Action Observation and Motor Imagery Induced Hypoalgesia in Asymptomatic Subjects

Pressure Pain Threshold (PPT) is one of these tests and it is defined as the minimum force applied which induces pain. The measurement shall be carried out by using an algometer (pressure device that induces mechanical stimuli) is to standardize the amount of pressure applied in the neck region. The reliability of pressure pain thresholds according to raters or measurement frequencies is relatively high

Visual and Kinesthetic Motor Imagery Ability will be measured with Movement Imagery Questionnaire-Revised (MIQ-R). MIQ-R has four movements repeated in two subscales, a visual and a kinesthetic one. Additionally, a score between 1 and 7 is assigned, with 1 representing difficulty in picturing the motor image or difficulty in feeling the movement previously made, and 7 representing the maximum ease. The internal consistencies of the MIQ-R have been consistently adequate with Cronbach's α coefficients ranging above 0.84 for the total scale, 0.80 for de visual subscale and 0.84 for the kinesthetic subscale (Campos & González, 2010).

The degree of physical activity was objectified through the The International Physical Activity Questionnaire (IPAQ) questionnaire, which allows the subjects to be divided into three groups according to their level of activity, which can be high, moderate, and low or inactive. The IPAQ consists of 7 questions about the frequency, duration and intensity of activity (moderate and intense) performed in the last seven days, as well as walking and sitting time on a workday. The IPAQ scoring protocol assigns the following MET values to walking, moderate, and vigorous intensity activity: 3.3 METs, 4.0 METs, and 8.0 METs, respectively.

Fear of movement or kinesiophobia will be quantified with the Spanish version of the Kinesiophobia Tampa Scale (TSK-11). This instrument demonstrates reliability and validity in patients with chronic pain, being shorter than the original scale. The total score ranges from 11 to 44 points, with the highest scores indicating greater fear of a new injury due to movement

Electrodermal Activity will be measured through the use of two electrodes that recorded changes in conductance through the skin located at the back of the dominant hand

Respiration Rate will be measured through a pressure transducer located in the centre of the chest, where it was fixed by a strap

Heart Rate will be measured by three electrodes located in the left area of the chest. One of the electrodes was placed in the middle zone while a second electrode was positioned on the lateral side, and a third one on the lower left side, below the first electrode.