Pressure pain threshold levels (amount of pressure where the perception of pressure changes to pain) 37 were assessed bilaterally in the anterior part of both temporal muscles (cephalic point), in both upper trapezius muscles (neck point) at a point 2 cm lateral to the halfway point between the spinous process of the seventh cervical vertebra (C7) and the lateral edge of the acromion 38 and over the supra-orbital (V1) nerve at the supra-orbital notch (the junction of the medial and intermediate thirds of the superior border of the orbit). 39 An electronic pressure algometer (Somedic® Algometer, Sollentuna, Sweden©) with a 1-cm2 rubber tipped plunger mounted on a force transducer was used. The subject pushed a button to stop the pressure stimulation when the threshold was reached. The instrument was calibrated at the start of each session. Pressure was applied at a rate of 30 kPa/second. The mean of 3 trials was calculated and used for the main analysis. A 30-second resting period was allowed between each trial. The reliability of algometry has been found to be high in both asymptomatic subjects 40 (ICC = 0.91 [95% CI 0.82-0.97]) and patients with neck pain 41 (ICC 0.78-0.93; 95% CI 0.53-0.97).