title: Back muscle activation patterns in chronic low back pain during walking: a "guarding" hypothesis.
abstract: OBJECTIVE
  To investigate whether patients with chronic low back pain (CLBP) show "guarded" movements during walking. It is hypothesized that guarding will be reflected by increased lumbar muscle activity during all periods of stride and secondary, relatively lesser relaxation during periods of swing compared with double support. Furthermore, it is hypothesized that higher levels of perceived fear and disability are related to increased muscle activity and less relative relaxation.
  
  
  METHODS
  In a cross-sectional study 63 patients with CLBP and 33 healthy controls walked on a treadmill at 3.8 km/h. Surface electromyography (sEMG) data of the erector spinae were obtained and smoothed rectified sEMG (SRE) values were calculated per period of swing and double support. The ratio of SRE values in swing to double support was used as a measure of relative relaxation (SRE ratio). In addition, the relationship between SRE values, the Roland Morris Disability Questionnaire, and the Tampa Scale for Kinesiophobia was analyzed in patients with CLBP.
  
  
  RESULTS
  Mean SRE values were significantly higher in patients with CLBP than in controls both during periods of double support and swing. SRE ratios were not significantly different between groups. Results showed no influence of disability or fear of movement on either SRE values or ratios.
  
  
  CONCLUSIONS
  In patients with CLBP, increased lumbar muscle activity during all periods of stride, with comparable alteration between swing and double support, suggests difficulties with total muscle relaxation. On the basis of this evaluation, it is concluded that patients with CLBP show a guarding mechanism during walking. No relationship is found between perceived fear, disability, and muscle activity.
authors.affiliation: Roessingh Research and Development, Rehabilitation Centre het Roessingh, Roessinghsbleekweg 33b, Enschede, The Netherlands. m.vanderhulst@rrd.nl
authors.forename: Marije
authors.initials: M
authors.lastname: van der Hulst
authors.forename: Miriam M
authors.initials: MM
authors.lastname: Vollenbroek-Hutten
authors.forename: Johan S
authors.initials: JS
authors.lastname: Rietman
authors.forename: Leendert
authors.initials: L
authors.lastname: Schaake
authors.forename: Karin G
authors.initials: KG
authors.lastname: Groothuis-Oudshoorn
authors.forename: Hermanus J
authors.initials: HJ
authors.lastname: Hermens
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D015992:Body Mass Index; D016009:Chi-Square Distribution; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D004576:Electromyography / Q000379:methods; D005080:Exercise Test / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D017116:Low Back Pain / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010147:Pain Measurement; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D016138:Walking / Q000502:physiology*; D055815:Young Adult