In the Manual manipulation group, the thrust was applied in the right side of C3/C4 with neutral flexion/extension, ipsilateral side bending and contralateral rotation. Then, a low amplitude, high velocity thrust in rotation was delivered.

In the Mechanical manipulation group, the Activator instrument was applied on the right transverse apophyses of C3.

The subjects were positioned in the same pre-manipulative position as the manual manipulation group, but the thrust didn't occur. Instead, the position was hold for 3 seconds and then the subject's head returned passively to neutral position.

The subjects stayed in supine position and no intervention occurred.

In the Manual manipulation group, the thrust was applied in the right side of C3/C4 with neutral flexion/extension, ipsilateral side bending and contralateral rotation. Then, a low amplitude, high velocity thrust in rotation was delivered.

To measure the pressure pain threshold, it was used an electronic pressure dynamometer FORCE ONE™ FDIX (Wagner Instruments - Greenwich, USA), with 1cm2 of surface. The values were expressed in Kg/cm2. The pressure was increased at a rate of 1 kg/cm2/s until the subject inform that the sense of pressure has become a sense of pain.

To evaluate the pressure pain perception, it was used a Visual Analogue Scale (VAS). The pressure increased until 2,5 kg/cm2 and was hold for 5 seconds, and the subject used the VAS scale to record the pressure pain perception he felt.

To measure muscle tone it was used the MyotonPro device. It was used to evaluate those parameters both on the biceps and on the upper trapezius, bilaterally. The device was located perpendicular to the middle point of each muscle and it were recorded 6 impulses in each one of them. The non-neural tone was recorded as frequency.