title: Ultrasound tissue Doppler imaging reveals no delay in abdominal muscle feed-forward activity during rapid arm movements in patients with chronic low back pain.
abstract: METHODS
  Cross-sectional study.
  
  
  OBJECTIVE
  Comparison of the timing of onset of lateral abdominal muscle activity during rapid arm movements in patients with nonspecific chronic low back pain (cLBP) and back-pain-free controls.
  
  
  BACKGROUND
  Rapid movements of the arm are normally associated with prior activation of trunk-stabilizing muscles in readiness for the impending postural perturbation. Using invasive intramuscular electromyography techniques, studies have shown that this feed-forward function is delayed in some patients with low back pain (LBP). Ultrasound tissue Doppler imaging (TDI) provides an ultrasound method for quantifying muscle activation in a noninvasive manner, allowing investigation of larger groups of patients and controls.
  
  
  METHODS
  Ninety-six individuals participated (48 patients with cLBP and 48 matched LBP-free controls). During rapid shoulder flexion, abduction, and extension, surface electromyographic signals from the deltoid and motion-mode TDI images from the contralateral lateral abdominal muscles were recorded simultaneously. The onset of muscle activity was given by changes in the tissue velocity of the abdominal muscles, as measured with TDI. Pain and disability in the patients were assessed using standardized questionnaires. Data were analyzed using repeated measures analysis of variance.
  
  
  RESULTS
  In both groups, feed-forward activity of the lateral abdominal muscles was recorded during arm movements in all directions. The main effect of "group membership" revealed no significant difference between the groups for the earliest onset of abdominal muscle activity (P = 0.398). However, a significant "group x body side" interaction (P = 0.015) was observed, and this was the result of earlier onsets in the cLBP group than controls for the abdominal muscles on the right (but not left) body side. No relationship was found between the time of onset of the earliest abdominal muscle activity and pain intensity, pain frequency, pain medication usage, or Roland Morris disability scores.
  
  
  CONCLUSIONS
  Patients with cLBP did not show a delayed onset of feed-forward activation of the lateral abdominal muscles during rapid arm movements. Earlier activation was observed for one body side compared with the controls. However, the clinical relevance of this finding remains obscure, especially because there was no relationship between the onset of activation and any clinical parameters.
authors.affiliation: Department of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Deborah
authors.initials: D
authors.lastname: Gubler
authors.forename: Anne F
authors.initials: AF
authors.lastname: Mannion
authors.forename: Peter
authors.initials: P
authors.lastname: Schenk
authors.forename: Mark
authors.initials: M
authors.lastname: Gorelick
authors.forename: Daniel
authors.initials: D
authors.lastname: Helbling
authors.forename: Hans
authors.initials: H
authors.lastname: Gerber
authors.forename: Valeriu
authors.initials: V
authors.lastname: Toma
authors.forename: Haiko
authors.initials: H
authors.lastname: Sprott
mesh_terms: D000009:Abdominal Muscles / Q000000981:diagnostic imaging* / Q000503:physiopathology; D000368:Aged; D001132:Arm / Q000502:physiology*; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D013997:Time Factors; D018608:Ultrasonography, Doppler / Q000379:methods