title: The relationship between EMG and change in thickness of transversus abdominis.
abstract: OBJECTIVE
  To investigate the relationship between changes in thickness and EMG activity in the transversus abdominis muscle of healthy subjects and the reliability of ultrasound measurements using different modes and transducers.
  
  
  METHODS
  Convenience sampling.
  
  
  BACKGROUND
  Chronic low back pain is associated with transversus abdominis dysfunction but EMG studies of this muscle are restricted to invasive techniques. Since the thickness of transversus abdominis changes with activity, such changes measured from ultrasound images might provide insight into this muscle's function non-invasively. In addition, little is known about the comparability of ultrasound measurements from different modes and transducers, nor the reliability of transversus abdominis measurements.
  
  
  METHODS
  In 9 healthy subjects (aged 29-52 years, four male) transversus abdominis was studied at rest and during activity (5-80% max) with simultaneous EMG and ultrasound (M mode, 5 MHz curvilinear transducer) measurements. Intra-rater reliability for thickness measurements was studied on 13 subjects using 7.5 MHz linear and 5 MHz curvilinear transducers in B and M modes.
  
  
  RESULTS
  Muscle thickness changes correlated well with EMG activity (P < 0.001, R2 = 0.87) and there were no significant differences between subjects (P > 0.05). Using 7.5 MHz head, the ICC for B mode was 0.989 and for M mode was 0.981 for between days reliability. The ICC for between transducer reliability was 0.817.
  
  
  CONCLUSIONS
  Changes in thickness of transversus abdominis can be used to indicate changes in the electrical activity in this muscle.
  
  
  CONCLUSIONS
  Ultrasound scanning can be used in the clinical setting to provide objective information about transversus abdominis function.
authors.affiliation: School of Physiotherapy, The University of Melbourne, Melbourne, Victoria 3010, Australia.
authors.forename: J M
authors.initials: JM
authors.lastname: McMeeken
authors.forename: I D
authors.initials: ID
authors.lastname: Beith
authors.forename: D J
authors.initials: DJ
authors.lastname: Newham
authors.forename: P
authors.initials: P
authors.lastname: Milligan
authors.forename: D J
authors.initials: DJ
authors.lastname: Critchley
mesh_terms: D000009:Abdominal Muscles / Q000000981:diagnostic imaging* / Q000502:physiology*; D000328:Adult; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D014463:Ultrasonography / Q000379:methods*