in fiber pennation and thickness as measured by sonography.
  
  
  METHODS
  Thirty healthy adults performed 3 isometric extensions at 45° from the vertical to calculate the MVC force. Contractions at 33% and 100% of the MVC force were then used during sonographic and EMG recordings. These measurements were used to observe the architecture and function of the muscles during contraction. Statistical analysis was performed using bivariate regression and regression equations.
  
  
  RESULTS
  The slope for each regression equation was statistically significant (P < .001) with R(2) values of 0.837 and 0.986 for the right and left ES, respectively. The standard error estimate between the sonographic measurements and the regression-estimated pennation angles for the right and left ES were 0.10 and 0.02, respectively.
  
  
  CONCLUSIONS
  Erector spinae muscle activation can be predicted from the changes in fiber pennation during isometric contractions at 33% and 100% of the MVC force. These findings could be essential for developing a regression equation that could estimate the level of muscle activation from changes in the muscle architecture.
authors.affiliation: Department of Physiotherapy, University of Malaga, Paseo de Martiricos, 29071 Malaga, Spain. acuesta@uma.es.
authors.forename: Antonio I
authors.initials: AI
authors.lastname: Cuesta-Vargas
authors.forename: Manuel
authors.initials: M
authors.lastname: González-Sánchez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D064131:Back Muscles / Q000000981:diagnostic imaging* / Q000502:physiology*; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D055815:Young Adult
keywords: electromyography; musculoskeletal ultrasound; regression analysis; sonography; spine