Current pain and fear of pain contribute to reduced maximum voluntary contraction of neck muscles in patients with chronic neck pain

Abstract

Objective: To assess a range of physical and psychological factors and determine which factors contribute the most to reduced strength in patients with neck pain.

Design: Regression.

Setting: Laboratory.

Participants: Women with chronic neck pain (n=34) and healthy controls (n=14).

Interventions: Not applicable.

Main outcome measures: Neck flexion, extension, and lateral flexion maximum voluntary contractions (MVC) were measured in patients and healthy controls. Additional parameters were collected for the patient group including: (1) questionnaires measuring general health (Medical Outcomes Study 36-Item Short-Form Health Survey), pain intensity, disability (Neck Disability Index [NDI]; Patient Specific Functional Scale), and fear of movement (Fear-Avoidance Beliefs Questionnaire [FABQ]), (2) pressure pain thresholds, (3) cross-sectional area of selected neck muscles, and (4) surface electromyography from selected neck muscles during a multidirectional isometric task. Univariate and multivariate regression analyses were applied with the average MVC (average of flexion, extension, and lateral flexion MVC) as the dependent variable.

Results: The average MVC was significantly lower in patients (mean ± SD, 130.0±6.0N) compared with controls (166.9±11.7N; P<.01). Univariate regression of the average MVC with the FABQ, NDI, or pain experienced during the MVC gave R(2) values of 13.4%, 13.8%, and 21.1%, respectively. Collectively, the FABQ and pain experienced during the MVCs resulted in an R(2) of 26.6% and the FABQ, contraction pain, and NDI, an R(2) of 28.2%.

Conclusions: The average maximum voluntary force produced in neck flexion, extension, and lateral flexion is inversely and moderately correlated with the pain experienced during maximal contraction, fear of movement, and aspects of neck disability in patients with chronic neck pain.