Localized pressure pain sensitivity is associated with lower activation of the semispinalis cervicis muscle in patients with chronic neck pain

To investigate the relation between localized pressure pain sensitivity and the amplitude and specificity of semispinalis cervicis muscle activity in patients with chronic neck pain. Pressure pain detection thresholds (PPDTs) were measured over the C2-C3 and C5-C6 cervical zygapophyseal joints in 10 women with chronic neck pain and 9 healthy age-matched and sex-matched controls. Intramuscular electromyography (EMG) was acquired from the semispinalis cervicis at the levels of C2 and C5 during isometric circular contractions in the horizontal plane at 15 and 30 N, with continuous change in force direction in the range 0 to 360 degrees. The average rectified value and directional specificity of semispinalis cervicis muscle activity were computed and regression analyses were performed between measures of EMG and PPDT. Patients showed significantly lower PPDT compared with controls (P