Decrease in elbow flexor inhibition after cervical spine manipulation in patients with chronic neck pain

Objectives. This study measured functional capacity and subjective pain in patients with chronic neck pain before and after manipulation of the cervical spine. Design. Outcomes study on 16 patients with chronic neck pain. Background. Muscle inhibition, i.e., the inability to fully activate a muscle, has been observed following joint pathologies and in low back pain conditions. Although chronic neck pain has been associated with changes in muscle recruitment and coordination in the shoulder and arms, the possibility of muscle inhibition has not been explored. Methods. Biceps activation during a maximal voluntary elbow flexor contraction was assessed using the interpolated twitch technique and electromyography. Cervical range of motion and pressure pain thresholds were measured using a goniometer and an algometer. Manipulation of the cervical spine was applied at the level of C5/6/7, and functional assessments were repeated. Results. Patients showed significant inhibition in their biceps muscles. Cervical range of motion was restricted laterally, and increased pressure pain sensitivity was evident. After cervical spine manipulation, a significant reduction in biceps inhibition and an increase in biceps force occurred. Cervical range of motion and pressure pain thresholds increased significantly. Conclusions. Significant dysfunction in biceps activation was evident in patients with chronic neck pain, indicating that this muscle group cannot be used to the full extent. Spinal manipulation decreased muscle inhibition and increased elbow flexor strength at least in the short term.