The Importance of Optimal Gaze Direction on Deep Neck Flexor Activation in Chronic Neck Pain

Chronic neck pain (CNP) patients have weak deep neck flexors (DNF) and a hyperactive sternocleidomastoid (SCM). The cranio-cervical flexion test (CCFT) promotes activation of the DNF and decreases activity of the SCM, promoting pain recovery, but research suggests SCM activation increases with increasing gaze direction. We aimed to investigate how DNF and SCM activation varies according to gaze direction in the CCFT, and to prescribe the appropriate gaze direction for CNP. Twenty-eight CNP subjects had their maximum strength pressure level determined by CCFT for strength (20-similar to 30 mmHg) and at each of the measured pressures, DNF and SCM thickness in each of four gaze directions (0 degrees, 20 degrees, 40 degrees, and 60 degrees) was measured by ultrasound imaging. The DNF to SCM ratio varied significantly according to gaze direction (p < 0.05), with gaze directions of 20 degrees and 0 degrees being significantly different from 40 degrees (p < 0.05). Although there was no significant difference in DNF activation according to gaze direction, there was in SCM activation (p < 0.05), with SCM 60 degrees significantly different from SCM 20 degrees and SCM 40 degrees (p < 0.05). In order to increase DNF activation efficiency during the CCFT, SCM activation should be controlled, and a gaze direction below 20 degrees is the most efficient. This can inform DNF training of CNP patients in a clinical environment.