title: Comparison of surface electromyography and myotonometric measurements during voluntary isometric contractions.
abstract: OBJECTIVE
  Muscle stiffness increases during muscle contraction. The purpose of this study was to determine the strength of the correlation between myotonometric measurements of muscle stiffness and surface electromyography (sEMG) measurements during various levels of voluntary isometric contractions of the biceps brachii muscle.
  
  
  METHODS
  Eight subjects (four female; four male), with mean age of 30.6 +/- 8.23, volunteered to participate in this study.
  
  
  METHODS
  Myotonometer and sEMG measurements were taken simultaneously from the right biceps brachii muscle. Data were obtained: (1) at rest, (2) while the subject held a 15 lb (6.8 kg) weight isometrically and, (3) during a maximal voluntary isometric contraction. Myotonometer force-displacement curves (amount of tissue displacement to a given unit of force applied perpendicular to the muscle) were compared with sEMG measurements using Pearson's product-moment correlation coefficients.
  
  
  RESULTS
  Myotonometer and sEMG measurement correlations ranged from -0.70 to -0.90. The strongest correlations to sEMG were from Myotonometer force measurements between 1.00 and 2.00 kg.
  
  
  CONCLUSIONS
  Myotonometer and sEMG measurements were highly correlated. Tissue stiffness, as measured by the Myotonometer, appears capable of assessing changes in muscle activation levels.
authors.affiliation: Motor Control Research Laboratory, Physical Therapy Department, School of Pharmacy and Health Sciences, University of Montana, Missoula, MT 59812, USA. charles.leonard@umontana.edu
authors.forename: Charles T
authors.initials: CT
authors.lastname: Leonard
authors.forename: Jason S
authors.initials: JS
authors.lastname: Brown
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Price
authors.forename: Susan A
authors.initials: SA
authors.lastname: Queen
authors.forename: Eugene L
authors.initials: EL
authors.lastname: Mikhailenok
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008365:Manometry; D018482:Muscle, Skeletal / Q000502:physiology*