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The Cervical Flexion-Relaxation Ratio: Reproducibility and Comparison Between Chronic Neck Pain Patients and Controls

Murphy, Bernadette A., DC, PhD*; Marshall, Paul W., PhD; Taylor, Heidi Haavik, BSc (Chiro), PhD

doi: 10.1097/BRS.0b013e3181cbc7d8
Cervical Spine

Study Design. 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.

Summary of Background Data. 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).

Conclusion. 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.

The cervical flexion-relaxation ratio measures the ability of the neck extensor muscles to relax during forward flexion. A cohort control study found the measure to be reliable when measured 4 weeks apart, and discriminate between people with chronic neck pain versus controls.

From the *Faculty of Health Sciences, University of Ontario Institute of Technology, Oshawa, Ontario, Canada; †Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand; and ‡New Zealand College of Chiropractic, Auckland, New Zealand.

Acknowledgment date: May 20, 2009. First revision date: August 12, 2009. Second revision date: October 26, 2009. Acceptance date: October 28, 2009.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Other funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Supported by Australian Spinal Research Foundation.

This research was approved by the University of Auckland Human Participants Ethics Committee.

Address correspondence and reprint requests to Bernadette Murphy, Faculty of Health Sciences, University of Ontario Institute of Technology, 2000 Simcoe St. North, L1H 7K4, Oshawa, Ontario, Canada; E-mail:

© 2010 Lippincott Williams & Wilkins, Inc.