title: The cervical flexion-relaxation ratio: reproducibility and comparison between chronic neck pain patients and controls.
abstract: METHODS
  Reliability study.
  
  
  OBJECTIVE
  To determine the reproducibility of the cervical flexion-relaxation ratio (FRR) measured 4 weeks apart in a group of chronic neck pain patients and healthy control group and to compare the FRR between the 2 groups.
  
  
  BACKGROUND
  The cervical FRR measures the ability of the neck extensor muscles to relax during forward flexion, similar to the lumbar FRR. Its reliability and ability to discriminate neck pain patients from controls has not been investigated.
  
  
  METHODS
  Fourteen participants with chronic neck pain and a control group of 14 individuals with no neck pain were recruited via advertisement and word of mouth. The cervical FRR was determined at baseline and 4 weeks later using standardized electromyographic data collection and analysis procedures.
  
  
  RESULTS
  The mean FRR value for the combined left and right side data for the neck pain groups was 1.93 ± 0.8, and 1.73 ± 0.61 at 4-week follow-up. The intraclass correlation coefficient (ICC) was 0.83 (95% CI = 0.67-0.92). Three participants in the control group developed neck pain in the 4 weeks and their data were not included in the reliability calculation. For the control group, the combined (left and right side) mean FRR value was 4.09 ± 1.58 at baseline and 4.27 ± 1.71 on retest 4 weeks later. The ICC (intraclass r) was 0.89 (95% confidence interval = 0.76-0.95). The overall ICC for the combined groups was 0.92 (95% confidence interval = 0.86-0.95). An independent 2 group t test revealed a significant difference in the baseline FRR data between the control group and the neck pain group (P < 0.001).
  
  
  CONCLUSIONS
  The cervical extensor muscles exhibit a consistent flexion-relaxation phenomenon in healthy control subjects and the measurement is highly reproducible when measured 4 weeks apart in both controls and chronic neck pain patients. The FRR in neck pain patients is significantly higher than in control subjects suggesting that this measure may be a useful marker of altered neuromuscular function.
authors.affiliation: Faculty of Health Sciences, University of Ontario Institute of Technology, Oshawa, Ontario, Canada. Bernadette.Murphy@uoit.ca
authors.forename: Bernadette A
authors.initials: BA
authors.lastname: Murphy
authors.forename: Paul W
authors.initials: PW
authors.lastname: Marshall
authors.forename: Heidi Haavik
authors.initials: HH
authors.lastname: Taylor
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002574:Cervical Vertebrae / Q000503:physiopathology*; D002908:Chronic Disease; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009126:Muscle Relaxation; D009334:Neck Muscles / Q000503:physiopathology*; D019547:Neck Pain / Q000175:diagnosis* / Q000503:physiopathology; D009520:New Zealand; D010147:Pain Measurement; D016059:Range of Motion, Articular; D015203:Reproducibility of Results