title: Muscle activation patterns in subjects with and without low back pain.
abstract: OBJECTIVE
  To analyze muscle activation patterns during various footplate perturbations, used as proprioceptive challenges in patients with low back pain (LBP) and in controls.
  
  
  METHODS
  A prospective and controlled comparative study.
  
  
  METHODS
  Outpatient clinic.
  
  
  METHODS
  Twenty subjects with chronic LBP and 20 age- and sex-matched controls.
  
  
  METHODS
  The subjects underwent 5 sets of footplate perturbations in 3 directions with 16 perturbations for each set.
  
  
  METHODS
  Latency, frequency, and asymmetry of muscle activation of the erector spinae, rectus abdominus, anterior tibialis, and gastrocnemius muscles were measured bilaterally with surface electromyography.
  
  
  RESULTS
  In the toes-up movements, subjects with LBP were significantly less likely to activate their rectus abdominus muscles (P=.02), and they were more likely to exhibit asymmetric muscle activation in the smaller forward movements (odds ratio=4.1, P=.03). The latter result appears to be driven by asymmetric contraction of the erector spinae and rectus abdominus.
  
  
  CONCLUSIONS
  Significantly more subjects with LBP than control subjects exhibited absent firing of trunk muscles during 2 of the 5 footplate perturbations. These results suggest an abnormality of the neuromuscular loop and may represent altered proprioception.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Newcomer
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Jacobson
authors.forename: David A
authors.initials: DA
authors.lastname: Gabriel
authors.forename: Dirk R
authors.initials: DR
authors.lastname: Larson
authors.forename: Robert H
authors.initials: RH
authors.lastname: Brey
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002908:Chronic Disease; D004576:Electromyography; D005260:Female; D006801:Humans; D016015:Logistic Models; D017116:Low Back Pain / Q000503:physiopathology* / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D016017:Odds Ratio; D011434:Proprioception; D011446:Prospective Studies