title: The Neuromuscular Response to Spinal Manipulation in the Presence of Pain.
abstract: The purpose of this study was to evaluate differences in muscle activity in participants with and without low back pain during a side-lying lumbar diversified spinal manipulation.
  
  
  
  Surface and indwelling electromyography at eight muscle locations were recorded during lumbar side-lying manipulations in 20 asymptomatic participants and 20 participants with low back pain. The number of muscle responses and muscle activity onset delays in relation to the manipulation impulse were compared in the 2 pain groups using mixed linear regressions. Effect sizes for all comparisons were calculated using Cohen's d.
  
  
  
  Muscle responses occurred in 61.6% ± 23.6% of the EMG locations in the asymptomatic group and 52.8% ± 26.3% of the symptomatic group. The difference was not statistically significant but there was a small effect of pain (d = 0.350). Muscle activity onset delays were longer for the symptomatic group at every EMG location except the right side indwelling L5 electrode, and a small effect of pain was present at the left L2, quadratus lumborum and trapezius surface electrodes (d = 0.311, 0.278, and 0.265) respectively. The indwelling electrodes demonstrated greater muscle responses (P ≤ .01) and shorter muscle activity onset delays (P < .01) than the surface electrodes.
  
  
  
  The results revealed trends that indicate participants with low back pain have less muscle responses, and when muscle responses are present they occur with longer onset delays following the onset of a manipulation impulse.
authors.affiliation: Graduate Research Assistant, Department of Mechanical and Materials Engineering, University of Denver, Denver, CO.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Currie
authors.affiliation: Graduate Research Assistant, Department of Mechanical and Materials Engineering, University of Denver, Denver, CO.
authors.forename: Casey A
authors.initials: CA
authors.lastname: Myers
authors.affiliation: Research Statistician, Center for Statistics and Visualization, University of Denver, Denver, CO.
authors.forename: Catherine
authors.initials: C
authors.lastname: Durso
authors.affiliation: Clinician, Integrative Medicine Program at University of Colorado Hospital, University of Colorado Denver School of Medicine, Aurora, CO.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Enebo
authors.affiliation: Assistant Professor, Department of Mechanical and Materials Engineering, University of Denver, Denver, CO. Electronic address: Bradley.davidson@du.edu.
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Davidson
mesh_terms: D000328:Adult; D064131:Back Muscles / Q000503:physiopathology*; D004576:Electromyography; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology; D020393:Manipulation, Spinal; D009119:Muscle Contraction / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
keywords: Biomechanical Phenomena; Chiropractic; Electromyography; Kinetics; Low Back Pain; Manipulation; Reflex; Spinal